Aromatic Carboxylate Ligands Research Articles

Sensitization of Europium Oxide Nanoparticles Enhances Signal-to-Noise over Autofluorescence with Time-Gated Luminescence Detection.

Clinical translation of nanoparticle-based therapeutics has been limited, and a lack of preclinical delivery characterization is partly to blame, limiting our understanding of the mechanisms of failure. The improvement of the preclinical delivery assessment requires nanoparticles with higher detectability. This work focused on the exploration of several aromatic carboxylic ligands (terephthalic acid, quinaldic acid, and kynurenic acid) for the sensitization of europium oxide nanoparticles with a long emission lifetime to overcome cellular autofluorescence, a key confounder of detection in luminescence-based bioimaging. A facile one-pot synthesis and ligand exchange process generated and sensitized ultrasmall Eu2O3 cores. As reflected in the emission spectra and lifetimes, ligand binding yielded unique coordination environments around Eu3+. Then, the efficacy of sensitization was tested against the autofluorescence provided by tissue lysate. Normal (simultaneous excite-read) measurements showed integrated signal improvements over autofluorescence of 2.2-, 3.9-, and 14.0-fold for EuTA, EuQA, and EuKA, respectively. In time-gated mode, the improvements over autofluorescence were more dramatic with fold differences of 75-, 89-, and 108-fold for EuTA, EuQA, and EuKA, respectively. The investigation of novel sensitizers expands the breadth of the field of sensitized lanthanide oxide nanoparticles, and the signal enhancement observed with sensitization and time-gating supports the utility of the generated samples for future bioimaging applications.

Synthesis, structure and photoluminescence properties of heterometallic-based coordination polymers of trimesic acid.

Reacting trimesic acid (H3TMA, C9H6O6) with CaCl2 and MCl2 at 110 °C under hydrothermal conditions gave the isostructural heterobimetallic coordination polymers (CPs) catena-poly[[tetraaquazinc(II)]-μ-5-carboxybenzene-1,3-dicarboxylato-[tetraaquacalcium(II)]-μ-5-carboxybenzene-1,3-dicarboxylato], [CaZn(HTMA)2(H2O)8]n, 1, and catena-poly[[tetraaquacobalt(II)]-μ-5-carboxybenzene-1,3-dicarboxylato-[tetraaquacalcium(II)]-μ-5-carboxybenzene-1,3-dicarboxylato], [CaCo(HTMA)2(H2O)8]n, 2. Compounds 1 and 2 crystallize in the monoclinic space group C2/c. The solid-state structures consist of eight-coordinate CaII ions and six-coordinate MII ions. These ions are connected by a doubly deprotonated HTMA2- ligand to create a one-dimensional (1D) zigzag chain. Poly[[decaaquabis(μ3-benzene-1,3,5-tricarboxylato)calcium(II)dizinc(II)] dihydrate], {[CaZn2(TMA)2(H2O)10]·2H2O}n, 3, was found incidentally as a minor by-product during the synthesis of 1 at a temperature of 140 °C. It forms crystals in the orthorhombic space group Ccce. The structure of 3 consists of a two-dimensional (2D) layer composed of [Zn(TMA)] chains that are interconnected by CaII ions. The presence of aromatic carboxylic acid ligands and water molecules, which can form numerous hydrogen bonds and π-π interactions, increases the stability of the three-dimensional (3D) supramolecular architecture of these CPs. Compounds 1 and 2 exhibit thermal stability up to 420 °C, as indicated by the thermogravimetric analysis (TGA) curves. The powder X-ray diffraction (PXRD) data reveal the formation of unidentified phases in methanol and dimethyl sulfoxide, while 1 exhibits chemical stability in a wide range of solvents. The luminescence properties of 1 dispersed in various low molecular weight organic solvents was also examined. The results demonstrate excellent selectivity, sensitivity and recyclability for detecting acetone molecules in aqueous media. Additionally, a possible sensing mechanism is also outlined.

