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Porous coordination polymers, or metal–organic frameworks (MOFs), provide a unique materials platform due to their regular structure that allows for almost unlimited tunability in terms of pore size, shape, dimensionality and chemical functionalisation. The ability of this class of material to act as agents for the selective capture or separation of small molecules has driven much of the research in the field over the past two decades. One of the major driving forces in recent years has been the ability of porous coordination polymers to act as selective hosts for carbon dioxide, with obvious potential environmental implications for successful materials. Efforts to enhance the selectivity for CO2 over other gases (particularly those present in exhaust flues) have explored chemical functionalisation of the interior pore space using amines, to give materials that to some extent mimic the standard solution-based processing methods of flue gas that are currently employed. This review examines the three major synthetic routes that are used in order to affect this chemical modification of porous frameworks; (i) post-synthetic grafting of amines to coordinatively unsaturated metal sites, (ii) incorporation of ligands that contain terminal amine groups, and (iii) incorporation of ligands that contain amine embedded within the core of the ligand. The relative merits and shortcomings of these different synthetic approaches are discussed alongside examples of the materials generated using each method.

Reactions of ortho-, para- and substituted meta-xylenyl bridged bis(tacn) ligands with two or three molar equivalents of Zn(NO3)2·6H2O at pH 5.0 in the presence of NaClO4 or NH4PF6 resulted in the formation of a range of crystalline zinc complexes. In the presence of perchlorate counter ions the Lpx and Lphx ligands gave rise to dinuclear Zn2+ coordination complexes [Zn2Cl2(Lpx)(H2O)2](ClO4)2(H2O) and [Zn2Cl2(Lphx)(H2O)2](ClO4)2(H2O)2 respectively, which formed infinite 1D polymeric chains. In contrast, in the presence of the hexafluorophosphate counter ion, the Lnix ligand formed a unique tetranuclear Zn2+ complex, [Zn2Cl2(Lnix)(H2O)3](Cl)(PF6)2(H2O)4, the Lcax ligand formed an octanuclear complex [Zn8Cl4(Lcax)4(H2O)10](PF6)6.7(NO3)1.3(H2O)3.3, whilst the Lox ligand formed a mononuclear sandwich structure, [Zn(Lox)](PF6)2(H2O). The protonated metal-free Lpx ligand crystallised as [H4(Lpx)](NO3)2(PF6)(H2O)2 with the stacked ligand cations forming a hydrogen-bonded network. These structural attributes provide an explanation for the significant differences in binding behaviour of recombinant N-terminally tagged proteins with the corresponding Zn2+-azamacrocyclic complexes, compared to the analogous Cu2+- or Ni2+-azamacrocyclic complexes, when immobilised onto support materials and used as immobilised metal affinity chromatographic (IMAC) adsorbents.

A new metal–organic framework having formula {[Cd3(H2O)(L)2][Cd(im)3(H2O)2]·3 H2O} (H4L = 5-bis(4-carbonylbenzyl)aminoisophthalic acid and im = imidazole) (1) has been synthesized. X-ray investigation reveals that 1 is rare 4,4,8-connected (46)(45 · 6)(411 · 615 · 82) topology. The present work indicates that 1 could be a prospective candidate for developing novel luminescence sensors for the selective sensing of nitrobenzene which can be used as a precursor for explosives. Furthermore, the luminescent property of 1 in different solvents analytes as well as nitrobenzene have been investigated and the observed quenching in fluorescence have been corroborated by theoretical calculations.

