Chemistry Reference
In-Depth Information
Molecular Belts
Paul J. Evans and Ramesh Jasti
Abstract Rigid hydrocarbon macrocycles with radially-oriented
-systems and
continuous conjugation have attracted great interest in recent years. These molecu-
lar belts have novel optoelectronic properties and host-guest behavior. Certain belts
may also ultimately lead to a rational synthesis of carbon nanotubes. The high strain
associated with the nonplanar, conjugated backbones requires the development of
new synthetic methods, and clever synthetic design. Herein we describe the
synthetic history and properties of these structurally simple but synthetically
challenging molecules.
π
Keywords Cyclacene
Cycloparaphenylene
Cycloparaphenyleneacetylene
Cyclophenacene
Molecular belt
Picotube
Contents
1 Radially Oriented
-Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
2 Hydrocarbon “Picotube” . ................................................................... 250
3 Cycloparaphenyleneacetylenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
3.1 First Synthesis by Kawase . . . ......................................................... 253
3.2 CPPAs as Novel Host Molecules ..................................................... 254
3.3 Synthesis of More Reactive CPPAs . . . . . ............................................. 256
4 Cycloparaphenylenes ....................................................................... 259
4.1 Early Attempts Towards Cycloparaphenylenes ...................................... 260
4.2 First Synthesis of Cycloparaphenylene .............................................. 261
4.3 Subsequent Syntheses: A New Field Emerges ....................................... 264
4.4 Better Synthetic Control and New CPP Sizes ....................................... 267
4.5 Host-Guest Behavior of [10]CPP·C
60
, a Fullerene Peapod . . . ...................... 274
4.6 Functionalized Cycloparaphenylenes ................................................ 275
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5
“Top-Down” Synthesis of [10]Cyclophenacene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
