N/O→B dative bonds supplemented by N–HN/HC hydrogen bonds make BN-cages an attractive candidate for DNA-nucleobase adsorption – an MP2 prediction

Abstract

The response of B₁₂N₁₂-nanocages towards DNA-nucleobases (adenine, guanine, cytosine, and thymine) is investigated using MP2 and DFT (M06-2X) levels of theory with the 6-311+G** basis set. Multiple BN-cage-nucleobase structures for each nucleobase emerged depending on the number of Lewis base centers of nucleobases. The main source of stability of these complexes is the N/O→B dative bond, where the N or O atom of nucleobases donates the lone-pair electron to one of the boron atoms of the nanocage. Nitrogen atoms of the BN-cage, adjacent to the B-site forming dative bond, act as a proton acceptor to form multiple (N–HN and N–HC) hydrogen bonds, where proton-donors NH and CH are part of nucleobases. MP2/6-311+G** adsorption energies are −43.1, −43.4 and −45.3 kcal mol⁻¹ (B₁₂N₁₂-adenine), −37.1, −41.9 and −43.3 kcal mol⁻¹ (B₁₂N₁₂-guanine), −41.3 and −43.4 (B₁₂N₁₂-cytosine), and −29.3 and −31.3 (B₁₂N₁₂-thymine). Similar adsorption energies were recorded for larger BN-fullerenes-nucleobases, namely B₁₆N₁₆ and B₂₄N₂₄. Changes in adsorption energies and structures of these nano-bio-hybrid materials in aqueous media are also discussed. Computationally cost-effective MP2 single point calculations at the M06-2X optimized geometries were found to be reliable in predicting adsorption energies. The effect of the BN-network and H-bonds on the adsorption process is assessed by comparing the results with simple BH₃-nucleobase models. BSSE correction to the adsorption energy is not recommended.