Solvent effect on geometry and nonlinear optical response of conjugated organic molecules

Abstract

ABSTRACT:In this paper the effect of solvents of different polarity (chloroform and acetone) on the geometry and static electric properties (dipole moment, polarizability, and first hyperpolarizability) of four nonlinear optical (NLO) chromophores is studied within the framework of the Polarizable Continuum Model (PCM) at the Self-consistent Field (SCF) level. The standard 6-31G** basis set is used for the chromophore geometry optimization both in the gas phase and in the solvents, and a moderate-size aug-cc-pVDZ* basis set is used for the calculation of electric properties of the chromophores under study. The effect of the solvent on the geometrical parameters of the chromophores is shown to be insignificant. However, to avoid inaccuracies in estimation of first hyperpolarizability, the use of chromophore geometries, optimized in a solvent, is recommended for chromophores with a rather long conjugation bridge between electron-donating and electron-withdrawing groups. The solvent effect on the calculated values of first hyperpolarizability results in its strong enhancement by a factor of 2.9 -2.3 in the case of chloroform and by a factor of 3.9 -2.8 in the case of acetone, the effect being somewhat attenuated with the lengthening of the conjugation bridge in the series of chromophores.

Distributed Atomic Polarizabilities of Amino Acids and their Hydrogen-Bonded Aggregates

“…43 The differences between experimental and calculated values are within 6%, a good result given that calculations do not account for wavelength dispersion or solvent effects. 44,45 Our results are also in good agreement with other additive models of dipole polarizabilities. 46 The isotropic polarizabilities computed via the transferable groups (shown in Table 2 In order to confirm the validity of the transferable functional groups, we computed the polarizability of some molecules, for example -alanine and -aminoisobutyric acid, that contain the same functional groups but that are outside the set used to construct the database.…”

The Role of Hydrogen Bond in Designing Molecular Optical Materials

“…For example, Balakina and coworkers [29,31], studied theoretically a series of non-linear optical chromophores and demonstrated that the formation of weak to moderate N-H⋅⋅⋅O bonds (with donor-acceptor Figure 2. Distributed atomic polarizability ellipsoids of a p-nitroaniline dimer extracted from the crystal structure, calculated at the CAM-B3LYP/cc-pVDZ level of theory.…”

“…This means that these interactions may be useful for controlling the anisotropy of crystalline optical properties, The cluster approach has been previously used to investigate the effect of hydrogen-bond formation on the (hyper)polarizabilities of a few other organic materials. For example, Balakina and coworkers [29,31], studied theoretically a series of non-linear optical chromophores and demonstrated that the formation of weak to moderate N-H¨¨¨O bonds (with donor-acceptor distances in the range 2.8-3.5 Å) results in an increment of only 10%-15% of the molecular polarizability α, whereas the first hyperpolarizability β may increase up to three times. It is anyway noteworthy that even small changes in α will significantly affect the calculation of the electric susceptibility through a lattice summation.…”

Solvent effects on optical properties of molecules: A combined time-dependent density functional theory/effective fragment potential approach

“…2 Furthermore, their optical properties in solvent environments are sensitive to the nature of the solvent and solute-solvent interactions, [3][4][5] which can be quite complex, involving hydrogen-bonding and long-range screening. To capture the effects of solvents on the optical properties of solutes, the DFT based EFP1 model ͑EFP1/DFT͒ 11 was employed.…”