Equal Occupancy Research Articles

Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy-ethyl)methylamino]ethanolato-2:1κ(4) O (1),N,O (2):O (1)}[μ-2,2'-(methylimino)diethanolato-1:2κ(4) O,N,O':O]dithiocyanato-1κN,2κN-chromium(III)copper(II).

The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal Cu(II)/Cr(III) complex. The mol-ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio-cyanato ligands. The Cu(II) ion adopts a distorted square-pyramidal coordination while the Cr(III) ion has a distorted octa-hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O-H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two -CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1).

Crystal structure of trans-bis-(ethane-1,2-diamine-κ(2) N,N')bis-(thio-cyanato-κN)chromium(III) perchlorate from synchrotron data.

The structure of the title compound, [Cr(NCS)2(C2H8N2)2]ClO4, has been determined from synchroton data. The asymmetric unit consists of one half of a centrosymmetric Cr(III) complex cation and half of a perchlorate anion with the Cl atom on a twofold rotation axis. The Cr(III) ion is coordinated by the four N atoms of two ethane-1,2-di-amine (en) ligands in the equatorial plane and two N-bound thio-cyanate (NCS(-)) anions in a trans-axial arrangement, displaying a slightly distorted octa-hedral geometry with crystallographic inversion symmetry. The Cr-N(en) bond lengths are in the range 2.053 (16)-2.09 (2) Å, while the Cr-N(thio-cyanate) bond length is 1.983 (2) Å. The five-membered en rings are disordered over two sites, with occupancy ratios of 0.522 (16):0.478 (16). Each ClO4 (-) anion is disordered over two sites with equal occupancy. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the en NH2 groups as donors and perchlorate O and thio-cyanate S atoms as acceptors.

Crystal structures of di-chlorido-palladium(II), -platinum(II) and -rhodium(III) complexes containing 8-(di-phenyl-phosphan-yl)quinoline.

The crystal structures of di-chlorido-palladium(II), -platinum(II) and -rhodium(III) complexes containing 8-(di-phenyl-phosphan-yl)quinoline, (SP-4)-[PdCl2(C21H16NP)], (1) [systematic name: di-chlor-ido-(8-di-phenyl-phosphanyl-quinoline)-palladium(II)], (SP-4)-[PtCl2(C21H16NP)]·CH2Cl2, (2) [systematic name: di-chlorido-(8-di-phenyl-phos-phanyl-quinoline)-platinum(II) dichlorometh-ane monosolvate], and (OC-6-32)-[RhCl2(C21H16NP)2]PF6·0.5CH2Cl2·0.5CH3OH, (3) [systematic name: cis-di-chlor-ido-bis-(8-di-phenyl-phosphanyl-quinoline)-rhodium(III) hexa-fluorido-phos-phate di-chloro-methane/-methanol hemisolvate] are reported. In these complexes, the phosphanyl-quinoline acts as a bidentate ligand, forming a planar asymmetrical five-membered chelate ring. The palladium(II) and platinum(II) complex mol-ecules in (1) and (2), respectively, show a typical square-planar coordination geometry and form a dimeric structure through an inter-molecular π-π stacking inter-action between the quinolyl rings. The centroid-centroid distances between the stacked six-membered rings in (1) and (2) are 3.633 (2) and 3.644 (2) Å, respectively. The cationic rhodium(III) complex in (3) has a cis(Cl),cis(P),cis(N) (OC-6-32) configuration of the ligands, in which two kinds of intra-molecular π-π stacking inter-actions are observed: between the quinolyl and phenyl rings and between two phenyl rings, the centroid-centroid distances being 3.458 (2) and 3.717 (2) Å, respectively. The PF6 (-) anion in (3) is rotationally disordered, the site occupancies of each F atom being 0.613 (14) and 0.387 (14). The CH2Cl2 and CH3OH solvent mol-ecules are also disordered and equal site occupancies of 0.5 are assumed.

Mechanical control of magnetism in oxygen deficient perovskite SrTiO3.

