Spin distribution and conductance variations in phenoxyl radical single-molecule junctions

Abstract This study explores the conductance characteristics and spin distributions in single-molecule junctions using phenoxyl radicals linked to bis(methylthio)triphenylene cores. Through a combination of UV-vis spectrophotometry, electron spin resonance (ESR) spectroscopy, and density functional theory (DFT) calculations, we examine how the structural modifications in phenoxyl radicals influence electron delocalization and molecular conductance. Initial tests confirmed the presence of radicals, and subsequent DFT analyses demonstrated significant shifts in electron spin densities affecting the conductive pathways. This study utilized scanning tunneling microscopy-break junction (STM-BJ) techniques to further elucidate the electronic properties of these radical-injected systems, highlighting the critical role of molecular architecture in defining conductive properties. Results indicate that the addition of phenyl rings leads to varying degrees of electron delocalization and corresponding changes in conductance, with a noted decrease in the HOMO-LUMO energy gap across different structures.