Trimethylamine sorption into thin layers of fluoroalkyloxy and alkyloxy substituted phthalocyanines: Optical detection and DFT calculations

• Films of phthalocyanines with nonfluorinated and fluorinated substituents were studied.
• Layers were used to detect trimethylamine using total internal reflection ellipsometry.
• Phthalocyanine with fluorinated substituents demonstrates the higher detection limit.
• Chemical binding with analyte was described by DFT calculations.

Octa-substituted zinc(II) phthalocyanines with nonfluorinated (ZnPc1) and fluorinated (ZnPc2) n-propanol in peripheral positions have been prepared as thin films by spin coating and examined for their potential as an optical membrane to detect trimethylamine. In this work, the method of spectroscopic ellipsometry in total internal reflection configuration has been used as the optical transduction method to study the interaction between trimethylamine and the ZnPc spun films. ZnPc2 has exhibited larger changes in the film's optical parameters compared to ZnPc1 with detection limit of 20 ppm of trimethylamine. The possible structure of the analyte/ZnPc complexes and their bond formation energies have been further analyzed using quantum chemical calculations in order to explain the different sensor responses of octa-substituted zinc(II) phthalocyanines with nonfluorinated and fluorinated substituents.