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Carbazole is an important compound in pharmaceuticals and functional materials. A new Pd(II) supramolecular cage-catalyzed protocol for the synthesis of multifunctional carbazoles from indoles is described through regioselective successive oxidative Heck reactions. This new protocol is highly efficient, with a low Pd (2.4 mol%) catalyst loading and good compatibility for both N-H free and N-protected indole substrates. Moreover, it can be used to synthesize carbazoles with various functional groups by a one-pot two-step procedure. The excellent catalytic activity can be attributed to the distinct properties of the supramolecular cage structure in uniformly distributive and well-defined Pd(II) active centers on the cage surfaces.

On the basis of hard soft acid base theory, two neutral heterometallic M2Pd3 supramolecular cages, [Al2Pd3(L)6Cl6] (1) and [Fe2Pd3(L)6Cl6] (2) (where HL is 1-(4-(1H-imidazol-1-yl)phenyl)butane-1,3-dione), have been constructed by using the tripodal M(L)3 as metalloligands in combination with PdCl2 or Pd(MeCN)2Cl2. The supramolecular cage can be described as a trigonal bipyramid with two M3+ ions occupying at the two axial sites in ΔΔ or ΛΛ configurations and three Pd2+ ions sitting in the three equatorial positions with square planar geometry in trans configuration. The supramolecular cages exhibit high catalytic activity for the Suzuki–Miyaura coupling with arylbromide or arylchrolide and phenylboronic acid in biorenewable solvent glycerol under mild conditions. Moreover, the catalyst can be readily recycled and reused at least five times without loss of catalytic activity. The high catalytic performance may be attributed to the distinct properties of the cage structure with uniformly distributive and well-defined Pd active centres on the cage surfaces. The high stability in the cage structure also prevents Pd leaching out and agglomeration.

A new chiral sensor assembly with enantiomeric Ir(III) complex Δ-[Ir(ppy)2(MeCN)2](PF6) (ppy is 2-phenylpyridine) and 3-hydroxypyridine-2-carboxaldehyde as anxiliaries for chiral amines and amino derivatives, including α-amines, α-amino alcohols, α-amino esters, β-amines and β-amino alcohols as well as amino ether, was developed on the basis of 1H NMR spectroscopy. The assembly reaction is rapid and quantitative in equivalent under mild conditions, generating the corresponding diastereomers that are applied to discriminate the absolute configuration and quantitatively determine the enantiomeric excess (ee) directly without physical separation. The chelating coordination to Ir(III) ion much enhances the stability of the formed Schiff base ligand. Furthermore, more than one pair of diastereotopic resonances in wide detection regions ensures a convenient and high degree of accuracy in quantifying the ee value of chiral amines and amino derivatives. The absolute errors of the ee determinations by 1H NMR spectroscopy in different detection windows are within 1.9%. The linear relationship between the experimentally measured ee values and the gravimetrically prepared samples is found to be excellent.

A convenient and practical procedure to prepare Pd(II) metallogel as a highly efficient and recyclable catalyst for Suzuki-Miyaura coupling has been developed. Such metallogel shows highly processable and reversible responses to thermal and mechanical stimuli. The xerogel is a highly efficient (0.005 mol% Pd) heterogeneous catalyst for Suzuki-Miyaura couplings with arylhalides and phenylboronic acids in excellent yield in water or ethanol under ambient atmosphere. The reaction could be scaled up to 10 gram scale with 0.001 mol% Pd catalyst loading with 99% yield. The catalyst can be recycled and reused at least seven times without loss of activity.

Aerobic oxidation of amino acid complexes is an important process for the functionalization of amino acids. However, the reaction mechanism is still uncertain. Two enantiopure imino acid complexes Δ-[Ir(pq)2(ala-2H)] and Δ-[Ir(ppy)2(ala-2H)] (where pq is 2-phenylquinoline, ppy is 2-phenylpyridine and ala is alanine) have been synthesized respectively via the dehydrogenated oxidation reaction of the corresponding amino acid complexes Δ-[Ir(pq)2( l -ala)] and Δ-[Ir(ppy)2( l -ala)] in EtOH using visible light as the driving force and oxygen as an oxidant under mild conditions. The imino acid complexes have been fully characterized by NMR and MS techniques as well as X-ray single-crystal determination. The mechanism studies show singlet oxygen (1O2) is the main reactive oxygen species (ROS) and the carbon radical intermediate may involve in the reaction process. Therefore, a reaction mechanism involving the formation of a ligand-radical intermediate rather than the higher oxidation state of the metal center was proposed.

