Ab initio SCRF study of solvent effect on the nonlinear polarizabilities of different intramolecular charge-transfer molecules

Performance of Hybrid DFT Compared to MP2 Methods in Calculating Nonlinear Optical Properties of Divinylpyrene Derivative Molecules

A series of divinyl-pyrene derivatives of the form D-vinyl-pyrene-vinyl-A, in which D corresponds to an electron donor group and A to an electron acceptor group, were studied in this work. The first purpose was to determine the optimal HF % exchange as incorporated in a range of hybrid functionals (M06HF, M062X, M06L, CAM-B3LYP, PBE0, BMK, and B3LYP) capable to produce, reliably and as close as possible to those obtained from MP2 calculations, NLO parameters and, in particular, first-order static hyperpolarizabilities. The CAM-B3LYP functional was revealed to be the most suitable one. The pair N(CH₃)₂/NO₂ was then determined as the most efficient pair of groups in producing appreciable NLO responses. The effect of the substitution position on the pyrene moiety was also investigated, whereby aligning the two substituents involving the D and A groups in the direction of the dipole moment as in the (1,6 DVP) derivatives was shown to be most favorable for increasing the NLO parameters.

Solvent effects on polarizability and hyperpolarizability of spirobifluorene derivative

We studied the solvent effect on the geometric structure and (hyper)polarizability of spirobifluorene derivative by using quantum chemistry calculations. We found that the geometric structure is slightly affected by the solvent polarity. However, solvent polarity significantly influences first hyperpolarizability and second hyperpolarizability respectively. In addition, the linear polarizability is less affected by the solvent than the hyperpolarizabilities. We also first studied the solvent effect on frontier molecular orbitals and found that the frontier molecular orbitals energy gap is strongly influenced by the surrounding solvent. Our results demonstrate frontier molecular orbitals energy gap and molecular hyperpolarizabilities can be tuned by a suitable choice of the solvent respectively. Such findings have crucial implications for organic nonlinear optical materials applications.

Electronic Structure and Spectroscopic Properties of the Two Structural Isomers of Donor−Acceptor Substituted Sesquifulvalene in the Gas and Solution PhasesA Case Study of Sudden Polarization

The ground state equilibrium structure and electric properties of two structural isomers of donor-acceptor substituted sesquifulvalene have been calculated at ab initio HF and MP2 levels for different conformations. The electronic properties of low lying excited singlets are calculated by using CI calculations including single excitations only. Isomer I in which the inter-ring charge transfer (CT) is reinforced in the presence of substituents shows sudden polarization in the ground and two lower lying excited states, while isomer II in which the longitudinal CT interaction is attenuated does not exhibit sudden polarization. The phenomenon of sudden polarization has been rationalized in terms of the easy polarization, smaller rotational barrier, and enhanced inter-ring CT on going from the planar to the orthogonal geometry. The appreciably large static second-order polarizability of I stems from its sudden polarized ground state. The solvent (using the conductor-like polarizable continuum model (CPCM)) plays a significant role on the modulation of ground and excited state electronic properties which, in general, predicts blue-shifts for I. However, for molecule II, the two lower energy transitions show a red-shift while the others show a weaker blue-shift at any conformation.