Two copper(II) complexes of pyridine betaine (C₅H₅N⁺CH₂COO^-; pyBET) were prepared and characterized by X-ray crystallography. In [Cu(pyBET)(H₂O₂)₂(SO₄)]_n (1), each Cu (II) atom is in a distorted square-pyramidal environment surrounded by a carboxylato oxygen atom [1.944(5) Å], two oxygen atoms [1.921 (5) basal, 2.268(5) apical Å] from different sulfato groups, and two aqua ligands [1.944(4) Å]. The primary coordination sphere is extended into a zigzag chain through sulfato bridging linkages, and hydrogen bonding involving the aqua ligands generates a three-dimensional network. [Cu(pyBET)(H₂O)₂Cl₂]·H₂O (2) features a discrete metal complex with its distorted square-pyramidal coordination sites occupied by a carboxylato oxygen atom [2.000(2) Å], two aqua ligands [1.968(3) Å], and two chloro ligands [2.266(1), 2.469(1) Å] of which one is apical. The lattice water molecules form hydrogen bonds with the aqua and chloro ligands to yield a layer structure.

小明 陈;Thomas C.W. Mak

Structural Chemistry

1992-10

Three tetrakis (μ₂-carboxylate) -bridged dicopper (II) complexes of betaines, [Cu₂ (pybet) ₄ (H₂O) ₂] (NO₃) ₂ (ClO₄) ₂ · 2H₂O (pybet = pyridinioacetate, C₅H₅N⁺CH₂CO^-₂, pybet) (1) , [Cu₂ (pybet) ₄ (H₂O) Cl] (ClO₄) ₃ · 2H₂O (2) and [Cu₂ (ppbet) ₄Cl₂] (ClO₄) ₂ (ppbet = pyridiniopropionate, C₅H₅N⁺ CH₂CH₂CO^-₂) (3) , have been synthesized and characterized by X-ray crystallography. These complexes all comprise [Cu₂ (μ₂-carboxylate) ₂] structures (Cu· · ·Cu = 2.677 (1) -2.760 (1) Å) with each copper (II) atom being coordinated in a square-pyramidal CuO₄L environment, in which the axial ligands (L) are two aqua molecules (Cu - O = 2.093 (2) Å) , one aqua molecule and one chloride ion (Cu - O = 2.130 (8) , Cu - Cl = 2.358 (4) Å) and, two chloride ions (Cu - Cl = 2.454 (2) Å) in complexes 1, 2 and 3, respectively. The intramolecular Cu· · ·Cu distance may correlate to the mutual repulsion between the axial and basal metal-ligand bonds. Temperature-dependent magnetic susceptibility data of the powder samples of the complexes have been fitted, yielding the intramolecular coupling constant 2J values of -340, -321 and -301 cm^-1 for 1, 2 and 3, respectively. The magnitudes of 2J may be inversely correlated to the displacement of the metal atom from the basal plane.

小明 陈;Xiao Long Feng;Zhi Tao Xu;Xiao Hong Zhang;Feng Xue;Thomas C.W. Mak

Polyhedron

1998-6-30

A porous ionic/molecular crystal composed of discrete triakis tetrahedral Co₈ clusters with an ideal T_d symmetry shows interesting magnetism and porosity.

Xiao Ning Cheng;Wei Xue;Jian Bin Lin;小明 陈

Chemical Communications

2010

The complex silver(I)3-carboxylato-1-pyridinioacetate monohydrate,[Ag(C5H4(COO)NCH2.COO)]n.nH2O, crystallizes in space group P21/c(No.14), with Z-4, a 12.233(6), b 5.049(1), c 14.418(7)Ǻ, and β 94.96(4)°; the structure was refined to RF -0.057 for 1721 observed [I≥3σ(I)]Mo Kα data. The silver(I) atom is coordinated by four carboxylato oxygen atoms in a distorted tetrahedral environment [Ag-O 2.284(5)-2.570(5)Ǻ].The tridentate acetato group bridges the Ag1 atoms into a zigzag chain featuring an uncommon [Ag2(carboxylato -O, O′)carboxylato-μ-1,1-O)]six- membered ring, and the coordination sphere about each metal centre is completed by the unidentate aromatic carboxylato group, resulting in a two-dimensional network in the solid. The lattice water molecule forms hydrogen bonds with the uncoordinated oxygen atom of the aromatic carboxylato group[2.755(9)Ǻ]and the coordinated oxygen atom of the acetato group [2.936(9)Ǻ].

小明 陈;C. W. Thomas Mak

Australian Journal of Chemistry

1991

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^-1s^-1, respectively.

La Sheng Long;小明 陈;Xiao Lan Yu;Zhong Yuan Zhou;Liang Nian Ji

Polyhedron

1999-5-28

The new planar aromatic tridentate nitrogen ligand 2,4-bis(3,5-dimethylpyrazol-l-yl)-6-methoxy-1,3,5-triazine (L) has been synthesized and the crystal structure of [EuL(NO₃)₃(H₂O)]·L revealed a mononuclear structure with a ten-co-ordinate metal centre; π-π stacking and hydrogen bonding between the co-ordinated and unco-ordinated L molecules sensitized Eu^III luminescence.

