Radical Cation Salts of Hetera‐Buckybowls: Polar Crystals, Negative Thermal Expansion and Phase Transition. - Wu, Lingxi; Li, Yecheng; Hua, Xinqiang; Ye, Lei; Yuan, Chengshan; Liu, Zitong; Zhang, Hao‐Li; Shao, Xiangfeng (Angewandte Chemie, 2024)