Thione Form Research Articles

Synthesis, Antimicrobial, DNA Interactions, In Vitro Cytotoxicity, and Cell Cycle Analysis Efficiency of Newly Nano‐Sized Cu (II), Ni (II), Co (II), and Zn (II) Thio‐Schiff Base Complexes of 2‐((E)‐((4,5‐Dimethyl‐2‐(((E)‐4‐Methylbenzylidene)Amino)Phenyl)imino)Methyl)‐Benzenethiol

ABSTRACTNano‐sized bivalent metal complexes, specifically [M(L)2] with L = 2‐((E)‐((4,5‐dimethyl‐2‐(((E)‐4‐methylbenzylidene)amino)phenyl)‐imino)methyl)benzenethiol] (C23H22N2S) and M = Cu (II) (C1), Co (II) (C2), Ni (II) (C3), and Zn (II) (C4), underwent synthesis and subsequent characterization. Elemental analyses, infrared, NMR, mass, electronic, magnetic susceptibility, conductivity assessments, and X‐ray diffraction studies were used to assess our bivalent metal complexes. DFT studies were used to study the tautomeric equilibrium of the tridentate thio‐Schiff base ligand (HL), via the DFT\B3LYP method in connection with a 6–311G* correlation consistent basis set. Two tautomers, which are thione and thiol forms, were studied to estimate the predominant one. The metal formed four coordinated with the tridentate N2S donor thio‐Schiff base to form octahedral geometry complexes. The SEM, TEM, XRD, AFM, and EDX of the studied complexes unveiled distinct and strong diffraction peaks, signifying their crystalline nature and providing evidence of their particle sizes being within the nano‐size. The crystal sizes calculated for all complexes were determined to be ranging from 27.73 to 76.39 nm. The interactions between metal complexes and calf thymus DNA, and their potential for mimicking insulin activity, were investigated in a controlled lab setting by measuring their ability to inhibit alpha‐amylase. The antimicrobial potential of thio‐Schiff base ligand (HL) plus complexes (C1–C4) were tested. The viscosity and UV–Vis absorption determinations were utilized to assess the calf thymus DNA (CT‐DNA) interaction with the nano‐sized metal (II) chelates. Our flow cytometry data indicate significant levels of apoptosis and cell cycle arresting in both liver and breast cancer cell lines.

Probing the Adsorption Sites of 5‐amino‐2‐mercaptobenzimidazole Conformations on Colloidal Gold Nanoparticles Investigated by SERS and DFT

AbstractGold nanoparticles (AuNP) have shown great potential in biomedical applications due to their unique and tunable properties. Understanding the ligand conformation on AuNP has profound interest in nanoparticle research leading to a precise drug delivery system. Colloidal AuNPs were synthesized using trisodium citrate as reducing agent. Normal Raman spectrum (NRS) in solid and aqueous phase identifies that 5‐amino‐2‐mercaptobenzimidazole (5A2MBI) mainly exist as thione form. Surface enhanced Raman scattering (SERS) investigation of 5A2MBI depending on pH was performed to explore the adsorption mechanism of thiolate and thione conformations on AuNPs. Density functional theory (DFT) calculations were used to find the band assignments and molecular electrostatic potential (MEP) mapping to identify the electron rich site where metal can interact preferentially. Using SERS spectral analysis and DFT results, surface adsorption scheme was proposed. At basic pH, 5A2MBI adsorbs on AuNP as thiolate form bidentately via Sulfur and nitrogen atom of imidazole ring with tilted geometry. However, in acidic condition the thione form adsorbs on nanosurface with perpendicular orientation.

O-versus S-Metal Coordination of the Thiocarboxylate Group: An NMR Study of the Two Tautomeric Forms of the Ga(III)-Photoxenobactin E Complex.

