Synthesis,electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new phthalocyanines peripherally fused to four flexible crown ether moieties

Novel Ni(II), Zn(II), Co(II) and Cu(II) phthalocyanines with four peripheral 4-[methyleneoxy(18-crown-6)] groups have been synthesized via the cyclic tetramerization of 4-[{(18-crown-6)-yl}methyleneoxy]phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The thermal stabilities of the metal-free and metallophthalocyanine compounds were determined by thermogravimetric analysis. The structures of the target compounds were confirmed using elemental analysis, IR, ¹H-NMR, ¹³C-NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while the cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, the metal-free, nickel, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes.     

Polytopic cation receptor functional phthalocyanines: Synthesis,characterization, electrochemistry and metal ion binding

Our efforts toward the development of the synthesis of a novel type of receptor ligand and its tetrasubstituted phthalocyanines, 2,9,16,23-tetrakis(6-hydroxyhexylsulfanyl) phthalocyanine, M[Pc(S–C₆H₁₃OH)₄] (M = Zn(II), Cu(II), Co(II)), bearing sulfur and oxygen donor atoms on the periphery together with hexyl moieties, have been carried out together with spectroscopic and electrochemical characterization. The newly synthesized functional phthalocyanines were soluble in MeOH, EtOH, THF, DMF, CNP (α-chloronapthalene), DMSO and quinoline, and less soluble in i-PrOH and CH₃CN. Cation binding abilities of the functional phthalocyanines with Ag⁺, Pd²⁺, Hg²⁺ and Cd²⁺, resulting in the formation of polynuclear phthalocyanine complexes, were evaluated by UV–Vis spectroscopic techniques. The spectroscopic properties of the complexes were affected strongly by the electron-donating sulfanyl units on the periphery. The cyclic voltammetry of the complexes were examined on a platinum electrode in DMSO. The new synthesized compounds have been characterized by elemental analysis, FTIR, ¹H and ¹³C NMR, MS (ESI and MALDI-TOF) and UV–Vis spectral data.     

Synthesis,electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new metal-free and metallophthalocyanines substituted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups

The synthesis of novel metal-free and metallophthalocyanines [Ni(II), Zn(II), Co(II), Cu(II)] were prepared by cyclotetramerization of a novel 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH₃COO)₂, CoCl₂ and CuCl₂). The structures of the target compounds were confirmed using elemental analysis, IR, ¹H NMR, ¹³C NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, metal-free, and zinc phthalocyanines show only ring-based reduction and oxidation processes. All complexes decomposed and coated on the electrode as nonconductive film at positive potential window of the electrolyte. An in situ electrocolorimetric method has been applied to investigate color of the electro-generated anionic and cationic forms of the complexes.     

Synthesis,characterization and fluorescence behavior of new fluorescent probe phthalocyanines bearing coumarin substituents

In this study, we report a new ligand, 6-hexyloxy-3-[p-(3′,4′-dicyanophenoxy)phenyl]coumarin, and its fluorescent tetrasubstituted phthalocyanines {M[Pc(OBzCou)₄], M = 2H, Zn(II), Co(II); Bz: Benzene}. The effect of the coumarin derivative on the intensity of the fluorescence spectra of the metal-free (H₂Pc) and zinc phthalocyanine (ZnPc) derivatives was investigated. The change of the emission properties of both the coumarin moieties and the phthalocyanine core in the presence of the metal ion and the ring-opening reaction of the coumarin were studied by means of steady-state fluorescence spectroscopy. The radiative decay of the Pcs and the treated coumarin substituents bound to the Pcs was examined. The novel chromogenic compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, Maldi-TOF, IR and UV–Vis spectral data. The photophysical properties of the Pcs are extensively affected by their state of aggregation: in particular, dimerization and aggregation result in a remarkable modification of the absorption and emission bands and may induce significant quenching of the usually strong Pc fluorescence. The electronic spectra exhibit a band of coumarin identity together with characteristic Q and B bands of the phthalocyanine core.     

