Alkynyl electronic absorption

Owing to the advances in the synthesis of organoplatinum(ii) alkynyl compounds as well as the intriguing physical and photophysical properties exhibited by these materials, the evaluation of their structure-property relationship is therefore attractive and feasible. The spectroscopic properties of mononuclear nickel(ii), palladium(ii) and platinum(ii) alkynyl complexes of the type trans-[M(C=CR)2L2] (R = alkyl, aryl L = phosphine, stibine) have been widely investigated [111-114]. The electronic absorption spectra of this class of complexes have been reported by Masai et al. [115], while the emission properties of a series of closely related platinum(ii) complexes were reported by Demas and coworkers [116]. The lowest... 

Table 10.2. Electronic absorption and photophysical data of selected Pd(ii) and Pt(ii) complexes of branched alkynyls.

Table 10.5. Electronic absorption and photophysical data of Re(i) metal alkynyl complexes. Data adapted from [89]. 

Table 10.6. Electronic absorption and emission data of Re-Fe mixed-metal alkynyl complexes in dichloromethane solution. Data adapted from [222].

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. 

H, alkyl, Ph, SiMe3) (15a-e). These dimetallapolyyne compounds are particularly suitable for the study of metal-alkynyl 7r-interactions by electronic spectroscopy because the formally metal-metal localized S HOMO and 8 LUMO are of ir-symmetry with respect to the alkynyl ligands, and hence the (8 -> 8 ) absorption band should manifest any M-CCR ir-interactions (Scheme 1). The (8 - 8 ) transition energies of these alkynyl derivatives are substantially smaller (M = Mo, =... 

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