1 research outputs found
Effects of Electronic and Nuclear Interactions on the Excited-State Properties and Structural Dynamics of Copper(I) Diimine Complexes
The effects of structural constraints on the metal-to-ligand
charge
transfer (MLCT) excited state structural dynamics of cuprous bis-2,9-diphenyl-phenanthroline
([CuÂ(I)Â(dpp)<sub>2</sub>]<sup>+</sup>) in both coordinating acetonitrile
and noncoordinating toluene were studied using X-ray transient absorption
(XTA) spectroscopy and density functional theory (DFT) calculations.
The phenyl groups attached to the phenanthroline ligands not only
effectively shield the CuÂ(I) center from solvent molecules, but also
force a flattened tetrahedral coordination geometry of the CuÂ(I) center.
Consequently, the MLCT state lifetime in [CuÂ(I)Â(dpp)<sub>2</sub>]<sup>+</sup> is solvent-independent, unlike the previously studied 2,9-methyl
substituted bis-phenanthroline CuÂ(I) complex. The MLCT state of [CuÂ(I)Â(dpp)<sub>2</sub>]<sup>+</sup> still undergoes a “pseudo Jahn-Teller
distortion,” with the angle between the two phenanthroline
ligand planes decreased further by 7°. The XTA results indicate
that, in the MLCT excited state of [CuÂ(I)Â(dpp)<sub>2</sub>]<sup>+</sup>, the phenyls at the 2, 9 positions of the phenanthroline rotate,
breaking the π–π interaction with the phenanthroline
ligands without ever rotating in-plane with the phenanthroline ligands.
Hence, the transferred electron density from the CuÂ(I) center is localized
on the phenanthroline moiety with no charge density present on the
phenyl rings. The insight about the effect of the structural constraints
on the MLCT state properties will guide the design of CuÂ(I) diimine
complexes with suitable excited-state properties to function as earth-abundant
dye sensitizers for solar electricity generation