Quantum-Chemical Study of Aggregation of 5-(4-Dimethylaminobenzylidene)Barbituric Acid

Birimzhanova D.A. Irgibaeva I.S. Barashkov N.N.
2023 E.A. Buketov Karaganda University Publish house

Eurasian Journal of Chemistry
2023 #111 Issue 3 114 - 121 pp.

Decreasing fluorescence efficiency in the solid-state is general and is mainly attributed to the intermolecular vibronic interactions, which induce the nonradiative deactivation process. Whereas the isolated dye molecules are virtually non-luminescent in dilute solutions, they become highly emissive upon solution thickening or aggregation in poor solvents or in the solid-state show an increase of luminescence intensity, the phenomenon of the aggregation-induced emission (AIE phenomenon). The development of efficient luminescent materials is a topic of great current interest. Theoretical calculation shows that the dye molecules aggregation-induced emission characteristics result from intermolecular interactions. Utilizing such features, the molecules can be employed as fluorescent probes for the detection of the ethanol content in aqueous solutions. Quantum-chemical calculations using the method of density functional theory the computations of structure and electronic spectra of aggregated forms of 5-(4’-dimethylaminobenzylidene)barbituric acid and the Gaussian 98 program packages have been performed. The unusual spectral behavior of 5-(4’-dimethylamino-benzylidene)barbituric acid was investigated theoretically by the DFT method and its time-dependent variant TDDFT. Carried out calculations using Zindo, as well as ab initio calculations, confirm the appearance of a new band during aggregation and its shift to the red region when the number of molecules increases.

aggregation-induced emission , barbituric acid , dye molecules , electronic spectra , electronic states , hydrogen bond , theoretical study , valence vibrations

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