Coordination Moieties Research Articles

Supramolecular assemblies of new pseudohalide end-to-end bridged copper(II) complex and molecular structural variety of penta and hexa-coordinted metal(II) complexes with hydrazido-based ligand

With an hydrazido-based ligand, C14H13N2O and Cu, Ni metal(II) salts, three new mononuclear [Ni(HL)(NO3)(H2O)]NO3,C14H15N5NiO8, 1, [Cu(HL)(H2O)2]2NO3, C14H17CuN5O4, 2, [Ni(HL)2]2ClO4, C28H30Cl2N6NiO12, 3 and one binuclear end-to-end thiocynate bridged [Cu2(μ-SCN)2(L)2], C30H24Cu2N8O2S2, 4 complexes have been synthesized and characterized by physico-chemical techniques. All of the complexes were structurally characterized using single crystal X-ray diffraction. Complexes 1 and 2 have a penta-coordinated environment around the metal(II) centre, whereas complex 3 has a distorted hexa-coordinated geometry. In complex 4 two symmetry related, adjacent copper(II) coordination moieties are joined end-to-end in an unprecedented manner forming a thiocynate bridged, yielding a dicopper entity. The presence of two “symmetric” thiocynate bridges with Cu-SCN and Cu-NCS distances of 2.832 Å and 1.925 Å, respectively, results in a Cu⋯Cu distance of 5.503 Å. Binuclear complex, 4 exhibits a weak antiferromagnetic interaction between adjacent copper(II) centres. These copper(II) mononuclear and binuclear complexes have also been studied by X-band EPR spectroscopy. The crystal packing of these new complexes is stabilized by H-bonding, weak intermolecular interactions, CH⋯π and π⋯π interactions. Electrochemical data (CV and DPV) for the complexes shows MII → MI reduction activity. Electronic spectroscopy and computational features are examined by quantum chemical studies. The inhibitory effect of the complexes were tested on a cell population with IMR 32 (neuroblastoma), MCF 7 (breast cancer), HepG2 (hepatocellular carcinoma), L132 (lung cells) cell lines by MTT assay. Complex 3 showed a prominent cytotoxicity against the all cell lines. Expression levels of the Bax (pro-apoptotic) and Bcl2 (anti-apoptotic) genes were also studied, wherein the genes of interest showed a moderate down regulation after treatment with complexes 1 and 3. Finally, antioxidant superoxide dismutase activity measurements show that the complexes behave as superoxide dismutase mimics.

Assembling Pentatopic Terpyridine Ligands with Three Types of Coordination Moieties into a Giant Supramolecular Hexagonal Prism: Synthesis, Self-Assembly, Characterization, and Antimicrobial Study

Three dimensional (3D) supramolecules with giant cavities are attractive due to their wide range of applications. Herein, we used pentatopic terpyridine ligands with three types of coordination moieties to assemble two giant supramolecular hexagonal prisms with a molecular weight up to 42 608 and 43 569 Da, respectively. Within the prisms, two double-rimmed Kandinsky Circles serve as the base surfaces as well as the templates for assisting the self-sorting during the self-assembly. Additionally, hierarchical self-assembly of these supramolecular prisms into tubular-like nanostructures was fully studied by scanning tunneling microscopy (STM) and small-angle X-ray scattering (SAXS). Finally, these supramolecular prisms show good antimicrobial activities against Gram-positive pathogen methicillin-resistant Staphylococcus aureus (MRSA) and Bacillus subtilis (B. subtilis).

Coordination of Eu(III) with 1,10-Phenanthroline-2,9-dicarboxamide Derivatives: A Combined Study by MS, TRLIF, and DFT.

