Molecular geometry of OC···AgI determined by broadband rotational spectroscopy and ab initio calculations.

Pure rotational spectra of the ground vibrational states of six isotopologues of OC···AgI have been measured by chirped-pulse Fourier transform microwave spectroscopy. The spectra are assigned to determine the rotational constant, B(0), centrifugal distortion constant, D(J), and nuclear quadrupole coupling constant of the iodine atom, χ(aa)(I). The complex is linear. Isotopic substitutions at the silver, carbon, and oxygen atoms allow bond lengths to be established by the r(0), r(s), and r(m)((1)) methods of structure determination. The length of the C-O bond, r(CO), in the r(0) geometry for OC···AgI is 0.008 Å shorter than that found in the free CO molecule. The length of the Ag-I bond, r(AgI), is 0.013 Å shorter than in free AgI. χ(aa)(I) is determined to be -769.84(22) MHz for OC···(107)AgI implying an ionic character of 0.66 for the metal halide bond. Attachment of carbon monoxide to the isolated AgI molecule results in an increase of the ionic character of AgI of 0.12. The molecular structure and spectroscopic parameters determined from the experimental data are presented alongside the results of calculations at the explicitly correlated coupled-cluster singles, doubles and perturbative triples level. Vibrational frequencies, the electric dipole moment, the nuclear quadrupole coupling constant, and the dissociation energy of the molecule have been calculated.