Interactions between the chloride anion and aromatic molecules: infrared spectra of the Cl-_C6H5CH3, Cl-_C6H5NH2 and Cl-_C6H5OH complexes

The Cl-−C6H5CH3·Ar, Cl-−C6H5NH2·Ar, and Cl-−C6H5OH·Ar anion complexes are investigated using infrared photodissociation spectroscopy and ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that for Cl-−C6H5NH2 and Cl-−C6H5OH, the Cl- anion is attached to the substituent group by a single near-linear hydrogen bond. For Cl-−C6H5CH3, the Cl- is attached to an ortho-hydrogen atom on the aromatic ring and to a hydrogen atom on the methyl group by a weaker hydrogen bond. The principal spectroscopic consequence of the hydrogen-bonding interaction in the three complexes is a red-shift and intensity increase for the CH, NH, and OH stretching modes. Complexities in the infrared spectra in the region of the hydrogen-bonded XH stretch band are associated with Fermi resonances between the hydrogen-stretching vibrational modes and bending overtone and combination levels. There are notable correlations between the vibrational red-shift, the elongation of the H-bonded XH group, and the proton affinity of the aromatic molecule\u27s conjugate base

Interactions between the chloride anion and aromatic molecules: Infrared spectra of the Cl--C6H5CH3, Cl--C6H5NH2 and Cl--C6H5OH complexes

The Cl--C6H5CH3 center dot Ar, Cl--C6H5NH2 center dot Ar, and Cl--C6H5OH center dot Ar anion complexes are investigated using infrared photodissociation spectroscopy and ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that for Cl--C6H5NH2 and Cl--C6H5OH, the Cl- anion is attached to the substituent group by a single near-linear hydrogen bond. For Cl--C6H5CH3, the Cl- is attached to an ortho-hydrogen atom on the aromatic ring and to a hydrogen atom on the methyl group by a weaker hydrogen bond. The principal spectroscopic consequence of the hydrogen-bonding interaction in the three complexes is a red-shift and intensity increase for the CH, NH, and OH stretching modes. Complexities in the infrared spectra in the region of the hydrogen-bonded XH stretch band are associated with Fermi resonances between the hydrogen-stretching vibrational modes and bending overtone and combination levels. There are notable correlations between the vibrational red-shift, the elongation of the H-bonded XH group, and the proton affinity of the aromatic molecule's conjugate base

Infrared spectra of Cl-_(C6H6)mM=1, 2

The Cl--(C6H6)Arn n = 0,1,2 and Cl--(C6H6)2 complexes are investigated using photodissociation infrared spectroscopy in the CH stretch region and through ab initio calculations at the MP2/aug-cc-pVDZ level. The results indicate that Cl--C6H6 possesses a planar structure in which the benzene molecule is attached to the Cl- anion by a double hydrogen bond. The calculations predict that Cl (C6H6)2 has a C2 symmetry structure in which the two face-to-face benzene molecules are attached to the Cl anion by double hydrogen bonds. This structure is compatible with the measured Cl--(C6H6)2 infrared spectrum

ROTATIONALLY RESOLVED IR SPECTRA OF LiD2+_2^+ AND LiH2+_2^+

Author Institution: Laser Spectroscopy Group, School of Chemistry, University of Melbourne, Parkville, VIC 3010 Australia; Fairfield University, Department of Chemistry, Fairfield, CT 06430 USAPhotodissociation infrared spectra of mass selected LiD$_2^+$ and LiH$_2^+$ have been obtained in the D-D and H-H stretch region respectively, using a tandem mass spectrometer and detecting the Li$^+$ loss channel. For the first time rotationally resolved spectra of these complexes are available providing structural parameters and allowing direct comparison with theoretical data } \textbf{96}, 2004, 205-216}. For LiD$_2^+$ around 100 lines of the K$_{\rm a}$=0$\leftarrow$K$_{\rm a}$=0, K$_{\rm a}$=1$\leftarrow$K$_{\rm a}$=1, and K$_{\rm a}$=2$\leftarrow$K$_{\rm a}$=2 parallel transitions were fitted to a Watson A-reduced Hamiltonian. The analysis of the spectrum was supported by quantum chemical calculations using the program TRIATOM } \textbf{75}, 1993, 339-364.} and the potential from Gianturco \textit{et al.} } \textbf{119}, 2003, 11241-11248}. The LiD$_2^+$ complex was found to have T-shaped structure in agreement with theoretical predictions. An analogous analysis has been performed for the LiH$_2^+$ spectrum which differs from the LiD$_2^+$ spectrum due to larger rotational constants and an altered ortho:para ratio

The Al+-H2 cation complex: Rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations

The infrared spectrum of the Al+-H-2 complex is recorded in the H-H stretch region (4075-4110 cm(-1)) by monitoring Al+ photofragments. The H-H stretch band is centered at 4095.2 cm(-1), a shift of -66.0 cm(-1) from the Q(1)(0) transition of the free H-2 molecule. Altogether, 47 rovibrational transitions belonging to the parallel K-a=0-0 and 1-1 subbands were identified and fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The results suggest that Al+-H-2 has a T-shaped equilibrium configuration with the Al+ ion attached to a slightly perturbed H-2 molecule, but that large-amplitude intermolecular vibrational motions significantly influence the rotational constants derived from an asymmetric rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 3.03 A, decreasing by 0.03 A when the H-2 subunit is vibrationally excited. A three-dimensional potential energy surface for Al+-H-2 is calculated ab initio using the coupled cluster CCSD(T) method and employed for variational calculations of the rovibrational energy levels and wave functions. Effective dissociation energies for Al+-H-2(para) and Al+-H-2(ortho) are predicted, respectively, to be 469.4 and 506.4 cm(-1), in good agreement with previous measurements. The calculations reproduce the experimental H-H stretch frequency to within 3.75 cm(-1), and the calculated B and C rotational constants to within similar to 2%. Agreement between experiment and theory supports both the accuracy of the ab initio potential energy surface and the interpretation of the measured spectrum