Density functional theory and the multiconfigurational CASSCF/CASPT2 method have been employed to study the low-lying states of VGe (n = 1-4) clusters. For VGe and VGe clusters, the relative energies and geometrical structures of the low-lying states are reported at the CASSCF/CASPT2 level. For the VGe and VGe clusters, the computational results show that due to the large contribution of the Hartree-Fock exact exchange, the hybrid B3LYP, B3PW91, and PBE0 functionals overestimate the energies of the high-spin states as compared to the pure GGA BP86 and PBE functionals and the CASPT2 method. On the basis of the pure GGA BP86 and PBE functionals and the CASSCF/CASPT2 results, the ground states of anionic and neutral clusters are defined, the relative energies of the excited states are computed, and the electron detachment energies of the anionic clusters are evaluated. The computational results are employed to give new assignments for all features in the photoelectron spectra of VGe and VGe clusters.

Density functional theory and multiconfigurational CASPT2 and RASPT2 methods are employed to investigate the low-lying states of CoGe ( n = 1-3) clusters. With the RASPT2 approach, the active space is extended to 14 orbitals for CoGe, 17 orbitals for CoGe, and 20 orbitals for CoGe. These active spaces include the 3d, 4s, and 4d of Co and 4p of Ge. The 4d of Co is incorporated into these active spaces in order to account for the important double-shell effect of Co. The structural parameters, vibrational frequencies, and relative energies of the low-lying states of CoGe ( n = 1-3) are reported. The ground states of CoGe ( n = 1-3) are computed to be Φ of linear CoGe, B of cyclic CoGe, and B of cyclic CoGe isomer. The ground states of the neutral clusters are calculated to be Δ of linear CoGe,B of cyclic CoGe, and A″ of tetrahedral CoGe isomer. The calculated adiabatic and vertical detachment energies of the anionic ground states are in agreement with the experimental values as observed in the 266 nm anion photoelectron spectra.

The geometrical and electronic structures of ScSi3 (-/0) clusters have been studied with the B3LYP, CCSD(T), and CASPT2 methods. The ground state of the anionic cluster was evaluated to be the (1)A1 of rhombic η(2)-(Si3)Sc(-) isomer, whereas that of the neutral cluster was computed to be the (2)A1 of the same isomer. All features in the 266 and 193 nm photoelectron spectra of ScSi3 (-) cluster were interpreted by the one- and two-electron detachments from the (1)A1 of rhombic η(2)-(Si3)Sc(-) isomer. The Franck-Condon factor simulation results show that the first broad band starting at 1.78 eV in the spectra comprises several vibrational progression peaks of two totally symmetric modes with the corresponding frequencies of 296 and 354 cm(-1).

Theoretical studies on lucidone, linderone and methyllinderone were performed to investigate factors that contribute to structural stability and to elucidate the antioxidant properties and mechanisms. The study was performed in different media utilising the density functional theory with different functionals and the 6-311 + G(d,p) basis set. The antioxidant activity has been considered through the electron transfer and metal chelation mechanisms. The results show that the stability of the tautomers and conformers is due to the presence of several intramolecular hydrogen bonds. The ionisation potential values suggest that the antiradical activity increases with the increase in the number of OCH 3 groups substituted on the cyclopentene-1,3-dione ring. In vacuo, the spin density of the Fe(II) cation upon ligand coordination decreases to 3.0−3.5, whereas the ligand spin density approaches 1, indicating that it is oxidised to a radical cation. The metal ion affinity (MIA) is influenced by the position and number of OCH 3 substituted on the acylcyclopentene-1,3-dione ring. A very favourable MIA, in vacuo, is obtained when Fe(II) is chelated between the sp 2 O and sp 3 O atoms. An estimation of MIA in an aqueous solution shows a remarkable decrease with respect to the results in vacuo.

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