Two coordination polymers based on conjugated pyrazine aromatic carboxylic acid ligands: Structural and magnetic research

Two new coordination polymers [M(L)(H2O)2]n (M=Co (1) and Mn (2)) (H2L=5-(pyrazin-2-yl) isophthalic acid) were synthesized by hydrothermal method and systematically characterized. The two compounds were analyzed in depth by x-ray single crystal diffraction, elemental analysis, IR spectroscopy, PXRD and thermal analysis. The x-ray single crystal diffraction results indicate that compound 1 is a 3D framework structure. Through the carboxyl oxygen atoms and pyrazine nitrogen atoms on different L2− ligands, two interesting infinitely extended right helix chains are formed along the c-axis, and the two helix chains are combined to form a 3D framework structure of 1. In compound 2, the adjacent Mn2+ is bridged with four carboxyl oxygen groups in the ligand to form a binuclear structure unit {Mn2O4}. Each {Mn2O4} is linked to six organic ligands, and each ligand is linked to three {Mn2O4}, which together form a (3,6) linked 3D coordination polymer material. It is noteworthy that the interconnections between the layers form a lantern-like structure when viewed from the b-axis direction. Additionally, compounds 1 and 2 demonstrated temperature-dependent magnetic susceptibility (dc) and negative values of θ (equal to -10.59 K and -6.38 K), which are indicates the presence of weak antiferromagnetic interactions in both compounds 1 and 2.

A series of lanthanide complexes with different aromatic carboxylic acid ligands: Synthesis, supramolecular structure, thermal properties and luminescence behaviors

Six noble two-dimensional lanthanide complexes [Ln(2,4-DFBA)3(terpy)·H2O]·H2O (Ln = Tb(1), Dy(2)), [Pr(2,4,6-TMBA)3(terpy)·H2O] (3) [Nd(2,4,6-TMBA)3(terpy)·H2O]·C2H5OH·H2O(4) and [Ln(2,4,6-TMBA)3(terpy)·H2O]·1.5H2O (Ln = Dy(5), Ho(6) (2,4-DFBA = 2,4-difluorobenzoate, 2,4,6-TMBA = 2,4,6-trimethylbenzoate, terpy = 2,2 ': 6′, 2 ''- terpyridine) were synthesized by conventional solution method with 2,4-difluorobenzoic acid and 2,4,6-trimethylbenzoic acid as main ligands and 2,2 ': 6′, 2 ''- terpyridine as auxiliary ligands. The complexes were characterized by infrared spectroscopy and Raman spectroscopy, and the thermal decomposition mechanism of the complex was studied by TG-DTG-DSC/FTIR coupling technology. The solid fluorescence test was also carried out for complexes 1,2 and 4. It was found that the complexes have good fluorescence properties, and the fluorescence lifetime of complex 1 was 0.541 ms.

The modulation effect of auxiliary ligands on photochromic properties of 3D naphthalene diimide coordination polymers.

Two novel naphthalene diimide (NDI) coordination polymers (CPs), [Cd(NicNDI)(4,4'-SBC)] (1) and [Cd(NicNDI)(2,2'-BPC)] (2) (NicNDI = (3-pyridylacylamino)-1,4,5,8-naphthalene diimide, 4,4'-SBC = 4,4'-stilbene dicarboxylic acid, 2,2'-BPC = 2,2'-biphenyl dicarboxylic acid), were designed and prepared by the combination of electron-deficient NicNDI and electron-rich aromatic carboxylic acid ligands in the presence of cadmium ions. The usage of aromatic carboxylic acid ligands with different conjugation degrees, sizes, shapes and charge densities leads to the generation of distinct interpenetrated three-dimensional (3D) frameworks. Interestingly, photochromism of 1 and weak photoactivity of 2 should be attributed to the introduction of different auxiliary ligands and consequently the formation of distinct interfacial contacts of electron donors (EDs)/electron acceptors (EAs) (dπ-π = 3.427 Å, infinite -ED-EA-ED-EA- for 1vs. dπ-π = 3.634 Å, discrete ED-EA-ED for 2), suggesting a subtle modulating effect of auxiliary ligands on interfacial contacts, photoinduced intermolecular electron transfer (PIET) and photoresponsive behaviors.

