Search

A series of isomorphous random bimetallic NiII-MnII compounds with N-methylpyridinium-4-carboxylate (4-mpc) and azide, have been synthesized and characterized. They are of formula [NiIIxMnII1−x(N3)2(4-mpc)] (1−6), (x = 1 (1), 0.86 (2), 0.83 (3), 0.71 (4), 0.56 (5), 0.47 (6)). Compounds 1–6 consist of one-dimensional uniform chains with [(μ-EO-N3)2(μ-COO)] triple bridges (EO = end-on). Magnetic measurements reveal that compounds 1–6 behave as antiferromagnets with a gradual ferromagnetic-to-antiferromagnetic evolution by the incorporating of isotropic MnII ions into NiII chain. The NiII-rich compounds 1–3 exhibit field-induced metamagnetism. And the TN of the heterometallic compounds exhibit a composition-dependence of the content of NiII.

The 2D CuII metal-organic framework [Cu2(bptc)(H2O)4]n·4nH2O (1) (H4bptc = biphenyl-2,2′,4,4′-tetracarboxylic acid) was hydrothermally synthesized and characterized by single-crystal X-ray diffraction and magnetic measurements. In the structure, bptc4– serves as a twisted Π-shaped organic building block to connect paddlewheel [Cu2(COO)4] dinuclear units and mononuclear units through 2-/2′-carboxylate and 4-/4′-carboxylate, respectively. According to the magnetic analysis using a dimer-plus-monomer model, strong antiferromagnetic coupling is operative within the dinuclear unit (J = –311 cm–1 based on H = –JS1S2), and the compound behaves like a mononuclear molecule at low temperature.

A new 3d-3d random bimetallic compound, [Co2.28Mn0.72(N3)6(mpc-3)2(CH3OH)2] (1) (mpc-3 = N-methylpyridinium-3-carboxylate), has been synthesized by the CoII ions in the homometallic compound being partly substituted by MnII. Meanwhile, complex 1 is structurally and magnetically characterized. It consists of one-dimensional chains with the neighboring metal ions being linked alternatively by [(m-EO-N3)2(m-COO)] (EO = end-on) triple bridges and double EO azide bridges. Hydrogen-bonding interactions and π-π interactions are involved in the formation of a three-dimensional supramolecular network. Magnetic measurements revealed that complex 1 exhibits slow relaxation which is similar to the homometallic CoII parent compound while the TB is lower than that of the CoII analog.

To explore the influence of different N-donor auxiliary ligands on the self-assembly and structures of CoII-based coordination polymers (CPs), six coordination compounds, formulated as {Co(dnpdc)(bipy)}n (1), {[Co3(dnpdc)3(bipy)3(H2O)2]·2H2O}n (1s), {[Co5(OH)2(dnpdc)4(bpp)2(H2O)2]·2H2O}n (2), {[Co5(OH)2(dnpdc)4(bpp)2(H2O)2]·2H2O}n (3), {Co(dnpdc)(bcim)·(H2O)0.5}n (4) and {Co2(dnpdc)2(bpee)(bpim)}n (5) where bipy = 4,4′-bipyridine, bpee = bis(4-pyridyl)ethene, bpp = 1,3-bis(4-pyridyl)propane, bimb = 1,4-bis(imidazolyl)benzene, bcim = 4-bis(imidazol-1-ylmethyl)benzene and bpim = 4,4′-bis(imidazolyl)biphenyl, have been rationally designed and generated through the hydrothermal reaction of the dicarboxylate derivative ligand (H2dnpdc), Co(NO3)2, and a series of different N-donor co-ligands. These N-donor ligands were employed in the crystal preparation of these CPs as structure-directing ligands owing to their structural specialties and size-matching fashions. X-ray analyses revealed that these compounds exhibit two- or three-dimensional architectures. Compounds 1 and 5 are iso-structural, and both exhibit 3D “pillared” frameworks based on 1D [Co(OCO)2]n chains. Compound 1s, prepared at higher temperature, displays unusual (4,6)-connected and three-fold interpenetrated frameworks based on mononuclear and dinuclear nodes. Compound 2 features a new 10-connected 3D topology net based on a novel Co5(μ-OH)2(μ-OCO)6 pentanuclear cluster linked by mixed bpp and dnpdc ligands. Compound 3 exhibits a 6-fold interpenetrated diamond net. Compound 4 shows 2D sheets constructed from flexible bcim and dnpdc ligands. The magnetic properties of compounds 1, 2 and 5 have also been investigated to help us tentatively understand their structure–property relationships.

