Remote modulation of singlet–triplet gaps in carbenes

Manipulation of N-heterocyclic carbene reactivity with practical oriented electric fields

Electric fields can be used to tune the nucleophilicity and electrophilicity of N-heterocyclic carbenes and enhance their catalytic activity.

Enhancement of Thermodynamic Gas-Phase Acidity and Basicity of Water by Means of Secondary Interactions

A series of A⋅water, B⋅water complexes (A=acid, B=base) are studied at the G4 level of theory to show that water acidity or basicity can be modulated by non-covalent interactions. Protic and non-protic acids interacting with water form hydrogen bonds or other kinds of non-covalent interactions, respectively, that may dramatically change the acidity of water up to almost 360 kJ ⋅ mol^-1 in terms of enthalpy. Similarly, hydrogen bonds responsible for the interaction between typical small nitrogen-containing Lewis bases and water can enhance the proton affinity of water by almost 300 kJ ⋅ mol^-1 . Our results reveal that these large enhancements are linearly related with the binding energy of the charged complexes, and are determined by the Lewis acid-base properties of the molecule involved in the interaction, allowing a quite precise modulation of the corresponding acid-base properties of water.