Influence of the Lewis basicity hardness of crystallization solvents on the coordination sphere of the complex [Co(3,5-dinitrobenzoate-O,O′)2]: crystallographic and theoretical analysis

Abstract

Complex [Co(DNB)₂] was recrystallized in water (H₂O), methanol (CH₃OH), ethanol : acetone (EtOH : Act), dimethyl sulfoxide (DMSO), acetone (Act), and acetonitrile (ACN). As a result, mono or trinuclear molecules were obtained depending on the solvent used. A combination of X-ray crystallography and DFT calculations demonstrated that this behavior is guided by a mixture of the closeness of the HOMOs of the solvents to the SOMOs of the Co(II) ions and the possibility to build intermolecular hydrogen bonds between the carboxylate group of the DNB ligands and the solvent. This conclusion is supported by the calculated energy of crystallization which reveals evidence that this process is thermodynamically controlled. As a consequence, the crystallizations in H₂O, CH₃OH, EtOH : Act, and DMSO produce mononuclear complexes, while Act and ACN induce the formation of trinuclear species.