Eutectic Media Open a Synthetic Route to Oligocitrazinic Acid Fluorophores of Purple Hue

Abstract

Under isochoric and solvent‐free conditions, the reaction between ammonium formate and citric acid results in a deeply purple reaction product with fluorescent properties. This brings this reaction in the realm of bio‐based fluorophores and bottom‐up carbon nanodots from citric acid. The reaction conditions are optimized in terms of UV–vis spectroscopic properties and, subsequently, the main reaction product is separated. While the structural analysis does not give any indication for carbon nanodots in a general sense, it points towards the formation of molecular fluorophores that consist of oligomerized citrazinic acid derivatives. Furthermore, EPR spectroscopy reveals the presence of stable free radicals in the product. We hypothesize that such open‐shell structures may play a general role in molecular fluorophores from citric acid and are not yet sufficiently explored. Therefore, we believe that analysis of these newly discovered fluorophores may contribute to a better understanding of the properties of fluorophores and CND from citric acid in general.

Halide Complexes of 5,6‐Dicyano‐2,1,3‐Benzoselenadiazole with 1 : 4 Stoichiometry: Cooperativity between Chalcogen and Hydrogen Bonding

“…Due to this, the hole-based SBIs are highly directional. [1,35,[51][52][53][54][55][56][57][58][59][60][61][62] In SBIs with anions σ-holes are mainly involved. [35,59,[63][64][65][66] Orbital contribution into ChB aligns with the well-established Alcock model [1] as an overlap of guest anion's unshared n-MO with σ*-MO of the chalcogen-containing host accompanied by donation of the electron density (charge transfer-CT) from the guest onto the host, i. e., by their negative hyperconjugation.…”