Solution State Properties Research Articles

Vanadium(IV) and vanadium(V) complexes of dipicolinic acid and derivatives. Synthesis, X-ray structure, solution state properties: and effects in rats with STZ-induced diabetes

Preparation and characterization of new vanadium compounds with insulin mimetic properties is important for investigations into the mechanism of action of these complexes. In this work, we report the synthesis of three new compounds related to the (dipicolinato)dioxovanadium(V) complex: (4-hydroxy-2,6-pyridinedicarboxylato)dioxovanadium(V), (diaqua)(4-hydroxy-2,6-pyridinedicarboxylato)oxovanadium(IV) and (4-amino-2,6-pyridinedicarboxylato)dioxovanadium(V), and present the first preliminary kinetic study of a vanadium dipicolinate system. One of these complexes, (4-hydroxy-2,6-pyridinedicarboxylato)oxovanadium(V), is investigated in greater detail with regard to chemistry, structure, kinetics and insulin-like properties in rats with streptozotocin-induced diabetes. Oral administration of [VO 2(dipic-OH)] − was found to be effective in lowering both the hyperglycemia and hyperlipidemia of diabetes. This is the first report of the effective lowering of diabetic hyperlipidemia by a vanadium(V) coordination complex.

Gold(I) and silver(I) metallocryptates based on 2,9-bis(diphenylphosphino)-1,8-naphthyridine.

In acetonitrile the rigid diphosphine ligand 2,9-bis(diphenylphosphino)-1,8-naphthyridine (dppn) reacts with (SMe2)AuCl in the presence of NaPF6 to produce a pale-yellow material identified as [Au2Na(mu-dppn)3](PF6)3 (1). In acetonitrile dppn reacts with 2 equiv of (SMe2)AuCl to form the simple Au-Cl adduct of the ligand, Au2Cl2dppn (2). In a fashion analogous to that of the synthesis of 1, the reaction of equimolar AgNO3 with dppn produces the trimetallic species [Ag2(mu-dppn)3Ag](PF6)3 (3) as a bright-yellow material. 1, 2, and 3 were characterized by 31P(1H) NMR spectroscopy, electronic absorption spectroscopy, X-ray crystallography, emission spectroscopy, and elemental analysis. Additionally 1 was further characterized by cyclic voltammetry and mass spectrometry. 1.4.5CH3CN.0.5(C2H5)2O (C107H72Au2F18N10.5NaO) crystallizes in the triclinic space group P1 with a = 15.408(3) A, b = 17.295(3) A, c = 22.425(5) A, alpha = 73.68(1) degrees, beta = 77.32(1) degrees, gamma = 74.18(1) degrees, V = 5451.4(19) A3, and Z = 2. C32H24Au2Cl2N2P2 (2) crystallizes in the monoclinic space group Cc with a = 10.936(2) A, b = 19.860(5) A, c = 20.864(2) A, beta = 118.182(1) degrees, V = 3127.3(8) A3, and Z = 4. Compound 3 crystallizes as the bis-DMSO adduct (C101H84Cl2F18N6O2P9S2) in the monoclinic space group C2/c with a = 28.825(7) A, b = 17.013(3) A, c = 23.916(7) A, beta = 115.23(1) degrees, V = 10609.6(44) A3, and Z = 4. The structures of 1 and 3 contain a three-coordinate metal capping the metallocryptate with an encapsulated ion. The central Ag(I) ion in 3 is positioned off-center to form a short Ag...Ag interaction of 3.145(2) A, while the central Na+ ion of 1 is centrally positioned with long Au...Na interactions of approximately 3.5 A. The solution-state properties of 1 were probed. 1 is emissive, as are the Li, K, and Cs analogues.

Small-angle X-ray scattering and crystallographic studies of arcelin-1: an insecticidal lectin-like glycoprotein from Phaseolus vulgaris L.

Arcelin-1 and alpha-amylase inhibitor are two lectin-like glycoproteins expressed in the seeds of the kidney bean (Phaseolus vulgaris). They display insecticidal activities and protect the seeds from predation by larvae of various bruchids through different biological actions. Solution-state investigations by small-angle X-ray scattering (SAXS) show the dimeric structure of arcelin-1, a requirement for its hemagglutinating properties. Anions were found to have specific properties in their effectiveness to disrupt protein aggregates, affect solubility, and improve crystallizability. The SAXS results were used to improve crystallization conditions, and single crystals diffracting beyond 1.9 A resolution were obtained. X-ray diffraction data analysis shows that noncrystallographic symmetry-related arcelin-1 molecules form a lectin-like dimer and reveals the presence of a solvent-exposed anion binding site on the protein, at a crystal-packing interface. The solution state properties of arcelin-1 and crystal twinning may be explained by the anion specificity of this binding site.

Synthetic and structural studies on Group 13 complexes containing the M(CO)3(η-C5H5) fragment (M = Cr or Mo). Part 1. Complexes [E{M(CO)3(η-C5H5)}3](E = In or TI)

The complexes [E{M(CO)3(η-C5H5)}3](E = In, M = Mo, 1; E = In, M = Cr, 8; E = TI, M = Cr, 5; E = TI, M = Mo, 6) have been prepared and their structures determined by X-ray crystallography. All contain a trigonal-planar indium or thallium centre bonded to three M(CO)3(η-C5H5) fragments (M = Cr or Mo) by unsupported element–element bonds. Synthetic and structural comparisons are made with related complexes and the solution-state properties of all complexes in a variety of solvents are described and discussed. These studies indicate a high degree of ionic character in solution. Extended-Huckel molecular orbital calculations have also been carried out on 1 which confirm the presence of polar In–Mo bonds and also reveal that In–Mo π bonding is quite weak.