Studies on mixed ligand complexes,part 5. Heterochelate complexes of cobalt(III) derived from the quadridentate NNNN donor ligand triethylenetetramine and bidentate OO,ON and NN donor ligands

Summary A series of new cobalt(III) complexes of general formula [Co(AA)(trien)]X_n (where AA = tropolone, acetoacetanilide, ethylacetoacetate, biguanide, 2-guanidinobenzimidazole, propylenediamine, picolylamine, 2,2-dipyridyl, 3-aminopyridine, picolinic acid and quinaldinic acid, trien = triethylenetetramine, X=Cl^–, Br^–, I^– and n=2–3) have been synthesized and characterized by elemental analysis, electronic and i.r. spectra, equivalent weight, conductance and magnetic measurements. The electronic spectra of the complexes exhibit one or two ligand field bands atca. 20000 and 29000 cm^–1 due to the¹ A _1g ¹ T _1g and¹ A _1g ¹ T _2g transitions respectively. Conductance measurements indicate the triunivalent nature of [Co(tropolone)(trien)]I₃, [Co(picolylamine)(trien)]I₃, [Co(3-aminopyridine)(trien)]I₃, [Co(2,2-dipyridyl)(trien)]Cl₃, [Co(biguanide)(trien)]I₃, [Co(propylenediamine)(trien)]I₃ and biunivalent nature of [Co(picolinate)(trien)]Cl₂, [Co(quinaldinate)(trien)]Cl₂, [Co(acetoacetanilido)(trien)]Cl₂, and [Co(ethylacetoacetato)(trien)]I₂. Equivalent weight determination by the ion-exchange resin (H⁺ form) method gives the values of molecular weights which are consistent with the theory. The complexes are diamagnetic.     

The kinetics of base hydrolysis of [Co(trien)(amine)Cl]2+ complexes (amine=imidazole,pyridine,n-butylamine and 2,2-dimethoxyethylamine)

Summary The complexescis--[Co(trien)(ImH)Cl]²⁺ (ImH=imidazole, trien=1,8-diamino-3,6-diazaoctane),cis--[Co(trien)(Buⁿ-NH₂)Cl^–]²⁺,cis--[Co(trien)(NH₂CH₂-CH(OMe)₂)Cl^–]²⁺ andcis-₂-[Co(trien)(py)Cl]²⁺ (py=pyridine) have been characterised and their kinetics of base hydrolysis studied. Thecis--isomers which have afac-fac arrangement of the trien ligand have values of k _OH ²⁵ in the 73 to 253 dm³ mol^–1 s^–1 range at I=0.1 mol dm^–3. Extremely rapid base hydrolysis is observed withcis-₂-[Co(trien)(py)Cl]²⁺ where k _OH ²⁵ is 6.65×10⁶ mol³ mol^–1 s^–1 at I=0.1 mol dm^–3. This complex has amer-fac arrangement of the trien ligand with flatsec-NH donor leading to rapid base hydrolysis due to good -overlap between the conjugate base and cobalt(III). The pyridine ligand causes aca. 30 fold rate increase compared with the hydrolysis ofcis-₂-[Co(trien)(NH₃)Cl]²⁺.     

Micellization of Metallosurfactant N-Dodecyl/Hexadecyl/Octadecyl Salicylaldimine Cobalt(III) Complexes in Nonaqueous Media

Abstract The critical micelle concentrations (CMC) of three metallosurfactant Schiff base cobalt(III) complexes of the type [Co(trien)(C₁₉H₃₀NO)]Cl₂,[Co(trien) (C₂₃H₃₈NO)]Cl₂ and [Co(trien)(C₂₅H₄₂NO)]Cl₂, where trien = triethylenetetramine, have been studied in n-alcohol and in formamide at different temperatures by the electrical conductivity method. CMCs have also been measured as a function of percentage concentration of alcohol in the mixed solvents with formamide. Specific conductivity data (at 303–323 K) served for the evaluation of the temperature-dependent CMC and thermodynamic parameters such as the standard Gibbs energy changes (DG^°_mic)\Delta G^{\circ}_{\mathrm{mic}}), enthalpy changes (DH^°_mic)\Delta H^{\circ}_{\mathrm{mic}}), and entropy changes (DS^°_mic)\Delta S^{\circ}_{\mathrm{mic}}) of micelle formation. It is suggested that addition of an alcohol leads to increased penetration of formamide into the micellar interface, the extent depending on the alcohol’s chain length. The results have been discussed in terms of the solvophobic interaction, dielectric constant of the medium, the chain length of the alcohol, and the surfactant in the solvent mixture.     