1,3-Bis(2-alkyltetrazol-5-yl)triazenes and their Fe(II), Co(II) and Ni(II) complexes: Synthesis,spectroscopy, and thermal properties. Crystal structure of Fe(II) and Co(II) 1,3-bis(2-methyltetrazol-5-yl)triazenide complexes

Complexes ML¹₂ and ML²₂, with M = Fe^II, Co^II, Ni^II, and 1,3-bis(2-R-tetrazol-5-yl)triazenide ligands L¹ (R = Me) and L² (R = ^tBu), have been synthesized by the reaction of corresponding 1,3-bis(2-R-tetrazol-5-yl)triazenes with metal(II) salts in basic media and characterized by IR, UV–Vis spectroscopy, thermal and X-ray diffraction analyses. Both 1,3-bis(2-R-tetrazol-5-yl)triazenes were found to deprotonate on coordination and act as tridentate chelating ligands forming distorted MN₆ octahedra around metal(II) cations.     

Synthesis,characterization, aggregation and thermal properties of a novel polymeric metal-free phthalocyanine and its metal complexes

A novel polymeric metal-free phthalocyanine (M = 2H) and its metal complexes (M = Zn, Cu, Co and Ni) were prepared by the tetramerization reaction of 3,6,9-Tris(p-tolylsulfonyl)-1,11-bis(3,4-dicyanophenoxy)-3,6,9-triazaundecane 5 with the appropriate materials. The electrical conductivities of the metal-free phthalocyanine and the metal complexes, measured in air, were found to be ∼10⁻⁶–10⁻⁵ S m⁻¹. The aggregation property of the zinc complex 7 was investigated with Ni²⁺, Cu²⁺, Co²⁺, Pb²⁺, Cd²⁺ and Ag⁺ cations. Thermal analysis of the polymers were done by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10 °C min⁻¹ under a nitrogen atmosphere. All the novel compounds were characterized by using elemental analysis, UV–Vis, FT–IR, NMR and MS spectral data and DSC, DTA/TG techniques.     

Synthesis and electrochemistry of tetrakis(7-coumarinthio-4-methyl)-phthalocyanines,and preparation of their cinnamic acid and sodium cinnamate derivatives

Novel water soluble free-base, Zn(II) and Co(II) metallo phthalocyanines with four cinnamic acid moieties were prepared from the corresponding tetrakis(7-coumarinthio-4-methyl)-phthalocyanine by the lactone ring opening reaction. The new compounds were purified and characterized by elemental analysis, ¹H NMR, Maldi-TOF, FT-IR and UV–Vis spectral data. Cyclic and differential pulse voltammetry and in situ spectroelectrochemistry of the 2,9,16,23-tetrakis(7-coumarinthio-4-methyl) substituted free-base 1a, Zn(II) 1b and Co(II) 1c phthalocyanines, employed as the starting compounds have been studied. This allowed us not only to identify metal- and phthalocyanine ring-based redox processes of the complexes, but also the effect of aggregation on these processes.     

Synthesis of novel unsymmetrical phthalocyanines substituted with crown ether and nitro groups

This work reports on the synthesis of new unsymmetrically substituted phthalocyanines (M = Zn, Cu, Co, Ni) bearing three benzo-15-crown-5 units through oxy bridges and a nitro group. Phthalocyanines were prepared by a statistical condensation of 4-nitro phthalonitrile and 1-{[(benzo-15-crown-5)-4′-yl]oxy}phthalonitrile in the presence of anhydrous metal salts. All the target unsymmetrical phthalocyanines were separated by column chromatography and characterized elemental analyses, ¹H NMR, IR, mass and UV–Vis spectral data. Electrochemical behaviors of Cu (II) phthalocyanine by cyclic voltammetry and differential pulse voltammetry techniques gave two common phthalocyanine ring reductions and one ring oxidation processes. Peak-to-peak separation of the processes II and III (388 mV) and the measure of gap (1.672 V) between the HOMO and LUMO for the complex, fits a phthalocyanine with electrochemically inactive metal center.     

