Photochemical Properties of a Mononuclear Mn(I) Triscarbonyl Complex in Water: An Insight into Different Oxidation States

Author(s)

Marchi, Rafael C. ^[1] ; Aguiar, Inara ^[1] ; Camilo, Mariana R. ^[1] ; Braga, Adriano H. ^[2] ; Do Nascimento, Eduardo S. P. ^[1] ; Santana, Vinicius T. ^[3] ; Nascimento, Otaciro R. ^[3] ; Carlos, Rose M. ^[1]

Affiliation

^[1] Univ Fed Sao Carlos UFSCar, Chem Dept, Rod Washington Luis, BR-13565905 Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos UFSCar, Chem Engn Dept, Rod Washington Luis, BR-13565905 Sao Carlos, SP - Brazil

^[3] Univ Sao Paulo EECC, Phys Inst, Av Trabalhador Sao Carlense, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: CHEMISTRYSELECT; v. 6, n. 33, p. 8746-8753, SEP 7 2021.
• Web of Science Citations: 0

Abstract

This study reports the photochemical behavior of fac-{[}Mn(phen)CO3(4MeImH)](+) in neutral aqueous solution. The complex presents two 4MeImH linkage isomers, adjacent (A) and remote (R), which coexist in solution although with marked stability differences. In water, the steric effect converts A into an aqua-complex while R remains stable. Photolysis of the mixture followed by UV-vis, infrared (IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and cyclic voltammetry showed changes in the coordination sphere and oxidation state of each Mn center. Upon light irradiation, the mixture behaves as an antenna system to absorb light, producing the [Mn(II)(phen(.-))](+) moieties and releasing CO, which provides open sites for water coordination. Upon successive irradiation, the EPR spectra showed an increasing signal at g=2.0 corresponding to Mn(II) centers, a phenanthroline anion (2.0046) that vanishes at longer irradiation time, and an increasing component (g(x)similar to 9.85 and g(y)similar to 3.9) corresponding to Mn(IV). This makes the spectroscopic properties, excited state character, and dynamics of fac-{[}Mn(phen)(CO)(3)(4MeImH)](+) significantly different from those of all manganese complexes studied so far. (AU)

• FAPESP's process: 19/21143-0 - Amyloid protein aggregates and the relationship between Alzheimer's Disease and type 2 Diabetes investigated by Ru(II) luminescent complexes
• Grantee: Rose Maria Carlos
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/06244-3 - Development of chemical processes following principles adopted by green chemistry: reduction and conversion of CO2 using Mn(I) compounds
• Grantee: Mariana Romano Camilo Casale
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/12538-8 - Development of luminescent transition metal complexes to recognize and map in real time the aggregation processes of the B-amyloid peptide and of tau protein and to investigate the antioxidant and acetylcholinesterase enzyme inhibition activity
• Grantee: Rose Maria Carlos
• Support Opportunities: Regular Research Grants