Two distinct manganese(II) complexes with hexadentate 1,3-propanediaminetetraacetate ligand: The ability of metal(II) complexes with 1,3-pdta ligand to form solid solutions

The ability of Mn(II) ion to form two distinctly different complexes with 1,3-propanediaminetetraacetate (1,3-pdta) ligand has been demonstrated by performing X-ray analyses of their crystalline Mg(II) salts. The two types of Mn(II) complexes have been obtained by different synthetic routes and their crystals constitute, respectively, the solid solution of the composition [Mg(H₂O)₆][Mg_0.5Mn_0.5(1,3-pdta)] · 2H₂O (1) and the ordered crystals of the composition [Mg(H₂O)₆][Mn(1,3-pdta)(H₂O)] · 2H₂O (2). In both, six- 1 and seven-coordinated 2 Mn(II) complexes the 1,3-pdta ligand acts as a hexadentate. As 2 makes the second example of the seven-coordinated 1,3-pdta complex with divalent transition metal ion, the other being the [Mg(H₂O)₆][Cd(1,3-pdta)(H₂O)] · 2H₂O (3) complex, the paper reports the results of X-ray investigations of both of these complexes at 130 K.     

Conformational study of Co(II), Ni(II), and Cr(III) complexes of the edta-type: Crystal structure of 1D polymeric trans(O)-Ba[Co(1,3-pddadp)] · 8H2O complex stabilized by infinite water tapes

The trans(O⁶) isomer of the Ba[Co(1,3-pddadp)] · 8H₂O complex (where 1,3-pddadp represents hexadentate 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) has been prepared and characterized by X-ray crystallography. In the crystal structure the complex cations and anions are bridged by carboxylate oxygen atoms from the in-plane coordinated glycinate rings (G-rings) of [Co(1,3-pddadp)]²⁻ and by the barium-coordinated water molecules, thus forming 1D polymeric chains, separated by infinite water tapes hydrogen bonded to the [Co(1,3-pddadp)]²⁻ carboxylate oxygens from the out-of-plane β-alaninate rings (R-rings). Conformational analysis of the three possible geometrical isomers: trans(O⁵), trans(O⁵O⁶), and trans(O⁶) of the [Co(1,3-pddadp)]²⁻ complex, with ligand acting as hexadentate, as well as of the corresponding complexes of Ni(II) and Cr(III) has been performed using the consistent force field (CFF) method, with the parameters developed previously for edta-type complexes of chromium(III) and supplemented with new parameters for cobalt(II) and nickel(II). The energy-minimized structure of the trans(O⁵O⁶) isomer represents the global minimum for the [M(1,3-pddadp)]ⁿ⁻ (M = Co(II), Ni(II), and Cr(III)) species. The occurrence of the least energetically favored trans(O⁶) isomer in a crystal and the exceptional conformation of the axially oriented β-alaninate rings can be accounted for by the stabilizing role of the infinite tapes of planar cyclic water pentamers and hexamers which act as a “glue” to reinforce the coordination polymeric chains.     

Reactivity of benzil bis(4-methyl-3-thiosemicarbazone) with cadmium nitrate. Crystal structure of [Cd(LMe2H4)(NO3)2][Cd(LMe2H4)(NO3)(H2O)]NO3 · H2O

The reaction between cadmium nitrate dihydrate and benzil bis(4-methyl-3-thiosemicarbazone), LMe₂H₄, depends on the working conditions. In methanol the reaction gives the novel complex [Cd(LMe₂H₄)(NO₃)₂][Cd(LMe₂H₄)(NO₃)(H₂O)]NO₃ · H₂O (1). Its crystal structure shows the presence of two cadmium atoms with different coordination numbers, seven and eight, and the ligands acting as N₂S₂ neutral molecules. One cadmium has the coordination sphere completed by a bidentate nitrato group and a water molecule, whereas the other one is bonded to two bidentate nitrato groups. Both molecules are joined to one nitrate ion and to an additional water molecule by hydrogen bonds. In the presence of lithium hydroxide, the reaction leads to a binuclear complex with the ligand doubly deprotonated [Cd(LMe₂H₂)]₂ (2). The complexes were characterized by elemental analysis, mass spectrometry, ¹³C and ¹¹³Cd CP/MAS NMR and, in the case of complex 1, by X-ray diffraction.     

