Bis((9H-(4,5-diazafluoren)-9-ylidene)methyl)arylenes: Design, synthesis, optoelectronic properties, sensorics and luminescent coordination polymers

Aggregation-induced emission (AIE) materials are highly demanded for practical applications in optoelectronics, sensorics, material science and bio-imaging. However, highly torsionally-flexible and hybrid organic/inorganic AIE materials are limited. In this work we designed, synthesized and comprehensively studied AIE-active bis((9H-(4,5-diazafluoren)-9-ylidene)methyl)arylenes demonstrating high torsional freedom coupled with electron-accepting character and N,N′-chelating ability. One-rotor nonplanar structure of phenylene-linked derivative (BDFMP) allowed us to demonstrate its polymorphic diversity both in neat state and in coordination polymers. X-ray diffraction analysis indicated formation of crystals with extensive π-stacking interactions and slipped/side-by-side packing motifs, the former crystals demonstrating a photoluminescence quantum yield of 25 %. The reaction of both BDFMP/BDFMT with ZnCl₂ resulted in formation of unique coordination polymers and porous metal organic frameworks with photoluminescence sensitive to heating and (de/re)hydratation. The latter effect was exploited for security painting and anti-counterfeiting demonstration.