Zhong-Sheng Cai

Multiple-Step Humidity-Induced Single-Crystal to Single-Crystal Transformations of a Cobalt Phosphonate: Structural and Proton Conductivity Studies.

Humidity-induced multiple-step single-crystal to single-crystal (SC-SC) transformations are observed in the cobalt phosphonate (NH4)3[Co2(bamdpH)2(HCOO)(H2O)2] (1), where bamdpH4 is (benzylazanediyl)bis(methylene)diphosphonic acid, [C6H5CH2N(CH2PO3H2)2]. Under high-humidity conditions (95% RH), compound 1 experiences hydrolysis at 60 °C which is accompanied by the transformation from a double-chain structure of compound 1 into a single-chain structure of [Co(bamdpH2)(H2O)2]·2H2O (2). When the humidity is below 10% RH, part of the lattice water in compound 2 can be released, forming a third phase, [Co(bamdpH2)(H2O)2]·H2O (3). The structural transformation processes have been monitored by infrared and proton conductivity measurements.

Homochiral Cobalt Phosphonates Containing Δ‐Type Chains with a Tunable Interlayer Distance and a Field‐Induced Phase Transition

Two pairs of enantiomeric Co(II) compounds with formulas [Co2 (μ3 -OH)(cyamp)(Cn H2n+1 COO)] (cyampH2 =(S)- or (R)-[(1-cyclohexylethyl)amino]methylphosphonic acid; n=1 (1); n=7 (2)) were synthesized. The structures of S-1 and S-2 were determined by single-crystal structural analyses. Both crystallize in a monoclinic chiral space group P21 , and exhibit layered structures in which the Δ-type chains of corner-sharing Co3 (μ3 -OH) triangles are connected by the phosphonate groups. The interlayer spaces are filled with the organic groups of the phosphonate and carboxylate ligands. Therefore, the distances between the layers can be manipulated by the length of the alkyl chain of the carboxylate ligands, from 14.6 Å in 1 to 20.0 Å in 2. Magnetic studies were carried out for compounds S-1 and S-2. Both show metamagnetism at low temperature. The critical field decreases with increasing interlayer distance from 8.18 kOe for S-1 to 7.01 kOe for S-2 at 1.8 K. The optical properties were also studied.

Synthetic-Method-Dependent Magnetic Relaxation in a Cobalt(II) Phosphonate Chain Compound

A polar cobalt(II) phosphonate Co(bamdpH2)(H2O) (1) [bamdpH4 = (benzylazanediyl)bis(methylene)diphosphonic acid] is reported. It shows a linear chain structure. The neighboring chains are connected by moderately strong hydrogen bonds forming a supramolecular layer. The interlayer spaces are filled with the organic groups of the phosphonate ligands. Compound 1 displays the coexistence of single-chain magnet behavior and canted antiferromagnetism below 2.8 K. Moreover, the magnetic dynamics is strongly dependent on the synthetic methods, a phenomenon that has not been documented before.

Mononuclear lanthanide complexes incorporating an anthracene group: structural modification, slow magnetic relaxation and multicomponent fluorescence emissions in Dy compounds

Four mononuclear lanthanide complexes, [Ln(hfac)3(depma)(H2O)] [Ln(III) = Dy (1), Gd (2)], [Dy(hfac)3(depma)2]2·H2O (3) and [Gd(hfac)3(depma)2]·2H2O (4), have been obtained (hfac = hexafluoroacetylacetonate, depma = 9-diethylphosphonomethyl anthracene) by using one (for 1 and 2) or two (for 3 and 4) depma molecules to substitute coordination water molecules of Ln(hfac)3(H2O)2. It was found that the number of introduced depma ligands can modify the coordination geometry of Ln(iii) ions, showing a distorted biscapped triangular prism geometry in isostructural 1 and 2 and a distorted square-antiprismatic geometry in 3 and 4. Magnetic studies reveal that both 1 and 3 show field-induced slow magnetic relaxation under the applied dc field of 1000 Oe. The solid-state fluorescence measurements indicate the presence of multicomponent emissions in 1 and 3, including ligand-centered (LC) emissions from hfac and depma, and yellow emission from Dy(III) ions and only ligand-centered (LC) emissions in 2 and 4.

