Valeri Pawlowski

Photoredox behavior of a trinuclear Ru(III),Ru(II),Co(III) complex induced by metal-to-metal charge transfer excitations

Abstract The trinuclear complex [(NH 3 ) 5 Ru(III)(μ-NC)Ru(II)(CN) 4 (μ-CN)Co(III)(NH 3 ) 5 ]Cl 2 ·2H 2 O was prepared and characterized by IR and UVVis spectroscopy. The aqueous complex shows two long-wavelength absorptions at λ max =647 and 372 nm which are assigned to Ru(Il) to Ru(III) and Ru(Il) to Co(III) MMCT transitions, respectively. Photolysis of the aqueous solution led to a redox decomposition. Co 2+ was formed with φ=2x10 −4 at λ irr =577 and 0.18 at 366 nm. The electronic spectrum as well as the photoreactivity of the trinuclear complex are discussed on the basis of a Hush diagram which accommodates three redox-active metal centers.

Electronic spectra and photoreactivity of (cyclopentadienyl)rhenium(I)(dicarbonyl)(nitrosyl) cation

Abstract The complex [CpReI(CO)2(NO)]+ with Cp=cyclopentadienyl shows two long-wavelength absorptions at λmax=380 and 330 nm which are assigned to ReI→NO+ metal-to-ligand charge transfer (MLCT) transitions. In the solid state [CpReI(CO)2(NO)]PF6 displays a luminescence at λmax=570 nm which is assumed to originate from the lowest-energy ReI→NO+ MLCT triplet. In solution the complex is not emissive but photoreactive. In the presence of PPh3, MLCT excitation leads to a photosubstitution yielding [CpRe(CO)(PPh3)(NO)]+. The dependence of the quantum yield on the PPh3 concentration is consistent with an associative mechanism.

Optical metal-to-metal charge transfer of (μ-cyano) decaamminediosmium((III)

Abstract The binuclear complex [(NH 3 ) 5 Os III (μ-CN)Os III (NH 3 ) 5 ] 5+ shows absorption bands in the visible region (a (at λ max = 523, 425 and 326 nm which are assigned to Os(III)-to-Os(III) metal-to-metal charge transfer (MMCT) transitions.

Electronic spectra and photochemistry of trichlorostannyl complexes of rhodium(III) and platinum(II)

The absorption spectra of [Rh(SnCl3)4Cl2]3− and [Pt(SnCl3)5]3− are characterized by a similar band pattern. It is suggested that the absorption spectra are dominated by bands which are assigned to intraligand transitions. While solid (NBu4)3[Pt(SnCl3)5] shows a low-temperature emission the rhodium complex is not luminescent. Both complex anions are light sensitive in acetonitrile solution. They undergo an efficient photosubstitution of the trichlorostannyl ligand.

Excited state properties of IrIII(phpy)2(naphthylalaninate) with phpyH = 2-phenylpyridine. Energy transfer and luminescence

Abstract The complex Ir III (phpy) 2 (nala) with phpyH = 2-phenylpyridine and nalaH = 3-(2-naphthyl)alanine was prepared and characterized. The electronic spectrum of the complex shows long-wavelength absorptions which are attributed to the Ir III (phpy) 2 chromophore. The lowest-energy excited state is a metal-to-ligand charge transfer (MLCT) triplet which is emissive under ambient conditions. Excitation of the naphthyl chromophore at shorter wavelength is followed by an efficient energy transfer to the Ir III (phpy) 2 fragment.

Electronic spectra and photochemistry of trichlorostannyl complexes of ruthenium(II) and osmium(II)

The absorption spectra and photochemistry of trichlorostannyl complexes [M(SnCl3)6]4−, [M(SnCl3)5Cl]4− and [M(SnCl3)5AN]3− (M = Ru, Os; AN = acetonitrile) in acetonitrile were investigated. In view of the similarity of all absorption spectra it is suggested that the lowest energy transitions are largely of the intraligand type. The photolysis of these complexes in acetonitrile leads to substitutions of SnCl3− or in the case of [Ru(SnCl3)6]4− to a ligand fragmentation as primary photoreactions. Owing to secondary processes [M(snCl3)4(AN)2]2− is the terminal product of all the photoreactions. It is assumed that the photoreactions are initiated by intraligand excitation.

Photochemical Generation of Tribromostannate(II) by Redox and Substitution Reactions

Hexabromostannate(IV) in acetonitrile undergoes a photochemical reductive elimination according to the equation [SnBr6]2- →[SnBr3]- + Br3- with ϕ= 0.06 at λirr = 313 nm. The formation of [SnBr3] - takes place also by irradiation of [Ru(SnBr3)5 Br]4- in acetonitrile with visible light. This photosubstitution occures with ϕ > 0.09 at λirr = 436 nm.

Photoluminescence of tetrachloroarsenate(III)

Glasses of (NBu4)AsCl4 in ethanol at 77 K show a red emission at λmax=617 nm with O≈ 10−4 and τ=0.46 μs. It is suggested that this luminescence originates from the sp excited state 3P1 of the As3+ ion. The excited state properties of AsCl−4 are discussed in comparison to those of SbCl−4 and BiCl−4.

Synthesis and Luminescence of RhIII(phpy)2(E∪O) Complexes with phpyH = 2-Phenylpyridine and E∪OH = Tropolone, Flavonol and Lumichrome

The complexes RhIII(phpy)2(E∪O) with phpy− = deprotonated 2-phenylpyridine and E∪O− = bidentate anions of the biologically important compounds E∪O (troH = tropolone, flaH = flavonol and lumH = lumichrome) have been prepared and characterized with regard to their optical properties. The RhIII(phpy)2 fragment is a useful probe for the emission behavior of these complexes since the phpy IL triplet can serve as a marker. Only the IL states of tp− and lum− are located below the phpy IL states. While RhIII(phpy)2(fla) is quite remarkable because it shows an IL (fla) fluorescence, RhIII(phpy)2(lum) displays an IL (lum) phosphorescence as expected owing to the heavy-atom effect.

Synthesis And Luminescence Of RhIII(phpy)2(S∪E) Complexes With phpy– = Deprotonated 2-Phenylpyridine And S∪E– = Diethyldithiocarbamate, 2-Pyridinethiolate And 2-Quinolinethiolate

Complexes of the general composition RhIII(phpy)2(S∪E) with phpy− = 2-(2-pyridyl)phenyl and S∪E− = diethyldithiocarbamate, 2-pyridinethiolate and 2-quinolinethiolate were prepared and characterized. The complexes with S∪E− = diethyldithiocarbamate and 2-pyridinethiolate show a low-temperature luminescence which originates from a phpy ππ∗ intraligand triplet. For the complex with S∪E− = 2-quinolinethiolate (or thiooxinate) the lowest-energy excited state is of the quinolinethiolate intraligand type. This complex displays a fluorescence as well as a phosphorescence under ambient conditions