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One-photon mass-analyzed threshold ionization (MATI) spectrum of CH2BrI was obtained using coherent vacuum-ultraviolet radiation generated by four-wave difference-frequency mixing in Kr. Unlike CH2ClI investigated previously, a very extensive bending (Br–C–I) progression was observed. Vibrational frequencies of CH2BrI+ were measured from the spectra and the vibrational assignments were made by utilizing frequencies calculated by the density-functional-theory (DFT) method using relativistic effective core potentials with and without the spin-orbit terms. A noticeable spin-orbit effect on the vibrational frequencies was observed from the DFT calculations, even though its influence was not so dramatic as in CH2ClI+. A simple explanation based on the bonding characteristics of the molecular orbitals involved in the ionization is presented to account for the above differences between the MATI spectra of CH2BrI and CH2ClI. The 0-0 band of the CH2BrI spectrum could be identified through the use of combined data from calculations and experiments. The adiabatic ionization energy determined from the position of this band was 9.5944±0.0006 eV, which was significantly smaller than the vertical ionization energy reported previously. [ABSTRACT FROM AUTHOR]

Detailed analysis of the one-photon mass-analyzed threshold ionization (MATI) spectrum of CH2ClI is presented. This includes the determination of the ionization energy of CH2ClI, complete vibrational assignments, and quantum-chemical calculations at the spin-orbit density-functional-theory (SODFT) level with various basis sets. Relativistic effective core potentials with effective spin-orbit operators can be used in SODFT calculations to treat the spin-orbit term on an equal footing with other relativistic effects and electron correlations. The comparison of calculated and experimental vibrational frequencies indicate that the spin-orbit effects are essential for the reasonable description of the CH2ClI+ cation. Geometrical parameters and thus the molecular shape of the cation are greatly influenced by the spin-orbit effects even for the ground state. Calculated geometrical parameters deviate substantially for different basis sets or effective core potentials. In an effort to derive the exact geometrical parameters for this cation, SODFT geometries were further improved utilizing Franck–Condon fit of the MATI spectral pattern. This empirical fitting produced the well-converged set of geometrical parameters that are quite insensitive to the choice of SODFT calculations. The C-I bond length and the Cl-C-I bond angle show large deviations among different SODFT calculations, but the empirical spectral fitting yields 2.191±0.003 Å for the C-I bond length and 107.09±0.09° for the Cl-C-I angle. Those fitted geometrical parameters along with the experimental vibrational frequencies could serve as a useful reference in calibrating relativistic quantum-chemical methods for radicals. [ABSTRACT FROM AUTHOR]

Treatment of AlMe3with 2 equiv of 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4,6-di-tert-pentylphenol (Lig1H) or 2-tert-butyl-6-(5-chloro-2H-benzo[d][1,2,3] triazol-2-yl)-4-methylphenol (Lig2H) and subsequent addition of ROH afford monomeric and heteroleptic (OR)AlL2complexes [R = C6H5, L = Lig1, 1; R = p-C6H4Ph, L = Lig1, 2; R = C6H5, L = Lig2, 3; R = p-C6H4Ph, L = Lig2, 4]. The simple reaction between a quantitative amount of water and compound 1gave the novel dimeric aluminum complex 5bridged by an oxygen atom. The crystal structures of 1, 3, and 5determined from X-ray diffraction studies reveal pentacoordination geometry around the Al center with the preference for the slightly distorted trigonal-bipyramidal geometry. Monomeric complexes 1−4showed emissions of the blue region (475 nm) with broad emission areas (half-width of peak = 150 nm) in the emission spectrum with high quantum yield. Dimeric aluminum complex 5with enhanced thermal stability has a similar absorption and emission pattern to complexes 1and 2, as predicted by DFT calculations. The DFT calculations suggested that the HOMO and LUMO orbitals are localized on the phenoxy group and benzotriazole group of the ligand and the effect of the phenoxide ligand is negligible. [ABSTRACT FROM AUTHOR]