Solid state synthesis of novel charge transfer complex and studies of its crystal structure and optical properties

Forecast of Phase Diagram for the Synthesis of a Complex for the Detection of Cr6+ Ions

A new organic complex (ANNBA) was synthesized using the solvent-free, solid-state reaction involving anthranilamide (AN)-m-nitrobenzoic acid (NBA). The established phase diagram specifies the formation of a complex in a 1:1 stoichiometric ratio which melts congruently at 142 °C. The diagram also infers the formation of two eutectics, E₁ and E₂, on either side of the complex with their respective melting at 118 and 106 °C. The stability and novelty of the synthesized complex was confirmed by differential scanning calorimetry, powder X-ray diffraction, and spectroscopic FTIR, ¹H, and ¹³C NMR studies. The significant thermodynamic parameters such as the heat of mixing, the entropy of fusion, the roughness parameter, the interfacial energy, and excess thermodynamic functions have been studied. The novel complex (ANNBA) material displayed intense fluorescent emission as compared to the parent and the other well-known fluorescent organic material "pyrene." The influence of solvent's polarity on the absorption and emission of the complex has been studied in different solvents. Herein, we have displayed remarkable affinity of the complex toward hexavalent chromium ions in water, affecting its fluorescent property. We have deployed the synthesized complex as a turn-off fluorescent sensor to detect the most hazardous hexavalent chromium ions in water for the first time.