M. V. Fomina

A Raman spectroscopic study of indolinium steryl dyes

Abstract Resonance Raman spectra have been obtained in the region 400–1700 cm −1 for several indolinium steryl dyes under various experimental conditions. The changes in vibrational frequencies have been correlated with changes in the UV—vis absorption maxima observed previously and which are due to solvent polarity variations, the complexation of the dye molecules containing a crown ether ring with Mg 2+ , and the variations in molecular structure. Preliminary assignments of the observed bands to particular vibrations are made.

Modern approaches to the synthesis and prospects for the use of cyanine dyes containing functional groups in the N-substituents

Methods for the synthesis of mono-, tri-, penta- and heptamethine cyanine dyes containing functional groups in N-substituents are considered. Approaches suitable for the preparation of both symmetrical and unsymmetrical cyanine dyes are presented. Examples of the practical use of this type of cyanine dyes as fluorescent labels and probes in biology and medicine, as well as of components of photoactive supramolecular structures, photosensitizers and photo- and electroluminescent materials are given. The bibliography includes 106 references.

Reactions of isoquinoline derivatives with pyridinium salts yielding 4-naphthylpyridines

Regiospecific introduction of the 2-naphthyl residue into position 4 of the pyridine ring occurs in the reactions of isoquinolinium salts with 4-methylpyridinium salts through the intermolecular transformation of the isoquinoline bicyclic system involving the methyl group of the pyridinium salt. The reaction occurs under the action of methylammonium sulfite in an aqueous medium on heating. This method provides ring transformation not only for isoquinolinium salts but even for unsubstituted isoquinoline.

Spectral properties of protonated naphthylpyridine in the presence of cyclodexrins

Electronic absorption and fluorescence spectroscopy showed that the addition of 2-hydroxypropyl cyclodextrin derivatives (HP-α-CD, HP-β-CD, and HP-γ-CD) to an aqueous solution of 4-(2-naphthyl)pyridinium perchlorate (2) results in its partial deprotonation and formation of an inclusion complex of 4-(2-naphthyl)pyridine (1) with the cavitand. The stoichiometry and stability of the inclusion complexes of compounds 1 and 2 and 1-methyl-4-(2-naphthyl)-pyridinium perchlorate (3) with cyclodextrins and their hydroxypropyl derivatives (logK = = 1.5–2.7) were studied by 1H NMR titration. Cyclodextrins with the neutral form 1 form more stable complexes than with ionic compounds 2 and 3. The protonation of the nitrogen atom of compound 2 in aqueous solutions can occur in both the ground and excited states, and the fluorescence spectrum exhibits only the band of the protonated form. Quantum chemical simulation of the deprotonation/protonation processes in an aqueous solution of compound 2 in the absence and presence of HP-β-CD was performed. A tendency for shifting the acid-base equilibrium towards the formation of deprotonated form 1 is observed upon the addition of 2-hydroxypropyl cyclodextrin derivatives to the solution.