Generation of chirality in 4,4′-azopyridine by co-crystallization with optically active dicarboxylic acids

Abstract

The co-crystals of anti-4,4′-azopyridine apy with optically active 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid 1 and trans-1,2-cyclohexanedicarboxylic acid 2 were prepared and their solid state CD spectra were measured. The positive Cotton effect sign, corresponding to the lowest energy n–π ∗ transition, was correlated with the M helicity of the twisted Ar–N N chromophore. The absolute sense of the twist of the guest apy molecule was deduced from the X-ray structures of the ( S,S)- 1· apy and ( S,S)- 2· apy complexes.