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Isomers sometimes play a fundamental role in the formation of coordination architectures. In this article, bifunctional 5-(n-pyridyl)tetrazole-2-isopropanoic acid (n = 2, 3) has been designed and prepared. Then, reactions of Ca(NO3)2·4H2O with isomeric 5-(n-pyridyl)tetrazole-2-isopropanoic acid (denoted as Hn-pytzipa, n = 2, 3) afforded mononuclear [Ca(2-pytzipa)2(H2O)4] (1) and one-dimensional [Ca(3-pytzipa)2(H2O)2]n (2), respectively. In 1, 2-pytzipa is a bidentate ligand which chelates one Ca(II) via the nitrogen atoms of the pyridine and tetrazole rings while in 2, 3-pytzipa bridges adjacent Ca(II) centers in a μ 1,1,3-COO mode. PEG-5000 (poly(ethyleneglycol-5000)) coated [Ca(2-pytzipa)2(H2O)4] (1) and [Ca(3-pytzipa)2(H2O)2]n (2) nanoparticles (NPs) show toxicity towards Hela cells, but the ligands are non-toxic in nature and 2 is superior to 1. Furthermore, cell migration across a 2D artificial gap indicates that both NPs can inhibit the migration of Hela cells.

Tetrazole–carboxylate ligands are excellent building blocks to construct novel coordination architectures. 5-Aminotetrazole-1-isopropionic acid (Hatzipa) and 3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4dtzpda) were prepared. And reactions of the two ligands with CdCl2·2.5H2O afforded [Cd(atzipa)2(H2O)(EtOH)] (1) and [Cd2(H2dtzpda)2(H2O)3]·3H2O (2), respectively. Compound 1 shows a two-dimensional layer structure, whereas compound 2 is a three-dimensional network composed of Cd2+ and octa-dentate H2dtzpda2− via the tetrazole-N and the carboxylate group in a μ1,1,3-COO mode. The luminescence properties of Hatzipa, H4dtzpda and the compounds were investigated at room temperature in the solid state.

{La(pytza)3(H2O)2·2H2O}n derived from 5-(4-pyridyl)tetrazole-2-acetic acid (Hpytza) has been synthesized by a solvothermal reaction of Hpytza and La(NO3)3·6H2O. In this compound, neighboring La3+ i...

Here we report two Ba(II) coordination compounds, 2D [Ba(btzphda)(H2O)4] (1) and 3D [Ba2(pytzipa)4(H2O)3]·2H2O (2) derived from 1,3-bis(tetrazol-5-yl)benzene-N2,N2′-diacetic acid (H2btzphda) and 5-(4-pyridyl)tetrazole-2-isopropionic acid (Hpytzipa). Furthermore, differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds. The relevant thermodynamic parameters (ΔH, ΔS, and ΔG) of the decomposition process of compounds 1 and 2 were calculated, as well.

Evaluation of the potential for metal–metal (M–M) cooperation to enable catalysis requires access to specific polynuclear aggregates that display appropriate geometry and size. Here we demonstrate ion metathesis within pre-formed metal–organic frameworks (MOFs) to prepare metastable Pd2 tetracarboxylates sites., Evaluation of the potential for metal–metal (M–M) cooperation to enable catalysis requires access to specific polynuclear aggregates that display appropriate geometry and size. In many cases, exerting synthetic control over the aggregation of simple metal salts is a challenge. For example, Pd(ii) acetate self assembles as a trimer (i.e. Pd3(OAc)6) both in the solid state and in solution and does not feature close Pd–Pd interactions. Related carboxylate-supported Pd2 aggregates (i.e. Pd2(OAc)4), which would feature close Pd–Pd interactions, are thermodynamically metastable in solution phase and thus largely unavailable. Here we demonstrate ion metathesis within pre-formed metal–organic frameworks (MOFs) to prepare metastable Pd2 tetracarboxylates sites. The newly synthesized materials are characterized by elemental analysis, PXRD, SCXRD, EXAFS, XANES, and gas adsorption analysis. In addition, the critical role of network solvation on the kinetics of ion metathesis was revealed by coupled TGA-MS and ICP-MS experiments. The demonstration of templated ion metathesis to generate specific metastable coordination sites that are inaccessible in solution phase chemistry represents a new opportunity to interrogate the chemistry of specific polynuclear metal aggregates.

