Regulating Structures and Properties of Overcrowded‐Ethylene Decorated (Diaza)Phosphinines via Tunable Main‐Group Element Hyperconjugation

Abstract Creating more sophisticated molecular systems that are responsive, dynamic, and controllable through a combination of chemical structure modification and external stimuli represents a pivotal challenge in the development of functional molecular machines. Herein, we report a new series of overcrowded‐ethylene (OCE) decorated (diaza)phosphinines. Combining with the main‐group element and nonplanar OCE structures, new P‐molecules showed the tunable folded(F)/twisted(T)‐conformations and physical properties via the distinct P‐hyperconjugation of the P─C and P─N bonds. Such hyperconjugation‐induced tunability is different from the classical OCEs where p‐π/π‐π conjugation effects are the dominating factors controlling the structures and properties. Furthermore, bromination of NP‐oxide derivative induced an unexpected chemochromic T→F isomerization, highlighting the dynamic conformation character. Leveraging on the different structures, CP and NP derivatives further enabled the formations of radical cations and anions having different spin characters on the P‐centers. As the new example of P‐Thiele's hydrocarbon family, combining the NP structure with the overcrowded anthraquinodimethane structure yielded a light‐responsive open‐shell NP‐anthraquinodimethane diradicaloid with a triplet ground state, which was influenced by the PN hyperconjugation effect in F‐conformation and the aromaticity gain in T‐conformation. Overall, our new strategy, namely the hyperconjugation‐regulated tunability, paves the way toward complex organic materials with tunable the structures and physical properties.