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N-(2-Hydroxyphenyl)salicylamide (H3L1) and N-(2-hydroxy-5-chlorophenyl)salicylamide (H3L2) formed diamagnetic nickel(II) and palladium(II) complexes of the composition (PBu4)2[M(L)(H2L)] (PBu4 + = tetrabutylphosphonium ion; M = Ni, Pd; L = L1, L2). Single-crystal X-ray analysis for (PBu4)2[Pd(L1)(H2L1)] revealed that one ligand (L1)3-coordinates terdentately and the other ligand (H2L1)-coordinates unidentately at the phenolic oxygen of the “salicylamide” entity, affording a planar configuration around the metal ion. In cyclic voltammograms both Ni and Pd complexes showed one oxidation wave attributable to the process M(II)/M(III) at a significantly low potential. The Ni(III) and Pd(III) species of the L2 complex were generated by electrochemical oxidation and identified by electronic absorption and ESR spectra. Based on electronic absorption and ESR spectra, a considerable delocalization of the unpaired electron onto the ligand orbitals was suggested for both Ni(III) and Pd(III) complexes.

The reaction of tetraammincopper(II) sulfate monohydrate in a solid state with H2 (10 MPa) was studied. The Cu(II) ion in the complex was reduced to Cu(0). The final product was a mixture of (NH4)2SO4 and colloidal black Cu(0) which showed a remarkable reactivity as follows. In thermogravimetric analysis up to 440°C under nitrogen atmosphere, the above product reacted between the components very much differently from a control sample with the same composition. The six intermediate samples, taken at successive reaction times, were examined by powder diffraction method. As one of the intermediates, the copper double salt, (NH4)2Cu(SO4)2, was identified.

A new dinucleating ligand 1,5-bis[bis(4-imidazolylmethyl)amino]-3-pentanol (Hbipl) has been synthesized. It forms the dicopper(II,II) and diiron(III,III) complexes, [Cu 2 (bipl)Cl](ClO 4 ) 2 ·H 2 O and [Fe 2 (bipl)(OAc) 2 ](ClO 4 ) 3 ·H 2 O, which are characterized by elemental analyses, magnetic susceptibility measurements, cyclic voltammetry, and IR and UV-Vis spectroscopies.

Heterodinucleating macrocycles with two 2,6-bis(iminomethyl)-4-methylphenolate entities combined through two lateral chains, -(CH 2 ) 2 - and -(CH 2 ) m NH(CH 2 ) m -(m=2, 3), at the imino nitrogens have been prepared as Cu II Pb II complexes of the formula [CuPb(L)]XY (L 2- =L1 for m=2 and L2 for m=3; XY=(ClO 4 ) 2 , (NO 3 )(PF 6 ), (AcO)(BPh 4 )).

The near-ultraviolet absorption band characteristic of dialkoxo-bridged binuclear copper(II) complexes was reinvestigated by using a series of binuclear copper(II) complexes with N,N-dialkyldiaminoalcohols, Cu2{R2N(CH2)mNH(CH2)nO}2X′2 (abbreviated as Cu(R-m-n)X′, X′ = ClO4, BF4). In this study eighteen complexes including ten new compounds were prepared and classified into two types, i.e., type-A and B according to Kida’s classification, based on their temperature dependencies of magnetic susceptibilities (80–300 K) and reflectance spectra. The crystal structures of Cu(n-Bu-3-2)ClO4 (10), Cu(H-3-3)BF4·EtOH (11b), and Cu(Me-3-3)ClO4 (12a) were determined by the single-crystal X-ray diffraction method. The detailed analysis of the structures and reflectance spectra led to the same conclusion as Kida’s one in assigning the near-ultraviolet absorption band. That is, the absorption was ascribed to the charge transfer (CT) from the bridging oxygen’s nonbonding orbital to vacant copper d-orbital. On the other ha...

Mixed-metal assemblies {NBu4[M(II)Fe(III)(ox)3]}3∞ (M = Ni (1), Fe (2), Mn, Zn) have been prepared and characterized, where NBu4+ = tetra(n-butyl)ammonium ion, ox2− = oxalate ion. Each assumes a three-dimensional network structure consisting of alternately arrayed Fe(III) and M(II) ions. The compounds 1 and 2 are shown to be ferrimagnet with a magnetic phase-transition temperature of 28 and 43 K, respectively.

