Molecular electronics is the concept of using molecules as the basic building blocks of electronic components. Molecules can show conducting, rectifying or insulating behavior in these components and therefore considered as complementary to solid state electronics. We are interested in developing metallosurfactants as molecular rectifiers which allows directional electron mobility. This is important in converting alternating current to direct current. We use the Langmuir-Blodgett technique to deposit ordered monolayers of metallosurfactants on electrodes to study their rectifying properties. The rectification mechanism depends on the energy compatibility between the frontier molecular orbitals of the complex and the Fermi energy levels of the electrode. Therefore, our approach is to modulate this energy gap by introducing electron donor and acceptor groups in the ligand system of the metallosurfactants. We hypothesize that molecular rectification will be attained in these asymmetric metal complexes with ligands having alternating donor/acceptor (push/pull) properties. This research project involves synthesis and characterization of heteroleptic polypyridine based Ru(II) complexes, where (octadecyloxy)benzene substituted terpyridine ligand acts as the donor and substituted phenanthroline or terpyridine ligands acts as the acceptor of the complex. The redox properties of asymmetric [(terpyD)RuII(terpyA)]2+ and [(terpyD)RuII(phenA)Cl]2+ surfactants indicate that the metal oxidation occur at ca. 0.86-0.87 V and 0.4-0.3 V respectively. In the cathodic region of the cyclic voltammogram, the complexes with electron withdrawing nitro groups shows the lowest reduction potential at ca.-1.0 and-1.3 V due to nitro group reduction. However, complexes with unsubstituted terpyridine and phenanthroline ligands show considerably higher reduction potentials at ca. -1.6 and -2.4 V range. These redox potentials demonstrate that the HOMO and LUMO energy levels of these complexes can be modulated by varying the electron accepting substituent in the ligand framework. Langmuir-Blodgett studies indicate these metallosurfactants form ordered, stable monolayers at the air/water interface. Preliminary Current-voltage studies shows that [(terpyD)RuII(phenNO2)Cl]2+ complex acts as a rectifier with a good rectification ratio. This research project allows us to evaluate a new class of asymmetric rectifier that depend on push/pull ligands to generate directional electron transport.

Evaluation of the effect of dissimilar push/pull ligands in octahedral metallosurfactants in the modulation of the LUMO/Fermi gap required for rectification

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.