Photodriven Energy Transfer from Cuprous Phenanthroline Derivatives

Abstract

An important goal in inorganic photochemistry is the development of new artificial photosynthetic assemblies capable of efficiently harvesting solar energy.' In this regard, the excited state properties of cuprous diimine chromophores have received considerable attention? Detailed studies have largely established the geometric and electronic nature of the metal-to-ligand charge-transfer (MLCT) excited states in these c o m p o~n d s .~-~ The luminescent excited states are quenched by a variety of inorganic and organic compounds, but the underlying mechanism-(s) remain speculative. In this communication, we report the first direct spectroscopic observation of energy transfer from cuprous diimine excited states. Specifically, photoexcited Cu-(dpp),(PFs) (dpp is 2,9-diphenyl-l,lO-phenanthroline) and Cu-(dmp)a(P&) (dmp is 2,9-dimethyl-1,lO-phenanthroline) transfer energy to anthracene in dichloromethane solution, eqs 1 and 2. These reactions are important in photocatalysis as anthracene can function as an efficient energy relay between light absorbing donors and electron acceptor^.^ (a) Fox, M. A.; Chanon, M. Photoinduced Electron Transfer; Elsevier: Amsterdam, 1988. (b) Gratzel, M. Heterogeneous Phorochemical Electron Transfer; CRC: Boca Raton, FL, 1989. For a recent review of copper(1) diamine excited states, see: (a) Kalyanasundaram, K. Photochemisrry of Polypyridine and Porphyrin Complexes; Academic Press: London, 1992; Chapter 9. (b) McMillin, D. R.; Kirchhoff, J. R.; Goodwin, K. V. Coord. Chem. Rev. 1985.64, 83. (a) McMillin, D. R.; Buckner, M. T.; Ahn, B. T.

Synthesis, Structure, and Spectroscopic and Electrochemical Properties of Copper(II/I) Complexes with Symmetrical and Unsymmetrical 2,9‐Diaryl‐1,10‐phenanthroline Ligands

“…In particular, the redox potential becomes more positive when the steric constraint in the 2-and 9-positions increases, as this can prevent the rearrangement of the coordination sphere to the favored square-planar for the oxidized Cu II species and thus stabilize the Cu I state. [14,33,34] A comparison of the complexes studied here revealed a complete agreement with this trend: increasing the 2,9-substituents on 1,10-phenanthroline from diphenyl (complexes 7, 10) to phenyl/naphthyl (8,11), and then to dinaphthyl (9,12) shifted the [CuL 2 ] 2+/+ couple to more positive potentials (Figure 6a,b (Table 2). For the complexes with the CuCl 2 -anion, 7-9, there is also an irreversible reduction peak at 0.2-0.3 V, which might be caused by the dissociation or ligand exchange during the redox process.…”

“…[16] The Cu I complex [Cu(dpp) 2 ](CuCl 2 )·2/3CH 3 CN was also structurally characterized. [20] Here we present the structures of three Cu II complexes (1, 3, and 6)and one Cu I complex (12). Single crystals suitable for X-ray diffraction were obtained from CH 2 …”

Taking Snapshots of Photoexcited Molecules in Disordered Media by Using Pulsed Synchrotron X‐rays

“…+ -the "Exciplex" [79,122] The MLCT excited states of cuprous diimine compounds are potential-energy and electron donors, [123][124][125][126][127][128] and functional moieties in molecular devices, because of their room temperature luminescence and structural reorganization upon Cu I -Cu II interconversion triggered electrochemically or photochemically. [129,130] Among these compounds, [Cu I (dmp) 2 ] + (dmp = 2,9-dimethyl-1,10-phenanthroline) is one of the most extensively studied, in which the photoinduced MLCT transition can be shown as, [Cu I (dmp) 2 ] + + hn!…”

Tetra‐ and Octalactam Macrocycles and Catenanes with Exocyclic Metal Coordination Sites: Versatile Building Blocks for Supramolecular Chemistry

“…The complexes of Cu I are of particular interest, because previous examples have shown their ability to effect the catalytic reduction of dioxygen, [17] their diverse activities in many biological systems, [18] and their ability to transfer energy to anthracene, which may prove useful in photocatalytic solar energy harvesting systems. [19] Also, the (bpy) 2 Ru II complex (bpy 2,2'-bipyridine) of the tetralactam macrocycle has been synthesized and its anion binding properties [20] have been examined in comparison to those of the tetralactam macrocycle alone.…”