Investigation of the Excited-State Intermolecular Proton Transfer Mechanism in New ZnABPT Coordination Compound

Advancements in stimulus-responsive coordination compounds underscore their potential in various scientific domains. Among these, photochromism is notable due to its rapid and reversible color changes upon radiation exposure, often involving mechanisms such as excited-state proton transfer (ESPT), which necessitates short hydrogen bonds and planar atomic interactions. While ESPT has been investigated with other ligands, the luminescence properties of complexes with ABPT ligands remain insufficiently explored. Preliminary laboratory findings suggest ESPT in ABPT-containing complexes, which is of particular interest due to the triazole core's pharmacological relevance. This study investigates the ZnABPT coordination complex utilizing single-crystal neutron diffraction on the SXD to examine the proton transfer mechanism and the role of crystalline structure and hydrogen bonding under UV exposure. Preliminary X-ray diffraction confirmed the complex's triclinic structure, while powder X-ray analyses revealed unchanged diffraction patterns post-UV exposure, indicating preserved overall structure with minor atomic displacements. Spectral shifts upon exposure to acids and bases support the luminescent properties' dependence on proton transfer, with infrared analyses indicating transfer from the ABPT ligand to the nitrate counterion. Single-crystal neutron diffraction will be crucial for elucidating the proton transfer mechanism in these complexes.