|||
Figure 1: Schematic representation of a convex template (orange) around which a macrocycle is formed (blue).
Example 1: Catenane synthesis has been done by metal ion templation, utilizing the tetrahedral metal-ligand coordination geometry of copper(I) (C. O. Dietrich-Buchecker, J.-P. Sauvage, J.-P. Kintzinger, Tetrahedron Lett. 1983, 24, 5095; C. O. Dietrich-Buchecker, J.-P. Sauvage, Chem. Rev. 1987, 87, 795).
Example 2: The following rotaxane synthesis through a convex anion template utilizes hydrogen bonding between chloride and amide protons and shows that convex templates do not necessarily involve cations (J. A. Wisner, P. D. Beer, M. G. B. Drew, M. R. Sambrook, J. Am. Chem. Soc. 2002, 124, 12469).
Figure 2: Schematic representation of a concave template (orange) which brings togehter two reacting subunits (blue) inside its cavity.
2.3 Linear templates
An excellent example for a linear template (Figure 3) from nature is single-stranded DNA, along which the complementary strand is synthesized. In artificial systems, linear templates transferring sequence information are rather scarce. A number of examples is known, where the fibers of gels have been used in mineralization experiments. The fiber templates the formation of tunnel-shaped hollow spaces inside the resulting solid after removal of the organic template.
Figure 3: Schematic representation of a linear template (orange) combining two building blocks (blue).
Example 5: Regioselective photodimerization of trans-1,2-bis(4-pyridyl)ethylene is possible through a linear template, utilizing hydrogen bonding between resorcinol-OH and pyridine-N atoms (L. R. MacGillivray, J. L. Reid, J. A. Ripmeester, J. Am. Chem. Soc. 2000, 122, 7817).
2.4 Planar templates:
A planar template is usually a surface which binds molecules specifically and enables the self-assembly of these molecules into ordered architectures (Figure 4). One example from our group is the deposition of metallosupramolecular squares on chloride-covered Cu(100) surfaces.
A nice example for a planar template is the electropolymerisation of 3,4-ethyldioxythiophene on the liquid crystalline phase serving as template (J. F. Hulvat, S. I. Stupp, Angew. Chem. 2003, 115, 802; Angew. Chem. Int. Ed. 2003, 42, 778).
3. Summary As shown in some of the examples, templates plays a major role in supramolecular chemistry as well as in nature and opens a pathway to complex molecular architectures - in particular, when combined with self-assembly processes. Understanding template effects is a key to sophisticated supramolecular design. The great variety of possible interactions between templates and reaction partners, encompassing covalent and non-covalent bonds, hydrogen bonds, metal-ligand-coordination and hydrophobic effects etc., makes templates a versatile tool in supramolecular synthesis which is applicable in a broad spectrum of reaction conditions.
This paper from Schalley Group homepage: http://userpage.chemie.fu-berlin.de/~schalley/research.html
Archiver|手机版|科学网 ( 京ICP备07017567号-12 )
GMT+8, 2024-10-19 22:46
Powered by ScienceNet.cn
Copyright © 2007- 中国科学报社