containing Sn-porphyrin, crown ether, and an aromatic dialkylammonium
spacer. As shown in Fig. 25, we first synthesized a Sn-porphyrin modified
crown ether and a dialkylammonium chain. Then we conveniently synthesized
the pretzelane in one step via a template-directed protocol due to the host-guest
interaction between the ammonium and crown ether. Finally, we studied its
property with NMR and UV-Vis spectroscopy to confirm its pretzelane architecture. We believe this new synthetic strategy for pretzelane could provide
fresh ideas for the designation and construction of even more interesting and
complicated systems.
4.6
Double-Lasso Macrocycle
In 2012, Coutrot et al. [49] linked the two ends of a nonsymmetrical [C2] daisy
chain composed of crown ether and secondary ammonium salt and obtained a
class of mechanically self-locked molecule as shown in Fig. 26. They called
this kind of architecture double-lasso macrocycle. The straightforward synthesis of this double-lasso macrocycle using “click” chemistry of alkyne and azide
on two [C2] daisy provided a new idea for polymerization at high concentration. Also the conformation transformation upon adjusting pH was studied, and
they found that the two macrocycles could slide along the alkyl chains thus
forming two conformations with great differences. At relatively low pH, the
double-lasso macrocycle adopted a loose conformation with a big cavity; while
upon deprotonation, the double-lasso presented with a spiral type and tightened
conformation with a small cavity. This novel type of self-locked structure
provided a new method for the construction of molecular machine.
Fig. 25 Pretzelane containing Sn-porphyrin and crown ether synthesized by template-directed
method [48]
4 Mechanically Self-Locked Molecules
103
spacer. As shown in Fig. 25, we first synthesized a Sn-porphyrin modified
crown ether and a dialkylammonium chain. Then we conveniently synthesized
the pretzelane in one step via a template-directed protocol due to the host-guest
interaction between the ammonium and crown ether. Finally, we studied its
property with NMR and UV-Vis spectroscopy to confirm its pretzelane architecture. We believe this new synthetic strategy for pretzelane could provide
fresh ideas for the designation and construction of even more interesting and
complicated systems.
4.6
Double-Lasso Macrocycle
In 2012, Coutrot et al. [49] linked the two ends of a nonsymmetrical [C2] daisy
chain composed of crown ether and secondary ammonium salt and obtained a
class of mechanically self-locked molecule as shown in Fig. 26. They called
this kind of architecture double-lasso macrocycle. The straightforward synthesis of this double-lasso macrocycle using “click” chemistry of alkyne and azide
on two [C2] daisy provided a new idea for polymerization at high concentration. Also the conformation transformation upon adjusting pH was studied, and
they found that the two macrocycles could slide along the alkyl chains thus
forming two conformations with great differences. At relatively low pH, the
double-lasso macrocycle adopted a loose conformation with a big cavity; while
upon deprotonation, the double-lasso presented with a spiral type and tightened
conformation with a small cavity. This novel type of self-locked structure
provided a new method for the construction of molecular machine.
Fig. 25 Pretzelane containing Sn-porphyrin and crown ether synthesized by template-directed
method [48]
4 Mechanically Self-Locked Molecules
103