Chi Yang;小明 陈;Wei Hong Zhang;Jian Chen;Yan Sheng Yang;Meng Lian Gong

Journal of the Chemical Society. Dalton Transactions

1996

The structure of the title complex, [Co(H₂O)₆][Co-(C₁₁H₁₄N ₂O₉)]₂, is comprised of discrete [Co(hpdta)]^- anions (H₄hpdta is 2-hydroxy-1,3-propanediamine-N,N,N′,N′-tetraacetic acid) and [Co(H₂O)₆]²⁺ cations in a 2:1 molar ratio. The trivalent Co atom in the anion is coordinated by the hexadentate hpdta chelate ligand, with two amino-N atoms [Co-N 1.948 (3) Å] and four O atoms of the four monodentate carboxylato groups [Co-O 1.869(2)-1.914(2) Å] in a distorted octahedral arrangement, whereas the divalent Co atom in the cation is coordinated in an octahedral manner by six aqua ligands [Co-O 2.078 (2)-2.124 (2) Å]. The crystal structure is stabilized by extensive hydrogen bonding. Each aqua ligand forms two donor hydrogen bonds with the carboxyl O atoms from adjacent anions and the hydroxyl group forms a hydrogen bond with an adjacent carboxyl O atom.

小明 陈;Hui An Chen;Bo Mu Wu;Thomas C.W. Mak

Acta Crystallographica Section C: Crystal Structure Communications

1996-11-15

We present a new hybrid compound, namely (Me₂NH₂)[KFe(CN)₅(NO)], possessing a unique nitroprusside-based inorganic host framework in 4-connected sra topology encapsulating organic guest cations. The flexible host-guest hydrogen bonds and synchronously deformed inorganic framework give rise to thermal-responsive switching behaviours on both thermal expansion and nonlinear optical properties during the phase transition at around room temperature.

Rong Guan Qiu;Xiao Xian Chen;Rui Kang Huang;Dong Dong Zhou;Wei Jian Xu;Wei Xiong Zhang;小明 陈

Chemical Communications

2020-5-21

A family of cyano-bridged perovskite-like coordination polymers (CPs), [(CH₃)_nNH_4-n]₂[KFe(CN)₆] (n = 1 (1), 2 (2), 3 (3), and 4 (4)), were synthesized and characterized. The differential scanning calorimetry measurements and variable-temperature single-crystal X-ray structural analyses revealed that, owing to the deformation of the host framework as well as the dynamic transition of the guest cation between the static/ordered and dynamic/disordered states, the four CPs undergo structural phase transitions (at 429, 226, 316, and 350 K, respectively) with the symmetry breakings dependent on the symmetries of the encapsulated guest cations. The modulated differential scanning calorimetry measurement suggested that the phase transitions of 1 and 3 have more striking kinetic processes related to their drastic deformation of the host framework as well as a very significant alteration of the host-guest interaction during the phase transition. Moreover, accompanying the transitions between low- and high-temperature phases, the step-like transitions between low and high dielectric states were observed in 1-3, and the corresponding change in amplitude of the dielectric constant is dependent on the total dipole moment of each cage in the high-temperature phase. The investigation on these host-guest CPs deepens the understanding of the relationship between the dipole moment of guest cations and the dielectric behaviour of materials, shedding light on the search for new switchable molecular dielectrics.

Wei Jian Xu;Shao Li Chen;Zhi Tao Hu;Rui Biao Lin;Yu Jun Su;Wei Xiong Zhang;小明 陈

Dalton Transactions

2016

Designing and synthesizing more advanced high-energetic materials for practical use via a simple synthetic route are two of the most important issues for the development of energetic materials. Through an elaborate design and rationally selected molecular components, two new metal-free hexagonal perovskite compounds, which are named as DAP-6 and DAP-7 with a general formula of (H₂dabco)B(ClO₄)₃ (H₂dabco²⁺ = 1,4-diazabicyclo[2.2.2]octane-1,4-diium), were fabricated via an easily scaled-up synthetic route using NH₃OH⁺ and NH₂NH₃⁺ as B-site cations, respectively. Compared with their NH₄⁺ analog ((H₂dabco)(NH₄)(ClO₄)₃; DAP-4), which has a cubic perovskite structure, DAP-6 and DAP-7 have higher crystal densities and enthalpies of formation, thus exhibiting higher calculated detonation performances. Specifically, DAP-7 has an ultrahigh thermal stability (decomposition temperatures (T_d) = 375.3 °C), a high detonation velocity (D = 8.883 km·s⁻¹), and a high detonation pressure (P = 35.8 GPa); therefore, it exhibits potential as a heat-resistant explosive. Similarly, DAP-6 has a high thermal stability (T_d = 245.9 °C) and excellent detonation performance (D = 9.123 km·s⁻¹, P = 38.1 GPa). Nevertheless, it also possesses a remarkably high detonation heat (Q = 6.35 kJ·g⁻¹) and specific impulse (I_sp = 265.3 s), which is superior to that of hexanitrohexaazaisowurtzitane (CL-20; Q = 6.23 kJ·g⁻¹, I_sp = 264.8 s). Thus, DAP-6 can serve as a promising high-performance energetic material for practical use.

Yu Shang;Zhi Hong Yu;Rui Kang Huang;Shao Li Chen;De Xuan Liu;Xiao Xian Chen;Wei Xiong Zhang;小明 陈

Engineering

2020-9