Organic ?-conjugated Molecules And Their Open-shell Systems Based On Twisted Perylene Building Block

Organic radicals have great potentials in electronic applications as thermoelectric materials,energy storage materials,organic field effect transistors and organic spintronic devices,owing to their unique optical,electronic and magnetic properties.In this thesis,we have designed and synthesized the ?-extended molecules and corresponding radicals within twisted conformation,followed by focused investigation of the relationship between molecular structure and electronic properties.The research contents are summarized as following:1.We have designed and synthesized quadruple helical tetraradicaloid,named as TBCP.We were interested in thermally induced stereoisomerization of this tetraradicaloid,which have the key impact on alternation of the magnetic characteristics.Both experimental and theoretical results deomonstrated that the magnetic swithing property were coming from the changing of electronic structure of the molecule during heating and cooling back,and thus magnetic hysteresis loops were observed in TBCP.2.We have designed and synthesized a series of di-naphtho/quinoperylene DNPs and DQPs,through longitudinal peri-extension of twisted perylene building block.Both DNPs and DQPs exhibited deep red fluorescencent emission.The nitrogen-doped DQPs even showed a fluorescence quantum yield as high as 94%,to the best of our knowledge,this is the highest value recorded for red-emissive polycyclic aromatic hydrocarbons.Additionally,DQPs could change their red color to blue under acidic condition,accompanied by emission red-shifted to the near infrared region(?700 nm),and reversibly returned to the original color under basic condition.3.By exploiting the resonance hybrid electronic effect,we have designed and synthesized stable organic radical cations with large-sized ?-conjugated system.Both experimental and theoretical results revealed that these radical cations were highly stable without decomposition in solutions and solids,mainly attributed to the high delocalization of spin and charge over the whole molecular framework,and the steric protection of the highly active sites.Besides,? radical cations had interesting global aromaticity,according to calculations of the corresponding anisotropy of the induced current density(AICD),corroborating again their thermodynamic stability.Importantly,these radical cations exhibited significant differences of magnetic properties in respective solid,solution and crystalline states.We therefore have investigated the intrinsic mechanism of the state-associated magnetic responses,with the help of various experimental means and theoretical calculations.4.We have designed and synthesized dichromenoperylene dication DCP-DC.DCP-DC show typical electronic structure in closed-shell form,but have strong magnetic response as temperature rising to 373 K,e.g.,the proton resonance peak gradually broadens and the electron spin resonance signal becomes more intense during the heating process.Experimental and theoretical results demostrated that DCP-DC had a low energy barrier(?30 kcal/mol)for conformational alternation,leading to a transition state with thermally excited open-shell triplet species.