A Molecular Leverage for Helicity Control and Helix Inversion

The helical tetranuclear complex [LZn3La(OAc)3] having two benzocrown moieties was designed and synthesized as a novel molecular leverage for helicity control and helix inversion. Short alkanediammonium guests H3N+(CH2)nNH3+ (n = 4, 6, 8) preferentially stabilized the P-helical isomer of [LZn3La(OAc)3], while the longer guest H3N+(CH2)12NH3+ caused a helix inversion to give the M-helical isomer as the major isomer. The differences in the molecular lengths were efficiently translated into helical handedness via the novel molecular leverage mechanism using the gauche/anti conversion of the trans-1,2-disubstituted ethylenediamine unit.