Construction Of Coordination Polymers Research Articles

An AIE-ligand-based coordination polymer with a new wheel-shaped Cd6 cluster, a unique bamboo-like architecture and highly efficient dual-response sensing properties

A novel bamboo-like coordination polymer is constructed using a new wheel-shaped Cd6 cluster and displays highly efficient dual-response sensing properties.

A new route for the syntheses of coordination polymers using magnetic influence: syntheses, crystal structures and fluorescence properties.

Five coordination polymers [TM1(absa)(H2O)4]n and [TM2(absa)(bipy)(H2O)]n [TM1 = Zn (1), Co (2); TM2 = Zn (3), Co (4), Cu (5); Na2absa = 5,5'-azobissalicylic acid disodium salt; bipy = 4,4'-bipyride] were synthesized by solvent evaporation under a magnetic field. It is evident that magnetic fields bring significant and noticeable changes to the absa2- ligand orientation and the component movement behaviors to construct coordination polymers. The absa2- ligands bind to the metal ions in bridging coordination mode through the carboxylate groups, in addition to the bipy molecules adopting bridging modes. Photoluminescence measurements indicate that the emissions of compounds 1-5 are at 626, 600, 632, 658 and 682 nm in the solid state, respectively.

Influence of the Substituent's Size in the Phosphinate Group on the Conformational Possibilities of Ferrocenylbisphosphinic Acids in the Design of Coordination Polymers and Metal-Organic Frameworks.

This paper illustrates how the size and type of substituent R in the phosphinate group of ferrocenyl bisphosphinic acids can affect conformational possibilities and coordination packing. It also demonstrates that H-phosphinate plays a key role in variational mobility, while Me- or Ph- substituents of the phosphinate group can only lead to 0D complexes or 1D coordination polymer. Overall, this paper provides valuable insights into the design and construction of coordination polymers based on ferrocene-contained linkers. It sheds light on how different reaction conditions and substituents can affect conformational possibilities and coordination packing, which could have significant implications for developing new polymers with unique properties.

The coordination chemistry of 2,4,6-oxy functionalised 1,3,5-triphosphinines.

A number of stable group 6 metal complexes bearing 2,4,6-oxy functionalised 1,3,5-triphosphinines, phosphorus containing heterocyclic ligands with a central C3P3 core, were synthesised such that a complete series of [M{P3C3(OX)3}(CO)3] compounds is obtained [M = Cr(0), Mo(0), W(0); X = H, SitBuPh2, B(ipc)2]. In all complexes, the triphosphinine coordinates in a η6-binding mode via the delocalized 6π-system of the ring. The ligand properties can be tuned by changing the substituent on the oxygen centre. The π-electron accepting properties of the ligand increases in the following order: P3C3(OH)3 < P3C3(OSitBuPh2)3 < P3C3(OB(ipc)2)3. This trend is reflected in the structures determined by X-ray crystallography, and the ν(CO) stretching frequencies determined by IR spectroscopy. The collected data raise questions with respect to the frequently made assumption that phosphinines act as stronger π-acceptors with respect to arenes and thereby deplete electron density at the metal centres. With P3C3(OH)3 as an η6-coordinated ligand further molecules can be coordinated in the second coordination sphere via hydrogen bonds, which may be of interest for the construction of coordination polymers.

Access to Green Pyrotechnic Compositions via Constructing Coordination Polymers: A New Approach to the Application of 3,4-Dinitropyrazole.

Alkali and alkaline-earth metal salts with 3,4-dinitropyrazole (DNP) were synthesized by the reaction of DNP with stoichiometric amounts of the corresponding metal hydroxide-, oxide-, or carbonate-based highly pure salts, and products were fully characterized. Determination of single-crystal structures of all new complexes except for the lithium and strontium salts was performed by X-ray diffraction techniques. The cesium salt crystallized no water among them. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) manifested that these salts have satisfactory thermal stabilities with decomposition temperatures above 210 °C. They also showed that there exists strong bonding of crystallized water among lattices, which disappeared at temperatures equal to or above 115 °C except for salts MES-3, MES-4, and MES-9. In addition, the percentage of water contents was confirmed by using DSC and TGA methods. The constant-volume combustion heats of these metal salts containing DNP anions were measured using an oxygen bomb calorimeter due to their expectant interest in energetic materials, and their standard molar formation enthalpies were obtained. The investigated salts were found to be insensitive toward friction and impact. Findings of burning tests performed with experimental formulations using MES-1, MES-7, MES-8, and MES-9 certify that these four salts might be more promising candidates for application in green pyrotechnics.