Isomers play a crucial role in the formation of coordination architectures. Herein we report two Sr(II) coordination compounds, mononuclear [Sr(2-pytzipa)2(H2O)4] (1) and 1D [Sr(3-pytzipa)2(H2O)2]n (2) derived from two isomers, 5-(n-pyridyl)tetrazole-2-isopropionic acid (Hn-pytzipa, n = 2, 3). Furthermore, differential scanning calorimetry and thermogravimetric-differential thermogravimetric analyses were applied to evaluate the thermal decomposition behavior of such compounds. The relevant thermodynamic parameters (ΔH, ΔS, and ΔG) of the decomposition process of 1 and 2 were calculated as well.

Tetrazole carboxylates are acknowledged as bifunctional ligands for the construction of new coordination architectures. Two new coordination compounds, [Ba(atzpa)2(H2O)3]n·2nH2O (1) and [Ba2(dtzpda)(H2O)]n (2) have been prepared by solvothermal reactions of BaCl2·2H2O with Hatzpa or H4dtzpda, respectively (Hatzpa = 5-aminotetrazole-1-propanoic acid, H4dtzpda = 3,3-di(1H-tetrazol-5-yl)pentanedioic acid). The X-ray diffraction results reveal that compound 1 is a linear chain in which atzpa acts as a tridentate ligand to bridge adjacent Ba2+ ions in a µ1,1,3-COO mode. In contrast, compound 2 is a three-dimensional network where dtzpda4− acts as a dode-dentate ligand to bridge various Ba2+ ions. Furthermore, the luminescence of Hatzpa, H4dtzpda, compounds 1 and 2 in the solid state at room temperature were investigated.

Mononuclear [Ce(pztza)2(H2O)6](pztza)·H2O (1) (pztza = 5-(2-pyrazinyl)tetrazole-2-acetato) has been prepared and characterized by IR, elemental analysis and single-crystal X-ray diffraction. PEG-5000 (poly(ethyleneglycol-5000)) coated [Ce(pztza)2(H2O)6](pztza)·H2O nanoparticles (NPs) can disperse into distilled water. In vitro study on Hela cells shows that Hpztza is nontoxic while [Ce(pztza)2(H2O)6](pztza)·H2O NPs show high toxicity with half-maximal inhibitory concentration (IC50) of 17 μg/mL (1.93 × 10−5 M). In addition, such NPs can inhibit the migration of Hela cells effectively.

3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4dtzpda) can display tunable valence when reacted with different metal ions because it has four acidic hydrogen atoms of both tetrazole rings and carboxylate groups. Solvothermal reactions of H4dtzpda with La(NO3)2·6H2O or La(NO3)3·6H2O/Cu(NO3)2·6H2O afforded a one dimensional [La(Hdtzpda)(H2O)4]·4H2O (1) and a three dimensional [La2Cu(dtzpda)2(H2O)10]·4H2O (2), respectively, where only three acidic hydrogen atoms of H4dtzpda are deprotonated in compound 1 while all the four acidic ones are deprotonated in compound 2. In compound 1, Hdtzpda3- is a penta-dentate ligand to bridge La(III) centers via only oxygen atoms of the carboxylate group while in compound 2, dtzpda4- is a hepta-dentate one via not only the oxygen atoms of the carboxylate group but also the nitrogen atoms of the tetrazole rings. PEG-5000 (poly(ethyleneglycol-5000)) coated compound 1 or 2 nanoparticles (NPs) have good dispersity in water. Cytotoxicity study on A549 cells (human caucasian lung carcinoma) shows that compound 2 (half-maximal inhibitory concentration, IC50～18 μg/mL) is superior to compound 1 (IC50～38 μg/mL). Furthermore, both NPs of the two compounds are able to inhibit the migration of A549 cells, indicating their potential to inhibit the transfer of tumors in vivo.

