Influence of intermolecular interactions on the conformation of a 2-[bis(2-ethylphenyl)thiophosphorylhydroxymethyl]-1-ethylbenzimidazole molecule (L) upon complex formation with ZnCl₂: Crystal and molecular structures of molecule L

Abstract

The structures and conformations of a 2-[bis(2-ethylphenyl)thiophosphorylhydroxymethyl]-1-ethylbenzimidazole (L) molecule in the free form (L_fr) and in the [ZnCl₂L]L complex (I) are compared using the X-ray diffraction data. In complex I, one ligand molecule (L_c) is coordinated to the zinc atom in the bidentate chelating mode and the second molecule (L_solv) accomplishes the solvating function. An isomer with the cis orientation of the O(1) atom to the N(1) atom is observed in the crystal structure of L_fr, like L_solv in complex I, with the formation of the five-membered corrugated H-heterocycle OC₂NH. L_fr and L_solv molecules differ in the arrangement of the aromatic rings of the 2R substituent of benzimidazole. Crystalline compound L forms dimeric associates in which three conjugate H-rings are closed by a bifurcate intermolecular hydrogen bond: two five-membered ONC₂H rings and one planar four-membered N₂H₂ ring ((N(1)…N(1A), 3.705 and H(1)…H(1A) 2.67 Å). Unlike crystals of compound I with the π-π-stacking interaction between the planar-parallel aromatic rings of benzimidazole of the L_solv and L_c molecules, the crystals of L have no similar interaction between the L_fr molecules.