Cation-anion radical interactions between halopyridinium cations and metal dithiolene complexes [M(C2S2)2CN]−•: A theoretical study of halogen bonds in conducting or magnetic molecular materials

Metal dithiolene complexes have been extensively used for the elaboration of conducting or magnetic materials, whose molecular arrangements can be sensitively influenced by strong and directional noncovalent interactions. In this work, halogen bonds between N-methyl-3-halopyridinium cations and cyano-substituted anion radicals, [M(C2S2)2CN]−• (M = Ni, Pd, and Pt), were systematically investigated at the M06 level of theory. The CN···X interactions in these systems are predicted to be considerably strong and play a vital role in the controlling of the crystal structures of molecular conductors and magnets. The electrostatics contributes mainly to the attraction of these halogen bonds, while the orbital interaction is also important. Particularly, the formation of these interactions has little effect on the distribution of SOMOs, which is strongly delocalized on the two dithiolene moieties. These results will assist in the design of functional materials that exhibit exotic conducting or magnetic properties.