Abstract
A variety of fluorescence-active fluorinated pyrazolines 13–33 was synthesized in good yields through cyclocondensation reaction of propenones 1–9 with aryl hydrazines 10–12. Some of the synthesized compounds provided promising fluorescence properties with quantum yield (Φ) higher than that of quinine sulfate (standard reference). Quantitative structure–property relationship studies were undertaken supporting the exhibited fluorescence properties and estimating the parameters governing properties. Five synthesized fluorescence-active pyrazolines (13, 15, 18, 19 and 23) with variable Φ were selected for treating two types of paper sheets (Fabriano and Bible paper). These investigated fluorescence compounds, especially compounds 19 and 23, provide improvements in strength properties of paper sheets. Based on the observed performance they can be used as markers in security documents.
Highlights
Fluorescence-active compounds are important materials due to their potential application in various fields, such as medicine, 2018 The Authors
The absorption spectra of the synthesized pyrazolines 13–33 were determined in chloroform with constant concentration (4 mg l−1)
The effect of introducing different electronic donating (EDG) and withdrawing groups (EWG) in R, R’ and R’ groups of 1,3,5- triaryl-4,5-dihydro-1H-pyrazoline had a remarkable effect on the differences in both the position and intensity of absorption peaks
Summary
Fluorescence-active compounds are important materials due to their potential application in various fields, such as medicine, 2018 The Authors. 1,3,5-Triaryl-2-pyrazolines are important fluorescence-active heterocycles characterized by blue fluorescence with high quantum yield [9] These properties make them accessible for many applications including photoconductive and emitting materials [10], as well as brightening agents for synthetic fibres, plastics and paper [10,11,12]. In our previous work on the subject of fluorescence heterocyclic compounds for safety paper purposes, we reported the synthesis of 2-alkoxy-3-pyridinecarbonitrile derivatives, as well as heterocyclic compounds gathering the whole functional moieties responsible for fluorescence properties, via a variety of pyridine derivatives possessing both amino and alkoxy groups oriented o- and o positions of the pyridine nucleus and neighbouring to nitrile functions [3] The behaviour of these compounds in nanoparticle form as security markers for production of unfalsifiable documents by erasure technique (chemical and mechanical) was studied [20]. This study was carried out as a precursor for the forthcoming work on evaluating the paper resistance to erasure as safety value documents
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