Structural diversities in the Zn(II), Mn(II) and Cd(II) coordination polymers induced by metal ions and/or anions

Under the same solvothermal conditions, nine novel coordination polymers (CPs), [Mn(L)(Cl)(H2O)] (1a), [Mn(L)(H2O)2]·(NO3) (2a), [MnL]·(HSO4)·MeCN·2H2O (3a), [Zn(L)2]·H2O (1b), [Zn(L)2] (2b and 3b), [Cd(L)]·Cl (1c), [Cd(L)(NO3)] (2c) and [CdL]·(HSO4)·2.5H2O (3c), were synthesized using a new ligand, namely 4-(2-chloroimidazo[1,2-a]pyridin-3-yl)-[2,4′-bipyridine]-6-carboxylic acid (HL). The Zn(II) CPs 1b-3b are similar 1D chains and their structures were mediated by the trigonal bipyramidal geometry of the Zn(II) cation, not by the counter-anions. However, when using Mn(II) and Cd(II) salts bearing various counter-anions (Cl−, NO3− or SO42−) as reagents, the Mn(II) (1a-3a) or Cd(II) (1c-3c) CPs do reveal different structures, which were induced by different anions acting as either a coordinated anion or a counter-anion for balancing the charge of 1a-3a or 1c-3c. When the larger NO3− anion replaced the Cl− anion, the 1D molecular box chain of 1a with a coordinated Cl− anion was changed to the 2D brickwall-type network of 2a with NO3− only as a counter-anion. However, the NO3− anion still could be coordinated to larger volume of the Cd(II) cation, leading to a 3D framework for 2c. Moreover, CPs 3a and 3c are isostructural, which could be induced by the much larger tetrahedral HSO4− counter-anion. Furthermore, the luminescent properties of the CPs have been investigated. The present work provides a promising approach to design and construct CPs or MOFs by adjusting metal salts bearing various counter-anions.

Acetonitrile coordination to silver(I) ions of 1‐D coordination polymers with 1,3‐di(nicotinoyloxy)‐2‐methylenepropane

AbstractThe fluorescent molecule 1,3‐di(nicotinoyloxy)‐2‐methylenepropane (L) can be a good candidate for construction of coordination polymers with photoluminescence (PL) properties. Self‐assembly of silver(I) hexafluorophosphate with this ligand in a mixture of methanol and dichloromethane produced a 1‐D helical coordination polymer consisting of [Ag(L)](PF6), whereas crystallization from an acetonitrile‐based medium afforded a 1‐D sinusoidal coordination polymer consisting of [Ag(L)(CH3CN)2](PF6) having intramolecular argentophilic Ag∙∙∙Ag and π∙∙∙π interactions arising from the eclipsed conformation of L. These findings suggest that the final structures of the two products can be controlled by the reaction solvent media rather than the crystallization method or concentration. The physicochemical properties of the present silver(I) compounds were fully characterized by means of infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, PL, single‐crystal x‐ray diffraction (XRD), and powder‐XRD measurements.

Three Co(II)-containing coordination polymers displaying solvent determined entanglement structures and different ammonia and amines selective sensing properties

Nowadays it is necessary to develop selective sensing materials of ammonia and amines because toxic ammonia and amines are widely distributed in the environment. In this work, π-electron-deficient N,N′-di(4-pyridyl)-1,4,5,8-naphthalene diimide ligand was used to construct coordination polymers with selective sensing behaviors towards electron-rich ammonia and amines vapors. Three coordination polymers 1–3 with solvents dependent entanglement structures have been successfully synthesized. Compounds 1 and 3 display similar 2D + 2D → 3D polycatenation architectures, but they have pores with different sizes that can accommodate different lattice solvent molecules. Compound 2 exhibits a 3D 2-fold interpenetrating framework with a 6-connected pcu net. Compounds 1 and 3 can selectively sense ammonia and amines vapors in solid state through visual color changes with different response time.

