Albany 2015:Book of Abstracts
June 9-13 2015
©Adenine Press (2012)
Covalence, not Resonance-Assistance, behind Cooperative Hydrogen and Halogen bonds in Quadruplexes
Halogen bonds are shown to possess the same characteristics as hydrogen bonds: charge transfer, resonance assistance and cooperativity. This follows from computational analyses of the structure and bonding in N-halo-base pairs and quartets (see Figure). The objective was to achieve understanding of the nature of resonance-assisted halogen bonds (RAXB): how they resemble or differ from the better understood resonance-assisted hydrogen bonds (RAHB) in DNA.
We present an accurate physical model of the RAXB based on molecular orbital theory, which is derived from corresponding energy decomposition analyses and study of the charge distribution. We show that the RAXB arise from classical electrostatic interaction and also receive strengthening from donor–acceptor interactions within the σ-electron system. Similar to the RAHB, there is also a small stabilization by π-electron delocalization. This resemblance leads to prove cooperativity in N-halo-guanine quartets, which originates from the charge separation that goes with donor–acceptor orbial interactions in the σ-electron system.
L.Wolters, N. W. G. Smits, C. Fonseca Guerra (2015). Covalency in Resonance-Assisted Halogen Bonds Demonstrated with Cooperativity in N-Halo-Guanine Quartets. Phys. Chem. Chem. Phys. 17, 1585-1592.
C. Fonseca Guerra, H. Zijlstra, G. Paragi, F. M. Bickelhaupt. (2011). Telomere Structure and Stability: Covalency in Hydrogen Bonds, Not Resonance Assistance, Causes Cooperativity in Guanine Quartets. Chem. Eur. J. 17, 12612-12622.
C. Fonseca Guerra