Thione Form Research Articles

Synthesis, Characterization, Crystal Structure and Molecular Docking Studies of a S-methyldithiocarbazate Derivative: Bis[2-hydroxy- benzylidenehydrazono) (methylthio)methyl]disulfide

The title compound bis[2-hydroxybenzylidenehydrazono)(methylthio)methyl]disulfide (1), an S-methyldithiocarbazate derivative with a disulfide bond has been synthesized by the condensation of 2-hydroxybenzaldehyde with S-methyldithiocarbazate. It has been characterized by elemental analyses, 1H, 13C NMR and FT-IR spectroscopy and mass spectrometry. The single crystal X-ray structure shows that the compound exists in a tautomeric thione form with the dithiocarbazate fragment adopting an EE configuration with respect to the C=N bond of the benzylidene moiety. The thermal behaviour of the compound has been studied using thermogravimetric analysis (TGA). The molecular geometry of the compound in the ground state has been optimized using density functional theory (DFT/B3LYP) method with the 6-311++G(d,p) basis sets. Molecular docking of the compound with human carbonic anhydrase II has been performed to probe the nature of interaction.

Synthesis, spectroscopic characterization, DFT and antibacterial studies of newly synthesized cobalt(II, III), nickel(II) and copper(II) complexes with salicylaldehyde N(4)-antipyrinylthiosemicarbazone

Salicylaldehyde N(4)-antipyrinylthiosemicarbazone (H2L) and its complexes of Co(III, II), Ni(II) and Cu(II) have been prepared and characterized. Elemental analyses, molar conductivities, magnetic measurements, spectral (IR, UV–vis, 1H and 13C NMR and ESR) and thermogravimetric studies have been used to characterize the complexes. The infrared spectra show that the thiosemicarbazone ligand behaves as tridentate ligand (ONS), either in the thione or thiolato form. Stereochemistries are proposed for the complexes on the basis of both spectral and magnetic properties. Along with the experimental spectral data of the starting ligand, its corresponding predicted ones were obtained using the state of art density functional theory (DFT) in gas and solvent phases. The obtained results showed a relatively good correlation between the calculated and experimental spectral data. Some of the complexes showed antibacterial activity against Staphylococcus aureus and Escherichia coli representing Gram-positive and Gram-negative bacteria respectively when compared with Enrofloxacin as a standard antibiotic.

New Tridentate Schiff Base, Product of Condensation of 4-Methyl-7-hydroxy-8-formylcoumarin and N-Aminomercaptotriazole: Synthesis, Structure, and Complex Formation

A new Schiff base was prepared by the reaction of 4-methyl-7-hydroxy-8-formylcoumarin with N-aminomercaptotriazole. In solution and in solid phase the compound was shown to exist in the thione form. The compound reacts with Cu(II), Ni(II), Zn(II) and Cd(II) ions depending on the metal salt to give complexes of composition ML2 or MHLX, where HL is monodeprotonated form of the ligand. Cu(II) and Ni(II) complexes were studied by spectral and magnetochemical methods. The Zn(II) and Cd(II) complexes exhibit fluorescence.

Structural studies and cytotoxic activity of a new dinuclear coordination compound of palladium(II)–2,2′:6′,2″‐terpyridine with rigid dianionic 1,2,4‐triazole‐3‐sulfonate linker

