Glycine Ligands Research Articles

Glycine-Templated Manganese Sulfate with New Topology and Canted Antiferromagnetism

A new glycine-templated manganese(II) sulfate, (C(2)NO(2)H(5))MnSO(4) (1), has been solvothermally synthesized and characterized crystallographically and magnetically. Crystal data for 1: monoclinic, space group P2(1)/m, a = 4.8884(10) A, b = 7.8676(14) A, c = 8.0252(15) A, beta = 106.524(2) degrees , V = 295.90(10) A(3), Z = 2. The glycine bridges Mn(II) ions in mu(2) mode and sulfate in eta(3),mu(4) mode. Along the b direction, the neighboring Mn(II) ions were bridged to each other by two sulfate ions and one glycine ligand to form a triple-stranded braid. The adjacent braids were connected via the sulfate ions to give a two-dimensional framework with a novel binodal 4,6-connected (3(2);4(2);5(2))(3(4);4(4);5(4);6(3)) topology. The compound exhibits a spin-canted antiferromagnetic behavior with a weak ferromagnetic transition below 9 K, and the estimated canting angle is 0.13 degrees.

Metal Flux in Ligand Mixtures. 2. Flux Enhancement Due to Kinetic Interplay: Comparison of the Reaction Layer Approximation with a Rigorous Approach

The revisited reaction layer approximation (RLA) of metal flux at consuming interfaces in ligand mixtures, discussed in the previous paper (part 1 of this series) is systematically validated by comparison with the results of rigorous numerical simulations. The current paper focuses on conditions under which the total metal flux is enhanced in the ligand (and complex) mixture compared to the case where the individual fluxes of metal complexes are independent of each other. Such an effect is exhibited only in ligand mixtures and results from the kinetic interplay between the various complexes with different labilities. It is exemplified by the Cu/NTA/N-(2-carboxyphenyl)glycine system (see part 1 paper), in which we show that the flux due to the less labile complex (CuNTA) is increased in the presence of a ligand (2-carboxyphenyl)glycine) that forms labile Cu complexes, even when the latter is in negligible proportion in the bulk solution. This paper first explains how the so-called composite and equivalent reaction layer thicknesses computed by RLA can be determined graphically from the concentration profiles of free metal and its complexes, as obtained by rigorous calculations. This approach allows comparison between the latter and RLA predictions. Comparison between these reaction layer thicknesses is then done using the chemical system mentioned above. The mechanism of flux enhancement with this system is studied in detail by following the change of the concentration profiles and reaction layer thicknesses with the increase of concentration of the ligand forming labile complexes. The mechanism of flux enhancement is well explained by the RLA and is validated by the concentration profiles obtained by rigorous numerical simulations. Based on this validation, the RLA is used to predict the conditions of the individual complex labilities and degree of complexation required to get flux enhancement in a two-ligand system. Due to compensation effects between kinetic and thermodynamic factors, a maximum flux enhancement is observed in a specific range of ratios of the lability indices of the two complexes. Flux enhancement might play a significant role in metal uptake in environmental or biological systems and should be considered in data interpretation.

Spectrophotometric Determination of Iron(III)–Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO3, I = 0.2 M at 28 ± 1 °C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN– was used as an indicator reaction. Under the specified conditions Fe(III) formed 1:1 complexes, [Fe(SCN)]2+ and [Fe(Gly)]2+, with both of these ligands. The molar absorption coefficient and the formation constant of the [Fe(SCN)]2+ complex were determined graphically as well as through dynamic optimization of six parallel equations using Solver tool in Excel. Values thus obtained were subsequently used to calculate concentrations of uncoordinated iron(III) and glycine in the mixed-ligand solution. The principal advantage of the proposed method is that it offers a simple and convenient approach for an undergraduate laboratory demonstration of quantitative comparisons of formation constants using an inexpensive spectrophotometer and Excel software that are readily available in most teaching laboratories.

