Exocyclic Sulfur Atom Research Articles

Incorporating pH into DFT-D+U and microflotation recovery studies on heterocyclic collector-pyrite interactions

This study adopted both computational and experimental approaches to design by modification of 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO) and 2-mercaptobenzimidazole (MBI) heterocyclic collectors by introducing a carbon sulphide (–CS2) group and forming 2-trithiocarbonatebenzothiazole (TTCBT), 2-trithiocarbonatebenzoxazole (TTCBO) and 2-trithiocarbonatebenzomidazole (TTCBI) derivatives collectors. The adsorption behaviour of the heterocyclic collectors (and derivatives) on pyrite and subsequent hydrophobicity at different pH conditions were characterised using molecular modelling and microflotation approaches, respectively. The computational adsorptions were performed on dry and hydrated surfaces in their neutral thiolate and thione (acidic) form on the pyrite (100) surface. It was found that under dry and neutral conditions the TTCBONa and TTCBTNa were more exothermic, while under dry and acidic conditions the TTCBIH was more exothermic followed by MBIH and MBTH. Under hydrated and neutral conditions MBONa was predicted as the most exothermic, while for hydrated and acidic conditions MBTH, TTCBTH and TTCBIH were more exothermic. It was found that under acidic conditions, the heterocyclic collectors were more exothermic than for neutral condition on the hydrated surface. The microflotation at pH = 8 showed that MBO achieved higher recoveries, while at pH = 6 MBT, TTCBT and TTCBI achieved higher recoveries that could reach 90 %. The derivatives under acidic conditions were found to have good recovery performance, which showed that the introduction of a –CS2 group on the exocyclic sulphur atom improved the affinity and therefore hydrophobicity of the mercapto-heterocyclic collectors on the pyrite surface, and thus these derivatives can enhance the flotation of pyrite minerals. In addition, the computational predictions complimented by experimental recoveries are essential to a meaningful development of modelling as a tool in mineral processing reagent design.

DFT investigation of 2-mercaptobenzothiazole adsorption on model oxidized copper surfaces and relationship with corrosion inhibition

2-mercaptobenzothiazole (MBT) is known as an efficient corrosion inhibitor for copper. In the present work, we performed quantum chemical DFT calculations of the interaction of MBT on Cu(111) surfaces covered by an ultrathin Cu2O(111) film, in order to bring atomic scale insight on the corrosion inhibition properties of MBT on oxidized copper surfaces. Thione and thiolate forms of MBT are found to interact strongly with the oxidized surfaces. The formation of a monolayer at full coverage is favored over single molecular adsorption at low coverage with the molecules adopting a perpendicular orientation. Thione binds strongly via covalent bonding between the exocyclic sulfur atom and the under coordinated Cu site, and additional H-bonding between the NH group and surface oxygen atoms (NH…O H-bond). Thiolate binds more strongly via a second covalent bond between the N atom and saturated Cu site. Bonding interaction is confirmed by the electronic structure analysis and charge transfer. The adsorption process leads to the reconstruction of the topmost oxide surface. The calculations suggest that both forms of MBT may substitute H2O and OH at the Cu2O film surface, and thus may form a protective layer on oxidized copper surfaces in aqueous environment.

DFT studies of 2-mercaptobenzothiazole and 2-mercaptobenzimidazole as corrosion inhibitors for copper

This work describes 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) adsorption on Cu(111) by a systematic DFT study. Whatever the surface coverage of the adsorbed molecule, the adsorption is favored when the exocyclic sulfur atom is unprotonated (i.e. thione and thiolate forms). At low molecular density, the molecules adsorb forming a Cu-S(exo) and a Cu-N bond, and the adsorption energies of both molecules are similar, around 1.2 eV. To investigate a coverage corresponding to the density of self-assembled films, two strategies were applied: on the one hand, the best epitaxial relationship between the molecular layer and the Cu(111) surface was searched. A reasonable accommodation was found for a molecular density of 3.9 molecule/nm² in the honeycomb (3 × 3) Cu(111) superstructure, in which the molecules are adsorbed with the C2v axis tilted, forming two Cu-S bonds for MBT and one Cu-S and one Cu-N bond for MBI. On the other hand, the best structure for atomic S on Cu(111), the (√7 x √7) R19° superstructure, with a molecular coverage of 5 molecule/nm2, was considered. We find that the honeycomb MBT and MBI layer is the most stable arrangement, showing that in this case, the molecular organization prevails over the head-group/surface interaction. The MBI molecule adsorbs more strongly than the MBT molecule, due to better lateral interactions in the organic layer.

