IR Shifts Research Articles

Synthesis, spectroscopic characterisation, DFT insight, and molecular docking studies of a coumarin derivative 3-acetyl-2-oxo-2H-chromene-6-carbohydrazide

In this study, a coumarin derivative, 3-Acetyl-2-oxo-2H-chromene-6-carbohydrazide that could be a new antifungal agent was synthesised, and characterised by elemental analysis, FT-IR, 1H and 13C NMR spectroscopic techniques. DFT calculation data (IR, 1H, and 13C NMR chemical shifts) reveals the good correlation with the experimental values to support the structure of the compound. Molecular geometry, stability, reactivity, and spontaneity were also predicted based on frontier molecular orbitals (FMO), electrostatic potential (ESP) and thermodynamic parameters like entropy, enthalpy, and Gibbs free energy. In addition, molecular docking study results implicate its strong binding (−7.1 to −7.8 kcal/mol) and inhibitory activity against four pathogenic fungal strains A. niger (5GHL), P. chrysogenum (3A72), S. cerevisiae (4G4S), and N. crassa (6MVJ). Thus, this compound may be considered biologically important and serve as a lead for the development of antifungal agents.

Dynamic Excitons in Nitrile-Functionalized Ladder-Type Oligo(p-Phenylene)s By Pulse Radiolysis Coupled with Time-Resolved Infrared Spectroscopy

Research and development efforts toward organic solar cells (OSCs) for large-scale power generation have continued unabated throughout the world. In recent years, OSCs based on π-conjugated polymers and small molecules have received increasing interest due to favorable electronic properties, component versatility, and low production and installation costs. Despite the progress, many improvements are still needed prior to widespread commercialization, involving device efficiency, lifetime, and cost. Of these, increasing device efficiency, particularly power conversion efficiency (PCE), is the most challenging task. The currently achievable PCE, for example, is only 17.3%.1 The key to achieving high PCE is the search for new organic conjugated molecules that are capable of harvesting light, and transferring and transporting charges promptly and efficiently. This requires a full understanding of how electrons and holes are localized and delocalized in organic conjugated molecules.Using time-resolved infrared (TRIR) detection combined with pulse radiolysis, Mani and co-workers2 have measured experimentally the degree of localization of an excess electron in a series of nitrile-functionalized oligofluorenes by the spectral shifts of nitrile vibrations. The nitrile vibrational bands in anions respond sensitively to the degree of electron delocalization (IR shifts) and the structural changes (IR linewidth). The electron is found to move back and forth within the oligomers, likely controlled by the movement of dihedral angles between monomer units.Unlike the non-coplanarity of the fluorenyl-fluorenyl backbone in oligofluorenes, the rigid and planar structure of ladder-type, oligo(p-phenylene)s (Scheme 1)3 would facilitate π-electron delocalization and thus improve the multiphoton absorption response. Such a structure would also increase photoluminescence efficiency with enhanced thermal and photochemical stability. To investigate the coupling between charge distribution and vibrational motion and vibronic coupling, we incorporate nitrile group in each compound as the infrared reporter group.In this talk, we report our molecular syntheses and characterizations of two of the title compounds (L3PCN and L4PCN, both neutral compounds and their radical anions) by TRIR followed by pulse radiolysis. Having no flexible dihedral angles, L3PCN and L4PCN exhibit sharper IR bands of the nitrile vibration than the oligofluorenes with the same number of benzene rings and some dihedral angles. Our results further demonstrate that the linewidth of the nitrile vibration, together with the IR shifts and intensities, reports on structural and accompanying electronic fluctuations,2 that is, on the dynamic excitons. References (1) Meng, L. X.; et al. Science 2018, 361, 1094.(2) Mani, T.; et al. Journal of the American Chemical Society 2015, 137, 10979.(3) Scherf, U.; et al. Makromolekulare Chemie-Rapid Communications 1991, 12, 489. Figure 1

Community Resilience in Belarus and the EU response

Community Resilience in Belarus and the EU response

Validation of potential energy distribution by VEDA in vibrational assignment some of β-diketones; comparison of theoretical predictions and experimental vibration shifts upon deutration

