Novel supramolecular charge-transfer systems based on bis(18-crown-6)stilbene and viologen analogues bearing two ammonioalkyl groups

Abstract

A series of new viologen analogues bearing two ammonioalkyl groups (2-4) were synthesized in order to study their complexation with bis(18-crown-6)stilbene (1b). Electronic spectroscopy and 1 H NMR measurements show that in acetonitrile, bis(crown) stilbene 1b forms highly stable 1 : 1 and 2 : 1 chargetransfer (CT) complexes with p-acceptors 2-4 owing to host-guest bonding. The influence of geometric and electronic factors on the complex formation constants are discussed. The structures of the supramolecular CT complexes are analyzed on the basis of 1 H and 13 C NMR data obtained in solution and in the solid state. X-Ray diffraction data for 1b and for model tetramethoxystilbene are also reported.

Stereoselective [2+2] photocycloaddition in bispseudosandwich complexes of bis(18-crown-6) stilbene with alkanediammonium ions

“…1, curves 1 and 2). The hypsochromic shift of the LA band maximum is characteristic of the formation of host-guest complexes by the chromogenous crown compounds 19, 20 and, undoubtedly, is due to the electron acceptor influ ence of ammonium groups of C4 linked with the crown ether fragments of (E) 1 through the N + -H...O hydrogen bonds. No considerable changes in the intensity and shape of the LA band in the presence of C4 indicates a weak intermolecular interaction through the space of chro mophoric fragments of (E) 1 in the complexes with the butanediammonium ion.…”

Equilibrium between Two Degenerated Forms during Complexation of Novel Bis-crown Containing Bithiophene and Alkanediammonium Cations

“…Такое явление может объясняться анизотропным эффектом, возникающим при расположении метиле-новой цепочки диаммония вдоль хромофорной протя-женной молекулы лиганда. Подобный эффект для комплекса бис-18-краун-6-стильбенов с солями алканди-аммония описан в работе [15] . Для подтверждения данного предположения в ходе исследований были получены двумерные спектры ЯМР Рисунок 1.…”

Crown Ether Based Optical Molecular Sensors and Photocontrolled Ionophores

“…[25][26][27][28] In solution, these compounds are capable of self-assembling into supramolecular ground-state charge-transfer complexes that shows very high thermodynamic stability. For example, the lgK value for complex 20 in MeCN was estimated to be 9.08.…”

“…[27] It was found that Ca 2+ or Ba 2+ ions are able to displace the acceptor component in complex 20, which leads to the appearance of the intense luminescence from the metal complexed biscrown stilbene. [28] PET luminosensors with cation-triggered long-lived emission can be constructed on the basis of metalorganic luminophores. The Eu III complex 21 [29] in methanol is characterized by weak delayed metal-centred emission.…”