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Pushkara Rao Varanasi

Bio: Pushkara Rao Varanasi is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Excited state & Ab initio. The author has an hindex of 1, co-authored 1 publications receiving 268 citations.

Papers
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TL;DR: In this paper, the first hyperpolarizabilities of a large number of push−pull substituted conjugated systems with heteroaromatic spacers were calculated at the ab initio level (4-31G basis) using the coupled perturbed Hartree−Fock approach and at the AM1 level employing the finite field method.
Abstract: First hyperpolarizabilities of a large number of push−pull substituted conjugated systems with heteroaromatic spacers have been calculated. The static, nonresonant components were computed at the ab initio level (4-31G basis) using the coupled perturbed Hartree−Fock approach and at the AM1 level employing the finite field method. Sum-over-states procedure has also been used with the AM1/CI method to compute β0 and β at an excitation energy of 1.17 eV. The computed β values at the various levels are reasonably similar and exhibit the same trends. The largest values are obtained with a donor on pyrrole and an acceptor on thiophene or thiazole. The variations do not always inversely follow the order of delocalization energies of the heterocyclic rings. The trends in the dipole moment changes and transition energies between the ground and first excited charge-transfer state primarily determine the variations in the computed β values.

271 citations


Cited by
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TL;DR: In this article, the tuning and structure-property relationships have been demonstrated on the particular A, π and D parts of the push-pull molecule, and special emphasis has been put on the tuning of the FMO levels and optical properties.
Abstract: Property tuning in selected examples of D–π–A molecules has been discussed and summarized in this review article. The tuning and structure–property relationships have been demonstrated on the particular A, π and D parts of the push–pull molecule. Special emphasis has been put on the tuning of the FMO levels and optical properties. Further prospective applications of the given chromophore have also been considered.

501 citations

Journal ArticleDOI
TL;DR: In this article, the linear and nonlinear optical properties of donor−acceptor π-electron chromophores having conjugated bridges varying in aromaticity and electron excessivity were investigated using the INDO/1 semi-empirical Hamiltonian.
Abstract: The linear and nonlinear optical properties of donor−acceptor π-electron chromophores having conjugated bridges varying in aromaticity and electron excessivity are investigated using the INDO/1 semiempirical Hamiltonian. NLO response properties of such chromophores are more sensitive to the electron excessivity of the bridges than to bridge aromaticity. Electron-excessive/deficient heterocyclic bridges have lesser/greater tendency to deplete the electron density from the donor/acceptor groups and thus increase their donor/acceptor ability. Thus, electron-excessive heterocyclic bridges act as auxiliary donors while electron-deficient heterocyclic bridges act as auxiliary acceptors, significantly enhancing NLO response. Interposing charged five-membered auxiliary donor and acceptor fragments between strong donor or acceptor groups results in large computed second-order NLO response.

342 citations

Journal ArticleDOI
TL;DR: A survey of NLO chromophores and materials incorporating them can be found in this article, where the authors provide a brief introduction explaining overall principles relating to the origin of second-order nonlinear optical properties.

338 citations

Journal ArticleDOI
TL;DR: In this paper, the first hyperpolarizability of several thiazole and thiophene analogues of donor−acceptor stilbene compounds using the ZINDO (sum-over-states) formalism was calculated.
Abstract: We calculate the first hyperpolarizability (β) of several thiazole and thiophene analogues of donor−acceptor stilbene compounds using the ZINDO (sum-over-states) formalism. Because of the inherent dipolar nature of thiazole, in which C2 is electron-poor and C5 is electron-rich, the relative orientation of the thiazole subunit in the dipolar chromophore dramatically affects the nonlinear optical properties. In the “mismatched” case, the dipole of the thiazole ring opposes the molecular dipole created by the donor−acceptor substituents, while in the “matched” case, the dipole of the thiazole ring reinforces the molecular dipole. The hyperpolarizability of the “mismatched” monothiazole 2 (βμ = 68 × 10-30 cm5 esu-1) exceeds that of stilbene 1 (βμ = 34 × 10-30 cm5 esu-1) but is smaller than that of monothiophene 4 (βμ = 90 × 10-30 cm5 esu-1). By contrast, the hyperpolarizability of the “matched” monothiazole 3 (βμ = 177 × 10-30 cm5 esu-1) exceeds not only that of the “mismatched” monothiazole 2, but also that ...

301 citations