Synthesis, optical spectroscopy and laser potential of pyrylium tosylates

Abstract

Safe and inexpensive methods for synthesis of a series of four substituted 2,4,6-triphenylyrylium tosylate salts with different substituents are reported. The synthesis methods use ptoluenesulfonic acid monohydrate instead of conventional acid catalysts including perchloric acid or boron trifluoride diethyl etherate that pose explosion danger and difficult storage problems, respectively. The chemical structures of these salts were established using FTIR, 1 H and 13 C NMR spectroscopic techniques and elemental analysis. Thermogravimetric analysis (TGA) showed that these salts have good thermal stability, and differential scanning calorimetry (DSC) analysis showed that they have lower melting transitions than the corresponding tetrafluoroborate and perchlorate salts. Solutions of the salts in organic solvents (such as acetonitrile and methanol) absorbed strongly in the blue-near-ultraviolet spectral range and emitted efficiently in the blue-green spectral range depending on the substituents in 2-and 6positions of phenyl groups. The fluorescence quantum yields of the salts ranged from 0.33 to 0.56. Under intense ultrashort laser pumping, an acetonitrile solution of the salt, 2,4,6triphenylpyrylium tosylate, the salt with the highest quantum yield, demonstrated stimulated emission and laser action with only nominal feedback.

Flavylium Salts: A Blooming Core for Bioinspired Ionic Liquid Crystals

“…[7,8] They have been successfully utilizedf or electron-transfer reactions, [9] (photo)organocatalysis, [10][11][12] whitelight fluorophores [13] and laser dyes. [14] Liquid crystalline oxoniums alts reported in the literature (Scheme 1) are solelyb ased on di-or triphenyl pyrylium cations 1, [15] 1,4-disubstituted benzenesf unctionalized with two pyrylium units 2 [16] and condensed xanthyliumd erivativeB NAX 3. [17] We founditq uite surprising that ILCs based on the probably most prominent organic oxonium salt, the flavylium cation A-Fla-B neverh as been reported to the best of our knowledge.…”

“…Such pyrylium derivatives, for example, 2,4,6‐triphenylpyrylium salts, show strong fluorescence and anion–π interactions . They have been successfully utilized for electron‐transfer reactions, (photo)organocatalysis, white‐light fluorophores and laser dyes …”

Synthesis of Triarylpyrylium Salts Using a Mild, Eco-friendly Route

“…Letter / Cluster / New Tools Template for SYNLETT Thieme and even explosive acid catalysts with toluenesulfonic acid which is non-oxidizing and offers safer handling as well as long shelf-life. , 20 However, this method like other current syntheses requires purification with substantial volumes of organic solvents including diethyl ether and chlorinated solvents.…”

“…handling as well as long shelf-life. 22 However, this method like other current syntheses requires purification with substantial volumes of organic solvents including diethyl ether and chlorinated solvents. Copious use of these nongreen solvents is unattractive since pyrylium salts are largely applied as greener, cost-effective alternatives to other chromophores.…”

Quantitative insights into noncovalent interactions involving halogen and tetrel bonds in 2,4,6-trimethylpyrylium tetrafluoroborate

“…In recent years, pyrylium salts have received considerable attention in the research community due to their unique absorption, fluorescence and electrontransfer properties. They have been widely applied as light emitters (Koh et al, 2018), photocatalysts (Hola & Ortyl, 2021) and sensitizers (Miranda & Garcia, 1994). Furthermore, pyrylium salts are excellent candidates to explore crystal structure, the close packing of molecules and the strength and nature of noncovalent interactions, as these constitute an O atom, with a formal positive charge, and a negatively charged anion in the crystal structure.…”