scholarly journals Synthesis and Coordination Chemistry of 2-(Di-2-pyridylamino)pyrimidine; Structural Aspects of Spin Crossover in an FeII Complex

2012 ◽  
Vol 65 (7) ◽  
pp. 842 ◽  
Author(s):  
Rachel S. Crees ◽  
Boujemma Moubaraki ◽  
Keith S. Murray ◽  
Christopher J. Sumby
Keyword(s):  
Spin Crossover ◽  
Palladium Complex ◽  
Magnetic Measurements ◽  
Structural Basis ◽  
Temperature Dependent ◽  
X Ray ◽  
X Ray Crystallography ◽  
Bridging Ligand ◽  
Metal Atoms ◽  
Structural Aspects

2-(Di-2-pyridylamino)pyrimidine (L), a potentially ditopic tetradentate ligand, was synthesized from commercially available di-2-pyridylamine and 2-chloropyrimidine. Despite being capable of bridging two metal atoms with bidentate chelation of both metal centres, L prefers to chelate or bridge through the more basic pyridyl donors of the di-2-pyridylamine moiety. Mononuclear trans-[Fe(NCS)2(L)2] and [Cu(L)2(H2O)](BF4)2·H2O complexes, and a discrete [Ag2(L)4](PF6)2 metallo-macrocycle, were isolated and structurally characterized by X-ray crystallography. A mononuclear palladium complex [PdCl2(L)]·(solvate), where solvate = 1/2H2O or CH2Cl2, was also readily obtained in 71 % yield. One example of the ligand acting as a bis(bidentate) bridging ligand was observed in a dinuclear [(PdCl2)2(L)]·3/4H2O complex that was obtained only in very low yield (~3 %) from the reaction that produced [PdCl2(L)]·1/2H2O. trans-[Fe(NCS)2(L)2] undergoes a temperature-dependent high-spin–low-spin crossover at ~205 K that was observed by X-ray crystallography and magnetic measurements, and attempts were made to understand the structural basis of this process. Despite efforts to isolate examples of L bridging two iron(ii) centres, only the mononuclear trans-[Fe(NCS)2(L)2] species could be obtained.

A Promising New Schiff Base-like Ligand for the Synthesis of Octahedral Iron(II) Spin Crossover Complexes

2010 ◽  
Vol 65 (3) ◽  
pp. 323-328 ◽  
Author(s):  
Wolfgang Bauer ◽  
Tanja Ossiander ◽  
Birgit Weber
Keyword(s):  
Schiff Base ◽  
High Spin ◽  
Spin Crossover ◽  
Magnetic Measurements ◽  
X Ray ◽  
X Ray Crystallography ◽  
Tetradentate Schiff Base ◽  
Spin Crossover Complexes

A new tetradentate Schiff base-like ligand H2L (1) ((E,E)-dimethyl-2,2´-[1,2-phenylenebis(aminomethylidyne)] bis[3-oxobutanoate]) was synthesised and structurally characterised. Its reaction with iron(II) acetate leads to the formation of the octahedral N2O4-coordinated complex [FeL(MeOH)2] (2). The complex is a pure high-spin (HS) compound as is evident from magnetic measurements and X-ray crystallography.

scholarly journals Solvent Effects on the Spin Crossover Properties of Iron(II) Imidazolylimine Complexes

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 116 ◽  
Author(s):  
Darunee Sertphon ◽  
Phimphaka Harding ◽  
Keith Murray ◽  
Boujemaa Moubaraki ◽  
Suzanne Neville ◽  
...  
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Solvent Effects ◽  
Spin Crossover ◽  
Magnetic Measurements ◽  
X Ray ◽  
Π Interactions ◽  
X Ray Crystallography ◽  
Solvent Loss

A series of Fe(II) complexes, fac-[Fe(4-ima-Bp)3](Y)2⋅sol (Y = ClO4; sol = 3EtOH 1, 3MeOH 2; Y= BF4; sol = EtOH⋅4H2O 3, 4H2O 4 and 3.5MeCN 5) have been prepared and structurally and magnetically characterized. The low temperature structures of 1, 2 and 5 have been determined by X-ray crystallography with LS Fe(II) centres found in all cases. Extensive C–H···π interactions between the cations form 2D layers, which are linked to one another through N-H···O and O-H···O hydrogen bonds, resulting in high cooperativity. Despite 5 containing MeCN, N-H···O/F hydrogen bonds, and C–H···π and π-π interactions combine to give similar 2D layers. Magnetic measurements reveal moderately abrupt spin crossover for 1-4; becoming more gradual and only 50% complete in 1 due to solvent loss. The MeCN solvate shows more gradual SCO and reinforces how subtle changes in packing can significantly influence SCO behaviour.

