Ichiro Murase

Molecular interaction of pyrophosphate with 1, 13-dioxa-4,7,10,16,20,24-hexaazacyclohexacosane (OBISDIPEN) and its mononuclear and dinuclear copper(II) complexes

Abstract The unsymmetrical hexabasic macrocyclic ligand 1,13-dioxa-4,7,10,16,20,24-hexaazacyclohexacosane ([26]aneN 6 O 2 , OBISDIPEN) forms an assortment of cationic species including mono- through hexaprotonated forms of ther macrocyclic ligand in the absence of metal ions as well as mononuclear and dinuclear Cu(II) complexes. These mononuclear and dinuclear Cu(II) complexes also form protonated and hydroxylated species. The cationic hosts combine with certain molecules and anions (guests) which have the requisite size, shape and donor groups. A bidentate guest molecule or anion can bridge the two metal ions and coordinate them simultaneously. This paper describes the reactions of OBISDIPEN and of its six mononuclear and four dinuclear Cu(II) complexes with the pyrophosphate bridging group to form complexes which exist in a variety of protonated conformations. The binding in these complexes consists of coulombic forces, hydrogen bonds and coordinate metal-donor bonds. The equilibrium constants were obtained by potentiometric titration at 25.0 ± 0.1°C and μ = 0.1 M KCl. These constants are compared to those of the analogous ligand 4,7,10,16,19,22-hexaaza-1,13-dioxacyclotetracosane (OBISDIEN).

Chelating tendencies of pyridyl-containing polyamines and oxygenation of the cobaltous complexes

The synthesis of the new pyridyl-containing, pentadentate ligands 1,9-bis(2-pyridyl)-2,5,8-triazanonane (pydien), 1 , l l bis(2-pyridyl)-2,6,1O-triazaundecane (pydpt), and 2,6-bis(5-( 1,4-diazahexyl))pyridine (epyden) is described. Acid dissociation constants, the stability constants of the Co(II), Ni(II), Cu(II), and Zn(I1) chelates, and the oxygenation constants (KO, = [MLO2ML]/[MLI2[O2]) of the cobaltous chelates have been determined. The cobalt(I1) chelates are shown to be exceptionally effective at coordinating molecular oxygen at low pH. Electronic spectra of the cobalt(I1) and nickel(I1) chelates indicate that the ligands form high-spin octahedral complexes in aqueous solution.

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.

Binuclear Copper(II) and Nickel(II) Complexes Containing Two N4−Macrocyclic Rings Connected with a Methylene Chain of Various Lengths

Abstract A series of complexes, [Cu2(n-dap)] (ClO4)3X mH2O (n = 2,3,4,5, and 6; m = 1∼4; X = ClO4 or Cl), [Cu2− (n-dfp)] (ClO4)3X mH2O(n = 2,3,4,5, and 6; m = 1∼4; X = ClO4 or Cl), and [Ni2(n-dap)] (ClO4)4mH2O(n =3, m = l; n = 4, m = 0) were prepared (for the abbreviation of the ligand see Fig. 1). ESR and magnetic measurements showed that weak antiferromagnetic interaction is operating between the two copper(II) ions. The interaction decreases with increasing length of the methylene chain.

Synthesis and X-ray structural characterization of novel binuclear complexes of copper(II), nickel(II), and cobalt(II) with an octadentate ligand, N,N′,N″,N‴tetrakis(2-aminoethyl)-1,4,8,11-tetra-azacyclotetradecane

The ligand N,N′,N″,N‴-tetrakis(2-aminoethyl)-1,4,8,11-tetra -azacyclotetradecane(taec) and its binuclear metal complexes, M2(taec)XnY4–n′ were synthesized and characterized for M = Cu, Ni, or Co and where X and Y are anions (Cl– Br–, ClO4–, or OH–). The crystal structures of Cu2(taec)(ClO4)4(1), Cu2(taec)Br(ClO4)3(2), and Ni2(taec)(ClO4)4(3) were determined by single-crystal X-ray analysis. In all the complexes each taec molecule incorporates two metal ions, each of which is coordinated by two ring- and two pendant-nitrogen atoms. Complexes (1) and (3) adopt similar structures, different to (2). In (1) each copper is weakly co-ordinated by perchlorate oxygen forming an elongated square pyramid. In (2), the bromide ion is bound by both copper atoms. This structure accords with the proposed structure deduced from the unusually high stability of the Cu–Br linkage against hydrolysis in water. In (3) the co-ordination geometry is essentially square planar, and compatible with the observed diamagnetism and visible spectrum. From the magnetic data it was concluded that Ni2(taec)Cl4·H2O consists of a diamagnetic nickel and a paramagnetic five- or six-co-ordinate nickel. All the cobalt(II) complexes are in the high-spin state. They are inert towards oxidation to cobalt(III), probably because of the difficulty of achieving six-co-ordination. In Co2(taec)(OH)(PF6)3 and Co2(taec)(OH)(ClO4)3 the hydroxide seems to be linked to both cobalt atoms, judging by the magnetic data.

