Synthesis and characterization of heterocyclic derivatives and studies on their photophysical properties

Title

Synthesis and characterization of heterocyclic derivatives and studies on their photophysical properties

Creator

Kumari, Rekha.

Contributor

Varghese, Anitha

Description

Photophysical properties such as absorption, fluorescence, quantum yields and lifetime of fluorescent heterocyclic compounds have been a subject of extensive research interest. Absorption and fluorescence emission of fluorescent molecules results in electronic transitions between ground and singlet excited state. The bathochromic or hypsochromic spectral shift brings a considerable change in dipole moment of both the electronic states through solute-solvent interactions. We have synthesized some heterocyclic compounds and studied thier photophysical properties. Different derivatives such as Schiff base, chalcone, maleimide and pyranopyrazole were synthesized and characterized by FTIR, 1H NMR, 13C NMR, mass spectrometry and elemental analysis. Photophysical properties of synthesized compounds have been studied through absorption and fluorescence spectroscopy and DFT calculations. We have used solvatochromic approaches such as Bilot-Kawski, LippertMataga, Bakhshiev, Kawski-Chamma-Viallet and Reichardt's solvent polarity parameters to evaluate dipole moments of ground state and singlet excited state of the synthesized heterocyclic compounds. The influence of specific and non-specific interactions on spectral properties was also investigated by using Kamlet-Abboud-Taft and Catalan multiple linear regression equations. X-ray diffraction analysis of hydroxyl Schiff base derivative has been carried out due to the presence of strong inter and intra molecular hydrogen bonding. Solvatochromic analyses of synthesized compounds were done using Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski- Chamma-Viallet and Reichardt methods. All Solvatochromic graphs have been plotted for spectral parameters against solvent polarity parameters using Origin 8 software. The obtained experimental results from all methods were compared with theoretical results. The correlation coefficient between microscopic solvent polarity parameter and spectral Stokes-shifts were higher in comparison to bulk solvent polarity functions. Graphs for each molecule provided good correlation based on least square analysis. Dipole moment values of ground and excited states were calculated using slopes of different solvatochromic methods. Higher value of singlet excited state dipole moment indicated that the molecules were more polarised in the singlet excited state. Kamlet-Abboud-Taft and Catalan multiple linear regression (MLR) analyses were used to analyse the solvent effects on absorption, emission and difference in spectral energies of the synthesized molecules. Single point method was used to calculate the quantum yields of the synthesized compounds in ethanol using an ethanolic solution of anthracene as a reference compound. Edwards atomic increment method was applied to calculate the Onsager cavity radii of all the molecules using van der Waals volume. DFT/TD-DFT was used for quantum mechanical calculations of all the molecules. The geometrical structures of the synthesized molecules were optimized using B3LYP/6-311G(d, p) basis set. The positions of HOMO-LUMO orbitals were identified and the band gaps for all the molecules were calculated. Mulliken atomic charges and electrostatic potential surface (MEP) have also been evaluated for all the molecules to identify the ICT pathway and evaluate electrophilic and nucleophilic reactive sites around the molecules . The fluorescence quenching studies of a chalcone derivative by aniline in n-butanol and 1,4-dioxane was performed at 25 ? C which indicated that quenching reactions are diffusion limited.

Source

Author's Submission

Date

2017-01-01

Publisher

Christ(Deemed to be University)

Subject

Chemistry

Rights

Open Access

Relation

61000076

Format

PDF

Language

English

Type

PhD

Identifier

http://hdl.handle.net/10603/254635