TY - JOUR

T1 - Highly insulating alkane rings with destructive σ-interference

AU - Ye, Jingyao

AU - Al-Jobory, Alaa

AU - Zhang, Qian-Chong

AU - Cao, Wenqiang

AU - Alshebab, Abdullah

AU - Qu, Kai

AU - Alotaibi, Turki

AU - Chen, Hang

AU - Liu, Junyang

AU - Ismael, Ali

AU - Chen, Zhong-Ning

AU - Lambert, Colin

AU - Hong, Wenjing

PY - 2022/9/30

Y1 - 2022/9/30

N2 - Destructive quantum interference (DQI) provides a unique approach to controlling the leakage current in the OFF state of molecular devices. However, the DQI in π-conjugated molecular building blocks cannot exhibit ultralow conductance due to the existence of covalently bonded σ-transport channels. Thus, suppressing the σ-contribution via σ-DQI is essential for the fabrication of molecular junctions with high insulation and effective modulation of conductance in single-molecule junctions.Here, we demonstrate the existence of σ-DQI even in a simple series of CmCn ring molecules, with parallel chains of m and n alkyl units (where m, n=6, 8 or 10), by measuring their electrical conductance and Seebeck coefficients. Counterintuitively, the conductance of the symmetric CnCn rings is lower than that of the corresponding single chains (Cn), which is in contrast to theconductance superposition law in multi-channeled systems. Combined theoretical calculations reveal that the gauche conformation in a shorter chain fixed by another chain leads to the decreased conductance in alkyl rings, which originates from the phase-coherent tunneling and DQI in σ-conjugated systems. Our 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.

AB - Destructive quantum interference (DQI) provides a unique approach to controlling the leakage current in the OFF state of molecular devices. However, the DQI in π-conjugated molecular building blocks cannot exhibit ultralow conductance due to the existence of covalently bonded σ-transport channels. Thus, suppressing the σ-contribution via σ-DQI is essential for the fabrication of molecular junctions with high insulation and effective modulation of conductance in single-molecule junctions.Here, we demonstrate the existence of σ-DQI even in a simple series of CmCn ring molecules, with parallel chains of m and n alkyl units (where m, n=6, 8 or 10), by measuring their electrical conductance and Seebeck coefficients. Counterintuitively, the conductance of the symmetric CnCn rings is lower than that of the corresponding single chains (Cn), which is in contrast to theconductance superposition law in multi-channeled systems. Combined theoretical calculations reveal that the gauche conformation in a shorter chain fixed by another chain leads to the decreased conductance in alkyl rings, which originates from the phase-coherent tunneling and DQI in σ-conjugated systems. Our 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.

U2 - 10.1007/s11426-022-1341-y

DO - 10.1007/s11426-022-1341-y

M3 - Journal article

VL - 65

SP - 1822

EP - 1828

JO - science china chemistry

JF - science china chemistry

IS - 9

ER -