Search results for "Hexacoordinate"
showing 10 items of 16 documents
Characterization of the Heme Pocket Structure and ligand binding kinetics of non-symbiotic hemoglobins from the model legume Lotus japonicus
2017
14 Pags.- 6 Figs. This article is part of the Research Topic: Advances in legume research ( http://journal.frontiersin.org/researchtopic/4288/advances-in-legume-research ). Copyright of the Authors through a Creative Commons Attribution License. This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.
Oxygen binding properties of non-mammalian nerve globins
2006
Oxygen-binding globins occur in the nervous systems of both invertebrates and vertebrates. While the function of invertebrate nerve haemoglobins as oxygen stores that extend neural excitability under hypoxia has been convincingly demonstrated, the physiological role of vertebrate neuroglobins is less well understood. Here we provide a detailed analysis of the oxygenation characteristics of nerve haemoglobins from an annelid (Aphrodite aculeata), a nemertean (Cerebratulus lacteus) and a bivalve (Spisula solidissima) and of neuroglobin from zebrafish (Danio rerio). The functional differences have been related to haem coordination: the haem is pentacoordinate (as in human haemoglobin and myogl…
Structural Characterization and Magnetic Properties of the First 2,2‘-Bipyrimidine-Containing Iron(III) Complexes
1998
Two new iron(III) complexes of the formulas [Fe(bpm)Cl3(H2O)]·H2O (1) and [Fe2(bpm)Cl6(H2O)2]·2H2O (2) (bpm = 2,2‘-bipyrimidine) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 and 2 crystallize in the monoclinic system, space group P21/n, with a = 8.593(2) A, b = 17.669(4) A, c = 8.928(2) A, β = 102.36(2)°, and Z = 4 for 1 and a = 6.422(3) A, b = 11.999(4) A, c = 12.297(6) A, β = 93.82(4)°, and Z = 2 for 2. The structure of complex 1 is made up of neutral [Fe(bpm)Cl3(H2O)] mononuclear units and water molecules of crystallization. The monuclear units are linked through hydrogen bonds involving the coordinated water molecule and one of the…
Organotin(IV) chloride complexes with phosphocholine and dimyristoyl-L-?-phosphatidylcholine
2000
Several complexes of R n SnCl 4-n (R = Me, Ph, n = 1-3; R = nBu, n = 2, 3) with phosphocholine and dimyristoyl-L-α-phosphatidylcholine (phospholipid) have been synthesized and characterized by means of Mossbauer spectroscopy and NMR. Triorganotin chlorides form complexes of (R 3 SnCl) 2 .L stoichiometry with a trigonal bipyramidal pentacoordinate tin environment, while the others form 1:1 complexes with an octahedral hexacoordinate tin environment, with the ligands coordinating through anionic phosphodiester moieties in all cases.
Tin(IV) complexes with O-ethyl(N-ethyl-N,N-dimethylammoniomethyl)phosphonate
1999
Abstract O,O-Diethyl-(N,N-dimethylaminomethyl)phosphonate undergoes ethyl migration leading to O-ethyl-(N-ethyl-N,N-dimethylammoniomethyl)phosphonate (L). Several new complexes of tin(IV) and organotin(IV) chlorides with the title ligand have been synthesized. The stoichiometry of the obtained complexes is as follows: (R3SnCl)2 · L (R=Me, Bu, Ph), R2SnCl2 · L (R=Me, Bu, Ph), RSnCl3 L (R=Me, Ph) and SnCl4 · L. All the complexes have been studied in solution by means of 1H-, 13C-, 31P- and 119Sn-NMR spectroscopy. Their solid state structures have been investigated by means of Mossbauer spectroscopy and the molecular structure of the complex (Ph3SnCl)2 · L has been determined by X-ray crystall…
Synthesis and spectroscopic investigations (IR, NMR and Mössbauer) of tin(IV) and organotin(IV) derivatives of bis(pyrazol-1-yl) alkanes: X-ray cryst…