Alkylation of 2-oxo(thioxo)-thieno[2,3-d]pyrimidine-4-ones: Experimental and theoretical study

An alkylation of 2-oxo(thioxo)-thieno[2,3-d]pyrimidine-4-ones is a versatile and feasible route to biologically active pyrimidines. Experimental and theoretical approaches via different types of atomic partial charges at different semiempirical and DFT levels of theory were used for the investigation of the regioselectivity of alkylation of 2-oxo(thioxo)-thieno[2,3-d]pyrimidine-4-ones. Alkylation of ambident 2-oxo(thioxo)-thieno[2,3-d]pyrimidine-4-one anion with substituted allyl (methallyl/cinnamyl) chlorides selectively leads to the formation of N- or S-substituted pyrimidines which is totally confirmed via NMR and XRD studies. Partial atomic charges are considered for prediction of a most reactive atom of the ambident anionic pyrimidine moiety in the three solvents (ethanol, N,N-dimethylformamide, dimethyl sulfoxide) modeled via CPCM and COSMO. It was shown that thioxo analog selectively reacts upon exocyclic sulfur atom in the solvents with different polarity, whereas in the case of dioxo pyrimidine anion tends to undergo N-alkylation.

TELLUROCYCLISATION OF CONDENSED N-ALKENYL DERIVATIVE 4-OXOPYRYMIDINE-2-TION

The derivatives of quinazolines and their fused analogues are promising objects for the rational design of biologically active compounds as prototypes for innovative medicines. This is due to the fact that the quinazoline fragment is a structural unit of many natural alkaloids. Electrophilic intramolecular heterocyclization is a promising method for the synthesis of fused derivatives of quinazoline.This research is devoted to the synthesis of new functionalized unsaturated condensed derivatives of quinazolin-4-one and the study of the regio chemistry of the process of electrophilic heterocyclization under the action of tellurium tetrachloride. The choice of such an electrophilic reagent is due to the fact that in recent years the organic synthesis of chalcogen-containing compounds, in particular, tellurium compounds that exhibit a wide range of biological activity, is increasingly developing.It was established that the electrophilic intramolecular cyclization of 3-alkenyl-2-thioquinazolin-4-one under the action of tellurium tetrachloride in an aqueous acetic acid medium at room temperature takes place with the participation of the alkenyl moiety and the exocyclic sulfur atom in the second position of quinazoline. As a result, thiazolidinequinazoline systems of linear structure were obtained. The structure and composition of the obtained tellurium-containing hydrochlorides has been proved by 1H, 13C NMR spectra and elemental analysis. In the PMR spectrum of hydrochlorides, signals of aliphatic cyclic methylene and methine groups and of the acyclic trichlorotellanylmethyl group are observed, which, together with the signals of aromatic protons, indicates on the formation of thiazolidinequinazolones. The absence of signals characteristic of the C=S group and presence of signals typical for the C-S bond in the 13C NMR spectra are in accord with the proposed structure of the cyclization products.Thus, we investigated the regio chemistry of the electrophilic intramolecular cyclization of 3-alkenyl-2-thioquinazolin-4-one under the action of tellurium tetrachloride. It was proved that the annelation of the thiazolidine cycle takes place with the participation of the sulfur atom in the second position of the pyrimidine, with the formation of tricyclic hydrochlorides of linear structure.

Perspective anti-thyroid drug 2-thioxo-5-(3,4,5-trimethoxybenzylidene) thiazolidin-4-one: X-ray and thermogravimetric characterization of two novel molecular adducts, obtained by interaction with I2

