Sigeo Kida

Crystal structure and magnetic property of the binuclear manganese(III) complex [Mn(L)H2O]2(ClO4)2(L N-(acetylaceto nylidene)-N′-(α-methylsalicylidene)-ethylenediamine)

Abstract The crystal structure and magnetic property of the title compound [Mn(L)H2O]2(ClO4)2 are described. The complex crystallizes in the triclinic space group P 1 with formula = MnClO7N2C15H20, a = 11.615(4), b = 11.955(4), c = 7.753(2) A, α = 104.65(2), β = 111.84(3), γ = 63.64(2)°, V = 890.5(6) A3 and Z = 2. The complex consists of a binuclear structure bridged by two phenoxo oxygen atoms O(1) and O(1)* of the quadridentate ligands in an out-of-plane mode, where the binuclear structure has a crystallographical center of symmetry, and the bond distances of MnMn* and MnO(1)* are 3.318(1) and 2.305(2) A, respectively. The magnetic susceptibility data (4.2–300 K) showed a maximum at 11 K and were closely reproduced by the spin-Hamiltonian H = 2JS1·S2 with J = −1.68 cm−1 and g = 2.01. The deviation of the observed values from the theoretical curve in the lower temperature region is due to the zerofield splitting term. The X-band ESR spectrum in frozen dichloromethane solution at 20 K showed a broad signal at 900 G and a multiline signal at 3300 G.

Correlation between magnetic and spectral properties of alkoxo-bridged copper(II) complexes with N,N-dialkyldiaminealcohols and N,N-dialkylaminoalcohols

Abstract Nine new alkoxo-bridged binuclear (or polynuclear) copper(II) complexes with N,N-dialkyldiaminealcohols, [Cu(R 2 N(CH 2 ) n NH(CH 2 ) m O]X, (where R = EH 3 or C 2 H 5 , n = 2 or 3, m = 2 or 3, X = ClO 4 or B(C 6 H 5 ) 4 ) and with N,N-dialkylaminoalcohols, [Cu ((CH 4 ) 2 N(CH 2 ) 3 O)X] (where X = Cl, Br), were prepared and characterized. The electronic spectra and temperature dependence of magnetic susceptibilities (80–295 K) of the alkoxo-bridged copper(II) complexes were measured. From the results, the empirical rule was established for the alkoxo-bridged copper(II) complexes, that is, “an intramolecular antiferromagnetic interaction is operative for the complexes which show distinct absorption bands in the near-ultraviolet region (24–29 kK), whereas no antiferromagnetic interaction but a weak ferromagnetic interaction is operative for the compounds which show no distinct absorption bands in the near-ultraviolet region’.

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.

Characterization and classification of ‘tervalent nickel complexes’, Ni(diamine)2ClX2 (X = Cl and CIO4)

Abstract The ESR, magnetic susceptibilities, IR and electronic spectra, and electric conductivities of solid state were measured for a series of nickel complexes of the general formula Ni(diamine) 2 ClX 2 which appeared to contain ‘tervalent nickel’ in order to elucidate to oxidation state of the nickel. Based on these data they were characterized and classified into the following three groups. A) Ni(en) 2 Cl 3 and Ni(tn) 2 Cl 3 , low-spin d 7 Ni(III) complexes; B) Ni(pn) 2 Cl 3 , Ni(cyn) 2 Cl 3 , Ni(btn) 2 Cl 3 and Ni(en) 2 Cl(ClO 4 ) 2 , Ni(II)Ni(IV) mixed valence complexes; and C) Ni(phn) 2 Cl 3 , probably Ni(II) complex with cation radical ligand.

Synthesis, structure, and spectral and magnetic properties of trinuclear copper(II) complexes bridged by glyoximate groups

Copper(II) complexes of composition Cu3L2L′2(ClO4)2 or Cu3L2L′2(CH3OH)2(NO3)2 were obtained where L = dimethylglyoximate (dmg), diphenylglyoximate (dpg), or o-benzoquinone dioximate (bqd) dianion, L′= 2,2′-bipyridyl (bipy) or 1,10-phenanthroline (phen). The crystal structures of Cu3(dmg)2(bipy)2(CH3OH)2(NO3)2 and Cu3(dpg)2(bipy)2(CH3OH)2(NO3)2 were solved by the single-crystal X-ray method. Both have an essentially similar trinuclear structure where the [CuL2]2– dianion functions as a bridge between two copper(II) ions through its deprotonated oximate oxygens. The configuration around the central copper (with two L2– ions) is an elongated octahedron with two NO3– ions above and below the [CuL2]2–. The configuration around the terminal copper is a square pyramid with two nitrogens of bipy and two oxygens of oximate groups in the basal plane and the methanol oxygen at the apical site. Cryomagnetic investigations (80–300 K) revealed the operation of a very strong antiferromagnetic spin exchange through the oximate bridges, causing complete or nearly complete spin coupling even at room temperature. Exchange integrals (–J) larger than 300 cm–1 were evaluated for all the complexes. Based on e.s.r. spectra in methanol, it is suggested that the unpaired electron is localized on the terminal copper atom. The complexes dimerized in dimethylformamide, especially at a low temperature, and their frozen solutions each showed an e.s.r. spectrum typical of the spin-triplet state.

