DOI: 10.1016/j.cplett.2018.08.027

Using protonation to change a Cl^...N halogen bond in N-Base:ClOH complexes to a Cl^...O halogen bond

Ab initio MP2/aug′-cc-pVTZ calculations demonstrate that protonation of N-Base:ClOH complexes at O leads to complexes (N-Base-Cl)+:OH2, as a traditional N^...Cl halogen bond is replaced by a chlorine-transferred Cl^...O bond. For a fixed base, the binding energies of the latter complexes are more than an order of magnitude greater than the former. As a function of the Cl-N distance, EOM-CCSD Cl-N coupling constants show the evolution of the traditional halogen bond in the N-Base:ClOH complexes, to a chlorine-shared halogen bond in N2:ClOH2+, to a covalent bond in (N-Base-Cl)+:OH2. 1J(Cl-N) values for these complexes resemble 1J(Cl-N) for the ions (N-Base-Cl)+.