Coordination chemistry and molecular recognition properties of a multifunctional-N-heterocyclic bis(bipyridine)ruthenium(II) complex

The 4,5-diamine-2,6-dimercaptopyrimidine (DAD) molecule contains an aromatic N-heterocyclic center with two amino and two thiol groups, providing an attractive multifunctional ligand to be explored in coordination chemistry and molecular recognition studies. It reacts with [Ru(bipy)2Cl2] in the presence of air, yielding a [Ru(bipy)2DAD]2+ complex, which converts into the corresponding Ru(II)-diimine form, leaving the pyrimidine N-atoms and thiol groups available for participating in intermolecular association through selective hydrogen bonding. This expectation has been confirmed by resonance Raman spectroscopy in solution and the solid state through the detailed analysis of the vibrational peaks of the Ru(II)-bipy and Ru(II)-DAD chromophores under resonance Raman condition. Accordingly, it was observed that the DAD vibrational profiles are sensitive to molecular interactions in the solid state and the presence of species, such as creatinine, thus expressing a typical molecular recognition behavior.