Steric and Conformational Effects in Molecular Junctions.

Molecular junctions, which comprise molecules bridging two electrodes, have emerged as valuable tools for investigating the conducting properties of molecules. Although electronic effects have been extensively investigated in molecular junctions, steric and conformational effects remain underexplored. Substituents, such as long alkyl chains, are frequently introduced into molecular backbones to facilitate synthesis or improve solubility. However, their effects on conductance and junction structure are frequently overlooked. Most junction studies have focused on rigid rod molecules; however, the conductance of flexible molecules can be modulated through conformational changes. The active harnessing of this structural flexibility enables effective conductance control. This review article discusses steric and conformational effects in molecular junctions, in terms of substituent effects, conformational dynamics, and mechanical manipulation, to elucidate their roles in molecular conductance.