Ballistic Transport of Vibrational Energy through an Amide Group Bridging Alkyl Chains

Abstract

Transport of vibrational energy via linear alkyl molecular chains can occur efficiently and with a high speed. This study addresses the question of how such transport is changed if an amide group is incorporated in the middle of such chain. A set of four compounds, Amn-4, was synthesized such that an amide group is connected to two alkyl chains. The alkyl chain on one side of the amide, featuring 4, 7, 11, or 15 CH2 units, is terminated by an azido group, while the alkyl chain on another side is of fixed length with four methylene groups terminated with a methyl ester group. The energy transport in Amn-4 in CD3CN solution, measured by relaxation-assisted two-dimensional infrared spectroscopy, was initiated and recorded using various combinations of tags and reporters, which included N3 and C═O stretching modes of the end groups and amide-I and amide-II modes at the amide. It was found that the transport initiated by the amide-I mode in the alkyl chain attached to C═O side of the amide proceeds with a cons...