Thermal and Photochemical Reactivity of Manganese Tricarbonyl and Tetracarbonyl Complexes with a Bulky Diazabutadiene Ligand

Abstract

The manganese tricarbonyl complex fac-Mn(Br)(CO)3((i)Pr2Ph-DAB) (1) [(i)Pr2Ph-DAB = (N,N'-bis(2,6-di-isopropylphenyl)-1,4-diaza-1,3-butadiene)] was synthesized from the reaction of Mn(CO)5Br with the sterically encumbered DAB ligand. Compound 1 exhibits rapid CO release under low power visible light irradiation (560 nm) suggesting its possible use as a photoCORM. The reaction of compound 1 with TlPF6 in the dark afforded the manganese(I) tetracarbonyl complex, [Mn(CO)4((i)Pr2Ph-DAB)][PF6] (2). While 2 is comparatively more stable than 1 in light, it demonstrates high thermal reactivity such that dissolution in CH3CN or THF at room temperature results in rapid CO loss and formation of the respective solvate complexes. This unusual reactivity is due to the large steric profile of the DAB ligand which results in a weak Mn-CO binding interaction.

PhotoCORMs: CO release moves into the visible

“…21), giving a system with an absorption maximum as 582 nm. 70 This system exhibits CO release at 560 nm as indicated by IR spectroscopy of the complex itself. The photolability of the Mn CO bond was assigned to a metal-ligand charge-transfer (MLCT) band to the di-imine π * orbitals from a combination of the Mn CO π orbital the bromide p orbital.…”

Exploring the effect of axial ligand substitution (X = Br, NCS, CN) on the photodecomposition and electrochemical activity of [MnX(N–C)(CO)3] complexes

“…[63][64][65][66][67][68][69][70][71][72][73][74] The mechanism of photodecomposition for [MnX(N-N)(CO) 3 ]-type compounds has been suggested to involve equatorial CO loss following the population of a dissociative ligand-field state after MLCT. [63][64][65][66][67][68][69][70][71][72][73][74] The mechanism of photodecomposition for [MnX(N-N)(CO) 3 ]-type compounds has been suggested to involve equatorial CO loss following the population of a dissociative ligand-field state after MLCT.…”

Green‐Light‐Induced PhotoCORM: Lysozyme Binding Affinity towards MnI and ReI Carbonyl Complexes and Biological Activity Evaluation

“…Organic (e.g. α,α‐dialkylaldehydes, and oxalates) and organometallic (borano carboxylates, sila‐carboxylates, and metal carbonyl complexes) compounds have been investigated as CORMs. Different triggering methods have been used to initiate the CO release.…”

“…Different triggering methods have been used to initiate the CO release. This includes change of pH value, and redox state, thermal, enzymatic, and photochemical ways . At first, the ability of [Mn 2 (CO) 10 ] (CORM‐1) and Fe(CO) 5 to release CO upon the exposure to a cold light was investigated by Motterlini et al In 2008, a group of fac ‐Mn(CO) 3 complexes bearing tris(pyrazolyl)methane derivatives was examined by Schatzschneider group as photoinduced CO molecules .…”

“…To decrease the detrimental problems of UV light and to increase the penetration depth of the light into tissues, synthesis of visible‐light triggered CORMs is one of the major challenges in this research area. For the class of metal carbonyl complexes, change of the metal ion (rhenium, manganese, iron, ruthenium, molybdenum, tungsten), and the axial ligand as well as extension of the ancillary ligand conjugation system led to modulation of the M–CO that influence in turn the electron density and consequently the energy of the incident light. Manganese(I) and ruthenium(II) carbonyl complexes have been widely studied in the context of CORMs because of their rich photochemical properties , .…”