Three new coordination polymers based on bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane: syntheses,structures, multiresponsive luminescent sensitive detection for antibiotics and pesticides,and antitumor activities

Three novel coordination polymers (CPs), namely, {[Ag₂(L)₂(Mo₄O₁₃)·(CH₃CN)]}_n (1), {[Zn(L)(1,4-bdc)₂·2(1,4-H₂bdc)]}_n (2), {[Cd(L)(1,4-bdc)_0.5]}_n (3) have been synthesized under solvothermal conditions by the reaction of bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane (L) and varied metal salts. Their structures are determined by single X-ray crystal diffraction, and further characterized by elemental analysis, IR, TGA and PXRD. CP 1 with ammonium molybdate as a secondary ligand displays a 2D network with (2,3,3,3,4)-connected net topology and the point symbol of {4·8²}₆{4·8⁴·10}₂{8}, CP 2 and CP 3 with 1,4-H₂bdc as a secondary ligand demonstrate 3D structures with different topologies. CP 2 exhibits high sensibility and low detection limit in the recognition of antibiotics (NZF, NFT and FZD) and pesticide (DCN) identification. CP 1 demonstrates good anti-tumor activity toward the tested glioma cells. The possible luminescent sensitivity and anti-tumor mechanisms are also discussed.

Three novel coordination polymers (CPs) have been synthesized under solvothermal conditions by the reaction of bis(4-(4H-1,2,4-triazol-4-yl)phenyl)methane (L) and varied metal salts.     

Photochromic properties of three 2D MOFs based on 1-carboxyethyl-4,4′-bipyridinine

Viologen units have been widely used to impart metal–organic frameworks (MOFs) with photochromic properties. However, construction of a stable photochromic system in viologen MOFs has not been fully explored. Herein, we report three examples of MOFs, namely, {[Cd(CEbpy)(m-BDC)(DMF)]·2H₂O}_n (1), {[Cd(CEbpy)(p-BDC)(H₂O)]·H₂O}_n (2), and {[Zn(CEbpy)(p-HBDC)(p-BDC)_0.5]·H₂O}_n (3) based on benzenedicarboxylic acids (m-H₂BDC = 1,3-benzenedicarboxylic acid, p-H₂BDC = 1,4-benzenedicarboxylic acid) and a viologen-derived ligand 1-carboxyethyl-4,4′-bipyridine (L = CEbpy). As expected, the incorporation of the viologen unit into the frameworks results in the predefined photochromism upon both sunlight and UV-light. Compounds 1–3 feature a two-dimensional (2D) layered structure and are all photochromic due to the formation of CEbpy radicals by photoinduced electron transfer (PET). The aggregates build an interesting stable crystalline framework that exhibits long-lived color constancy in the solid state.

Viologen units have been widely used to impart metal–organic frameworks (MOFs) with photochromic properties.     

Assembly of a series of zinc coordination polymers based on 5-functionalized isophthalic acids and dipyridyl

To investigate the influence of different 5-functionalized isophthalate ligands on the self-assembly and structures of Zn(ii)-based coordination polymers (CPs), we selected four 5-functionalized isophthalate ligands coordinated with 4,4′-bipyridyl (bpy) and Zn(ii) salt, and four new CPs, namely, {[Zn(EtOip)(bpy)]·2H₂O}_n (1), {[Zn(PrOip)(bpy)]·2H₂O}_n (2), [Zn(ⁿBuOip)(bpy)]_n (3) and [Zn(ⁿPeOip)(bpy)]_n (4) (where EtOip = 5-ethoxyisophthalate, PrOip = 5-n-propoxyisophthalate, ⁿBuOip = 5-n-butoxyisophthalate and ⁿPeOip = 5-n-pentyloxyisophthalate), were prepared under hydrothermal conditions. Moreover, we considered changing the features of the N-ligands (length), which are expected to alter the structural diversities and properties of the resultant CPs. We used 1,2-bis(4-pyridyl)ethene (bpe) to replace bpy; and obtained four new coordination polymers (CPs), namely, {[Zn(EtOip)(bpe)]·H₂O}_n (5), {[Zn(PrOip)(bpe)]·H₂O}_n (6), {[Zn(ⁿBuOip)(bpe)]·0.5DMF}_n (7) and [Zn(ⁿPeOip)(bpe)]_n (8). All of these compounds were characterized by single crystal X-ray diffraction, infrared spectroscopy, elemental analysis and powder X-ray diffraction measurements. Single-crystal X-ray analysis reveals that the structure of complexes 1–4 are very similar, although different functionalized-isophthalate ligands are employed. Complexes 5, 6 and 7 possess a two-dimensional (2D) layered structure, and the 2D framework of complexes 5 and 7 can be rationalized to be a threefold interpenetrating four-connected {4⁴·6²} topological sql network, while 6 exhibits a twofold interpenetrating 4-connected 2D framework. Compound 8 features a 6-connected 3D topology net based on a novel bimetallic unit [(Zn)₂(CO₂)₂] linked by mixed ⁿPeOip and bpe ligands. Moreover, thermal and photoluminescence properties of the synthesized complexes were also studied in detail.

