Room‐Temperature Phosphorescence in Pure Organic Materials: Halogen Bonding Switching Effects

Organic room‐temperature phosphorescence (ORTP), when combined with external stimuli‐responsive capability, is very attractive for sensors and bio‐imaging devices, but remains challenging. Herein, by doping two β‐iminoenamine‐BF 2 derivatives (S‐2CN and S‐2I) into a 4‐iodoaniline (I−Ph−NH 2 ) crystalline matrix, the formation of S‐2CN⋅⋅⋅I−Ph−NH 2 and S‐2I⋅⋅⋅I−Ph−NH 2 halogen bonds leads to bright‐red RTP emissions from these two host–guest doped crystals (hgDCs) with quantum efficiencies up to 13.43 % and 15.96 %, respectively. Upon treatment with HCl, the competition of I−Ph−NH 2 ⋅ HCl formation against S‐2I⋅⋅⋅I−Ph−NH 2 halogen bonding switches off the red RTP from S‐2I/I−Ph−NH 2 hgDCs, whereas the stable halogen‐bonded S‐2CN⋅⋅⋅I−Ph−NH 2 ensures red RTP from S‐2CN/I−Ph−NH 2 hgDCs remains unchanged. A security protection luminescence pattern by using these different HCl‐responsive RTP behaviors was designed.