pH is sometimes fundamental to the formation of coordination compounds. Here we report two new Zn(II)-tetrazole-carboxylate coordination compounds derived from Hatzipa, namely two dimensional [Zn(atzipa)2]n (1) and [Zn(atzipa)2(H2O)(EtOH)]n (2), where Hatzipa = 5-aminotetrazole-1-isopropanoic acid. The structures of the two compounds are controlled by pH value of the reaction system. Compound 1 crystallizes in an achiral space group while 2 in a chiral space group P2(1)2(1)2. Furthermore, nanoparticles (NPs) of the two compounds can be obtained by co-precipitation with PEG-5000 (Polyethylene Glycol-5000). And [Zn(atzipa)2]n (1) NPs with a relatively low IC50 (half-maximal inhibitory concentration) on Hela cells of 23 μg/mL (6.1 μM) is superior to [Zn(atzipa)2(H2O)(EtOH)]n (2) NPs (58 μg/mL, 13.2 μM). Both NPs of the two compounds can inhibit the migration of Hela cells and compound 1NPs can be used as a cell imaging agent. The results show that pH influences the resulting structures and [Zn(atzipa)2]n (1) NPs capable of inhibiting the growth of tumor in vitro may be a potential candidate against cancer.

A novel [Dy4(pytza)5(OH)4(H2O)7Cl]Cl2·4H2O compound based on 5-(4-pyridyl)tetrazole-2-acetic acid (Hpytza) has been designed and prepared. This compound is an unprecedented two dimensional network consisting of a tetranuclear cubic [Dy4(OH)4]8 + secondary building unit (SBU) and tridentate pytza via the pyridine-N and the carboxylate group in a μ1,3-COO syn-syn bridging mode. PEG-5000 (poly(ethyleneglycol-5000)) coated [Dy4(pytza)5(OH)4(H2O)7Cl]Cl2·4H2O nanoparticles (NPs) have good dispersity in distilled water. In vitro study on Hela cells shows that such NPs show high toxicity while Hpytza is non-toxic in nature. Furthermore, such NPs can effectively inhibit the migration of Hela cells even at a low concentration, indicating their potential to inhibit the transfer of tumors in vivo.

Ru(II) compounds are potential candidates for photodynamic therapy (PDT). In the present study, a Ru(II) compound based on 3-(2-pyridyl)pyrazole (Hpypz) and 2,2′-bipyridine has been prepared and characterized. This compound can self-assemble to form nanoparticles (NPs) by nanoprecipitation in distilled water. These NPs with a mean size of 92 nm have good passive targeting by enhanced permeability and retention effect (EPR). In vitro studies on HeLa cells show that these NPs have high phototoxicity and a low IC50 (half-maximal inhibitory concentration) of only 8 μg mL−1 (12 μM), but they also have negligible dark toxicity. Moreover, such NPs can inhibit the migration of HeLa cells, indicating their potential to interfere with the transfer of tumors in vivo. Furthermore, in vivo investigations on nude mice demonstrate that such NPs can effectively inhibit the growth of the tumor. After treatment for 10 cycles, an obvious decrease in the tumor volume can be observed and in addition, the main organs (heart, liver, spleen, lung and kidney) suffer no damage, which indicates the high phototoxicity, low toxicity and excellent biocompatibility of these NPs.

It is of great importance for a photosensitizer to be soluble in aqueous solutions, while simultaneously remaining highly fluorescent. Towards this goal, (2-(4-bromophenyl)ethene-1,1,2-triyl)tribenzene (denoted as TPE-Br) with aggregation induced emission (AIE) was prepared. 1,2-Distearoyl-sn-glycero-3-phospho-ethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-PEG-2000) coated TPE-Br nanoparticles (NPs) have a strong ability to generate singlet oxygen using singlet oxygen sensor green (SOSG) as a probe and still retain high fluorescence in aqueous solutions. In vitro cytotoxicity assays demonstrate that these NPs are able to kill HeLa cells effectively and the half-maximal inhibitory concentration (IC50) is as low as 12 μg mL−1. Furthermore, in vivo investigation suggests that TPE-Br NPs are able to inhibit the growth of the tumors after irradiation without adverse effects to normal organs, including the heart, liver, spleen, lung and kidney. This indicates the significantly low dark toxicity and excellent biocompatibility of such NPs.