A series of zinc coordination polymers based on 5-functionalized isophthalate and flexible dipyridyl ligands have been prepared. Their thermal and luminescent properties in the solid state were also investigated.     

Three pairs of luminescent coordination polymers based on CoII and CdII clusters for the detection of antibiotics,pesticides and chiral nitro aromatic compounds

Three couples of coordination polymers (CPs), namely, [Co((R/S)-Hcna)₂]_n (1-D/L), [Cd₆((1R,2R/1S,2S)-cpba)₄(phen)₆(H₂O)₃]_n (2-D/L) and [Cd₂((1R,2R/1S,2S)-Hcpba)₂(phen)₂]_n (3-D/L) {(R/S)-H₂cna = (R/S)-6-(1-carboxyethoxy)-2-naphthoic acid, (1R,2R/1S,2S)-H₃cpba = (1R,2R/1S,2S)-2,2′-((5-carboxy-1,3-phenylene)bis(oxy))dipropionic acid, phen = 1,10-phenanthroline} are successfully synthesized under hydrothermal conditions. Structural analysis shows that CP 1 has a 3D 3,6-c net structure with a point symbol of (4·6²)₂(4²·6¹⁰·8³). CPs 2 and 3 are obtained under very similar reaction conditions except using different solvent ratios. The presence of the planar chelating ligand phen in CPs 2 and 3 limited the spatial growth of the structure, resulting in the formation of different 1D structures. All CPs crystallized in the chiral space group P2₁, CPs 1–3 are all SHG active. Their luminescence sensing activities for organics such as antibiotics, pesticides and nitro aromatics are also investigated. The results showed that CP 1 can effectively identify trace amounts of nitrofurans (NFs) and CP 3 has obvious recognition ability toward nitrofurans (NFs) and nitroimidazoles (NMs). Both CPs 1 and 3 could selectively detect 2,6-dichloro-4-nitroaniline (DCN). The luminescence of CPs 1 and 3 can also be quenched by (D/L)-4-nitrophenylalanine ((D/L)-NPA) and (1R,2R/1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diol ((1R,2R/1S,2S)-ANPO).

Three pairs of luminescent coordination polymers based on (R/S)-H₂cna and (1R,2R/1S,2S)-H₃cpba for the detection of antibiotics, pesticides and chiral nitro aromatic compounds.     

Synthesis,crystal structures and,magnetic and photoluminescence properties of lanthanide-based metal–organic frameworks constructed with 2,5-dihydroxybenzene-1,4-dicarboxylic acid

