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Phthalazine-trione as a blue-green light-emitting moiety: crystal structures, photoluminescence and theoretical calculations

Abstract

Phthalazine (2,3-diazanaphthalene) and phthalhydrazide (2,3-dihydro-1,4-phthalazinedione) compounds are heterocycles with several biological properties. Most recently, analogous phthalazine-triones have also emerged as drug candidates. Here we introduced phthalazine-trione moiety as a promising fluorophore in the blue and green spectral regions, besides rationalizing this desired optical property based on their crystal structure and time-dependent density functional theory (TD-DFT) calculations. Under ultraviolet (UV) excitation (ca. 360 nm), two light emission maxima at ca. 460 nm and 480 nm were observed for ten phthalazine-triones, regardless of the substitution pattern. This conservation in the light-emitting property was rationalized by our time-dependent DFT calculations for the three phthalazine-triones whose crystal geometries were also determined here (4-chlorophenyl, 3-methoxyphenyl and4-nitrophenyl derivatives) and those available in literature (4-fluorophenyl and 4-bromophenyl derivatives). Electronic transitions with the largest oscillator strengths were near to 360 nm, in excellent agreement with the experimental excitation energy (UV-Visible and photoluminescence spectra). Also, lifetime values of sellected samples could be determined, being between 1.59 ns and 3.21 ns. In all compounds, the frontier molecular orbitals involved in these excitations are distributed over the phthalazine-trione moiety and are not localized on the changeable substituent.

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Publication details

The article was received on 14 Jun 2018, accepted on 03 Dec 2018 and first published on 04 Dec 2018


Article type: Paper
DOI: 10.1039/C8NJ02976H
Citation: New J. Chem., 2018, Accepted Manuscript
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    Phthalazine-trione as a blue-green light-emitting moiety: crystal structures, photoluminescence and theoretical calculations

    F. T. Martins, L. J. Q. Maia, G. Gasparotto, A. K. S. M. Valdo, J. A. do Nascimento Neto, L. Ribeiro, Y. de Freitas Rego, C. da Silva and A. de Fatima, New J. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C8NJ02976H

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