Molecular self-assembly composed of aromatic hydrogen-bond donor-acceptor complexes

Molecular self-assembling systems derived from the clustering of acid and base molecules have been investigated by mass spectrometric analysis of clusters isolated hem liquid droplets. N-H ... N and O-H ... N hydrogen-bonded acid-base systems were compared When heteroaromatic N-H ... N hydrogen-bonding acid-base: systems, such as 7-azaindole dimer, the indole-quinoline pair, etc. were used as acid-base pairs, the clusters composed of equimolar acid and base molecules were generated. This means that the hydrogen-bonding acid-base complex, N-H ... N, behaves like a single molecule in cluster formation. On the other hand, clustering of the aromatic O-H ... N hydrogen-bonding systems, such as phenol-pyridine, phenol-pyrazine, etc., was controlled by the acid-base interaction determined by the pK(a) values, giving a multilayer structure for a relatively strong acid-base pair and a monolayer structure for a relatively weak acid-base pair. Molecular self-assembling systems containing hydrogen-bond donor and acceptor molecules have been systematically described here.