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High connectivity octacarboxylate ligands containing non-coordinating diamine cores lead to a wide variety of new MOFs, many containing cage-like pores.

Three new amine functionalised tetracarboxylate linkers with a variety of arm lengths were synthesised, namely N,N,N′N′-tetrakis(R1, R2 or R3)-trans-1,4-diaminocyclohexane, R1 = (4-carboxyphenyl)-1-methyl; R2 = (4-cinnamic)-1-methyl; R3 = 1′-carboxy-[4,4′-biphenyl]-1-methyl. The diagonal length of the linkers, from single crystal structural analysis and obtained by measuring between the furthest oxygen atoms, is 19.4, 24.6 and 27.5 A for L1, L2 and L3, respectively. The sp3 hybridization of the amino groups of the cyclohexyldiamine core and the carbon atoms of methylene spacers permits the rotation of the attached groups to occur around these atomic sites, giving the ligands a flexibility that manifests itself in two main dominant conformations: convergent, where carboxyl arm groups connected to the same nitrogen atom are π⋯π stacking, and divergent, where two carboxyl arms occupy equatorial positions and two occupy the axial positions relative to the ligand's cyclohexyl core. Analysis of the overall ligand conformations obtained from crystal structures of sixteen new coordination polymers showed that the overwhelmingly most common conformation (93%) was the divergent one. The formulae and topologies of the coordination polymers obtained were: poly-[Cd2(H2L1)(Cl)2(OH2)2]·5H2O (1) 2D (4,4), poly-[M2L2(OH2)2]·DMA M = Cd (2Cd) or Mn (2Mn) 3D (4·62·7·8)(42·66·75·82), poly-[Cd2(L3)(OH2)4(DMF)2] (3) 1D ladder, poly-[Cd2(L3)]·4DMA·16H2O (4) 3D fsc, poly-{((CH3)2NH2)4[Zn4Na4(L1)4(OH2)4(DMF)2]} (5) 3D pts, poly-[M5(HL1)2(O)2(OH2)2(DMF)2]·solv M/solv = Zn/2DMF·18H2O (6Zn) or Co/9DMF·10H2O (6Co) 3D cyc, poly-[Zn3(L1)(OH)2]·2DMF (7) 3D fsc, poly-{((CH3)2NH2)[Zn2(HL2)(O)]·DMF} (8) 3D pts, poly-[Zn8(L3)3(O)2]·16DMF (9) 3D fsy, poly-[Cu2(L1)(DMF)2] (10) 2D (4,4), poly-[Cu2(L2)(OH2)2] (11) 3D lvt, poly-[Na4Zr2(L1)3(DMF)4] (12) 3D (44·52)2(44·5·6)(46·513·68·7)2, poly-[Zr6(HL1)2(O)8(CH3COO)2(OH2)6] (13) 3D scu, and poly-[Co2K4(L1)2(DMF)3] (14) 3D (42·64)(42·610·83). Although we applied similar reaction conditions, none of the coordination polymers obtained with L1, L2 & L3 were isoreticular upon ligand change. The overall trend is of void space increase by using longer ligands but with no notable increase in the level of interpenetration. The predictability and control of the obtained frameworks was hindered by the formation of non-default topologies due to the high flexibility of the tetracarboxylate linkers used and the variety of metal nodes observed.

The use of flexible ligands in coordination polymers provides both opportunities and unpredictability. A new series of flexible ligands derived from p-xylylenediamine, which vary in the positioning of carboxylic acid functional groups, have been found to form a series of coordination polymers and a discrete coordination complex. Use of the tetra-substituted meta-carboxylic acid ligand N,N,N′,N′-tetra(3-carboxybenzyl)-p-xylylenediamine, isolated as its dihydrochloride salt (H6M4pxy)Cl2, resulted in the simultaneous formation of two products from the same synthetic conditions. One of these products was a discrete cage-type coordination complex of the form [Cu4(M4pxy)2(DMF)2(OH2)] (1), while the other product was the two-dimensional coordination polymer poly-[Cu2(M4pxy)(OH2)2] (2). Synthesis utilising the tetra-substituted para-carboxylic acid ligand, isolated as N,N,N′,N′-tetra(4-carboxybenzyl)-p-xylylenediamine dihydrochloride (H6P4pxy)Cl2, resulted in the formation of multiple two-dimensional coordination polymers, poly-[Cu2(P4pxy)(DMF)(OH2)]·2DMF·3H2O (3·2DMF·3H2O), poly-[Mn2(P4pxy)(DMA)2] (4), poly-[Co4(P4pxy)2(DMF)2(μ-OH2)2(OH2)2]·6DMF·4H2O (5·6DMF·4H2O) and poly-[Cd2(P4pxy)(OH2)2]·DMA·3H2O (6·DMA·3H2O). The last of these materials, a three-dimensional coordination polymer, was found to adsorb approximately 32 cm3 g−1 STP of CO2 at atmospheric pressure at 273 K.