Tetrazole–carboxylate ligands with both rigid tetrazole ring and flexible carboxylate group have a great potential in the construction of coordination architectures. Here, we report four new samarium(III) compounds based on four tetrazole–carboxylate ligands 5-(2-pyrimidyl)tetrazole-2-acetic acid (Hpmtza), 5-aminotetrazole-1-propanoic acid (Hatzpa), 5-(4-pyridyl)tetrazole-2-acetic acid (Hpytza), and 3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4dtzpda), namely mononuclear [Sm(pmtza)2(H2O)6]Cl·3H2O (1), binuclear [Sm2(atzpa)4(H2O)8](NO3)2·2H2O (2), one-dimensional [Sm(pytza)3(H2O)2]·2H2O (3) and [Sm(Hdtzpda)(H2O)4]·4H2O (4). The effect of different counter anion (ClO4 −, Cl−, NO3 −) on the formation of such compounds was also investigated. Furthermore, the luminescence of compounds 1–4 shows intraligand emission, whereas the characteristic peaks of Sm3+ may be overlapped.

Bifunctional tetrazole-carboxylates, 5-(n-pyridyl)tetrazole-2-isopropionic acid (denoted as Hn-pytzipa, n = 2, 3) have been selected to be reacted with CdCl2·2.5 H2O under solvothermal conditions, [Cd3(2-pytzipa)2(MeOH)2Cl4]n (1) and [Cd(3-pytzipa)2]n (2) were obtained. In compound 1, 2-pytzipa is a pentadentate ligand to bridge adjacent Cd(II) centers to generate a fascinating 3D dinodal 4-connected, 5-connected net with point symbol of (42·84)(43·64·73). In 2, each 3-pytzipa bridges three Cd(II) atoms in a μ 1,3-COO syn-anti mode to generate a fascinating 3D one-nodal 6-connected net with point symbol of (42·52·66·75). Photoluminescence properties of compounds 1 and 2 in the solid state show enhanced ligand centered emission. Furthermore, thermogravimetric-differential (TG-DTG) and differential scanning calorimetry (DSC) were used to evaluate the thermal decomposition behavior of compounds 1 and 2, showing that the decomposition process of compound 2 is much more intense than that of compound 1. The thermal parameters (∆S, ∆H and ∆G) of the decomposition of compound 2 were calculated, as well.

Isomer plays a significant role in the formation of coordination compounds. Reactions of isomeric 5-(n-pyridyl)tetrazole-2-isopropionic acid (denoted as Hn-pytzipa, n = 2, 3) with Pb(NO3)2 under solvothermal conditions afforded two compounds with the same formula [Pb(2-pytzipa)2]n (1) and [Pb(3-pytzipa)2]n (2), respectively. In compound 1, 2-pytzipa acts as a tetradentate ligand via the pyridine-N and the tetrazole-N in a chelating mode and the carboxylate group in a μ1,3-COO chelating mode. In contrast, 3-pytzipa in compound 2 acts as a tridentate ligand by only the pyridine-N and the carboxylate group in a μ1,3-COO chelating mode, whereas all the nitrogen atoms of the tetrazole ring are uncoordinated. Compound 1 shows a ladder-like chain while compound 2 displays a wave like chain. In addition, the photoluminescence properties of these ligands and compounds 1 and 2 in the solid state were investigated at room temperature. The thermal behavior of such compounds were also discussed.

