<title>Quantum chemical calculations, synthesis, and properties of novel organic molecules with photo-induced intramolecular electron transfer and giant change of the electric dipole moment in the exited s</title>

Abstract

The research objects are bipolar organic compounds containing both charged electron donor and electron acceptor groups interconnected with some kind of bridges <SUP>-</SUP>D-X- A <SUP>+</SUP>. Such types of compounds are named as betaines and the betaines are peculiar for photoinduced intramolecular electron transfer (PIET), a large change of the dipole moment in the exited state and a considerable hyperpolarizability which causes large nonlinear optical effects in solutions and LB-films. The quantum chemical calculations (CNDO/S) of some types of betaines containing, 1,3-indandione anion or diazole anion electron donor part and N-pyridinium cation electron acceptor part show that the HOMO and LUMO are strongly localized and an effective PIET takes place. The calculated change of the dipole moment in the exited state, (Delta) (mu) equals (mu) <SUB>g</SUB>-(mu) <SUB>e</SUB>, is essential (8-20 D) and in many cases the direction of (mu) changes to opposite. The character of the bridge X in betaines shows the largest effect on (mu) <SUB>g</SUB> and (Delta) (mu) especially in the case of X equals p - phenylene. The pyrazole anion part is a better electron donor than the 1,3- indandione anion. These are synthesis of betaines containing the 1,3-indandione anion part and the N-pyridinium cation part interconnected directly or through p-phenylene bridge has been fulfilled and the electron absorption spectra have been investigated. The preliminary experiments confirm NLO effects in solutions and LB-films. The synthesis of novel substituted betaines is unlimited, synthesis of polymer- bonded or surface-bonded betaines is possible.