Photoxenobactin E (1) is a natural product with an unusual thiocarboxylic acid terminus recently isolated from an entomopathogenic bacterium. The biosynthetic gene cluster associated with photoxenobactin E, and other reported derivatives, is very similar to that of piscibactin, the siderophore responsible for the iron uptake among bacteria of the Vibrionaceae family, including potential human pathogens. Here, the reisolation of 1 from the fish pathogen Vibrio anguillarum RV22 cultured under iron deprivation, its ability to chelate Ga(III), and the full NMR spectroscopic characterization of the Ga(III)-photoxenobactin E complex are presented. Our results show that Ga(III)-photoxenobactin E in solution exists in a thiol-thione tautomeric equilibrium, where Ga(III) is coordinated through the sulfur (thiol form) or oxygen (thione form) atoms of the thiocarboxylate group. This report represents the first NMR study of the chemical exchange between the thiol and thione forms associated with thiocarboxylate-Ga(III) coordination, including the kinetics of the interconversion process associated with this tautomeric exchange. These findings show significant implications for ligand design as they illustrate the potential of the thiocarboxylate group as a versatile donor for hard metal ions such as Ga(III).

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.

Unravelling the effects of functional groups on the adsorption of 2-mercaptobenzothiazole on a copper surface: a DFT study.

The adsorption of organic compounds onto metal surfaces holds significant importance across various applications, where understanding the intricate interactions between the compounds and the metal surfaces is indispensable. By using density functional theory calculations, this study investigated the impact of functional groups on the interaction between the thione form of 2-mercaptobenzothiazole (MBT) and the Cu(111) surface. The results indicated that substituting functional groups at the C6 position exerts a dual influence on the covalent and non-covalent interactions (NCI). Electron-donating groups enhanced both covalent and non-covalent interactions, whereas electron-withdrawing groups decreased covalent while increasing non-covalent interactions. The covalent interaction between MBTs and Cu(111) is mainly governed by the electron donation from the occupied orbitals of the molecules to the conduction band of copper, with the absolute interaction energies (eV) increasing in the order of MBT-NO2 (0.629) < MBT-COOH (0.660) < MBT-Cl (0.699) < MBT (0.715) < MBT-SH (0.727) < MBT-OH (0.733) < MBT-CH3 (0.735) < MBT-OCH3 (0.749) < MBT-NH2 (0.781) < MBT-NHCH3 (0.792). The influence of functional groups on covalent interactions is clarified by examining changes in the molecule's electronic structure, revealing a linear relationship between covalent interaction energy and HOMO energy, or the Hammett substituent constant. However, the impact of functional groups on non-covalent interactions is more complex and cannot be described by changes in the electronic structure. A novel parameter, the substitution interaction energy, was proposed to capture the effect of functional groups on the NCI-included adsorption energy of MBT derivatives on the Cu(111) surface. The stronger the substitution interaction, the stronger the NCI-included interaction of MBTs on Cu(111). The absolute NCI-included interaction energies follow the order of MBT (2.141) < MBT-Cl (2.213) < MBT-COOH (2.266) < MBT-CH3 (2.294) < MBT-OH (2.331) < MBT-OCH3 (2.379) < MBT-NO2 (2.461) = MBT-NH2 (2.461) < MBT-SH (2.530) < MBT-NHCH3 (2.565). These insights offer valuable guidance for manipulating the adsorption of organic substances on metal surfaces through functional groups in diverse applications.

Synthesis, crystal structure, Hirshfeld surface analysis, DFT, molecular docking and in vitro antitumor studies of (2E)-2-[4-(diethylamino)benzylidene]-N-ethylhydrazinecarbothioamide

