Mixed Carboxylate Research Articles

Mixed Carboxylate Ligands Bridging Tetra-Pr3+-Encapsulated Antimonotungstate: Syntheses, Structure, and Catalytic Activity for Imidazoles Synthesis.

Multinuclear Pr-containing antimonotungstate [Pr4(H2O)10W6O13(mal)2(OAc)(B-α-SbW9O33)4]21- (Pr-1, mal = malate anion, OAc = acetate anion), bridged by organic carboxylic acid, was synthesized through a one-pot assembly reaction and structurally characterized. Pr-1 is composed of four [B-α-SbW9O33]9- fragments fused together by an organic-inorganic hybrid central [Pr4(H2O)10W6O13(mal)2(OAc)]15+ cluster core through 24 μ2-O atoms. Notably, the central cluster comprises unprecedented decanuclear Pr4(H2O)10W6O13 jointly decorated by two types of carboxylic acid ligands. This integration of rare earth-containing antimonotungstate with mixed organic carboxylate ligands is very rare in POMs chemistry. Pr-1 exhibits excellent catalytic activity in the cyclo-condensation reaction involving benzil, aldehyde, and NH4OAc. A series of 2,4,5-trisubstituted imidazoles were synthesized in remarkable yields using iPrOH as a green solvent.

Supramolecular hydrogen-bonded networks formed from copper(II) carboxylate dimers.

The well-known copper carboxylate dimer, with four carboxylate ligands extending outwards towards the corners of a square, has been employed to generate a series of crystalline compounds. In particular, this work centres on the use of the 4-hydroxybenzoate anion (Hhba-) and its deprotonated phenolate form 4-oxidobenzoate (hba2-) to obtain complexes with the general formula [Cu2(Hhba)4-x(hba)xL2-y]x-, where L is an axial coligand (including solvent molecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hydrogen bonds result in complexes which may be represented as [Cu2(Hhba)2(H0.5hba)2L2]-. The main focus of the investigation is on the formation of a variety of extended networks through hydrogen bonding and, in some crystals, coordinate bonds when bridging coligands (L) are employed. Crystals of [Cu2(Hhba)4(dioxane)2]·4(dioxane) consist of the expected Cu dimer with the Hhba- anions forming hydrogen bonds to 1,4-dioxane molecules which block network formation. In the case of crystals of composition [Et4N][Cu2(Hhba)2(H0.5hba)2(CH3OH)(H2O)]·2(dioxane), Li[Cu2(Hhba)2(H0.5hba)2(H2O)2]·3(dioxane)·4H2O and [Cu2(Hhba)2(H0.5hba)2(H0.5DABCO)2]·3CH3OH (DABCO is 1,4-diazabicyclo[2.2.2]octane), square-grid hydrogen-bonded networks are generated in which the complex serves as one type of 4-connecting node, whilst a second 4-connecting node is a hydrogen-bonding motif assembled from four phenol/phenolate groups. Another two-dimensional (2D) network based upon a related square-grid structure is formed in the case of [Et4N]2[Cu2(Hhba)2(hba)2(dioxane)2][Cu2(Hhba)4(dioxane)(H2O)]·CH3OH. In [Cu2(Hhba)4(H2O)2]·2(Et4NNO3), a square-grid structure is again apparent, but, in this case, a pair of nitrate anions, along with four phenolic groups and a pair of water molecules, combine to form a second type of 4-connecting node. When 1,8-bis(dimethylamino)naphthalene (bdn, `proton sponge') is used as a base, another square-grid network is generated, i.e. [Hbdn]2[Cu2(Hhba)2(hba)2(H2O)2]·3(dioxane)·H2O, but with only the copper dimer complex serving as a 4-connecting node. Complex three-dimensional networks are formed in [Cu2(Hhba)4(O-bipy)]·H2O and [Cu2(Hhba)4(O-bipy)2]·2(dioxane), where the potentially bridging 4,4'-bipyridine N,N'-dioxide (O-bipy) ligand is employed. Rare cases of mixed carboxylate copper dimer complexes were obtained in the cases of [Cu2(Hhba)3(OAc)(dioxane)]·3.5(dioxane) and [Cu2(Hhba)2(OAc)2(DABCO)2]·10(dioxane), with each structure possessing a 2D network structure. The final compound reported is a simple hydrogen-bonded chain of composition (H0.5DABCO)(H1.5hba), formed from the reaction of H2hba and DABCO.

