title: Introducing [Mn(CO)3(tpa-κ(3)N)](+) as a novel photoactivatable CO-releasing molecule with well-defined iCORM intermediates - synthesis, spectroscopy, and antibacterial activity.
abstract: [Mn(CO)3(tpa-κ(3)N)]Br was prepared as a novel photoactivatable CO-releasing molecule (PhotoCORM) from [MnBr(CO)5] and tris(2-pyridylmethyl)amine (tpa) for the delivery of carbon monoxide to biological systems, with the κ(3)N binding mode of the tetradentate tpa ligand demonstrated by X-ray crystallography. The title compound is a CORM prodrug stable in solution in the dark for up to 16 h. However, photoactivation at 365 nm leads to CO release from the metal coordination sphere and transfer to haem proteins, as demonstrated by the standard myoglobin assay. Different iCORM intermediates could be detected with solution IR spectroscopy and assigned using DFT vibrational calculations. The antibacterial activity of the complex was studied on Escherichia coli. No effects were observed when the cultures were either kept in the dark in the presence of PhotoCORM or illuminated in the absence of metal complex. However, photoactivation of [Mn(CO)3(tpa-κ(3)N)]Br at 365 nm led to the appearance of the spectral signatures of CO-coordinated haems in the terminal oxidases of the bacterial electron transport chain in whole-cell UV/Vis absorption spectra. Significant internalization of the PhotoCORM was demonstrated by ICP-MS measurement of the intracellular manganese concentration. In particular when using medium with succinate as the sole carbon source, a very pronounced and concentration-dependent decrease in the E. coli growth rate could be observed upon illumination in the presence of metal complex, which is attributed to the constrained energy metabolism under these conditions and a strong indicator of terminal oxidase inhibition by carbon monoxide delivered from the PhotoCORM.
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. ulrich.schatzschneider@uni-wuerzburg.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Nagel
authors.forename: Samantha
authors.initials: S
authors.lastname: McLean
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.forename: Thomas
authors.initials: T
authors.lastname: Kramer
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schatzschneider
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects; D002248:Carbon Monoxide / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D008345:Manganese / Q000737:chemistry / Q000494:pharmacology / Q000528:radiation effects; D009211:Myoglobin / Q000737:chemistry / Q000528:radiation effects; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D056831:Coordination Complexes; D009211:Myoglobin; D008345:Manganese; D002248:Carbon Monoxide