Synthesis, structure and magnetocaloric properties of a new two-dimensional gadolinium(III) coordination polymer based on azobenzene-2,2',3,3'-tetracarboxylic acid.

A new Gd3+ coordination polymer (CP), namely, poly[diaqua[µ4-1'-carboxy-3,3'-(diazene-1,2-diyl)dibenzene-1,2,2'-tricarboxylato]gadolinium(III)], [Gd(C16H7N2O8)(H2O)2]n, (I), has been synthesized hydrothermally from Gd(NO3)3·6H2O and azobenzene-2,2',3,3'-tetracarboxylic acid (H4abtc). The target solid has been characterized by single-crystal and powder X-ray diffraction, elemental analysis, IR spectroscopy and susceptibility measurements. CP (I) crystallizes in the monoclinic space group C2/c. The structure features a 4-connected topology in which Gd3+ ions are connected by carboxylate groups into a linear chain along the monoclinic symmetry direction. Adjacent one-dimensional aggregates are bridged by Habtc3- ligands to form a two-dimensional CP in the (10-1) plane. A very short hydrogen bond [O...O = 2.4393 (4) Å] links neighbouring layers into a three-dimensional network. A magnetic study revealed antiferromagnetic Gd...Gd coupling within the chain direction. CP (I) displays a significant magnetocaloric effect (MCE), with a maximum -ΔSm of 27.26 J kg-1 K-1 for ΔH = 7 T at 3.0 K. As the MCE in (I) exceeds that of the commercial magnetic refrigerant GGG (Gd3Ga5O12, -ΔSm = 24 J kg-1 K-1, ΔH = 30 kG), CP (I) can be regarded as a potential cryogenic material for low-temperature magnetic refrigeration.

A novel three-dimensional tetranuclear CoII coordination polymer with water hexamers based on the V-shaped tetracarboxylate ligand 4-(2,4-dicarboxylatophenoxy)phthalate.

A new coordination polymer (CP), namely, poly[[diaquatris[µ2-1,4-bis(1H-imidazol-1-yl)benzene]bis[µ6-4-(2,4-dicarboxylatophenoxy)phthalato]tetracobalt(II)] hexahydrate], {[Co4(C16H6O9)2(C12H10N4)3(H2O)2]·6H2O}n, has been synthesized by solvothermal reaction. The CP was fully characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. It presents a three-dimensional (3D) structure based on tetranuclear CoII secondary building units (SBUs) with a tfz-d net and point symbol (43)2(46·618·84). The 4-(2,4-dicarboxyphenoxy)phthalic acid (H4dcppa) ligands are completely deprotonated and link {Co4(COO)4}4- SBUs into two-dimensional (2D) layers. Furthermore, adjacent layers are connected by 1,4-bis(1H-imidazol-1-yl)benzene (bib) ligands, giving rise to a 3D supramolecular architecture. Interestingly, there are numerous elliptical cavities in the CP where isolated unique discrete hexameric water clusters have been observed. The results of thermogravimetric and magnetic analyses are described in detail.

A new family of lanthanide coordination polymers based on 3,3'-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoate: synthesis, crystal structures and magnetic and luminescence properties.

Six two-dimensional (2D) coordination polymers (CPs), namely, poly[{µ5-3,3-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoato-κ6O1:O1':O3,O3':O5:O5'}bis(N,N-dimethylformamide-κO)lanthanide(III)], [Ln(C21H11O8)(C3H7NO)2]n, with lanthanide/Ln = cerium/Ce for CP1, praseodymium/Pr for CP2, neodymium/Nd for CP3, samarium/Sm for CP4, europium/Eu for CP5 and gadolinium/Gd for CP6, have been prepared by solvothermal methods using the ligand 3,3'-[(5-carboxy-1,3-phenylene)bis(oxy)]dibenzoic acid (H3cpboda) in the presence of Ln(NO3)3. The complexes were characterized by single-crystal X-ray and powder diffraction, IR spectroscopy, elemental analysis and thermogravimetric analysis (TGA). All the structures of this family of lanthanide CPs are isomorphous with the triclinic space group P-1 and reveal that they have the same 2D network based on binuclear LnIII units, which are further extended via interlayer C-H...π interactions into a three-dimensional supramolecular structure. The carboxylate groups of the cpboda3- ligands link adjacent LnIII ions and form binuclear [Ln2(RCOO)4] secondary building units (SBUs), in which each binuclear LnIII SBU contains four carboxylate groups from different cpboda3- ligands. Moreover, with the increase of the rare-earth Ln atomic radius, the dihedral angles between the aromatic rings gradually increase. Magnetically, CP6 shows weak antiferromagnetic coupling between the GdIII ions. The solid-state luminescence properties of CP2, CP5 and CP6 were examined at ambient temperature and CP5 exhibits characteristic red emission bands derived from the Eu3+ ion (CIE 0.53, 0.31), with luminescence quantum yields of 22%. Therefore, CP5 should be regarded as a potential optical material.

