Insight into the structural transformation of tetraphenylethylene acids at liquid–solid interface induced by linear amino-functionalized triazine derivatives and annealing treatment

The interaction between organic photoelectric molecules leads to the formation of a certain aggregation structure, which plays a pivotal role in the charge transport at the intermolecular interface. In view of this, we investigated the mechanism and law of intermolecular interaction by detecting the self-assembled behaviors between organic photoelectric molecules at the interface by scanning tunneling microscopy (STM). In this work, the structural transformations of tetraphenylethylene acids (H₄ETTCs) on graphite surface induced by temperature and triazine derivatives (zcy-19, zcy-27, and zcy-38 molecules) were studied by STM technology and density functional theory (DFT) calculations. At room temperature, zcy-19 and H₄ETTC molecules formed a small range of ordered co-assembled nanostructure, while for zcy-27 or zcy-38 molecules, no co-assembled nanostructures were observed and only their own self-assembled structures existed on graphite surface, individually. In the thermal annealing trials, the original co-assembled H₄ETTC/zcy-19 structure disappeared, and only zcy-19 and H₄ETTC self-assembled in separate domains. Nevertheless, new well-ordered H₄ETTC/zcy-27 or H₄ETTC/zcy-38 co-assembled structures appeared at different annealing temperatures, respectively. Combined with DFT calculations, we further analyzed the mechanism of such structural transformations by triazine derivatives and temperature. Results reveal that triazine derivatives could interact with H₄ETTC by N–H···O and O–H···N hydrogen bondings, and whether temperature or zcy series compounds could achieve successful regulation of H₄ETTC assembly behavior is closely associated with the conjugated skeleton length of zcy series compounds.