Abstract
Very high pressure is becoming increasingly important for investigating electronic structure. The relative shift in energy of electronic orbitals which is commonly observed at high pressure can frequently lead to a new ground state for the system. These electronic transitions may result in changes in electrical, optical, or magnetic properties as well as changes in chemical reactivity. Electronic transitions in metals and insulatorβmetal transitions have been widely studied by physicists. Recently, it has been found that electronic transitions in aromatic hydrocarbons and their electron donorβacceptor complexes can induce chemical reactivity and lead to the formation of new classes of hydrocarbons.
Electronic transitions in transition metal complexes may lead to changes in spin state; both increase and decrease in multiplicity with increasing pressure have been observed. In addition, it has been shown that Fe(III) and Cu(II) reduce at high pressure in a variety of compounds. The behavior of these transition metal ions is described in some detail in relation to the general area of high pressure and electronic structure.