Coordination Polymers Constructed from Pyrogallol[4]arene-Assembled Metal–Organic Nanocapsules

Coordination polymers, commonly known as infinite crystalline lattices, are versatile networks and have diverse potential applications in the fields of gas storage, molecular separation, catalysis, optics, and drug delivery, among other areas. Secondary building blocks, mainly incorporating rigid polydentate organic linkers and metal ions or clusters, are commonly employed to construct coordination polymers. Recently, novel building blocks such as coordination polyhedra have been utilized as metal nodes to fabricate coordination polymers. Benefiting from the rigid porous structure of the coordination polyhedron, prefabricated designer "pores" can be incorporated in this type of coordinate polymer. In this Account, coordination polymers built by pyrogallol[4]arene-assembled metal-organic nanocapsules are summarized. This class of metal-organic nanocapsule possesses the following advantages that make them excellent candidates in the construction of coordination polymers: (i) Various geometrical shapes with different volumes of the inner cavities can be obtained from these capsules. Among them, the two main categories illustrated are dimeric and hexameric capsules, which comprise two and six pyrogallol[4]arenes units, respectively. (ii) A wide range of possible metal ions ranging from main group metals to transition metals and even lanthanides have been demonstrated to seam the capsules. Therefore, these coordination polymers can be endowed with fascinating functionalities such as magnetism, semiconductivity, luminescence, and radioactivity. (iii) Up to 24 metal ions have been successfully embedded on the surface of the nanocapsule, each a potential reaction site in the construction of coordination polymers, opening up pathways for the formation of multidimensional frameworks.In this Account, we focus primarily on the synthesis and the structural information on pyrogallol[4]arene-derived coordination polymers. Coordination polymers can be formed by introducing linkers with two coordination sites, using pyrogallol[4]arenes with coordination sites on the tail, or even via metal ions cross-linking with each other. Machine learning was recently developed to help us predict and screen the structures of the coordination polymers. With single crystal analysis in hand, detailed structural information provides a molecular-level perspective. Significantly, following the formation of coordination polymers, the overall shape and structure of the discrete metal-organic nanocapsules remains essentially unchanged, with full retention of the prefabricated pores. If a rigid linker is used to connect capsules, more than one lattice void with different volumes can be found within the framework. Thus, molecules with different sizes could potentially be encapsulated within these coordination polymers. In addition, flexible ligands can also be employed as linkers. For example, polymers have been employed as large linkers that transform the crystalline coordination polymers into polymer matrices, paving the way toward the synthesis of advanced functional materials. Overall, coordination polymers constructed with pyrogallol[4]arene-assembled metal-organic nanocapsules show wide diversity and tunability in structure and fascinating properties, as well as the promise of built-in functionality in the future.

Syntheses and structures of three macrocyclic supramolecular complexes and one ZnII-containing coordination polymer generated from a semi-rigid multidentate N-containing ligand.

Semirigid organic ligands can adopt different conformations to construct coordination polymers with more diverse structures when compared to those constructed from rigid ligands. A new asymmetric semirigid organic ligand, 4-{2-[(pyridin-3-yl)methyl]-2H-tetrazol-5-yl}pyridine (L), has been prepared and used to synthesize three bimetallic macrocyclic complexes and one coordination polymer, namely, bis(μ-4-{2-[(pyridin-3-yl)methyl]-2H-tetrazol-5-yl}pyridine)bis[dichloridozinc(II)] dichloromethane disolvate, [Zn2Cl4(C12H10N6)2]·2CH2Cl2, (I), the analogous chloroform monosolvate, [Zn2Cl4(C12H10N6)2]·CHCl3, (II), bis(μ-4-{2-[(pyridin-3-yl)methyl]-2H-tetrazol-5-yl}pyridine)bis[diiodidozinc(II)] dichloromethane disolvate, [Zn2I4(C12H10N6)2]·2CH2Cl2, (III), and catena-poly[[[diiodidozinc(II)]-μ-4-{2-[(pyridin-3-yl)methyl]-2H-tetrazol-5-yl}pyridine] chloroform monosolvate], {[ZnI2(C12H10N6)]·CHCl3}n, (IV), by solution reaction with ZnX2 (X = Cl and I) in a CH2Cl2/CH3OH or CHCl3/CH3OH mixed solvent system at room temperature. Complex (I) is isomorphic with complex (III) and has a bimetallic ring possessing similar coordination environments for both of the ZnII cations. Although complex (II) also contains a bimetallic ring, the two ZnII cations have different coordination environments. Under the influence of the I- anion and guest CHCl3 molecule, complex (IV) displays a significantly different structure with respect to complexes (I)-(III). C-H...Cl and C-H...N hydrogen bonds, and π-π stacking or C-Cl...π interactions exist in complexes (I)-(IV), and these weak interactions play an important role in the three-dimensional structures of (I)-(IV) in the solid state. In addition, the fluorescence properties of L and complexes (I)-(IV) were investigated.