Four new lanthanide(iii) coordination polymers (1–4) have been synthesized by using 2,5-dihydroxybenzene-1,4-dicarboxylate (Dhbdc, C₈H₆O₆²⁻) as a ligand and characterized by elemental analysis, infrared spectroscopy, TGA-DSC (Thermogravimetric Analysis-Differential Scanning Calorimetry) and single crystal X-ray diffraction studies. The isolated complexes include; [Ce(Dhbdc)(H₂O)₃Cl]_n (1) and [Ln(Dhbdc)_1.5(H₂O)₂]_n·3n(C₂H₆O)·nH₂O [Ln = Eu (2), Gd (3) and Tb (4)]. The structural analysis reveals that compound 1 is a two-dimensional polymer in which the cerium atoms are coordinated by six oxygen and two bridging chloride ions adopting a dodecahedral geometry. The compounds 2–4 are isomorphous and their extended structures consist of three-dimensional supramolecular frameworks encapsulating [001] channels occupied by the guest water and ethanol molecules. The metal atoms in 2–4 exhibit a square antiprism geometry. All these compounds have O–H⋯O hydrogen bonds originating from the coordinated water and solvent molecules that help to consolidate the structures. The compounds 1, 3 and 4 were investigated for magnetic properties and they exhibited weak antiferromagnetic coupling interactions between the lanthanides as per the Curie Weiss law. Anisotropic nature of 3 and 4 has been depicted as per magnetization versus field plots. Complex 4 behaves as a soft magnetic material as compared to 3. The luminescence studies indicate that compounds 2, 3 and 4 show ligand-centred fluorescence, which is significantly enhanced in the case of 4.

Four new lanthanide(iii) coordination polymers (1–4) have been synthesized by using 2,5-dihydroxybenzene-1,4-dicarboxylate as a ligand and investigated for magnetic and photo-luminescence properties.     

Effects of N-oxidation on the molecular and crystal structures and properties of isocinchomeronic acid,its metal complexes and their supramolecular architectures: experimental,CSD survey,solution and theoretical approaches

Nine coordination complexes and polymer (M/L/X) based on Co, Ni, Zn, Cu (M), pyridine-N-oxide-2,5-dicarboxylic acid (H₂pydco) (L) and either isonicotinamide (Ina), piperazine (pipz), 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) (X) were synthesized and characterized by elemental analyses, infrared spectroscopy and single crystal X-ray diffraction. The resulting empirical formulae of the prepared complexes are [Co(H₂O)₆][Co(pydco)₂(H₂O)₂]·2H₂O (1), [M(pydco)(H₂O)₄]₂ [M = Co (2), Ni (3), Zn (4)], [Co(pydco)(bipy)(H₂O)₂]·4H₂O (5), [Co(pydco)(phen)(H₂O)₂]·5.135(H₂O)·0.18(EtOH) (6), [Cu(Hpydco)(bipy)Cl]·2H₂O (7), [Cu(Hpydco)(bipy)Cl]₂·2H₂O (8), and {[AgCu(H₂O)₂(phen)(pydco)]NO₃}_n (9). With the exception of 9, which forms an extended structure via multiple coordination modes, all the complexes contain (H)pydco as a bidentate ligand coordinated to the metal ion via the N-oxide and the adjacent carboxylate group oxygen atom, creating a chelate ring. The metal centers exhibit either distorted octahedral (1–6) or square pyramidal (7–9) geometry. Our results demonstrate that, when acting cooperatively, non-covalent interactions such as X–H⋯O hydrogen bonds (X = O, N, C), C–O⋯π and π⋯π stacking represent driving forces for the selection of different three-dimensional structures. Moreover, in compounds 2–4, 1D supramolecular chains are formed where O⋯π–hole interactions are established, which unexpectedly involve the non-coordinated carboxylate group. The non-covalent interaction (NCI) plot index analysis reveals the existence of the O⋯π–hole interactions that have been evaluated using DFT calculations. The Cremer and Pople ring puckering parameters are also investigated. The complexation reactions of these molecules with M were investigated by solution studies. The stoichiometry of the most abundant species in the solution was very close to the corresponding crystals. Finally, the effect of N-oxidation on the geometry of complexes has been also studied using the Cambridge Structural Database. It shows that complexes containing N-oxidized H₂pydc are very rare.

A series of new coordination complexes bearing H₂pydco, an O-donor ligand, were synthesized and compared to corresponding complexes with H₂pydc. The molecular and supramolecular structures were investigated using crystallography, solution phase and high level DFT studies.     

