Synthesis,characterization, equilibrium studies,and biological activity of complexes involving copper(II), 2-aminomethylthiophenyl-4-bromosalicylaldehyde Schiff base,and selected amino acids

Ternary complexes of copper(II) with 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS) and some amino acids have been isolated and characterized by elemental analyses, IR, magnetic moment, molar conductance, UV–vis, mass spectra, and ESR. The proposed general formulas of the prepared complexes are [Cu(ATS)(AA)]·nH₂O (where AA?=?glycine, alanine, and valine). The low molar conductance values suggest the non-electrolytic nature of the complexes. IR spectra show that ATS is coordinated to copper in a bidentate manner through azomethine-N and phenolic-OH. The amino acids also are monobasic bidentate ligands via amino and ionized carboxylate groups. The magnetic and spectral data indicate the square-planar geometry of Cu(II) complexes. The geometry of the Cu(II) complexes has been fully optimized using parameterized PM3 semiempirical method. The Cu–N bond length is longer than that of Cu–O in the isolated complexes. Also, information is obtained from calculations of molecular parameters for all complexes including net dipole moment of the metal complexes, values of binding energy, and lipophilicity value (log P). The antimicrobial activity studies indicate significant inhibitory activity of complex 3 against the selected types of bacteria. The mixed ligand complexes have also been studied in solution state. Protonation constants of ATS and amino acids were determined by potentiometric titration in 50% (v/v) DMSO–water solution at ionic strength of 0.1?M NaCl. ATS has two protonation constants. The binary and ternary complexes of copper(II) involving ATS and some selected amino acids (glycine, alanine, and valine) were examined. Copper(II) forms [Cu(ATS)], [Cu(ATS)₂], [Cu(AA)], [Cu(AA)₂], and [Cu(ATS)(AA)] complexes. The ternary complexes are formed in a simultaneous mechanism.     

以2-(1-吡唑基甲基)吡啶类化合物为配体的羰基钼、钨衍生物的合成及结构

合成了2-[1-(3-叔丁基)吡唑基甲基]吡啶(CH2(Py)(3-ButPz)),并研究了羰基钼(钨)与该配体及其类似物2-(1-吡唑基甲基)吡啶(CH2(Py)(Pz))和2-[1-(3,5-二甲基)吡唑基甲基]吡啶(CH2(Py)(3,5-Me2Pz))的反应,合成了6个含双齿螯合的2-(1-吡唑基甲基)吡啶类配体的四羰基金属衍生物CH2(Py)(3-ButPz)M(CO)4,CH2(Py)(Pz)M(CO)4和CH2(Py)(3,5-Me2Pz)M(CO)4(M=Mo或W)。当用SnCl4处理CH2(Py)(3,5-Me2Pz)M(CO)4时,Sn-Cl键对金属中心发生氧化加成得到2个杂双核金属有机化合物CH2(Py)(3,5-Me2Pz)M(CO)3(Cl)SnCl3。所有新化合物均通过了红外和核磁的表征,CH2(Py)(3-ButPz)W(CO)4和CH2(Py)(3,5-Me2Pz)W(CO)3(Cl)SnCl3的结构还得到了X-射线单晶衍射的确证。用循环伏安法测定了四羰基金属衍生物的电化学性质。     

Computational (DFT) and Experimental (EXAFS) Study of the Interaction of [Ir(IMes)(H)2(L)3] with Substrates and Co‐substrates Relevant for SABRE in Dilute Systems

Signal amplification by reversible exchange (SABRE) is an emerging hyperpolarization method in NMR spectroscopy, in which hyperpolarization is transferred through the scalar coupling network of para‐hydrogen derived hydrides in a metal complex to a reversibly bound substrate. Substrates can even be hyperpolarized at concentrations below that of the metal complex by addition of a suitable co‐substrate. Here we investigate the catalytic system used for trace detection in NMR spectroscopy with [Ir(IMes)(H)₂(L)₃]⁺ (IMes=1,3‐dimesitylimidazol‐2‐ylidene) as catalyst, pyridine as a substrate and 1‐methyl‐1,2,3‐triazole as co‐substrate in great detail. With density functional theory (DFT), validated by extended X‐ray absorption fine structure (EXAFS) experiments, we provide explanations for the relative abundance of the observed metal complexes, as well as their contribution to SABRE. We have established that the interaction between iridium and ligands cis to IMes is weaker than that with the trans ligand, and that in mixed complexes with pyridine and triazole, the latter preferentially takes up the trans position.     

