2-([1,1′-Biphenyl]-4-yl)-2,3,4,5-tetrahydro-1H-benzo[c]azepin-1-one

The previously unreported seven-membered-ring benzanilide derivative, 2-([1,1′-biphenyl]-4-yl)-2,3,4,5-tetrahydro-1H-benzo[c]azepin-1-one (1), was synthesized and structurally characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. The crystal structures of 1 and the known six-membered-ring analogue (2) were compared with that of the corresponding five-membered-ring analogue (3). Increasing ring size was found to induce steric distortions around the amide moiety, resulting in systematic changes in the π-conjugation with the adjacent phenyl groups. This study establishes a structural basis for controlling the electronic properties of ring-fixed benzanilides through ring-size engineering.