Determination of the optimal energy denominator shift parameter of KRb electronic states in quantum chemical computations using perturbation theory

The infl uence of the energy denominator shift (EDS) parameter and the quantitative and qualitative compositions of electronic states included in CASSCF(2,14)/XMCQDPT2 ab initio calculations of the ground state equilibrium internuclear distance and dissociation energy of polar KRb was determined

Optical cycle modelling for RbYb and CsYb molecules

The probabilities of two-step schemes (optical cycles) for the transition of polar RbYb and CsYb molecules from highly excited vibrational states into the ground vibronic state were calculated. It was shown that the most effective optical cycles involved the excited 2 2 Σ 1/2 + -state

Ab initio multi-reference perturbation theory calculations of the ground and some excited electronic states of the RbYb molecule

The potential energy curves of the ground and twelve low-lying excited electronic states of the RbYb molecule have been calculated using the multi-reference perturbation theory method at the CASSCF/ XMCQDPT2 level of theory including the spin-orbit coupling. The electronic term energies, equilibrium internuclear distances, dissociation energies, transition dipole moments, the sequences of vibrational energies, the harmonic vibrational frequencies, and the Franck–Condon factors have been predicted. The potential energy curves at the asymptotic limits are in a good agreement with the experimental data for rubidium and ytterbium atoms. The obtained data would be useful for spectral experiments with RbYb molecules

Indotricarbocyanine dyes relevant for photodynamic therapy and their radicals: Substituent effects studied by optical and electrochemical methods

Photodynamic therapy is an effective and minimally invasive treatment method for cancer. A deeper under- standing of the photocytotoxicity mechanism of cyanine dyes is necessary for the development of more efficient photosensitizers. We combine electrochemistry, optical and ESR spectroscopy, and quantum chemical calcula- tions to study indotricarbocyanine dyes relevant for photodynamic therapy. The incorporation of 4-meso-chloride and a 3,5-o-phenylene bridge into the polymethine chain results in a hypsochromic shift of the absorption spectrum by ca. 30 nm and in a downward shift of the frontier orbitals energy levels by 0.1–0.3 eV. In addition, such substitution imparts stability to the electrogenerated radical dications of the dyes. The presence of 4-meso- chloride and a 3,5-trimethylene bridge in the polymethine chain causes the absorption spectrum to shift bath- ochromically by almost 40 nm and the HOMO–LUMO energy gap to decrease by ca. 0.1 eV. The radical dication of the dye with such substitution is particularly stable and exhibits improved electron delocalization. The radical dication of the dye with an unsubstituted polymethine chain is unstable due to its propensity to form dimers. The substituents at the nitrogen atoms are shown to have almost no influence on the optical and electrochemical properties of the indotricarbocyanine dyes. The radical dications of the dyes with an o-phenylene bridge can oxidize bromide ions, unlike the radical dications of the dyes with an unsubstituted polymethine chain or with a trimethylene bridge. The reported data can be used to develop new indotricarbocyanine dyes with desired characteristics

Ab initio multi-reference perturbation theory calculations of the ground and low-lying electronic states of the KRb molecule

The potential energy curves of the low-lying electronic states correlating up to the limit K(4p) + Rb(5s) of KRb molecule have been calculated using the multi-reference perturbation theory method at the CASSCF/ XMCQDPT2 level of theory without and with spin–orbit coupling. The calculated parameters of the ground X 1 R + state are in the best agreement among all previously performed ab initio calculations for the KRb molecule. The calculated vibrational intervals of the ground electronic term of the 39 K 85 Rb molecule describe the experiment with the accuracy within ±1 cm ?1 . The calculated intensities of the 2 1 R + (v 0 = 3, J 0 = 26) ? X 1 R + (v 00 = 0...24, J 00 = 25, 27) transitions satisfactory reflect the experimentally observed intensities distribution

Spectral analysis of 3-(adamantan-1-YL)-4-ethyl-1-[(4-phenylpiperazin-1-yl) methyl]-1H-1,2,4-triazole-5(4H)-thione

Vibrational IR (3200–650 cm –1) and Raman spectra (3200–150 cm –1) of adamantane-containing 3-(adamantan-1-yl)-4-ethyl-1-[(4-phenylpiperazin-1-yl)methyl]-1H-1,2,4-triazole-5(4H)-thione, which is promising for drug design, were examined. The UV/Vis spectrum (450–200 nm) of the compound in EtOH was measured. Full geometry optimization using density functional theory (DFT) in the B3LYP/cc-pVDZ approximation allowed the equilibrium configuration of the molecule to be determined and IR and Raman spectra to be calculated. Based on these, thee xperimental vibrational IR and Raman spectra were interpreted and the biological activity indices were predicted. The UV/Vis spectrum of the title compound was simulated at the time-dependent DFT/CAM-B3LYP / cc-pVDZ level with and without solvent effects and at the ab initio multi-reference perturbation theory XMCQDPT2 level. The UV / Vis spectrum that was simulated using the multi-reference XMCQDPT2 approximation agreed very successfully with the experimental data, in contrast to the single-reference DFT method. This was probably a consequence of intramolecular charge transfer

Structure of N' -(adamantan-2-ylidene)benzohydrazide, a potential antibacterial agent, in solution: Molecular dynamics simulations, quantum chemical calculations and Ultraviolet–visible spectroscopy studies

The molecular dynamics simulations of the structure of the N' -(adamantan-2-ylidene)benzohydrazide followed by the quantum chemical calculations at the DFT level of theory have identified four stable conformers of this potential antibacterial agent in solution: one “central” cis- and three (“central”, “left” and “right”) transconformers. The UV-Vis absorption spectrum in the 220–320nm region in the ethanol solution reveals two bands that can be primarily explained based on the ab initio calculations of the spectral characteristics of the “side” transconformers at the MRPT level of theory. However, the close energy values for the calculated cis- S 1 ← S 0 and “side” trans- S 2 ← S 0 transitions cannot exclude the presence of cis-conformer in solution. Therefore, the data obtained show that the coexistence of both trans-conformers and cis-conformer should be taken into consideration when studying the pharmaceutical properties of the title molecule