Photoinduced Multistep Charge Separation in a Heteroleptic Cu(I) Bis(phenanthroline)-Based Donor–Chromophore–Acceptor Triad

Abstract

A molecular triad assembly consisting of an electron donor, a bis(phenanthroline)copper(I) chromophore, and an electron acceptor has been prepared. Under visible-light excitation, this assembly undergoes efficient (ca. 50%) photoinduced, multistep formation of a diradical cation charge-separated state that has a lifetime of >100 ns and stores >1.0 eV of energy. This system constitutes an earth-abundant functional analogue of related Ru(bpy)(3) triad systems.

Long‐Lived, Emissive Excited States in Direct and Amide‐Linked Thienyl‐Substituted RuII Complexes

“…Although Δ-and Λ-isomers of these heteroleptic complexes are possible, no efforts were made to isolate the isomers. 1 H and 13 C NMR spectra are consistent with symmetrical species in solution, confirm-ing the expected C 2 symmetry of these ML 2 L′-type complexes. [37] Solid State Characterization X-ray quality crystals of heteroleptic complexes 1-4 were grown from concentrated CH 2 Cl 2 or CH 3 CN solutions layered with Et 2 O, allowing for characterization of these complexes in the solid state.…”

“…All chemical shifts in 1 H and 13 C spectra were referenced to residual solvent, and the splitting patterns are designated as s (singlet), d (doublet), t (triplet), m (multiplet) or br (broad). NMR solvents (Cambridge Isotope Laboratories or Sigma) were used as received.…”

“…The resulting residue was treated with a saturated NH 4 PF 6(aq) solution to yield the title complex as a dark orange precipitate, yield 25 mg (30 %). 1 …”

“…Photoexcitation of rationally designed donor-acceptor (D-A) dyads or donor-chromophoreacceptor (D-C-A) triads may lead to the formation of chargeseparated states via intramolecular electron transfer. [1][2][3][4][5] These charge-separated states, if sufficiently long-lived and storing a does not act as a conjugated bridge to the peripheral substituents, it does not preclude possible electron transfer processes. Complexes bearing directly bound thienyl and bithienyl substituents exhibit long excited state and emission lifetimes (τ em = 2 and 15 μs), with high emission quantum yields in solution (Φ = 0.35) and slow rates of non-radiative decay.…”

Functional Arrays for Light Energy Capture and Charge Separation

“…On the other hand, the use of Cu(I) bis‐phenanthroline as photosensitizer with a phenothiazine as donor and a methyl viologen as acceptor, proposed by Elliott, resulted in a CS yield of ca. 50% and a lifetime on the order of one hundred nanoseconds 39. This is very valuable for the use of a relatively cheap, non‐precious metal center, which is unquestionably important for the practical use of these arrays.…”