الفهرس 
Experimental and theoretical studies on the structure and spectral properties of 5-(3-PHENYL-2- Propenylidene)-2-THIOXO-4- thiazolidinone derivatives
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Abstract
A conformational analysis of 5-(3-phenyl-2-propenylidene)-2-thioxo-4- thiazolidinones (5pR-PPTT, R = H, Cl, CH₃, CH₃O, and N(CH₃)₂) compounds in gasphase has been performed at the LC-wPBE/6-311+G(d,p) level and the relative energies (xE) of the four possible configurational isomers (namely ZE; ZZ; EZ; and EE) resulted from rotations around C-C double bonds have been estimated. The planar conformations (ZE and EE) are found to be more stable than the nonplanar ones (EZ and ZZ) and the ZE conformation is the most stable isomer for all studied derivatives. The optimized structures of the thione, thiol, and enol tautomers and the corresponding thione-thiol and thione-enol transition states of the ZE isomer of the parent molecule (5pH-PPTT) were calculated. It was found that the calculated geometry of the thione form is in good agreement with the crystal structure data suggesting the predominance of the thione tautomer. The substituent and solvent effects on the relative stabilities of the three tautomeric forms of 5pR-PPTT (R = H, Cl, CH₃, CH₃O, and N(CH₃)₂) were investigated. The relative stabilities were found to be in the order thione{uFF1E} thiol {uFF1E} enol in gas phase as well as in solutions. UV-Visible absorption spectra of four of 5pR-PPTT (R = H, CH₃, CH₃O, and N(CH3)₂) were measured in different solvents. A benchmark evaluation against experimental results on the accuracy of different DFT functionals in predicting both reliable ground state geometries and electronic absorption spectra is carried out. The benchmark of the geometric structure indicated that long-range corrected hybrid functionals are found to be the most satisfied functionals. The best agreement with x-ray data is achieved by using the LC-wPBE functional. from a spectral point of view, we found that PBE0 provides the most accurate {uFF7D} max for the studied compounds. It was found that the expansion of the лconjugation system at position 5 of Rd ring leads to significant bathochromic shift. It was concluded that the red shifting of {uFF7D} max is mainly regulated by the solvent polarizability and much less by solvent polarity