The luminescent behaviors based on Ambroxol: Syntheses, crystal structure and Hirshfeld surface analysis

Two new salts containing Ambroxol, namely, [HAX]+ S–·nCH3OH (S = HCOO (n = 0) (1) and CH3COO (n = 1) (2)) [AX = 4-((2-amino-3,5-dibromobenzyl)amino)cyclohexan-1-ol], were obtained by the reaction of AX and two organic acids, respectively. The AX crystals were obtained through the solvent evaporation method. The emission maxima can be found at 386, 411 and 372 nm for AX, 1 and 2 in the solid state at room temperature, respectively. Compared with the free AX, the emission maxima of compounds 1 and 2 are obviously red/blue-shifted about 14 and 25 nm for 1 and 2, suggesting that the emission maxima are proportional to the intermolecular interactions. Compounds AX, 1 and 2 were structurally characterized by single crystal X–ray diffraction, FT-IR and powder X-ray diffraction. Single crystal X-ray diffraction analysis results show that there exist a set of hydrogen bonds of N/O-H···N/O and N-H···Br. The Hirshfeld surface analysis results reveal that the order of the H···H close contacts is consistent with that of the luminescent emission maxima. Meanwhile, the O···H/H···O and N···H/H···N close contacts are responsible for the melting points of these compounds. Additionally, the thermal stability of compounds 1 and 2 were investigated in detail.