Quantum-Chemical Study of Adducts of Silicon Halides with Nitrogen-containing Donors: IV. Adducts with Pyridine

The structural and thermodynamic characteristics of SiX₄·Py and SiX₄·2Py adducts (X = H, F, Cl, Br) were calculated by ab initio and DFT methods (RHF and B3LYP). The resulting data were used to estimate for the first time the enthalpies of sublimation of trans-SiX₄·2Py complexes. The distortion energies of the donor and acceptor fragments and the energies of the Si-N bonds in the 1:1 and 1:2 halide complexes were calculated. The high distortion energy makes thermodynamically unfavorable equatorial monopyridine adducts with Si-N bond energies of 150-200 kJ/mol. In trans 1:2 complexes, pyridine acts as a weaker donor than ammonia with respect to silicon tetrahalides.     

Bis(dimethyldithiocarbamato)(pyridine)zinc and -copper(II) and Their Benzene Solvates: EPR and Solid-State Natural Abundance (13C, 15N) CP/MAS NMR

Adducts of bis(dimethyldithiocarbamato)zinc and -copper(II) complexes with pyridine, [M(Py)(Mdtc)₂], and their benzene solvates [M(Py)(Mdtc)₂] · 0.5C₆H₆ were synthesized. The electron paramagnetic resonance method and solid-state ¹³C and ¹⁵N CP/MAS NMR spectroscopy were used to perform a comparative study of the compounds obtained. The EPR data showed that the geometry of Cu(II) coordination polyhedra both in the adduct itself [Cu(Py)(Mdtc)₂], and in its solvate, [Cu(Py)(Mdtc)₂] · 0.5C₆H₆ is intermediate between a square pyramid (SP) and a trigonal bipyramid (TBP), the contribution from the latter being dominant (75%) in [Cu(Py)(Mdtc)₂]. In the solvated adduct [Cu(Py)(Mdtc)₂] · 0.5C₆H₆, the copper(II) polyhedron is distorted to form an SP-enriched structure (the contribution from TBP is reduced to 55%). It was found NMR data that [Zn(Py)(Mdtc)₂] exists in a single high-symmetry molecular form. Coordinated pyridine molecule shows molecular motion about the Zn–N bond. The solvation of the adduct results in structural nonequivalence of the Mdtc^–ligands in [Zn(Py)(Mdtc)₂] · 0.5C₆H₆. Signals in the ¹⁵N NMR spectra were assigned to the structural positions of the atoms in the previously described molecular structure of a solvated adduct. It was found that the heterogeneous reaction of adduct formation during the absorption of pyridine from the gas phase by polycrystalline [Zn₂(Mdtc)₄] species is accompanied by the dissociation of binuclear molecules.     

Interactions of Zn(II) with single and multiple amino acids. Insights from density functional and ab initio calculations