The reaction of K 3 [Cr(ox) 3 ].3H 2 O, a metal(II) salt, and tetra(n-butyl)ammonium bromide in the molar ratio of 1:1:1.5 in water at room temperature afforded a series of mixed-metal assemblies with the formula {NBu 4 [MCr(ox) 3 ]} x (M=Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ).

Three imidazolate-bridged binuclear copper(II) complexes [Cu(A)Cu(Ln)]ClO4, 1 (n = 1), 2 (n = 2), and 3 (n = 3), have been prepared and characterized, where H2A = 4-(6-methyl-8-hydroxy-2,5-diazanonane-1,5,7-trienyl)imidazole, HL1 = N-salicylidene-2-(2-pyridyl)ethylamine, HL2 = N-(1-methyl-3-oxobutylidene)-2-(2-pyridyl)ethylamine, and HL3 = 3,3′-(trimethylenedinitrilo)-bis[2-butanone oximate]. The cryo-magnetic susceptibility data (4.2–300 K) of 1 and 2 were well reproduced by the Bleaney–Bowers equation based on H = −2JSCu · SCu with the J values of −46.1 and −36.6 cm−1, respectively, while the magnetic data of 3 showed no magnetic interaction. The reference complexes [Cu(Ln)(py)]ClO4 (n = 1,2; py = pyridine) have been subjected to single-crystal X-ray diffraction analysis.

The complexation of tridentate trianionic chelating ligands, N-(2-hydroxyphenyl)salicylamide (H3L1) and its homologs with a substituent on the 2-hydroxyphenyl moiety (5-CH3, H3L2; 5-Cl, H3L3), toward iron ion has been studied. The ligand H3L1 formed a high-spin iron(III) complex K3[Fe(L1)2] when treated with FeCl3 in an alkaline solution under open atmosphere. This complex was oxidized with Ce(IV) to a high-spin iron(IV) complex (NPr4)2[Fe(L1)2]. The ligand H3L2 formed a low-spin iron(IV) complex K2[Fe(L2)2] under open atmosphere, whereas the ligand H3L3 gave a high-spin iron(III) complex (PBu4)3[Fe(L3)2]. The complexes were characterized by means of cyclic voltammetry, electronic spectra and Mossbauer spectra.

A 36-membered macrocycle with four ethylenediamine entities, 1,10,19,28-tetraoxa-4,7,13,16,22,25,31,34-octaazacyclohexatriacontane (L), has been synthesized and characterized by 1H and 13C NMR and fast atom bombardment (FAB) mass spectra. Its complexing behaviour toward copper(II) ion was investigated spectroscopically and the macrocycle shown to incorporate four copper(II) ions in the range pH 6–9. A tetranuclear complex [Cu4L(OH)4][ClO4]4·2H2O was obtained and characterized to be of a cubane-type Cu4(OH)4 core surrounded by the macrocycle, according to IR, visible, FAB and ESR spectra, cyclic voltammetry, and cryomagnetic susceptibility.

Coordination of 1,2-bis(6-methyl-2-pyridyl)ethane(endip),2,6-bis [2-(6-methyl-2-pyridyl)ethyl]-pyridine (entrip), and 1,2-bis[6-[2-(6-methyl-2-pyridyl)ethyl]-2-pyridyl]ethane (entetp) ligands towards cobalt(II), zinc(II), and copper(I) ions have been examined and the following complexes have been obtained: Co(endip)Cl2 (1), Co(endip)(NCS)2 (2), Zn(endip)Cl2 (3), Cu(endip)ClO4 (4), CO3(entrip)2Cl6 (5), Zn3(entrip)2Cl6 (6), Cu2(entrip) ClO4 (7), CO2(entetp)Cl4 (8), Zn2(entetp) Cl4 (9), Zn(entetp)SO4 (10), and CU2(entetp) (ClO4)2 (11). X-ray structure analysis for 3 has revealed a distorted environment about the zinc(II) ion with bidentate endip (ZnN: 2.09 A) and two chloride ions (ZnCl: 2.24 A). The seven-membered chelate ring formed by endip assumes a non-planar conformation and the NZnN bite angle is fairly large (119.0°). The ClZnCl bite angle is also large (122.0°). A similar tetrahedral structure is assigned to 1, 2 and 4. In 5–7, entrip functions as a tridentate ligand to form tetrahedral [M(entrip)X]n+ (X = Cl− and n = 2 for 5 and 7, X = ClO4− and n = 1 for 6). In 8 and 9 the tetrakis-pyridine ligand, entetp, incorporates two cobalt(II) ions at “endip”-like coordination sites to form two {CONNClCl} chromophores separated by an ethylene bridge. In the zinc(II) complex 10 entetp functions as a quadridentate ligand to form a tetrahedral [Zn(entetp)]2+ core. The copper(I) complex 11 is suggested to have an oligomeric structure.

