3.1 Octopus LCs

Up to now two families of such systems have been identified, namely the willow-like and the octopus dendrimers. The so-called willow-like dendrons and corresponding dendrimers based on terphenylene monomeric AB2–type units, were first reported and showed mainly enantiotropic N and smectic phases, depending on some specific structural features [7]. As for the octopus dendrimers, they result from the coupling of segmented and symmetrical dendritic branches containing mesogenic moieties at each generational level (junction) onto a small tetra-podand core (Fig. 2). The modular construction elaborated for their synthesis (independent construction of individual blocks prior to their covalent connections according to a predefined framework) allowed a wide range of possible interesting structural combinations to be envisaged for the elaboration of original multicomponent supermolecules, including homolithic (Fig. 2, one type of building block, A) and heterolithic (Fig. 2, several different blocks, B–D) dendrimers with alternated and/or segmented supermolecular architectures.

In our first study, the anisotropic units selected were tolane- and stilbene-based moieties, because of both their excellent thermal stability and chemical versatility. Homolithic and alternated heterolithic octopus dendritic materials (Fig. 3, 1) bearing these units within the framework were synthesized by an efficient modular synthesis. It consisted of the preparation of the individual anisotropic segments by Sonogashira and Heck Pd-catalyzed cross-coupling reactions, respectively, for tolane- and stilbene-based systems [8], followed by their selective association into precursory dendritic branches, and their final connection to a central tetra-podand amino-core unit (derived from polypropyleneimine: PPI). Such poor mesogenic segments, despite respecting structural requirements for mesophase induction (adequate intrinsic anisotropy and rigidity), were chosen on purpose, in order to evaluate the “mesogenic amplification effect” by means of additivity and/or synergy between the individual components forming these novel structures, i.e. whether mesomorphism could be induced solely by the dendrimerization process. Thus, a number of homolithic (Fig. 3, 1, X = Y) and alternated heterolithic (Fig. 3, 1, X ≠ Y) octopus dendrimers were synthesized, further differing in the number of terminal chains (Fig. 3, 1, R¹, R², R³ = H or OC₁₂H₂₅) [9].

We showed that all these dendrimers were mesomorphic and that the mesophases structures were solely dependent on the ratio number of terminal chains/end groups [9]. The dendrimers bearing one terminal aliphatic chain per peripheral unit (Fig. 3, 1, X: = /≡ and Y: ≡, R¹ = R³ = H and R² = OC₁₂H₂₅) exhibited smectic phases (homolithic tolane derivative: SmB 101 SmA 121 I; heterolithic derivative: SmB 109 SmA 132 I); in contrast, none of the precursory branches was mesomorphic. The mesomorphic behaviour was explained by the elongated (prolate) molecular conformation adopted by the dendrimers. Indeed, the lamellar periodicities were rather large (10–12 nm), consistent with a fully stretched molecular conformation, and with the mesogenic groups homogeneously distributed on both sides of the tetravalent core [9b]. The formation of the smectic phases resulted therefore from the parallel disposition of these giant rod-like supermolecules into layers. In this case, the structure of the smectic phases is quite unique and consists of a highly segregated, subleveled, molecular organization made of an internal sub-layer containing tilted rigid segments (segments of the first generation, randomly tilted to compensate the molecular area), flanked by outer slabs inside which the mesogenic groups are arranged perpendicular to the layer (Fig. 4); these various sublayers are separated by the aliphatic continuum. Molecular modeling supports this view of strongly segregated multilayer structures, with interfaces between the various molecular parts. Obviously, these interfaces are not so well defined due to thermal fluctuations. Nevertheless, let us point out that because of this peculiar structural feature, such layered mesophases cannot exactly be described as purely SmA or SmB phases, and were referred to as “supersmectic” phases.

In contrast, the increase of the chain/end-group ratio prevents such a parallel disposition of the pro-mesogenic groups, and the dendrimers bearing two or three aliphatic chains per outer tolane or stilbene unit (Fig. 3, 1, X,Y: =/≡, R¹ = R² = H and R³ = OC₁₂H₂₅, R¹ = R³ = H and R² = OC₁₂H₂₅, or R¹ = R² = R³ = OC₁₂H₂₅) formed systematically a Col_h phase [9]. The formation of these columnar superstructures is a consequence of the mismatch between the surface areas of the aromatic cores and the cross-sections of the aliphatic chains, resulting in the curvature of all the interfaces, as in polycatenar liquid crystals [10] and dendromesogens [11]. Consequently, the octopuses adopt a wedge-like conformation (or cone-like), authorized by the great flexibility of the G0-PPI core (zeroth generation polypropyleneimine), allowing the pro-mesogenic groups to be radially distributed with uniform interfaces at the different generational levels. With such a folded or fan conformation, the dendrimers self-assemble into (supra)molecular discs or columns which further self-organize into a hexagonal net (Fig. 5, top). Depending on the number of terminal chains per terminal mesogenic units (2 or 3), 3 or 2 folded dendrimers, respectively, can perfectly pave the hexagonal lattice, consistent with the hexagonal parameters (9–10 nm). Considering the diblock, alternated chemical nature of these dendrimers, a leek morphology for the columns is most likely (intracolumnar segregation) (Fig. 5). This model of a multi-segregated internal structure of the columns was supported by molecular dynamics on the homolithic stilbenoid system (Fig. 3, 1, X = Y: = ; R¹ = R² = OC₁₂H₂₅, R³ = H). It showed good segregation at the molecular level by means of interlocked concentric crowns of stilbenoid units belonging to the same generation, such crowns being further stabilized by intermolecular interactions. Each crown is separated by “inert” aliphatic films (Fig. 5).

The mesophase stability was found to greatly depend on the disposition of the terminal chains attached onto the peripheral groups (positions 3,5-, 3,4- and 3,4,5-) and, for the heterolithic systems, on the precise localization of these various units (tolane/stilbene), and thus of their respective proportion, within the branched scaffolding (Fig. 6). Thus, the homolithic stilbene octopuses are all mesomorphic. Whilst systems with the 3,5- and 3,4,5-chain-substitution per terminal units exhibit a room temperature Col_h phase, the derivative with the 3,4-chain substitution exhibits a much higher phase stability, and is crystalline up to ca 100 °C, before self-assembling into the Col_h mesophase (Fig. 6, top). Interestingly, mesomorphism was induced in the latter compound while its corresponding precursory branch was deprived of mesophase, in contrast to the other branches (with the chain' substitution 3,5- and 3,4,5- both having a room temperature Col_h phase). Note also the substantial decrease of the Col_h phase lattice parameters in the case of the dendritic branches with respect to that of their parent octopuses (15–20 Å smaller), resulting in a lesser number of free branches (about 6 with respect to 8–10 i.e. 2–2.5 folded dendrimers) to sufficiently fill an elementary stratum of column 4.5 Å-thick [9a]. The proportion and localization of those groups within the dendritic skeleton have also dramatic effects on the mesophase stability; here only the systems with the 3,4-chain substitution were considered. A great enhancement of the Col_h mesophase stability was clearly observed on increasing the number of stilbene units at the expense of the tolane ones (Fig. 6, bottom). This illustrates rather nicely the strength of the intra- and intermolecular interactions within the octopuses (and thus the different types of mesogenic units and their respective position within the dendritic frame), the higher the number of stilbene groups, the more stabilized the dendritic wedge conformation, and thus the column. Quasi similar observations were made with the non-mesomorphic corresponding acidic dendritic branches, for which the melting temperatures were found to increase from the pure tolane to the pure stilbene system. Interestingly, only one of these branches was mesomorphic, namely the heteroltithic one with two stilbene groups in the periphery (Fig. 3, 1, X: ≡, Y: =, R¹ = R² = OC₁₂H₂₅ and R³ = H).

In this study, new potentially challenging LC materials, possessing a segmented block structure have been synthesized, and it was shown that straightforward structural modifications of the dendritic scaffold or the change in the chains substitution pattern drastically modify the mesomorphism of these dendrimers. These variations permit to better control and tune the mesophase types and their stability, potentially interesting in the design of specific multi-component, polyfunctional materials for technological applications.

Several structurally related octopus dendrimers bearing longer oligo(phenylene–vinylene) terminal groups were also prepared in order to combine luminescent properties with self-organisation (Scheme 1) [12]. For the dendrimer shown in Scheme 1, the terminal OPV3 unit was prepared by two consecutive Heck coupling reactions, and the dendritic branches (4–6) and the final dendrimer (7) were prepared according to the same procedures used for dendrimers 1 [9]; the only difference was in the activation of the acid to react with the PPI-G0 core, which was achieved by the formation of the corresponding pentafluorophenol-derived ester (6). Both the acidic branch (5) and the dendrimer (7) exhibit a Col_h phase (G 47 Col_h 93 I and Cr 90 Col_h 145 I, respectively), with a great enhancement of the phase stability with respect to the homologous homolithic stilbene octopus 1 (Cr -3 Col_h 84 I) and corresponding acid (Col_h 52 I) (Fig. 3, 1, X, Y: =; R¹ = R² = R³ = OC₁₂H₂₅) [9b]. This phase stability increase is clearly due to the elongation of the terminal chromophore, and the consequent increase of intermesogenic interactions. Three of these dendrimers self-assemble together into a supramolecular disc of 5.7 Å thick, and the paving of the hexagonal lattice (a = 100 Å) is total; as for the dendritic branches, 12 of them fulfil the geometrical requirement of the hexagonal lattice (a = 98 Å). Both the dendron and dendrimer exhibit interesting luminescent properties in solution [12].