Synthesis,Characterization, and DNA Binding Properties of Dinuclear Copper（Ⅱ） Complex [Cu2（TATP）2（L-Leu）2（CIO4）2]2·2H2O

A dinuclear copper（Ⅱ） complex[Cu2（TATP）2（L-Leu）2（CIO4）2]2·2H2Owas synthesized and characterized, where, TATP=1,4,8,9-tetraazatriphenylene, and L-Leu=L-leucinate. The complex was crystallized in the triclinic space group P1, with two independent molecules in a unit cell. Two Cu（Ⅱ） ions in each complex [Cu2（TATP）2（L-Leu）2（CIO4）2] molecule were found to be in different coordination geometries, i.e., Cu2 or Cu4 of a distorted square-pyramidal geometry coordinated with two nitrogens of TATP, the amino nitrogen and one carboxylate oxygen of L-Leu and one oxygen of perchlorate, and Cul or Cu3 with an octahedral geometry coordinated with the above stated similar coordinated atoms, and another carboxylate oxygen of L-Leu coordinating to Cu2 or Cu4. The complex can interact with CT-DNA by an intercalative mode and cleave pBR322 DNA in the presence of ascorbate.     

Structures and thermal properties of strontium and barium 1,3-propanediaminetetraacetates

In neutral and acidic solution, homonuclear s-block metal complexes [Sr₂(1,3-pdta)(H₂O)_3.5] _n (1), {[Ba₂(1,3-pdta)(H₂O)₆]·H₂O} _n (2), {[Sr(1,3-H₂pdta)]·(H₂O)} _n (3), and [Ba(1,3-H₂pdta)(H₂O)₃] _n (4) {1,3-H₄pdta=1,3-propanediamine-N,N,N′,N′-tetraacetic acid, CH₂[CH₂N(CH₂CO₂H)₂]₂} were isolated. In 1 and 2, hexadentate 1,3-pdta joins two metal ions via the diamine chain. In 3 and 4, the nitrogens of 1,3-H₂pdta were protonated and show no coordination. There is no coordinated water in 3, unusual coordination for strontium. In 4, the coordination number is nine and there are three coordinated waters for each barium. One carboxy group of pdta is free without coordination. Thermal decomposition shows that temperatures of ligand elimination start at 408, 423, 298, and 250?°C for 1–4, respectively. Acidic condition is favorable for preparation of metal oxide at low temperature.     

Preparation, crystal structure and magnetic properties of Ni2(dpa)2(pyz)(H2O)4

A Ni(II)-based dimer structure, Ni₂(dpa)₂(pyz)(H₂O)₄ (dpa = 2,6-pyridine dicarboxylic acid dianion, pyz: pyrazine), has been prepared using hydrothermal synthesis and the solid-state magnetic properties have been evaluated. In the dimeric structure, the planar tridentate 2,6-pyridine dicarboxylic acid dianion coordinates to a Ni(II) ion in a meridional fashion and defines the equatorial plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Ni(II) complexes to form a dimer. The axial positions of each Ni(II) complex are occupied by two water molecules to form a distorted octahedral geometry. Susceptibility and magnetization measurements show that both intra-dimer and inter-dimer exchange interactions are weakly antiferromagnetic. The fitting of the magnetic data also indicates the existence of a large axial zero-field splitting term that contributes to the small magnetization even under high fields.     