Effects of template molecules on the structures and luminescence intensities of a series of porous Tb-MOFs based on the 2-nitroterephthalate ligand

Four novel porous Tb(iii) metal–organic frameworks (Tb-MOFs) have been designed and prepared hydrothermally from 2-nitroterephthalate (2-H₂ntp), namely {[Tb(2-ntp)_1.5(H₂O)]·H₂O}_n (1), {[Tb(2-ntp)₂(H₂O)]·4,4′-Hbipy}_n (2), {[Tb(2-ntp)₂(H₂O)]·2,4-Hbipy}_n (3), and {[Tb(2-ntp)₂(H₂O)]·(1,4-H₂bbi)_0.5}_n (4) (4,4′-bipy = 4,4′-bipyridine; 2,4-bipy = 2,4-bipyridine; 1,4-bbi = 1,4-bisbenzimidazole). X-ray diffraction structural analyses show these Tb-MOFs are porous and are based on Tb³⁺ ions and 2-nitroterephthalate, in which water molecules (1) or protonated N-donor ligands (2–4) exist as templates. The fluorescence properties of complexes 1–4 could be associated with the characteristic peaks of Tb(iii) ions, and the existence of different guest molecules affects the intensities of peaks, which means that these could be potential fluorescence materials, with intensities adjusted using guests.

Four porous Tb-MOFs based on 2-nitroterephthalate are described, in whose pores water (1) or co-ligands (2–4) exist in the pores as templates. The emissions could be related to the characteristic peaks of Tb(iii) ions, and their intensities are affected and adjusted by templates.     

Three cobalt-based coordination polymers with tripodal carboxylate and imidazole-containing ligands: syntheses,structures, properties and DFT studies

Three cobalt-based coordination polymers [Co(Htatb)(1,3-bimyb)] (1), [Co(Htatb)(bimbp)]·DMF (2), and [Co(Htatb)(1,4-bimyb)]·H₂O (3) [H₃tatb = 4,4′,4′′-s-triazine-2,4,6-tribenzoic acid, 1,3-bimyb = 1,3-bis(imidazole-1-ylmethyl)benzene, bimbp = 4,4′-bis(imidazolyl)biphenyl, 1,4-bimyb = 1,4-bis (imidazole-1-ylmethyl)benzene] were synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, thermogravimetric analyses, IR spectroscopy, UV-vis spectroscopy and elemental analysis. Compound 1 shows a double-strand chain structure, due to the intermolecular O–H⋯O hydrogen bonds and aromatic π–π stacking interactions, the adjacent chains are connected to produce a 3D supramolecular structure. Compound 2 shows a 2D structure with a 1D channel. Compound 3 displays a 2D layer structure, furthermore these layers are joined by O–H⋯O hydrogen bonding to generate a four-fold interpenetrating 3D architecture. The fluorescence properties of 1–3 and the magnetic behavior of 1 and 2 have also been investigated. Based on their crystal structures, compounds 1 and 2 were investigated using hybrid DFT methods at the B3LYP/6-31G (d) level. The DFT-BS approach was applied to study the magnetic coupling behavior. The results reveal that the calculated exchange coupling constants J were in good agreement with the experimental data.

The tripodal carboxylate ligand can be employed in Co(ii) salt/imidazole-containing ligand systems to generate 1D chain, 2D layer, and 2D to 3D network, and the fluorescence properties of 1–3 and magnetic behavior of 1 and 2 have been investigated.     

Structures and photocatalytic properties of two new Zn(ii) coordination polymers based on semi-rigid V-shaped multicarboxylate ligands

