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The gas phase infrared band contours of s-triazine and s-triazine-d3

1976; Elsevier BV; Volume: 62; Issue: 3 Linguagem: Inglês

10.1016/0022-2852(76)90277-0

1096-083X

S. J. Daunt, H. F. Shurvell,

Porphyrin and Phthalocyanine Chemistry

The systematic application of band contour techniques to account for most of the observed features of the ir spectra of s-triazine and s-triazine-d3 have been made as well as a critique as to the limitations of such methods. The experimental and computer methods used to study the gas phase infrared band contours of s-triazine and s-triazine-d3 are out-lined. Contours of the five E′ fundamentals of s-triazine have been recorded under moderate resolution and analyzed to give the Coriolis constants ζiz, i = 6–10. The effects of l-resonance are very apparent for ν8 and ν9, in the form of holes in the Q branches of these bands. Under the highest resolution available, ν6 and ν10 also show l-resonance effects. Values of the l-doubling constants qi(+) were obtained for these four fundamentals. One of the parallel A2″ fundamentals of C3H3N3 (ν12) has also been studied. It lies close to ν10(E′) and an A × E type of second-order Coriolis resonance may be the cause of the intensity enhancement observed in the inner wings of the ν12 and ν10 bands. Hot bands of the type (νi + nν14 − nν14) have been observed in the contours of ν8, ν10, and ν12. This is felt to be responsible for the large difference between our observed zeta sum (−1.30) and the theoretical sum (−1.00). The gas phase infrared band contours of the five E′ and 2A2″ fundamentals of C3N3D3 have also been recorded under moderate resolution. From P-R separations and by computer simulation of the contours, values of the Coriolis constants ζiz have been obtained for the E′ modes. The effects of l-resonance have been observed for ν8(E′) and ν10(E′) and values of the l-doubling constants qi(+) have been estimated. An extensive series of hot bands of the type (ν12 + nν14 − nν14) has been observed in the contour of the ν12 (A2″) fundamental. The mass effect on the Coriolis constants has been discussed. Infrared band contours of the overtone 2ν7 and seven degenerate E′ combination bands of C3N3H3 have been recorded under moderate resolution. Analysis of these contours using the P-R separation method and computer simulation of the contours has given values of ζeffz for these bands. Fermi resonance between 2ν7 and ν6 has been analyzed. The importance of considering both the observed contour as well as the observed frequency when assigning higher tone bands is illustrated.