A new dinuclear coordination compound of palladium(II), [Pd2(terpy)2(μ‐tas‐N1,N4)]SO4⋅11H2O (1), was synthesized by tethering a doubly deprotonated 1,2,4‐triazole‐3‐sulfonate (tas) linker generated in situ via oxidation of 1,2,4‐triazole‐3‐thione (tat) under the synthetic conditions. X‐ray diffraction analysis reveals that tat molecules adopt the thione form in the solid state, and are combined in infinite chains by symmetrically related classical intermolecular hydrogen bonds N1─H1⋅⋅⋅S1, N3─H3⋅⋅⋅N2 to give rise to R22(7) pattern in one‐dimensional chains along the b‐axis propagating along the a‐axis. Further short contacts through lone pairs of N2⋅⋅⋅S1 on the rings between the adjacent chains along the a‐axis lead to a two‐dimensional network structure. Compound 1 was characterized using infrared, 1H NMR and UV–visible spectroscopies, electrospray ionization mass spectrometry and X‐ray crystallography. The crystal structure determination of 1 reveals that the Pd(II) ions are coordinated with four nitrogen atoms: three from terpy and one from tas acting as an end‐to‐end (μ‐1,4) bridging ligand. The Pd(II) ions in 1 adopt a distorted square planar geometry. The anti‐growth effect of 1 was tested on colorectal cancer (HCT‐15), non‐small‐cell lung cancer (A549), prostate cancer (PC‐3) and cervical cancer (HeLa) cell lines using sulforhodamine B viability assay. The cytotoxic effect was further confirmed using adenosine triphosphate viability assay. Compound 1 shows a promising cytotoxic activity in the diverse cancer cell models in vitro (p <0.0001).

UV and Resonance Raman Spectroscopic and Theoretical Studies on the Solvent-Dependent Ground and Excited-State Thione → Thiol Tautomerization of 4,6-Dimethyl-2-mercaptopyrimidine (DMMP)

The vibrational spectra of 4,6-dimethyl-2-mercaptopyrimidine (DMMP) in acetonitrile, methanol, and water were assigned by resonance Raman spectroscopy through a combination of Fourier-transform infrared spectroscopy (FT-IR), FT-Raman UV-vis spectroscopy, and density functional theoretical (DFT) calculations. The FT-Raman spectra show that the neat solid DMMP is formed as a dimer due to intermolecular hydrogen bonding. In methanol and water, however, the majority of the Raman spectra were assigned to the vibrational modes of DMMP(solvent) n ( n = 1-4) clusters containing NH···O hydrogen bonds. The intermolecular NH···O hydrogen bond interactions, which are key constituents of the stable DMMP thione structure, revealed significant structural differences in acetonitrile, methanol, and water. In addition, UV-induced hydrogen transfer isomeric reactions between the thione and thiol forms of DMMP were detected in water and acetonitrile. DFT calculations indicate that the observed thione → thiol tautomerization should occur easily in lower excited states in acetonitrile and water.

IR spectroscopy study of SBA-15 silicas functionalized with the ethylthiocarbamidepropyl groups and their interactions with Ag(I) and Hg(II) ions

Mesoporous structure of silica is determined by the type of template, but the introduction of functional groups during the synthesis has additional influence. The structure of SBA-15 may be violated by the introduction of long functions, such as ≡Si(CH2)3NHC(=S)NHC2H5. These ethylthiocarbamidepropyl groups can form complexes with metal ions in thiol or thione tautomeric forms. We determined that the 2D hexagonal p6 mm structure is preserved for SBA-15 with thiourea groups at maximal TEOS:trifunctional silane ratio (mol) = 10:2, which was confirmed by TEM and by the presence of an intense reflex in the small-angle region of diffractograms of the final product. It was shown that the obtained sorbents possess high kinetic characteristics. The experimental data fit pseudo-second-order kinetic equation, but the rate constants depend on the content of functional groups in the surface layer. Template Pluronic P-123 defines the porosity of functional mesoporous silica materials even at increasing content of trifunctional silane in the initial solution. Infrared spectroscopy analysis showed that thione form of thiourea ligand is prevalent on the surface of pores of mesoporous samples. However, during the sorption of silver(I) ions, there are both thione and thiol forms on the surface. Thione form is transformed into thiol with increasing concentration of mercury(II) ions in the sorption solution. Adsorption experiments showed that the SBA-15 silicas functionalized with ethylthiocarbamidepropyl groups had high selectivity for silver(I) ions and could concentrate Ag(I) ions from metal ions mixture at pH ~ 2.

