Synthesis And Properties Of Organic Functional Materials Based On Imidazo(1,2-a)pyridine

This thesis reviewed the progresses of organic functional materials including organic molecular conductors and organic molecular magnets based on stable radicals, and phosphorescent iridium (III) complexes molecular materials. Organic radical conductors include the charge transfer complexes based on perylene ions or TTF derivative ions as electron donars, and the neural radical molecular conductors, such as phenalenyl radicals, thiazolyl radicals. Organic radical magnets include nitroxide radicals, thiazolyl radicals and verdazyl radicals. Organic phosphorescent iridium (III) complexes include red, green, blue and yellow emission complexes.In this thesis, a novel zwitterionic radical based on 2,3'-biimidazo[1,2-a]pyridine- 2'-one (Hbipo–?) was successfully isolated from an anion radical coordination polymer by EDTA extraction in KOH solution. It is found that this zwitterionic radical possesses higher conductivity (σRT≈10–4 S cm–1) and the temperature dependence of net magnetization reversal over 242 K. This zwitterionic radical can be converted into protonated cation radical by reaction with perchlorate solution, and two different cation radical perchlorate salt crystals were obtained. According that two perchlorate salt crystals have different 1Dπ-stacking structure, they display different light-emitting properties and magnetic properties. One of them has potential as an effective constituent for the multi-component white light luminescence materials, and exhibits long-range ferromagnetic order phase transition with magnetic ordering temperature of 86 K. Both crystals show ferromagnetic to antiferromagnetic phase transition, and one of which even occurs at near room temperature (257 K).Zwitterionic radical Hbipo–? can also be converted into another new neutral radical, [2-(imidazo[1,2-a]pyridin-2-yl)-2-oxo-N-(pyridin-2-yl)acetamide]?, via in situ KO2- promoted ring opening reaction of aromatic N-heterocycle under air and room temperature conditions. The neutral radical has 1Dπ-stacking structure, and shows two long-range ferromagnetic order phase transitions with the higher magnetic ordering temperature (about 225 K) near room temperature. This unique magnetic property can be explained by the low-temperature single crystal structure analyses. All radicals (zwitterionic radical, cation radicals, neutral radical) exist in solution as diamagnetic (S = 0)π-dimers, and have normal NMR (dmso-d6) with silent EPR. In the solid states, however, their EPR spectra exhibit a narrow line and different lower field satellite lines which exhibit anisotropic changes with magnetic field lying on different orientation of crystals.A series of phosphorescent heteroleptic iridium (III) complexes with new fused imidazo-carboxylate as ancillary ligands were designed and synthesized. One of complexes almost covers the range from 460 nm (blue emission) to 592 nm (orange-red emission), and may be used as potential white phosphorescent materials. Other complexes exhibit purple emission and green emission. The phosphorescent colors can be effectively tuned only by the nature of the fused imidazo-carboxylate ancillary ligands.