Mavila C. Sreenath

Triphenylamine Derived 3-Acetyl and 3-Benzothiazolyl Bis and Tris Coumarins: Synthesis, Photophysical and DFT Assisted Hyperpolarizability Study

Triphenylamine derived bis- and tris-branched donor-pi-acceptor coumarins with acetyl and benzothiazolyl acceptors are studied for their linear and nonlinear optical properties that originate from their photophysical and molecular structure. Plots of solvent polarities versus the Stokes shift, frontier molecular orbital analysis and Generalised Mulliken Hush analysis have established their strong charge transfer character supported by the strong emission solvatochromism of these chromophores. On the basis of excited state intramolecular charge transfer, the first-, second- and third-order polarizability of these dyes are determined by a solvatochromic method and supported by density functional theory calculations using CAM-B3LYP/6-31g(d). Compared to the acetyl group, the benzothiazolyl group is a strong acceptor, and its corresponding derivatives show enhanced absorption, emission maxima and non-linear optical response. Bond length alternation and bond order alternation analysis reveals that these chromophores approach the cyanine-like framework which is responsible for maximum perturbation to produce high nonlinear optical response. Third order nonlinear susceptibility for dyes 1 and 2 is determined by Z-scan measurement. All of these methods are used to determine the nonlinear optical properties, and thermogravimetric analysis suggests that these chromophores are thermally robust and efficient nonlinear optical materials.

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 (β) 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 β0 value of all the three dyes was found to be superior to that of urea (βo = 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.