Yun Ti Chen

Synthesis, crystal structure and spectroscopic characterization of the complex of palladium(II) with tris(2-pyridylmethyl)amine

Abstract A complex of palladium(II) chloride with tris(2-pyridylmethyl)amine (TPA) has been synthesized and characterized. The single-crystal structure has been determined by X-ray diffraction analysis. The palladium(II) atom in the title complex is in a square planar environment surrounded by three nitrogen atoms of TPA and one chlorine atom, with bond lengths in the range of 2.004–2.012 A for PdN and 2.296 A for PdCl. The properties of [Pd((TPA)Cll)]·ClO 4 have been further studied with IR and UV-vis techniques. IR spectra show that most of the bands of [Pd((TPA)Cl)]·ClO 4 are shifted to lower wavenumbers in comparison with those of the TPA ligand.

Synthesis, crystal structure and properties of the copper(II) complex of a new dioxocyclam appended with two 8-methylquinolines as additional donor pendants (dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione)

A macrocyclic dioxotetraamine ligand 1,11-bis(quinolin-8-ylmethyl)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L) has been newly synthesized and characterized. The resulting dioxyclam readily coordinates Cu(II) with concomitant double deprotonation of the ligand. The Cu(II) complex of H2L has been isolated as a single crystal and the structure determined by X-ray diffraction analysis. Cul·CH3COOH, C32H36CuN6O4, crystallizes in the triclinic crystal system P-1 space group with a=11.162(2), b=12.246(3), c=13.347(3) A, α = 67.76(2), β = 65.36(2), γ = 67.70(2)°, Z = 2, R(rw) = 0.058(0.063) for 2300 observed reflections with I>3δ(I)). The solution behaviors of CuL (1) have been further studied with ESR and UV-Vis techniques. A remarkable red-shift was observed for the maxima absorption band of the electronic spectra of CuL (1) in comparison to that of CuL0 (H2L0, dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione).

Novel structure of an unusual cis nickel(II) complex of a new dioxocyclam bearing 2- methylfuran pendants

Abstract A new dioxocyclam ligand bearing two 2-methylfuran pendants has been synthesized and its nickel(II) complex isolated as a single crystal and the structure determined. The complex takes an unusual cis-configuration and, to our knowledge, this is the first crystal structure of a dioxocyclam-Ni(II) complex.

Synthesis, magnetism and crystal structure of a chloride-bridged binuclear nickel(II) complex of tris(2-pyridylmethyl)amine

SummaryA new binuclear NiII complex, [{(TPA)Ni(μ-Cl)}2]-(ClO4)2·H2O (1), where TPA = tris(2-pyridyl-methyl) amine, has been prepared and characterized. The X-ray crystal structure and variable temperature magnetic susceptibility (4–300 K) of the complex have been determined. The two NiII atoms of (1) are in a distorted octahedral environment and are bridged by Cl atoms. Ni-Cl distances are 2.363(6) and 2.503(7) Å, and the Ni-Cl-Ni angle is 92.7(2)°. The metal atoms are separated by a non-bonding distance of 3.523 Å.The effective magnetic moment of (1) increases slightly with decreasing temperature and appears to reach a maximum before decreasing. The observed data were fitted to the Heisenberg model and the results indicate that there is a ferromagnetic interaction (positive J) and weak antiferromagnetic intermolecular interaction (negative θ).

Crystal structure and properties of the nickel(II) complex of a dioxo[13]aneN4 ligand bearing quinoline pendants. Striking differences between the nickel(II) and copper(II) analogues of (dioxo[13]aneN4 = 1,4,7,10-tetraazacyclotridecane-11,13-dione)

Abstract The Ni(II) complex of dioxo[13]aneN4 ligand bearing two 8-methylquinoline as additional donor pendants (H2L) has been prepared and its crystal structure and properties studied. The NiII atom is in square-planar coordination whilst the two 8-methylquinoline pendants are not coordinated. In contrast, in the Cu(II) analogue CuL(2), the Cu(II) atom is five coordinate and forms a distorted square-pyramidal configuration with one of the quinoline pendants coordinated. Electrochemical studies of 1 in aqueous solution revealed that L can further stabilize the trivalent state of nickel ( E 1 2 (+2 → + 3) = 0.60 V versus SCE] compared with unsubstituted L ° [ E 1 2 (+ 2 → + 3) = 0.92 V versus SCE]. This behaviour is also in contrast with that observed for CuL under the same conditions. An unusual red-shift was observed for the maximum absorption band of the electronic spectrum of NiL in comparison to that of NiL°.

