Search

Fifty eight inclusion crystals of cholamide (CAM) with aliphatic alcohols have been systematically investigated by X-ray crystallography. The host frameworks of the inclusion crystals can be categorized into three structural types: bilayer, herringbone, and crossing structures. Most of the guests are included in bilayer structures, which can be further divided into four sub-types. The host frameworks isomerize depending on the size and shape of the guest molecules. This dependence is clearly evaluated by the relationship between the volume of the guest molecules and the packing coefficient of the void space in the host frameworks. Although the host frameworks with the cavities and the structural isomerization are very similar to those of the inclusion crystals of cholic acid (CA), the inclusion behavior of aliphatic alcohols in the two hosts is completely different: fifty four alcohols can be included in the bilayer-type structures of CAM, but only two in those of CA. This is attributed to their different functional groups, which lead to different hydrogen-bond networks with the guest alcohols. The result in the two hosts is a good example to understand the effect of host–guest hydrogen bonds on guest inclusion in cavities that are identical in size and shape. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Carbon nanocoils with a coil diameter of 50–450 nm were prepared by the catalytic pyrolysis of acetylene, and the preparation conditions and morphology were examined. To clarify the growth mechanism, the carbon nanocoils were also heat treated at 2500 °C for 8 h in a N2 atmosphere, then partially oxidized in air at 600 °C for 15 min. The carbon nanocoils could be grown at 740–770 °C either by applying a magnetic field to the reaction zone or by using sputtered thin films of Au or Au/Ni as a catalyst. Carbon nanocoils are generally single coils, while carbon microcoils are generally double coils. There are two kinds of nanocoils with differing microstructures. One is formed from a carbon fiber with a double microstructure of thin core fiber and clad, while the other is formed from a fiber with a “herring-bone” structure.

Chiral compounds, N-methyl-, N-ethyl-, and N-n-propylcholamides, form crystalline inclusion compounds with water or small organic substances. The compounds were analyzed by X-ray diffraction methods. It was found that the crystals have bilayered structures accumulated by chiral molecular sheets. The chiral molecules associate in a unique head-to-head/tail-to-tail and right-to-left motif to give chiral and amphiphilic sheets. Such sheets stack by adhesions between the hydrophilic sides and between the lipophilic sides. The alkyl groups of the amides prompt the formation of a hydrogen-bonding network between the tails instead of a cyclic one between the head and tail. The guest molecules are accommodated into small cavities between the steroidal side chains. Chirality 10:600–618, 1998. © 1998 Wiley-Liss, Inc.

A hydroxybenzaldehyde derivative which has isobutenyl linkage reacts with a variety of diamines to efficiently result in a 2∶2 macrocyclic compound.