Synthesis and characterization of ether-derivatized aminophosphines and their application in C-C coupling reactions

Four new bis(phosphino)amine ligands (Ph₂P)₂N-C₆H₃-R, where R = 3,5-OMe (1), 2,5-OMe (2), 2,4-OMe (3) or 3,4-OMe (4), were prepared via aminolysis of the corresponding dimethoxyanilines with 2 equiv. of diphenylphosphine chloride in the presence of triethyl amine. Oxidation of these ligands with aqueous H₂O₂, elemental S₈ or Se powder afforded the corresponding chalcogen oxides 1a-4a, sulfides 1b-4b and selenides 1c-4c in good yields. Reaction of 1-4 with [MCl₂(cod)] (M = Pt, Pd; cod = cycloocta-1,5-diene) in equimolar ratios afforded cis-[MCl₂{(Ph₂P)₂N-C₆H₃-R}] (M = Pt; R = 3,5-OMe 1d, R = 2,5-OMe 2d, R = 2,4-OMe 3d, and R = 3,4-OMe 4d. M = Pd; R = 3,5-OMe 1e, R = 2,5-OMe 2e, R = 2,4-OMe 3e, and R = 3,4-OMe 4e). Similarly, reaction of [Cu(CH₃CN)₄]PF₆ with the 1-4 in 1:2 ratio gave [Cu{(Ph₂P)₂N-C₆H₃-R}₂]PF₆ (R = 3,5-OMe 1f, 2,5-OMe 2f, 2,4-OMe 3f and 3,4-OMe 4f). All new compounds were fully characterized by spectroscopy and elemental analysis and the molecular structures of seven representative compounds were determined by single-crystal X-ray crystallography. In addition, the palladium complexes were investigated as pre-catalysts in C-C coupling reactions.     

Reactions of 1,8-bis(diphenylphosphino)naphthalene with ruthenium cluster carbonyls: C-H and C-P bond cleavage reactions

Reactions between Ru₃(CO)₁₂ and 1,8-bis(diphenylphosphino)naphthalene (dppn) have given the four complexes Ru₃(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(CO)₈ (1), Ru₄(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(μ-CO)₃(CO)₇ (2) and Ru₄(μ-H)(μ₃-C₆H₄){μ-PPh(nap)PPh₂}(CO)₁₁ (3) (in refluxing thf), and Ru₄{μ₄-P(nap)PPh₂}(μ₄-C₆H₄)(μ-CO)(CO)₉ (4) (in refluxing toluene) which have been characterised by single crystal X-ray studies. They have been formed by aryl C-H and aryl C-P bond cleavage reactions, presumably from an initial (unobserved) chelate dppn complex. The unchanged chelating ligand is found in Ru₃(μ-dppm)(CO)₈(dppn) (5), obtained from Ru₃(μ-dppm)(CO)₁₀ and dppn in refluxing thf.     

Activation and deactivation of a carbene containing non-classical ruthenium hydride complex in catalytic processes involving C-H bond cleavage

The carbene-containing non-classical ruthenium hydride complex [(PCy₃)Ru(H)₂(H₂)₂(IMes)] 1 (IMes=1,3-Bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene) is an active catalyst for H/D exchange in aromatic ketones. It is also capable of combining sp² C-H bond activation with C-C bond formation. Comparing the chemo- and regio-selectivities of the H/D exchange process and the C-C bond formation clearly indicates that different intermediates are involved in the two processes. High pressure NMR studies provide strong evidence that the key intermediate for the C-C coupling reaction is analogous to that for other ruthenium catalysts reported previously. Catalytic turnover is limited by the instability of this intermediate in the presence of the olefinic coupling partner.     

Oxidative cleavage of the C-C bond of 3,6-dialkylcyclohexane-1,2-diones by cell suspension cultures of Marchantia polymorpha

Biotransformation of 3,6-dialkylcyclohexane-1,2-diones by cell suspension cultures of Marchantia polymorpha involves regioselective oxidative cleavage of the C-C bond to give the corresponding oxocarboxylic acids shortened by one carbon unit. In the case of cyclohexane-1,2-dione, adipic acid was obtained.     