Two novel two-dimensional (2D) compounds of 3-(5-tetrazolate)-N-oxide-pyridine (L) and azide, have been synthesized and characterized. They are of formula [Cu(II)(L)(N3)]·0.5H2O (1) and [Cd(II)(L)(N3)·(H2O)]·0.5H2O (2). Both compounds 1 and 2 consist of 2D layers with similar double-bridged ((μ-EO-N3)(μ-N-N-tetrazolate), EO = end-on) one-dimensional (1D) chains being linked by the N-oxide-pyridine ligands. However, compounds 1 and 2 crystallize in different space group (C2/c (1), P21/c (2)) and exhibit different coordination geometry of central metal ions (square pyramidal (1), octahedral (2)). Magnetic investigations suggest that the mixed double [(μ-EO-N3)(μ-N-N-tetrazolate)] bridges in compound 1 transmit antiferromagnetic couplings between Cu(II) ions (J = −16.1 cm−1 above 46 K). And also, the emission spectra of the L ligand and complex 2 were studied in the solid state at room temperature, and an obvious blue-shift was observed in complex 2 compared with the emission of the free L ligand.

In this paper, the initial stage of the pyrolysis process of phenolic resin has been simulated by ReaxFF (reactive force field) molecular dynamics simulation under various temperatures (3000 K, 3250 K, and 3500 K), to study the behavior of phenolic hydroxyl groups and to investigate the correlation between the production of small oxygen-containing molecules (including H 2 O, CO and CO 2 ) and the quantity of hydroxyl radicals at different temperatures. We observed that the highly active phenolic hydroxyl groups would be easily turned into phenoxyl radicals and hydroxyl radicals in primary evolution. And also, both the phenoxyl radicals and hydroxyl radicals had remarkable impact on the following process of pyrolysis in secondary evolution: the formation of phenoxyl radicals reduced the stability of the benzene ring and damaged backbone of phenolic resin accompanying with the release of CO molecules, while the hydroxyl radicals increased the amount of CO molecules and converted them into CO 2 molecules, to reduce the char yield of resin. We found that the amounts of small oxygen-containing molecules increased with the rise in the number of phenolic hydroxyl groups or the rise in the temperature. We also found that both the two evolution modes of phenolic hydroxyl groups (I. phenolic hydroxyl groups – phenoxyl radicals – small oxygen-containing molecules; II. phenolic hydroxyl groups – hydroxyl radicals – small oxygen-containing molecules) can reduce the thermal stability of the backbone of resin. The negative effect of phenolic hydroxyl groups on the thermal stability of cured PR is valuable to the understanding of the pyrolytic process and char forming mechanism, and also the enhancement of the thermal stability of resin.

Seven isomorphous 2D CoNi (0 ≤ x ≤ 1) compounds based on ferromagnetic chains with mixed double [(μ-EO-N3)(μ-N-N-tetrazolate)] (EO = end-on) were synthesized and then structurally and magnetically characterized. They are formulated as [CoNi(L)(N3)(H2O)]·H2O (), (x = 1 (), 0.86 (), 0.74 (), 0.39 (), 0.14 (), 0.10 (), 0 (); L = 3-(5-tetrazole)-N-oxide-pyridine). Magnetic studies revealed that the homo-metallic compounds ( and ) behave as metamagnets, while the hetero-metallic compounds () show interesting composition-dependent slow relaxation due to the synergy effect of Co(II) and Ni(II) ions.

Benzoxazine resins (BZs) as a novel type of phenolic resin are high-performance matrix resin for advanced composites. Yet there still exist some deficiencies when used as ablative material in aerospace applications, such as high curing temperature and poor thermal stability. In the present study, the phenylboronic acid (PBA) modified BZs (PBBZs) exhibiting excellent processibilities and thermal properties were prepared by incorporating PBA into BZ. The viscosity, gel time and curing behaviors were examined to demonstrate that PBBZs possessed better processibilities than the BZ, representing the catalytic effect of PBA in this case. The incorporation of PBA accelerated the ring-opening polymerization of BZ, leading to the lower curing temperature. TGA results reveal that the cured PBBZs exhibit excellent thermal properties, where the char yield at 800 °C (nitrogen atmosphere) reaches 63.7% and is increased by 14.1 percentage points than that of BZ. The formed phenylboronates during curing act as additional cross-linking points and increase the cross-linking density of the cured resin, which results in the enhancement of the glass transition temperature of BZ ranging from 165 °C to 219 °C. This study provides a new vision for the preparation of high-performance matrix resin for ablative materials by introducing aryl-boron backbone.