Electron density effect of aromatic carboxylic acids in naphthalenediimide-based coordination polymers: from thermal electron transfer and charge transfer to photoinduced electron transfer.

Various naphthalenediimide (NDI) based electron donor-acceptor coordination polymers (D-A CPs) have been constructed and used to explore charge transfer (CT) and electron transfer (ET) behaviors. Up to now, significant progress has been made in the interface contact and electron donor-acceptor ability matching mechanism, while the electronic density effect of the electron donors on the CT and ET behaviors is still not known. Herein, two NDI-based D-A CPs, [Cd2(H2NDI)(IPA)2(H2O)2] (1) and [Cd2(H2NDI)(IPA-OH)2(H2O)2] (2), are constructed using an NDI-based ligand and two aromatic carboxylic acid ligands (H2NDI = 2,7-bis(3,5-dimethyl) dipyrazol-1,4,5,8-naphthalene tetracarboxydiimide, H2IPA = isophthalic acid; and H2IPA-OH = 5-hydroxyisophthalic acid). UV-vis and EPR spectroscopy and DFT calculations analyses reveal that the occurrence of themal electron transfer (TET) in 1 and 2 results from the HOMO of the IPA and IPA-OH lying higher than the LUMO of the NDI. Meanwhile, compared to 1, the UV-vis absorption spectrum of 2 exhibits a significant red shift, which suggests higher electron density of the donor and more electron transfer pathways are beneficial for the occurrence of intermolecular CT. After UV light irradiation, the comparison of the photochromic behavior of 1 and 2 confirms the negative effect of the stronger CT on photoinduced electron transfer (PET). The present study illustrates the delicate modulating effect of electron density on the CT and ET behaviors in D-A CPs.

A new method for fabrication of gel emulsions and their application in preparation of novel porous materials.

In the research of gel emulsions, it is a great challenge to develop a new method for fabrication of gel emulsions and utilize them in preparing novel porous materials containing metal complexes. In this work, we proposed to use coordination self-assemblies of two building blocks, organic ligands and metal ions, as stabilizers to prepare gel emulsions, which could be used as templates to prepare porous materials containing metal complexes. Aromatic carboxylic ligands CDCn (n = 4, 6, 8, and 10) containing cholesterol groups were designed and synthesized, and were used as organic ligands to fabricate new W/O gel emulsions through the coordination self-assembly with Tb3+/Eu3+ at the oil-water interface. The gel emulsions based on CDC6 possess injection molding properties, which were rarely seen in conventional gel emulsions. EDX mapping and XPS and FTIR analyses revealed that the coordination self-assembly of CDC6 and Tb3+ at the oil-water interface was the main driving force for the gel emulsion formation. CDC6/Tb3+/styrene/H2O gel emulsions could be further used as templates to prepare low-density porous metal complex/polymer composites with typical luminescence emissions of terbium complexes. This work extends the method for preparation of gel emulsions and develops a novel approach to obtain porous materials containing metal complexes.

Construction of ZnII/CdII-based MOFs containing a tripodal aromatic carboxylate ligand with unequal arms and their fluorescence detection for Cu2+ and Fe3+ cations

Four MOFs have been synthesized and characterized. The luminescent sensing investigation indicates that compound 1 exhibits extremely sensitive and selective detection of Cu2+ and compounds 2–4 show extremely sensitive and selective detection of Fe3+.

Two novel cadmium coordination polymers bearing viologen-derived ligand: Structure and photochromism properties

