Bridging Carboxylate Research Articles

A new series of Schiff base Ni(II)4 cubanes: Evaluation of magnetic coupling via carboxylate bridges

The Schiff base ligand H2L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction between H2L and Ni(OOCR3)2, R = H in 1, –CH3 in 2, Cl in 3, yielded three new tetranuclear Ni(II) complexes. The complexes have been characterized by elemental analysis, IR- and ES-MS spectroscopy. Their structures as well as structure of ligand were determined by single-crystal X-ray diffraction. Compounds 1–3 possesses tetranuclear cubane-like structures containing [Ni4L4(R3COO)2]2− complex anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1–3, in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

Structural Insights into New Bi(III) Coordination Polymers with Pyridine-2,3-Dicarboxylic Acid: Photoluminescence Properties and Anti-Helicobacter pylori Activity.

Two novel coordination polymers, [Bi2(2,3pydc)2(2,3pydcH)2(H2O)]n (1) and {(Et3NH)2[Bi(2,3pydc)(2,3pydcH)Cl2]}n (2) were prepared using as a prolinker pyridine-2,3-dicarboxylic acid (2,3pydcH2). The obtained complexes were fully characterized by elemental analysis, TG/DTG, FT-IR, solid-state photoluminescence, DFT calculations and single-crystal X-ray diffraction. The obtained complexes crystallized in the triclinic P-1 space group (1) and comprise dimeric units with two crystallographically different Bi(III) centers (polyhedra: distorted pentagonal bipyramid and bicapped trigonal prism) and monoclinic P21/c space group (2) with a distorted monocapped pentagonal bipyramid of Bi(III) center. The various coordination modes of bridging carboxylate ligands are responsible for the formation of 1D chains with 4,5C10 (1) and 2C1 (2) topology. The photoluminescence quantum yield for polymer 2 is 8.36%, which makes it a good candidate for more specific studies towards Bi-based fluorescent materials. Moreover, it was detected that polymer 1 is more than twice as active against H. pylori as polymer 2. It can be concluded that there is an existing relationship between the structure and the antibacterial activity because the presence of chloride and triethylammonium ions in the structure of complex 2 reduces the antibacterial activity.

Triorganotin(IV) derivatives with semirigid heteroditopic hydroxo‐carboxylato ligands: Synthesis, characterization, and cytotoxic properties

Three organic hydroxy‐carboxylic acids separated by a semirigid aromatic diaza scaffold and carrying alkyl groups of different steric hindrance (H′HL1, cyclopropyl; H′HL2, cyclohexyl; H′HL3, adamantyl) were employed as pro‐ligands. Their reaction with suitable triorganotin precursors leads to 10 complexes of compositions: [Me3Sn(HL1)]n·0.5nC6H5CH3 1, [Et3Sn(HL1)]n 2, [nBu3Sn(HL1)]n 3, [Ph3Sn(HL1)]n 4, [Me3Sn(HL2)]2·2CH2Cl2 5, [Et3Sn(HL2)]2 6, {[nBu3Sn(HL2)][nBu3Sn(HL2)(H2O)]} 7, [Ph3Sn(HL2)]n·nC2H5OH 8, [nBu3Sn(HL3)]n 9, and [Ph3Sn(HL3)]n 10. The solid‐state structures of 1–10 were deduced from single‐crystal X‐ray diffraction studies along with two of the pro‐ligands: H′HL1 and H′HL2. In the solid state, four different extended structure types were observed. In compounds 1–3 with aliphatic substituents at the tin atoms and a small substituent at the ligand backbone (cyclopropyl), 1D coordination polymers based on carboxylate bridging were observed, whereas compounds 4 and 8–10 with large substituents attached to the metal and the ligand (cyclohexyl and adamantyl) were 1D coordination polymers based on heteroditopic binding of the ligands. Albeit having essentially the same ligand conformation, the compounds having smaller substituents at the tin atoms (5, R = Me; 6, R = Et) comprise 24‐membered macrocyclic ring structures. In 7, water molecules are coordinated to half the tin atoms, giving dinuclear fragments {[HL2][nBu3Sn][HL2][nBu3Sn(H2O)]}, which are linked through OwH···Osal hydrogen bonds into 1D hydrogen‐bonded tapes. In solution, the tin atoms in 1–10 are coordinated to a single monoanionic [HL1–3]− ligand molecule utilizing anisobidentate coordination with the carboxylate group, as revealed from 119Sn nuclear magnetic resonance spectral results. The antiproliferative activity of the tri‐n‐butyl and triphenyltin compounds 3, 4, and 7–10 was evaluated against the cervical cancer cells (HeLa) and normal kidney cells (HEK) using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay. Of these, the adamantyl‐substituted tin complexes 9 and 10 present increased activity with IC50 values of 0.51 ± 0.01 and 0.41 ± 0.03 (μM) and good selectivity. The cell death mechanism was identified as apoptosis based on dual staining with fluorescent dyes (Hoechst 33342/propidium iodide and acridine orange/ethidium bromide) and might be related to reactive oxygen species.