The two-dimensional (2D) layer CuII compound [Cu3(L)2(N3)4] (1) [L = 2-amino-3-(5-tetrazole)-methyate-N-pyridine] was synthesized by in-situ hydrothermal reaction of CuCl2·2H2O, NaN3, and 3-(5-tetrazole)-methyate-N-pyridine. The central Cu1 and Cu2 atoms are located in five-coordinate and six-coordinate arrangements, respectively. Three CuII ions are linked by mixed double EO (end-on)-azido-tetrazole bridges to give trinuclear CuII clusters, which are further extended by EE (end-to-end) azido bridges to form 2D metal-organic layers. The magnetic exchange interactions in complex 1 were investigated by DFT calculations, and the calculated exchange interaction (J = –849 cm–1) revealed that the double EO-azido-tetrazole bridges transmit antiferromagnetic coupling between CuII ions.

Three extended three-dimensional CuII-based metal–organic frameworks (MOFs) have been separated successfully from reactions of 2,2′-dinitro-biphenyl-4,4′-dicarboxylate (H2dnpdc) and Cu(NO3)2 under controllable solvothermal conditions. The resulting structures of the MOFs are highly dependent on the solvent used during the synthesis. Compound 1, [Cu(dnpdc)(H2O)]n·(DMA)4(H2O)2, is a two-fold interpenetrated three-dimensional framework with NbO topology based on a binuclear [Cu2(O2C)4] “paddle-wheel” secondary building unit. In compound 2, [Cu9(dnpdc)6(OH)6(H2O)2]n·{(DMF)8(EtOH)3(H2O)12}n, the complicated one-dimensional [Cu(OH)(OCO)]n chains are cross-linked into three-dimensional frameworks by the dnpdc2− ligands. Compound 3, {Cu4(dnpdc)3(OH)2(py)4}n, displays three-dimensional nets with pcu topology based on 6-connected [Cu(μ3-OH)2(OCO)4] tetracopper clusters. Magnetically, compound 2 exhibits homo-spin topological ferrimagnetic behavior. Compound 3 features antiferromagnetic interactions mediated by μ3-OH and syn–syn-OCO heterobridges between the CuII ions.

Two coordination compounds of the ligand tetrazolate-5-carboxylate (tzc) with zinc(II), namely, [Zn2(tzc)2(bpp)] (1) and [Zn2(tzc)2(bpea)] (2) [bpp = 1,3-bis(4-pyridyl)propane, bpea = 1,2-bis(4-pyridyl)ethane] were synthesized by hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Both compounds 1 and 2 exhibit a three-dimensional structure with 3,4-connected self-penetrating net topology in which two-dimensional ZnII-tzc layers are interlinked by the bpp or bpea spacers, with the tzc ligand being in the μ3-N1,O1:N4,O2:N2 coordination mode. The luminescence properties of 1 and 2 were also investigated.

Seven isomorphous 2D CoNi (0 ≤ x ≤ 1) compounds based on ferromagnetic chains with mixed double [(μ-EO-N3)(μ-N-N-tetrazolate)] (EO = end-on) were synthesized and then structurally and magnetically characterized. They are formulated as [CoNi(L)(N3)(H2O)]·H2O (), (x = 1 (), 0.86 (), 0.74 (), 0.39 (), 0.14 (), 0.10 (), 0 (); L = 3-(5-tetrazole)-N-oxide-pyridine). Magnetic studies revealed that the homo-metallic compounds ( and ) behave as metamagnets, while the hetero-metallic compounds () show interesting composition-dependent slow relaxation due to the synergy effect of Co(II) and Ni(II) ions.

