Novel H-bonded base dimers as repeat units for information-bearing self-associative duplexes: a B3LYP/6-31G* search

Density functional theory at the B3LYP/6-31G* level with counterpoise correction has been employed to study six sets of nitrogenous bases for the capacity of each to form H-bonded dimers restricted to a chosen pairing configuration. These results are augmented by MP2/6-311++G(d,p) single point calculations on the B3LYP/6-31G* optimized geometries. Each set has two bases, including substituted azoles, imidazoles, pyrimidines, and fused ring systems. This study aims to determine the suitability of each set to furnish H-bonded base pairs which may serve as repeat units for self-associative H-bonded macromolecular duplexes with the capacity to store and replicate information at the molecular level. Out of the various possibilities tested here, a set of two substituted pyrimidines best satisfies the prescribed criteria and may be put forward as a good candidate to yield isomorphic repeat units for designing such synthetic information-bearing macromolecular duplexes. The optimized configurations of these chosen base pairs as calculated at the B3LYP/6-31G* level compare well with those calculated at the B3LYP/6-31++G(d,p) and MP2/6-31G(d,p) levels, and indicate that isomorphism of the two base pairs is independent of method used. Assuming a one-to-one correspondence for encoding information in the macromolecule, such a set of two bases can allow the macromolecule to encode up to 8 types of encrypted species.