scholarly journals Unravelling the Chemistry of the [Cu(4,7-Dichloroquinoline)2Br2]2 Dimeric Complex through Structural Analysis: A Borderline Ligand Field Case

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 477 ◽  
Author(s):  
Giada Finocchio ◽  
Silvia Rizzato ◽  
Giovanni Macetti ◽  
Gers Tusha ◽  
Leonardo Lo Presti
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Electrostatic Interactions ◽  
Electronic States ◽  
Relative Energy ◽  
Electronic Charge ◽  
Ligand Field ◽  
Coordination Geometry ◽  
Dimeric Complex ◽  
Frontier Orbitals

Large dark prismatic crystals (P 1 ¯ ) consisting of closely packed centrosymmetric [Cu(4,7-dichloroquinoline)2]2Br4 binuclear units are formed when 4,7-dichloroquinoline (DCQ, C9H5NCl2) binds copper(II). Cu2+ adopts a strongly distorted square pyramidal coordination geometry, perturbed by electrostatic interactions with two axial μ–Br ligands acting as highly asymmetric bridges. It is shown that, as electronic states of ligands are higher in energy than the metal ones, antibonding orbitals bear significant ligand-like character and electronic charge is partially transferred from inner-sphere coordinated halogen atoms to copper. Overall, the title compound sits on the Hoffman’s border between main group and transition chemistry, with non-negligible contributions of the ligands to the frontier orbitals. The relative energy placement of metal and ligand states determines an internal redox process, where the metal is slightly reduced at the expense of partial oxidation of the bromide ligands. In fact, the crystal structure is partially disordered due to the substitution of some penta-coordinated Cu(II) centers with tetra-coordinated Cu(I) ions. The geometry of the complex is rationalized in terms of electrostatic-driven distortions from an ideal octahedral prototype. Implications on the reactivity of Cu(II)–quinoline complexes are discussed.

scholarly journals Structural Analysis of a Nitrogenase Iron Protein from Methanosarcina acetivorans: Implications for CO2 Capture by a Surface-Exposed [Fe4S4] Cluster

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Lee A. Rettberg ◽  
Wonchull Kang ◽  
Martin T. Stiebritz ◽  
Caleb J. Hiller ◽  
Chi Chung Lee ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Methanosarcina Acetivorans ◽  
Ambient Conditions ◽  
Content Type ◽  
Fe Protein ◽  
Nitrogenase Iron Protein

ABSTRACT Nitrogenase iron (Fe) proteins reduce CO2 to CO and/or hydrocarbons under ambient conditions. Here, we report a 2.4-Å crystal structure of the Fe protein from Methanosarcina acetivorans (MaNifH), which is generated in the presence of a reductant, dithionite, and an alternative CO2 source, bicarbonate. Structural analysis of this methanogen Fe protein species suggests that CO2 is possibly captured in an unactivated, linear conformation near the [Fe4S4] cluster of MaNifH by a conserved arginine (Arg) pair in a concerted and, possibly, asymmetric manner. Density functional theory calculations and mutational analyses provide further support for the capture of CO2 on MaNifH while suggesting a possible role of Arg in the initial coordination of CO2 via hydrogen bonding and electrostatic interactions. These results provide a useful framework for further mechanistic investigations of CO2 activation by a surface-exposed [Fe4S4] cluster, which may facilitate future development of FeS catalysts for ambient conversion of CO2 into valuable chemical commodities. IMPORTANCE This work reports the crystal structure of a previously uncharacterized Fe protein from a methanogenic organism, which provides important insights into the structural properties of the less-characterized, yet highly interesting archaeal nitrogenase enzymes. Moreover, the structure-derived implications for CO2 capture by a surface-exposed [Fe4S4] cluster point to the possibility of developing novel strategies for CO2 sequestration while providing the initial insights into the unique mechanism of FeS-based CO2 activation.

scholarly journals Crystal structure of μ-peroxido-κ4O1,O2:O1′,O2′-bis[(nitrato-κO)(2,2′:6′,2′′-terpyridine-κ3N,N′,N′′)dioxidouranium(VI)]

2015 ◽  
Vol 71 (5) ◽  
pp. m122-m123 ◽  
Author(s):  
Takeshi Kawasaki ◽  
Takafumi Kitazawa
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Coordination Geometry ◽  
Dimeric Complex ◽  
Π Interactions ◽  
Dimensional Network ◽  
Dimeric Complexes ◽  
Centroid Distance ◽  
The Mean ◽  
Equatorial Ligand

