Electronic spectra of phenyl‐, 3‐pyridyl‐, furfuryl‐, and 2‐theinyl‐imino derivatives of thiazole: Molecular orbital treatment (original) (raw)
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Electronic Structure and Physico-Chemical Property Relationship for Thiazole Derivatives
Electronic structure, effect of the substitution and structure physico-chemical property relationship for thiazole derivatives, has been studied by ab initio and DFT method. In the present work, the calculated values, i.e., net charges, bond lengths, dipole moments, electronaffinities, heats of formation and QSAR properties, are reported and discussed in terms of the reactivity of thiazole derivatives.
2019
In the present study, ethyl-2-(2-(2-methylbenzylidene)hydrazinyl)thiazole-4-carboxylate (1) and ethyl-2-(2-(4-bromobenzylidene)hydrazinyl)thiazole-4-carboxylate (2) were synthesized. The characterization of synthesized compounds was accomplished by employing analytical techniques of spectroscopy as 1H-NMR, 13C-NMR, FT-IR, UV-Vis and final confirmation was furnished using single crystal X-ray diffraction (SC-XRD) technique. The informations regarding optimized geometry, nonlinear optical (NLO) properties and frontier molecular orbitals (FMOs) were obtained by applying B3LYP level of DFT and 6-311+G(d,p) basis set. As a whole, the computed results from DFT were found in close agreement to that of experimental results. The combination of B3LYP level of time dependent DFT (TDDFT) and 6-311+G (d,p) basis set were employed for computational calculations of vertical electronic transition states. The stability on account of hyperconjugation and charge delocalization factors was evaluated through the study of natural bond orbitals (NBO). The capabilities of the title compounds withrespect to charge transfer and involvement of various sites in chemical activities were evaluated quantitatively by employing the analysis involving frontier molecular orbitals (FMOs). The studies revealed that the compounds possess sizable NLO character as the NLO properties of urea molecule were found smaller as compared to the compounds under investigation which means that such compounds are significant in perspective of technology applications.
Revue Roumaine de Chimie, 2019
The equilibrium geometries of 1,3,4-thiadiazole derivatives have been determined and analyzed at DFT level employing B3LYP/6-31G(d) basis set. The molecular electrostatic potential surface (MESP) that reveals centers of reactivity of the molecule and substitution effects of the molecular system have been studied using the HSAB principle (Hard Soft Acid and Base).Results such us, fundamental vibrational modes, 1 H NMR isotropic chemical shifts, frontier orbital energies (HOMO, LUMO), band gap energy, dipole moments, net charges are reported and discussed in terms of reactivity of 1,3,4-thiadiazole derivatives. The HOMO and LUMO analysis were used to elucidate information regarding charge transfer within the molecule. Isotropic chemical shifts were calculated using the Gauge-Independent Atomic Orbital (GIOAO) method. Finally, a comparison between the experimental data and the calculated results appeared a good agreement and show exceptional reactivity.
