Wavelength‐Dependent Control of the CO Release Kinetics of Manganese(I) Tricarbonyl PhotoCORMs with Benzimidazole Coligands

Abstract

A series of photoactivatable CO‐releasing molecules (PhotoCORMs) was prepared from manganese pentacarbonyl bromide and 1H‐benzimidazol‐2‐ylmethyl‐(N‐phenyl)amine ligands (L) bearing different electron‐donating and electron‐withdrawing groups R = H, 4‐CH3, 4‐OCH3, 4‐Cl, 4‐NO2, 2‐, 3‐, and 4‐COOCH3 on the phenyl substituent to give octahedral manganese(I) complexes of the general formula [MnBr(CO)3(L)]. Aerated DMSO solutions of the compounds are stable in the dark for 16 h with no CO release. However, the compounds rapidly release CO upon illumination at 412–525 nm, depending on the substitution pattern. Its influence on the photophysical and photochemical properties was systematically explored using UV/Vis spectroscopy and CO release measurements with a commercial gas sensor system. In the nitro‐substituted compound, the electronically excited state switched from benzimidazole‐ to phenyl‐centered, leading to a markedly different photochemical behavior of this visible‐light activated PhotoCORM.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

“…In the dark, complexes 236a and 236b were stable but the electron-poor complexes 236c – e slowly released CO. A series of 8 benzimidazole-based photoCORMs 230 was recently studied by Schatzschneider. 1151 These compounds rapidly released CO upon illumination, and their photochemistry was sensitive to their substitution. The 4-NO 2 substituted derivative 230 exhibited the most bathochromically shifted absorption but released CO with the lowest observed chemical yield because of a competing photodecomposition process.…”

“…Complex 236e , which bore the strongest electron-withdrawing groups (CF 3 and Cl) was even activatable at the tail of the absorption range (810 nm). In the dark, complexes 236a and 236b were stable but the electron-poor complexes 236c – e slowly released CO. A series of 8 benzimidazole-based photoCORMs 230 was recently studied by Schatzschneider . These compounds rapidly released CO upon illumination, and their photochemistry was sensitive to their substitution.…”

Evaluation of cytotoxic properties of two fluorescent fac-Re(CO)3 complexes bearing an N,N-bidentate benzimidazole coligand

“…The 1 H -benzimidazol-2-ylmethyl-( N -aryl)amine derivatives ( 1 and 2 ) (Scheme 1) were made using a two-step technique described in the literature. 44–46 First, o -phenylenediamine was reacted with chloroacetic acid in 4 N HCl (aq) to produce 2-chloro methylbenzimidazole, which was then condensed with 4-chloro aniline and methyl-4-aminobenzoate in ethanol in presence of a small quantity of sodium iodide. In the absence of light, bromo tricarbonyl Re( i ) complexes ( 3 and 4 ) were made by reacting ligands ( 1 and 2 ) with [ReBr(CO) 5 ] (Scheme 1).…”

Role of Carbon Monoxide in Host–Gut Microbiome Communication

“…Motterlini and Mann were the first to examine carbonylmetal complexes for their pharmacological actions and coined the term CO releasing molecules (CORMs). 130−132 Along the same line, Ford, 133 Mascharack, 134 Schmalz, 135 Schatzschneider, 136 Ramao, 137 Matson and Stupp, 138,139 Schiller, 140 and many others have developed CORMs using metals such as ruthenium, iron, molybdenum, and manganese 14 including enzyme-controlled 135,141 and encapsulated metal-based CORMs, 138,142−146 and CO immobilized on modified hemoglobin. 147,148 Motterlini and colleagues also published CORMs conjugated with an additional agent that induces HMOX1 expression to create synergy.…”

“…Later, the further development of carbonyl-metal complex chemistry laid a strong foundation for the development of such complexes for the exploitation of their pharmacological functions. Motterlini and Mann were the first to examine carbonyl-metal complexes for their pharmacological actions and coined the term CO releasing molecules (CORMs). − Along the same line, Ford, Mascharack, Schmalz, Schatzschneider, Ramao, Matson and Stupp, , Schiller, and many others have developed CORMs using metals such as ruthenium, iron, molybdenum, and manganese including enzyme-controlled , and encapsulated metal-based CORMs, ,− and CO immobilized on modified hemoglobin. , Motterlini and colleagues also published CORMs conjugated with an additional agent that induces HMOX1 expression to create synergy. , Similarly, photosensitive organic CORMs − and a CO oral formulation have been reported. Recently, metal-free organic CO prodrugs ,,, capable of releasing CO under physiological conditions without the need for light activation have been reported.…”