Tetradentate 1,10-phenanthroline-2,9-dicarboxamide (PDAM) derivatives have been well documented as effective binding ligands toward MA(III) and Ln(III), while the structural analysis and species determination of the complexes are still limited. Herein, we report a combined study on the coordination of Eu(III) with PDAM derivatives using electrospray ionization mass spectrometry (ESI-MS), time-resolved laser-induced fluorescence (TRLIF), and density functional theory (DFT) calculations. PDAM derivatives here involve N,N'-diethyl-N,N'-diethyl-2,9-diamide-1,10-phenanthroline (Et-Et-DAPhen), N,N'-dibutyl-N,N'-dibutyl-2,9-diamide-1,10-phenanthroline (But-But-DAPhen), and N,N'-dihexyl-N,N'-dihexyl-2,9-diamide-1,10-phenanthroline (Hex-Hex-DAPhen). The collision-induced dissociation (CID) test shows that these alkyl-DAPhen ligands coordinate strongly with Eu(III), given that the coordination moieties remain intact during CID. The 1/2 EuIII-L species was found to be the dominant component for all three ligands, as evidenced by ESI-MS and fluorescence titration. The fluorescence decay results indicate that the hydration numbers of Eu(III) are reduced from 9 to 1 upon complexation, in agreement with the fact that the 1/2 EuIII-L species are formed, and eight water molecules are exactly replaced by eight donor atoms of two alkyl-DAPhen ligands. In addition, the DFT calculations suggest that the 1:2 EuIII-L species is more stable than the 1/1 EuIII-L species and the Eu-oxygen/nitrogen (Eu-O/N) bonds have a dominant ionic character, with the O atoms having stronger electron-donating abilities toward Eu(III) in comparison to the N atoms.

Synthesis and Characterisation of Helicate and Mesocate Forms of a Double-Stranded Diruthenium(II) Complex of a Di(terpyridine) Ligand

A diruthenium(ii) complex involving the di(terpyridine) ligand 1,2-bis{5-(5″-methyl-2,2′:6′,2″-terpyridinyl)}ethane was synthesised by heating an equimolar ratio of RuCl3 and the ligand under reflux conditions in ethylene glycol for 3 days, realising double-stranded helicate and mesocate forms which were chromatographically separated. The two species were obtained in relatively low yield (each ~7–9%) from the reaction mixture. X-Ray structural studies revealed differences in the cavity sizes of the two structures, with the helicate structure having a significantly smaller cavity. Furthermore, the helicate and mesocate forms pack with notably different arrangements of the structures with the helicate having large solvent and anion filled pores. 1D/2D NMR studies revealed rigidity in the mesocate structure relative to that of the helicate, such that the –CH2CH2– signal was split in the former and appeared as a singlet in the latter. In a manner analogous to the behaviour of the parent [Ru(tpy)2]2+ coordination moiety (tpy=2,2′:6′,2″-terpyridine), photophysical studies indicated that both the helicate and mesocate forms were non-emissive at ~610nm at room temperature, but at 77K in n-butyronitrile, both isomers showed emission at ~610nm (λex 472nm). However, the temporal emission characteristics were very different: time-resolved studies showed the emission of the helicate species decayed with a dominant emission lifetime of ~10 μs (similar to the emissive properties of free [Ru(tpy)2]2+ under the same conditions), whereas for the mesocate the emission lifetime was at least three orders of magnitude lower (~4 ns).

ZIF-8 with Ferrocene Encapsulated: A Promising Precursor to Single-Atom Fe Embedded Nitrogen-Doped Carbon as Highly Efficient Catalyst for Oxygen Electroreduction.

The oxygen reduction reaction (ORR) plays an important role in the fields of energy storage and conversion technologies, including metal-air batteries and fuel cells. The development of nonprecious metal electrocatalysts with both high ORR activity and durability to replace the currently used costly Pt-based catalyst is critical and still a major challenge. Herein, a facile and scalable method is reported to prepare ZIF-8 with single ferrocene molecules trapped within its cavities (Fc@ZIF-8), which is utilized as precursor to porous single-atom Fe embedded nitrogen-doped carbon (Fe-N-C) during high temperature pyrolysis. The catalyst shows a half-wave potential (E1/2 ) of 0.904 V, 67 mV higher than commercial Pt/C catalyst (0.837 V), which is among the best compared with reported results for ORR. Significant electrochemical properties are attributed to the special configuration of Fc@ZIF-8 transforming into a highly dispersed iron-nitrogen coordination moieties embedded carbon matrix.

