Structures And Properties Of Polymorphs Based On β-diketone Derivatives

Organic light-emitting materials have broad development prospects in some fields,such as organic light-emitting diodes,solar cells,field effect transistors and organic sensors.Organic crystals constructed by π-conjugated molecules have attracted great attention in the field of organic optoelectronic materials due to their highly ordered structure and high carrier mobility.However,traditional organic crystals are prone to fracture under external force,which greatly limits their application to a large extent.In recent years,some organic crystals can undergo special mechanical bending,which makes the application of organic flexible crystals in flexible components developed.So far,there are few reports on organic flexible light-emitting crystals,so the design and application of such materials have great research value.In this paper,we synthesized two simple β-diketone derivatives,and obtained a variety of organic crystals with different luminescence and mechanical properties by solvent evaporation method.On this basis,we proposed a strategy to adjust the luminescence color and mechanical properties by controlling the crystal form.Through the characterization and analysis of these crystals,the relationship between crystal structure and function has been deeply studied.This research is not only of great scientific significance for the design of organic light-emitting flexible crystals,but also provides new possibilities for organic flexible crystals as light transmission and laser gain medium materials.1.In the second chapter,we prepared a β-diketone derivative through a one-step reaction,and compound 1 is(z)-1-(4-(dimethylamino)phenyl)-3-hydroxy-3-(3-fluor-ophenyl)propyl-2-ene-1-one.By adjusting the growth conditions of recrystallization,crystals with three different luminescence and mechanical properties can be obtained(Crystal 1G,1Y and 1O).The fundamental reason for the different luminescence properties and mechanical properties of the three crystals is the different molecular stacking structure by X-ray diffraction analysis There are isotropic forces in the crystal structure of crystal 1G,and there are weak and dispersed interaction forces in the three perpendicular directions of the a,b,and c axes.There is an interlocking stacking structure in the molecule,which can hinder the long-distance movement of the molecule,and the elastic bending occurs under the action of external force.The force in the crystal structure of 1Y belongs to anisotropy,that is,there are strong and weak interaction forces in two almost vertical directions,and the slip of the molecular surface occurs when bending.These two conditions make the crystal 1Y exhibits plastic bending characteristics.Needle crystals 1G and 1Y have good optical waveguide properties in the initial state and bending state,and the low optical loss coefficient indicates that it has great application value in flexible waveguide devices.The amplified spontaneous emission properties indicate that the crystal can be an ideal candidate for the flexible laser gain medium.2.In the third chapter,we prepared another β-diketone derivative through a one-step reaction,and compound 2 is(z)-1-(4-(dimethylamino)phenyl))-3-hydroxy-3-(3-iodophenyl)propyl-2-en-1-one.In the process of growing crystals by solvent slow volatilization,we obtained two different crystal phases by choosing different bad solvents and adjusting the ratio of solvents.They are crystal 2G with green luminescence and crystal 2O with orange luminescence.In the process of grinding,heating and acid/ alkali fumigation,we found that there was a phase transition.The crystals were analyzed by single crystal X-ray diffraction,powder X-ray diffraction and differential scanning calorimetry,which further clarified the relationship between crystal structure and properties.Organic crystals with multiple stimulus response characteristics have great research value in the fields of security,anti-counterfeiting and multiple sensing.In conclusion,we designed and synthesized two kinds of β-diketone derivatives,and successfully obtained a variety of organic crystals with different luminescent properties and mechanical properties by adjusting the growth environment.We conducted a series of tests to characterize the multiple crystal phases of the two compounds to explore the differences in optical and mechanical properties that depend on the difference in the packing structure of the polycrystalline phases.The relationship between the structure and properties of organic small molecule crystals is further explained clearly,which provides some new strategies for the design and development of organic flexible light-emitting materials.At the same time,through the study of the optical waveguide,amplified spontaneous emission and stimulation response properties of these crystals,the application value of flexible organic crystals in fully flexible electronic devices is improved.