1995
A series of 1:1 adducts of the type [(L)R(n)SnX(4-n)] . zH(2)O (L = bis(4-methylpyrazol-1-yl)methane (L(4)), bis(3,4,5-trimethylpyrazol-1-yl)methane (L(T)), 1,2-bis(pyrazol-1-yl)ethane (L(A)) or 1,2-bis(3,5-dimethylpyrazol-1-yl)ethane (L(B)); R = Me, Et, Bu or Ph; X = I, Br or Cl; n = 0, 1 or 2; z = 1, 1.5 or 2), and the likely polynuclear [(L(A))(5)(SnCl4)(4)] . (H2O)(5) and [(L(B))(2)(SnCl4)(3)] . 1/2[Et(2)O] have been characterized in the solid state and in solution by analyses, spectral (IR, Mossbauer, and H-1, C-13 and Sn-119 NMR) data and conductivity measurements. When L(T) reacts with SnCl4, cleavage of a carbon (sp(3))-nitrogen bond was observed and the adduct [(3,4,5-trimethylpyra…
Cyanide binding and heme cavity conformational transitions in **Drosophila melanogaster** hexacoordinate hemoglobin
2006
The reason for the presence of hemoglobin-like molecules in insects, such as Drosophila melanogaster, that live in fully aerobic environments has yet to be determined. Heme endogenous hexacoordination (where HisE7 and HisF8 axial ligands to the heme Fe atom are both provided by the protein) is a recently discovered mechanism proposed to modulate O-2 affinity in hemoglobins from different species. Previous results have shown that D. melanogaster hemoglobin 1 (product of the glob1 gene) displays heme endogenous hexacoordination in both the ferrous and ferric states. Here we present kinetic data characterizing the exogenous cyanide ligand binding process, and the three-dimensional structure (a…
Heterometallic Pentanuclear [Ni 4 Ln] (Ln III = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions
2014
The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square-antiprism geometry. All the NiII ions are connected to the central LnIII ion through μ2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxy…
Isomorphous replacement of MII ions in MII–GdIII dimers (MII = CuII, MnII, NiII, CoII, ZnII): magnetic studies of the products
2011
Complexes [M(II)Gd(III){pyCO(OEt)pyC(OH)(OEt)py}₃](ClO₄)₂·EtOH [M(II) = Cu(II) (1), Mn(II) (2), Ni(II) (3), Co(II) (4) and Zn(II) (5)] crystallize in the monoclinic Cc space group and contain one hexacoordinate M(II) ion and one enneacoordinate Gd(III) ion, bridged by three {pyCO(OEt)pyC(OH)(OEt)py}⁻ ligands. Magnetic susceptibility measurements indicate a ferromagnetic interaction for 1 and antiferromagnetic interactions for 2-4. Using the Ĥ = -JŜ(Gd(III))Ŝ(M(II)) spin Hamiltonian formalism, fits to the magnetic susceptibility data yielded J values of +0.32 cm⁻¹ for 1, -1.7 cm⁻¹ for 2, and -0.22 cm⁻¹ for 3. In complex 4, the orbital contributions of Co(II) precluded the determination of th…
Investigations on organoantimony compounds XI. Triorganoantimony(V) compounds containing potentially tridentate ligands
1974
Triorganoantimony(V) compounds of the types RSbVL, in which R = Me or Ph, and L represents a potentially tridentate dianionic Schiff base ligand of the ONO or SNO type, have been synthesized and investigated by spectroscopic (UV, IR, PMR) methods. Molecular weight determinations in benzene reveal the monomeric nature of these compounds. The free ligands, HL, used in this study are:,′-(methylidynenitrilo)diphenol (HSab), -(o-hydroxyphenyl)benzothiazoline (H-Sat), -(o_hydroxyanilino)crotonophenone (HBah), 4-(o-hydroxyphenylimino)--pentanone (HAah) and -acetonyl--methylbenzothiazoline (HAat). Both the UV and the IR data suggest hexacoordinate molecular structures for the complexes RSbL in whic…