Molecular Construction and Application in Materials Sciences
Molecular Construction Based on Globular Moledules
The potential of carboranes as components or building blocks in supramolecular
systems is beginning to be explored. Recent studies in this area include
analyses of the effects of pai-bonding interactions between cage CH and
calix[5]arene, and hydrogen-bonding interactions between cage CH and diaza-18-crown-6.
The construction of linear and macrocyclic molecules, in which carboranes
are linked through organic groups or mercury atoms has also progressed.
The carboranes have several desirable features in this regard. Their rigid
three-dimensional structures hold substituents in well-defined spatial
relationships. The two carbon vertices of carboranes bear relatively acidic
protons and readily allow substitution with metal and organic groups. Substituents
can also be introduced at certain boron vertices.
Recently, We synthesized several aromatic multilayered molecules based
on the cis-preference of N-methyl aromatic ureas in combination with regulation
of the C-substituent on the o-carborane cage. The imposition of the cis-orientation
of urea or amide is achieved by using the o-carborane cage, which is prepared
by the reaction of decaborane(14) with acetylenic compounds in the presence
of a Lewis base. Similarly, it should be possible to construct carborane-containing
three-dimensional structures from two-dimensional arylacetylenic arrays,
which have been developed in nanoscale architecture. We here describe the
structural analysis of aromatic compounds composed of benzene nuclei linked
through o-carborane. Compounds which are composed of benzene nuclei linked
through o-carborane, were synthesized and their structures were determined
by X-ray crystallography. 1,3-Bis (2-phenyl-o-carboran-1-yl)benzene and
1,3,5-tris(2-phenyl-o-carboran-1-yl)benzene have syn stereochemistry of
all the terminal benzene rings, despite their steric crowdedness.
Crystal structure of 1,3.5-tris(2-phenyl-o-carboran-1-yl)benzene (Tetrahedron Lett. 2001)
Application of Carboranes for Materials Sciences
The unusual properties of carboranes have been utilized in materials chemistry
in the preparation of materials for liquid crystals and non-linear optics.