Mechanical control of magnetism in perovskite oxides is an important and promising approach in spintronics. Based on the first-principles calculations, we demonstrate that a negative pressure leads to a great enhancement of magnetic moment in deficient SrTiO3 with oxygen vacancies, whereas a positive pressure results in the gradual disappearance of magnetism. Spin charge density, Bader charge analysis and electronic density of states successfully elucidate the origin and underlying physics of the enhancement and disappearance of magnetism. It is found that the split electronic states of dz(2), dyz and dzx in the 3d orbitals of Ti atoms remarkably contribute to the occupancy of majority spin states under negative pressure, which induces a large magnetic moment. Under positive pressure, however, the equal occupancy of both majority and minority t2g and eg states leads to the disappearance of magnetization. In addition, both negative and positive pressures can largely lower the vacancy formation enthalpy, suggesting that the oxygen vacancy is preferable with pressure. Our findings may provide a mechanism to achieve the pressure control of magnetization in nonmagnetic perovskite oxides.

Bis{2-meth-oxy-6-[(E)-(4-methyl-benz-yl)imino-meth-yl]phenolato}palladium(II) chloro-form monosolvate.

In the title complex, [Pd(C16H16NO2)2]·CHCl3, the PdII cation lies on an inversion center. One Cl atom of the CHCl3 solvent mol­ecule lies on a twofold axis and the C—H group is disordered with equal occupancies about this axis with the other Cl atom in a general position with full occupancy. The PdII cation is four-coordinate and adopts a square-planar geometry via coordination of the imine N and phenolic O atoms of the two bidentate Schiff base anions. The N and O atoms of these ligands are mutually trans. The plane of the benzene ring makes a dihedral angle of 73.52 (10)° with that of the meth­oxy­phenolate ring. In the crystal, mol­ecules of the PdII complex are arranged into sheets parallel to the ac plane, and the chloro­form solvent mol­ecules are located in the inter­stitial areas between the complex mol­ecules. Weak inter­molecular C—H⋯O and C—H⋯π inter­actions stabilize the packing.

Joint on-the-fly network coding/video quality adaptation for real-time delivery

This paper introduces a redundancy adaptation algorithm based on an on-the-fly erasure network coding scheme named Tetrys in the context of real-time video transmission. The algorithm exploits the relationship between the redundancy ratio used by Tetrys and the gain or loss in encoding bit rate from changing a video quality parameter called the Quantization Parameter (QP). Our evaluations show that with equal or less bandwidth occupation, the video protected by Tetrys with redundancy adaptation algorithm obtains a PSNR gain up to or more than 4dB compared to the video without Tetrys protection. We demonstrate that the Tetrys redundancy adaptation algorithm performs well with the variations of both loss pattern and delay induced by the networks. We also show that Tetrys with the redundancy adaptation algorithm outperforms traditional block-based FEC codes with and without redundancy adaptation.

Bis(2-amino-5-benzyl-3-ethoxycarbonyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridin-5-ium) bis(4-methoxyphenyl)diphosphonate

The asymmetric unit of the title salt, 2C17H21N2O2S+·C14H14O7P2 2−, contains half of a centrosymmetric bis­(4-meth­oxy­phen­yl)di­phospho­nate anion and one 2-amino-5-benzyl-3-eth­oxy­carbonyl-4,5,6,7-tetra­hydro­thieno[3,2-c]pyri­din-5-ium cation. In the anion, the O atoms of the di­phospho­nate group are disordered over two positions with equal occupancies. In the cation, the ethyl group is disordered over two orientations with a refined occupancy ratio of 0.753 (5):0.247 (5), and the tetra­hydro­pyridinium ring adopts a distorted half-chair conformation. In the crystal, the ions are linked by C—H⋯O, N—H⋯O and C—H⋯S hydrogen bonds into a three-dimensional network.

Crystal structure, vibrational and thermal behavior of Ba(NH4)[Co(CN)6]·4H2O: A new precursor for the synthesis of hexagonal BaCoO3

The crystal structure of Ba(NH4)[Co(CN)6]·4H2O complex was determined by X-ray diffraction methods. It crystallizes in the hexagonal P63/m space group with a=b=7.6882(2)Å, c=14.4764(4)Å, and Z=2 molecules per unit cell. The structure was solved from 475 reflections with I>2σ(I) and refined to an agreement R1-factor of 0.0214. The cobaltocyanide anion has an octahedral shape with its Co(III) ion sited at a crystallographic special position of point symmetry 3¯ (S6) [d(Co-C)=1.886(3)Å and d(C–N)=1.143(4)Å]. The barium ion is in a 9-fold environment at a crystal special position 6¯ (C3h), coordinated to cyanide N-atoms of neighboring complexes [d(Ba–N)=2.862(3)Å] and to one type of water molecule laying onto an m mirror plane [d(Ba–Ow)=2.924(4)Å]. The ammonium ion and the other type of water molecule share four symmetry-related C3 lattice sites with equal occupancy. Under the P63 subspace group these four sites split into two independent pairs of C3 sites, one occupied by two symmetry-related ammonium ions, the other by two (disordered) water molecules. The complex was characterized by UV–Vis, IR and Raman spectroscopy and the thermal decomposition was studied to investigate the formation of BaCoO3−δ. This compound, in its hexagonal form, could be synthesized at temperatures as low as 675°C. At 750°C a new orthorhombic poly-type is obtained in a mixture with the hexagonal form which is associated with the appearance of oxygen vacancies. These temperatures of synthesis and reaction times are lower than those reported by ceramic and sol–gel synthesis. These soft treatments gave rise to homogeneous particles of small grain size.

