Resonance Raman spectroscopy of photolabile transition metal carbonyls: controlled photoalteration with continuous wave lasers to record spectra of reactants or transient species.
A method has been developed that enables resonance Raman spectra of photolabile species in solution to be recorded under conditions where the level of photoalteration is controlled: a low level enables reactant spectra to be recorded, whereas a high level enables the spectra of short-lived transient species to be recorded in real time using continuous-wave (CW) lasers and standard Raman detection equipment. The design includes a sealed flow system, enabling air-sensitive species to be studied under an inert atmosphere. A simple theoretical model has been developed to aid the interpretation of experimental results, and its applicability is demonstrated. Controlled photoalteration and its theory are demonstrated with 413.1-nm excitation of carbonmonoxymyoglobin (MbCO), which generates deoxymyoglobin (deoxy-Mb) on photolysis, and for which the spectra of both species are well established. The methods have also been applied to two air-sensitive, photolabile transition metal carbonyls using 514.5-nm wavelength excitation: for Cp2Mo2(CO)6 (Cp = eta5-C5H5), increasing levels of photoalteration result only in a decrease in the parent band intensities, relative to the solvent bands; for Cp2Fe2(CO)4, increasing levels of photoalteration result in the appearance of additional bands that are assigned to the transient species CpFe(mu-CO)3FeCp, formed following the loss of a CO ligand.
Abbott
Laurence C
LC
Department of Chemistry, The University of York, Heslington, York YO10 5DD, UK.
Feilden
Caroline J
CJ
Anderton
Clare L
CL
Moore
John N
JN
D007834:Lasers; D008027:Light; D009211:Myoglobin / Q000032:analysis; D009942:Organometallic Compounds / Q000032:analysis*; D010777:Photochemistry; D013059:Spectrum Analysis, Raman / Q000379:methods*; D028561:Transition Elements / Q000032:analysis*
D009211:Myoglobin; D009942:Organometallic Compounds; D028561:Transition Elements; C018013:carboxymyoglobin