Fluorescence of crowned butadienyl dye and its metal complexes

The absorption and fluorescence spectra of complexes of butadienyl dye (1) with lithium, sodium, magnesium, and calcium cations in MeCN were investigated. The addition of Li, Na, Mg, and Ca perchlorates to the solution of dye 1 in acetonitrile results in a significant (up to 5900-cm-1) shortwavelength shift of the absorption spectrum and a small (about 200-cm-1) short-wavelength shift of the fluorescence spectrum. The recoordination reaction in metal complexes of 1 takes place by intramolecular mechanism. The fluorescence quantum yield of ILi+, INa+, and Ca2+ is approximately two times higher than that for 1. It was supposed that Li+ cation coordinates predominantly with oxygen atoms of macrocycle and, hence, influences weakly macrocycle nitrogen atoms conjugated with a molecule π-system. © 1999 Plenum Publishing Corporation.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

DFT calculations on the electronic and geometrical structure of 18-crown-6 complexes with Ag+, Hg2+, Ag-0, Hg+, (HgAgNO3)-Ag-0, and HgX2 (X = Cl, Br, and I)

Density functional theory is used for molecular simulation of the electronic and geometrical structure of 18-crown-6, its complexes with A

Photoinduced and dark complexation of unsaturated viologen analogues containing two ammonium tails with cucurbit[8]uril.

Complex formation between cucurbit[8]uril (CB[8]) and unsaturated viologen analogues 1a,b bearing two ammoniopropyl substituents was studied using 1H NMR spectroscopy and X-ray diffraction. The complex stability constants were measured by 1H NMR titration. CB[8] was found to encapsulate 1,2-di(4-pyridyl)ethylene derivative (E)-1a in water/acetonitrile solution to form only inclusion complex of 1 : 1 composition. The high stability of CB[8]·1a (lg K1:1 ≥ 5) is apparently due to the possibility of hydrogen bond formation between two NH3+ groups of 1a and the O[double bond, length as m-dash]C fragments of both portals of CB[8]. Contrarily, the derivative of 1,2-di(4-quinolyl)ethylene (E)-1b gave three types of inclusion complexes upon mixing with CB[8]. The stability of the 1 : 1 complex (lg K1:1 = 4.6) is decreased compared to (E)-1a, suggesting a poorer fit with respect to the bulky (E)-1b in the cavity of CB[8] for the simultaneous hydrogen bonding of the both ammonium groups. This is the driving force for the formation of an unusual 2 : 1 complex, {CB[8]}2·(E)-1b. The expanded π-system of (E)-1b allows also two tetracationic molecules of the acceptor to form a 1 : 2 complex owing to stacking interactions. Crystallization of a 1b/CB[8] mixture under irradiation resulted in an inclusion complex of the Z-isomer of 1b. The supramolecular complex is formed because the shape of (Z)-1b fits well to the host cavity and the ammonium groups form a system of hydrogen bonds with oxygen atoms of both portals of CB[8]. The features of crystalline complexes CB[8]·(Z)-1b and CB[8]·HClO4 are discussed

Crown-containing butadienyl dyes 1. synthesis, structure, fluorescence, and complex formation of chromogenic aza-15-crown-5 ethers

Crown-containing butadienyl dyes containing various heterocyclic moieties and azacrown ether fragments were synthesized for the first time. The spatial structures and the absorption and fluorescence spectra of crown-containing butadienyl dyes and their complexes with metal cations were examined. The effects of the nature of the heterocyclic and crown ether fragments on fluorescence and generation of dyes and their complexes with metal cations were revealed based on the spectral data.SCOPUS: ar.jinfo:eu-repo/semantics/publishe