OPTICAL ISOMERS OF 2,2′-DIAMINOBIPHENYLBIS(ETHYLENEDIAMINE) COBALT(III) CHLORIDE AND ITS RELATED COMPLEXES1

Abstract

Several cobalt(III) complexes incorporating 2,2′-diaminobiphenyl(dabp) and other 2(2N)- or 4N-type ligands were prepared and resolved by chemical and chromatographic methods: (1) [Co(en)₂(dabp)]Cl₂2H₂O, (2) [Co(l-pn)₂(dabp)] (ClO₄)₃4H₂O, (3) [Co(l-chxn)₂(dabp)](ClO₄)₃3H₂O, (4) α-[Co(trien)(dabp)](ClO₄)₃, (5) α-[Co(2S,9S-dimetrien)(dabp)] (ClO₄)₃ 2H₂O, (6) α-[Co(3S,8S-dimetrien)(dabp)] (ClO₄)₃3H₂O, (7 [Co(tren)(dabp)]Cl₃5H₂O, (8) [Co(bpy)₂(dabp)] Cl₃3H₂O. The complexes (1), (4) and (8) gave one pair of enantiomers, Δ(Λ) and Λ(δ), and the complexes (2) and (3) gave only one Δ-isomer. The absolute configuration of the complexes (5) and (6) was found to be Λ, and that of (7) was not determined because of unsuccessful resolution. The three geometric isomers of the complex (2) were separated and their structures assigned.     

Preparation and properties of some water-soluble cobalt (III)–poly-4-vinylpyridine complexes

Water-soluble cobalt(III) chelates having a polymeric ligand such as cis-[Co(en)_2-PVPCl]Cl₂ and cis-[Co-(trien)PVPCl]Cl₂ (PVP = poly-4-vinylpyridine) were prepared by substitution reactions between cobalt(III) chelate and PVP in water–alcohol solution. PVP of different degrees of polymerization was used as the ligand in preparation of these complexes. The PVP complexes were identified and their properties ascertained by microanalysis and by a study of the infrared, ultraviolet, visible, and PMR spectra. Most of the characteristic properties of these complexes may be ascribed to the polymeric structure of the PVP ligand.     

Synthesis and NMR Characterization of Cobalt(III) Complexes with 1,8-diamino-3,6-dithiaoctane, 2,2-Bipyridine,and 1,10-phenanthroline

The complexes [Co(eee)(bipy)]Cl₃ and [Co(eee)(phen)]Cl₃ (eee, 1,8-diamino-3,6-dithiaoctane) were synthesized and characterized by two-dimensional NMR spectroscopy. The presence of the bidentate aromatic ligands 2,2-bipyridine and 1,10-phenanthroline caused the ¹H resonances to be spread into a wider spectral width than previously observed for [Co(eee)(NO₂)₂]Cl and [Co(eee)Cl₂]Cl. Separate multiplets were observed for the four protons in the terminal ethylene linkage. It was possible to positively assign each multiplet and to determine the relative spatial orientations of the corresponding protons.     

ASYMMETRIC SYNTHESIS OF PROLINE USING COBALT(III)-TETRAAMINE COMPLEXES

Abstract

The decarboxylation reaction of δ -cis-β-[Co(L₁)(pdH)]²⁺ complex yielded δ -cis-β-[Co(L₁) (R-pro)]²⁺, while the δ -cis-β-[Co(L₂) (S-pro)]²⁺ was obtained from the reaction of δ -cis-β-[Co(L₂) (pdH)]²⁺, where L₁ is (3R)3-methyl-1, 6-bis[(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, L₂ is (3S) 3-methyl-1, 6-bis-[(2S)-pyrrolidin-2-yl]-2, 5-diazahexane, and pdH is the pyrrolidine-2, 2-dicarboxylate ion. The asymmetrically synthesized prolines were isolated via the decomposition of the decarboxylated complexes. The proline isolated from δ -cis-β-[Co(L₁) (R-pro)]²⁺ showed a specific rotation of +12.0, representing a 24% excess of R-proline over S-proline, while the proline isolated from δ -cis-β-[Co(L₂) (S-pro)]²⁺ showed a specific rotation of -10.0, indicating a 20% excess of S-proline over R-proline.     