Structure of tetra-kis-(μ-deca-noato-κ2 O:O')bis-[(4-methyl-pyridine-κN)copper(II)], a dimeric copper(II) complex.

The 4-methyl-pyridine (4-Mepy) based dimeric copper(II) carboxyl-ate complex [Cu2(C10H19O2)4(C6H7N)2] or [Cu2(μ-O2CC9H19)4(4-Mepy)2] crystallizes with triclinic (P ) symmetry. The two CuII ions exhibit a distorted square-pyramidal environment and are connected into a centrosymmetric paddle-wheel dinuclear cluster [Cu⋯Cu = 2.6472 (8) Å] via four bridging carboxyl-ate ligands arranged in the syn-syn coordination mode. The apical positions around the paddle-wheel copper centers are occupied by the N atoms of the 4-methyl-pyridine ligands. The structure exhibits disorder of the terminal alkyl carbon atoms in the deca-noate chains.

Three Co/Ni(II)-MOFs with dinuclear metal units constructed by biphenyl-3,3′,5,5′-tetracarboxylic acid and N-donor ligands: Synthesis, structures, and magnetic properties

Three new dinuclear complexes {[Co2(bpta)(2,2′-bipy)(H2O)]·2CH3CN·3H2O}n (M ​= ​Co (1), Ni (2)), and {[Co(H2bpta)(4,4′-bipy)]·H2O}n (3) have been obtained through a mixed-ligands strategy. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction and powder X-ray diffraction analysis. Structural analysis reveals that different dinuclear SBUs are formed by carboxylate groups of H4bpta ligands binding with metal ions in 1−3. The H4bpta ligands act as μ7-κ2:κ2:κ1:κ2 and μ3-κ2:κ0:κ1:κ0 coordination modes, respectively. For 1 and 2, the hexa-coordinated Co/Ni(II) ions are connected to form [M2(OCO)2(μ2-O)] SBUs by syn−syn-OCO− and μ2–oxo carboxylate bridges. The structures show (4,4)-connected 3D net with {42.84}-pts topology by bpta4− ligands linking [M2(OCO)2(μ2-O)] SBUs. Complex 3 possesses penta-coordinate geometry and displays a (2,6)-connected 2D layer formed by H2bpta2− and 4,4′-bipy ligands linking dinuclear [Co2(OCO)2] SBUs. The studies of the magnetic properties of 1−3 in the temperature range 1.8–300 ​K reveal that weak antiferromagnetic interaction exists in the triple and double bridging SBUs of the complexes 1 (J ​= ​−11.32 (6) cm−1) and 3 (J ​= ​−0.84(4) cm−1). Complex 2 exhibits ferromagnetic exchange (J ​= ​1.02(7) cm−1) in dinuclear [Ni2(OCO)2(μ2-O)] units.

