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Saponification, resulting from pigment–binder interactions, is one of the most endangering phenomena affecting the appearance and stability of painted works of art. The crystallization of metal carboxylates (soaps) in paint layers is recently assumed as the most critical point for the development of undesirable changes induced by saponification, however, the factors triggering it are not fully understood. The red pigment cinnabar (HgS) has been suspected of contributing to saponification, however, the paucity of reliable reference structural data limited the experimental research of its effect at the molecular level. Within this study we synthesized mercury(II) carboxylates of the formula Hg(C16)x(C18)2−x (x = 0.0; 0.2; 0.5; 0.8; 1.0; 1.2; 1.5; 1.8; 2.0) where C16 and C18 are hexadecanoate (palmitate) and octadecanoate (stearate), respectively, and characterize them by combination of X-ray powder diffraction (XRPD) and 13C and 199Hg solid state NMR (ssNMR). For a more detailed interpretation of their structural and thermal behavior, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used. The crystal structure of the studied mercury carboxylates was described on the basis of complementary ssNMR and XRPD measurements, Rietveld refinement and DFT calculations. All the subjected compounds crystallize in a monoclinic lattice of the C2/c symmetry. Mercury atoms are arranged in a slightly distorted square antiprismatic geometry and are monodentatically bonded to carboxylate anions. The structural disorder at the aliphatic end of the stearic acid chains was detected in the mixed carboxylates. Within the paper, the structural (dis)similarity with the corresponding lead carboxylates is discussed. The synthesized and characterized mercury carboxylates were applied to describe neo-formed mercury soaps in a model experiment simulating an egg-based paint system. [ABSTRACT FROM AUTHOR]

Coordination polymers (CPs) in recent times have emerged as active constituents in many semiconductor devices like light emitting diodes (LED), field effect transistors (FET), photovoltaic devices and Schottky barrier diodes. An intelligent choice of linkers, careful selection of metal ions and post synthetic modification (PSM) can provide a better pathway for charge transportation. However, a proper understanding of the charge transport mechanism in CPs is still inadequate due to the lack of considerable experimental and theoretical work. In this paper, we address the theoretical elucidation of semiconducting properties and a probable pathway for charge transportation in three of our previously published CPs using density functional theory (DFT). These results help us to recognize the orbitals that have major contributions in the formation of the valence band and also provide the most likely pathway for optimum electronic communication. In this regard, the role of hydrogen bonding and unpaired electrons of metal d-orbitals is also established. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are commonly prepared using a “bottom-up” synthetic procedure. The alternative “top-down” approach of disassembling a pre-formed POM unit to generate new synthetic intermediates is promising, but relatively comparatively underused. In this paper, a rationale for the top-down method is provided, demonstrating that this approach can generate compounds that are fundamentally inaccessible from simple bottom-up assembly. We demonstrate this principle through the synthesis of a series of 10, new, mixed-metal, hybrid compounds with the general formula [TBA]2[MoVI10CoII6O30(RpPO3)6(RcCOO)2(L)x(H2O)6] (TBA = tetrabutylammonium, Rp = phosphonate moiety, Rc = carboxylate moiety, L = pyridyl ligand, and x = 2–4), including a one-dimensional polyoxometalate-based coordination polymer. We propose that these structures are generated from {MoxO3x−1} fragments that cannot be accessed from bottom-up assembly alone. The POM clusters are stabilised by three distinct classes of organic ligand – organophosphonate, carboxylate and pyridyl ligands – which can each be substituted independantly, thus providing a controlled route to ligand functionalisation. [ABSTRACT FROM AUTHOR]

Chiral nickel complexes containing NHC-carboxylate chelate ligands derived from the (S)-isomeric form of amino acids have been synthesised from the corresponding imidazolium salt and nickelocene. The presence of the carboxylate on the N-side arm of the heterocycle results in the competing formation of mixtures of mono- and bis-NHC complexes (i.e., [Ni(η5-Cp)(κ2-C,O-NHC)] and [Ni(κ2-C,O-NHC)2]), both of which retain the (S)-configuration of the stereogenic center and which can be separated by chromatography. Both the 18e− and 16e− complexes are found to be very stable and cannot be interconverted. The composition of the resulting mixtures depends mainly on the entity of the amino acid residue and, of more practical interest, on the reaction conditions. Thus, microwave heating and MeCN as a solvent favor the formation of the half-sandwich nickel complexes, rather than the bis-NHC compounds. Some of the [Ni(η5-Cp)(κ2-C,O-NHC)] complexes turn out to be among the best nickel catalysts for the hydrosilylative reduction of p-acetophenones described to date, although without chiral induction, in the absence of activating additives and under mild catalytic conditions. [ABSTRACT FROM AUTHOR]

A series of medium- and long-chain zinc carboxylates (zinc octanoate, zinc nonanoate, zinc decanoate, zinc undecanoate, zinc dodecanoate, zinc pivalate, zinc stearate, zinc palmitate, zinc oleate, and zinc azelate) was analyzed by ultra-high-field 67Zn NMR spectroscopy up to 35.2 T, as well as 13C NMR and FTIR spectroscopy. We also report the single-crystal X-ray diffraction structures of zinc nonanoate, zinc decanoate, and zinc oleate—the first long-chain carboxylate single-crystals to be reported for zinc. The NMR and X-ray diffraction data suggest that the carboxylates exist in three distinct geometric groups, based on structural and spectroscopic parameters. The ssNMR results presented here present a future for dynamic nuclear polarization (DNP)-NMR-based minimally invasive methods for testing artwork for the presence of zinc carboxylates. [ABSTRACT FROM AUTHOR]

Using a dicarboxylic acid, [1,1′-biphenyl]-4,4′-dicarboxylic acid (H2L1) and an exobidentate ligand, (1E,1′E)-N,N′-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) (L2), two 3D interpenetrated networks, {[Zn3(L1)3(L2)]·9H2O}n (Zn-MOF) and {[Co3(L1)3(L2)(DMF)]·0.5DMF}n (Co-MOF), have been prepared in good yields. The crystal structure analysis of Zn-MOF and Co-MOF revealed that both have a 3D pillared-layer structure based on pinwheel trinuclear metal–carboxylate clusters as secondary building units (SBUs). Furthermore, the structures also exhibited three-fold interpenetration. Although the overall networks in Zn-MOF and Co-MOF showed significant resemblances, there are marked differences in their crystal structures, which are associated with the coordination environment of the metal centre and the binding modes of the carboxylates. Gas adsorption studies (N2 at 77 K and 1 bar) indicated that Co-MOF is more porous than Zn-MOF. Magnetic measurements on Co-MOF indicate a significant antiferromagnetic interaction (45 K to 303 K) between trimeric Co(II) S = 3/2 spins through syn–syn carboxylato bridges. Both MOFs were studied for the Lewis acid catalyzed Knoevenagel condensation reactions between benzaldehydes and malononitrile with an active methylene group, where Zn-MOF was found to be a better catalyst than Co-MOF. This was supported by the Monte Carlo simulations indicating the better substrate binding ability of Zn-MOF than Co-MOF. [ABSTRACT FROM AUTHOR]

The paper reports the syntheses, crystal structures, thermal and (photo)magnetic properties of spin crossover salts of formula [Fe(bpp)2](C6H8O4)·4H2O (1·4H2O), [Fe(bpp)2](C8H4O4)·2CH3OH·H2O (2·2MeOH·H2O) and [Fe(bpp)2](C8H4O4)·5H2O (2·5H2O) (bpp = 2,6-bis(pyrazol-3yl)pyridine; C6H8O4 = adipate dianion; C8H4O4 = terephthalate dianion). The salts exhibit an intricate network of hydrogen bonds between low-spin iron(ii) complexes and carboxylate dianions, with solvent molecules sitting in the voids. Desolvation is accompanied by a low-spin (LS) to high-spin (HS) transformation in the materials. The dehydrated phase 2 undergoes a two-step transition with a second step showing thermal hysteresis (T1/2↑ = 139 K and T1/2↓ = 118 K). 2 displays a quantitative LS to HS photomagnetic conversion, with a T(LIESST) value of 63 K. [ABSTRACT FROM AUTHOR]