The reactions of 3,5-di-t-butyl- o -benzoquinone (DBQ) with the Co(II)M(III) (M=Y, La) complexes of N,N′ -bis(3-carboxysalicylidene)ethylenediamine have been studied in dmf solutions by means of ESR spectroscopy. The ESR spectral study has shown that DBQ oxidizes the Co(II) ion of the Co(II)M(III) complexes to afford a Co(III)M(III)-DBSQ species (DBSQ=semiquinone form of DBQ) but the DBSQ is bound to the M(III) ion but not to the Co(III). The reaction of the mononuclear cobalt(II) complex [Co(H 2 L)] with DBQ afforded [Co(H 2 L)(DBSQ)] where DBSQ coordinates to the cobalt(III) ion as a bidentate chelate.

A study was made to see if it is possible to enhance the heat transfer in the downstream region of a backward-facing step, where heat transfer is normally deteriorated, by the insertion of a cylinder near the top corner of the step. Cylinder size and streamwise position of the cylinder were kept constant but the cross-stream position of the cylinder was changed in three steps. Results of the heat transfer experiment, flow visualization, and measurement of the averaged and fluctuating flow fields were reported. When the cylinder was mounted at a position, a little higher than the top surface of the step, a jet-like flow pattern emerged in the averaged velocity profile beneath the cylinder and the recirculating flow was intensified. Therefore, the velocity of recirculating flow near the wall is increased at some streamwise positions. Additionally, the velocity fluctuation was intensified not only in the shear layer between the jet-like flow and the recirculating flow regions but also in the near wall region, resulting in the effective augmentation of heat transfer in this case. Therefore, it is concluded that the mounting of a cylinder is effective in the enhancement of deteriorated heat transfer in the recirculating flow region, if its is mounted in a proper position.

Stereoselectivity of bis[N-(l-menthyl)salicylideneaminato]cobalt(II) [Co(sal-ment)2] has been studied by single crystal X-ray analysis and molecular mechanics calculations. The X-ray analysis has revealed a nearly tetrahedral surrounding (dihedral angle of 82.5°) and Δ configuration about the metal ion. Molecular mechanics calculations were made based on MM2 program, assuming a tetrahedral surrounding about the metal ion and fixing the four donor atoms and six atoms adjacent to the donor atoms at the positions as determined by the single crystal X-ray analysis. The most stable structure obtained from the MM2 calculation coincides well with that from the crystal structure analysis. Together with the X-ray structural results for [Cu(sal-ment)2] and bis[N-[(R)-1-phenylethyl]salicylideneaminato]cobalt(II) [Co(sal-Rmb)2] studied in this study and for related [Zn(sal-Rmb)2] and [Cu(sal-Rmb)2] studied previously, the factors responsible for the stereoselectivities of those bis(salicylideneaminato)metal(II) compl...

Imidazolate-bridged trinuclear Cu(II)–Fe(III)–Cu(II) complexes [Cu(A)Fe(acen)Cu(A)]ClO4·2H2O (1) and [Cu(A)Fe(salen)Cu(A)]ClO4·2H2O (2) are synthesized and characterized by magnetic susceptibilities, Mossbauer spectra, and ESR spectra, where H2A = 4-(6-methyl-8-oxo-2,5-diazanonane-1,5,7-trienylimidazole. The Fe(III) of 1 is in low-spin state (S = 1/2) and the spin-coupling between the Fe(III) and Cu(II) ions is ferromagnetic. On the other hand, the Fe(III) of 2 is in high-spin state (S = 5/2) and the spin-coupling is antiferromagnetic.