A new ruthenium biimidazole-like anion receptor featuring two “chelating” N H⋯O intramolecular hydrogen bonds, [Ru(bpy)2(DNBbimH2)](PF6)2 (2·(PF6)2) (bpy = 2,2′-bipyridine; DNBbimH2 = 5,5′,6,6′-tetramethyl-7,7′-dinitro-2,2′-bibenzimidazole), has been synthesized. Its anion-binding ability towards different anions in acetonitrile has been studied.

Three novel coordination polymers have been synthesized via hydrothermal reactions at different temperatures, namely [Cu2(H2tcbi)(H2O)4] (1), [Cd3(H3tcbi)2(H2O)6]·2H2O (2) and [Ca(H4tcbi)(H2O)2] (3) (H6tcbi = 4,4′,5,5′-tetracarboxyl-2,2′-biimidazole). This is the first report on complexes of the Hntcbi ligand. Single crystal X-ray analyses reveal that they have rich structural chemistry, ranging from one-dimensional (1), to two-dimensional (2 and 3). Three different coordination modes of the H6tcbi ligand, μ2, μ3 and μ4, have been observed. The coordination geometries of the metal sites vary from five-coordinate square pyramidal, six-coordinate octahedral to seven-coordinate pentagonal bipyramidal. The H6tcbi ligand in complexes 1, 2 and 3 is tetra-deprotonated to H2tcbi4−, tri-deprotonated to H3tcbi3− and bi-deprotonated to H4tcbi2−, and coordinates to the metal ions as a tetradentate, pentadentate and pentadentate ligand respectively, resulting in the formation of 1D, 2D and 2D coordination polymers. Photoluminscent investigation of complexes 2 and 3 shows intense blue and green fluorescent emissions respectively.

The novel three-dimensional chiral framework of the four-coordinate zinc complexes, [Zn 4 (biim) 3 (ina) 2 ] ( 1a and 1b ) (H 2 biim = 2,2′-biimidazole, ina = isoniconate), has been prepared via hydrothermal reaction. X-ray single crystal diffraction analysis shows the biim 2− in title complexes acts as a tetradentate ligand and links four different Zn 2+ ions. Spontaneous chiral resolution occurs in solvo-thermal reaction, which was confirmed by solid-state circular dichroism spectra. Photoluminescent spectra of compound 1 exhibit an intense blue emission at 440 nm.

Two new mercury(II) complexes [Hg(TDMPT)Cl2] (1) and [Hg37(TDMPT)12Br74] (2) (TDMPT = 2,4,6-tris(3,5-dimethylpyrazolyl)-1,3,5-triazine) have been prepared and characterized by X-ray structural analysis. Mercury(II) complex 1 is a mononuclear coordination compound. Meanwhile, mercury(II) complex 2 is the first example of the 3D coordination polymer with a 1D inorganic chain based on the Lindqvist-type [Hg6Br19]7− anion as building blocks. Furthermore, the bromide anions act as terminal, μ2- and μ6-bridge ligands.

The reaction of 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag2(bib)2](NO3)2 · 2H2O, in which bib ligand displayed in cis configuration. When the additional competing ligands/counterions, such as oxlate salt, 1,2-diaminoethene (en), 1,3-diaminopropane (pn), NO 2 - and VO 3 - were introduced, respectively, to the above-mentioned reaction solution, ring-open polymerization of sliver(I) complexes {[Ag(bib)]NO3 · H2O}n (1), {[Ag(bib)2]X}n ( X = NO 3 - (2), ClO 4 - (3)), {[Ag2(bib)2(NO2)](NO2) · 19/8H2O}n (4) and {[Ag2(bib)2](V4O12)0.5 · 3H2O · 2MeCN}n (5) were generated. In compounds 1, 4 and 5, bib ligand adopts trans configuration and twists around the Ag–Ag axis, giving rise to single-stranded helical structure with short adjacent Ag⋯Ag distances of 3.56, 3.56, 3.50 and 3.63 A, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag2(bib)2]2+, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag⋯Ag distances of 8.52 A in 2 and 8.61 A in 3 along with the strong intracyclicπ–π interactions between phenyl groups. Cis and trans configurations of bib coexist in solution and crystallize in complexes 1 and 2 in the solid state in the presence of en or pn. The solution of 1 and 2 can be converted into 3 via the addition of the bulky ClO 4 - counter anion or into 4 through introduction of the competing ligand/conuterion NO 2 - .

