Synthesis and properties of a binuclear rhenium(III) compound with cinnamic acid

A synthetic method has been developed for the preparation and isolation of a dirhenium(III) complex with cinnamic acid in solid form. Optimal synthesis conditions were established: the molar ratio of the starting materials, (NBu4)2Re2Cl8 and cinnamic acid, was 1:5, and the reaction was carried out in an organic medium (CH3CN) under an inert atmosphere at room temperature. The structure and properties of the obtained complex were investigated using physicochemical analysis methods, including electronic absorption spectroscopy (EAS), infrared (IR) spectroscopy, and proton magnetic resonance (PMR) spectroscopy. The EAS spectrum of the target compound in solution displayed an absorption maximum at 630 nm, corresponding to the * metal-metal electronic transition characteristic of dirhenium(III) chloride cis-di--carboxylates. The IR spectrum exhibited a characteristic intense vibrational band at 1419 cm–1, corresponding to the stretching vibrations of the coordinated carboxylate group. Additional absorption bands in the range of 2930–3100 cm–1 were attributed to the stretching vibrations of CH groups in the benzene ring and the alkyl chain of cinnamic acid. In the PMR spectrum recorded in DMSO-d6, a signal at 7.8 ppm was assigned to the proton of the C=C group, while a low-intensity signal at 6.5 ppm corresponded to the -CH proton. Multiplets at approximately 7.7, 7.5, and 7.4 ppm were attributed to the aromatic protons of the cinnamic acid moiety. Based on these data, the resulting compound was identified as dirhenium(III) tetrachlorodi--cinnamate of cis configuration with acetonitrile molecules as axial ligands. The antiradical properties of Re2(cinnamate)2Cl4(CH3CN)2 in CH3CN were studied via its interaction with the 1,3,5-triphenylverdazyl radical. The characteristic absorption band of the 1,3,5-triphenylverdazyl radical disappeared completely from the spectral pattern within approximately 8.1 days. The antiradical activity of the dirhenium(III) complex compound with cinnamic acid was found to be about 1.4 times higher than that of free cinnamic acid.