X-ray Structures, Photophysical Characterization, and Computational Analysis of Geometrically Constrained Copper(I)−Phenanthroline Complexes

• Published in: Inorganic chemistry 2003-08, Vol.42 (16), p.4918-4929
• Main Authors: Cody, John, Dennisson, Jeanette, Gilmore, Joshua, VanDerveer, Donald G, Henary, Maged M, Gabrielli, Alan, Sherrill, C. David, Zhang, Yiyun, Pan, Chia-Pin, Burda, Clemens, Fahrni, Christoph J
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic034529j

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.