Modulating the microporosity of cobalt phosphonates via positional isomerism of co-linkers

By incorporating co-ligands 1,2-bis(imidazol-1-ylmethyl)benzene (1,2-bix), 1,3-bis(imidazol-1-ylmethyl)benzene (1,3-bix) and 1,4-bis(imidazol-1-ylmethyl)benzene (1,4-bix), three isomeric cobalt phosphonates Co5(1,2-bix)2(pbtc)2(H2O)4·8H2O (1), Co5(1,3-bix)2(pbtc)2(H2O)4·7.5H2O (2), and Co5(1,4-bix)2(pbtc)2(H2O)4·6H2O (3) (pbtcH5 = 5-phosphonatophenyl-1,2,4-tricarboxylic acid) have been isolated successfully. Compound 1 shows a layer structure in which chains containing alternately arranged Co3O2 trimers and Co2 dimers are connected by pbtc5− ligands. The 1,2-bix co-ligand adopts a cis-mode, and coordinates to the cobalt atoms from the same chain. Upon dehydration, compound 1 undergoes single-crystal-to-single-crystal (SC–SC) structural transformation forming a new crystal phase Co5(1,2-bix)2(pbtc)2(H2O)4 (1a). The process is reversible upon rehydration, showing a breathing effect. In compounds 2 and 3, similar layers composed of cobalt phosphonate chains and pbtc5− linkages are also found, which are further cross-linked by 1,3-bix or 1,4-bix to form 3D framework structures. The three compounds show different microporosities, as confirmed by their different N2 gas adsorption behaviors.

Polymorphic Lanthanide Phosphonates Showing Distinct Magnetic Behavior

A series of layered lanthanide phosphonates α-Ln(2-qpH)(SO4)(H2O)2 (α-Ln; Ln = Gd, Tb, Ho, Er) and β-Ln(2-qpH)(SO4)(H2O)2 (β-Ln; Ln = Gd, Tb, Ho, Er, Yb) (2-qpH2 = 2-quinolinephosphonic acid) have been synthesized and characterized. Compounds α-Ln crystallize in monoclinic space group P21/c, while compounds β-Ln crystallize in triclinic space group P1̅. Magnetic studies reveal that dominant ferromagnetic interactions are propagated between the magnetic centers in all cases. Field-induced magnetic relaxation is observed in compounds β-Er and β-Yb.

Assembly of {Mn2(salen)2}2+ Dimers by Cyclic V4O124− Clusters: A 3 D Compound with Open-Framework Structure Exhibiting Slow Magnetization Relaxation

