Copper(I) Donor–Chromophore–Acceptor Assembly for Light-Driven Oxidation on a Zinc Oxide Nanowire Electrode

Abstract

Dye-sensitized photoelectrochemical cells have emerged as a potential candidate for solar-to-fuel conversion. Herein, we report a Cu(I)-based donor− chromophore−acceptor triad comprising a triphenylamine electron donor and a dipyrido[3,2-a:2′,3′-c]phenazine electron acceptor as the active material for photoanodes. Energy levels of this triad are carefully aligned for thermodynamically favorable photoinduced electron transfer. Once this triad is surface-grafted onto zinc oxide nanowires, photoelectrochemical studies confirm the utility of this architecture for oxidative processes such as alcohol oxidation with modest yields.

Effects of increasing ligand conjugation in Cu(i) photosensitizers on NiO semiconductor surfaces

“…S4†). 15 The free energy change for electron transfer from the excited 3 MLCT state to the electron acceptor upon photoexcitation was estimated using . The Gibbs free energy change for forward electron transfer (Δ G et ) for A-Cu(I)-L1 , A-Cu(I)-L2 and A-Cu(I)-L3 was calculated to be 0.10 eV, 0.03 eV and −0.17 eV respectively.…”

“…S4 †). 15 The free energy change for electron transfer from the excited 3 MLCT state to the electron acceptor upon photoexcitation was estimated using…”

“…5,[7][8][9][10] There has also been increased interest in developing photosensitizers using Earth-abundant first-row transition metals. [11][12][13][14][15] In recent years, copper(I)-bisdiimine photosensitizers have evolved considerably in this area because of their photo-physical similarities to their ruthenium(II) analogs. 11,[16][17][18] The prototypical photosensitizer [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) and its analog [Cu(dmp) 2 ] + (dmp = 2,9-dimethyl-1,10-phenanthroline) absorb similarly in the visible region of the electromagnetic spectrum because of 1 MLCT transitions arising from the promotion of electrons from the d orbitals of the metal to the π* antibonding orbitals of the ligand.…”

“…5,7–10 There has also been increased interest in developing photosensitizers using Earth-abundant first-row transition metals. 11–15…”

Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines

“…Two classes of Cu­(I) bis -phenanthrolines engender either homoleptic or heteroleptic ligand topologies. Homoleptic cuprous phenanthrolines have been studied since the 1970s for their potent photoreducing capabilities, long-lived excited states, and tremendous durability to high-power laser excitation. ,,− Heteroleptic complexes using diimine- and bis -phosphine-type ligands have been growing in interest, especially for applications in dye-sensitized solar cells, − photoredox catalysis, − and the construction of supramolecular donor–acceptor architectures. ,,− The HETPHEN strategy leverages 2,9-mesityl-1,10-phenanthroline (mesPhen), ,, which is unable to form a bis -homoleptic complex but enables the binding of another suitable phenanthroline, assisted through π-interactions with the 2,9-mesityl substituents and the B-ring of the orthogonally coordinated phenanthroline. This platform facilitates a facile pathway for obtaining heteroleptic Cu­(I) complexes with the generic formula [Cu­(mesPhen)­(L)] + , where L is a second and distinct phenanthroline ligand (Chart ).…”