Phospholyl and Arsolyl Triple-Decker Sandwich Complexes of Europium(II) and Strontium(II)

To study the influence of heteroatoms on the photophysical
properties
of divalent Eu and Sr complexes, the synthesis of the phospholyl and
arsolyl compounds [{(Dtp)(thf)M}2{μ-η8:η8-C8H8}] (M = EuII and SrII; Dtp = 3,4-dimethyl-2,5-bis(tert-butyl)phospholyl) and [{(Dtas)(thf)M}2{μ-η8:η8-C8H8}] (M = EuII and SrII; Dtas = 3,4-dimethyl-2,5-bis(tert-butyl)arsolyl) is reported. Organometallic compounds
of divalent europium with P and As heterocyclic ligands have not been
described previously. They were prepared by salt elimination reactions
from potassium phospholyl or arsolyl, K2C8H8, and EuI2(thf)2 or SrI2.
Photophysical properties were investigated alongside a reference cyclopentadienyl
complex with a comparable structure. Critically, the influence of
the heteroatom on the photoluminescence emission and excitation and
quantum yields of the complexes is significant. Density functional
theory calculations were performed to rationalize the ligand influences.