Juliusz G. Radziszewski

Site-population conserving and site-population altering photo-orientation of matrix-isolated free-base porphine by double proton transfer: IR dichroism and vibrational symmetry assignments

Abstract Free-base porphine isolated in rare-gas matrices has been photo-oriented by double-proton transfer upon irradiation with linearly polarized light into either the x - or the y -polarized vibronic peaks in its Q x band. Evidence for two limiting situations has been obtained, depending on the conditions of irradiation: site-population conserving and site-population altering. Quantitative agreement with the theory of photoselection has been found. The dichroism in the polarized FT IR spectra of the oriented samples directly yields the absolute symmetry assignments of over 150 vibrations. Site structure has been observed both in the visible and in the IR absorption; the two are correlated. This permitted the recording of separate IR spectra of porphine in the two major different sites. These spectra are quite distinct, with the vibrational frequencies differing by as much as 5 cm −1 .

FT visible absorption spectroscopy of porphine in noble gas matrices

Abstract Polarized visible absorption spectra of free-base porphine photo-oriented in noble gas matrices were observed by Fourier-transform spectroscopy. The symmetries of over 60 vibronic transitions in the Qx region and about 20 in the Qy region were assigned and the symmetric NH stretching vibration in the Qx state was identified (3386 and 3392 cm−1 in the two sites in xenon matrix).

Symmetry assignment of vibrations in anthracene, phenazine, and acridine from infrared dichroism in stretched polyethylene

Polarized Fourier transform infrared spectra of anthracene, phenazine, and acridine in stretched polyethylene and stretched perdeuterated polyethylene permitted complete symmetry assignment for the IR‐active vibrations throughout the 100–3200 cm−1 region.

Bridgehead double bonds

A survey is given of recent progress in our laboratory in the preparation and spectroscopic characterization of compounds containing highly twisted bridgehead CN and CC double bonds.

Infrared linear dichroism of the T1 state of acridine in stretched polyethylene

Abstract We report the first determination of the symmetry of an excited-state vibration observed with direct infrared absorption. We assign the excited triplet-state vibration of acridine at 751 cm −1 to b 1 symmetry.

Doubled Multiplexing in Fourier Transform Raman Spectroscopy

The use of a Chevron filter for the rejection of light at the 1064-nm excitation wavelength permits the simultaneous detection of Stokes and anti-Stokes Raman lines (doubled multiplexing). This enhances spectrometry and photometric accuracy and permits a measurement of the true vibrational temperature of the sample. Down to Raman shifts as low as 40 cm−1, near-IR Raman spectra recorded on an optimized Nicolet SXR 60 instrument are distinctly superior to previously reported spectra of similar samples recorded on FT or, more slowly, on dispersive instruments.

Vibrational transition moment directions in medium-size molecules: Experiment and theory

Abstract Linear dichroism is observed in the infrared spectra of dimethyl ether, isobutene, 2-butyne, and n-butane dissolved in stretched sheets of ordinary and perdeuterated poly-ethylene. For each observed vibrational band the orientation factor has been determined and related to the transition-moment direction for the vibration, providing information on its symmetry species. For n-butane, the angles of the vibrational transition moment directions in the molecular framework have been derived and compared with the angles calculated at various levels of semiempirical and ab initio theory.