Synthesis, Structure And Properties Of Metal - Organic Coordination Polymers Based On Tetrazole Derivatives

Tetrazoles and their derivatives attract much attention used as ligands in complex since they are multidentate ligands which tend to form multinuclear or multidimensional complexes with a variety of properties include photoluminescence, catalysis and even the application in energetic materials. In this paper, four novel multiligand coordination complexes,[Ni(en)3]AZTTHF (1), [Ni(AZT)(pn)2]n (2), [Ag(ATA)]n (3) and [Ag2(en)2(AZT)]n (4) (en= ethylene diamine, THF= tetrahydrofuran, pn= propylene diamine, ATA=5-amino-tetrazole and AZT=5,5-zaotetrazolate), were prepared from corresponding metal salts. By virtue of crystal engineering method, we can research the relationship between properties and structures in these neotype compounds.Complexes have been structurally characterized by elemental analysis, Fourier transform infrared spectroscopy and single crystal X-ray diffraction. Crystals of 1 and 2 crystallize in the triclinic space group P-1.1 presents a zero-dimensional unit, while 2 exhibits a one-dimensional zigzag chains. The neighbouring tetrazole rings of 2 show the face-to-face anion-anion π--π- stacking interactions, In complex 3, each ATZ2’ligand is bonded to three Ag(I) ions in μ3-1,2,4 bridging mode to give a 2-D three-connected (4,8) planar layer containing 6-membered rings (Ag2N4) and 16-membered rings (Ag4N12).In the structure of 4, each silver(I) ion is coordinated within a strongly distorted tetrahedron by four nitrogen atoms from different ligands and the trans-AT2- ligand chelates two Ag(I) ion in an unprecedented coordination modes. Both compounds 3 and 4 consist of 2-D three-connected layers that are linked by π-π overlap interactions between the tetrazolate fragments in the neighboring lays to form a 3-D supramolecular.Their thermal decomposition and corresponding effects on propellants also have been explored by TG-DTG and DSC technologies. TG-DTG and DSC studies indicate there is one intense exothermic decomposition for both 1 and 2 around 247℃. The activation energy of the first exothermic process of compound 1 is a little higher than that of the compound 2. DSC experiments reveal that both complexes show prominent effect on the thermal decomposition of RDX, HMX and AP, The highest drop value for mixture systemsof 2/RDX,2/HMX is 44℃ and 38℃ respectively, both compounds have decreased the decomposition temperature of AP by 58℃. The exothermic quantity of 1/RDX,2/RDX, 1/AP and 2/AP has increased by 323 J/g,269 J/g,573 J/g and 399 J/g respectively. Control experimentswith Ni(en)3SO4 and SAZT indicate that the metal Ni2+ part in complex mainly contributes to temperature drop while the AZT2- part can offer more decomposition heat. Both complexes 1 and 2 could be useful promoters in propellants.The photoluminescent properties and photocatalystic abilities were measured by fluorescence spectrophotometer and UV/Vis spectrophotometer, respectively. The results of photoluminescent experiments reveal that compound 3 is a potential blue fluorescence material with high quantum yield (0.12). Compounds 3 and 4 represent the first example of coordination polymers with a Ag ion that exhibit high efficient photocatalystic abilities for R6G degradation under UV light and show good stability toward photocatalysis, their rate constant for 4 was found to be 3.321 h-1, whereas the rate constant for 3 under UV-light irradiation was 1.989 h-1. Control experiments also show that compounds 3 and 4 are more superior photocatylysts than Degussa P-25.