• NAGAIYAN SEKAR

      Articles written in Journal of Chemical Sciences

    • Enhanced NLO response in BODIPY-coumarin hybrids: density functional theory approach

      YOGESH ERANDE NAGAIYAN SEKAR

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      We have thoroughly investigated the first, second and third polarizability characteristics of four hybrid chromophores by spectroscopic and computational methods. B3LYP, CAMB3LYP and BHandHLYP functionals in combination with 6-311+G(d,p) basis set were used to evaluate the polarizability and hyperpolarizability characteristics of these chromophores. Generalized Mulliken Hush analysis and frontier molecular orbital electronic distribution images of chromophores obtained from Density functional theory computation has established the charge transfer characteristics of these hybrid chromophores. On the basis of charge transfer characteristic, these red absorbing and NIR emissive chromophores possess high nonlinear optical response. Comparison of isolated units with their analogous hybrid chromophores shows that fusion ofcoumarin with BODIPY enhances the nonlinear optical response.

    • Fluorescent vinyl and styryl coumarins: A comprehensive DFT study of structural, electronic and NLO properties

      KIRAN AVHAD AMOL JADHAV NAGAIYAN SEKAR

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      Nonlinear optical properties of 3-styryl and 3-vinyl coumarin dyes have been investigated with Density Functional Theory (DFT) using global hybrid (GH) and range-separated hybrid (RSH) functionals. The performance of GHs - B3LYP, BHHLYP, PBE0, M06, M06L, M062X, and M06HF and RSHs - CAM-B3LYP,HISSbPBE, HSEH1PBE, wB97, wB97X, and wB97XD in combination with 6-311++G(d,p) basis set has been analyzed. Estimated (hyper) polarizability (α0, β0) obtained from the GHs - M06, M062X and PBE0 are in agreement with each other. The RSHs - wB97 and wB97X estimate very close values of β0. The β0 value of 3-styryl and 3-vinyl coumarins reaches the maximum as the bond length alternation and bond order alternation parameters tend to zero. Natural bond orbital analysis shows there is extensive charge transfer in the excitedstate leading to large value of β0. The vibrational contribution to α0 and β0 is significantly less when the donor is methoxy group and acceptor is nitro group in the 3-styryl coumarin. The dye, (E)-7-(diethylamino)-3-(4-nitrostyryl)-2H-chromen-2-one (3c) is found to give the highest NLO response. An increasing electrophilicity originating from the decreased HOMO-LUMO band gap leads to an increase in α0 and β0 in all the cases.

    • Investigation of photophysical, structural aspects and nonlinear optical properties of Foron blue SR analogs using Density Functional Theory (DFT)

      ARCHANA A BHAGWAT NAGAIYAN SEKAR

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      Analogs of 2-[(2Z)-2-[[4-(dihexylamino)-2-methylphenyl]methylidene]-1,1-dioxo-1-benzothiophen-3-ylidene]propanedinitrile (Foron blue SR, Disperse Blue 354) are studied in terms of photophysical,structural aspects and its nonlinear optical properties evaluated by using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT). The structures were optimized by using function B3LYP and basis set used was 6-31G(d). Polarizability (α), first and second order hyperpolarizability (β and γ ) was determined by three density functionals B3LYP, CAM-B3LYP and BHandHLYP. B3LYP functional and the basis set 6-311+G(d,p) shows high values of α, β and γ . The B3LYP functionalgives the highest first order hyperpolarizability value for (Z)-2-(2-(4-(dimethylamino)benzylidene)-1,1-dioxidobenzo[b]thiophen-3(2H)-ylidene)malononitrile (3a) is 373.31 × 10-30 e.s.u and 486.32 × 10-30 e.s.uin ethylacetate and dimethylformamide respectively. Effect of bond length alteration (BLA) and bond order alteration (BOA) on first order hyperpolarizability was evaluated. Intrinsic hyperpolarizability shows the compound (Z)-2-(4-(dimethylamino)benzylidene)benzo[b]thiophen-3(2H)-one 1,1-dioxide (1a) intrinsically good. Perturbation potential is found to decrease as absorption energy deceases and hyperpolarizability increases

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