Hydrothermal reactions of Cu(II) salts and 2,2′,4,4′-biphenyltetracarboxylic acid (2,2′,4,4′-H4bptc) in the presence of pyridyl ligands yielded three isomorphous 3D metal–organic coordination polymers formulated as [Cu2(2,2′,4,4′-bptc)(L)x]·H2O [x = 2 for L = pyridine; x = 1 for L = bis(4-pyridyl)ethene and bis(4-pyridyl)ethane]. In the structure, the distorted paddlewheel [Cu2(COO)4] motif and the twisted Π-shaped 2,2′,4,4′-bptc serve as dissimilar 4-connected SBUs to generate a 3D [Cu2(2,2′,4,4′-bptc)] mother framework with the PtS topology, which selectively accommodates pyridine or bis(pyridyl) ligands of appropriate size.

A novel coordination polymer with 4-sulfonyl-2,6-naphthalenedicarboxylic acid (H3SNDC), {[Cd3(NDSC)2(H2O)10]·6H2O}n (1), has been prepared and characterized by single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic system, space group P21/c with a = 12.324(4), b = 22.572(7), c = 7.1472 A, β = 91.469(5)°, V = 1987.4(11) A3. In the structure, the ligands use the carboxylate groups to connect Cd(II) ions into 1D chains, and the chains are linked into 2D undulated layers through the coordination of the sulfonate groups to additional Cd(II) ions. The compound exhibits two distinct weight loss steps due to the release of all water molecules and the decomposition of the SNDC ligand, and it displays photoluminescence around 448 nm, which is blue-shifted compared with the ligand. A new Cd(II) coordination polymer with 4-sulfonyl-2, 6-naphthalenedicarboxylate (NDSC) is reported. The NDSC ligand anions act as T-shape building blocks to link the metal ions into a two-dimensional coordination network resembling the brick-wall topology.

Herein we present a systematic study of the structures and magnetic properties of six coordination compounds with mixed azide and zwitterionic carboxylate ligands, [M(N(3) )(2) (2-mpc)] (2-mpc=N-methylpyridinium-2-carboxylate; M=Co for 1 and Mn for 2), [M(N(3) )(2) (4-mpc)] (4-mpc=N-methylpyridinium-4-carboxylate; M=Co for 3 and Mn for 4), [Co(3) (N(3) )(6) (3-mpc)(2) (CH(3) OH)(2) ] (5), and [Mn(3) (N(3) )(6) (3-mpc)(2) ] (6; 3-mpc=N-methylpyridinium-3-carboxylate). Compounds 1-3 consist of one-dimensional uniform chains with (μ-EO-N(3) )(2) (μ-COO) triple bridges (EO=end-on); 5 is also a chain compound but with alternating [(μ-EO-N(3) )(2) (μ-COO)] triple and [(EO-N(3) )(2) ] double bridges; Compound 4 contains two-dimensional layers with alternating [(μ-EO-N(3) )(2) (μ-COO)] triple, [(μ-EO-N(3) )(μ-COO)] double, and (EE-N(3) ) single bridges (EE=end-to-end); 6 is a layer compound in which chains similar to those in 5 are cross-linked by a μ(3) -1,1,3-N(3) azido group. Magnetically, the three Co(II) compounds (1, 3, and 5) all exhibit intrachain ferromagnetic interactions but show distinct bulk properties: 1 displays relaxation dynamics at very low temperature, 3 is an antiferromagnet with field-induced metamagnetism due to weak antiferromagnetic interchain interactions, and 5 behaves as a noninnocent single-chain magnet influenced by weak antiferromagnetic interchain interactions. The magnetic differences can be related to the interchain interactions through π-π stacking influenced by different substitution positions in the ligands and/or different magnitudes of intrachain coupling. All of the Mn(II) compounds show overall intrachain/intralayer antiferromagnetic interactions. Compound 2 shows the usual one-dimensional antiferromagnetism, whereas 4 and 6 exhibit different weak ferromagnetism due to spin canting below 13.8 and 4.6 K, respectively.

Four coordination compounds of tetrazolate-5-carboxylate (tzc) with cobalt(II), [Co2(tzc)2(H2O)6]·2H2O (1), [Co2(tzc)2(phen)2(H2O)2]·2H2O (2), [Co2(tzc)2(2,2′-bpy)2(H2O)2]·H2O (3), and [Co(tzc)(4,4′-bpy)] (4), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, and 4,4′-bpy = 4,4′-bipyridyl, have been synthesized by the hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Compounds 1, 2 and 3 all contain dinuclear molecules in which metal ions are linked by the double N–N bridges from two tzc ligands in the μ2-N1,O1:N2 mode, and the dinuclear molecules are associated into 3D architecture through extensive hydrogen bonding and π–π stacking interactions in various fashions. Compound 4 exhibits a two-dimensional layer structure in which Co(tzc) chains with μ3-N1,O1:O1:N2 tzc are cross-linked by 4,4′-bpy. Magnetic investigations on 1–3 revealed intramolecular ferromagnetic coupling through the double N–N bridges with intermolecular ferromagnetic or antiferromagnetic interactions. The interaction through the mixed N–N and μ2-Ocarboxylate bridges in 4 is antiferromagnetic.