Calculations were performed to study the interactions of metal ions (M) with (multiple) amino acids (AA) and fill the gap between single AA and proteins. A complete conformational search results in nine and eleven ZnGly isomers at B3P86 and MP2 levels, respectively, and four populated conformers of glycine are responsible for production of these isomers. For all M, the isomers via the OO and NO binding modes are the main constituents, and the OO mode is favored by stronger electrostatic interactions. Binding with more glycines causes larger structural distortions, improves relative stabilities of monodentate binding isomers and generates new binding modes (e.g. ZnB_III via only the hydroxyl group). The scaling factor of Zn(Gly)_n structures, the ratio of its binding affinity versus the sum of comprising ZnGly isomers, is linear with glycine number (n), and the linear relationship may not be altered by mutations of glycines and M. It thus allows to estimate M(AA)_n binding affinities (n ≥ 2) from the comprising MAA structures and analyze their structures with kinetic methods. The DFT and MP2 results become comparable by increasing metal coordination, e.g. the ZnB_III versus ZnA_I (zwitterionic) relative energy differs by 41.9 kcal mol^?1 at B3P86 and MP2 levels and is close by addition of three water molecules (4.1 kcal mol^?1). The presence of water solvent improves the relative stabilities of monodentate binding isomers and results in a broader conformational distribution. Copyright © 2012 John Wiley & Sons, Ltd.     

Sequential bond energies of water to sodium glycine cation

Absolute bond dissociation energies of water to sodium glycine cations and glycine to hydrated sodium cations are determined experimentally by competitive collision-induced dissociation (CID) of Na⁺Gly(H₂O)_x, x = 1–4, with xenon in a guided ion beam tandem mass spectrometer. The cross sections for CID are analyzed to account for unimolecular decay rates, internal energy of reactant ions, multiple ion–molecule collisions, and competition between reaction channels. Experimental results show that the binding energies of water and glycine to the complexes decrease monotonically with increasing number of water molecules. Ab initio calculations at four different levels show good agreement with the experimental bond energies of water to Na⁺Gly(H₂O)_x, x = 0–3, and glycine to Na⁺(H₂O), whereas the bond energies of glycine to Na⁺(H₂O)_x, x = 2–4, are systematically higher than the experimental values. These discrepancies may provide some evidence that these Na⁺Gly(H₂O)_x complexes are trapped in excited state conformers. Both experimental and theoretical results indicate that the sodiated glycine complexes are in their nonzwitterionic forms when solvated by up to four water molecules. The primary binding site for Na⁺ changes from chelation at the amino nitrogen and carbonyl oxygen of glycine for x = 0 and 1 to binding at the C terminus of glycine for x = 2–4. The present characterization of the structures upon sequential hydration indicates that the stability of the zwitterionic form of amino acids in solution is a consequence of being able to solvate all charge centers.     

The base hydrolysis ofmer-[Co(1,5-diamino-3-azapentane)(amino acidate)X]+ (X = Cl or NO2) complexes and base hydrolysis of complexed peptides in the coordination sphere of the [Co(dien)]3+ moiety

Summary A variety ofmer-[Co(dien)(AA)X]⁺ (AA = amino acidate, dien = 1,5-diamino-3-azapentane) andmer-[Co(dien)(dipeptideOR)X]²⁺ complexes (X = Cl or NO₂) have been prepared and characterised. Base hydrolysis of the peptide bond in the carbonyl bonded glycyl peptides has been studied at 25°C and I = 0.1 mol dm^–3. The rate constants k_OH for peptide bond hydrolysis fall within the 0.67–0.88 mol dm^–3s^–1 range. Base hydrolysis of the complexed peptide isca. 2×10⁴ times faster than for the uncomplexed peptide ligand at 25 °C. The base hydrolysis of the chloro- and nitro-ligands in these complexes has also been studied. Very rapid hydrolysis occurs if the dien ligand adopts amer-configuration and the reactions are 10²–10⁴ times faster than for analogous complexes where the dien ligand adopts afac-configuration. These results are in agreement with Tobe's criteria for rapid base hydrolysis in cobalt(III) complexes.The following abbreviations are used thoughout this paper; dien 1,5-diamino-3-azapentane - dpt 1,7-diamino-4-azaheptane - glyO glycinate - glyOH glycine - glyOR glycine ester - glyNH₂ glycine amide - glyglyO glycylglycinate - glyglyOR glycylglycine ester - glyglyglyOH triglycine - -alaO -alaninate     