The crystal structure and spectral characterization of a new proligand, (2E)-2-[4-(diethylamino)benzylidene]-N-ethylhydrazinecarbothioamide is described. The compound was crystallized in the monoclinic space group P21/c; Z = 8, V = 3192.7(8) Å3 with unit cell parameters a = 26.232(4) Å, b = 7.9196(10) Å, c = 15.369(3) Å,α = 90°, β = 90.217(6)° and γ = 90°. There are two independent molecules in the asymmetric unit. The crystal structure reveals that the compound exists in the thione form and S1 and N2 are at E configuration to each other with respect to N3–C12 bond. Similarly, S2 and N6 are trans to each other with respect to N7–C26 bond in the second molecule of the asymmetric unit. The packing of the molecules in the crystal lattice is stabilized by intermolecular hydrogen bonds, which are quantified with Hirshfeld surface analysis. The synthesized compound was characterized by IR, UV–vis, 1H and 13C NMR spectra. DFT study indicates the molecular chemical stability with a HOMO-LUMO energy gap of 3.79 eV. The molecule is soft with preference for NS coordination mode. The azomethine nitrogen and thione sulfur region are electron rich and can act as a nucleophilic site to bind with the electrophilic regions of DNA or protein receptors. The in silico docking study with 1BNA suggests that the compound can fit comfortably in the curved shape of the DNA target like a minor groove mode of binding. The in vitro cytotoxicity of the compound, which was screened for DLA tumour cells aspirated from the peritoneal cavity of tumor bearing mice, is indicative of its antitumor potential.

Synthesis, spectroscopic characterization, molecular studies, and biological evaluation of (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide and some of its transition metal complexes

Novel Ni(II), Cu(II), Zn(II), Cd(II), and Pd(II) complexes (1–6) with (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide ligand (HL) were prepared and characterized via different analytical and spectroscopic techniques. The spectral data showed that the ligand is bound with copper(II) chloride, zinc(II) chloride, cadmium(II) chloride, and potassium tetrachloropalladate(II) in its neutral thione form in complexes 2, 4, 5, and 6, respectively. Furthermore, the ligand was coordinated with nickel (II) chloride and copper(II) acetate in complexes 1 and 3 as a monobasic tridentate in its thiol form. Thermogravimetric studies were performed for the prepared compounds and the pyrolytic mechanism was proposed for some complexes. DFT, TD-DFT, and NBO calculations were achieved at the B3LYP/LanL2DZ level of theory. Computational studies showed that the investigated compounds have high hyperpolarizability values (β) suggesting their potential use in the creation of non-linear optical materials. Many bacterial and fungal strains were used to assess the ligand and its metal complexes' antibacterial activities. In general, metal complexes have been shown to possess a stronger antibacterial and antifungal effect thanthe free ligand. Complex 5 exhibited respectable antibacterial activity versus Gram-positive bacteria. Furthermore, Zn(II) and Cd(II), complexes 4 and 5 have shown excellent activity against Gram-negative bacteria. Complex 4 exhibited a superior antifungal activity against two types of tested fungi compared with other compounds and standard Ketoconazole. Molecular docking of the ligand and its complexes 1, 2, and 5 were performed against tyrosyl-tRNA synthetase. The more negative values of the binding energy indicate that complexes 1 and 5 have higher inhibition efficiency than the free ligand.

Synthesis, Structural Characterization and Antimicrobial Activity of New Substituted Oxazole Thiosemicarbazone Ligand and its Co (II) and Ni (II) Complexes

The New ligand 5-methyl-2-(2-thienyl)-1,3-oxazole-4-carbaldehyde thiosemicarbazone (HL)(1) was synthesized. This ligand reacted with Co(II) and Ni(II) chloride in ratio 1:2 metal:ligand afforded two complexes, [Co(LH)]Cl2 (2) and [Ni(HL)2]Cl2 (3). The ligand and its metal (II) complexes have been characterized by spectroscopic techniques. The X-ray structural studies revealed that the free ligand exist in thione form and remain as neutral tridentate with NNS donor atoms in the tow complexes beside presence of uncoordinated chloride ions in the cavities of the crystal lattice of the complexes. One of these chlorides in complex (2) is hydrogen bonded to a proton of the amine of the ligand. While in complex (3) the chloride bonded to proton of imine (-N2H) of the ligand and the coordination environment has a distorted octahedral. The oxazole N and S atoms in the two complexes are cis to each other whereas the azomethine N atoms are trans coordinated. The ligand and its metal complexes were tested for their in vitro biological activity against six standard microorganisms: two Gram positive namely Bacillus subtilis and Micrococcus luteus, and one Gram negative bacteria Escherichia coli and three fungi: Saccharomyces cerevisiae (Baker’s yeast), Mucor spec., and Aspergillus niger, at a concentration 100µg/ml.