Kinetic study of the protonations and substitutions of different cobalt(III)–nta complexes

The behaviour of the Cobalt(III)–nta (nta = nitrilotriacetate) system in an acidic medium was investigated. The acid dissociation constant, pK _a1, of [(nta)(H₂O)Co(-OH)Co(H₂O)(nta)]^– was determined as 3.09(3) and the pK _a of the cis-[Co(nta)(H₂O)₂]/[Co(nta)(H₂O)(OH)]^– equilibrium was determined as 6.71(1). cis-[Co(nta)(H₂O)₂] undergoes ring-opening upon acidification below pH = 2.0. The formation of [Co( ³-nta)(H₂O)₃]⁺ was also studied. The substitutions between cis-[Co(nta)(H₂O)₂] and NCS^– ions were investigated in the pH = 2–7 ranges. [Co(nta) (H₂O)(OH)]^– reacts ca. 70 times faster at 24.7 °C with NCS^– ions than cis-[Co(nta)(H₂O)₂], indicating a cis-labilising effect of the OH^– ligand.     

Substitution-Inert Metal Complex Mobile Phases in Non-Suppressed Cation Chromatography

Substitution-inert metal complexes, [Co(edda)(H₂O)₂]⁺, (Co(edda)(en)]⁺, [Co(edda)(dmen)]⁺, [Co(en)₂-(gly)]²⁺, [Co(en)₂(acac)]²⁺, and [Co(trien)(gly)]²⁺ in their nitrate salt solutions are used as eluents in nonsuppressed cation chromatography (where edda = ethylenediamine-N,N′-diacetic acid, en = ethylenediamine, dmen = N,N′-dime-thylethylenediamine, gly = glycine, acac = acetylacetone, and trien = triethylenetetraamine). It is found that all the mono- and di-valent charged complexes can be used to separate alkali and alkaline earth metal cations, respectively. The separations for monovalent cations are sometimes comparable to those using ultrapure HNO₃ solutions. However, the divalent Ca²⁺ and Sr²⁺ ions cannot be resolved using the metal complex eluents. On the other hand, a selected, direct non-suppressed IC separation of zinc(II) and cadmium(II) ions is demonstrated for the first time using a substitution-inert metal complex eluent and a conductivity detector. Comparisons of these eluents with those reported previously, i. e. HNO₃ and ethylenediammonium salt solution are made and explanations are proposed to account for the different selectivities observed where possible. The future development of this technique is also briefly discussed.     

Chemistry of Ruthenium Polypyridine Complexes: VI. Synthesis and Photochemistry of cis-[Ru(bpy)2(bipy)X]q Complexes

Complexes cis-[Ru(bpy)₂(bipy)(X)] ^{n +} [bpy = 2,2'-bipyridyl, bipy = 4,4'-bipyridyl, X = Br^-, ONO^-, CN^- (n = 1); MeCN, PPh₃ (n = 2), and NO⁺ (n = 3)] were synthesized. Irradiation of acetonitrile solutions of the complexes with X = Cl^-, Br^-, ONO^-, NO₂-, CN^-, NH₃, MeCN, and PPh₃ by visible light results in photosubstitution of 4,4'-bipyridyl by a solvent molecule. The electronic absorption spectra of the complexes were assigned on the basis of quantum-chemical calculations. A correlation was revealed between photolysis quantum yields and charges transferred from ligands X upon their coordination.     

Solvent and structural effects on the electro- and photo-reduction of cis - β -Co(trien)(RC6H4NH2)Cl]Cl2 type complexes in water/1,4-dioxane media

The electro- and photo-reduction of a series of cobalt(III) complexes of the type cis-β-[Co(trien)(RC₆H₄NH₂)Cl]Cl₂ where R=H, p-OMe, p-OEt, p-Me, p-Et, p-F and m-Me has been studied in 1,4-dioxane/water. The redox potential (E _1/2) and photo-reduction quantum yield (φ_Co(II)) data were correlated with solvent and structural parameters to shed light on the mechanism of these reactions. Correlation of E _1/2 and φ_Co(II) with macroscopic solvent parameters viz. relative permittivity indicates that the reactivity is influenced by both specific and non-specific solute-solvent interactions. The Kamlet-Taft solvatochromic comparison method was used to separate and quantify these effects. Increasing the percentage of organic co-solvent in the medium enhances both reduction processes; there exists good correlation between E _1/2 and φ_Co(II) suggesting a similar solvation in these redox processes.     

Crystal and Molecular Structures of Three Salts of Λ-β 1-[Co(R,R-Picchxn)(R-Phe)]2+ (Picchxn=N,N 1-DI(2-Picolyl)-1,2-Diaminocyclohexane; Phe = Phenylalaninato(1−))

Single-crystal X-ray structures of Λ-β ₁-[Co(R,R-picchxn)(R-phe)]Br₂, Λ-β ₁-[Co(R,R-picchxn)(R-phe)]Br₂·3H₂O and Λ-β ₁-[Co(R,R-picchxn)(R-phe)]I₂ are reported. In each structure there are three formula units in the asymmetric unit. Considerable disorder attends the anions and water molecules of crystallisation. In every case the conformer adopted by the coordinated aminoacidate is such that the phenylalaninato side chain is extended in order to minimize non-bonded steric interactions with the Co(tetradentate)fragment. Such an arrangement is in accord with the fact that this kind of diastereoisomer does not participate in any strong intramolecular π-π or NH-π interaction.     

