Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C16 alkyl groups during hetero-double-helix formation

1 : 1 mixtures of aminomethylenehelicene (P)-tetramer and (M)-pentamer with terminal C16 alkyl groups in fluorobenzene showed structural changes between hetero-double-helices B and C and random-coils 2A. Figure-eight thermal hysteresis appeared when the solution was cooled and heated at a constant rate and involved the crossing of cooling and heating curves in Δε/temperature profiles. This unusual thermal hysteresis emerged in the intermediate state between counterclockwise and clockwise thermal hystereses. This phenomenon arose from the competition between self-catalytic reactions to form B and C from 2A. Significant effects of terminal C16 alkyl groups on the thermodynamic and kinetic phenomena are also described.


<Constant-rate cooling and heating experiments>
A mixture of (P)-1-C16 and (M)-2 in fluorobenzene (0.5 mM) was heated at 70 °C for 10 min, cooled to 5 °C, and heated to 70 °C at the rates shown in Figures 3a and 3b, during which Δε at 314 nm and ε at 314 nm were monitored. Content/temperature profiles are also shown (Figures 3d and S2).
Experiments were also conducted at the concentration of 0.4 and 0.6 mM ( Figure S3)

<Figure-eight hysteresis experiments>
A mixture of (P)-1-C16 and (M)-2 in fluorobenzene (0.5 mM) was heated at 70 °C for 10 min, and cooled and heated at the rates and ranges shown in Figures 5, S7, and S8, during which Δε and ε at 314 nm were monitored. Content/temperature profiles are also shown (Figures 5c, S8e and S8f). S11 Figure S7. Figure

<Constant-rate cooling and heating experiment>
A mixture of (P)-1 and (M)-2-C16 in fluorobenzene (0.5 mM) was heated at 70 °C for 10 min, cooled to 5 °C, and heated to 70 °C at the rates shown in Figures 6a, 6b, and S10, during which Δε and ε at S13 Figure   Temperature was decreased from 70 °C to 5 °C and then increased from 5 °C to 70 °C.

<Constant-rate cooling and heating experiment>
A mixture of (P)-1 and (M)-2 in fluorobenzene (0.5 mM) was heated at 70 °C for 10 min, cooled to 5 °C, and heated to 70 °C at constant rates between 0.4 and 0.8 K/min, during which Δε and ε at 314 nm were monitored (Figures 9a and 9b).