Studying the catecholamine effect on the electronic delocalization of the paramagnetic [Ru(NH3)4(catecholamine)]+ complex through 1H-NMR, theoretical calculations, and resonance Raman

Ruthenium complexes containing catecholamines and catechol as ligands with general formula [Ru(NH3)(4)(catecholamine)]Cl, where "catecholamine" is isoproterenol (in complex 1), dopamine (in complex 2), noradrenaline (in complex 3), catechol (in complex 4), or adrenaline (in complex 5), were synthesized. The complexes were characterized by vibrational and NMR spectroscopies, mass spectrometry, cyclic voltammetry, and spectroeletrochemistry. The electronic and electrochemical features were analyzed in terms of the electronic density, which is affected by ruthenium complexation and different substituent groups on the aromatic ring. Resonance Raman spectra displayed bands assigned to the Ru(II)-semiquinone stretching frequencies, which agreed with the charge transfer band. Theoretical calculations helped to evaluate the metal-non-innocent ligand orbital mixing. All the results suggested that Ru(II)-semiquinone complexes are formed, and that the unpaired electron is delocalized between the metal ion and the non-innocent ligand.