Luminescent coordination polymers with mixed carboxylate and triazole ligands for rapid detection of chloroprene metabolite

Chloroprene is a monomer widely used in the production of neoprene, and 1-hydroxy-2-butanone (1H2B) is one of the metabolites of chloroprene in urine, which can place a significant impact on human health by disrupting the normal structure and function of DNA. Herein, a three-dimensional Zn-based coordination polymer (1) and a two-dimensional Cd-based coordination polymer (2) were synthesized with mixed ligands of 2,5-furandicarboxylic acid (H2FDA) and 1,2,4-triazole (Htrz) and fully characterized. 2 exhibits excellent stability and superior sensing performance for 1H2B with fast response within 15 s, good recyclability and a detection limit of 9.24 μM. In addition, 2 demonstrates good selectivity in presence of main coexisting compounds in urine. In-depth investigations of the sensing mechanism revealed that the luminescence sensing is based on the competitive absorption and photoelectron transfer processes.

Enhancing the Green Synthesis of Glycerol Carbonate: Carboxylation of Glycerol with CO2 Catalyzed by Metal Nanoparticles Encapsulated in Cerium Metal-Organic Frameworks.

The reaction of glycerol with CO2 to produce glycerol carbonate was performed successfully in the presence of gold nanoparticles (AuNPs) supported by a metal-organic framework (MOF) constructed from mixed carboxylate (terephthalic acid and 1,3,5-benzenetricarboxylic acid). The most efficient were two AuNPs@MOF catalysts prepared from pre-synthesized MOF impregnated with Au3+ salt and subsequently reduced to AuNPs using H2 (catalyst 4%Au(H2)@MOF1) or reduced with NaBH4 (catalyst 4%Au@PEI-MOF1). Compared to existing catalysts, AuNPs@MOFs require simple preparation and operate under mild and sustainable conditions, i.e., a much lower temperature and the lowest CO2 overpressure ever reported, with MgCO3 having been found to be the optimal dehydrating agent. Although the yield of the process is still not competitive with previously developed systems, the most promising advantage is the highest TOF (78 h-1) ever reported for this reaction. The optimal parameters observed for AuNPs were also tested on AgNPs and CuNPs with promising results, suggesting their great potential for industrial application. The catalysts were characterized by XRD, TEM, SEM-EDS, ICP-MS, XPS, and porosity measurements, confirming that AuNPs are present in low concentration, uniformly distributed, and confined to the cavities of the MOF.

Facile Layer Diffusion Technique for Synthesis of Terbium-Based Metal Organic Framework for Fluorometric Sensing of Hydroquinone.

A photoluminescent terbium (III)-based Metal Organic Framework (MOF) was synthesized at room temperature by layer diffusion method utilizing mixed carboxylate linkers (4,4'-oxybis(benzoic acid) and benzene-1,3,5 tricarboxylic acid). Synthesized MOF has crystalline nature and rod-shaped morphology and is thermally stable up to 455°C. The fluorescence emission spectra and theoretical results revealed that carboxylate linkers functioned as sensitizers for Tb(III) photoluminescence which resulted in four distinct emission peaks at 495, 547, 584, and 621nm corresponding to the transitions 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3. Using synthesized MOF as fluorescent probe, hydroquinone was detected in aqueous medium with a detection limit of 0.048μM, remarkable recovery (95.6-101.1%), and relative standard deviation less than 2.25%. The quenching phenomenon may be ascribed to electron transfer from synthesized probe to oxidized hydroquinone via carboxylic groups on thesurface of MOF, which is further supported by photo-induced electron transfer mechanism. This study introduces a cheaper, faster, and more accurate method for hydroquinone detection.

Influence of nuclearity and coordination geometry on the catalytic activity of Zn(II) carboxylate complexes in ring-opening polymerization of ε-caprolactone and lactides

A series of nine Zn(II) carboxylate complexes stabilized by monodentate pyridyl Schiff base ligands have been synthesized and characterized by IR, NMR, mass spectroscopy and elemental analysis. The molecular structures of three of the nine complexes were established from single-crystal X-ray diffraction studies and found to have different nuclearity (mono-, -di or tri-). As catalysts in the ring-opening polymerization (ROP) of ε-caprolactone (ɛ-CL) and rac-lactide (rac-LA), the carboxylate complexes were active and afforded low molecular weight polymers with moderate to broad polydispersity (Ð) at elevated temperatures. The catalytic activity examined under various polymerization conditions was found to be influenced by the nuclearity and coordination geometry adopted by the carboxylate complexes. Complexes with higher nuclearity and particularly those with mixed carboxylate systems displayed higher catalytic activities with and without alcohol initiators. The dinuclear and trinuclear complexes exhibited superior catalytic activities and for the polymerization of L-LA they gave predominantly isotactic poly-lactides while polymerization of rac-LA gave heterotactic polymers with Pr of 0.68 and 0.69 for complexes 1 and 2, respectively.