Two new isomeric bis(tacn) ligands, 3,5-bis(1,4,7-triazacyclonon-1-ylmethyl)-1-(hydroxymethyl)-benzene (HLhyx) and 2,6-bis(1,4,7-triazacyclonon-1-ylmethyl)anisole (Lanx) have been synthesised. In addition, 2,6-bis(1,4,7-triazacyclonon-1-ylmethyl)-4-methylphenol (HLohx) was also synthesised in a considerably higher yield than the previously reported method. The ligands were reacted with two equivalents of Cu(NO3)2·3H2O at pH 5 resulting in the formation of three binuclear complexes. The ligands Lanx and HLhyx form complexes [Cu2Cl3(L)(H2O)](PF6) containing two unique Cu2+ centres coordinated to the ligand. In contrast, the phenolic HLohx ligand forms a bridged complex [Cu2(μ-Cl)(Lohx)](PF6)2, with the two Cu centres further linked by (μ-Cl) and (μ-O) bridges.

A highly connected metal–organic framework (MOF), namely, [Co5(μ3-OH)2(iapt)4(4,4′-bipy)0.5(H2O)·CH3CN·3H2O] (1) (H2iapt = 5-aminoisophthalic acid and 4,4′-bipy = 4,4′-bipyridine), is reported. 1 shows a complicated pentanodal 4,4,4,4,13-c 3D net with (43)(43)(43)(43)(420·514·623·78·813) topology based on an uncommon Co5 cluster. The magnetic analysis reveals antiferromagnetic interactions in 1, and both the local spin–orbit coupling of octahedral Co(II) ions and the antiferromagnetic interactions are the primary factors in the magnetic behaviour.

The effect of a common surfactant, cocamidopropyl betaine (CAPB), on the growth and meso- to micro-structural morphology of a prototypical metal–organic framework, HKUST-1 (Hong Kong University of Science and Technology-1, copper 1,3,5-benzenetricarboxylate) has been investigated. Surfactant molecules direct growth of HKUST-1 into wheat sheaf-shaped structures, comprising flat, ribbon-like individual ‘stems’ of HKUST-1. Comparison of wheat sheaf-like structures to bulk HKUST-1, as well as their respective decomposition products, was made. Upon pyrolysis, both bulk and wheat sheaf structures thermally decomposed to amorphous carbon decorated with metallic copper nanoparticles, that in each case retained the base morphology of the starting MOF.

The synthesis, characterizations and crystal structures for [Cu(ipnm)(hmpH)] (1), mixed-valent tetranuclear [MnII2MnIII2(dcnm)2(hmp)6Cl2] (2) and the homo-valent hexanuclear [FeIII6(dcnm)6(hmp)8O2] (3), (where ipnm = imido[cyano (picolinoyl)methyl]nitrosomethanide, hmpH = 2-hydroxymethylpyridine; dcnm = dicyanonitrosomethanide) are reported. The formation of new dianionic ligand, ipnm which is also an imide derivative, represents the scarce example of metal-mediated in-situ dehydrogenative cross-coupling between amide derivatives with primary alcohol. Structure of 2 is known as ‘butterfly’ type structure while hexanuclear cluster 3 exists in chair-like conformation which in both structures, the dcnm acting as a terminal ligand.

A new metal–organic framework having formula {[NH2(CH3)][Cu6(L)3(OAc)(H2O)4]·xsolvent} (H4L = 3,5-bis(isophthalic acid)-1H-1,2,4-triazole) (1) was synthesized, in which two types of polyhedral cages and one-dimensional channels coexist. The incorporation of the drug 5-fluorouracil (5-FU) into the desolvated 1 was around 24.9 wt% per gram of dehydrated 1. 5-FU is released in a controlled and progressive fashion with 98% of the drug released after 120 h at PBS. The result from this work provides a new avenue for MOF to be used as potential drug delivery.

