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

Abstract

In the present work, we report the vapochromic behaviour of PMMA films doped with small amounts of 1a:Zn fluorophore, a Zn 2+ 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.

Fluorescent Polystyrene Films for the Detection of Volatile Organic Compounds Using the Twisted Intramolecular Charge Transfer Mechanism

“…The emission intensity dropped by about 80% after 8 s of exposure. This extremely sensitive solvent dependence, never achieved previously by our research group [ 22 , 24 , 25 , 28 , 40 ], agrees well with the characteristics of JCBF. Notably, the progressive VOC adsorption and successive absorption by the polymer matrix triggers the reorganization energy of the JCBF excited transition state from the LE to the non-emissive TICT.…”

Fluorescent vapochromism in synthetic polymers

“…Another contribution of organometallic fluorophores was recently demonstrated by Platonova et al who reported the vapochromic behaviour of PMMA films doped with small amounts of a Zn adduct of the bisthienylethynylbipyridine ligand . The Zn(II) complex exhibited polarity‐dependent changes in fluorescence spectral properties when dissolved in solvents with different polarity index, indicating that its fluorescence states are of intramolecular charge transfer (ICT) character (Fig.…”

“…Emerging strategies for the colorimetric and specific detection of VOCs are based on fluorophores embedded in plastic materials or in fluorescent conjugated polymers . Notable is the fact that the optical behaviour of these polymer‐based VOC sensors is tunable by specific interactions between the polymer matrix and the fluorophore units.…”

Vapochromic polyketone films based on aggregation‐induced enhanced emission

“…In addition, pressing issues in global security are triggering the design of novel chromogenic compounds aimed at detecting environment changes with optical responses even more effective. For example, thermoplastic indicators containing fluorophore sensitive to viscosity changes have been used with success for the detection of VOCs . Notably, plastic films containing moderate amounts of the chromophoric probe (<0.1 wt%) display fluorescence variations upon the exposure to well‐interacting VOCs due to an induced plasticization of the continuous polymer phase .…”

“…For example, thermoplastic indicators containing fluorophore sensitive to viscosity changes have been used with success for the detection of VOCs. [3][4][5][6][7][8][9][10][11][12] Notably, plastic films containing moderate amounts of the chromophoric probe (<0.1 wt%) display fluorescence variations upon the exposure to well-interacting VOCs due to an induced plasticization of the continuous polymer phase. [3][4][5][6]9,13 Plasticization means also viscosity decreasing, thus allowing the dispersed fluorophores to aggregate together upon a certain concentration threshold, which in turn causes evident color changes.…”