752207-05-9Relevant academic research and scientific papers
Rhenium-to-benzoylpyridine and rhenium-to-bipyridine MLCT excited states of fac-[Re(Cl)(4-benzoylpyridine)2(CO)3] and fac-[Re(4-benzoylpyridine)(CO)3(bpy)]+: A time-resolved spectroscopic and spectroelectrochemical study
Busby, Michael,Matousek, Pavel,Towrie, Michael,Clark, Ian P.,Motevalli, Majid,Hartl, Franti?ek,Vl?ek Jr., Antonín
, p. 4523 - 4530 (2004)
The lowest allowed electronic transition of fac-[Re(Cl)(CO) 3(bopy)2] (bopy = 4-benzoylpyridine) has a Re → bopy MLCT character, as revealed by UV-vis and stationary resonance Raman spectroscopy. Accordingly, the lowest-lying, long-lived, excited state is Re → bopy 3MLCT. Electronic depopulation of the Re(CO)3 unit and population of a bopy π* orbital upon excitation are evident by the upward shift of v(C=O) vibrations and a downward shift of the ketone v(C=O) vibration, respectively, seen in picosecond time-resolved IR spectra. Moreover, reduction of a single bopy ligand in the 3MLCT excited state is indicated by time-resolved visible and resonance Raman (TR3) spectra that show features typical of bopT.-. In contrast, the lowest allowed electronic transition and lowest-lying excited state of a new complex fac-[Re(bopy)(CO)3(bpy)]+ (bpy = 2,2′-bipyridine) have been identified as Re → bpy MLCT with no involvement of the bopy ligand, despite the fact that the first reduction of this complex is bopy-localized, as was proven spectroelectrochemically. This is a rare case in which the localizations of the lowest MLCT excitation and the first reduction are different. 3MLCT excited states of both fac-[Re(Cl)(CO) 3(bopy)2] and fac-[Re(bopy)(CO)3(bpy)] + are initially formed vibrationally hot. Their relaxation is manifested by picosecond dynamic shifts of v(C≡O) IR bands. The X-ray structure of fac-[Re(bopy)(CO)3(bpy)]PF6·CH 3CN has been determined.