Ruthenium mediated C-H activation of benzaldehyde thiosemicarbazones: Synthesis, structure and, spectral and electrochemical properties of the resulting complexes

Reaction of five 4R-benzaldehyde thiosemicarbazones (R = OCH₃, CH₃, H, Cl and NO₂) with [Ru(PPh₃)₃(CO)(H)Cl] in refluxing methanol in the presence of a base (NEt₃) affords complexes of two different types, viz. 1-R and 2-R. In the 1-R complexes the thiosemicarbazone is coordinated to ruthenium as a dianionic tridentate C,N,S-donor via C-H bond activation. Two triphenylphosphines and a carbonyl are also coordinated to ruthenium. The tricoordinated thiosemicarbazone ligand is sharing the same equatorial plane with ruthenium and the carbonyl, and the PPh₃ ligands are mutually trans. In the 2-R complexes the thiosemicarbazone ligand is coordinated to ruthenium as a monoanionic bidentate N,S-donor forming a four-membered chelate ring with a bite angle of 63.91(11)°. Two triphenylphosphines, a carbonyl and a hydride are also coordinated to ruthenium. The coordinated thiosemicarbazone ligand, carbonyl and hydride constitute one equatorial plane with the metal at the center, where the carbonyl is trans to the coordinated nitrogen of the thiosemicarbazone and the hydride is trans to the sulfur. The two triphenylphosphines are trans. Structures of the 1-CH₃ and 2-CH₃ complexes have been determined by X-ray crystallography. All the complexes show intense transitions in the visible region, which are assigned, based on DFT calculations, to transitions within orbitals of the thiosemicarbazone ligand. Cyclic voltammetry on the complexes shows two oxidations of the coordinated thiosemicarbazone on the positive side of SCE and a reduction of the same ligand on the negative side.     

Mononuclear and tetranuclear palladacycles with terdentate [C,N,N] and [C,N,O] Schiff base ligands. C-H versus C-Br activation reactions

Reaction of the Schiff base ligands 2-Br-4,5-(OCH₂O)C₆H₂C(H)NCH₂CH₂NMe₂ (a) and 4,5-(OCH₂CH₂)C₆H₃C(H)NCH₂CH₂NMe₂ (b) with Pd(OAc)₂ or K₂[PdCl₄] leads to the mononuclear cyclometallated compounds [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)NCH₂CH₂NMe₂-C6,N,N}(OCOMe)] (1a) and [Pd{4,5-(OCH₂CH₂)C₆H₂C(H)NCH₂CH₂NMe₂-C6,N,N}(Cl)] (1b), derived from C-H activation at the C6 carbon. Treatment of a with Pd₂(dba)₃ gave [Pd{4-5-(OCH₂O)C₆H₂C(H)NCH₂CH₂NMe₂-C2,N,N}(Br)] (2a), via C-Br activation.The metathesis reaction of 1a with aqueous sodium chloride gave [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)NCH₂CH₂NMe₂-C6,N,N}(Cl)] (3a), with exchange of the acetate group by a chloride ligand. Treatment of the cyclometallated monomers 1a-3a with PPh₃ in a 1:1 molar ratio yielded the mononuclear complexes [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)NCH₂CH₂NMe₂-C6,N}(L)(PPh₃)] (L: OAc, 4a; Cl, 5a) and [Pd{4-5-(OCH₂O)C₆H₂C(H)NCH₂CH₂NMe₂-C2,N}(Br)(PPh₃)] (6a), with Pd-NMe₂ bond cleavage. However, treatment of a solution of 3a or 2a with silver trifluoromethanesulfonate, followed by reaction with PPh₃ in acetone yielded the cyclometallated complexes [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)NCH₂CH₂NMe₂-C6,N,N}(PPh₃)][CF₃SO₃] (7a) and [Pd{4-5-(OCH₂O)C₆H₂C(H)NCH₂CH₂NMe₂-C2,N,N}(PPh₃)][CF₃SO₃] (8a), respectively, where the Pd-NMe₂ bond was retained.The reaction of the ligands 2-Br-4,5-(OCH₂O)C₆H₂C(H)N(2′-OH-5′-^tBuC₆H₃) (c) and 4,5-(OCH₂CH₂)C₆H₃C(H)N(2′-OH-5′-^tBuC₆H₃) (d) with Pd(OAc)₂ gave the tetranuclear complexes [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)N(2′-O-5′-^tBuC₆H₃)-C6,N,O}]₄ (1c) and [Pd{4,5-(OCH₂CH₂)C₆H₂C(H)N(2′-O-5′-^tBuC₆H₃)-C6,N,O}]₄ (1d), respectively. Treatment of 1c with PPh₃ in 1:4 molar ratio, gave the mononuclear species [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)N(2′-(O)-5′-^tBuC₆H₃)-C6,N,O}(PPh₃)] (2c) with opening of the polynuclear structure after P-O_bridging bond cleavage.The structure of compounds 2a, 1c and 1d has been determined by X-ray diffraction analysis.     

