Studies on Monolayer Formation and Electron Transport in Au|LB|Au Junctions Containing 3d(4) Mn-III Metallosurfactants

Threenew metallosurfactants containing 3d(4) manganese(III)ions, namely, [Mn-III(LNO2-N2O2)-Cl(MeOH)](1), [Mn-III(L-N2O2)(H2O)-(MeOH)]Cl (2), and [Mn-III(L-N2O3)] (3), bound to three distinct phenylenediamine-bridgedphenolate-rich ligands were designed, deposited as Langmuir-Blodgettmonolayer films on gold electrodes, and probed for directional electrontransfer in Au|LB|Au junctions. All three Mn-III metallosurfactantspromote current rectification, and we compare the behavior of thesemetallosurfactants with that of our previously studied 3d(1) V O-IV, 3d(3) Cr-III, and 3d(5) Fe-III species in similar environments througha rigorous effort. Based on the analysis of electrochemical, spectroscopic,microscopic, and DFT results, we propose distinct mechanisms by whichelectronic configurations and ligand frameworks influence and modulatethe energy gap between the electrode Fermi levels and the molecularorbitals responsible for electron transport. Our previous work characterizeddistinct mechanisms, i.e., electron transport throughbelow-Fermi for (VO)-O-IV-based SOMOs and above-Fermi for Fe-III-based SOMOs and ligand-based HOMOs for the Cr-III species. These Mn-III species show electron transportsimilar to Fe-III; however, low current capacities suggestthat film quality is an important factor to be considered.

Automated summary

Three new metallosurfactants containing 3d(4) manganese(III) ions were designed and deposited as Langmuir-Blodgett monolayers on gold electrodes for directional electron transfer. All three Mn-III metallosurfactants exhibited current rectification, and their behavior was compared with other 3d metal species. Through rigorous analysis, distinct mechanisms were proposed for how electronic configurations and ligand frameworks influence electron transport. The Mn-III species showed similar electron transport to Fe-III, but with lower current capacities, indicating the importance of film quality.