Conventional bench top and solvothermal synthesis are determined to be reliable methods in the synthesis of coordination compounds containing the dicyanonitromethanide (dcnom) anion. From conventional bench top synthesis, [Ni(phen)3](dcnom)2 (1a), [Cu(phen)3](dcnom)2 (1b), [Cu(en)3](dcnom)2 (4), [Cu3(Hpz)3(H2O)(OH)(pz)3]Cl(dcnom)·H2O (7) and [Ag(Hpz)2(dcnom)] (8) (where phen = 1,10-phenanthroline, en = 1,2-ethylenediamine, Hpz = pyrazole and pz = pyrazolate) are obtained. With solvothermal synthesis, [Ni(phen)2(H2O)(dcnom)](dcnom) (2), [Cu(phen)2(dcnom)](dcnom) (3), [Cu(en)2(dcnom)2] (5) and [Cu(pn)2(dcnom)2] (6) (where pn = 1,3-propylenediamine) are formed. Both nitro κ1(O) and nitrile κ1(N) coordination modes are observed for the dcnom anion.

The transition metal-promoted in situ nucleophilic addition of methanol and ethanol to a nitrile arm of dicyanonitrosomethanide (dcnm) resulted in the formation of cyano[imino(methoxy)methyl]nitrosomethanide (cmnm) and cyano[imino(ethoxy)methyl]nitrosomethanide (cenm) respectively. In the presence of 4,4′-bipyridine (4,4′-bipy), [Ni(cmnm)2(4,4′-bipy)]·½DMF (1), [Ni(cenm)2(4,4′-bipy)]·EtOH (2) and [Zn(cmnm)2(4,4′-bipy)]·2H2O (3) were isolated as 1D chains. When copper ions were used, a dinuclear structure, namely [Cu2(cmnm)4(4,4′-bipy)] (4) was observed. Synthesis of 1, 2 and 4 also required the presence of CeCl3·6H2O. The cmnm ligands in complex 3 display unique coordination modes to the metal ions, namely κ2(N,O)Zn. Finally, the hydrogen bonding in 3 generates three interpenetrating 3D networks with unusual bsn (or β-Sn) net topology.

This review gives an account of the coordination polymers that can be attained with ligands containing the sulphur-based dithiocarbamate (dtc), dithiocarboxylate and xanthate functional groups. The coordination modes adopted by the different sulphur-based ligands are discussed, and methods of attaining higher dimension complexes outlined. The review also addresses potential applications of such materials.

Three manganese clusters have been synthesised via the reaction of Mn II with cyano(imino(methoxy)methyl)nitrosomethanide (cmnm), obtained from the in situ nucleophilic addition of MeOH to dicyanonitrosomethanide (dcnm). X-ray crystallographic studies show that the complex [Mn II 3 (cmnm) 6 ]·MeOH ( 1 ) is a linear trinuclear species, with a central octahedral and two outer trigonal-prismatic manganese(II) ions. Two mixed-valent tetranuclear complexes [Mn II 2 Mn III 2 O 2 (cmnm) 4 Cl 2 (MeOH) 6 ] ( 2 ) and [Mn II 2 Mn III 2 O 2 (cmnm) 4 Cl 2 (MeOH) 4 (pzH) 2 ]·2MeOH ( 3 ) (pzH = pyrazole) contain two Mn II and two Mn III ions in butterfly-type structures, with the six-coordinate ‘body’ Mn III ions bridged to the seven-coordinate ‘wingtip’ Mn II ions by μ 3 -O 2− and by nitroso oxygen atoms of the cmnm ligands. The formation of the trinuclear and tetranuclear manganese clusters is dependent on the stoichiometry used in the reactions. Solid state DC magnetic susceptibility studies on complexes 1 and 3 reveal that antiferromagnetic interactions are dominant within the clusters. Fits of the data reveal an S = 5 / 2 ground state for 1 and a S = 0 ground state for 3 , with several close lying excited states found in both cases.