Synthesis, Characterization, and Optoelectronic Properties of Iridium Complexes Bearing Nonconjugated Six-Membered Chelating Ligands.

We report the synthesis, characterization, and optoelectronic properties of a series of four new luminescent iridium(III) complexes, 1-4, of the form [Ir(C∧N)2(N∧N)]PF6 (where C∧N is the nonconjugated benzylpyridinato (bnpy) and N∧N is a neutral diimine ancillary ligand) with the goal of investigating the effect of the methylene spacer between the coordination moieties of the C∧N ligand on the optoelectronic properties of the complexes. The crystal structures of 1-3 illustrate two possible orientations of the methylene unit of the bnpy ligand. The formation of these two separate conformers is a result of the conformational flexibility of the bnpy ligand. In complexes 3 and 4, mixtures of the two conformers were observed by 1H NMR spectroscopy in CDCl3 at room temperature, whereas only a single conformer is detected for 1 and 2. Detailed DFT calculations corroborate NMR experiments, accounting for the presence and relative populations of the two conformers. The optoelectronic properties of all four complexes, rationalized by the theoretical study, demonstrate that the interruption of conjugation in the C∧N ligands results in a reduced electrochemical gap but similar triplet state energies and lower photoluminescence quantum yields in comparison to the reference complexes R1-R4. Depending on the nature of the N∧N ligand, we observe (1) marked variations of the ratio of the conformers at ambient temperature and (2) phosphorescence ranging from yellow to red.

A novel photosensitizer based on a ruthenium(ii) phenanthroline bis(perylenediimide) dyad: synthesis, generation of singlet oxygen andin vitrophotodynamic therapy

In this study, a novel photosensitizer having two perylenediimide units and a phenanthroline ruthenium(ii) coordination moiety (Ru-BP)has been developed for photodynamic therapy (PDT) of cancer cells.

Structural Diversification of Light‐Metal Coordination Polymers Using 4‐(Methylsulfonyl)benzoate with a Charge‐Polarized Neutral Methylsulfonyl Coordination Moiety

We attempted the synthesis and crystallographic characterization of light‐metal coordination polymers (CPs) using a 4‐(methylsulfonyl)benzoate (msbza–) ligand with a charge‐polarized neutral methylsulfonyl coordination moiety, in order to diversify the limited structures of light‐metal CPs, as compared with heavy‐metal CPs. As expected from the results of DFT calculations, all of the obtained CPs {three‐dimensional (3D) [Mg2Na2(msbza)6(H2O)3]n (1), two‐dimensional (2D) [KH(msbza)2]n (2) and 2D [Na(msbza)]n (3)} exhibited coordination of the methylsulfonyl moiety to light‐metal cations, in addition to coordination of the carboxylate. These structural features suggest that the use of a neutral methylsulfonyl coordination site is a powerful tool for the structural diversification of light‐metal CPs. In addition, the 3D CP 1, with the rare and unique tetranuclear Mg2Na2 secondary building unit, showed an unprecedented single‐crystal‐to‐single‐crystal transformation via the low‐crystalline state.

Structural insights into the usage of carboxylate ions as molecular pins

Two series of new isostructural coordination compounds containing cobalt, nickel, copper butyrates (butyr) or isobutyrates (ibutyr) and 1,10-phenanthroline (phen), of general formulas [M(phen)3]2+·2(butyr−)·11H2O and [M(phen)3]2+·2(ibutyr−)·14H2O, were synthesized in water solutions and characterized by X-ray crystallography, IR, UV–Vis and fluorescence spectroscopy, elemental and thermal analysis. The carboxylate anions are located in an outer coordination sphere, which is a unique phenomenon in case of ibutyr coordination compounds. The studied compounds exhibit layered packing in crystal net. The “aqueous layers” consist of water molecules and carboxylate groups of carboxylate anions, assembled via hydrogen bonds to the two dimensional supramolecular networks containing multiple different cyclic motifs. Coordination units together with aliphatic ends of carboxylate anions form the “coordination moieties layers”, which are internally connected via π⋯π and C–H⋯π intermolecular interactions. The carboxylate anions function as supramolecular linkers between these layers and allow pinning them together. The spectroscopic and thermal properties have been discussed and correlated with molecular structures of the studied compounds. Due to placement of carboxylate anions out of coordination moieties, the presented compounds can be ideal standards in spectroscopic determinations of coordination type of butyr and ibutyr ions in coordination compounds. The thermal analyses of the studied compounds revealed the possibility of formation of dihydrate forms, and such dihydrated compounds cannot be produced in direct synthesis performed in aqueous media. In properly set environment the studied compounds can be thermally converted to micro- and nanoparticles of respective metal oxides.

