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Combining the advantages of energetic heterocycles to achieve high-energy insensitive explosives is a significant challenge. Herein, based on high-energy tetrazole rings and highly stable 1,3,4-oxadiazole rings, a series of novel nitrogen rich energetic compounds 5–9 were successfully constructed. The related compounds were fully characterized by EA, FT-IR, NMR, DSC, and MS, and compounds 6–9 were further confirmed by X-ray single crystal diffraction. Among them, the energetic ion salts 6–8 show high thermal stability (Tdec > 250 °C) and low mechanical sensitivity (IS > 40 J, FS > 360 N), as well as good energy properties (7552–8050 m s−1, 19.4–23.3 GPa). In particular, the azo compound 9 exhibits competent comprehensive performances (Tdec = 226.2 °C, D = 8502 m s−1, P = 28.9 GPa, IS = 32 J, FS = 320 N). These results suggest that the strategy of integrating tetrazole and 1,3,4-oxadiazole and employing an azo structure as a bridging unit are effective approaches to construct high-energy insensitive materials. [ABSTRACT FROM AUTHOR]

Tetranitroethane (TNE), an energetic compound with high-nitrogen (N%, 26.7%) and oxygen (O%, 60.9%) content, is deprotonated by alkali and alkaline earth metal bases to form the corresponding metal salts of TNE which are characterized by FT-IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. All the prepared energetic metal salts show excellent thermal stabilities, and the decomposition temperatures of EP-3, EP-4, and EP-5 are higher than 250 °C, due to the numerous coordination bonds of the complexes. Furthermore, the energy of formation of the nitrogen-rich salts were calculated utilizing heat of combustion. The detonation performances were calculated with the EXPLO5 software, and the impact and friction sensitivities were determined. EP-7 shows excellent energy performance (P = 30.0 GPa, VD = 8436 m s−1). EP-3, EP-4, EP-5, and EP-8 are more sensitive to mechanical stimulation. These alkali and alkaline earth metal salts of TNE show good monochromaticity by atomic emission spectroscopy (visible light), and may be used as potential flame colorants in pyrotechnics. [ABSTRACT FROM AUTHOR]

Two bimetallic complexes of 4-hydroxy-3,5-dinitropyrazole, [K2Mn(DNPO)2(H2O)4]n·2H2O (BMEP-1) and [K2Zn(DNPO)2(H2O)6]n (BMEP-2), were synthesized and characterized by IR spectroscopy and elemental analysis. The crystal structures of BMEP-1 and BMEP-2 were determined by single-crystal X-ray diffraction. It is noteworthy that these complexes presented different metal–organic frameworks. The thermal behaviors of BMEP-1 and BMEP-2 were investigated by differential scanning calorimetry and thermogravimetric analysis measurements. These bimetallic complexes exhibited high thermal stability (348.0 °C and 331.0 °C) due to their large coordination bonds and three-dimensional interconnected structure. The catalytic performances of BMEP-1 and BMEP-2 on the thermal decomposition of ammonium perchlorate were investigated by TGA-DSC, TGA-FTIR, and non-isothermal kinetic analyses. The results showed that BMEP-1 and BMEP-2 exhibited excellent catalytic performance in the thermal decomposition of ammonium perchlorate. Notably, there was only a single exothermic peak at 302.6 °C and 318.6 °C, and the activation energy values of ammonium perchlorate decreased to 123.88 kJ mol−1 and 128.43 kJ mol−1, respectively. TGA-FTIR results showed that BMEP-1 and BMEP-2, as effective components of catalysis, will promote the production of H2O, N2O, NO2, and HCl in advance, during the thermal decomposition of ammonium perchlorate. BMEP-1 and BMEP-2 are expected to be two candidate additives for the catalytic decomposition of ammonium perchlorate in composite solid propellants. [ABSTRACT FROM AUTHOR]

