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With the idea of supramolecular hosts encircling monoanions, a series of urea-containing trinuclear cationic copper complexes were designed, prepared and structurally analyzed. Copper(I) acetylides [Cu3(μ-dppm)3(μ3-η1-CCC6H4-4-NHC(O)NHC6H4-4-R)2]+ (dppm = bis(diphenylphosphino)methane; R = NO2 (1), CF3 (2), Cl (3), H (4), tBu (5), and OCH3 (6)) were prepared with F−, BF4−, or NO3− present as the anion. Eight 1-D anion coordination polymers (ACPs), 1·F, 2·F, 3·BF4, 4·F, 5·F, 5·BF4, 5·NO3 and 6·0.5F·0.5BF4, were clearly determined by X-ray diffraction. Diversity in the polymeric architecture is generated by both the choice of R-group used and anion present. 2·F, 3·BF4, 4·F, and 5·F show linear 1-D structures; 5·BF4 and 5·NO3 feature single-stranded helical structures; 1·F and 6·0.5F·0.5BF4 exhibit meso-helical structures. Solid state UV-vis absorption and luminescence properties are also discussed.

Five new silver(I) complexes with dimeric units, namely [Ag2(bib)2](BrO3)21, [Ag2(bib)2](ClO3)22, [Ag2(bib)2](ClO4)23, [Ag2(bib)2](NO3)2·2H2O 4 and [Ag2(bib)2(SCN)2] 5 (bib = 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene), have been synthesized and characterized by X-ray diffraction to observe the influence of the counter anions on crystal structures. Each bib acts as a bidentate ligand and every two bib ligands ligate a pair of Ag(I) ions resulting in a [2∶2] metallomacrocyclic motif that is further stabilized by intracyclic π–π interactions. 3 exhibits a dimeric structure, while 1, 2 and 4 are 1-D coordination polymers extended via interconnection of the dimeric units by the oxygen atoms from XO3− (X = Br and Cl) anions or Ag(I)⋯Ag(I) interactions. In 5, each Ag(I) ion is four-coordinate, and each dimeric unit is linked to the four adjacent dimeric units by four μ-sulfur atoms from SCN− groups into 2-D layer and further packed in 3-D network via hydrogen bonds. The photoluminescent properties of 1–4 have been observed in the solid state and dichloromethane solution at room temperature. The possible emission mechanisms have been proposed based on molecular orbital (MO) calculations.

A novel asymmetric ligand 3-(pyrazin-2-yl)-as-triazino[5,6-f ]1,10-phenanthroline (pztp) and its mono- and bi-nuclear complexes [Ru(bpy)2(pztp)]2+ 1 and [(bpy)2Ru(pztp)Ru(bpy)2]4+ 2 (bpy = 2,2′-bipyridine) have been synthesized and characterized by UV/VIS, IR, 1H NMR and mass spectra. The electrochemical behaviours of complexes 1 and 2 were observed and displayed oxidation potentials at 1.37 and 1.39 and 1.60 V vs. saturated calomel electrode, respectively. The binding of the two complexes with calf thymus DNA has also been investigated by a spectrophotometric method and viscosity measurements. The results indicated that the two complexes interact with DNA in sharply different ways. The mononuclear complex 1 intercalates into DNA base pairs despite its small hypochromicity value, while the binuclear complex 2 binds to DNA via electrostatic interaction. The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA are discussed.

The ruthenium(II) complexes [Ru(dmb)2(LH)][ClO4]2 [dmb = 4,4′-dimethyl-2,2′-bipyridine; LH = 2-(4-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (PNOPH), 2-(3-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (MNOPH) and 2-(2-nitrophenyl)imidazo[4,5-f][1,10]phenanthroline (ONOPH)] and their deprotonated complexes have been synthesized and characterized. The electrochemical behaviour of these complexes were examined and compared to that of [Ru(dmb)3]2+. Non-linear optical (NLO) properties of the complexes were investigated using Z-scan techniques. All of the complexes exhibit both NLO absorption and self-defocusing effect (n2 = –0.79 × 10–17 to –1.44 × 10–17 m2 W–1, α2 = 3.00 × 10–11 to 7.09 × 10–11 m W–1, [M] = 5 × 10–5 mol dm–3 in acetonitrile solution). The corresponding effective NLO susceptibilities |χ (3)| of the complexes are 2.86 × 10–12 to 5.07 × 10–12 esu. The results indicate that the substitution and deprotonation of the ligand have an effect on the NLO properties of the complexes. Finally, the crystal structure of [Ru(dmb)2(PNOP)][ClO4]·H2O·0.5C6H6 was determined by X-ray diffraction analysis; it contains two twisted dmb ligands and the bidentate ligand PNOP with torsional angles between each dmb ring pair of 3.4 and 8.7°.