An octopus dendrimer based on a pentaerythritol core was prepared in order to test the effect of another type of core on the mesomorphic properties. Dendrimer 11 was prepared from an extended pentaerythritol core (10), as shown in Scheme 2. The coupling reaction between the dendron and this core was realized in dichloromethane using DMAP, CMC (1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide) instead of DCC, and yielded the corresponding pure dendrimer although in rather low yield (25%). Unfortunately, mesophase formation was simply inhibited and a room temperature oily material was obtained instead. The absence of mesomorphism was credited to the relative rigidity of the tetrahedral pentaerythritol unit versus the deformable PPI one. The latter will force the branches to radiate isotropically to generate a protean structure unable to self-organize into a mesophase rather than the required wedge-like structure (the branch itself was mesomorphic, vide infra). The chemical nature of the core is therefore another important aspect in the design and the control of the properties of these octopus dendrimers. It can however be speculated that the grafting of a more anisometric monomeric units at the periphery of dendrimer 11, such as for example the OPV3 moiety instead of the stilbene one, would have likely promoted the formation and stabilization of a mesophase.

There are other examples in the literature of pentaerythritol based-liquid crystals which support our observations that the pentaerythritol core is not such a judicious choice for designing liquid crystalline dendrimers due to restricted molecular topologies and limited molecular flexibility with respect to other G0 cores [6e]. However, providing that the peripheral units, preferentially grafted in the end-on configuration, are strong liquid-crystalline promoters (e.g. calamitic [13], discotic [14], or conical “DOBOB” [15] pro-mesogens), or that micro-segregation is enhanced by the insertion of amphipathic groups either between the core and the rigid units (e.g. silylated spacers [16]) or at the periphery (e.g. carbohydrate groups [17], fluorinated chains [18]), induction of stable mesophases (enantiotropic phases) is nevertheless observed. This core was considered as a potential source for the fabrication of non-symmetrical segmented dendrimers (Fig. 2, structures C and D) by regio-selective chemistry leading to a “selective multifunctionalization” of the pentaerythritol unit [16,19]. However, the synthesis of the symmetrical dendrimer was already found to be rather difficult itself, and this approach was later abandoned as totally inapplicable for the synthesis of Janus-like dendrimers.

3.2 Multipodal main-chain LCs

The effect of the core connectivity on the mesomorphism was also investigated [20]. Three main-chain dendrimers (with the same heterolithic branch, Fig. 7) were prepared from various amido-cores of zeroth generation and with different multiplicities: 1,4- diaminobutane (N_C = 2), tris(2-aminoethyl) amine (N_C = 3) and PAMAM-G0 (N_C = 4); the latter was also prepared for the possibility to rigidify the core by additional hydrogen-bonds (amido groups) and enhance the mesomorphic temperature range as already observed with some side-chain LCDs [21]. They all exhibit a broad Col_h phase (expected since there are two terminal chains per end-group) and the transition temperatures and mesophase stability were found to be influenced by the nature and the connectivity number of the core. In particular, the mesophase stability was greatly enhanced in the tetrapode 12 and the PAMAM derivative 14 (Fig. 7). Moreover, a stepwise increase of the hexagonal lattice parameter was correlated to the increase of the core connectivity (a = 81 → 86 → 95 Å for N_C = 2 → 3 → 4, respectively). The mesophases are formed through the same process of self-organisation as described above. But since the overall number of peripheral chains per dendritic molecule is changed, and while the lattice parameter of the Col_h phases increases concomitantly with the N_C value, the number of dendrimers self-assembling within an elementary slice of column (same height) is therefore different; this number is deduced by the total number of radiating chains, varying from 36 to 48 throughout the series. Thus, within a slice of 4.6 Å, it was found that 4.5 molecular equivalents of 12, 3.3 of 13 and 3 of 14 (3 with the PPI-G0 core, Fig. 3, 1, X: =,Y: ≡, R¹ = R² = OC₁₂H₂₅ and R³ = H) were needed to completely fill the available volume.

The next structural modification concerned the effect of the degree and toplogy of branching (N_B) on the mesomorphic properties. A dendrimer with N_B = 1 was prepared (Scheme 3, 18), whilst none with ternary branching (N_B = 3) could be prepared, as due to strong steric constraints, the branches could not be grafted onto the core. Thus, following the same global methodology, 18 was prepared and obtained as a pure material. It exhibited a Col_h phase (Cr 106 Col_h 153 I). In this case, considering a similar mode of packing into columns (fan-shape conformation, self-assembling) about 6 tetrapodes (or molecular equivalents) associate to fill a slice of 4.5 Å.

3.3 Effect of generation

For a fully comprehensive study, several G0 dendrimers (tetramers) were synthesized, as well as the preparation of a second generation was attempted, in order to evaluate the impact of the generation on the mesomorphic properties. The various G0 systems (21–23, 27) were directly obtained from the coupling of the acidic anisotropic segment onto the PPI-G0 core, as shown in Scheme 4. A side-chain G1 was also prepared from one of the available acids (Scheme 4, 24) and PPI-G1.

The four G0 dendrimers (Table 1) exhibit a hexagonal columnar phase characterized by a series of three or four sharp and intense diffraction peaks in the small-angle region, in the ratio 1, √3, √4, √7 which is typical for a hexagonal two-dimensional arrangement of columns. The X-ray diffraction patterns contain also a diffuse signal at 4.5–4.6 Å, which is attributed to the liquid-like ordering of the molten terminal aliphatic chains (Table 1). The hexagonal cell parameters are almost the same for 21 and 23 bearing tricatenar sub-units, and do not vary significantly as a function of temperature within the stability temperature range of the mesophase. The stilbene-containing dendrimer also exhibit more stable phases than the tolane system. The decrease of the number of chains coincides with an increase of the phase stability but with a narrowing of the temperature range (21 versus 22). The phase stability is enhanced upon generation increase (22 versus 24) or by elongation of the rigid unit (21 versus 27). In a first approximation, the three G0 dendrimers 21–23 likely adopt a folded conformation, with an angle at the summit of the fan-shape of nearly 120° for 21 and 23 and ca 90° for 22, which then self-assemble to form columns (see Fig. 8 for a typical columnar optical texture). Using a straightforward geometrical approach, which takes into account the relationships between the planar angle α, that represents the projection of the tapered dendrons solid angle, ω, ω/2 = α, and N, the number of dendrimers covering the columnar cross-section area, through the equation α = 2π/N [11,22], it was found that three (21, 23) and four (22) dendrimers occupy an “elementary” slice of column with a thickness close to 8–9 Å. The presence of the numerous terminal chains (36 and 32 chains, respectively) forces the rigid sub-units to tilt out of the plane in order to accommodate a tight packing of the chains. For 27, bearing longer arms, in its fan-like shape, the cone angle is a smaller than for 21, closer to 90°. Considering a similar thickness (h = 8 Å), about 4.5 molecular equivalents are required to pave the hexagonal lattice, in agreement with the increase of the lattice dimensions, much larger than that of 21. The columnar mesophase is formed by the self-assembling of folded dendrimers (3–4.5) into a supramolecular disk or column; this model of these zeroth generation (G0) dendrimers is similar to that already described for mesomorphic side-chain dendrimers [21].

A good agreement is also found with the relation dendron–dendrimer between the precursory, mesomorphic acid 25 and the corresponding dendrimer 27, where, considering the same thickness value for the columnar slice, almost four times more of the former are needed for a good filling of the cylinder. Nevertheless, one striking result is the transition from a hexagonal columnar phase to a cubic mesophase when the length of the peripheral group increases (21 → 27). Once more, the observation of such mesophases is not surprising when considering the strong curvature at the interface between the dendritic cores and the peripheral groups.

Thus, a clear stabilization, or even induction, of the mesophases is observed upon dendrimerisation, i.e. from the acid to the corresponding dendrimer. None of the precursory acids of 21–23 were mesomorphic, while their connection to PPI-G0 produced large temperature ranges Col_h phases; between 25 and 27, not only the phase stability is enhanced, the apparition of a new phase was also observed. The same observations can be made for the G1 systems, i.e. between 5 and 7 and between the precursory acids of 1 and dendrimers 1 [9]. The effect of generation is not as positive as expected: except for the non-mesomorphic stilbene acid precursors, the increase of generation is concomitant with a decrease of the mesophase stability (reduction of the mesophase temperature ranges, substantial decrease of the isotropic transition temperatures e.g. 25 → 5, 21, 22 → 1, 27 → 7).