Three different tetrazole-carboxylate ligands, monotetrazole-carboxylate H 2 tza (H 2 tza=1,5-tetrazole-diacetic acid), Hpztza (Hpztza=5-(2-pyrazinyl)tetrazole-2(1-methyl)acetic acid), ditetrazole-carboxylate H 2 tzpha (H 2 tzpha=1,3-di(tetrazole-5-yl)benzene-N2,N2′-diacetic acid) have been chosen to react with CdCl 2 ·6H 2 O, resulting in the formation of three new compounds [Cd 2 (tza) 2 ] ( 1 ), [Cd(pztza) 2 ] ( 2 ) and [Cd(tzpha)(CH 3 OH) 2 ] ( 3 ). The coordinate sites of the three ligands are major influenced by the different substituted group of tetrazole ring. These compounds have been characterized by elemental analysis, IR and single crystal X-ray diffraction. Compound 1 displays a complex 3D structure; compound 2 shows a 3D network and compound 3 features a 2D layer network. Furthermore, the luminescence properties investigated at room temperature in the solid state showed excellent ligand-centered luminescence. The obvious enhancement in luminescence makes these compounds potential materials for optical use. The differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds, showing that compounds 2 and 3 can be used as potential energetic materials. The relevant thermodynamic parameters ΔH, ΔS and ΔG were calculated as well.

Isomer is sometimes fundamental to the self-assembly of the resulting coordination compounds. Pyridine-tetrazole-carboxylate ligands are outstanding building blocks to construct novel coordination architectures. 3-(5-Tetrazolyl)pyridine-1-acetic acid (H3-tzpya) or its isomer 5-(4-pyridyl)tetrazole-2-acetic acid (H4-pytza) were prepared. Reactions of the two ligands with TbCl3·6H2O afforded [Tb(3-tzpya)2(H2O)5]Cl·4H2O (1) and [Tb4(4-pytza)5(OH)4(H2O)7Cl]nCl2n·4nH2O (2), respectively. The different position of the carboxylate group control the coordination mode of these isomer, thus leading to structural variation. Compound 1 shows a mononuclear structure whereas compound 2 is an unprecedented two dimensional network composed of tridentate 4-pytza via the pyridine-N and the carboxylate group in a μ1,3-COO bridging mode and a tetranuclear cubane-shaped [Tb4(OH)4]8+ cluster secondary building unit (SBU). The luminescence properties investigated in the solid state show intense green light emission at room temperature.

Ru(II) compounds are potential candidates for photodynamic therapy (PDT) and auxiliary ligands may have an impact on the property of the resulting coordination compounds. In the present study, two Ru(II) compounds based on 5-(2-pyrazinyl)tetrazole (Hpztz) and two classic auxiliary ligands, 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) have been prepared and characterized, namely [Ru(pztz)(bipy) 2 ][PF 6 ] ( 1 ) and [Ru(pztz)(phen) 2 ][PF 6 ] ( 2 ). The nanoparticles (NPs) of the two compounds have been prepared by self-assembly in aqueous solution. In vitro MTT assay on HeLa cells show that [Ru(pztz)(phen) 2 ][PF 6 ] with a lower IC 50 (half-maximal inhibitory concentration) of only 7.4 μg/mL is superior to that of [Ru(pztz)(bipy) 2 ][PF 6 ] (17.8 μg/mL) under irradiation. Meanwhile, negligible dark toxicity have been also observed for the two compounds. In addition, in vivo fluorescence imaging suggests that [Ru(pztz)(phen) 2 ][PF 6 ] NPs are able to target to the tumor by enhanced permeability and retention effect (EPR). Furthermore, in vivo phototherapy on nude mice demonstrate that such NPs can effectively inhibit the growth of the tumor. After treatment for 10 cycles, an obvious decrease in the tumor volume can be observed while the normal tissues, including heart, liver, spleen, lung and kidney, suffer from no damage, indicating the high phototoxicity, low dark toxicity and excellent biocompatibility of [Ru(pztz)(phen) 2 ][PF 6 ] NPs.