Efficient near-infrared emitting tetradentate bis-cyclometalated platinum (IV) complexes for solution-processed polymer light-emitting diodes

Two novel tetradentate bis-cyclometalated platinum (IV) complexes of TPA-2q-PtCl2 and 3TPA-2q-PtCl2 with CˆN*NˆC cyclometalated ligands and two coordinated chlorine atoms were synthesized and characterized. The crystal structure of TPA-2q-PtCl2 shows a trans-form irregular octahedral geometry by measurement of single-crystal X-ray diffraction, where two CˆN coordination moieties are twisted and two chlorine atoms are located on both sides of platinum atom. A medium absorption band in a range of 450–474 nm is observed, which is assigned to the metal-to-ligand charge-transfer (MLCT) and intramolecular charge transfer (ILCT). And two obvious emission peaks at about 635 and 750 nm are displayed for both platinum (IV) complexes in 2-methyltetrahydrofuran solutions, which originate from the ILCT and MLCT characters to the lowest excited state. Using one of platinum (IV) complexes as a single dopant and a blend of poly(vinylcarbazole) as a host matrix, their single-emissive-layer polymer light-emitting diodes (PLEDs) exhibit an outstanding near-infrared emission with an electroluminescent (EL) peak of 750 nm. The better electroluminescent properties are obtained in the 3TPA-2q-PtCl2 doped devices with an external quantum efficiency of 0.85% and a radiance of 164 μW/cm−2. This is the first reported sample about tetradentate biscyclometalated platinum (IV) complexes used as organic NIR electroluminescent materials for promising application in PLEDs.

Control of Complex Formation through Peripheral Substituents in Click-Tripodal Ligands: Structural Diversity in Homo- and Heterodinuclear Cobalt-Azido Complexes.

The azide anion is widely used as a ligand in coordination chemistry. Despite its ubiquitous presence, controlled synthesis of azido complexes remains a challenging task. Making use of click-derived tripodal ligands, we present here various coordination motifs of the azido ligands, the formation of which appears to be controlled by the peripheral substituents on the tripodal ligands with otherwise identical structure of the coordination moieties. Thus, the flexible benzyl substituents on the tripodal ligand TBTA led to the formation of the first example of an unsupported and solely μ1,1-azido-bridged dicobalt(II) complex. The more rigid phenyl substituents on the TPTA ligand deliver an unsupported and solely μ1,3-azido-bridged dicobalt(II) complex. Bulky diisopropylphenyl substituents on the TDTA ligand deliver a doubly μ1,1-azido-bridged dicobalt(II) complex. Intriguingly, the mononuclear copper(II) complex [Cu(TBTA)N3]+ is an excellent synthon for generating mixed dinuclear complexes of the form [(TBTA)Co(μ1,1-N3)Cu(TBTA)]3+ or [(TBTA)Cu(μ1,1-N3)Cu(TPTA)]3+, both of which contain a single unsupported μ1,1-N3 as a bridge. To the best of our knowledge, these are also the first examples of mixed dinuclear complexes with a μ1,1-N3 monoazido bridge. All complexes were crystallographically characterized, and selected examples were probed via magnetometry and high-field EPR spectroscopy to elucidate the electronic structures of these complexes and the nature of magnetic coupling in the various azido-bridged complexes. These results thus prove the power of click-tripodal ligands in generating hitherto unknown chemical structures and properties.