Responsive molecular chromic materials have shown potential applications in molecular optical switches and sensor devices as they undergo reversible colour changes upon application of external stimuli. Herein, six host–guest coordination polymers 1–6 and one organic supramolecular compound 7 containing viologens have been synthesized under hydrothermal conditions. Compound 1 shows thermochromic behavior with a colour change from green to blue upon heating at 150 °C in air. Compounds 3, 4 and 7 display photochromic behaviors with a colour change from pale yellow to green under UV light, visible light or sunlight. The relationship between their structures and chromic behaviors has been discussed. Thermo/photochromic mechanisms have been investigated by infrared spectroscopy, powder X-ray diffraction analysis, UV-vis absorption spectroscopy, electron paramagnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. The results demonstrate the generation of viologen radicals caused by thermo/photo-induced electron transfer. It is found that compound 4 can be used as an inkless and erasable printing medium. In addition, compounds 3, 4, and 7 can be used as anti-counterfeiting materials for QR codes. Our findings demonstrate the possibility of applying thermo/photochromic coordination polymers in molecular devices. [ABSTRACT FROM AUTHOR]

In this study, we fabricated a novel non-enzymatic glucose sensor based on prism-like bimetallic alkaline carboxylate (CoNi–MIM). The morphology and structure of CoNi–MIM were carefully investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical glucose oxidation of the synthesized sensor was then explored by cyclic voltammetry (CV) and chronoamperometry in alkaline medium. It was found that CoNi–MIM is the optimal choice with a remarkably high sensitivity of 5024.4 μA mM−1 cm−2, low detection limit of 56.1 nM (S/N = 3), linear response of up to 14.3 mM and excellent selectivity compared to Co-MIM, CoFe-MIM and CoMn-MIM. Furthermore, the as-fabricated sensor demonstrated appreciable practicality for the determination of glucose in real samples. These results indicate that CoNi–MIM holds a good application prospect in non-enzymatic glucose sensing. [ABSTRACT FROM AUTHOR]

The novel coordination polymer [Eu(O2CCF3)2(dmf)2]∞ (1) (dmf = N,N-dimethylformamide) containing europium(II) and the two new compounds (NH4)2[Eu6F8(O2CCF3)12(CF3COOH)6] (2) and (NH4)2[Eu6F8(O2CC2F5)12(C2F5COOH)6]·8C2F5COOH (3), both based on hexanuclear europiate(III) complexes, were synthesized from precursors with a Eu2+ : Eu3+ ratio >1, obtained by reaction of europium metal with ammonium perfluorocarboxylates in liquid ammonia. In the crystal structure of 1 the europium(II) ions are bridged by carboxylate groups and N,N-dimethylformamide to form polymeric chains with Eu2+⋯Eu2+ distances of 408.39(13)–410.49(13) pm. The compound crystallizes in the triclinic space group P1¯ (Z = 2). To the best of our knowledge, this is the first example of a (solvated) perfluorocarboxylate containing a lanthanoid in a subvalent oxidation state. In the crystal structures of 2 and 3 the europium(III) ions are bridged by fluoride ions and carboxylate groups to form hexanuclear complex anions with an octahedral arrangement of the cations. The Eu3+⋯Eu3+ distances are in the range of 398.27(15)–400.93(15) pm in 2 and 395.37(4)–399.78(5) pm in 3, respectively. Both compounds crystallize in the monoclinic space group type P21/n (Z = 4) and are the first examples of octahedro-hexanuclear europium carboxylates for which fluoride is reported as a bridging ligand. In all compounds the oxidation state of europium was monitored via151Eu Mössbauer and photoluminescene spectroscopy. [ABSTRACT FROM AUTHOR]

Three novel fluorescent Zn(II) frameworks, namely [Zn(DPA)(NDA)]2·2DMF (1), [Zn2(DPA)(OBA)2]·2DMF·4H2O (2) and [Zn(DPA)(HNTB)]·H2O (3) (DPA = 2,5-di(pyridin-4-yl)aniline, H2NDA = 1,4-naphthalenedicarboxylic acid, H2OBA = 4,4′-oxydibenzoic acid, H3NTB = 4,4′,4′′-nitrilotribenzoic acid, DMF = N,N-dimethylformamide), were successfully fabricated and structurally characterized. Due to the variety of organic linkers, 1–3 exhibit varied topologies: 1 is a 4-c three-dimensional (3D) framework with {65·8} topology, 2 is a 6-c 3D net with point symbol of {44·610·8}, and 3 is a 4-c two-dimensional network that further stacks into a 3D structure by hydrogen bonding interactions with {44·62} topology. Experiments related to fluorescence show that 1–3 can be utilized to quickly identify specific anions of CrO42−/Cr2O72−, and organic molecules such as 2,4,6-trinitrophenol and benzaldehyde. [ABSTRACT FROM AUTHOR]

Four cobalt(II)–carboxylate complexes [(6-Me3-TPA)CoII(benzoate)](BPh4) (1), [(6-Me3-TPA)CoII(benzilate)](ClO4) (2), [(6-Me3-TPA)CoII(mandelate)](BPh4) (3), and [(6-Me3-TPA)CoII(MPA)](BPh4) (4) (HMPA = 2-methoxy-2-phenylacetic acid) of the 6-Me3-TPA (tris((6-methylpyridin-2-yl)methyl)amine) ligand were isolated to investigate their ability in H2O2-dependent selective oxygenation of C–H and C＝C bonds. All six-coordinate complexes contain a high-spin cobalt(II) center. While the cobalt(II) complexes are inert toward dioxygen, each of these complexes reacts readily with hydrogen peroxide to form a diamagnetic cobalt(III) species, which decays with time leading to the oxidation of the methyl groups on the pyridine rings of the supporting ligand. Intramolecular ligand oxidation by the cobalt-based oxidant is partially inhibited in the presence of external substrates, and the substrates are converted to their corresponding oxidized products. Kinetic studies and labelling experiments indicate the involvement of a metal-based oxidant in affecting the chemo- and stereo-selective catalytic oxygenation of aliphatic C–H bonds and epoxidation of alkenes. An electrophilic cobalt–oxygen species that exhibits a kinetic isotope effect (KIE) value of 5.3 in toluene oxidation by 1 is proposed as the active oxidant. Among the complexes, the cobalt(II)-benzoate (1) and cobalt(II)-MPA (4) complexes display better catalytic activity compared to their α-hydroxy analogues (2 and 3). Catalytic studies with the cobalt(II)–acetonitrile complex [(6-Me3-TPA)CoII(CH3CN)2](ClO4)2 (5) in the presence and absence of externally added benzoate support the role of the carboxylate co-ligand in oxidation reactions. The proposed catalytic reaction involves a carboxylate-bridged dicobalt complex in the activation of H2O2 followed by the oxidation of substrates by a metal-based oxidant. [ABSTRACT FROM AUTHOR]

Herein we report a new series of bifunctional chelators (BFCs) with high affinity for amyloid β aggregates, strong binding affinity towards Cu(II), and favorable lipophilicity for potential blood–brain barrier (BBB) penetration. The alkyl carboxylate ester pendant arms show high binding affinity towards Cu(II). The BFCs form stable 64Cu-radiolabeled complexes and exhibit favorable partition coefficient (log D) values of 0.75–0.95. Among the five compounds tested, 64Cu-YW-1 and 64Cu-YW-13 complexes exhibit significant staining of amyloid plaques in ex vivo autoradiography studies. [ABSTRACT FROM AUTHOR]