Improved In Vitro Antimycobacterial Activity of Trinuclear Complexes Cobalt(II,III) and Iron(III) with 2‐Furoic Acid against Mycolicibacterium smegmatis

AbstractThe reaction of cobalt(II) and iron(III) pivalates with anions of 2‐furancarboxylic acid (pyromucic acid, Hfur) yielded trinuclear homometallic complexes with linear ([Co3(fur)6(phen)2] (1, phen=1,10‐phenanthroline)) and triangular ([Co3O(fur)6(H2O)3] (3), [Fe3O(fur)6(THF)3] ⋅ 3THF (4)) structures of the metal moiety. The hexanuclear mixed carboxylate cobalt complex [Co6(piv)8(Hpiv)4(fur)2(OH)2] (2, piv−=(CH3)3COO−) was isolated as an intermediate in the synthesis of 3. According to CVA data, complex 3 contains bivalent and trivalent cobalt ions. According to Mossbauer spectroscopy data, all the iron(III) atoms in 4, which is an isostructural analogue of 3, are solely in the high‐spin state. The antibacterial activity of compounds 1–4, K(fur) (5) and Na(fur) (6) was determined in vitro against a non‐pathogenic Mycolicibacterium smegmatis strain. The results of in vitro biological tests against Mycolicibacterium smegmatis showed a high bioactivity of complexes 1 and 4.

Effective C2H2 Separation and Nitrofurazone Detection in a Stable Indium-Organic Framework.

Based on the mixed carboxylate ligands synthesis strategy, an indium-organic framework, (Me2NH2)1.5[In1.5(FBDC)(BDC)]·2.5NMF·CH3CN (1) has been constructed by using the mixed (2,5-di(2',5'-dicarboxylphenyl)-difluorobenzene (H4FBDC) and terephthalic acid (H2BDC). Compound 1 contains a 3D intersecting pore system which surface is modified by F atoms, and it has excellent stability in pH = 2-12 aqueous solutions. The activated 1 shows high separation for C2H2/CO2 and C2H2/CH4. Moreover, 1 not only has strong luminescence but also has the high selectivity and sensibility of fluorescence detection to nitrofurazone (NZF) in antibiotic sensing experiments, which can be used as a luminescence sensor for NZF detection.

Series of Cadmium(II) Coordination Polymers Based on a Versatile Multi-N-Donor Tecton or Mixed Carboxylate Ligands: Synthesis, Structure, and Selectively Sensing Property.

Five Cd(II) metal–organic frameworks (MOFs), [Cd(HL)2] (1), [Cd(HL)2(H2O)2] (2), [Cd3(HL)2(obda)2] (3), [Cd2(HL)2(ohmbda)(DMA)(H2O)] (4), and [Cd2(HL)(btc)(H2O)2]·3H2O (5), were prepared by reactions of Cd(NO3)2·4H2O with 1-(1H-imidazol-4-yl)-4-(4H-tetrazol-5-yl)benzene (H2L) or mixed carboxylate ancillary ligands of 1,2-benzenedicarboxylic acid (H2obda), 5-hydroxy-1,3-benzenedicarboxylic acid (H2ohmbda), and 1,3,5-benzenetricarboxylic acid (H3btc), respectively. Their structures have been characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy (IR), thermogravimetric analysis, and powder X-ray diffraction. Compounds 1 and 2 are supramolecular isomeric frameworks without consideration of the solvent molecules. Complex 1 exhibits a binodal (3, 5)-connected two-dimensional (2D) layer structure with the point (Schläfli) symbol of (52·6)(55·64·7), while complex 2 shows a 2D + 2D → 3D (three-dimensional) framework. Complex 3 is a (3, 5, 6)-connected tetranodal 3D net with the point (Schläfli) symbol of (4·82)2(45·6·84)2(45·65)2(48·66·8). Compound 4 is a (3, 3, 8)-connected trinodal 3D net with the point (Schläfli) symbol based on a binuclear [Cd2N2O] subunit, while 5 is a 2-nodal (3, 4)-connected 2D V2O5-type network based on [Cd2N2(COO)2] SBU. The studies of molecular sensing properties show that the luminescent MOFs can be employed as fluorescent sensors for the detection of Fe3+ and nitro compounds. Compound 1 and 3 exhibit quenching responses for Fe3+ in dimethylformamide solution with detection limits of 2.3 × 10–6 and 8.6 × 10–7 M, respectively. Meanwhile, compound 5 can sense 4-nitrophenol with a detection limit as low as 5.75 × 10–7 M.

