Theoretical study of structural properties, infrared spectra, and energetic properties of C4H4 isomers

A high level of ab initio and several density functional theory studies wer e performed with the target being to elucidate structural, spectroscopic, a nd energetic properties of triafulvene, cyclobutadiene, and tetrahedrane as three C4H4 isomers. For triafulvene all of the experimental values are ava ilable, but for cyclobutadiene only the IR spectra is known, while for tetr ahedrane none of these physical values have been estimated experimentally. An excellent agreement between the computed and the experimental values wer e obtained where data are available, which makes it confident that the comp uted data should be very accurate. New structural data, IR spectra, and ent halpies of formation for both cyclobutadiene and tetrahedrane are offered. (C) 2000 Elsevier Science B.V. All rights reserved.