An 18-metal lanthanide nanoring [Yb18(L1)8(HL2)2(OAc)20(MeOH)8(EtOH)6(H2O)4] (1), which shows a ratiometric fluorescent response to DPA, was constructed through the strategy of using two types of polydentate organic ligands. The addition of DPA increases the visible ligand-centered emission, but decreases the NIR lanthanide luminescence of 1. The limit of luminescent detection of 1 for DPA is 1.5 μM. The high fluorescence sensitivity of 1 to DPA is not affected by the existence of interferents such as aromatic carboxylates and ions. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of the adducts of n-alkyl amine and palladium n-alkyl carboxylate, [Pd(R2NH2)2(R1COO)2] (R1 = 1, 7, and 11; R2 = 8, 12, and 16), as precursors for the synthesis of palladium nanoparticles (PdNPs) was carried out via differential scanning calorimetry, FT-IR, Raman and UV-Vis spectroscopy, NMR spectroscopy (1H, 13C pulsed field gradient spin-echo (PGSE), and 13C CP-MAS), and powder X-ray diffraction. Pd n-alkyl carboxylates were obtained by a ligand exchange reaction from palladium acetate and the appropriate aliphatic carboxylic acid. It is proposed that carboxyl moieties in the presence of amine ligands are bound to palladium ions via monodentate bonding as opposed to bridging bidentate coordination of pure palladium carboxylate which exists in the form of polymer aggregates. All the studied palladium carboxylate/amine complexes form bilayer lamellar structures and exhibit first-order melting transitions. The evidence presented in this study shows that the phase behavior of bivalent metal carboxylates is mainly controlled by the type of coordination of carboxylate head groups. For n-alkyl carboxylates, linear chain type aggregates replace the trimeric units of Pd acetate. In solution, in the presence of amine, palladium salt aggregates disintegrate and the Pd complex is isolated and stabilized by amine molecules. Using bis(amine) palladium carboxylate adducts as precursors, palladium nanoparticles were fabricated. During high temperature thermolysis, the bis(amine) Pd carboxylate complex decomposes to form small sized Pd nanoparticles. Combining NMR techniques with FTIR spectroscopy, it was possible to follow an original stabilization mechanism. PdNPs are stabilized by weakly interacting long chain aliphatic amide and carboxylic acid derived from the palladium precursor. [ABSTRACT FROM AUTHOR]

The precious group metal (PGM) analogues of the iconic metal–organic framework [Cu3(BTC)2] (HKUST-1; BTC = 1,3,5 benzenetricarboxylate) still represent a synthetic challenge, especially if targeting the univalent and ideally defect-free RuII,II variant. Herein we present a systematic study employing the controlled secondary building unit approach (CSA) by using a variety of diruthenium tetracarboxylate complexes [Ru2(RCO2)4] as precursors in the synthesis of univalent Ru-HKUST-1 samples. Carboxylate ligand exchange test reactions suggest the importance of a pKa match between precursor ligand and BTC linker. For example, L -mandelate substituted precursors resulted in the most "perfect" samples of the investigated series with a fourfold increase in crystalline domain sizes compared to the established acetate route (according to PXRD and HR-TEM), high compositional purity (FT-IR, Raman, TGA and elemental analysis) and feature a so far unprecedentedly high BET surface area of 1789 m2 g−1 with the expected pore size distribution and total pore volume all similar to the ideal HKUST-1 parent structure. [ABSTRACT FROM AUTHOR]

The structures of the single crystals of compounds K2UO2(tca)4(tcaH)2 (I), K4NpO2(tca)6(tcaH)(H2O)3 (II), Rb4UO2(tca)6(tcaH)(H2O)3 (III), and Cs3UO2(tca)5(tcaH)2·H2O (IV), where tca is the trichloroacetate ion, were established by X-ray diffraction analysis. The crystals of II–IV have a framework structure, whereas in the layered crystals of I, neighboring layers are connected to each other via halogen bonds. In this regard, the crystals of I possess perfect cleavage along the (001) plane: the crystals are easily cut into stacks of very thin layers. Halogen bonds in the structures of all title compounds were characterized using the method of molecular Voronoi–Dirichlet polyhedra. The donor–acceptor halogen bond synthon, where the same halogen atom is both the donor towards one halogen atom and the acceptor from the second halogen atom, is recognized for its usefulness in the crystal design. The description of the ligand coordination modes and crystal chemical formulae of complexes is adapted for cases when ligands have chemically non-equivalent and unobvious donor atoms (for example, oxygen and halogen atoms in halogen-substituted carboxylate anions). [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have attracted significant attention as sorbents due to their high surface area, tunable pore volume and pore size, coordinatively unsaturated metal sites, and ability to install desired functional groups by post-synthetic modification. Herein, we report three new MOFs with pillar–paddlewheel structures that have been synthesized solvothermally from the mixture of the carboxylate–pyrazole flexible linker (H2L), 4,4-bipyridine (BPY)/triethylenediamine (DABCO), and Zn(II)/Cu(II) ions. The MOFs obtained, namely [ZnII(L)BPY], [CuII(L)BPY], and [CuII(L)DABCO], exhibit two-fold interpenetration and dinuclear paddle–wheel nodes. The Zn(II)/Cu(II) cations are coordinated by two equatorial L linkers that result in two-dimensional sheets which in turn are pillared by BPY or DABCO in the perpendicular direction to obtain a neutral three-dimensional framework that shows one-dimensional square channels. The three pillar-layered MOFs were characterized as microporous materials showing high crystalline stability after activation at 120 °C and CO2 adsorption. All MOFs contain uncoordinated Lewis basic pyrazole nitrogen atoms in the framework which have an affinity toward CO2 and hence could potentially serve as CO2 adsorption material. The CO2 uptake capacity was initially enhanced by replacing Zn with Cu and then replacing the pillar, going from BPY to DABCO. Overall, all the MOFs exhibit low isosteric heat (Qst) of adsorption which signifies an advantage due to the energy required for the adsorption and regeneration processes. [ABSTRACT FROM AUTHOR]

The self-assembly of Mn(II), bis(tridentate) ligands and bent dicarboxylate linkers under ambient conditions has been exploited to generate a series of 1D coordination polymers in good yields. For a set of seven compounds, structural isomerization of these architectures is demonstrated through the variation of length and nature of the spacer between the tridentate capping sites of the bis(tridentate) ligands, such as tpbn (N,N′,N′′,N′′′-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane), tphxn (N,N′,N′′,N′′′-tetrakis-(2-pyridylmethyl)-1,6-diaminohexane), and tpxn (N,N′,N′′,N′′′-tetrakis-(2-pyridylmethyl)-xylylamine) or by varying the bent dicarboxylate linker 4,4′-(dimethylsilanediyl)bis-benzoic acid (H2L1) or 4,4′-oxybis-benzoic acid (H2L2). These compounds have been structurally characterized by single-crystal and powder X-ray diffraction, FTIR, and thermogravimetric and elemental analyses. This study reveals that the supramolecular structural variation can be precisely controlled either by a judicious selection of reaction conditions or linker/ligand combinations. For example, the self-assembly of Mn(II), tpbn and H2L1 in DMF/EtOH/water affords a mixture of products (1 and 1a) while changing the solvent combination to EtOH/water results in the generation of a single isomer (1a) in a highly selective manner. On the other hand, for the Mn(II)-tphxn system, different structural isomers have been isolated by varying the dicarboxylates, H2L1 and H2L2 (2vs.5). Similarly, for the Mn(II)-H2L2 system, a variation in the spacer chain length of bis(tridentate) ligands, tpbn and tphxn resulted in the formation of different structural isomers (4vs.5). [ABSTRACT FROM AUTHOR]

We describe the synthesis and characterization of a new trinuclear Ni(II) Schiff base complex of formula [Ni3(L)2(NCS)2(OAc)2(CH3OH)2] (1) where HL is the 1 : 1 condensation product of 2-picolylamine and o-vanillin. The crystal structure of complex 1 shows that the two terminal Ni(II) ions are connected to the central one through a phenoxido- and a syn–syn acetato bridge, giving rise to a very bent configuration in the Ni3-core. Magnetic susceptibility measurements show the presence of a weak antiferromagnetic coupling with J = −3.22(2) cm−1. We also report a magneto-structural correlation, performed with all the magnetically characterized Ni(II) trimers with similar bridges, showing a linear dependence between the J value and the dihedral angle () between the planes containing the Ni–O–Ni and the carboxylate bridges. The super-exchange interaction is investigated by extensive density functional calculations within the broken symmetry approximation which show good agreement with the experimental data. The analysis of the spin density distribution and the shape of the magnetically active single occupied molecular orbitals (SOMO) provide a mechanism of exchange coupling through the bridging groups. [ABSTRACT FROM AUTHOR]

