Polyamine ligands. II. Nickel(II) complexes with the tridentate ligand 5-(2'-Pyridyl)-3-azapentan-1-amine

1970 ◽  
Vol 23 (11) ◽  
pp. 2257 ◽  
Author(s):  
AT Casey ◽  
W Peters ◽  
AT Phillip
Keyword(s):  
Electronic Absorption Spectra ◽  
Complex Structure ◽  
Molar Conductance ◽  
Tridentate Ligand ◽  
Tridentate Ligands ◽  
Nickel Ion ◽  
First Order ◽  
Distorted Octahedral ◽  
Geometrical Isomerism ◽  
Structure In Solution

The tridentate amine 5-(2'-pyridyl)-3-azapentane-1-amine (pap) forms a series of stable nickel(II) complexes of the composition Ni(pap)X2 (X = Cl, Br, I, NO3, SCN, �SO4) and [Ni(pap)2]X2 (X = ClO4, I). Measurements of their electronic absorption spectra, infrared spectra, molar conductance, and magnetic susceptibility indicate that the complexes contain the amine coordinating as a tridentate ligand. In general, the Ni(pap)X2 compounds appear to possess a tetragonally distorted, octahedral structure with bridging anions in the solid state and a solvated complex structure in solution. The [Ni(pap)z]X2 compounds contain two tridentate ligands coordinated to one nickel ion, forming the octahedral NiN6 structure. Geometrical isomerism has been observed in the [Ni(pap)2]I2 compound which can be isolated as a yellow or a pink modification; this isomerism has been attributed to the alternative modes of coordination by the tridentate ligand. The isomerization of the unstable yellow form to the more stable pink form has been followed spectrophotometrically at 28� and appears to be first order in concentration.

SAC3B is a target of CML19, the centrin 2 of Arabidopsis thaliana

2020 ◽  
Vol 477 (1) ◽  
pp. 173-189 ◽  
Author(s):  
Marco Pedretti ◽  
Carolina Conter ◽  
Paola Dominici ◽  
Alessandra Astegno
Keyword(s):  
Excision Repair ◽  
Complex Structure ◽  
Binding Motif ◽  
C Terminus ◽  
Repair Protein ◽  
Nucleotide Excision ◽  
Ef Hand ◽  
Molecular Determinants ◽  
Structure In Solution

Arabidopsis centrin 2, also known as calmodulin-like protein 19 (CML19), is a member of the EF-hand superfamily of calcium (Ca2+)-binding proteins. In addition to the notion that CML19 interacts with the nucleotide excision repair protein RAD4, CML19 was suggested to be a component of the transcription export complex 2 (TREX-2) by interacting with SAC3B. However, the molecular determinants of this interaction have remained largely unknown. Herein, we identified a CML19-binding site within the C-terminus of SAC3B and characterized the binding properties of the corresponding 26-residue peptide (SAC3Bp), which exhibits the hydrophobic triad centrin-binding motif in a reversed orientation (I8W4W1). Using a combination of spectroscopic and calorimetric experiments, we shed light on the SAC3Bp–CML19 complex structure in solution. We demonstrated that the peptide interacts not only with Ca2+-saturated CML19, but also with apo-CML19 to form a protein–peptide complex with a 1 : 1 stoichiometry. Both interactions involve hydrophobic and electrostatic contributions and include the burial of Trp residues of SAC3Bp. However, the peptide likely assumes different conformations upon binding to apo-CML19 or Ca2+-CML19. Importantly, the peptide dramatically increases the affinity for Ca2+ of CML19, especially of the C-lobe, suggesting that in vivo the protein would be Ca2+-saturated and bound to SAC3B even at resting Ca2+-levels. Our results, providing direct evidence that Arabidopsis SAC3B is a CML19 target and proposing that CML19 can bind to SAC3B through its C-lobe independent of a Ca2+ stimulus, support a functional role for these proteins in TREX-2 complex and mRNA export.