The reactions of manganese(II) acetate or perchlorate, sodium azide, and the inner-salt-type dicarboxylate ligand 1,3-bis(4-carboxylato-1-pyridinium)propane (L) under different conditions yielded four different Mn(II) coordination polymers with mixed azide and carboxylate bridges: {[Mn(L)(N(3))]ClO(4).0.5H(2)O}(n) (1), {[Mn(2)(L)(2)(N(3))(2)][Mn(N(3))(4)(H(2)O)(2)].2H(2)O}(n) (2), {[Mn(2)(L)(2)(N(3))(2)(H(2)O)(2)]Br(N(3)).2H(2)O}(n) (3), and [Mn(4) (L)(2)(N(3))(8)](n) (4). The compounds exhibit great diversity in their structures and magnetic properties. Both 1 and 2 contain anionic chains featuring a mixed (OCO)(2)(EO-N(3)) triple bridge (EO = end-on) between adjacent Mn(II) ions. In 1, two independent sets of triple bridges with apparently different structural parameters alternate in the AABB sequence, and the resulting alternating chains are cross-linked into a cationic 3D framework by the cationic dipyridinium spacers. Differently, the chains in 2 have uniform bridges and are interlinked into a 2D coordination layer. An expression of the magnetic susceptibility for 1D systems with alternating J(1)J(1)J(2)J(2) interactions has been deduced and applied to 1. Magnetic studies on 1 and 2 reveal that the (OCO)(2)(EO-N(3)) triple bridges induce antiferromagnetic coupling between Mn(II) ions, and magnetostructural analyses suggest that the magnitude of the coupling can be correlated to the Mn-N and Mn-N-Mn parameters. Compound 3 contains 2D coordination layers in which the chains with alternating double EO-azide and double carboxylate bridges are interlinked by the dipyridinium spacers, and magnetic studies suggest alternating ferro- and antiferromagnetic interactions through the alternating bridges. The 3D framework of compound 4 is formed by the organic ligands interlinking the unique manganese-azide-carboxylate layers in which the [Mn(4)(mu(3)-N(3))(2)(mu(2)-N(3))(2)(mu(2)-COO)(4)] clusters are interlinked through EE-azide bridges (EE = end-to-end). The structure represents a novel type of self-catenated 8-connected 3D net. Magnetostructural analyses suggest that all of the short bridging moieties in 4, including (mu(3)-EO-N(3))(2), (OCO)(EO-N(3)), (OCO)(EO-N(3))(2), and single EE-N(3), propagate antiferromagnetic coupling.

Two metal–organic compounds, [Co2(NNDC)2(H2O)6]·2H2O (1) and [Ni(NNDC)(H2O)4]n (2) (where H2NNDC = 1,5-dinitronaphthalene-3,7-dicarboxylic acid) have been synthesized under hydrothermal reaction conditions, which are characterized by single crystal X-ray determination, IR and Thermogravimetric Analysis (TGA). Compound 1 consists of binuclear Co(II) molecules with di(μ-aqua)di(μ-carboxylato) bridges. In the compound, each dicarboxylate ligand bridges metal ions using only one carboxylate group, with the other carboxylate group involved in extensive hydrogen bonding with coordinated and uncoordinated water molecules. The 1,5-dinitronaphthalene groups serve as pillars between the hydrogen-bonded layers in which the dinuclear moieties are connected through the O–H⋯O⋯H–O hydrogen bonds mediated by uncoordinated carboxylate groups and lattice water molecules. In 2, the ligands serve as long bridges to link the metal ions into infinite chains. The uncoordinated oxygen atoms of carboxylate are hydrogen bonded to coordinated water molecules from the same and different chains to link the metal spheres into (4,4) layers, which are formally pillared by the 1,5-dinitronaphthalene spacers to generate a 3D architecture with the α-Po topology. Based on a model taking into account both magnetic coupling and single-ion magnetic effects, detailed magnetic analysis on the Co(II) compound revealed a ferromagnetic intradimer interaction through the mixed aqua and carboxylate bridges.

