Search results for "iTED"
showing 10 items of 2408 documents
Electro-optical and laser spectrofluorimetry study of coumarins 7 and 30: evidence for the existence of the close-lying electronic states and conform…
1997
Our experiments and calculations reveal a set of anomalous and interesting properties of coumarin 7 (CU7) and coumarin 30 (CU30) in solution. The spectral dependence of electro-optical coefficients and, consequently, dipole moments indicates that the absorption band is a superposition of several (at least two) electronic transitions. Probably, there are two close-lying π,π* singlet electronic excited states which contribute to the first absorption band. The calculations using the MM2 program show that both dyes in the ground state have two stable plane anti conformers. From time-resolved spectrofluorimetric measurements we obtained evidence for the existence of conformers in paraffin oil so…
Molecular Stark-effect spectroscopy of Prodan and Laurdan in different solvents and electric dipole moments in their equilibrated ground and Franck–C…
2007
Abstract The results from electrooptical absorption measurements (EOAM) on the ground and excited Franck–Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane and cyclohexane are presented. The ground and excited Franck–Condon state electric dipole moments as well as the respective transition moment of both probes are parallel. The electric dipole moments of Prodan and Laurdan in the ground state in cyclohexane and 1,4-dioxane have values within the range (15.7–16.5) × 10 −30 C m. On optical excitation the dipole moments increase by (42.1–49.5) × 10 −30 C m. The obtained results are compared with the values of the dipole moments of Prodan and Laurdan determined by other methods.
Magnetic Excitations in Polyoxometalate Clusters Observed by Inelastic Neutron Scattering: Evidence for Ferromagnetic Exchange Interactions and Spin…
1999
The ground-state properties of the tetranuclear Ni2+ cluster [Ni4(H2O)2(PW9O34)2]10- were investigated by combining magnetic susceptibility and magnetization measurements with a detailed inelastic neutron scattering (INS) study on a fully deuterated sample of K6Na4[Ni4(H2O)2(PW9O34)2]·24H2O. The temperature dependence of the magnetic susceptibility indicates a ferromagnetic coupling of the four constituent Ni2+ ions (s = 1), and a low-temperature magnetization study provides the magnitude of the S = 4 ground-multiplet splitting due to the single-ion anisotropy of the Ni2+ ions. Besides a more direct and precise determination of the anisotropic S = 4 ground-multiplet splitting, INS enabled t…
A theoretical study of the electronic spectrum of styrene
1999
Abstract The electronic spectrum of styrene has been studied by using multiconfigurational second-order perturbation theory (CASPT2). The study includes geometry optimization of the ground state, the lowest triplet state, and the lowest singlet excited state. The covalent 2 1 A ′ state placed vertically at 4.34 eV is assigned to the first band. The 1 1 A ′→3 1 A ′ transition located at 4.97 eV is responsible for the second band. The most intense feature involves the 5 1 A ′ state, which is calculated to lie 6.19 eV above the ground state. The lowest singlet–singlet Rydberg transition (3s) is predicted to occur at 5.85 eV.
Excited state dipole moments and polarizabilities of centrosymmetric and dimeric molecules. I. Model study of a bichromophoric molecule
1988
Abstract Refractometric, dielectric and electro-optical absorption measurements are reported for 1-dimethylamino-2,6-dicyano-4-methyl-benzene (I) and 1,4-bis(4′-dimethylamino-3′,5′-dicyanophenyl)bicyclo[2.2.2]octane (II). The evaluation leads to dipole moments and polarizabilities of the ground state as well as the first dipole allowed singlet state. The experimental res excellently substantiate the method of electro-optical absorption measurements in solution. It is shown that the excited dimer wavefunctions of the bichromophoric molecule II localize by solvent induced local site perturbations.
Multireference equation-of-motion coupled cluster theory.
2012
A generalization of the equation-of-motion coupled cluster theory is proposed, which is built upon a multireference parent state. This method is suitable for a number of electronic states of a system that can be described by similar active spaces, i.e., different linear combinations of the same set of active space determinants. One of the suitable states is chosen as the parent state and the dominant dynamical correlation is optimized for this state using an internally contracted multireference coupled cluster ansatz. The remaining correlation and orbital relaxation effects are obtained via an uncontracted diagonalization of the transformed Hamiltonian, Ĥ = e(-T) Ĥe(T), in a compact multire…
Electronic nature of the emitting triplet in SF 5 -substituted cationic Ir(III) complexes
2018
Abstract A theoretical density functional theory study has been performed on a family of cationic iridium(III) complexes of the form [Ir(C^N)2(dtBubpy)]+ (dtBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine), that incorporate 2-phenylpyridine (1, 2) and 1-phenylpyrazole (3, 4) cyclometallating C^N ligands functionalized with SF5 groups. The goal is to investigate the effect that the inclusion of SF5 groups in meta (1, 3) and para position (2, 4) with respect to the Ir–C bond has on the electronic nature of the emitting triplet state and the emission wavelength. The attachment of the electron-withdrawing groups induces the stabilization of the molecular orbitals localized on the C^N ligands and, in…
Photophysical Properties of Oligo(phenylene ethynylene) Iridium(III) Complexes Functionalized with Metal-Anchoring Groups
2016
[EN] The electrochemical and photophysical properties of a family of conjugated ligands and their iridium(III) cyclometallated complexes are described. They consist of a series of monocationic Ir-III bis-2-phenylpyridine complexes with p-phenylethynyl-1,10-phenanthroline ligands of different length. The structure of these ligands includes terminal acetylthiol or pyridine groups, which can provide good electrical contacts between metal electrodes. Cyclic voltammetry, absorption and emission spectroscopy, laser flash photolysis and density functional theory calculations reveal that the high conjugation of the diimine ligand affords small energy gaps between the frontier orbitals. Nevertheless…
Intramolecular pi-stacking in a phenylpyrazole-based iridium complex and its use in light-emitting electrochemical cells.
2010
A novel iridium(III) complex, [Ir(dmppz)(2)pbpy][PF(6)] (Hdmppz = 3,5-dimethyl-1-phenylpyrazole and pbpy = 6-phenyl-(2,2'-bipyridine)), is reported. The complex shows an intramolecular face-to-face pi-stacking between the phenyl ring of the dmppz ligand and the pendant phenyl of the pbpy ligand. This interaction provides a supramolecular cage formation that holds also in the excited states. Light-emitting electrochemical cells (LECs) using the novel complex show extraordinary lifetimes of approximately 2000 h. The high stability is favored by the presence of pendant methyl groups on the dmppz ligands that hinder the entrance of water molecules rendering the degradation of the complex more d…
Dissociative charge transfer from highly excited Na Rydberg atoms to vibrationally excited Na2 molecules
2001
Abstract We report the observation of the vibrational dependence of dissociative charge transfer (DCT), Na2(X1Σg+, v″) + Na∗∗(nl) → Na− + Na + Na+, in a single Na/Na2 supersonic beam at low intrabeam collision energies (1.6 meV) using the STIRAP technique for selective vibrational excitation of Na2 in the electronic ground state and time-of-flight mass analysis of the ions. The efficiency of this process increases by about an order of magnitude in the range 13 ≤ v″ ≤ 22. Some perspectives are discussed regarding the implementation of a field-free ion-imaging technique for the detection of ions that will allow the direct determination of the kinetic energy distributions of product negative i…