title: Synthesis and characterization of a high-symmetry ferrous polypyridyl complex: approaching the 5T2/3T1 crossing point for Fe(II.).
abstract: Electronic structure theory predicts that, depending on the strength of the ligand field, either the quintet ((5)T2) or triplet ((3)T1) term states can be stabilized as the lowest-energy ligand-field excited state of low-spin octahedral d(6) transition-metal complexes. The (3)T1 state is anticipated for second- and third-row metal complexes and has been established for certain first-row compounds such as [Co(CN)6](3-), but in the case of the widely studied Fe(II) ion, only the (5)T2 state has ever been documented. Herein we report that 2,6-bis(2-carboxypyridyl)pyridine (dcpp), when bound to Fe(II), presents a sufficiently strong ligand field to Fe(II) such that the (5)T2/(3)T1 crossing point of the d(6) configuration is approached if not exceeded. The electrochemical and photophysical properties of [Fe(dcpp)2](2+), in addition to being of fundamental interest, may also have important implications for solar energy conversion strategies that seek to utilize earth-abundant components.
authors.affiliation: Department of Chemistry, Michigan State University , 578 South Shaw Lane, East Lansing, Michigan 48824, United States.
authors.forename: Lindsey L
authors.initials: LL
authors.lastname: Jamula
authors.forename: Allison M
authors.initials: AM
authors.lastname: Brown
authors.forename: Dong
authors.initials: D
authors.lastname: Guo
authors.forename: James K
authors.initials: JK
authors.lastname: McCusker