5 Metal centers in hydrogenase enzymes studied by X-ray spectroscopy

Two copper(II) azido complexes of the types mononuclear [Cu(TMEDA)2(N3)2] (1) and dinuclear [Cu(TMEDA)(μ1,1-N3)(N3)]2 (2) [TMEDA = trimethylenediamine; N3 – = azide ion] have been synthesized and characterized. X-ray structural analysis revealed that each copper(II) center in complex 1 adopts a distorted octahedron geometry with a CuN6 chromophore ligated through four N atoms of two different symmetrical TMEDA ligands as bidentate chelator and two N atoms of two terminal azides. In complex 2, each copper(II) center adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of TMEDA as bidentate chelator and two N atoms of two different azides as μ1,1-N3 bridging mode and one N atom of terminal azide ion. The two copper centers are connected through double μ1,1-N3 bridges affording a dinuclear structure with Cu···Cu separation 3.327(2) Å. In crystalline state, mononuclear units in complex 1 are associated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 2D sheet structure viewed along crystallographic b-axis, whereas dinuclear entities in complex 2 are propagated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 3D network structure viewed along crystallographic a-axis. The Variable-temperature magnetic susceptibility measurement evidenced a dominant antiferromagnetic interaction between the metal centers through μ1,1-azide bridges in complex 2 with J = − 0.40 cm-1. The antibacterial activities of the complexes have also been studied.

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Synthesis, Structure and Fluorescence Properties of a Trinuclear Zn(II) Complex with N,N,O-donor Schiff Base Ligands and Bridging Acetates

Zeitschrift für Naturforschung B ◽

10.1515/znb-2009-0408 ◽

2009 ◽

Vol 64 (4) ◽

pp. 403-408 ◽

Cited By ~ 15

Author(s):

Shyamapada Shit ◽

Joy Chakraborty ◽

Brajagopal Samanta ◽

Georgina M. Rosair ◽

Samiran Mitra

Keyword(s):

Schiff Base ◽

Schiff Base Ligand ◽

Fluorescence Properties ◽

Schiff Base Ligands ◽

Thermal Methods ◽

Metal Centers ◽

X Ray ◽

Octahedral Environment ◽

Distorted Octahedral ◽

Ft Ir

A new centrosymmetric trinuclear Zn(II) complex [Zn3L2(CH3COO)4] (1) has been synthesized by the reaction of Zn(CH3COO)2 · 2H2O with a tridentate N,N,O-donor Schiff base ligand HL [C5H4NC(CH3)=NC6H4(OH)] and systematically characterized by elemental analysis, FT-IR, UV/Vis and thermal methods. Single crystal X-ray structure analysis reveals that three Zn(II) centers are in two different coordination environments. Two terminal Zn(II) centers adopt a distorted squarepyramidal geometry leaving the central Zn(II) in a distorted octahedral environment. Two adjacent metal centers are connected through single μ2-phenolato as well as double μ-acetato-O,O´ syn-syn bridges. Fluorescence properties of the complex as compared to the ligand indicate that the former can serve as a potential photoactive material.

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Tb2(bpdc)3 and Eu2(bpdc)3 Nanoparticles (bpdc: 2,2ʹ-Bipyridine-4,4ʹ- dicarboxylate) and Their Luminescence

Zeitschrift für Naturforschung B ◽

10.5560/znb.2014-3293 ◽

2014 ◽

Vol 69 (2) ◽

pp. 248-254 ◽

Cited By ~ 1

Author(s):

Ana Kuzmanoski ◽

Claus Feldmann

Keyword(s):

Colloidal Stability ◽

Aqueous Suspension ◽

Earth Metal ◽

Quantum Yields ◽

X Ray Diffraction ◽

Antenna Effect ◽

Metal Centers ◽

X Ray ◽

Suspension Particle ◽

Absolute Quantum

Tb2(bpdc)3 and Eu2(bpdc)3 nanoparticles (bpdc: 2,2ʹ-bipyridine-4,4ʹ-dicarboxylate) have been prepared via straightforward precipitation from aqueous solution. The nanoparticles exhibit mean diameters of 41(5) nm (Tb2(bpdc)3) and 56(4) nm (Eu2(bpdc)3) and show a very good colloidal stability in aqueous suspension. Particle size and chemical composition have been characterized based on electron microscopy, X-ray diffraction, infrared spectroscopy and thermogravimetry. Photoluminescence validates an efficient excitation of Tb3+/Eu3+ via the bpdc ligand as an antenna that leads to intense characteristic green and red emissions. The absolute quantum yields of Tb2(bpdc)3 and Eu2(bpdc)3 have been determined at 28 and 12%, respectively. Although rare-earth metal-based photoluminescence is typically quenched in water due to vibronic loss processes (v(O-H)), here, the antenna effect and the shielding of the metal centers via the bpdc ligand are very efficient, allowing for an intense green and red emission of the Tb2(bpdc)3 and Eu2(bpdc)3 nanoparticles even in aqueous suspension.