By utilizing the hybrid-ligand conception, three novel dysprosium complexes Dy(2-py-4-pmc)(L)(H2O) (H2-py-4-pmc = 2-(2-pyridyl)pyrimidine-4-carboxylic acid; L = fumarate (fum, 1), succinate (suc, 2), or pimelate (pim, 3)) have been successfully synthesized. Structural analysis reveals that the dicarboxylate ligands connect 2-py-4-pmc−-protected Dy3+ to form one-dimensional molecular ribbons. Magnetic measurements indicate that the three complexes exhibit typical slow magnetic relaxation under a zero dc field with effective reversal barriers Ueff of 180 K, 145 K and 137 K for 1–3, respectively, which is mainly attributed to the strong Ising anisotropy of dysprosium ions induced by the appropriate arrangement of carboxylate groups. Ab initio calculations demonstrate that the charge distribution around dysprosium ions and the magnetic interactions between them are key contributions to their different dynamic behaviour. [ABSTRACT FROM AUTHOR]

The Cu(II) heptanuclear complex (Cu7atac) was synthesised using the hydrated amino acid ligand 2-(5-amino-1H-1,2,4-triazol-3-yl)acetic acid (Hatac·H2O). Single crystal X-ray diffraction analysis revealed a μ3-hydroxo bridged Cu(II) heptanuclear complex, consisting of two triangular subunits and one Cu(II) ion as a bridge with the formula [Cu7(atac)6(μ3-OH)2(NO3)2(H2O)10](NO3)4. The magnetic behaviour of this discrete 0D complex shows strong antiferromagnetic couplings between Cu(II) mediated by N,N bonding and an anti–anti modes of the carboxylate anion of the ligand atac−. The magnetic data were fitted considering a 3J model. To support the model used to fit the magnetic data of the Cu7atac complex, theoretical calculation methods (complete active space self-consistent field, CASSCF, density functional theory (DFT) using the UKS TPSS/Def2-TZVP//Def2-SVP level and periodic boundary conditions (PBC) using PBE/DZVP-MOLOPT-GTH) were performed to obtain the spin states, spin density map and J couplings. The theoretical results suggest that Cu7atac is a spin-frustrated complex in the ground state, in which the doublet spin state co-exists with the quartet spin state. [ABSTRACT FROM AUTHOR]

Incorporating molecular catalysts into metal–organic frameworks (MOFs) is a promising strategy for improving their catalytic longevity and recyclability. In this article, we investigate and compare synthetic routes for the incorporation of the potent water oxidation catalyst Ru(tda)(pyCO2H)2 (tda = 2,2′:6′,2′′-terpyridine-6,6′′-dicarboxylic acid, pyCO2H = iso-nicotinic acid) as a structural linker into a Zr-based UiO-type MOF. The task is challenging with this particular metallo-linker because of the equatorial dangling carboxylates that can potentially compete for Zr-coordination, as well as free rotation of the pyCO2H groups around the HO2Cpy⋯Ru⋯pyCO2H axis. As a consequence, all attempts to synthesize a MOF with the metallo-linker directly under solvothermal conditions led to amorphous materials with the Ru(tda)(pyCO2H)2 linker coordinating to the Zr nodes in ill-defined ways, resulting in multiple waves in the cyclic voltammograms of the solvothermally obtained materials. On the other hand, an indirect post-synthetic approach in which the Ru(tda)(pyCO2H)2 linker is introduced into a preformed edba-MOF (edba = ethyne dibenzoic acid) of UiO topology results in the formation of the desired material. Interestingly, two distinctly different morphologies of the parent edba-MOF have been discovered, and the impact that the morphological difference has on linker incorporation is investigated. [ABSTRACT FROM AUTHOR]

In a one-pot self-assembly reaction of Co(OAc)2·4H2O, thiophene-2,5-dicarboxylic acid (H2tdc) and four different bis(tridentate) polypyridyl spanning ligands under ambient conditions, a series of structurally diverse metal–organic frameworks has been synthesised and characterized by single crystal X-ray diffraction: {[Co2(tdc)2(tpbn)(H2O)2]·solvent}n (solvent = 2H2O, 1; solvent = 2CH3OH, 2H2O, 1a), {[Co2(tdc)2(tphn)]·solvent}n (solvent = H2O, 2; solvent = CH3OH, 2.5H2O, 2a), {[Co2(tdc)2(tpchn)(H2O)2]·solvent}n (solvent = 5H2O, 3; solvent = C2H5OH, 2H2O, 3a), and {[Co2(tdc)2(tpxn)]·solvent}n (solvent = 6H2O, 4; when no solvent, 4a), where tpbn (N,N′,N′′,N′′′-tetrakis(2-pyridylmethyl)-1,4-diaminobutane), tphn = N,N′,N′′,N′′′-tetrakis(2-pyridylmethyl)-1,6-diaminohexane, tpchn = N,N′-(cyclohexane-1,4-diylbis(methylene))bis(1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine) and tpxn = N,N′-(1,4-phenylenebis(methylene))bis(1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine). There is a profound effect of the nature of spacer between the alkyl nitrogens in the spanning ligands (flexible vs. semiflexible) on the molecular structures of 1a–4a. The notable differences are (a) the binding mode of the tridentate part of polypyridyl ligands to the Co(II) center is facial in 1a, 3a and 4a but meridional in 2a, (b) the Co(II) centers in 1a–3a are hexacoordinated (with a coordinated water in 1a and 3a) but are pentacoordinated in 4a, and (c) the binding mode of tdc linker is bis(monodentate) in 1a, 3a and 4a but chelated in one end and monodentate in the other end in 2a. Thus, the overall framework structure of 1a, 2a, 3a and 4a is cis-decalin type 2D polymer, ladder-shaped 1D polymer, hexagonal 2D net and cis-decalin type 2D polymer, respectively. Their thermal stabilities have been established by thermogravimetric analysis (TGA). The presence of an unsaturated metal center in 4 has provided us an opportunity for its use as an efficient Lewis acid catalyst for the Knoevenagel condensation reaction of malononitrile with various aldehydes (100% conversion in 60 minutes with 2 mol% catalyst in methanol). [ABSTRACT FROM AUTHOR]

A porous Zn(II)-coordination polymer, namely {[Zn2(μ8-abtc)(betib)]·DMF}n (1), was solvothermally synthesized from 3,3′,5,5′-azobenzenetetracarboxylate (abtc4−) and 1,4-bis(2-ethylimidazol-1-yl)butane (betib) ligands and {[Zn2(μ8-abtc)(betib)]·H2O}n (2) was obtained through the immersion of 1 in methanol. Compounds 1 and 2 were structurally characterized via numerous techniques. Both compounds displayed a 3D porous framework with a 3,6-connected sqc5381 net. Compound 2a obtained at 140 °C from 2 exhibited gas and iodine adsorption properties. Interestingly, the compound adsorbed selectively CO2 with the uptake capacity of 54.02 cm3 g−1 (13.26%) over N2 (5.43 cm3 g−1) and CH4 (14.53 cm3 g−1) at 273 K. The compound also adsorbed iodine with the weights of 19.99% and 30.26% in solution and vapor phases, respectively. The single crystal X-ray result and Raman spectra showed the presence of iodine units in the pores of the framework. [ABSTRACT FROM AUTHOR]

The cationic acetate ruthenium complex [Ru(η1-OAc)(CO)(dppb)(phen)]OAc (1) is easily prepared in 83% yield from [Ru(η1-OAc)(η2-OAc)(CO)(dppb)] (dppb = 1,4-bis(diphenylphosphino)butane) and 1,10-phenanthroline (phen) in MeOH. The derivative 1 undergoes easy substitution of the coordinated acetate by reaction with NaOPiv, KSAc, and KSCN in MeOH, affording the corresponding complexes [RuX(CO)(dppb)(phen)]X (X = OPiv, 2; SAc, 3; and NCS, 4), whereas its reaction with NaCl and NH4PF6 affords [RuCl(CO)(dppb)(phen)]PF6 (5). Carboxylate complexes 1 and 2 show high solubility in water, enabling easy exchange of the coordinated carboxylate by water and other ligands (CH3CN, glutathione). Cationic complexes 1–5, compared to Cisplatin, display a strong cell viability decrease in two human anaplastic thyroid cancer cell lines (SW1736 and 8505C), ranging from 3.10 μM to 0.09 μM EC50 values. The most active compounds 1–3 show a marked increment of apoptosis and decrease of cancer cell aggressiveness, making them promising candidates for further evaluation studies. [ABSTRACT FROM AUTHOR]