Synthesis,characterization and spectroscopic studies of a new ligand [N′-(2-methoxybenzoyl)hydrazinecarbodithioate] ethyl ester and its Mn(II) and Cd(II) complexes: X-ray structural study of Mn(II) complex

A new dithioligand [N′-(2-methoxybenzoyl)hydrazinecarbodithioate] ethyl ester (H₂mbhce, 1) formed complexes [M(Hmbhce)₂]_n {M = Mn(II), Cd(II)} which have been characterized with the help of elemental analyses, magnetic susceptibility measurements, IR, UV–Vis, ¹H and ¹³C NMR and mass spectrometry. [Mn(Hmbhce)₂]_n (2) crystallized in monoclinic system with space group P₂₁/n. In the polymeric structure of 2, the ligand acts as an uninegative tridentate N(1), O(1), S(3) donor and forms a five membered chelate ring with N(1), C(2) and O(1). The intermediate bond lengths (between single and double bond distances) O(1)–C(2) = 1.241(3), N(2)–C(2) = 1.325(3), N(1)–N(2) = 1.393(2), N(1)–C(8) = 1.311(3) ? and C(8)–S(3) = 1.704(2) Å suggest considerable delocalization of charge which develops slightly aromatic character in the chelate ring.     

Dinuclear copper(II) perchlorate complexes with 6-(benzylamino)purine derivatives: Synthesis,X-ray structure,magnetism and antiradical activity

The reactions of Cu(ClO₄)₂·6H₂O with 6-(benzylamino)purine derivatives in a stoichiometric 1:2 metal-to-ligand ratio led to the formation of penta-coordinated dinuclear complexes of the formula [Cu₂(μ-L^1–8)₄(ClO₄)₂](ClO₄)₂·nsolv, where L¹ = 6-(2-fluorobenzylamino)purine (complex 1), L² = 6-(3-fluorobenzylamino)purine (2), L³ = 6-(4-fluorobenzylamino)purine (3), L⁴ = 6-(2-chlorobenzylamino)purine (4), L⁵ = 6-(3-chlorobenzylamino)purine (5), L⁶ = 6-(4-chlorobenzylamino)purine (6), L⁷ = 6-(3-methoxybenzylamino)purine (7) and L⁸ = 6-(4-methoxybenzylamino)purine (8); n = 0–4 and solv = H₂O, EtOH or MeOH. All the complexes have been fully characterized by elemental analysis, FTIR, UV–Vis and EPR spectroscopy, and by magnetic and conductivity measurements. Variable temperature (80–300 K) magnetic susceptibility data of 1–8 showed the presence of a strong antiferromagnetic exchange interaction between two Cu(II) (S = 1/2) atoms with J ranging from −150.0(1) to −160.3(2) cm⁻¹. The compound 6·4EtOH·H₂O was structurally characterized by single crystal X-ray analysis. The Cu?Cu separation has been found to be 2.9092(8) Å. The antiradical activity of the prepared compounds was tested by in vitro SOD-mimic assay with IC₅₀ in the range 8.67–41.45 μM. The results of an in vivo antidiabetic activity assay were inconclusive and the glycaemia in pre-treated animals did not differ significantly from the positive control.     

DNA binding and antimicrobial studies of some polyethyleneimine-copper(II) complex samples containing 1,10-phenanthroline and l-theronine as co-ligands

The polymer–copper(II) complex samples, [Cu(phen)(l-Thr)(BPEI)]ClO₄ · 2H₂O (l-Thr = l-theronine, phen = 1,10-phenanthroline and BPEI = branched polyethyleneimine), with varying degrees of copper(II) chelate content in the polymer chain, were prepared by ligand substitution method in water–ethanol medium and characterized by Infra-red, UV–Vis, EPR spectral and elemental analysis methods. The binding of these complex samples with calf thymus DNA (CT-DNA) has been investigated by absorption spectroscopy and emission spectroscopy and gel electrophoresis techniques. The experimental results indicate that the polymer–copper(II) complex is an avid DNA binder and the binding constant increased with the increase in amount of copper(II) chelate content in the polymer chain. Besides the electrostatic interaction between a negatively charged DNA molecule and a positively charged polymer–copper(II) complex molecule, other binding modes, such as van der Waals interaction, hydrogen bonding and partial intercalation binding modes may also exist in this system. A sample of polymer–copper(II) complex was tested for its antibacterial and antifungal activity and it was found to have good antibacterial and antifungal activities.     

