Striking Effect of Intra- versus Intermolecular Hydrogen Bonding on Zwitterions: Physical and Electronic Properties

We report the synthesis, characterization,
and application of novel
zwitterions. The zwitterionic structures consist of a positively charged
cyanine and negatively charged dienolate moieties, confirmed by experimental
observations and theoretical calculations. Single crystal X-ray studies
revealed that BIT-(NPh)2 is a
coplanar molecule that forms 1-D chains via π–π
interactions. In contrast, BIT-(NHexyl)2 is a twisted molecule with a dihedral angle of 78° between
the charged planes. In charge transport studies, thin films of the
flat zwitterion show semiconducting properties, with a hole mobility
of 2.1 × 10–4 cm2 V–1 s–1 while the twisted zwitterion is a high resistivity
insulator.

本工作报道了新型两性离子（zwitterions）的合成、表征与应用。该类两性离子的结构由带正电荷的花菁（cyanine）基团与带负电荷的二烯醇负离子（dienolate）基团构成，这一结论经实验观测与理论计算得以证实。单晶X射线研究表明，BIT-(NPh)2为共平面分子，可通过π-π相互作用形成一维（1-D）链状结构。与之相反，BIT-(NHexyl)2为扭曲型分子，其带电平面间的二面角为78°。在电荷传输研究中，平面型两性离子的薄膜表现出半导体特性，其空穴迁移率为2.1 × 10⁻⁴ cm²·V⁻¹·s⁻¹；而扭曲型两性离子则为高电阻率绝缘体。