Two novel coordination polymers [Sm2(Pzdc)3(H2O)]x · 2xH2O and [Nd2(Pzdc)3(H2O)]x · 2xH2O: Synthesis, structure, and photoluminescent properties

Coordination polymers, [Sm₂(Pzdc)₃(H₂O)] _x · 2xH₂O (I) and [Nd₂(Pzdc)₃(H₂O)] _x · 2xH₂O (II), were obtained by hydrothermal reactions with 2,3-pyrazinedicarboxylic acid (H₂Pzdc) and the salts nitrates, and characterized by single crystal X-ray structure, thermogravimetric analysis, element analysis and infrared spectroscopy. The X-ray crystal diffraction data indicates that two complexes crystal in a monoclinic system with the space group P2₁/c, of the three dimensional framework. The Pzdc ligand in the complexes I and II adopts tetradentate, hexadentate, and heptadentate bridging modes. The influences of coordination modes of the Pzdc ligand on the superstructural diversity is discussed. The photoluminescent data suggest that the ligands act as efficient “antennas” sensitizing the luminescence of the Sm³⁺ ion. Complex I exhibits strong fluorescent emission bands in the solid state at room temperature.     

Cobalt(II) complexes with aminopolycarboxylate 1,3-pdta-type ligands: synthesis and characterization of trans(O6)-[Mg(H2O)6][CoII(1,3-pddadp)]·H2O

Starting from Ba₂(1,3-pddadp)·8H₂O (1,3-pddadp=1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) and CoSO₄, a new hexadentate [Co^II(1,3-pddadp)]²⁻ complex has been prepared. The trans(O₆) geometry of this complex was confirmed by comparison of its i.r. and u.v.–vis. spectra with those of [Co^II(1,3-pdta)]²⁻ (1,3-pdta is the 1,3-propanediaminetetraacetate ion) and trans(O₆)-[Co^III(1,3-pddadp)]⁻ complexes of known X-ray crystal structure. Magnetic and electrolytic conductivity properties of these complexes have also been discussed.     

The first bis(orotato–N,O) complex: Synthesis,crystal structure,spectroscopic and thermal characterization of (chaH)2[Cu(HOr–N,O)2(cha)] · 2H2O (cha = cyclohexylamine and HOr = orotate(2−))

The novel bis(cyclohexylaminium) cyclohexylaminebis(orotate–N,O)cuprate(II) dihydrate, (C₆H₁₅N)₂[Cu(C₅H₂N₂O₄)₂(C₆H₁₄N)] · 2H₂O, has been prepared and characterized by elemental analysis, magnetic measurements, FT-IR and UV–Vis spectroscopy, thermal analysis and X-ray diffraction. The Cu(II) complex crystallizes in the monoclinic space group P2₁/c. The copper atom in the five-coordinated (chaH)₂[Cu(HOr–N,O)₂(cha)] · 2H₂O is chelated by a deprotonated pyrimidine nitrogen atom and carboxylate oxygen atom as a bis(bidentate) ligand and the cyclohexylamine ligand completes the square-pyramidal coordination. The thermal decomposition of the complex has been predicted by the help of thermal analysis (TG, DTG and DTA).     

Syntheses and study on nickel and copper complexes with 1,3,5-benzenetricarboxylic acid. Crystal and molecular structure of [Cu3(mdpta)3(btc)](ClO4)3 · 4H2O

Nickel and copper complexes containing 1,3,5-benzenetricarboxylic acid, with a combination of selected N-donor ligands and Schiff bases, of the composition Ni₃(bimz)₆(btc)₂ · 12H₂O (1), Ni₃(btz)₉(btc)₂ · 12H₂O (2), Ni₂(L₁)(btc) · 7H₂O (3), Ni₃(L₂)₂(Hbtc) · 9H₂O (4), Ni₂(L₃)(btc) · 4H₂O (5), Cu₂(L₄)(btc) · 7H₂O (6), [Cu₃(pmdien)₃(btc)](ClO₄)₃ · 6H₂O (7) and [Cu₃(mdpta)₃(btc)](ClO₄)₃ · 4H₂O (8); H₃btc = 1,3,5-benzenetricarboxylic acid, bimz = benzimidazole, btz = 1,2,3-benztriazole, L₁ = 2-[(phenylimino)methyl]phenol, L₂ = N,N′-bis-(salicylidene)propylenediamine, L₃ = 2-{[(2-nitrophenyl)methylene]amino}phenol, L₄ = 2-[(4-methoxy-phenylimino)methyl]phenol, pmdien = N,N,N′,N″,N″-pentamethyldiethylenetriamine, mdpta = N,N-bis-(3-aminopropyl)methylamine, have been synthesized. The complexes have been studied by elemental analysis, IR, UV–Vis spectroscopies, magnetochemical and conductivity measurements and selected compounds also by thermal analysis. The crystal and molecular structure of complex 8 was solved. The complex is trinuclear with btc³⁻-bridge. The coordination polyhedron around each copper atom can be described as a distorted square with a CuON₃ chromophore formed by one oxygen atom of carboxylate and three nitrogen atoms of mdpta. The magnetic properties of 8 have been studied in the 1.8–300 K temperature range revealing a very weak antiferromagnetic exchange interaction with J = −0.56 cm⁻¹ for g = 2.13(9). The antimicrobial activities against selected strains of bacteria were evaluated. It was found that only complex 5 is able to inhibit the growth of Staphylococcus strains.     

