Effect of the Solvent Nature on a Spin Equilibrium in the Solutions of the Phenylboron-Capped Hexa-n-Butylsulfide Cobalt(II) Clathrochelate Stadied by the Paramagnetic NMR Spectroscopy

Abstract

A spin state of the phenylbon-capped hexa-n-butylsulfide cobalt(II) clathrochelate in solutions was studied by paramagnetic NMR spectroscopy. This cage complex is found to undergo the temperature – induced spin crossover in solvents of different nature (acetonitrile, chloroform, dichloromethane, and benzene). The previously developed method for an analysis of paramagnetic shifts in NMR spectra allows to calculate of the thermodynamic parameters (enthalpy and entropy) of a given spin equilibrium in the solutions. In spite of the conformational rigidity of the macrobicyclic tris-α-dioximate molecules, the substantial changes in their electronic structures and spin crossover parameters were observed, being affected by a polarity of the solvent used. This provides an opportunity for the fine tuning of spin switch characteristics by changing this medium parameter.