8 Conclusions
An strategy to obtain new helical polymers based on the incorporation, as pendants
of PPAs, of known CDAs with successful past records in other research areas such
as configurational assignment by NMR, i.e. PGME (1), MPA (2), MTPA (3), has
been tested. The corresponding polymers [poly-(R)-1, poly-(S)-1; poly-(R)-2, poly(S)-2; and poly-(R)-3, poly-(S)-3] behave as sensors of metal cation valence and/or
the polar and donor character of solvents. Phenomena such as helical inversion,
chiral amplification and axial chirality selection that are displayed by these polymers make them versatile materials.
Furthermore, the formation of HPMCs has led to a new family of nanospheres
made by complexation of divalent metals and MPA-containing PPAs. These HPMC
nanospheres present interesting properties such as: (1) their diameter can be tuned
to different sizes, i.e. to grow or to shrink, by changing the metal ion or the metal
ion to polymer ratio; and (2) the helicity of the polymeric material can be tuned to
either of the two helical senses by selection of the starting polymer, or by adequate
use of mono- and divalent ions if using a single polymer.
Rational explanations have been given for the helical changes and the process of
nanostructure formation, based on the complexation of the pendants, the role of the
metal ions, the helicity of the polymer and the character of the solvent.
The fact that these chiral nanoparticles are able to encapsulate different types of
inorganic and organic substances opens the door to new supramolecular assemblies
with controlled size and tuneable chiral core/surface that can be of great interest in
the future as functional matrices for encapsulation and recognition processes.
Although a large number of functional metal–organic particles have been prepared with a wide diversity of metal ions and/or organic ligands, to our knowledge
the cases reported here constituted the first examples of HPMCs producing functional nanoparticles.
References
1. Lam JWY, Tang BZ (2005) Acc Chem Res 38:745–754
2. Yashima E, Maeda K, Lida H, Furusho Y, Nagai K (2009) Chem Rev 109:6102–6211
3. Simionescu CI, Percec V, Dumitrescu S (1977) J Polym Sci Polym Chem Ed 15:2497–2509
4. Rudick JG, Percec V (2008) Acc Chem Res 41:1641–1652
5. Rosen BM, Wilson CJ, Wilson DA, Peterca M, Imam MR, Percec V (2009) Chem Rev
109:6275–6540
6. Okoshi K, Sakurai S, Ohsawa JK, Yashima E (2006) Angew Chem Int Ed 45:8173–8176
7. Seco JM, Quin ˜oa ´ E, Riguera R (2004) Chem Rev 104:17–118
8. Seco JM, Quin ˜oa ´ E, Riguera R (2012) Chem Rev 112:4603–4641
9. Louzao I, Seco JM, Quin ˜oa ´ E, Riguera R (2010) Angew Chem Int Ed 49:1430–1433
10. Latypov S, Seco JM, Quin ˜oa ´ E, Riguera R (1995) J Org Chem 60:1538–1545
11. Seco JM, Latypov S, Quin ˜oa ´ E, Riguera R (1997) J Org Chem 62:7569–7574
12. Lo ´pez B, Quin ˜oa ´ E, Riguera R (1999) J Am Chem Soc 121:9724–9725
Helical Polymer–Metal Complexes: The Role of Metal Ions on the Helicity and. . .
139
An strategy to obtain new helical polymers based on the incorporation, as pendants
of PPAs, of known CDAs with successful past records in other research areas such
as configurational assignment by NMR, i.e. PGME (1), MPA (2), MTPA (3), has
been tested. The corresponding polymers [poly-(R)-1, poly-(S)-1; poly-(R)-2, poly(S)-2; and poly-(R)-3, poly-(S)-3] behave as sensors of metal cation valence and/or
the polar and donor character of solvents. Phenomena such as helical inversion,
chiral amplification and axial chirality selection that are displayed by these polymers make them versatile materials.
Furthermore, the formation of HPMCs has led to a new family of nanospheres
made by complexation of divalent metals and MPA-containing PPAs. These HPMC
nanospheres present interesting properties such as: (1) their diameter can be tuned
to different sizes, i.e. to grow or to shrink, by changing the metal ion or the metal
ion to polymer ratio; and (2) the helicity of the polymeric material can be tuned to
either of the two helical senses by selection of the starting polymer, or by adequate
use of mono- and divalent ions if using a single polymer.
Rational explanations have been given for the helical changes and the process of
nanostructure formation, based on the complexation of the pendants, the role of the
metal ions, the helicity of the polymer and the character of the solvent.
The fact that these chiral nanoparticles are able to encapsulate different types of
inorganic and organic substances opens the door to new supramolecular assemblies
with controlled size and tuneable chiral core/surface that can be of great interest in
the future as functional matrices for encapsulation and recognition processes.
Although a large number of functional metal–organic particles have been prepared with a wide diversity of metal ions and/or organic ligands, to our knowledge
the cases reported here constituted the first examples of HPMCs producing functional nanoparticles.
References
1. Lam JWY, Tang BZ (2005) Acc Chem Res 38:745–754
2. Yashima E, Maeda K, Lida H, Furusho Y, Nagai K (2009) Chem Rev 109:6102–6211
3. Simionescu CI, Percec V, Dumitrescu S (1977) J Polym Sci Polym Chem Ed 15:2497–2509
4. Rudick JG, Percec V (2008) Acc Chem Res 41:1641–1652
5. Rosen BM, Wilson CJ, Wilson DA, Peterca M, Imam MR, Percec V (2009) Chem Rev
109:6275–6540
6. Okoshi K, Sakurai S, Ohsawa JK, Yashima E (2006) Angew Chem Int Ed 45:8173–8176
7. Seco JM, Quin ˜oa ´ E, Riguera R (2004) Chem Rev 104:17–118
8. Seco JM, Quin ˜oa ´ E, Riguera R (2012) Chem Rev 112:4603–4641
9. Louzao I, Seco JM, Quin ˜oa ´ E, Riguera R (2010) Angew Chem Int Ed 49:1430–1433
10. Latypov S, Seco JM, Quin ˜oa ´ E, Riguera R (1995) J Org Chem 60:1538–1545
11. Seco JM, Latypov S, Quin ˜oa ´ E, Riguera R (1997) J Org Chem 62:7569–7574
12. Lo ´pez B, Quin ˜oa ´ E, Riguera R (1999) J Am Chem Soc 121:9724–9725
Helical Polymer–Metal Complexes: The Role of Metal Ions on the Helicity and. . .
139