The unusual stability of H‐bonded complexes in solvent caused by greater solvation energy of complex compared to those of isolated fragments

Abstract

Here, the effect of solvent on the stability of non‐covalent complexes, was studied. These complexes were from previously published S22, S66, and X40 datasets, which include hydrogen‐, halogen‐ and dispersion‐bonded complexes. It was shown that the charge transfer in the complex determines whether the complex is stabilized or destabilized in solvent.

Trends in the stability of covalent dative bonds with variable solvent polarity depend on the charge transfer in the Lewis electron-pair system

“…As expected, a decrease in stability with increasing solvent polarity was observed in most complexes. 13,14 However, our research has shown that certain hydrogen-bonded complexes unexpectedly stabilize with increased solvent polarity.…”

Unexpected Strengthening of the H-Bond Complexes in a Polar Solvent Due to a More Efficient Solvation of the Complex Compared to Isolated Monomers

“…Charge transfer based on NBO atomic charges plays an essential role in the complex’s characterization in the present paper. Although the whole concept of charge transfer in NBO analyses is not well-defined and its value depends on a computation strategy, we rely on our previous experience gained in the calculations performed on noncovalent complexes from S20, S66, and X40 data sets . In this study, we used the CT values determined by a Řezáč and de la Lande technique based on the spatial definition of molecular fragments using the superimposed electron density of isolated noninteracting fragments as a reference state.…”

“…In addition, the solvent-accessible surface area (SASA) of a complex is systematically smaller than the sum of SASA of individual subsystems. 7 Our preliminary results performed on the set of noncovalent complexes 15 indicated that the effect of solvent is more complex.…”

“…Although the whole concept of charge transfer in NBO analyses is not well-defined and its value depends on a computation strategy, we rely on our previous experience gained in the calculations performed on noncovalent complexes from S20, S66, and X40 data sets. 15 In this study, we used the CT values determined by a R ̌ezać̌and de la Lande technique 32 based on the spatial definition of molecular fragments using the superimposed electron density of isolated noninteracting fragments as a reference state. These benchmark CT values were closely correlated with the CT values based on NBO charges, justifying the use of the latter approach in the present paper.…”

Impact of dielectric constant of solvent on the formation of transition metal‐ammine complexes

“…While the SASA consistently destabilizes the complex, the effect of charge redistribution depends on the bond type and the extent of the charge redistribution. The destabilizing effect predominates for complexes with small charge redistribution, such as those formed by sharing electrons to create a covalent bond, and most non‐covalent complexes 1–3 . The dative bond (DB) complexes, which have a dual bonding character combining covalent and ionic contributions (see Equation ), are an intriguing group in this regard 4,5 …”