Thermochemistry of R-SH group in gaseous phase: Experimental and theoretical studies of three sulfur imidazole derivatives

Abstract In the present work, we report the standard combustion energies of 2-mercapto-1-methylimidazole, 2-mercapto-5-aminobenzimidazole and 2-mercapto-5-methoxybenzimidazole, obtained experimentally from measurements with a rotatory-bomb combustion calorimeter. With these data, for each one of the three aforementioned compounds, the corresponding standard molar combustion enthalpies and the standard molar enthalpies of formation, in the crystalline phase, are calculated. The enthalpies of sublimation of each compound, obtained experimentally using a Calvet Setaram HT 1000 microcalorimeter, are also reported. Using the values of the enthalpies of formation in the crystalline phase and the enthalpies of sublimation, both at 298.15 K, for each compound, the corresponding standard molar enthalpies of formation in gas phase were calculated. Complementary, the enthalpies of formation in the gaseous phase were derived from theoretical calculations made with Gaussian-n composite methodology with n = 3 and 4. The experimental and computational studies suggest that in gaseous phase, the form more stable of each compound is the thione form.

Controlled light-driven switching in 2-thiobenzimidazole

The optically-controllable reversible single-molecule photoswitching in 2-thiobenzimidazole (C7H6N2S; 2TBI) is experimentally demonstrated. Monomers of the target compound were isolated in low temperature argon matrices and investigated by infrared spectroscopy. After matrix deposition, only the thione tautomer of the compound was observed. Such result is in accordance with the predicted relative energy of the two tautomers (thione and thiol forms; ΔE(thiol-thione) = 44.6 kJ mol−1, as obtained at the DFT(B3LYP)/6−311 + +G(d,p) level of approximation). In situ irradiation of the initially deposited matrix at λ = 307 nm, using an UV tunable narrowband light source, led to conversion of the thione form of 2TBI into the thiol tautomer. In turn, subsequent irradiation at λ = 246 nm resulted in the reverse, thiol→thione, photoconversion, demonstrating that the two tautomers can be selectively interconverted through optical control. Noteworthy, both photoprocesses take place without simultaneous significant photodecomposition of the compound, thus making this chemical system a promising candidate for acting as a molecular switch. The observed phototautomerizations are rationalized in terms of the Photo-Induced hydrogen-atom Detachment-Association (PIDA) mechanism.

An insight into methimazole phototautomerism: Central role of the thiyl radical and effect of benzo substitution

The thione/thiol tautomerism in methimazole (1-methyl-2-thioimidazole; MTI) and 1-methyl-2-thiobenzimidazole (MTBI) has been investigated by matrix isolation infrared spectroscopy and quantum chemical calculations performed at the DFT(B3LYP)/6-311++G(d,p) level. The two compounds were shown to pass to the gas phase from the crystalline state, where they exist in the thione form, upon sublimation, without tautomerizing. The thione form of the compounds could then be isolated in the cryogenic matrices and vibrationally characterized. Narrowband UV-irradiation of the thione forms at 261 or 307 nm, for MTI and MTBI, respectively, allowed their conversion into the corresponding thiol forms, which were observed experimentally for the first time and could then be also characterized vibrationally in details. MTBI thiol could subsequently be converted back to the thione form upon irradiation at 246 nm, while the thiol→thione tautomerization could not be induced for MTI. The experimental results were rationalized in terms of the PhotoInduced Detachment Association (PIDA) mechanism and taking into account both the structures of the thiyl radicals resulting from the photodetachment process and the effects due to the benzo-substituent. In the case of MTI, besides the photoinduced thione→thiol tautomerization, photofragmentation was observed, through imidazole ring disassembling, yielding N-vinylidenemethanamine (NVM). On the whole, this study aims to further understanding on thione/thiol tautomerism and photochemistry of thiones and thiols.