scholarly journals Simple Methylcadmium Alkoxides

2007 ◽  
Vol 62 (10) ◽  
pp. 1339-1342 ◽  
Author(s):  
Surajit Jana ◽  
Tania Pape ◽  
Norbert W. Mitzel
Keyword(s):  
Mass Spectrometry ◽  
Solid State ◽  
Molecular Formula ◽  
Equimolar Ratio ◽  
X Ray ◽  
X Ray Crystallography ◽  
Elemental Analyses ◽  
Solid State Structures ◽  
Structural Aspects ◽  
C Nmr

The reaction of dimethylcadmium with alcohols R-OH in equimolar ratio leads to the formation of tetrameric methylcadmium alkoxides with molecular formula [(MeCd)4 (OR)4] [R = Me (1), Et (2) and iPr (3)]. These compounds have been characterised by 1H, 13C NMR and IR spectroscopy, by mass spectrometry, elemental analyses and by X-ray crystallography (for 2 and 3). The solid state structures show distorted cubane-type aggregates with Cd4O4 cores. The structural aspects and the spectroscopic characterisations of these compounds are discussed.

scholarly journals Crystal structure of bis{(3,5-dimethylpyrazol-1-yl)dihydro[3-(pyridin-2-yl)pyrazol-1-yl]borato}iron(II)

2020 ◽  
Vol 76 (8) ◽  
pp. 1266-1270
Author(s):  
Sascha Ossinger ◽  
Christian Näther ◽  
Felix Tuczek
Keyword(s):  
Spin Crossover ◽  
Magnetic Measurements ◽  
Complex Molecule ◽  
High Spin State ◽  
Methyl Groups ◽  
Asymmetric Unit ◽  
Pure Sample ◽  
X Ray ◽  
Classical Hydrogen Bond

The structure determination of [Fe(C13H15BN5)2] was undertaken as part of a project on the modification of the recently published spin-crossover (SCO) complex [Fe{H2B(pz)(pypz)}2] (pz = pyrazole, pypz = pyridylpyrazole). To this end, a new ligand was synthesized in which two additional methyl groups are present. Its reaction with iron trifluoromethanesulfonate led to a pure sample of the title compound, as proven by X-ray powder diffraction. The asymmetric unit consists of one complex molecule in a general position. The FeII atom is coordinated by two tridentate N-binding {H2B(3,5-(CH3)2-pz)(pypz)}− ligands. The Fe—N bond lengths range between 2.1222 (13) and 2.3255 (15) Å, compatible with FeII in the high-spin state, which was also confirmed by magnetic measurements. Other than a very weak C—H...N non-classical hydrogen bond linking individual molecules into rows extending parallel to [010], there are no remarkable intermolecular interactions.

A new Co(II) coordination polymer with the 2-(4-pyridyl)-terephthalate ligand: synthesis, crystal structure and magnetic properties

2019 ◽  
Vol 74 (7-8) ◽  
pp. 619-622
Author(s):  
Danian Tian ◽  
Runmei Ding ◽  
Bingbing Chen ◽  
Peipei Cen
Keyword(s):  
Magnetic Measurements ◽  
Layer Structure ◽  
Octahedral Geometry ◽  
Supramolecular Network ◽  
Asymmetric Unit ◽  
Temperature Dependent ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Bimetallic Layer ◽  
Ferromagnetic Interactions

AbstractA new Co(II) complex, [Co(pta)(H2O)2]n (1), with the 2-(4-pyridyl)-terephthalate ligand (pta2−) has been synthesized and structurally and magnetically characterized. Single crystal X-ray analysis indicates that the unique Co(II) ion in the asymmetric unit of 1 displays stretched octahedral geometry. Compound 1 presents a bimetallic layer structure which is further expanded to a 3D supramolecular network through hydrogen bonding interactions. Magnetic measurements have revealed the temperature-dependent existence of antiferromagnetic and ferromagnetic interactions in compound 1.

scholarly journals Synthesis and characterization of a new bis-NHC palladium complex and its catalytic activity in the Mizoroki–Heck reaction