Coordination polymer incorporating cobalt(II) and glycine acid: structure and magnetism

We report the structure and magnetism of a cobalt(II) compound with glycine acid, Co(C2H4NO2)2 · H2O (1). It crystallizes in the orthorhombic system, space group P2(1)2(1)2(1) with a = 5.2301(10) Å, b = 10.837(2) Å, c = 13.542(3) Å, R 1 = 0.0448, wR 2 = 0.1151. In 1, Co(II) has a slightly distorted square-pyramidal geometry defined by two O atoms and two N atoms from two glycine ligands, and by one O atom from an aqua ligand in the apical position. The molecules form a three-dimensional supramolecular network through O–H ··· O and N–H ··· O hydrogen bonds. Magnetic characterization shows 1 exhibits a negative Curie–Weiss constant and dominant spin-orbit coupling for Co(II).

Aqueous V(V)-Peroxo-Amino Acid Chemistry. Synthesis, Structural and Spectroscopic Characterization of Unusual Ternary Dinuclear Tetraperoxo Vanadium(V)-Glycine Complexes

Vanadium participation in cellular events entails in-depth comprehension of its soluble and bioavailable forms bearing physiological ligands in aqueous distributions of binary and ternary systems. Poised to understand the ternary V(V)-H(2)O(2)-amino acid interactions relevant to that metal ion's biological role, we have launched synthetic efforts involving the physiological ligands glycine and H(2)O(2). In a pH-specific fashion, V(2)O(5), glycine, and H(2)O(2) reacted and afforded the unusual complexes (H(3)O)(2)[V(2)(O)(2)(mu(2):eta(2):eta(1)-O(2))(2)(eta(2)-O(2))(2)(C(2)H(5)NO(2))] x 5/4 H(2)O (1) and K(2)[V(2)(O)(2)(mu(2):eta(2):eta(1)-O(2))(2)(eta(2)-O(2))(2)(C(2)H(5)NO(2))] x H(2)O (2). 1 crystallizes in the triclinic space group P1, with a = 7.805(4) A, b = 8.134(5) A, c = 12.010(7) A, alpha = 72.298(9) degrees, beta = 72.991(9) degrees, gamma = 64.111(9) degrees, V = 641.9(6) A(3), and Z = 2. 2 crystallizes in the triclinic space group P1, with a = 7.6766(9) A, b = 7.9534(9) A, c = 11.7494(13) A, alpha = 71.768(2) degrees, beta = 73.233(2) degrees, gamma = 65.660(2) degrees, V = 610.15(12) A(3), and Z = 2. Both complexes 1 and 2 were characterized by UV/visible, LC-MS, FT-IR, Raman, NMR spectroscopy, cyclic voltammetry, and X-ray crystallography. The structures of 1 and 2 reveal the presence of unusual ternary dinuclear vanadium-tetraperoxo-glycine complexes containing [(V(V)=O)(O(2))(2)](-) units interacting through long V-O bonds and an effective glycinate bridge. The latter ligand is present in the dianionic assembly as a bidentate moiety spanning both V(V) centers in a zwitterionic form. The collective physicochemical properties of the two ternary species 1 and 2 project the chemical role of the low molecular mass biosubstrate glycine in binding V(V)-diperoxo units, thereby stabilizing a dinuclear V(V)-tetraperoxo dianion. Structural comparisons of the anions in 1 and 2 with other known dinuclear V(V)-tetraperoxo binary anionic species provide insight into the chemical reactivity of V(V)-diperoxo species in key cellular events such as insulin mimesis and antitumorigenicity, potentially modulated by the presence of glycinate and hydrogen peroxide.

Mechanistic Studies of Cu(II) Binding to Amyloid-β Peptides and the Fluorescence and Redox Behaviors of the Resulting Complexes