Iridium assisted S-H and C-H activation of benzaldehyde thiosemicarbazones. Synthesis, structure and electrochemical properties of the resulting complexes

Reaction of five 4-R-benzaldehyde thiosemicarbazones (R = OCH₃, CH₃, H, Cl and NO₂) with [Ir(PPh₃)₃Cl] in refluxing ethanol in the presence of a base (NEt₃) affords complexes of three different types, viz. 1-R, 2-R and 3-R. In the 1-R complexes the thiosemicarbazone is coordinated to iridium as a monoanionic bidentate N,S-donor forming a four-membered chelate ring. Two triphenylphosphines, a hydride and a chloride are also coordinated to the metal center. The 2-R complexes are very similar in composition and stereochemistry to the corresponding 1-R complexes, except that a second hydride is bound to iridium instead of the chloride. In the 3-R complexes, the thiosemicarbazones are coordinated to iridium as dianionic tridentate C,N,S-donors forming two adjacent five-membered chelate rings. Two triphenylphosphines and a hydride are also coordinated to the metal center. Structures of the 1-NO₂, 2-NO₂ and 3-NO₂ complexes have been determined by X-ray crystallography. Reaction of the same 4-R-benzaldehyde thiosemicarbazones with [Ir(PPh₃)₃Cl] in refluxing toluene in the presence of NEt₃ affords complexes of two types, viz. 3-R and 4-R. The 4-R complexes are very similar in composition and stereochemistry to the corresponding 3-R complexes, except that a chloride is bound to iridium instead of the hydride. Structure of the 4-CH₃ complex has been determined by X-ray crystallography. In all the complexes the two PPh₃ ligands are trans. All the complexes show intense MLCT transitions in the visible region. Cyclic voltammetry on the complexes shows an Ir(III)-Ir(IV) oxidation on the positive side of SCE followed by an oxidation of the coordinated thiosemicarbazone. A reduction of the coordinated thiosemicarbazone is also observed on the negative side of SCE.     

CpFe-induced hexafunctionalization of hexamethylbenzene in [FeCp(η-C6Me6][PF6] using dendronized benzyl bromide derivatives at room temperature for the direct synthesis of metallodendrimers

Reaction of [FeCp(η⁶-C₆Me₆][PF₆] with KOH and benzylbromides parasubstituted with a functional dendron at room temperature selectively gives the hexasubstitution without decomplexation providing functional dendrimers, that were characterized by their molecular peaks in MALDI-TOF spectroscopy whereas, this chemistry was previously carried out at 60 °C which led to partial decomplexation and less selective reactions.     

Nickel promoted C-H, C-C and C-O bond activation in solution

Reaction of NiI₂ with the PCP-ligand {1-Et-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (1) results in selective activation of the strong sp²-sp³ aryl-ethyl bond to afford the aryl-nickel complex [Ni{2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (2), whereas reaction of NiI₂ with {1,3,5-(CH₃)₃-2,6-(CH₂PⁱPr₂)₂-C₆H} (4) leads to the formation of the benzylic complex [Ni{1-CH₂-2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (5) by selective C-H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (6) by activation of the sp²-sp³ C-C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI₂ with {1,3-(CH₂PⁱPr₂)₂-C₆H₄} (3) and {1,3-(CH₃)₂-4,6-(CH₂PⁱPr₂)₂-C₆H₂} (7), respectively, lacking the aryl-alkyl groups between the “phosphines arms” (alkyl=ethyl, methyl). Complexes 2 and 5 have been fully characterized by X-ray analysis. Nickel-based activation of an unstrained C-O single bond was observed as well. Reaction of the aryl-methoxy bisphosphine {1-OMe-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (8) with NiI₂ results in the formation of the phenoxy complex [Ni{1-O-2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (9) by selective sp³-sp³ C-O bond activation.     