The attention of many researchers has focused on the search of novel, specific thyreostatics and study the mechanism of their interaction with molecular iodine. However, the study of rhodanine derivatives as the potential thyreostatics was not carried out. The reaction product of 2-thioxo-5-(3,4,5-trimethoxybenzylidene) thiazolidin-4-one is presented by two types of adducts – stoichiomorphs: C13H13NO4S2·I2 and (C13H13NO4S2)2·I2 in chloroform and methylene chloride, respectively. According to the single crystal X-ray diffraction method the I1I2 bond length (2.762 Å) is rather elongated with respect to the average distance in gas phase II 2.662 Å and the S1⋯I1 distance is shortened 2.905 Å (0.875 Å less than VdW radii sum) in adduct 1. The iodine molecule in adduct 2 coordinated by two heterocycle molecules forms two contacts: the S (exocyclic) … I - 3.203 Å (0.577 less than VdW radii sum) and S (endocyclic) … I – 3.532 Å (0.248 less than VdW radii sum), respectively. The results of thermogravimetric analysis have revealed that the product 2 is more stable than product 1 due to each atom of iodine molecule is coordinated by endo and exocyclic sulfur atoms of two heterocycle molecules. The presence of thyreostatic properties is a main starting point in further investigations of rhodanine series as the potential pharmaceuticals.

ELECTROPHYLIC HETEROCYCLIZATION OF 5-METHYL-6-TIOXOPYRAZOLO[3,4-d]PYRIMIDINE-4-ON

Derivatives of pyrazolo[3,4-d]pyrimidine have valuable biological activity. The structural fragment of pyrazolopyrimidines is widely used to develop new effective pharmaceuticals. A new promising direction in the construction of polycyclic systems based on pyrazolopyrimidine is the method of electrophilic intramolecular heterocyclicization.The halogenation of 5-methyl-6-thioxopyrazolo[3,4-d]pyrimidin-4-one was carried out in acetic acid medium at room temperature with twice the excess of halogen. It was found that halogenation (with bromine and iodine) of 5-methyl-6-thioxopirazolo[3,4-d]pyrimidin-4-one results the annelation of the thiazolinic cycle with the formation of linear polynuclear systems of a salt-like structure. 7-Halogenomethyl-7-methyl-1,4,6,7-tetrahydropyrazolo[3,4-d][1,3]thiazolo[3,2-a]pyrimidin-4-one was obtained via the action of sodium sulfite in the DMSO-water medium.To study the effect of the nature of the electrophilic reagent on the direction of the electrophilic intramolecular cyclization of 5-methyl-6-thioxopyrazolo[3,4-d]pyrimidin-4-one the p-methoxyphenyltetrachloride was used (tested). Electrophilic heterocyclization take place under similar conditions (room temperature, glacial acetic acid medium), with the formation of the tricyclic system with an exocyclic aryltellurium moiety – 7-(dichloro-(4-methoxyphenyl) telluromethyl)-7-methyl-1,4,6,7-tetrahydropyrazolo[3,4-d][1,3]thiazolo[3,2-a]pyrimidin-4-one. Thus, the direction of electrophilic intramolecular cyclization of 5-methyl-6-thioxopyrazolo[3,4-d]pyrimidine-4-one using as electrophilic agents of halogens (bromine, iodine) and p-methoxyphenyltetrachloride does not depend on the nature of the electrophile and takes place with the participation of the exocyclic sulfur atom in the second position of the pyrimidine and lead to the formation of a condensed system of linear structure – halogenomethyl or aryl telluromethyl derivatives of pyrazolo[3,4-d][1,3]thiazolo[3,2-a]pyrimidin-4-one. The composition and structure of all synthesized compounds were proved by elemental analysis and 1H-NMR spectra.

Convenient Synthesis and Biological Activity of Mono and Diacyl 2,5‐Dimercapto‐1,3,4‐thiadiazole Derivatives

New derivatives of 2,5‐dimercapto‐1,3,4‐thiadiazole substituted both at one or two exocyclic sulfur atoms with a series of aroyl or ethoxycarbonyl groups were synthesized in reactions of 2,5‐dimercapto‐1,3,4‐thiadiazole salts with appropriate acid chlorides or ethyl chloroformate in mild conditions. The products were characterized by spectroscopy (1H NMR, 13C NMR, IR, and HRMS). Some from the synthesized compounds were screened in vitro and in vivo for antibacterial and antifungal activities against a panel of reference strains of microorganisms. The study revealed that ethyl S‐(5‐mercapto‐1,3,4‐thiadiazol‐2‐yl) carbonothioate seems to be the most active and versatile compound against Gram‐positive bacteria, Gram‐negative bacteria, and plant pathogenic fungi.

