Aufbau Rules for Solvated Electron Precursors: Be(NH 3 ) 4 0,± Complexes and Beyond.

Tetra-amino beryllium complexes and ions, Be(NH ₃ ) ₄ ^0,± , have a tetrahedral Be(NH ₃ ) ₄ ²⁺ core with one, two, or three outer electrons orbiting its periphery. Our calculations reveal a new class of molecular entities, solvated electron precursors, with Aufbau rules (1s, 1p, 1d, 2s, 1f, 2p, 2d) that differ from their familiar hydrogenic counterparts and resemble those of jellium or nuclear-shell models. The core's radial electrostatic potential suffices to reproduce the chief features of the ab initio results. Wave function and electron-propagator methods combined with diffuse basis sets are employed to calculate accurate geometries, ionization energies, electron affinities, and excitation energies.