Zhong-Yuan Zhou

Syntheses, characterization and crystal structure of copper(II) α,β-unsaturated carboxylate complexes with imidazole

Abstract Four copper(II) α,β-unsaturated carboxylate complexes with imidazole, Cu(CH2=CH–COO)2(imH)2 (1), Cu2(CH2=CH–COO)4(imH)2 (2), Cu[CH2=C(CH3)–COO]2(imH)2 (3) and Cu2[CH2=C(CH3)–COO]4(imH)2 (4) (where imH=imidazole) have been prepared and characterized by elemental analyses, IR, ESR and electronic reflectance spectroscopies. The single crystal X-ray diffraction study of complex 3 shows that the copper(II) atom is in a symmetric centre of a square planar environment completed by two monodentate α-methacrylate groups and two imidazole ligands displayed in trans position. Each molecular unit is linked with four neighbouring units by hydrogen-bond interactions forming a two-dimensional supramolecular compound (dN⋯O=2.781 A). Complex 1 has a similar structure as complex 3, while complexes 2 and 4 have a binuclear cage structure. The ESR spectra show that the spin coupling between the unpaired electrons of Cu(II) atoms present in complexes 2 and 4, is not observed in complexes 1 and 3. The electronic reflectance spectra suggest that the d–d transitions of complexes 1 and 3 are in a square planar ligand field, while that of complexes 2 and 4 are in a tetragonal ligand field, and the ligand field strength of acrylate group and α-methacrylate group is similar. Complexes 1 and 2 as well as 3 and 4, were produced simultaneously in the reaction of the corresponding copper(II) α,β-unsaturated carboxylate with imidazole in methanol solution.

Bis(2,2′-bipyridine)ruthenium(II)complexes withimidazo[4,5-f ][1,10]-phenanthroline or2-phenylimidazo[4,5-f ][1,10]phenanthroline

Imidazo[4,5-f]1,10-phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip) and their (bipy) 2 Ru 2+ complexes (bipy = 2,2′-bipyridine) have been synthesized and characterized. The oxidation potentials of [Ru(bipy) 2 (ip)] 2+ and [Ru(bipy) 2 (pip)] 2+ were found to be 1.254 and 1.284 V vs. saturated calomel electrode respectively; the reduction of ip and pip appears to be irreversible at ca. -0.85 V. The photophysical properties of the complexes were perturbed in the presence of calf thymus DNA. The distinct changes including hypo- or hyper-chromicity at different UV/VIS absorption bands, enhancements of integrated emission intensity and excited-state lifetime, and efficiency of emission quenching by [Fe(CN) 6 ] 4- all indicate the stronger binding affinity to DNA of [Ru(bipy) 2 (pip)] 2+ over that of [Ru(bipy) 2 (ip)] 2+ , consistent with the greater planar area and extended π system of the pip ligand. The luminescence of the complexes showed monoexponential decay at any [DNA]∶[Ru] ratio. The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA suggest that the complexes bind to the DNA with enantioselectivity favouring the Δ isomers. These phenomena all suggest that the complexes bind through intercalation of ip or pip into base pairs. The crystal structure of [Ru(bipy) 2 (ip)][ClO 4 ] 2 ·H 2 O was determined; it contains the planar bidentate ligand ip and two twisted bipy ligands with torsional angles between each bipyridine ring pair of 5.7 and 8.6°.

Synthesis and crystal structure of the potassium lanthanum complex with triethylenetetra-aminehexaacetic acid (H6TTHA): K[KLa(HTTHA)(H2O)]·8H2O

Abstract The title complex, K[KLa(HTTHA)(H2O]·8H2O, was synthesized in aqueous solution and its crystal structure was determined by X-ray diffraction. In the complex, the ten-coordinated lanthanum ion is bonded by four nitrogen atoms and six carboxyl oxygen atoms of the same triethylenetetraaminehexaacetic acid (H6TTHA) molecule. The coordination polyhedron of lanthanum can be described as a distorted bicapped square antiprism. The crystal is composed of one dimensional infinite chains.

SYNTHESIS AND CRYSTAL STRUCTURE OF THE POTASSIUM YTTERBIUM COMPLEX WITH TRIETHYLENETETRAAMINEHEXAACETIC ACID : K3YB(TTHA)(H2O)5

Abstract The title complex [K3Yb(TTHA)(H2O)5], where TTHA6− is triethylenetetraaminehexaacetic acid anion was synthesized in aqueous solution, and its crystal structure was determined by X-ray diffraction. In the complex, the ytterbium ion is coordinated by four nitrogen atoms and five carboxyl oxygen atoms of the same TTHA6− anion. The coordination number of the ytterbium ion is 9, and its coordination polyhedron can be described as a distorted monocapped square antiprism. Each Yb(TTHA)3− is further connected by K+ ions through carboxyl groups of TTHA6− ion to form a three dimensional network structure.

