Noncovalent nanohybrids of nickel(II) complex of 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine (NiTMTAA) with carbon nanotubes (CNTs) is a more complex and interesting case in structural terms as compared to the related materials functionalized with porphyrins and phthalocyanines. Saddle-shaped NiTMTAA molecule adsorbed can adopt different, energetically non-equivalent orientations with respect to CNT, depending on whether CH3 or C6H4 groups contact the latter. The main goal of the present work was to provide information on the interactions of NiTMTAA with simple single-walled CNT (SWNT) models. We employed three dispersion-corrected DFT functionals: M06-2X and LC-BLYP as implemented in Gaussian 09 package, and PBE-G as implemented in Materials Studio 6.0. We considered one armchair (A) and one zigzag (Z) short closed-end SWNT models (also referred to as 'elongated fullerenes'), derived from C60 and C80 hemispheres. The geometries obtained with M06-2X and LC-BLYP functional were very similar. In most complexes, the interaction between NiTMTAA and SWNT was noncovalent. The exception was the geometry of one complex with Z, in which a new C-C covalent bond spontaneously formed: one carbon atom forming this bond belongs to the pentagon of the nanotube tip, and another one is the γ-C atom of NiTMTAA. In an attempt to explain this phenomenon, we performed an additional series of calculations with fullerene C60, as well as with Ih and D5h C80. In the case of C80 Ih, from which (10,0) Z model is derived, we found again the covalent bonding with NiTMTAA in M06-2X calculations. Apparently, the possibility of addition has to do, on one hand, with the reactivity of pentagonal defects responsible for spherical curvature and kinks of pristine nanotubes, and on the other hand, with the reported reactivity of the γ-C atom of transition metal complexes of TMTAA. In the case of PBE-G calculations, all the complexes were noncovalent. The general trend was that the ‘embracing’ contact of o-phenylene rings of NiTMTAA with SWNT gives rise to stronger complexation due to π-π interactions. Financial support from UNAM (grant DGAPA-IN101313) and CONACyT (grant 127299) is greatly appreciated. L. V. H.-H. is indebted to the Doctorate Program in Chemical Sciences of UNAM and CONACyT for a Ph. D. fellowship.

Interaction of a Ni(II) tetraazaannulene complex with spherical and elongated fullerenes: A DFT study

249th National Meeting (2015)

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