Syntheses and Structures of Isomeric Diaminotriazinyl-Substituted 2,2′-Bipyridines and 1,10-Phenanthrolines

Isomeric 2,2′-bipyridines <b>4a</b>−<b>6a</b> and 1,10-phenanthrolines <b>7a</b>−<b>9a</b> with two diaminotriazinyl (DAT) substituents were synthesized to explore their dual ability to direct association by the chelation of metals and the characteristic hydrogen bonding of DAT groups. Crystals of compounds <b>4a</b>−<b>6a</b> and <b>7a</b>−<b>9a</b> were grown under diverse conditions, and their structures were solved by X-ray crystallography. Analysis revealed multiple shared features analogous to those observed in the structures of simpler DAT-substituted pyridines <b>1</b>−<b>3</b>. For example, the bipyridines and phenanthrolines favor flattened conformations except in the cases of compounds <b>8a</b> and <b>9a</b>, where the patterns of substitution prevent the DAT groups from lying in the plane of the phenanthroline core. As expected, the DAT groups form approximately coplanar hydrogen bonds according to standard motifs <b>I</b>−<b>III</b>, which play a key role in directing molecular organization. However, the structures of simple pyridines <b>1</b>−<b>3</b>, which favor efficiently packed chains and sheets, differ predictably from those of bipyridines <b>4a</b>−<b>6a</b> and phenanthrolines <b>7a</b>−<b>9a</b> in two ways: (1) The larger number of DAT groups in compounds <b>4a</b>−<b>9a</b> typically leads to complex three-dimensional networks held together by a larger number of hydrogen bonds per molecule, and (2) the need to respect multiple directional interactions prevents compounds <b>4a</b>−<b>9a</b> from forming closely packed structures, and significant quantities of guests are included. Together, these observations confirm the effectiveness of incorporating special groups such as DAT within more complex molecular structures to control association according to reliable patterns. Bipyridines <b>4a</b>−<b>6a</b> and phenanthrolines <b>7a</b>−<b>9a</b> promise to be particularly rich sources of new supramolecular chemistry because they have well-defined molecular topologies and a dual ability to direct association by chelating metals and by engaging in multiple hydrogen bonds according to reliable patterns.