QUANTUM CHEMICAL TOPOLOGY: PREDICTION AND INTERPRETATION OF DNA BASE-PAIRS

Quantum Chemical Topology(QCT)1,2 is an increasingly popular3,4 way of extracting chemical insight from modern wave functions. However, QCT can also predict geometries of complexes by providing atom-centered multipole moments to a formula of high-rank electrostatic interaction. We present two related case studies, one concerning geometry prediction5 and one concerning interpretation6of stability of 27 gas-phase DNA base pairs. Case study 1: High-order electrostatic moments are computed within the compact spherical tensor formalism from ab initio wave functions of rigid geometry-optimised monomers. When combined with a simple hard-sphere or Lennard-Jones(LJ) potential this topological electrostatic interaction potential correctly predicts the geometries of 27 DNA base pairs. With the LJ potential internuclear distances of frontier atoms between base pairs differ only by 0.08Å compared to supermolecular calculations at B3LYP/6-31G(d,p) level. The discrepancy of angles involved in hydrogen bond contacts amounts to only 3.50. Our model globally reproduces the correct ranking in intermolecular interaction energy. Subsequently we compare the interaction energy profiles of the topological model with Distributed Multipole Analysis, Merz-Kollman charges and the Natural Population Analysis at B3LYP/6-311+G(2d,p) level. The convergence of the topological multipol