5-Chloro-2-methylsulfanyl-6-(naphthalen-1-yloxy)-1H-benzimidazole methanol monosolvate

In the title compound, C18H13ClN2OS·CH3OH, the dihedral angle between the benzimidazole group and the naphth­yloxy moiety [82.89 (5)°] very near to orthogonality. The H atom in the five-membered ring is disordered with equal occupancies at the two N atoms and the H atom of the methano­lic hy­droxy group is disordered with equal occupancies over two sites at the O atom. The methanol mol­ecule acts as a hydrogen-bond acceptor for the amino H atom and donates a hydrogen bond to the nonprotonated ring N atom. As a result, chains are formed running along the a axis.

Triphenyl(pyrrolidine-1-carbodithioato-κS)tin(IV)

In the title compound, [Sn(C6H5)3(C5H8NS2)], the SnIV atom adopts a distorted SnC3S tetra­hedral coordination geometry [spread of bond angles = 94.43 (7)–120.74 (7)°]. A short intra­molecular Sn⋯S contact [3.0270 (9) Å] occurs and two intra­molecular C—H⋯S inter­actions help to establish the conformation. Three of the methyl­ene groups of the pyrrolidine-1-carbodi­thio­ate ligand are disordered over two sets of sites of equal occupancy. In the crystal, very weak C—H⋯S inter­actions link the mol­ecules into a three-dimensional network, with both S atoms acting as acceptors.

(2E)-3-(2-Chloro-7-methylquinolin-3-yl)-1-(6-chloro-2-methyl-4-phenylquinolin-3-yl)prop-2-en-1-one ethanol monosolvate

In the title ethanol solvate, C29H20Cl2N2O·C2H5OH, the quinolinyl residues form a dihedral angle of 46.41 (4)° with each other, and each is inclined [Cp—C—C=O and C=C—C—Cp (p = pyridyl) torsion angles = 54.8 (2) and 144.44 (19)°, respectively] with respect to the almost planar bridging prop-2-en-1-one residue [O=C—C=C torsion angle = −4.1 (3)°]. The ethanol solvent mol­ecule is disordered over two positions of equal occupancy and is located close to a centre of inversion. These mol­ecules reside in cavities defined by the organic mol­ecules, which are connected into a three-dimensional architecture by C—H⋯Cl, C—H⋯O and C—H⋯N inter­actions, as well as π–π contacts [inter-centroid distances = 3.5853 (10) and 3.8268 (11) Å], each involving pyridyl rings.

1,3-Bis[(5-amino-furan-2-yl)meth-yl]-3,4,5,6-tetra-hydro-pyrimidin-1-ium hexa-fluoro-phosphate.

The asymmetric unit of the title salt, C16H21N2O2 +·PF6 −, contains half of the whole ion pair, which has crystallographic mirror symmetry. Two F atoms related by the mirror plane are disordered over two sites of equal occupancy. The dihedral angle between the central ring and the furan ring is 59.3 ()°. In the crystal, the anions and cations are linked through C—H⋯F inter­actions, forming a three-dimensional network.

