Zn(II)-bisthienylethynylbipyridine complex: Preparation, characterization and vapochromic behaviour in polymer films

• Bisthienylethynylbipyridines were easily prepared using a rapid and convenient procedure.
• Zinc bisthienylethynylbipyridines exhibited polarity-dependent fluorescence in solution.
• The emission of Zinc bisthienylethynylbipyridines was studied also in the PMMA matrix.
• The blend films exhibited strong variation of the emission when exposed to dichloromethane.
• The vapochromism was affected by solvent composition and determined by fluorescence.

In the present work, we report the vapochromic behaviour of PMMA films doped with small amounts of 1a:Zn fluorophore, a Zn2+ adduct of the bisthienylethynylbipyridine ligand.1a:Zn exhibited polarity-dependent changes in the fluorescence spectral properties when dissolved in solvents with different polarity index, indicating that its fluorescence states are of intramolecular charge transfer character. When 1a:Zn was dispersed in the PMMA matrix, its emission resulted barely influenced by the polymer environment. By contrast, 1a:Zn/PMMA films showed a significant variation of its emission with a 40 nm red-shift when exposed to a saturated atmosphere of dichloromethane. This vapochromic behaviour was much less evident when progressive amounts of methanol were added to dichloromethane due to both lower vapour pressure and limited interaction of the former with PMMA. The experiments revealed also that the rate constants associated with the vapochromic behaviour were affected by solvent composition and easily determined by luminescent experiments.

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