Photocolouration of 2,4,4,6-Tetraaryl-4H-pyrans and Their Heteroanalogues: Importance of Hypervalent Photoisomers

1995 ◽  
Vol 60 (10) ◽  
pp. 1621-1633 ◽  
Author(s):  
Stanislav Böhm ◽  
Mojmír Adamec ◽  
Stanislav Nešpůrek ◽  
Josef Kuthan
Keyword(s):  
Reaction Kinetics ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Theoretical Data ◽  
Order Reaction ◽  
Bleaching Process ◽  
First Order ◽  
Photodegradation Products ◽  
Hypervalent Molecules

Molecular geometries of 2,4,4,6-tetraphenyl-4H-pyran (Ia), 4,4-(biphenyl-2,2e-diyl)-2,6-diphenyl-4H-pyran (Ib) and their heterocyclic isomers II-V were optimized by the PM3 method and used for the calculation of electronic absorption spectra by the CNDO/S-CI procedure. Comparison of the theoretical data with experimental UV-VIS absorption spectra made possible to select hypervalent molecules IIIa, IIIb, IVa and IVb being responsible for the photocolouration of 4H-pyrans Ia, Ib, while compounds Va, Vb, VI and VII come into account as possible photodegradation products. The bleaching process of the UV illuminated compound Ia is analyzed in terms of dispersive first-order reaction kinetics.

New chiral tridentate ligands for asymmetric catalysis

2006 ◽  
Vol 78 (2) ◽  
pp. 311-320 ◽  
Author(s):  
Kevin Murtagh ◽  
Brian A. Sweetman ◽  
Patrick J. Guiry
Keyword(s):  
Asymmetric Catalysis ◽  
High Performance ◽  
Aromatic Aldehydes ◽  
Asymmetric Induction ◽  
Tridentate Ligand ◽  
Coupling Reactions ◽  
Tridentate Ligands ◽  
Molecular Complexation ◽  
Cross Coupling Reactions ◽  
Moderate Yield

The synthesis of new tridentate, isoquinoline-derived ligands, involving successive Suzuki cross-coupling reactions, is described. We were able to resolve 1-[3-(2-hydroxy-phenyl)-isoquinolin-1-yl]-naphthalen-2-ol via molecular complexation with N-benzylcinchonidinium chloride, whereas 1,3-bis(2-hydroxy-naphthalen-1-yl)-isoquinoline was resolved by chromatographic separation of its epimeric camphorsulfonates. Their barrier to rotation about the central biaryl axis was evaluated via racemization studies. Application of enantiopure 1,3-bis(2-hydroxynaphthalen-1-yl)-isoquinoline in the addition of diethylzinc to aldehydes proceeded in moderate yield but without asymmetric induction. A new tridentate ligand, 4-tert-butyl-2-chloro-6-[1-(2-hydroxymethyl-naphthalen-1-yl)-isoquinolin-3-yl]-phenol, was prepared in good yield and resolved by semipreparative high-performance liquid chromatography (HPLC). Its application in the addition of diethylzinc to a range of aromatic aldehydes proceeded in near perfect enantioselectivities at low ligand loadings of 1 mol %.

scholarly journals Transition Metal Complexes with Tridentate Ligand: Preparation, Spectroscopic Characterization, Thermal Analysis and Structural Studies

2016 ◽  
Vol 13 (4) ◽  
pp. 770-781 ◽  
Author(s):  
Baghdad Science Journal
Keyword(s):  
Gas Phase ◽  
Transition Metal Complexes ◽  
Spectroscopic Characterization ◽  
Heat Of Formation ◽  
Electronic Energy ◽  
Molar Conductance ◽  
Tridentate Ligand ◽  
Structural Studies ◽  
1H And 13C Nmr ◽  
Ft Ir

New series of metal ions complexes have been prepared from the new ligand 1,5- Dimethyl-4- (5-oxohexan-2- ylideneamino) -2-phenyl- 1H-pyrazol-3 (2H)-one derived from 2,5-hexandione and 4-aminophenazone. Then, its V(IV), Ni(II), Cu(II), Pd(II), Re(V) and Pt(IV) complexes prepared. The compounds have been characterized by FT-IR, UV-Vis, mass and 1H and 13C-NMR spectra, TGA curve, magnetic moment, elemental microanalyses (C.H.N.O.), chloride containing, Atomic absorption and molar conductance. Hyper Chem-8 program has been used to predict structural geometries of compounds in gas phase, the heat of formation, (binding, total and electronic energy) and dipole moment at 298 K.

