Structure of the chlorobenzene-argon dimer:Microwave spectrum and ab initio analysis

摘要

The rotational spectra of the ~(35)Cl and ~(37)Cl isotopes of the chlorobenzene-argon van der Waals dimer have been assigned using Fourier transform microwave spectroscopy techniques. Rotational constants a nd chlorine nuclear quadrupole coupling constants were determined which confirm that the cdomplex has C_s symmetry. The argon is over the aromatic ring, shifted from a position above the geometrical ring center towards the substituted carbon atom, and tat a distance of about 3.68 A from it. This distance is 0.1-0.2 A shorter than the similar distance in the benzene-argon and fluorobenzene-argon complexes. Experimental results are confirmend and explained with the help of second-order Moller-Plesset perturbation calculations using a VDZP + diff basis set. The complex binding energy of the chlorobenzene-argon complex is 1.28kcal/mol(fluorobenzene-argon, 1.17; benzene-argon, 1.12 kcal/mol)reflecting an increase in stability caused by larger dispersion interactions when replacing one benzene H atom by F or b Cl. The structure and stability of Ar. C_6H_5-X complexex are explained in terms of a balance betwee nstabilizing dispersion and destabilizing exchange repulsion interactions between the monomers