Four D–A type Zn(II) coordination complexes, [Zn(C29H29N3O2)·(CH3OH)]·(CH3OH) (1), Zn2(C74H90N6O4)·(CH3OH) (2), [Zn(C30H28N4O2)·(CH3OH)]·(CH3OH) (3) and [Zn(C38H44N4O2)·(C2H5OH)]·(C2H5OH) (4), were designed, synthesized, and studied. Their fluorescence properties in the solid state and in THF solution were comprehensively analysed based on their single-crystal structures. The results showed that the red-shift of fluorescence emission from complexes 1 to 4 was successfully achieved via the strategy of enhancing intramolecular charge transfer (ICT) effects by increasing the number of electron-pulling and pushing groups gradually. Meanwhile, because of the fluorescence recognition abilities of these four complexes towards iodide anions in THF, they could be regarded as potential fluorescent sensors for I− in this organic solution in the future. [ABSTRACT FROM AUTHOR]

Four novel polyoxouranium-based uranyl carboxylates have been constructed by using a combination of three silicon-centered carboxylate ligands and polyoxouranium building blocks. Interesting oligomerization of the uranyl groups from three types of tetrameric units in 1 and 2 to octameric [(UO2)8(μ3-OH)6(μ2-OH)2(H2O)4]8+ in 3 and ultimately infinite polyoxouranium chains in 4 was observed. The 3D structure of 2 contains two different linear tetramers, whose structures are totally different from seven types of tetranuclear motifs previously observed in uranyl carboxylates. Compound 3 displays a rare octanuclear polyoxouranium brick; it is fabricated by the association of eight uranyl units in pentagonal-bipyramidal geometry that involves the edge-sharing polyhedral connection mode, which are further linked by four isolated UO7 pentagonal bipyramids to create a complicated 3D framework. These newly synthesized hybrid materials were extensively characterized by single crystal analysis, thermogravimetric analysis (TG) and different spectroscopic techniques (IR, UV-vis, and luminescence spectroscopy), which show well-resolved characteristic "five-finger" emission of the uranyl ions under excitation at 420 nm. Relativistic density functional theory (DFT) was used to explore five model compounds that theoretically simulate experimental real compounds. Experimental spectroscopy was rationalized by electronic-structure analysis. [ABSTRACT FROM AUTHOR]

This work reports a series of five-acetate triruthenium clusters [Ru3O(OAc)5(L)(py)2]PF6, where L = dppn (benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine, 1); dppz (dipyrido[3,2-a:2′,3′-c]phenazine, 2); CH3-dppz (7-methyldipyrido [3,2-a:2′,3′-c] phenazine, 3); Cl-dppz (7-chlorodipyrido [3,2-a:2′,3′-c] phenazine, 4); and phen (1,10-phenanthroline, 5). The EPR spectra collected at 10 K displayed one isotropic signal without a hyperfine structure and with g values of ∼2.0, which showed that the five-acetate triruthenium clusters are paramagnetic, and that their electronic delocalization resembled the electronic delocalization of the parent hexa-acetate complexes. 1H NMR analysis showed that the orthometalated phenazines lowered the symmetry of the compounds significantly. Inductive effects from the carbanion and ring current effects outweighed the effect of paramagnetic anisotropy and dominated the spectra. This resulted in a lack of typical correlations with ligand parameters such as pKa that are observed for the parent hexa-acetate compounds. DFT calculations allowed for a discussion of those parameters in terms of the optimized geometry of compound 2. Natural bond orbital (NBO) results, in turn, aided the rationalization of the orthometalation reaction. The intra-cluster transitions (IC) at ∼690 nm consistently shifted to higher energies, and the redox pair [Ru3O]0/+1 also shifted to more positive E1/2 values. Again, the shifts were small and produced poor correlations with phenazine basicity. Overall, the substitution of one acetate bridge caused poor π-interactions between the delocalized [Ru3O] unit and the phenazine electron cloud. fsTA experiments, performed for the first time for such systems, showed that an 2IC excited state decayed very fast on the picosecond timescale. [ABSTRACT FROM AUTHOR]

Diphenic acid (H2dip) has been used to synthesize nine homo- or heterometallic uranyl ion complexes under solvo-hydrothermal conditions. The diphenate ligand dip2− adopts different coordination modes, mixtures of κ2-O,O′-chelation by individual carboxylate groups, chelation involving both carboxylate groups, and bridging, resulting in different associations of the cations present. [UO2(dip)] (1), [UO2(dip)(bipy)] (2), and [UO2(dip)(phen)] (3) crystallize as monoperiodic coordination polymers, complex 1 with the bridging and both chelation modes of the ligand, and 2 and 3 with only the bis-κ2-O,O′-chelated mode and further chelation by 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen). The two isomorphous complexes [H2NMe2]2[(UO2)2(dip)3] (4) and [(UO2)2Ag2(dip)3(H2O)(CH3CN)] (5) display ladder-like monoperiodic arrangements with the hydrogen bonded H2NMe2+ or carboxylate-bound, decorating Ag+ cations occupying similar positions within the chains. [Ni(R,S-Me6cyclam)(H2O)2][UO2(dip)2] (6) contains a discrete dianionic mononuclear species, while [(UO2)2(dip)2(Hdip)2Ni(cyclam)]·2H2O·2CH3CN (7) crystallizes as a monoperiodic, heterometallic polymer, with further formation of layers through reciprocal hydrogen bonding of the carboxylic acid groups. A discrete dinuclear dianionic complex is present in [Cu(R,S-Me6cyclam)][UO2(dip)(NO3)]2 (8), which crystallizes together with [(UO2)3(dip)4Cu(R,S-Me6cyclam)(H2O)2]·6H2O (9), a diperiodic assembly in which uranyl-containing dimeric units are assembled in chains through diaxial carboxylate coordination of Cu(R,S-Me6cyclam)2+ cations, with further bridging by uranyl cations generating a network with the fes topology. The uranyl emission spectra of complexes 3, 4 and 5 show the usual vibronic fine structure, while uranyl emission in 7 is largely quenched. [ABSTRACT FROM AUTHOR]

A novel 3D coordination polymer {[Cu4.5 (BTZE)1.5 (μ3-OH)3(μ-OH)(SO4)(H2O)1.5·4H2O]}n (1) was synthesized by a solvothermal reaction of 1,2-bis(tetrazol-5-yl) ethane (BTZE) with copper sulfate. Compound (1) contained triangular [Cu3(μ3-OH)] cluster based magnetic Δ-chains linked with in situ generated μ2-BTZE ligands to form a 2D cyclic annular layer. This 2D layer structure was further modified with sulfate and symmetry-related μ3-OH groups, extending to a 3D coordination framework structure. The magnetic performance of (1) was characterized in the temperature range of 2–300 K in terms of direct-current and alternating-current magnetic susceptibilities, revealing that (1) was a canted ferromagnet with a critical temperature (Tc) of 9.5 K. Notably, (1) behaved as a hard magnet with a coercive field of 2.3 kOe at 2 K, showing significant unique characteristics compared to those of the reported spin canting systems based on pure Cu(II) ions. [ABSTRACT FROM AUTHOR]

By adjusting carboxylates, six Cd(II) coordination polymers based on a naphthalene–methylene mixed-bridged-amide ligand, [Cd(L)(DNBA)2] (1), [Cd2(L)2(BDC)2(H2O)2]·2H2O (2), [Cd(L)(1,4-CHDA)] (3), [Cd(L)(HIPA)(H2O)]·H2O (4), [Cd(L)(MIP)]·H2O (5), and [Cd(L)(PMA)0.5(H2O)]·H2O (6) [L = N,N′-bis(4-methylenepyridin-4-yl)-1,4-naphthalene dicarboxamide, HDNBA = 3,5-dinitrobenzoic acid, H2BDC = 1,4-benzenedicarboxylic acid, 1,4-H2CHDA = 1,4-cyclohexanedicarboxylic acid, H2HIPA = 5-hydroxyisophthalic acid, H2MIP = 5-methylisophthalic acid and H4PMA = pyromellitic acid] have been synthesized under hydrothermal conditions. 1 shows a 4-c sql coplanar structure. 2 exhibits a 2-fold vertical interpenetrating structure based on wave-like 4-c sql layers. 3 shows a (3,5)-c pnh network containing a unique μ3-L. 4 features a 4-c sql wave-like network. 5 and 6 exhibit 3D structures with 6-c pcu and 4-c mog topologies. The number of carboxyl groups and functional group positions of the carboxylates have an important influence on the structures of the title complexes. The fluorescent responses of 1–6 towards Fe3+, anions, aspartic acid and bovine serum albumin were investigated. Among them, 4 shows sensitivity and selectivity (KSV = 1.16 × 104 L mol−1 for Fe3+, 1.03 × 104 L mol−1 for CrO42−, 1.08 × 104 L mol−1 for Cr2O72−, 1.17 × 104 L mol−1 for MnO4− and 1.05 × 104 L mol−1 for aspartic acid). [ABSTRACT FROM AUTHOR]