Due in large part to the lack of crystal structures of the amyloid-beta (Abeta) peptide and its complexes with Cu(II), Fe(II), and Zn(II), characterization of the metal-Abeta complex has been difficult. In this work, we investigated the complexation of Cu(II) by Abeta through tandem use of fluorescence and electron paramagnetic resonance (EPR) spectroscopies. EPR experiments indicate that Cu(II) bound to Abeta can be reduced to Cu(I) using sodium borohydride and that both Abeta-Cu(II) and Abeta-Cu(I) are chemically stable. Upon reduction of Cu(II) to Cu(I), the Abeta fluorescence, commonly reported to be quenched upon Abeta-Cu(II) complex formation, can be regenerated. The absence of the characteristic tyrosinate peak in the absorption spectra of Abeta-Cu(II) complexes provides evidence that the sole tyrosine residue in Abeta is not one of the four equatorial ligands bound to Cu(II), but remains close to the metal center, and its fluorescence is sensitive to the copper oxidation state and perturbations in the coordination sphere. Further analysis of the quenching and Cu(II) binding behaviors at different Cu(II) concentrations and in the presence of the competing ligand glycine offers evidence supporting the operation of two binding regimes which demonstrate different levels of fluorescence recovery upon addition of the reducing agent. We provide results that suggest the fluorescence quenching is likely caused by charge transfer processes. Thus, by using tyrosine to probe the coordination site, fluorescence spectroscopy provides valuable mechanistic insights into the oxidation state of copper ions bound to Abeta, the binding heterogeneity, and the influence of solution conditions on complex formation.

Two Novel Flexible Multidentate Ligands for Crystal Engineering: Syntheses, Structures, and Properties of CuII, MnII Complexes with N‐[(3‐Carboxyphenyl)sulfonyl]glycine and N,N′‐(1,3‐Phenylenedisulfonyl)bis(glycine)

AbstractOne novel N‐[(3‐carboxyphenyl)sulfonyl]glycine (H3L1) ligand (1) was prepared in high yield, and its structure was determined by single‐crystal X‐ray diffraction. Reaction of H3L1 with Mn(ClO4)2·6H2O at different pH values gave two new dinuclear complexes: [Mn2(HL1)2(phen)4]·16H2O (2) and [Mn2L1(phen)4(H2O)]ClO4·3H2O (3) (phen = 1,10‐phenanthroline). Additionally, two copper(II) complexes, [K2Cu(L2)2(H2O)2]n (4) and [CuL2(H2O)]2·2H2O (5), involving another novel ligand, N,N′‐(1,3‐phenylenedisulfonyl)bis(glycine) (H2L2), were prepared by a one‐pot reaction of 1,3‐phenylenebis(sulfonyl chloride), glycine, and KOH or triethylamine in the presence of CuII ions. A self‐assembled (H2O)30 cluster containing a puckered (H2O)12 ring core was found in 2, which presents a new mode of association of water molecules not predicted theoretically or previously observed experimentally. Furthermore, 2 forms a 2‐D supramolecular structure through hydrogen bonding and unique π–π stacking interactions. In 3, there also exist discrete trimeric water clusters. The identity of the base determines the specific structural characteristics of 4 and 5. When potassium hydroxide was used for the synthesis of 4, it led to a 3‐D copper(II)–potassium(I) coordination polymer; when triethylamine was used, paddle‐wheel dinuclear units of copper(II) carboxylate were produced. Magnetic measurements show that there are weak antiferromagnetic interactions in 2–4. In 5 the χMT vs. T curve shows a minimum at 110 K and a climb from 110 K to 5 K, then a long‐range antiferromagnetic ordering occurs, as revealed by a decrease in χMT with T. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Bis(glycinato-κ2N,O)dinitrosylmolybdenum(0) and bis(2-aminoethanethiolato-κ2N,S)dinitrosylmolybdenum(0) acetonitrile monosolvate

The title compounds, [Mo(C(2)H(4)NO(2))(2)(NO)(2)], (I), and [Mo(C(2)H(6)NS)(2)(NO)(2)].CH(3)CN, (II), contain distorted octahedral complexes in which the monoanionic N,S- and N,O-bidentate ligands coordinate the molybdenum centres in different modes. The anionic O atoms of the glycinate ligands in (I) are coordinated trans to the nitrosyl ligands and the amine N atoms are located trans to each other, whereas in (II) the anionic S atoms are coordinated trans to each other and the amine N atoms are located trans to the nitrosyl ligands. Each compound has a single complete complex in the asymmetric unit on a general position. Six N-H...O contacts with N...O distances of less than 3.2 A are observed in (I) between the amine groups and the nitrosyl and carboxylate O atoms. In the 1:1 solvate (II), the acetonitrile molecule forms short N-H...N contacts (N...N < 3.2 A) between the solvent N atoms and one of the amine H atoms. In addition, three weak intermolecular N-H...S interactions (N...S > 3.3 A) contribute to the stabilization of the structure of (II).

