Real-time Fourier transform IR (FTIR) spectroscopy in organometallic chemistry: mechanistic aspects of the fac to mer photoisomerization of fac-[Mn(Br)(CO) 3(R-DAB)

Abstract

Real-time Fourier transform IR (RT/FTIR) spectroscopy was used to study the photoisomerization of fac-[Mn(Br)(CO) 3(R-DAB)] (R-DAB, N, N′-di-R-1,4-diazabutadiene; R iPr, tBu) to mer-[Mn(Br)(CO) 3(R-DAB)]. The primary photoproduct [Mn(Br)(L)-(CO) 2(R-DAB)] could be detected at room temperature for LMeCN and identified at 273 K as a cis-cis isomer for LP(OMe) 3. RT/FTIR spectroscopy was also used to determine the thermodynamic parameters E a , ΔH ‡ and ΔS t of the thermal backreaction of this mer product to the parent fac isomer. For slow reactions, GC/FTIR software was used to provide a real-time screen display of the IR spectral changes. For fast reactions (10 −1−1 s), the high speed collect (HSC) kinetic software was used to collect 12 spectra s −1 at 2 cm −1 resolution, recording one spectrum per scan.