Recent advances in DFT assisted optimized energy,stability and distortions of optimized topologies of certain biopotent dimethyltin(IV) complexes

The generation, structural elucidation, reactivity, bonding, stability, optimized energy, distortions of optimized topologies of some non-bridged mononuclear and carboxylate bridged binuclear dimethyltin(IV) complexes of N-protected amino acids and 2-aminophenol/2-amino-4-methylphenol were studied experimentally and theoretically with the assistance of density functional theory (DFT). These complexes were synthesized by the reactions of Me₂SnCl₂ with sodium salts of N-protected amino acids and 2-aminophenol/2-amino-4-methylphenol in 1:1:1 ?molar ratio in refluxing dry THF. These complexes were characterized and their plausible structures were suggested with the assistance of spectroscopic [IR and NMR (¹H,¹³C and ¹¹⁹Sn)] evidences, mass studies and DFT investigation. Mass spectral data indicated the tendency of the complexes to undergo dimerization on aging. The ¹¹⁹Sn NMR data demonstrated the presence of penta-coordinated tin centres in these complexes. DFT (B3LYP) was used to study the molecular orbitals, optimized bond lengths and bond angles, optimized energy, stability, distortions of optimized topologies and energy gap of representative complexes. One representative complex, Me₂SnL₍₂₎L’₍₂₎ was screened for its possible antimicrobial activities against gram negative bacteria, E. coli and polymorphic fungal pathogen, Candida albicans, respectively. The structure-activity relationship of this complex has also been investigated.     

Adsorption of Proline and Glycine on the TiO2(110) Surface: A Density Functional Theory Study

The optimal adsorption modes for the amino acids glycine and proline on the ideal TiO₂(110) surface are investigated by using density functional theory (PBE) applying periodic boundary conditions. Binding modes with anionic acid moieties bridging two titanium atoms after transferring a proton to the surface are the most stable configurations for both molecules investigated—similar to previous results for carboxylic acids. In contrast to the latter compounds, amino acids can form hydrogen bonds via the amino group towards the surface‐bound proton; this provides an additional stabilisation of 15–20 kJ mol^?1. Zwitterionic binding modes are less stable (by 10–20 kJ mol^?1) and are less important for proline. Neutral modes are energetically even less favourable. Calculations of vibrational frequencies and core‐level shifts complement the adsorption study and provide guidance for future experimental investigations. Control of the computational parameters is crucial for the derivation of accurate results. The layout and thickness of the slab model used are also shown to be decisive factors. Calculations with a different GGA‐functional (PW91) provide very similar relative energies, although the absolute energies change by about 20 kJ mol^?1. Results derived with the hybrid functional PBE0 show an even greater stabilisation of the anionic binding modes with respect to the zwitterionic modes. A previously observed discrepancy between experimental and theoretical results for glycine could be solved, although the experimentally proposed free rotation of the C? C bond could not be reproduced.     

Hyperpolarization of Amino Acids in Water Utilizing Parahydrogen on a Rhodium Nanocatalyst

NMR offers many possibilities in chemical analysis, structural investigations, and medical diagnostics. Although it is broadly used, one of NMR spectroscopies main drawbacks is low sensitivity. Hyperpolarization techniques enhance NMR signals by more than four orders of magnitude allowing the design of new contrast agents. Parahydrogen induced polarization that utilizes the para-hydrogen's singlet state to create enhanced signals is of particular interest since it allows to produce molecular imaging agents within seconds. Herein, we present a strategy for signal enhancement of the carbonyl ¹³C in amino acids by using parahydrogen, as demonstrated for glycine and alanine. Importantly, the hyperpolarization step is carried out in water and chemically unmodified canonical amino acids are obtained. Our approach thus offers a high degree of biocompatibility, which is crucial for further application. The rapid sample hyperpolarization (within seconds) may enable the continuous production of biologically useful probes, such as metabolic contrast agents or probes for structural biology.     

