Rotational spectrum and theoretical structure of the carbene HC 4 N

Abstract

M. C. McCarthy,a) A. J. Apponi, V. D. Gordon (currently with UT Austin), C. A. Gottlieb, and P. Thaddeus are with the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 -- T. Daniel Crawford and John F. Stanton are with the Institute for Theoretical Chemistry, Departments of Chemistry and Biochemistry, The University of Texas,Following a high-level coupled cluster calculation, the rotational spectrum of the bent HC4N singlet carbene was detected in a supersonic molecular beam by Fourier transform microwave spectroscopy. The three rotational constants, the leading centrifugal distortion constants, and two nitrogen hyperfine coupling constants were determined to high accuracy. The rotational constants agree with those calculated ab initio to better than 0.5%. Like the isoelectronic C5H2 carbene of similar structure, HC4N was found to have fairly large centrifugal distortion and a large inertial defect. The calculated dipole moment of HC4N is 2.95 D. © 1999 American Institute of Physics. @S0021-9606~99!00339-6#Chemistr