Tetrazole–carboxylates with both rigid tetrazole rings and flexible carboxylate groups provide excellent building blocks for the construction of diverse coordination architectures. We have selected a bistetrazole–carboxylate, H2btzphda [H2btzphda = 1,3-bis(tetrazol-5-yl)benzene-N2,N2′-biacetic acid] and a tristetrazole–carboxylate, H3ttzphta [H3ttzphta = 1,3,5-tris(tetrazol-5-yl)benzene-N2,N2′,N2′′-trisacetic acid] to construct new coordination compounds with CoCl2·6H2O, [Co(btzphda)(CH3OH)(H2O)2]·H2O (1), [Co3(ttzphta)2(H2O)12]·H2O (2). These coordination compounds were structurally characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. Complex 1 has a two-dimensional layer structure with (4,4) grid topology, while complex 2 has a one-dimensional beaded chain structure. The luminescence spectra of complexes 1 and 2 at room temperature in the solid state show weaker emissions than those of the corresponding free ligands. The thermogravimetric properties of complexes 1 and 2 are presented and discussed.

The NdIII coordination compounds [Nd(4-pytza)3(H2O)2]·2H2O (1) and [Nd(4-pytza)2(H2O)4]Cl·2H2O (2) [H4-pytza = 5-(4-pyridyl)tetrazole-2-acetic acid] were synthesized by reactions of K4-pytza and NdCl3·6H2O at different pH values. Single crystal X-ray diffraction analysis reveals that 4-pytza ligands in 1 in a μ1,3-COO syn-syn or μ1,1,3-COO bridging mode coordinate to two central NdIII atoms to display a dinuclear unit, which is connected by one of these 4-pytza ligands acting in end-to-end bridging mode to form a 1D ladder-like chain. Different from 1, each 4-pytza in 2 with a μ1,3-COO syn-anti bridging mode coordinates to two NdIII atoms to display a 1D zigzag chain. Furthermore, the luminescence properties of 1 and 2 were investigated at room temperature in the solid state.

Reactions of four different tetrazole-containing carboxylic acids with GdCl3·6H2O, produced the coordination compounds, [Gd4(pytza)5(H2O)10(μ-O) Cl]·4H2O·2Cl (1) [pytza = 2-(5-(pyridine-4-yl)-2H-tetrazole-2-yl)acetato], [Gd(pztza)2(H2O)6]·pztza·3H2O (2), [pztza = 2-(5-(pyrazin-2-yl)-2H-tetrazol-2-yl) acetato], [Gd(pmtza)2(H2O)6]Cl·2H2O (3), [pmtza = 2-(5-(pyrimidyl-2-yl)-2H-tetrazol-2-yl) acetato], and Gd(tzpya)2(H2O)5]Cl·4H2O (4) [tzpya = 2-(4-(5H-tetrazol-5-yl)pyridin-1(4H)-yl) acetato]. The compounds were structurally characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that compound 1 displays a 2D single layered network and compounds 2–4 are mononuclear. Compounds 1–4 are self-assembled to form 3D networks by hydrogen bonding interactions. Furthermore, the luminescent properties in the solid state at room temperature were investigated.

Two ZnII-tetrazole-carboxylate coordination compounds are reported, mononuclear [Zn(atzpa)2(H2O)4]·2H2O (1) and one-dimensional [Zn(atzpa)2(H2O)2]n (2), derived from 5-aminotetrazole-1-propanoic acid (Hatzpa). The structures of both compounds are determined by the pH value of the reaction system. The luminescence properties of Hatzpa and the compounds were investigated at room temperature in the solid state. Furthermore, differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds. The relevant thermodynamic parameters (ΔH, ΔS, and ΔG) of the decompostion process of compound 1 were calculated, as well.

