No abstract

No abstract

We have synthesized polyester type dendrimers containing azobenzene chromophore in the core and trityl groups at the periphery using divergent growth strategy up to 3rdgeneration. We analyzed dendrimer samples using NMR, HPLC, TG, DSC and UV-Vis techniques. We found out that functionalization of dendrimer periphery is not complete. Dendrimers with trityl groups at the periphery have glass transition temperatures in the range 73-87 °C.

No abstract

New chromophores have been synthesized and investigated containing as acceptor a quaternized pyridine unit with mobile bromine in the structure conjugated with two donor units -the indan-1,3-dione anion and the dihydroxyethylamino group through a -conjugated spacer.Organic nonlinear optical (NLO) materials have the potential for various applications in the field of optical signal processing, giving the impulse to design more and more chromophores with enhanced NLO properties [1].Among the most investigated subjects are azobenzene derivatives particularly "push-pull" azobenzenes with asymmetric electron distribution because of the substitution pattern at the 4 and 4' positions with electron-releasing (donor, D) and electron-withdrawing (acceptor, A) groups. Due to their large dipole moments and photochemistry (trans to cis isomerization), they have been investigated as components for NLO devices, lithography, all-optical switches, and data storage [2]. Incorporation of the π-deficient pyridine moiety as acceptor by noncovalent interactions (hydrogen bonds) gives additional advantage to obtain liquid crystals [3], liquid crystalline polymers [4], proton-responsive photo switches [5], and three-dimensional octupolar structures by complexation to transition metals [6].Azopyridine-based chromophores could be bound covalently to functionalized surfaces by reaction with alkyl-or benzyl halides, simultaneously creating the pyridinium group [7,8]. Quaternization of pyridine provides a way of enhancing its acceptor capability. Recently, potential NLO and electro-optical properties have been demonstrated for several pyridinium intramolecular salts [9, 10], including N-(1,3-dioxoindan-2-yl)pyridinium betaine (IPB) [11].In order to extend the scope of compounds with NLO activity, we aim to synthesize the dual chromophore 1 by linking the azopyridine-based chromophore with IPB via the common pyridinium moiety. The dioxyethylamino substituent in compound 1 makes it useful for synthesis of polymers. The constitution of molecule 1 can be described by two important mesomeric formulas: C O O N N N R N CH 2 CH 2 OTHP CH 2 CH 2 OTHP 1 a-c a R = R 1 = Br, b R = Br, R 1 = CN, c R = R 1 = Ph THP = tetrahydro-2H-pyran-2-yl O O N N N R