Estimation of the ability of the π-system of pseudohalides (azide and thiocyanate) to participate in CH···π interactions in cyclic hetero-tetranuclear cobalt(III)/sodium and linear trinuclear mixed valence cobalt(III/II/III) complexes

Abstract

A cyclic tetranuclear cobalt(III)/sodium complex, [{(N3)CoIII(L1)Na(DMSO)}(μ1,3-N3)2{(N3)CoIII(L1)Na(OH2)}]2⋅0.5CH3OH (1) and a bent trinuclear mixed valence complex [CoII{(μ-L2)(μ-OAc)CoIII(NCS)}2]⋅CH3CN⋅0.5H2O (2) have been prepared and their molecular structures have been determined by X-ray crystallography [H2L1 = N,N'-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminoproane, H2L2 = N,N'-bis(2-hydroxynaphthylmethylidene)propane-1,3-diamine]. Complex 1 contains two cobalt(III) and two sodium centers, while on the other hand, complex 2 contains a high-spin Co(II) and two terminal low-spin Co(III) centers in a CoIII(S = 0)-CoII(S = 3/2)-CoIII(S = 0) trimer, as confirmed by DFT calculations Theoretical calculations have been used to analyze the importance of CH···π interactions involving the π-systems of the pseudohalide ligands. Indeed apart from the formation of conventional π···π stacking and CH···π(arene) interactions both complexes exhibit CH···π(pseudohalide) interactions that have been evaluated energetically by using mutated dimers and characterized by means of QTAIM and NCI plot computational methods which can be used to clarify interactions in real space.