Synthesis and characterization of the trans(O6) isomer Ni(II) complex containing symmetrical edta-type ligand with mixed carboxylate and diamine rings: Quantum-mechanical evaluation of different isomers

The trans(O6) isomer (trans(O6) refer to two six-membered rings in trans position) of the [Ba(H2O)4][Ni(1,3-pddadp)]·4H2O (1,3-pddadp = 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate) was synthesized and spectroscopically characterized (IR, UV–Vis). The trans(O6) geometry was confirmed by X-ray diffraction analysis. Single crystal X-ray diffraction of the complex revealed an octahedral geometry around the Ni(II) centre. Extensive strain analysis of [M(edta-type)]2− complexes (M = Ni, Co, Cu) has been performed and discussed in detail. DFT/NBO analysis (DFT = Density Functional Theory, NBO = Natural Bond Orbital) was performed for all isomers of [Ni(1,3-pddadp)]2− complex. DFT theory shows that trans(O6) isomer is 0.53 kcal mol−1 more stable than trans(O5O6) and 1.95 kcal mol−1 more stable than trans(O5). NBO analysis for all three isomers predicts the existence of a 3-center 2-electron (β system) A: -Ni-: B hyperbonds along with O:-C-:O carboxylate triads. The Second-Order Perturbation Theory Analysis predicts molecular stabilization that comes from delocalization caused by nA → σNiB* or nB → σNiA* charge transfer.

Construction of mixed carboxylate and pyrogallate building units for luminescent metal–organic frameworks

A metal-organic framework, Ce-FDM-50, was constructed by employing gallic acid featuring both carboxylate and pyrogallate as the coordinating sites and Ce(III). The co-assembly of the carboxylates and pyrogallates with two metal ions have achieved a new type of paddle wheel secondary building unit. These building units were further joined by organic struts to obtain frameworks in sql topology. This synthetic approach could be expanded to five different lanthanide metals (Nd, Eu, Gd, Tb, Yb) for the construction of a series of isoreticular MOFs based on FDM-50, and even MTV-MOFs in which mixed lanthanide metals with specific ratios were distributed. In addition, featuring the lanthanide metals as the inorganic nodes in the network, Tb-FDM-50 showed distinct luminescence properties that could be furtherly tuned for variable applications.

Structural and theoretical investigations of the Rh(III) and Co(III) complexes containing symmetrical edta-type ligands with mixed carboxylate and diamine rings: Quantum-mechanical/NBO insight into stability of geometrical isomers

The trans(O5O6) isomer of the Na[Rh(eddadp)]·4H2O and the K[Co(eddadp)]·3H2O (eddadp = ethylenediamine-N,N′-diacetate-N,N′-di-3-propionate) were synthesized and Na[Rh(eddadp)]·4H2O structure was confirmed by X-ray diffraction analysis. The percentage of particular isomers found in reaction equilibrium mixtures of [M(eddadp)]− complex has been reported. Single crystal X-ray diffraction of the complex revealed an octahedral geometry of the Rh(III) centre. Improved structural distortion analysis of M(III) (M = Rh, Co) complexes with symmetric edta-type of ligands containing mixed carboxylate and diamine rings was made. Structural distortion analysis has determined high values of total deviation of the octahedral angles (Δ(Oh)) for both existing trans(O5) (34°) and trans(O5O6) (41°) isomers of [Rh(eddadp)]− complex, while in the case of a similar Co(III) complex, relatively low value (31°) for trans(O5) has been established. Extensive QM/NBO calculations were made for both systems [M(eddadp)]− and [M(1,3-pddadp)]− using different DFT methods (B3LYP/SDD, M06/SDD, MP2/SDD). By correlating the structural parameters obtained from X-ray and DFT optimized 3D structures, the B3LYP/SDD method was used as the method of choice. Based on the correlation between the energies of the optimized systems and the strain parameters, the existence of the trans(O6) isomer of the [Rh(1,3-pddadp)]− complex was predicted. NRT (Natural Resonance Theory) analysis gave the best resonances for each isomer. Here the stability of particular isomer has been described in terms of 3-CHB bonds involving metal ions and Second Order Perturbation Theory analysis using Donor/Acceptor energies. Further, to explain the bonding nature of M-edta-type complexes the Natural Coulomb Electrostatics (NCE) analysis has been done as well. The pairwise steric exchange interaction EI,Jpwx results obtained for the best-ranked resonances of different isomers are in excellent agreement with favored isomers reported so far. For the energy limit of the possibility of forming geometric isomers, a value of about 6 kcal mol−1 is proposed.

