Chemical Physics Letters, Vol.350, No.1-2, 39-50, 2001
A gas phase complex of acetylene and bromine: geometry, binding strength and charge transfer from rotational spectroscopy
Ground-state rotational spectra of a 1:1 complex of acetylene and bromine were observed with a Fourier-transform microwave spectrometer. Rotational, centrifugal distortion and Br nuclear hyperfine coupling constants were determined for the isotopomers C2H2 ... (BrBr)-Br-79-Br-79, C2H2 ... (BrBr)-Br-79-Br-81, C2H2 ... (BrBr)-Br-81-Br-79 and C2H2 ... (BrBr)-Br-81-Br-81. The complex possesses a T-shaped, C,, geometry at equilibrium with a zero-point distance 3.144 Angstrom between the centre (*) of the C-C bond and the inner bromine atom. The inter- and intra-molecular electron transfers on complex formation are delta(* --> Br-i)e = 0.010e and delta(Br-i --> Br-o)e = 0.037e, respectively, where i = inner and o = outer. The inter-molecular stretching force constant is k(sigma) = 7.80(6) N m(-1).