Since the discovery of the first single-molecule magnet (SMM), [Mn12O12 ACHTUNGTRENNUNG(O2CMe)16ACHTUNGTRENNUNG(H2O)4],[1] paramagnetic systems exhibiting slow reversal of magnetization and hysteresis below their blocking temperatures have received great attention. Such SMMs also display quantum tunneling of magnetization (QTM) and quantum phase interference and thus have potential applications in quantum computation and molecular spintronics. More interestingly, QTM behavior can be modulated by weak interactions between SMMs, manifested as exchange-biased QTM steps and quantum entanglement of the two SMMs. Weak intermolecular interactions such as hydrogen bonds and p–p stacking are difficult to control, and so using covalent bonds to connect the SMMs is a more efficient approach. The efforts along this line have resulted in a number of discrete or polymeric compounds containing SMM building units. In many cases, however, the coupling between the SMMs is so strong that the SMM identity is lost, giving single chain magnet (SCM) behavior or long-range magnetic ordering (LRO). There are only a few examples of polymer compounds with embedded covalently linked SMMs that exhibit slow magnetization relaxation. As one of the smallest SMMs, the out-of-plane Mn Schiff base (SB) dimers {Mn2(SB)2}, such as {Mn2ACHTUNGTRENNUNG(saltmen)2 ACHTUNGTRENNUNG(ReO4)2}[9a] and {{MnACHTUNGTRENNUNG(salen) ACHTUNGTRENNUNG(NCO)}2}[9b] (saltmen =N,N’(1,1,2,2-tetramethylethylene)bis(salicylideneiminate), salen = N,N’-bis(salicylidene)ethylenediamine dianion) could be useful uniaxial anisotropic building units to design complexes with extended structures, because their two axial positions are readily substituted by other bridging ligands. By using paramagnetic linkages such as {Ni ACHTUNGTRENNUNG(pao)2(py)2}[10a] (pao = pyridine-2-aldoximate) and {Fe(CN)6} 3 [10b] or diamagnetic linkages such as the carboxylate groups, a few complexes with chain or layer structures have been reported that show SCM behavior or LRO at low temperature. In the case of layered compound [{Mn ACHTUNGTRENNUNG(saltmen)}4{Co(CN)6}] ACHTUNGTRENNUNG(ClO4)·9 H2O, the SMM behavior of the {Mn2(SB)2} dimer is found to be maintained. Recently, the groups of Wang and Miyasaka reported that diamagnetic polyoxometalate (POM) clusters can be used as magnetic separators between {Mn2 ACHTUNGTRENNUNG(salen)2}2+ dimers through Coulombic aggregations. The SMM behavior of the {Mn2 ACHTUNGTRENNUNG(salen)2}2+ species reappears, in contrast to the non-SMM behavior of the [{Mn ACHTUNGTRENNUNG(salen)ACHTUNGTRENNUNG(H2O)}2]ACHTUNGTRENNUNG(ClO4)2 precursor. As far as we are aware, polymeric compounds containing covalently linked {Mn2(SB)2} dimers and POM clusters have never been documented in literature. Herein, we report a novel {Mn2(SB)2}–POM compound with formula [Mn6ACHTUNGTRENNUNG(salen)6 ACHTUNGTRENNUNG(H2O)V4O12] ACHTUNGTRENNUNG(ClO4)2·7 H2O (1). This compound possesses a three-dimensional openframework structure in which the {Mn2ACHTUNGTRENNUNG(salen)2}2+ dimers are covalently linked by the cyclic V4O12 4 clusters. More interestingly, slow magnetization relaxation behavior is observed for 1. Compound 1 is obtained as dark brown crystals by treating [MnACHTUNGTRENNUNG(salen) ACHTUNGTRENNUNG(H2O)]2ACHTUNGTRENNUNG(ClO4)2 with NH4VO3 in a mixed solvent of methanol and water (1:1) at room temperature. It crystallizes in the triclinic space group P1. The asymmetric unit contains six Mn ACHTUNGTRENNUNG(salen)+ cations, one V4O12 anion, two ClO4 anions, one coordinating water molecule, and seven lattice water molecules. The oxidation states of V and Mn ions are confirmed by the bond valence sum calculations (Table S1 in the Supporting Information). The cyclic V4O12 4 unit is made up of four corner-sharing VO4 tetrahedra (V O 1.611(7)–1.817(6) ). Each V4O12 unit is linked to five {Mn ACHTUNGTRENNUNG(salen)}+ and one {Mn ACHTUNGTRENNUNG(salen) ACHTUNGTRENNUNG(H2O)}+ unit by using six of its eight terminal oxygen atoms (O13, O14, O18, O20, O21, O23), forming a decanuclear building unit of {Mn6 ACHTUNGTRENNUNG(salen)6ACHTUNGTRENNUNG(H2O)V4O12}2+ (Figure 1). There are three kinds of coordination modes of the four vanadium atoms within the V4O12 4 cluster. The coordination modes of V2 and V4 atoms are similar. Each connects to one {MnACHTUNGTRENNUNG(salen)}+ moiety, for example, {Mn3 ACHTUNGTRENNUNG(salen)}+ for V2 and {Mn6 ACHTUNGTRENNUNG(salen)}+ for V4, leaving a single terminal oxygen atom pendent. In contrast, the V1 and V3 atoms each connect to two {Mn ACHTUNGTRENNUNG(salen)}+ moieties through their two terminal oxygen atoms, for example, {Mn1 ACHTUNGTRENNUNG(salen)}+ and {Mn2[a] T.-T. Wang, Dr. S.-S. Bao, M. Ren, Z.-S. Cai, Z.-H. Zheng, Z.-L. Xu, Prof. Dr. L.-M. Zheng Nanjing National Laboratory of Microstructure State Key Laboratory of Coordination Chemistry School of Chemistry and Chemical Engineering Nanjing University, Nanjing 210093 (P. R. China) Fax: (+86) 25-83314502 E-mail : lmzheng@nju.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201300167.