Below the Col_h phase, 27 exhibits a cubic phase as well. The small-angle X-ray diffraction pattern exhibits three sharp, small-angle reflections, for which the reciprocal d-spacings were in the ratios √4:√5:√6, pointing to a cubic supramolecular organization [(h² + k² + l²)^1/2 = a/d_hkl] and an additional, very intense, but diffuse, halo in the wide-angle region at about 4.4–4.6 Å confirming the liquid nature of the mesophase. Cubic mesophases are ordered three-dimensional supramolecular edifices, with a multi-continuous [23–25], or a discrete micellar structure [26], depending on the molecular self-organisation within the cubic cell [11,22,27]. Bi- and tri-continuous cubic structures consist of two or three regular, interwoven, infinite, interconnected rod networks (referred to as Im-3m (P) and Im-3m (I) structures, respectively [24]); the columnar rods are formed by the rigid part of the molecules, and the networks are separated by lipophilic films (their associated minimal surfaces). The difference between the bicontinuous and the micellar structures lies in the periodic discontinuities along the rods in the x, y, z directions (bicontinuous model) that appear at mid-height of the cubic-cell edges; the junctions between three connecting rods then correspond to the gravity centres of the micelles (micellar model). It is therefore not trivial to choose one model preferentially to the other. For the present system, the micellar model is unlikely due to the too high number of molecules per cubic cell (about 470 for P, 1300 for I and 3700 for F), which should be further distributed equitably within the micelles. As far as the bicontinuous structure is concerned, the molecules need to be able to stack to form the columns, with the required molecular conformation as that found in the columnar phase. Thus, on the basis of their molecular conformations and packing considerations, the micellar model does not appear appropriate in the present situation and a multi-continuous model is more probable.

The determination of the cubic symmetry is generally not trivial, but the possibilities can be considerably reduced. All non-centro-symmetric groups (groups with the 23, 432 and -43m Laue classes) can be disregarded, a consequence of the Friedel's law [28,29], thus leaving only 17 cubic space groups to consider out of initially 36 of them. However, with three reflections only, the correct determination is unlikely. Indeed, this sequence of ratios is compatible with a face centred cubic network (Fm-3, Fm-3m and Fm-3c), primitive Bravais lattice (Pm-3, Pa-3, Pm-3m and Pm-3n) and with a body-centered cubic lattice (Im-3, Im-3m). The F-type can be a priori disregarded since a number of absent reflections is not explained by the conditions on the reflections. However, this is difficult to discriminate between a body-centered and primitive space group. The distribution of the reflections' intensities often helps distinguishing both phases: on the basis of other studies [30], the intensity of the reflections decreases on increasing the diffraction angle, in agreement with a body-centered symmetry.

An aggregation into the highest symmetry is generally admitted and accordingly, the Im-3m (No. 229) [29] space group can be retained. For the body-centered cubic lattice, the considered sequence in this case is √8:√10:√12 and the reflections can be indexed as (220), (310) and (222). The multicontinuous models of the Im-3m phase could also render account of the self-organization. In the network model of the Im-3m (P) bicontinuous cubic phase, two networks are interpenetrated and separated by lipophilic fragments, whereas in the triple network (Im-3m (I) structure), there are three interpenetrating continuous networks (Fig. 9) [24].

As for the G1 dendrimer, 24, a Col_h phase was also observed. The thermal stability of the mesophase increases slightly when increasing the generation (22 → 24). Such a larger stability could be related to a better nano-segregation due to the larger core size, in agreement with previous results [21]. A molecular dynamic study of 24 (side-chain dendrimer) was performed in order to optimize the geometry of organization. Thus, three molecules were assembled in a hexagonal cell with a thickness of 9 Å, corresponding to the thickness of one folded molecule. The hexagonal parameter, a, is not imposed so that no constraint exists during the optimization process. It has to be noted that this simulation has been studied at a temperature lower than the stability domain of the mesophase, in order to avoid any eccentric distortion. The result of this molecular dynamic study at 80 °C is presented in Fig. 10a. The arrangement of the molecules is not random, and it is possible to distinguish three main zones. The central part is constituted by all the dendritic cores, while the rigid molecular moieties are building an internal corona; finally the disorganized aliphatic chains are located at the periphery. It is worth to mention that the hexagonal cell parameter determined after such a simulation is in good agreement with that found experimentally by X-ray diffraction. The organization of the columns in a two-dimensional hexagonal lattice is easily obtained through interdigitation of the aliphatic chains (Fig. 10b).

At this stage, it became obvious to synthesize main-chain dendrimers of the second generation, with the expectation to enlarge further the molecular variety as well as the mesophases morphology. A straight convergent synthesis was used for the preparation of the G2 dendrons 34 (Scheme 5). Connection of the readily available trialkoxytolanol derivative (28) with the core 29 by standard etherification led to the first precursory branch (30). The iodide group was converted into the acetylenic function (32) using the Sonogashira coupling, followed by deprotection of TMS by TBAF. A second Sonogashira coupling between 32 and iodophenol led to the desired functional branch 33. The final dendron was obtained by etherification between the precursory branching stilbene (vide supra) and 33. All the steps proceeded in good yields. However, despite various attempts, it was not possible to couple the acidic dendron onto the PPI-G0 core. Unfortunately, both the dendrons 34a and 34b were devoid of mesomorphism (33 was not liquid crystalline either), probably due to a too great flexibility and entropy winning over the enthalpic intramolecular interactions. It can, however, be speculated that mesomorphism could be induced in G2 dendrons, providing the use of longer anisotropic units, such as OPV3 basic units; this work is still in progress.

5.1 Preparation of the octopus 7 (Scheme 1)

Compound 2: A solution of 3,4,5-tridodecyloxystyrene (5.6 g, 8.52 mmol) [9a], Pd(OAc)₂ (70 mg, 0.3 mmol), ToP (374 mg, 1.23 mmol) and 4-bromoiodobenzene (2.9 g, 10.2 mmol) in NEt₃ (50 mL) was stirred at 60 °C under argon (2 h) and at 80 °C (2 d). A yellow precipitate was observed during this time. The mixture was cooled to RT, diluted (CH₂Cl₂) and filtrated on celite. The crude product was extracted (CH₂Cl₂), washed (H₂O), dried (MgSO₄). Purification by column chromatography (SiO₂, 1:4 CH₂Cl₂/cyclohexane) and crystallization in acetone gave a slightly yellow solid (5.35 g, 77%). ¹H NMR (CDCl₃): δ 7.46 (m, 2H), 7.36 (m, 2H), 6.95 (dd, 2H, J = 16 Hz), 6.7 (s, 2H), 4.0 (m, 6H), 1.8 (m, 6H), 1.3 (m, 54H), 0.89 (m, 9H).

Compound 3: Prepared in three steps: i) To a suspension of Ph₃PCH₃Br (42 g, 116 mmol) in THF (100 mL) under argon was added in a small portion t-BuOK (13.1 g, 116 mmol). The resulting yellow mixture was stirred at RT (30 min). The solution of the TBDMS-protected aldehyde (23 g, 97 mmol) in dry THF (30 mL) was then added dropwise [12]. The mixture was stirred at RT (2 h), and then was quenched by adding 30 mL of a saturated aqueous solution of NH₄Cl. The crude product was extracted (CH₂Cl₂), washed (H₂O), and dried (MgSO₄). Purification by chromatography (SiO₂, 3:7 CH₂Cl₂/cyclohexane) provided the TBDMS-protected styrene as a colourless oil (19.4 g, 85%). ¹H NMR (CDCl₃): δ 7.29 (d, 2H, ³J = 9 Hz), 6.8 (d, 2H, ³J = 9 Hz), 6.66 (dd, 1H, J = 11 Hz, J = 17 Hz), 5.61 (dd, 1H, J = 0.9 Hz, J = 17 Hz), 5.13 (dd, 1H, J = 0.9 Hz, J = 11 Hz), 0.99 (s, 9H), 0.26 (s, 6H). ii) As for 2: 2 (4.82 g, 5.94 mmol), Pd(OAc)₂ (54 mg, 0.24 mmol), ToP (217 mg, 0.7 mmol), NEt₃ (60 mL), 60 °C (2 h). The protected styrene (1.67 g, 7.12 mmol) in xylene (60 mL) was then added, and the reaction mixture was heated to 110 °C (2 d). The crude was diluted (CH₂Cl₂), filtrated (celite), extracted (CH₂Cl₂), washed (H₂O), and dried (MgSO₄). The yellow solid protected OPV3 derivative (4.6 g, 80%) was obtained by two successive chromatography columns (SiO₂, 1:4 CH₂Cl₂/cyclohexane). ¹H NMR (CDCl₃): δ 7.47 (s, 4H), 7.4 (d, 2H, ³J = 8.55 Hz), 7.02 (m, 4H), 6.84 (d, 2H, ³J = 8.55 Hz), 6.72 (s, 2H), 4.0 (m, 6H), 1.8 (m, 6H), 1.27 (m, 54H), 1.01 (s, 9H), 0.89 (t, 9H, ³J = 6.9 Hz), 0.22 (s, 6H). iii) To a solution of this protected alcohol (2.3 g, 2.37 mmol) in THF (20 mL) was added dropwise TBAF (3.6 mL, 3.56 mmol). The yellow mixture was stirred at RT overnight. Purification by column chromatography (SiO₂, CH₂Cl₂) yielded a fluorescent yellow solid (1.63 g, 80%). ¹H NMR (CDCl₃): δ 7.47 (s, 4H), 7.42 (d, 2H, ³J = 8.77 Hz), 7.03 (AB, 2H, ³J = 16.22 Hz), 6.99 (m, 2H), 6.84 (d, 2H, ³J = 8.55 Hz), 6.72 (s, 2H), 4.87 (s, 1H), 4 (m, 6H), 1.8 (m, 6H), 1.27 (m, 54H), 0.89 (t, 9H, ³J = 6.9 Hz).

