chloroform in the presence of the corresponding optically inactive carboxylic acid dimer or optically active amidine dimer linked by a trans-azobenzene unit as the template, respectively. The cis-azobenzene-linked carboxylic acid template markedly slowed the monomer conversions, and hence a reversiblephotocontrolled dimerization was achieved by light-induced cis–trans isomerization upon alternative
The dimerization of carboxylic acid derivatives bearing an amino or a formyl group at one end was significantly enhanced in benzene in the presence of an optically active amidine dimer to afford a complementary double helix stabilized with salt bridges.