Mossbauer studies in transition metal chemistry. III. Compounds of iron with some sulphur-containing Schiff base ligands

1974 ◽  
Vol 27 (11) ◽  
pp. 2307 ◽  
Author(s):  
M Bond ◽  
RL Martin ◽  
IAG Roos
Keyword(s):  
Schiff Base ◽  
Tridentate Ligand ◽  
Coordinate Structure ◽  
Schiff Base Ligands ◽  
Tridentate Ligands ◽  
Cubic Symmetry ◽  
Field Gradients ◽  
Metal Atoms ◽  
Different Types ◽  
Local Symmetries

M�ssbauer spectra are reported for a series of iron complexes with sulphur-containing Schiff base ligands. These tridentate ligands are based on the Schiff base formed by the condensation of dithiocarbazic acid and pyridine-2-carbaldehyde and form complexes with a metal-to-ligand ratio of 1 : 1 and 1 : 2. The M�ssbauer study confirms that most of these complexes contain iron(11) with examples of both high-and low-spin and one example of a spin crossover. Several iron(111) complexes were also studied. The quadrupole splittings show the anisotropy in bonding expected for metal atoms coordinated to different types of atoms within the same chelate ring. However, for some complexes the splittings are small, showing that low local symmetries need not produce large electric field gradients. In cases where it is applicable, the temperature dependence of the quadrupole splitting has been used to derive a splitting of the t2 and e orbitals produced by the non-cubic symmetry. For compounds of the form Fe(L)X2, where X is a halide and L the tridentate ligand, the Mossbauer results are best interpreted in terms of a five-coordinate structure rather than a six-coordinate bridged dimer.

Manganese-Catalyzed Enantioselective Hydrogenation of Simple Ketones Using an Imidazole-Based Chiral PNN Tridentate Ligand

Synlett ◽  
2020 ◽  
Vol 31 (03) ◽  
pp. 285-289 ◽  
Author(s):  
Fei Ling ◽  
Jiachen Chen ◽  
Sanfei Nian ◽  
Huacui Hou ◽  
Xiao Yi ◽  
...  
Keyword(s):  
Functional Group ◽  
Asymmetric Hydrogenation ◽  
Enantioselective Hydrogenation ◽  
Tridentate Ligand ◽  
Easy Access ◽  
Tridentate Ligands

A series of Mn(I) catalysts containing imidazole-based chiral PNN tridentate ligands with controllable ‘side arm’ groups have been established, enabling the inexpensive base-promoted asymmetric hydrogenation of simple ketones with outstanding activities (up to 8200 TON) and good enantioselectivities (up to 88.5% ee). This protocol features wide substrate scope and functional group tolerance, thereby providing easy access to a key intermediate of crizotinib.

scholarly journals Synthesis, Characterization and Antifungal Studies of Adducts of p- Ethylphenyldithiocarbonates of Copper(II)

2019 ◽  
Vol 31 (8) ◽  
pp. 1819-1824
Author(s):  
Shivangi Sharma ◽  
Renu Sachar ◽  
G.D. Bajju ◽  
Vikas Sharma
Keyword(s):  
Magnetic Susceptibility ◽  
Electron Spin Resonance ◽  
Room Temperature ◽  
Molar Conductance ◽  
Octahedral Geometry ◽  
Molar Ratio ◽  
Spectral Studies ◽  
Distorted Octahedral Geometry ◽  
Distorted Octahedral ◽  
Spin Resonance

A series of adducts of p-ethylphenyldithiocarbonates of copper(II) [(p-C2H5C6H4OCS2)2Cu] with ethyl pyridines and chloro pyridines have been synthesized in 1:2 molar ratio. They were characterized by elemental analysis, magnetic susceptibility and molar conductance measurements, infrared, electronic, electron spin resonance and mass spectroscopy, NMR and thermogravimetric analysis. In addition, antifungal studies of these adducts were also performed. The results revealed that the adducts have 1:2 stoichiometry, non-electrolytic and paramagnetic at room temperature. On the basis of spectral studies, a distorted octahedral geometry is proposed around copper(II) ion. ESR studies depicted elongated axial symmetry of Cu(II)adducts with nitrogen donors. Moreover, the adducts also showed potential antifungal activity against Fusarium oxysporium.

