Novel C-H center dot center dot center dot C contacts involving 3,5-dimethylpyrazole ligands in a tetracoordinate Co(II) complex

A violet-blue cobalt(II) complex [Co(4-nbz)(2)(DMP)(2)] (1), where 4-nbz = 4-nitrobenzoate and DMP = 3,5-dimethylpyrazole, has been prepared at room temperature. Crystallographic studies on 1 center dot 0.5H(2)O reveal that the molecules of 1 are linked by a variety of non-covalent bonds including a novel type of C-H center dot center dot center dot C contact forming, with assistance from N-H center dot center dot center dot O, C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions, an intricate 3-D supramolecular network. Theoretical calculations suggest that the observed C-H center dot center dot center dot C interactions are energetically quite significant.