Ya-Mei Guo

Ferromagnetic coupling in a unique Cu(II) metallacyclophane with functionalized diazamesocyclic ligands formed by Cu(II)-directed self-assembly: magneto-structural correlations for dichloro-bridged Cu(II) dinuclear complexes

Two new di-μ-Cl dinuclear CuII complexes [Cu(HL1)Cl2]2(ClO4)2 (1) and [Cu2(L2)2Cl2](ClO4)2 (2) with the pyridyl-functionalized diazamesocyclic ligands 1,5-bis(pyridin-4-ylmethyl)-1,5-diazacyclooctane (L1) and 1-(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L2) have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 is a unique paramagnetic CuII metallamacrocycle (ca. 14.1 × 3.5 A2) directly self-assembled by metal ions and the organic spacer under strongly acidic conditions. The magnetic properties of both complexes have been investigated by variable-temperature magnetic susceptibility measurements. Although complexes 1 and 2 have almost the same geometrical parameters for CuII, their magnetic parameters vary from ferromagnetic for 1 to antiferromagnetic for 2. The magneto-structural correlation of such complexes has been further developed.

Crystal structures, spectra and magnetic properties of di-2-pyridylamine (dpa) CuII complexes [Cu(dpa)2(N3)2]·(H2O)2 and [Cu2(μ-ox)(dpa)2(CH3CN)2](ClO4)2

Abstract Two CuII complexes with di-2-pyridylamine (dpa) and combined bridging ligands (azide or oxalato anions), [Cu(dpa)2(N3)2]·2H2O (1) and [Cu2(μ-ox)(dpa)2(CH3CN)2](ClO4)2 (2), have been synthesized and characterized by IR spectra, elemental analyses, TGA, UV–Vis spectra and ESR technique. The crystal structures of both complexes have been determined by single crystal X-ray diffraction analyses. In the mononuclear complex 1, the CuII center is coordinated to four N atoms of dpa and two N donors of azide (CuN6), taking an elongated octahedral geometry. The solvent water molecules interlink the neutral [Cu(dpa)2(N3)2] units through hydrogen bonds to form a two-dimensional (2D) layered structure with strong π–π stacking interactions between the adjacent pyridine rings. Complex 2 is made up of centro-symmetric dinuclear [Cu2(μ-ox)(dpa)2(CH3CN)2]2+ cation and non-coordinated perchlorate anions, assembling into a one-dimensional (1D) ladder structure through hydrogen bonding with π–π stacking co-effect. The magnetic properties of 2 have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, indicating a very strong anti-ferromagnetic coupling between the intra-molecular CuII centers (having the perfect square-pyramidal geometry) with J=−382 cm−1. The strength of the exchange interaction is discussed in detail on the basis of the structural feature.

Structural and first magnetic characterization of unique mono-μ-chloro bridged dinuclear CuII complexes with heterocycle-functionalized diazamesocyclic ligands

Two new diazamesocyclic ligands based on 1,4-diazacycloheptane (DACH), functionalized by additional heterocyclic donor groups, 1,4-bis(pyridin-2-ylmethyl)-1,4-diazacycloheptane (L1) and 1,4-bis(imidazol-4-ylmethyl)-1,4-diazacycloheptane (L2), together with their CuII complexes [Cu2(μ-Cl)(L1)2](ClO4)3 (1) and [Cu2(μ-Cl)(L2)2](ClO4)3 (2), have been synthesized and characterized. Single crystal X-ray diffraction analyses revealed that both complexes have the unique mono-μ-Cl dimeric [Cu2(μ-Cl)(L)2]3+ structural motif. For both complexes, each CuII center is penta-coordinate in a distorted square-pyramidal environment with the bridging chloride atom at the apical position. The magnetic properties of mono-μ-chloro CuII dinuclear complexes have been investigated for the first time through the study of complexes 1 and 2 by variable temperature magnetic susceptibility and magnetization measurements. Weak ferromagnetic (for 1) or anti-ferromagnetic (for 2) interactions between the two CuII centers have been found and possible magneto-structural correlations have been analyzed.

A novel oxalato-bridged dinuclear copper(II) complex with diazamesocyclic terminal ligand: crystal structure, spectroscopy and magnetism

Abstract The synthesis of a new oxalato-bridged dinuclear Cu(II) complex, [Cu2(DACO)2(μ-ox)Br2]·CH3OH (1), where DACO=1,5-diazacyclooctane, together with its spectral and magnetic characterization, are reported. Crystal structure of 1 has been determined by X-ray diffraction analysis, which is made up of centrosymmetric dinuclear [Cu2(DACO)2(μ-ox)Br2] unit and noncoordinated methanol molecule, assembling into a novel two-dimensional step-like extended network through hydrogen bonds. The magnetic susceptibility indicates that complex 1 is anti-ferromagnetic coupling with 2J=−242 cm−1. The strength of the exchange interaction is discussed on the basis of the structural feature.