Thione-thiol tautomerism in new 4-methyl-3-nitopyridine derivative in the solid state – X-ray, electron absorption and emission, IR and Raman studies discussed in term of quantum chemical DFT calculations

Theoretical and experimental studies of new 4-methyl-3-nitropyridine-2-thione and its thiol tautomer were synthesized and characterized by means of structural and spectroscopic studies. X-ray diffraction, IR, Raman, UV–VIS and emission spectra were measured and analyzed. The quantum chemical DFT calculations were applied in the analysis of the obtained results. The effect of the temperature change on the structural and spectroscopic properties was studied. The vibrational characteristics and dynamical properties of the ϕ-S-H and ϕ=S type compounds are discussed where ϕ is a heterocyclic ring. The results of structural and spectroscopic studies were used to find a diagnostic tool on the structure of thione and tiol forms and their optic properties.

An Efficient Catalyst-Free Direct Approach to 5-Polyfluoroalkyl-1,2,4-triazole-3-thiones

AbstractAn easy to handle high-efficient approach to 5-polyfluoroalkyl-1,2,4-triazole-3-thiones (11 examples, up to 91% yield) is reported. The tautomerism of thione and thiol forms for the obtained products is discussed. A one step procedure for 6,6-dimethyl-3-(trifluoromethyl)-5,6-dihydro[1,3]thiazolo[2,3-c][1,2,4]triazole formation from trifluoroacetic acid and 4-methallylthiosemicarbazide has been developed. The structures of the products were unambiguously determined by complex NMR investigation and by single crystal X-ray diffraction.

Synthesis, crystal structure, molecular dynamics, docking and in-vitro studies of cyclododecanonethiosemicarbazone, a promising anti tuberculosis agent

Cyclododecanonethiosemicarbazone (CDT), crystallises in triclinic crystal system in spacegroup P-1 having unit cell parameters as a = 5.6152(2)Å, b = 8.3747(4) Å, c = 16.1901(7) Å, α = 91.186(2)°, β = 90.880(2)° and γ = 108.014(2)°, V = 723.68(5) Å3 and Z = 2.The macrocyclic ring structure shows close resemblance to the most stable conformation for a 12 membered aliphatic cyclic ketone, where three C-C bonds are present on each side of the heavy atom framework's square structure. Existence as thione form of the compound is confirmed by IR, NMR and Crystallographic data. There is extensive electron delocalisation along its thiosemicarbazone moiety. A number of short term interactions, including three intermolecular H-bonding interactions involving each S, forms infinite interlinked chains of molecules along a axis. Results of anti tuberculosis activity studies reveal that minimum inhibitory concentration (MIC) of CDT is 800 µg/mL for the test organism Mycobacterium smegmatis. Hirshfeld surface analysis, docking and molecular dynamics studies suggest stable protein –ligand binding with the related 1TEX protein.

Spectroscopic, biological activity studies, and DFT calculations, of Pd(II) and Pt(II) complexes of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione

Four palladium (II) and platinum(II) complexes with the formula [MCl2(HPhqS)2] and [M(PhqS)2] (MII = Pd and Pt), were synthesized by treating Na2PdCl4 or K2PtCl4 with 2 mol of 4-Methylene-3-phenyl-3,4-dihydroquinazoline-2(1H)-thione (HPhqS) with or without the present base. The geometry around the Pd(II) and Pt(II) ions was a square planner and the HPhqS ligand was bonded as monodentate through the sulfur atom in complexes (1) and (2), while as bidentate chelating ligand through the nitrogen and sulfur atoms in complexes (3) and (4) as revealed by the data collection from spectroscopic studies. The prepared compounds were fully characterized by different physicochemical and spectroscopic methods. Furthermore, the free HPhqS ligand and its complexes were evaluated in vitro in regard to their antimicrobial activity against five bacteria species (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, staphylococcus epidermidis and staphylococcus aureus). Moreover, the cytotoxic activity of the compounds was examined against breast (MCF-7) and lung (A549) cancer cell lines, and the [PdCl2(LH)2] (1) and [PtCl2(LH)2] (2) appeared a highest inhibitory effect against MCF-7 cell lines with IC50 = 4.291 ± 0.181 μM and 3.479 ± 0.162 μM, respectively, in comparison to the standard control and other complexes. The prepared ligand accompanied by the synthesized complexes were optimized using B3LYP method and 6–311++G(d,p) biases sets for the ligand and SDD basis set for the central metal. Different quantum parameters including electron affinity, ionization energy, dipole moment, hardness and vibrational frequencies were calculated for the ligand and its complexes. The total energy calculated for the two tautomeric structures of the ligand HPhqS showed a slightly higher value of the thione form over the thiol form. In addition, the trans-[PdCl2(HPhqS)2] complex possessed the highest dipole moment values while the cis-[PtCl2(HPhqS)2] showed non. In general, the obtained theoretical results showed a good match to the experimental findings.

Synthesis, characterization, and x-ray crystallography of unexpected chloro-substitution on 1-(4-chlorophenyl)-3-phenylthiourea platinum(II) complex with tertiary phosphine ligand

The reaction of 1-(4-chlorophenyl)-3-phenylthiourea (CPTH2) with [PtCl2(PPh3)2] moiety in a 1:1 molar ratio in a basic solution afforded unexpected Pt(II) thiourea dianion complex. The crystal structure revealed that the second phenyl ring of the parent ligand was substituted with a chlorine atom. Chlorine substitution on the phenyl ring might have been aided by the solvent CH2Cl2. The crystal structure revealed a platinum(II)-centered four-membered ring structure. FT-IR, 1H-NMR, and 31P-NMR spectroscopy were also utilized to study the complex. The crystal packing environment is explored by Hirshfeld surface analysis, enrichment ratio calculations and void analysis. Various quantum calculations were performed on both the ligand and its complex, and the calculated values were compared to the experimental ones. The energies of the two resonance structures of the CPTH2 ligand are very close. However, the stability of the thione form was slightly greater than that of the thiol form. The bond lengths and bond angles calculated by Orca for the Pt(II) complex were nearly identical to the experimental values. The biological assessment of the Pt(II) complex was evaluated against four pathogenic bacteria: Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and Salmonella typhi (S. typhi). The Pt(II) complex exhibited moderate inhibition values against all bacterial species, with the exception of Pseudomonas aeruginosa (P. aeruginosa), which exhibited the greatest activity.

Tautomeric, spectroscopic, electronic and NLO analyses of purpald (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole)

Thione and thiol tautomeric structural forms of 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole (purpald) were theoretically analyzed based on energetic and molecular structural geometry by using the DFT/B3LYP method with the 6–311++G(3df,3pd) basis set. The existence of the inter-molecular H-bond or close contact interactions within solid state crystal packing diagram was determined by Hirshfeld surface analysis. The experimental and theoretical investigations on the NMR chemical shifts were used for determination of more dominant tautomeric form between thione and thiol structures. The characteristic vibrations of functional groups within the compound were analyzed with IR and Raman wavenumbers. The experimental and computational UV spectral study was made to examine nature of the intra-molecular electronic transitions within DMSO solution phase. Some global quantum mechanical descriptors were determined with FMOs (HOMO and LUMO) investigation. The presence of hyperconjugation interactions within NBO analysis helped to explain thione-thiol tautomeric equilibrium and inter-molecular N4-H15···N8′ and N7′-H12′···S9 interactions within thione dimeric form. The reactive sites of all tautomeric forms were examined with MEP surface analysis. The static NLO properties were theoretically investigated to test whether all tautomeric forms have a non-linear optical material profile. A theoretical investigation on the molar volume, dielectric constant and refractive index of the compound was carried out at mentioned computational level of theory. Comparison and detailed presentation of the structural and spectral experimental and calculated related properties of the compound were done in this study.