NEW MACROCYCLIC DIOXOTETRAAMINES BEARING 2-METHYLFURAN PENDANT(S) : SYNTHESIS, PROPERTIES AND CRYSTAL STRUCTURE OF THE COPPER(II) COMPLEXES

Abstract A series of new macrocyclic dioxotetraamine ligands having 2-methylfuran pendent(s), 4-(2-methylfuran)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H2L1), 4,7-bis(2-methylfuran)-1,4,7,10-tetraazacyclotri-decane-11,13-dione (H2L2), 1-(2-methylfuran)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L3) and 1,11bis(2-methylfuran)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L4), have been synthesized and characterized. The solution behaviours of the copper(II) complexes of the four ligands have been studied with ESR, cyclic voltammetry (CV) and UV-vis techniques. A red-shift has been observed for the maximum absorption band of the electronic spectra of CuL1, CuL3 and CuL2, CuL4 in comparison to those of the corresponding unsubstituted copper(II) complexes CuL01 and CuL02, respectively. Electrochemical studies suggest that the introduction of 2-methylfuran pendant(s) to the macrocyclic dioxotetraamines destabilizes the CuIII ion comparing with the unsubstituted species for both of the two kinds of macrocycles (13-membered and 14-membered macrocycles). The copper(II) complex of (H2L2), has been isolated as a single crystal and the crystal structure determined by X-ray diffraction analysis. It is interesting that the complex has an N-meso chiral nitrogen configuration. The CuII atom is in five coordination environment with four basal nitrogen atoms and one axial oxygen atom from H2O, and it adopts a distorted square pyramidal configuration.

Chiral recognition of amino acid esters by zinc porphyrin derivatives

Three novel chiral zinc porphyrins (4a–4c) with protected chiral amino acid substituents as chiral sources were synthesized. Their chiral recognition of amino acid methyl esters was investigated using UV-vis spectrophotometric titration. Some enantioselectivities obtained are higher than that of the known system, and the highest achieved in our study is 21.54 using host 4a with PheOCH3 as guest. We also show that higher enantioselectivity can be obtained at lower temperature. Circular dichroism spectra of chiral porphyrin derivatives binding to enantiomers of guests show great shape and intensity differences. Molecular modeling was performed to understand chiral recognition on a molecular level, and the results are in good agreement with the experimental data.

Synthesis and properties of a novel nickel(II) cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex covalently attached to Ru(bpy)2+3 (bpy = 2,2′-bipyridyl)

Abstract A ditopic ligand bpy-cyclam (1) and its heterometallo-binuclear complex Ru (bpy)2(bpy-cyclam-Ni)4+ (3) as well as the related intermediate complex Ru(bpy)2(bpy-cyclam-2H)4+ (2) have been synthesized and characterized. Their spectroscopic and redox properties have been studied. An efficient intramolecular fluorescence quenching phenomenon was observed for complex 3, which was composed of an Ru(bpy)2+3 core and an Ni(cyclam)2+ subunit, and is shown to be an interesting hybrid molecule with novel functions.

Synthesis, crystal structure and properties of the nickel(II) complex of a new dioxocyclam bearing 2-methylfuran pendants

A new dioxocyclam ligand, bearing two 2-methylfuran pendants, has been synthesized and its nickel(II) complex isolated as a single crystal. The crystal structure of the complex has been determined by X-ray diffraction analysis. The complex adopts an unusual cis-configuration. The square-planar N4 coordination of the four basal nitrogen atoms with Ni II is evident, with the dioxocyclam moiety composed of two tertiary amine Ns and two deprotonated amide N; s; the latter nitrogens have stronger coordination bonds than those in the tertiary amines. There is a hydrogen bond between O(1) and a water molecule [O(1) H2O = 2.698]. The solution behaviour of NiL (1) has been further studied by u.v.-vis. and cyclic voltammetric techniques. A remarkable red-shift was observed for the maxima absorption band of the electronic spectra of NiL (1) in comparison to that of NiL 0 (H2L0, dioxocyclam = 1,4,8,11-tetraazacyclo-tetradecane-5,7-dione).

Stabilization of nickel(III) ion by new macrocyclic dioxotetraamines bearing functional pendant donors

Abstract Two new macrocyclic dioxotetraamine ligands bearing 2-methyl pyridine and 8-methylquinoline as additional pendant donors have been found to stabilize the trivalent oxidation state of nickel, but destabilize the trivalent oxidation state of copper