Synthesis,crystal structure and magnetic properties of the helical oxalate-bridged copper(II) chain {[(CH3)4N]2[Cu(C2O4)2] · H2O}n

The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH₃)₄N]₂[Cu(C₂O₄)₂] · H₂O}_n (1) [(CH₃)₄N⁺ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm⁻¹, the Hamiltonian being defined as H = –J ∑_nmS_i · S_j]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway.     

Structure of Ba Na Ethylenediaminetetraacetatocobaltate(III) Perchlorate, Na[Ba6(H2O)25][Co(Edta)]4(ClO4)9 · 5H2O

Crystals with uncommon composition NaBa₆[Co(Edta)]₄(ClO₄)₉ · 30H₂O (Edta⁴⁻ is ethylenediaminetetraacetic acid anion) were obtained with the following unit cell parameters: a = 14.8513(9) Å, b = 26.2361(15) Å, c = 15.1789(9) Å, α = 91.661(7)°, β = 113.035(7)°, γ = 89.897(7)°, space group P1¯. Each complex anion [Co(Edta)]⁻ is bonded through the carboxyl O atoms to five Ba atoms to give three-dimensional framework in a crystal. One perchlorate ion forms Ba-O-Cl-O-Ba bridge between the Ba atoms; four ClO ₄ ⁻ ions are isolated, while the remaining four ions act as monodentate ligands at the Ba atoms. The water molecules (25 in sum) complete the coordination sphere of the Ba atoms to eight-, nine-, or ten-vertex polyhedron. Four water molecules are in the closest surrounding of the Na atom, one H₂O molecule is isolated.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 590–595.Original Russian Text Copyright © 2005 by Zabel, Poznyak, Pawlowski.     

Synthesis and characterization of some novel cadmium(II) complexes with 3-hydroxypicolinic acid (3-OHpicH): Crystal and molecular structures of [CdI(3-OHpic)(3-OHpicH)(H2O)]2, [Cd(3-OHpic)2(H2O)2] and [Cd(3-OHpic)2]n

Cadmium(II) complexes of 3-hydroxypicolinic acid, namely [CdI(3-OHpic)(3-OHpicH)(H₂O)]₂ (1), [Cd(3-OHpic)₂(H₂O)₂] (2) and [Cd(3-OHpic)₂]_n (3) were prepared and characterized by spectroscopic methods (IR, NMR) and their molecular and crystal structures were determined by X-ray crystal structure analysis. Complexes 1 and 2 were prepared in similar reaction conditions using different cadmium(II) salts: cadmium(II) iodide and cadmium(II) acetate dihydrate, respectively, while 3 was prepared by recrystallization of 2 from N,N-dimethylformamide solution. Various coordination modes of 3-OHpicH in 1–3 were established in the solid state: bidentate N,O-chelated mode in 1 and 2, monodentate mode through the carboxylate O atom from zwitterionic ligand in 1 and bidentate N,O-chelated and bridging mode in 3. In the DMF solution of all prepared complexes, only monodentate mode of 3-OHpicH binding to cadmium(II) through the carboxylate O atom was established by ¹H, ¹³C, ¹⁵N and ¹¹³Cd NMR spectroscopy.     

