Dissociation Potential Curves of Low-Lying States in Transition Metal Hydrides. 3. Hydrides of Groups 6 and 7

Spin–orbit coupling analyses of phosphorescent processes in Ir(Zppy)3 (Z = NH2, NO2 and CN)

Appropriate combinations of substituents provide brighter blue-color emission in OLEDs. The present MCSCF + SOCI + SOC calculations suggest that the best material for blue-color emission is fac-Ir(5-NO₂ppy)₃ or fac-Ir(5-NO₂-4,6-dfppy)₃, or practically fac-Ir(5-CN-3,4,6-tfppy)₃.

Potential energy curves and electronic structure of 3d transition metal hydrides and their cations

We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese-Martin for kinetics (BMK) and Tao-Perdew-Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.

The permanent electric dipole moment of chromium monodeuteride, CrD

A number of low-N lines of the X (6)Sigma(+)<--A (6)Sigma(+)(0,0) band of chromium monodeuteride, CrD, have been recorded at near the natural linewidth limit by high resolution laser excitation spectroscopy of a supersonic molecular beam sample. The shifts and splitting of these lines caused by a static electric field have been analyzed to give the permanent electric dipole moments of the X (6)Sigma(+)(upsilon=0) and A (6)Sigma(+)(upsilon=0) states as 3.510(33) and 1.153(3) D, respectively. The dipole moment of the A (6)Sigma(+)(upsilon=0) state can be measured with higher precision because of some interesting near degeneracies in its level structure. The trends in the observed dipole moments for the first-row transition metal monohydrides are rationalized and compared with theoretical predictions.

The Zeeman tuning of the A 6Σ+–X 6Σ+transition of chromium monohydride

The magnetic tuning of the low-rotational levels of the A (6)Sigma(+) (v = 1 and 0) states of chromium monohydride, (52)CrH, have been experimentally investigated using optical spectroscopy of the (0, 0) and (1, 0) bands of the A (6)Sigma(+)-X (6)Sigma(+) transition. The tuning of the numerous low-rotational lines in the A (6)Sigma(+)-X (6)Sigma(+) (0, 0) band can be accurately modeled using a single set of g-factors (g(S) and g(l)) which are close to the expected values. In contrast, the g-factors for the A (6)Sigma(+) (v = 1) state required to model the magnetic tuning of low-rotational lines in the A (6)Sigma(+)-X (6)Sigma(+) (1, 0) band are strongly dependent upon rotational and fine structure component and the determined effective values for g(S) deviate significantly from 2.002. Interpretation of the quantum level variation of g(S) is presented. The magnetic hyperfine structure of the (0, 0) and (1, 0) bands of the A (6)Sigma(+)-X (6)Sigma(+) transition is analyzed to produce proton Fermi contact, b(F) and dipolar, c, magnetic hyperfine parameters of 19(1) MHz and 34(5) MHz for the A (6)Sigma(+) (v = 0) state and 21(2) MHz and 30(7) MHz for the A (6)Sigma(+) (v = 1) state.

Relativistic Study on Emission Mechanism in Palladium and Platinum Complexes

The present study investigates the spin-orbit coupling (SOC) effects in the radiative processes from the electronically excited states of bis[-2-(2-thienyl)-pyridine] platinum (Pt(thpy)2) and palladium (Pd(thpy)2). The transition probabilities among the low-lying spin-mixed states in these complexes are estimated using the discrete variable representation (DVR) method based on the assumption that the system obeys Fermi's golden rule. It is revealed that the low-lying excited singlets and triplets are strongly mixed with each other by SOC in Pt(thpy)2 and, as a result, a fast nonradiative transition occurs to the low-lying excited spin-mixed states. This is followed by the radiative transition from these low-lying spin-mixed states to the lowest spin-mixed state (the ground state); that is to say, a phosphorescence should be observed from these low-lying excited spin-mixed states in Pt(thpy)2. On the contrary, weak SOCs are obtained in Pd(thpy)2 and no phosphorescence at room temperature is expected to be observed in Pd(thpy)2. These results are in good agreement with the experimental reports.