Preparation And Properties Of Three Organic-inorganic Hybrid Crown Ether Crystals

Organic-inorganic hybrid crystal materials is a new kind of composite crystalline materials formed by organic cation and inorganic anion self-assembly.It has the merits of both organic and inorganic compounds,such as low cost,simple synthesis,light weight,adjustable structure,easy processing,mechanical flexibility and environmental friendliness.18-crown-6 has good modifiability,controllable structure and functional diversity.Crown framework organic-inorganic hybrid crystal materials with different structure and properties based on 18-crown-6,are prepared by introducing different inorganic acids and organic amines.It has phase transition,optical,dielectric,semiconductor,piezoelectric,ferroelectric or thermoelectric properties and it has potential applications in information storage,signal processing,microwave devices,electro-optic modulators,piezoelectric sensors,transducers and other fields.Most of the crown ether hybrid molecular crystals reported before have lower phase transition temperature(some properties only exist below the phase transition temperature,such as ferroelectricity)or lower decomposition temperatures,which seriously limits the practical application of the materials.Therefore,in order to find new organic-inorganic crown ether crystals with high phase transition temperature and explore the effects of organic and inorganic components on the properties of crystals,three kinds of organic-inorganic hybrid crystal materials based on 18-crown-6 framework were designed and synthesized,and their structures and related physical properties were carefully analyzed.The thesis is divided into two parts.In the first part,two new organic-inorganic hybrid crown ether crystals were synthesized by solution volatilization method:[(C₆H₇Cl N)(18-crown-6)]⁺[Cl O₄]^-(CH₃COCH₃)(1),[(C₆H₇Cl N)(18-crown-6)]⁺[BF₄]^-(CH₃COCH₃)(2).Their physical properties,such as structure,infrared spectrum,temperature stability,dielectric,piezoelectric,absorption spectrum and fluorescence spectrum,were systematically studied.It was found that crystal 1 and crystal 2exhibited high phase transition temperatures,which were about 71°C.They all belong to the space group P2₁2₁2₁ in orthorhombic system and exhibit asymmetric structure,which indicates that two crystals have piezoelectric effect.In this work,the existence of piezoelectric domain was found by atomic force microscope(AFM),which confirmed the existence of piezoelectric effect.Compared with the crown ether homologue[(C₆H₇IN)(C₁₂H₂₄O₆)]⁺[Cl O₄]^-and[(C₆H₇IN)(C₁₂H₂₄O₆)]⁺[BF₄]^-,it is speculated that the acetone molecules in crystal 1 and crystal 2 are responsible for the asymmetric structure and piezoelectric effect,and the phase transition at 71°C is due to the acetone molecules volatilizing away from the crystal structure.Crystal 1 and 2are two novel organic-inorganic hybrid crown ether piezoelectric crystal materials with high phase transition temperature,two crystals have potential application prospect in resonators,sensors,energy converters and other electronic components used in the field of communication technology.In the second part,a new organic-inorganic hybrid crown ether crystal,[(C₈H₁₂NO)(18-crown-6)]⁺[BF4]^-(3),was synthesized by solution volatilization method.The structure,infrared spectrum,temperature stability,dielectric,absorption spectrum,fluorescence spectrum and other physical properties were systematically studied.It is found that crystal 3 has no decomposition,melting or phase transition in the temperature range from 100 K to 298 K.It has good temperature stability and good luminescence properties.In addition,by analogy with the structures and properties of crystal 3 and its homologues[(C₇H₁₀NO)(C₁₂H₂₄O₆)]⁺[BF₄]^-and[(C₈H₁₂NO)(C₁₂H₂₄O₆)]⁺[Cl O₄]^-,the roles of organic and inorganic components in the crown ether inclusion complexes were preliminarily determined:inorganic acids affect its thermal stability,and organic amines mainly affect its structure and physical properties determined by its structure,such as piezoelectric and ferroelectric properties.