title: X-ray structures, photophysical characterization, and computational analysis of geometrically constrained copper(I)--phenanthroline complexes.
abstract: A series of three geometrically constrained C(2)-symmetric Cu(I) mono-phenanthroline complexes were characterized by X-ray structural analysis, and their photophysical properties were investigated by absorption and emission spectroscopy. Visible light excitation yielded metal-to-ligand charge-transfer (MLCT) excited states with luminescence lifetimes up to 155 ns. Ultrafast transient absorption spectroscopy provided further insights into the excited-state dynamics and suggests for all three complexes the formation of a phenanthroline radical anion. In agreement with electrochemical measurements, the data further indicate that coordinative rearrangements are involved in nonradiative deactivation of the excited states. According to time-dependent density functional theory calculations (B3LYP/6-31G), the major MLCT transitions are polarized along the C(2) axis of the complex and originate predominantly from the copper d(xz) orbital. The computational analysis identifies an excited-state manifold with a number of close-lying, potentially emissive triplet states and is in agreement with the multiexponential decay kinetics of the MLCT luminescence. The relationship between structural and photophysical data of the studied Cu(I) mono-phenanthroline complexes agrees well with current models describing the photophysics of the related Cu(I) bis-diimine complexes.
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta, Georgia 30332, USA.
authors.forename: John
authors.initials: J
authors.lastname: Cody
authors.forename: Jeanette
authors.initials: J
authors.lastname: Dennisson
authors.forename: Joshua
authors.initials: J
authors.lastname: Gilmore
authors.forename: Donald G
authors.initials: DG
authors.lastname: VanDerveer
authors.forename: Maged M
authors.initials: MM
authors.lastname: Henary
authors.forename: Alan
authors.initials: A
authors.lastname: Gabrielli
authors.forename: C David
authors.initials: CD
authors.lastname: Sherrill
authors.forename: Yiyun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Chia-Pin
authors.initials: CP
authors.lastname: Pan
authors.forename: Clemens
authors.initials: C
authors.lastname: Burda
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Fahrni