Facile Access to Phosphorus Ylide‐fused Heteroarenes Possessing Tunable Optoelectronic Properties and High Nonlinear Optical Performances

Abstract We report here a novel family of ylidic P‐heteroarenes ( P1 – P6 ), structurally featuring unique phosphonium cyclopentadienylide (P−Cp)‐fused π‐skeletons and synthetically prepared via an unexpected one‐pot [2+3]/[3+3] phospha‐annulation reaction. While the facile and modular synthesis allows the fine‐tuning of their optical absorptions and redox properties, single‐crystallographic and theoretical analysis of these P‐heteroarenes further reveal that the fusion of P−Cp moiety leads to substantial intramolecular charge‐separated features with high ylidic character values of up to 84 %. Benefitted from such dipolar structures, these P‐heteroarenes not only allows stepwise electrophilic substitution reaction for further structural π‐expansions, but also exhibit excellent nonlinear optical (NLO) responses and optical limiting (OL) performances comparable to or exceed those of C 60 . As a model compound, the persistent radical‐anion salt of P5a was also prepared through chemical reduction, thus offering valuable insights into the electronic structures of reduced P‐ylidic species. Our work not only established a highly efficient synthetic method toward new P‐heteroarenes, but also provide fundamental understanding of those fused‐ring ylidic P‐heterocycles with promising NLO/OL applications.