Synthesis and characterization of novel binuclear copper(II) and nickel(II) complexes with N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) containing various anions. X-ray analyses of [Cu2F(tpmc)](ClO4)3·2CH3CN and [Cu2Cl(tpmc)](ClO4)3·H2O

Abstract Seven copper(II) and three nickel(II) complexes with N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,4,8,11- tetraazacyclotetradecane(tpmc), [Cu2X(tpmc)](ClO4)3 (X=Cl, Br, I, N3, NO2), [Cu2Y2(tpmc)](ClO4)2 (Y=NCS, N3), [Ni2(tpmc)](ClO4)4 (orange and blue forms) and [Ni2Br2(tpmc)](ClO4)2 have been synthesized. The formation constants for the reaction [Cu2(tpmc)]4+ + X− ⇌ [Cu2X(tpmc)]3+ X=F, Cl, Br, I, NO2 were determined spectrophotometrically, and were revealed to be very high for the CuX binding in aqueous solution. X-ray analyses of [Cu2F(tpmc)](ClO4)3·2CH3CN and [Cu2Cl(tpmc)](ClO4)3·H2O showed halogeno bridged dinuclear structure. On the basis of the electronic spectra, IR spectra, stability constants and magnetic moments it is assumed that bromo, iodo, azido and nitrito complexes have similar structures to those of the fluoro and chloro complexes. The orange form of [Ni2(tpmc)](ClO4)4 was diamagnetic and its visible spectra was consistent with square-planar coordination. The blue form was paramagnetic (μ=2.96 BM/Ni), hence the nickel ions are five coordinated.

Synthesis and reactivities of binuclear iron(III) complexes with ligands composed of two tridentate chelating groups

Abstract Several new binuclear iron( III ) complexes were prepared using the binucleating ligands in which two molecules of N,N-bis(2-benzimidazolymethyl)amine are linked by a polyatomic chain, such as-(CH 2 ) 4 (L-4), -(CH 2 ) 6 - (L-6), and -CH 2 CH(OH)CH 2 H(L-3), etc., and were characterized in terms of the magnetic measurements and cyclic voltammetry. The complexes, Fe 2 (L-3′0(NO 3 ) 5 showed subnormal magnetic moments, 4.10 BM at 299 K and 2.22 BM at 87 K, respectively, suggesting the presence of an alkoxo-bridge structure. This complex showed much higher catalytic activity for the O 2 oxidation of N, N, N′,N′-tetramethyl-1-1,4-diaminobenzene than those of the relevant mononuclear complexes and other binuclear complexes studied here which have no alkoxo-bridge. The complex reacts with catechol and hydrogen peroxide to form 1:1 adducts.

Alkoxo-bridged copper(II) complexes: Magnetic and spectral studies of alkoxo-bridged copper(II) complexes with N,N-dialkylaminoalcohols

Sixteen new binuclear (and/or polynuclear) copper(II) complexes with N,N-dialkylaminoalcohols, [Cu(R2NCH2CH2O)X] and [Cu(R2NCH(CH3)CH2O)X], (where R = CH3, C2H5, n-C3H7, n-C4H9, X = Cl−, Br−, NCS−) were prepared. The electronic spectra and temperature dependence of magnetic susceptibilities (80–295 K) of the compounds were measured. From the results, it was shown that (1) the complexes with X = NCS− have the alkoxo-bridged binuclear structure, similar to those of chloro- and bromo-complexes and (2) the empirical rule on the magnetic and spectral properties of the alkoxo-bridged binuclear copper(II) complexes, that is, “an antiferromagnetic (intramolecular) interaction is operative for the complexes which show distinct absorption bands in the near-UV region (24–29 kK), whereas a weak ferromagnetic interaction is operative for the complexes which show no distinct absorption bands in the near-UV region” is valid for all the complexes investigated. Based on the results, we proposed a new criterion for the classification of binuclear copper(II) aminoalcohol complexes.

Bioinorganic approach to the type-I and type-II copper proteins. Synthesis and properties of copper(II) complexes with tripod-like ligands containing three or four door species

Abstract Copper(II) complexes with new tripod-like quadridentate ligands containing three or four donor species, such as benzimidazole, thioether and phenol, were prepared. The ESR and electronic spectral studies have revealed that these complexes are classified into three types, that is, four-coordinated, five-coordinated trigonal bipyramindal and five-coordinated tetragonal pyramidal complexes, and that some of them are good models for blue(Type-I) and non-blue(Type-II) copper proteins.

Bis(isocyclam)dicopper(II) complexes with a linear methylene chain bridge

New binucleating ligands, bis(isocyclam) with a linear methylene chain bridge, n-bicy (n = 2, 3, 4) and their copper(II) complexes, Cu2(n-bicy)(ClO4)4· xH2O and Cu2(n-bicy)(NCS)4·yH2O have been synthesized. The magnetic moments of these complexes were normal, but the presence of magnetic coupling between copper(II) ions were clearly demonstrated by the hyperfine structure in the ESR spectra.