nephelauxetic
/ˌnɛfəlɔːkˈsɛtɪk/Chemistry
adjective
Relating to or designating the effect of a ligand in causing expansion of the d-electron cloud of a transition metal ion in a complex, resulting in decreased separation of electron energy levels compared with the free ion. Chiefly in nephelauxetic series noun a series of ligands arranged in order of the magnitude of this effect.
Origin
1950s. From nephelo- + auxetic. Apparently coined by Kaj Barr, Danish professor of Iranian philology.