A molecular leverage for helicity control and helix inversion.

The helical tetranuclear complex [LZn(3)La(OAc)(3)] having two benzocrown moieties was designed and synthesized as a novel molecular leverage for helicity control and helix inversion. Short alkanediammonium guests H(3)N(+)(CH(2))(n)NH(3)(+) (n = 4, 6, 8) preferentially stabilized the P-helical isomer of [LZn(3)La(OAc)(3)], while the longer guest H(3)N(+)(CH(2))(12)NH(3)(+) 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.