Tuning the selectivity of complementary quadruple hydrogen bonding

We have investigated the influence of the dimerization const. of quadruple hydrogen bonded 2-ureido-ureidopyrimidinone (UPy) dimer on the reversible complexation with 2,7-diamido-1,8-naphthyridine. Various new UPy derivs. have been synthesized bearing electron donating and electron withdrawing groups at the C6 position of the pyrimidinone ring. The reversible assocn. of these new UPy derivs. with 2,7-diamido-1,8-naphthyridine was investigated with UV-Vis titrns. From these titrns., it appears that UPy derivs. bearing an electron-donating dibutyl-amino group show an enhanced selectivity towards hetero-complexation with 2,7-diamido-1,8-naphthyridine. Finally, different UPy-NaPy AB monomers were prepd. and the influence of the increased selectivity on the supramol. ring-chain equil. of the resulting supramol. polymers was studied both by expt. and by theory.