Fourteen three-dimensional (3D) lanthanide coordination polymers (CPs) with dicarboxylate mixed ligands, [Ln(fum)1.5(H2O)2]·0.5(H2bdc)·H2O (Ln = Sm (1), Tb (2)), [Ln2(fum)2(bdc)(H2O)4]·2H2O (Ln = Sm (3), Eu (4), Tb (5), Er (6)), [Ln(fum)0.5(bdc)] (Ln = Sm (7), Eu (8), Tb (9), Er (10)), and [Ln2(bdc)2(ox)(H2O)4]·0.7H2O (Ln = Sm (11), Gd (12), Tb (13), Dy (14)), have been synthesized hydrothermally from the self-assembly of lanthanide(III) ions (Ln3+), fumaric acid (H2fum), and terephthalic acid (H2bdc) in the presence of potassium hydroxide at different temperatures. The compounds fall into four classes. Compounds 1 and 2 were isolated from hydrothermal reactions performed at a relatively low temperature of 100 °C and found to crystallize in the triclinic space group P. The 3D framework is assembled from 2D layers of [Ln(fum)(H2O)2] units pillared by the chelating fum ligands and has 1D rhombic channels templated by H2bdc and lattice H2O molecules. The framework presents a binodal (4,5)-connected tcs topology with the point symbol (44·62)(44·66). Raising the reaction temperature to 140 °C resulted in the formation of compounds 3–6. These materials crystallize in the monoclinic system with the polar space group P21 and feature a 3D network constructed from dinuclear {Ln2(OCO)6(H2O)4} units interlinked by fum and bdc ligands, showing a uninodal 6-connected two-fold interpenetrated pcu topology. The small channels of the framework are occupied by lattice H2O molecules. Further increase of the reaction temperature to 160 °C gave rise to the formation of compounds 7–10, crystallizing in the orthorhombic space group Pbca. The 3D framework is generated from 2D corrugated sheets of [Ln(fum)]2+ bound by bdc ligands and contains no intercalated H2O molecules in the lattice. The framework possesses a trinodal (4,6,7)-connected net with the point symbol (42·64)2(46·68·8)(412·69)2. Finally, compounds 11–14 contained an in situ generated oxalate (ox) ligand formed under hydrothermal conditions conducted at a high reaction temperature of 180 °C. These compounds crystallize in the monoclinic space group P21/c and possess a 3D open framework consisting of a dinuclear [Ln2(ox)(H2O)4]2+ unit linked by bridging bdc ligands and has small void channels occupied by lattice H2O molecules. The frameworks were topologically simplified as a binodal (4,5)-connected tcj/hc net with a total point symbol of (42·52·72)(42·53·75). In the solid state at room temperature, the Tb (2, 5, 9, and 13) and Eu (4 and 8) compounds emit green and red light, respectively.

A traditionally good chelating motif has been incorporated into a ligand for the synthesis of coordination polymers with vacant amine sites. A novel tetracarboxylic acid diamine ligand, isolated as N,N,N′,N′-tetra(4-carboxybenzyl)-1,3-diaminopropane dihydrochloride trihydrate (H6L1)Cl2·3H2O, has been prepared, structurally characterised, and subsequently used in the formation of three new coordination polymers. Poly-[Cu2(L1)(OH2)2]·6DMF·3H2O 1 consists of (4,4) sheets formed by each L1 ligand coordinating to four copper(II) ‘paddlewheel’ dinuclear clusters. The amines of the ligand are non-coordinating. After solvent exchange and evacuation, 1 was found to adsorb approximately 23 cm3(STP) g−1 of CO2 at atmospheric pressure at 273 K. The isostructural compounds poly-[Zn(H2L1)(OH2)]·DMF·4H2O and poly-[Cd(H2L1)(OH2)]·DMF·3H2O 2Zn/2Cd are self-penetrating (10,3) coordination polymers containing square-shaped one-dimensional solvent channels. After solvent exchange it was found that 2Zn and 2Cd lost crystallinity, which accounts for the low N2 and CO2 uptakes observed.