Calorimetric study and thermal analysis of [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O (Gly: glycin)

Two solid-state coordination compounds of rare earth metals with glycin, [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O and [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 342.90 K, while [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol⁻¹ and 53.9 J K⁻¹ mol⁻¹ for [Gd_4/3Y_2/3(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, 1.82 kJ mol⁻¹ and 5.5 J K⁻¹ mol⁻¹ for [ErY(Gly)₆(H₂O)₄](ClO₄)₆·5H₂O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.     

Formation of [CoCl4(H2O)2] complex in CoCl2·MgCl2·8H2O double salt: structural and energetic properties of [MCl4(H2O)2] and [M(H2O)6] (M=Mg, Co)

The crystal structure of the double salt CoCl₂·MgCl₂·8H₂O has been determined by the X-ray diffraction method. It crystallizes in the space group with a=6.0976(9), b=6.308(1), c=8.579(3) Å, α=81.99(2)°, β=88.40°, γ=84.61(1)°, Z=1, and R=0.027. The crystal consists of two kinds of well separated octahedra, [CoCl₄(H₂O)₂]²⁻ and [Mg(H₂O)₆]²⁺. The former is unique as aquachloro complexes of Co²⁺. In order to elucidate the reason prepared as such unique complexes in the double salts, formation energies for [MCl₄(H₂O)₂]²⁻ and [M(H₂O)₆]²⁺ (M=Co, Mg) have been calculated by using the density functional methods, and it has been revealed that the formation energies of the first coordination sphere for the metal ions and the Cl⁻?H₂O hydrogen bond networks around [CoCl₄(H₂O)₂]²⁻ play a decisive role in forming [CoCl₄(H₂O)₂]²⁻ with the regular octahedral geometry in the double salt.     

Evaluation of the antimicrobial activity of some chloro complexes of imidazole-2-carbaldehyde semicarbazone: X-ray crystal structure of cis-NiCl2(H2L)(H2O)

Some first row transition metal(II) complexes of imidazole-2-carbaldehyde semicarbazone (H₂L) have been synthesised and characterised. Single crystal X-ray diffraction studies have revealed the molecular structure of the neutral complex NiCl₂(H₂L)(H₂O). This latter complex shows a pseudo-octahedral geometry, with both chloride ions displaying a cis disposition. The asymmetry of this complex allows the formation of two enantiomers in the racemic crystal structure. The non-deprotonated semicarbazone ligand behaves as an N,N,O-donor, through the imidazole and imine N atoms and the O_keto atom. The coordinative behaviour of H₂L in CuCl₂(H₂L)(H₂O), ZnCl₂(H₂L)₂·0.5EtOH and CoCl₂(H₂L)₂·0.5H₂O is reported as only N,O-donor. The antimicrobial activity of the semicarbazone ligand and its metal complexes has been tested against some representative bacteria and fungi. A moderate inhibitory activity of the cobalt complex was detected towards the assayed phytopathogenic fungi Alternariatenuis and Sclerotinia minor (MIC 50 μg/mL).     

Metal(II)-promoted hydrolysis of pyridine-2-carbonitrile to pyridine-2-carboxylic acid. The structure of [Cu(pyridine-2-carboxylate)2] · 2H2O

Pyridine-2-carbonitrile (2-CNpy) undergoes Cu(II) or Co(II)-promoted hydrolysis to pyridine-2-carboxamide (piaH) and/or pyridine-2-carboxylic acid (pycH). The pathway of pycH formation depends on the presence of 2-amino-2-hydroxymethyl-1,3-propanediol (AL¹) and on the central atom. In the absence of AL¹, Co(II) or Cu(II) ions mediate piaH formation under mild reaction conditions in the first hydrolytic step. Cu(II) ions assist in piaH transformation to pycH by subsequent reflux. In the presence of AL¹ and Co(II), a Co(II) complex containing pyoxaL¹ (2-(2-pyridinyl)-4,4-bis(hydroxymethyl)-2-oxazoline) is formed in the first stage; subsequent decomposition of pyoxaL¹ under the reflux yields pycH. Under similar conditions, no solid Cu(II) complex with pyoxaL¹ can be isolated, but a Cu(II) complex with coordinated pyc⁻ anions precipitates from the reaction mixture. The synthesis, spectral and magnetic properties of the complexes [Co(H₂O)₂ (piaH)₂]Cl₂, [Co(H₂O)₂(pyc)₂] · 2H₂O, [Cu(H₂O)₂(piaH)₂]Cl₂, [Cu(pyc)₂] and [Cu(pyc)₂] · 2H₂O, including the structure determination of the latter one, are described.     