Chain, Pillar, Layer, and Different Pores: AN-[(3-Carboxyphenyl)-sulfonyl]glycine Ligand as a Versatile Building Block for the Construction of Coordination Polymers

Five novel coordination polymers containing N-[(3-carboxyphenyl)-sulfonyl]glycine (H3L), namely [Co3L2(μ2-bipy)2(H2O)6]n·2nCH3OH·8nH2O (1), [Mn(HL)(μ2-bipy)(H2O)2]n·nH2O (2), [Mn(HL)(μ2-bipy)(H2O)]n·3nH2O (3), [Mn(HL)(bipy)(μ2-bipy)0.5(H2O)]n·4nH2O (4), [Ca(H2O)4Cu2(μ2-bipy)2L2]n·4nH2O (5) (bipy = 4,4′-bipyridine), were prepared under control by tuning the reaction conditions such as pH value, reaction temperature, and starting materials. X-ray structural analyses of 1–5 reveal their structural diversity ranging from one-dimensional (1D) (1), two-dimensional (2D) (2), and noninterpenetrating 3-D porous coordination polymers (3, 4) to a 2-fold 3D interpenetrating network (5). Compound 1 presents a 1D chain structure with alternating [CoL(H2O)]22− binuclear and [Co(4,4′-bipy)2(H2O)4]2+ mononuclear units along the a-axis. Polymer 2, which was formed at a comparatively lower temperature, has a 2D structure extended by a HL2− ligand and a monopillar of bipy. A higher temperature was used in the preparation of ...

Structures and Interaction with DNA of Ternary Palladium(II) Complexes: [Pd(Gly)(X)] (Gly=Glycine; X=2,2&amp;prime;-Bipyridine, 1,10-Phenanthroline and 2,2&amp;prime;-Bi-pyridylamine)

The structures of the ternary palladium(II) complexes of the formulations [Pd(Gly)(bpy)](+)Cl(-).4H(2)O (Gly=glycine; bpy=2,2'-bipyridine) (1), [Pd(Gly)(phen)](+)Cl(-).4H(2)O (2) (phen=1,10-phenanthroline) and {[Pd(Gly)(bpa)](+)Cl(-)}(2).6H(2)O (3) (bpa=2,2'-bipyridylamine) were determined. All complexes are positively charged and neutralized by the chloride anion located nearby the complexes. The central Pd(II) atoms of the complexes 1, 2 and 3 have a similar distorted square planar coordination geometry, in which each Pd(II) atom is coordinated to two N atoms of the bidentate heterocyclic ligand, and N and O atoms of the bidentate glycine ligand. The interaction of the complexes with calf thymus (CT) DNA was also studied using the fluorescence method. All complexes showed the inhibition of ethidium bromide binding to CT DNA, and the DNA-binding strengths were reflected as the relative order 2>1>3. The remarkable reduction of UV absorption intensity of 2 caused in the presence of DNA suggests the presence of pi-pi stacking interaction between the heterocyclic ring of the phen ligand and nucleobases. The intercalative DNA-binding of 2 is suggested by UV and CD measurements. DNA cleavage studies indicated that the cleavage of the plasmid supercoiled pBR322 DNA in the presence of H(2)O(2) and ascorbic acid could be enhanced by the complexes.

Synthesis and X-ray structural characterization of tris( l-glycinato)vanadium(III) and trans-tetraquadichlorovanadium(III) chloride

