Mechanochromic and vapochromic fluorescence of a bulky π‐system: Alkyl chain‐length effects, triplex emission, and differential sensing of aniline vapors

• Published in: Journal of the Chinese Chemical Society (Taipei) Vol. 67; no. 11; pp. 1957 - 1970
• Main Authors: Lee, Chin‐Han, Hsu, Li‐Yun, Lien, Chen‐Yu, Huang, Pei‐Yu, Yang, Jye‐Shane
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley‐VCH Verlag GmbH & Co. KGaA 01.11.2020; Wiley Subscription Services, Inc
• Subjects: Aniline; Anthracene; Chains; Fluorescence; Grinding; Homology; mechanochromism; Mechanoluminescence; sensors; Thermogravimetric analysis; vapochromism
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.202000080

The interplay of mechanical grinding and aniline vapor fuming on the fluorescence of the pentiptycene‐anthracene‐pentiptycene π‐conjugated molecules PAP‐Cn, where n is 4, 8, 12, or 16 and refers to the number of carbon atom in the terminal alkyl chains, in solid films are reported. The differences and similarities among the four homologs have led to a conclusion of the formation of an emissive triplex state for the ground and fumed films. Thermogravimetric analysis reveals the guest‐host molar ratio and the retention ability of the aniline on the various types of films. A stepwise protocol of fuming‐grinding‐annealing is developed for fluorimetric differential sensing of eight substituted aniline vapors with a single probe of PAP‐C8. The role of the bulky pentiptycene groups in the observed fluorescence properties is also discussed. The bulky π‐system PAP‐C8 and its alkyl‐chain homologs display synergistic fluorescence color responses to mechanical grinding and aniline vapor fuming as a result of both prolonged aniline guest trapping and forming triplexes in the solid‐state. A fuming‐grinding‐annealing protocol that creates a sensor array for fluorimetric differential sensing of eight substituted aniline vapors with a single probe of PAP‐C8 is also demonstrated.