Selective inclusion of DMF molecules within non-covalent cavity

Me₄P]₄Cu₄(mnt)₄]·2CH₃CN (1), Me₄P]₄Cu₄(mnt)₄]·2CH₃NO₂ (2), Me₄P]₄Cu₄(mnt)₄]·2DMF (3) and Me₄P]₄Cu₄(mnt)₄]·2C₃H₃N (4) (mnt = maleonitriledithiolate, S₂C₂(CN)₂]²⁻) clusters are readily synthesized in several solvents like acetonitrile, nitromethane, N,N-dimethylformamide and acrylonitrile to provide respective solvent as guest within the non-covalent cavity of the cluster ion. The guest species is accommodated within non-covalent cavity that is generated by two adjacent {Cu₄(mnt)₄} cores bridging with tetramethylphosphonium cation through hydrogen bonding. These hydrogen bonds are not strong and when mixed solvents were used selective DMF binding takes place to yield only complex 3 over other complexes.