Theoretical determination of corrosion inhibitor activities of 4-allyl-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol-thione tautomerism

Using the density functional method B3LYP/6-311G(d,p) calculations, the inhibitor activity of 4-allyl-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol tautomerism against corrosion of neutral copper surfaces has been investigated. Among the inhibitors tested, the 4-allyl-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol inhibitor has the inhibition performance for both forms (thiol and thione). Quantum chemical parameters that are correlated to the inhibition efficiency including highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital, (LUMO), energy bandgap (ΔE), electronegativity (χ), Hardness (ɳ), softness (σ), dipole moment (μ), the fraction of the electrons transferred (ΔE), and Total energy (TE) has been calculated. In addition, the adsorption of inhibitors on the neutral copper surface reveals that nitrogen adsorption is preferred over sulfur adsorption. The results show that the thione form has the highest inhibitor compared to the thiol form.

Synthesis, characterisation and coordination properties of 5-methyl-3-formylpyrazole 4 N-benzylthiosemicarbazone (HMPzNB) Cobalt(III), nickel(II) and copper(II) complexes with a NNS donor system

The title ligand, 5-methyl-3-formylpyrazole 4 N-benzylthiosemicarbazone (abbreviated as HMPzNB) has been synthesised and physicochemically characterised by elemental analysis, IR, PMR and mass spectrum. The ligational behaviour of the pyrazole-derived thiosemicarbazone, HMPzNB, has been examined by isolation and characterisation of its complexes with Co III , Ni II and Cu II with different counterions. Elemental analyses, magnetic and spectral features indicate [Co(MPzNB) 2 ]X (X = Cl - , Br - , NO - 3 , ClO - 4 or BF - 4 ) as the diamagnetic octahedral species with the ligand in the deprotonated thiol form, while [Ni(HMPzNB) 2 ]X 2 (X = Cl - , Br-, NO - 3 or ClO - 4 ) is proposed as octahedral complex with the ligand in the neutral thione form. However, in the neutral condition (pH ∼6) nickel(II) salt affords octahedral bis-nickel(II) complex, Ni(MPzNB) 2 , while copper(II) salt gives [Cu(MPzNB)]X (X = Cl - , Br - , NO - 3 or ClO - 4 ), with the deprotonated ligand. 5-Methyl-3-formylpyrazole 4N-benzylthiosemicarbazone possesses in its structure, the tertiary nitrogen atom ( 2 N) of the pyrazole ring, the azomethine nitrogen and the sulphur atom as potential binding sites; thus the title ligand is expected to behave as a potential NNS tridentate during complex formation with a metal ion.

Structure and toxicity of N-donor thionate Zn complexes

The reaction of thiosaccharin (thiosaccharin: the thione form of saccharin) and N-donor bases with Zn2+ yielded three new thionate complexes: [Zn(tsac)2(imidazole)2], [Zn(tsac)2(benzimidazole)2]·H2O and [Zn(tsac)2(2-methylimidazole)2]·2 H2O (tsac: thiosaccharinate, C6H4C(S)NSO2). The new complexes were characterized employing Fourier Transform Infrared Spectroscopy (FTIR) and elemental analysis (EA). [Zn(tsac)2(imidazole)2] and [Zn(tsac)2(benzimidazole)2]·H2O crystal structures were determined with the aid of single crystal X-ray diffraction analysis (XRD). Both complexes exhibit a tetrahedral S2N2Zn environment, with the thiosaccharinate anions coordinated through their exocyclic Sulphur atoms. The structure of [Zn(tsac)2(2-methylimidazole)2]·2 H2O was proposed based on spectroscopic analysis.Moreover, a study on the effects of the three coordination compounds on erythrocyte sedimentation rate and osmotic fragility of red blood cells were held. Results revealed that these compounds at concentrations up to 10 μg/mL do not affect the activity of pro-sedimentation and anti-sedimentation factors. Only [Zn(tsac)2(2-methylimidazole)2]·2 H2O at 10 μg/mL induced fragility on red blood cells membrane.