Anion‐Templated Self‐Assembly of Silver(I) Frameworks Bridged by μ‐, μ3‐, μ4‐1,2,4,5‐Tetrazine

The formation of Ag(I)‐1,2,4,5‐tetrazines(ttz) based coordination polymers via the Ag−N coordination and anion−π interactions is described. Coordination‐driven self‐assembly is a key step to construct coordination polymers, and ttz, an electron‐deficient aromatic ring compound, forms interesting anion−π interactions. In this study, a series of silver salts, AgX [X = BF4, PF6 and CF3SO3 (OTf)], is introduced to determine the influence of shape and size of anions on the formation of coordination polymers, {[Ag(ttz)](BF4)}n (1), {[Ag2(ttz)3](PF6)2}n (2) and {[Ag2(ttz)3(OTf)](OTf)}n (3). It shows different types of channels in polymers and the coordination modes of ttz (μ, μ3, and μ4). The structure of coordination polymers and the influence of anion−π interactions are revealed by single crystal X‐ray diffraction. In particular, 3 shows not only the anion−π interaction but also the coordination between the anion and Ag(I) which contributes to the unique framework compared to 1 and 2.

Co(II) and Mn(II) coordination polymers: Ligand functional and positional isomeric effects, structural diversities, luminescence sensing and magnetic properties

Two new isostructural 3D Co(II) and Mn(II) coordination polymers (CPs) [M(L1′)2] (M = Co(1) and Mn (2)) were prepared by reactions of metal salts and 2-connected 4-(4-(3-cyanophenyl)-[2,3′-bipyridin]-6-yl)benzoic acid ligand (HL1′). Interestingly, when simple modification of the ligand functional group (from the cyano to carboxylate group), other two new 3D Co(II) [Co(HL2′)2] (3) and Mn(II) [Mn(L2′)(H2O)] (4) CPs are constructed by using 3-connected 3-(6-(4-carboxyphenyl)-[2,3′-bipyridin]-4-yl) benzoic acid (H2L2′), which are ascribed to the change in ligand functionality (from the cyano to carboxylate group). Moreover, the variable positions of cyano group (or carboxylate group) at the ligand isomers also can tune structural diversities. Present and previous works indicate that the isomeric effects of the ligand isomers play important role in adjusting structures of the Co(II) CPs. 1–4 were fully characterized by IR, elemental analyses, TGA, PXRD, and single-crystal X-ray diffraction. Interestingly, 2 and 4 can serve as sensing materials for detecting Fe3+ and Cr2O72− ions. Furthermore, the magnetic properties of four CPs have been investigated. The present work provides a promising approach to design and construct CPs or MOFs by adjusting ligand functionality and positional isomeric effects.

A Lanthanide-Containing Coordination Polymer Using Tetraphenylethene-Based Linkers with Selective Fe3+ Sensing and Efficient Iodine Adsorption Activities.

As a star ligand, the construction of coordination polymers (CPs) based on tetrakis(4-carboxyphenyl)ethylene (H4TCPE) has drawn much attention, due to not only the various coordination configurations but also the intriguing chromophore feature causing aggregation-induced emission (AIE). Herein, by the solvothermal reaction of H4TCPE as connected nodes with lanthanide La(III) salts, the first example of the La(III)-TCPE-based CP (1) has been obtained. The structural analyses indicate that 1 exhibits a 3D framework connected by the sharing carboxylate groups with two kinds of 1D rhombic channels when viewed along the c direction. The photophysical properties of 1 have been explored by luminescence, photoluminescence decay, and quantum yield in the solid state. 1 shows strong luminescence in tetrahydrofuran that was attributed to a "pseudo-AIE process" and sensitive and selective sensing activity of Fe3+ toward metal ions via the obvious luminescent quenching. The sensing mechanism has been investigated and reveals a synergetic effect of the competitive absorption and weak interactions between 1 and Fe3+. Moreover, the high porosity, multiple conjugated π-electrons within the tetrakis(4-carboxyphenyl)ethylene backbone, and the uncoordinated carboxyl oxygen sites in this material also provide the capacity for iodine adsorption. The adsorption experiments indicate that 1 could efficiently remove almost complete I2 from the cyclohexane solution after 24 h contact time with an adsorption capacity of 690 mg/g toward I2.

