HIGH HYPERPOLARIZABILITIES OF DONOR-PI-ACCEPTOR-FUNCTIONALIZED CALIX[4]ARENE DERIVATIVES BY PRE-ORGANIZATION OF CHROMOPHORES

A systematic investigation of the concept of pre-organization of nonli near optical (NLO) active chromophoric groups in calix[4]arene derivat ives and the influence on the absolute second-order nonlinear optical coefficients is reported. Several calix[4]arenes were synthesized by m odification of the electron-withdrawing groups at the upper rim of the aromatic and extension of the conjugated a system of the preorganized chromophoric groups. Electrical field induced second harmonic generat ion (EFISH) experiments showed high mu beta(0) values up to 1165.10(-4 8) esu. Compared with the corresponding reference compounds, enhanceme nts of the mu beta(0) values varying up to 2.5 times per chromophore w ere observed which proves the benefit of pre-organization of NLO-activ e units in a multi-chromophoric system. Another important advantage is that the increase in NLO activity observed for these systems is not a ccompanied with a shift of the absorption band to longer wavelengths e xceeding 20 nm. This makes these calix[4]arene derivatives promising b uilding blocks for the development of stable, NLO-active materials tha t are suitable for frequency doubling.