A new fluorescent chemosensor 5-( p - N , N ′-bis(2-pyridyl)amino)phenyl-10,15,20-tris( p -methoxyphenyl)porphyrin zinc has been designed and synthesized by the Ullmann-type coupling. It displays high selectivity for Cu 2+ ion and exhibits fluorescence quenching upon binding of Cu 2+ ion with an “on–off” type fluoroionophoric switching property, and its fluorescence can be revived by addition of EDTA disodium solution.

Four dimeric and polymeric coordination compounds [Zn 2 (bimb) 2 (pdc) 2 ]·6H 2 O ( 1 ), [Cd 2 (bimb) 2 (tp) 2 ]·H 2 O ( 2 ), [Cd(bimb)(ada)] ( 3 ) and [Co(bimb)(ada)] ( 4 ) (bimb, 4,4′-bis(imidazol-1-ylmethyl)biphenyl; pdc, pyridine-2,6-dicarboxylate; tp, terephthalate and ada, adipate) have been synthesized under hydrothermal conditions. Complex 1 is a discrete dinuclear metallomacrocycle featuring a 34-membered ring, in which the flexible bimb ligand acts as syn -conformation. While complexes 2 – 4 are 3D network structures connected by bimb and dicarboxylate ligands, the bimb ligand displays anti -confromation.

This review provides an overview on the crystal structures and properties of metal carboxylate coordination compounds with 2,2′-bipyridyl-like ligands reported in the past 4 years, which exhibit interesting structural features. This covers coordination polymers in one, two and three dimensions, as well as molecular architectures assembled by hydrogen-bonding and/or π–π stacking interactions from low-dimensional entities to higher-dimensional supramolecular architectures.

Two new linear and V-shaped tetradentate ligands, namely 1,4-bis(2-hexahydropyrimidyl)benzene (L) and 1,3-bis(2-hexahydropyrimidyl)benzene (L′), and their silver(I) complexes, [Ag2L(μ-ONO2)](NO3) · 2H2O (1), [Ag2L(μ-pn)](NO3)2 (2), [Ag2L(μ-pn)](ClO4)2 (3) and [Ag4L′2(H2O)](NO3)4 · 5H2O (4) (pn=1,3-diaminopropane) have been synthesized in situ and structurally characterized by single-crystal X-ray diffraction. 1 and 2 were obtained from the same reaction solution but different crystallization conditions. 1 is an one-dimensional chain featuring cuboid tetranuclear silver(I) units interconnected through monoatomic nitrate bridges. Both 2 and 3 are ribbon-like helical compounds in which each L ligand acts in a tetradentate bridging mode to interconnect four metal atoms, and each pn ligand functions in a bidentate bridging mode to link a pair of metal atoms. 4 shows a truncated square-pyramidal tetranuclear motif arose by the V-shaped L′ ligand. Close Ag⋯Ag separations (2.901–2.939 A) assisted by bis(hexahydropyrimidine) bridges were observed in 1 and 4, indicating metal–metal interactions. Photoluminescence of 1–4 has also been observed in the solid state and solution at room temperature and low temperature, respectively.

A novel method has been developed to regiospecifically synthesize water-soluble sulfonated porphyrin monomers tetrakis(4′-sulfonatophenyl)porphyrin, tetrakis(3′-sulfonatophenyl)porphyrin, tetrakis(2′-sulfonatophenyl)porphyrin, tetrakis(2′,5′-dimethyl-4′-sulfonatophenyl)porphyrin, the dimers of 1,2-bis[5,10,15-tri(4′-sulfonatophenyl)porphyrinyl]benzene and 1,2-bis[5,10,15-tri(2′,5′-dimethyl-4′-sulfonatophenyl)porphyrinyl]benzene in high yields through introduction of the trimethylsilyl group on the phenyl rings and reaction with trimethylsilyl chlorosulfonate in CCl4 solvent.

