Synthesis, photophysical studies, solvatochromic analysis and TDDFT calculations of diazaspiro compounds

Solvent Effect on the Photophysical Properties of Terpyridine Incorporating Pyrene Moiety: Estimation of Dipole Moments by Solvatochromic Shift Methods

The absorption and fluorescence emission spectra of terpyridine incorporating pyrene moiety (Tpy-pyr) have been recorded in extensive variety of solvents having different polarities. The effect of the solvent on the spectral characteristics are examined. It is shown that Tpy-pyr exhibit positive solvatochromism, large Stokes shift values in polar solvents, and fluorescence in the long wavelength region of the visible range. A linear increasing trend with Stokes shift indicates the presence of Tpy-pyr - solvent interaction. The acquired results could be attributed to the formation of excited states with intramolecular charge transfer. The fluorescence quantum yield was drastically reduced in polar protic solvents and the formation of the twisted states with charge transfer was proposed. Both ground and excited state dipole moments (µg and µe) were determined experimentally by Lippert-Mataga, Reichardt, Bilot-Kawski, Bakhshiev and Kawski-Chamma-Viallet solvatochromic methods analyzed on the base of the microscopic solvent polarity functions. The µg and µe dipole moment of Tpy-pyr estimated from density functional theory (DFT) and those determined experimentally from solvatochromic methods are compared and the results are discussed.

Small isomeric push-pull chromophores based on thienothiophenes with tunable optical (non)linearities

Fourteen new D-π-A push-pull chromophores based on two isomeric thienothiophene donors and seven acceptors of various electronic natures have been designed and conveniently synthesized. In contrast to known thienothiophene push-pull molecules, the prepared small chromophores proved to be organic materials with easily tunable thermal, electrochemical and (non)linear optical properties. It has also been shown that small structural variation may result in significantly improved/varied fundamental properties. Very detailed structure-property relationships were elucidated within the systematically developed series of push-pull molecules, which may serve as a useful guide in designing new D-π-A molecules based on fused thiophene scaffolds.

Noncovalent interactions from electron density topology and solvent effects on spectral properties of Schiff bases

Two Schiff bases were prepared by the condensation of o-allyl substituted 2,4-dihydroxy acetophenone with 1,2-diaminopropane (L1) and ethanediamine (L2) and characterized by elemental analysis, and ESI-MS, IR, UV-Vis, ¹H and ¹³C NMR spectral techniques. The effect of solvents with respect to different polarities on UV-Vis and emission spectra of L1 and L2 was investigated at room temperature show that the compounds exist in keto and enol forms in solution and may be attributed to the intramolecular proton transfer in the ground state. The solute-solvent interactions, change in dipole moment and solvatochromic properties of the compounds were studied based on the solvent polarity parameters. For L1 and L2, the ground and excited state electronic structure calculations were carried out by DFT and TD-DFT at B3LYP/6-311G (d,p) level, respectively. The IR, NMR and electronic absorption spectra computed were compared with the experimental observations. The intramolecular charge transfer within the molecule is evidenced from the HOMO and LUMO energy levels and surface analysis. The noncovalent interactions like hydrogen bonding and van der Waals interactions were identified from the molecular geometry and electron localization function. These interactions in molecules have been studied by using reduced density gradient and graphed by Multiwfn.

N. S. Effect of solvent polarity on the photophysical properties of chalcone derivatives

The photophysical properties were studied for FNPO, AFPO and FHPO in different organic solvents. The excited state of the molecules were found to be more polar than the ground state.