Despite the importance of V III in biology, only three V III complexes of naturally occurring amino acids have been structurally characterized. We report the structure of the first vanadium complex incorporating a glycine ligand, [V(Gly) 3] · 2DMSO, which crystallizes in a monoclinic system with space group Cc, a = 8.9186(5) Å, b = 21.5347(9) Å, c = 9.9064(5) Å and β = 110.536(3)°. The X-ray structural data show the central V III metal octahedrally coordinated by three bidentate glycinato ligands arranged a mer configuration, with both Δ and Λ enantiomers present in the unit cell. The bulk sample was isolated as [V(Gly) 3] · DMSO · NaCl. Structural comparisons are made with the corresponding homoleptic glycinato complexes of Co III, Cr III and Ni II. The structure of trans-[V(OH 2) 4Cl 2]Cl · 2H 2O has also been re-determined. This latter complex crystallizes in a monoclinic system in the P2(1)/ c space group, a = 6.4381(9) Å, b = 6.3843(9) Å, c = 11.7980(17) Å and β = 98.057(2)°. The vanadium atom lies at a crystallographic inversion centre within the distorted octahedron formed by the four water and two chloride ligands.

μ-Glycine-κ2O:O′-di-μ-sulfido-bis[(glycinato-κ2N,O)oxidomolybdenum(V)

In the title compound, [Mo2(C2H4NO2)2O2S2(C2H5NO2)], the two MoV atoms are bridged by two μ2-S atoms and one glycine ligand in an O:O′-bidentate mode. In addition, each MoV atom is bonded to one terminal oxygen ligand and chelated by one N,O-bidentate glycinate ligand, resulting in a distorted octa­hedral coordination. A complex hydrogen-bonding network is constructed by inter­molecular N—H⋯O hydrogen bonds.

Two novel molybdenum complexes containing [Mo2O2S2]2+ fragment: synthesis, crystal structures and catalytic studies

AbstractMo2O2S2(HGly)(Gly)2 1 and K6[Mo2O2S2(nta)2][Mo2O2S2(ntaH)2]·4H2O 2 were synthesized by the reactions of (NH4)2MoS4 and amino acids L (L = glycine, nitrilotriacetic acid) in ethanol–water medium at ambient temperature. The two complexes were characterized by elemental analysis, infrared spectra, UV–visible spectra, TG–DTA and XPS. X‐ray crystallographic structural analyses revealed that compound 1 is a binuclear MoSglycinate complex, a glycinate ligand is coordinated to each molybdenum atom through its amine nitrogen and carboxylato oxygen, respectively, and the third glycinate acts as a bridge through its two carboxylato oxygens linking the two molybdenum atoms. Compound 2 is also a binuclear MoS complex with two nitrilotriacetate ligands, each of which is coordinated to a molybdenum atom via its two β‐carboxylato oxygens and a nitrogen atom. Simultaneously, each molybdenum atom in 1 and 2 is chelated to a terminal oxygen and two bridging sulfurs to complete the octahedral configuration. Their catalytic activities in the reduction from C2H2 to C2H4 as well as other binuclear MoSpolycarboxylate complexes, a [Fe4S4] single cubane and a chainlike MoFeS compound were investigated and it was found that 1 exhibited relatively good catalytic activity. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Catena-Poly[[[aquazinc(II)]-μ-N-(3-carboxy-2-oxidobenzylidene)glycinato-κ4O,N,O′:O′′] monohydrate

The title polymeric compound, {[Zn(C10H7NO5)(H2O)]·H2O}n, consists of a one-dimensional chain, in which the Zn2+ centre is coordinated by two O atoms and one N atom from the tridentate dianionic N-(3-carb­oxy-2-oxidobenzyl­idene)glycinate ligand, one water mol­ecule and a bridging carboxyl­ate O atom from an adjacent ligand. This results in a square-based pyramidal coordination.

Novel unexpected Tb 3+ coordination polymer containing two carboxylate ligands: Syntheses, structure and photoluminescent properties

Novel unexpected coordination polymer [Tb(PHTHGLY)(CBGLY)(H 2O) 2](H 2O) 3 complex containing simultaneously N-phthaloylglycinate and N-(2-carboxybenzoyl)glycinate ligands has been prepared and characterized by single crystal X-ray structure, thermogravimetric analysis and infrared spectroscopy. The X-ray crystal diffraction indicates that the Tb 3+-complex crystallizes in a triclinic crystal system and space group P 1 ¯ , forming a 1D polymer where carboxylate groups bridge the Tb 3+ ions. The photoluminescence data revel that the ligands act as efficient “antennas” sensitizing the luminescence of the Tb 3+ ion showing a strong green emission color arising from intraconfigurational 5D 4 → 7F J transitions ( J = 0–6).