Self‐assembly of a Linear Ni9 Triple‐helical Supramolecule with Dominant Ferromagnetic Interactions

A linear triple-helical supramolecule Ni9 L6 has been prepared through a controllable self-assembly approach using 1,3-bis-(3-oxo-3-phenylpropionyl)-2-hydroxy-5-methylbenzene (H3 L) and Ni(OAc)2 under solvothermal conditions. Single-crystal X-ray diffraction analysis confirms the axial C3 symmetrical helical structure of the product and the temperature-dependent magnetic susceptibility corresponds to a typical shape of a paramagnet showing dominant ferromagnetic exchange couplings between the neighboring Ni(II) ions.

Successive Phase Transition, Dielectric Ordering, and Liquid Crystalline Behavior of Simple (Laurylammonium)(Phenyl Phosphates) Salts

Successive phase transitions of three kinds of simple 1:1 organic salts of laurylammonium (LA)-phenyl (3-pyridyl) phosphate derivative were examined in terms of thermal properties, single crystal X-ray structural analyses, powder X-ray diffractions, and dielectric responses, where the phosphate anion was chemically modified from phenylphosphate (1) and 3-pyridylphosphate (2) to m-fluorophosphate (3). All 1:1 simple organic salts showed the successive solid-solid and solid-smectic A (SmA) phase transition with high thermal stability. Isostructural alternate cation-anion layer was observed in LA-1 and LA-2, and the packing structure of LA-3 was different from those of the former salts. The L-shaped cation-anion conformation in the molecular assemblies was transformed to the rod-like conformation through the phase transition to SmA phase, where both conformations coexisted in the intermediate solid phase of LA-2 and LA-3. The DSC, PXRD, and dielectric responses of LA-2 showed the antiferroelectric-paraelectric phase transition couple with the flip-flop motion of 3-pyridyl ring along the long axis of the molecule. On the contrary, such molecular motion of the phenyl ring did not show the dielectric phase transition due to no dipole change during molecular rotation of phenyl ring. The motional freedom of m-fluorophenyl ring in LA-3 was completely suppressed by the steric hindrance from the neighboring anions in the absence of dielectric ordering.

Na2IrIVCl6: Spin–Orbital-Induced Semiconductor Showing Hydration-Dependent Structural and Magnetic Variations

Iridium(IV) oxides have gained increased attention in recent years owing to the presence of competing spin-orbit coupling and Coulomb interactions, which facilitate the emergence of novel quantum phenomena. In contrast, the electronic structure and magnetic properties of IrIV-based molecular materials remain largely unexplored. In this paper, we take a fresh look at an old but puzzling compound, Na2IrCl6, which can be hydrated to form two stable phases with formulas Na2IrCl6·2H2O and Na2IrCl6·6H2O. Their crystal structures are well illustrated based on X-ray powder diffraction data. Magnetic studies reveal that Na2IrCl6 and Na2IrCl6·2H2O are canted antiferromagnets with ordering temperatures of 7.4 and 2.7 K, respectively, whereas Na2IrCl6·6H2O is paramagnetic down to 1.8 K. First-principle calculations on Na2IrCl6 reveal a Jeff = 1/2 ground state, and the band structures show that Na2IrCl6 is a spin-orbital-induced semiconductor with an indirect gap of about 0.18 eV.