Research Journal of Pharmaceutical, Biological and Chemical Sciences
Geometric and electronic structure of oxazole and thiazole and the effect of methyl group substitution in thiazole and oxazole have been studied by PM3, ab initio method and density functional Theory. In the present work, the calculated values, namely net charges, bond length, dipole moments, ionization potentials, electronaffinities and heats of formation are reported and discussed in terms of the reactivity of oxazole and thiazole systems. Keywords: PM3, DFT, HOMO, LUMO, oxazole and thiazole
Journal of Molecular Structure, 2001
Single-crystal X-ray diffraction studies are reported for 3,4-diphenyl-1,2,5-thiadiazole 1-monoxide (I). Ab initio MO calculations on the electronic structure, conformation and reactivity for this compound are also reported and compared with the X-ray results. A charge sensitivity analysis is performed on the results applying concepts derived from density functional theory (DFT), obtaining several sensitivity coef®cients such as the molecular energy, net atomic charges, global and local hardness, global and local softness and Fukui functions. With these results and the analysis of the dipole moment and the total electron density and electrostatic potential maps, several conclusions have been inferred about the preferred sites of chemical reaction of the compound. q
Journal of Sulfur Chemistry, 2020
It has been uncovered that compounds containing thiazole moiety display noteworthy biological properties, which have attracted the attention of many researchers in chemical biology as well as in medicinal chemistry. In the current examination, ten 2-(2hydrazineyl)thiazole derivatives were studied using density functional theory (DFT). The geometry of all ten molecules was optimized by employing the DFT method with the B3LYP/6-311G (d,p) basis set. For the detailed structural and spectroscopic examination, the (E)-4phenyl-2-(2-(1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-ylidene)hydrazineyl)thiazole (PIFHT) was studied as a representative molecule. The bond lengths and bond angles of the PIFHT molecule were discussed for the detailed understanding of the structural entities. The electronic parameters of all ten molecules were analyzed by computing HOMO and LUMO pictures. Using frontier molecular orbital analysis, spectroscopic and quantum chemical parameters were evaluated and discussed to explore the chemical reactivity of the molecules. Besides, absorption energies, oscillator strength, and electronic transitions of PIFHT molecule were explored using time-dependent density-functional theory (TD-DFT) at the B3LYP/6-311G (d,p) level of theory in the gas phase, dichloromethane, and dimethyl sulfoxide solvents. The TD-DFT computed theoretical UV-Visible spectra of the PIFHT molecule were compared with the experimental UV-Visible spectra. The scaled vibrational frequencies were compared with the experimental frequencies for the assignment of the vibrational bands. The comparisons between computed and experimental UV-Visible and IR spectral results are gratifying. The molecular electrostatic surface potential plots were computed for locating the reactivity sites. Mulliken atomic charges were also studied for acquiring insights into charge density.
Physical Chemistry Chemical Physics, 2010
A detailed spectroscopic and photophysical study has been carried out on a series of heterocyclic compounds-known to display nonlinear optical properties-consisting on a electron donating thienylpyrrolyl p-conjugated system functionalized with an electron acceptor benzothiazole moiety. The absorption, emission and triplet-triplet absorption together with all relevant quantum yields (fluorescence, intersystem crossing and internal conversion), excited state lifetimes and the overall set of deactivation rate constants (k F , k IC and k ISC) were obtained in solution at room (293 K) and low (77 K) temperature. The optimized ground-state molecular geometries for the compounds together with the prediction of the lowest vertical one-electron excitation energy and the relevant molecular orbital contours for the compounds were also determined using density functional theory (DFT) at the B3LYP/3-21G* level. The experimental results showed that the photophysical properties are influenced by the relative position of the pyrrole and thiophene relative to the benzothiazole group.
A detailed spectroscopic analysis of two dichloro substituted phenyl-N-(1,3-thiazol-2-yl)acetamides at 2,4 and 3,4 positions of the phenyl ring has been carried out by using B3LYP method with 6-31+G(d, p) basis set within density functional scheme. The scaled theoretical wave numbers are in perfect agreement with the experimental values and the vibrational modes are interpreted in terms of potential energy distribution (PED). The internal coordinates are optimized repeatedly to maximize the PED contributions. The molecular HOMO-LUMO surfaces, their respective energy gaps, and MESP surfaces have also been drawn to explain the chemical activity of both molecules. Various thermodynamic parameters are presented at the same level of theory.
Charge transfer complexes of some thiazoles and benzothiazoles with certain nitrobenzene derivatives
Spectrochimica Acta Part A: Molecular Spectroscopy, 1990
Interaction of some thiazole and benzothiazole derivatives as donors with certain di-and trinitrobenzene derivatives as acceptors results in the formation of 1:l molecular species. The infrared, NMR and ultraviolet analysis of the complexes with non-acidic acceptors reveals the presence of R--A* interaction from a HOMO of the thiazole nucleus or the phenyl moiety of the benzothiazoles to a LUMO of the benzene ring of the acceptors. The existence of this type of interaction is supported by HMO calculations on the donor molecules. On the other hand, the molecular complexes derived from acidic acceptors are stabilized, in addition to the n-JC* interaction, by proton transfer from the hydroxyl or carboxylic group of the acceptor to the amino group of the aminothiazole donors. The ionization potentials of donors, electron affinities of acceptors as well as the energy of the CT complexes were computed from their U.V. and visible spectra.