H-type aggregation of functional metal ion sensing phthalocyanines: Synthesis,characterization and electrochemistry

We report, in this study, the preparation and physical characterization of the peripherally functionalized ionophore ligand, 4,5-bis(6-hydroxyhexan-3ylthio)-1,2-dicyanobenzene (1) and its branched thioalcohol-substituted phthalocyanines, 2,3,7,8,12,13,17,18-octakis{6-hydroxyhexan-3-ylthio)-metal (II) or (III) phthalocyanines {M{Pc[SCH(C₃H₇)(C₂H₅OH)]₈} {M = Pb(II) (2), Zn(II) (3), Cu(II) (4), Co(II) (5) and Mn(III), X = Cl⁻ (6)} which can selectively bind soft-metal ions such as silver (I) and palladium (II). It was observed by means of UV–Vis absorption spectrophotometry that the aggregates formed lead to a low solubility of the phthalocyanines in protic solvents, such as low molecular alcohols. However, the addition of AgNO₃ and Na₂PdCl₄ into a THF–MeOH solution of {M{Pc[SCH(C₃H₇)(C₂H₅OH)]₈X} {M = Pb(II) (2), Zn(II) (3), Cu(II) (4), Co(II) (5) and Mn(III), X = Cl⁻ (6)} induced optical changes, which indicated the formation of twisted H-type dimers (blue shift, face-to-face fashion) of {M{Pc[SCH(C₃H₇)(C₂H₅OH)]₈} complexes, bound by four PdCl₂ and AgNO₃ units in THF solution. Elemental analysis data, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS), FT-IR, ¹H, ¹³C NMR, and UV–Vis spectral data were used as complementary techniques. Voltammetry and in situ spectroelectrochemistry of the complexes were performed on Pt in DMSO/TBAP. The first reduction and oxidation processes of 5 were found to be split due to the presence of facile equilibria between the species coordinated differently at axial positions. The Mn(III)Pc(−2)X⁻ complex (6) displayed well-defined colour changes during its reduction processes. The redox behaviour of the Mn(III)Pc(−2)X⁻ complex was observed to be affected significantly by the existence of oxygen in solution due to the formation of μ-oxo MnPc species, Mn(III)Pc–O–PcMn(III). This effect was clarified well by in situ spectroelectrochemical measurements.     

A new water-soluble metal-free phthalocyanine substituted with naphthoxy-4-sulfonic acid sodium salt. Synthesis,aggregation, electrochemistry and in situ spectroelectrochemistry

A new water-soluble metal-free phthalocyanine, 2,9,16,23-tetrakis(4-(1-naphthoxy-4-sulfonic acid sodium salt))phthalocyanine NhtH₂Pc, where Nht indicates naphthoxy-4-sulfonic acid sodium salt, was synthesized and its aggregation, electrochemical and spectroelectrochemical properties were investigated in non-aqueous solutions. The aggregation study of NhtH₂Pc showed that NhtH₂Pc had both aggregated and non-aggregated mono phthalocyanine forms in the case of the 1:1 ratio of methanol and water, while it exhibited only the characteristic UV–Vis absorption of monomeric phthalocyanine in methanol and DMSO. NhtH₂Pc displayed three reversible one-electron reductions waves, assigned to Pc³⁻/Pc²⁻, Pc⁴⁻/Pc³⁻ and Pc⁵⁻/Pc⁴⁻ couples, respectively. The electrochemical half-wave potentials of the reduction processes were located at E_1/2 = −0.510, −0.924 and −1.24 V, respectively while the anodic potential of the oxidation process was displayed at E_1/2 = 0.590 V versus pseudo Ag/AgCl. The half-wave potentials of the first and second reductions were positively shifted by 0.150 and 0.136 V compared with those of the unsubstituted metal-free phthalocyanine (H₂Pc). These shift values are almost the same as those observed for [(SO₃)₄H₂Pc]. The electrochemical studies showed that the electron-withdrawing sulfonated-naphthoxy groups on the macrocycle core made the reduction processes of NhtH₂Pc easier in DMSO solution. The well-defined UV–Vis spectra of the electro-reduced species [NhtH₂Pc]⁻ were obtained with an applied potential (E_app = −0.70 V) in a thin-layer cell. The spectroelectrochemical results showed that the first reduction product exhibited characteristic spectral changes corresponding to mono-anionic species of metal-free phthalocyanines, having long-term stability during the reduction process.     