Compound 4: To a solution of 3 (1 g, 1.17 mmol) and internal stilbene block (0.36 g, 0.48 mmol) [9a] in DMF (20 mL) was added slowly K₂CO₃ (1.6 g, 11.7 mmol). The mixture was stirred (80 °C, 2 d). The solvent was then removed under vacuum and the crude product extracted (CH₂Cl₂, 50 mL), washed (50 mL saturated solution of NH₄Cl, and 50 mL of H₂0), dried (MgSO₄), and purified by column chromatography (SiO₂, 3:7 CH₂Cl₂/cyclohexane) to afford a yellow solid (1.03 g, 93%). ¹H NMR (CDCl₃): δ 8.02 (d, 2H, ³J = 8.85 Hz), 7.55 (d, 2H, ³J = 8.55 Hz), 7.47 (s, 10H), 7.44 (d, 4H, ³J = 8.99 Hz), 7.0 (m, 10H), 6.89 (d, 4H, ³J = 8.55 Hz), 6.72 (s, 4H), 6.68 (d, 2H, ³J = 2.19 Hz), 6.43 (t, 1H), 4.0 (m, 20H), 3.92 (s, 3H), 1.79 (m, 20H), 1.37 (m, 136H), 0.89 (t, 18H, ³J = 6.68 Hz).

Compound 5: To 4 (1.03 g, 0.45 mmol) in THF (20 mL) was added an aqueous solution of KOH (1.01 g, 18.04 mmol). The reaction mixture was heated at reflux (2 d). The acid was then precipitated in an aqueous solution of HCl (10%), cooled (0 °C), filtrated, washed (H₂O), and dried (MgSO₄). Crystallization in acetone afforded a yellow solid (0.963 g, 95%). ¹H NMR (CDCl₃): δ 8.08 (d, 2H, ³J = 8.55 Hz), 7.58 (d, 2H, ³J = 8.55 Hz), 7.47 (s, 8H), 7.44 (d, 4H, ³J = 8.99 Hz), 7.04 (m, 10H), 6.89 (d, 4H, ³J = 8.7 Hz), 6.72 (s, 4H), 6.69 (d, 2H, ⁴J = 2.19 Hz), 6.44 (m, 1H), 4.0 (m, 20H), 1.79 (m, 20H), 1.37 (m, 136H), 0.89 (t, 18H, J = 6.9 Hz). ¹³C NMR (CDCl₃): δ 160.5, 158.9, 153.3, 142.6, 138.5, 138.3, 136.9, 136.3, 132.6, 131.8, 130.6, 129.9, 128.5, 128.1, 127.9, 127.7, 127.3, 126.6, 126.5, 126.4, 126, 114.7, 105.4, 105.2, 73.5, 69.2, 68.1, 68, 31.93, 31.91, 30.3, 29.74, 29.72, 29.7, 29.6, 29.53, 29.5, 29.4, 29.35, 29.25, 26.1, 26, 22.7, 14.1. Elemental analysis calculated for C₁₅₃H₂₃₂O₁₂: C, 81.19, H, 10.33; found: C, 80.97, H, 10.77.

Compound 6: To a solution of 5 (1.5 g, 0.66 mmol) and pentafluorophenol (0.146 g, 0.79 mmol) in CH₂Cl₂ (10 mL) stabilized by amylene, was added under argon DCC (0.164 g, 0.79 mmol). The white solid precipitated suddenly. The reaction mixture was stirred at RT overnight. The dicyclohexylurea which is the secondary product of the reaction was then eliminated by filtration. The solvent was removed under reduced pressure. Purification by column chromatography (SiO₂, 3/7 CH₂Cl₂/cyclohexane) afforded a yellow solid (1.39 g, 86%). ¹H NMR (CDCl₃): δ 8.18 (d, 2H, J = 8.33 Hz), 7.66 (d, 2H, J = 8.55 Hz), 7.47 (s, 8H), 7.45 (d, 4H, J = 8.98 Hz), 7.08 (m, 10H), 6.89 (d, 4H, J = 8.77 Hz), 6.72 (s, 4H), 6.7 (d, 2H, J = 2.2 Hz), 6.46 (m, 1H), 4.0 (m, 20H), 1.79 (m, 20H), 1.37 (m, 136H), 0.89 (t, 18H, J = 6.9 Hz). ¹³C NMR (CDCl₃): 162.29, 160.56, 158.88, 153.27, 143.59, 138.30, 138.20, 136.85, 136.29, 132.62, 132.55, 131.17, 129.92, 128.50, 128.06, 127.65, 127.31, 126.68, 126.62, 126.49, 126.01, 125.36, 114.68, 105.49, 105.15, 101.76, 73.50, 69.15, 68.11, 68.03, 31.9, 30.33, 29.73, 29.51, 29.47, 29.24, 26.10, 22.73, 14.06.

Compound 7: To a solution of 6 (1.34 g, 0.55 mmol) in CH₂Cl₂ (5 mL) stabilized by amylene, PPI-G0 (39.7 g, 0.13 mmol) in CH₂Cl₂ (5 mL) was added slowly; a few drops of NEt₃ were also added. After stirring (3 d), the crude product was taken up in CH₂Cl₂ and precipitated in cyclohexane. The precipitate was eliminated by filtration and the filtrate was concentrated in vacuum. Purification by column chromatography (Al₂O₃, with CH₂Cl₂ and then with THF) afforded a waxy yellow solid (270 mg, 23%). ¹H NMR (CDCl₃): δ 7.76 (d, 8H, ³J = 8.11 Hz), 7.46 (m, 40H), 7.42 (d, 16H, ³J = 8.99 Hz), 7.0 (m, 40H), 6.87 (d, 16H, ³J = 8.55 Hz), 6.71 (s, 16H), 6.61 (d, 8H), 6.39 (m, 4H), 4.0 (m, 80H), 3.48 (m, 8H), 2.48 (m, 12H), 1.77 (80H), 1.45 (m, 556H), 0.88 (m, 72H). ¹³C NMR (CDCl₃): δ 167.12, 160.50, 158.90, 153.28, 140.15, 138.62, 138.36, 136.89, 136.31, 133.34, 132.59, 130.69, 129.92, 128.53, 128.09, 127.66, 127.47, 127.32, 126.64, 126.51, 126.01, 114.69, 105.22, 101.40, 73.52, 69.18, 68.05, 52.35, 43.44, 39.11, 31.91, 30.84, 30.36, 30.16, 29.75, 29.70, 29.66, 29.56, 29.47, 29.44, 29.38, 29.35, 29.31, 26.88, 26.14, 26.07, 22.68, 14.09. Elemental analysis calculated for C₆₂₈H₉₆₀N₆O₄₄: C, 81.12, H, 10.41, N, 0.9; found: C, 82.09, H, 10.62, N, 0.76. MS-MALDI-TOF (m/z): found 9298.1 g mol⁻¹ [M + H]⁺, calculated 9298.36 g.mol⁻¹. SEC: M_w = 12.633, M_n = 11.271, IP: 1.12.

5.2 Preparation of the octopus based on the pentaerythritol core, 11 (Scheme 2)

Compound 8: To pentaerythritol (9.2 g, 67 mmol) in 33% NaOH solution (150 mL), is added TBAI (7.24 g, 19 mmol), and the mixture is heated under stirring at 40 °C. Then, allyl bromide is slowly added (43.8 g, 0.36 mol), and the reaction is kept stirring at RT (2 d). The product is extracted (toluene), washed (H₂O), dried (MgSO₄), filtered and the solvent evaporated. The crude product was purified by chromatography (SiO₂, CH₂Cl₂) yielded 7 g of a yellowish oily liquid (35%). ¹H NMR (CDCl₃): δ 5.89 (m, 4H), 5.21 (m, 8H), 3.96 (m, 8H), 3.47 (s, 8H).