Outer-sphere electron-transfer reactions of co(III)–polymer complexes in relation to its polymer effects

The outer-sphere electron-transfer reactions between [Co(III)(NH₃)₅L] (CIO₄)₃ [L = polyethyleneimine (PEI), L = NH₃(Amm)] or cis-[Co(III)(en)₂L′Cl]Cl₂ [L′ = poly-N-vinyl-2-methylimidazole(PVI), poly-4-vinylpyridine (PVP), N-ethylimidazole (NEI), pyridine (Py)] and various Fe(II) were studied. In the reaction with Fe(II)-(phen)₃²⁺, the reactivity of Co(III)–PEI was smaller than that of Co(III)–Amm due to the larger electrostatic repulsion. On the other hand, the reactivity of Co(III)–PEI was larger by a factor of 80 in the reaction with Fe(II)(H₂O)₆²⁺. From the results of rapid-scanning spectroscopy, the higher reactivity of Co(III)–PEI is caused by the coordination of free ethyleneimine residues in the Co(III)–PEI to Fe(II)–ion. Further more, the hydrophobic interaction between heteroaromatic polymer ligands and Fe(II)-(phen)₃²⁺ brought about the higher reactivities of Co(III)–PVI and Co(III)–PVP. Three interactions caused by the essential properties of polymers are discussed in relation to conformational changes.     

Synthesis and DFT calculations of oxido and phenylimido-rhenium(V) complexes incorporating the N,O donor ligand 2-[(2-hydroxyethylimino)methyl]phenol

The reactions of equimolar amounts of trans-[ReOC1₃(PPh₃)₂] or trans-[Re(NPh)(PPh₃)₂Cl₃] with a Schiff base formed by condensation of 2-hydroxy-4-methoxybenzaldehyde and ethanolamine (H₂L) result in the formation of cis-[ReO(HL)PPh₃Cl₂] (1a) and trans-[Re(NPh)(HL)(PPh₃)Cl₂] (2b), respectively, in good yields. 1a and 2b have been characterized by a range of spectroscopic and analytical techniques. The X-ray crystal structures of 1a and 2b reveal that 1a is an octahedral cis-Cl,Cl oxorhenium(V) complex, while 2b is a trans-Cl,Cl phenylimidorhenium(V) complex. The complexes are weakly emissive at room temperature with quantum yields of 10^?4. Density functional theory calculations of the electronic properties of the complexes were performed and are in agreement with the experimental results. The complexes display quasi-reversible Re(V)/Re(VI) redox couples in acetonitrile. There is reasonable agreement between the experimental and calculated redox potentials of 1a and 2b.     

Nitric oxide and singlet oxygen photo-generation by light irradiation in the phototherapeutic window of a nitrosyl ruthenium conjugated with a phthalocyanine rare earth complex

The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] (H₂-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na₄[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] was obtained from cis-[Ru(H₂-dcbpy)₂Cl₂]·2H₂O, whereas Na₄[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] displays a band in the region of 305 nm (λ_max in 0.1 mol L⁻¹ HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na₄[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λ_max in H₂O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] FTIR spectrum displays a band at 1932 cm⁻¹ (Ru–NO⁺). The cyclic voltammogram of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO^+/0) and E = −0.50 V (NO^0/−) versus Ag/AgCl. The NO concentration and ¹O₂ quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L⁻¹ and ø_OS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L⁻¹ The photochemical pathway of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)]/Na₄[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy^-)₂(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and ¹O₂ could improve PDT and be useful in cancer treatment.     

Base hydrolysis ofcis-dichlorobis(1,2-diaminoethane),cis-α-dichloro(1,8-diamino-3,6-diazaoctane) andcis-α-chlorohydroxo-(1,8-diamino-3,6-diazaoctane) ruthenium(III) complexes

The kinetics of base hydrolysis ofcis-[RuCl₂(en)₂]⁺ (en=1,2-diaminoethane),cis-α-[RuCl₂(trien)]⁺ andcis-α-[RuCl(OH)(trien)]²⁺ (trien=1,8-diamino-3,6-diazaoctane) have been studied. All the reactions are fast and obey the second-order rate law,-d[complex]/dt=k[OH⁻][complex], with complete retention of configuration. A conjugate base mechanism involving a squarepyramidal intermediate is suggested. The Arrhenius parameters and rate constants found are respectively: ΔH^≠ 14.2±0.5, 7.2±0.1, 10.9±0.1 M cal mol⁻¹; ΔS^≠ 1.3, 29, 22 cal deg⁻¹ mol; log A 13.5, 6.9, 8.6 k_OH 533 (27.2°C) 14.5 (24.4° C) 1.65 (25°C) M⁻¹s⁻¹.     

