Microwave spectroscopic and theoretical studies on the phenylacetylene center dot center dot center dot H2O complex: C-H center dot center dot center dot O and O-H center dot center dot center dot pi hydrogen bonds as equal partners

作者：Goswamiz Mausumi; Arunan E^*

来源：Physical Chemistry Chemical Physics, 2011, 13(31): 14153-14162.

DOI：10.1039/c1cp20690g

Rotational spectra of five isotopologues of the title complex, C6H5CCH center dot center dot center dot H2O, C6H5CCH center dot center dot center dot HOD, C6H5CCH center dot center dot center dot D2O, C6H5CCH center dot center dot center dot(H2O)-O-18 and C6H5CCD center dot center dot center dot H2O, were measured and analyzed. The parent isotopologue is an asymmetric top with kappa = -0.73. The complex is effectively planar (ab inertial plane) and both 'a' and 'b' dipole transitions have been observed but no c dipole transition could be seen. All the transitions of the parent complex are split into two resulting from an internal motion interchanging the two H atoms in H2O. This is confirmed by the absence of such doubling for the C6H5CCH center dot center dot center dot HOD complex and a significant reduction in the splitting for the D2O analog. The rotational spectra, unambiguously, reveal a structure in which H2O has both O-H center dot center dot center dot pi (pi cloud of acetylene moiety) and C-H center dot center dot center dot O (ortho C-H group of phenylacetylene) interactions. This is in agreement with the structure deduced by IR-UV double resonance studies (Singh et al., J. Phys. Chem. A, 2008, 112, 3360) and also with the global minimum predicted by advanced electronic structure theory calculations (Sedlack et al., J. Phys. Chem. A, 2009, 113, 6620). Atoms in Molecule (AIM) theoretical analysis of the complex reveals the presence of both O-H center dot center dot center dot pi and C-H center dot center dot center dot O hydrogen bonds. More interestingly, based on the electron densities at the bond critical points, this analysis suggests that both these interactions are equally strong. Moreover, the presence of both these interactions leads to significant deviation from linearity of both hydrogen bonds.

• 出版日期2011