Two novel cadmium viologen coordination polymers (CPs) {[Cd(BTC)(H2O)]·(Mebpy)}n (1) and {[Cd1.5(Mebpy)(BDC)1.5Cl]·(DMF)}n (2) (Mebpy+ = N-methyl-4,4′-bipyridinium cation, DMF = N,N-Dimethylformamide) were prepared in the reaction of CdCl2 with different aromatic carboxylic acid ligands such as 1,3,5-benzenetricarboxylic acid (H3BTC) or 1,4-dicarboxybenzene acid (H2BDC) under hydrothermal conditions in the presence of N-carboxymethyl-4,4′-bipyridinium chloride (CEbpy·Cl). Single-crystal structure analysis revealed that the Cd(II) ions are bridged by BTC3- anions to form a 3D structure with the Mebpy+ cations occupying channel pores in compound 1, while the metal ions are bridged by BDC2- and Cl- anions to form a 3D structure with Mebpy+ cations in compound 2. Interestingly, it has been found that the structure of the two compounds depends on aromatic carboxylic acid ligands. Compounds 1 and 2 exhibit photochromic behavior under xenon lamp irradiation, accompanied by visible color changes from original color to blue.

A stable 3-D Cd(II) metal–organic framework formed by aromatic carboxylate and flexible imidazole ligand for sensing of nitroaromatic explosives

A stable 3-D metal–organic framework (MOF), [Cd(H2DTPA)(1.2-mbix)] n (1), has been constructed with aromatic 2,3-dihydroxy terephthalic acid (H4DTPA) and cadmium salt under solvothermal conditions. The structure shows that H2DTPA2+ concatenates two Cd(II) cations to form a 1-D folded chain; the flexible nitrogen-containing 1,2-mbix sections link two adjacent 1-D chains into a 3-D framework. Complex 1 exhibited strong ligand-derived photoluminescence and was sensitive to nitroaromatic explosives (2-nitrophenol, nitrobenzene, 4-nitrophenol, 4-nitrotoluene and 4-nitrochlorobenzene).

Mild oxidative functionalization of cycloalkanes catalyzed by novel dicopper(II) cores

The search for new transition metal based catalytic systems that are active in the oxidative functionalization of such inert substrates as saturated hydrocarbons continues to be an important research direction in molecular catalysis. In the present study, two new copper(II) coordination compounds, namely a discrete dimer [Cu2(μ-H2tea)2(nfa)2]·2H2O (1) and a 1D coordination polymer [Cu2(μ-H2tea)2(μ-Htma)]n·4nH2O (2) were synthesized and applied as homogeneous catalysts for the mild oxidative functionalization of cycloalkanes (cyclopentane, cyclohexane, cycloheptane, and cyclooctane). Both products 1 and 2 were self-assembled in aqueous medium from copper(II) nitrate, triethanolamine (H3tea), sodium hydroxide, and 2-naphthoic (Hnfa) or trimesic (H3tma) acids, isolated as stable crystalline solids, and fully characterized by standard methods including single-crystal X-ray diffraction. Their structures feature a similar type of dicopper(II) triethanolaminate cores that are decorated by terminal or bridging aromatic carboxylate ligands. Two model catalytic reactions were investigated, namely the oxidation of cycloalkanes by H2O2 to produce cycloalkyl hydroperoxides as intermediate products and then a mixture of cyclic alcohols and ketones as final products, and the carboxylation of cycloalkanes with CO/S2O82−/H2O to form cycloalkanecarboxylic acids as main products. These model reactions undergo under very mild conditions (50−60 °C) and show good efficiency. Substrate scope, selectivity features, and the effects of reaction parameters were investigated and discussed in detail. This study widens the family of multicopper(II) cores capable of catalyzing the oxidative functionalization of saturated hydrocarbons under mild conditions.

New triorganotin(iv) compounds with aromatic carboxylate ligands: synthesis and evaluation of the pro-apoptotic mechanism.

