Physico-chemical Properties of the Strong Tobacco Smoke Carcinogen NNK Diazonium Ion

Abstract

We have explored the physico-chemical properties of the NNK diazonium ion to gain insight into its shape, bonding, charge distribution, and ro-vibrational features. This information is essential if the chemical reactivity and spectroscopic properties of this important intermediate are to be predicted. NNK diazonium ion is a well-known alkylating agent. Its enzymatic production, its reaction with DNA, and its role in mutagenesis/carcinogenesis have all received significant study. The ion itself, however, is relatively unstable and its direct observation has not yet been reported. Likewise, data on its shape, spectroscopic properties, bonding, and charge distribution are lacking. The species is sufficiently small such that its properties may be probed using sophisticated model chemistries. We present the first computational investigation of NNK diazonium ion deploying Kohn-Sham Density Functional Theory (B3LYP/6-311G∗∗) and Coupled Cluster theory (CCSD(T)/cc-pVDZ). We have obtained energies, geometries, electrostatic potential surfaces, molecular orbitals, and vibrational analyses for several energy-minimized structures. By providing detailed information on the geometry of and ro-vibrational motion in this ion, we hope to inform future, molecular dynamics, electronic structure, and/or spectroscopic work on this important reactive intermediate and on its interaction with DNA.