Inhibition effect and adsorption behavior of two pyrimidine derivatives as corrosion inhibitors for Q235 steel in CO2-saturated chloride solution

• The studied inhibitors exhibit excellent and long-lasting inhibition performance. • 2-MP shows better inhibiting effect due to its tautomers of thiol and thione forms. • The adsorption process of the inhibitors is a mix of physisorption and chemisorption. • The adsorption process is spontaneous, exothermic and follows Langmuir isotherm. The anticorrosion performance of two pyrimidine derivatives 2-mercaptopyrimidine (2-MP) and 4-methyl-2-mercaptopyrimidine (4 M−2MP) on Q235 plain carbon steel in CO 2 -saturated 3 wt% NaCl aqueous solution has been comparatively examined utilizing weight loss methods, electrochemical techniques as well as surface analysis. The results indicate that the two kinds of pyrimidine derivatives serve as mixed-type inhibitors and show excellent and long-lasting inhibitory effect for Q235 steel against general and localized corrosion even at very low concentrations. The inhibition efficiencies increase with a rise in concentration but decrease with temperature rising. Compared with 4 M−2MP inhibitor, the 2-MP exhibits stronger adsorption ability and higher inhibition efficiency due to the existence of two tautomers of thiol and thione forms. The adsorption of both inhibitors over Q235 steel surface can be well fitted by Langmuir adsorption isotherm. The values of standard Gibbs free energy of adsorption ( Δ G a d s 0 ) indicate that both physisorption and chemisorption processes have taken place. Furthermore, thermodynamic parameters are extracted from Langmuir rule to discuss the adsorption mechanism and the XPS analysis is applied to describe the bonding characteristics between inhibitors and steel substrate.

Thermodynamic properties of 2-mercapto-, 2,5-dimethyl- and 2-mercapto-5-methyl-1,3,4-thiadiazole

The focus of this work is the establishment of energetic-structural correlations of compounds containing a pentagonal heterocyclic ring with different substituents, and consequent contribution on the assessment of their thermodynamic stability and a thorough insight on the thiol-thione tautomeric equilibrium. In this work we report an experimental and computational thermochemical study of three mercaptothiadiazoles: 2-mercapto-1,3,4-thiadiazole, 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,5-dimethyl-1,3,4-thiadiazole. The experimental data were determined mainly from calorimetric techniques and from effusion method. Thermochemical properties such as the enthalpies of formation, both in crystalline and gaseous phases, the enthalpies of fusion and of sublimation of each compound, as well as the Gibbs energies of formation were derived. Thus, the methyl-substituted thiadiazole is the more stable species in both gaseous and crystalline phases. In addition, quantum chemical calculations were carried out for those isolated molecules. This approach confirms the thione form as the predominant tautomer for the mercaptothiadiazoles. Finally, the activation energies of the tautomeric equilibrium of the mercaptothiadiazoles were calculated in the gas-phase, aqueous and dimethylsulfoxide solutions, showing that the thiol → thione single hydrogen transfers are quite unfavourable reactions in gas phase and in a presence of polar solvents.

The Coordination chemistry and cyclic voltammetry exploration of Cu(II), Co(II), Ni(II) and Zn(II) complexes of novel (E)-3,4-dichloro-N-(2-(1-(pyridin-2-yl)ethylidene)hydrazine-1-carbonothioyl) benzamide ligand