Four novel aqua-bridged dinuclear complexes with a formula M 2 (μ-H 2 O)(μ-OAc) 2 (Im) 4 (OAc) 2 (where Im=imidazole, M=Mg 2+ 1 , Mn 2+ 2 , Ni 2+ 3 and Co 2+ 4 ) have been synthesized and characterized. Complexes 1 , 2 and 3 have been characterized by X-ray crystallography. Two M 2+ ions are bridged by an aqua molecule and two carboxylate anion with M⋯M=3.635–3.777 A, M–OH 2 =2.109–2.246 A and M–OH 2 –M=114.4–119.0°, respectively. Each complex is further stabilized by two intramolecular hydrogen bonds between the hydrogens of the bridging aqua and the oxygens of the terminal monodentate acetates with a distance of O⋯O=2.6 A. The terminal monodentate acetates display ‘reversed’ C–O distances, namely the C–O(free) distances are actually longer than the C–O(coordinating) distances. This abnormal geometry of a monodentate carboxylate would be caused by the strong ‘pulling effect’ on the terminal carboxylates by intra- and intermolecular hydrogen bonds. The O–H stretching vibration of the bridging water was identified at ca. 2328 cm −1 in IR spectra based on the deuterium isotope shift. The solid state 13 C and 15 N NMR spectra of 1 displayed two sets of peaks for acetate and Im ligands, respectively, consistent with the presence of two types of coordination modes of acetate and the two symmetrically non-equivalent Im as revealed by X-ray structure. 15 N chemical shift of NH in Im ligands underwent about 6 ppm downfield shift due to its involvement in an intermolecular hydrogen bond.

Two structurally related complexes [Ru(phen)2taptp]2+ (1) and [Ru(phen)2dptatp]2+ (2), where taptp is 4,5,9,18-tetraazaphenanthreno[9,10-b]triphenylene and dptatp is 2,3-diphenyl-1,4,8,9-tetraazatriphenylene, were synthesized and characterized by elemental analyses and 1H NMR. The spectroscopic and electrochemical properties of complexes 1 and 2 were also examined. Both complexes can luminesce in organic solvent but are quenched in water to different extents. The interaction of the complexes with calf thymus DNA was studied by absorption and emission spectra, as well as viscosity and lifetime measurements. All the data indicate that both complexes bind with double-stranded calf thymus DNA via intercalative mode. Unlike its analog [Ru(bpy)2taptp]2+, [Ru(phen)2taptp]2+ shows negligible luminescence in water buffer but bright luminescence on binding to DNA, enabling it to be a sensitive probe for DNA conformation.

The reactions of divalent metal acetate (M=Cd II , Co II , Cu II , Mn II and Ni II ) with 2,2′-bipyridine (bpy) were systematically observed at a ratio of 1:1 in methanol solution. Three kinds of complexes were isolated: mononuclear [Ni(bpy)(OAc) 2 (H 2 O) 2 ] ( 6 ), binuclear [Cd 2 (bpy) 2 (OAc) 4 (H 2 O) 2 ] ( 7 ) and [Cu 2 (bpy) 2 (OAc) 4 ]·2H 2 O ( 8 ), linear trinuclear [M 3 (bpy) 2 (OAc) 6 ] (M=Co II ( 11 ) and Mn II ( 12 )). When 1.5 equivalent NaClO 4 was added to the reaction solution, respectively two kinds of complexes were obtained: mononuclear [M(bpy) 2 (OAc)](ClO 4 )· n H 2 O (M=Cd II ( 1 ), Co II ( 2 ), Mn II ( 3 ) and Ni II ( 4 )) and binuclear [M 2 (bpy) 2 (μ-OAc) 3 ](ClO 4 ) (M=Cu II ( 9 ) and Zn II ( 10 )). The structures of complexes 1 , 7 and 11 were determined by X-ray diffraction analysis. Complex 7 is the first example of a dicadmium complex linked by two monoatomic bridging acetate ligands with the longest distance of 3.380(4) A between the dangling acetate oxygen and metal atoms. Several novel structural features in complex 7 have been found in comparison with the monodentate bridging carboxylate with no or only weak interaction between the dangling acetate oxygen atom and metal atom. The structure of complex 11 consists of linear trinuclear molecules; each pair of cobalt atoms are bridged by three acetate groups, two of them acting as bidentate bridging mode and the third as a monoatomic bridge plus bidentate chelating mode, at a distance of 3.459 A. The central cobalt(II) coordinates by six oxygen atoms from six different acetate groups, and the terminal ones have a distorted environment of four oxygen atoms and two nitrogen atoms from a bpy ligand.

