Abstract
<jats:p>Individual hydrogen bond (HB) energies and cooperativity contributions were characterized across 66 HBs in twelve cyclic neutral (HF)m(NH3)n clusters (m + n = 3–7) using a molecular tailoring approach (MTA)-based fragmentation method at the MP2/aug-cc-pVTZ level. Four HB types follow an unambiguous energetic hierarchy: F–H···N (mean 22.7 ± 4.1 kcal mol-1) > F–H···F (12.1 ± 3.3 kcal mol-1) > N–H···F ≈ N–H···N (both 4.7 kcal mol-1). Network cooperativity accounts for 27.5% of F–H···N strength but reaches 68% for N–H···F HBs, revealing a striking inversion between absolute strength and cooperative enhancement. Twelve of 66 HBs (18.2%) exhibit the Cooperativity-Amplified Bond (CAB) effect: dimer energies below 4.0 kcal mol-1 yet MTA in-cluster energies exceeding 6.0 kcal mol-1, driven entirely by network polarization from adjacent F–H···N anchors. Two HBs in the F2N5 cluster show anti-cooperativity through a competition mechanism arising from bifurcated 2D-2A topology, mechanistically distinct from the directional anti-cooperativity reported in other HB cluster systems. HF fraction correlates strongly with both average MTA HB energy (R2= 0.85) and average cooperativity per HB (R2 = 0.79), establishing HF content as the primary compositional determinant of cooperative efficiency. Donor bond elongation r(D–H) serves as a purely geometric structural fingerprint for classifying cooperativity. QTAIM-derived topological parameters corroborate the energetic results from MTA. Notably, the electron density at the bond critical point (ρBCP) correlates strongly with MTA HB energy (R2 = 0.97) across all 66 HBs. These results provide a quantitative, topologyresolved framework for HB cooperativity in F/N systems, relevant to atmospheric aerosol nucleation, astrochemistry, crystal engineering, ion-transport materials, benchmarking of force fields and machine-learning potentials, and protontransfer reactivity in interstellar HF/NH3 ices for prebiotic chemistry.</jats:p>