An unexpected mechanism of halogen bonding that cannot be rationalized within the accepted sigma-hole model was found in the co-crystal of N-methylpyrazine iodide with molecular iodine via the topological analysis of the electron density distribution derived from the high-resolution X-ray diffraction data.

Outer-sphere charge transfer (OSCT) transitions are shown to correlate with previously published photoelectron emission threshold energies. From these data it is possible to generate a set of parameters, I(D) and I(A), which define these OSCT energies, where I(D) is identified as the solution phase vertical ionization potential, and I(A) is the solution phase vertical electron affinity. An easy procedure for deriving these data for a wide variety of cations and anions is presented. The application of these data leads to a powerful procedure for extracting reorganization and solvation energies of value in a variety of applications.

The experimental charge density in the crystal of disodium pentacyanonitrosoferrate (sodium nitroprusside) dihydrate was analyzed in detail by means of Bader's atoms in molecules theory. It was shown that nitroprusside anion is involved in relatively strong self-interactions through the nitroso group. The obtained results agree well with the spectroscopic data, indicating the tendency of the corresponding moiety to the formation of anion-anion association both in solutions and in the crystalline phase.

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