Three mononuclear, dinuclear and one-dimensional dysprosium(III) complexes based on 3-azotriazolyl-2,6-dihydroxybenzoic acid (H4ATB) of [Dy(H3ATB)3]·3H2O (1), [Dy2(H2ATB)2(H2DHB)2(H2O)4]·2CH3CN·5H2O (2), and [Dy2(H2ATB)2(DCB)(DMF)2(H2O)2]·4DMF (3) were synthesized and structurally characterized by X-ray single crystal diffraction (H3DHB = 2,6-dihydroxybenzoic acid, H2DCB = 1,4-dicarboxybenzene). Complex 1 was used as a precursor to synthesize complexes 2 and 3, and 2 was further used to synthesize 3. Complex 1 is a mononuclear complex, in which the Dy(III) ion is in a nine-coordinated structure surrounded by three tridentate chelate H3ATB− ligands. Complex 2 displays a dinuclear structure bridged by two μ2 carboxyl groups of two H2DHB− ligands and two μ1,1-O atoms from the phenolic hydroxyl groups of two H2ATB2− ligands. Complex 3 shows a one-dimensional structure formed by two bridging DCB2− ligands. The magnetic measurements were performed on three complexes 1–3, and they showed different magnetic behavior. Complex 1 shows a field-induced slow magnetic relaxation. Complexes 2 and 3 display distinct slow magnetic relaxation under zero dc field with energy barriers (Ueff) of 26(2) cm−1 and 11(1) cm−1, respectively. The magnetic behavior of three complexes 1–3 was investigated by ab initio calculations. [ABSTRACT FROM AUTHOR]

Two ion-pair Fe(III) complexes (PPh4)[FeIII(HATD)2]·2H2O (1, H3ATD = azotetrazolyl-2,7-dihydroxynaphthalene) and [FeII(phen)3][FeIII(HATD)2]2·3DMA·3.5H2O (2, phen = 1,10-phenanthroline, DMA = N,N-dimethylformamide) were synthesized by employing the tridentate ligand H3ATD. Crystal structure analyses reveal that complexes 1 and 2 consist of FeIII ions in an octahedral environment where a FeIII ion is coordinated by two HATD2− ligands forming the [FeIII(HATD)2]− core. The shortest cation⋯anion distance between the phosphorus ion of the (PPh4)+ cation and the ferric ion of the [FeIII(HATD)2]− anion is 13.190 Å in complex 1, whereas that between the ferrous ion of the [FeII(Phen)3]2+ cation and the ferric ion of the [FeIII(HATD)2]− anion is 7.821 Å in complex 2. C–H⋯C and C–H⋯O hydrogen interactions between the [FeII(phen)3]2+ cation and the [FeIII(HATD)2]− anion are observed in 2. Face-to-face π-π stacking interactions between naphthalene rings with the separated interplanar center to center distances of 3.421–3.680 Å were observed, which result in a one-dimensional supramolecular chain in complexes 1 and 2. Magnetic measurements show that complex 1 is in the low-spin (LS) state below 500 K, whereas 2 undergoes a high temperature spin crossover (SCO) between 360 and 500 K. Magneto-structural relationship studies reveal that π-stacking, hydrogen interactions and Coulomb interactions between the [FeIII(HATD)2]− anion and the [FeII(phen)3]2+ cation play a crucial role in the high temperature Fe(III) SCO behaviour of complex 2. [ABSTRACT FROM AUTHOR]

Herein, a novel and fluorescent zinc-organic framework sensor [Zn3(μ3-Hbptc)2(μ2-4,4′-bpy)2(H2O)4]n·2nH2O (1) (H4bptc = 2,3,3′,4′-biphenyl tetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine) is synthesized and characterized, demonstrating its excellent fluorescence performance for Cu2+ detection and the enrichment of Cu2+ in aqueous media. The fluorescence intensity of 1 can be selectively quenched by Cu2+ in a linear range of Cu2+ concentrations of 0–0.7 μM. The limit of detection (LOD) value is as low as 32.4 nM, which is superior to those of most of the fluorescent sensors based on metal–organic frameworks (MOFs). It is also far below the maximum allowable concentration of Cu2+ in drinking water as defined by the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO), so it is employed for the detection of Cu2+ in actual water samples. More importantly, the nature of the interaction between the active coordination site (COO−) of 1 and Cu2+ determines the quenching mechanism, that is Cu2+ in the analyte is captured by MOF 1, which has been investigated by ICP, luminescence, UV-vis, XPS, and lifetime studies. Besides, the chemosensor shows regeneration performance without the loss of performance in five consecutive cycles. So MOF 1 is a simple and convenient probe used not only for the rapid detection but also for the enrichment of trace amounts of Cu2+ in aqueous media, and the application can be further extended to a variety of environmental and biological analysis processes. [ABSTRACT FROM AUTHOR]