S- and N-alkylation of 2,2′-(alkane-α,ω-diyldisulfanediyl)-bis(1,3-benzothiazoles) with 1-iodopropan-2-one in the presence of iodine

The alkylation of 2,2′-(methylenedisulfanediyl)- and 2,2′-(ethane-1,2-diyldisulfanediyl)bis-(1,3-benzothiazoles) with 1-iodopropan-2-one involves exclusively the exocyclic sulfur atoms. The presence of an electron-withdrawing carbonyl group between the bridging methylene units in 1,3-bis(1,3-benzothiazol-2-ylsulfanyl)propane-2-one forces the alkylation to occur at the endocyclic nitrogen atoms.

Preparation and biological properties of 2-thio-containing pyrimidines and their condensed analogs.

The known methods for synthesis of thioxopyrimidines and their condensed analogs with exocyclic sulfur atom are summarized and discussed. The most popular approaches are based on [3+3], [4+2], [5+1] cyclization processes or domino reactions. The literature data analysis shows that the title compounds possess diverse biological activities, such as antioxidant, radioprotective, analgesic, antiinflammatory, antihypertensive, anxiolytic, anamnestic, anticonvulsant, antimicrobial, fungicidal, herbicidal, antiviral, and anticancer.

Study of the mechanism of formation of heterocyclic disulfonium dications from 1,3-benzothiazole-2-thiol and 1-iodopropan-2-one

The potential energy surface for the formation of heterocyclic disulfonium dications from 1,3-benzothiazole-2-thiol and 1-iodopropan-2-one has been analyzed at the DFT B3LYP level of theory. The reaction involves oxidation of 1,3-benzothiazole-2-thiol to the corresponding disulfide, followed by alkylation of the exocyclic sulfur atoms. Stabilization of the salt with iodide anion is initiated by thermodynamically controlled reaction with molecular iodine, leading to the formation of stable structure with triiodide anion.

Novel gold(I) complexes with 5-phenyl-1,3,4-oxadiazole-2-thione and phosphine as potential anticancer and antileishmanial agents

The current anticancer and antileishmanial drug arsenal presents several limitations concerning their specificity, efficacy, costs and the emergence of drug-resistant cells lines, which encourages the urgent need to search for new alternatives. Inspired by the fact that gold(I)-based compounds are promising antitumoral and antileishmanial drug candidates, we synthesized novel gold(I) complexes containing phosphine and 5-phenyl-1,3,4-oxadiazole-2-thione and evaluated their anticancer and antileishmanial activities. Synthesis was performed by reacting 5-phenyl-1,3,4-oxadiazole-2-thione derivatives with chloro(triphenylphosphine)gold(I) and chloro(triethylphosphine)gold(I). The novel compounds were characterized by infrared, Raman, 1H, 13C nuclear magnetic resonance, high-resolution mass spectra, and x-ray crystallography. The coordination of the ligands to gold(I) occurred through the exocyclic sulfur atom. All gold(I) complexes were active at low micromolar or nanomolar range with IC50 values ranging from <0.10 to 1.66 μM against cancer cell lines and from 0.9 to 4.2 μM for Leishmania infantum intracellular amastigotes. Compound (6-A) was very selective against murine melanoma B16F10, colon cancer CT26.WT cell lines and L. infantum intracellular amastigotes. Compound (7-B) presented the highest anticancer activity against both cancer cell lines while the promising antileishmanial lead was compound (6-A). Tiethylphosphine gold(I) complexes were more active than the conterparts triphenylphosphine derivatives for both anticancer and antileishmanial activities. Triethylphosphine gold(I) derivatives presented antimony cross-resistance in L. guyanensis demonstrating their potential to be used as chemical tools to better understand mechanisms of drug resistance and action. These findings revealed the anticancer and antileishmanial potential of gold(I) oxadiazole phosphine derivatives.

Synthesis of 4- and 5-arylthiazolinethiones as inhibitors of indoleamine 2,3-dioxygenase

Docking studies of 4-phenylthiazolinethione on human IDO1 suggest complexation of the heme iron by the exocyclic sulfur atom further reinforced by hydrophobic interactions of the phenyl ring within pocket A of the enzyme. On this basis, chemical modifications were proposed to increase inhibition activity. Synthetic routes had to be adapted and optimized to yield the desired substituted 4- and 5-arylthiazolinethiones. Their biological evaluation shows that 5-aryl regioisomers are systematically less potent than the corresponding 4-aryl analogs. Substitution on the phenyl ring does not significantly increase inhibition potency, except for 4-Br and 4-Cl derivatives.

