The near ultra-violet absorption spectrum of tropolone vapour

Abstract

A vibrational analysis of the 370 nm system of tropolone (-OH) and (-OD) has shown that pairs of bands, resembling the O₀ ⁰ and H₁ ¹ bands (where v _H is the internal hydrogen-bonding vibration), dominate the spectrum. Pairs built on O₀ ⁰ and H₁ ¹ and due to the excitation of totally symmetric vibrations in the ground or excited electronic state are well-behaved in the sense that their separations and rotational contours are very similar to those of O₀ ⁰ and H₁ ¹. About seven sequence intervals, in vibrations other than v _H, have also been identified and it is observed that rotational contours of Z₁ ¹H₁ ¹ bands in five sequence-forming vibrations Z are quite strongly perturbed (four of them in a very similar way) while the corresponding Z₁ ¹ bands are unperturbed. It is concluded that the unusual nature of v _H is in some way responsible for the rotational perturbations and also for the very unusual behaviour of some quite intense vibronic bands in the region 290–540 cm^-1 to high wavenumber of the O₀ ⁰ band: however, the evidence is only circumstantial.