During the systematic investigation of the ternary system Ca(CH3COO)2–Ca(HCOO)2–H2O at room temperature, the congruent crystallisation of two solid calcium acetate formates was observed: the hitherto unknown Ca3(CH3COO)4(HCOO)2·4H2O and the poorly characterised Ca(CH3COO)(HCOO)·H2O. The latter is a frequently observed efflorescence phase found on calcareous objects and it could be also identified as a corrosion phase in a natural history collection of birds' eggs. Elemental and thermal analyses were employed to determine the phase compositions and by Raman and IR spectroscopy the presence of acetate and formate anions in both solids was confirmed. Laboratory X-ray powder diffraction data were used to solve the crystal structures. Ca3(CH3COO)4(HCOO)2·4H2O crystallises in a primitive tetragonal unit cell with space group P41212 and lattice parameters of a = 6.8655(1) Å and c = 45.5454(6) Å, while Ca(CH3COO)(HCOO)·H2O crystallises in a primitive monoclinic unit cell with space group P21/c and lattice parameters of a = 9.2729(1) Å, b = 6.8002(1) Å, c = 11.2219(2) Å and β = 121.232(1)°. Calcium carboxylate zig-zag chains [Ca(μ2-RCOO)+]n (R = CH3 or H) are the main motif of both crystal structures. In Ca3(CH3COO)4(HCOO)2·4H2O these chains are exclusively composed of acetate anions, whereas in Ca(CH3COO)(HCOO)·H2O only formate anions are situated in the chains. The remaining places in the 7–8 fold coordination sphere of the calcium cations are filled by water molecules and additional carboxylate anions that interconnect neighbouring chains, which eventually leads to layered motifs in both structures. [ABSTRACT FROM AUTHOR]

A porous Zr-based MOF, [Zr6(BTEB)4(μ3-O)4(μ3-OH)4(H2O)4], which contains partially hydrated, 12-connected {Zr6} nodes and extended carboxylate ligands (BTEB3−), was synthesized and physicochemically characterised. The resulting (12,3)-connected, 3D framework adopts an uncommon llj topology with a large, solvent accessible void volume of ca. 79% of the unit cell volume. The porous structure facilitates the uptake of N2 and activated samples give rise to BET surface areas of >1000 m2 g−1. Furthermore, the porosity and accessibility of Lewis acidic Zr(IV) sites promote the catalytic transformation of gaseous CO2 to cyclic carbonates via cycloaddition reactions using epoxide reactants, whereby solvated MOFs exhibit higher catalytic performance than thermally treated samples. [ABSTRACT FROM AUTHOR]

A new flexible triazine-based polycarboxylate coordination polymer, {[Co3(H3TTHA)2(4,4′-bipy)5(H2O)8]·12H2O}n (1), where H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid, has been synthesized under hydrothermal conditions and structurally characterized by infrared spectroscopy, elemental analysis, TGA, XRD and X-ray single-crystal diffraction. Structural analysis indicates that 1 displays a planar structure with alternate rectangular structures of 22.695 × 11.485 Å2. The investigation of water vapor adsorption shows that the adsorption capacity of 1 is comparable to that of the typical adsorption material of MCM-41 with 73.86% (41.03 mmol g−1) water uptake at 90% relative humidity (RH). Based on the resistance to water and high-density hydrophilic units as well as abundant hydrogen-bonding networks in the complex, the proton conductivities of 1 under different conditions were measured. The results indicate that the proton conductivity values are highly temperature and relative humidity dependent, with the highest conductivity of nearly 10−3 S cm−1 at 353 K and 98% RH. The Arrhenius activation energy derived in the wide temperature range of 293–353 K is 0.32 eV, corresponding to a typical Grotthuss mechanism. [ABSTRACT FROM AUTHOR]

Two macrocyclic titanium-oxo clusters, namely, [Ti32(μ3-O)8(μ2-O)8(OCH2CH2O)32(OCH2CH2OH)16(BTA)16]·44H2O (BTA = butyrate) and [Ti32(μ3-O)8(μ2-O)8(OCH2CH2O)32(OCH2CH2OH)16(DMBTA)16(HDMBTA)2]·24H2O (DMBTA = 2,2-dimethylbutyrate) were synthesized and structurally characterized. The framework of the Ti32-oxo macrocycle was cyclically fixed by the double-deprotonated ethylene glycolate ligands, which exhibit an inner cavity of about 1.2 × 1.2 nm. The catalytic properties of the Ti32-oxo macrocycles towards the oxidative desulfurization (ODS) reaction were investigated. The structure-dependent catalytic properties towards oxidative desulfurization were observed for the Ti32-oxo macrocycles functionalized with the different carboxylate ligands. [ABSTRACT FROM AUTHOR]

Three 3D polymeric complexes containing polynuclear Co(II) units, [Co3(bpda)3(bib)2]·H2O (1), [Co5(OH)2(H2O)2(bpda)4(bib)2]·2H2O (2), and [Co2(OH)(bib)(bpt)]·H2O (3) (H2bpda = biphenyl-2,4′-dicarboxylic acid, H3bpt = biphenyl-3,4′,5-tricarboxylic acid, bib = 1,4-bis(1-imidazolyl)benzene), have been prepared by urothermal synthesis. Complex 1 exhibits an unusual (4,6)-connected 3D network based on binuclear Co(II) clusters and Co2+ centers bridged by bpda2− and bib ligands. Complex 2, containing a novel pentanuclear Co(II) cluster, features a porous 3D MOF with a regular nanosized tunnel. Complex 3 contains an interesting tetranuclear Co(II) cluster and displays an amazing 3D porous MOF built from double-layered 2D [Co2(μ3-OH)(bpt)3]n networks pillared by two rows of bib spacers. In the title complexes, polycarboxylate acids serve to construct and stabilize the polynuclear Co(II) clusters, while bis(imidazole)s help to expand the dimensionality of MOFs. Complexes 2 and 3 show antiferromagnetic properties. Compound 3 with high surface area, high yield, high purity, and high chemical stability was used as a precursor to fabricate Co,N-codoped porous carbon materials by simple carbonization under an Ar atmosphere. The catalytic properties of the Co,N-codoped porous carbon material derived from complex 3 (denoted as CoNC-3) as an ORR electrocatalyst were studied. CoNC-3 displays superior electrocatalytic performances for the ORR. [ABSTRACT FROM AUTHOR]

A praseodymium(III)-containing arsenotungstate K16H15Li7[Pr2(H2O)3(pzdc)As3W29O103]2·38H2O (1) (pzdc = pyrazine-2,3-dicarboxylic acid) was synthesized by a conventional aqueous solution method and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. Structural analysis revealed that compound 1 was constructed by two identical subunits {Pr2(H2O)3(AsW9O33)3W2O4} bridged together by two pzdc ligands. In addition, compound 1 could act as an efficient catalyst for the epoxidation of olefins and oxidation of alcohols with hydrogen peroxide (H2O2) as the oxidant. In particular, the turnover frequency (TOF) in the oxidation of 1-phenylethanol reached up to 10 170 h−1, which is higher than that of previously reported catalysts. [ABSTRACT FROM AUTHOR]

