Oxygen Atom Of Phosphoryl Group Research Articles

In English

During last decades сoordination compounds of lanthanides with polychelating β-diketones and their derivatives have attracted increasing interest due to the possibility of using such compounds in biomedical research, as contrast reagents for NMR tomography studies and MOLED technology. That is why the selection of appropriate ligands, which are effective sensitizers of lanthanide luminescence and can form thermodynamically stable complexes, is especially important. Carbacylamidophosphates (CAPh ligands) of general formula (R 1 )C(O)NHP(O)(R 2 ) 2 are structural analogues of β-diketones, which can serve as an antenna providing more efficient energy transfer to the lanthanide ion followed by Ln(III) luminescence. The present work is devoted to the mass-spectrometric studies of the stability of coordination compound of terbium(III) with new CAPh ligand using methods of soft ionization such as matrix activated laser desorption / ionization (MALDI), its modification – LDI (laser desorption ionization). The main preference of the «soft ionization» methods is the possibility of unfragmented ions registration. Terbium coordination compound with new bis-chelating carbacylamidophosphate ligand (Tb(HL) 2 (NO 3 )) (where HL – = tetramethyl[pyridine-2,6-diyldi(iminocarbonyl)]diamidophosphate anion) has been synthesized and studied by IR spectroscopy and X-ray diffraction. It was shown that the deprotonated arm of each ligand is coordinated to the terbiumion in the bidentate manner and the protonated arm in monodentate manner via the oxygen atom of phosphoryl group. The nitrate ion is bidentate coordinated, completing coordination number of terbium to eight. The components of the LDI mass spectrum of the synthesized coordination compound have been identified. The positive region of the mass spectrum of the complex Tb(HL) 2 (NO 3 ) is characterized by the presence of smaller fragments due to the effect of the metal ion on the fragmentation of the ligand molecules and the molecular ion is not observed due to formation of more complex and stable structures based on Tb(III) ions.

A novel Zn(II) complex of N-nicotinyl phosphoramide: Combined experimental and computational studies

Abstract A novel Zn(II) coordination polymer of N-nicotinyl phosphoric triamide ligand, {[Zn(L)2(H2O)2]⋅(NO3)2}n C1 (L = 3-NC5H4C(O)NHP(O)(NC6H12)2), has been synthesized and characterized by IR and 1H, 13C, 31P NMR spectroscopy. Crystal structure analysis of C1 demonstrates a distorted octahedral geometry for Zn(II) ions. The oxygen atom of phosphoryl group (Ophosphoryl) and the nitrogen atom of pyridine ring (Npyridine) of ligand take part in coordination to Zn(II) centers in a bidentate bridging mode. This coordination pattern results in infinite 1D polymeric chains along c axis, which are composed of metal shared 16-membered puckered rings. Structural data show that despite binding through Ophosphoryl, the P O bond distance unexpectedly shortens in C1 when compared to that of the ligand, conceivably due to the steric factors in the solid state. This is confirmed by comparing the structural and electronic properties of C1 and L in the gas phase by using density functional theory (DFT) calculations. Natural bond orbital (NBO) analysis reveals the metal–ligand interaction for C1 as donor–acceptor type delocalizations (charge transfer). Besides, on the basis of the quantum theory of atoms in molecules (QTAIM) analysis, the nature of Zn O and Zn N bondings is found to be mainly electrostatic with a small amount of covalent character.

Structural basis for the reaction mechanism of UDP-glucose pyrophosphorylase.

UDP-glucose pyrophosphorylases (UGPase; EC 2.7.7.9) catalyze the conversion of UTP and glucose-1-phosphate to UDP-glucose and pyrophosphate and vice versa. Prokaryotic UGPases are distinct from their eukaryotic counterparts and are considered appropriate targets for the development of novel antibacterial agents since their product, UDP-glucose, is indispensable for the biosynthesis of virulence factors such as lipopolysaccharides and capsular polysaccharides. In this study, the crystal structures of UGPase from Helicobacter pylori (HpUGPase) were determined in apo- and UDP-glucose/Mg(2+)-bound forms at 2.9 A and 2.3 A resolutions, respectively. HpUGPase is a homotetramer and its active site is located in a deep pocket of each subunit. Magnesium ion is coordinated by Asp130, two oxygen atoms of phosphoryl groups, and three water molecules with octahedral geometry. Isothermal titration calorimetry analyses demonstrated that Mg(2+) ion plays a key role in the enzymatic activity of UGPase by enhancing the binding of UGPase to UTP or UDP-glucose, suggesting that this reaction is catalyzed by an ordered sequential Bi Bi mechanism. Furthermore, the crystal structure explains the specificity for uracil bases. The current structural study combined with functional analyses provides essential information for understanding the reaction mechanism of bacterial UGPases, as well as a platform for the development of novel antibacterial agents.

β-Diketonates and their Analogs: Stabilization of the Dimeric M2{L}4(D)2 (M = Co, Ni) Core in the Complexes with Dimethyl-N-trichloroacetylamidophosphate {Cl3C(O)NP(O)(OCH3)2}-

The coordination compounds of general formula [M{X}2(2-propanol)]2 (M = Co(II) (1), Ni(II) (2); {X} = Cl3CC(O)NP(O)(OCH3)2) have been prepared and characterized by means of IR, UV-VIS spectroscopy and X-ray analysis. The compounds are isomorphous according to X-ray powder diffraction studies. Crystal data for 1: triclinic, P1̄, with a = 9.510(2), b = 12.053(2), c = 23.594(5) Å ,a = 84.74(3), b = 86.47(3), g = 75.45(3)°, Z = 2, V = 2604.7(9) Å3, R1 = 0.067, wR2 = 0.143 for 6299 unique reflection used). The complex adopts a dimeric centrosymmetric molecular array with Co-O-Co bridges formed via the oxygen atoms of phosphoryl groups. This structure is stabilized by intradimeric hydrogen bonds of the type P = O---H with the coordinated 2-propanol. The metal atoms are coordinated in slightly distorted octahedra (Co-O 2.050(5)-2.140(5) Å). Unlike the β-diketonate compounds of similar structure, the dimeric complexes are stable towards donor species and in 2-propanol solution.