Structural diversity, magnetic properties and luminescence of NiII, CoII and ZnII coordination polymers derived from 3,3'-[(5-carboxy-1,3-phenylene)bis(oxy)]dibenzoic acid and 1,10-phenanthroline.

Three novel coordination polymers (CPs), namely poly[[di-µ-aqua-bis{µ4-3,3'-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoato-κ5O1:O1',O3:O5:O5'}bis(1,10-phenanthroline-κ2N,N')trinickel(II)] dimethylformamide 1.5-solvate trihydrate], {[Ni3(C21H11O8)2(C12H8N2)2(H2O)2]·1.5C3H7NO·3H2O}n, (I), poly[[di-µ-aqua-bis{µ4-3,3'-[(5-carboxylato-1,3-phenylene)bis(oxy)]dibenzoato-κ5O1:O1',O3:O5:O5'}bis(1,10-phenanthroline-κ2N,N')tricobalt(II)] diethylamine disolvate tetrahydrate], {[Co3(C21H11O8)2(C12H8N2)2(H2O)2]·2C2H7N·4H2O}n, (II), and catena-poly[[aqua(1,10-phenanthroline-κ2N,N')zinc(II)]-µ-5-(3-carboxyphenoxy)-3,3'-oxydibenzoato-κ2O1:O3], [Zn(C21H12O8)(C12H8N2)(H2O)]n, (III), have been synthesized by the reaction of different metal ions (Ni2+, Co2+ and Zn2+), 3,3'-[(5-carboxy-1,3-phenylbis(oxy)]dibenzoic acid (H3cpboda) and 1,10-phenanthroline (phen) under solvothermal conditions. All the CPs were characterized by elemental analysis, single-crystal and powder X-ray diffraction, FT-IR spectroscopy and thermogravimetric analysis. Complexes (I) and (II) have isomorphous structures, featuring similar linear trinuclear structural units, in which the central NiII/CoII atom is located on an inversion centre with a slightly distorted octahedral [NiO6]/[CoO6] geometry. This comprises four carboxylate O-atom donors from two cpboda3- ligands and two O-atom donors from bridging water molecules. The terminal NiII/CoII groups are each connected to the central NiII/CoII cation through two µ1,3-carboxylate groups from two cpboda3- ligands and one water bridge, giving rise to linear trinuclear [M3(µ2-H2O)2(RCOO)4] (M = Ni2+/Co2+) secondary building units (SBUs) and the SBUs develop two-dimensional-networks parallel to the (100) plane via cpboda3- ligands with new (32·4)2(32·83·9)2(34·42.82·94·103) topological structures. Zinc complex (III) displays one-dimensional coordination chains and the five-coordinated Zn atom forms a distorted square-pyramidal [ZnO3N2] geometry, which is completed by two carboxylate O-atom donors from two distinct Hcpboda2- ligands, one O atom from H2O and two N atoms from a chelating phen ligand. Magnetically, CP (I) shows weak ferromagnetic interactions involving the carboxylate groups, and bridging water molecules between the nickel(II) ions, and CP (II) shows antiferromagnetic interactions between the Co2+ ions. The solid-state luminescence properties of CP (III) were examined at ambient temperature and the luminescence sensing of Cr2O72-/CrO42- anions in aqueous solution for (III) has also been investigated.