Abstract A novel thiosemicarbazone derivative (DEHC-H), (E)-3,4-dichloro-N-(2-(1-(pyridin-2-yl)ethylidene) hydrazine-1-carbonothioyl) benzamide was synthesized after three steps. Firstly, the reaction between acetyl pyridine with hydrazine hydrate at room temperature obtaining (E)-2-(1-hydrazonoethyl)pyridine. Secondly, 3,4-dichlorobenzoyl chloride was refluxed with potassium thiocyanate in acetonitrile solvent forming 3,4-dichlorobenzoyl isothiocyanate. The last step of the reaction is summarized by the refluxing the mixture of (E)-2-(1-hydrazonoethyl) pyridine and 3,4-dichlorobenzoyl isothiocyanate in acetonitrile solvent. A series of eight new metal complexes, Copper(II), Cobalt(II), Nickel(II) and Zinc(II) chloride and acetate complexes of the thiosemicarbazone ligand (DEHC-H) were accomplished in DMF/H2O or CHCl3/CH3OH mixture solvents. The {[(DEHC)CuCl], [(DEHC)CoCl], [(DEHC)NiCl], [(DEHC-H)ZnCl2], [(DEHC-H)2Cu](CH3COO)2, [(DEHC-H)2Co](CH3COO)2, [(DEHC-H)2Ni](CH3COO)2 and [(DEHC-H)2Zn](CH3COO)2} were prepared by the reaction of the free ligand with chloride and acetate metal salts, CuCl2.2H2O, CoCl2.6H2O, NiCl2.6H2O, ZnCl2, Cu(CH3COO)2.H2O, Co(CH3COO)2.4H2O, Ni(CH3COO)2.4H2O and Zn(CH3COO)2.2H2O. The preparation of the metal complexes was achieved in 1:1 and 1:2 mole ratios of (Metal salt : free Ligand). The identities of the (DEHC-H) ligand and its metal chloride and acetate complexes were characterized and confirmed by 1HNMR, 13CNMR, UV-visible, Infrared, mass spectroscopy, elemental analysis, solubility test, magnetic moments and conductivity measurements. The spectroscopic techniques and measurements indicate that metal chloride complexes were formed with the neutral structural formula [(DEHC)MCl], where M= Copper(II), Cobalt(II) and Nickel(II) and with the neutral structural formula [(DEHC-H)ZnCl2] for Zinc(II) complexes in spite of two mole ratios were examined. Moreover, the acetate complexes were formed as anionic formula [(DEHC-H)2M](CH3COO)2. The employed techniques indicate that thiosemicarbazone chloride complexes with formula [(DEHC)MCl], one tridentate [(DEHC) ligand coordinating in the thiole form with the metal ion and the fourth site was the chloride anion to form square planar geometry. While Zinc(II) complex [(DEHC-H)ZnCl2] show coordinating of the one tridentate [(DEHC-H) ligand as thione where the fourth and the fifth sites coordinating with the Zinc(II) ion to adopt a square pyramidal geometry. The characterization of the all acetate complexes [(DEHC-H)2M](CH3COO)2 pointed to two moles of tridentate [(DEHC-H) ligands in thione form coordinating with the metal ions to fill six sites forming octahedral geometry as well as to two moles of acetate ions as counter ions. It is worth noting that tridentate thiosemicarbazone [(DEHC-H) ligand coordinates through the nitrogen pyridyl, thionic sulfur and the azomethine nitrogen atoms. The observed magnetic moments data exhibit diamagnetic properties of Zinc(II) chloride and acetate complexes and Nickel(II) square planar chloride complexes. While Cu(II) and Co(II) square planar chloride compounds and Copper(II), Cobalt(II) and Nickel(II) octahedral acetate complexes appeared as paramagnetic species. The electrochemical behavior of a set Copper(II), Cobalt(II) and Nickel(II) chloride and acetate complexes of free ligand were recorded using cyclic voltammetry technique. The voltammetric analysis of Copper(II) chloride and acetate complexes displays a quasi-reversible one electron reduction in the range –1.0728 to –1.1439 volt versus Fc/Fc+ ascribable to the Copper(II)/Copper(I) redox couple. The Co(II) and Ni(II) chloride and acetate compounds display one and two irreversible oxidation processes respectively in the range +0.419 to +0.479 in Co(II) compounds and +0.449 to +0.491 as well as to +0.656 to +0.721 volt versus Fc/Fc+ in Ni(II) compounds.