Three monomeric nickel complexes [Ni(bipy)(O2CMe)2(H2O)2] 1 (bipy = 2,2′-bipyridine), [Ni(dmbipy)(O2CMe)2(H2O)2] 2 (dmbipy = 4,4′-dimethyl-2,2′-bipyridine) and [Ni(phen)(O2CMe)2(H2O)2]·0.5H2O 3 (phen = 1,10-phenanthroline) have been synthesized and characterized by single-crystal X-ray diffraction methods. In complexes 1 and 2 the molecules are self-assembled via double intermolecular hydrogen bonds to form one-dimensional infinite zigzag chains, which are stacked next to each other through the diimine aromatic rings in a zipper-like fashion, giving a novel two-dimensional co-operating structure. In 3 the molecule is linked by a hydrogen bond to form a one-dimensional chain, which is further associated with another adjacent chain via double hydrogen bonds forming a double chain. These double chains are intercalated to each other through the π–π interaction giving a novel two-dimensional structure.

Imidazo[4,5-f]1,10-phenanthroline (ip), 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip) and their (bipy) 2 Ru 2+ complexes (bipy = 2,2′-bipyridine) have been synthesized and characterized. The oxidation potentials of [Ru(bipy) 2 (ip)] 2+ and [Ru(bipy) 2 (pip)] 2+ were found to be 1.254 and 1.284 V vs. saturated calomel electrode respectively; the reduction of ip and pip appears to be irreversible at ca. -0.85 V. The photophysical properties of the complexes were perturbed in the presence of calf thymus DNA. The distinct changes including hypo- or hyper-chromicity at different UV/VIS absorption bands, enhancements of integrated emission intensity and excited-state lifetime, and efficiency of emission quenching by [Fe(CN) 6 ] 4- all indicate the stronger binding affinity to DNA of [Ru(bipy) 2 (pip)] 2+ over that of [Ru(bipy) 2 (ip)] 2+ , consistent with the greater planar area and extended π system of the pip ligand. The luminescence of the complexes showed monoexponential decay at any [DNA]∶[Ru] ratio. The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA suggest that the complexes bind to the DNA with enantioselectivity favouring the Δ isomers. These phenomena all suggest that the complexes bind through intercalation of ip or pip into base pairs. The crystal structure of [Ru(bipy) 2 (ip)][ClO 4 ] 2 ·H 2 O was determined; it contains the planar bidentate ligand ip and two twisted bipy ligands with torsional angles between each bipyridine ring pair of 5.7 and 8.6°.

Two monomeric complexes [M(Him)2(O2CMe)2](M = ZnII1 or CoII2, Him = imidazole) have been synthesized and structurally characterised by X-ray analysis. The complexes are isostructural. In each structure the metal atom is co-ordinated by a pair of acetate groups and a pair of Him ligands in a distorted-tetrahedral N2O2 environment with M–O 1.965(3)–1.991(2) and 1.972(4)–2.013(4)A, and M–N 1.996(2)–2.005(2) and 2.020(4)–2.030(5)A for 1 and 2, respectively. The solid-state structures of both complexes involve intermolecular N–H ⋯ O hydrogen bonds between the non-co-ordinated Him nitrogen atoms and the acetate oxygen atoms, with the acetate groups acting in both syn and anti modes, resulting in two types of carboxylate–imidazole–metal systems analogoues to those found for metalloenzymes. The IR, Raman and 13C NMR spectra of the complexes have been recorded and discussed in relation to the crystal structures.

