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

Abstract

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.

Graphical Abstract

Keywords:

• Ruthenium complexes
• catecholamines
• non-innocent ligands
• orbitals

Acknowledgements

The authors would like to thank Dr. Bruna Possato, Me. Clóvis Reis da Silva Júnior, and Me.Vinicius Palaretti for their assistance during the project, and the Brazilian agencies CNPq and FAPESP for financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

Conception and design of the work: Jacqueline Q. Alves, Roberto S. da Silva. Acquisition and analysis of data: Jacqueline Q. Alves, Rogéria R. Gonçalves, André B. Formiga. Interpretation of data: Jacqueline Q. Alves, Roberto S. da Silva, Rogéria R. Gonçalves, André B. Formiga. Drafting and revision of the work: Jacqueline Q.Alves, Roberto S. da Silva, Rogéria R. Gonçalves, André B. Formiga. Final approval of the work: Jacqueline Q.Alves, Roberto S. da Silva, Rogéria R. Gonçalves, André B. Formiga.

Additional information

Funding

This work was supported by the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, #141825/2013-8) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, #2016/12707-0).