Water-Assisted Proton Transfer in the Sequential Hydration of Benzonitrile Radical Cation C6H5CN•+(H2O)n: Transition to Hydrated Distonic Cation •C6H4CNH+(H2O)n with n ≥ 4

Long-Lived Multiple Charge Separation by Proton-Coupled Electron Transfer

Multiple charge separation has been successfully realized by a proton-coupled electron transfer reaction in an organic cocrystal. Benefiting from the adjustable electronic energy level of the electron donor and acceptor through thermal-induced proton migration, distinct optical absorption behaviors combined with color changes to blue or green are observed in these charge-separated states. It is of interest to note that such charge-separated states exhibit a longer lifetime of over a month as a result of the excellent coplanarity and π-π interaction of the electron acceptors. Moreover, the enhanced absorption toward longer wavelengths endows the charge-separated state with near-infrared (808 nm) photothermal conversion for imaging and bacterial inhibition, whereby the conversion performance can be controlled by the degree of proton migration.

Insights into the regioselectivity and diastereoselectivity of the Nazarov cyclization of 3-alkenyl-2-indolylmethanol with tryptophol

Density functional theory calculations of Nazarov cyclizations showed that 3-alkenyl-2-indolylmethanol and tryptophol formed binary and ternary complexes, respectively, in the presence and absence of H2O to produce C–N and C–C products.

Gas-Phase External Solvation of Protonated Benzonitrile by Eight Methanol Molecules

The gas-phase sequential association of methanol onto protonated benzonitrile (C₆H₅CNH⁺) and the proton-bound dimer (C₆H₅CN)₂H⁺ have been examined experimentally by equilibrium thermochemical measurements and computationally by density functional theory (DFT). The bonding enthalpy (ΔH°) for the association of methanol with protonated benzonitrile (25.2 kcal mol^-1) reflects the strong electrostatic interaction provided by the formation of an ionic hydrogen bond in the C₆H₅CNH⁺OHCH₃ cluster in excellent agreement with a DFT-calculated binding energy of 24.9 kcal mol^-1. The sequential bonding enthalpy within the (C₆H₅CN)H⁺(OHCH₃)_n clusters decreases from 25.2 to 10.6 kcal mol^-1 for the eighth solvation step (n = 8), which remains more than 25% above the enthalpy of vaporization of liquid methanol (8.4 kcal mol^-1). The nonbulk convergence of ΔH°_n-1,n with eight solvent molecules is attributed to the external solvation of a benzonitrile molecule by an extended hydrogen bonding network of protonated methanol clusters H⁺(CH₃OH)_n. In the external solvation of protonated benzonitrile by methanol, the proton resides on the methanol subcluster and the neutral benzonitrile molecule remains outside and bonded to the surface of the protonated methanol cluster. The bonding enthalpy of methanol to the proton-bound benzonitrile dimer (C₆H₅CN)H⁺(NCC₆H₅) is measured to be 18.0 kcal mol^-1, in good agreement with a DFT-calculated value of 17.1 kcal mol^-1, which reflects the association of the proton with the lower proton affinity methanol molecule, thus forming a highly stable structure of protonated methanol terminated by two ionic hydrogen bonds to the two benzonitrile molecules. The external solvation of benzonitrile by methanol ices in space allows benzonitrile to remain on the ice grain surface rather than being isolated inside the ice. This could provide accessibility for reactions with incoming ions and molecules or for photochemical processes by UV irradiation, leading to the formation of complex organics on the surface of ice grains.