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X-Ray Absorption Spectroscopy and the Structures of Transition Metal Centers in Proteins

Advances in Inorganic Chemistry ◽

10.1016/s0898-8838(08)60042-2 ◽

1991 ◽

pp. 303-339 ◽

Cited By ~ 20

Author(s):

C. David Garner

Keyword(s):

Transition Metal ◽

Absorption Spectroscopy ◽

Metal Centers ◽

X Ray ◽

X Ray Absorption

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Thermal, spectroscopic, X-ray and theoretical studies of metal complexes (sodium, manganese, copper, nickel, cobalt and zinc) with pyrimidine-5-carboxylic and pyrimidine-2-carboxylic acids

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-019-08594-x ◽

2019 ◽

Vol 138 (4) ◽

pp. 2813-2837 ◽

Cited By ~ 1

Author(s):

G. Świderski ◽

R. Świsłocka ◽

R. Łyszczek ◽

S. Wojtulewski ◽

M. Samsonowicz ◽

...

Keyword(s):

Carboxylic Acid ◽

Nitrogen Atom ◽

Metal Complexes ◽

General Formula ◽

Pyrimidine Ring ◽

Carboxylate Ligand ◽

Metal Centers ◽

X Ray ◽

Carboxylate Oxygen ◽

3D Metal Complexes

Abstract The new 3d metal complexes of pyrimidine-2-carboxylic (2PCA) and pyrimidine-5-carboxylic (5PCA) acids were synthesized and characterized using thermal analysis (TG–DSC, TG–FTIR), X-ray, spectroscopic (IR, Raman) methods and theoretical (DFT) studies. In the complexes of pyrimidine-2-carboxylic acid of the general formula M(2PCA)2·xH2O (where 2PCA-pyrimidine-2-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 0 for Mn and Cu; x = 2 for Co, Ni and Zn) coordination of metal ions occurs through nitrogen atom from pyrimidine ring and carboxylate oxygen atom. The complexes of pyrimidine-5-carboxylic acid of the general formula M(5PCA)2·xH2O (where 5PCA—pyrimidine-5-carboxylate; M = Mn(II), Co(II), Ni(II), Cu(II) and Zn; x = 6 for Cu and 4 for remaining complexes) were obtained as monomeric isostructural compounds. Coordination of metal centers occurs through two nitrogen atom from different pyrimidine-5-carboxylate ligand and four oxygen atoms from water molecules. The IR and Raman spectra of free acids as well as obtained metal(II) complexes were described in detail. Aromaticity (HOMA, EN, GEO and I6) of complexes was determined and discussed. The investigated compounds decompose in air in two main stages connected with dehydration and decomposition/burning of anhydrous compounds to the suitable metal oxides. Thermal decomposition in nitrogen leads to the evolution of water, carbon oxides, ammonia and pyrimidine molecules.

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[NiFe], [FeFe], and [Fe] hydrogenase models from isomers

Science Advances ◽

10.1126/sciadv.aaz8181 ◽

2020 ◽

Vol 6 (24) ◽

pp. eaaz8181

Author(s):

Seiji Ogo ◽

Takahiro Kishima ◽

Takeshi Yatabe ◽

Keishi Miyazawa ◽

Ryunosuke Yamasaki ◽

...

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Catalytic Properties ◽

Electrochemical Measurement ◽

Hydrogen Energy ◽

X Ray ◽

Energy Economy ◽

Hydrogenase Enzymes ◽

Nuclear Magnetic

The study of hydrogenase enzymes (H2ases) is necessary because of their importance to a future hydrogen energy economy. These enzymes come in three distinct classes: [NiFe] H2ases, which have a propensity toward H2 oxidation; [FeFe] H2ases, which have a propensity toward H2 evolution; and [Fe] H2ases, which catalyze H− transfer. Modeling these enzymes has so far treated them as different species, which is understandable given the different cores and ligand sets of the natural molecules. Here, we demonstrate, using x-ray analysis and nuclear magnetic resonance, infrared, Mössbauer spectroscopies, and electrochemical measurement, that the catalytic properties of all three enzymes can be mimicked with only three isomers of the same NiFe complex.

