Molecular geometries and other properties of H2O ••• AgI and H3N ••• AgI as characterised by rotational spectroscopy and ab initio calculations

The rotational spectra of H3N center dot center dot center dot AgI and H2O center dot center dot center dot AgI have been recorded between 6.5 and 18.5 GHz by chirped-pulse Fourier-transform microwave spectroscopy. The complexes were generated through laser vaporisation of a solid target of silver or silver iodide in the presence of an argon gas pulse containing a low concentration of the Lewis base. The gaseous sample subsequently undergoes supersonic expansion which results in cooling of rotational and vibrational motions such that weakly bound complexes can form within the expanding gas jet. Spectroscopic parameters have been determined for eight isotopologues of H3N center dot center dot center dot AgI and six isotopologues of H2O center dot center dot center dot AgI. Rotational constants, B-0; centrifugal distortion constants, D-J, D-JK or triangle(J), triangle(JK); and the nuclear quadrupole coupling constants, chi(aa)(I) and chi(bb)(I)-chi(cc)(I) are reported. H3N center dot center dot center dot AgI is shown to adopt a geometry that has C-3v symmetry. The geometry of H2O center dot center dot center dot AgI is C-s at equilibrium but with a low barrier to inversion such that the vibrational wavefunction for the v = 0 state has C-2v symmetry. Trends in the nuclear quadrupole coupling constant of the iodine nucleus, chi(aa)(I), of L center dot center dot center dot AgI complexes are examined, where L is varied across the series (L = Ar, H3N, H2O, H2S, H3P, or CO). The results of experiments are reported alongside those of ab initio calculations at the CCSD(T)(F12*)/AVXZ level (X = T, Q). Published by AIP Publishing.