Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

Three dendrimers, (t-Bu-G 2 N) 2 , CC(t-Bu-G 1 N) 3 and (t-Bu-G 1 N) 2 , with 3,5-di-tert-butyl amidobenzene as a common peripheral moiety were prepared in 64-83% yields and characterized. The bulk solids had high BET surface areas of 136-138 m2/g, which were similar for the three dendrimers in spite of their different molecular weight (ranging from 1791 to 2890). It was concluded that the peripheral amide groups do not imbed in the interstitial space of neighbouring dendrimer molecules but rather build a supramolecular architecture through strong intermolecular H-bonds. This mode of assembly generates voids in the bulk dendrimers responsible for sorption properties. The X-ray crystal structure analysis of a compound representing the peripheral moiety of the dendrimers and the FT-IR and powder-XRD data for (t-Bu-G 1 N) 2 suggest the proposed supramolecular structure. The isosteric heats of CO2 sorption (Q st) for (t-Bu-G 2 N) 2 were significantly higher than those for the other two dendrimers, which is consistent with the formation of a different type of voids within the interstitial space of the molecule. It is suggested that the interstitial void space can be designed and tuned to adjust its properties to a particular task, such as the separation of gases or a catalytic reaction facilitated by the dendrimer.

Janus second-order nonlinear optical dendrimers: their controllable molecular topology and corresponding largely enhanced performance

A new type of Janus dendrimers, consisting of two different side dendrons with the dipole orientation of the second-order nonlinear optical (NLO) chromophore moieties partially in a non-centrosymmetric direction, was intelligently designed and synthesized in order to enhance the macroscopic NLO performance and break through the limitation of NLO efficiency in the current molecular topological structure of azo chromophore-based polymers. This kind of Janus dendritic structure was constructed by the combination of convergent and divergent methods, with the utilization of a powerful "click chemistry reaction". The obtained three dendrimers, D-13N, D-17N and D-21N, show very high NLO performance, especially the dramatically enhanced NLO coefficient of 299 pm V-1 for D-13N, which is the highest value ever reported for polymers containing a simple azo chromophore. The new dendrimers provide a clear structure-properties relationship between high NLO efficiency and the controllable molecular topology with the non-centrosymmetrical alignment of dipole orientation, thus opening up a new avenue for the further development of NLO dendrimers with high performance and more importantly providing some clues for the rational design of functional dendrimers with controllable molecular topology.

Converting Nonliquid Crystals into Liquid Crystals by N-Methylation in the Central Linker of Triazine-Based Dendrimers

Two triazine-based dendrimers were successfully prepared in 60-75% yields. These newly prepared dendrimers 2a and 2b containing the -NMe(CH2)2NMe- and the -NMe(CH2)4NMe- linkers between two G3 dendrons, respectively, exhibit columnar phases during the thermal process. However, the corresponding dendrimers 1a and 1b containing the -NH(CH2)2NH- and the -NH(CH2)4NH- linkers between two G3 dendrons, respectively, do not show any LC phases on thermal treatment. Computational investigations on molecular conformations reveal that N-methylation of the dendritic central linker leads dendrimers to possess more isomeric conformations and thus successfully converts non-LC dendrimers (1a and 1b) into LC dendrimers (2a and 2b).

A series of dendronized hyperbranched polymers with dendritic chromophore moieties in the periphery: convenient synthesis and large nonlinear optical effects

Excellent optical transparency and NLO coefficients were achieved by introducing dendritic chromophore moieties to the periphery of dendronized hyperbranched polymers.

Design and preparation of hybrid films containing three-branched chromophores for nonlinear optical applications

A new hybrid film with homogeneous morphology is fabricated and exhibits excellent second nonlinear optical properties.

Encapsulation of dyes in metal–organic frameworks and their tunable nonlinear optical properties

Two series of cationic dyes have been encapsulated in the 1D channel of MOFs, and the tunable second order nonlinear optical properties of these MOF⊃dye materials were observed.

Microwave-assisted synthesis of novel julolidinyl-based nonlinear optical chromophores with enhanced electro-optic activity

Under microwave (MW) irradiation at a proper temperature, three chromophores (A, B and C) with julolidinyl-based donors and TCF or CF₃-Ph-TCF acceptors have been synthesized in high overall yields compared with the conventional heating method.

Dendrimers with large nonlinear optical performance by introducing isolation chromophore, utilizing the Ar/ArF self-assembly effect, and modifying the topological structure

By the combination of divergent and convergent approach, a new series of NLO dendrimers (G1-PFPh-NS-GL to G3-PFPh-NS-GL) was conveniently prepared with satisfied yields through the powerful "click chemistry" reaction, in which perfluoroaromatic rings were introduced in the periphery, two types of chromophores were arranged with regular AB structure, and their topological structure was improved to a more spherical shape. All the dendrimers demonstrated good processability, and G1-PFPh-NS-GL exhibited the highest NLO effect of 221 pm/V among the three dendrimers.