Surface Structure Controls Self-Metalation: In-Situ IR Studies of Anchored Porphyrins on Atomically-Defined Cobalt Oxide Surfaces

The functionality of porphyrin/oxide interfaces depends on both the structure of the organic layer and the metalation of the porphyrin units. While the structure of the porphyrin film is known to be controlled by the oxide surface, little is known on the structure dependence of the self-metalation reaction. In this work, we investigated both the anchoring and the self-metalation reaction of 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (MCTPP) on three atomically-defined oxide thin films, namely Co3O4(111), CoO(111), and CoO(100), under ultrahigh vacuum conditions. We used infrared reflection absorption spectroscopy to follow the growth and self-metalation reaction in-situ as a function of coverage and temperature. At 300 K, MCTPP binds to Co3O4(111) in the form of a chelating surface bidentate carboxylate, whereas bridging carboxylates are found on CoO(111) and CoO(100). MCTPP multilayers desorb between 450 and 460 K on all oxides. However, monolayer species reside on the Co3O4(111) surface up to temperatures of 590 ± 5 K, similar as observed for CoO(100) (575 ± 5 K). On CoO(111), the anchored carboxylates are more strongly bound and remain up to 690 ± 5 K. Finally, we observed that the self-metalation reaction is strongly dependent on the surface structure and temperature. At 300 K, the degree of metalation is low (<10%) on all surfaces. At 450 K, however, we observe self-metalation of 60 ± 10% of the porphyrins on CoO(111) and CoO(100) in the monolayer. In sharp contrast, no increase in the metalation rate is observed for the deposition of MCTPP on Co3O4(111) at 450 K. Our results show that the adsorption motif, the molecular orientation, and the metalation reaction are strongly dependent on the oxide surface structure and, in particular, on the arrangement and distance of the Co cations in the surface region.

Combining valproate and bipyridyl ligands to construct a 0D core-shell Zn5(μ3-OH)2 cluster and a 2D layered coordination network with a [Zn3(μ3-OH)]2 SBU.

Starting from the proposed zinc carboxylate cluster tetrakis(μ-2-propylpentanoato)dizinc(II), Zn2(μ2-valp)4 (I), of valproic acid, a branched short-chain fatty acid, and bipyridine ligands, two new mixed-ligand coordination compounds, namely, bis(2,2'-bipyridine)di-μ3-hydroxido-hexakis(μ-2-propylpentanoato)bis(2-propylpentanoato)pentazinc(II), [Zn5(C8H15O2)8(OH)2(C10H8N2)2] (II), and poly[[bis(μ-4,4'-bipyridine)di-μ3-hydroxido-octakis(μ-2-propylpentanoato)bis(2-propylpentanoato)hexazinc(II)] dimethylformamide disolvate], {[Zn6(C8H15O2)10(OH)2(C10H8N2)2]·2C3H7NO}n (III), were synthesized. Compound II is a core-shell-type zero-dimensional discrete Zn5(μ3-OH)2 metal-organic cluster with Zn ions in double-triangle arrangements that share one Zn ion coincident with an inversion centre. The cluster contains three crystallographically non-equivalent Zn ions exhibiting three different coordination geometries (tetrahedral, square pyramidal and octahedral). The cluster cores are well separated and embedded in a protective shell of the aliphatic branched short chains of valproate. As a result, there is no specific interaction between the discrete clusters. Conversely, compound III, a 2D layered coordination network with a secondary building unit (SBU), is formed by Zn6(μ3-OH)2 clusters exhibiting a chair-like hexagonal arrangement. This SBU is formed from two Zn3(μ3-OH) trimers related by inversion symmetry and connected by two syn-anti bridging carboxylate groups. Each SBU is connected by four 4,4'-bipyridine ligands producing a 63-hcb net topology. 2D coordination layers are sandwiched within layers of dimethylformamide molecules that do not interact strongly with the network due to the hydrophobic protection provided by the valproate ligands.

