Hydrazine-Modified Topology-Dependent Conductivity of Cyclic NDI as a Molecular Circuit

Significant conductance enhancement can be achieved by topology
modification of n-type semiconducting naphthalenediimide (NDI) as
a molecular circuit. Hydrazine not only reduces electron-deficient
NDI to NDI•–radical anions but also modifies
the topology by selectively replacing the amino acid methyl esters
from NDI 1 and forms a cyclic NDI nanorim. On treatment
with hydrazine, the NDI 1 emission band at 525 nm gradually
disappears, and a new band appears at 607 nm, presumably due to NDI
oligomer formation. Eventually, a shiny black, almost insoluble precipitate
of the NDI nanorim appeared. The cyclic NDI nanorim was characterized
by powder X-ray diffraction, high-resolution mass spectrometry, Fourier
transform infrared, and 13C CP-MAS NMR spectroscopy. Cyclic
voltammetry (CV) of NDI 1 possesses two sequential one-electron
cathodic waves at −0.4661 and −0.9456 V versus Ag/Ag+ due to NDI•– and NDI2– formation. However, CV of the NDI nanorim reveals four distinct
reversible one-electron waves due to electronic communication between
the four NDI redox centers within the nanorim. The I–V measurements show sevenfold conductance
enhancements by topology modification from linear NDI to a nanorim.