Synthesis,characterization and catalytic studies of ruthenium(II) chalconate complexes

Stable ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh₃)(B)(L)] (E = P or As; B = PPh₃, AsPh₃ or Py; L = 2′‐hydroxychalcones) were synthesized from the reaction of [RuHCl(CO)(EPh₃)₂(B)] (E = P or As; B = PPh₃, AsPh₃ or Py) with 2′‐hydroxychalcones in benzene under reflux. The new complexes were characterized by analytical and spectroscopic (IR, electronic ¹H, ³¹P and ¹³C NMR) data. They were assigned an octahedral structure. The complexes exhibited catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide (NMO) as co‐oxidant and were also found to be efficient transfer hydrogenation catalysts. Copyright © 2008 John Wiley & Sons, Ltd.     

Facile P−C/C−H Bond‐Cleavage Reactivity of Nickel Bis(diphosphine) Complexes

Unusual cleavage of P?C and C?H bonds of the P₂N₂ ligand, in heteroleptic [Ni(P₂N₂)(diphosphine)]²⁺ complexes under mild conditions, results in the formation of an iminium formyl nickelate featuring a C,P,P‐tridentate coordination mode. The structures of both the heteroleptic [Ni(P₂N₂)(diphosphine)]²⁺ complexes and the resulting iminium formyl nickelate have been characterized by NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Density functional theory (DFT) calculations were employed to investigate the mechanism of the P?C/C?H bond cleavage, which involves C?H bond cleavage, hydride rotation, Ni?C/P?H bond formation, and P?C bond cleavage.     

Weak interactions between furfuryl and equatorial dioxime ligand in furfuryl(O2)Co(dmgH)2Py: NMR, X-ray and DFT calculations

The crystal and molecular structure of furfuryl(O₂)Co(dmgH)₂Py (1) has been determined by X-ray diffraction analysis. In the molecular structure of 1, the furfuryl ring oxygen is pointing inwards and is very close to one of the dmgH (Me) (2.625 Å). It shows unusual C-H···O weak interaction which must be responsible for the observed 1:3 ratio of dmgH methyl protons in NMR spectrum. Also, theoretical calculations using DFT have been performed on 1 for the Co-O and CH₂-C(furfuryl) bond rotation. Conformational energy diagrams derived from theoretical calculations also indicate that in most stable conformer the furfuryl ring oxygen is very close to one of the dmgH (Me) groups.     

Properties of fluoroantimonates(III) complexes with amino acids

Crystalline complex fluoroantimonates(III) with amino acids (glycine, β-alanine, DL-serine, DL-valine, L-leucine, and L-phenylalanine) have been prepared. The complexes stability in aqueous solutions has been studied with the cementation method. ¹H NMR studies of aqueous solutions of the amino acids complexes with SbF₃ at pH 1–6 and room temperature are reported. Preparation of polycrystalline metal antimony in aqueous solutions of tetrafluoroantimonates(III) complexes with the protonated amino acids has been demonstrated.     

Polymorphism of Ph2P(CH2Py)(NSiMe3) and the Staudinger Reaction of Ph2P(CH2Py) with Hydrogenazide1)

A new polymorph of the iminophosphorane Ph₂P(CH₂Py)(NSiMe₃), ( 1 ), is compared to a just recently published. The reaction of the starting material, the phosphane Ph₂P(CH₂Py) with N₃SiMe₃ in the presence of water gives [Ph₂P(CH₂Py)(NH₂)][N₃], ( 2 ). A comparison of the structural and NMR parameters of 2 with previously reported derivatives of 1 , suggests that 2 is best described as a phosphonium salt in which the negatively charged imino nitrogen atom is protonated, according to [Ph₂(CH₂Py)P⁺—NH₂][N₃]^—, rather than as an iminiumphosphane salt [Ph₂(CH₂Py)P=⁺NH₂][N₃]^—.     