Compound 9: Under argon, 8 (1 g, 3.4 mmol) in THF (200 mL) and 9-BBN (60 mL, 30 mmol) are heated at reflux (1 h), under stirring. The excess of hydride is neutralized by small portion of H₂O. The solution is cooled down to 0 °C, 30 mL of NaOH 3 M added dropwise, and then 30 mL of a 30% of H₂O₂ solution. Stirring is maintained at RT (4 h), and then the solution saturated with K₂CO₃. The product is extracted (THF), dried (MgSO₄), filtered, and the solvent evaporated. Then, the residue is solubilised in 25 mL of pyridine, and 25 mL of acetic anhydride added, and stirred at RT (8 h). Purification by chromatography (SiO₂, 4:6 EtOAC/petroleum ether) afforded 1.35 g of a colorless oil (75%). ¹H NMR (CDCl₃): δ 4.13 (t, ³J = 7 Hz, 8H), 3.44 (t, ³J = 7 Hz, 8H), 3.35 (s, 8H), 2.05 (s, 12H), 1.86 (q, ³J = 7 Hz, 8H).

Compound 10: To a vigorously stirred solution of 9 (1.35 g, 2.5 mmol) in MeOH (60 mL), a piece of sodium is added, and the mixture kept at RT under vigorous stirring (12 h). The solution is then neutralized (DOWEX, W50 H+). After filtration and evaporation 0.9 g (100%) of a yellowish oil is obtained. ¹H NMR (CD₃OD): δ 3.72 (t, ³J = 7 Hz, 8H), 3.56 (t, ³J = 7 Hz, 8H), 3.45 (s, 8H), 1.83 (q, ³J = 7 Hz, 8H).

Compound 11: Under argon, 10 (0.012 g, 0.03 mmol) and CMC (0.138 g, 0.33 mmol) are dissolved in CH₂Cl₂ stabilized by amylene (5 mL). The suspension is then stirred at RT (4 d), and the appropriate dendritic branch [9a] (0.46 g, 0.27 mmol) and a catalytic quantity of DMAP are introduced. The product is then extracted (CH₂Cl₂), washed (H₂O), dried (MgSO₄), filtered and the solvent evaporated. Purification by chromatography (SiO₂, 7:3 CH₂Cl₂/petroleum ether) yielded 50 mg of a viscous white solid (25%). ¹H NMR (CD₂Cl₂): δ 7.95 (d, ³J = 9 Hz, 8H), 7.50 (d, ³J = 9 Hz, 8H), 7.32 (d, ³J = 9 Hz, 16H), 7.00 (m, 40H), 6.61 (d, ⁴J = 2 Hz, 24 H), 6.33 (t, ⁴J = 2 Hz, 12H), 4.33 (t, ³J = 7 Hz, 8H), 3.95 (m, 64H), 3.51 (t, ³J = 7 Hz, 8H), 3.40 (s, 8H), 1.95 (q, ³J = 7 Hz, 8H), 1.78 (m, 64H), 1.27 (m, 400H), 0.89 (m, 48H). ¹³C NMR (CDCl₃): δ 160.5, 158.9, 139.6, 129.9, 129.8, 129.3, 129.1, 128.6, 127.7, 126.6, 126.3, 114.7, 104.9, 68.1, 31.9, 29.7, 29.6, 29.4, 29.3, 26.1, 22.7, 14.1. Elemental analysis calulated for C₄₆₉H₇₁₆O₄₄: C, 79.80, H, 10.22; found: C, 79.61, H, 10.31. SEC: IP = 1.06. MS-MALDI-TOF: calculated, 7058.82 g mol⁻¹; found, 7060.06 g mol⁻¹.

5.3 Preparation of tetrapode 18 (Scheme 3)

Compound 16: Prepared in two steps. i) By a Heck coupling as 2: TBDMS-protected styrene (7.75 g, 0.033 mol, see 3), Pd(OAc)₂ (0.3 g, 0.001 mol), ToP (0.6 g, 0.002 mol), ethyl-4-iodobenzoate (9.13 g, 0.033 mol). Purification by column chromatography (SiO₂, 3/7 CH₂Cl₂/petroleum ethers) afforded a yellow solid (12 g, 65%). ¹H RMN (CDCl₃): δ 8.02 (d, ³J = 8 Hz, 2H), 7.78 (d, ³J = 9 Hz, 2H), 7.53 (d, ³J = 8 Hz, 2H), 7.17 (d, ³J = 16 Hz, 1H), 6.98 (d, ³J = 16 Hz, 1H), 6.93 (d, ³J = 9 Hz, 2H), 4.39 (q, ³J = 7 Hz, 2H), 1.42 (t, ³J = 7 Hz, 3H), 1.0 (s, 9H), 0.26 (s, 6H). ii) as in 3iii: protected alcohol (12 g, 0.031 mol), THF (100 mL), TBAF (8.2 g, 0.031 mol), stirring (RT, 1 h) and filtration on silica gel. Purification by crystallization in petroleum ether yielded a white solid (5.1 g, 60%). ¹H NMR (CDCl₃): δ 8.02 (d, ³J = 8 Hz, 2H), 7.53 (d, ³J = 8 Hz, 2H), 7.44 (d, ³J = 9 Hz, 2H), 7.17 (d, ³J = 16 Hz, 1H), 6.98 (d, ³J = 16 Hz, 1H), 6.86 (d, ³J = 9 Hz, 2H), 4.39 (q, ³J = 7 Hz, 2H), 1.42 (t, ³J = 7 Hz, 3H).

Compound 17: Prepared in three steps. i) (E)-Ethyl 4-(4-(11-bromoundecyloxy)styryl) benzoate was prepared from 16 (5 g, 0.018 mol), bromoundecanol (6.18 g, 0.024 mol), PPh₃ (5.31 g, 0.023 mol) and DIAD (4.75 g, 0.023 mol) according to the Mitsonobu procedure. Purification by chromatography (SiO₂, 7:3 CH₂Cl₂/petroleum ethers), and crystallisation in petroleum ether yielded 7.5 g of a white solid (95%). ¹H NMR (CDCl₃): δ 8.02 (d, ³J = 8 Hz, 2H), 7.53 (d, ³J = 8 Hz, 2H), 7.46 (d, ³J = 9 Hz, 2H), 7.17 (d, ³J = 16 Hz, 1H), 6.98 (d, ³J = 16 Hz, 1H), 6.91 (d, ³J = 9 Hz, 2H), 4.39 (q, ³J = 7 Hz, 2H), 3.99 (t, ³J = 7 Hz, 2H), 3.41 (t, ³J = 7 Hz, 2H), 1.87 (m, 4H), 1.31 (m, 14H). ii) 15 [9b] (1.41 g, 2.51 mmol) was reacted with the alkyl bromide just prepared (1 g, 2.28 mmol) according to the Williamson etherification procedure. Purification by chromatography (SiO₂, 7:3 CH₂Cl₂/petroleum ethers) yielded 1.6 g of the ester branch as a white solid is obtained (76%). ¹H NMR (CDCl₃): δ 7.98 (d, ³J = 9 Hz, 2H), 7.53 (d, ³J = 9 Hz, 2H), 7.45 (m, 4H), 6,92 (m, 9H), 4.39 (q, ³J = 7 Hz, 2H), 3.99 (m, 8H), 1.82 (m, 8H), 1.27 (m, 53H), 0.89 (m, 6H). iii) As in 5: Crystallisation from petroleum ether (1.4 g, white solid, 100%). ¹H NMR (CDCl₃): δ 7.94 (d, ³J = 9 Hz, 2H), 7.53 (d, ³J = 9 Hz, 2H), 7.45 (m, 4H), 6.93 (m, 9H), 3.97 (m, 8H), 1.82 (m, 8H), 1.27 (m, 50H), 0.89 (m, 6H). MS-FAB+: calculated, 955.42 g mol⁻¹; found, 954.85 g mol⁻¹.

Compound 18: This compound was prepared from 17 (0.3 g, 0.34 mmol), DDTBP (0.14 g, 0.37 mmol) and PPI-G0 (0.022 g, 0.07 mmol) as in 7. Purification by column chromatography (Al₂O₃ with CH₂Cl₂ and then THF) afforded a yellow solid (160 mg, 60%). ¹H NMR (CDCl₃): δ 7.72 (d, ³J = 9 Hz, 8H), 7.38 (m, 28H), 7.04 (m, 12H), 6.85 (m, 24H), 3.95 (m, 32H), 3.50 (m, 8H), 2.50 (m, 8H), 2.40 (m, 4H), 1.81 (m, 44H), 1.27 (m, 200H), 0.89 (m, 24H). ¹³C NMR (CDCl₃): δ 148.7, 132.8, 128.0, 126.1, 114.7, 114.5, 31.9, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 26.0, 22.7, 14.1. Elemental analysis calculated for C₂₇₂H₃₉₂N₆O₂₀: C, 80.35, H, 9.72, N, 2.07; found: C, 80.54, H, 10.01, N, 1.85. MS-MALDI-TOF: found, 4066.84 g mol⁻¹; calculated, 4066.13 g mol⁻¹.

