Stopped-flow ultra-rapid-scanning Fourier transform infrared spectroscopy on the millisecond time scale.

Full-range mid-infrared spectra were measured during the reaction of CpCo(CO)(2) with nitrosyl chloride by interfacing a rapid-mixing stopped-flow device with an ultra-rapid-scanning Fourier transform infrared (FT-IR) spectrometer having a temporal resolution of 5 ms. Changes to the data acquisition hardware of this spectrometer now allow a sequence of well over 2000 spectra to be collected without interruption. Two transient species were observed spectroscopically during the first 500 ms of the reaction of CpCo(CO)(2) with nitrosyl chloride. The shortest-lived species that was observed, [CpCo(CO)(2)(NO)](+), had a half-life of approximately 20 ms at 25 degrees C and approximately 70 ms at 10 degrees C. This intermediate transformed into a longer-lived (approximately 0.5 s) intermediate, CpCo(NO)Cl. Potential intermediate species with one CO and one NO ligand, such as [CpCo(CO)(NO)](+) and CpCo(CO)(NO)Cl, were not observed, although the possibility that they exist cannot be ruled out.

Characterization of an optoelectronic polymer, poly(2-phenoxy p-phenylene vinylene), and its precursor polymer by dynamic infrared spectroscopy.

Numerous applications of dynamic infrared spectroscopy to study a variety of polymer systems have been described in the literature. Typically, dynamic spectral changes are used to determine the molecular and submolecular reorientations that give rise to a material's observable mechanical properties. In the present study, the normal modes are characterized by their time-dependent response to an applied perturbation as an aid to assignment of the observed vibrational bands. Characterization of a newly synthesized optoelectronic polymer, poly(2-phenoxy p-phenylene vinylene), and its precursor polymer, is described. Vibrational modes along the backbone and side chain are expected to exhibit significantly different responses to mechanical perturbation due to delayed phase response of the phenoxy substituent. In-phase spectra, quadrature spectra, and two-dimensional infrared correlation maps are included in this characterization. This study has demonstrated that dynamic infrared spectroscopy can be used to distinguish backbone phenylene ring stretches from ring stretches associated with the phenoxy substituent. Density functional theory calculations are applied to confirm infrared spectral assignments. The mechanical properties are briefly discussed in light of the dynamic response.