Solvent-Dependent Core-Modified Rubyrin Self-Assembly at Liquid/Solid Interfaces

Scanning tunneling microscopy (STM) was utilized to disclose four novel core-modified rubyrin self-assembly behaviors on the highly-oriented pyrolytic graphite (HOPG) surface, of which N2S4-OR(1)/N2Se4-OR(2) had no phenanthrene pyrrole ring and N2S4-OR(3)/N2Se4-OR(4) had phenanthrene-fused pyrrole rings and meso-aryl substituents. It was discovered that the core-modified rubyrin could self-assemble into either face-on or edge-on monolayer structures selectively at the liquid/HOPG interface in different solvents. There was an obvious solventdependent self-assembly for N2S4-OR(3)/N2Se4-OR(4), which adopted an edge-on and face-on structure in 1-phenyloctane and 1-heptanoic acid solvents, respectively, whereas N2S4-OR(1)/ N2Se4-OR(2) showed no obvious difference in the assembly structure, which both adopted a face-on structure in the two solvents. Density functional theory (DFT) calculations were also utilized to reveal the relevant self-assembly mechanisms. This study shows a typical solvent effect regulating core-modified rubyrin self-assembly, which is essential for porphyrin-based functional devices' design and manufacture.