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Article

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

Supporting Info

John Cody,^† Jeanette Dennisson,^† Joshua Gilmore,^† Donald G. VanDerveer,^† Maged M. Henary,^† Alan Gabrielli,^† C. David Sherrill,*^† Yiyun Zhang,^‡ Chia-Pin Pan,^‡ Clemens Burda,*^‡ and Christoph J. Fahrni*^†

School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta, Georgia 30332, and Center for Chemical Dynamics, Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106

Inorg. Chem., 2003, 42 (16), pp 4918–4929

DOI: 10.1021/ic034529j

Publication Date (Web): July 18, 2003

†

Georgia Institute of Technology.

Corresponding authors. E-mail: fahrni@chemistry.gatech.edu (C.J.F.); sherrill@chemistry.gatech.edu (C.D.S); cxb77@cwru.edu (C.B.).

‡

Case Western Reserve University.

Abstract

A series of three geometrically constrained C₂-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 C₂ 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.

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