Luminescent and magnetic bifunctional coordination complex based on a chiral tartaric acid derivative and europium.

A new mononuclear europium complex incorporating the (+)-di-p-toluoyl-D-tartaric acid (D-H2DTTA) ligand, namely, catena-poly[tris{µ2-3-carboxy-2,3-bis[(4-methylphenyl)carbonyloxy]propanoato}tris(methanol)europium(III)], [Eu(C20H17O8)3(CH3OH)3]n, (I), has been synthesized and characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. The structure analysis indicates that complex (I) crystallizes in the trigonal space group R3 and exhibits an infinite one-dimensional chain structure, in which the Eu3+ ion is surrounded by six O atoms from six D-HDTTA- ligands and three O atoms from three coordinated methanol molecules, thus forming a tricapped trigonal prism geometry. The D-H2DTTA ligand is partially deprotonated and adopts a µ1,6-coordination mode via two carboxylate groups to link adjacent Eu3+ ions, affording an infinite one-dimensional propeller-shaped coordination polymer chain along the c axis, with an Eu...Eu distance of 7.622 (1) Å. Moreover, C-H...π interactions lead to the formation of helical chains running along the c axis and the whole structure displays a snowflake pattern in the ab plane. The circular dichroism spectrum confirms the chirality of complex (I). The solid-state photoluminescence properties were also investigated at room temperature and (I) exhibits characteristic red emission bands derived from the Eu3+ ion (CIE 0.63, 0.32), with a reasonably long lifetime of 0.394 ms, indicating effective energy transfer from the ligand to the metal centre. In addition, a magnetic investigation reveals single-ion magnetic behaviour. The spin-orbit coupling parameter (λ) between the ground and excited states is fitted to be 360 (2) cm-1 through Zeeman perturbation. Therefore, complex (I) may be regarded as a chiral optical-magneto bifunctional material.

Structural diversity, magnetic property, or luminescence sensing of Co(ii) and Cd(ii) coordination polymers derived from designed 3,3'-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid.

Five novel coordination polymers (CPs), formulated as {[Co3(µ4-cpboda)2(µ1,1-OH2)2(2,2-bipy)2]·1.5DMF·2H2O}n (1), {[Co3(µ3-cpboda)2(4,4'-bpy)3(H2O)2]·4H2O}n (2), {[Co(µ2-H2cpboda)2(1,4-bib)3(H2O)2]·H2O·DMF·1.5HCOOH}n (3), [Cd(µ3-Hcpboda)(1,4-bib)]n (4), and {[Cd3(µ4-cpboda)2(µ1,1-OH2)2(phen)2]·2DMF·1.5H2O}n (5) (H3cpboda = 3,3'-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid, 2,2-bipy = 2,2-bipyridine, 4,4'-bpy = 4,4'-bipyridine, 1,4-bib = 1,4-di(1H-imidazol-1-yl)benzene, phen = 1,10-phenanthroline) have been synthesized under solvothermal conditions and characterized by elemental analyses (EAs), single-crystal X-ray diffraction analyses, X-ray powder diffraction analyses (PXRD), FT-IR spectra, and thermogravimetric analyses (TGAs). The structural analyses reveal that these complexes have four 2D coordinate polymers and one 3D framework, in which metal ions are in octahedral coordination geometries in 1-3 and 5, but seven-coordinated disordered pentagonal bipyramids in 4. Complexes 1 and 5 represent linear trinuclear [M3(µ1,1-OH2)2(µ1,3-COO)4] SBUs in 1 (M = Co(ii)) and in 5 (M = Cd(ii)) based on a 3,4,6-connected net with a point symbol (32·4)2(32·83·9)2(34·42·82·94·103) net, complex 2 exhibiting a (3-c)2(4-c)(4-c)2 3D structure with the (52·6·82·9)2(52·62·92)(52·6)2 topology and complexes 3 and 4 having a novel 2D framework with the point symbol of (44·62). Magnetization analyses disclose the antiferromagnetic (AF) behaviors between Co(ii) ions in complexes 1 & 3 and S = 3/2 (Co2+) spin Heisenberg chains with alternating magnetic sequences (F/F/AF)n in 2. Fluorescence measurements indicate that 4 and 5 are promising luminescence sensors for the detection of CrO42- and Cr2O72- anions in aqueous solution.

