Electronic structure of frontier states in an evaporated thin film of a highly amphoteric and polar molecule

Abstract

{4-[4,5-Bis(methylsulfanyl)-1,3-dithiol-2-ylidene]cyclohexa-2,5-dien-1-ylidene}malononitrile (BMDCM) is designed toward a highly amphoteric and polar molecule (HAPM). Its electron donating and accepting abilities in the solid state were examined from the measurements of its electronic structure using ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES): The threshold ionization energy I s th and electron affinity A s th in the solid state were determined to be 5.1 ± 0.1 5 and 3.5 ± 0.4 eV, respectively. These values turn out to be comparable to the corresponding values of typical donor or acceptor compounds, indicating high abilities in both electron donating and accepting nature of BMDCM. The origin of such a nature of BMDCM is discussed in terms of aromatic stabilization in its ionic states.