Aliphatic and aromatic C-H activation of benzo[h]quinolines by Rh(I). Unique precursor dependent formation of mono-, di- and trinuclear complexes

Treatment of 7,8-benzo[h]quinoline (bhq-H, 1) and 10-methyl benzo[h]quinoline (bhq-Me, 3) with [Rh(C₂H₄)₂(THF)₂][BF₄] resulted in double C-H activation of aliphatic and aromatic C-H bonds, yielding the Rh(III) complexes 4 and 5, respectively. The structures of 4 and 5 were revealed by X-ray diffraction. The reaction of 1 with two other slightly different rhodium precursors, [Rh(olefin)_n(THF)₂][BF₄] (COE (n = 2), COD (n = 1)), led to completely different products, a dinuclear complex 7 and a trinuclear complex 6, respectively, which were characterized by X-ray diffraction. Complex 6 exhibits a rare linear Rh-Rh-Rh structure. Utilizing excess of 1 with [Rh(COD)(THF)₂][BF₄] led to the formation of a new product 8 with no C-H bond activation taking place. Additional C-H activation products of 1, cationic and neutral, in the presence of PⁱPr₃ (9a, 9b and 10) are also presented.     

A novel 1,2,4-triazole-based copper(II) complex: Synthesis, characterization, magnetic property and nuclease activity

A novel binuclear copper(II) complex [Cu₂L(μ-SO₄)](PF₆)₂ (1) (L = 3,5-bis (bis(pyridine-2-ylmethyl)amino)methyl)-4H-1,2,4-triazol-4-amine) has been synthesized and structurally characterized. X-ray structure shows that the two copper(II) atoms are bridged by one bidentate sulfate ion and the 1,2,4-triazole ring of L with Cu1?Cu2 distance of 4.404 Å. Each copper(II) center has a distorted trigonal-bipyramidal configuration. Variable-temperature magnetic susceptibility studies (2-300 K) indicate the existence of weak antiferromagnetic coupling between the copper(II) ions in complex 1. The interaction of complex 1 with calf thymus DNA (CT-DNA) has been studied by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy, viscosity and cyclic voltammetry. Furthermore, complex 1 was able to promote single and double strand DNA cleavage in both aerobic and anaerobic conditions, the pseudo-Michaelis-Menten kinetic parameters k_cat = 2.58 h⁻¹ and K_m = 1.2 × 10⁻⁴ M were obtained for 1. The hydrolytic cleavage of DNA by the complex was supported by the evidence from free radical quenching, anaerobic experiment, thiobarbituric acid-reactive substances (TBARS) assay.     

Targeted expression,purification, and cleavage of fusion proteins from inclusion bodies in Escherichia coli

Today, proteins are typically overexpressed using solubility-enhancing fusion tags that allow for affinity chromatographic purification and subsequent removal by site-specific protease cleavage. In this review, we present an alternative approach to protein production using fusion partners specifically designed to accumulate in insoluble inclusion bodies. The strategy is appropriate for the mass production of short peptides, intrinsically disordered proteins, and proteins that can be efficiently refolded in vitro.     

Synthesis, DNA binding, photo-induced DNA cleavage, cytotoxicity and apoptosis studies of copper(II) complexes

Two new Cu(II) complexes, [Cu(acac)(dpq)Cl] () and [Cu(acac)(dppz)Cl] () (acac = acetylacetonate, dpq = dipyrido[3,2-d:20,30-f]quinoxaline, dppz = dipyrido[3,2-a:20,30-c] phenazine), have been synthesized and their DNA binding, photo-induced DNA cleavage activity and cell cytotoxicity are studied. The complexes show good binding propensity to calf thymus DNA in the order: 2(dppz) > 1(dpq). Furthermore, two complexes exhibit efficient DNA cleavage activity on natural light or UV-A (365 nm) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. The photo-induced DNA cleavage activity of the dppz complex 2 is found to be more efficient than its dpq analogue. In vitro study of the photocytotoxicity of two complexes on HeLa cells indicate that both of them have the potential to act as effective anticancer drugs, with IC₅₀ values of 5.25 ± 0.83 μM (1) and 4.40 ± 0.52 μM (2) in the natural light, and 2.57 ± 0.92 μM (1) and 2.18 ± 0.52 μM (2) in UV-A light. In addition, to detect an apoptotic HeLa body, cells were stained with Hoechst 33342 dye.     

