Toward electron encapsulation: polynitrile approach.

Area of Science:

• Supramolecular Chemistry
• Physical Chemistry
• Organic Chemistry

Background:

• The concept of solvated electrons in polar liquids is well-established.
• Designing artificial systems to mimic this solvation, specifically electron encapsulation in supramolecular cages, is an area of interest.

Purpose of the Study:

• To investigate the feasibility of creating supramolecular cages for "solvated" excess electrons.
• To explore strategies for electron localization using polar groups within or outside a cage structure.

Main Methods:

• Experimental investigation of electron attachment to nitrile-containing molecules.
• Theoretical modeling using Density Functional Theory (DFT) to understand electron trapping mechanisms.
• Analysis of binding energies and entropy of electron attachment.

Main Results:

• Electron attachment to nitrile groups leads to bent C-C-N fragments, incurring significant energy costs.
• Low binding energies and anomalously small entropy of electron attachment were observed for mononitriles and dinitriles in n-hexane.
• DFT modeling suggests solute molecules (mononitriles) solvate the electron via methyl groups, forming multimer radical anions rather than true cavity electrons.

Conclusions:

• The strategy of electron encapsulation using external polar groups (polynitrocles) is limited due to the high energy cost of nitrile group bending.
• The observed phenomena challenge the direct analogy of "solvated electrons" in organic liquids, as species resemble multimer radical anions.
• A clear distinction between "solvated electrons" and certain radical anions in organic media is difficult to establish.