Investigation of the reactions of hexanitrocobaltate(III) with amino acids. XIII. The structure and absolute configuration of (–)589-ab-(histidinato-N,N')-cdf-(histidinato-O,N,N')-e-nitrocobalt(III) monohydrate
Abstract:Theoretically, 18 geometrical isomers can appear,i.e. three groups of six isomers; in each of the six in one group histidine as a bidentate ligand is coordinated either through Ni and N~, Nt and O-or N~ and Orespectively. The second notable feature of the structure of histidine compounds is that the histidine moiety occurs in two conformations, 'open' and 'closed'; the magnitude of the torsion angle about the C~-C ~ bond differentiates between the two conformers. The total number of geometrical isomer-conforme… Show more
“…A cis,cis arrangement would lead to very short contacts between the H 2 atoms of the two coplanar imidazole moieties, and this geometry has not been observed so far in crystal structures of bis-histidine complexes. [36][37][38][39][40][41][42][43][44][45][46][47][48][49] Elemental analysis and mass spectrometry are consistent with the formula proposed. In the IR spectrum, the ν(RedO) vibration is observed as a very strong band at 960 cm -1 , whereas the nearby ligand bands appear weakly at 985 and 1038 cm -1 .…”
Section: Oxorhenium(v) Complexessupporting
confidence: 71%
“…In our complex, the configuration is believed to be trans,trans. A cis,cis arrangement would lead to very short contacts between the H 2 atoms of the two coplanar imidazole moieties, and this geometry has not been observed so far in crystal structures of bis-histidine complexes. − 2 …”
Equivalent amounts of ReOX(3)(OPPh(3))(Me(2)S) (where X = Cl, Br) and L-histidine (L-hisH) in acetonitrile yield ReOX(2)(L-his), in which the amino acid monoanion is N,N,O-tridentate. X-ray diffraction work on both compounds shows that the three donors occupy a face in a distorted octahedron and the carboxylate oxygen is coordinated trans to the Re=O bond. The 2:1 complex [ReO(L-his)(2)]I is obtained by reacting 2 equiv of L-histidine with ReO(2)I(PPh(3))(2) in methanol in the presence of NaOCH(3). (1)H NMR spectroscopy indicates that these complexes contain one N,N,O-tridentate histidine anion coordinated as above and one N,N-bidentate histidine anion, whose carboxylate group is free. By refluxing ReOX(2)(L-his) in methanol, the carboxylic groups esterify and two octahedral units condense into an oxo-bridged dinuclear complex [ReOX(2)(L-hisMe)](2)O containing N,N-bidentate histidine methyl ester. The O=Re-O-Re=O backbone is approximately linear, and the two ReOX(2)(L-hisMe) units are related by a 2-fold axis through the central oxygen. Crystals of [ReOBr(2)(L-hisMe)](2)O consist of an ordered phase containing two of the possible diastereoisomers in a 1:1 ratio. (1)H NMR spectra of these crystals include two sets of signals, consistent with the presence of two isomers with C(2) symmetry, and the spectra of the nonrecrystallized material confirm that these are the only two isomers formed.
“…A cis,cis arrangement would lead to very short contacts between the H 2 atoms of the two coplanar imidazole moieties, and this geometry has not been observed so far in crystal structures of bis-histidine complexes. [36][37][38][39][40][41][42][43][44][45][46][47][48][49] Elemental analysis and mass spectrometry are consistent with the formula proposed. In the IR spectrum, the ν(RedO) vibration is observed as a very strong band at 960 cm -1 , whereas the nearby ligand bands appear weakly at 985 and 1038 cm -1 .…”
Section: Oxorhenium(v) Complexessupporting
confidence: 71%
“…In our complex, the configuration is believed to be trans,trans. A cis,cis arrangement would lead to very short contacts between the H 2 atoms of the two coplanar imidazole moieties, and this geometry has not been observed so far in crystal structures of bis-histidine complexes. − 2 …”
Equivalent amounts of ReOX(3)(OPPh(3))(Me(2)S) (where X = Cl, Br) and L-histidine (L-hisH) in acetonitrile yield ReOX(2)(L-his), in which the amino acid monoanion is N,N,O-tridentate. X-ray diffraction work on both compounds shows that the three donors occupy a face in a distorted octahedron and the carboxylate oxygen is coordinated trans to the Re=O bond. The 2:1 complex [ReO(L-his)(2)]I is obtained by reacting 2 equiv of L-histidine with ReO(2)I(PPh(3))(2) in methanol in the presence of NaOCH(3). (1)H NMR spectroscopy indicates that these complexes contain one N,N,O-tridentate histidine anion coordinated as above and one N,N-bidentate histidine anion, whose carboxylate group is free. By refluxing ReOX(2)(L-his) in methanol, the carboxylic groups esterify and two octahedral units condense into an oxo-bridged dinuclear complex [ReOX(2)(L-hisMe)](2)O containing N,N-bidentate histidine methyl ester. The O=Re-O-Re=O backbone is approximately linear, and the two ReOX(2)(L-hisMe) units are related by a 2-fold axis through the central oxygen. Crystals of [ReOBr(2)(L-hisMe)](2)O consist of an ordered phase containing two of the possible diastereoisomers in a 1:1 ratio. (1)H NMR spectra of these crystals include two sets of signals, consistent with the presence of two isomers with C(2) symmetry, and the spectra of the nonrecrystallized material confirm that these are the only two isomers formed.
“…In addition to the imidazole group, histidine can also coordinate to metal centers through its amino and carboxyl groups. In most known metal−histidine complexes, histidine binds with metal centers (e.g., V, Co, Ni, Cu, and Zn) in chelating modes using two or all three available functional groups (i.e., amino, carboxyl, imidazole). , Because of its strong tendency to form metal chelates, histidine is rarely known to function as the bridging ligand for the creation of open-framework materials. ,, One rare example of the bridging histidine is [Ag(Hhis)] n , in which Ag + and anionic histidine alternate along the chain 1 Molecular Structure of Histidine in the Neutral Zwitterionic Form …”
Despite there being numerous examples of metal-organic frameworks in which metal centers or clusters are joined together by bi-or polydentate ligands into extended structures, biologically important amino acids, histidine in particular, are rarely known to serve as bridging ligands for the construction of openframework architectures. Here, we report hydrothermal self-assembly between neutral zwitterionic histidine molecules and inorganic secondary building units (i.e., (Zn-O-P-O) 2 four-rings) into a crystalline solid containing infinite two-dimensional arrays. We demonstrate that the acid-base and coordination chemistry of histidine can be controlled to promote the formation of open architectures with bridging histidine ligands instead of the commonly observed metal-chelates with chelating histidine ligands. Crystallographic data for Zn(HPO 3 )(DL-C 6 H 9 N 3 O 2 )(H 2 O) 1/2 , C2/c, a ) 15.1307(3) Å, b ) 8.4230(2) Å, c ) 16.6322(4) Å, β ) 100.420(1)°, V ) 2084.75(8) Å 3 , Z ) 8.
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