The structure and magnetic properties of double azido-bridged CuII binuclear complex 1 with the chelating chiral ligand (S,S)-2,2′-isopropylidenebis(4-phenyl-2-oxazoline) were analyzed by combining experimental and theoretical techniques. The CuII ions adopt a square pyramidal geometry with different degrees of distortion, whereas the two end-on azido bridges disposed at the equatorial positions exhibit significantly different Cu–N–Cu angles, 110.6 and 97.3°, which are respectively smaller and larger than the critical 108° value distinguishing the ferromagnetic and antiferromagnetic regimes. The asymmetry in 1 arises from the use of the bulky asymmetric ligand, giving rise to two different magnetic pathways between the CuII ions. The magnetic pathway along the large Cu–N–Cu angle value dominates over the small one, resulting in a net antiferromagnetic behavior with J = –78.6 cm–1. On the basis of wavefunction calculations, we investigate the exchange interactions in synthetic compound 1 and fictitious analogs 2 and 3 holding either two large (i.e., 110.6°) or two small (i.e., 97.3°) Cu–N–Cu angles. The calculated exchange interaction in 1(–104 cm–1) is in relatively good agreement with the experimental value and corresponds precisely to the average between the antiferromagnetic value in 2 (–218 cm–1) and the ferromagnetic one in 3 (21 cm–1). The significant enhancement in the antiferromagnetic contribution accompanying the expansion of one of the Cu–N–Cu bridging angles is undoubtedly the driving force for the observed antiferromagnetic behavior in 1. The control of the local metal environments allowed us to monitor the exchange coupling interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A pure hydrated potassium borate K 2 B 5 O 8 (OH)·2H 2 O has been synthesized under mild hydrothermal conditions and characterized by single-crystal X-ray diffraction, XRD, FT-IR, Raman spectra and DTA-TG. The crystal structure consists of two K–O polyhedra and [B 5 O 8 (OH)] 2− polyborate anion. The enthalpy of formation was determined to be −4772.6 ± 4.0 kJ mol −1 by solution calorimetry.

The 4,4'-bipyridine-based zwitterionic monocarboxylate ligand, 4,4'-dipyridinio-1-acetate (L), is used as coligand to construct novel magnetic coordination polymers with mixed azide and carboxylate bridges. Two compounds, [Co(2)(L)(2)(N(3))(4)(H(2)O)] x 4 H(2)O (1) and [Mn(6)(L)(4)(N(3))(12)(H(2)O)] x 5 H(2)O (2), have been structurally and magnetically characterized. Compound 1 consists of one-dimensional (1D) coordination chains in which the unprecedented binuclear motifs with mixed (mu-EO-N(3))(mu-COO)(2) (EO = end-on) triple bridges are cross-linked by the 4,4'-dipyridinium-N-methylene spacers. In compound 2, the azide anions link the metal ions into a very complicated three-dimensional (3D) network with unprecedented topology, and the zwitterionic coligand is embedded in and serves as additional supports for the 3D network. Magnetic studies reveal that the mixed (mu-EO-N(3))(mu-COO)(2) triple bridges transmit ferromagnetic coupling in the Co(II) compound, and the overall antiferromagnetic interactions exist in the Mn(II) compound.

The flexibility of the 3D framework derived from Ni(II) and an aromatic dicarboxylate allows for the incorporation of different second bridges, and the resulting materials can be a metamagnet or a paramagnet depending upon the length of the second bridge.

By using a neutral inner-salt-type dicarboxylate as coligand, a novel two-dimensional (2D) manganese(II) coordination polymer, [Mn(L)(N(3))]ClO(4) x 1/2 H(2)O (L = 1,3-bis(3-carboxylatopyridinium)propane), was synthesized, and characterized by X-ray crystallography and magnetic measurements. The compound contains uniform Mn(II) chains with simultaneous azide and carboxylate bridges between adjacent Mn(II) ions. The formally negative chains are interlinked by the positively-charged 1,3-bis(pyridinium)propane spacer, and the spiral conformation of the spacer imports intriguing helical features to the resulting 2D network, in which [MnL] helices are connected by sharing metal centers with alternating centro- and C(2)-symmetry. The triple (azide)bis(carboxylate) bridge mediates overall antiferromagnetic coupling with J = -3.0 cm(-1), as a result of the competition between the antiferromagnetic (carboxylate) and ferromagnetic (azide) pathways.