The harmonic vibrational frequencies of the cis-enol forms of some of β-diketones with different substitution in beta position, vis. H, CH3, and Ph ring, as the symmetric and asymmetric molecules, were calculated using density functional theory (DFT) at the B3LYP/6–311++G(d,p) level of theory. The results of DFT calculations were used to obtain the potential energy distribution (PED) by VEDA software. The PED results compared with the Gauss View animation, as our reassignments, and the experimental IR shifts upon deuteration of hydrogen in the OH and CHα. According to our study, the PED contributions, Gauss View animation and observed shifts show similar results for most of the bands which are not coupled with the OH and/or CHα bending, such as asymmetric and symmetric CH3 stretching and in-plane deformations, CH3 rocking vibrations and 8a, 19b, 9a, 15, 18a, and 12 motions of the phenyl ring. The largest discrepancies were observed in the 1700-1000 cm−1 region, likely due to the coupling with the OH and CHα in-plane bending vibrations, such as νaC = C–C = Ο, νsC = C–C = Ο and δOH. Furthermore, the calculated PED contributions by VEDA software do not well define the vibrational contributions to those groups in the molecule that are directly involved in the intramolecular hydrogen bond and the observed failure of the VEDA procedure is possibly due to inappropriateness of the default options.

First Principles Calculations of the Energetic, Structural, Electronic, and Magnetic Properties of Fe/Ir(100) System

Although the Fe/Ir(100) system has been extensively investigated, contradictory conclusions were drawn from different experimental and theoretical studies about its magnetic ground state. In this work, density functional theory calculations are performed for the adsorption of Fe on the Ir(100) surface with different coverages to resolve this contradiction. The obtained adsorption energy decreases as the coverage increases, which reflects the effect of repulsive interaction between the adsorbates. Antiferromagnetic (AFM) configuration is found to be more stable than the ferromagnetic (FM) configuration for the 0.50 and 1.00 monolayer (ML) coverages. Fe atoms start to form a body centered cubic (BCC) structure, with the basis of a lattice parameter of Ir and have a pseudomorphic growth. The FM configuration is found to be more stable than the AFM configuration for Fe bilayer on Ir(100) surface with c/a ≈ 0.53, which predicts a BCC Fe precursor due to the small lattice mismatch between Fe and Ir surface. The electronic properties predict that the reactivity of Ir surface decreases beyond Fe coverage of 0.50 ML since the d band center of 5d Ir shifts to the left of Fermi energy as Fe coverage increases.

Experimental and Computational Modeling of H-Bonded Arginine-Tyrosine Groupings in Aprotic Environments.

H-bonds between neutral tyrosine and arginine in nonpolar environments are modeled by small-molecule phenol/guanidine complexes. From the temperature and concentration dependence of UV spectra, a value of ΔH° = −74 ± 4 kJ mol–1 is deduced for the formation of H-bonded p-cresol/dodecylguanidine in hexane. ΔE = −71 kJ mol–1 is computed with density functional theory (in vacuo). In dimethyl sulfoxide or crystals, (p-phenolyl)alkylguanidines form head-to-tail homodimers with two strong H-bonding interactions, as evidenced by UV, IR, and NMR spectral shifts, strong IR continuum absorbance bands, and short O···N distances in X-ray crystal structures. Phenol/alkylguanidine H-bonded complexes consist of polarizable rapidly interconverting tautomers, with the proton shift from phenol to guanidine increasing with increase in the polarity of the aprotic solvent. As measured by NMR, both groups in these strongly H-bonded neutral complexes can simultaneously appear to be predominantly protonated. These systems serve as models for the hypothetical hydrogen-Bonded Uncharged (aRginine + tYrosine), or “BU(RY)”, motifs in membrane proteins.

Probing Intermolecular Electron Delocalization in Dimer Radical Anions by Vibrational Spectroscopy.

Delocalization of charges is one of the factors controlling charge transport in conjugated molecules. It is considered to play an important role in the performance of a wide range of molecular technologies, including organic solar cells and organic electronics. Dimerization reactions are well-suited as a model to investigate intermolecular spatial delocalization of charges. While dimerization reactions of radical cations are well investigated, studies on radical anions are still scarce. Upon dimerization of radical anions with neutral counterparts, an electron is considered to delocalize over the two molecules. Here, by using time-resolved infrared (TRIR) detection coupled with pulse radiolysis, we show that radical anions of 4-n-hexyl-4'-cyanobiphenyl (6CB) undergo such dimerization reactions, with an electron equally delocalized over the two molecules. We have recently demonstrated that nitrile ν(C≡N) vibrations respond to the degree of electron localization of nitrile-substituted anions: we can quantify the changes in the electronic charges from the neutral to the anion states in the nitriles by monitoring the ν(C≡N) IR shifts. In the first part of this article, we show that the sensitivity of the ν(C≡N) IR shifts does not depend on solvent polarity. In the second part, we describe how probing the shifts of the nitrile IR vibrational band unambiguously confirms the formation of dimer radical anions, with Kdim = 3 × 104 M-1. IR findings are corroborated by electronic absorption spectroscopy and electronic structure calculations. We find that the presence of a hexyl chain and the formation of π-π interactions are both crucial for dimerization of radical anions of 6CB with neutral 6CB. The present study provides clear evidence of spatial delocalization of electrons over two molecular fragments.

