Synthesis, Structures, and Properties for P^III-Doped Hetero-Buckybowls and Their Phosphonium Salts

Doping polycyclic aromatic hydrocarbons with heteroatoms enables manipulation of their electronic structures. Herein, the structures and properties of phosphorus (P) doped heterosumanenes (HSEs) are regulated by varying the valence states of P-dopant. The phosphine sulfide (P^V) and chalcogens (S, Se, Te) co-doped HSEs (1-3) are reduced to trivalent phosphorus (P^III) doped analogues 4-6. Then, the P^III-dopants on 4-6 are converted to phosphonium salts (R₄P⁺), giving 7-9. The valence states of P-dopant show great influence on molecular geometries and electronic structures. Taking P and S co-doped HSEs as example, bowl-depths increase in the order of 1 (P^V)<7 (R₄P⁺)<4 (P^III), and the HOMO energy levels and HOMO-LUMO gaps increase to be 7<1<4. Consistent with the theoretical calculation, the first oxidation potentials decrease and the absorption/emission bands show blue shift from 7 to 1 to 4. The transformation of P^V to P^III leads to large variations on the coordination with Ag⁺, owing to the alteration of coordination site from P=S to P^III. The phosphonium salts show ring-opening of phosphole rings under electrochemical reduction. It is found that chalcogen atoms play pivotal roles on coordination patterns of coordination complexes and the conversion rates of ring-opening reactions.