Experimental and DFT studies on the vibrational and electronic spectra of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

Two-Dimensional WSe2/Organic Acceptor Hybrid Nonvolatile Memory Devices Based on Interface Charge Trapping

Two-dimensional (2D) materials, with atomic thickness and unique electronic structure, hold great potentials in electronic device applications. Charge transfer at the interface of 2D materials further provides a versatile platform for applications in electronics. Here, we report nonvolatile memory devices based on interface charge trapping between 2D WSe₂ and organic electron acceptors. The 2D WSe₂-organic acceptor hybrid structure exhibits a high storage performance, such as large gate memory windows, high on/off ratios (>10³), and long retention time (>1000 s). Further analysis revealed that organic acceptors with a stronger electron affinity (i.e., higher redox potential) have a larger electron-trapping ability and hence a better memory performance.

Spin-coupling in dimers of 2,3-dicyano-5,6-dichlorosemiquinone radical anions in the crystalline state

A crystal engineering approach is used to stabilize a radical anion in the crystalline state and to modulate the separation distance within π-stacks of anion radicals. Alkali metal salts of 2,3-dicyano-5,6-dichlorosemiquinone (C8Cl2N2O2, DDQ∙- radical anions were prepared and their crystal structures determined: LiDDQ·2H2O·(CH3)2CO, RbDDQ·2H2O and CsDDQ·2H2O. In these structures, stacked dimers of radical anions are formed within π-stacked columns. Within the stacked dimers, interplanar separation distances are significantly shorter than the sum of the van der Waals radii for two C atoms; the shortest is 2.812 Å for the Li salt and the longest is 2.925 Å for the Cs salt. Diamagnetic character, observed by electron paramagnetic resonance spectroscopy, indicates spin-coupling of the unpaired electrons within the radical anion dimer. The electron-rich cyano substituents on DDQ∙- influence the electron redistribution within the ring skeleton. The crystalline compounds are also characterized by IR spectroscopy, complemented by quantum-chemical calculations based on both isolated and periodic models.