Synthesis and magneto-structural analysis of H-bonded Cu/Ni-orotato coordination polymers

Orotato based coordination network of formula [Cu(HOr)2]2−. 2(CH3)2―NH2+]n(1), and [Ni(HOr).3H2O]n (2), have been synthesized hydrothermally by self-assembly of orotic acid (H3Or) with metal salts Cu(OAc)2.H2O and Ni(NO3)2•6H2O respectively. Single crystal X-ray study confirms that in 1 electroneutrality is obtained with a compensating cation i.e. (CH3)2‒NH2+ and trans-trans μ2η1:η1 bridging carboxylate extend the Cu-Orotate moiety into 2D coordination network showing square lattice topology (sql) which through {…H‒N‒C = O} dimer yields into 3D hydrogen bonded coordination polymer.Temperature dependent measurements of magnetic susceptibility reveals the occurrence of competitive exchange interactions with weak ferromagnetic character in 1 (J = +0.31 cm–1) and weak antiferromagnetic interaction in 2 (J = - 0.52 cm–1). The dominantzero – field splitting effect is observed in Ni(II) ion. Two important magneticsuper exchange pathway transmitted through carboxylate oxygen of ligand through N‒H…O, and O‒H…O supramolecular synthons along with long Cu•••Cu separation of 6.635 Å (1) or Ni•••Ni separation of 7.700 Å (2). The DFT calculation analysis is used to rationalized the magnetic behavior in these coordination polymers.

Bimetallic Ni(II) complex with carboxylate bridging for homogeneous hydrogenation of alkenes with NaBH4

In this study, we present the synthesis and full characterization of the dimer Ni(II) complex, [Ni2(dpaa)2(bpy)2(SO4)(H2O)]CH3OH, (dpaa = diphenyl acetic acid, bpy = 2,2′-bipyridine) with an N2O4 donor set and its hydrogenation activity on linear and cyclic alkenes (1-octene, t-2-octene, 1-hexene, cyclohexene, cyclopentene, benzene and styrene) with NaBH4 as a hydrogen source. 1-Octene and 1-hexene were reduced to the corresponding alkanes as the major products (81.3 and 91.2%, respectively), and the substrate isomerized the terminal alkenes to a mixture of internal alkenes as minor products (1–4%) under the studied conditions (subs/cat/reduct. 100/1/1 in methanol, 40 °C, 6 h). To optimize the reaction conditions for the reduction of styrene to ethyl benzene in methanol, the effect of subs./NaBH4 ratio, solvent and temperature were also investigated.

Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore.

The stereoselective synthesis of truxillic bis-amino esters from polyfunctional oxazolones is reported. The reaction of 4-((Z)-arylidene)-2-(E)-styryl-5(4H)-oxazolones 2 with Pd(OAc)2 resulted in ortho-palladation and the formation of a dinuclear open-book complexes 3 with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In 3 the two exocyclic C=C bonds of the oxazolone are in a face-to-face arrangement, which is optimal for their [2 + 2] photocycloaddition. Irradiation of dimers 3 in CH2Cl2 solution with blue light (465 nm) promoted the chemo- and stereoselective [2 + 2] photocycloaddition of the exocyclic C=C bonds and the formation of cyclobutane-containing ortho-palladated complexes 4. Treatment of 4 with CO in a MeOH/NCMe mixture promoted the methoxycarbonylation of the palladated carbon and the release of the corresponding ortho-functionalized 1,3-diaminotruxillic bis-amino esters 5 as single isomers.

Coordination polymers incorporating Bi(III) and 2,4,6-pyridine tricarboxylic acid and its derivatives: Synthesis, structure and topology

Bi(III) as its oxide combined with 2,4,6-pyridine tricarboxylic acid, H2pdc-COOH, and various pyridine-derived additives in dimethylformamide (dmf) under solvothermal conditions produced three novel bismuth coordination polymers, {[Bi(μ-pdc-COO)2][NH2Me2]3}n, 1, {[Bi(μ-pdc-COO)2][C5H7N2]3·C5H6N2}n, 2, and {[Bi2(μ-pdc-COO)2(μ-pdc-COOH)(pdc-COOH)][NH2Me2]4·2dmf·NHMe2}n, 3. The anionic coordination network topologies are two-dimensional, chains-of-loops and ladders, respectively, but the local 8-coordinate environments about the bismuth(III) centres are in each case between that of a square antiprism and that of a hexagonal bipyramid. When the 4-carboxy substituent in H2pdc-COOH is replaced by another potentially coordinating substituent to give 4-R-2,6-pyridine dicarboxylic acid, H2pdc-R (R = OH, NH2, Cl), the salts obtained contain discrete centrosymmetric dinuclear 8-coordinate bismuth anions with either double O-bridges between the metal centres, [Bi2(μ-pdc-R)2(pdc-R)2(dmf)2][NH2Me2]2 (R = OH, NH2), 4 and 5, or double carboxylate bridges with one long Bi–O bond, [Bi2(μ-pdc-NMe2)2(pdc-NMe2)2(dmf)2][NH2Me2]2, 6 (R = Cl, but replaced by dimethylamine during the reaction). The structures and supramolecular networks of 1–6 are described and compared as an exploration of alternatives to the conventional carboxylate-based organic linking units.