Asymmetric diosmium sawhorse complexes.

Three asymmetric diosmium(I) carbonyl sawhorse complexes have been prepared by microwave heating. One of these complexes is of the type Os2(μ-O2CR)(μ-O2CR')(CO)4L2, with two different bridging carboxylate ligands, while the other two complexes are of the type Os2(μ-O2CR)2(CO)5L, with one axial CO ligand and one axial phosphane ligand. The mixed carboxylate complex Os2(μ-acetate)(μ-propionate)(CO)4[P(p-tolyl)3]2, (1), was prepared by heating Os3(CO)12 with a mixture of acetic and propionic acids, isolating Os2(μ-acetate)(μ-propionate)(CO)6, and then replacing two CO ligands with two phosphane ligands. This is the first example of an Os2 sawhorse complex with two different carboxylate bridges. The syntheses of Os2(μ-acetate)2(CO)5[P(p-tolyl)3], (3), and Os2(μ-propionate)2(CO)5[P(p-tolyl)3], (6), involved the reaction of Os3(CO)12 with the appropriate carboxylic acid to initially produce Os2(μ-carboxylate)2(CO)6, followed by treatment with refluxing tetrahydrofuran (THF) to form Os2(μ-carboxylate)2(CO)5(THF), and finally addition of tri-p-tolylphosphane to replace the THF ligand with the P(p-tolyl)3 ligand. Neutral complexes of the type Os2(μ-O2CR)2(CO)5L had not previously been subjected to X-ray crystallographic analysis. The more symmetrical disubstituted complexes, i.e. Os2(μ-formate)2(CO)4[P(p-tolyl)3]2, (8), Os2(μ-acetate)2(CO)4[P(p-tolyl)3]2, (4), and Os2(μ-propionate)2(CO)4[P(p-tolyl)3]2, (7), as well as the previously reported symmetrical unsubstituted complexes Os2(μ-acetate)2(CO)6, (2), and Os2(μ-propionate)2(CO)6, (5), were also prepared in order to examine the influence of axial ligand substitution on the Os-Os bond distance in these sawhorse molecules. Eight crystal structures have been determined and studied, namely μ-acetato-1κO:2κO'-μ-propanoato-1κO:2κO'-bis[tris(4-methylphenyl)phosphane]-1κP,2κP'-bis(dicarbonylosmium)(Os-Os) dichloromethane monosolvate, [Os2(C2H3O2)(C3H5O2)(C21H21P)2(CO)4]·CH2Cl2, (1), bis(μ-acetato-1κO:2κO')bis(tricarbonylosmium)(Os-Os), [Os2(C2H3O2)2(CO)6], (2) (redetermined structure), bis(μ-acetato-1κO:2κO')pentacarbonyl-1κ2C,2κ3C-[tris(4-methylphenyl)phosphane-1κP]diosmium(Os-Os), [Os2(C2H3O2)2(C21H21P)(CO)5], (3), bis(μ-acetato-1κO:2κO')bis[tris(4-methylphenyl)phosphane]-1κP,2κP-bis(dicarbonylosmium)(Os-Os) p-xylene sesquisolvate, [Os2(C2H3O2)2(C21H21P)2(CO)4]·1.5C8H10, (4), bis(μ-propanoato-1κO:2κO')bis(tricarbonylosmium)(Os-Os), [Os2(C3H5O2)2(CO)6], (5), pentacarbonyl-1κ2C,2κ3C-bis(μ-propanoato-1κO:2κO')[tris(4-methylphenyl)phosphane-1κP]diosmium(Os-Os), [Os2(C3H5O2)2(C21H21P)(CO)5], (6), bis(μ-propanoato-1κO:2κO')bis[tris(4-methylphenyl)phosphane]-1κP,2κP-bis(dicarbonylosmium)(Os-Os) dichloromethane monosolvate, [Os2(C3H5O2)2(C21H21P)2(CO)4]·CH2Cl2, (7), and bis(μ-formato-1κO:2κO')bis[tris(4-methylphenyl)phosphane]-1κP,2κP-bis(dicarbonylosmium)(Os-Os), [Os2(CHO2)2(C21H21P)2(CO)4], (8).

