X-ray structures, photophysical characterization, and computational analysis of geometrically constrained copper(I)--phenanthroline complexes.
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.
Cody
John
J
School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta, Georgia 30332, USA.
Dennisson
Jeanette
J
Gilmore
Joshua
J
VanDerveer
Donald G
DG
Henary
Maged M
MM
Gabrielli
Alan
A
Sherrill
C David
CD
Zhang
Yiyun
Y
Pan
Chia-Pin
CP
Burda
Clemens
C
Fahrni
Christoph J
CJ