A DFT study on tautomerism of selenorhodanine and its substituted derivatives

Rhodanine (2-thioxo-4-thiazolidinone) is a compound with a strong biological activity. It is also a ligand widely used in coordination chemistry. Replacing its exocyclic sulfur atom with selenium generates so called selenorhodanine. Selenorhodanine can exist in several tautomeric forms. Thus, the main aim of our research is to study the tautomeric equilibria in un substitued and substituted selenorhodanines. Substitution of nitrogen as well as the carbon atoms of the selenorhodanine ring with several substituents is considered. In order to achieve this goal we performed DFT calculations at the B3LYP/6-311++G∗∗ level for five theoretically possible tautomers of selenorhodanine. The results of performed calculations show that the most stable structure of selenorhodanine is similar to the equilibrium structures of rhodanine and thiazolidine-2,4-dione. We also calculated tautomeric equilibria for substituted selenorhodanines at the same level of theory and analyzed how the formation of intramolecular hydrogen bonds between some substituents and selenorhodanine ring can influence tautomeric equilibria in the compounds of interest.

Novel antitumor adamantane-azole gold(I) complexes as potential inhibitors of thioredoxin reductase.

Gold complexes that could act as antitumor agents have attracted great attention. Heterocyclic compounds and their metal complexes display a broad spectrum of pharmacological properties. The present study reports the preparation and characterization of four novel gold(I) complexes containing tertiary phosphine and new ligands 5-adamantyl-1,3-thiazolidine-2-thione, 3-methyladamantane-1,3,4-oxadiazole-2-thione. Spectroscopic data suggest that gold is coordinated to the exocyclic sulfur atom in all cases, as confirmed by X-ray crystallographic data obtained for complex (1) and supported by quantum-mechanical calculations. The cytotoxicity of the compounds has been evaluated in comparison to cisplatin and auranofin in three different tumor cell lines, colon cancer (CT26WT), metastatic skin melanoma (B16F10), mammary adenocarcinoma (4T1) and kidney normal cell (BHK-21). The gold complexes were more active than their respective free ligands and able to inhibit the thioredoxin reductase (TrxR) enzyme, even in the presence of albumin. Molecular modeling studies were carried out to understand the interaction between the compounds and the TrxR enzyme, considered as a potential target for new compounds in cancer treatment. The docking results show that the adamantane ring is essential to stabilize the ligand-enzyme complex prior the formation of covalent bond with gold center. The structure of the new gold compounds was established on the basis of spectroscopic data, DFT calculations and X-ray diffraction. TrxR inhibition was evaluated and the results correlated with the assays in tumor cells, suggesting the TrxR as possible target for these compounds.

A sulfur-rich π-electron acceptor derived from 5,5′-bithiazolidinylidene: charge-transfer complex vs. charge-transfer salt

Novel π-electron acceptors are still highly desirable for the formation of conducting salts or as n-dopable semiconductors. We describe here two synthetic approaches to substitute a dicyanovinylidene group, CC(CN)2 to a thioketone (CS) in the recently described DEBTTT acceptor where DEBTTT stands for (E)-3,3′-diethyl-5,5′-bithiazolidinylidene-2,4,2′,4′-tetrathione. These electron withdrawing groups enhance the electron accepting ability as demonstrated through electrochemical investigations, without hindering the formation of short intra- and intermolecular S⋯S contacts in the solid state. Association of this acceptor 1 with tetramethyltetrathiafulvalene (TMTTF) and decamethylferrocene (Fe(Cp*)2) afforded 1 : 1 adducts which were analyzed by single crystal X-ray diffraction. Combined with vibrational and magnetic properties, it appears that [TMTTF][1] behaves as a neutral charge-transfer complex while [Fe(Cp*)2][1] is an ionic salt. The concentration of the spin density on the exocyclic sulfur atoms in 1−˙ favors the setting of direct antiferromagnetic interactions in [Fe(Cp*)2][1].