A new Cd(II) based metal–organic framework (MOF), having formula {(CH3)2NH2)6[Cd5(L)4]·H2O·3DMF}n (1), has been synthesized based on a rigid tetracarboxylate ligand of terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H4L). 1 shows a complicated 3D tetranodal 3,3,4,8-c network with uncoordinated –COO− groups. The highly selective luminescent sensing of 2,4-dinitrophenol (2,4-DNP), 2,4,6-trinitrophenol (TNP) and ferric ions was studied for 1 through the alleviation in its fluorescence intensity. The detection limit of 2,4-DNP was found to be 0.84 ppm, which is 20 times higher than that of 1,3,5-trimethylbenzene, demonstrating greater and selective quenching ability. The possible mechanism associated with the decrease in fluorescence intensity of 1 in the presence of nitroaromatics (NACs) has been addressed by theoretical calculations. Furthermore, 1 displays excellent capacity to adsorb methylene blue (MB) with high selectivity, and it maintains an almost identical adsorption performance after being recycled five times.

A new metal–organic framework, formulated as {[Zn2(L)(DMF)3]·2DMF·2H2O} (1), has been synthesized using a symmetrical rigid carboxylate ligand terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H4L). Single-crystal X-ray diffraction analysis shows that 1 possesses a 3D uninodal 4-c lonsdaleite (lon) topology based on binuclear Zn clusters. 1 behaves as a fluorescent chemosensor for highly selective and sensitive detection of Fe3+/Fe2+ ions, 2,4-dinitrophenol (2,4-DNP), p-nitrophenol (PNP) and 2,4,6-trinitrophenol (TNP). Furthermore, the photocatalytic properties of 1 for degradation of methyl violet (MV) and Rhodamine B (RhB) have been explored. The possible emission quenching of 1 in the presence of aromatic compounds has been addressed by theoretical calculations and the photocatalytic activity of 1 against organic dyes has been addressed using density of states (DOS) calculations.

An unexploited pentacarboxylate ligand, 2,5-bis(3′,5′-dicarboxylphenyl)-benzoic acid (H5L), was designed and used for the preparation of metal organic material using Zn2+ as a node. The new compound, {(Me2NH2)[Zn2(L)(H2O)]·0.5DMF}n (1) (DMF = dimethylformamide), has been synthesized and structurally characterized. The topology of the 5-connected anionic framework may be described as (44)(66) (Schlafli symbol) based on {M2(CO2)5} molecular building blocks (MBBs) and L ligands in 1. It has been demonstrated that 1 can act as a fluorescent sensor for highly sensitive detection of nitroaromatics and Fe3+, with a detection limit of 0.54 ppm for 2,4,6-trinitrophenol (TNP) and 0.81 ppm for Fe3+. The possible emission quenching mechanism in the presence of nitroaromatics has been addressed by theoretical calculations.

A new piperazine-derived ligand has been prepared and used to synthesise a porous coordination polymer which displays selective carbon dioxide uptake after solvent exchange and thermal activation. The ligand N,N′-bis(4-carboxyphenylmethylene)piperazine H2L1 was prepared from piperazine in three steps and good yield. A structure containing the deprotonated form K2L1·2H2O was determined and consists of a three-dimensional coordination polymer containing inorganic K2(COO)2(OH2) layers separated by the long organic bridging linker. The free compound H2L1 displays a one-dimensional hydrogen-bonded polymeric structure in the solid state with hydrogen bonding interactions between carboxylic acids and piperazine groups tightly linking molecules together. The two-dimensional polymeric complex [Zn3(L1)2(OH)2]·2DMF·0.5H2O 1 was prepared and analysed in the solid state to reveal tubular one-dimensional channels which, when activated by solvent exchange and evacuation, displayed selective affinity for CO2 over N2 and H2.

