Interaction of Glycine with BC2N Nanotubes: Dative Covalent and Hydrogen Bonding

Immobilization of biomolecules on the inorganic nanostructured materials have attractedmuch attention during the last years as they exhibit unique features derived from combiningsynergistically the properties of the interacting components. We aimed to investigate theinteraction of BC2N nanotubes by glycine using density functional theory. For all the BC2Nsystems, six initial structural guesses were considered: pure interaction between the NH2 groupof Gly and one nanotube B/C/N atom plus H-bonding between the Gly OH group and onenanotube N atoms; interaction between the Gly CO group and one nanotube B/C/N atom plus Hbondingbetween the Gly OH group and one nanotube N atom. Our DFT results clearly indicatethat the most stable adduct results from dative covalent interactions between the Gly NH2 groupand the B atoms, which act as Lewis acid sites and the N atoms acting as H-bonding acceptorgroups. These findings are consistent with the polar character of BN bonds in BC2N nanotubes.Based on NBO analysis the computed charge transfers values from Gly to the BNNTs, being 0.30e, confirms the formation of charge transfer complexes for the complexes. The interaction of Glythrough the COOH group by means of a simultaneous CO–B dative bond and a OH···N(BC2N)H-bond was also considered. For the BN/COOH-1 adduct, Gly adsorption on the (4,0) BC2Nresults in a spontaneous proton transfer from the Gly COOH group to the N nanotube atom,hence forming a COO-/ BC2N -H+ ion pair. Such a proton transfer is attributed to the net chargetransfer occurring from Gly to the BC2N, which induces an increase of the COOH acidity and thenanotube basicity up to the point of promoting the proton transfer to a nearby N atom of thenanotube.

Keywords:

BC2N Nanotube , Hydrogen Bonding , Glycine , DFT , NBO