Eiji Asato

Preparation and characterization of copper(II) complexes with 1,4,8,11-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane

Abstract Eight copper(II) complexes of the title ligand (tpmc) were synthesized, and characterized by elemental analyses, IR and Vis spectra, and magnetic measurements. The results are discussed in comparison with the previously reported results for taec complexes, where taec represents 1,4,8,11-tetrakis(2- aminoethyl)-1,4,8,11-tetraazacyclotetradecane. One of these is a 1:1 complex, though the others are dinuclear as in the case of taec complexes. Of these the crystal structures of [Cu 2 OH(tpmc)](ClO 4 ) 3 · 2H 2 O ( 2 ) and [Cu 2 NO 3 (tpmc)](PF 6 ) 3 ( 5 ) were determined by X-ray diffraction analyses. The hydroxo complex 2 crystallizes in the monoclinic space group Cm with unit cell parameters a = 11.048(1), b = 22.318(3), c = 9.459(1) A, β = 111.95(1)°, V = 2163.2(5) A 3 and Z = 2 and was refined to R = 0.041 and R w = 0.052. The nitrato complex 5 crystallizes in the monoclinic space group P 2 1 / n with unit cell parameters a = 18.685(4), b = 25.563(5), c = 9.393(1) A, β = 92.59(2)°, V = 4482(2) A 3 and Z = 4 and was refined to R = 0.083 and R w = 0.110. In either compound the anion, OH −− or NO 3 −− , is bound to both copper ions, but their coordination modes are substantially different from each other. No appreciable spin exchange coupling was observed for these complexes except the hydroxo complex in which an antiferromagnetic interaction is operating (—2 J = 86 cm −1 ). The result was reasonably explained in terms of the molecular structure.

Mixed oxidation state trinuclear cobalt complexes with bridging sulphito and Schiff-base ligands. Part 1. Preparation of the complexes [CoII(µ-SO3)2(µ-L)2COIII2(ROH)2](L = Schiff base anion, R = alkyl) and structure determination of [CoII(µ-SO3)2(µ-α,α′-Me2-salpd)2CoIII2(PrnOH)2]·2PrnOH

Mixed-valence complexes of the type [CoII(µ-SO3)2(µ-L)2CoIII2(H2O)n(ROH)2–n](n= 0, 1, or 2; R = Me or Prn) have been prepared and characterized, where the deprotonated Schiff-base ligands L2– are either symmetrical, such as N,N′-ethylenebis(salicylideneiminate)(salen), N,N′-ethylenebis(α-methylsalicylideneiminate)(α,α′-Me2-salen), propane-1,3-diylbis(salicylideneiminate)(salpd), and propane-1,3-diylbis(α-methylsalicylideneiminate)(α,α′-Me2-salpd), or unsymmetrical such as propane-1,3-diyl(α-methylsalicylideneiminate)(salicylideneiminate)(α-Me-salpd). An X-ray structure determination of [COII(µ-SO3)2(µ-α,α′Me2-salpd)2CoIII2(PrnOH)2]·2PrnOH showed the presence of bridging phenolic oxygens and sulphite ions. The mixed-valence state CoIII(S= 0)–CoII(S=)–CoIII(S= 0) in these trinuclear complexes has been demonstrated by cryomagnetic measurements because the effective magnetic moments (4.40–5.00) at room temperature correspond to the monomeric complex of a cobalt(II) ion in a high-spin state. Down to 77 K, no spin-exchange interaction was observed between the cobalt(III) and cobalt(II) ions. I.r. spectra and thermal gravimetric-differential thermal analysis data have been obtained and discussed with regard to the co-ordination modes of the solvent molecules water, methanol, ethanol, and propan-1-ol.

