Dynamic Motion of Organic Ligands in Polar Layered Cobalt Phosphonates.

By introducing the polar methoxy group into phenyl- or benzyl-phosphonate ligands, four cobalt phosphonates with layered structures are obtained, namely, [Co(4-mopp)(H2 O)] (1), [Co(4-mobp)(H2 O)] (2), [Co(3-mopp)(H2 O)] (3), and [Co(3-mobp)(H2 O)] (4), where 4- or 3-moppH2 is (4- or 3-methoxyphenyl)phosphonic acid and 4- or 3-mobpH2 is (4- or 3-methoxybenzyl)phosphonic acid. Compounds 1, 2, and 4 crystallize in the polar space groups Pmn21 or Pna21 , whereas compound 3 crystallizes in the centrosymmetric space group P21 /n. The layer topologies in the four structures are similar and can be viewed as perovskite type, where the edge-sharing [Co4 O4 ] rhombi are capped by the PO3 C groups. The phenyl and MeO groups in compounds 1-3 are heavily disordered, whereas that in 4 is ordered. Structural comparison based on the data at 296 and 123 K reveals distinct dynamic motion of the organic groups in compounds 1 and 2. The fluctuation of the polar MeO groups in these two compounds is confirmed by dielectric relaxation measurements. In contrast, the fluctuation of polar groups in compounds 3 and 4 is not evident. Interestingly, the dehydrated samples of 3 and 4 (i.e., 3-de and 4-de) exhibit one-step and two-step phase transitions associated with the motion of polar organic groups, as proven by DSC and dielectric measurements. The magnetic properties of compounds 1-4 are investigated, and strong antiferromagnetic interactions are found to mediate between the magnetic centers through µ-O(P) and O-P-O bridges.

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.

Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility.

The construction of highly stable metal-porphyrinic frameworks (MPFs) is appealing as these materials offer great opportunities for applications in artificial light-harvesting systems, gas storage, heterogeneous catalysis, etc. Herein, we report the synthesis of a novel mesoporous metal-porphyrinic framework (denoted as NUPF-1) and its catalytic properties. NUPF-1 is constructed from a new porphyrin linker and a Zr6 O8 structural building unit, possessing an unprecedented doubly interpenetrating scu net. The structure exhibits not only remarkable chemical and thermal stabilities, but also a distinct structural flexibility, which is seldom seen in metal-organic framework (MOF) materials. By the merit of high chemical stability, NUPF-1 could be easily post-metallized with [Ru3 (CO)12 ], and the resulting {NUPF-1-RuCO} is catalytically active as a heterogeneous catalyst for intermolecular C(sp(3) )-H amination. Excellent yields and good recyclability for amination of small substrates with various organic azides have been achieved.

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 ß-Ln(2-qpH)(SO4)(H2O)2 (ß-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 ß-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 ß-Er and ß-Yb.

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.

Chirality- and pH-Controlled Supramolecular Isomerism in Cobalt Phosphonates and Its Impact on the Magnetic Behavior.

Two pairs of enantiomeric compounds with formulas (S)- or (R)-Co3 (ppap)2 (4,4'-bpy)2 (H2 O)2 ⋅4 H2 O [(S)-1 or (R)-1], (S)- or (R)-Co3 (ppap)2 (4,4'-bpy)2 (H2 O)2 ⋅3 H2 O [(S)- or (R)-2), and related racemic compound Co3 (ppap)2 (4,4'-bpy)2 (H2 O)2 ⋅4 H2 O (rac-3; 4,4'-bpy=4,4'-bipyridine, H3 ppap=3-phenyl-2-[(phosphonomethyl)amino]propanoic acid) are reported. Compounds 1 and rac-3 show identical three-dimensional framework structures, whereas compounds 2 have two-dimensional layer structures. Compounds 1 and 2 are catenation isomers, formation of which is controlled solely by the pH of the reaction mixtures, whereas the formation of isomeric compounds 1 and rac-3 is controlled purely by the chirality of the phosphonate ligand. The magnetic properties of fully dehydrated (S)-1, (S)-2, and rac-3 are highly dependent on both structure and chirality.

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 Šin 1 to 20.0 Šin 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.

Effect of structural isomerism on magnetic dynamics: from single-molecule magnet to single-chain magnet.

This Paper reports the first examples of O-P-O bridged Mn2(salen)2 (salen = N,N'-bis(salicylidene)ethylenediamine) chain compounds, namely, [Mn2(salen)2(2-FC6H4PO3H)](ClO4)·1/2CH3OH (1) and [Mn2(salen)2(4-FC6H4PO3H)](ClO4) (2). The phosphonate ligands adopt a syn-anti bidentate bridging mode in 1 and a syn-syn bidentate bridging mode in 2, originated from the isomeric phosphonate ligands. The different bridging modes cause a significant change in the Mn-O···O-Mn torsion angle over the O-P-O bridge, which are 96.6 and 1.9° for 1 and 2, respectively. As a result, the antiferromagnetic (AF) exchange couplings mediated through the O-P-O pathway are extremely weak in 1, and the overall magnetic behaviors are dominated by the Mn2(salen)2 moieties. Single-molecule magnetic behavior is observed in 1. For compound 2, the AF interaction over the O-P-O bridge is much stronger. The coexistence of metamagnetism and single-chain magnetic behavior is observed for 2.

Enantiopure phosphonic acids as chiral inducers: homochiral crystallization of cobalt coordination polymers showing field-induced slow magnetization relaxation.