Observational Evidence Linking Interstellar UV Absorption to PAH Molecules

Abstract The 2175 Å UV extinction feature was discovered in the mid-1960s, yet its physical origin remains poorly understood. One suggestion is absorption by polycyclic aromatic hydrocarbon (PAH) molecules, which is supported by theoretical molecular structure computations and by laboratory experiments. PAHs are positively detected by their 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm IR emission bands, which are specified by their modes of vibration. A definitive empirical link between the 2175 Å UV extinction and the IR PAH emission bands, however, is still missing. We present a new sample of hot stars that have both 2175 Å absorption and IR PAH emission. We find significant shifts of the central wavelength of the UV absorption feature, up to 2350 Å, but predominantly in stars that also have IR PAH emission. These UV shifts depend on stellar temperature in a fashion that is similar to the shifts of the 6.2 and 7.7 μm IR PAH bands, that is, the features are increasingly more redshifted as the stellar temperature decreases, but only below ∼15 kK. Above 15 kK both UV and IR features retain their nominal values. Moreover, we find a suggestive correlation between the UV and IR shifts. We hypothesize that these similar dependences of both the UV and IR features on stellar temperature hint at a common origin of the two in PAH molecules and may establish the missing link between the UV and IR observations. We further suggest that the shifts depend on molecular size, and that the critical temperature of ∼15 kK above which no shifts are observed is related to the onset of UV-driven hot-star winds and their associated shocks.

Effect of acetate and nitrate anions on the molecular structure of 3-(hydroxyimino)-2-butanone-2-(1H-benzimidazol-2-yl)hydrazone

A novel Schiff base ligand 3-(hydroxyimino)-2-butanone-2-(1H-benzimidazol-2-yl)hydrazone has been synthesized by the condensation reaction of 2-Hydrazinobenzimidazole with diacetyl monoxime in presence of acetic acid catalyst. The ligand has crystallized as its acetate salt, due to the charge-assisted hydrogen bonding between protonated benzimidazole ring and acetate anion. Efforts to synthesize the zinc(II) complex of the title compound, has resulted in the formation of a nitrate salt of the ligand, instead of coordination complex of zinc(II). Acetate salt has crystallized in monoclinic P 21/n, while the nitrate salt has crystallized in a triclinic crystal system with P -1 space group. Hirshfeld surface analysis is presented for both of the crystal structures. Structures of synthesized molecules are even computationally optimized using DFT. A comparative structural approach between the synthesized molecules and DFT optimized structure of bare ligand without any counterions is analyzed in terms of bond parameters. Hydrogen bonding is explained keeping the anions as the central dogma. Mass fragmentation pattern of the organic molecule and comparative account of IR, 1H and 13C NMR chemical shifts are also presented. Compounds are screened for their antibacterial and antifungal potencies against few pathogenic microorganisms. The organic motif is found be an excellent antifungal agent.

Vibrational Stark Effects of Carbonyl Probes Applied to Reinterpret IR and Raman Data for Enzyme Inhibitors in Terms of Electric Fields at the Active Site.

IR and Raman frequency shifts have been reported for numerous probes of enzyme transition states, leading to diverse interpretations. In the case of the model enzyme ketosteroid isomerase (KSI), we have argued that IR spectral shifts for a carbonyl probe at the active site can provide a connection between the active site electric field and the activation free energy (Fried et al. Science 2014, 346, 1510-1514). Here we generalize this approach to a much broader set of carbonyl probes (e.g., oxoesters, thioesters, and amides), first establishing the sensitivity of each probe to an electric field using vibrational Stark spectroscopy, vibrational solvatochromism, and MD simulations, and then applying these results to reinterpret data already in the literature for enzymes such as 4-chlorobenzoyl-CoA dehalogenase and serine proteases. These results demonstrate that the vibrational Stark effect provides a general framework for estimating the electrostatic contribution to the catalytic rate and may provide a metric for the design or modification of enzymes. Opportunities and limitations of the approach are also described.