Fourier transform infrared spectrum, vibrational analysis and structural determinations of the trans-bis(glycine)nickel(II) complex by means of the RHF/6-311G and DFT:B3LYP/6-31G and 6-311G methods

The trans-bis(glycine)nickel(II) complex was synthesized, and the Fourier transform infrared spectra in the regions 4000–370 cm −1 and 700–30 cm −1 were measured. Band deconvolution analysis and the second derivative of the infrared spectrum were also performed. The determination of the geometrical structure in the trans position of the glycine ligands around Ni(II) for the trans-bis(glycine)nickel(II) complex as well as the vibrational assignment were assisted by RHF/6-311G and by Density Functional Theory calculations, DFT:B3LYP/6-31G and 6-311G basis sets. A full discussion of the framework vibrational modes was done using as criteria the geometry study of distorted structures generated for the vibrational modes. Incidentally, Normal Coordinate Analysis was carried out for the Ni(N) 2(O) 2 structural fragment. The calculated DFT spectra in the high- and low-energy regions agree with the observed ones.

Tris(glycinato-κ2 N,O)cobalt(III)

The title compound, [Co(C2H4NO2)3], is a mononuclear cobalt(III) complex. The CoIII atom is six-coordinated by three N atoms and three O atoms from three chelating glycinate ligands, forming a slightly distorted octahedral configuration. In the crystal structure, the molecules are linked together by intermolecular N—H...O hydrogen bonds, forming a three-dimensional network.

A novel zigzag chain based on polyoxomolybdate decorated by glycine ligand in covalent bond

An unusual compound, K2[Mo4O13(NH3CH2COO)2] · 2H2O (1), has been synthesized and structurally characterized by the XRD, elemental analysis, IR spectrum, TG analyses and the single crystal X-ray diffraction. The structure of 1 exhibits a zigzag chain based on corner-shared tetramolybdate chelated by two bidentate glycine ligands.

Poly[[diaquacadmium(II)]-μ4-[N-(phosphonatomethyl)ammonio]acetato

The title compound, [Cd(C3H6NO5P)(H2O)2]n, is a three-dimensional polymeric complex. The asymmetric unit contains one Cd atom, one N-(phosphonomethyl)glycine zwitterion [(O-)2OPCH2NH2+CH2COO-] and two water molecules. The coordination geometry is a distorted CdO6 octahedron. Each N-(phosphonomethyl)glycine ligand bridges four adjacent water-coordinated Cd cations through three phosphonate O atoms and one carboxylate O atom, like a regular PO(4)3- group in zeolite-type frameworks. One-dimensional zigzag (-O-P-C-N-C-C-O-Cd-)n chains along the [101] direction are linked to one another via Cd-O-P bridges and form a three-dimensional network motif with three types of channel systems. The variety of O-H...O and N-H...O hydrogen bonds is likely to be responsible for stabilizing the three-dimensional network structure and preventing guest molecules from entering into the channels.

Molecular Dynamics Simulations of the Ligand-binding Domain of an N-Methyl-d-aspartate Receptor

The mechanism of partial agonism at N-methyl-D-aspartate receptors is an unresolved issue, especially with respect to the role of protein dynamics. We have performed multiple molecular dynamics simulations (7 x 20 ns) to examine the behavior of the ligand-binding core of the NR1 subunit with a series of ligands. Our results show that water plays an important role in stabilizing different conformations of the core and how a closed cleft conformation of the protein might be stabilized in the absence of ligands. In the case of ligand-bound simulations with both full and partial agonists, we observed that ligands within the binding cleft may undergo distinct conformational changes, without grossly influencing the degree of cleft closure within the ligand-binding domain. In agreement with recently published crystallographic data, we also observe similar changes in backbone torsions corresponding to the hinge region between the two lobes for the partial agonist, D-cycloserine. This observation rationalizes the classification of D-cycloserine as a partial agonist and should provide a basis with which to predict partial agonism in this class of receptor by analyzing the behavior of these torsions with other potential ligands.