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Tuning the Linear and Nonlinear Optical Properties of Pyrene-Pyridine Chromophores by Protonation and Complexation to d10 Metal Centers †

Inorganics ◽

10.3390/inorganics7030038 ◽

2019 ◽

Vol 7 (3) ◽

pp. 38 ◽

Cited By ~ 2

Author(s):

Elena Lucenti ◽

Alessandra Forni ◽

Daniele Marinotto ◽

Andrea Previtali ◽

Stefania Righetto ◽

...

Keyword(s):

Nonlinear Optical ◽

Second Harmonic ◽

Protonated Form ◽

Lewis Acidity ◽

X Ray Diffraction ◽

Metal Centers ◽

X Ray ◽

Nlo Response ◽

D10 Metal ◽

Simple Exposure

The linear and second-order nonlinear optical (NLO) properties of two pyrene-pyridine chromophores, namely, 4-(pyren-1-yl)pyridine (L1) and 4-(2-(pyren-1-yl)ethyl)pyridine (L2), were investigated and modulated by performing protonation/deprotonation cycles or by complexation to d10 metal centers such as Zn(II) and Cu(I) to form the monomeric [Zn(CH3CO2)2(L1)2] complex and the [CuI(L2)]n coordination polymer, respectively. The structures of L1, L2, [Zn(CH3CO2)2(L1)2] and [CuI(L2)]n were determined by means of single-crystal X-ray diffraction studies. The NLO response, measured by the electric-field-induced second harmonic generation (EFISH) technique, was positive for both chromophores and showed an inversion of the sign after exposure to HCl vapors. This process was completely reversible and the original values were restored by simple exposure to NH3 vapors. Coordination of L1 to Zn(II) also resulted in a negative NLO response, although smaller in magnitude compared to the protonated form, due to the weak Lewis acidity of the “Zn(CH3CO2)2” fragment. The results were also interpreted on the basis of DFT/TDDFT calculations.

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A New Binuclear Lutetium(III) Dimethyl-N-trichloroacetylamidophosphate Complex with a γ, γ'-Dipyridyl Bridge, {Lu[CCl3C(O)NP(O)(OCH3)2]3}2-μ(γ,γ'-dipy)

Zeitschrift für Naturforschung B ◽

10.1515/znb-2001-0306 ◽

2001 ◽

Vol 56 (3) ◽

pp. 249-254 ◽

Cited By ~ 8

Author(s):

Victor A. Trush ◽

Jolanta Swiatek-Kozlowska ◽

Victor V. Skopenko ◽

Vladimir M. Amyrkhanov

Keyword(s):

Crystal And Molecular Structure ◽

Carbonyl Oxygen ◽

Carbonyl Groups ◽

X Ray Diffraction ◽

Triclinic Space Group ◽

Metal Centers ◽

X Ray ◽

Heterocyclic Ligand ◽

New Type ◽

Ir Spectroscopic

Abstract A new type of binuclear coordination compound of lutetium, {Lu2L6 · μ-(γ,γ '-dipy)} (where L = dimethyl-N-trichloroacetylamidophosphate anion and γ,γ '-dipy = 4,4'-dipyridyl), has been obtained. The IR spectroscopic data reveal that the ambidentate phosphoryl ligand is coordinated to the metal center in a bidentate manner via the phosphoryl and carbonyl oxygen atoms. The crystal and molecular structure of {Ln2L6-μ-(γ ,γ '-dipy)} has been determined by means of X-ray diffraction (triclinic, space group P i with parameters: a = 9.259(2), b = 12.530(3), c = 16.548(3) Å, α = 85.44(3)°, β = 75.64(3)°, γ = 70.56(3)°, Z = 1). The structure is made up of centrosymmetric binuclear molecules, in which the neutral heterocyclic ligand is coordinated to the metal centers in a bidentate bridging manner via its nitrogen atoms. The coordination number of each Lu(III) atom is 7 [60(L-) + N((γ ,γ '-dipy)]. Phosphoryl and carbonyl groups of the L- ligands are disposed in syn-position and are included in the six-membered chelate metallocycles. The coordination polyhedron of lutetium can be described as distorted mono-capped octahedron.

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