Electron density distribution in tetralithium hypodiphosphate hexahydrate, Li4P2O6·6H2O

The Synthesis of Hypodiphosphoric Acid and Derivatives with P-P Bond, including Esters and Diphosphine Dioxides: A Review

The synthesis of hypodiphosphoric acid and its related compounds began in 1877, but no summary of the synthetic efforts has been reported. This review includes published papers related to the molecules containing the >P(=O)-P(=O)< fragment, which notably resembles the structure of the >P(=O)-O-P(=O)< moiety, the essential building block of many important molecules found in nature and in the field of medicinal chemistry. This review covers the strategies related to the synthesis of hypodiphosphoric acid (former name hypophosphoric acid), its ester form, and diphosphine dioxides. Finally, some properties and applications of these structures studied during this period are presented.

Crystal structures and phase transitions of imidazolium hypodiphosphates

Two imidazolium hypodiphosphates, (C₃H₅N₂)(H₃P₂O₆) (I) and (C₃H₅N₂)₂(H₂P₂O₆) (II), have been synthesized and structurally characterized. In both metal-free organic-inorganic hybrids (I) and (II), the hypodiphosphate mono- and dianions, (H₃P₂O₆)^- and (H₂P₂O₆)^2-, form hydrogen-bonded frameworks of different types, to which the organic cations are linked via N-H...O and C-H...O hydrogen bonds. The purity of the compounds was confirmed by powder X-ray diffraction. Differential scanning calorimetry of compound (I) revealed two structural phase transitions: continuous at 311.8 K [cooling/heating; from high-temperature phase (HTP) to room-temperature phase (RTP)] and a discontinuous one at 287.9/289.2 K [RTP → low-temperature phase (LTP)]. Compound (I) is characterized in a wide temperature range by single-crystal and powder X-ray diffraction methods. Crystal structures of high- and low-temperature phases are determined, which show orthorhombic (HTP, Pnna, No. 52) → monoclinic (LTP, P2₁/n11, No. 14, a-axis doubled) structural change on cooling with an intermediate incommensurately modulated phase (RTP). Dynamic properties of polycrystalline (I) were studied by means of dielectric spectroscopy. The dielectric behaviour is explained by the motion of imidazolium cations.

Analysis of charge density in nonaaquagadolinium(III) trifluoromethanesulfonate - insight into GdIII-OH2 bonding

The experimental charge-density distribution in [Gd(H₂O)₉](CF₃SO₃)₃ has been analysed and compared with the theoretical density functional theory calculations. Although the Gd-OH₂ bonds are mainly ionic, a covalent contribution is detectable when inspecting both the topological parameters of these bonds and the natural bond orbital results. This contribution originates from small electron transfer from the lone pairs of oxygen atoms to empty 5d and 6s spin orbitals of Gd³⁺.

Adenosine hypodiphosphate ester, an analogue of ADP: analysis of the adenine-hypodiphosphate interaction mode in hypodiphosphate nucleotides and adenine salts