The combination of the azide bridge and a neutral inner-salt-type dicarboxylate ligand leads to a three-dimensional coordination framework that contains unprecedented azide-bridged tetramanganese(II) clusters and defines a novel self-catenated, eight-connected net of 4(16) x 6(12) topology.

Two isomorphous Co(II) and Mn(II) three-dimensional coordination polymers with tetrazolate-5-carboxylate as magnetic mediator exhibit an unprecedented 3,4-connected self-penetrating net topology; a combination of canted antiferromagnetism and metamagnetism was observed in the Co(II) compound, whereas the Mn(II) compound shows typical antiferromagnetic behaviors.

The coordination of pyridazine-3,6-dicarboxylate by manganese(II) leads to unusual anionic binuclear trigonal prisms, which coassemble with the hexaaquamanganese(II) antiprisms to generate a hydrogen-bonded CsCl-type three-dimensional network.

A single-chain magnet consisting of Co(II) chains with (EO-N(3))(2) and (μ-COO)(2)(μ-EO-N(3)) bridges reversibly transforms into an antiferromagnetic phase with metamagnetic character and modified slow magnetic relaxation upon dehydration.

Six Mn(II) coordination compounds with tetrazolate-5-carboxylate (tzc), have been synthesized and characterized. They are of the formula [Mn2(tzc)2(H2O)2]·4H2O (1), Mn(tzc)(H2O)2 (2), [Mn2(tzc)2(phen)2(H2O)2] (3), [Mn(tzc)(2,2′-bpy)(H2O)2] (4), [Mn(tzc)(4,4′-bpy)] (5) and [Mn2(tzc)2(H2O)2]·(bpp) (6), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, 4,4′-bpy = 4,4′-bipyridyl, and bpp = 1,3-di(4-pyridyl)propane. Versatile coordination modes of the tzc ligand have been recognized in these compounds. In the absence of auxiliary ligands, a dinuclear compound (1) with the Mn2(N–N)2 moiety and a 1D coordination polymer (2) consisting of two types of disordered Mn(tzc) chains have been obtained at different temperatures. The incorporation of chelating auxiliary ligands (2,2′-bpy and phen) leads to a mononuclear (4) and a dinuclear (3) compounds, the structure of the latter resembling that of 1. The use of the ditopic auxiliary ligand 4,4′-bpy gives a 2D coordination polymer (5) in which disordered Mn(tzc) chains are cross-linked by 4,4′-bpy. However, the potentially ditopic ligand bpp is not involved in coordination but serves as hydrogen-bonded bridge between the Mn(tzc) chains to give compound 6. Magnetic investigations suggest that the double N–N bridges in the dinuclear compounds (1 and 3) mediate weak ferromagnetic coupling. However, in compounds 2, 5 and 6, which consist of 1D disordered Mn(tzc) chains with different bridging moieties, the intra-chain interactions are dominated by antiferromagnetic coupling.

Hydrothermal reactions of 2-cyanopyrimidine and CdCl2 in the absence and presence of sodium azide yielded two coordination polymers, [Cd3(ox)2(pymc)2]·2H2O (1) and [Cd2(pymtz)2(ox)]·H2O (2), respectively, where pymc = 2-pyrimidinecarboxylate, pymtz = 5-(2′-pyrimidyl)tetrazolate and ox = oxalate. All the ligands in these compounds were generated in situ by the hydrolysis of 2-cyanopyrimidine (pymCN) or the [2 + 3] cycloaddition of the azide ion to the nitrile. In compound 1, seven-coordinated Cd ions are linked by oxalate bridges into a diamond network based on Cd2O2 nodes, and eight-coordinated Cd ions are linked to the network through pymc and oxalate bridges. In compound 2, seven-coordinated Cd ions are bridged by oxalate ions into 1D Cd2(ox) ribbons, which are further linked by bis(chelating) pymtz to give a 3D framework that exhibits the 5-connected 4466 net topology based on Cd2O2 nodes. The compounds exhibit intense luminescence in the solid state.