An ab initio study on substituent and cooperative effects in bifurcated fluorine bonds

Bifurcated fluorine bond (BFB) interactions are studied in model binary complexes pairing N-formyl formamide derivatives and FX molecules (X = F, CN, NC, CF3 and CCH) by means of ab initio calculations. The calculated F center dot center dot center dot O binding distances in these complexes are in the range of 2.813-3.048 angstrom. The corresponding interaction energies lie in a narrow range, from -2.25 to-16.49 kJ/mol. The nature of BFBs is analysed by a vast number of methods including molecular electrostatic potential, quantum theory of atoms in molecules, non-covalent interaction index and natural bond orbitalmethods. According to the energy decomposition analysis, the electrostatic and dispersion effects have a dominant role in the formation of these complexes. The formation of a hydrogen-and lithium-bonding interaction tends to increase the strength of BFBs in the ternary XF:NFF-H:NH3 and XF:NFF-Li:NH3 complexes, respectively. [GRAPHICS] .