Potentiometric and DFT studies of Cu(II) complexes with glycylglycine and methionine of interest for the brain chemistry

A large number of copper (II) complexes have been used as mimetic models for metalloproteins and metalloenzymes. Due to the lack of structural information about copper (II) complexes in aqueous solution, the coordination environment of this metal is not well established. In this work, pKa values of the complexes in the Cu:GlyGly, Cu:Met and Cu:GlyGly:Met systems were calculated by potentiometric titration at 25 °C and ionic strength of 0.1 mol L−1. The coordination modes of the ligands were explored for the main hydrolytic species throught RI-PBE/def2-SVP/COSMO level. In the Cu:GlyGly system, DFT results indicated that the NamineNpept coordination of dipeptide is 2.1 kcal mol−1 more stable than the tridentate NamineNpeptOcarboxy coordination moiety. The deprotonation of the peptide nitrogen is 13.7 kcal mol−1 more favorable than the hydrolysis of the water molecule coordinated to the metal. In the Cu:GlyGly:Met system, the sulfur atom does not belong to the copper (II) coordination sphere. Once the copper ion is incorporated into peptides, another ligand as methionine could bind to this system and carry an antioxidant site to different brain regions.

Nonlinear optical (NLO) properties and temperature-dependent photoluminescence in activator-doped noncentrosymmetric (NCS) bismuth tellurite solid solutions, Bi2−xLnxTeO5 (Ln = Ce and Eu)

Activator-doped noncentrosymmetric (NCS) bismuth tellurite solid solutions, Bi2−xLnxTeO5 (Ln = Ce and Eu), have been successfully synthesized by solid state reactions. Crystal structure determination by powder X-ray diffraction using Rietveld method suggests that the solid solutions crystallize in the polar space group, Abm2 with pseudo-three-dimensional frameworks consisting of asymmetric polyhedra. Powder nonlinear optical (NLO) measurements, using 1064 nm radiation, reveal that the origin of large second-harmonic generation (SHG) efficiency of Bi2−xLnxTeO5 is the polarization arising from the alignment of lone pair cation, Bi3+. Photoluminescence (PL) intensity of Bi1.9Ce0.1TeO5 increases as temperature increases attributed to the greater occupation of the higher excited state. PL intensity of Bi1.9Eu0.1TeO5, however, increases as temperature decreases attributable to the distinct emission mechanisms at different temperatures. PL measurements also strongly suggest that the Bi3+ sites are in unsymmetrical coordination moieties within the framework.

New quaternary oxides with both families of second-order Jahn–Teller (SOJT) distortive cations: Solid-state synthesis, structure determination, and characterization of YNbTe2O8 and YNbSe2O8

Two novel quaternary mixed metal tellurite and selenite, YNbTe2O8 and YNbSe2O8, respectively, have been synthesized through standard solid-state reactions using Y2O3, Nb2O5, TeO2 or SeO2 as reagents. Single crystal X-ray and powder neutron diffraction analyses have been utilized to determine the structures of the reported materials. YNbTe2O8 and YNbSe2O8 are isostructural to each other and crystallize in the monoclinic centrosymmetric space group, C2/m (No. 12). Due to the two families of constituent second-order Jahn–Teller (SOJT) distortive cations, i.e., Nb5+ and Te4+/Se4+, local asymmetric environments occur from the three-dimensional frameworks. Intra-octahedral distortions along the local C4 direction and asymmetric trigonal pyramidal coordination moieties generated by stereoactive lone pairs are observed from the NbO6 octahedra and TeO3 (or SeO3) polyhedra, respectively. Thermogravimetric analysis, infrared and UV–vis diffuse reflectance spectroscopies, elemental analysis, out-of-center distortions, dipole moment calculations, and electronic structure calculations for the reported materials are presented.

A new salicylate synthase AmS is identified for siderophores biosynthesis in Amycolatopsis methanolica 239(T).