Anti‐neurotoxic evaluation of synthetic and characterized metal complexes of thiosemicarbazone derivatives

Quinoline‐2‐caboxyaldehyde thiosemicarbazone (HL1) and quinoline ‐2‐caboxyaldehyde N‐dimethyl thiosemicarbazone (HL2) metal complexes were prepared and characterized using analytical and spectroscopic techniques. The measurements showed that ligands behave as monovalent or neutral tridentate ligands bonding via azomethine, quinoline ring nitrogen atoms and sulfur atoms in thiol or thion forms. The anti‐neurotoxic effect of ligands and their complexes showed that, exposure to aluminum increase oxidative stress in the brain, an effect that could be offset by concomitant thiosemicarbazone complexes. Complexes could be having an effect on absorption or excretion of aluminum, due to their chelating activity. These findings may shed light on the potential clinical importance of thiosemicarbazone complexes in Alzheimer's disease.

SYNTHESIS, SPECTRAL AND QUANTUM CHEMICAL RESEARCHES OF (Z)-10-(2-(4-AMINO-5-THIOXO-4,5-DIHYDRO-1H-1,2,4-TRIAZOLE-3-IL)HYDRAZONO)-9-PHENANTHRONE

(Z)-10-(2-(4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-il)hydrazono)-9-phenanthrone (I) was obtained by a condensation of 4-amino-5-hydrazino-4H-1,2,4-triazole-3-thiol with 9,10-phenanthrenequinone. The compound I was characterized by IR, UV-VIS, 1Н, 13С NMR and chromatography-mass spectrometry. The electronic absorption spectra of I in aproton solvents (DMF, DMSO) are characterized by the existence of an intensive long-wave band in the range of 468 - 485 nm. The absorption maximum of a freshly prepared solution of I (485 nm) after 48 h gradually undergoes hypsochromic shift to 474 nm, and after 72 h it shifts to 468 nm. In the UV-VIS spectrum of I, at addition of NaOH the batochromic shift of a long wave band to 511 nm with a significant increase in intensity is observed. The presence of one isobestic point in the spectrum indicates the formation of a mono-anion. In the UV-VIS spectrum of I at addition of HCl solution, the long wave absorption band undergoes hypsochromic shift to 376 nm with a small decrease in intensity. In the 1Н NMR spectrum of I, in the range of 15.08 ppm a singlet signal of a proton of a hydrazo-group is observed. In the 13С NMR spectrum of I, in the range of 180.80 ppm a signal which corresponds to carbonyl C-atom is observed. Quantum chemical modeling of the electronic structure of I as well as its ionic forms was performed in the frames of the density functional theory approach (DFT) using of a hybride tri-parametric exchange Becke functional with a correlational Lee-Yang-Parr functional (B3LYP) and basis sets def2-SV(P), def2-TZV(P). According to the spectral and quantum chemical studies, in the crystalline state and saturated solution the compound I exists in the form of the thione quinone hydrazone tautomer stabilized by intramolecular hydrogen bonds. The thione tautomer is 44 kJ/mol more stable than a thiol tautomer, the transition barrier is 135 kJ/mol. However, it is not possible to exclude possibility of transition of the thione form into the thiol one in the diluted solutions. Forcitation:Polyanskaya N.A., Ryabov M.A., Strashnov P.V., Linko R.V., Davydov V.V., Kobrakov K.I., Karavaeva E.B. synthesis, spectralandquantumchemicalresearchesof (Z)-10-(2-(4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-il)hydrazono)-9-phenanthrone. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 55-65

UV-Induced Hydrogen-Atom-Transfer Processes in 3-Thio-1,2,4-triazole Isolated in Ar and H2 Low-Temperature Matrixes.

