Hydrogen bonded supramolecular structures: a further insight into the diamine-diol recognition and self-assembly

A new H-bonded supramolecular assembly of the diamine-diol family has been obtained from (1R,2R)-1,2-diaminocyclohexane (DAC) and (S)-1-phenyl-1,2-eth anediol (PED). The structure was characterized by single-crystal X-ray anal ysis and showed the typical architecture of DAC based assemblies, consistin g of a three-stranded helicate coiling around a H-bonded core, with a predi ctable helicity sense determined by the configuration of DAC. The new assem bly, while reconfirming the unique role of DAC as a powerful assembler of s upramolecular structures, demonstrated that the C-2 symmetry of diol partne rs employed so far is not essential for assembling helicates, although chir ality is. In the case of the adduct between (1R,2R)-1,2-diaminocyclohexane and (2R,3R)-2,3-butanediol, molecular recognition and self-assembly have be en shown to take place even in the absence of solvent, in the gas phase, wh ere long crystals were formed by spontaneous organized aggregation of diami ne-diol units. A thorough analysis of the results from the present and prev ious investigations has lead to a deeper understanding of the key features of the diamine-diol molecular code and of the requirements for recognition and assembly.