sigma-Hole halogen bonding interactions in a mixed valence cobalt(iii/ii) complex and anti-electrostatic hydrogen bonding interaction in a cobalt(iii) complex: a theoretical insight

A mixed valence cobalt(iii/ii) complex, [((1,3)-OAc)(2){(SCN)Co-III(L-1)}(2)Co-II] H 2O (1), and an ionic coordination complex of cobalt(iii), [Co-III(L-2)(2)][Co-III(L-2)(N-3)(3)] (2), have been synthesized and characterized {H2L1 = N,N-bis(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine and HL2 = N(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine}. Energetic features of the supramolecular interactions involved in both complexes have been studied through DFT calculations, which indicate that the trinuclear structure of complex 1 has been stabilized via sigma-hole halogen bonding interactions in the solid state. On the other hand, counterintuitive anionanion interactions are present in the solid state structure of complex 2, which have been stabilized through anti-electrostatic H-bonds (AEHB). The dissociation scan plot for the AEHB dimer has showed the existence of a significantly high energetic barrier.