Miao Du

Unprecedented 4- and 6-Connected 2D Coordination Networks Based on 44-Subnet Tectons, Showing Unusual Supramolecular Motifs of Rotaxane and Helix

Two unprecedented 2D coordination polymers with 4- and 6-connected topological nets, arising from the different linkages of two adjacent 4(4) layers, were prepared from Co(II), 1,3-bis(4-pyridyl)propane, and different isophthalate tectons.

MnII Coordination Polymers Based on Bi-, Tri-, and Tetranuclear and Polymeric Chain Building Units: Crystal Structures and Magnetic Properties

Five new Mn(II) coordination polymers, namely [Mn(2)(tbip)(2)(bix)] (1), [Mn(3)(tbip)(3)(bix)(2)] (2), [Mn(3)(tbip)(2)(Htbip)(2)(bib)(2)]·4H(2)O (3), [Mn(4)(tbip)(4)(bbp)(2)(H(2)O)(2)] (4), and [Mn(4)(tbip)(4)(bip)]·2H(2)O (5), were prepared by hydrothermal reactions of Mn(II) acetate with H(2)tbip (5-tert-butyl isophthalic acid) in the presence of different di-imidazolyl coligands (bix =1,4-bis(imidazol-1-ylmethyl)benzene, bib =1,4-bis(imidazol) butane, bbp =1,3-bis(benzimidazol)propane, bip =1,3-bis(imidazol)propane). All complexes were characterized by elemental analysis, IR spectra, thermogravimetric analysis, single-crystal X-ray crystallography, and powder X-ray diffraction. Single crystal X-ray studies show that these coordination polymers contain homometallic clusters varying from dimeric, trimeric, and tetrameric motifs to polymeric chains depending upon the coligands used. Complex 1 has a 3D 6-connected polycatenane network with dinuclear [Mn(2)O(2)] secondary building units. Complex 2 possesses a 3D 8-connected structure with trinuclear [Mn(3)(COO)(6)] units. Complex 3 shows a 3D pcu net based on trinuclear [Mn(3)(COO)(6)] clusters as nodes. Complex 4 features a 3D 8-connected structure constructed from the distorted square-grid tetranuclear [Mn(4)(μ(2)-COO)(8)(μ(2)-H(2)O)] units. Complex 5 shows a 3D (4,5,6)-connected net containing 1D μ-O/μ-COO alternately bridged chains. Magnetic susceptibility measurements indicate that complexes 1 and 3-5 show weak antiferromagnetic interactions between the adjacent Mn(II) ions, whereas 2 is a three-spin center homometallic ferromagnetic system.

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.

Novel homobinuclear lanthanide(III) complexes with isonicotinoyl hydrazone: synthesis and coordination chemistry

Abstract Two novel homobinuclear lanthanide(III) complexes with isonicotinoyl hydrazone ligand [Ho2(L)3(H2O)](NO3)2·(OH)·3.5H2O (I) and [Lu2(L)3](OH)3 (II) (where HL=N,N′-diisonicotinoyl-2-hydroxy-5-methylisophthalaldehyde dihydrazone) have been synthesized and characterized by infrared spectra, elemental analyses, thermal analyses and UV–Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. In complex I, the two intramolecular holmium(III) centers have different coordination environments with nine and ten coordination numbers, respectively; however, in complex II, both lutetium(III) centers have the same structure with nine coordination number. In both complexes, the lanthanide(III) ions are intramolecularly bridged by three phenolic oxygen atoms forming a dimeric complex with Ho⋯Ho distance of 3.5398(7) and Lu⋯Lu distance of 3.3960(9) A, respectively. L acts as a pentadentate ligand with keto-form coordination in both complexes as indicated by the results of crystal structures and infrared spectral analysis.

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.

A 3D Cu(II) coordination framework with μ4-/μ2-oxalato anions and a bent dipyridyl coligand: unique zeolite-type NiP2 topological network and magnetic properties.

