Solvent-Dependent Conformational Switching of N-Methyl-N,N'-diarylsquaramide.

N , N '-Diarylsquaramide and N , N '-dialkylsquaramide are conformationally stable linkers with extended (trans, trans) and folded (cis, cis) structures, respectively, independently of external conditions. Here, we show that N -monomethylated N , N '-diarylsquaramides generally take a (trans, cis) structure in the crystal but show a solvent-dependent conformational equilibrium in solution. In particular, the stable conformer of N -methyl- N , N '-bis(1-naphthyl)squaramide ( 1f ) changes depending upon the solvent. Thus, aromatic N -monomethylated squaramides could find application as components of environment-responsive molecular switches.