Neutral mononuclear luminescent Pd(II) complexes with heterocyclic thiolate ligands and chelating phosphines. Structural and photophysical assignments

Two heterocyclic thiolate ligands, namely pymt and py2S (pymt=pyrimidine2-thiolate and py2S=pyridine-2-thiolate) and the diphosphines bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), were used in the synthesis of three neutral Pd(II) complexes (cis-[Pd(dppm)(pymt)2] (1), cis-[Pd(dppe)(pymt)2] (2) and cis-[Pd(dppp)(pyrt)2] (3)). Crystallographic analysis of the isolated complexes reveals their square planar arrangement and the coordination of the thiolate moieties through their exocyclic sulfur atom. The complexes absorb in the visible part of the spectrum through charge transfer transitions while after photoexcitation at 385nm they appear to emit with a broad band located at 465nm.

Alkylation of 1,3-benzothiazin-4-one 2-oxo-, 2-arylimino-, and 2-thioxo derivatives

Sodium salt of 3Н -benzo[e][1,3]thiazine-2,4-dione is easily alkylated at position 3. In the case of 2-(arylimino)-2,3-dihydrobenzo[e][1,3]-thiazin-4-ones, the alkylation reaction at this position occurs regioselectively. Alkylation of 2-thioxo-2,3-dihydrobenzo[e][1,3]thiazin-4-one under the same conditions produced regioisomers, but S-alkylation at the exocyclic sulfur atom occurred in the presence of triethylamine. The reaction of 1-(4-oxo-3,4-dihydrobenzo[e][1,3]thiazin-2-ylidene)guanidine with methyl anthranilate led to the formation of tetracyclic quinazolinо[2,1-b]quinazolinedione.

Formation and structure of two luminescent salts of [Au(SCSN3)2]- obtained through the [2 + 3] cyclization of carbon disulfide and azide ion.

The colorless, two-coordinate gold(i) complex, [(H2O)3Na][Au(SCSN3)2], has been synthesized through the [2 + 3] cyclic reaction of carbon disulfide and sodium azide in the presence of the labile complex (tht)AuCl. Metathesis of [(H2O)3Na][Au(SCSN3)2], with tetra(phenyl)arsonium chloride produced colorless needles of (Ph4As)[Au(SCSN3)2]. The structure of [(H2O)3Na][Au(SCSN3)2] involves linear gold coordination by two exocyclic sulfur atoms of the 1,2,3,4-thiatriazole-5-thiolate anions. These two-coordinate anions self-associate to form extended, zig-zag chains that are connected by aurophilic bonding with Au∙∙∙Au distances of 3.2653(3) Å and 3.3090(3) Å. Remarkably, the individual S-Au-S units that are connected though aurophilic interactions are eclipsed. The structure of (Ph4As)[Au(SCSN3)2] also contains linear, two-coordinate gold ions with bonding to the 1,2,3,4-thiatriazole-5-thiolate anionic ligands through the exocyclic sulfur atoms. However, in this salt, the anions self-associate through AuAu bonds (Au∙∙∙Au distance of 3.2007(3) Å) to form simple dimers, which also have an eclipsed arrangement of the ligands. Electronic structure calculations strongly suggest that the staggered geometry for the [(Au(SCSN3))2](+) dimer is energetically favored relative to the eclipsed geometry. However, attractive π-stacking interactions appear to promote the observed eclipsed arrangement of the ligands.

Synthesis and Characterization of 5-Substituted- (2-methylbenzimidazol-1-yl)-1,3,4-oxadiazole-2-thione and Its Metal Complexes of Fe(III), Hg(II), Zn(II) and Sn(II)

A ligand 5-Substituted-(2-methylbenzimidazol-1-yl)-1,3,4-oxadiazole-2-thione (L) and its Fe(III),Hg(II),Sn(II) and Zn(II) complexes were synthesized. The authenticity of the ligand and its transition metal complexes were established by elemental analyses, conductance and magnetic susceptibility measurements, as well as spectroscopic (IR, 1 H NMR, UV-Vis and Mass) and thermal studies. All complexes exhibit the composition ML2X2 where M =Fe(III),Hg(II), Zn(II) and Sn(II), L=Ligand, X=OAc and chloride ions. The IR spectral studies revealed the existence thiol-thione tautamerism in the ligand molecule. The ligand acts as a bidentate coordinating through the N-3 nitrogen and the exocyclic sulfur atoms of ox diazole rings. Antimicrobial screening of the ligand and its metal complexes were determined against the bacteria Escherichia coli and Salmonella paratyphi A.