Infrared Spectra of Vapors, Solutions, and Crystals of Biphenylene and Biphenylene-d8

Abstract

The absorption spectra in the conventional and far‐infrared region of biphenylene and biphenylene‐d 8 as a solid, as a solution and as a vapor are presented. Forced crystallization from the melt allowed us to obtain the (100) crystal plane whose spectra in polarized light were measured from 4000 to 400 cm−1. A comparison between the observed and predicted dichroism for those bands whose symmetry classes are distinguishable on the basis of the vapor spectra band contours, shows that the oriented gas model is an approximation which is more acceptable here than in other similar cases. The vibrational assignment of the 22 infrared‐active fundamentals is discussed taking into account band contours, isotopic shifts, and dichroism. Only a few band splittings can be attributed to the correlation crystal field on the basis of comparison between pure oriented crystals and dilute isotopic solutions. Such effects are minor in relation to those observed in some aromatic hydrocarbons where the shortest intermolecular distances are comparable in the crystal phase.