Two isostructural series of compounds NH4[Ln(cdm)4(H2O)4]·18c6·3H2O (1Ln) and [K(18c6)(H2O)2][Ln(cdm)4(H2O)4]·H2O (2Ln) have been synthesised and structurally characterised (Ln = Gd, Dy, Er, cdm = C(CN)2(CONH2)−). These two classes of compounds are shown to be essentially isostructural to each other despite the change in counter-cation (ammonium vs. potassium) and the ensuing changes in coordination and hydrogen-bonding of water molecules in the structure. Structural data for 1Dy and 2Dy have been obtained using single crystal Laue neutron diffraction, allowing the precise location of all hydrogen atoms to be determined using fully anisotropic models. Both 1 and 2 contain the anionic complex [Ln(cdm)4(H2O)4]− in which the 8-coordinate lanthanoid is coordinated by a ring of four O-bound cdm ligands supported by inter-ligand N–H⋯O hydrogen bonds. The structures pack with complicated hydrogen-bonding networks in which both coordinated and non-coordinated water molecules are hydrogen-bond donors and all of the nitrile groups of the cdm ligands are hydrogen-bond acceptors. The change in cation between ammonium and potassium affects two water molecule sites which are both coordinated in 2Ln but not in 1Ln; in 1Ln one of these water molecules forms a hydrogen bond with NH4+ whilst the other has neither a coordination interaction nor a hydrogen bond to its oxygen atom.

The initial pH in the preparation of STA-16(Co) was found to have a great impact on the assembly of the MOF and the resulting porosity. The formation of a non-porous Co(II)-phosphonate pillared layer-structure was observed after changing the initial pH from 6.2 to 7.2 with distinct differences in the coordination environment of the cobalt centres.

Two new bis-(cyanobenzyl)piperazine ligands have been prepared, and have been used to prepare five Ag(I) coordination polymers which have been structurally characterised. Ligand N,N′-bis((4-cyanophenyl)methyl)piperazine L1 gave two structurally related two-dimensional coordination polymers poly-[Ag2(L1)(CF3SO3)2] 1 and poly-[Ag2(L1)(CF3SO3)2(C3H6O)1.5] 2 when reacted with silver trifluoromethanesulfonate in tetrahydrofuran and acetone, respectively. Compounds 1 and 2 display similar ligand geometries but form different extended networks, as a result of the inclusion of coordinating solvent molecules and the resulting influence on the flexible metal geometry. Reaction of N,N′-bis((3-cyanophenyl)methyl)piperazine L2 with silver ions gave rise to three new structurally characterised species. Complex poly-[Ag2(L2)(C3H6O)2]2(PF6) 3 forms a one-dimensional chain structurally related to 1. Complex poly-[Ag2(L2)(C3H8O)2(CF3SO3)2] 4 formed under similar conditions to 3, except with the inclusion of a coordinating anion which links equivalent chains to those found in 3 into a two-dimensional sheet. Finally, complex poly-[AgL2]CF3SO35 was formed simply by altering the reaction stoichiometry, producing a three-dimensional PtS network containing linear, acentric anion channels. Analysis of the structures reveals that the ligand geometries are largely consistent, leading to the extended structures being more influenced by the nature of the anions and solvent molecules.

Two divergent ligands 1,4,7,10-tetrakis-(4-cyanobenzyl)-1,4,7,10-tetraazacyclododecane L1 and 1,4,7,10-tetrakis-(4-carboxybenzyl)-1,4,7,10-tetraazacyclododecane dihydrochloride dihydrate H6L2·2Cl·2H2O have been prepared and structurally characterised, and the solid-state structures of four new metal complexes have been elucidated. Ligand L1 was found to form a dimeric complex of the form [Ag2(L1)2]·2ClO4 when reacted with silver perchlorate, in which a macrocycle-bound Ag(I) ion is coordinated by the nitrile group of an adjacent ligand, forming a tightly-bound pair of Ag(I) ions supported by intramolecular π–π interactions. Compound H6L2·2Cl·2H2O was prepared by a solvothermal recrystallization following hydrolysis of the ester precursor, and forms a densely packed three-dimensional structure containing numerous hydrogen bonding interactions. Complexes [Ni(H4L2)Cl]2·[NiCl4]·2EtOH 2 and [Co(H4L2)Cl]2·[CoCl4]·2EtOH 3 were characterised as isostructural discrete macrocycle-bound Ni(II) and Co(II) species where the formation of rare hydrogen-bonded carboxylic acid tetramers gives rise to a series of 2-dimensional sheets, containing checkerboard-type cavities encapsulating alternating tetrachloridometallate anions and regions containing disordered solvent molecules. Complex poly-{[Cu2Cl(H2L1)(HOEt)]2·[CuCl4]·5H2O} 4 consists of a series of two-dimensional sheets formed from a macrocycle-bound CuCl species linked by copper paddlewheel clusters and hydrogen-bonded carboxylic acid dimers. Charge balance is again achieved by tetrachloridometallate anions, and the sheets undergo parallel 2D → 2D interpenetration. The influence of the flexible geometry and donor ability of the methylene-linked pendant arms is clearly visible when comparing discrete complex 1 with hydrogen-bonded networks 2 and 3 and polymeric species 4. The presence of tetrachloridometallate counterions resulting from the presence of excess chloride ions in the reaction mixtures also provides powerful structure-directing effects in complexes 2, 3 and 4.