The recent studies on supramolecular system assembled by Ru(II) polypyridyl complexes and B-form double-stranded DNA is reviewed. These complexes have been studied as DNA spectroscopic tags and structural probes. The studies focus on the recognition parameters of these complexes binding to DNA, including the influence of the shape and size of intercalative ligand, the ancillary ligands and the effects of hydrogen bonding. Enantioselectivities of these complexes binding to DNA are also briefly discussed.

Two new ligands containing an intramolecular hydrogen bond, 2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline (HPIP) and 2-(2-hydroxy-1-naphthyl)imidazo[4,5-f][1,10]phenanthroline (HNAIP), and their complexes [Ru(bpy)2(HPIP)](PF6)2·H2O (1) and [Ru(bpy)2(HNAIP)](PF6)2·2H2O (2) (bpy=2,2′-bipyridine) have been synthesized and characterized by UV–Vis, IR, 1H NMR, and mass spectra. The electrochemical behaviors of the two complexes were studied by cyclic voltammetry. The binding of the two complexes with calf thymus DNA has been investigated by absorption, luminescence titrations, steady-state emission quenching, and viscosity measurements. The results suggest that complex 1 intercalates into DNA base pairs via the ligand HPIP, while complex 2 binds with DNA by partially intercalating the ligand HNAIP. Complex 1 shows higher affinity to DNA than complex 2. The intrinsic binding constants K for complexes 1 (6.5±0.3×105 M−1) and 2 (8.3±0.4×104 M−1) together with [Ru(bpy)2PIP]2+ (4.7±0.2×105 M−1, PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline) were determined by absorption titration.

Two monomeric zinc complexes, [Zn(H2biim)2(H2O)2](OAc)2·OHCH2CH2OH (H2biim=2,2′-biimidazole) (1) and [Zn(bipy)2(H2O)(CF3CO2)](ClO4) (bipy=2,2′-bipyridine) (2), have been synthesized and characterized by NMR and single-crystal structural analysis. The zinc ions in both complexes are coordinated in a distorted N4O2 octahedral geometry: the zinc ion in complex 1 is surrounded by two aqua [Zn–O 2.150 (3) A] and two H2biim ligands (Zn–N 2.150 A), the acetate groups act as counter-anions and form hydrogen bonds with H2biim; the zinc ion in 2 is ligated by two bipy ligands (Zn–N 2.144 A), one aqua molecule [Zn–O 2.148(2) A] and one monodentate carboxylate [Zn–O 2.154(2) A]. In both complexes, the aqua ligand forms strong donor hydrogen bonds with the hydroxyl or carboxylate groups, being analogous to those found for the active sites of several zinc enzymes.

A novel ruthenium(II) complex of dipyridophenazine (DPPZ) with the ancillary ligand imidazole[4,5- f ] [1,10]phenanthroline (IP), [Ru(IP) 2 (DPPZ)] (PF 6 ) 2 , has been synthesized and characterized by elemental analysis, 1D and 2D 1 H NMR, fast-atom bombardment mass spectra (FABMS), electronic spectroscopy and cyclic voltammetry. The DNA-binding properties of the complex were studied by spectroscopic methods. The intrinsic binding constant, K =2.1 × 10 7 M −1 , of the complex to calf thymus DNA has been determined by absorption titration in 5 mmol dm −3 Tris-HCl, 50 mmol dm −3 NaCl buffer (pH 7.0). The excited state lifetimes and luminescence quenching with [Fe(CN) 6 ] 4− as the quencher in the presence of DNA were also tested and mono-exponentiality was observed for the emission decay curves. Viscosity measurements together with the optical titrations unambiguously proved that the complex bound with DNA intercalatively and that the binding affinity to DNA was several times larger than that of the parent complex [Ru(bpy) 2 (DPPZ)] 2+ .

Two one dimension copper (II) polymer chain complexes with an identical molecular formula, [Cu (dien) (OAc) ] n (ClO4) n, but different stuctural features were synthesized through the reaction of Cu2 (OAc) 4 · 2H2O with M (dien) 2 (ClO4) 2 (M = Cu2, Ni2 and Zn2 ; dien = diethylenetriamine) . In complex 1, the geometry at each Cu (II) ion is a distorted octahedron (4+2) (D. K. Towle, et al. Inorg. Chem. 1988, 27, 394–399) ; while in complex 2, that is pentacoordinate and best described as a distorted trigonal bipyramid. The acetate groups act as monodentate bridging mode in 1, but as single syn-anti bridging fashion (Cu — O = 2.008 (10) and 2.062 (11) A) in 2. These provide a good example for the suggested pathway in the ‘‘carboxylate shift’’. The isomer can also be diagnosed by FT-IR and FT-Raman spectroscopies, and X-ray powder diffraction.