A thermally stable three-dimensional cobalt(II) coordination polymer based on the V-shaped ligand 4-(4-carboxyphenoxy)isophthalate.

A new cobalt(II) coordination polymer (CP), poly[[bis[µ6-4-(4-carboxylatophenoxy)benzene-1,3-dicarboxylato-κ6O1:O1:O3:O3':O4:O4']bis(1,10-phenanthroline-κ2N,N')tricobalt(II)] 0.72-hydrate], {[Co3(C15H7O7)2(C12H8N2)2]·0.72H2O}n, (I), is constructed from CoII ions and 4-(4-carboxyphenoxy)isophthalate (cpoia3-) and 1,10-phenanthroline (phen) ligands. Based on centrosymmetric trinuclear [Co3(phen)2(COO)6] secondary building units (SBUs), the structure of (I) is a three-dimensional CP with a (3,6)-connected net and point symbol (42.6)2(44.62.87.102). The positions of four [Co3(phen)2(COO)6] SBUs and four cpoia3- ligands reproduce a Chinese-knot-shaped arrangement along the ab plane. (I) has been characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD) and thermostability analysis. It shows a good thermal stability from room temperature to 673 K. In addition, the temperature dependence of the magnetic properties was measured.

Irreversible solvent-assisted structural transformation in 3D metal-organic frameworks: Structural modification and enhanced iodine-adsorption properties.

In this work, we demonstrate a solvent-assisted structural transformation between two 3D metal-organic frameworks (MOFs) ([Zn4(α-bptc)2(H2O)3]n (1) → {[Zn2(α-bptc)(H2O)4]·(pra)}n (2)) (α-H4bptc = 2,3,3',4'-biphenyl tetra-carboxylic acid and pra = pyridin-2-amine) at room temperature by immersing complex 1 in a mother solution. The structural transformation involves not only solvent exchange but also the cleavage and formation of coordination bonds, which is confirmed by infrared spectroscopy, single-crystal X-ray diffraction analysis, powder X-ray diffraction patterns, and thermogravimetric analysis. Structural analyses revealed that significant modifications occurred during the transformation including the changes in lattice parameters, unit cell volume, space group, coordination number, secondary building units, and topological type. In the case of drastic structural transitions, significant changes in properties were also observed. Complex 2 displayed the interesting uptake and release of iodine with the changes in visible color, UV and fluorescence spectra, and fully reversible I2 uptake of 8.5 mg g-1, which further suggested about its future application as iodine absorbing material.

A three-dimensional twofold interpenetrated cobalt(II) MOF containing a flexible carboxylate-based ligand: synthesis, structure and magnetic properties.

The design and synthesis of coordination polymers (CPs) have attracted much interest due to the intriguing diversity of their architectures and topologies. The functional solid catena-poly[µ2-aqua-triaqua{µ4-5-[4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylato}{µ3-5-[4-carboxyphenoxy)methyl]benzene-1,3-dicarboxylato}dicobalt(II)], [Co2(C16H10O7)2(H2O)4]n or [Co2(HL)2(µ2-H2O)(H2O)3]n, was synthesized successfully by self-assembly of CoII ions with 5-[(4-carboxyphenoxy)methyl]isophthalic acid (H3L). The title compound was obtained under hydrothermal conditions and exhibits a twofold interpenetrated three-dimensional skeleton with hms 3,5-conn topology according to the cluster representation for valence-bonded metal-organic frameworks (MOFs). It has been characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis and susceptibility measurements. The antiferromagnetic coupling between adjacent CoII centres occurs via superexchange through the ligands.

Synthesis, crystal structure and characterization of a three-dimensional CdII coordination polymer constructed from 2,5-bis(1H-1,2,4-triazol-1-yl)terephthalate.