The consequences upon the structures of coordination polymers of introducing fluoro substituents into the terminal phenyl domain of 4' (biphenyl 4 yl) 42':6'4'' terpyridine (1) have been investigated. Reaction between Cu(OAc)2.H2O and 4' (2'3'4'5'6' pentafluorobiphenyl 4 yl) 42':6'4'' terpyridine (2) yields the one dimensional coordination polymer [Cu2(µ OAc)4(2)]n which contains paddle wheel {Cu2(OAc)4} nodes bridged by ligands 2. The compound is isostructural with [Cu2(µ OAc)4(1)]n. When Cu(OAc)2.H2O reacts with a 1 : 1 mixture of 1 and 2 [Cu2(µ OAc)4(1)]n and [Cu2(µ OAc)4(2)]n co crystallize with 1 and 2 disordered over one ligand site; the one dimensional coordination polymer is isostructural with each of [Cu2(µ OAc)4(1)]n and [Cu2(µ OAc)4(2)]n indicating that replacing H by F substituents in the peripheral arene ring has no effect on the overall solid state structure: tpy...tpy p stacking is preserved arene...arene pH...pH interactions are replaced by perfluoroarene..arene pF...pH interactions and H...H contacts are replaced by H...F interactions. In stark contrast to the latter observations the reaction of Zn(OAc)2.2H2O with perfluoro derivative 2 yields [Zn5(OAc)10(2)4.11H2O]n as the dominant one dimensional polymer; minor amounts of the anticipated polymer [Zn2(µ OAc)4(2)]n are also formed. The solid state structure of [Zn5(OAc)10(2)4.11H2O]n consists of quadruple stranded polymer chains assembled from {Zn5(2)4} subchains interconnected by {Zn5(OAc)10} units. Within each chain pF...pF and pH...pH stacking interactions are dominant while the observed assembly of chains into sheets and p stacking between arene units in adjacent sheets mimics the dominant interactions in the single stranded chains observed in [Zn2(µ OAc)4(1)]n [Zn2(µ OAc)4(2)]n [Cu2(µ OAc)4(1)]n [Cu2(µ OAc)4(2)]n and [Cu2(µ OAc)4(1)]n.[Cu2(µ OAc)4(2)]n.

Five new coordination compounds, namely [Zn(Hbtc)(1,3-bix)(H2O)]n (1), {Zn2(µ-O)(btc)(timp)]·3(H2O)}n (2), {[Zn3(4,4′-bibp)2(btc)2(H2O)2]·4(H2O)}n (3), {[Ni3(4,4′-bibp)2(btc)2(H2O)2]·3(H2O)}n (4), {[Cu3(4,4′-bibp)2(btc)2(H2O)]·2(H2O)}n (5), where 1,3 - bix = 1- (3 - (1H -inidazol - 1 − yl)methyl)benzyl)-1H-imidazole, timp = 1- (3,5-di (1H-imidazol-1-yl)phenyl)-1H-imidazole, 4,4′-bibp = 4,4′-bisimidazolylbiphenyl, and btc = 1,3,5-benzenetricarboxylate anion, were synthesized under hydrothermal conditions. In compound 1, both 1,3-bix ligand and btc anion act as bidentate bridging ligands, and connect the zinc cations into a one-dimensional chain. In compound 2, timp and btc anions as tridentate ligands coordinate to zinc cations to form a three-dimensional 3,6-connected network. Compounds 3–5 have similar structures, 4,4′-bibp and btc anions act as bidentate and tetradentate ligands, respectively, and coordinate to metal cations to form a three dimensional 4,4-connected network. The luminescence properties for 1–3 and magnetic properties for 4–5 are also discussed in detail.

