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A series of carbazole-based diphenyl maleimide dyes with different N-substituent were synthesized through an Ullmann reaction in high yields. The dyes exhibit an intense emission in the solid state for their twisted conformation fixed by weak intermolecular interactions, resulting in the hindrance of the internal rotations. Their solid-stated emission wavelength and intensity are sensitive to external stimuli (like heat, pressure and vapor), due to a crystal-to-crystal or crystal-to-amorphous phase transition. Based on the multi-stimuli-responsive fluorescence properties of the N-benzyl analogue, two kinds of applications were explored. One is rewritable data recording processes including solvent writing and vapor writing. The other is sensing for low hydrostatic pressure (0–25 MPa). Interestingly, nanoparticles of the dyes formed in aqueous solution could effectively detect explosive and pH changes. A 15 ppm concentration of picric acid quenched the fluorescence of the N-methyl analogue with the detectable limit calculated to be 0.13 ppm. The N-methyl analogue also showed a different emission color and intensity over the pH range 12–14, which originated from the hydrolysis of the dye molecules in the strongly basic solution.

Luminescent materials with aggregation-induced emission (AIE) have attracted extensive attentions for their strong emission in aggregated states. Although all kinds of AIE luminogens have been recently developed, it is difficult to realize full-color AIE which is popular for the various applications in optoelectronic fields. Herein, a class of diphenylfumaronitrile core-based dyes emitting in a wide region from near ultraviolet (382 nm) to near-infrared (682 nm) have been synthesized and well characterized. It is found that the emission wavelength of the dyes severely depends on the peripheral substituent, including electron-withdrawing trifluoromethyl (1), methyl (2), electron-pushing methoxyl (3), and bulky aromatic amine (7–9), and that the substituting location imposes great effect on the emission intensity of multiple-substituted dyes (4–6). Compound 4 with two methyl substituting at 3,4-position gives a ultrahigh quantum yield of 93% for unique packing structure. 1–3 and 7 can be used in explosive detecting and data storage for their emission sensitive to picric acid and external stimuli, respectively. When 4 and 8 applied in white-light-emitting diodes (WLEDs), a pure white emission can be obtained with 90 of CRI and (0.32, 0.32) of CIE.

A series of diarylmaleimide derivatives and polymers based on amide group were designed and synthesized to detect anions selectively and sensitively. Three bisindolylmaleimide derivatives (FAM-p, FAM-m and FAM-o) employing trifluoroacetamide as receptor exhibited strong fluorescent quenching upon fluoride and cyanide. Trifluoroacetamide receptor was replaced by acetamide to obtain other two derivatives (AM-p and AM-o) which showed higher selectivity than FAMs with sensing for only fluoride. The diarylmaleimide derivatives were introduced into the backbone of polyfluorene by Suzuki reaction to prepare polymer PFAM and PAM with same sensing selectivity for anions as FAM and AM, respectively. PFAM and PAM were found to be ratiometric fluorescence sensors for a fluorescence resonance energy transfer (FRET) from fluorene segments to diphenylmaleimide units. The experimental and DFT/TDDFT calculation results demonstrated that the interaction mechanism of FAMs with F− and CN− was hydrogen bond interaction and nucleophilic addition reaction, respectively.