The reaction of copper(II) nitrate, oxamide, and an angular bridging ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) under hydrothermal conditions affords a 3D pillared-layer coordination framework {[Cu(2)(4-bpo)(ox)(2)](H(2)O)(4)}(n) (1) (ox = oxalate), featuring the unique zeolite-type NiP(2) network and interesting properties.

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.

Structural diversity and modulation of metal–organic coordination frameworks with a flexible V-shaped dicarboxyl building block

A family of new coordination polymers based on a V-shaped flexible dicarboxyl building block 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) and familiar metal ions (MnII, CoII, NiII, CuII, ZnII, and AgI) have been prepared and structurally characterized. Their thermal stability and solid state luminescent properties of the ZnII and AgI complexes have also been investigated. Single-crystal X-ray diffraction analysis reveals a significant structural diversity of these coordination frameworks, such as the 1-D zigzag chain, 2-fold interpenetrating layer composed of 21 helical arrays, and 3-D open network with 42 helicity and pcu topology based on the rod-shaped secondary building units (SBUs). Additionally, hydrogen bonding interactions are found in these structures to further extend or stabilize the coordination motifs. A comprehensive analysis of the coordination systems based on this dicarboxyl tecton also demonstrates that it is an excellent candidate for the design and construction of multiform metal–organic frameworks (especially helical arrays), which can be dominated by metal ions and/or synthetic conditions.

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.

Coordinative versatility of 2,3-bis(2-pyridyl)-5,8-dimethoxyquinoxaline (L) to different metal ions: syntheses, crystal structures and properties of [Cu(I)L]2 2+ and [ML]2+ (M=Cu(II), Ni(II), Zn(II) and Co(II))

Abstract The complexes of Cu(I), Cu(II), Ni(II), Zn(II) and Co(II) with a new polypyridyl ligand, 2,3-bis(2-pyridyl)-5,8-dimethoxyquinoxaline ( L ), have been synthesized and characterized. The crystal structures of these complexes have been elucidated by X-ray diffraction analyses and three types of coordination modes for L were found to exist in them. In the dinuclear complex [Cu(I) L (CH 3 CN)] 2 ·(ClO 4 ) 2 ( 1 ), L acts as a tridentate ligand with two Cu(I) centers bridged by two L ligands to form a box-like dimeric structure, in which each Cu(I) ion is penta-coordinated with three nitrogen atoms and a methoxyl oxygen atom of two L ligands, and an acetonitrile. In [Cu(II) L (NO 3 ) 2 ]·CH 3 CN 2 , the Cu(II) center is coordinated to the two nitrogen atoms of the two pyridine rings of L which acts as a bidentate ligand. The structures of [Ni(II) L (NO 3 )(H 2 O) 2 ]·2CH 3 CN·NO 3 ( 3 ), [Zn(II) L (NO 3 ) 2 (H 2 O)]·2CH 3 CN ( 4 ) and [Co(II) L Cl 2 (H 2 O)] ( 5 ) are similar to each other in which L acts as a tridentate ligand by using its half side, and the metal centers are coordinated to a methoxyl oxygen atom and two bipyridine nitrogen atoms of L in the same side. The formation of infinite quasi-one-dimensional chains ( 1 , 4 and 5 ) or a quasi-two-dimensional sheet ( 2 ) assisted by the intra- or intermolecular face-to-face aryl stacking interactions and hydrogen bonds may have stabilized the crystals of these complexes. Luminescence studies showed that 1 exhibits broad, structureless emissions at 420 nm in the solid state and at 450 nm in frozen alcohol frozen glasses at 77 K. Cyclic voltammetric studies of 1 show the presence of an irreversible metal-centered reduction wave at approximately −0.973 V versus F c +/0 and a quasi-reversible ligand-centered reduction couple at approximately −1.996 V versus Fc +/0 . The solution behaviors of these complexes have been further studied by UV–Vis and ESR techniques.