5.4 Prepration of dendrimers G0, 21, 22, 23, 27, (Scheme 4)

Compound 19a: As for 2: under argon 3,4,5-tridodecyloxystyrene (3 g, 6.35 mmol) [9a], Pd(OAc)₂ (0.13 g, 0.57 mmol), ToP (1.05 g, 3.46 mmol), 4-ethyl iodobenzoate (0.96 mL, 5.77 mmol), NEt₃ (50 mL), stirring (2 h, 60 °C and for 24 h at 80 °C). The crude product was extracted (CH₂Cl₂), washed (H₂O), and dried (MgSO₄). Purification by column chromatography (SiO₂, 4:6 CH₂Cl₂/petroleum ethers) yielded a white solid (2.4 g, 60%). ¹H NMR (CDCl₃): δ 8.02 (d, ³J = 8 Hz, 2H), 7.54 (d, ³J = 8 Hz, 2H), 7.05 (m, 5H), 4.39 (q, ³J = 7 Hz, 2H), 4.04 (m, 4H), 1.85 (m, 4H), 1.37 (m, 39H), 0.89 (m, 6H).

Compound 19b: As in 2: 3,4-didodecyloxystyrene [9a] (7 g, 10.7 mmol), Pd(OAc)₂ (87 mg, 0.04 eq.), ToP (354 mg, 0.12 eq.), 4-ethyl iodobenzoate (2.27 g, 9.7 mmol), NEt₃ (50 mL), stirring (2 h at 60 °C under argon and for 2 d at 80 °C). The mixture was cooled to RT, diluted (CH₂Cl₂) and filtrated on celite, and the crude extracted (CH₂Cl₂), washed (H₂O), and dried (MgSO₄). Purification by column chromatography (SiO₂, 4:6 CH₂Cl₂/cyclohexane) yielded a white solid (6.25 g, 78%). ¹H NMR (CDCl₃): δ 8.03 (d, 2H, ³J = 8.33 Hz), 7.54 (d, 2H, ³J = 8.33 Hz), 7.06 (AB, 2H, ³J = 16.22 Hz), 6.74 (s, 2H), 4.4 (t, 2H, ³J = 7 Hz), 4 (m, 6H), 1.8 (m, 6H), 1.36 (m, 57H), 0.88 (t, 9H, ³J = 6.6 Hz).

Compound 19c: Prepared in three steps from 3,4,5-tridodecyloxybenzaldehyde [9a]: i) CBr₄ (25.2 g, 0.076 mol), PPh₃ (19.96 g, 0.076 mol), and Zn (4.96 g, 0.076 mol) are dissolved in CH₂Cl₂ (200 mL) and stirred at RT (1 d). Then, 3,4,5-tridodecyloxybenzaldehyde (10 g, 0.015 mol) in CH₂Cl₂ (100 mL) is added and the mixture left stirred (1 d). Filtration over silica, purification by column chromatography (SiO₂, 5:5 CH₂Cl₂/petroleum ethers) and crystallisation in petroleum ethers yielded 11 g of a white solid (90%). ¹H NMR (CDCl₃): δ 7.39 (s, 1H), 6.56 (s, 2H), 3.95 (t, ³J = 6 Hz, 6H), 3.0 (s, 1H), 1.77 (m, 6H), 1.27 (m, 54H), 0.89 (m, 9H). ii) Under argon, a solution of the dibromo derivative just prepared (15 g, 0.018 mol) in THF (50 mL) is cooled down to −78 °C, and LDA (10 g, 0.09 mol) added dropwise. The temperature is slowly raised to RT, and the mixture stirred (3 h); the reaction mixture is then quenched by addition of a saturated solution of NH₄Cl, diluted (hexane), washed (H₂O), and dried (MgSO₄). Purification by column chromatography (SiO₂, 3:7 CH₂Cl₂/petroleum ethers) yielded 9.5 g of a white solid (80%). ¹H NMR(CDCl₃): δ 6.69 (s, 2H), 3.95 (t, ³J = 6 Hz, 6H), 3.0 (s, 1H), 1.77 (m, 6H), 1.27 (m, 54H), 0.89 (m, 9H). iii) A solution of ethyl-4-iodo-benzoate (1.23 g, 0.44 mmol), Pd(PPh₃)₂Cl₂ (0.16 g, 0.22 mmol), CuI (0.034 g, 0.18 mmol) and PPh₃ (0.023 g, 0.09 mmol) in 50 mL of NEt₃ was stirred under argon (15 min) and the solution of 3,4,5-tridodecyloxyphenylacetylenene (3 g, 4.67 mmol) in 50 mL of NEt₃ was added. The mixture was heated at 70 °C (2 d). Purification by column chromatography (SiO₂, 4:6 CH₂Cl₂/petroleum ethers), and crystallization in methanol yielded a white solid (3.2 g, 90%). ¹H NMR (CDCl₃): δ 8.03 (d, ³J = 9 Hz, 2H), 7.57 (d, ³J = 9 Hz, 2H), 6.76 (s, 2H), 4.39 (q, ³J = 7 Hz, 2H), 3.99 (t, ³J = 7 Hz, 6H), 1.78 (m, 6H), 1.28 (m, 57H), 0.89 (m, 9H).

Compound 20a: As 5: 19a (2.2 g, 3.54 mmol), THF (30 mL), KOH (8 g, 0.14 mol), H₂O (10 mL), reflux (2 d), and then HCl (10%, 300 mL) at 0 °C, filtrated, solubilized (CHCl₃), washed (H₂O), dried (MgSO₄). Purified by crystallization in THF/petroleum ethers afforded 2 g of a white solid (100%). ¹H NMR (CDCl₃): δ 8.08 (d, ³J = 8 Hz, 2H), 7.58 (d, ³J = 8 Hz, 2H), 7.05 (m, 5H), 4.04 (m, 4H), 1.85 (m, 4H), 1.27 (m, 36H), 0.89 (m, 6H).

Compound 20b: As 5: 19b (6.25 g, 7.8 mmol), THF (20 ml), KOH (17.44 g, 312 mmol, 40 eq.), reflux (2 d). Precipitation in HCl (10%), cooled to 0 °C. Crystallization in acetone (5.9 g, 98%, white solid). ¹H NMR (CDCl₃): δ 8.09 (d, 2H, ³J = 8.55 Hz), 7.59 (d, 2H, ³J = 8.55 Hz), 7.08 (AB, 2H, ³J = 16.22 Hz), 6.74 (s, 2H), 4 (m, 6H), 1.8 (m, 6H), 1.36 (m, 54H), 0.88 (t, 9H, ³J = 6.6 Hz). ¹³C NMR (CDCl₃): 171.44, 153.34, 142.81, 138.96, 131.93, 131.78, 130.64, 127.68, 126.37, 126.19, 105.58, 73.54, 69.22, 31.88, 30.31, 29.71, 29.66, 29.62, 29.57, 29.39, 29.34, 29.33, 26.08, 22.65, 14.06. Elemental analysis calculated for C₅₁H₈₄O₅: C, 78.81, H, 10.89; found: C, 79.48, H, 11.05.

Compound 20c: As 5: 19c (3 g, 3.79 mmol). Purification by crystallization in THF/petroleum ethers (2.3 g, 80%, white solid). ¹H NMR (CDCl₃): δ 8.10 (d, ³J = 9 Hz, 2H), 7.61 (d, ³J = 9 Hz, 2H), 6.77 (s, 2H), 3.99 (t, ³J = 7 Hz, 6H), 1.80 (m, 6H), 1.29 (m, 54H), 0.89 (t, 9H). ¹³C NMR (CDCl₃): δ 171.1, 153.0, 139.6, 131.4, 130.1, 129.1, 128.3, 116.9, 110.3, 93.4, 87.3, 73.5, 69.2, 31.9, 30.3, 29.7, 29.6, 29.5, 29.4, 29.3, 26.0, 14.1. Elemental analysis calculated for C₅₁H₈₂O₅: C, 79.02, H, 10.66; found: C, 78.90, H, 10.68. MS-FAB+: found, 774.g mol⁻¹; calculated, 775.21 g mol⁻¹.

Compound 21: As in 18: 20a (0.5 g, 0.84 mmol), DDTBP (0.36 g, 0.93 mmol), Et₃N (0.2 mL), NMP (5 mL), 60 °C (3 h), then PPI-G0 (0.056 g, 0.17 mmol), NMP(1 mL). The mixture was stirred at 60 °C (2 d) and then precipitated in an aqueous solution of NaHCO₃ (1%, 100 mL). The solid was recovered by filtration, washed (H₂O), purified by column chromatography (Al₂O₃ with CH₂Cl₂ and then THF). Crystallization in THF/petroleum ether yielded a white solid (160 mg, 35%). ¹H NMR (CDCl₃): δ 7.76 (d, ³J = 8 Hz, 8H), 7.44 (d, ³J = 8 Hz, 8H), 7.3 (m, 4H), 6.93 (m, 20H), 4.01 (m, 16H), 3.50 (m, 8H), 2.53 (m, 12H), 1.61 (m, 172H), 0.89 (m, 24H). ¹³C NMR (CDCl₃): δ 177.5, 171.1, 167.2, 149.3, 148.8, 140.6, 132.9, 130.5, 129.8, 127.4, 126.1, 125.6, 120.5, 113.5, 111.6, 69.3, 69.1, 31.9, 29.7, 29.6, 29.5, 29.4, 29.3, 26.1, 22.7, 14.1. Elemental analysis calculated for C₁₇₂H₂₇₂N₆O₁₂: C, 78.98, H, 10.48; found: C, 78.53, H, 10.42. MS-FAB+: found, 2617.2 g mol⁻¹, calculated, 2616.08 g mol⁻¹.

