Anion-Assisted Formation
of Discrete Homodimeric and
Heterotetrameric Assemblies by Benzene Based Protonated Heteroaryl
Receptors
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Abstract
Anion-assisted formation of discrete homodimeric and
heterotetrameric
assemblies by benzene based protonated heteroaryl receptors <b>L</b><sup><b>1</b></sup>–<b>L</b><sup><b>6</b></sup> have been studied thoroughly by single crystal X-ray
diffraction studies. Crystallographic results elucidate the fact that
protonated tripodal receptor <b>L</b><sup><b>1</b></sup> formed staggered homodimeric capsular assemblies <b>2</b> and <b>3</b> with CF<sub>3</sub>COO<sup>–</sup> and ClO<sub>4</sub><sup>–</sup> ions, respectively. Protonation of <b>L</b><sup><b>3</b></sup> with trimesic acid also showed the formation
homodimeric assembly, <b>6</b>. In all these cases the anions
are hydrogen bonded to the receptor molecules and show remarkable
influence on the outcome of the self-assembly process to form discrete
capsules. The necessity of the alkyl substitution on the benzene platform
has been established from complexes <b>8</b>, <b>9</b>, and <b>10</b>, which were obtained upon protonation of <b>L</b><sup><b>6</b></sup> with HNO<sub>3</sub>, HI, and HClO<sub>4</sub>, respectively. Interestingly, when a 1:1 mixture of <b>L</b><sup><b>1</b></sup> (tripodal) and <b>L</b><sup><b>5</b></sup> (dipodal) were treated with HClO<sub>4</sub> and HBF<sub>4</sub>, discrete heterotetrameric assemblies have been
isolated as complexes <b>11</b> and <b>12</b>. The detailed
solid state structural analysis of these complexes revealed the formation
of heterotetrameric assemblies assisted by anion–water clusters.
Correlation of these solid state structural assemblies with our previously
reported complexes <b>1</b>, <b>4</b>, <b>5</b>,
and <b>7</b> has also been described. The role of anionic templates
in assisting the formation of discrete capsular assemblies from receptors
possessing heteroaryl units and 1,3,5-methyl substituted benzene platform
has been established