Adenosine diphosphate (ADP) plays a crucial role in cell biochemistry, especially in metabolic pathways and energy storage. ADP itself, as well as many of its analogues, such as adenosine hypodiphosphate (AhDP), has been studied extensively, in particular in terms of enzymatic activity. However, structural studies in the solid state, especially for AhDP, are still missing. An analogue of ADP, i.e. adenosine hypodiphosphate ester, has been synthesized and characterized in the crystalline form as two hydrated sodium salts of 2':3'-isopropylideneadenosine 5'-hypodiphosphate (H₃AhDP, C₁₃H₁₉N₅O₉P₂ for the neutral form), namely pentasodium tetrakis(2':3'-isopropylideneadenosine 5'-hypodiphosphate) tetracosahydrate, 5Na⁺·3C₁₃H₁₈N₅O₉P₂^-·C₁₃H₁₇N₅O₉P₂^2-·24H₂O or Na₅(H₂AhDP)₃(HAhDP)·24H₂O, (I), and sodium tetrakis(2':3'-isopropylideneadenosine 5'-hypodiphosphate) pentadecahydrate, Na⁺·C₁₃H₂₀N₅O₉P₂⁺·2C₁₃H₁₈N₅O₉P₂^-·C₁₃H₁₉N₅O₉P₂·15H₂O or Na(H₄AhDP)(H₃AhDP)(H₂AhDP)₂·15H₂O, (II). Crystal structure analyses of (I) and (II) reveal two nucleoside hypodiphosphate ions in the asymmetric units with different ionization states of the hypodiphosphate unit and adenine base. For all AhDP nucleotides, the same anti conformation about the N-glycosidic bond and similar puckering of the ribose ring have been found. AhDP geometry and interactions have been compared to ADP nucleotides deposited in the Cambridge Structural Database. The adenine-hypodiphosphate interactions, identified as defining nucleotide self-assembly, have been analysed in model systems, i.e. the adenine (Ade) salts of hypodiphosphoric acid, namely bis(adeninium) hypodiphosphate dihydrate, 2C₅H₆N₅⁺·H₂P₂O₆^2-·2H₂O or (AdeH)₂(H₂P₂O₆)·2H₂O, (III), and bis(adeninium) hypodiphosphate, 2C₅H₆N₅⁺·H₂P₂O₆^2- or (AdeH)₂(H₂P₂O₆), (IV).

Oxyanion clusters with antielectrostatic hydrogen bonding (AEHB) in tetraalkylammonium hypodiphosphates

Organic–inorganic salts of hypodiphosphoric acid with tetraalkylammonium cations have been synthesized and characterized by X-ray crystallography and IR spectroscopy.

Multi-temperature study of potassium uridine-5'-monophosphate: electron density distribution and anharmonic motion modelling

Uridine, a nucleoside formed of a uracil fragment attached to a ribose ring via a β-N1-glycosidic bond, is one of the four basic components of ribonucleic acid. Here a new anhydrous structure and experimental charge density distribution analysis of a uridine-5'-monophosphate potassium salt, K(UMPH), is reported. The studied case constitutes the very first structure of a 5'-nucleotide potassium salt according to the Cambridge Structural Database. The excellent crystal quality allowed the collection of charge density data at various temperatures, i.e. 10, 100, 200 and 300 K on one single crystal. Crystal structure and charge density data were analysed thoroughly in the context of related literature-reported examples. Detailed analysis of the charge density distribution revealed elevated anharmonic motion of part of the uracil ring moiety relatively weakly interacting with the neighbouring species. The effect was manifested by alternate positive and negative residual density patterns observed for these atoms, which `disappear' at low temperature. It also occurred that the potassium cation, quite uniformly coordinated by seven O atoms from all molecular fragments of the UMPH^- anion, including the O atom from the ribofuranose ring, can be treated as spherical in the charge density model which was supported by theoretical calculations. Apart from the predominant electrostatic interactions, four relatively strong hydrogen bond types further support the stability of the crystal structure. This results in a compact and quite uniform structure (in all directions) of the studied crystal, as opposed to similar cases with layered architecture reported in the literature.

Charge density distribution and theoretical analysis of low and high energy phosphate esters

There is a strict relation between the energy of hydrolysis of phosphate esters and the extent of interactions between the p ester oxygen lone pair and the antibonding orbitals of the rest of the molecule. Its impact on experimental charge density distribution is analyzed.

Charge-density distribution in sodium bis(4-nitrophenyl)phosphate

The electron-density distribution in sodium bis(4-nitrophenyl)phosphate has been analyzed using the multipole refinement of X-ray diffraction data and of theoretical density-functional theory (DFT) calculations. The ester P—O bonds are particularly long and their topological parameters (density at the bond critical point, Laplacian) are lower than for other P—O bonds. Some disagreement between the experimental and theoretical charges of atoms constituting the nitro groups has been observed and the possible reasons are discussed. Weak polarization effects produced by sodium cations may be observed within the phosphate fragment; they are more manifest in the case of the nitro groups.