A new macrocyclic oxamido carboxylate metalloligand was designed and three heteronuclear coordination polymers of the metalloligand and metal nodes Cu2+, Zn2+ and Cd2+ were prepared. X-ray single crystal analyses (CIF files CCDC nos. 1025722–1025724 for I–III) revealed that multiple favourable features endowed the metalloligand with a strong power to force the metal nodes to generate 1D helical coordination polymers. Thermogravimetric analyses showed that the complexes with Cu2+ and Zn2+ nodes exhibited moderate thermal stability. The three complexes were also characterized by IR spectra and PXRD.

A new macrocyclic oxamido-nickle(II) complex Na2NiL was synthesized. L denotes the doubly deprotonated forms of (13Z, 19Z)-16-methyl-6,7-dioxo-5,6,7,8-tetrahydrotriben-zo[b,f,l][1,4,8,11]tetraazacyclotetradecine- 13,20-dicarboxylate. Based on the complex ligand Ni(L2–), two heterometallic complexes [Ca2(NiL)2(H2O)8] · 10H2O (I) and [Co(NiL)2(H2O)2][Co(H2O)6] · 2.8H2O (II) were prepared. X-ray single crystal analyses (CCDC nos. 914618 (I), 914616 (II)) revealed that [Ca2(NiL)2(H2O)8] in I is a molecular box and the trinuclear complex anion [Co(NiL)2(H2O)2]2–in II is centrosymmetric. Thermogravimetric analyses showed that I exhibited moderately good stability and Co(II) catalyzed the thermal decomposition of II.

Three new coordination polymers, {[Mg(NiL1)(H2O)3]·CH3CH2OH·2H2O}n (1), {[Zr2(NiL1)2(OH)4(H2O)2]·8H2O}n (2) and {[Pb(NiL1)(H2O)2]·3H2O}n (3), were prepared from a macrocyclic metalloligand NiL1. H2L1 denotes 1,4-dihydro-2,3-dioxo-5,6:- 9,10:13,14-tribenzo[1,4,8,11]tetraazacyclotetradeca-7,11-diene-7,12-dicarboxylate. Single crystal X-ray diffraction studies revealed that 1, 2 and 3 have infinite single stranded helical structures. In each of the three compounds, NiL1 plays the role of the bridging ligand by chelating one node via two oxamido carbonyls and binding to another through a carboxylate oxygen atom. 1D helical coordination polymers of macrocyclic metalloligands and those of Mg2+, Zr4+ and Pb2+ nodes are all not common. The generation of the three complexes manifests further that NiL1 is a bridging ligand unprecedentedly powerful in directing the formation of single stranded helical coordination polymers. It is the combination of multiple features of NiL1 that are responsible for its high powerfulness of inducing these helical structures. The outcome implies that combining multiple features surporting the formation of such helices into one ligand should be an effective strategy for the design and selection of bridging ligands powerful for the production of such structures.

A porous metal–organic material of the doubly deprotonated form of a new bis(aroylhydrazone) ligand (L12−) was self-assembled from 2,3-butanedione, isonicotinoyl hydrazine and lead nitrate. X-ray single crystal analysis revealed that six L12− and six Pb2+ are arranged alternately to form a metallomacrocycle in the porous material. Weak coordination bonds together with π⋯π interactions connect the metallomacrocycle units rather strongly into two interpenetrating unique 3D networks. TG, PXRD and dehydration investigation showed that all of the coordination and guest water molecules in the material can be removed upon heating to give the activated structure with vacant pores and open Pb sites. The material can reversibly adsorb/desorb water and small alcohol molecules.

The high rigidity, asymmetric exoditopic coordination mode, angular orientations of the coordination tops and good coordination adaptability of the metalloligand, the π⋯π stacking between the adjacent metalloligands in the polymeric chains and the coordination characteristics of the nodes are responsible for the formation of the eight 1D helices.

