Hypoligated Transition Metal Complexes, such as High-spin

2 Hypoligated transition metal complexes, such as high-spin (5=2) [Fe(H20)6]2+ 

Each of the latter AOs overlaps with an oxygen lone-pair AO (n) on an H2O ligand,  

In alkaline-earth oxides CaO and MgO, F-type defect centres (i.e. anion vacancies with trapped electrons) are responsible for many of the luminescence bands which have been observed [29], The defects produced by elastic collisions act as traps for free electrons [29]. The trapping may be described as the donation of one or more electrons to a Mg + site which is adjacent to the anion vacancy. The donation of one electron into the magnesium 3s AO, which overlaps with the doubly-occupied 2pO AO of an adjacent O2-, enables an (Mg 0) three- 

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