Infrared Spectroscopy and Anharmonic Vibrational Analysis of (HO-Kr) ( = 1-3): Hemibond Formation of the Water Radical Cation.

The hemibond is a nonclassical covalent bond formed between a radical (cation) and a closed shell molecule. The hemibond formation ability of water has attracted great interest, concerning its role in ionization of water. While many computational studies on the water hemibond have been performed, clear experimental evidence has been hardly reported because the hydrogen bond formation overwhelms the hemibond formation.

Effects of Alkyl Groups on Excess-Electron Binding to Small-Sized Secondary Amide Clusters: A Combined Experimental and Computational Study.

Excess-electron binding to dimers and trimers of secondary amide molecules was studied by a combination of photoelectron spectroscopy and theoretical calculations. Vertical detachment energies (VDEs) of the cluster anions were measured in the range of a few hundred millielectronvolts. We found a tendency for VDE to decline with extension of alkyl side chains.

Photodetachment spectroscopy of fluorenone radical anions microsolvated with methanol: rationalizing the anomalous solvatochromic behavior due to hydrogen bonding.

The attribution of the extraordinary blue shift for the intramolecular charge-transfer absorption band of fluorenone radical anion solvated in protic media was investigated by means of photodetachment spectroscopy of the gas-phase anions microsolvated with methanol, in conjunction with quantum chemical calculations based on density functional theory. Sequential shifts of the vertical detachment energy as a function of the cluster size are consistent with theoretical predictions, where up to two methanol molecules can directly attach to the carbonyl group. In the photodetachment excitation spectra as alternatives to the photoabsorption spectra, with increasing cluster size, a new absorption band grows in the higher-energy region, which coincides with the blue-shifted band in protic media.

Size-dependent metamorphosis of electron binding motif in cluster anions of primary amide molecules.

Electron binding motifs in cluster anions of primary amides, (acetamide)(n)(-) and (propionamide)(n)(-), were studied with photoelectron spectroscopy. For both the amides, two band series due to distinct isomeric species in the multipole-bound states were found in the low electron binding energy region (<~0.4 eV) of the photoelectron spectra at the excitation wavelength of 1064 nm.

Interpreting the physical background of empirical solvent polarity via photodetachment spectroscopy of microsolvated aromatic ketyl anions.

The physical background of empirical solvent polarity is explored in regard to trends in solute-solvent intermolecular potential energy functions. Aromatic ketyl anions, benzophenone, and 9-fluorenone radical anions, are chosen for a model solute molecule showing solvatochromic behavior similar to betaine-30 dye, which provides the most established solvent polarity scale, E(T)(30). Common features among the ketyl anions and betaine-30 were examined with quantum chemical calculations for the electronic states and solvation structure.

Stepwise solvatochromism of ketyl anions in the gas phase: photodetachment excitation spectroscopy of benzophenone and acetophenone radical anions microsolvated with methanol.

Electronic absorption spectra of bare and methanol-solvated radical anions of benzophenone ((C6H5)2CO) and acetophenone ((C6H5)CH3CO) were measured by monitoring the photodetachment efficiency in the gas phase. Strong absorption bands due to autodetachment after transitions to bound excited states were observed. Stepwise spectral shifts approaching the limit of the condensed phase spectra were found to occur as the cluster size increases.

Infrared vibrational autodetachment spectroscopy of microsolvated benzonitrile radical anions.

Vibrational spectra of microsolvated benzonitrile radical anions (C6H5CN- -S; S = H2O and CH3OH) were measured by probing the electron detachment efficiency in the 3 microm region, representing resonance bands of autodetachment via OH stretching vibrations of the solvent molecules. The hydrogen-bonded OH band for both the cluster anions exhibited a large shift to the lower energy side with approximately 300 cm-1 compared to those for the corresponding neutral clusters. The solvent molecules are bound collinearly to the edge of the CN group of the benzonitrile anion in the cluster structures optimized with the density functional theory, in which the simulated vibrational energies are in good agreement with the observed band positions.

Electron localization in negatively charged formamide clusters studied by photodetachment spectroscopy.

Size-dependent features of the electron localization in negatively charged formamide clusters (FAn-, n = 5-21) have been studied by photodetachment spectroscopy. In the photoelectron spectra for all the sizes studied, two types of bands due to different isomers of anions were found. The low binding energy band peaking around 1 eV is assigned to the solvated electron state by relative photodetachment cross-section measurements in the near-infrared region.