Synthesis And Structural Phase Transition Of Organic-Inorganic Hybrid Materials Induced By Organic Amines

In this paper,we designed and synthesized a series of lead halide,bismuth organic-inorganic hybrid complexs and formate triangular iron organic-inorganic hybrid compounds by solvothermal synthesis.Eight organic-inorganic hybrid materials were successfully synthesized by controlling the reaction conditions,in 5 of which obvious phase transitions were found.This report was divided into two parts to introduce the eight kinds of complexs synthesized in the experiment.Part ?:Using 1.3-propanediamine,ethylenediamine,lead nitrate,bismuth nitrate,formic acid,hydroiodic acid and hydrochloric acid as reagents,six kinds of crystals were synthesized by solvothermal conditions:(C₄H₉N₂)Pb I₃(1)?(C₃H₇N₂)Pb I₃(2)?[NH₃(CH₂)₂NH₃]_0.5[NH₃(CH₂)₂NHCOH]Pb I₄(3)?[NH₃(CH₂)₃NH₃]Pb Cl₄(4)?(C₄H₉N₂)₃Bi₂I₉(5)and(C₃H₇N₂)₃Bi₂I₉(6).The DSC measurement of the complexs showed that four complexs had reversible obvious phase transition,among which 5and 6 had multiple DSC signal peaks in the measurement temperature range.The analysis of the single crystal structure showed that 1.3-propanediamine and ethylenediamine in 1,2,5,and 6 respectively reacted with formic acid to form a six-membered ring(1,4,5,6-tetrahydropyrimidine)and a five-membered ring(1,4,5-trihydroimidazole).In addition,the phase transition study of 1,4,and 5 showed that the phase transition of these complexs was caused by the order and disorder of amines.In particular,the complex 4 had an abnormal phase transition caused by multiple hydrogen bonds.Part ?:Using 1.3-propanediamine,N,N?-dimethyl-1.4-butanediamine,ferric chloride,ferrous chloride and formic acid as raw materials to synthesize two kinds of crystals by solvothermal conditions:[Fe₃(?₂-O)(?₁-O₂CH)₉][(C₄H₉N₂)₂](7)and[Fe₃(?₂-O)(?₁-O₂CH)₉][CH₃NH₂(CH₂)₄NH₂CH₃](8).Single crystal structure analysis showed that 1.3-propanediamine and formic acid reacted to form a six-membered ring(1,4,5,6-tetrahydropyrimidine)in 7.The organic amine in 8 did not react with formic acid.The study of the crystal phase transition showed that 7 undergoed a reversible phase transition around 253 K and 283 K,respectively.And the phase transition was related to the order-disorder of organic amine and the orientation of terminal formic acid on the formate triangular iron.