Three new organotin(iv) carboxylate compounds were synthesized and structurally characterized by elemental analysis and FT-IR and multinuclear NMR (1H, 13C, 119Sn) spectroscopy. Single X-ray crystallography reveals that compound C2 has a monoclinic crystal system with space group P21/c having distorted bipyramidal geometry defined by C3SnO2. The synthesized compounds were screened for drug-DNA interactions via UV-Vis spectroscopy and cyclic voltammetry showing good activity with high binding constants. Theoretical investigations also support the reactivity of the compounds as depicted from natural bond orbital (NBO) analysis using Gaussian 09. Synthesized compounds were initially evaluated on two cancer (HeLa and MCF-7) cell lines and cytotoxicity to normal cells was evaluated using a non-cancerous (BHK-21) cell line. All the compounds were found to be active, with IC50 values less than that of the standard drug i.e. cisplatin. The cytotoxic effect of the most potent compound C2 was confirmed by LDH cytotoxicity assay and fluorescence imaging after PI staining. Apoptotic features in compound C2 treated cancer cells were visualized after DAPI staining while regulation of apoptosis was observed by reactive oxygen species generation, binding of C2 with DNA, a change in mitochondrial membrane potential and expression of activated caspase-9 and caspase-3 in cancer cells. Results are indicative of activation of the intrinsic pathway of apoptosis in C2 treated cancer cells.

How Does the Fluorination of the Linker Affect the Structural Chemistry of Trimesate‐Based Metal‐Organic Frameworks (MOFs)?

FMOFs, i.e. metal‐organic frameworks with linkers with fluoro substituents, were supposed to show enhanced thermal and chemical stability as well as high gas affinity and hydrophobicity. However, at least for aromatic carboxylate ligands it was shown in a subsequent work that fluoro substituents weaken the C(phenyl)‐COO– bond and thus facilitate decarboxylation leading to a decreased chemical and thermal stability. Nonetheless, it was concluded that linker fluorination leads to a rich structural chemistry, as the torsion angle between the phenyl ring and the carboxylate group is significantly increased in these compounds. Here, we present the very first examples of four MOFs all based on Sr2+ cations and trimesate‐based linkers with three different degrees of fluorination as well as the known non‐fluorinated counterpart: [Sr(HL)(H2O)]·n H2O [1: L = mF‐BTC3–, n = 0.5, P1, Z = 2; 2: L = dF‐BTC3–, n = 0.5, C2/c, Z = 8; 3: L = pF‐BTC3–, n = 1.5, C2/c, Z = 8; 4: L = BTC3–, n = 0.5, P1, Z = 2; BTC3– ≡ 1,3,5‐benzenetricarboxylate (trimesate); mF‐BTC3– ≡ monofluorinated trimesate, dF‐BTC3– ≡ difluorinated trimesate, pF‐BTC3– ≡ per‐(tri‐)fluorinated trimesate]. Whereas 1 and known 4 are found to crystallize in isotypic structures and 2 in a very similar structural arrangement [all CN(Sr2+) = 9], 3 with the highest degree of fluorination exhibits a completely different crystal structure [CN(Sr2+) = 8], which is already obvious from the different composition. It is shown that the torsion angles between the phenyl ring and the carboxylate groups play an important structure‐directing role. DSC/TGA investigations confirm that with increasing fluorination the thermal stability is decreased. However, the release temperature of water, i.e. the affinity to water, increases with the number of fluoro substituents.

Syntheses, crystal structures and properties of four metal coordination complexes constructed from aromatic carboxylate and benzimidazole-based ligands

Four metal–organic coordination complexes, namely {[Zn(SIP)(mbi)2]·(Hmbi)·(H2O)2}n (1), {[Cd3(SIP)2(bbhb)3(H2O)4]·(H2O)2}n (2), [Co3(SIP)2(bbhb)4(H2O)2]n (3) and [Zn2(NIPA)2(mbi)2(H2O)3] (4) (H3SIP = 5-sulfoisophthalic acid, mbi = 2-methylbenzimidazole, bbhb = 1,1′-(1,4-butanediyl)bis-1H-benzimidazole and H2NIPA = 5-nitroisophthalic acid), have been hydrothermally synthesized. Single-crystal X-ray analyses show that these complexes have different structural features. In complex 1, the SIP3− anions bridge Zn(II) atoms to form 1D right-handed helical chains, which are further interconnected by hydrogen-bond interactions, forming a 3D supramolecular architecture. In complex 2, the Cd1 and Cd2 atoms are bridged by SIP3− ligands to form 1D chains, which are extended to 2D layer with Cd3 atoms as hinges. The 2D layers are further connected by bbhb ligands to give a 3D framework. The Co(II) atoms in compound 3 are bridged by SIP3− anions to generate 1D ladder-like chain; then, the 1D chains extend to 2D network by the connection of “L”-shaped bbhb ligands. Finally, the 2D networks are bridged by “S”-shaped bbhb ligands to give rise to the formation of 3D framework. In compound 4, the binuclear molecules are connected through hydrogen bonds to generate a 2D layer. The results illustrate that the carboxylate ligands and the versatile conformations of the bbhb ligands contribute to the structural diversity of these complexes. The photoluminescent properties of complexes 1, 2 and 4 are also studied.