A mononuclear macrocyclic oxamide complex CuL was used as a new metalloligand to prepare polynuclear complexes, by which a new tetranuclear complex {Mn[CuL(ClO4)]3}·H3O·2.5H2O (1) and a new trinuclear complex {Cu[CuL(CH3OH)]2(ClO4)2} (2) were obtained (H2  L = dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo-[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate). X-ray single crystal analysis revealed that every Cu(II) centre of the CuL metalloligand is coordinated by the four N atoms from the macrocyclic oxamide ligand and an O atom from a ClO4− anion in 1 or a CH3OH molecule in 2, with the four N atoms forming the square base and the O atom occupying the vertex of the distorted square pyramidal coordination geometry. Plasmid DNA cleavage experiments showed that complexes CuL, 1 and 2 all have cleavage activities in the absence of any added oxidizing agents and that 2 has the highest cleavage efficiency among the three complexes in Tris–HCl buffer. Synergistic effects between the Cu(II) centers may contribute to the higher DNA cleavage efficiency of 2 in Tris–HCl buffer. Magnetism studies over the temperature range 2–300 K showed pronounced antiferromagnetic interactions between the oxamido-bridged metal centers in both 1 and 2.Graphical abstractThe new tetranuclear complex and trinuclear complex both contain a new macrocyclic oxamide metalloligand. The metalloligand and the two polynuclear complexes all have DNA cleavage activities. Antiferromagnetic interactions exist between the oxamido-bridged metal centers in the two polynuclear complexes.Highlights► The two new polynuclear complexes contain a new macrocyclic oxamide metalloligand. ► They are a tetranuclear [MnIICuII3] complex and a trinuclear [CuII3] complex. ► The metalloligand and the two polynuclear complexes all have DNA cleavage activities. ► Antiferromagnetic interactions exist between the oxamido-bridged metal centers in the two polynuclear complexes.

Six new complexes 1–6 with the common formula [M(NiL)4][M(NCS)4] (M = Mn, Fe, Co, Ni, Cu and Zn for 1, 2, 3, 4, 5 and 6, respectively; the same below) were synthesised and structurally characterised by X-ray single crystal analysis. NiL acts as a complex ligand. L denotes the dianion of dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo-[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. Each M(II) centre of the [M(NiL)4]2 + complex cations in 1–6 adopts a distorted square-antiprism coordination geometry with a O8 donor set. All the MO bonds in the six complexes are abnormally long (2.444–2.528 Å). M(II) complexes having such weak coordination environments have not been reported, and eight-coordinate M(II) complexes with all the eight oxygen donor atoms coming from metalloligands have also not been documented. Each M(II) centre of the [M(NCS)4]2 − anions in 1–6 has a distorted tetrahedral coordination environment with a N4 donor set. Theoretical calculations for the bond dissociation energies (BDEs) of the MO semi coordinate bonds were performed using density functional theory at B3LYP level. The calculated BDE values are 23.8, 25.5, 20.0, 22.3, 19.8 and 18.2 kcal/mol for 1, 2, 3, 4, 5 and 6, respectively. The BDE values suggest that the long MnO bonds in 1 and the long CoO bonds in 3 are significantly weaker than their significantly shorter counterparts in the formerly reported [Mn(NiL)2(NCS)2] and [Co(NiL)2(NCS)2], respectively.All the M(II) centres (M = Mn, Fe, Co, Ni, Cu or Zn) in the six complexes adopt coordination environments featuring eightfold oxygen coordination and all the MO bonds being abnormally long.Highlights► The six complexes have centres adopting unprecedented coordination environments. ► All the MO bond distances are abnormally long. ► M(II) centres having the high coordination number of 8 often form long MO bonds. ► Complexes with weak coordination environments would present different properties. ► The BDEs suggest that the long MO bonds in 1–6 are significantly weak.

Tetrapod-shaped zinc oxide (T-ZnO) whiskers and boron nitride (BN) flakes were employed to improve the thermal conductivity of phenolic formaldehyde resin (PF). A striking synergistic effect on thermal conductivity of PF was achieved. The in-plane thermal conductivity of the PF composite is as high as 1.96 W m−1 K−1 with 30 wt.% BN and 30 wt.% T-ZnO, which is 6.8 times higher than that of neat PF, while its electrical insulation is maintained. With 30 wt.% BN and 30 wt.% T-ZnO, the flexural strength of the composite is 312.9% higher than that of neat PF, and 56.2% higher that of the PF composite with 60 wt.% BN. The elongation at break is also improved by 51.8% in comparison with that of the composite with 60 wt.% BN. Such a synergistic effect results from the bridging of T-ZnO whiskers between BN flakes facilitating the formation of effective thermal conductance network within PF matrix.

New macrocyclic oxamide complexes suitable for being used as metalloligands to link metal ions were designed. Six coordination compounds containing a member of the new metalloligands as the bridging ligand were prepared. X-ray single crystal analysis revealed that the six compounds include a dodecanuclear structure, three 1D helical chainlike coordination polymers and two 2D layered coordination polymers. All of the nickel centres of the metalloligands in the six compounds are exposed on both sides of the corresponding square coordination planes, and all the bonds (Ni–N) formed by the open metal sites are significantly short (ranging from 1.848 to 1.888 Å). Thermogravimetric analysis of four of the six compounds showed that their thermal stabilities differ to a considerable extent and that the Na+-containing dodecanuclear structure, which began to decompose at ca. 400 °C, has the highest thermal stability.