The UV-induced thione → thiol phototautomeric reaction has been studied for monomeric 3-thio-1,2,4-triazole (3-ST) isolated in low-temperature Ar and n-H2 (normal hydrogen) matrixes. Prior to any UV irradiation, monomers of 3-ST isolated in solid Ar or solid n-H2 adopted mainly the most stable thione tautomeric form, as revealed by the IR spectra. Upon UV (λ > 275 nm) irradiation of 3-ST isolated in Ar matrixes, the IR bands due to this thione form decreased, while a set of initially weak bands increased in intensity. Growing bands indicated generation of a photoproduct, which was identified as the thiol tautomer with labile hydrogen atoms attached to sulfur and N(2) atoms. The UV-induced spectral changes allowed also identification of another minor thiol tautomer of 3-ST, which was present in the matrix prior to any irradiation and did not change its population upon exposure to UV light. The identification of the observed isomeric forms was supported by comparison of their separated experimental IR spectra with the spectra theoretically predicted for the various structures of 3-ST. The thione → thiol phototautomerization that was the main UV-induced process observed for 3-ST in Ar matrixes did not occur for monomers of the compound trapped in solid n-H2.

1,2,4-triazole derivative with Schiff base; thiol-thione tautomerism, DFT study and antileishmanial activity

Thiol-thione tautomerism of 1,2,4-triazole derivative with Schiff base was investigated by spectroscopic methods and quantum mechanical calculations. Theoretical study of thiol-thione tautomeric forms of 1,2,4-triazole derivative with Schiff base; 1,2,4-triazole-thiol form, 1-((5-mercapto-4-(thiophene-2-ylmethyleneamino)-4H-1,2,4-triazole-3-yl)methyl)-3-(thiophene-2-ylmethyl)-4-(thiophene-2-ylmethyleneamino)-1H-1,2,4-triazole-5(4H)-one (I) and 1,2,4-triazole-thione form, 3-(thiophene-2-ylmethyl)-4-(thiophene-2-ylmethyleneamino)-1-((4-(thiophene-2-ylmethyleneamino)-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-yl)methyl)-1H-1,2,4-triazole-5(4H)-one (II) was performed by the density functional theory (DFT) method with 6–311++G(d,p) basis set. Structural parameters were obtained and spectral parameters of NMR, FTIR and UV–vis were compared with experimental ones to determine structural details. In vitro antileishmanial activity was studied against Leishmania infantum promastigots by microdilution broth assay with Alamar Blue Dye. The results indicate that 1,2,4-triazole derivative exists in both thiol and thione form and, can be evaluated as antiparasitic in term of antileishmanial activity.

Tautomerism and isomerism in some antitrichinellosis active benzimidazoles: Morphological study in polarized light, quantum chemical computations

The morphology of the crystal structure of some antitrichinellosis active benzimidazole derivatives including (1H-benzimidazol-2-ylthio)acetic acids, [1,3]thiazolo[3,2-a]benzimidazol-3(2H)-ones, 1H-benzimidazol-2-ylthioacetylpiperazines and starting 2-mercapto benzimidazoles, was studied by the use of Polarized Light Microscopy (PLM). Characterization of the crystal phase was complimented by Differential scanning calorimetry analysis (DSC) and spectroscopic data. DFT computations were performed in order to investigate the prototropic tautomerism and the geometry of the molecule of the synthesized compounds.One distinct type of crystal structure for each one of 5 or 6-methyl-(1H-benzimidazol-2-ylthio)acetic acid 6 was observed by PLM – dendritic and needle-shaped formations. Compound 14, containing a methyl substituent in the benzimidazole ring crystallized also into two phases; while for the unsubstituted compound 13 a separation of phases does not take place. The influence of the both solvents - chloroform and ethanol on the phase separation and the formation of the crystalline structure of compound 14 was investigated.The morphological study showed that the cyclization of 6 in the presence of acetic anhydride in pyridine medium led to a mixture of 6-methyl-[1,3]tiazolo[3,2-a]benzimidazol-3(2H)-one (10a) and 7-methyl-[1,3]thiazolo[3,2-a]-benzimidazole-3(2H)-one (10b), which crystallized in the form of fibrils and spherulites respectively.It was found that a difference in the crystal structures of substituted and unsubstituted benzimidazol-2-thiones, respectively benzimidazol-2-thiol derivatives exists, which may be due not only to the thiol-thione tautomerism but to the prototropic properties of the hydrogen atom in first position of the ring. The calculation results indicated that the thione form is more stable than the thiol tautomer by 51–55 kJ mol−1. But at the same time ΔG for the two thiol tautomers is below 0.5 kJ mol−1. In solid phase the 5(6)-substituted-1H-benzimidazol-2-thiols crystallized in two different crystal structures while the unsubstituted 1H-benzimidazol-2-thiol possess one type of crystal structure.