Luminescent lanthanide metallogels: situ fabrication, self-healing and rheological properties

We have presented a simple method for situ fabrication of photoluminescent lanthanide metallogels. A series of lanthanide metallogels could be rapidly formed through mixing the aqueous solution of Tb3+ or Eu3+ and organic solution of synthesized aromatic carboxylic ligands (DCn, n = 14, 16,18) at room temperature. The gelation tests revealed that the ligand with longer alkyl chain (DC18) showed stronger gelling abilities, indicating that the structure of non-coordinated groups in ligand molecules could affect self-assembly processes and, hence, the microstructures and properties of lanthanide metallogels. FT-IR measurements demonstrated that the driving force of formation of the metallogels was the coordination interaction between DCn and Tb3+ or Eu3+. XRD analysis revealed that DC14 metallogels took a mixture of hexagonal and tetragonal packing modes. All obtained metallogels have shown typical luminescent emissions of the lanthanide complex. In particular, DC18/Tb(NO3)3 metallogel in DMF/H2O (v:v = 1:1) has shown excellent self-supporting, self-healing, film-forming, and rheological properties.

Synthesis, Structural Characterization and Antimicrobial Evaluation of Ruthenium Complexes with Heteroaromatic Carboxylic Acids.

The antibacterial and antibiofilm activities of two new ruthenium complexes against E. coli, S. aureus, P. aeruginosa PAO1 (laboratory strain) and P. aeruginosa LES B58 (clinical strain) were evaluated. Complexes, mer-[RuIII (2-bimc)3 ] ⋅ H2 O (1) and cis-[RuIV Cl2 (2,3-pydcH)2 ] ⋅ 4H2 O (2), were obtained using aromatic carboxylic acid ligands, namely, 1H-benzimidazole-2-carboxylic acid (2-bimcH) and pyridine-2,3-dicarboxylic acid (2,3-pydcH2 ). Compounds were physicochemically characterized using X-ray diffraction, Hirshfeld surface analysis, IR and UV/VIS spectroscopies, as well as magnetic and electrochemical measurements. Structural characterization revealed that Ru(III) and Ru(IV) ions in the complexes adopt a distorted octahedral geometry. The intermolecular classical and weak hydrogen bonds, and π⋅⋅⋅π contacts significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. Biological studies have shown that the Ru complexes inhibit the growth of bacteria and biofilm formation by the tested strains and the complexes seem to be a potential as antimicrobial agents.

Solvothermal syntheses, crystal structures and luminescence properties of Zn(II) coordination compounds based on imidazophenanthroline carboxylate derivative ligand

Four new zinc(II) coordination compounds, [Zn2(Hcpip)4]·8H2O (1), [Zn4(Hcpip)4(1,3-bdc)2]n·5nH2O (2), [Zn(Hcpip)(1,4-bdc)0.5]n (3), [Zn2(Hcpip)2(H1,3,5-btc)]n·2nH2O (4), (H2cpip = 2-(2-carboxyphenyl)imidazo[4,5-f]1,10-phenanthroline, H2(1,3-bdc) = benzene-1,3-dicarboxylic acid, H2(1,4-bdc) = benzene-1,4-dicarboxylic acid, H3(1,3,5-btc) = benzene-1,3,5-tricarboxylic acid) have been synthesized under solvothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 is a dinuclear molecular structure, and further linked by π … π interactions to form a 2D supramolecular layer. Compounds 2–4 display different 2D layer structures with 1D chains and aromatic carboxylate ligands. In addition, their luminescence properties and thermal stabilities have been investigated.

