Quantitative analysis of extremely strong contiguous hydrogen bond arrays

We propose a programme to quantitatively investigate the thermodynamics and kinetics of the strongest hydrogen bonded small molecule complexes known. AAA-DDD triple hydrogen bond arrays can be up to a hundred million times stronger than the triple hydrogen bonds formed between nucleic acid base pairs. We wish to measure a series of AA-DD, AAA-DDD, AAAA-DDDD and AAAAA-DDDDD systems to build up a structure-property profile of such contiguous hydrogen bonding arrays. We will measure the thermodynamics of binding through Ka measurements (using NMR, UV, fluorescence tritrations, competition experiments and microcalorimetry, depending on the binding regime, and use evolutionary algorithms to improve on the values currently obtained using titration methods). We will measure the kinetics of binding in very strong complexes using EXSY NMR techniques. We also intend to develop stimuli-responsive complexes which assemble or fall apart in response to an external signal (chemical or photonic) and can be used to assemble supramolecular polymers. The result will be a fundamental mechanistic understanding of the relationship between chemical structure and hydrogen bonding strength for such contiguous hydrogen bonding arrays.