Vibrational spectroscopic study of intensities and shifts of symmetric vibration modes of ozone diluted by cumene

In the current research, ATR–FTIR and FT–Raman spectroscopies was used to investigate the effect of concentration on IR and Raman intensities and shifts of symmetric vibration modes of Ozone diluted by Cumene. The symmetric vibration mode of Ozone was observed at IR and Raman shifts of 850 and 975 cm-1, respectively. By reducing the concentration of Ozone, its intensity also was reduced and the symmetric vibration mode of Cumene was observed at IR and Raman shifts of 1050 and 1185 cm-1, respectively. The concentration has not influence on IR and Raman shifts of vibration modes. The experimental results were confirmed the linear dependency of IR and Raman intensities to the concentration of sample.Ozone molecule (left illustration) and Cumene molecule (right illustration) (Santiago-López et al. 2010; Guevara-Guzmán et al. 2009; Pereyra-Muñoz et al. 2006; Foucaud et al. 2006; Elsayed 2001; van Hoof et al. 1997; Chrostowski et al. 1983; Boehme et al. 1992; Catalá et al. 2013; Balvers et al. 1992; Marker et al. 1986).

Molecular structure, spectroscopic properties and quantum chemical calculations of a novel 2,2′-Dicarboxy-4,4′-(propane-2,2-di-yl)diphenol

The synthesis, spectroscopic (IR, 1H and 13C NMR chemical shifts) investigations of 2,2′-Dicarboxy-4,4′-(propane-2,2-di-yl)diphenol molecule have been confirmed. Molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of the compound in the ground state have been calculated using the density functional method (DFT) with 6-311G++(d,p) basis set. The calculated values are in good agreement with the experimental values. The energetic behavior of the compound in solvent media has been examined using B3LYP method with the 6-311G++(d,p) basis set by applying the polarizable continuum model (PCM). The total energy of the compound decreases with increasing polarity of the solvent. Besides, molecular electrostatic potential (MEP), non-linear optical (NLO) properties of the compound have been investigated by using theoretical calculations.

The spectroscopic and electronic properties of dimethylpyrazole and its derivatives using the experimental and computational methods.

In this paper the spectroscopic and the geometric properties of four ligands with pyrazole unit are studied at both experimental and computational levels. The computational results are perfectly in good agreement with the experimental results especially in terms of the IR, H-NMR and 13C-NMR shifts. The spectroscopic features as well as the computed properties help to establish the successful synthesis of ligands bdmpzm and bdmpza. The theoretical and the experimental IR and Raman significantly help in distinguishing the four ligands. The results show that the Raman spectral is better applicable in characterising the CH3 deformation, the C-H, CNN and CCNNout of the ligands but vibrations like N-H in dmpz and O-H, C=O in bdmpza are observed to be Raman inactive. A significant variations are observed among the two available * N atoms characterising the bidentate features of bdmpzm, bdmpza and bdcpzm which indicates a possible different affinities for metal coordination: Also the result suggest that bdmpza will be the best starting material for NLO application than other while bdcpzm is predicted to have potential of been a poor coordinating ligand. The computed variations in the properties of * N atoms that are the characteristic features of their power of coordination can be of immense help since these type of ligands have a wide application in transition metal coordination.

Quantum Chemical Study of the Initial Step of Ozone Addition to the Double Bond of Ethylene

The mechanisms of the initial step in chemical reaction between ozone and ethylene were studied by multireference perturbation theory methods (MRMP2, CASPT2, NEVPT2, and CIPT2) and density functional theory (OPW91, OPBE, and OTPSS functionals). Two possible reaction channels were considered: concerted addition through the symmetric transition state (Criegee mechanism) and stepwise addition by the biradical mechanism (DeMore mechanism). Predicted structures of intermediates and transition states, the energies of elementary steps, and activation barriers were reported. For the rate-determining steps of both mechanisms, the full geometry optimization of stationary points was performed at the CASPT2/cc-pVDZ theory level, and the potential energy surface profiles were constructed at the MRMP2/cc-pVTZ, NEVPT2/cc-pVDZ, and CIPT2/cc-pVDZ theory levels. The rate constants and their ratio for reaction channels calculated for both mechanisms demonstrate that the Criegee mechanism is predominant for this reaction. These results are also in agreement with the experimental data and previous computational results. The structure of DeMore prereactive complex is reported here for the first time at the CCSD(T)/cc-pVTZ and CASPT2/cc-pVDZ levels. Relative stability of the complexes and activation energies were refined by single-point energy calculations at the CCSD(T)-F12/VTZ-F12 level. The IR shifts of ozone bands due to formation of complexes are presented and discussed.