Five novel coordination polymers (CPs), formulated as {[Co3(μ4-cpboda)2(μ1,1-OH2)2(2,2-bipy)2]·1.5DMF·2H2O}n (1), {[Co3(μ3-cpboda)2(4,4′-bpy)3(H2O)2]·4H2O}n (2), {[Co(μ2-H2cpboda)2(1,4-bib)3(H2O)2]·H2O·DMF·1.5HCOOH}n (3), [Cd(μ3-Hcpboda)(1,4-bib)]n (4), and {[Cd3(μ4-cpboda)2(μ1,1-OH2)2(phen)2]·2DMF·1.5H2O}n (5) (H3cpboda = 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid, 2,2-bipy = 2,2-bipyridine, 4,4′-bpy = 4,4′-bipyridine, 1,4-bib = 1,4-di(1H-imidazol-1-yl)benzene, phen = 1,10-phenanthroline) have been synthesized under solvothermal conditions and characterized by elemental analyses (EAs), single-crystal X-ray diffraction analyses, X-ray powder diffraction analyses (PXRD), FT-IR spectra, and thermogravimetric analyses (TGAs). The structural analyses reveal that these complexes have four 2D coordinate polymers and one 3D framework, in which metal ions are in octahedral coordination geometries in 1–3 and 5, but seven-coordinated disordered pentagonal bipyramids in 4. Complexes 1 and 5 represent linear trinuclear [M3(μ1,1-OH2)2(μ1,3-COO)4] SBUs in 1 (M = Co(ii)) and in 5 (M = Cd(ii)) based on a 3,4,6-connected net with a point symbol (32·4)2(32·83·9)2(34·42·82·94·103) net, complex 2 exhibiting a (3-c)2(4-c)(4-c)2 3D structure with the (52·6·82·9)2(52·62·92)(52·6)2 topology and complexes 3 and 4 having a novel 2D framework with the point symbol of (44·62). Magnetization analyses disclose the antiferromagnetic (AF) behaviors between Co(ii) ions in complexes 1 & 3 and S = 3/2 (Co2+) spin Heisenberg chains with alternating magnetic sequences (F/F/AF)n in 2. Fluorescence measurements indicate that 4 and 5 are promising luminescence sensors for the detection of CrO42− and Cr2O72− anions in aqueous solution. [ABSTRACT FROM AUTHOR]

Three tacn (1,4,7-triazacyclononane)-based ligands substituted by methylthiazolylcarboxylate (tha) and/or methylthiazolyl (th) arms have been examined for copper complexation with the aim to study the impact of carboxylate groups on the complexation of Cu(ii), which can present an endo- or exo-cyclic coordination. Two new ligands have been synthesised: H3no3tha, tacn bearing three methylthiazolylcarboxylate arms, and H2no1th2tha, tacn with one methylthiazolyl and two methylthiazolylcarboxylate arms, while Hno2th1tha had already been described. Their complexation behaviour with 1 or 1.5 equivalents of metal was studied on the basis of preliminary results showing the tendency of tha arms to form exocyclic polynuclear species. The solid state studies of the Cu(ii) and Zn(ii) complexes were investigated and some of their structures were characterised by X-ray diffraction. The physicochemical properties of the complexes in solution were also investigated by means of potentiometric measurements, UV-vis spectroscopy, EPR and computational studies, NMR characterisation of the corresponding Zn(ii) complexes and redox behaviour by electrochemistry. Mono- and tri-nuclear complexes ML and M3L2 were formed and isolated, highlighting the tendency of methylthiazolylcarboxylate arms, when carried by a tacn platform, to form exo-cyclic and polynuclear complexes. However, this exhaustive study evidences that the “out of cage” and “in cage” present different behaviour in terms of stability. [ABSTRACT FROM AUTHOR]

A heterocyclic fluorogenic linker, thiadiazole dicarboxylate (H2tdz), offering diverse coordination modes has been utilized to synthesize two three-dimensional (3D) metal organic frameworks {[Cd2(tdz)2(4,4′-bpy)2]·6.5H2O}n (1) and [Cu(tdz)(4,4′-bpy)]n (2) from a one-pot self-assembly reaction under ambient conditions in high yields. MOFs 1 and 2 are structurally characterized by elemental analysis, FTIR and UV-Vis spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Their single crystal molecular structures reveal that 1 contains a permanent pore along the b-axis with dimensions of 14.576 × 17.567 Å2 while 2 forms a 3D two-fold interpenetrated structure with an extensively reduced pore size. The effect of interpenetration has been further elaborated by a comparison of their CO2 uptake capacities at 263 K, 273 K and 298 K. The uptake value of CO2 for non-interpenetrated 1 (24.8 cm3 g−1) is much higher compared to that of interpenetrated 2 (5 cm3 g−1) at 298 K. Furthermore, to obtain an insight into the adsorbate–adsorbent interaction owing to the presence of the polar thiadiazole moiety and polarizable CO2 molecules, the isosteric heat of adsorption (Qst) was calculated for 1 (29.1 kJ mol−1) and 2 (23.4 kJ mol−1). Thermal and chemical stabilities of 1 in water were ascertained by variable temperature powder X-ray diffraction (VT-PXRD) analysis. MOF 1 having a d10 metal center was utilized to harness the availability of nitrogen atoms in the tdz2− linker for the selective sensing of nitrophenols in water with a detection limit for TNP as low as 1.4 ppm. Moreover, 1 is found to be stable and recyclable up to four cycles. [ABSTRACT FROM AUTHOR]

The reactions of a series of carboxylic acids with H2B(C6F5)·SMe2 are shown to afford species of the form [RC(O)OB(C6F5)]2O, (R = Tol 1, Ph 2, C6F53, Me2BrC 4, Me 5) in 87–95% yields with the concurrent reduction of the carboxylic acid to the corresponding aldehyde. A mechanism for the formation of 1–5 is proposed to proceed via a cyclic eight-membered ring species. Analogues of these species were prepared via reactions of carboxylic and phosphinic acids with HB(C6F5)2 and H2B(C6F5)·SMe2, respectively, to give [TolC(O)OB(C6F5)2]26, [(C6F5)C(O)OB(C6F5)2]27, and [Ph2P(O)OBH(C6F5)]28. These products react subsequently to give TolC(O)OBH(C6F5)(NC5H4NMe2) 9 and Ph2P(O)OBH(C6F5)(NC5H4NMe2) 10. The acyloxyborate derivatives 1–4 were shown to be inactive in mediating the direct amidation of carboxylic acids, consistent with previous observations that infer the need for a sterically congested environment about the boron centres. [ABSTRACT FROM AUTHOR]

Octacalcium phosphate (OCP) is a layered compound capable of incorporating carboxylate ions within its interlayer structure. In this study, we successfully synthesised OCP with incorporated 3,3’- dithiodipropionate ions. Our finding is beneficial for the development of novel OCP-based materials with dynamic properties derived from disulfide bonds. [ABSTRACT FROM AUTHOR]

A microporous metal–organic framework, {[Co2(4,4′-bpy)(L)]·H2O·0.5(DMF)}n (1), was obtained from the self-assembly of cobalt(ii) nitrate hexahydrate, rigid tetrapodal carboxylic acid 4,4′,4′′,4′′′-silanetetrayltetrabenzoic acid (H4L) and a rigid bifunctional linker 4′4′-bipyridine (4,4′-bpy) under solvothermal conditions. It was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and powder and single crystal X-ray diffraction. Its single crystal structure reveals the presence of a Co(ii)-paddle wheel core as the SBU, which is extended to form a doubly interpenetrated 3D framework with a (4,6)-connected sqc422-type uninodal net topology with the Schläfli point symbol {42·510·72·8}{42·54}. There are two types of open channels in this framework (rhombic and trigonal), which run along all three axes. Its thermal and chemical stabilities were established based on thermogravimetric analysis and in situ variable temperature powder X-ray diffraction. The activated framework (lattice solvent free) of 1 exhibits modest uptake of CO2 (53.8 and 36.4 cm3 g−1 at 273 and 298 K at 1 bar pressure, respectively), with moderately high selectivities for CO2/N2 and CO2/CH4 gas separation under ambient conditions (298 and 273 K under 1 bar pressure). [ABSTRACT FROM AUTHOR]