A series of five salts of carboamoyldicyanomethanide, C(CN)2(CONH2)−cdm, have been synthesised and structurally characterised using different cations; ammonium (1), methylammonium (2), dimethylammonium (3), trimethylammonium (4) and tetramethylammonium (5). These organic salts vary in the degree of hydrogen-bonding interactions that the cation can partake in with minimal change in the size of the cation. The structure of 1 shows the NH4 cation involved in extensive hydrogen bonding to the cdm anions to form a 3D network with minimal interaction between anions and the disruption of previously observed supramolecular synthons that occur between cdm anions. In contrast to this the structure of 5 contains no hydrogen-bonding between cations and anions and leads to the formation of a corrugated sheet containing only interactions between neighbouring anions. The intermediate cases involving the MeH3N+ (2), Me2H2N+ (3) and Me3HN+ (4) cations, display a 2D hydrogen bonded sheet in the case of 2 and 1D chains in the structures of 3 and 4. The structure of a larger tetraalkylammonium salt, (Et3MeN)cdm (6) contains a similar sheet network to that of the Me4N+ compound with subtle changes due to the increase in size of the counter cation. The role of the steric bulk of the counter-cation has been further investigated by the synthesis of the benzyltrimethylammonium salt of cdm (7) in which the anions form a previously observed 1D chain motif and are well separated due to the bulk of the cation.

Several CuII complexes of carbamoyldicyanomethanide (cdm, C(CN)2(CONH2)−) with various bidentate co-ligands have been prepared and characterised to examine the persistence of a previously observed dual-synthon ‘heterotape’ hydrogen-bonding motif that incorporates both amide and nitrile functionalities. Using 2,2′-bipyridine or 1,10-phenanthroline as co-ligands yields dimeric complexes of the form [Cu(cdm)Cl(L)]2·2MeOH (L = 2,2′-bipy 1 or 1,10-phen 2). However, the bridging species in these two dimers are different; μ2 chloride bridging in the bipyridine dimer and η1(N):η1(N′) cdm bridging in the phenanthroline complex. The subtle change in co-ligand prompts a change in the bridging mode that prevents the desired motif from forming in the phenanthroline structure, an effect that appears to arise from the greater π-stacking of the phenanthroline groups. The dimeric complex [Cu(cdm)(acac)(H2O)]23 and the monomeric complexes [Cu(cdm)2(NH2(CH2)3NH2)] 4 and [Mn(cdm)Cl(1,10-phen)2] 5 also fail to display the expected tape motif, although other complicated hydrogen bonding is present, and their structures are discussed.

A series of four- and six-connected entangled structures, namely [Cd(oba)(bbi)]·0.5H2O (1), [Ni(oba)(bbi)]2·H2O (2), [Co(bpea)(bbi)]·H2O (3), [Co2(bpea)2(bbi)2]·1.5H2O (4), [Cd(oba)(1,4-bix)] (5), and [Ni2(oba)2(1,4-bix)(H2O)2] (6), where oba = 4,4′-oxybis(benzoate), bpea = biphenylethene-4,4′-dicarboxylate, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene, and bbi = 1,1′-(1,4-butanediyl)bis(imidazole), have been successfully synthesized through a hydrothermal process. The structures of 1 and 2 both consist of two interpenetrating CdSO4 nets. In 1, the two nets are related by symmetry. By comparison, the individual nets are, unusually, crystallographically distinct in 2. The structures of 3 and 4 both contain interpenetrating diamond networks. In 3, there are 6 interpenetrating nets, and they show the usual mode of interpenetration. For 4, however, there are 7 nets, and a rare ‘abnormal’ [4 + 3] interpenetration mode is observed. In 5, the oba and 1,4-bix ligands linked the Cd(II) atoms into a deeply corrugated 2D sheet. The corrugated 2D sheets polycatenate each other in a parallel manner with DOC (degree of catenation) = 2, yielding a rare 2D → 3D parallel polycatenation net. In 6, the dinuclear Ni(II) units are bridged by the oba ligands to generate a 2D (4,4) square-grid with a rhombic window. It is interesting that the two identical (4,4) square-grids show 2D → 2D parallel interpenetration but are then further crosslinked by the 1,4-bix ligands to yield an unusual 3D self-penetrating net with an unique 6-connected 44.611 topology. The importance of bbi conformations and metal sources in the framework formation of complexes 1–6 was unraveled. Their infrared spectra, powder X-ray diffraction (XRD) and photoluminescent properties were also investigated in detail.