Polynuclear zinc(II) complexes of phenol–imine and –amine macrocycles

The template condensation of 2,6-diformyl-4-methylphenol with 1,11-diamino-3,6,9-trioxaundecane using zinc(II) acetate as the metal source, followed by addition of an excess of NaClO4, gave a tetranuclear zinc(II) complex [Zn4L1(µ-O2CMe)4][ClO4]21, where H2L1 is a [2 + 2] tetra-Schiff-base macrocycle. A single-crystal X-ray analysis of the dichloromethane adduct, 1·2CH2Cl2, revealed that this complex cation is centrosymmetric and contains two pairs of zinc ions bridged by a phenolic oxygen and two acetate ligands. Recrystallisation of this complex from a hydrous methanolic solution gave another tetranuclear complex, [Zn4L1(µ-OH)2(µ-O2CMe)2][ClO4]2·2H2O 2, which was also structurally characterised. While the four zinc ions are encapsulated in the macrocycle as observed for 1, in complex 2 the two dimeric units formed by phenoxo- and acetato-bridges are further connected by two hydroxyo bridges. Proton NMR spectroscopy has shown that this structural conversion is reversible and depends on the presence of water or acetic acid in solution. Treatment of complex 1(or 2) with NaBH4 in methanol gave a dinuclear zinc complex, [Zn2L2][ClO4]2·H2O3, together with a metal-free phenol–amine macrocycle, H2L2, which is a reduced form of H2L1. Both complex 3 and H2L2, have been characterised on the basis of spectroscopic data.

Synthesis, crystal structure, and quasi-reversible dioxygen binding of [Cu2(tpmc)]X2[tpmc = 1,4,8,11-tetrakis(2′-pyridylmethyl)-1,4,8,11-tetra-azacyclotetradecane; X = ClO4, PF6, or CF3SO3]

Dicopper(I) complexes of tpmc [1,4,8,11-tetrakis(2′-pyridylmethyl)-1,4,8,11-tetra-azacyclotetradecane] have been synthesized. The complexes reacted with dioxygen at low temperature (below –60 °C) to form two species of adduct quasi-reversibly, which were characterized by Resonance Raman spectra (16O–16O stretching at 820 and 771 cm–1 and Cu–16O stretching at 529 and 491 cm–1 which shifted to lower energy when 18O2 was substituted for 16O2). From an acetone solution of the dioxygen adducts bis(pyridine-2-carboxylato)copper(II) was isolated. The molecular structure of the dicopper(I) complex [Cu2(tpmc)][CF3SO3]2 was determined by X-ray diffraction analysis. The complex crystallizes in the monoclinic space group P21/n with a= 14.341(4), b= 15.392(4), and c= 9.700(2)A, β= 93.95(2)°, and Z= 2, and the structure was refined to R= 0.055 and R′= 0.058. The complex cation has a centre of symmetry and each copper atom is co-ordinated by one nitrogen of the macrocyclic ring and two pendant pyridyl nitrogens forming a distorted trigonal plane with a Cu ⋯ Cu separation of 6.739(2)A.

Cobalt(II)–lanthanoid(III)(Ln = La, Nd, or Gd) complexes of N,N′-ethylenebis(3-carboxysalicylideneimine). Interaction of ligating groups on the Co–Ln centre

Cobalt(II)–lanthanoid(III) complexes of N,N′-ethylenebis(3-carboxysalicylideneimine)(H4csalen), [CoLa(csalen)(CH3OH)(NO3)], [CoNd(csalen)(H2O)2(NO3)], and [CoGd(csalen)(H2O)(NO3)], have been prepared and characterized, where the cobalt ion is bound at the N2O2 site and the lanthanoid ion at the O4 site of the binucleating ligand. Based on electronic and e.s.r. spectra the configuration around the cobalt ion was shown to be planar at room temperature in dimethylformamide (dmf) or dimethyl sulphoxide (dmso) while square pyramidal at liquid-nitrogen temperature with a solvent molecule at the axial site. When a nitrogen-containing base such as pyridine or n-propylamine was added to dmf solutions of the Co–Ln complexes the base was co-ordinated to the cobalt ion to afford five-co-ordination around the metal at room temperature. At liquid-nitrogen temperature the configuration around the cobalt was dependent upon the nature of the added base: six-co-ordination for pyridine or its derivatives and five-co-ordination for aliphatic amines. It is suggested that substrates possessing N- and O-donor groups such as 2-aminoethanol are specifically bound at the Co–Ln centre, via N to the cobalt and O to the lanthanoid ion.