Bifunctional organic ligands are very popular for the design of coordination polymers because they allow the formation of a great diversity of structures. In the title coordination polymer, the new bifunctional inversion-symmetric ligand 2,5-bis(1H-1,2,4-triazol-1-yl)terephthalic acid (abbreviated as H2bttpa) links CdII cations, giving rise to the three-dimensional CdII coordination polymer catena-poly[diaqua[µ4-2,5-bis(1H-1,2,4-triazol-1-yl)terephthalato-κ4O1:O4:N4:N4']cadmium(II)], [Cd(C12H6N6O4)(H2O)2]n or [Cd(bttpa)(H2O)2]n. The asymmetric unit consists of half a CdII cation, half a bttpa2- ligand and one coordinated water molecule. The CdII cation is located on a twofold axis and is hexacoordinated in a distorted octahedral environment of four O and two N atoms. Four different bttpa2- ligands contribute to this coordination, with two carboxylate O atoms in trans positions and two triazole N atoms in cis positions. Two aqua ligands in cis positions complete the coordination sphere. The fully deprotonated bttpa2- ligand sits about a crystallographic centre of inversion and links two CdII cations to form a chain in a µ2-terephthalato-κ2O1:O4 bridge. This chain extends in the other two directions via the triazole heterocycles, producing a three-dimensional framework. O-H...O hydrogen bonds and weak C-H...N interactions stabilize the three-dimensional crystal structure. The FT-IR spectrum, X-ray powder pattern, thermogravimetric behaviour and solid-state photoluminescence of the title polymer have been investigated. The photoluminescence is enhanced and red-shifted with respect to the uncoordinated ligand.

A new family of 1D, 2D and 3D frameworks aggregated from Ni5, Ni4 and Ni7 building units: synthesis, structure, and magnetism.

Three new Ni(ii)-clusters based on a Y-shaped ligand (biphenyl-3,4',5-tricarboxylate, H3BPT), [Ni5(HBPT)4(OH)2(H2O)12]n (), [Ni4(BPT)2(OH)2(H2O)6]n·4nH2O (), and [Ni7(BPT)2(1,4-bib)2(OH)6(HCO2)2]n·3nH2O () (1,4-bib = 1,4-bi(1H-imidazol-1-yl)benzene), have been synthesized under solvothermal conditions. They were studied by infrared spectroscopy (IR), single crystal X-ray diffraction, thermogravimetric analysis (TGA), and magnetochemistry. The complexes contain low nuclear Ni-clusters as building units (BUs). Structurally, in , the cluster BUs of [Ni5(µ3-OH)2](8+) can be viewed as two reverse triangles sharing a common vertex, which are connected by the partially deprotonated µ2-η(1):η(1)-HBPT(2-) forming 1D chains. The BUs of [Ni4(µ3-OH)2](6+) clusters in can be considered as two reverse triangles sharing a common edge and extended by deprotonated µ6-η(1):η(1):η(1):η(1):η(2)-BPT(3-) constructing a 2D framework. The 3D framework of complex consists of a [Ni7(µ3-OH)4(R-COO)7(HCO2)3] cluster BUs with fully deprotonated µ5-η(1):η(1):η(1):η(1):η(1):η(1)-BPT(3-) and 1,4-bib ligands. In addition, TGA reveals that the complexes are stable in the range of 293-548 K. Magnetostructural analyses indicate ferromagnetic coupling of J1 = 1.85(3) and J2 = 2.25(4) cm(-1) in and J = 5.76(6) cm(-1) in , whereas magnetic parameters J1 = -2.64(3), J2 = -23.22(19) and J3 = 12.02(5) cm(-1) indicate an alternating magnetic chain (AF/F) in .

A three-dimensional mixed-valence Cu(II)/Cu(I) coordination polymer constructed from biphenyl-3,4',5-tricarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands.

