Combined Experimental and Computational Study of V-Substituted Lindqvist Polyoxotungstate: Screening by Docking for Potential Antidiabetic Activity.

In the current work, a novel vanadotungstate compound, (C6H9N2)4[V2W4O19]·2H2O (1), is isolated by a simple stepwise synthesis method and characterized by a combined experimental and computational study. Molecular docking is conducted for the first time for this kind of substituted Lindqvist polyoxometalates to elucidate for potential antidiabetic activity. Hence, the modeling results revealed a significant docking score of the reported compound to bind to the active sites of α-glucosidase with the lowest binding energy of -5.7 kcal/mol, where the standard drug acarbose (ACB) had -4.6 kcal/mol binding energy. The stability of binding was enhanced by strong H-bonding, van der Waals, and electrostatic interactions occurring in the three-dimensional (3D) supramolecular network of polyanionic vanadotungstate subunits templated with organic moieties as shown by X-ray diffraction and Hirshfeld analyses. Furthermore, density functional theory (DFT) calculations supported with photophysical measurements are also discussed to predict the most chemical and biological reactivity. In this view, the complete description of electronic and biological features of (1) is enhanced by determination of the highest occupied molecular orbital (HOMO)/least unoccupied molecular orbital (LUMO) energy, electronic density, ionization potential, electron affinity, etc. These chemical descriptors, intermolecular interactions, docking score, and binding free energy estimation are essential in understanding the reactivity of this bioactive compound offering potential inhibition of the α-glucosidase enzyme.

Bis(2-meth-oxy-benzyl-ammonium) di-aqua-bis-(di-hydrogen diphosphato-κ(2) O,O')cobaltate(II) dihydrate.

The title compound, (C8H12NO)2[Co(H2P2O7)2(H2O)2]·2H2O, crystallizes isotypically with its Mn(II) analogue. It consists of alternating layers of organic cations and inorganic complex anions, extending parallel to (100). The complex cobaltate(II) anion exhibits -1 symmetry. Its Co(2+) atom has an octa-hedral coordination sphere, defined by two water mol-ecules in apical positions and two H2P2O7 (2-) ligands in equatorial positions. The cohesion between inorganic and organic layers is accomplished by a set of O-H⋯O and N-H⋯O hydrogen bonds involving the organic cation, the inorganic anion and the remaining lattice water mol-ecules.

Bis(2,6-di-methyl-anilinium) di-aqua-bis-(di-hydrogen diphosphato-κ(2) O,O')cobaltate(II).

In the title compound, (C8H12N)2[Co(H2P2O7)2(H2O)2], the Co(2+) ion lies on a crystallographic inversion centre and adopts a slightly distorted octa-hedral CoO6 coordination geometry arising from two chelating diphosphate [H2P2O7](2-) ligands and two trans water mol-ecules. In the crystal, the components are linked by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds and weak aromatic π-π stacking [shortest centroid-centroid separation = 3.778 (2) Å] inter-actions. (001) layers of alternating organic cations and complex inorganic anions are apparent.

m-Xylylenediaminium di-aqua-bis-[di-hydrogen diphosphato(2-)]cobaltate(II) dihydrate.

In the title complex, (C8H14N2)[Co(H2P2O7)2(H2O)2]·2H2O, the Co(II) ion lies on an inversion center and is coordinated by two bidentate diphosphate ligands and two water mol-ecules in a slightly distorted octa-hedral coordination geometry. The m-xylylenediaminium cation is located on a twofold rotation axis. In the crystal, a three-dimensional supra-molecular assembly is constructed by O-H⋯O and N-H⋯O hydrogen bonds between the organic cations, complex anions and uncoordin-ated water mol-ecules.

Bis(4-meth-oxy-benzyl-ammonium) dihydrogen diphosphate.

In the title compound, 2C(8)H(12)NO(+)·H(2)P(2)O(7) (2-), the linked PO(4) groups of the diphosphate anion are almost eclipsed and the P-O-P angle is 134.45 (7)°. In the crystal, infinite ribbons of H(2)P(2)O(7) (2-) anions propagate in [100], being linked by strong O-H⋯O hydrogen bonds. The 4-meth-oxy-benzyl-ammonium cations bond to the diphosphate chains by N-H⋯O and C-H⋯O links, and are themselves linked by C-H⋯π inter-actions.

