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Photochemical Properties of a Mononuclear Mn(I) Triscarbonyl Complex in Water: An Insight into Different Oxidation States
Author(s) -
Marchi Rafael C.,
Aguiar Inara,
Camilo Mariana R.,
Braga Adriano H.,
Do Nascimento Eduardo S. P.,
Santana Vinicius T.,
Nascimento Otaciro R.,
Carlos Rose M.
Publication year - 2021
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202102283
Subject(s) - electron paramagnetic resonance , chemistry , photochemistry , photodissociation , manganese , aqueous solution , steric effects , irradiation , coordination sphere , cyclic voltammetry , oxidation state , resonance (particle physics) , excited state , ion , crystallography , stereochemistry , nuclear magnetic resonance , catalysis , electrochemistry , organic chemistry , physics , electrode , particle physics , nuclear physics
This study reports the photochemical behavior of fac ‐[Mn(phen)CO 3 (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 ∼9.85 and g y ∼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.