Amino-substituted diazocines as pincer-type photochromic switches

Azobenzenes are robust, reliable, and easy to synthesize photochromic switches. However, their high conformational flexibility is a disadvantage in machine-like applications. The almost free rotation of the phenyl groups can be restricted by bridging two ortho positions with a CH2CH2 group, as realized in the dihydrodibenzo diazocine framework. We present the synthesis and properties of 3,3'-amino- and 3,3'-acetamido substituted diazocines. Upon irradiation with light of 405 and 530 nm they isomerize from the cis to the trans configuration and back, and thereby perform a pincer-like motion. In the thermodynamically more stable cis isomer the lone pairs of the amino nitrogen atoms point towards each other, and in the trans form they point in opposite directions. The distance between the amino nitrogen atoms changes between 8 angstrom (cis) and 11 angstrom (trans isomer).