Compound 22: As in 18: 20b (1 g, 0.13 mmol), PPI-G0 (0.085 g, 0.27 mmol), DDTBP (0.55 g, 1.4 mmol). Purification by column chromatography (Al₂O₃ with CH₂Cl₂ and then THF) afforded a white solid (298 mg, 33%). ¹H NMR (CDCl₃): δ 7.78 (d, 8H, ³J = 8.11 Hz), 7.49 (d, 8H, ³J = 8.33 Hz), 7 (AB, 8H, ³J = 16 Hz), 6.69 (s, 8H), 4.0 (m, 24H), 3.5 (m, 8H), 2.47 (m, 12H), 1.7 (m, 24H), 1.38 (m, 216H), 0.88 (t, 36H, ³J = 6.8 Hz). ¹³C NMR (CDCl₃): δ 167.12, 153.32, 151.48, 140.41, 138.73, 135.74, 133.06, 131.93, 130.83, 128.20, 127.42, 126.39, 126.25, 125.47, 105.37, 73.50, 69.17, 53.95, 52.39, 39.14, 34.18, 31.89, 30.35, 30.28, 29.73, 29.68, 29.64, 29.44, 29.36, 29.33, 26.81, 26.12, 25.88, 24.92, 22.67, 21.14, 14.07. Elemental analysis calculated for C₂₂₀H₃₆₈N₆O₁₆: C, 78.8, H, 11.06, N, 2.51; found: C, 78.09, H, 11.75, N, 2.14. MS-MALDI-TOF (m/z): found, 3348.63 g mol⁻¹ [M + H]⁺, calculated, 3353.31 g mol⁻¹.

Compound 23: As in 18: 20c (0.5 g, 0.65 mmol), PPI-G0 (0.043 g, 0.14 mmol) and DDTBP (0.27 g, 0.72 mmol). Purification by column chromatography (Al₂O₃ with CH₂Cl₂ and then THF), and crystallization in THF–petroleum ethers afforded a white solid (140 mg, 30%) as. ¹H NMR (CDCl₃): δ 7.79 (d, ³J = 8 Hz, 8H), 7.53 (d, ³J = 8 Hz, 8H), 7.35 (m, 4H), 6.73 (s, 8H), 3.96 (m, 24H), 3.50 (m, 8H), 2.50 (m, 8H), 2.38 (m, 4H), 1.77 (m, 36H), 1.27 (m, 216H), 0.89 (m, 36H). ¹³C NMR (CDCl₃): δ 166.8, 153.0, 139.4, 133.7, 131.5, 127.0, 126.5, 117.0, 110.2, 92.2, 87.3, 73.5, 69.1, 31.9, 30.3, 29.7, 29.6, 29.4, 29.3, 26.1, 22.6, 14.1. Elemental analysis calculated for C₂₂₀H₃₆₀N₆O₁₆: C, 78.99, H, 10.85, N, 2.51; found: C, 78.02, H, 10.77, N, 2.52. MS-FAB+: found, 3346.46 g mol⁻¹; calculated, 3345.31 g mol⁻¹. CES: M_n = 3650; M_w = 3800; IP = 1.03.

Compound 25: In two steps: i) as in 2, 2 (7 g, 10.7 mmol), Pd(OAc)₂ (30 mg, 0.04 eq.), ToP (121 mg, 0.12 eq.), NEt₃ (30 mL), stirring (2 h at 60 °C), methylbenzoate styrene [12] (2.68 g, 3.3 mmol), xylene (30 mL), heating (110 °C, 2 d). The mixture was diluted (CH₂Cl₂), filtrated (celite), extracted (CH₂Cl₂), washed (H₂O), and dried (MgSO₄). Purification by column chromatography (SiO₂ 3:7 CH₂Cl₂/cyclohexane) yielded a yellow solid (2.11 g, 72%). ¹H NMR (CDCl₃): δ 8.04 (d, 2H, ³J = 8.33 Hz), 7.58 (d, 2H, ³J = 8.55 Hz), 7.52 (m, 4H), 7.18 (AB, 2H, ³J = 16.44 Hz), 7.00 (AB, 2H, ³J = 16.22 Hz), 6.73 (s, 2H), 4.01 (m, 6H), 3.93 (s, 3H), 1.8 (m, 6H), 1.36 (m, 54H), 0.88 (t, 9H, ³J = 6.7 Hz). ii) as 5: ester (2.17 g, 2.5 mmol), THF (20 ml), KOH (5.6 g, 100 mmol), reflux (2 d). Precipitation in HCl (10%) at 0 °C, filtrated, solubilized (CHCl₃), washed (H₂O), dried (MgSO₄). Crystallization in acetone yielded a yellow solid (1.85 g, 87%). ¹H NMR (CDCl₃): δ 8.10 (d, 2H, ³J = 8.55 Hz), 7.61 (d, 2H, ³J = 8.55 Hz), 7.53 (m, 4H), 7.20 (AB, 2H, ³J = 16.23 Hz), 7.02 (d, 2H, ³J = 16 Hz), 6.73 (s, 2H), 4.0 (m, 6H), 1.8 (m, 6H), 1.36 (m, 54H), 0.88 (t, 9H, ³J = 6.6 Hz). ¹³C NMR (CDCl₃): δ 171.25, 153.30, 142.71, 138.52, 137.53, 135.73, 132.37, 131.25, 130.67, 129.29, 127.85, 127.18, 127.12, 127.06, 126.73, 126.32, 105.31, 73.53, 69.19, 31.89, 30.31, 29.72, 29.67, 29.63, 29.43, 29.43, 29.39, 29.35, 29.32, 26.09, 22.65, 14.07. Elemental analysis calculated for C₅₉H₉₀O₅: C, 80.59, H, 10.32; found: C, 80.69, H, 10.22.

Compound 26: As in 6: 25 (1.5 g, 1.8 mmol), pentafluorophenol (0.41 g, 2.2 mmol), CH₂Cl₂ stabilized by amylene (25 mL), DCC (0.378 g, 1.8 mmol). Purification by column chromatography (SiO₂, 4:6 CH₂Cl₂/cyclohexane), afforded a yellow solid (1.71 g, 93%). ¹H NMR (CDCl₃): δ 8.19 (d, 2H, ³J = 8.55 Hz), 7.67 (d, 2H, ³J = 8.55 Hz), 7.54 (m, 4H), 7.27 (AB, 2H, ³J = 16.44 Hz), 7.03 (AB, 2H, ³J = 16.23 Hz), 6.74 (s, 2H), 4.04 (t, 4H, ³J = 6.57 Hz), 3.98 (t, 2H, ³J = 6.58 Hz), 1.8 (m, 6H), 1.38 (m, 54H), 0.89 (t, 9H, ³J = ,6.7 Hz).

Compound 27: As in 18: 26 (1.67 g, 1.64 mmol), CH₂Cl₂ stabilized by amylene (5 mL), PPI-G0 (123 mg, 0.39 mmol), CH₂Cl₂ (5 mL) and drops of NEt₃. Stirring (RT, 3 d). The crude product was taken up in CH₂Cl₂ and precipitated in cyclohexane. Purification by column chromatography (Al₂O₃ with CH₂Cl₂ and then THF) afforded a waxy yellow solid (1.36 mg, 90%). ¹H NMR (CDCl₃): δ 7.77 (d, 8H, ³J = 8.33 Hz), 7.48 (d, 8H, ³J = 8.33 Hz), 7.44 (s, 16H), 7.08 (AB, 8H, ³J = 16.23 Hz), 6.96 (AB, 8H, ³J = 16.23 Hz), 6.69 (s, 8H), 4.01 (t, 16H, ³J = 6.57 Hz), 3.96 (t, 8H, ³J = 6.57 Hz), 3.5 (m, 8H), 2.47 (m, 12H), 1.7 (m, 24H), 1.38 (m, 216H), 0.88 (t, 36H, ³J = 6.8 Hz). ¹³C NMR (CDCl₃): δ 167.15, 153.29, 140.28, 138.51, 137.26, 135.83, 133.27, 132.33, 130.10, 129.17, 127.45, 127.16, 127.05, 126.69, 126.38, 105.27, 73.49, 69.17, 53.36, 52.38, 39.13, 31.88, 30.34, 29.73, 29.69, 29.63, 29.44, 29.33, 26.13, 22.65, 14.05. Elemental analysis calculated for C₂₅₂H₃₉₂N₆O₁₆: C, 80.46, H, 10.05, N, 2.23; found: C, 80.61, H, 10.33, N, 2.00. MS-MALDI-TOF (m/z): found, 3762.36 g mol⁻¹ [M + H]⁺, calculated 3761.84 g mol⁻¹.