Synthesis, crystal structure and spectroscopic characterization of mono- and tetra-nuclear molybdenum(VI) complexes with 2-mercaptopyridine N-oxide: (n-Bu4N)2[MoO2(PT)2·Mo4O8(μ-O)2(μ3-O)2(PT)2]

Abstract(n-Bu4N)4[Mo8O26] reacts with the Na salt of 2-mercaptopyridine N-oxide (NaPT) in MeCN to give the complex (n-Bu4N)2[MoO2(PT)2·Mo4O8(μ-O)2(μ3-O)2(PT)2] (1) which contains two metal centres: one being mononuclear molybdenum chelating to two PT ligands, and the other a tetranuclear oxomolybdenum cluster with two PT ligands at the terminal point. The i.r. spectrum of the title complex exhibits absorption bands at 911.5 and 881.9 cm−1, characteristic of the [cis-MoO2]2+ fragment.

On the preference for the sym-fac isomer in the [Co(N, N'-bis(2-aminomethyl)amine)(2,2'-bipyridine)Cl]2+ system

Abstract The sym–fac isomer of [Co(bpma)(bipy)Cl]2+ is the only one synthesised for this system where, in principle, four exist (bpma=N,N′-bis(2-aminomethyl)amine, bipy=2,2′-bispyridine). This observation is supported by ab initio energy calculations which reveal this to be the most stable form, and the unsym–fac isomer the highest in energy. It is one of only two cobalt(III) complexes known that contain a single NH centre trans to Cl−. The structure is deduced from the 13C NMR spectrum and 2D NMR techniques and confirmed by the X-ray crystal structure determination. The agreement between the single crystal data and the calculated ab initio molecular parameters is excellent (within ±3%).

Synthesis, crystal structure and spectroscopic properties of a copper(II) complex of the Schiff-base derived from picolinaldehyde N-oxide and 4-aminoantipyridine

The Schiff-base (PNOAAP) derived from picolinaldehyde N-oxide and 4-aminoantipyrine, and its copper(II) complex: [Cu(PNOAAP)2(EtOH)2]2(ClO4)4(1) has been prepared and characterized by elemental analysis, i.r., 1H-n.m.r. spectrum, and single crystal X-ray crystallographic determination. The PNOAAP ligand isomerizes from trans to cis after chelating to copper(II).

Structure of [Ru(phen)3](ClO4)2.(C2H5)2O

The title solvated complex, in Which phen denotes 1,10-phenanthroline, crystallizes in the monoclinic space group P2 1 /n with a = 13.313 (3), b = 15.980 (3), c = 18.392 (4) A, α = 96.76 (3)°, Z = 4, V = 3885.4 (14) A 3 , D cal = 1.564 Mg-m -3 . The crystal is composed of racemic layers of complex cations, with the ether solvents located near, and the perchlorate anions sandwiched between, indicating the hydrophobic environment in the complex layer and the stacking interaction between the enantiomeric cations. The average length of the Ru-N bonds is 2.064 (2) A and the average ligand bite angle is 80.00 (7)°.

Synthesis, structures and hydrolytic properties of metal complexes with 1,3-bis (4-methyl-5-imidazol-1-yl)ethylideneamino propan-2-ol

Abstract Synthesis of a polydentate ligand comprising imidazole donors, 1,3-bis[(4-methyl-5-imidazol-1-yl)ethylideneamino]propan-2-ol (BIPO), and its Zn II ( 1 ), Mn II ( 2 ), Ni II ( 3 ) and Cu II ( 4 ) complexes are reported. Single-crystal structural analysis shows that complex 1 adopts a distorted square-pyramidal coordination geometry with the basal positions occupied by the four nitrogen atoms of a tetradentate BIPO ligand and the apical position by a water molecule, complexes 2 and 3 exhibit elongated octahedral coordination geometries with the axial positions occupied by a pair of aqua molecules, whereas complex 4 exhibits an elongated octahedral geometry with the axial positions occupied by an aqua molecule and a perchlorate oxygen atom. The crystal structures of the four complexes are discussed in relation to the preference of zinc ion in carbonic anhydrase, and suggest that in the presence of nitrogen donor ligands, Zn II has a significant tendency to form a four- or five-coordination. Hydrolysis of 4-nitrophenyl acetate with complexes 1 – 3 shows that the k obs for complexes 1 , 2 and 3 were 2.74×10 −2 ± 0.01, 1.45×10 −2 ± 0.01 and 0.98×10 −2 ± 0.01 M −1 s −1 , respectively.

Synthesis and structure of a dimeric hydroxobridged erbium(III) complex, di-μ-hydroxo-bis[(1,4,7,10,13,16-hexaazacyclooctadecane) erbium(III)] tetra(trifloromethanesulfonate)

Abstract The title complex was synthesized by the reaction of 1,4,7,10,13,16-hexaazacyclooctadecane abbreviated as hexacyclen) with erbium(III) trifloromethanesulfonate in 1:1 (molar ratio) in acetonitrile under nitrogen. The crystal structure determination shows that the complex is dinuclear with two erbium ions bridged by two hydroxide ions. Each of the two metal ions is coordinated similarly by the two bridging hydroxide groups and six nitrogen atoms of a hexacyclen molecule, giving a coordination number eight and a slightly distorted dodecahedron geometry. The four trifloromethanesulfonate ions are not included in the coordination of the metal ions.