Bis(2-meth-oxy-benzyl-ammonium) di-aqua-bis-(di-hydrogen diphosphato-κ(2) O,O')manganate(II) dihydrate.

The asymmetric unit of the title compound, (C8H12NO)2[Mn(H2P2O7)2(H2O)2]·2H2O, consists of half an Mn(II) complex anion, a 2-meth-oxy-benyl-ammonium cation and a solvent water mol-ecule. The Mn(II) complex anion lies across an inversion center, and has a slightly distorted octa-hedral coordination environment for the Mn(II) ion, formed by two bidentate dihydrogendiphosphate ligands and two water mol-ecules. In the crystal, the components are linked by O-H⋯O and N-H⋯O hydrogen bonds, forming layers parallel to (100). An intra-molecular N-H⋯O hydrogen bond is also observed.

Bis(3-azoniapentane-1,5-diaminium) cyclo-hexa-phosphate dihydrate: a monoclinic polymorph.

In the title hydrated mol-ecular salt, 2C(4)H(16)N(3) (3+)·P(6)O(18) (6-)·2H(2)O, the complete cyclo-hexa-phosphate anion is generated by crystallographic inversion symmetry. The six P atoms of the P(6)O(18) (6-) anion form a chair conformation and the organic cation has a corrugated linear geometry. In the crystal, the cations and the anions are connected by N-H⋯O hydrogen bonds into slabs propagating in the ac plane. The water mol-ecules link the slabs by accepting N-H⋯O links and forming O-H⋯O links. The triclinic polymorph was reported by Gharbi et al. [(1995). J. Solid State Chem.114, 42-51].

2-Amino-pyrimidinium hydrogen sulfate.

In the crystal structure of the title compound, C(4)H(6)N(3) (+)·HSO(4) (-), hydrogen sulfate anions self-assemble through O-H⋯O hydrogen bonds, forming chains along the b axis, while the cations form centrosymmetric pairs via N-H⋯N hydrogen bonds. The 2-amino-pyrimidinium pairs are linked to the sulfate anions via N-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (10[Formula: see text]). In addition, weak inter-molecular C-H⋯O contacts generate a three-dimensional network.

2-Amino-3-nitro-pyridinium perrhenate.

In the title mol-ecular salt, (C(5)H(6)N(3)O(2))[ReO(4)], the cations and tetrahedral anions are linked by trifurcated N-H⋯(O,O,O) and bifurcated N-H⋯(O,O) hydrogen bonds, as well as weak C-H⋯O inter-actions. This results in alternating corrugated inorganic and organic layers in the crystal.

2-Amino-3-nitro-pyridinium perchlorate.

The title compound, C(5)H(6)N(3)O(2) (+)·ClO(4) (-), is comprised of discrete perchlorate anions and 2-amino-3-nitro-pyridinium cations. The anion has a typical tetra-hedral geometry while the cation presents a nearly planar [maximum deviation = 0.007 (8) Å] pyridinium ring. Undulating [C(5)H(6)N(3)O(2) (+)](n) chains extending along the c-axis direction are linked via N-H⋯O hydrogen bonds. The cations are further connected to the anions by N-H⋯O hydrogen bonds and weak C-H⋯O inter-actions, leading to the formation of a three-dimensional network.

Bis(2-amino-3-nitro-pyridinium) dihydrogen-diphosphate.

The structure of the title compound, 2C(5)H(6)N(3)O(2) (+)·H(2)P(2)O(7) (2-), contains infinite (H(2)P(2)O(7) (2-))(n) layers stacked perpendicular to the a axis. The 2-amino-3-nitro-pyridinium cations are arranged in pairs and are anchored between these layers, linking them by N-H⋯O and C-H⋯O hydrogen-bonding and electrostatic inter-actions between anionic and cationic species to form a three-dimensional network.

Tris(1,10-phenanthroline)cobalt(II) bis-(perrhenate) monohydrate.

In the title compound, [Co(C(12)H(8)N(2))(3)][ReO(4)](2)·H(2)O, the Co(II) atom is coordinated by three 1,10-phenanthroline ligands in a distorted octa-hedral arrangement. In the crystal, the components are linked by O-H⋯O, C-H⋯O and aromatic π-π stacking [shortest centroid-centroid separation = 3.659 (5) Å] inter-actions.

2,6-Diethyl-anilinium dihydrogen phosphate-phospho-ric acid (1/1).

