Ultrafast primary processes of an iron-(III) azido complex in solution induced with 266 nm light.
The ultrafast photo-induced primary processes of the iron-(III) azido complex, [Fe(III)N(3)(cyclam-acetato)] PF(6) (1), in acetonitrile solution at room temperature were studied using femtosecond spectroscopy with ultraviolet (UV) excitation and mid-infrared (MIR) detection. Following the absorption of a 266 nm photon, the complex undergoes an internal conversion back to the electronic doublet ground state at a time scale below 2 ps. Subsequently, the electronic ground state vibrationally cools with a characteristic time constant of 13 ps. A homolytic bond cleavage was also observed by the appearance of ground state azide radicals, which were identified by their asymmetric stretching vibration at 1659 cm(-1). The azide radical recombines in a geminate fashion with the iron containing fragment within 20 ps. The cage escape leading to well separated fragments after homolytic Fe-N bond breakage was found to occur with a quantum yield of 35%. Finally, non-geminate recombination at nanosecond time scales was seen to further reduce the photolytic quantum yield to below 20% at a wavelength of 266 nm.
AG Reaktionsdynamik, Max-Planck-Institut für biophysikalische Chemie, Am Fassberg 11, 37077 Göttingen, Germany.
Hendrik
H
Vennekate
Dirk
D
Schwarzer
Joel
J
Torres-Alacan
Oliver
O
Krahe
Alexander C
AC
Filippou
Frank
F
Neese
Peter
P
Vöhringer
D001386:Azides / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D055668:Photochemical Processes; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
D001386:Azides; D009942:Organometallic Compounds; D012996:Solutions; D007501:Iron