Verification and Temperature-Dependent Rectification by HBQ, the Smallest Unimolecular Donor-Acceptor Rectifier

Yingmei Han; Li Jiang; Joseph E Meany; Yulong Wang; Stephen A Woski; Marcus S Johnson; Christian A Nijhuis; Robert M Metzger

doi:10.1021/acsomega.2c01182

Verification and Temperature-Dependent Rectification by HBQ, the Smallest Unimolecular Donor-Acceptor Rectifier

ACS Omega. 2022 Aug 10;7(33):28790-28796. doi: 10.1021/acsomega.2c01182. eCollection 2022 Aug 23.

Authors

Yingmei Han¹, Li Jiang¹, Joseph E Meany^{2

3}, Yulong Wang¹, Stephen A Woski², Marcus S Johnson², Christian A Nijhuis^{1

4}, Robert M Metzger²

Affiliations

¹ Department of Chemistry, and Centre for Advanced 2D Materials, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
² Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35487-0336, United States.
³ Savannah River National Laboratory, Aiken, South Carolina 29808, United States.
⁴ Hybrid Materials for Opto-Electronics Group, Department of Molecules and Materials, MESA+ Institute for Nanotechnology and Center for Brain-Inspired Nano Systems, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.

Abstract

Five years ago, rectification of electrical current was found in 4'-bromo-3,4-dicyano-2',5'-dimethoxy-[1,1'-biphenyl]-2,5-dione (1), a hemibiquinone (which we will call either 1 or HBQ) that has a very small working length (1.1 nm). Monolayers of HBQ on Au^TS were detected by "nanodozing" atomic force microscopy (AFM) and were contacted with two types of top electrodes: either cold Au or eutectic Ga-In. Here, we describe cyclic voltammetry of a self-assembled monolayer (SAM) of HBQ and its orientation on a gold substrate with angle-resolved X-ray photoelectron spectroscopy. New measurements of its rectification as a monolayer as a function of bias range and temperature confirm and prove that HBQ is truly the smallest donor-acceptor rectifier and provide some insight into the mechanism of rectification.