NLOphoric benzyl substituted BODIPY and BOPHY: A comprehensive linear and nonlinear optical study by spectroscopic, DFT and Z-scan measurement.

BOPHY (BPY) and BODIPY (BDY) dye bearing benzyl group (Bn) at 4,4' and 2,6 position respectively were synthesized and characterized. The fluorescence decay measurements were performed which reveal that benzyl BOPHY (Bn-BPY) has shorter fluorescence lifetime compared to benzyl BODIPY (Bn-BDY). The difference in transition dipole moment is found to be 6.93 and 11.3 D for Bn-BDY and Bn-BPY respectively in toluene. The molecular electrostatic potential (MEP) plot shows Bn-BDY is more polarised compared to Bn-BPY. The nonlinear optical (NLO) property was evaluated using Z-scan measurement. The molecular electronic arrangement of Bn-BPY significantly affects the nonlinear absorption properties resulting into reverse saturable absorption (nonlinear absorption coefficient ß = 0.256 × 10-11 m/W). In contrast, the Bn-BDY displays saturable absorption character. The calculated third-order nonlinear susceptibility χ(3) value is 12.23 × 10-13 esu and 2.49 × 10-13 esu for Bn-BDY and Bn-BPY respectively. The power limiting behaviour of Bn-BPY displays limiting threshold energy around 70 Jcm-2 with clamped output at ~35 Jcm-2.

Non-linear optical response of meso hybrid BODIPY: Synthesis, photophysical, DFT and Z scan study.

Hybrid meso BODIPY dyes are synthesized and their linear and non-linear optical properties are studied. Time-resolved fluorescence lifetime decay is found to be identical for all dyes irrespective of meso substituents. The Z-scan experiment performed to calculate the nonlinear absorption coefficient (ß) and third-order nonlinear susceptibility (χ3). Global hybrid (B3LYP and BHHLYP) and range-separated hybrid (CAM-B3LYP) functional with the basis set 6-311++G(d,p) was employed to determine the theoretical linear and non-linear optical properties. The computed ß0 value of all the three dyes was found to be superior to that of urea (ßo = 0.371 × 10-30 esu). Introduction of meso substituent directly affects the polarizability and second-order hyperpolarizability of the dyes. Thermal and reorientational effect of the investigated NLOphoric dyes were studied.

Novel Rhodafluors: Synthesis, Photophysical, pH and TD-DFT Studies.

An efficient protocol for the synthesis of new rhodol derivatives has been developed. The synthesis involves condensation of 2-hydroxy benzophenone derivatives with 1, 3-dihydroxy benzene derivatives in solvents such as ionic liquid (N-methyl-2-pyrrolidonium hydrogen sulfate) and methane sulphonic acid. Both ionic liquid and methane sulphonic acid were found to be promising self-catalyzed solvents to bring out the conversion to form desired rhodols in excellent yields. In N-methyl-2-pyrrolidonium hydrogen sulfate reaction proceeds faster compared to methane sulphonic acid. The new fluorophores are investigated for their photophysical properties in various microenvironments and systematically characterized by means of density functional theory and time dependent density functional theory. Photophysical properties of the new rhodafluors found sensitive towards change in the pH of media and thus can be used as efficient pH sensors.

Congeners of Pyrromethene-567 Dye: Perspectives from Synthesis, Photophysics, Photostability, Laser, and TD-DFT Theory.

In an attempt to develop photostable and efficient BODIPY (PM) dyes for use in liquid dye lasers, three new congeners of widely used laser dye, PM567, were synthesized and their photophysical properties in various organic solvents, laser performances, and photostabilities in a selected solvent, 1,4-dioxane, have been investigated using a frequency doubled Q-switched (10 Hz) Nd:YAG laser at 532 nm. The results of photostability study in nonpolar 1,4-dioxane revealed the remarkable enhancement in stability of the novel dyes compared to that of PM567 as well as improved laser performances. Cyclic voltammetry study strongly supports the observed enhancement in photostability of the novel dyes compared to that of PM567. The observed properties of the novel dyes in relation to those of PM567 have been rationalized by extensive use of DFT and TD-DFT using the B3LYP/6-31G(d) method of theory.