Siderophores are important for the growth of bacteria or the applications in treatment of iron overload-associated diseases due to the iron-chelating property. Salicylate synthase played a key role in the biosynthesis of some NRPS-derived siderophores by the providing of an iron coordination moiety as the initial building block. A new salicylate synthase, namely AmS, was identified in the biosynthesis pathway of siderophore amychelin in Amycolatopsis methanolica 239(T), since it shunt chorismate, an integrant precursor, from primary to secondary metabolite flow. The amino acid sequence alignment and phylogenetic analysis showed that AmS grouped into a new cluster. In vitro assays of AmS revealed its wide temperature tolerance ranged from 0 to 40 °C and narrow pH tolerant ranged from 7.0 to 9.0. AmS was resistant to organic solvents and non-ionic detergents. Moreover, AmS converted chorismate to salicylate with K m of 129.05 μM, k cat of 2.20 min(-1) at optimal conditions, indicating its low substrate specificity and comparable velocity to reported counterparts (Irp9 and MbtI). These properties of AmS may improve the iron-seizing ability of A. methanolica to compete with its neighbors growing in natural environments. Most importantly, serine and cysteine residues were found to be important for the catalytic activity of AmS. This study presented AmS as a new cluster of salicylate synthase and the reaction mechanism and potential applications of salicylate synthase were highlighted as well.

Synthesis, Characterization and Catalytic Performance of a Novel Picolinic Acid-12-Molybdophosphoric Acid Hybrid Catalyst

A novel 12-molybdophosphoric acid (HPM)-based complex (H2PI)2(H3O)[PMo12O40][Mo2O5(H2O)2(PI)2]·11H2O (PI-HPM) was prepared by modification with picolinic acid (HPI) and characterized by the methods of Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), X-ray powder and single crystal diffraction. The complex retained the classical Keggin structure of bulk HPM, there were some strong hydrogen bonds existing between the [PMo12O40]3- polyanion, the [Mo2O5(H2O)2(PI)2] coordination moiety, the protonated HPI and the lattice water molecules. Then PI-HPM was employed as heterogeneous catalyst for esterification reaction to evaluate its acid-catalytic activity. The complex exhibited high activity and good durability in reaction mixtures, indicating that it was a promising heterogeneous acid catalyst for esterification that including the conversion of oleic acid to oleates.

Rich structural chemistry in scandium selenium/tellurium oxides: mixed-valent selenite-selenates, Sc2(SeO3)2(SeO4) and Sc2(TeO3)(SeO3)(SeO4), and ternary tellurite, Sc2(TeO3)3.

Both single crystals and pure bulk phases of three new scandium selenium/tellurium oxides, Sc2(SeO3)2(SeO4), Sc2(TeO3)(SeO3)(SeO4), and Sc2(TeO3)3, have been synthesized through hydrothermal and solid-state reactions. X-ray diffractions were used to determine the structures and confirm the phase purities of the reported materials. Isostructural Sc2(SeO3)2(SeO4) and Sc2(TeO3)(SeO3)(SeO4) reveal three-dimensional frameworks with ScO7 pentagonal bipyramids, SeO3 (and TeO3) trigonal pyramids, and SeO4 tetrahedra. A novel ternary scandium tellurite, Sc2(TeO3)3, also shows a three-dimensional framework that is composed of ScO6 octahedra, ScO7-capped octahedra, and TeO3 trigonal pyramids. All three materials accommodate local asymmetric coordination moieties owing to the lone pairs on Se(4+) and Te(4+) cations. The effect of coordination environments of constituent cations on the frameworks, dimensionalities, and centricities of products is discussed. Thorough characterizations including elemental analyses, infrared and UV-vis diffuse reflectance spectroscopies, thermal analyses, and dipole moment calculations for the reported materials are reported. Crystal data: Sc2(SeO3)2(SeO4), monoclinic, space group P21/c (No. 14), a = 6.5294(2) Å, b = 10.8557(4) Å, c = 12.6281(6) Å, β = 103.543(3)°, V = 870.21(6) Å(3), and Z = 4; Sc2(TeO3)(SeO3)(SeO4), monoclinic, space group P21/c (No. 14), a = 6.5345(12) Å, b = 10.970(2) Å, c = 12.559(2) Å, β = 102.699(10)°, V = 878.3(6) Å(3), and Z = 4; Sc2(TeO3)3, monoclinic, space group P21/n (No. 14), a = 5.2345(3) Å, b = 24.3958(15) Å, c = 6.8636(4) Å, β = 106.948(2)°, V = 838.42(9) Å(3), and Z = 4.