Studies on Hydrophobic Effect and Micelle Formation of Some Surfactant-Cr(III)-Cetylamine Complexes in Non-aqueous Solvents

Surface active micelle formable surfactant-Cr(III) complexes of the type cis-α-[Cr(trien)(C₁₆H₃₃NH₂)X]²⁺ (where trien = triethylenetetramine; X = F⁻, Cl⁻, Br⁻) have been studied in n-alcohol and in formamide at different temperatures by conductance measurements. Standard Gibbs energy changes (ΔG ^o _mic), enthalpies (ΔH ^o _mic) and entropies (ΔS ^o _mic) of micelle formation have been determined by studying the variation of the Critical Micelle Concentration (CMC) with temperature. Critical micelle concentrations have also been measured as a function of percentage concentration of alcohol added. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols and the surfactant in the solvent mixture.     

1-β-D-呋喃核糖基-1,2,4-三唑-3-酰胺铂配合物的合成研究

cis-[Pt(DMSO)₂Cl₂], K[Pt(DMSO)Cl₃]分别与两摩尔1-β-D-呋喃核糖基-1,2,4-三唑-3-酰胺(Ribavirin)进行络合反应, 制得了高收率的二配位铂配合物; 讨论了不同摩尔的1-β-D-呋喃核糖基-1,2,4-三唑-3-酰胺与cis-[Pt(DMSO)₂Cl₂]和K[Pt(DMSO)Cl₃]进行络合反应的结果; 对[Pt (N⁴,N⁷-Ribavirin)(DMSO)Cl]配合物(1)的X衍射晶体结构进行了测定.     

Metallosurfactants of Chromium(III) Coordination Complexes. Synthesis, Characterization and Determination of CMC Values

A number of mixed ligand chromium(III)–surfactant coordination complexes, of the type cis-[Cr(en)₂(A)X]²⁺ and cis-α-[Cr(trien)(A)X]²⁺ (A = Dodecyl or Cetylamine; X = F⁻, Cl⁻, Br⁻) were synthesized from the corresponding dihalogeno complexes by ligand substitution. These compounds form foam in aqueous solution when shaken. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for evaluation of the temperature-dependent critical micelle concentration (cmc) and the thermodynamics of micellization (Δ G_m⁰, Δ H_m⁰ and Δ S_m⁰).     

Über Reaktionen oxygenierter Kobalt(II)-Komplexe. V. Reaktivität diastereoisomerer μ-Peroxo-μ-hydroxo-dikobalt(III)-Ionen

On Reactions of oxygenated Cobalt(II) Complexes. V. Reactivity of diastereoisomeric μ-peroxo-μ-hydroxo-dicobalt(III) Ions The kinetics of dissociation of μ-peroxo-μ-hydroxo-dicobalt(III) chelates have been reinvestigated using a stopped flow technique. The binuclear cations [(trien)Co(O₂, OH) Co(trien)]³⁺, [(tren)Co(O₂, OH)Co(tren)]³⁺ and [(en)₂Co(O₂, OH)Co(en)₂]³⁺ dissociate on acidifying to Co²⁺ and the protonated ligand and up to 100% of the bound O₂ is evolved. The dissociation is H⁺-catalyzed and first order in complex. The observed rate constants at pH 2 are in the range of 10^?3 to 10^?1 s^?1 (20°). They depend not only on the nature of the ligand and on ligand configuration but also on the diastereoisomeric structure of the binuclear cation. In the case of trien there are 8 possible chemically different isomers. On oxygenation of Co(trien)²⁺ in dilute solution 3 of those isomers seem to be formed preferentially. Their rate constants are separated over a factor of 50. For [(en)₂ Co(O₂, OH)Co(en)₂]³⁺ there exist a meso form and a chiral structure. On oxygenation of Co(en)₂²⁺ in dilute solution the meso form and the racemate are formed to about equal amounts. The racemate dissociates about 5 times slower. Of the 3 possible achiral isomers of [(tren)Co(O₂, OH)Co(tren)]³⁺ one is formed stereoselectively by oxygenation in solution.