Theoretical predication of third-order optical nonlinearities of [Al4MAl4] n− (n = 0–2, M = Ti, V and Cr) clusters

Design and structural characterization of the all-metal aromatic sandwich species [Bi3Au3Bi3]3−: insight from density functional theory

The [Bi₃Au₃Bi₃]³⁻ species, with hollow features, has a unique all-metal sandwich aromatic structure.

THEORETICAL STUDY OF ONE- AND TWO-PHOTON ABSORPTION PROPERTIES FOR THREE SERIES OF DIPHENYLAMINE AND DIFLUORENYLAMINE SUBSTITUTED CONJUGATED COMPOUNDS

The one-photon (OPA) and two-photon (TPA) absorption properties of three series of symmetrically substituted quadrupolar compounds with structure of donor-π bridge-donor (D–π–D) were investigated by time-dependent density functional theory (TDDFT) based on the Hartree–Fock (HF)-optimized geometrical structures. These compounds were constructed with either phenyl or fluorenyl groups connected by vinylene unit as the central π-conjugated bridges and either diphenylamine or difluorenylamine groups as terminal electron donors. The calculated OPA spectra are dominated by two strong transitions which are attributed to the charge transfers from the donor groups to central conjugated chains. The OPA and TPA transition strength all increase with the extension of conjugated chain length in each series and the corresponding wavelength shifts red in general. The transition strength in either OPA or TPA process also increases from series one to series two or three by replacing the phenyl groups with fluorenyl groups. The intramolecular charge transfers make significant contributions to the TPA activity. According to the three-state model, the enhanced TPA activity comes from the enhancement of transition moment between states–states as conjugated chain increases.

Molecular structure, spectroscopic investigations, second-order nonlinear optical properties and intramolecular proton transfer of (E)-5-(diethylamino)-2-[(4-propylphenylimino)methyl]phenol: a combined experimental and theoretical study

This work presents a combined experimental and theoretical study on an ortho-hydroxy Schiff base compound, (E)-5-(diethylamino)-2-[(4-propylphenylimino)methyl]phenol. The crystal structure and spectroscopic properties of the compound have been determined by using X-ray diffraction, IR and UV-vis spectroscopy techniques. The electronic structure, vibrational frequencies and electronic absorption spectra have been investigated from the calculative point of view. A relaxed potential energy surface scan has been performed based on the optimized geometry of OH tautomeric form to describe the potential energy barrier belonging to intramolecular proton transfer and to observe the effects of transfer on the molecular geometry. The second-order nonlinear optical properties have been investigated based on the first static hyperpolarizability (β) by using the density functional theory.

Vibrational spectroscopic studies and DFT calculations of 4-bromo-o-xylene

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-bromo-o-xylene (BOX). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-3500 cm(-1)) of BOX were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of BOX in the ground state have been calculated by using the density functional B3LYP method with 6-311++G(d,p)/6-311+G(d,p) higher basis sets. The energy and oscillator strength are calculated by time-dependent density functional theory (TD-DFT). To determine conformational flexibility, molecular energy profile of BOX was obtained by B3LYP method with 6-311++G(d,p) basis set with respect to selected degree of torsional freedom, which gives three stable conformers. Besides, molecular electrostatic potential (MEP), non-linear properties and NMR analysis were performed at DFT level of theory.

THERMODYNAMIC AND SECOND-ORDER NON-LINEAR OPTICAL PROPERTIES OF TAUTOMERIC FORMS OF (E)-4-METHOXY-2-[(4-NITROPHENYL)IMINOMETHYL]PHENOL: A DENSITY FUNCTIONAL STUDY

This work presents a computational study on the tautomeric forms of (E)-4-Methoxy-2-[(4-nitrophenyl)iminomethyl]phenol, an ortho-hydroxy Schiff base compound. The electronic structure of title compound has been characterized at the B3LYP/6-311G(d,p) level of density functional theory. The first hyperpolarizability values have been obtained from the molecular polarizabilities for both tautomers. The second-order non-linear optical properties have been investigated based on their relationships with the natural bond orbitals and frontier molecular orbitals. The changes of thermodynamic properties with temperature going from 100 K to 300 K have been investigated for the reactants and the reaction products tautomers. Tautomeric equilibrium constant derived from the difference between the Gibbs free energies of tautomers has been obtained at different temperatures. The relationship between formation enthalpy and entropy changes has been investigated with the enthalpy-entropy compensation.

Spectroscopic investigations and quantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenol

In this work the electronic structure of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenol has been characterized by the B3LYP/6-31G(d) level by using density functional theory. The experimental infrared and electronic absorption spectra have been obtained and compared with the theoretically obtained ones. Molecular electrostatic potential map has been evaluated; natural bond orbital and frontier molecular orbitals analysis have been performed from the optimized geometry. The energetic behavior of the title compound has been examined in solvent media using polarizable continuum model. The non-linear optical properties have been computed with the same level of theory. In addition, the changes of thermodynamic properties have been obtained in the range of 100-500 K.

Density functional theory for transition metals and transition metal chemistry

We introduce density functional theory and review recent progress in its application to transition metal chemistry. Topics covered include local, meta, hybrid, hybrid meta, and range-separated functionals, band theory, software, validation tests, and applications to spin states, magnetic exchange coupling, spectra, structure, reactivity, and catalysis, including molecules, clusters, nanoparticles, surfaces, and solids.