New organic–inorganic hybrid assemblies based on copper(I) ion, bichelate-bridging ligand and Lindqvist-type polyoxometalate

Three new organic–inorganic hybrid compounds, namely [CuILp]2[W6O19]·H2O (1), [CuILp]3[W6O19]Cl (2) and [CuILp]2[W6O19]·2H2O (3) (Lp=α,α′-bis-[3-(2-pyridyl)pyrazol-1-yl]-1,4-dimethylbenzene) based on copper(I) ion, a neutral N-donor bichelate-bridging ligand (Lp) and a Lindqvist-type polyoxometalate (POM) [W6O19]2−, have been hydrothermally prepared under different synthetic conditions and structurally characterized by elemental analyses, IR spectra, TG analyses, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction analyses. Compounds 1 and 2 contain two different but topologically similar meso-helical chainlike coordination moieties. Compound 3 contains both left- and right-handed chiral “mobius strip” units. These cationic meso-helical chains and “mobius strip” units in compounds 1–3 are further combined with Lindqvist-type polyoxoanions to form 3-D supramolecular assemblies through extensive electrostatic forces and/or π–π interactions. The photo-luminescent properties of 1–3 have also been investigated, which are mainly attributed to the Lp ligand-centered emission.

A water-soluble fluorescent probe for Fe(III): Improved selectivity over Cr(III)

A water-soluble rhodamine-based fluorescent probe (RD2) was designed and synthesized. Compared with the precursor RD1, RD2 shows excellent selectivity for Fe3+ over Cr3+ during the detection. The enhanced selectivity was achieved by incorporating another coordination moiety to the chelating moiety of the precursor RD1. Furthermore, bioimaging studies indicated that RD2 was cell permeable and suitable for the real-time imaging of Fe3+ in the living cells by confocal microscopy.

New organic–inorganic hybrid assemblies based on metal–bis(betaine) coordination complexes and Keggin-type polyoxometalates

The slow diffusion reactions of a double-betaine-containing ligand with YbH[SiMo12O40]·nH2O and Ca2[SiMo12O40]·nH2O led to the isolation of two new organic–inorganic hybrid assemblies, [Yb(O)(HL)2(H2L)0.5(H2O)3][SiMo12O40]·2.5CH3CN·1.5H2O (1) and [Ca(HL)2(L)0.5(H2O)4] [SiMo12O40]·5CH3CN·H2O (2) (L=1,4-bis(pyridinil-4-carboxylato)-l,4-dimethylbenzene). Compounds 1–2 were characterized by elemental analyses, TG, IR, XPS and single-crystal X-ray diffraction. Compound 1 contains the dinuclear [(YbO)(HL)2(H2O)3]2 coordination moieties and discrete protonated L ligands, which are connected together by H-bonds and π–π interactions to form a 3D supramolecular framework with the Keggin-type [SiMo12O40]4− polyoxoanions and solvent molecules encapsulated. Compound 2 possesses discrete [Ca(HL)2(L)0.5(H2O)4]2 coordination units that are linked by the extensive intermolecular H-bonds and π–π interactions to form a 3D supramolecular framework with the [SiMo12O40]4− polyoxoanions and solvent molecules are encapsulated in the interbedded cavities. The structural motifs of the metal–organic coordination units can be obviously modulated by the use of chemically different cationic nodes. The degradation of Rhodamine-B (RhB) under UV irradiation with compounds 1 and 2 as heterogeneous photocatalysts were investigated, both exhibiting good photocatalytic properties. Furthermore, these hybrid compounds display luminescent properties induced by organic ligands.