Optical Observation of Lung Cancer With Attenuated Total Reflectance–Fourier Transform Infrared Microscope (ATR-FTIR) and Confocal Raman Microscope

ABSTRACT Optical observation of lung cancer tissues using attenuated total reflectance–Fourier transform infrared microscope (ATR-FTIR) and confocal Raman microscope were performed. A total of six malignant tissues, seven tissues adjacent to cancer, and nine normal tissues from nine patients with known lung cancer were studied. High-quality spectra from human tissues were obtained only in a few seconds. The results revealed that some of the spectral characteristics varied significantly between normal and malignant tissues, that is, IR peak positions, Raman shift, and the spectral intensities. Differences in positions of 10 main peaks in IR shifts and 13 main peaks in Raman shifts were listed, and the intensity changes were also studied between the malignant and normal tissues. The ratios of 1453-cm−1/1645-cm−1 intensity in IR spectrum and 1245-cm−1/1571-cm−1 intensity in Raman spectrum were found with the most significant difference (p < 0.0001 and p < 0.05 separately) in statistics and may be used in combination to differentiate the normal and malignant tissues. ATR-FTIR spectrum and Raman spectrum were mutually complementary in the observation of many materials and were both found with high sensitivities and spatial resolutions in the observation of human tissues. This study will be helpful to developing rapid and accurate cancer detection techniques in future clinical diagnosis.

Blue- and Red-Shifting CH···O Hydrogen Bonded Complexes between Haloforms and Ethers: Correlation of Donor νC−H Spectral Shifts with C−O−C Angular Strain of the Acceptors

In 1:1 CH...O hydrogen bonded complexes between haloforms and ethers, a correlation of the spectral shifts of nu(C-H) bands (Deltanu(C-H)) of the donors (haloforms) with C-O-C angular strain of the acceptors (ethers) is investigated by the electronic structure theory method at the MP2/6-311++G** level. The calculation predicts that the three-member cyclic ether (oxirane) that has the smallest C-O-C angle induces a much larger blue shifting effect on nu(C-H) transition of fluoroform compared with that by the open chain analogue, dimethyl ether. The natural bond orbital (NBO) analysis reveals that the effect originates because of higher "s" character in the hybrid lone electron pair orbital of the oxygen atom of the former, which is responsible for a smaller contribution to n(O) --> sigma*(C-H) hyperconjugation interaction energy between the donor-acceptor molecules. The optimized structures of the two complexes are largely different with respect to the intermolecular orientational parameters at the hydrogen bonding sites, and similar behavior is also predicted for the two chloroform complexes. Partial optimizations on a series of structures show that the total binding energy of the complexes are insensitive with respect to those geometric parameters. However, the Deltanu(C-H), hyperconjugation interaction energies and hybridization of the carbon-centric bonding orbital of the C-H bond are sensitive with respect to those parameters. The predicted Deltanu(C-H) of each complex is analyzed with respect to the IR spectral shift measured by van der Veken and coworkers in cryosolutions of inert gases. The disagreement found between the measured and calculated IR shifts is interpreted to be the outcome of deformation of the complex geometries along shallow binding potential energy surfaces owing to solvation in the liquefied inert gases.

