Interrelation Between the Spiropyran-Merocyanine Isomerism and the Metal Coordination in 3d Metal Complexes of a Functionalized Spiropyran of the 2-Oxaindane Series

Possible isomers of the N-(3,4-dimethylphenyl)-2-[(7-hydroxy-3′,3′-dimethyl-3′H-spiro[chromene-2,1′-isobenzofuran]-8-yl)methylidine]hydrazinocarbothioamide (HL) spiropyran of the 2-oxaindane series and the [ML(H2O)3]+ (M = Mn(II), Fe(II), Co(II)) complexes on its basis are calculated by the quantum chemical DFT (CAM-B3LYP/6-311++G(d,p)) method. It is shown that complexation inverts the relative stability of spiro- and acyclic isomers of L; the acyclic isomer of the ligand is the most stable one among all the complexes for all metals. The effect of ligand structural isomerism on the relative stability of high- and low-spin states of coordination compounds is estimated.