Two new metal–organic coordination polymers (CPs), aqua-2,2′-bipyridine-5-(4′-carboxylphenoxy)isophthalatezinc(ii) polymer [Zn(HL)(2,2′-bipy)(H₂O)]_n (1) and tris-4,4′-bipyridine-bis-5-(4′-carboxylphenoxy)isophthalatetrizinc(ii) polymer [Zn₃(L)2(4,4′-bipy)₃]_n (2) (H₃L = 5-(4′-carboxylphenoxy)isophthalic acid, 4,4′-bipy = 4,4′-bipyridine and 2,2′-bipy = 2,2′-bipyridine), were obtained under hydrothermal conditions and characterized by microanalysis, FTIR spectroscopy and single crystal X-ray diffraction. The single crystal X-ray diffraction indicated that in both the CPs the coordination networks exhibited varied topologies and coordination modes around the Zn(ii) centers. CP 1 exhibits a one-dimensional (1D) chain structure, which further forms a 3D supramolecular architecture via intermolecular π⋯π and hydrogen bonding interactions, while 2 possesses a 3D framework generated from a 2D layered motif comprising zinc and tripodal carboxylate subunits pillared by 4,4′-bpy ligands. Apart from the structural investigation, the photocatalytic performances of both the coordination polymers to photodecompose an aqueous solution of methyl violet (MV) were examined. The results indicated that both the CPs displayed the potential to photodecompose aromatic dyes and in particular 2 showed good photocatalytic activity for dye degradation under light irradiation. The photocatalytic mechanism through which these CPs executed degradation of dyes has been explained with the assistance of band gap calculations using density of states (DOS) and its decomposed partial DOS calculations.

Two new Zn(ii) coordination polymers having semi-rigid V-shaped polycarboxylate ligands were synthesized and their photocatalytic performances to photodegrade methyl violet were assessed.     

Synthesis,structures and properties of six lanthanide complexes based on a 2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline ligand

Six lanthanide complexes [Tb(2-NCP)₂(NO₃)]_n (1), [Eu(2-NCP)₂(3-PYC)]_n (2), [Sm(2-NCP)₂(3-PYC)]_n (3), [Eu(2-NCP)(SA)]_n (4), [Tb(2-NCP)(SA)]_n (5) and [Tb(2-NCP)(AA)]_n (6) (2-HNCP = 2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline, 3-HPYC = pyridine-3-carboxylic acid, H₂SA = succinic acid, H₂AA = adipic acid) have been synthesized by hydrothermal route, and the crystal structures were analyzed through elemental analysis, infrared spectroscopy, single crystal X-ray diffraction. Complexes 1 and 6 present two-dimensional (2D) layers, which are further connected to three-dimensional (3D) supramolecular architectures through C–H⋯π interactions. Complexes 2 and 3 exhibit infinite one-dimensional chains. Finally, the neighboring chains are packed by C–H⋯π interactions, giving rise to 3D supramolecular network. Complexes 4 and 5 display 2D layers, which are further extend to 3D supramolecular structures via C–H⋯O intermolecular hydrogen bonding. Six complexes possess good thermal stabilities, characteristic photoluminescence properties, and photocatalytic activities for the degradation of organic dyes under visible light irradiation. In addition, the complex 6 exhibits significantly enhanced photocatalytic activity for methylene blue, and the degradation rate could reach 81.2% in 370 min. Meanwhile trapping experiments indicated that the hole, ·O₂⁻ and ·OH are the main activated species. Furthermore, by comparing the photoluminescent and photocatalytic mutation results of same metal complexes induced by interconversion of coligands, we confirm that the properties mutation induced by coligands is much obvious and controllable.

Six lanthanide complexes based on 2-HNCP possess good thermal stabilities, characteristic photoluminescence properties, and photocatalytic activities for organic dyes degradation under visible light irradiation.     

Four rare structurally characterized hetero-pentanuclear [Zn4Ln] bis(salamo)-type complexes: syntheses,crystal structures and spectroscopic properties

Four new hetero-pentanuclear 3d–4f complexes [Zn₄(L)₂La(NO₃)₂(OEt)(H₂O)] (1), [Zn₄(L)₂Ce(NO₃)₂(OMe)(MeOH)] (2), [Zn₄(L)₂Pr(NO₃)₂(OEt)(EtOH)] (3) and [Zn₄(L)₂Nd(NO₃)₂(OMe)(MeOH)] (4) were synthesized by the reactions of a newly synthesized octadentate bis(salamo)-based tetraoxime ligand (H₄L) with Zn(OAc)₂·2H₂O and Ln(NO₃)₃·6H₂O (Ln = La, Ce, Pr and Nd), respectively, and characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and single crystal X-ray crystallography. The X-ray crystallographic investigation revealed that all Zn^II ions were located in N₂O₃ coordination spheres, and possessed a trigonal bipyramid coordination environment. The Ln^III ion lay in an O₈ coordination sphere, and adopted a distorted square antiprismatic coordination environment. Furthermore, supramolecular interactions and fluorescence properties were investigated.