Comparative characterization of four laccases from Trametes versicolor concerning phenolic C-C coupling and oxidation of PAHs

The laccase genes lccα, lccβ, lccγ and lccδ encoding four isoenzymes from Trametes versicolor have been cloned and expressed in Pichia pastoris. Biochemical characterization allowed classification of these laccases into two distinct groups: Lccα and Lccβ possessed higher thermal stability, but lower catalytic activity towards 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) compared to Lccγ and Lccδ. Activities of the laccases were quite different as well. Laccase Lccδ showed highest phenolic C-C coupling activity with sinapic acid, but lowest oxidizing activity towards polycyclic aromatic hydrocarbons (PAHs). Highest activity towards PAHs was observed with Lccβ. After 72 h, more than 80% of fluorene, anthracene, acenaphthene and acenaphthylene were oxidized by Lccβ in the presence of ABTS. Investigation of the structural basis of the different activities of the laccases demonstrated the impact of positions 164 and 265 in the substrate binding site on oxidation of PAHs.     

Synthesis, structure, DNA binding and cleavage properties of ternary amino acid Schiff base-phen/bipy Cu(II) complexes

Ternary Cu(II) complexes [Cu(II)(saltrp)(B)] (1,2), (saltrp = salicylidene tryptophan, B = 1,10 phenathroline (1) or 2,2′ bipyridine (2)) were synthesized and characterized. Complex 2 was structurally characterized by single crystal X-ray crystallography. The molecular structure shows a distorted square pyramidal coordination geometry (CuN₃O₂) in which the ONO donor Schiff base is bonded to the Cu(II) in the basal plane. The N,N donor heterocyclic base displays an axial-equatorial binding mode. CT-DNA binding studies revealed that the complexes show good binding propensity (Intrinsic binding constant, K_b = 3.32 × 10⁵ M⁻¹ for 1 and K_b = 3.10 × 10⁵ M⁻¹ for 2). The catalytic role of these complexes in the oxidative and hydrolytic cleavage of DNA was studied in detail. Complex 1 binds and cleaves DNA more efficiently as compared to 2. From the kinetic experiments, rate constants for the hydrolysis of phosphodiester bond of DNA backbone were determined as 1.94 h⁻¹ and 1.05 h⁻¹ for 1 and 2 respectively. It amounts to (2.93-5.41) × 10⁷ fold rate enhancement compared to uncatalyzed double stranded DNA, which is impressive as compared to related Cu(II) Schiff base complexes.     

Synthesis and structure of a silanetriol via hydroxodearylation involving C-Si bond cleavage

The reaction of tris-iso-propylphenyl-tert-butyl-difluorosilane with KOH using ultra sonication leads to the selective formation of tert-butylsilanetriol, 3. The hydroxodearylation reaction involves C-Si bond cleavage and its mechanism is discussed on the basis of the steric situation of the starting material, which also explains the selectivity of the reaction. The crystal structure of a new polymorph of 3 features a sheet-like hydrogen bonded network.     

Synthesis and characterization of cationic rhodium(I) dicarbonyl complexes

Treatment of Rh(acac)(CO)₂ (acac = acetoacetonate) with perchloric acid followed by addition of an α-diimine (α-diimine = 1,4-bis(Ar)-2,3-dimethyl-1,4-diaza-1,3-butadiene, Ar = 3,5-dimethylphenyl, 1; 3,5-di-tert-butylphenyl, 2; and 3,4,5-trimethoxyphenyl, 3; phenyl, 4; and 4-chlorophenyl, 5) generates a series of complexes of the type [Rh(α-diimine)(CO)₂][ClO₄] 6-10 with varying electronic properties of the supporting diimine ligand. X-ray crystal structures have been determined for the α-diimine ligands 1-5, and complexes 6, 8, and 10.     