Coordination polymers (CPs) built by coordination bonds between metal ions/clusters and multidentate organic ligands exhibit fascinating structural topologies and potential applications as functional solid materials. The title coordination polymer, poly[diaquabis(µ4-biphenyl-3,4',5-tricarboxylato-κ(4)O(3):O(3'):O(4'):O(5))tris[µ2-1,4-bis(1H-imidazol-1-yl)benzene-κ(2)N(3):N(3')]dicopper(II)dicopper(I)], [Cu(II)2Cu(I)2(C15H7O6)2(C12H10N4)3(H2O)2]n, was crystallized from a mixture of biphenyl-3,4',5-tricarboxylic acid (H3bpt), 1,4-bis(1H-imidazol-1-yl)benzene (1,4-bib) and copper(II) chloride in a water-CH3CN mixture under solvothermal reaction conditions. The asymmetric unit consists of two crystallographically independent Cu atoms, one of which is Cu(II), while the other has been reduced to the Cu(I) ion. The Cu(II) centre is pentacoordinated by three O atoms from three bpt(3-) ligands, one N atom from a 1,4-bib ligand and one O atom from a coordinated water molecule, and the coordination geometry can be described as distorted trigonal bipyramidal. The Cu(I) atom exhibits a T-shaped geometry (CuN2O) coordinated by one O atom from a bpt(3-) ligand and two N atoms from two 1,4-bib ligands. The Cu(II) atoms are extended by bpt(3-) and 1,4-bib linkers to generate a two-dimensional network, while the Cu(I) atoms are linked by 1,4-bib ligands, forming one-dimensional chains along the [20-1] direction. In addition, the completely deprotonated µ4-η(1):η(1):η(1):η(1) bpt(3-) ligands bridge one Cu(I) and three Cu(II) cations along the a (or [100]) direction to form a three-dimensional framework with a (10(3))2(10)2(4(2).6.10(2).12)2(4(2).6.8(2).10)2(8) topology via a 2,2,3,4,4-connected net. An investigation of the magnetic properties indicated a very weak ferromagnetic behaviour.

4-Bromo-2-[(phenyl-imino)-meth-yl]phenol.

The title compound, C13H10BrNO, is essentially planar (r.m.s. deviation = 0.026 Å) and the dihedral angle between the planes of the two aryl rings is 1.5 (3)°. An intra-molecular O-H⋯N hydrogen bond generates an S(6) ring.

4-[(5-Bromo-2-hy-droxy-benzyl-idene)amino]-3-ethyl-1H-1,2,4-triazole-5(4H)-thione.

The title compound, C11H11BrN4OS, crystallized as a racemic twin with two symmetry-independent mol-ecules in the asymmetric unit. The dihedral angles between the benzene and triazole rings of the two independent mol-ecules are 56.41 (18) and 54.48 (18)°. An intra-molecular O-H⋯N hydrogen bond occurs in each mol-ecule. In the crystal, pairs of symmetry-independent mol-ecules are linked by pairs of almost linear N-H⋯S hydrogen bonds, forming cyclic dimers characterized by an R 2 (2)(8) motif. There are weak π-π inter-actions between the benzene rings of symmetry-independent mol-ecules, with a centroid-centroid distance of 3.874 (3) Å.

4-[(5-Chloro-2-hy-droxy-benzyl-idene)amino]-3-ethyl-1H-1,2,4-triazole-5(4H)-thione.

The title compound, C11H11ClN4OS, crystallizes with two mol-ecules, A and B, in the asymmetric unit in which the dihedral angles between the triazole and benzene rings are 54.6 (3) and 56.0 (3)°. Both mol-ecules feature an intra-molecular O-H⋯N hydrogen bond, which generates an S(6) ring. In the crystal, A-B dimers are linked by pairs of weak C-H⋯S hydrogen bonds along with π-π stacking inter-actions between the triazole rings [centroid-centroid separations = 3.631 (3) and 3.981 (4)Å]. N-H⋯S hydrogen bonds link the dimers into [100] chains, which feature R 2 (2)(8) loops.

2-[(E)-(4-Bromo-phenyl)imino-methyl]-4-chloro-phenol.