In the crystal structure of the title salt, C(10)H(16)N(+)·H(2)PO(4) (-)·H(3)PO(4), the H(2)PO(4) (-) and H(3)PO(4) components are connected into infinite chains extending along the b-axis direction by way of O-H⋯O links. These chains are also linked through O-H⋯O hydrogen bonds thus building up a supra-molecular two-dimensional framework extending parallel to (001). The organic cations cross-link the anionic layers by way of multiple N-H⋯O inter-actions, leading to a cohesive network.

Bis(2-methyl-anilinium) diaqua-bis[dihydrogendiphosphato(2-)]cobaltate(II).

In the title cobalt(II) complex with 2-methyl-anilinium and diphosphate, (C(7)H(10)N)(2)[Co(H(2)P(2)O(7))(2)(H(2)O)(2)], a three-dimensional network is built up from anionic layers of [Co(H(2)P(2)O(7))(2)(H(2)O)(2)](2-) units and 2-methyl-anilinium cations located between these layers. The dihydrogendiphosphate groups present a bent eclipsed conformation, while the Co(2+) ions lie on inversion centers. An intricate network of O-H⋯O and N-H⋯O hydrogen bonds is established between the different components, assuring the cohesion of the network with other inter-actions, being of electrostatic and van der Waals nature.

2-Amino-5-nitro-pyridinium hydrogen selenate.

There are two cations and two anions in the asymmetric unit of the title compound, C(5)H(6)N(3)O(2) (+)·HSeO(4) (-). In the crystal, there are two independent chains of HSeO(4) (-) anions running along the a axis, linked by O-H⋯O hydrogen bonds. Ribbons of cations linked by N-H⋯O hydrogen bonds run along the b-axis direction, and are further hydrogen bonded to the anions by N-H⋯O and C-H⋯O links, generating a three-dimensional network.

2-Amino-3-nitro-pyridinium hydrogen oxalate.

In the non-centrosymetric title compound, C(5)H(6)N(3)O(2) (+)·C(2)HO(4) (-), the hydrogen oxalate anions form corrugated chains parallel to the c axis, linked by O-H⋯O hydrogen bonds. The 2-amino-3-nitro-pyridinium cations are anchored between theses chains by N-H⋯O and C-H⋯O hydrogen bonds and van der Waals and electrostatic inter-actions, creating a three-dimensional network.

2-Amino-3-nitro-pyridinium hydrogen selenate.

The asymmetric unit of the title compound, C(5)H(6)N(3)O(2) (+)·HSeO(4) (-), contains two monoprotonated 2-amino-3-nitro-pyridinium cations and two hydrogen selenate anions which are connected through N-H⋯O and O-H⋯O hydrogen bonds, building chains parallel to the a direction. These chains are further connected to each other by weaker C-H⋯O hydrogen-bonding inter-actions, leading to the formation of a three-dimensional network.

2-Methyl-anilinium dihydrogen phosphate-phospho-ric acid (1/1).

In the title compound, C(7)H(10)N(+)·H(2)PO(4) (-)·H(3)PO(4), there is a clear distinction between the P-O/P=O and P-OH bond lengths. In the crystal, the H(2)PO(4) (-) anions and H(3)PO(4) mol-ecules are linked by O-H⋯O hydrogen bonds, leading to layers propagating in the bc plane. The organic cations are located between these layers and inter-act with them by way of N-H⋯O hydrogen bonds.

3-Chloro-2-methyl-anilinium dihydrogenphosphate.

The structure of the title compound, C(7)H(9)ClN(+)·H(2)PO(4) (-), contains inorganic layers built by (H(2)PO(4))(-) anions and which are parallel to the ab planes around z = . 3-Chloro-2-methyl-anilinium cations are anchored between the inorganic layers through N-H⋯O hydrogen bonds. Electrostatic and van der Waals inter-actions, as well as hydrogen bonds, maintain the structural cohesion.

Bis(2-amino-3-nitro-pyridinium) dichromate(VI).

The title compound, (C(5)H(6)N(3)O(2))(2)[Cr(2)O(7)], consists of 2-amino-3-nitro-pyridinium cations and discrete dichromate anions linked together by N-H⋯O and C-H⋯O hydrogen bonds, forming thick layers parallel to (101). Layer cohesion is ensured by N-H⋯O hydrogen bonding in addition to electrostatic and van der Waals inter-actions, forming a three-dimensional framework. The dichromate anion is located on a twofold axis that passes through its bridging O atom.