Effect of the substituted location on luminescent behaviors with Ambroxol moieties: Synthesis, crystal structure and Hirshfeld surface

Abstract

To further exploit the new materials, a set of new salts containing ambroxol and hydroxyl aromatic carboxylate moieties, namely, [HAXE]+B– (B = MSA (1), 23A (2) and 26A (3)) [AXE = 4-((2-amino-3,5-dibromobenzyl)amino) cyclohexan-1-ol, MSA = 5-methyl salicylic acid, 23A = 2‑hydroxy-3-naphthoic acid, and 26A = 2‑hydroxy-6-naphthoic acid], were obtained by the reaction of AXE and a set of aromatic carboxylic acid, respectively. The emission maxima can be found at 386, 445, 523 and 452 nm for AXE and its compounds 1–3 in the solid state at room temperature, respectively. Compared with the free AXE, the emission maxima of compounds 1–3 are obviously red-shifted about 59, 137 and 66 nm, respectively, revealing that the intermolecular packing interactions affect the emission maxima. Compounds 1–4 were structurally characterized by X–ray single crystal diffraction and FT-IR. Single crystal X-ray diffraction analysis shows that there exist π⋯π packing interactions and a set of hydrogen bonds. The shortest distances of π⋯π stacking interactions are 3.693(6) and 3.86(2) Å in compounds 2 and 3, respectively. The Hirshfeld surface analysis reveals that the order of the C···H/H···C close contacts coincides with that of the luminescent maxima. Meanwhile, the intermolecular contacts of O···H/H···O and N···H/H···N can quantitatively account for the melting points of these compounds. Additionally, the thermal properties of compounds 1–3 were estimated in detail.