Integrating the merits of different components to construct heterostructures for energy storage and conversion has attracted intensive attention. Herein, taking advantage of bimetallic MOFs and transition bimetal hydroxide, we have successfully used nanoflower-like Ni1−xCox(OH)2 as both the precursor and template to in situ construct three dimensional (3D) NiCo-MOF@Ni1−xCox(OH)2 (denoted as MOF@TMH) hierarchical heterostructures. Benefiting from the optimized composition with hierarchical heterostructures assembled by ultrathin nanosheets, MOF@TMH-2 possesses rich effective active sites and high electrochemical reactivity, delivering superior pseudocapacitor performance with a specific capacitance of 1855.3 F g−1 at 2 A g−1 and good rate performance. Besides, MOF@TMH-2 also exhibits excellent OER activity with small overpotentials of 193 mV and 310 mV at 10 and 100 mA cm−2, respectively. [ABSTRACT FROM AUTHOR]

By employing the ligand azotetrazolyl-2,7-dihydroxynaphthalene (H3ATD), two linear trinuclear mixed-valence cobalt complexes [CoIICo III2 (HATD)4(H2O)4]·4DMA·3H2O (1, DMA = N,N-dimethylacetamide) and [CoIICo III2 (HATD)4(DMF)2(H2O)2]·2DMF·2H2O (2, DMF = N,N-dimethylformamide) were synthesized. Two [2 × 2] grid-like tetranuclear ion-pair complexes [Co II2 Co III2 (HATD)4(bpp)2(H2O)2][CoIII(HATD)2]2·8DMF·6H2O (3, bpp = 2,6-di(pyrazol-1-yl)pyridine) and [Co II2 Co III2 (HATD)4(bpp)2(H2O)2][CoIII(HATD)2]2·8DMSO·4MeOH (4, DMSO = dimethyl sulphoxide) were obtained by the reaction of complex 1/2 with tridentate-chelating bpp in DMF and DMSO, respectively. The single-crystal X-ray diffraction analysis indicated that complexes 1 and 2 have a similar core, in which the DMA in 1 acts as a guest molecule, and the DMF in 2 acts as a coordinated molecule and guest molecule. Complexes 3 and 4 are isostructural. All the Co(II) ions in 1–4 are present in a distorted octahedral geometry. The ac susceptibility measurements show that all complexes display frequency-dependent peaks in the out-of-phase (χm′′) component of the alternating-current (ac) magnetic susceptibility data, which is the characteristic behavior of single molecule magnets (SMMs). [ABSTRACT FROM AUTHOR]

Four 3-(tetrazol-5-yl)-5-(pyrid-2-yl)-1,2,4-triazole (H2TPT) based complexes of [Co2(TPT)2(H2O)2] (1), [Mn2(TPT)2(H2O)2] (2), [Mn(TPT)(H2O)2]n (3) and [Cu(TPT)]n (4) have been solvothermally synthesized and structurally characterized by X-ray single-crystal diffraction analysis. Complexes 1 and 2 display isostructural dinuclear structures, while complex 3 exhibits a 1D zigzag chain structure. The structural difference for 2 and 3 may be caused by 100 and 160 °C temperature-controlled conditions. Complex 4 is a 3D framework structure in which the Cu2+ ion is in square pyramid coordination geometry. Complexes 1–4 display good thermal stability evaluated by thermogravimetric analysis. Complexes 1 and 4 show very strong antiferromagnetic interactions. The electrocatalytic oxygen evolution of complexes 1–4 was tested under neutral conditions, which revealed that the four complexes possess electrocatalytic oxygen evolution activity. Complex 1 exhibits a current density of 10.0 mA cm−2 at a potential of 2.00 V (vs. RHE), presenting 50-fold improvement in specific activity over the glassy carbon electrode. [ABSTRACT FROM AUTHOR]

A new salicylaldehyde-based azo dye 5-azotriazolyl-3-methoxysalicylaldehyde (H2TMSA) and its two Ln3+ complexes {[Ln(HTMSA)3(H2O)2][Ln(HTMSA)3(DMF)(H2O)]}·15H2O (Ln = Dy(1) and Tb(2)) have been synthesized and characterized by IR, Raman, 1H NMR and single-crystal X-ray diffraction techniques. H2TMSA shows an azo form in acidic (pH ＜ 5.05) and strong basic (pH ＞ 12.41) conditions, and a pH-dependent azo-hydrazone tautomerism in the range of pH 5.05 to 12.41, which is demonstrated by the time-dependent density functional theory (TD-DFT) calculations. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the Ln3+ ions are surrounded by six oxygen atoms from three dichelate HTMSA− ligands and two oxygen atoms from two solvent molecules forming a distorted square-antiprismatic geometry. Complex 1 shows distinct slow magnetic relaxation under a zero dc field, while 2 displays field-induced slow magnetic relaxation. Ab initio calculations were performed on the two complexes to understand their magnetic anisotropy and their different magnetic dynamics. [ABSTRACT FROM AUTHOR]

