Nonlinear optical (NLO) properties of thiazolopyrimidoquinoline derivatives containing different substituents on the benzene ring were studied. Correlation between the molecular structure and the dipole moment of compounds investigated by the Z-scan technique and density functional theory (DFT) of the Gaussian 09 program. All the structures were optimized at the M06-2X/6-311G level. It was found that one of the thiazolopyrimidoquinoline derivatives, 6-(3,4-dihydroxyphenyl)-9,9-dimethyl-1,2,6,9,10,11-hexahydro-5H-thiazolo[2\\\\\\\',3\\\\\\\':2,3]pyrimido[4,5-b]quinoline-5,7(8H)-dione (4a) has larger nonlinear absorption coefficient (β), nonlinear refractive index n2 and dipole moment compare to other derivatives, showing promising properties for NLO applications. The study on absorption and fluorescence also showed that compound 4a has a large base-level dipole. This situation occurred while the optical band gaps is the same (2.8±0.4 eV) for all compounds. Experimental and theoretical results confirmed that NLO properties of 4a related to the dipole moment.

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