2D Organic Radical Conjugated Skeletons with Paramagnetic Behaviors. Issue 18 (31st August 2021) - Li, Hao
Abstract: 2D conjugated polymers (2D CPs) with high crystallinity and proper bandgaps have attracted much attention. However, the development of magnetic 2D CPs still remains a challenge. It is urgently needed to develop graphene‐like 2D CPs with tunable structural properties under relatively mild reaction conditions. Herein, two 2D CPs (TAPA‐HKH and HAB‐HKH) with fused rings bridged by pyrazine are synthesized by reacting 2, 3, 7, 8‐tetraaminephenazine (TAPA) and 1, 2, 3, 4, 5, 6‐hexaaminebenzene (HAB) with hexaketocyclohexane octahydrate (HKH), respectively. Both the TAPA‐HKH and HAB‐HKH have nanoporous graphene‐like skeletons with unique N‐embedded zigzag edges. Moreover, few‐layer nanosheets of the 2D CPs are further obtained by liquid‐phase exfoliation. The magnetic properties and radical characteristics of the TAPA‐HKH and HAB‐HKH nanosheets are further studied by superconducting quantum interference device magnetometer and electron spin resonance spectroscopy, respectively. At 2 K, the saturation magnetizations of the TAPA‐HKH and HAB‐HKH nanosheets reach up to 0.30 and 0.10 emu g −1, respectively. In addition, TAPA‐HKH nanosheets even show a high localized spin magnetic moments of 12.4 μB in 1000 nitrogen atoms. The intrinsic magnetism of TAPA‐HKH and HAB‐HKH nanosheets can be attributed to the highly stable radicals, nanoporous structures, and N‐doped zigzag edges existing in their graphene‐like skeletons. Abstract : 2D crystalline conjugated polymers (TAPA‐HKH and HAB‐HKH) with only pyridinic‐N atoms are prepared by a bottom‐up strategy. The types of nitrogen at the zigzag edges of their graphene‐like skeletons can be manipulated precisely. Furthermore, stable few‐layer nanosheets of both samples are obtained by the liquid‐phase exfoliation, and paramagnetic properties of the nanosheets are further studied.