Molecular Dynamics Simulations of Barley and Maize Lipid Transfer Proteins Show Different Ligand Binding Preferences in Agreement with Experimental Data

Experimental studies of barley and maize lipid transfer proteins (LTPs) show that the two proteins bind the ligand palmitate in opposite orientations in their internal cavities. Moreover, maize LTP is reported to bind the ligand caprate in the internal cavity in a mixture of two orientations with approximately equal occupancy. Six 30 ns molecular dynamics (MD) simulations of maize and barley LTP with ligands bound in two orientations (modes M and B) have been used to understand the different ligand binding preferences. The simulations show that both maize and barley LTP could bind palmitate in the orientation observed experimentally for maize LTP (mode M), with the predominant interaction being a salt bridge between the ligand carboxylate headgroup and a conserved arginine side chain. However, the simulation of barley LTP with palmitate in the mode B orientation shows the most favorable protein-ligand interaction energy. In contrast, the simulations of maize LTP with palmitate and with caprate in the mode B orientation show no persistent ligand binding, the ligands leaving the cavity during the simulations. Sequence differences between maize and barley LTP in the AB loop region, in residues at the base of the hydrophobic cavity, and in the helix A region are identified as contributing to the different behavior. The simulations reproduce well the experimentally observed binding preferences for palmitate and suggest that the experimental data for maize LTP with caprate reflect ligand mobility in binding mode M rather than the population of binding modes M and B.

N—H...O, O—H...O hydrogen-bonded supramolecular sheet formation in the bis(2-aminoanilinium) fumarate, 3-methylanilinium hydrogen fumarate and 4-chloroanilinium hydrogen fumarate salts

In bis(2-aminoanilinum) fumarate, 2C₆H₉N₂⁺·C₄H₂O₄²⁻, (I), the asymmetric unit consists of two aminoanilinium cations and one fumarate dianion, whereas in 3-methylanilinium hydrogen fumarate, C₇H₁₀N⁺·C₄H3O₄⁻, (II), and 4-chloroanilinium hydrogen fumarate, C₆H₇ClN⁺·C₄H3O₄⁻, (III), the asymmetric unit contains two symmetry-independent hydrogen fumate anions and anilinium cations with a slight difference in their geometric parameters; the two salts are isostructural. In (II) and (III), the carboxylic acid H atoms of the anions are disordered across both ends of the anion, with equal site occupancies of 0.50. Both the 4-chloroanilinium cations of (III) are disordered over two orientations with major occupancies fixed at 0.60 in each case. The hydrogen fumarate anions of (II) and (III) form one-dimensional anionic chains linked through O-H∙∙∙O hydrogen bonds. Salts (II) and (III) form two-dimensional supramolecular sheets built from R₄⁴16), R₄⁴(18), R₅⁵(25) and C₂²(14) motifs extending parallel to the (010) plane, whereas in (I), an (010) sheet is formed built from two R₄³(13) motifs, two R₂²(9) motifs and an R₄⁴(18) motif.

Dichloridobis[3-(4-chlorophenyl)-2,N,N-trimethyl-2,3-dihydro-1,2,4-oxadiazole-5-amine-κN4]platinum(II)–4-chlorobenzaldehyde (1/1)

In the title 1:1 co-crystal, [PtCl2(C11H14ClN3O)2]·C7H5ClO, the coordination polyhedron of the PtII atom is slightly distorted square-planar with the chloride and 2,3-di­hydro-1,2,4-oxa­diazole ligands mutually trans, as the Pt atom lies on an inversion center. The 4-chloro­benzaldehyde mol­ecules are statistically disordered about an inversion centre with equal occupancies for the two positions. The PtII complex forms a three-dimensional structure through C—H⋯Cl and weaker C—H⋯O inter­actions with the 4-chloro­benzaldehyde mol­ecule.

Bis[μ-1,3-bis(diphenylphosphanyl)propane-κ2P:P′]digold(I) tetrachloridonickelate(II) diethyl ether monosolvate

The title compound, [Au2(C27H26P2)2][NiCl4]·C4H10O, consists of a digold(I) complex cation, an [NiCl4]2− complex anion and a diethyl ether solvent mol­ecule. Two 1,3-bis­(di­phenyl­phosphan­yl)propane (dppp) ligands bridge two AuI atoms, forming a metallacycle in which each of the AuI atoms is coordinated in a slightly distorted linear environment by two P atoms. In the complex anion, the NiII atom is coordinated by four chloride ligands in a distorted tetra­hedral geometry. The complex cation and the complex anion form a cation–anion pair through two Au⋯Cl contacts of 3.040 (1) and 3.021 (2) Å. One of the phenyl groups of the dppp ligand is disordered over two positions with equal occupancies.

