Drug Ambroxol-based luminescent materials with sulfonate group: Synthesis, crystal structure and Hirshfeld surface analysis

Abstract

Two new salts with ambroxol moieties, namely, n[HAX]+ nRT– H2O (RT ​= ​MBS (n ​= ​2, 1) and SBS (n ​= ​1, 2)) [AX ​= ​4-((2-amino-3,5-dibromobenzyl)amino) cyclohexan-1-ol, MBS ​= ​p-toluenesulfonic acid, SBS ​= ​sulfosalicylic acid], which were obtained through the mixture of AX and two phenyl sulfonic acid, respectively. The emission peaks located at 526 and 471 ​nm can be observed for compounds 1 and 2 in the solid state at room temperature, respectively. Compared with the AX itself, the red-shifted values can be observed to be 140 and 85 ​nm for compounds 1 and 2, respectively, revealing that the luminescent maxima are proportional to the intermolecular stacking distances. The decay lifetimes of AX, 1 and 2 can be found to be 0.643, 0.671 and 0.589 ns, respectively. Additionally, the quantum yields of 14.7%, 1.2% and 37.1%, respectively. Compounds 1 and 2 were structurally characterized by X–ray single crystal diffraction, EA, UV–Vis and FT-IR spectra. Single crystal X-ray diffraction reveals that there exists an order of packing distances, which is in a good agreement with that of luminescent maxima. The results calculated by Hirshfeld surface show that the close contacts of C⋯H/H⋯C can be responsible for the luminescent behaviors. The O⋯H/H⋯O close contacts can account for the melting points of compounds. Additionally, the thermal properties for compounds 1 and 2 have been discussed in detail.