Two new 3D frameworks [(WS4Cu6Br4)(timp)8/3(H2O)40/3]n (1) and [(WS4Cu6Br4) (timtz)8/3(H2O)40/3]n (2), containing heptanuclear cluster blocks (one W atom and six Cu atoms) bridged by trigonal ligands timp or timtz (timp = 1-(3,5-di (1H-imidazol-1-yl)phenyl)-1H-imidazole; timtz = 2,4,6-tri(1H-imidazol-1-yl)-1,3,5-triazine), were successfully synthesized. Both compounds were characterized by single-crystal X-ray diffraction, elemental analysis, XRD, IR, TGA. X-ray determination shows that 1 and 2 can be topologically represented as (3,4)-connected networks with α-C3N4 (or ctn) topology where [WS4Cu6] act as the 4-connecting nodes, and the timp or timtz ligands bridge in pairs that act as the three-connecting nodes. Both compounds have the high symmetry of space group I-43d, which is the maximum symmetry for this net topology. The luminescent spectra and N2 absorption behaviors for 1 and 2 have also been investigated.

Two 1D coordination polymers of copper(II) acetylenedicarboxylate, [Cu(O2CCCCO2)(C5H5N)2(MeOH)] (1) and [Cu(O2CCCCO2)(Me2C5H3N)2(MeOH)]·MeOH (2), have been synthesised and structurally characterised by single crystal X-ray diffraction. In both cases the square pyramidal CuII atoms have trans coordinated pyridyl ligands and trans η1 carboxylates in the equatorial sites with methanol occupying the apical position. The linear dicarboxylate ligand results in the formation of near linear coordination polymers. The polymeric chains in 1 form 2D hydrogen bonded (4,4) sheets whereas in 2 this topology is not possible, due to the extra steric bulk of the pyridine methyl groups, and a 3D hydrogen bonded network with CdSO4 (cds) topology is formed in which the lattice methanol molecules are also incorporated into the hydrogen bonding bridges.

Reported herein is the synthesis and structural characterisation of the novel ligand, 4,4′,6,6′-tetracarboxylic acid-2,2′-bipyridine (H4tcbp), along with an investigation of its coordination chemistry. Single crystal X-ray diffraction studies showed H4tcbp crystallises as a dihydrate and that intermolecular hydrogen bonding involving adjacent 4,4′-carboxylic acid groups form a R22(8) dimer motif whereas the 6,6′-carboxylic acid groups hydrogen bond together via the lattice water molecules [R44(12)] to form a 2D grid which is 3-fold interpenetrated and yields a 3D hydrogen bonded network. The reaction of H4tcbp under solvothermal conditions in MeOH with Ln(III) (Ln = Yb, Gd and Sm) lead to the isolation of {[Yb(Me2tcbp)2]·H2O·MeOH·H3O}, 1, and {[Ln(Me2tcbp)2]·2H2O·H3O}, where Ln = Gd, 2, or Sm, 3, and when in the presence of Yb(III) and Cu(II) to the mixed-metal species, {[Yb2(Me2tcbp)2]2Cu(OMe)2(H2O)2]·6MeOH}, 4, which were structurally characterised. Under these synthetic conditions the H4tcbp ligand di-esterified in situ at the remote 4- and 4′-carboxylic acid groups to form the 4,4′-dimethylcarboxy-6,6′-dicarboxy-2,2′-bipyridine ligand (Me2tcbp2–). Although 1 is monomeric, extensive hydrogen bonding between lattice water molecules, hydronium counterions and deprotonated carboxylate oxygen atoms results in 2D bilayer structure. Isostructural 2 and 3 are discrete mononuclear complexes whereas the tri-nuclear 4 forms a 2D sheet through face-to-face π–π interactions between adjacent units. In addition, the structural characterization and thermal analysis of four alkaline earth metal 3D coordination networks are reported, two of which feature the H4tcbp ligand: [Ba2(tcbp)(H2O)2] 5 and [CuSr(tcbp)(H2O)3] 6 (a 5,6-connected net), with the remaining two featuring the related 4,4′-dicarboxy-2,2′-bipyridine (H2dcbp) ligand: {[Ba(dcbp)(H2O)0.4]·0.6H2O} 7 (a bi-nodal 6-connected net) and {[Sr(dcbp)]·H2O} 8 (a uni-nodal 6-connected net).

