Syntheses, Structural Characterization And Thermoanalyses Of Transition-Metal Complexes Derived From 3-amino(3,5-diamino)-1,2,4-Triazole

Since each nitrogen atom of a triazole ring has lone-pair electrons,1,2,4-triazole and its derivatives prefer coordination with transition-metal ions. Thesenitrogen donors thereby bridge metal ions to form dinuclear, trinuclear or polynuclearmetal complexes. These complexes can be used for the synthesis of information-storagematerials, adsorption materials, metal-organic materials and nanomaterials. Much moreattention has been paid in these years on the triazole-containing complexes. It istherefore of importance to study these complexes.In this dissertation, we synthesized and characterized 35 complexes derived from3-amino-1,2,4-triazole(3AT) and 3,5-diamino-1,2,4-triazole(HdaTrz) and transition-metal ions including Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺. Their physicochemicalproperties were characterized by Elemental Analysis, FT-IR and TG-DSC analyses.Single crystals of four complexes of them, suitable for X-ray diffraction analysis, weresuccessfully grown and their structures were determined. Their molecular structuresrevealed that complexes [Ni₃(HdaTrz)₆(daTrz)₂(H₂O)₄]Cl₄·6H₂O 22, [Ni₃(HdaTrz)₆(H₂O)₆(SO₄)₃·8H₂O 24 and [Ni₃(HdaTrz)₆(H₂O)₆]Br₆·8H₂O 25 are each trinuclearcomplex. The cationic part of them has each a centrosymmetric center located at themiddle nickel atom. Unlike its partners 24 and 25, complex 22 contains twodeprotonated ligands besides six neutral ligands. The cadium complex,[Cd(HdaTrz)₂(SO₄)]·H₂O 31, is a 3D coordination polymer linked by ligands andsulfate anions.Transition-metal complexes deriverd from triazoles can be used as potentialenergetic materials due to high-percent of nitrogen element in the five-numbered ring oftriazole. We carried out the investigations on the thermal decomposition mechanisms ofthese complexes in order to understand their thermal decomposition rules. The resultsshowed that the first stag is the loss of crystal water and (or) coordinated watermolecules if the complexes contain them; the second stage is the decomposition ofanions accompanied with the destruction of ligands by one or more steps; the final reside is the corresponding metal oxide as the last stage. It was also founded that thedecomposition process of a complx is dependent partly on the anion: if the anion issimple such as Cl^-, decomposition process is also simple with one exothermic peak inthe DSC curve and less decomposition stages in its TG curve; if the anion is complexsuch as SO₄^2- or NO₃^-, decomposition route is also complex with more exothermic andendothermic peaks in the DSC curve and more stages in the TG curve. Obviously, thiswork enriches the thermochemical database and provides a theoretical basis forapplications of these complexes.