Four new coordination polymers with a Y-shaped tricarboxylic acid ligand: Structural diversities, luminescence sensing and magnetic properties

A new aromatic tricarboxylic acid with pyridine core, 4,4′-(4-(3-carboxyphenyl) pyridine-2,6-diyl)dibenzoic acid (H3cpdba), was used as a Y-shaped building block for the hydrothermal syntheses of four coordination polymers (CPs), namely [M(H2cpdba)2] (M = Zn, 1; Co, 2), [Zn4(cpdba)2(μ-OH)2(py)4]∙H2O (3), and [Co3(cpdba)2(py)6] (4). 1–4 were fully characterized by IR, elemental analyses, TGA, PXRD, and single-crystal X-ray diffraction. Their dimensionality ranges from 2D networks (1 and 2) to 3D frameworks (3 and 4), showing the dimensional/structural diversity of 1–4 is influenced by the level of deprotonation of H3cpdba ligand adjusted via organic solvent types, and the type of metal nodes (ZnII or CoII). Interestingly, 1 and 3 can serve as multi-responsive sensing materials for detecting Fe3+, Cr2O72− and nitrobenzene (NB). Moreover, the mechanism of the selective luminescence quenching response for Cr2O72− can be mainly ascribed to the competitive adsorption of excitation wavelength energy between 1 or 3 and Cr2O72−, meanwhile, Fe3+ ions and NB molecules contact with Lewis-base sites and aromatic rings respectively of H3cpdba ligand in 1 or 3, leading to the luminescent quenching. Furthermore, the magnetic properties of two Co-based CPs (2 and 4) have been investigated. The present work provides a promising approach to design and construct CPs or MOFs by adjusting types of solvents and/or metal nodes.

Coordination Polymers Based on Highly Emissive Ligands: Synthesis and Functional Properties.

Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4′-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4′,4′′-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

The effects of the coordination orientation and steric hindrance of ligands on the structural diversity of Pb(II) coordination polymers

Five new lead(II) coordination polymers, [Pb(L)]n (1), [Pb3(L)3]n·4nH2O (2), [Pb2(L)(1,2-bdc)]n·nH2O (3), [Pb2(L)(1,3-bdc)]n·nH2O (4) and [Pb4(L)2(1,4-bdc)2(H2O)2]n·2nH2O (5) (H2L = 4′-(4-carboxyphenyl)-6′-carboxycalte-2,2′-bipyridine, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid, H2(1,3-bdc) = benzene-1,3-dicarboxylic acid and H2(1,4-bdc) = benzene-1,4-dicarboxylic acid) were prepared under hydrothermal conditions. Compound 1 shows a 2D ladder single-layer with the hcb topology. Compound 2 presents a 2D ladder double-layer, which shows a 3-connected hcb topology. Compound 3 exhibits a 1D loop chain based on [Pb4(COO)6] tetranuclear units. Compound 4 displays a (3,4)-connected 3D framework with 3,4T10 topology consisting of [Pb2O2] units. Compound 5 exhibits a self-penetrating 3D network based on [Pb4(COO)2] units, which features an intriguing new topological net. The structural diversity of 1–5 gives some insights that the pH value and coordination orientations of aromatic dicarboxylates play significant roles in construction of coordination polymers. Meanwhile, the hemi-directed or holo-directed coordination geometries depend on coordination numbers of Pb(II) ions. Furthermore, tetrel bonds enhance the structural stability of these Pb(II) coordination polymers.

5-Aminopyridine-2-carboxylic acid as appropriate ligand for constructing coordination polymers with luminescence, slow magnetic relaxation and anti-cancer properties

Five new coordination polymers (CPs) constructed of aminopyridine-2-carboxylate (ampy) ligand have been synthesized and fully characterized. Three of them correspond to metal-organic chains built from the coordination of ampy to sodium and lanthanides with formulae [MNa(ampy)4]n (M = terbium (2), erbium (1) and ytterbium (3)) resembling a previously reported dysprosium material which shows anticancer activity. On another level, the reaction of Hampy with cobalt and copper ions ({[CoK(ampy)3(H2O)3](H2O)3}n (4) and [Cu(ampy)2]n (5)) lead to CPs with variable dimensionalities, which gives the opportunity of analyzing the structural properties of this new family. Lanthanide materials display solid state intense photoluminescent emissions in both the visible and near-infrared region and exhibit slow relaxation of magnetization with frequency dependence of the out-of-phase susceptibility. More interestingly, in our search for multifunctional materials, we have carried out antitumor measurements of these compounds. These multidisciplinary studies of metal complexes open up the possibility for further exploring the applications in the fields of metal-based drugs.