Unusual affinities of monovalent anions to dicopper(II) complexes with N,N′,N″,N‴-tetrakis(2-aminoethyl)-tetra-azacycloalkanes

Abstract The equilibrium constants for [Cu 2 L] 4+ + X − = [CuXL] 3+ were determined spectrophotometrically in aqueous solution at 25 °C, where L represents the title ligands and X denotes Cl, Br, I and CH 3 COO. The formation constants of [Cu 2 XL] 3+ thus obtained were unusually large compared to those of common copper(II) complexes with CuX bonds, and decrease in the order Cl − > Br − > I − > CH 3 COO − for a given L, and taec > taep > taeh for a given X − . The origin of the surprisingly high stabilities was discussed.

Synthesis, properties, molecular structure and electron transfer salts of 13,13,14,14-tetracyano-1,6- and -1,8-pyrenoquinodimethanes (1,6-TCNP and 1,8-TCNP)

A guideline for a stable π-extended Wurster type redox system is proposed and two new acceptor molecules having a pyrene π-system were prepared and structurally characterised. 3,8-Bis(3′,5′-di-tert-butylphenyl)-13,13,14,14-tetracyano-1,6-pyrenoquinodimethane gave an electron transfer complex with Mn(TPP) (H2TPP = m-tetraphenylporphyrin) containing a coordination bond.

Construction of a mixed valence trinuclear MnIIMnIIIMnII aggregate into a large macrocyclic ligand

A Schiff-base [2 + 2] macrocycle obtained by the reaction of 2,6-diformyl-4-methylphenol with 1,11-diamino-3,9-dimethyl-3,9-diazo-6-oxaundecane encapsulates three manganese ions into its cavity; EPR, UV–VIS–NIR, XPS spectroscopic data, X-ray crystallography and magnetic measurements showed that the metal ions are in a mixed valence state (II, III, II) which is rare for trimanganese systems.

Insertion of a π-π Stacked Chloranilate Pair into Two Phenoxo-Bridged Dinuclear Metal Cores

Tetranuclear zinc(II) and nickel(II) complexes formulated as [M 4 (bpmp) 2 (CA) 2 ](CIO 4 ) 2 (M = Zn: 1 , Ni: 2 ) have been synthesized, where Hbpmp and H 2 CA are a multidentate dinucleating ligand and chloranilic acid, respectively. X-ray crystallography of 1 2BuCN has revealed that the phenoxide moiety from bpmp m bridges two Zn(II) ions, which are further connected to another -phenoxo zinc pair by two ~ - ~ stacked CA 2 m units in a double bis-bidentate fashion. Electrochemical study combined EPR techniques revealed that 1 was reduced at E 1/2 = m 1.10 V in a one-step 2-electron process and the resultant two CA 3 m radicals are antiferromagnetically coupled. tetranuclear metal complexes phenoxide bridge chloranilate ion ~ - ~ stacking X-ray crystallography

Insertion of a strongly π–π stacked chloranilate pair into an M4 arrangement preorganized within a large macrocyclic ligand (M = Zn2+ and Cu2+)

Four Zn(II) ions arranged within a pyridine-modified large phenolate-containing macrocyle Lpy2- encapsulate two chloranilate ions in a double bis-didentate bridging fashion; the ligands are strongly pi-pi stacked with each other with a short distance of 3.27 A and are electrochemically reduced at the same potential of -1.00 V to produce a reasonably stable biradical species with T1/2 = 60 min at 25 degrees C.