[M(L)2(NCS)2(H2O)2] (M=MnII or CoII and L=2,5-bis(4-pyridyl)-1,3,4-oxadiazole): three-dimensional extended networks built from hydrogen bonds and π–π stacking interaction—syntheses and crystal structures

Abstract Two three-dimensional (3D) supramolecular compounds of the general formula [M(L) 2 (NCS) 2 (H 2 O) 2 ], where M is Mn II or Co II and L is 2,5-bis(4-pyridyl)-1,3,4-oxadiazole), have been synthesized and structurally determined by X-ray diffraction analyses. The crystal structures of both complexes reveal that they are isomorphic neutral molecules and the metal ions are at the center of symmetry. Each metal center is six-coordinated and the MN 4 O 2 coordination sphere can be considered as an octahedron. The most striking feature of both complexes resides in the formation of a 3D network through hydrogen bonds and π–π stacking co-effection.

First tetrameric NiII cluster with planar triangular topology exhibiting ferromagnetic pathways

[Ni4L3(H2O)2](ClO4)2.2H2O 1, the first tetranuclear NiII cluster showing triangle planar geometry, formed with a new carboxylic-functionalized 1,5-diazacyclooctane bridging ligand has been presented; the global magnetic coupling is ferromagnetic and anisotropic calculations have been made.

Isolation of a thermodynamically unfavorable [Ni(DACO)2]2+ complex and its isomer: syntheses, characterization, crystal structures and theoretical study (DACO=1,5-diazacyclooctane)

Two NiII complexes of 1,5-diazacyclooctane (DACO), [Ni(DACO)2]Br2 (I) and [Ni(DACO)2]Br·ClO4 (II) have been newly synthesized and characterized. Single crystal X-ray diffraction analysis of DACO and both NiII complexes reveals that DACO takes boat/chair conformation in the solid state and its NiII complexes. In complex I, NiII ion is at the center of symmetry, which is four-coordinated by nitrogen donors of DACO. However, in complex II, an unexpected coordination mode of [M(DACO)2]2+ (M=CuII and NiII) was found, in which two DACO ligands are related to each other by a mirror plane and the coordination sphere of NiII is a distorted planar geometry. Furthermore, complexes I and II form quite different packing patterns (macrocycle or chain) through hydrogen bonds, which may be a key role to stabilize the crystals. The results of theoretical calculation indicate that complex I has thermodynamic stability, while II has chemical stability. Therefore, both of them have the probability to be obtained from different reaction processes or conditions.

Structural and spectral studies of some coordination complexes of a phenol-functionalized diazamesocyclic ligand 1,4-bis-(3-tert-butyl-5-methyl-2-hydroxybenzyl)-1,4-diazacycloheptane (H2L)

Abstract A series of four-coordinated monomeric Cu II , Co II , and Ni II complexes of a tetradentate diazamesocyclic ligand containing bulky phenolate donor pendants, [Cu L ] ( 1 ), [Cu( HL )]ClO 4 ( 2 ), [Co L ] ( 3 ), and [Ni L ] ( 4 ), where H 2 L =1,4-bis-(3- tert -butyl-5-methyl-2-hydroxybenzyl)-1,4-diazacycloheptane, have been synthesized and characterized by elemental analyses, IR, UV–vis and ESR spectra. The crystal structure of complex 1 has been determined by X-ray diffraction analysis.

Proton-controlled inter-conversion between an achiral discrete molecular square and a chiral interpenetrated double-chain architecture

Proton-controlled reversible inter-conversion between an achiral CuII molecular square, and a 1D spontaneously resolved chiral interpenetrated double-chain with Cu4 cavities, based on bis(3-propionyloxy)-1,5-diazacyclooctane (H2L), has been successfully achieved.

Synthesis, spectral and structural characterization of a novel phenoxo-bridged dinuclear CoII complex with a tridentate phenol-functionalized diazamesocyclic ligand

Abstract A novel phenoxo-bridged dinuclear Co II complex with a diazamesocyclic ligand bearing one additional phenol functional donor group, [CoLCl] 2 ·2C 3 H 6 O ( 1 ) (where HL=1-(2-hydroxybenzyl)-1,5-diazacyclooctane), has been synthesized and characterized by elemental analyses, conductance, thermal analyses, IR and UV–vis spectra. The crystal structure of complex 1 has been determined by X-ray diffraction technique, which reveals that it is a neutral complex and resides on a crystallographic inversion center. The two Co II centers bridged by the phenoxo groups are penta-coordinated, taking a coordination sphere in the midst of the ideal square-pyramid and trigonal bipyramid. 1,5-Diazacyclooctane of the ligand takes a boat / chair conformation and an H atom from it effectively blocks the axial coordination site opposite the Cl − ligand to form CoN 2 O 2 Cl geometry. The crystal structure is stabilized by the N–H⋯O hydrogen bond between the amino group and the acetone molecule.