Diaquasesqui(nitrato-κO)hemi(perchlorato-κO)copper(II)]-μ-{bis[5-methyl-3-(pyridin-2-yl)-1H-pyrazol-4-yl] selenide}-[triaqua(perchlorato-κO)copper(II)] nitrate monohydrate

In the binuclear title complex, [Cu2(ClO4)1.5(NO3)1.5(C18H16N6Se)(H2O)5]NO3·H2O, both CuII ions are hexa­coordinated by O and N atoms, thus forming axially elongated CuO4N2 octa­hedra. The equatorial plane of each octa­hedron is formed by one chelating pyrazole–pyridine fragment of the organic ligand and two water mol­ecules. The axial positions in one octa­hedron are occupied by a water mol­ecule and a monodentately coordinated perchlorate anion, while those in the other are occupied by a nitrate anion and a disordered perchlorate/nitrate anion with equal site occupancy. The pyrazole–pyridine units of the organic selenide are trans-oriented to each other with a C—Se—C angle of 96.01 (14)°. In the crystal, uncoordinated nitrate anions and the coordinating water mol­ecules are involved in O—H⋯O and N—H⋯O hydrogen bonds, forming a bridge between the pyrazole group and the coordinating water mol­ecules. Further O—H⋯O hydrogen bonds between the complex mol­ecules and a π–π stacking inter­action with a centroid–centroid distance of 3.834 (4) Å are also observed.

2-(4-Methylphenyl)-6-nitro-1,3-benzoxazole

The title compound, C14H10N2O3, is a π-conjugated mol­ecule containing a benzoxazole aromatic fused heterobicycle. The benzoxazole ring system is planar within 0.01 Å. The mol­ecule assumes an approximately flat conformation, the benzoxazole ring system forming dihedral angles of 6.52 (12) and 7.4 (3)° with the benzene ring and the nitro group, respectively. In the crystal, mol­ecules are connected by very weak C—H⋯O hydrogen inter­actions, forming chains running parallel to the a or c axes. The methyl H atoms are disordered over two sets of sites of equal occupancy rotated by 60°.

Some new compounds with P(E)NHC(O) (E = lone pair, O, S) linkage: synthesis, spectroscopic, crystal structures, theoretical studies, and antimicrobial evaluation

New phosphinoamides, chalcogenides, and amidophosphates were synthesized and characterized by 1H, 13C, 31P NMR, IR spectroscopy, and elemental analysis. The 13C NMR spectra of two phosphinoamides exhibit obvious differences between their 1 J(P,C) coupling constants (128.3 Hz in one compound vs. 439.2 Hz in another compound). Natural bond orbital analysis was performed to clarify the electronic behavior of the title molecules. The crystal structures of three derivatives were determined by X-ray crystallography. The structure of N-(Diphenylphosphino)-2-pyrazinecarboxamide contains two symmetry-independent forms of the molecule with equal occupancy in the lattice. Density functional theory calculations indicate that two conformers of this compound are identical from an energy point of view. Strong intermolecular N–H···O(P) hydrogen bonds lead to a centrosymmetric dimer in Diphenyl N-(2-pyrazinylcarbonyl)phosphoramidate, whereas N–H···(O)C and N–H···N hydrogen bonds in N-(Diphenylphosphino)-2-pyrazinecarboxamide and N-(Diphenylphosphinothioyl)-2-pyrazinecarboxamide sulfide, respectively, form a one-dimensional polymeric chain in their structures. The in vitro antimicrobial activity of the amidophosphates was evaluated against various microbial strains of Gram positive and Gram negative bacteria and fungi.

Catena-Poly[[[(2,2′-bipyridine-κ2N,N′)manganese(II)]-μ-(2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-diolato)-κ4O1,O6:O3,O4] ethanol disolvate

The asymmetric unit of the title coordination polymer, {[Mn(C6Cl2O4)(C10H8N2)]·2C2H5OH}n, consists of one MnII ion, one 2,2′-bipyridine (bpy) ligand, one chloranilate (CA2−) ligand and two ethanol solvent mol­ecules. The MnII ion is octa­hedrally coordinated by two N atoms of one bpy ligand and four O atoms of two chloranilate ions. The chloranilate ion serves as a bridging ligand between the MnII ions, leading to an infinite zigzag chain along [101]. π–π stacking inter­actions [centroid–centroid distance = 4.098 (2) Å] is observed between the pyridine rings of adjacent chains. The ethanol mol­ecules act as accepters as well as donors for O—H⋯O hydrogen bonds, and form a hydrogen-bonded chain along the a axis. The H atoms of the hy­droxy groups of the two independent ethanol mol­ecules are each disordered over two sites with equal occupancies.