Donor-acceptor (DA) conjugated polymers (CPs) with narrow bandgaps and open-shell (diradical) character represent an emerging class of materials whose rich behavior emanates from their collective electronic properties and diminished electron pairing. However, the structural and electronic heterogeneities that define these materials complicate bandgap control at low energies and connections linking topology, exchange interactions, and (opto)electronic functionality remain nascent. To address these challenges, we demonstrate structurally rigid and strongly π-conjugated copolymers comprised of a solubilizing thiadiazoloquinoxaline acceptor and cyclopenta[2,1-b:3,4-b′]dithiophene or dithieno[3,2-b:2′,3′-d]thiophene donors. Atom-specific substitution modulates local aromatic character within the donor resulting in dramatic differences in structural, physicochemical, electronic, and magnetic properties of the polymers. These long-range π-mediated interactions facilitate control between low-spin aromatic and high-spin quinoidal forms. This work provides a strategy to understand the evolution of the electronic structure within DA CPs, control the ground state spin multiplicity, tune spin-spin interactions, and articulate the emergence of their novel properties.

具有窄带隙和开壳（双自由基）特性的供体 - 受体（DA）共轭聚合物（CP）代表了一类新兴的材料，其丰富的行为源于它们的集体电子特性和减少的电子配对。然而，定义这些材料的结构和电子异质性使低能量的带隙控制复杂化，连接拓扑、交换相互作用和（光）电子功能的连接仍然处于起步阶段。为了应对这些挑战，我们展示了由增溶性噻二唑并喹喔啉受体和环戊二烯 [2,1- b :3,4- b '] 二噻吩或二噻吩并 [3,2- b :2'组成的结构刚性和强 π 共轭共聚物， 3′- d]噻吩供体。原子特异性取代调节供体内的局部芳香特性，导致聚合物的结构、物理化学、电子和磁特性发生显着差异。这些长程 π 介导的相互作用促进了低自旋芳香族和高自旋醌型之间的控制。这项工作提供了一种策略来理解 DA CP 内电子结构的演变、控制基态自旋多重性、调整自旋-自旋相互作用并阐明其新特性的出现。