First Principle Calculations of the Electronic and Vibrational Properties of the 3-(1,1-Dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole Molecule

Abstract

Results of first principle quantum chemical calculations of electronic and vibrational properties of the push-pull 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) molecule are reported and discussed. The structure of DCNP was optimized with HF/6-311G methodology and found to be planar. On the basis of obtained geometry, infrared absorption and Raman spectra were computed within the HF/6-311++G** formalism. They allow to conclude that the changes of molecule dipole moment and variation of its polarizability appear at the same vibrational mode and affect the optical properties of the DCNP. Four different methodologies: time-dependent HF and time-dependent DFT method with B3LYP, LC-BLYP, and CAM-B3LYP potentials were used to compute the optical absorption spectra of DCNP. Influence of solvent on molecular electronic structure was studied within the C-PCM model. It predicts the DFT/B3LYP methodology as the best one to compute the NLO properties of the DCNP. The computed HOMO and LUMO orbitals show evidence that the ground state of the molecule is located at its aromatic part. The discussion of charge transfer during the excitation process for the transition S0-S1 was performed. The charge transfer parameter calculated in vacuum and in solvent gives the evidence that the solvent environment weakly enhance the molecular charge transfer. It confirms the tendency of an occurrence of the intermolecular charge transfer in DCNP which is crucial for its hyperpolarizability magnitude. It was proved that the second-order susceptibility corresponding to SHG may be calculated for host-guest polymer/DCNP composite using the simple oriented gas model and the rigorous local field approach should not necessarily be applied.

All‐Optical Switching and Two‐States Light‐Controlled Coherent‐Incoherent Random Lasing in a Thiophene‐Based Donor‐Acceptor System

“…The polarizability and hyperpolarizability of a medium exposed to an intense laser light giving the electric field has been a subject of broad interest toward understanding various linear and nonlinear optical processes. Many experimental and theoretical studies on the optical nonlinearities have been performed to explore the relationship between the nonlinear optical properties, and the electronic structure and therefore to design new multifunctional materials …”

“…Many experimental and theoretical studies on the optical nonlinearities have been performed to explore the relationship between the nonlinear optical properties, and the electronic structure and therefore to design new multifunctional materials. [39] The ground and the first excited state dipole moments for the Th-pNO 2 isomers were calculated. The orientation of the dipole moments for all isomers is presented in Figure S4 in ESI.…”

Photo-Physical Transformations in Pyrazoline Derivative Based Systems

“…In view of experimental findings evidencing the existence of two PY-pNO 2 isomers of E and Z type at room temperature able to crystallize in two different structures, we have undertaken preliminary quantum chemical calculation for this dye. The detailed quantum chemical calculations that have been reported for cis form of DCNP recently 46 were directed toward its electronic and nonlinear optical properties only. We performed the DFT quantum chemical calculations for both DCNP and PY-pNO 2 isomers in the gas phase including molecular geometry optimization, configurational analysis, and transition barriers between stable ground states isomers.…”

Long-living optical gain induced by solvent viscosity in a push–pull molecule

“…2 During the last few decades, the excited state dynamics of these systems have been the subject of many experimental and computational studies. 1,[3][4][5] It has been proven that after photoexcitation the excited singlet state can relax to a different conformation with higher charge transfer character (Intramolecular Charge Transfer state, ICT), which can be twisted (TICT) 2,6 or planar (PICT). 7 From an electronic point of view, the TICT conformation involves a large charge separation because the mesomeric interaction between D and A is blocked owing to their reciprocal twisting, while the PICT model postulates an ICT quinoidal structure with partial positive charges on the D and A groups.…”