New one-, two-, and three-dimensional metal-organic frameworks based on magnesium(II): synthesis and structure

Six new metal-organic frameworks based on magnesium(II) ions of various dimensionality were synthesized: chain-like [Mg(Hazdc)2(nmp)2] (1, H2azdc is 4,4′-azobenzenedicarboxylic acid, nmp is N-methylpyrrolidone), layered [Mg(H2btc)(nmp)2] (2, H4btc is 1,2,4,5-benzene-tetracarboxylic acid), [Mg3(sdc)3(def)4] •3DEF (3, H2sdc is 4,4’-stilbenedicarboxylic acid, def or DEF is N,N-diethylformamide), [Mg3(azdc)3(dma)4] • 3DMA (4, dma or DMA is N,N-di-methylacetamide), [Mg3(azdc)3(dmf)4] (5, dmf is N,N-dimethylformamide), and doubly-interpenetrated three-dimensional [Mg3(azdc)3(nmp)4] •NMP (6, NMP is N-methylpyrrolidone). According to the single-crystal X-ray dif raction data, compounds 1 and 2 are built from mononuclear carboxylate units {Mg(RCOOH)2(RCOO)2(nmp)2}. Compounds 3-6 are composed on trinuclear carboxylate units {Mg3(RCOO)6}. In isostructural compounds 3-5, these units are linked to each other through carboxylate bridges to form polymer layers; in compound 6, these units are linked together to form a doubly-interpenetrated three-dimensional metal-organic framework.

Molecular Dynamic Simulation on the Stability of Corporated Metal Organic Framework and Choline Based Ionic Liquids

A compatibility and stability of Isoreticular Metal Organic Framework (IRMOF-1) impregnated with choline based ionic liquids (ILs) are studied by molecular dynamic simulation. Among three proposed IL/IRMOF-1 hybrid composites, cholinium formate, ([Chl][Fm]) is nominated as the best IL to be incorporated with IRMOF-1 since it shows the lowest RMSD value (0.502 nm, 0.637 nm, 0.923 nm) at three IL/IRMOF-1 w/w ratio (0.4%, 0.8% and 1.2%) respectively and become representative to all three ILs. Oxygen atom in the bridging carboxyl group shows the most flexible atom through RMSF analysis since it shows the highest fluctuation (1.001 nm) at WIL/IRMOF-1 = 0.4%. The RDF shows that the interaction between [Chl]+ and [Fm]− is higher in composite phase compare to bulky phase due to confinement effect of IRMOF-1. Both [Chl]+ and [Fm]− seem to be preferred to locate around carboxylate group inside the IRMOF-1 whereby [Fm]− shows the dominant interaction and strongly interacts with IRMOF-1 compared to [Chl]+. In terms of mobility, the cation shows high mobility with SDF value of 0.0419 nm2 in which mobility is expected to be increased with increasing of ILs ratio (0.4%, 0.8% and 1.2%) respectively. Intensity of the ions population around IRMOF-1 is interpreted by density map which is in agreement with the RDF analysis. Finally, the stability of the IRMOF-1 is confirmed by the radius of gyration (Rg) analysis in which 0.4% ILs shows the most stable conformation with the lowest Rg value = 1.667 nm that is in consistent with the RMSD analysis. Overall, the structural stability of IRMOF-1 is well interpreted and impregnation of ILs literally increase the stability of framework at lower IL/IRMOF-1 w/w ratio.