The hydrogen bonding and deprotonation processes between four ruthenium biimidazole complexes, namely [Ru(bpy)(2)(BiimH(2))](PF(6))(2) (1, bpy is bipyridine, BiimH(2) is 2,2'-biimidazole), [Ru(bpy)(2)-(BbimH(2))](PF(6))(2) (2, BbimH(2) is 2,2'-bibenzimidazole), and [Ru(bpy)(2)(DMBbimH(2))](PF(6))(2) (3, DMBbimH(2) is 7,7'-dimethyl-2,2'-bibenzimidazole) and [Ru(bpy)(2)(TMBbimH(2))](2+) (4, TMBbimH(2) is 5,6,5',6'-tetramethyl-2,2'-bibenzimidazole), and acetate are investigated. Their hydrogen bonded adducts are indeed trapped and observed by absorption spectra and electrochemical experiments in acetonitrile solution in the presence of an excess of acetic acid for the first time. The binding constants log K(B) for these adducts are 6.74 for 1·OAc, 7.11 for 2·OAc, 7.26 for 3·OAc, and 6.99 for 4·OAc. A new approach to calculate the deprotonation constant is also developed by establishing a set of circular equilibria. The equilibrium constants for the first deprotonation step of the complexes log K(A) are 2.74 for 1, 5.19 for 2, 4.54 for 3, and 3.78 for 4. The pK(a1) values of the complexes in acetonitrile solution are calculated by subtracting log K(A) from pK(a) (HOAc in acetonitrile), giving 19.6 for 1, 17.1 for 2, 17.8 for 3, and 18.5 for 4. The degree of proton transfer (D(PT)) can be quantified by the calculation of absorption spectral and redox data, which is 0.41 for 1·OAc, 0.53 for 2·OAc, 0.57 for 3·OAc, and 0.47 for 4·OAc. Interestingly, the binding constant log K(B) (7.26) and D(PT) value (0.57) both reach their maxima at a critical point, where pK(a1) for the complex is 17.8 and ΔpK(a) for the adduct is 4.5 (ΔpK(a) = pK(a)(HOAc) - pK(a1), in acetonitrile solution). Moreover, the binding constant log K(B) shows linear correlation with the degree of proton transfer D(PT).

A stable nanocomposite metallogel was obtained by the addition of [Na(L)(H2O)]·2H2O (HL = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol) to an aqueous solution of Cu2(OAc)4·2H2O in a molar ratio of Cu/L = 4 (5.6 wt% gelator concentration), from which 1D coordination polymers [Cu2L(μ-OAc)2(μ-OH)] (1) and coordination nanoclusters {[Cu9L4(OAc)7(OH)5]2+}2 (3) were afforded. The nanoclusters 3 stabilize the 1D coordination polymers 1 and inhibit crystallization of 1 from the system, generating a coordination-based heat-set nanocomposite hydrogel at room and higher temperatures that flows upon cooling to 4 °C, in sharp contrast to most supramolecular gels. Reversible thermo and pH responsive solution–gel phase transitions were observed. The results described herein may open a novel avenue for functional coordination nanocomposite materials.

The homochiral self-assembly of [M(H2biim)3]SO4 (M2+ = Ru, 1; Co, 2; Ni, 3; Mn, 4; Fe, 5; and Zn, 6; H2biim = 2,2′-biimidazole) complexes have been systematically observed. For complexes 1 and 2, the spontaneous resolution processes not only depend on the counter anion but are also impacted by the pH value of the reaction solution. The enantiomers Δ-1 and Λ-1, and Δ-2 and Λ-2 were isolated in acidic conditions, while rac-1 and rac-2·5H2O were obtained in neutral conditions, respectively. For complexes 3–6, however, the spontaneous resolution processes are independent on the pH value of the reaction solution. Single crystal X-ray diffraction analysis reveals the enantiomers Δ and Λ are homochiral (10,3)-b three-dimensional networks constructed by the hydrogen bonds between the sulfate and H2biim ligand, whereas rac-1 assembles into (6,3) two-dimensional layers (see CrystEngComm, 2009, 11, 1114–1121) and rac-2 into one-dimensional chains. The data observed here seem to suggest that the hydrogen bonding modes between the sulfate and H2biim ligand play a crucial role in spontaneous resolution of the enantiomers. Furthermore, the solid state CD spectra and powder XRD patterns were also used to diagnose the obtained complexes.

Two new complexes [Cu4(2-OBPT)2(μ-OAc)4(μ-OH)2]·H2O (1) and [Cu2(2-OBPT)(μ-OAc)2(μ-OH)]·1.75H2O (2) (2-HOBPT = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol) have been synthesized and characterized by single-crystal X-ray diffraction. Complex 1 is a tetranuclear macrocycle with a centrosymmetric space groupP, while complex 2 is a zigzag chain coordination polymer with a P21/c space group. They are supramolecular isomers based on the dicopper [Cu2(μ-OAc)2(μ-OH)] core and 2-OBPT ligand. Interestingly, each isomer can be afforded by control of the crystallization temperature. A mixture of complexes 1 and 2 were obtained in the range of 60–100 °C, while the unique 2 crystallized at 20 °C in a high yield of 82% and the sole 1 was afforded at 120 °C. Moreover, both the complexes are antiferromagnetic and the theoretical fit of the magnetic susceptibility data in the temperature range of 2–300 K gives J1/kB = −33.6(5) K, g = 2.26(1) for 1 and J1 = −29.1(6) K, g = 2.30(1) for 2.