The ground state geometries, scaled quantum mechanical (SQM) quadratic force fields, and infrared and Raman intensities of magnesium and zinc porphyrins (MgP and ZnP), and of (H 2 O) 2 MgP have been determined from density functional theory, using the Becke-Lee-Yang-Parr composite exchange-correlation functional (B3-LYP)_and the 6-31G ∗ basis set. The geometry of (H 2 O)MgP has also been determined. The calculated force fields have been transformed to non-redundant natural internal coordinates and scaled by six scaling factors optimized earlier for free base porphyrin. Infrared and normal Raman spectra (the latter excited with 1064 nm infrared radiation) of the title compounds have been recorded. The calculated spectra compare excellently with the experimental ones, showing the accuracy of the SQM force field, and enabling a complete assignment of the fundamentals. According to the calculations, both MgP and ZnP are planar. The Mg ion in (H 2 O)MgP is about 0.28 A out of the N 4 plane. The calculations give reliable estimates for the force constants associated with the inactive vibrations. Some of these, e.g. the ruffling of the porphyrin ring, are important and are difficult to determine experimentally.

Two ruthenium(II) complexes with polypyridyl, Ru(bipy)2(phen)](ClO4)2·H2O (1) and [Ru(bipy)2(Me-phen)](ClO4)2 (2), (phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine, Me-phen = 5-methyl-1,10-phenanthroline), were synthesized and characterized by IR, MS and NMR spectra. Their structures were determined by single crystal X-ray diffraction techniques. The strong steric interaction between the polypyridyl ligands was relieved neither by the elongation of the RuN bonds nor increase of the NRuN bite angles. The coordination sphere was distorted to relieve the ligand interaction by forming specific angles (δ) between the polypyridyl ligand planes and coordination planes (NRuN), and forming larger twisted angles between the two pyridine rings for each bipy. The bond distances of RuN(bipy) and RuN(phen) were virtually identical with experimental error, as expected of π back-bonding interactions which statistically involve each of the ligands present in the coordination sphere.

The hydrothermal reaction of Cu(OAc)2 · H2O with thiophene-2,5-dicarboxylic acid (H2tdc) and 4,4′-bipyridine (bpy) gave a copper(II) coordination polymer {[Cu(tdc)(bpy)(H2O)](bpy)}n (1), in which the (4,4) layers are assembled via strong hydrogen bonds between the aqua ligands and the uncoordinated carboxylate oxygen atoms into a porous 3-D molecular architecture with parallelogrammic channels. The guest bpy molecules reside in the channels, involving intermolecular C–H⋯N hydrogen bonds with the host framework, can be removed upon heating at reduced pressure.

Two cobalt(III) complexes with phenanthroline, [Co(phen)2(gly)]Cl2 · 4H2O (1) and [Co(phen)2(H2O)2](NO3)3 · 2H2O (2), (phen = phenanthroline and gly = glycine), were synthesized and characterized by IR and NMR spectra. Their structures were determined by single crystal X-ray diffraction techniques. The coordinated cations all contain a six-coordinated cobalt atom chelated by two phen ligands and one gly anion or two aqua ligands in cis arrangement. The CoN bond distances in the cations lie in the range 1.934–1.952 A, the bond distances of CoO = 1.919 A (H2O) are significantly longer than that of CoO = 1.884 A (COO−). The complex 2 contains a crystallographic two-fold axis.

Complex [(bpy) 2 Ru(bpibH 2 )Ru(bpy) 2 ](ClO 4 ) 4 ·3H 2 O ( 1 ) (bpy=2,2′-bipyridine and bpibH 2 =1,4-bis([1,10]phenanthroline[5,6- d ]imidazol–2-yl)benzene), which contains two metallolumophores and a two receptor system, acts as an `off–on–off' luminescent pH sensor through protonation and deprotonation in MeOH–H 2 O (1:1 v/v) solution at room temperature.