The microwave spectrum of tellurophene

The microwave spectrum of tellurophene, C4H4Te, has been recorded between 8 and 27 GHz. The rotational constants obtained from least-squares fitting of low-J lines are: for (C4H4Te)-Te-130, A = 7.08215 (48), B = 2.51931 (1), C = 1.85764 (2) GHz; for (C4H4Te)-Te-128, A = 7.08220 (43), B = 2.52926 (1), C = 1.86304 (1) GHz. for C4H4 (126) Te. A = 7.08242 (64). B = 2.53952 (2). C = 1.86859 (2) GHz. Figures in parentheses are uncertainties in last place of decimal (95%, confidence limit). Corresponding inertial defects are 0.094 (7). 0.095 (6) and 0.097 (10) amu A(2), respectively, indicating the essential planarity of the molecule. Stark shift measurements correspond to a dipole moment of mu(a) = 0.619 X 10(-30) C m (0.186 D). An approximate structure, based on bond lengths of CC and CH bonds adopted from related molecules, implies that r (Te - C) = 205.5 pm and angle C (5) TeC (2) = 82.53 degrees.