The complexes of formulae M(dca)2(bpeado) (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5); dca = dicyanamide; bpeado = 1,2-bis(4-pyridyl)ethane-N,N′-dioxide) have been synthesized and characterized by X-ray single crystal diffraction. Compounds 1–5 contain 3D self-penetrating networks, in which bidentate dca ligands bridge the octahedral metal ions to form square-grid like M(dca)2 sheets and these sheets are further connected by criss-crossing bpeado to give a 3D self-penetrating network. Variable temperature magnetic susceptibility studies have shown that these compounds generally display very weak antiferromagnetic coupling because of the long bpeado and μ1,5-dca pathways. Consequently, no magnetic ordering was found.

A hydrogen-bonded (6,3)-sheet similar to that of trimesic acid, containing asymmetric anions as the three-connecting nodes joined by NH⋯nitrile interactions, is templated by a cationic Cu(II) guest species.

The structure of the title complex has ladder-like 1D nets containing bridging μ-dca anions and both bridging and terminal nic anions; no long-range magnetic ordering is observed.

One-dimensional coordination polymer chains of M(tcm)2(H2O)2 (M⊕=⊕Co, Ni; tcm⊕=⊕tricyanomethanide, C(CN)3−, Me4pyz⊕=⊕tetramethylpyrazine) are linked into 3D networks by hydrogen bonding between the chains and the intercalated Me4pyz molecules, and between the chains themselves. Very weak magnetic coupling is observed for the high-spin d7 and d8 ions with no evidence of long-range order.

Treatment of the dipyridylazacrown ether ligand N,N′-bis(4-pyridyl-methyl)diaza-18-crown-6 (bpmdc), with hydrated transition metal perchlorate salts resulted in 2D networks with the composition [M(H2O)2(Hbpmdc)2](ClO4)4·xH2O (M2+ = Ni, x = 4 (1); Cu, x = 2 (2) and Zn, x = 4 (3)). The addition of sodium thiocyanate led to displacement of the aqua ligands, yielding [M(NCS)2(Hbpmdc)2](ClO4)2·2H2O (M2+ = Fe (4), Ni (5)), as well as a THF containing variant of Fe (6). A five-coordinate, copper-containing 2D network, [Cu(NCS)(bpmdc)2](NCS) (7), was isolated in the case of copper, while zinc proved to be the exception to the 2D coordination polymer motif, yielding a 1D chain motif [Zn(NCS)2(bpmdc)2] (8). Across these structures the dipyridylazacrown ether ligand showed a remarkably consistent adoption of the S-configuration when empty or singly protonated with a water guest, with bridging lengths varying by only 1.3 A. The magnetic behaviour of the Fe2+ network 4 was investigated and the d6 compound was found to remain high spin at all temperatures between 300 and 2 K, and thus did not show spin-crossover behaviour.

The reaction of the polydentate N-donor ligands bmtz, H2bmtz, and bptz with various silver salts was investigated. New 1D coordination polymers [Ag2(bmtz) (ClO4)]ClO4 (1), [Ag(bmtz)]ClO4·MeCN (2), [{Ag(tcm)}2(H2bmtz)(MeCN)] (3) and [Ag(bptz)(NO3)] (5), and 2-D sheet structures, [{Ag(tcm)}2bmtz] (4), were synthesized. The structures are built up through the combination of coordination bonds, hydrogen bonding, Ag–π, π–π, and anion–π interactions to generate new supramolecular architectures. The supramolecular structure of the protonated amine salt [H2bptz](NO3)2 (6) is also described.