Building Fluorinated Hybrid Crystals: Understanding the Role of Noncovalent Interactions

Noncovalent interactions play a key role in functional materials. Metal-organofluorine interactions are of special interest because they directly affect the structure and reactivity of hybrid fluorinated materials. In-depth understanding and modulating of these interactions would enable the rational design of functional materials from fundamental chemical principles. In this work, we propose a computational approach that enables a comprehensive and quantitative characterization of noncovalent interactions (NCIs) in hybrid fluorinated crystals. Our approach couples dispersion-corrected density functional theory to NCI analysis. Additionally, we determine electron densities at bond critical points and identify electrostatic interactions using a simple electrostatic model. The versatility of this approach to probe a wide range of NCIs is demonstrated for a series of four bimetallic fluorinated crystals incorporating alkali-manganese(II) pairs and trifluoroacetato ligands. Noncovalent interactions in these hybrid crystals include metal-oxygen, metal-fluorine, hydrogen bonds, and van der Waals forces. Using K2Mn2(tfa)6(tfaH)2·H2O as an example, we demonstrate that its two-dimensional layered structure stems from a unique balance between these four NCIs. The computational approach presented herein should have general applicability to the quantitative study of NCIs in hybrid crystals, thereby serving as a guide for crystal engineering of novel hybrid materials