Counter anion and pH play important roles in the self-assembly process of coordination compounds. Tetrazole carboxylate ligands are outstanding candidates for construction of coordination architectures. Four new compounds based on Htzpya, Hatzpa, Hpytza and europium(III) salts, namely mononuclear [Eu(tzpya)2(H2O)5]Cl·4H2O (1), binuclear [Eu2(atzpa)4(H2O)8](NO3)2·2H2O (2), one dimensional [Eu(pytza)3(H2O)2]n·2nH2O (3) and [Eu(pytza)2(H2O)4]nCln (4) were obtained, where Htzpya = 3-(5-tetrazolyl)pyridine-1-acetic acid, Hatzpa = 5-aminotetrazole-1-propanoic acid and Hpytza = 5-(4-pyridyl) tetrazole-2-acetic acid. Different europium(III) salts EuX3·6H2O (X = Cl−, NO3−) and pH values were selected to investigate the influence of both the counter anions and the pH on the formation of such compounds. Furthermore, the luminescence properties of 1–4 in the solid state were also investigated at room temperature, showing both intraligand emission and characteristic peaks of Eu3+ for compounds 1–4.

Two novel coordination compounds, [Sr(atzp)2(H2O)2]·CH3OH (1) and [Sr(dtzpha)(H2O)3]·4H2O (2) [Hatzp=5-aminotetrazole-1-propionic acid, H2dtzpha=1,3-di(tetrazol-5-yl)benzene-N2,N2′-diacetic acid)], have been generated by using 5-aminotetrazole-1-propionic acid and 1,3-di(tetrazol-5-yl)benzene-N2,N2′-diacetic acid to react with strontium salts, respectively. X-ray diffraction analysis reveals that carboxylic groups of two ligands show the same coordination mode (the μ 1,1,3-COO coordination mode), compound 1 displays a 1D structure while compound 2 shows a 2D structure, which implies the influence of the number of the carboxylic acid groups. Luminescence properties of 1 and 2 were investigated at room temperature in the solid state.

Tetrazole and its derivatives with rich nitrogen atoms may be potential candidates for energetic materials. Alkaline earth metal coordination compounds based on such ligands are relatively less investigated. Hpytza was prepared from 4-cyanopyridine and sodium azide, ethyl bromoacetate, where Hpytza = 5-(4-pyridyl)tetrazole-2-acetic acid. Hpytza and four alkaline earth metal coordination polymers [Mg(pytza)2]n (1), [Ca(pytza)2(H2O)2]n·3nH2O (2), [Sr(pytza)2(H2O)2]n (3) and [Ba(pytza)2(H2O)2]n·nH2O (4) were prepared under solvothermal conditions. The thermal behavior of these compounds were characterized by the differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses. Furthermore, the critical temperature of thermal explosion and relevant thermal parameters ΔS, ΔH, ΔG of Hpytza and polymers 1–4 were calculated, as well, indicating that these compounds are potential energetic materials.

Tetrazole and its derivatives with rich nitrogen atoms are usually considered as potential candidates for energetic materials. The different substituents may have an impact on either the rigidity and flexibility or the energetic performance of such compounds. Here, 1,2-bis(tetrazol-5-yl)ethane (H2btze) was prepared from succinonitrile and sodium azide from a [2+3] cycloaddition reaction, which was further reacted with chloroacetic acid to afford 1, 2-bis(tetrazol-5-yl)ethane diacetic acid (H2btzeda). In order to explore their potential as energetic materials, differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses were applied to investigate the thermal decomposition behavior of such compounds. Thermodynamic parameters (ΔH, ΔS and ΔG) and explosion property parameters (critical temperature of thermal explosion, detonation heat, specific volume of explosion, detonation temperature, detonation velocity, detonation pressure, working capacity) were calculated according to literature and the law of thermodynamics base on DSC data. The results show H2btze and H2btzeda with both high enthalpy can be used as potential energetic materials. Furthermore, H2btze has higher specific volume of explosion (943.94 L.kg−1) but lower detonation temperature (1994.44 K), compared with trinitrotoluene (TNT).