Two difunctional Co(II) coordination polymers for natural sunlight photocatalysis of methylene blue and selective fluorescence sensing of Cr(VI) ion in water media

Two new difunctional Co(II) coordination polymers (CPs), namely, [Co(TBTA)(L)1.5]n (1) and {[Co(NPHT)(L)]·H2O}n (2) were hydrothermally synthesized from 4,4′-bis(imidazole-1-yl)-biphenyl and different aromatic carboxylic acid ligands (H2TBTA = tetrabromoterephthalic acid, and H2NPHT = 3-nitrophthalic acid). Two CPs feature 2D (3,6)-connected hcb, and (4,4)-connected sql topologies for 1, and 2, respectively. 1 further extends into a three dimensional supramolecular architecture through π···π stacking interactions. Both of CPs exhibit high photocatalytic activities for degradation of methylene blue (MB) with remarkable efficiencies (85.83% for 1, and 93.76% for 2) under natural sunlight irradiation. 1 can sensitively and selectively detect Cr(VI) anions in water media with the Stern-Volmer quenching constant (Ksv) of 4.79 × 104 M−1 for Cr2O72− (pH = 3) or 2.36 × 104 M−1 for CrO42− (pH = 12). The linear detection ranges are 0–350 μM, and 0–200 μM for Cr2O72−, and for CrO42−, severally.

Two new ternary Mn(II) coordination polymers by regulation of aromatic carboxylate ligands: Synthesis, structures, photocatalytic and selective ion-sensing properties

Two new Mn(II) coordination polymers, namely, [Mn(NDC)(L)(H2O)]n (NCST-3) and {[Mn2(HBTC)2(L)2(H2O)2]·2H2O}n (NCST-4) (L = 1,4-bis(5,6-dimethylbenzimidazole)butane, 1,4-H2NDC = 1,4-naphthalene dicarboxylic acid, and H3BTC = 1,3,5-benzenetricarboxylic acid) (NCST = North China University of Science and Technology) were synthesized and structurally characterized by single crystal and powder X-ray diffractions, elemental analysis, FT-IR spectroscopy and TGA. NCST-3 exhibits 2D 3,5L2 network, whereas NCST-4 possesses an unusual (3,4,5)-connected framework defined by the point symbol of (53)(55.6)(56.62.82). Furthermore, the photocatalytic activities of two complexes were evaluated for the degradation of methylene blue (MB), Rhodamine B (RhB), methyl violet (MV) and methyl orange (MO) under the UV irradiation. Finally, two compounds as probes displayed favorable ion-sensing performance for Cr3+/Ag+ through fluorescence quenching.

Terminal Ligand (L) Effects on Zero-Magnetic-Field Splitting in the Excited Triplet States of [{Mo6Br8}L6]2- (L = Aromatic Carboxylates).

We report the emission properties of the octahedral hexamolybdenum(II) bromide-core ({Mo6Br8}4+) clusters having a series of terminal aromatic carboxylate ligands (RCOO), [{Mo6Br8}(RCOO)6]2-, in solution and crystalline phases. The acid dissociation constant of RCOOH (p Ka(L)) was shown to govern the redox and emission properties of the clusters. Temperature ( T)-controlled emission experiments (3-300 K) demonstrated that the clusters showed large T-dependent emission energies (ν̃em) and lifetimes (τem) because of zero-magnetic-field splitting in the emissive excited triplet (T1) states. The spin sublevel (Φ n, n = 1-4) model in the T1 state of the cluster explained very well the T-dependent emission characteristics (ν̃em and τem), irrespective of the clusters studied. Furthermore, we revealed that the energy difference between the lowest-energy (Φ1) and energetically upper-lying third (Φ3) or fourth spin sublevels (Φ4), Δ E13 or Δ E14, respectively, correlated very well with p Ka( L). The results are discussed in terms of the variation of the effective nuclear charge of the Mo metal center(s) in [{Mo6Br8}(RCOO)6]2- with that of p Ka(L).