In the title dimeric complex, [{UO2(NO3)(C15H11N3)}2O2], a peroxide ion bridges the two uranyl(VI) [O=U=O]2+ions. The O—O bond length of the peroxide is 1.485 (6) Å and the mid-point of this bond is located at the inversion centre of the dimer. The U atom exhibits a distorted hexagonal–bipyramidal coordination geometry with two uranyl(VI) O atoms occupying the axial positions and one O atom of the monodentate nitrate ion, both O atoms of the peroxide ion and the three N atoms of the chelating tridentate 2,2′:6′,2′′-terpyridine (terpy) ligand in the equatorial positions. Two of the N atoms of the terpy ligand lie above and below the mean plane containing the equatorial ligand atoms and the U atom [deviations from the mean plane: maximum 0.500 (2), minimum −0.472 (2) and r.m.s. = 0.2910 Å]. The dihedral angle between the terpy ligand and the mean plane is 35.61 (7)°. The bond lengths around the U atom decrease in the order U—N > U—Onitrate> U—Operoxo> U=O. The dimeric complexes pack in a three-dimensional network held together by weak π–π interactions [centroid–centroid distance = 3.659 (3) Å] between pyridyl rings of the terpy ligands in neighbouring dimers, together with intermolecular C—H...O and C—H...π interactions. Weak intramolecular C—H...O interactions are also observed.

scholarly journals Structural analysis of human dual-specificity phosphatase 22 complexed with a phosphotyrosine-like substrate

2015 ◽  
Vol 71 (2) ◽  
pp. 199-205 ◽  
Author(s):  
George T. Lountos ◽  
Scott Cherry ◽  
Joseph E. Tropea ◽  
David S. Waugh
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Phosphatase Activity ◽  
Small Molecule ◽  
Molecular Basis ◽  
Protein Tyrosine Phosphatases ◽  
Simple Method ◽  
Dual Specificity Phosphatase ◽  
Dual Specificity ◽  
Nitrophenyl Phosphate

4-Nitrophenyl phosphate (p-nitrophenyl phosphate, pNPP) is widely used as a small molecule phosphotyrosine-like substrate in activity assays for protein tyrosine phosphatases. It is a colorless substrate that upon hydrolysis is converted to a yellow 4-nitrophenolate ion that can be monitored by absorbance at 405 nm. Therefore, the pNPP assay has been widely adopted as a quick and simple method to assess phosphatase activity and is also commonly used in assays to screen for inhibitors. Here, the first crystal structure is presented of a dual-specificity phosphatase, human dual-specificity phosphatase 22 (DUSP22), in complex with pNPP. The structure illuminates the molecular basis for substrate binding and may also facilitate the structure-assisted development of DUSP22 inhibitors.

scholarly journals Crystal structure of bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]cobalt(II)

2015 ◽  
Vol 71 (5) ◽  
pp. 452-454 ◽  
Author(s):  
Abdelhakim Laachir ◽  
Fouad Bentiss ◽  
Salaheddine Guesmi ◽  
Mohamed Saadi ◽  
Lahcen El Ammari
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Title Complex ◽  
Octahedral Coordination ◽  
Maximum Deviation ◽  
Coordination Geometry ◽  
Acta Cryst ◽  
Π Interactions ◽  
The Mean

In the mononuclear title complex, [Co(N3)2(C12H8N4S)2], the cobalt(II) atom is located on an inversion centre and displays an axially weakly compressed octahedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole ligands, whereas the axial positions are occupied by N atoms of the azide anions. The thiadiazole and pyridine rings linked to the metal are almost coplanar, with a maximum deviation from the mean plane of 0.0273 (16) Å. The cohesion of the crystal is ensured by weak C—H...N hydrogen bonds and by π–π interactions between pyridine rings [intercentroid distance = 3.6356 (11) Å], forming a layered arrangement parallel to (001). The structure of the title compound is isotypic with that of the analogous nickel(II) complex [Laachiret al.(2013).Acta Cryst.E69, m351–m352].

scholarly journals The crystal structure of szenicsite, Cu3MoO4(OH)4

1998 ◽  
Vol 62 (04) ◽  
pp. 461-469 ◽  
Author(s):  
Peter C. Burns
Keyword(s):  
Crystal Structure ◽  
Goodness Of Fit ◽  
Direct Methods ◽  
Ligand Field ◽  
Area Detector ◽  
Vertex Sharing ◽  
Distorted Octahedral ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Least Squares Techniques

Abstract The crystal structure of szenicsite, Cu3MoO4(OH)4, orthorhombic, a = 8.5201(8), b = 12.545(1), c = 6.0794(6) Å, V = 649.8(2) Å3, space group Pnnm, Z = 4, has been solved by direct methods and refined by least-squares techniques to an agreement index (R) of 3.34% and a goodness-of-fit (S) of 1.11 for 686 unique observed [|F| ⩾ 4σF] reflections collected using graphite-monochromated Mo-Kα X-radiation and a CCD area detector. The structure contains three unique Cu2+ positions that are each coordinated by six anions in distorted octahedral arrangements; the distortions of the octahedra are due to the Jahn-Teller effect associated with a d 9 metal in an octahedral ligand-field. The single unique Mo6+ position is tetrahedrally coordinated by four O2− anions. The Cu2+ϕ6 (ϕ: unspecified ligand) octahedra share trans edges to form rutile-like chains, three of which join by the sharing of octahedral edges to form triple chains that are parallel to [001]. The MoO4 tetrahedra are linked to either side of the triple chain of Cu2+ϕ6 octahedra by the sharing of two vertices per tetrahedron, and the resulting chains are cross-linked through tetrahedral-octahedral vertex sharing to form a framework structure. The structure of szenicsite is closely related to that of antlerite, Cu3SO4(OH)4, which contains similar triple chains of edge-sharing Cu2+ϕ6 octahedra.