The dicyanonitrosomethanide (dcnm) ligand undergoes an in situ transition metal promoted nucleophilic addition of methanol to a nitrile group to form cyano(imino(methoxy)methyl)nitrosomethanide (cmnm) in the formation of the 3d/4f heterometallic complexes (Me4N)[{Ni(cmnm)3}2Ln(cmnm)2] (1Ln; 1Ln = 1La, 1Ce, 1Pr, 1Nd, 1Sm). A change in the counter-ions of the metal and ligand salts employed under alternate reaction conditions results in the formation of (Et4N)2[{Ni(cmnm)3}2Ln(dcnm)2](ClO4) (2Ln; 2Ln = 2La, 2Ce), in which unreacted dcnm ligands are coordinated to the central lanthanoid. In both types of complexes three cmnm ligands chelate to a nickel metal centre to form a [Ni(cmnm)3] metalloligand. Two of these metalloligands are then bound to a central lanthanoid via the nitroso oxygen atoms, resulting in a trinuclear complex in which each nickel cation is connected to the lanthanoid by three bridging nitroso groups. Variable temperature magnetic susceptibilities on these {Ni(S = 1), Ln(f0 to f5), Ni(S = 1)} spin systems reveal very weak to zero Ln–Ni or Ni–Ni exchange coupling with the thermal depopulation between Stark levels on the Ln centres being of similar magnitude, and the Ni2Ce and Ni2Pr cases giving strongest evidence for exchange coupling.

A cobalt(II) coordination polymer, [Co(L1)(H2L2)]·2.5H2O, 1, has been prepared via the hydrothermal reaction of cobalt(II) chloride with the novel dicarboxy-Troger’s base ligand 2,8-dicarboxy-6H,12H-5,11-methano-dibenzo[b,f][1,5]diazocine, H2L1, and the bis-pyrazole ligand 4,4′-methylenebis-(3,5-dimethylpyrazole), H2L2. The structure of 1 contains 2D (4,4) networks showing 2D → 3D parallel interpenetration, whereby adjacent 2D sheets interlock through the apertures defined by the cleft-like Troger’s base ligand, to realise an overall 3D entanglement. The interlocking also forms one-dimensional solvent filled channels which are easily disturbed on drying resulting in framework collapse. The crystal structure of H2L1 is also reported, and represents a rare example of homochiral hydrogen bonded [6,4] dia networks interpenetrated by their enantiomeric partner frameworks.

The synthesis, structure and magnetic property of a new coordination network {[Co2(bcp)2(bpt)2]·2H2O}n (1) (H2bcp = 1,3-bis(4-carboxy-phenoxy)propane and bpt = 2,5-bis(4-pyridyl)-1,3,4-thiadiazole), is reported. Complex 1 shows a 3D 48.66.8 topology with unusual self-penetration, in which represents a new example of 6-connected networks. In addition, the magnetic property of 1 has also been investigated.

A novel hexanuclear complex [{(CuL)2Cu}2(μ-dca)2](ClO4)2·2L′(1) (where H2L = (OH)C6H4C(CH3) N(CH2)3N C(CH3)C6H4(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)2− and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV–Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ2-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)2Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)2Cu}2(μ-dca)2]2+. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm−1) between the copper(II) centers.

The flexible ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazol-1-yl)ethane (L4Et) displays remarkable versatility in the complexes that it forms with transition metals with products ranging from 1D chains to interpenetrating 3D networks. The L4Et ligand itself crystallises in the space group P21, adopting a helical twist, although it is found in a variety of other conformations in its complexes. Coordination polymers containing the L4Et ligand vary from almost straight, parallel 1D chains of [Ag2(L4Et)2(ClO4)2(DMF)]·DMF (1), through interdigitating helical complexes containing tetrahedral Zn(II), [Zn(NCS)2(L4Et)]·DMF·H2O (2) to 2D sheets of [Cu(L4Et)2(H2O)2](PF6)2·xH2O (3) and the three-fold interpenetrating 3D network of [Co(L4Et)2(NCS)2] (4). The 3D network adopts an unusual 3D 4-connected dmp (65.8) topology. Dimensionality can be limited by the use of chelating co-ligands, demonstrated by the formation of the dinuclear complex [{Cu(py-2,6-CO2)(H2O)}2(L4Et)] (5).