5.5 Prepration of dendrimer G1, 24 (Scheme 4)

Compound 24: As in 18: 20b (5 g, 2.53 mmol), DDTBP (1.07 g, 2.79 mmol), PPI-G1 (0.192 g, 0.26 mmol). Purification by column chromatography (Al₂O₃ eluting with CH₂Cl₂ and then THF), crystallization in petroleum ethers afforded a yellow solid (250 mg, 20%). ¹H NMR (CDCl₃): δ 7.79 (d, ³J = 9 Hz, 16H), 7.70 (m, 8H), 7.41 (d, ³J = 9 Hz, 16H), 6.94 (m, 24H), 6.74 (d, ³J = 9 Hz, 8H), 3.97 (m, 32H), 3.49 (m, 16H), 2.40 (m, 36H), 1.80 (m, 60H), 1.27 (m, 288H), 0.89 (m, 48H). ¹³C NMR (CDCl₃): δ 167.3, 149.6, 149.2, 140.5, 132.8, 130.4, 129.8, 127.6, 126.1, 125.3, 120.5, 113.4, 111.5, 69.3, 69.1, 52.1, 38.9, 31.9, 30.3, 29.7, 29.6, 29.5, 29.4, 26.9, 26.1, 22.7, 14.1. Elemental analysis calculated for C₃₅₂H₅₆₀N₁₄O₂₄: C, 78.70, H, 10.51, N, 3.65; found: C, 78.01, H, 10.60, N, 3.63. MS-MALDI-TOF: found, 5373.44 g mol⁻¹, calculated, 5372.40 g mol⁻¹.

5.6 Prepration of dendrons G2, 34 (Scheme 5)

Compound 28: as 19ciii: 3,4,5-tridodecylophenylacetylenene (5 g, 7.78 mmol), 4-iodo-phenol (1.56 g, 7.07 mmol), Pd(PPh₃)₂Cl₂ (0.25 g, 3.53 mmol), CuI (0.054 g, 2.83 mmol) and PPh₃ (0.037 g, 1.41 mmol) in of NEt₃ (100 mL). Purification by column chromatography (SiO₂, CH₂Cl₂), yielded a white solid (4.5 g, 85%). ¹H NMR (CDCl₃): δ 7.41 (d, ³J = 8 Hz, 2H), 6.80 (d, ³J = 8 Hz, 2H), 3.97 (m, 6H), 1.78 (m, 6H), 1.28 (m, 54H), 0.89 (m, 9H).

Compound 29: In three steps: i) To a suspension of 3,5-dimethoxyaniline (10 g, 0.065 mol) in 20 mL of an aqueous solution of HCl (15%) was added dropwise NaNO₂ (5.23 g, 0.076 mol) solubilized in 40 mL of H₂O; the temperature was kept below 10 °C during the addition. The aqueous solution of KI (11 g, 0.066 mol) in 40 mL of H₂O was then added with precaution. The mixture was stirred at RT overnight. The product was then extracted (ether), washed (saturated aqueous solution of NaHSO₃), dried (MgSO₄), filtrated and evaporated to dryness. The purification by column chromatography (SiO₂, 3:7 CH₂Cl₂/petroleum ethers) afforded a white solid (8.2 g, 50%). ¹H NMR (CDCl₃): δ 6.86 (d, ⁴J = 2 Hz, 2H), 6.41 (t, ⁴J = 2 Hz, 1H), 3.77 (s, 6H). ii) The dihydroxy was prepared by demethylation of the dimethoxy (5 g, 0.032 mol) using BBr₃. Purification by filtration over silica (THF), and crystallisation in petroleum ethers yielded 3 g of a white solid (70%). ¹H NMR (CDCl₃): δ 6.80 (d, ⁴J = 2 Hz, 2H), 6.32 (t, ⁴J = 2 Hz, 1H), 4.89 (s, 2H). iii) To a solution of 3,5-dihydroxy-iodobenzene (3 g, 5.58 mmol), bromoundecanol (9.57 g, 0.038 mol) and PPh₃ (13.33 g, 0.05 mol) in 30 mL of THF, was added dropwise DIAD (10.27 g, 0.05 mol) at 0 °C. The mixture was stirred at RT overnight. The crude product was purified by column chromatography (SiO₂, 2:8 CH₂Cl₂/petroleum ethers) to yield a white solid (3 g, 75%). ¹H NMR (CDCl₃): δ 6.86 (d, ⁴J = 2 Hz, 2H), 6.41 (t, ⁴J = 2 Hz, 1H), 3.96 (t, ³J = 7 Hz, 4H), 3.41 (t, ³J = 7 Hz, 4H), 1.87 (m, 8H), 1.27 (m, 28H).

Compound 30: 28 (3,65 g, 4,97 mmol), 29 (1.58 g, 2.26 mmol) as in 4. Purification by column chromatography (SiO₂, 3:7 CH₂Cl₂/petroleum ethers) afforded 3 g (50%) of a yellow oil. ¹H NMR (CDCl₃): δ 7.45 (d, ³J = 9 Hz, 4H), 6.84 (m, 6H), 6.71 (s, 4H), 6.39 (t, ⁴J = 2 Hz, 1H), 3.97 (m, 20H), 1.78 (m, 20H), 1.27 (m, 136), 0.89 (m, 18H).

Compound 31: 30 (3 g, 1.47 mmol), CuI (0.011 g, 0.06 mmol), PPh₃ (0.08 g, 0.03 mmol), trimethylsilylacetylene (0,176 g, 1,79 mmol) as in 19c. Purification by column chromatography (SiO₂, 1:1 CH₂Cl₂/petroleum ethers) afforded a yellow oil (2.5 g, 85%). ¹H NMR (CDCl₃): δ 7.45 (d, ³J = 9 Hz, 4H), 6.84 (d, ³J = 9 Hz, 4H), 6.71 (s, 4H), 6.63 (d, ⁴J = 2 Hz, 2H), 6.39 (t, ⁴J = 2 Hz, 1H), 3.97 (m, 20H), 1.78 (m, 20H), 1.27 (m, 136), 0.89 (m, 18H), 0.26 (s, 9H).

Compound 32: 31 (2.5 g, 1.25 mmol), TBAF (0.12 g, 0.44 mmol) as in 3iii. Purification by column chromatography (SiO₂, 1:1 CH₂Cl₂/petroleum ethers) afforded a white solid (2.3 g, 100%). ¹H NMR (CDCl₃): δ 7.45 (d, ³J = 9 Hz, 4H), 6.85 (d, ³J = 9 Hz, 4H), 6.71 (s, 4H), 6.65 (d, ⁴J = 2 Hz, 2H), 6.43 (t, ⁴J = 2 Hz, 1H), 3.96 (m, 20H), 3.05 (s, 1H), 1.80 (m, 20H), 1.27 (m, 136H), 0.89 (m, 18H).

Compound 33: 32 (2.5 g, 1.29 mmol), Pd(PPh₃)₂Cl₂ (0.044 g, 0.06 mmol), CuI (0.009 g, 0.05 mmol), PPh₃ (0.006 g, 0.02 mmol), 4-iodophenol (0.27 g, 1.25 mmol) as in 19c. Purification by column chromatography (SiO₂, CH₂Cl₂) afforded a viscous white solid (2 g, 80%). ¹H RMN (CDCl₃): δ 7.42 (m, 6H), 6.85 (d, ³J = 9 Hz, 4H), 6.78 (d, ³J = 9 Hz, 2H), 6.71 (s, 4H), 6.65 (d, ⁴J = 2 Hz, 2H), 6.44 (m, 1H), 5.04 (s, 1H), 3.96 (m, 20H), 1.80 (m, 20H), 1.27 (m, 136H), 0.89 (m, 18H).

Compound 34a: 33 (0.5 g, 0.25 mmol), the internal branch (0.08 g, 0.11 mmol) [9] as in 4. Purification by column chromatography (SiO₂, 3:7 CH₂Cl₂/petroleum ethers) afforded a yellow oil (0.25 g, 50%). ¹H NMR (CDCl₃): δ 8.02 (d, ³J = 8 Hz, 2H), 7.55 (d, ³J = 8 Hz, 2H), 7.43 (d, ³J = 9 Hz, 12H), 7.11 (m, 2H), 6.85 (d, ³J = 9 Hz, 12H), 6.69 (m, 14H), 6.43 (t, ⁴J = 2 Hz, 3H), 3.96 (m, 51H), 1.78 (m, 48H), 1.27 (m, 300H), 0.89 (m, 36H).

Compound 34b: 34a (0.24 g, 0.05 mmol) as in 5: Triturating in petroleum ether afforded a yellow oil (0.24 g, 100%). ¹H NMR (CDCl₃): δ 8.04 (d, ³J = 8 Hz, 2H), 7.59 (d, ³J = 8 Hz, 2H), 7.43 (d, ³J = 9 Hz, 12H), 7.13 (m, 2H), 6.85 (d, ³J = 9 Hz, 12H), 6.69 (m, 14H), 6.43 (t, ⁴J = 2 Hz, 3H), 3.96 (m, 48H), 1.78 (m, 48H), 1.27 (m, 300H), 0.89 (m, 36H).