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The topic of this paper is bipolar organic compounds containing both charged electron donor and electron acceptor groups interconnected by various kinds of bridges (–D–X–A+). Such betaines are subject to photoinduced intramolecular electron transfer (PIET), large change in dipole moment in the excited state and considerable hyperpolarisability, which causes large non‐linear optical effects in solutions and Longmuir–Blodgett (LB) films. Quantum chemical calculations (CNDO/S, ZINDO/S) of some types of betaines containing a 1,3‐indandione anion or diazole anion electron donor part and an N‐pyridinium cation electron acceptor part show that the HOMO and LUMO are strongly localized and an effective PIET takes place. The calculated change in dipole moment in the excited state, δμ=μg−μex , is substantial (8–20 D) and in many cases the direction of μ is reversed. The character of the bridge X in betaines shows the largest effect on μg and δμ, especially in the case of X=p‐phenylene. The pyrazole anion is a better electron donor than the 1,3‐indandione anion. The synthesis of betaines containing a 1,3‐indandione anion part of an N‐pyridinium cation part interconnected directly or through a p‐phenylene bridge has been achieved and their electron absorption spectra have been investigated. Preliminary experiments confirm NLO effects in solutions and LB films. The synthesis of novel substituted betaines is unlimited and the synthesis of polymer‐bonded or surface‐bonded betaines is possible. Copyright © 1999 John Wiley & Sons, Ltd.

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Isomers of a macrocycle containing two tetrathiafulvalene structural units joined by propylenedithio bridges are prepared. The electrochemical oxidation potentials are determined. Possible conformations qf tetramethoxvearbonyl [5.5] tetrathiafulvalenophane are analyzed using the AM1 method.The unusual electron-donating properties of tetrathiafulvalenes that enable them to undergo redox reactions have stimulated during the last 20 years research on organic conductors and superconductors [1][2][3][4][5][6]. The electronic properties of charge-transfer complexes of tetrathiafulvalenes with electron-acceptors have also been extensively studied. Investigations of macrocycles containing tetrathiafulvalenes [7] were started in 1980 with the publication of the synthesis of the first tetrathiafulvalenoparacyclophanes and tetrathiafulvalenophanes [8, 9]. Recently several new derivatives of tetrathiafulvalenoparacyclophanes and tetrathiafulvalenophanes containing two and more tetrathiafulvalene structural units [10][11][12][13][14][15][16][17], catenanes [17, 18], crown ethers [19], oligomeric macrocyclic tetrathiafulvalenes [20], and tetrathiafulvalenes with a cage structure [21, 22] have been prepared.We used readily available derivatives of a 1,3-dithiol-2-thione, namely 4-mercapto-5-methoxycarbonyl-1,3-dithiol-2-thione [23], to prepare the macrocyclic tetrathiafulvalenes I according to the following scheme: oow, Ilia n -2, IIIb n = 3 MeO0 S(Ctt2)3S COOMe I (mixture of isomers A1. A2,