Several new 1D coordination polymers have been synthesised using the anionic ligand carbamoyldicyanomethanide, C(CN)2(CONH2)− (cdm). The polymeric complexes [Cu(cdm)2(py)2]·2MeOH (1), [Cu(cdm)2(4-Etpy)2]·2MeOH (2), [Cu(cdm)2(3,5-Me2pzH)2]·2MeOH (3) and [Cu(cdm)2(3-HOCH2py)2]·2MeOH (4) (py = pyridine; 3,5-Me2pzH = 3,5-dimethylpyrazole) contain Cu(II) atoms bridged by μ2-(N,N′) cdm ligands between equatorial and axial coordination sites. The use of monodentate co-ligands brings about polymeric products, in contrast to the use previously of chelating co-ligands which facilitate the formation of discrete products. These 1D polymeric complexes are connected by hydrogen bonding between the amide functionalities and the lattice solvent. In the structures of 3 and 4 the neutral ligands also contain hydrogen bond donor groups that supplement the amide ring motif. Two other complexes have been obtained that are polymeric chains of alkoxide-bridged Cu(II) dimers. The complexes [Cu(cdm)(MeO)(2-amp)] (5) and [Cu(cdm)(dmap)] (6) (2-amp = 2-(aminomethyl)pyridine and dmap = dimethylaminopropoxide) are remarkably similar despite the different ligands that they contain. Bridging between dimers is via μ2-(N,O) cdm ligands, consequently altering the nature of the hydrogen bonding between adjacent chains compared to the simple polymeric species 1–3.

A series of complexes of the form [M(Bp 3(4Bz) )(Tp 3(4Bz) )] containing a mixture of novel dihydrobis(3-(4-benzonitrile)pyrazolyl)borato (Bp 3(4Bz) ) and hydrotris(3-(4-benzonitrile)pyrazolyl)borato (Tp 3(4Bz) ) ligands have been synthesised and structurally characterised. The ligands, both containing 3-(4-benzonitrile)pyrazole arms, form isostructural complexes with a variety of transition metals although different crystalline solvates have been obtained depending upon the crystallisation conditions, namely [M(Bp 3(4Bz) )(Tp 3(4Bz) )] (M = Ni, Co), [Ni((Bp 3(4Bz) )(Tp 3(4Bz) )]·2MeOH and [M(Bp 3(4Bz) )(Tp 3(4Bz) )]·MeOH (M = Mn, Cd). In all cases the metal atoms are five-coordinate with an additional agostic B–H interaction from the bis(pyrazolyl)borate ligand.

Two cyano-bridged cadmium(II) and copper(II)–copper(I) mixed-valence polymer compounds [ Cu II ( en ) 2 ] { [ Cu II ( en ) 2 ] 2 - μ - ( CN ) 4 - [ Cd 3 Cu 6 I ( CN ) 14 ] } 1 and [Cu II (en) 2 ] 0.5 [CdCu I (CN) 3 ] · Cl · H 2 O 2 (en = 1,2-ethanediamine) through systematically varying the solution environment have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. The cyano anions connected the copper and cadmium centres with bidentate or tridentate bridging modes resulting in two complicated 3D networks for 1 and 2 . Compound 1 has a rare 5,6-connected network, while compound 2 can be reduced to a 6-connected α-Po net. The magnetic and thermal properties of 1 and 2 are also studied.

