Photoinduced charge-transfer electronic excitation of tetracyanoethylene/tetramethylethylene complex in dichloromethane

Electronic structure and second-order nonlinear optical properties of lemniscular [16]cycloparaphenylene compounds

Chiral organic compounds are excellent second-order nonlinear optical (NLO) materials due to their inherent non-symmetric electronic structures combined with the advantages of organic compounds. At present, density functional theory (DFT) has become a powerful tool for predicting the properties of novel materials. In this paper, based on chiral lemniscular [16]cycloparaphenylene, three novel compounds are designed by introduction of donor/acceptor units and their combinations. The geometrical/electronic structure, electronic absorption, and the second-order NLO properties of these compounds have been systematically investigated by DFT/TDDFT theory. The simulated UV-Vis/CD spectra of compound 1 are in good agreement with the experimental ones, enabling us to assign their electronic transition characteristics and absolute configuration with high confidence. The investigations show that energy gaps, absorption wavelength and second-order NLO response may be effectively tuned by the introduction of the donor or acceptor units or their combinations. For instance, the second-order NLO value of compound 4 is about 207 times as large as the average second-order polarizability of the organic molecule urea. Thus, the studied compounds are expected to be potential large second-order NLO materials.

Electronic structure and second-order nonlinear optical properties of linear [3]spirobifluorenylene compounds

The nonlinear optical property of the studied compounds were studied with the aid of the DFT calculations.

Theoretical study on functionalized acrylonitrile compounds with a large second-order nonlinear optical response

The nonlinear optical properties of the studied compounds were studied with the help of DFT calculations.

Solvent effects for vertical absorption and emission processes in solution using a self-consistent state specific method based on constrained equilibrium thermodynamics

A self-consistent state specific (SS) method in the framework of TDDFT is presented to account for solvent effects on absorption and emission processes for molecules in solution. In these processes, the initial state is an equilibrium state, while the polarization of the solvent is in nonequilibrium with the electron density of the solute in the final state. Nonequilibrium solvation free energy is calculated based on a novel nonequilibrium solvation model with constrained equilibrium manipulation. The bulk solvent effects are considered using the polarizable continuum method (PCM), where the solvent-solute interaction is described with a reaction field. Molecular orbitals and orbital energies in the presence of the reaction field corresponding to the excited state are employed and the response of the solvent is not included in the TDDFT calculations. A self-consistent procedure is designed to obtain the excited state reaction field. The equations based on this new nonequilibrium solvation model in the framework of the self-consistent SS-PCM/TDDFT method for calculation of vertical absorption and emission energies are presented and implemented in the Q-Chem package. Vertical absorption and emission energies for several small molecules in solution using the newly developed code are calculated and compared with available experimental data and the results of other theoretical studies. Solvent shifts of absorption and emission energies are reasonably reproduced with this approach. The new model is a promising approach to study nonequilibrium absorption and emission processes in solution.

Solvent effects on excitation energies obtained using the state-specific TD-DFT method with a polarizable continuum model based on constrained equilibrium thermodynamics

Nonequilibrium solvation effects need to be treated properly in the study of electronic absorption processes of solutes since solvent polarization is not in equilibrium with the excited-state charge density of the solute. In this work, we developed a state specific (SS) method based on the novel nonequilibrium solvation model with constrained equilibrium manipulation to account for solvation effects in electronic absorption processes. Time-dependent density functional theory (TD-DFT) is adopted to calculate electronic excitation energies and a polarizable continuum model is employed in the treatment of bulk solvent effects on both the ground and excited electronic states. The equations based on this novel nonequilibrium solvation model in the framework of TDDFT to calculate vertical excitation energy are presented and implemented in the Q-Chem package. The implementation is validated by comparing reorganization energies for charge transfer excitations between two atoms obtained from Q-Chem and those obtained using a two-sphere model. Solvent effects on electronic transitions of coumarin 153 (C153), acetone, pyridine, (2E)-3-(3,4-dimethoxyphenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (DMHP), and uracil in different solvents are investigated using the newly developed code. Our results show that the obtained vertical excitation energies as well as spectral shifts generally agree better with the available experimental values than those obtained using the traditional nonequlibrium solvation model. This new model is thus appropriate to study nonequilibrium excitation processes in solution.