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis, Structural Characterization, Acid‐base, and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl2 (1), Ni(HL)Cl2 (2), Cu(HL)Cl2 (3), and Zn(HL)3Cl2 (4) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the CuII complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1, 2, and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the ZnII ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine CoII, NiII, and ZnII complexes in 10/90 (v/v) DMSO/water solution, whereas the CuII complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with CoII, NiII and ZnII, the 2:1 species with CoII and ZnII, and the 3:1 species with ZnII. A distorted tetrahedral arrangement of the CuII complex was suggested on the basis of EPR and Vis/NIR spectra.

Synthesis, characterization, molecular modeling and biological activity of metal complexes derived from (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide

A new series of some biologically active Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes was synthesized from the novel thiosemicarbazone ligand; (E)-N'-(furan-2-ylmethylene)morpholine-4-carbothiohydrazide (HL). Elemental, spectral, thermal analyses, magnetic susceptibility and molar conductivity measurements were used to elucidate the structure of separated compounds. The data prove that the ligand reacts with all metal ions in a neutral thione form. The electrolytic tetra-coordinate Cu(II); Zn(II) complexes (5, 6; 10) bind through the thione sulfur, furfural oxygen and azomethine nitrogen atoms of the ligand (NSO type) to construct fused five membered rings. However, the rest non-electrolyte octahedral complexes chelate via the furfural oxygen and azomethine nitrogen atoms of the ligand (NO type). Molecular modeling was conducted for the ligand and two representative complexes (1, 5) in order to substantiate their chemical structures. Thermal analyses are compatible with molecular modeling studies to support the proposed thermal decomposition pathways of metal complexes which start with the rupture of the long and weak N–NH bond. The thermal stability of metal complexes varies according to the number of solvents of crystallization, ionic radii and steric effect of anions. The ESR spectra of Cu(II) complexes are compatible with a primarily (dx2–y2)1 ground state with axial symmetry. The ligand and its Co(II); Cu(II); Cd(II) complexes (1; 5, 8; 11) along with their mixtures with metaldehyde were screened in vitro for their molluscicidal activity against Eobania vermiculata. Combination with metaldehyde enhances the toxicity effect of the tested compounds through reducing the period required for mortality and increasing the percentage of mortality after 24 h of treatments. The tested compounds gathered with metaldehyde are strongly affecting on the activity of ACP and ALP enzymes and TP content which are very important factors in the mucous secretion of Eobania vermiculata. These effects lead to excess mucous secretion, causing dryness and death for the snails.

Blue-light induced CO releasing properties of thiourea based manganese(I) carbonyl complexes

A new class of blue-light triggered carbon monoxide releasing molecules based on Mn(CO)3Br(N,S) ((N,S)=N,S-bidentate thiourea ligands) has been reported in this work. The 1H and 13C NMR analysis indicated that the thioureas coordinate to Mn(I) in the thione form. The stability test and the ability to derive CO to DMSO and myoglobin solution upon the exposure to 468nm light source have been investigated. The benzothiazole-thiourea-CORM released only one CO equivalent, while the pyridine-analogs offered two molecules at the same experimental conditions. Natural bond orbital analysis has been carried out to give details about the hybridization of MnC and CO bonds, natural charge, electronic arrangement of metal ion and strength of interaction between Mn(I) and the coordination sites. Both functional, B3LYP and CAM-B3LYP compare well with the experimental findings, where the longest wavelength band is assigned to MLCT.