Preparation, spectroscopic properties of 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) lanthanide complexes and the supramolecular structure of [Nd2L2(NO3)6(H2O)2]·H2O

The reaction of lanthanide nitrate with 1,4-di (N,N-diisopropylacetamido)-2,3(1H,4H)-quinoxalinedione (L) yields six novel Ln(III) complexes ([Ln₂L₂(NO₃)₆(H₂O)₂]·H₂O) which are characterized by elemental analysis, thermogravimetric analysis (TGA), conductivity measurements, IR, electronic and ¹H NMR spectroscopies. A new quinoxalinedione-based ligand is used as antenna ligand to sensitize the emission of lanthanide cations. The lowest triplet state energy level of the ligand in the nitrate complex matches better to the resonance level of Eu(III) and Sm(III) than Tb(III) and Dy(III) ion. The f-f fluorescence is induced in the Eu³⁺ and Sm³⁺ complexes by exciting into the π-π* absorptions of the ligand in the UV. Furthermore, the crystal structures of a novel binuclear complex [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O has been determined by single-crystal X-ray diffraction. The binuclear [Nd₂L₂(NO₃)₆(H₂O)₂]·H₂O complex units are linked by the intermolecular hydrogen bonds and π-π interactions to form a two-dimensional (2-D) layer supramolecule.     

Preparation, Crystal Structure and Thermal Decomposition Character of [Ni(CHZ)3]SO4·3H2O

A new coordination compound [Ni(CHZ)₃]SO₄·3H₂O (CHZ=carbohydrazide) was synthesized and characterized by elemental analysis and fourier transform infrared (FTIR) spectra, and its crystal structure was determined by X-ray single crystal diffraction. The crystal belonged to the triclinic system, space group with a=0.85237(1) nm, b=0.90964(1) nm, c=1.22559(2) nm, β=96.731(2)°, V=0.8849(2) nm³, Z=2, D_c=1.798 g·cm⁻³. In the asymmetric unit, three carbohydrazide (CHZ) bidentate ligands were coordinated with a Ni(II) cation by carbonyl O atoms and terminal N atoms of the hydrazine groups to form three planar chelate rings which were vertical to one another. Ni(II) cations, CHZ ligand molecules, sulfate anions, and lattice water molecules were jointed to a complicated three-dimensional network structure through coordination bonds, electrostatic forces and extensive hydrogen bonds. Natural bond orbital (NBO) atomic charges of CHZ were obtained from the density functional theory (DFT) method at the B3LYP/6-311+G^** level to interpret the reason why the coordination sites in carbohydrazide molecule were the oxygen atom of the carbonyl group and terminal N atoms of the hydrazine group. The thermal decomposition mechanism was tested through differential scanning calorimetry (DSC), thermogravimetric analyses, and Fourier transform infrared spectra. The kinetic parameters of the two exothermic processes of the title compound were studied applying the Kissinger's and Ozawa-Doyle's methods. The results indicated that the title complex possessed high energy and good thermal stability.     

Synthesis, Crystal Structures and Thermal Decomposition of Two Novel Supramolecular Complexes [Ni(cyclen)(H2O)2] (tpa) and [Cu(cyclen)H2O](tpa)?3H2O (Cyclen = 1,4,7,10? Tetraazacyclododecane, tpa = Dianion of Terephalic Acid)

Two novel supramolecular complexes [Ni(cyclen)(H₂O)₂](tpa)(1) and [Cu(cyclen)H₂O](tpa)⋅3H₂O (2) were synthesized and their structures were characterized with elemental analysis, IR spectrum, TGA and X-ray diffractometer, indicating that the complexes 1 and 2 consist of one-dimensional chain and two-dimensional net-work structures formed by intermolecular hydrogen-bonding interaction, respectively. TGA curves show the similar steps of weightloss for 1 and 2.