Synthesis and characterization of new polymeric phthalocyanines substituted with diaza-18-crown-6 macrocycles through ethyleneoxy bridges

A tetranitrile monomer was synthesized by nucleophilic aromatic substitution of N,N′-bis(2-hydroxyethyl)-4,13-diaza-18-crown-6 onto 4-nitrophthalonitrile. A series of polymeric metal-free and metallophthalocyanine (M = 2H, Zn, Cu, Co and Ni) polymers was prepared by polymeric tetramerization reaction of the tetranitrile monomer with proper materials. The electrical conductivities of the polymeric phthalocyanines measured as gold sandwiches were found to be ∼10⁻⁹–10⁻⁴ S cm⁻¹ in a vacuum and in argon. The extraction ability of the metal-free polymeric phthalocyanine was evaluated in tetrahydrofuran using several alkali metal picrates such as Li⁺, Na⁺, K⁺ and Cs⁺. The extraction affinity of the metal-free polymeric phthalocyanine for K⁺ was found to be highest in the heterogeneous solid–liquid phase extraction experiments. The disaggregation property of the metal-free polymeric phthalocyanine was investigated with sodium, potassium and ammonium ions and methanol. All the novel compounds were characterized by using elemental analysis, UV–Vis, FT-IR, NMR and MS spectral data and DTA/TG.     

Synthesis and spectroscopic investigations of Rh(III) and Pd(II) complex compounds with N-(pyridine-2-yl)morpholine-4-carbothioamide

The present paper describes the synthesis and spectral properties of Rh(III) and Pd(II) coordination compounds with N-(pyridine-2-yl)morpholine-4-carbothioamide (PMCTA). The compounds have the general composition [RhL₂Cl₂]Cl · C₂H₅OH (1), [PdL₂]Cl₂ (2), [PdL₂](ClO₄)₂ · 2C₃H₆O (2a), [PdLCl₂] · 2H₂O (3). All complexes were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, XPS and UV–Vis spectra. It has been shown that PMCTA behaves as a bidentate (N,S)-ligand, forming six membered metallocycles and coordinating to the metal ion through the carbothioamide sulfur atom and the pyridine nitrogen atom. The UV–Vis spectra suggest that the Pd(II) complexes are square planar, while the Rh(III) complex has an octahedral geometry. The molecular structure of the Pd(II) complex with PMCTA (M:L = 1:2) was determined by single-crystal X-ray diffraction.     

Synthesis,DNA binding and antitumor activities of some novel polymer–cobalt(III) complexes containing 1,10-phenanthroline ligand

