image: The blue star signs of saturated alkane rings show exponentially decay conductance and the decay trend is similar to saturated alkane chains, which is presented by orange squares. The alkane rings are more insulating than alkane chains when compare the identical molecular length. view more
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This study is led by Dr. Junyang Liu and Prof. Wenjing Hong from Xiamen University. The molecular synthesis is done by Prof. Zhong-Ning Chen (State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences) and the theoretical calculation is processed by Dr. Ali Ismael and Prof. Colin Lambert (Lancaster University).
Destructive quantum interference (DQI) provides a possibility to significantly suppress the leakage current in the OFF state of molecular devices. However, the DQI in π-conjugated molecules cannot exhibit ultralow conductance due to the existence of covalently bonded σ-transport channels. Thus, suppressing the σ-contribution via σ-DQI is essential. Here researchers proposed the symmetric alkane ring CnCn (n = 6, 8 or 10) molecules, which were synthesized, and the corresponding electrical properties were measured. Comparing the results with the alkane chain Cn (n = 6, 8 or 10) molecules, the alkane rings show lower conductance which contradicts the conductance superposition law in multi-channeled systems. Combined theoretical calculations reveal that the gauche conformation in a shorter chain fixed by another chain leads to decreased conductance in alkyl rings, which originates from the phase-coherent tunneling and DQI in σ-conjugated systems. Their finding suggests that through appropriate conformation locking by cyclization, the covalent alkane system can exhibit DQI, which offers strategies for future designs of molecular electronic devices and materials.
Journal
Science China Chemistry