Fluorines in Tetrafluoromethane as Halogen Bond Donors: Revisiting Address the Nature of the Fluorine's sigma(hole)

摘要

It has been demonstrated in several instances that the 0.001 a.u. (electrons per bohr(3)) isodensity mapped electrostatic surface potentials on the fluorines along the outermost extensions of the CF covalent bonds in tetrafluoromethane (CF4) are entirely negative, they are thereby unable to engage in sigma(hole) bonding interactions with the negative sites on another molecules. In this study, we have attempted at resolving this controversy by performing various high-level electronic structure calculations with Quadratic Configuration Integrals of Singles and Doubles QCISD(full), second-order MOller-Plesset MP2(full), and 12 other Density Functional Theory (DFT) based functionals with and without dispersion corrections, all in conjunction with the 6-311++G(2d,2p) basis set. The results achieved with all the levels of theory utilized suggest that the fluorine's sigma(holes) in CF4 are positive regardless of the 0.001-, 0.0015-, and 0.002-a.u. isodensity mapped electrostatic surfaces examined. Because of this specific quality, the fluorines in CF4 have displayed their capacities to form not only 1:1 clusters with the Lewis bases such as water (H2O), ammonia (NH3), formaldehyde (H2CO), hydrogen fluoride (HF), and hydrogen cyanide (HCN), but also 1:2, 1:3, and 1:4 clusters with the latter three randomly chosen Lewis bases. Various topological and nontopological features obtained from applications of atoms in molecules, noncovalent interaction reduced-density-gradient and natural bond orbital analytical tools reveal that the NF, OF, and FF long-ranged interactions developed between the interacting monomers in H3NFCF3, H2OFCF3, and (YD)(n=1-4)F4C (YD = H2CO, HCN, and HF) are reminiscent of halogen bonding. The nonadditive cooperative and anticooperative energetic effects emerged on cluster formations are discussed in detail. (c) 2015 Wiley Periodicals, Inc.