Three new double-chain coordination polymers {[Pr(NiL1)2(H2O)3](ClO4)3·2H2O}∞ (1), {[Sm(NiL1)2(H2O)3](ClO4)3·2H2O}∞ (2) and {[Gd(NiL1)2(H2O)3](ClO4)3·2H2O}∞ (3) were prepared and structurally characterized by X-ray single-crystal analyses. L1 denotes the doubly deprotonated form of 2-hydroxyethoxyethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazabicyclo[12.4.015,16]-13,18-dicarboxylate. The new mononuclear macrocyclic complex NiL1 acts as the bridging ligand with a monodentate coordination top (one of the alcohol hydroxyls) and a bidentate one (the oxamido carbonyls) between two Ln(III) (Ln = Pr, Sm and Gd in 1, 2 and 3, respectively) nodes to enclose the rectangular Ln2(NiL1)2 subunits. Most of the corresponding metal-to-metal distances in the subunits of the three compounds decrease following the variation trend identical to that of the ionic radii of Pr(III), Sm(III) and Gd(III). The studies with plasmid DNA showed that 1, 2 and 3 induced DNA cleavage. Luminescence investigation displayed that no emission occurred for the three coordination polymers in DMF at room temperature.Graphical abstractThese coordination polymers possess the features of being hetero-metallic, having rectangular subunits arranged alternately in two orientations and containing lanthanide metal ion nodes and a new macrocyclic complex bridging ligand. All the three new compounds showed DNA cleavage activity.Highlights► These infinite duoble chains contain a new macrocyclic complex bridging ligand. ► They are hetero-metallic and possess both lanthanide(III) and nickel(II) centers. ► Their rectangular subunits are arranged alternately in two orientations. ► All the three new compounds showed DNA cleavage activity.

A new complex [Fe(N-isonicotinamidosalicylaldimine)Cl2] has been synthesized by template reaction at room temperature and structurally characterized by X-ray single-crystal analysis. The complex crystallizes in triclinic crystal system, Pī space group, a = 7.273(6) Å, b = 10.015(8) Å, c = 10.479(8) Å, α = 71.067(10)°, β = 89.964(11)°, γ = 75.528(10)°, V = 696.4(9) Å3 and Z = 2. The coordination geometry around the Fe(III) ion is a distorted trigonal bipyramid with a O2N1Cl2 donor set. In the crystal structure, N–H···Cl, C–H···O and C–H···Cl hydrogen bonds and π···π stacking interactions involving aromatic and unclosed π-systems link the molecules to form supramolecular double layers.

A molecular rectangle [Cu{CuL1(NO3)}(H2O)(NO3)]2 (1) and two infinite molecular rectangle strands {[Cu{CuL1(NO3)}2] · 2H2O}∞ (2) and [Cu{CuL2(ClO4)}2]∞ (3) were prepared by reaction of “naked” Cu(II) ions with macrocyclic complex ligands CuL1 for 1 and 2 and CuL2 for 3 in metal-to-ligand molar ratios of 1:1, 1:2 and 1:2, respectively. L1 and L2 denote the dianions of diethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate and diethyl 5,6,7,8,15,16-hexahydro-15-methyl-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate, respectively. The structures of 1–3 were determined by X-ray single-crystal analyses. CuL1 in 1 and 2 and CuL2 in 3 act as angular linkers with a monodentate coordination top and a bidentate one between two Cu(II) nodes to enclose the molecular rectangle of 1 and the rectangular subunits of 2 and 3. The angular shape, the monodentate top plus bidentate top coordination mode and the self-complementarity for π⋯π interactions of the macrocyclic complex linkers, the ratio between the reactants and the octahedral coordination geometry of the naked Cu(II) ions jointly determined the interesting structures of metallocyclophane 1 and 1D double chain coordination polymers 2 and 3. The cavities of the rectangular molecules of 1 are arranged into infinite strands so that parallel channels occur in the crystal. The molecules of 2 and 3 all pack parallel in the crystals.The features, i.e. the monodentate top plus bidentate top coordination mode, the self-complementarity for π⋯π interactions and the angular shape, of the macrocyclic linkers are important for the formation of the molecular metallorectangle and the two infinite metallorectangle strands.