Copper(II) complexes with tridentate pyrazole-based ligands: synthesis, characterization, DNA cleavage activity and cytotoxicity

Tridentate pyrazole-containing ligands of the Schiff base type, SalPz — HL¹, Cl₂SalPz — HL² and I₂SalPz — HL³, were used to prepare a series of new Cu(II) complexes (CuSalPz — 1, CuCl₂SalPz — 2 and CuI₂SalPz — 3). These new complexes have been studied by different analytical techniques (electrospray ionization mass spectrometry (ESI-MS), elemental analysis, FT-IR and EPR). The spectroscopic properties of 1-3 are consistent with the formation of Cu(II) complexes coordinated by monoanionic and tridentate (N,N,O)-chelators, behaving as monomeric species in aqueous solution, as shown by EPR studies. Crystals of 2 and 3, obtained by slow concentration of methanolic solutions of the compounds, were also analyzed by X-ray diffraction analysis. The X-ray structural study has shown that 2 crystallized as a dinuclear compound, [Cu₂(μ-Cl)₂(Cl₂SalPz)₂], while the solid state structure determined for 3 is best described by monomeric units of [CuCl(I₂SalPz)] displaying short Cu···Cl intermolecular contacts. The in vitro evaluation of 1-3 comprised the study of their DNA-cleaving ability using plasmid DNA and the assessment of their cytotoxic activity against several human cancer cell lines (PC-3 prostate, MCF-7 breast and A2780 and A2780cisR-ovary). The studies with plasmid DNA have shown that 2 and 3 induce extensive DNA cleavage in the presence of different additives. The cytotoxic activity of 2 and 3 is comparable to the one presented by cisplatin, with the exception of the A2780 cell line where cisplatin is more active. It has been found that the introduction of halogen substituents in the phenolate rings of the chelators enhanced the cytotoxicity of the respective Cu(II) complexes.     

Synthesis, spectroscopy, electrochemistry, and photochemistry of cyano-bridged mixed-valence coordination compounds containing two different types of intervalent charge-transfer bands

The tetranuclear and pentanuclear mixed-valence coordination compounds Na[(NC)₅Fe^II-μ(CN)-Pt^IV(NH₃)₄-μ(NC)-Fe^II(CN)₄-μ(CN)-Ru^III(NH₃)₅], or FePtFeRu, and [Ru^III(NH₃)₅-μ(NC)-Fe^II(CN)₄-μ(CN)-Pt^IV(NH₃)₄-μ(NC)-Fe^II(CN)₄-μ(CN)-Ru^III(NH₃)₅](OSO₂CF₃)₂, or RuFePtFeRu, were synthesized and characterized by IR and UV-Vis spectroscopy, electron microprobe analysis (EPMA), inductively coupled plasma (ICP), and cyclic voltammetry (CV). Both molecules exhibit Fe^II → Pt^IV intervalent charge transfer (IVCT) absorptions in the 400-450 nm range and Fe^II → Ru^III transition(s) between 750 and 950 nm. The energies, intensities, and half-widths of these transitions correspond well with those of model compounds. The cyclic voltammogram of FePtFeRu between 0.00 and 0.90 V versus SCE exhibits two quasi-reversible Fe waves at 0.56 and 0.74 V versus SCE, while that for RuFePtFeRu has only one Fe redox event at 0.72 V versus SCE. When the potential of the working electrode is scanned negative of −0.38 V versus SCE, however, both complexes undergo an ECE (electrochemical-chemical-electrochemical) mechanism whereby the electrochemical reduction of Ru(III) is followed by a double electron transfer to reduce Pt(IV) to Pt(II). Upon reduction to Pt(II), the cyanide bridges break and the complexes dissociate into smaller fragments. Irradiation of the Fe^II → Pt^IV IVCT transition in both compounds leads to a photolysis solution that contains dissociated Fe(II)-Ru(III) as one of its products. Irradiation of the Fe^II → Ru^III IVCT transition yields a similar UV-Vis spectrum, suggesting that the same intermediate is common to both photolysis mechanisms. The implications of this research within the larger context of multiple electron transfer are also discussed.