Structures and binding energies for complexations of different spin states of Ni⁺ and Ni²⁺ to aromatic molecules

Abstract

Density functional theory calculations, using the B3LYP parameterisation, were performed to determine structures, vibrational frequencies, and binding energies for complexation of Ni⁺ and Ni²⁺ cations with benzene and naphthalene molecules and clusters. The calculations employed the Stuttgart basis set with ECP pseudo potentials for the Ni cations and basis sets of at least triple ζ plus polarisation, and diffuse quality for C and H. The effect of electron correlation on non-bonded interactions was accounted for by the Grimme GD3 dispersion correction. Counterpoise computations were made for BSSE. Comparison between experiment and theory provide fascinating new insight into the bonding for these prototypical organometallic (OM) complexes. These structures have a sandwich topology, indicating major structural reorganisations occuring when benzene or naphthalene interact with Ni cations. Adiabatic electron affinities and ionisation potentials agree well with experiment when available. Binding energies were also determined, providing insight into the stability of the complexes. The results presented here provide important information for future studies to address additional investigations of both problems of the electronic structure properties of these complexes, as well as the role of the polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium (ISM) and soot formation in combustion. The Ni⁺/Ni²⁺ + aromatic organometallic bonding is of the same order of stability as an aromatic C–H bond. Such bonding modifies the IR spectrum of the complexed aromatic molecules by enhancing the 3.3 μm feature and decreasing the C–H bands in the 11–12 μm range (γ C–H). Organometallic complexation reactions may contribute significantly to metal depletion in the ISM.

GRAPHICAL ABSTRACT

KEYWORDS:

• Benzene
• naphthalene
• transition metal complexations
• gas phase organometallic ion chemistry

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The calculations were performed at the IDRIS and CINES French National Computer Centres under Projects 2012046838 and 2013046838. The research at Texas Tech University (TTU) is based upon work supported by the Air Force Office of Scientific Research (AFOSR) [grant number FA9550-16-1-0133] and the Welch Foundation [grant number D-0005]. BK was supported by a one month invited visiting Professorship at TTU by these two grants.