Eleven new dinuclear and tetranuclear compounds of general formulae [Zn(μ-L)(μ-X)Ln(NO3)2]·nS, [Zn2Dy2(μ3-L′)2(μ-sal)2(NO3)(CH3OH)](NO3)·5CH3OH and [Zn2Er2(μ3-L′)2(μ-sal)2(CH3OH)2](NO3)2·4CH3OH (X = benzoate, anthracenate, diclofenac, salicylate, 2,6-dihydroxybenzoate; Ln = Dy, Er; S = water, acetonitrile, methanol) were prepared from the N,N′-dimethyl-N,N′-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine compartmental ligand (H2L). Complexes 1–6 and 9–11 consist of diphenoxido-carboxylate triply bridged compounds, which differ mainly in the carboxylate bridging ligand. It should be noted that the acidic character of the salicylic acid promotes, in the presence of methanol, the methoxylation of the H2L ligand thereby yielding a hemiacetal H3L′, which is able to connect the Ln(iii) ions of two ZnLn dinuclear units forming the Zn2Ln2 tetranuclear complexes 7 and 8. All compounds display SMM behaviour in the presence of an external field with effective energy barriers (Ueff) as high as 61 K. Magneto-structural data for these complexes reveal that their SMM behaviour is not only significantly affected by the type of Ln(iii) ion but also by the carboxylate bridging ligand connecting the Zn(ii) and Ln(iii) ions. Photoluminescence properties have also been accomplished, showing that the ligands are able to sensitize lanthanide centred emissions in the visible and near-infrared regions with variable capacity. Moreover, the analysis of the luminescence decay curves reveals emission lifetimes in the range of few microsecond or hundreds of nanoseconds for Dy(iii)-based or Er(iii)-based luminophores, respectively. [ABSTRACT FROM AUTHOR]

Herein we present platinum(iv) bioconjugates with polyarginine peptides as prospective prodrug delivery systems. Asymmetrical platinum(iv) complexes 3 were obtained via oxidation of parent platinum(ii) complexes 2 with N-bromosuccinimide (NBS) in the presence of succinic anhydride. The combination of these two oxidation reagents furnishes the platinum(iv) environment with two different axial ligands, one of which bears a free carboxylic acid. All platinum(ii) and (iv) compounds were characterized by FT-IR, ESI-MS, HPLC, 1H-, 13C- and 195Pt-NMR. Standard solid-phase peptide chemistry was used for the synthesis of polyarginine (R9) peptides. Coupling of the platinum complexes with peptides N-terminally afforded peptide monoconjugates, which were purified by semi-preparative HPLC and characterized by analytical HPLC and ESI-MS. Platinum(iv)–peptide bioconjugates as well as platinum(ii) and platinum(iv) complexes were tested as cytotoxic agents against two different human cancer cell lines (MCF-7, HepG2) and normal human fibroblasts cell lines (GM5657T). Preliminary in vitro data showed that all platinum(iv) complexes exhibit lower activity than their platinum(ii) precursors towards most cell lines. Interestingly, in the case of HepG2 cells, the Pt(iv)-(R)9-G-A-L bioconjugate (4a) showed even higher activity compared to the non-targeting platinum(iv) parent compound. [ABSTRACT FROM AUTHOR]

Three bismuth-2,5-thiophenedicarboxylates (Bi-TDC) and two europium-2,5-thiophenedicarboxylates (Eu-TDC) were synthesized under ambient conditions. The structures were determined through single crystal X-ray diffraction, and three of the phases were further characterized by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Reactions of bismuth nitrate, 2,5-thiophenedicarboxylate, and pyridine in an acidic solution of acetic acid and ethanol yield Hpy[Bi(TDC)2(H2O)]·1.5H2O (1), whereas reactions in a water/ethanol mixture produce a minor phase, [Hpy]3 [Bi2(TDC)4(HTDC) (H2O)]·xH2O (2) along with a major product, (Hpy)2[Bi(TDC)2(HTDC)]·0.36H2O (3). The structures of 1-3 are all built from anionic Bi-TDC chains that are further bridged through additional TDC linkages into interpenetrated 2D sheets. Addition of an aqueous lanthanide solution to the reaction mixtures that yielded 1 and 2-3 resulted in the formation of doped phases, Hpy[Bi1-xLnx(TDC)2(H2O)]·1.5H2O (Bi1-xLnx-1), where Ln = Nd, Sm, Eu, Tb, Dy, and Yb, and (Hpy)2[Bi0.99Eu0.01 (TDC)2(HTDC)]·0.36H2O (Bi0.99Eu0.01-3). Using europium nitrate rather than the bismuth precursor resulted in the formation of two homometallic europium based phases, [Eu(TDC)(NO3)(H2O)]n (4) and [Eu2(TDC)3(H2O)9]·5H2O (5), which adopt an extended 3D network and an interpenetrated 2D structure, respectively. Photophysical measurements were carried out for 1 and the lanthanide containing phases and quantum yield and lifetime values were determined for the visible light emitters. Herein, the structural chemistry, spectroscopic properties, and luminescence of the bismuth phases, their lanthanide doped analogs, and the europium compounds are presented. [ABSTRACT FROM AUTHOR]

The first examples of crystalline coordination polymers containing the tetraarylpyrrolo[3,2-b]pyrrole (TPP) fluorophore are presented. We have prepared three new TPP ligands L1, H2L2 and H2L3, containing nitrile, carboxylate and mixed imidazole-carboxylate donor functionality, respectively. The ligands themselves each show significant fluorescence in the solution phase, with the nitrile species exhibiting solvatofluorochromism and the two carboxylate-containing compounds exhibiting concentration-dependent emission colour suggesting aggregation processes in solution. Three 3-dimensional polymeric structures are then presented. The compound poly-[AgL12]SbF6·3THF·2H2O 1 is an eightfold-interpenetrated diamondoid material, while poly-[Zn4O(L2)3]·20DMA·10H2O 2 is a porous Metal–Organic Framework with pcu topology, and both 1 and 2 show notable luminescence in the solid state. Complex 2 readily undergoes guest exchange accompanied by a reversible switching in emission colour with no change in chemical structure. While complex poly-[CdL3]·2.5DMA·3.5H2O 3 is non-emissive, it displays a twofold interpenetrated pts topology with hexagonal symmetry and an extremely long hexagonal pitch of 100.3 Å, and shows an impressive 22 wt% CO2 uptake capacity at 278 K and 1 bar. [ABSTRACT FROM AUTHOR]

Tin chalcogenides are important semiconducting materials due to their non-toxic nature, cost effectiveness and layered structure. In this study, a facile synthetic route has been employed for the synthesis of a bis(selenobenzoato)dibutyltin(iv) complex, and used along with the bis(thiobenzoato)dibutyltin(iv) complex, as single source precursors, to prepare binary tin chalcogenides and their solid solution (SnS1−xSex) in the entire range. The synthesis of the solid solution was carried out by colloidal and melt methods. The comparative analysis of the solid solution obtained from both routes indicates that the colloidal method provides superior control over composition. The UV-Vis-NIR analysis showed a gradual change in the band gap, while moving from SnS to SnSe. [ABSTRACT FROM AUTHOR]

Two linear-shaped heterometallic trinuclear {ZnII2DyIII} clusters were prepared with a compartmental Schiff-base ligand and carboxylate as the co-ligand. The central DyIII ion is sandwiched by two [ZnHhms(RCOO)2] (H2hms = (2-hydroxy-3-methoxybenzylidene)-semicarbazide) units to form a distorted square antiprismatic (SAP) geometry with D4d symmetry. The DyIII and ZnII ions are triply bridged by one unique monophenoxido/dicarboxylate group, where one of the carboxylates shows a severe angular distortion. The magnetic analysis revealed a field-dependent change with two relaxation processes in 1 and 2, which originated from the molecular magnetic center and dipolar–dipolar coupling. The dipole-induced slow relaxation disappeared upon magnetic-site dilution, while another faster relaxation appeared in the high frequency region associated with the different distortions of the antiprismatic sites for 1 and disordered structures for 2. Ab initio calculations revealed that two {ZnII2DyIII}-carboxylate complexes are axial in nature, but the remarkable quantum tunnelling of the magnetization exists in the ground state, which lowers the anisotropic barrier and prohibits zero-field single-molecule magnet behavior. The crystal field of the carboxylato ancillary ligands produces a competitive effect with the phenoxido bridging ligands on the magnetic anisotropy of the lanthanide ions, which greatly affects the electrostatic distribution of this type of {ZnII2DyIII} single-ion magnets (SIMs). The results offer a model for further investigating structural factors in the relaxation mechanism of SIM systems. [ABSTRACT FROM AUTHOR]