Synthesis and characterisation of double-layered octahedral coordination polymers built up from divalent metal ions, mixed carboxylate anions, and ethyl carbazate ligands

A new family of mixed formate–acetate containing coordination polymers of formulae M(HCOO)2–x(CH3COO)x(C3H8N2O2) [M = Mn (1), Co (2), Zn (3) and Cd (4)] and Cd(CH3COO)2(C3H8N2O2) (5) (C3H8N2O2 = ethyl carbazate) are described. The compounds have been crystallised from aqueous solution and characterised using elemental analysis, IR and UV/visible spectroscopy, TGA, NMR and PXRD and the single-crystal structures of 1 and 3 have been determined. These isostructural compounds consist of M2+ ions coordinated by N,O-chelating ethyl carbazate molecules and four bridging acetate or formate anions (some of which are disordered). The resulting coordination polyhedra for the metal atoms are distorted MO5N octahedra. The polyhedral connectivity (via both formate and acetate bridges) generates double layers propagating in (100) with the topology of a square grid for the metal … metal links. Intra-layer NH…O hydrogen bonds help to establish the structures.

Novel cadmium(II) frameworks with mixed carboxylate and imidazole-containing ligands for selective detection of antibiotics

With increasing and abuse of antibiotics, selective and sensitive detection of specific antibiotics is required. In this work, we report novel Cd(II)-based metal–organic framework (MOF) [Cd2(L)(bpda)2]·4DMF·4H2O·MeOH (1) by using mixed organic ligands 3,3′,5,5′-tetra(1H-imidazol-1-yl)biphenyl (L) and 4,4′-carbonyldibenzoic acid (H2bpda). MOF 1 transformed to [Cd2(L)(bpda)2]·3DMF·H2O (2) at room temperature via a single-crystal-to-single-crystal process, and the emission of 2 can be quenched efficiently by trace amounts of NFs (nitrofurazone, NZF; nitrofurantoin, NFT; furazolidone, FZD) antibiotics with detection limits of 252 ppb, 465 ppb, 969 ppb for NZF, NFT and FZD, respectively, even in the presence of other competing antibiotics such as sulfadiazine (SDZ). The results show that 2 is a potential luminescent sensor for antibiotics.

Structures and magnetic properties of 3D manganese(II)- and 2D pillar-layered copper(II)-organic framework derived from mixed carboxylate ligands

Two new metal–organic frameworks [Mn3(MMA)2(INA)2]n (1) and [Cu2(FA)(INA)3(H2O)]n (2, FA = formate) were prepared solvothermally by using mixed methylmalonic acid (H2MMA) and isonicotinic acid (HINA) as the initial reactants. Single-crystal X-ray diffraction analyses reveal that complex 1 has a 3D framework structure consisting of 2D [Mn3] layer units and INA connector, and 2 owns a 2D pillar-layered structure constituted of mononuclear-Cu(II)-based 2D layer unit and paddle-wheel dinuclear Cu(II) cluster-based pillared linker, which further interspersed with each other to form a 3-fold interpenetrated framework with a (48.62)-SP topology. The magnetic studies show that 1 displays antiferromagnetic ordering at low temperature, and a strong antiferromagnetic interaction exists in 2.

Mixed metal CoII 1-x ZnII x -organic frameworks based on chains with mixed carboxylate and azide bridges: magnetic coupling and slow relaxation.

A series of isomorphous three-dimensional metal–organic frameworks [CoII1−xZnIIx(L)(N3)]·H2O (x = 0.26, 0.56 and 0.85) based on bimetallic CoII1−xZnIIx (x = 0.26, 0.56 and 0.85) chains with random metal sites have been synthesized and magnetically characterized. The CoII1−xZnIIx series, which intrinsically feature random anisotropic/diamagnetic sites, shows complex magnetic interactions. By gradually introducing the diamagnetic ZnII ions into the pure anisotropic CoII single-chain magnets system, the ferromagnetic interactions between CoII ions are gradually diluted. Moreover, the slow magnetic relaxation behaviour of the mixed metal CoII1−xZnIIx systems also changes. In this bimetallic series CoII1−xZnIIx, the Co-rich materials exhibit slow relaxation processes that may arise from SCM mechanism, while the ZnII-rich materials show significantly low slow magnetic relaxation. A general trend is that the activation energy and the blocking temperature decrease with the increase in diamagnetic ZnII content, emphasizing the importance of anisotropy for slow relaxation of magnetization.