Two NbO frameworks are constructed by the reaction of Co(OAc)2·4(H2O)/Zn(OAc)2·2(H2O) with 1-(4-(1H-benzimidazol-1-yl)phenyl)butane-1,3-dione in the ratio of 1:2, in which they are isostructural and the NbO net exhibits a two-fold interpenetration featuring hexameric 1D channels. Theses channels are occupied by unprecedented tetrahedral tetramer water clusters.

Six possible isomers of mer-[M(II)(N,N,O-L)(2)] complex were observed in the solid state, in which spontaneous resolution of S,S-Lambda and R,R-Delta enantiomers of mer-[Co(N,N,O-L3)(2)] was achieved via pi-pi interactions.

A novel μ3-cyano-bridged heterotrimetallic 2-D coordination polymer constructed from rectangular grids was isolated and characterized crystallographically.

Two new isomorphous complexes [M(OBPT)2]·0.6H2O (M = Co, (1), M = Ni, (2), HOBPT = 4,6-bis(4-pyridyl)-1,3,5-triazin-2-ol) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Each ligand bridges two metal ions and each metal ion links to four ligands, resulting in a (4,4) 2D framework with rhombic cavities. Furthermore, the uncoordinated pyridine rings are further linked to each other via forming hydrogen bonding with the lattice water molecules into 3D three-fold interpenetrated, hydrogen-bonded networks. Interestingly, they are high stable up to 450 °C and exhibit reversible single crystal to single crystal transformation triggered by thermal treatment involving dehydration and rehydration processes. Moreover, they selectively adsorb/desorb water molecules over organic solvents much depending on the strength of hydrogen bonding between water molecule and solvent.

Two polymorphs formulated as [Ru(H2biim)3]SO4 (H2biim = 2,2′-biimidazole) have been solvothermally synthesized through changing the pH value of the reaction solution in an identical solvent at 120 °C. The α-[Ru(H2biim)3]SO4 (1) crystallizes in the monoclinic space groupP21/c with a = 8.1802(9) A, b = 21.293(2) A, c = 15.2116(14) A, β = 121.357(4)°, Z = 4. The β-[Ru(H2biim)3]SO4 (2) crystallizes in a chiral space groupI41 with a = 12.6267(10) A, c = 14.244(2) A, Z = 4. Complex 1 assembles into homochiral (Δ and Λ), (6,3) honeycomb two-dimensional layers, which further alternately stack in racemic, hydrogen-bonded networks, whereas 2 is a chiral, (10,3)-b 3-D network. Thus 1 and 2 are topological isomers. Importantly, their formations are much dependent on the pH value of the reaction solution. The data observed in this study seem to suggest that the diverse hydrogen bonding modes between the sulfate and H2biim ligand identified here play a crucial role in the formation of the polymorphs and topological isomers. The powder XRD patterns and infrared spectra also provide valuable information in the diagnosis of the polymorphs.

A (10,3)-b framework is constructed by the reaction of [Ru(H2Biim)3](PF6)2 and trimesic acid in a ratio of 1 : 1, in which the (10,3)-b net exhibits a two-fold interpenetration featuring 1D nano-sized channels. An unprecedented water nanotube consisting of the fused (H2O)28 with a double crown fashion, anchors in the channel.

Two novel complexes Mg2(µ-H2O)(µ-OAc)2(L)4(OAc)2 (L = imidazole or benzimidazole) have been synthesized and characterized; they contain the first example of an aqua-bridged dimagnesium core, and may have implications for the hydrolytic activity of dimetallic hydrolases.

A novel tetranuclear iron(III) complex, [{Fe2(tren)2(µ-O)}2(µ4-PO4)][ClO4]5·2.5H2O 1 [tren = tris(2-aminoethyl)amine], is synthesized; X-ray crystal structure analysis reveals that 1 contains a tetranuclear cation in which the iron atoms are linked by a µ4-PO43– bridge, which is a hydrolytic product from 4-nitrophenyl phosphate.