Structure and optical properties of 2,3,7,9-polysubstituted carbazole derivatives. Experimental and theoretical studies

Push-pull organic molecules that combine a polyfunctionalized aromatic elec tron-donating carbazole moiety with nitro or cyano acceptor groups, linked directly or through a polyenic chain, have been prepared and characterized as nonlinear optical (NLO) chromophores. A methoxycarbonyl group has been i ntroduced to prepare future polysiloxane side-chain liquid-crystal polymers (SCLCPs) with NLO properties. The effect of this linking group as well as the influence of an additional methoxy donor group on the second-order NLO response have been experimentally and theoretically examined. Semiempirical calculations have been performed at the PM3 level using the time-dependent Hartree-Fock technique. Solvent influence on calculated mu beta values has been studied via the COSMO algorithm implemented in the MOPAC program.