Four new hetero-pentanuclear 3d–4f complexes 1–4 were synthesized and characterized. Supramolecular interactions and fluorescence properties of complexes 1–4 were investigated.     

Low pH constructed Co(ii) and Ni(ii) 1D coordination polymers based on Cα-substituted analogues of zoledronic acid: structural characterization,and spectroscopic and magnetic properties

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the C_α carbon, isomorphous [Co(H₂cppZol)(H₂O)]·H₂O (1a), [Ni(H₂cppZol)(H₂O)]·H₂O (1b) and [Co(H₂cbtZol)(H₂O)]·H₂O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig–zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (–O–P–O–)₂ bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H₂L)(H₂O)_x]·yH₂O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to ca. 320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic–ferromagnetic exchange interactions propagated between the magnetic centres through double (–O–P–O–)₂ bridges. The boundary between antiferro- and ferromagnetic couplings for the Co–O⋯O–Co angle in 1a and 2a was estimated to be ca. 80°. This value is also applicable for recently reported [M₃(HL)₂(H₂O)₆]·6H₂O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.

1D Co(ii)/Ni(ii) coordination polymers with alternating antiferromagnetic–ferromagnetic exchange interactions between metal centers propagated through double (–O–P–O–)₂ bridges.     

Four new Zn(ii) and Cd(ii) coordination polymers using two amide-like aromatic multi-carboxylate ligands: synthesis,structures and lithium–selenium batteries application

Four new coordination polymers, {[Zn(3-PBI)(H₂O)]·2DMF}_n (1), [Cd(3-PBI)(DMF)]_n (2), {[Zn₄(μ₄-O)(4-PBI)₃]·3DMF}_n (3), {[Cd₄(4-PBI)₄(H₂O)₆]·13H₂O}_n (4), have been constructed from two isomeric flexible multi-carboxylate ligands, 3-H₂PBI = 5-(3-(pyridin-3-yl)benzamido)isophthalic acid and 4-H₂PBI = 5-(3-(pyridin-4-yl)benzamido)isophthalic acid. Structural analysis reveals that compound 1 is a one-dimensional (1D) ladder-like chain assembled by Zn(ii) ions and 3-PBI²⁻ ligands, which further extend into a 3D supramolecular structure through π⋯π stacking and interlayer (O–H⋯O) hydrogen bonding interactions. In compound 2, Cd²⁺ metal ions are connected by carboxylate groups to form [Cd₂(COO)₄] secondary building units (SBUs). The whole framework possesses a quadrilateral channel and constitutes a unique 3D (3,6)-connected rutile net with the Schläfli symbol of (4²·6¹⁰·8³)(4·6²)₂. As for 3, Zn(ii) ions are bridged by one μ₄-O and six carboxylate groups to form a tetranuclear [Zn₄(μ₄-O)(COO)₆] cluster, resulting in a rare (3,9)-connected 3D network. Compound 4 has an appealing 2D layered architecture involving two distinct topologies in the crystal structure, stacking in an unusual ABBABB mode (where A represents (4·8²) topology and B denotes kgd topology). Moreover, compound 2 is prepared as a support for active selenium through a melt-diffusion method. The obtained Cd-CP/Se electrode can be tested for lithium–selenium batteries and shows an initial capacity of 514 mA h g⁻¹ and a reversible capacity of 200 mA h g⁻¹ at 1C after 500 cycles. The good storage performance of Cd-CP/Se demonstrates it to be a prospective cathode material for lithium–selenium batteries.

Four new coordination polymers were constructed and compound 2 was used as a host to active selenium for Li–Se batteries.     

