Search results for "visual_art"
showing 10 items of 2987 documents
Characterization of oriented protein-ceramic and protein-polymer-composites for cartilage tissue engineering using synchrotron μ-CT
2007
Abstract In this paper we report on the synthesis of three different gelatine based scaffold materials for the reconstruction of articular cartilage defects. The first scaffold design is based on an unmodified, oriented gelatine network, while the second design further comprises an attached inorganic hydroxyapatite layer and the third design includes poly(l-lactide) microspheres as a model material for future drug-release applications. All three scaffold designs were characterized and imaged using synchrotron μ-CT, obtaining a complete volumetric reconstruction of a previously defined sample region. Furthermore, two unmodified scaffolds were cultivated for one week with porcine chondrocytes…
Topology and Spin Polarization in Sheetlike Metal(II) Polymers: [ML2X2] (M ˭ Mn, Fe, Co or Ni, L = Pyrimidine or Pyrazine and X = NCS or NCO)
1999
The preparation and the structural and magnetic characterization of a series of sheetlike transition metal polymers of formula [ML2X2] [M ˭ Mn(II), Fe(II), Co(II) and Ni(II): L = pyrazine (pyz) and...
Spin-State-Dependent Redox-Catalytic Activity of a Switchable Iron(II) Complex
2017
The spin state of catalytically active 3d metal centers plays a significant role for their activity in enzymatic processes and organometallic catalysis. Here we report on the catalytic activity of a Fe(II) coordination compound that can undergo a cooperative switch between low-spin (LS) and high-spin (HS) states. Catalytic measurements within 291 - 318 K temperature region reveal a drastic drop of the catalytic activity upon conversion of metallic centers from the LS to the HS form. For a thermoswitchable [Fe(NH2trz)3]Br2 complex (Tup = 305 K), an activation energy is found to be considerably lower for the LS state (158 kJ mol-1) comparing to the HS state (305 kJ mol-1). Mossbauer analysis …
Bistable Hofmann-Type FeII Spin-Crossover Two-Dimensional Polymers of 4-Alkyldisulfanylpyridine for Prospective Grafting of Monolayers on Metallic Su…
2021
Aiming at investigating the suitability of Hofmann-type two-dimensional (2D) coordination polymers {FeII(Lax)2[MII(CN)4]} to be processed as single monolayers and probed as spin crossover (SCO) junctions in spintronic devices, the synthesis and characterization of the MII derivatives (MII = Pd and Pt) with sulfur-rich axial ligands (Lax = 4-methyl- and 4-ethyl-disulfanylpyridine) have been conducted. The thermal dependence of the magnetic and calorimetric properties confirmed the occurrence of strong cooperative SCO behavior in the temperature interval of 100-225 K, featuring hysteresis loops 44 and 32.5 K/21 K wide for PtII-methyl and PtII/PdII-ethyl derivatives, while the PdII-methyl deri…
30-Norfriedelane triterpenes from the stem bark ofCaloncoba glauca
1992
Abstract The stem bark of Caloncoba glauca has yielded three friedelane triterpenes of which two are characterized by the loss of C-30 and the presence of a C-27, C-15 lactone. They were identified, with considerable use of long-range C H coupling studies, as the known compound trichadonic acid (3-oxofriedelan-27-oic acid) and two new 30-norfriedelane derivatives, 3,27-dioxo-30-norfriedelan-20(29)-en-27,15α-lactone (caloncobalactone) and 3,27-dioxo-21β-hydroxy-30-norfriedelan-20(29)-en-17,15α-lactone (21β-hydroxycaloncoba lactone).
Friedelane triterpenes from the stem bark of Caloncoba glauca
1993
Further investigation of the stem bark of Caloncoba glauca has yielded three minor (D:A)-friedo-oleanane derivatives. These have been identified, on the basis of NMR studies, as the known compound kokoonol [3-oxo-(D:A)-friedo-olean-27-ol] and the novel natural products kokoonal [3-oxo-(D:A)-friedo-olean-27- al] and 3β,21β-dihydroxy-30-nor-(D:A)-friedo-olean-27-oic acid.
Synthesis and Structural Characterization of a Cyclen-Derived Molecular Cage
2015
Reaction of a tetrafunctionalized cyclen derivative containing four aldehyde groups with an appropriate diamine followed by reduction and demetalation highly efficiently affords a bis(cyclen)-derived molecular cage. Potentiometric investigations show that this compound forms dimetallic complexes with copper(II), with the two metal ions selectively coordinated to the cyclen units. X-ray crystallography indicates that these complexes could give rise to new cascade complexes after incorporation of anions between the metal centers.
Remarkably Robust Group 4 Metal Half-Sandwich Complexes Containing Two Higher Alkyl Ligands: X-ray Structure and Reactivity of the Di-n-butyl Comple…
1997
The reaction of LiR with M(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)Cl2 (1, M = Zr (a), Hf (b)) gives the isolable, thermally stable complexes M(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)R2 (R = Et (2), nPr (3), nBu(4)), which contain two alkyl ligands with β-hydrogen atoms.
Bimetallic Cyanide-Bridged Complexes Based on the Photochromic Nitroprusside Anion and Paramagnetic Metal Complexes. Syntheses, Structures, and Physi…
2000
The synthesis, crystal structure, and physical characterization of the coordination compounds [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]x5H2O (1), [Ni(en)2][Fe(CN)5NO]x3H2O (2), [Mn(3-MeOsalen)(H2O)]2[Fe(CN)5NO] (3), and [Mn(5-Brsalen)]2[Fe(CN)5NO] (4) are presented. 1 crystallizes in the monoclinic space group P2(1)/n (a = 7.407(4) A, b = 28.963(6) A, c = 14.744(5) A, alpha = 90 degrees, beta = 103.26(4) degrees, gamma = 90 degrees, Z = 2). Its structure consists of branched linear chains formed by cis-[Ni(en)2]2+ cations and ferrocyanide and nitroprusside anions. The presence of two kinds of iron(II) sites has been demonstrated by Mossbauer spectroscopy. 2 crystallizes in the monoclinic space group …
Organocyanide coordination chemistry: Syntheses, structural characterisations and magnetic properties of copper (II) complexes with a di-imine/pyridi…
2005
Abstract The reactions between the copper (II) salts [CuXL]PF6 (L: 2,6-[1-(2,6-diisopropylphenylimino)ethyl]pyridine) (X = Cl 1, X = Br 2) and LiTCNQ, in a DMF/water mixture, or Et3NH(TCNQ)2, in acetone, produced the new complexes [CuXL(TCNQ)] (X = Cl 3, X = Br 4). For both compounds, crystallographic studies have clearly evidenced the existence of dimeric complexes [{CuClL}(TCNQ)]2 owing to π–π overlap between two adjacent TCNQ − radical anions. Compound 1 reacted with Et4N(C10N7) to afford the mononuclear derivative [CuClL(C10N7)] (5), while its reaction with K2C10N6 produced the dinuclear complex [(CuClL)2(C10N6)] (6). The crystal structures of complexes 5 and 6 have been determined by X…