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PiPr3)2 System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Ru(CH═CHFc)Cl(CO)(PiPr3)2 (Fc = ferrocenyl, (η5-C5H4)Fe(η5-C5H5)), 1, has been prepared by hydroruthenation of ethynylferrocene and characterized by NMR, IR, ESI-MS, and Moessbauer spectroscopy and by X-ray crystallography. Complex 1 features conjoined ferrocene and (vinyl)ruthenium redox sites and undergoes two consecutive reversible oxidations. Pure samples of crystalline, monooxidized 1•+ have been prepared by chemical oxidation of 1 with the ferrocenium ion. Structural comparison with 1 reveals an increase of Fe−C and Fe−Cpcentr. bond lengths and ring tilting of the Cp decks, as is typical of ferrocenium ions, but also a discernible lengthening of the Ru−C(CO) and Ru−P bonds and a shortening of the Ru−C(vinyl) bond upon oxidation. This supports the general idea of charge delocalization over both redox sites in 1•+. Band shifts of the charge-sensitive IR labels (ν(CO) for Ru, ν(C−H, Cp) for Fc), the rather small g-anisotropy in the ESR spectrum of 1•+, and the results of quantum chemical calculations indicate that in solution the positive charge partly resides on the vinyl ruthenium moiety. Comparison of IR shifts in the solid state and in solution and the quadrupole splitting in the Moessbauer spectrum of powdered 1•+ point to a larger extent of charge localization on the ferrocenyl site in solid samples. This is probably due to CH···F hydrogen bonding interactions between the cyclopentadienyl hydrogen atoms of the radical cations and the PF6− counterions. Monooxidized 1•+ displays low-energy electronic absorption bands at 1370 and 2150 nm. According to quantum chemical calculations, the underlying transitions are largely localized on the ferrocene part of the molecule with only little charge transfer into the vinyl ruthenium subunit. The second oxidation is more biased toward the (vinyl)ruthenium site.

Synthesis of rhodium(III) complexes with tris/tetrakis‐benzimidazoles and benzothiazoles—quick identification of cyclometallation by nuclear magnetic resonance spectroscopy

Reactions of rhodium(III) halides with multidentate N,S-heterocycles, (LH3) 1,3,5-tris(benzimidazolyl)benzene (L1H3; 1), 1,3,5-tris(N-methylbenzimidazolyl) benzene (L2H3; 2) and 1,3,5-tris(benzothiazolyl)benzene (L3H3; 3), in the molar ratio 1:1 in methanol-chloroform produced mononuclear cyclometallated products of the composition [RhX2(LH2)(H2O)] (X = Cl, Br, I; LH2 = L1H2, L2H2, L3H2). When the metal to ligand (1-3 or 1,2,4,5-tetrakis(benzothiazolyl)benzene [L4H2; 4]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh2Cl5(LH2)(H2O)3] (LH2 = L1H2, L2H2, L3H2) and [Rh2X4(L4)(H2O)2] (X = Cl, Br, I). Elemental analysis, IR and 1H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13C NMR spectra that showed a doublet around approximately 190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1-3. Cyclometallation was substantiated by two-dimensional 1H-1H correlated experiments (gradient-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1H-13C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1H-15N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen.

Synthesis, spectroscopic characterization and antimicrobial studies of mercury(II) complexes of thiolates

Mercury(II) complexes of thiolates having the general formula [Hg(RS)Cl2]−and [Hg(RS)2] have been prepared and characterized by IR and NMR (1H and13C) spectroscopy (RSH = 2-aminoethanethiol hydrochloride (Aet), cysteine (Cys), thiosalicylic acid (Ts) and 2-mercaptonicotinic acid (Mnt)). The spectral data suggests that the coordination of thiolates to mercury(II) occurs through the sulfur as indicated by the absence of S–H vibrations in IR and significant downfield shifts in the C–S resonance in13C NMR. However, in Mnt complexes, coordination through both sulfur and nitrogen is indicated. Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentration and the results showed that the complexes exhibited a wide range of activities against gram-negative bacteria (E. coli, P. aeruginosa), while moderate activity was observed against a mold,P. citrinum.

Synthesis, spectroscopic characterization and antimicrobial studies of mercury(II) complexes of thiolates

Mercury(II) complexes of thiolates having the general formula (Hg(RS)Cl2) − and (Hg(RS)2) have been prepared and characterized by IR and NMR ( 1 Ha nd 13 C) spectroscopy (RSH = 2-aminoethanethiol hydrochloride (Aet), cysteine (Cys), thiosalicylic acid (Ts) and 2-mercaptonicotinic acid (Mnt)). The spectral data suggests that the coordination of thiolates to mercury(II) occurs through the sulfur as indicated by the absence of S-H vibrations in IR and significant downfield shifts in the C-S resonance in 13 C NMR. However, in Mnt complexes, coordination through both sulfur and nitrogen is indicated. Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentration and the results showed that the complexes exhibited a wide range of activities against gram-negative bacteria (E. coli, P. aeruginosa), while moderate activity was observed against a mold, P. citrinum.