Coordination polymers based on mixed carboxylate ligands: synthesis and thermal studies

The synthesis of Co II , Cu II , Fe II and Zn II based coordination compounds using terephthalic acid BDC , tartaric acid DHB , and 4- hydroxybenzoic acid 4-HBA as ligands by a solvent-based and solvent-free methods were reported. Thermal studies of the complexes performed in the temperature range of 30 ºC-950 °C showed a 9.406% weight loss observed between 200 ºC-517 ºC for [Co DHB 4-HBA ] complex, and a 1.883 % weight loss observed between 80 ºC352.68 ºC for [Cu DHB 4-HBA ] complex.

Ideal CdSe/CdS Core/Shell Nanocrystals Enabled by Entropic Ligands and Their Core Size-, Shell Thickness-, and Ligand-Dependent Photoluminescence Properties.

This work explored possibilities to obtain colloidal quantum dots (QDs) with ideal photoluminescence (PL) properties, i.e., monoexponential PL decay dynamics, unity PL quantum yield, ensemble PL spectrum identical to that at the single-dot level, single-dot PL nonblinking, and antibleaching. Using CdSe/CdS core/shell QDs as the model system, shell-epitaxy, ligand exchange, and shape conversion of the core/shell QDs were studied systematically to establish a strategy for reproducibly synthesizing QDs with the targeted properties. The key synthetic parameter during epitaxy was application of entropic ligands, i.e., mixed carboxylate ligands with different hydrocarbon chain length and/or structure. Well-controlled epitaxial shells with certain thickness (∼3-8 monolayers of the CdS shells) were found to be necessary to reach ideal photoluminescence properties, and the size of the core QDs was found to play a critical role in determining both photophysical and photochemical properties of the core/shell QDs. Effects of shape of the core QDs were unnoticeable, and shape of the core/shell QDs only affected photophysical properties quantitatively. Surface ligands, amines versus carboxylates, were important for photochemical properties (antiblinking and antibleaching) but barely affected photophysical properties as long as entropic ligands (mixed carboxylate ligands with distinguishable hydrocarbon chain lengths) were applied during epitaxy. Chemical environment (in polymer or in air), coupled with surface ligands, determined photochemical properties of the core/shell QDs with a given core size and shell thickness.

Two unique hydroxyl bridged lanthanide polymers incorporating mixed carboxylate ligands: Syntheses, structures, luminescence and magnetic property

Two lanthanide–organic coordination polymers incorporating both substituted imdazole dicarboxylate and benzene monocarboxylate auxiliary ligand, namely, {[Gd2(μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (1) and {[Tb2((μ3-OH)(pimda)(imba) (H2pimda) H2O]·2H2O}n (2) (H3pimda=2-propyl-1H-imidazole-4,5-dicarboxylic acid and H2imba=4-(1H-imidazole-1-ly) benzoic acid) have been obtained under the hydrothermal conditions, and have been structurally characterized by elemental analysis, IR spectrum and single X-ray diffraction. The polymers are isostructural, both crystallizing in the triclinic system, with space group of p-1. They display one dimensional (1-D) double-stranded ribbon chains based on hydroxyl-bridged [Ln4pimda2] tetranuclear unit as second building block, which are interlinked forming 2-D corrugated layer. The extensive hydrogen bondings further extend these 2-D lamellar networks into 3-D supramolecular architecture. The emission spectrum of polymer 1 exhibits ligand-to-ligand charge-transfer (LLCT) transition luminescence; polymer 2 shows characteristic f-f transition luminescence, which can be considered as a fluorescent molecular sensor for zinc(II) ions in environment. Variable-temperature magnetic susceptibility measurement reveals that multi-bridging fashion of carboxylic group in 1 results in depopulation of the stark levels for a single Gd(III) ion and/or possible antiferromagntic interactions between adjacent Gd(III) cations within the carboxylato bridged binuclear unit.