Synthesis, Characterization and Thermal Studies of a Nanosized 1D l-Arginine/Copper(II) Coordination Polymer by Sonochemical Method: A New Precursor for Preparation of Copper(II) Oxide Nanoparticles

In the present work, 1D-copper(II) coordination polymer, {[Cu(μ-l-Arg)2(H2O)]SO4}n (1); (l-Arg: l-Arginine), was synthesized and identified by elemental analysis, FT-IR spectroscopy, molar conductivity, thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and single-crystal X-ray diffraction. The compound 1 was also prepared by a sonochemical process in the form of nanoparticles. The particle size and morphology of the synthesized nanoparticles were investigated by powder X-ray diffraction (PXRD) and field emission scanning electron microscopy (FE-SEM). In the crystal structure of 1, the copper atoms are coordinated in a distorted octahedral geometry. In this geometry, the cis-equatorial plane (N2O2) is constructed by two NO-donor l-Arg ligands. The remaining coordination sites in the apical positions are occupied by an oxygen atom of the neighboring l-Arg and the oxygen atom of a water molecule. In 1, infinite one-dimensional (1D) networks are constructed through carboxylate bridges. Finally, CuO nanoparticles were produced by thermal decomposition of the sonochemically prepared nanoparticles of 1, and characterized by FT-IR, XRD, FE-SEM and EDS.

Coordination control of a semicarbazide Schiff base ligand for spontaneous aggregation of a Ni2Ln2 cubane family: influence of ligand arms and carboxylate bridges on the organization of the magnetic core

A new family of tetranuclear [Ni2Ln2O4] cubane complexes has been assembled from carbazido ligand by altering the 4f ions without changing the core topology, which provided weak ferromagnetic and antiferromagnetic interactions.

А New Series of Schiff Base Ni(II)4 Cubanes: Evaluation of Magnetic Coupling Via Carboxylate Bridges

The Schiff base ligand H 2 L has been synthesized by condensation of 2-aminophenol with 3-methyl-1-phenyl-4-formylpyrazol-5-one and reaction with Ni(OOCR 3 ) 2 , R = H in 1 , -CH 3 in 2 , Cl in 3 , to yield three new tetranuclear Ni(II) complexes The ligands and the complexes have been characterized by elemental analysis, IR- and NMR- spectroscopy. Their structures were determined by single-crystal X-ray diffraction. Compounds 1 - 3 possesses tetranuclear cubane-like structures containing [Ni 4 L 4 (R 3 COO) 2 ] 2- complex as anions, which are charge balanced by two triethyl ammonium cations. Furthermore, the crystal structure of the Ni(II) cubane compound containing trichloroacetate bridging ligands, is reported for the first time,. Variable temperature magnetic susceptibility measurements revealed interplay between ferromagnetic and antiferromagnetic exchange in the tetranuclear cubane-like compounds 1-3 , in which ferromagnetic interactions were enhanced by introducing carboxylate bridging groups. DFT calculations supported the analysis of magnetic data.

Heterometallic trinuclear oxo-centered clusters as single-source precursors for synthesis of stoichiometric monodisperse transition metal ferrite nanocrystals.

The use of heterobimetallic metal complexes as molecular single-source precursors is a promising strategy for the targeted synthesis of phase-pure stoichiometric ternary metal oxide nanocrystals. However, the design and synthesis of these precursors is not trivial and can require considerable effort. Using spinel metal ferrite nanocrystals of formula MFe2O4 (M = Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) as a model system, this paper evaluates the efficacy of the single-source precursor approach by comparing directly nanocrystals synthesized from the solvothermal reaction of heterobimetallic trinuclear oxo-bridged clusters of formula MIIFeIII2(μ3-O)(μ2-O2CR)6(H2O)3, R = CF3 to nanocrystals synthesized from the solvothermal reaction of stoichiometric mixtures of multi-source precursors, such as metal acetate or nitrate salts. For each M explored here, the clusters form phase-pure MFe2O4 nanocrystals with significantly narrower size distributions than nanocrystals synthesized from multi-source-precursors. In the case of M = Cu, the multi-source metal salt precursors produce a mixture of CuO and CuFe2O4. Additionally, changing the electronic nature of the R-group on the bridging carboxylate ligand from electron withdrawing (CF3) to electron donating (CH3 or C(CH3)3) decreases the average diameter of the resulting nanocrystals by a factor of two. The cluster molecules therefore offer superior control over both morphology and composition for transition metal ferrite nanocrystals. We hypothesize that this remarkable performance arises from the presence of pre-formed M2+-O-Fe3+ moieties in the cluster molecules that enable direct nucleation of MFe2O4 and preclude nucleation of binary oxide impurities.

Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe3+ and Nitroaromatics

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C5H6O4)(H2O)4]Cl}n, (1) and [Tb(C5H7O4)(C5H6O4)(H2O)2]n, (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO9 distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO9 polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln2O2 diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O–H···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the 5D0 → 7FJ (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the 5D4 → 7FJ (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe3+ ions due to luminescence quenching compared with other metal ions, which include; Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.

Benzoate substituents effects on the structure of Zn(II) complexes and 1D 4,4′-bipyridine derived coordination polymers

The aim of this work is to study the influence of different substituents in two closely related ligands, 3,5-dihydroxybenzoate (3,5-(HO)2Bz) and 3,5-dimethoxybenzoate (3,5-(MeO)2Bz), in the structure of zinc complexes. The compound [Zn(3,5-(MeO)2Bz)2(CH3OH)]2 (2) has been synthesized, characterized and its crystal structure elucidated, showing a paddle wheel type dinuclear molecule, with four bridging carboxylate ligands in a syn-syn coordination mode and methanol molecules in the apical positions. This discrete structural array is different than the polymeric structure observed in {[Zn(µ-3,5-(HO)2Bz)(µ-OH2)(H2O)2]·3,5-(HO)2Bz·4H2O}n, previously reported in our group. These two zinc complexes were used as precursor for the synthesis of coordination polymers (CPs) with the 4,4′-bipyridine (4,4′-bpy) linker. The solvent used in their synthesis influences the chemical composition of this CPs. Thus, {[Zn(3,5-(HO)2Bz)2(µ-4,4′-bpy)]·2DMSO}n (3) was achieved in dimethylsulfoxide (DMSO) while {[Zn(3,5-(HO)2Bz)2(µ-4,4′-bpy)]·4,4′-bpy·1/2CH3OH}n (4) was formed in methanol (MeOH) as solvent. The reaction of 2 with 4,4′-bpy yielded [Zn2(μ-3,5-(MeO)2Bz)4(µ-4,4′-bpy)]n (5) in methanol, while after recrystallization in boiling water, complex {[Zn(3,5-(MeO)2Bz)2(µ-4,4′-bpy)]·H2O}n (6) was isolated in low yield. This compound 6 can also be synthesized by a mechanochemical approach, using water in a liquid assisted grinding. The crystal structures of complexes 3, 4 and 6 were elucidated, all three showing zigzag polymeric arrays. Both polymers containing 3,5-(MeO)2Bz (5 and 6), showed solid state luminescence.

A novel mixed ligand Zn-coordination polymer: Synthesis, crystal structure, thermogravimetric analysis and photoluminescent properties

A novel mixed ligand based coordination network of Zn, having formula [Zn8(Or)8(dpp)4(H2O)8]n (1), have been engineered and synthesized at room temperature by self-assembly of potassium orotate (OrK) and 1,3 di(4-pyridyl)propane (dpp) with metal salt, Zn(OAc)2·2H2O Single crystal X-ray structural analysis reveals that coordination sphere around Zn(II) ions, in Or-Zn-dpp moiety, having different atomic arrangement with distorted square pyramidal geometry. The syn-anti μ2η1:η1 bridging carboxylate and pyridyl moieties extended the Or-Zn-dpp skeleton into 2D coordination network showing square grid sheet. The emission spectrum of Zn-complex was recorded with 290 nm excitation wavelength which reflects that 1 has strong luminescence with peak maximum of 380 nm (3.2627 eV) and is a result of the n–π* and π–π* transitions of H3Or and dpp ligand. Thermogravimetric analysis shows that when the coordinated water molecule completely comes out from the complex around 320 °C, the dehydrated forms steadily starts to degrade, and the complete decomposition is observed above 350 °C.