Heavy chalcogenide-transition metal clusters as coordination polymer nodes.

While metal–oxygen clusters are widely used as secondary building units in the construction of coordination polymers or metal–organic frameworks, multimetallic nodes with heavier chalcogenide atoms (S, Se, and Te) are comparatively untapped. The lower electronegativity of heavy chalcogenides means that transition metal clusters of these elements generally exhibit enhanced coupling, delocalization, and redox-flexibility. Leveraging these features in coordination polymers provides these materials with extraordinary properties in catalysis, conductivity, magnetism, and photoactivity. In this perspective, we summarize common transition metal heavy chalcogenide building blocks including polynuclear metal nodes with organothiolate/selenolate or anionic heavy chalcogenide atoms. Based on recent discoveries, we also outline potential challenges and opportunities for applications in this field.

Synthesis, band structure and multi-responsive luminescence sensing behavior of two Cd(II) coordination polymers

Rapid and sensitive sensing of toxic aromatic compounds has become one of the most important issues. Herein, we use the multifunctional 5-amino-2,4,6-tribromoisophthalic acid (H2ATBIP) to assemble with the Cd(II) ion in the presence of the N-donor bis(imidazole) ligand 1,2-bis(imidazol-1-yl-methyl)benzene (obix) and 1,4-bis(imidazole-l-yl)butane (bib) to construct coordination polymers with pleasing supramolecular architectures and potential interesting luminescent sensing properties. As a result, two Cd(II) coordination polymers, namely, {[Cd(ATBIP)(obix)2(H2O)]·3H2O}n (1) and [Cd(ATBIP)(bib)]n (2), were obtained successfully using the typical solution evaporation method. Single-crystal X-ray diffraction analyses reveal that (1) shows tubular chain structure, while (2) is a necklace-like chain. The central Cd(II) ions in (1) and (2) show slightly distorted octahedral geometry. The ATBIP2- ligand shows monodentate coordination mode in (1) and bischelating coordination mode in (2). With the aid of the hydrogen bonding and the C-Br⋯π interaction, (1) and (2) further extend into a 3D supramolecular network. The analysis of the solid-state diffuse reflectance UV–Vis spectrum reveals that the wide indirect band gaps Eg exist in (1) and (2), which are confirmed by the theoretical calculation based on the density functional theory (DFT). Interestingly, the fluorescence properties of (1) and (2) are greatly dependent on the solvents. Both compounds show multi-responsive sensitive “turn-on” sensing for toluene and “turn-off” sensing for some nitro aromatics (NACs). The sensing limits for toluene and NACs reach to ppm level.

A Three-Dimensional Cadmium(II) Coordination Network Based on 1,3-Di-(1,2,4-triazole-4-yl)benzene: Synthesis, Structure, and Luminescence Properties

1,2,4-Triazole and its derivatives have been investigated extensively in the construction of coordination polymers. Using a 1,2,4-triazole ligand 1,3-di-(1,2,4-triazole-4-yl)benzene (dtb), a new three-dimensional coordination polymer, {[Cd2(dtb)2(SO4)(H2O)]·(1,2-H2bdc)·SO4}n (1) (1,2-H2bdc = 1,2-benzenedicarboxylic acid), was synthesized under solvothermal conditions. Single-crystal X-ray diffraction analysis revealed that there are two crystallographically different Cd(II) ions in 1 with distorted pentagonal bipyramidal [CdN4O3] geometry and distorted octahedral [CdN4O2] geometry, respectively. The Cd1 atoms are connected by dtb ligands to generate Cd4(dtb)8 secondary building units (SUBs), and the SUBs are further linked by Cd2 atoms into a three-dimensional network with two different one-dimensional channels of 14.63(2) × 14.63(2) and 7.54(2) × 7.54(2) Å2 along the c axis. The topological analysis of the framework has also been discussed. In addition, compound 1 exhibits strong fluorescence emission in the solid state at room temperature.