In the title compound, C13H9BrClNO, the dihedral angle between the substituted benzene rings is 44.25 (11)°. There are strong intra-molecular O-H⋯N hydrogen bonds, which generate S(6) rings, and also inter-molecular Cl⋯Cl [3.431 (3) Å] and Br⋯ Br [3.846 (1) Å] contacts. The crystal packing a C-H⋯O and C-H⋯π inter-actions.

Analogy to a Chinese knot in an ion-pair copper(II)-neodymium(III) complex based on a hexadentate Schiff base condensation product of 5-bromosalicylaldehyde and glycylglycine.

Self-assembly of CuCl2, NdCl3, 5-bromosalicylaldehyde and glycylglycine yields the ion-pair copper(II)-neodymium(III) complex, poly[[decaaquabis[µ3-2-({2-[(5-bromo-2-oxidobenzylidene)amino]acetyl}azanidyl)acetato]bis[µ2-2-({2-[(5-bromo-2-oxidobenzylidene)amino]acetyl}azanidyl)acetato]tetracopper(II)dineodymium(III)] bis{[2-({2-[(5-bromo-2-oxidobenzylidene)amino]acetyl}azanidyl)acetato]cuprate(II)} tetradecahydrate], {[Cu4Nd2(C11H8BrN2O4)4(H2O)10][Cu(C11H8BrN2O4)]2·14H2O}n. The anion is planar and mononuclear, showing an approximately square-planar coordination of the metal atom, while the cation is a hexanuclear centrosymmetric transition metal-lanthanide (Cu-Nd) heterometallic complex, with the independent copper cations in square-planar and square-pyramidal coordinations. The asymmetric unit comprises one half of this cation, one anion and seven solvent water molecules. The positions of the six metal centres in the cation reproduce a Chinese knot arrangement. The dipeptidic Schiff base releases three H atoms and can act as a tetradentate, a pentadentate or a hexadentate ligand. Longer interactions between the pentadentate ligands and the Jahn-Teller Cu(II) cation link the hexanuclear aggregates into cationic chains in the [010] direction in which 14- and 22-membered subloops occur. Extensive hydrogen bonding in three dimensions involves both the coordinated and the solvent water molecules.

4-[(5-Bromo-2-hy-droxy-benzyl-idene)amino]-3-propyl-1H-1,2,4-triazole-5(4H)-thione.

The asymmetric unit of the title compound, C(12)H(13)BrN(4)OS, contains two independent mol-ecules in which the dihedral angles between the triazole and benzene rings are 2.9 (3) and 7.5 (3)°. The thione group is of the form R(2)C=S. An intra-molecular O-H⋯N hydrogen bond occurs in each mol-ecule. The crystal structure features weak N-H⋯S inter-actions and π-π stacking of the benzene rings [centroid-centroid distance = 3.667 (3) Å].

The crucial role of C-H...O and C=O...pi interactions in the building of three-dimensional structures of dicarboxylic acid-biimidazole compounds.

The supramolecular architectures of three dicarboxylic acid-biimidazole compounds, namely, 2,2'-biimidazolium malonate, C(6)H(8)N(4)(2+).C(3)H(2)O(4)(2-), (I), 2,2'-bi(1H-imidazole) succinic acid, C(6)H(6)N(4).C(4)H(6)O(4), (II), and 2,2'-biimidazolium 2,2'-iminiodiacetate chloride, C(6)H(8)N(4)(2+).C(4)H(6)NO(4)(-).Cl(-), (III), are reported. The crystal structures are assembled by the same process, namely double conventional N-H...O or O-H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair-aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C-H...O interactions. The C=O...pi interactions involved in stacking the tapes in (II) and the C-H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively.

Bis(2,2'-bi-1H-imidazole-κN,N)(thio-cyanato-κN)copper(II) chloride.

In the title salt, [Cu(NCS)(C(6)H(6)N(4))(2)]Cl, the Cu(II) atom adopts a five-coordinated square-pyramidal geometry consisting of an N atom from a thio-cyanate anion and four N atoms from two chealting biimidazole ligands. The thio-cyanate ligand occupies the axial position and is, like the Cu(II) centre, located on a mirror plane. The cation and anion are linked into a linear chain by N-H⋯S and N-H⋯Cl hydrogen bonds.