Anticooperativity of FH···Cl − hydrogen bonds in [FH) n Cl] − clusters ( n = 1…6)

The change of cooperativity of FH···Cl − hydrogen bonds upon sequential addition of up to six FH molecules to the Cl − first coordination sphere is investigated. The geometry of clusters [(FH) n Cl] − ( n = 1…6) was calculated (CCSD/aug‐cc‐pVDZ) and compared with [(FH) n F] − clusters. The geometry is determined by the symmetry‐driven electrostatic requirements and also by the fact that formation of each new FH···Cl − bond creates a depression in the chlorine's electron cloud on the opposite side of Cl − (σ‐hole), which limits the range of directions available for subsequent H‐bond formation. The mutual influence of FH···Cl − hydrogen bonds is anticooperative—the addition of each FH molecule weakens H‐bonds by 23–16% and decreases their covalent character (as seen by LMO‐EDA decomposition and QTAIM analysis). Anticooperativity effects could be tracked by spectroscopic parameters (frequency of local HF mode ν FH , chemical shift δ H , spin–spin coupling constants 1 J FH , 1h J HCl , 2h J FCl and nuclear quadrupolar constants χ 18F , χ D , and χ 35Cl . © 2019 Wiley Periodicals, Inc.