Microwave Spectra, Molecular Structure, and Electric Dipole Moment of 1,2-Dithiin

• Published in: Journal of molecular spectroscopy 1996-11, Vol.180 (1), p.139-144
• Main Authors: Gillies, J.Z., Gillies, C.W., Cotter, E.A., Block, E., DeOrazio, R.
• Format: Article
• Language: English
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1006/jmsp.1996.0232

A pulsed-beam Fourier transform microwave spectrometer was used to investigate the rotational spectrum of 1,2-dithia-3,5-cyclohexadiene in the range 8 to 18 GHz. The observeda-type transitions were fit to a Watson asymmetric top Hamiltonian, giving the following rotational constants for the normal isotopomer:A= 3326.362(2) MHz,B= 3102.842(2) MHz,C= 1756.0026(7) MHz. An electric dipole moment of μtotal= μa= 1.850(1) D was determined from Stark effect measurements. Observed nuclear spin statistical weights, an inertial defect of Δ =Ic− Ia− Ib= −27.00685 uÅ2, and zero μband μcelectric dipole components show the molecule hasC2symmetry which corresponds to a twisted conformation about the S−S bond. Spectral assignments were obtained for the singly substituted34S and two13C isotopomers in natural abundance. The moments of inertia of the four isotopomers were used to determine the followingrsstructural ring parameters:r(S−S) = 2.051(3) Å,r(C−S) = 1.759(4) Å,r(C=C) = 1.353(3) Å,r(C−C) = 1.451(1) Å, θ(SSC) = 98.7(2)°, θ(SCC) = 121.4(2)°, θ(CCC) = 124.2(2)°, φ(SSCC) = 41.2°, φ(SSCC) = 41.2°, φ(SCCC) = −0.3°, φ(CCCC) = 29.0°, and φ(CSSC) = 53.9°.