A Novel Method for Synthesizing Crystalline Copper Carbodiimide, CuNCN. Structure Determination by X-Ray Rietveld Refinement

2005 ◽  
Vol 60 (6) ◽  
pp. 593-596 ◽  
Author(s):  
Xiaohui Liu ◽  
Martial Aime Wankeu ◽  
Heiko Lueken ◽  
Richard Dronskowski
Keyword(s):  
Small Temperature ◽  
Interatomic Distances ◽  
X Ray ◽  
First Order ◽  
Metallic Conductor ◽  
Distorted Octahedral ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Novel Method ◽  
Aqueous Conditions

Well-crystallized copper carbodiimide, CuNCN, was synthesized by the slow oxidation of a copper(I) cyanamide precursor under aqueous conditions. The X-ray powder data evidence the orthorhombic system and space group Cmcm with a = 2.9921(1), b = 6.1782(1), c = 9.4003(2) Å , V = 173.769(5) Å3 and Z = 4. There is a strongly distorted octahedral Cu2+ coordination reflecting a typical first-order Jahn-Teller effect, with interatomic distances of 4×Cu-N = 2.001(2) Å and 2×Cu-N = 2.613(3) Å ; the NCN2− unit adopts the carbodiimide shape with C-N = 1.227(4) Å . Despite the formal d9 electron count of Cu2+, CuNCN exhibits a small temperature-independent paramagnetism and is likely to be a metallic conductor.

MOYAL STAR PRODUCT OF μ-HOLOMORPHIC j-DIFFERENTIALS

2008 ◽  
Vol 05 (03) ◽  
pp. 363-373
Author(s):  
M. KACHKACHI
Keyword(s):  
Riemann Surface ◽  
Riemann Surfaces ◽  
Quantum Effect ◽  
Star Product ◽  
Complex Structure ◽  
Complex Structures ◽  
Star Products ◽  
First Order ◽  
Conformal Fields ◽  
Conformal Covariance

It was shown in [1], only for scalar conformal fields, that the Moyal–Weyl star product can introduce the quantum effect as the phase factor to the ordinary product. In this paper we show that, even on the same complex structure, the Moyal–Weyl star product of two j-differentials (conformal fields of weights (j, 0)) does not vanish but it generates the quantum effect at the first order of its perturbative series. More generally, we get the explicit expression of the Moyal–Weyl star product of j-differentials defined on any complex structure of a bi-dimensional Riemann surface Σ. We show that the star product of two j-differentials is not a j-differential and does not preserve the conformal covariance character. This can shed some light on the Moyal–Weyl deformation quantization procedure connection's with the deformation of complex structures on a Riemann surface. Hence, the situation might relate the star products to the Moduli and Teichmüller spaces of Riemann surfaces.

Structures of 2 Vanadium(V) Complexes With Tridentate Ligands

1986 ◽  
Vol 39 (7) ◽  
pp. 1081 ◽  
Author(s):  
AA Diamantis ◽  
JM Frederiksen ◽  
MA Salam ◽  
MR Snow ◽  
ERT Tiekink
Keyword(s):  
Tridentate Ligand ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Tridentate Ligands ◽  
Tetragonal Pyramid ◽  
Coordination Environment ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Oxo Ligand

The crystal structures of two vanadium(v) complexes, VOL(OCH2CH3)(1) and (VOL)2O (2), where L is the dinegative , tridentate ligand 4- phenylbutane-2,4-dione benzoylhydrazonato (2-), were determined by X-ray diffraction methods. Crystals of (1) are monoclinic, space group P21/n, a 11.064(4), b 7.565(1), c 21.786(5) Ǻ and β 95.93(2)° and Z 4; those of (2) are also monoclinic, C2/ c, with unit cell dimensions a 18.287(3), b 14.991(2), c 11.643(2)Ǻ, β 92.85(2)° for Z 4. The structures were refined by full-matrix least-squares methods to final R 0.036 for 1801 reflections with I ≥ 2.5σ(I) for (1), and R 0.061 for 1272 reflections with I ≥ 2.5σ(I) for (2). The coordination environment of the vanadium atom in both structures is a tetragonal pyramid with the oxo ligand occupying the apical positon.

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