The novel water-soluble polymer–cobalt(III) complex samples, cis-[Co(phen)₂(BPEI)Cl]Cl₂ · 4H₂O (phen = 1,10-phenanthroline, BPEI = branched polyethyleneimine), with different amounts of cobalt complex content in the polymer chain, were prepared by ligand substitution method in water–ethanol medium and characterized by Infra-red, UV–Vis, ¹H NMR spectral and elemental analysis methods. The interaction of these polymer–cobalt(III)-phenanthroline complex samples with calf thymus DNA has been explored using electronic absorption spectroscopy, emission spectroscopy and gel electrophoresis techniques. The presence of multiple small size molecular binding sites, namely, the cobalt(III)–phenanthroline complex moieties, and free amino groups in a single big sized polymer molecule enhanced both the electrostatic and/or van der Waals interaction and partial intercalative bindings with calf thymus DNA. The antitumor activity of a sample of polymer–cobalt(III) complex was determined using HEp-2 cell line and different cell death indicator stains and MTT assay. Many of the cultured HEp-2 cells treated with this complex suffered loss of viability and death mostly through apoptosis as evidenced by the nuclear and cytoplasmic morphology.     

Synthesis and electrochemical characterization of biphenyl-malonic ester substituted cobalt,copper, and palladium phthalocyanines

Phthalocyanines with four biphenyl-malonic ester groups on the periphery were synthesized by cyclotetramerization of 4-(1,1-dicarbethoxy-2-(4-biphenyl)-ethyl)-phthalonitrile. The new compounds were characterized by elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, UV–Vis, and MASS spectral data. Electrochemical behaviors of novel Co(II), Cu(II), and Pd(II) phthalocyanines were investigated by cyclic voltammetry, potential differential pulse voltammetry, and applied potential chronocoulometry techniques. While Cu(II) and Pd(II) phthalocyanines give up to four common phthalocyanine ring reductions, Co(II) phthalocyanine gave two ligand-centered and two metal-centered redox processes. HOMO–LUMO gap of the complexes are comparable with the reported MPc papers.     

Half-sandwich para-cymene ruthenium(II) naphthylazophenolato complexes: Synthesis,molecular structure,light emission,redox behavior and catalytic oxidation properties

A series of conformationally rigid half-sandwich organoruthenium(II) complexes with the general formula [(η⁶-p-cymene)RuCl(L)] (where L = mono anionic 2-(naphthylazo)phenolato ligands) have been synthesized from the reaction of [{(η⁶-p-cymene)RuCl}₂(μ-Cl)₂] with a set of 2-(naphthylazo)phenolato O,N-donor ligands. All the ruthenium complexes were fully characterized by FT-IR, ¹H NMR, and UV–Vis spectroscopy as well as elemental analysis. In dichloromethane solution all the metal complexes exhibits characteristic metal-to-ligand charge transfer bands (MLCT) and emission bands in the visible region. The molecular structure of one of the complexes [Ru(η⁶-p-cymene)(Cl)(L2)] (2) was determined by X-ray crystallography. Electrochemical data of all the ruthenium complexes show a two metal centered voltammetric responses with respect to Ag/AgCl at scan rate 100 mV s⁻¹. Further, the complex (2) efficiently catalyzes the oxidation of a wide range of alcohols to their corresponding carbonyl compounds in the presence of N-methylmorpholine-N-oxide (NMO) up to 97%.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Synthesis and characterization of metal diselenophosphates: M[Se2P(OR)2]2 (M = Pd,Pt; R = Et,Pr, Pr)

The first Pd(II) and Pt(II) complexes incorporating diselenophosphate (dsep) ligands are presented. Treatment of M(II) (M = Pd, Pt) salts with two equivalents of the dsep ligand in CH₂Cl₂ yielded square-planar compounds of the type M[Se₂P(OR)₂]₂ (M = Pd, Pt; R = Et, ⁱPr, ⁿPr) (1a–2c). These complexes were characterized by elemental analysis, multinuclear NMR spectroscopy and X-ray diffraction (1b and 2b). The dsep ligands coordinate to the metal in an approximately isobidentate fashion and form four-membered Se–P–Se–M chelate rings. Structural elucidations indicated that minute differences exist in the M–Se bond distances and these were observed from solution ³¹P NMR studies, which exhibited two sets of satellites arising from one-bond coupling to ⁷⁷Se nuclei. A packing diagram showed a chain-like motif which was composed of square-planar M[Se₂P(OR)₂]₂ units and occurred via non-covalent Se?Se secondary interactions.