A novel fluorescence phenomenon caused by amine induced ion-exchange between Cd2+ and Fe3+ ions

A 3D metal–organic framework {[Cd(5-Brp)(dpa)]·0.5DMF·H₂O}_n (1) was successfully synthesized and characterized, which markedly recognized iron ions under the induction of an amino group. With the concentration of Fe³⁺ increasing, the emission of 1 first declined, then enhanced with a red shift and was finally quenched, which was different from the reference compound [Cd(5-Brp)(bpp)(H₂O)]_n (2). This result drew our attention to amine induced ion-exchange. This peculiar phenomenon inspired us to construct an effective ion detector.

A 3D metal–organic framework {[Cd(5-Brp)(dpa)]·0.5DMF·H₂O}_n (1) was successfully synthesized and characterized, which markedly recognized iron ions under the induction of an amino group.     

Polytorsional-amide/carboxylates-directed Cd(ii) coordination polymers exhibiting multi-functional sensing behaviors

By rational assembly of polytorsional-amide [N,N′-bis(4-methylenepyridin-4-yl)-1,4-naphthalene dicarboxamide (L)] and polytorsional-carboxylates [H₂ADI = adipic acid, H₂PIM = pimelic acid, H₂SUB = suberic acid], three new Cd-based coordination polymers (CPs) C₃₀H₃₀CdN₄O₇ (1), C₃₁H₃₂CdN₄O₇ (2) and C_31.03H_30.55CdCl_0.24N₄O_5.52 (3) were successfully synthesized. CPs 1–2 and 3 are 2D networks and a 3D framework, which all display 3,5-connected topologies with different structural details. The effects of carboxylates with different carbon chains on the structure of the complexes were studied. Fluorescence experiments show that CPs 1–3 have good multi-functional sensing ability for metal cations (Fe³⁺), anions (MnO₄⁻, CrO₄²⁻, Cr₂O₇²⁻) and organochlorine pesticides (2,6-dichloro-4-nitroamine) with good anti-interference and recyclable characteristics. The possible sensing mechanism is also investigated in detail.

Three (3,5)-connected Cd(ii) coordination polymers induced by polytorsional-amide/carboxylates exhibiting controllable multifunctional fluorescent sensing activities.     

The modulation effect of pi–pi interactions on the electronic and photochromic properties of viologen complexes containing N,N′-bis(carboxyethyl)-4,4′-bipyridinium

Two viologen complexes containing N,N′-bis(carboxyethyl)-4,4′-bipyridinium (BCEbpy) were prepared, namely [Zn(H₂O)₆]·(BCEbpy)·(p-BDC)·3H₂O (1) and [Co(H₂O)₆]·(BCEbpy)·(p-BDC)·3H₂O (2) (p-H₂BDC = 1,4-benzenedicarboxylic acid), and their crystal structures, photochromism, frontier molecular orbitals, Hirshfeld surfaces and 2D fingerprint plots were investigated. The modulation effects of pi–pi interactions were explored on the electronic and photochromic properties of compounds 1 and 2. Due to the existence of photo-response viologen radicals, both complexes 1 and 2 display excellent photo-response properties in the sequence 1 < 2. The results indicate that compound 1 exhibits intramolecular electron transfer; compound 2 exhibits both intramolecular and intermolecular electron transfer, which is mainly due to the change of electronic and steric structures caused by pi–pi interactions with a faster photo-response rate than that of compound 1. The donor–acceptor modes, matching principles and inter/intramolecular atom–atom close contacts were illustrated by the density functional theory (DFT)-B3LYP/6-311(d,p) method.

Two viologen complexes containing BCEbpy were prepared and displayed excellent photo-response properties by the modulation effect of pi–pi interactions.     

