A New Quadruple Hydrogen-Bonding Module Based on Five-Membered Heterocyclic Urea Structure

N,N′-Di-4-triazolylurea (DTU) has developed as a new ADDA module and DTU forms a stable ADDA•DAAD heterocomplex with 2,7-diamido-1,8-naphthyridine (DAN) (K_s = 2.6 × 10⁵ M⁻¹ in CHCl₃). The K_s value of the complex between DTU and DAN is 100-fold greater than that of the complex between N,N′-di-2-pyridylurea and DAN due to replacement of a pyridine ring with a 1,2,3-triazole ring.