Polymorphism and the influence of crystal structure on the luminescence of the opto-electronic material 4,4′-bis(9-carbazolyl)biphenyl

CrystEngComm ◽  
2014 ◽  
Vol 16 (33) ◽  
pp. 7621-7625 ◽  
Author(s):  
Cody J. Gleason ◽  
Jordan M. Cox ◽  
Ian M. Walton ◽  
Jason B. Benedict
Keyword(s):  
Crystal Structure ◽  
Electronic Structure ◽  
Electronic Material ◽  
Single Crystal ◽  
Charge Transport ◽  
Luminescent Properties ◽  
Electronic Structure Calculations ◽  
Electronic Charge ◽  
Single Crystal Structures ◽  
Structure Calculations

Single crystal structures, luminescent properties and electronic structure calculations of three polymorphs of the opto-electronic charge transport material 4,4′-bis(9-carbazolyl)biphenyl.

Molecular tapes in the structure of isoguaninium chloride

2017 ◽  
Vol 74 (1) ◽  
pp. 108-112 ◽  
Author(s):  
Urszula Anna Budniak ◽  
Paulina Maria Dominiak
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Charge Density ◽  
Interaction Energy ◽  
Electrostatic Interaction ◽  
Electrostatic Interactions ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Structure

Isoguanine, an analogue of guanine, is of intrinsic interest as a noncanonical nucleobase. The crystal structure of isoguaninium chloride (systematic name: 6-amino-2-oxo-1H,7H-purin-3-ium chloride), C5H6N5O+·Cl−, has been determined by single-crystal X-ray diffraction. Structure analysis was supported by electrostatic interaction energy (E es) calculations based on charge density reconstructed with the UBDB databank. In the structure, two kinds of molecular tapes are observed, one parallel to (010) and the other parallel to (50\overline{4}). The tapes are formed by dimers of isoguaninium cations interacting with chloride anions. E es analysis indicates that cations in one kind of tape are oriented so as to minimize repulsive electrostatic interactions.

scholarly journals Multi-scale structural analysis of the A-site and oxygen deficient perovskite Sr11Mo4O23

2017 ◽  
Vol 46 (37) ◽  
pp. 12466-12473 ◽  
Author(s):  
Graham King ◽  
Maxim Avdeev ◽  
Ilyas Qasim ◽  
Qingi Zhou ◽  
Brendan J. Kennedy
Keyword(s):  
Crystal Structure ◽  
Structural Analysis ◽  
Multi Scale ◽  
Local Correlations ◽  
A Site

The crystal structure of Sr11Mo4O23 and the local correlations between the disordered sites are examined.

The search for formal electrostatic effects on molecular conformation and crystal packing: crystal structure of 2,2′′-disubstituted (HversusPPh2) 1,1′-(1,2-phenylene)bis(3-methyl-1H-imidazol-3-ium) bis(trifluoromethanesulfonate)

2016 ◽  
Vol 72 (3) ◽  
pp. 198-202
Author(s):  
Carine Duhayon ◽  
Yves Canac ◽  
Laurent Dubrulle ◽  
Carine Maaliki ◽  
Remi Chauvin
Keyword(s):  
Crystal Structure ◽  
Electrostatic Interactions ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Relative Orientation ◽  
Electron Delocalization ◽  
Electrostatic Effects ◽  
Conformational Freedom ◽  
The Stability ◽  
Bond Character

Electrostatic interactions between localized integral charges make the stability and structure of highly charged small and rigid organics intriguing. Can σ/π-electron delocalization compensate reduced conformational freedom by lowering the repulsion between identical charges? The crystal structure of the title salt, C14H16N42+·2CF3SO3−, (2), is described and compared with that of the 2,2′′-bis(diphenylphosphanyl) derivative, (4). The conformations of the dications and their interactions with neighbouring trifluoromethanesulfonate anions are first analyzed from the standpoint of formal electrostatic effects. Neither cation exhibits any geometrical strain induced by the intrinsic repulsion between the positive charges. In contrast, the relative orientation of the imidazolium rings [i.e. antifor (2) andsynfor (4)] is controlled by different configurations of the interactions with the closest trifluoromethanesulfonate anions. The long-range arrangement is also found to be specific: beyond the formal electrostatic packing, C—H...O and C—H...F contacts have no definite `hydrogen-bond' character but allow the delineation of layers, which are either pleated or flat in the packing of (2) or (4), respectively.

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