Copper(II) and nickel(II) complexes of N,N′,N″,Nâ—-tetrakis(2-aminoethyl)-1,4,7,11-tetra-azacyclotetradecane (taei), -1,4,8,12-tetra-azacyclopentadecane (taep), and -1,5,9,13-tetra-azacyclohexadecane (taeh). Crystal structures of [Cu2(taep)][ClO4]4, [Cu2(taeh)][ClO4]4, and [Cu2(N3)(taeh)][ClO4]3

New octaamine dinucleating ligands, N,N′,N″,N‴-tetrakis(2-aminoethyl)-1,4,7,11-tetra-azacyclo-tetradecane (taei), -1,4,8,12-tetra-azacyclopentadecane (taep), and -1,5,9,13-tetra-azacyclohexadecane (taeh) and their complexes with CuII and NiII were synthesized. Of the 19 complexes isolated, the structures of [Cu2(taep)][ClO4]4, [Cu2(taeh)][ClO4]4, and [Cu2(N3)(taeh)][ClO4]3 were determined by X-ray crystal analysis. In all these complexes each copper is co-ordinated by two ring nitrogens and two pendant amino nitrogens, and the two CuN4 co-ordination sets face each other. In the azido complex the N3– is bonded to both coppers in an end-to-end fashion. The dinuclear complexes [Cu2L][ClO4]4(L = taei or taep) further incorporate various anions between the two coppers to form [Cu2X(L)][ClO4]3. However, only the azido complex was obtained with taeh. The results are discussed in terms of the ring-size effect.

Crystal and molecular structure of a novel mixed-spin binuclear nickel(II) complex with N,N′,N″,N‴-tetrakis(2-aminoethyl)-1,4,8,11-tetra-azacyclotetradecane

The crystal structure of [Ni2(taec)Cl]Cl3·H2O was determined by the single-crystal X-ray diffraction method, where taec is N,N′,N″,N‴-tetrakis(2-aminoethyl)-1,4,8,11-tetra-azacyclotetradecane. The [Ni2(taec)Cl]3+ cation has a novel binuclear structure in which one of the nickel ions is co-ordinated by a square-planar N4 donor set and the other by a distorted square-pyramidal N4Cl donor set.

Resonance raman spectra of molecular oxygen adducts of Co(salen) and its derivatives in solution

Abstract Resonance Raman spectra of the molecular oxygen adducts of six Co(salen) derivatives have been measured in CH2Cl2 or CHCl3 containing pyridine using the mini-bulb method (∼−80°C, ∼4 atm O2 pressure). These adducts exhibit the O2 and CoO stretching bands at 1146−1143 and 530−515 cm−1, respectively. Although the former is insensitive to the nature of the in-plane ligand, the latter is sensitive to the geometry of the CoN2O2 core (steric effect) and the degree of π-conjugation over the entire chelate ring (electronic effect).

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 and structure of metal chelates of stilbenediamine schiff bases

Abstract Copper(II), Ni(II) and Co(II) chelates of Schiff bases derived from dl- and meso -stilbenediamine with acetylacetone, salicylaldehyde, and o -hydroxyacetophenone have been prepared. The structures of the metalchelates were inferred by means of electronic absorption spectra and found to be essentially square-planar. Exceptions are bis(acetylacetone)- meso -stilbenediiminatocopper(II) and bis( o -hydroxyacetophenone)- meso -stilbenediiminatocopper(II), which are fairly distorted from square-planar, probably because of the steric interactions between the equatorial phenyl group and the methyl group on the azomethine carbon atom. The conformation of the phenyl groups in the metal-chelates of the dl-isomers was investigated by the spectral behavior in pyridine and was concluded to be essentially diaxial relative to the metal-chelate plane. However, it is reasonable to conclude that conversion from the planar conformation takes place upon apical pyridine coordination in the case of bis(salicylaldehyde)-dl-stilbenediiminatocopper(II).