Using Cu(II), Mn(II) or Co(II) salt and the flexible ligands, N-[(4-carboxyphenyl)-sulfonyl]glycine (H3L1) and N-[(3-carboxyphenyl)-sulfonyl]glycine (H3L2), a series of new coordination polymers, [Mn(phen)(H2O)4][HL1 ]( 1), [Co3(L1)2(bipy)3(H2O)6]n� 8nH2 O( 2), [Cu4(L1)2(OH)2(bipy)4]n� 12nH2 O( 3), [Na(H2L1)

Two new three-dimensional (3D) coordination polymer [Cu2(tetrazolate)3(OH)]n (1) and [Cd2(tetrazolate)3Br]n (2) were synthesized and structurally characterized. By the topology analysis, the complicated architecture of 1 and 2 are all simplified to be the 6-connected pcu-type net. The variable-temperature magnetic susceptibilities (5–300 K) of 1 shows antiferromagnetic interactions of copper(II) ions bridged tetrazolate ligands and/or hydroxide anion.

The reaction of AgClO4 with anthracene-9,10-dicarboxylic acid (H2L) and hexamethylenetetramine (hmt) in the presence of 2,6-dimethylpyridine afforded a photoluminescent three-dimensional (3D) AgI coordination polymer {[Ag8(L)3(μ4-hmt)2(H2O)6](ClO4)2}∞ (L = anthracene-9,10-dicarboxylate) exhibiting binodal 4-connected (43·63)2(42·62·82)3 topological network. The relevant result reveals that the anthracene skeleton of L ligand bearing a large π-conjugated ring system plays an important role in the formation of the final structure.

The effects of pseudohalides on the modes of binding of a hydrazone ligand are investigated and we report here four new hydrazone complexes [Co(L) 2 ] · ClO 4 ( 1 ), [Co(L) 2 ] 2 [Co(SCN) 4 ] ( 2 ), [Mn(L) 2 ] ( 3 ) and [Mn(N 3 ) 2 ( LH ) 2 ] · H 2 O ( 4 ) [where LH = condensation product of pyridine-2-carboxaldehyde and benzhydrazide]. The hydrazone ligand is quite diverse in its chelating ability and can act as a neutral or mononegative ligand and as a bidentate or tridentate unit. In this paper, we report structures showing different denticities of the ligand having different charges. The complexes are characterized by IR, UV–Vis spectroscopy and cyclic voltammetric studies and the structures are conclusively established by single crystal X-ray diffraction study. Of the complexes, 1 and 3 are purely metal hydrazone complexes whereas 2 and 4 incorporate coordinated pseudohalides in their crystal structures, and 4 shows different coordination modes of the hydrazone ligand.

Two new Cd(II) complexes, having one binuclear structure [Cd2(L)2(Cl)2] (1) and another azido bridged one-dimensional zig-zag polynuclear network [Cd3(μ1,1-N3)4(L)2{H2N(CH2)2N(C2H5)2} · H2O]n (2) have been synthesized from a tridentate N2O donor Schiff base ligand LH, [LH = (OCH3)(OH)C6H3CHN(CH2)2N(C2H5)2], which is the condensation product of 2-hydroxy-4-methoxybenzaldehyde and 2-diethylaminoethylamine. Both the complexes 1 and 2 have been characterized by elemental analyses, IR & 1H NMR spectroscopy, TGA and fluorescence studies. Finally their structures have been established by single crystal X-ray diffraction method. Structural study reveals that in the complex 1, two Cd(II) centers are held together by two μ2-phenolato oxygen atoms and the terminal chlorine atom occupies the apical site of the square pyramidal environment of each metal center. In case of complex 2, the trinuclear asymmetric unit contains octahedral Cd(II) centers which are further held together by doubly end-on azido bridging to form a zig-zag polynuclear structure. It also displays intraligand 1(π–π∗) fluorescence and can potentially serve as photoactive material.

The reaction of AgNO3 with bulky anthracene-9-carboxylic acid (HL1) in the presence of 2,6-dimethylpyridine (dmp) afforded a photoluminescent hexanuclear discrete AgI complex [Ag6(L1)6(dmp)2] exhibiting C–H⋯Ag interactions whose total interaction energy were further estimated by DFT calculations. The relevant results reveal that the steric bulk of the anthracene ring skeleton of L1 may play important roles in the formation of the final structure.