Temperature tuned syntheses of two new d10-based Cd(ii) cluster metal–organic frameworks: luminescence sensing and photocatalytic properties

The solvothermal reactions of 5,5′-(1,4-phenylenebis(methyleneoxy))diisophthalic acid (H₄L) and the N-donor ancillary ligand 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (bpz) with cadmium(ii) salts at two different reaction temperatures yielded two new metal–organic frameworks (MOFs), viz., [Cd(H₂L)(bpz)]_n (1) and [Cd₂(H₄L)(L)(bpz)₂]_n (2), which have been characterized by FTIR and single crystal X-ray diffraction. The single crystal X-ray diffraction studies revealed that 1 displays a 3-periodic network with monometallic SBU, while 2 exhibits a 3-periodic network with a 2-fold interpenetration feature. The effects of variation in reaction temperature on the architecture of MOFs 1 and 2 have been discussed. The luminescence investigation indicates that both 1 and 2 displayed good turn-off luminescence sensing against nitroaromatic compounds (NACs), especially m-nitrophenol (MNP), via a decrease in their luminescence intensities with a K_sv value of 6.43 × 10³ for 1 and 2.03 × 10⁴ for 2 and LOD values of 1.09 and 0.81 ppm for 1 and 2, respectively. The plausible mechanism for the decline in luminescence intensity of the MOFs with NACs has been addressed using theoretical calculations. The photocatalytic properties for both the MOFs demonstrated that they display efficient photocatalytic performances to degrade methyl violet (MV) under UV irradiation. The plausible mechanism through which these MOFs exhibited photocatalytic properties has been suggested using band gap calculations.

Two new d¹⁰-based Cd(ii) MOFs were synthesized and their photoluminescence sensing to selectively detect m-nitrophenol (MNP) and ability to decompose the organic dye methyl violet (MV) were explored.     

A neutral Cu-based MOF for effective quercetin extraction and conversion from natural onion juice

We report herein a new microporous neutral three-dimensional (3D) metal–organic framework [Cu₂(L)(DMF)(H₂O)]·guest (1·guest) composed of copper paddle-wheel and flexible tetracarboxylic acid linkers (DMF = N,N-dimethylformamide, H₄L = tetrakis[(6-carboxynaphthoxy)methyl]methane). Surprisingly, this MOF with neutral cavities can not only extract pure quercetin (QT) but also convert it into Cu–QT during the desorption process. It has been well characterized by UV-vis, IR, ESI-MS and TEM-EDS studies. Moreover, it can efficiently extract natural product QT from fresh QT-rich onion juice and rapidly convert it into Cu–QT with a relatively high conversion rate.

A new neutral metal–organic framework can efficiently extract natural product quercetin (QT) from fresh QT-rich onion juice and rapidly convert it into Cu–QT with a relatively high conversion rate.     

Selective fluorescent sensing of LMOFs constructed from tri(4-pyridylphenyl)amine ligand

Three new luminescent metal–organic frameworks (LMOFs), [Zn(tppa)(ndc)]_n (1), [Cd(tppa)(oba)]_n (2), [Zn₂(tppa)(bpdc)₂]_n (3) (tppa = tri(4-pyridylphenyl)amine, ndc = 1,4-naphthalenedicarboxylic acid, oba = 4,4′-oxydibenzoic acid, bpdc = 4,4′-biphenyldicarboxylic acid) have been synthesized by solvothermal method. Complexes 1 and 2 are 2-D two-fold interpenetrating structures, aligning into a 3-D structure through C–H⋯π stacking interactions, while 3 is a 5-fold interpenetrating three-dimensional structure. The internal quantum yields (IQYs) of complexes 1–3 are 32.7%, 45.7% and 24.0% (λ_ex = 365 nm), separately. Furthermore, all the complexes show different luminescence signal changes towards aromatic volatile organic compounds (AVOCs). Complex 1 exhibits a high sensitivity in the detection of both Fe³⁺ and Cr³⁺ with large quenching coefficients of K_sv 2.57 × 10⁴ M⁻¹ and 2.96 × 10⁴ M⁻¹, respectively. All these results demonstrated potential applications in chemical sensing.

Three new LMOFs, complexes 1–3, have been solvothermally synthesized. 1 and 2 are 2-D structures, whiles 3 is a 3-D structure. And 1 exhibits in detecting Fe³⁺ and Cr³⁺. All of them have potential applications in chemical sensing.