2020 ◽  
Vol 44 (11-12) ◽  
pp. 684-688
Author(s):  
Can Feng ◽  
Cheng-xin Liu ◽  
Yu-fang Wang ◽  
Jin Cui ◽  
Ming-jie Zhang
Keyword(s):  
Palladium Complex ◽  
Coupling Reaction ◽  
Aryl Halides ◽  
Heck Coupling ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Excellent Stability ◽  
C Nmr

A new bis- N-heterocyclic carbene palladium complex, (C13H9N2F2)2PdCl2, is synthesized by a three-step reaction and characterized by 1H NMR and 13C NMR spectroscopy as well as by X-ray crystallography. This new bis- N-heterocyclic carbene palladium complex has excellent stability and is capable of efficiently catalyzing the Mizoroki–Heck coupling reaction of aryl halides with acrylates.

scholarly journals Structural basis for the binding of SNAREs to the multisubunit tethering complex Dsl1

2020 ◽  
Author(s):  
Sophie M. Travis ◽  
Kevin DAmico ◽  
I-Mei Yu ◽  
Safraz Hamid ◽  
Gabriel Ramirez-Arellano ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Relative Orientation ◽  
Snare Complex ◽  
Structural Basis ◽  
Binding Modes ◽  
Range Interaction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Long Range Interaction ◽  
Target Membrane

AbstractMultisubunit tethering complexes (MTCs) are large (250 to >750 kDa), conserved macromolecular machines that are essential for SNARE-mediated membrane fusion in all eukaryotes. MTCs are thought to function as organizers of membrane trafficking, mediating the initial, long-range interaction between a vesicle and its target membrane and promoting the formation of membrane-bridging SNARE complexes. Previously, we reported the structure of the Dsl1 complex, the simplest known MTC, which is essential for COPI-mediated transport from the Golgi to the endoplasmic reticulum (ER). This structure suggested how the Dsl1 complex might function to tether a vesicle to its target membrane by binding at one end to the COPI coat and at the other end to ER SNAREs. Here, we use x-ray crystallography to investigate these Dsl1-SNARE interactions in greater detail. The Dsl1 complex comprises three subunits that together form a two-legged structure with a central hinge. Our results show that distal regions of each leg bind N-terminal Habc domains of the ER SNAREs Sec20 (a Qb-SNARE) and Use1 (a Qc-SNARE). The observed binding modes appear to anchor the Dsl1 complex to the ER target membrane while simultaneously ensuring that both SNAREs are in open conformations with their SNARE motifs available for assembly. The proximity of the two SNARE motifs, and therefore their ability to enter the same SNARE complex, depends on the relative orientation of the two Dsl1 legs.

scholarly journals Crystal structure of glycosyltrehalose synthase fromSulfolobus shibataeDSM5389

2018 ◽  
Vol 74 (11) ◽  
pp. 741-746
Author(s):  
Nobuo Okazaki ◽  
Michael Blaber ◽  
Ryota Kuroki ◽  
Taro Tamada
Keyword(s):  
Crystal Structure ◽  
Amino Acids ◽  
Catalytic Mechanism ◽  
Catalytic Domain ◽  
Structural Basis ◽  
Hyperthermophilic Archaeon ◽  
X Ray ◽  
X Ray Crystallography ◽  
Sulfolobus Shibatae ◽  
Glucosidic Bond

Glycosyltrehalose synthase (GTSase) converts the glucosidic bond between the last two glucose residues of amylose from an α-1,4 bond to an α-1,1 bond, generating a nonreducing glycosyl trehaloside, in the first step of the biosynthesis of trehalose. To better understand the structural basis of the catalytic mechanism, the crystal structure of GTSase from the hyperthermophilic archaeonSulfolobus shibataeDSM5389 (5389-GTSase) has been determined to 2.4 Å resolution by X-ray crystallography. The structure of 5389-GTSase can be divided into five domains. The central domain contains the (β/α)8-barrel fold that is conserved as the catalytic domain in the α-amylase family. Three invariant catalytic carboxylic amino acids in the α-amylase family are also found in GTSase at positions Asp241, Glu269 and Asp460 in the catalytic domain. The shape of the catalytic cavity and the pocket size at the bottom of the cavity correspond to the intramolecular transglycosylation mechanism proposed from previous enzymatic studies.

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