A 4-amino-1,2,4-triazole (NH2-trz) based linear trinuclear Fe(ii) complex of [Fe3(NH2-trz)6(SCN)4(H2O)2](SCN)2·H2O (1) has been hydrothermally synthesized by the reaction of a NH2-trz ligand with FeSO4. A single crystal of complex 1 is able to extrude one lattice water and one coordinated water, leading to another single crystal of complex 1a with a formula [Fe3(NH2-trz)6(SCN)5(H2O)](SCN) by heating. Complex 1a can be reversed to 1 upon the reabsorption of water. Single-crystal X-ray diffraction analysis reveals that these two complexes consist of a linear trinuclear core where a central Fe1 ion is coordinated to six nitrogen atoms from six bridged NH2-trz ligands and one of the terminal Fe2 ions is coordinated to five nitrogen atoms and one oxygen atom. The terminal Fe3 ion in 1 coordinates to five nitrogen atoms and one oxygen atom; however, the terminal Fe3 ion in 1a coordinates to six nitrogen atoms. Magnetic susceptibility measurements demonstrate that they exhibited gradual spin crossover (SCO) for the central Fe(ii) ion; however, different spin transition temperatures were displayed for complexes 1 and 1a (T1/2 = 202 K for 1 and 160 K for 1a). These different spin transition temperatures arise from the different intermolecular hydrogen bonding interactions in the two complexes. [ABSTRACT FROM AUTHOR]

By utilizing symmetrical pentacarboxylate ligands, 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid (H5L1) and 3,5-di(2′,4′-dicarboxylphenyl)benzoic acid (H5L2), two novel porous Zn-MOFs, [Zn5(μ3-H2O)2(L1)2]·3DMA·4H2O (CTGU-3) and [Zn3(μ3-OH)L2(H2O)3]·H2O (CTGU-4) have been synthesized under solvothermal conditions. CTGU-3 and CTGU-4 exhibit 3D microporous frameworks with flu and dia topologies and possess unique secondary building units [Zn5(μ3-H2O)2(RCO2)6] and [Zn3(μ3-OH)(RCO2)3], respectively. Such porous systems create a unique space or surface to accommodate Ag nanoparticles (Ag NPs), which could efficiently prevent Ag NPs from aggregation and leaching. In this work, two new Ag@Zn-MOF composites, denoted as Ag@CTGU, have been successfully fabricated through solution infiltration, for the reduction of nitrophenol. Compared with CTGU-4, CTGU-3 shows enhanced catalytic efficiency toward the reaction when it is used as a catalyst support of Ag NPs. Moreover, gas sorption and luminescence properties of two compounds were also investigated. [ABSTRACT FROM AUTHOR]

A super-stable multifunctional terbium(iii)–organic framework, namely {[Tb(TATAB) (H2O)2]·NMP·H2O}n (Tb-MOF, H3TATAB = 4,4′,4′′-s-triazine-1,3,5-triyltri-m-aminobenzoic acid, NMP = N-methyl-2-pyrrolidone) was synthesized. Tb-MOF exhibits a 2D sql structure with binuclear [Tb2(COO)4(H2O)4]2+ units as 4-connected nodes, and free water and NMP molecules are inserted between 2D layers through hydrogen-bonding interactions, forming a sandwich-type architecture. Observably, such a framework remains intact in a remarkable variety of environments such as common solvents and aqueous solutions with metal cations and inorganic anions, as well as with a pH ranging from 1 to 13. In particular, Tb-MOF can not only detect small organic molecules, metal cations and inorganic anions with high sensitivity and high selectivity, but also can accurately detect explosive 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and 2,4,6-trinitrophenol in water. Its luminescence quenching response to Fe3+ and Cr2O72− ions can be explained in terms of the competitive absorption mechanism. In addition, the luminescence intensity of Tb-MOF is strongly correlated with the pH value in a pH range from 1 to 13. Thus, this material can be potentially used as a multi-responsive luminescent sensor. [ABSTRACT FROM AUTHOR]

Two unique six-connected self-penetrating coordination polymers with a new (44.610.8) network topology, derived from the cross-linking of two 66-diasubnets, were constructed from NiIIor CoIIand two types of V-shaped tectons. The NiIIcomplex 1shows an antiferromagnetic coupling viaμ-carboxylate and μ-H2O pathways, whereas the CoIIcomplex 2exhibits the single-ion behavior in 300–34 K and then a ferromagnetic coupling at lower temperatures. [ABSTRACT FROM AUTHOR]