Photochemical properties, copper

Photochemical properties of copper complexes. G. Ferraudi and S. Muralidharan, Coord. Chem. Rev., 1981,36,45-88(115). 

The most easily identifiable characteristics are those related to the shape of the complexes, with their double-stranded helical cores. In this respect, the electrochemical and photochemical properties of Cu2(K-84)2+ are not much different from those of the open-chain helical precursor or its O-methylated version. The strong electronic coupling between the two copper centers is clearly a consequence of the 1,3-phenylene bridges between the two complex subunits and the topological properties of the ligand have virtually no influence. 

The copper(I) alkynyls displayed rich photochemistry and particularly strong photoreducing properties. The transient absorption difference spectrum of [Cu3(dppm)3(/X3-) -C=CPh)2]+ and the electron acceptor 4-(methoxycarbonyl)-A-methylpyridinium ion showed an intense characteristic pyridinyl radical absorption band at ca. 400 nm. An additional broad near-infrared absorption band was also observed and it was assigned as an intervalence-transfer transition of the mixed-valence transient species [Cu Cu Cu (dppm)3(/x3- -C=CPh)2] +. The interesting photophysical and photochemical properties of other copper(I) alkynyl complexes such as [Cu(BTA)(hfac)], 2 [Cui6(hfac)8(C=C Bu)8], and [Cn2o(hfac)8(CsCCH2Ph)i2] have also been studied. 

A review of the photochemical properties of copper complexes includes a survey of the photocatalysed reactions of copper-olefin complexes. The addition of acetonitrile to norbornene may be induced by irradiation in the presence of silver ions. The reaction appears to involve excitation of a LMCT excited state of the norbomene-silver complexes and the formation of norbornene radical cations. 

Metalloporphyrins electrical properties, 144 in oxygen production from water, 522 photochemical properties, 510 in photoproduction of hydrogen from water, 511, 510-513 structure, 615 Mctallothioncins cobalt(II), 673 copper and zinc storage, 672 EXAFS, 673 mammals... 

Preliminary studies on the photochemical properties of thiacyAn and of its copper(II) and copper(I) complexes have been carried out in an anhydrous and desaerated acetonitrile solution and the results are summarized in Figure 16. 

In a series of papers, Ford and co-workers described the photophysical and photochemical properties of these luminescent clusters in detail [46-58]. In addition to complexes 4a and 4b, time-resolved emission spectra of the tetranu-clear copper(I) iodide clusters [Qi4l4(L)4] with a series of substituted pyridines [L = 4-tert-butylpyridine (4c), 4-benzylpyridine (4d), pyridine-dj (4e), 4-phe-nylpyridine (4f), 3-chloropyridine (4g), piperidine (4h), P"Bu3 (4i)] have also been studied [49]. The photophysical data are summarized in Table 1. In general, in toluene solution at 294 K, the complexes revealed a low-energy emission at 678-698 nm and a weaker, higher energy emission at 473-537 nm. The emission spectrum of 4a in toluene at 294 K is shown in Fig. 2... 

Porphyrins, owing to their outstanding photophysical and redox properties [74], are extensively used for the construction of photochemical molecular devices to achieve charge separation over nanometric distance [75]. Porphyrin units have been successfully incorporated into rotaxane structures [76, 77], first playing the role of stoppers. In CHjCN solution at room temperature, [2]rotaxane 17 (Fig. 15) [78, 79] undergoes a very fast (ca. 2 ps) electron transfer process from the Zn(II) to the Au(III) porphyrin upon excitation of the Zn(II) porphyrin moiety (process 1 in Fig. 15). Although direct back electron transfer from the Au(II) to the Zn(III) porphyrin indeed occurs (530 ps), the initial state is restored mainly via oxidation/reduction of the central copper unit, that is, through an electron transfer from... 

The idea of metal-metal bond establishment in the excited state of this complex has also stimulated the interest on the photophysical and photochemical investigations of related d -d complexes. In 1970, Dori and co-workers first reported the luminescence properties of phosphine complexes of d metal centers such as copper(I), silver(I), gold(I), nickel(0), palladium(0), and platinum(0) [12]. Later in 1985, Caspar reported the luminescence properties of polynuclear nickel(O), palladium(O), and platinum(O) complexes of phosphine, phosphite, and arsine [13]. Similar to the related d -d systems, the emissive states of [Pd2(dppm)3] and [Pd Cdpam),] have been suggested to be metal-centered (d-p) in nature modified by metal-metal interaction. 

In conclusion, we believe that the photophysical and photochemical studies on polynuclear d " complexes are at a stage of rapid expansion. With the highly flexible molecular geometry and characteristic emissive properties, it is conceivable that luminescent polynuclear copper(I), silver(I), and gold(I) complexes will play a unique and crucial role in inorganic photochemistry. 

Endicott, J. F. Ramasami, T Tamilarasan, R. Lessard, R. B. Brubaker, G. R. Structuie and Reactivity of the Metal-Centered Transition Metal Excited States, Coord. Chem. Revs. 1987,77,1. Ferraudi, G. Thotochemical Properties of Copper Complexes, Coord. Chem. Revs. 1981,36,45. Ford, P. C. Vogler, A. Photochemical and Photophysical Properties of Tetranuclear and Hexanuclear Clusters of Metals with and Electronic Configurations, Acc. Chem. Res. 1993,26,220. 

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