Search

Two novel bicapped Keggin polyoxidovanadates with organic cations, (C6H8N)5[H4PV14O42]·5H2O (1) and (C6H14N4)2(NH4)[H4PV14O42]·11H2O (2), (PV14O426- = PV14, C6H7N = 3-picoline and C6H12N4 = methenamine) were synthesized. These compounds were isolated and characterized in the solid state and in solution by elemental analysis, powder X-ray diffraction, FTIR, UV-vis, 51V, 31P, 13C and 1H NMR, and fluorescence spectroscopy. Further confirmation of the PV14 structures was obtained by single-crystal X-ray diffraction studies of 1 and 2. The Hirshfeld surface analysis was performed to confirm that within the intermolecular interactions occurring in the two crystals, the O⋯H/H⋯O, O⋯O and H⋯H interactions dominate. The protonation and one-electron reduction of the PV14 moiety were also analysed by means of DFT calculations; besides confirming the protonation sites and correctly predicting the pKa values, the DFT results also indicate that molecular reduction is energetically more favourable in protonated PV14 anions. Upon the addition of PV14 anions to bovine serum albumin (BSA) up to a ratio of 1 : 1, the fluorescence decreased by 45% for both 1 and 2, indicating that the interaction of vanadium-containing species with this protein takes place; log(KSV) values of ca. 5.5 were obtained in both systems. Upon the addition of 1 or 2 to solutions of calf-thymus DNA (ctDNA), changes were observed in the UV-vis absorption and circular dichroism spectra. The significance of the changes observed is discussed considering the several V-containing species that form in the solution.

Two novel decavanadate salts with organic cations, (C H N) [H V O ]·3.25H O (I) and (C H N(OH) ) [H V O ]·10H O (II), have been synthesized in aqueous solution and characterized by IR, UV–Vis spectroscopies, EDX-SEM and single crystal X-Ray diffraction completed by DFT calculations. The asymmetric unit of (C H N) [H V O ]·3.25H O is composed of one decavanadate [H V O ] , four piperidinium cations and water molecules. The structures of (II) is based on one decavanadate cluster, two triethanolaminum cations (TEAH) and ten water molecules. The cohesion of the crystal packing in both compounds is provided by a complex network of N[sbnd]H ··· O, O -H ···O and O[sbnd]H ···O hydrogen bonds involving water molecules and organic molecules as well as vander Waals interactions for the connection between the organic molecules. The IR spectra confirmed the presence of organic cations, decavanadate (V O ) groups and water molecules. The UV–Vis diffuse reflectance spectrum shows that these compounds exhibit semiconducting behavior with an optical band gap of 2.22 eV and 2.13 eV, respectively for compound (I) and (II). Furthermore the Hirshfeld surface analysis shed more light on the intermolecular interactions occurring in the two crystals and the structure-properties relationships. 5 12 4 2 10 28 2 6 12 3 2 4 10 28 2 5 12 4 2 10 28 2 2 10 28 w 10 28 4− + 6−