Structure and magnetic properties of the copper(II) complexes with diacyl hydrazides of salicylic acid

The structures and results of the static magnetic susceptibility investigation of the copper(II) binuclear complex with salicylic acid diacyl hydrazide (H₂L), [Cu₂(L)(Py)₄] (I), and the copper(II) trinuclear complex with diacyl dihydrazide of salicylic and glutaric acids (H₆L′), [Cu₃(L′)(Py)₄] · 2Py (II), are described. The exchange antiferromagnetic interactions between the paramagnetic centers with the exchange interaction parameter −2J = 119 cm⁻¹ for dimer I and 14 cm⁻¹ for trinuclear complex II are detected.     

C−H and Si−H Activation Reactions at Ru/Ga Complexes: A Combined Experimental and Theoretical Case Study on the Ru−Ga Bond

Treatment of [Ru(COD)(MeAllyl)₂] and [Ru(COD)(COT)] with GaCp* under hydrogenolytic conditions leads to reactive intermediates which activate Si−H or C−H bonds, respectively. The product complexes [Ru(GaCp*)₃(SiEt₃)H₃] ( 1 ) and [Ru(GaCp*)₃(C₇H₇)H₃] ( 2 ) are formed with HSiEt₃ or with toluene as the solvent, respectively. While 1 was isolated and fully characterized by NMR, MS, IR and SC-XRD, 2 was too labile to be isolated and was observed and characterized in situ by using mass spectrometry, including labelling experiments for the unambiguous assignment of the elemental composition. The structural assignment was confirmed by DFT calculations. The relative energies of the four isomers possible upon toluene activation at the ortho-, meta-, para- and CH₃-positions have been determined and point to aromatic C−H activation. The Ru−Ga bond was analyzed by EDA and QTAIM and compared to the Ru−P bond in the analogue phosphine compound. Bonding analyses indicate that the Ru-GaCp* bond is weaker than the Ru-PR₃ bond.     

N‐[Tris(hydroxymethyl)methyl]glycine (tricine)

The title compound, C₆H₁₃NO₅, adopts a zwitterionic form where the carboxylic acid H atom is transferred to the amino group. The methyl–glycine backbone is planar. The tris(hydroxy­methyl)­methyl group is rotated as a rigid group around the amino–methyl bond by 22 (1)° and the carboxylic acid plane is rotated by 19.76 (12)° from the plane of the main skeleton. Apart from their H atoms, the three hydroxy­methyl groups adopt a propeller‐like conformation around the amino–methyl bond, close to C₃ symmetry.     

Neutral Penta‐ and Hexacoordinate Silicon(IV) Complexes Containing Two Bidentate Ligands Derived from the α‐Amino Acids (S)‐Alanine, (S)‐Phenylalanine,and (S)‐tert‐Leucine

The neutral hexacoordinate silicon(IV) complex 6 (SiO₂N₄ skeleton) and the neutral pentacoordinate silicon(IV) complexes 7 – 11 (SiO₂N₂C skeletons) were synthesized from Si(NCO)₄ and RSi(NCO)₃ (R=Me, Ph), respectively. The compounds were structurally characterized by solid‐state NMR spectroscopy ( 6 – 11 ), solution NMR spectroscopy ( 6 and 10 ), and single‐crystal X‐ray diffraction ( 8 and 11 were studied as the solvates 8? CH₃CN and 11? C₅H₁₂ ? 0.5 CH₃CN, respectively). The silicon(IV) complexes 6 (octahedral Si‐coordination polyhedron) and 7 – 11 (trigonal‐bipyramidal Si‐coordination polyhedra) each contain two bidentate ligands derived from an α‐amino acid: (S)‐alanine, (S)‐phenylalanine, or (S)‐tert‐leucine. The deprotonated amino acids act as monoanionic ( 6 ) or as mono‐ and dianionic ligands ( 7 – 11 ). The experimental investigations were complemented by computational studies of the stereoisomers of 6 and 7 .