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Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation
Author(s) -
Zappimbulso Nicola,
Capozzi Maria Annunziata M.,
Porcheddu Andrea,
Farinola Gianluca M.,
Punzi Angela
Publication year - 2021
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202002763
Subject(s) - squaric acid , solvent , boiling , irradiation , condensation , chemistry , green chemistry , thermal decomposition , absorption (acoustics) , materials science , chemical engineering , organic chemistry , photochemistry , catalysis , reaction mechanism , physics , nuclear physics , engineering , composite material , thermodynamics
Squaraines and croconaines are organic dyes characterized by intense absorption in the visible or near‐infrared spectral regions with applications ranging from biology to material sciences. They are commonly synthesized by condensation reactions of oxocarbonic acids (squaric or croconic acid, respectively) with electron‐rich aromatic compounds in high‐boiling organic solvents. Here, a simple, cost‐effective, and environmentally benign process was developed for the synthesis of indolenine‐based squaraines and croconaines under solvent‐free conditions. Protocols based on conventional thermal heating, mechanochemical milling, and IR‐light activation were compared.