This Communication reports, for the first time, that enantiopure phosphonic acids can serve as chirality-inducing agents towards homochiral coordination polymers. Hence homochiral chain compounds (M)- or (P)-Co(SO4)(1,3-bbix)(H2O)3 (1M or 1P) are obtained successfully using an achiral precursor of 1,3-bis((1H-benzo[d]imidazol-1-yl)methyl)benzene (1,3-bbix) in the presence of a catalytic amount of (S)- or (R)-3-phenyl-2-((phosphonomethyl)amino)propanoic acid [(S)- or (R)-2-ppapH3]. Furthermore, compound 1M provides the first example of homochiral cobalt compounds showing field-induced single ion magnet behavior.

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.

Racemic cobalt phosphonates incorporating flexible bis(imidazole) co-ligands.

By incorporating flexible bis(imidazol-1-ylmethyl)benzene (bix) co-ligands, four new racemic cobalt phosphonates with formulae Co3(3-ppap)2(1,4-bix)2(H2O)4·4H2O (1), Co3(3-ppap)2(1,3-bix)2(H2O)4·5H2O (2), Co3(3-ppap)2(1,2-bix)2(H2O)4·4H2O (3) and Co3(ppa)2(1,2-bix)2·4H2O (4) are isolated, where 3-ppapH3 represents 3-phenyl-3-((phosphonomethyl)amino)propanoic acid and ppaH3 is 2-phenyl-2-(phosphonomethylamino)acetic acid. Compounds 1-3 crystallize in the monoclinic space group P21/c and show two-dimensional structures in which the Co3(3-ppap)2 chains are bridged by 1,4-bix, 1,3-bix and 1,2-bix ligands in trans-modes, respectively. Within the chain, a racemic dimer of Co2(3-ppap)2(2-) is found, where the Co atoms are doubly bridged by O-P-O units from the (S)- and (R)-3-ppap(3-) ligands. The dimers are connected by another crystallographically independent Co atom through O-P-O linkages to form an infinite racemic chain. The packing modes of the layers in 1-3 are quite different, however, which are ABAB in the cases of 1 and 3 while ABCDABCD in the case of 2, attributed to the positional isomerism of the bix co-ligands. Compound 4 displays a chain structure in which the 1,2-bix bridges the Co atoms in cis-mode within the chain. Magnetic properties are investigated for all compounds.

Cobalt and copper pyridylmethylphosphonates with two- and three-dimensional structures and field-induced magnetic transitions.

Two novel metal pyridylmethylphosphonates, namely, [Co(4-pmp)] (1) and [Cu(4-pmp)(H2O)] (2), (4-pmpH2 = 4-pyridylmethylphosphonic acid), have been hydrothermally synthesized and characterized by X-ray diffraction, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. In compound 1, each {PO3C} tetrahedron is corner-shared with three {CoNO3} tetrahedra and vice versa, thus forming a one-dimensional (1-D) inorganic chain along the a axis containing 8-membered rings of [(Co-O-P-O)2]. The inorganic chains are further connected by a 4-pmp(2-) ligand, generating a 2-D layered structure. Compound 2 displays a three-dimensional (3-D) framework structure, in which the inorganic layers are pillared by the pyridyl groups of the ligand, generating a 3-D pillared-layered structure. The magnetic properties of 1 and 2 have been studied. Compounds 1 and 2 behave as metamagnets at low temperature. The critical fields are about 70 kOe for 1 and 47 kOe for 2 at 1.8 K.

The O-P-O bridged Mn2(salen)2 chains showing coexistence of single chain magnet and metamagnet behaviour.

Three new chain compounds in which the Mn2(salen)2 dimers are bridged by O-P-O units are reported, namely, [Mn2(salen)2(C6H9PO3H)](ClO4) (1), [Mn2(salen)2(C6H5PO3H)](ClO4) (2) and [Mn2(salen)2(C6H5PHO2)](ClO4) (3). The phosphonate or phosphinate ligands adopt a syn-anti bidentate bridging mode in 1, while a syn-syn bidentate bridging mode in 2 and 3, thus leading to a difference in the Mn-O···O-Mn torsion angle over the O-P-O bridge. Compound 1 shows a paramagnetic behavior with dominant antiferromagnetic interactions. In compounds 2 and 3, the antiferromagnetic interactions through the O-P-O bridges are considerably stronger than those in 1. They display coexistence of single chain magnet (SCM) behaviour with a spin canted structure and metamagnetism at low temperature. The results demonstrate that the magnetic dynamics of the O-P-O bridged Mn2(salen)2 chains may be modulated by selecting suitable phosphonate or phosphinate ligands.

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.

Co(II) and Ni(II) complexes based on anthraquinone-1,4,5,8-tetracarboxylic acid (H4AQTC): canted antiferromagnetism and slow magnetization relaxation in {[Co2(AQTC)(H2O)6]·6H2O}.

Three coordination polymers {[Co2(AQTC)(H2O)6]·6H2O}n (1), {[M2(AQTC)(bpym)(H2O)6]·6H2O}n (M = Co(2), Ni(3)) have been synthesized and structurally characterized, where H4AQTC is anthraquinone-1,4,5,8-tetracarboxylic acid and bpym is 2,2'-bipyrimidine. Complex 1 features a 3-D structure, where layers of Co2(AQTC) are cross-linked by Co-H2O chains. Complexes 2 and 3 are isostructural and display 1-D chain structures. The chains are connected through hydrogen-bonding interactions to form 3-D supramolecular structures. Magnetic properties of these complexes are investigated. Compound 1 shows canted antiferromagnetism and slow relaxation below 4.0 K. For complexes 2 and 3, dominant antiferromagnetic interactions are observed. The luminescent properties of the three complexes are investigated as well.