Energetic, structural and tautomeric analysis of 2-mercaptobenzimidazole

This paper reports an experimental and theoretical study about the energetic and structural characteristics of the 2-mercaptobenzimidazole (MBI) tautomeric forms (thione and thiol). The standard (p° = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, in the gaseous phase, for MBI was derived from its enthalpies of combustion and sublimation, obtained by rotating-bomb calorimetry and by the Knudsen effusion technique, respectively. The results are compared with the corresponding data for MBI thione/thiol tautomers calculated by the G3(MP2)//B3LYP approach that suggest the thione form as the preferred form of MBI in gaseous phase. Computationally, the molecular structures of both tautomers were established and the geometrical parameters were determined at the B3LYP/6-31G(d) level of theory. In addiction, the G3(MP2)//B3LYP tautomerization energy at 0 K for thione/thiol forms of MBI was calculated and also evidences that the tautomeric equilibrium favours the thione tautomer. The standard Gibbs energy of formation in crystalline and gaseous phases was also derived, allowing an analysis of the thermodynamic stability of MBI in comparison with other related compounds.

Theoretical study addressing the effects of tautomerism and explicit/implicit water molecules on NQR and NMR parameters of tetrazole-5-thione.

DFT/B3LYP calculations were employed to study the effects of tautomerism and explicit/implicit water molecules on Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) tensors of nitrogen nuclei in tetrazole-5-thione structure. The obtained results revealed that nuclear quadrupole coupling constant (χ) and isotropic chemical shielding (σiso ) values of nitrogen nuclei in tetrazole ring of five possible tautomeric forms of tetrazole-5-thione, i.e. two thione forms called tautomers A and E and three thiol forms called tautomers B, C, and D, were functions of resonance energy(E2 ) values of nitrogen lone pairs. Furthermore, it was observed that by increasing participation of lone pairs of nitrogen atoms in the ring resonance interactions, the σiso values around them were increased, while their χ and qzz values were decreased. However, the results indicated that with exception of tautomer B, the order of qzz and χ values of nitrogen nuclei in tetrazole ring was exactly opposite of the order of resonance energy values for the same nitrogen nuclei in all tautomers and their mono-hydrated complexes. In addition, a significant decrease was noticed in χ and qzz values when a water molecule was put in different positions near the tetrazole ring in tautomers A-E. The mentioned result can be attributed to hydrogen bond formation between nitrogen nuclei and the oxygen of water. In mono-hydrated complexes, the σiso values around nitrogen atoms acting as hydrogen donors in hydrogen bond formation (N-H….OH2 ) were decreased, while its values were increased for nitrogen atoms acting as hydrogen acceptors in hydrogen bond formation(N….H-OH). Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, structural and spectral characterization, and in vitro nuclease activity of new thiosemicarbazone derivatives

Two new compounds, ( E )-2-(3-ethoxy-2-hydroxybenzylidene)hydrazinecarbothioamide (1) and ( E )- N -ethyl-2-((2-hydroxynaphthalen-1-yl)methylene)hydrazinecarbothioamide (2) have been synthesized. The prepared compounds have been characterized by CHN analysis, FT-IR, UV-Vis, 1 H and 13 C NMR spectroscopic techniques as well as the fluorescence emission spectroscopy. The molecular structures of the compounds have also been determined by X-ray single crystal diffraction analysis. The crystal structures revealed that the compounds are remain as a thione form in the solid state and are different in their geometrical, conformational and symmetrical structures. The nuclease activity of compounds to cleave pBR 322 has been investigated using agarose gel electrophoresis assay. The compound 2 revealed a significant nuclease activity which was attributed to the lipophilic properties that provided by substituent moieties of the compound.