Yunseul Kim1,Minji Kang2,Yeon-Ju Kim1,Dongseong Yang1,Eunhwan Jung3,Dong-Yu Kim1,4
Gwangju Institute of Science and Technology1,Korea Research Institute of Chemical Technology2,University of Cologne3,Heeger Center of Advanced Materials (HCAM)4
Yunseul Kim1,Minji Kang2,Yeon-Ju Kim1,Dongseong Yang1,Eunhwan Jung3,Dong-Yu Kim1,4
Gwangju Institute of Science and Technology1,Korea Research Institute of Chemical Technology2,University of Cologne3,Heeger Center of Advanced Materials (HCAM)4
Quinoidal compounds have attracted much attention due to their unique optical, electrochemical, electrical and magnetic properties, and considered as promising candidates for a wide range of organic electronics, such as organic field-effect transistors (OFETs), organic thermoelectrics and next-generation organic spintronics. They exhibit low band-gap with NIR absorption and redox amphoterism arising from stable quinoid-aromatic resonance form, and high structural planarity because of double bond linkage between each rings. Reported various quinoidal molecules and polymers demonstrated high charge carrier mobility up to > 5 cm<sup>2</sup>/Vs for both hole and electron in OFET devices.<br/>In terms of the electronic state, the quinoid has a closed-shell structure. When the energetically stable quinoid form is extended, this structure is transformed to open-shell diradical form at the either end due to the energy gain by total aromatization. The diradical contributes to increase the electrical conductivity by acting as a carrier, and exhibits high spin-induced magnetic behaviors due to stable triplet states with parallel spins.<br/>In this presentation, we will present our recent results on the investigation of charge transport and spin-magnetic properties of open-shell and closed-shell quinoidal conjugated polymers. We designed and synthesized <i>i</i>) two quinoidal conjugated polymers with different length of quinoidal core and <i>ii</i>) open-shell azaquinoidal polymer with stable radicals. The quinoidal polymers show low band-gap and amphoteric redox behavior. The OFET devices based on these open-shell quinodal polymers demonstrate high charge carrier mobilities. We performed DFT calculations to predict diradical character index (<i>y<sub>0</sub></i>) and singlet-triplet energy gap, and spin distribution. Moreover, we characterized and discussed their spin-magnetic properties via Raman spectroscopy, electron spin resonance (ESR) and magnetic property measurement system (MPMS). The quinoidal conjugated polymer exhibits ferromagnetism with magnetic hysteresis loop at low temperature as well as room temperature.