The different substituted group will have a substantial effect on the crystal structures of the resulting compounds. Tetrazole–carboxylate ligands are outstanding blocks for construction of novel coordination architectures. Three derivative ligands of tetrazole-2-acetic acid, H3-pytza, H4-pytza and H3tzpha, where H3-pytza = 5-(3-pyridyl)tetrazole-2-acetic acid, H4-pytza = 5-(4-pyridyl)tetrazole-2-acetic acid and H3tzpha = 1,3,5-tris(tetrazol-5-yl)benzene-N2,N2′,N2″-triacetic acid, have been chosen to be reacted with Mg(NO3)2·6H2O, resulting in the formation of three new compounds, [Mg(H2O)6](3-pytza)2·2H2O (1), [Mg(4-pytza)2(H2O)4] (2) and [Mg3(tzpha)2(H2O)12]·10H2O (3). These compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The X-ray diffraction reveals that compounds 1 and 2 are mononuclear structures, while compound 3 shows a one-dimensional chain. The structures of these compounds are controlled by not only the different 5-substituted group of the tetrazole-2-acetic acid, but also the complementary hydrogen bonds. Furthermore, the luminescence studies show that compounds 1–3 show stronger emission than the corresponding ligands. Three Mg(II) coordination compounds 5-substituted group derivative of tetrazole-2-acetic acid (H3-pytza, H4-pytza and H3tzpha) show different luminescence properties.

An energetic material [Zn2(btzphda)2(H2O)4(dpp)2]·2DMF·4H2O with high decomposition enthalpy of − 748.35 J/g was prepared by the reaction of H2btzphda, dpp and Zn(NO3)2·6H2O under solvothermal conditions, where btzphda = 1,4-bis(tetrazol-5-yl)benzene-N2,N2′-diacetato, dpp = 1.3-di(4-pyridyl)propane and DMF = N,N′-dimethylformamide. The luminescence properties of H2btzphda and [Zn2(btzphda)2(H2O)4(dpp)2]·2DMF·4H2O were investigated at room temperature in the solid state (Hitachi F4600 spectrofluorometer). Furthermore, the thermal decomposition behavior of the compound is characterized by differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses. The entropy of activation (ΔH), enthalpy of activation (ΔS) and the free energy of activation (ΔG) for the decomposition temperature were ΔH = 250.64 kJ/mol, ΔS = 222.75 J·mol− 1·K− 1 and ΔG = 134.10 kJ/mol.

Isomer is sometimes fundamental to the formation of the resulting compounds. The design and preparation of coordination compounds based on isomers is of tremendous paramount since they have a lot in common but simultaneously some difference, which can lead to variation of both the topologies and properties. Solvothermal reactions of Hn-pytza (n = 3, 4) with Co(ClO4)2·6H2O, afforded two interesting coordination polymers, one dimensional [Co(3-pytza)2(H2O)2]n·2nH2O (1) and three dimensional [Co(4-pytza)2]n (2), where Hn-pytza = 5-(n-pyridyl)tetrazole-2-acetic acid (n = 3, 4). The thermal decomposition behavior of the two compounds were characterized by the differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG), showing [Co(4-pytza)2]n is superior to [Co(3-pytza)2(H2O)2]n·2nH2O in terms of energetic performance. Furthermore, the entropy of activation (∆S), enthalpy of activation (∆H), and free energy of activation (∆G) were calculated, as well.

Three different tetrazole-carboxylate ligands, Hpymtza, Hpytza, and H2dtzeda were chosen to be reacted with Ca(NO3)2·4H2O, resulting in the formation of three coordination compounds, [Ca(pymtza)2(H2O)4] (1), [Ca(pytza)2(H2O)2] (2), and [Ca(dtzeda)(H2O)2] (3) [Hpymtza = 5-(2-pyrimidyl)tetrazole-1-acetic acid, Hpytza = 5-(3-pyridyl)tetrazole-2-acetic acid, and H2dtzeda = 1, 2-bis(tetrazol-5-yl)ethane-N1, N1′-diacetic acid]. X-ray diffraction analysis revealed that compound 1 displays a mononuclear structure, compound 2 is a one dimensional zigzag chain structure, whereas 3 shows a three-dimensional structure. The structures were controlled by not only the different substituents of the tetrazolyl ring, but also the complementary hydrogen bonds. Furthermore, the luminescence properties of compounds 1–3 were investigated at room temperature in the solid state. These emissions can be tentatively attributed to the ligand centered emission.