Three oxalate-bridged binuclear Cu(II)–Cr(III) complexes [(salen)Cr(ox)Cu(Lm)] (1, HL1 = N-salicylidene-N-(2-pyridylethyl)amine; 2, HL2 = N-acetylacetonylidene-N-(2-pyridylethyl)amine; 3, HL3 = N-salicylidene-N′,N′-diethylethylenediamine) have been prepared and the cryomagnetic susceptibility measurements(4.2–300 K) revealed that the spin-coupling is ferromagnetic with the J values +2.8, +2.2, and +2.7 cm−1 for 1, 2, and 3, respectively, based on H = −2JSCuSCr. The J values are well compatible with J = +2.9 cm−1 of {NBu4[CuCr(ox)3]}x evaluated from the equation Tc=nJ/3k[SCr(SCr+1)SCu(SCu+1)]1/2 (Tc = 7 K, n = 3) based on Heisenberg’s theory of ferromagnetism.

The reaction of 2,6-diformyl-4-methylphenol, triethylenetetramine, and copper(II) perchlorate hexahydrate in the 2:2:4 molar ratio formed a macrocyclic tetracopper(II) complex [Cu4(L)(OH)2](ClO4)4 where H2L denotes the macrocycle formed by two molecules of 2,6-diformyl-4-methylphenol and two molecules of triethylenetetramine. The two hydroxide groups, each bridging a pair of copper(II) ions, are facing each other in a close distance so as to be replaced by an azide ion, affording [Cu4(L)(N3)](ClO4)5.

A new triazamacrocycle, 1,6,11-triazacyclopentadecane (tacpd), has been synthesized and its complexation behaviors toward nickel(II), copper(II) and zinc(II) ions have been examined. tacpd formed a Zn(II) complex of the composition Zn 3 (tacpd) 2 Cl 6 but no discrete complexes with Ni(II) and Cu(II) ions. The 1 H and 13 C NMR spectra indicated that the zinc complex is stable in N,N -dimethylformamide and formulated as [Zn(tacpd)Cl] 2 [ZnCl 4 ] in which [Zn(tacpd)Cl] + assumes a tetrahedral structure formed by the chloride ion and three nitrogens of tacpd.

A dihydroxo-bridged binuclear Cr(III)-Cu(II) complex, [Cr(tet b)(OH) 2 Cu(bpy)(CH 3 OH)](ClO 4 ) 3 (and its methanol-free complex, and a trinuclear Cr(III)-Cu(II)-Cr(III) complex, {Cu[Cr(tet b)(OH) 2 ] 2 }(ClO 4 ) 4 •H 2 O have been synthesized and characterized. The cryomagnetic measurements (4.2-300 K) indicated the operation of a ferromagnetic interaction between the adjacent chromium(III) and copper(II) ions in both complexes

The binucleating ligand N,N′-bis-(3-carboxysalicylidene)ethylenediamine (H4fsaen) formed copper(II)-dimethyltin(IV) and cobalt(II)-dimethyltin(IV) complexes [MSn(CH3)2(fsaen)] (M=Cu, Co) where the copper(II) or cobalt(II) ion is bound at the N2O2 site and the tin(IV) ion at the O4 site with two methyl groups at the axial positions. Both complexes are fairly stable towards atmospheric moisture in the solid state but decomposed into a mononuclear complex [M(H2fsaen)] by a trace amount of water when dissolved in solution. Spectroscopic investigations on the Cu-Sn complex in pyridine revealed that the coordination of pyridine to the copper(II) is sterically hindered by the methyl groups attached to the neighbouring tin(IV). In the case of the Co-Sn complex such a steric effect of the methyl groups is not pronounced enough to binder the coordination of pyridine to the axial site of the cobalt(II). ESR spectra at liquid nitrogen temperature revealed that the cobalt(II) ion adopts a pentacoordinate structure at room temperature and a hexacoordinate structure near liquid nitrogen temperature with pyridine molecule(s) at the axial site(s).

A study was conducted to see if it is possible to enhance the heat transfer in the downstream region of a backward-facing step, where heat transfer is normally deteriorated, by the insertion of a cylinder near the top corner of the step. The flow Reynolds number, cylinder size and streamwise position of the cylinder were kept constant but the cross-stream position of the cylinder was changed in three steps. The results of the heat transfer experiment, flow visualization and measurement of the averaged and fluctuating flow fields were reported. When the cylinder was mounted in a position a little higher than the step top surface, a jetlike flow pattern appeared in the averaged velocity profile beneath the cylinder, and the recirculating flow was intensified. Therefore, the velocity of recirculating flow near the wall is increased at some streamwise positions. Additionally, velocity fluctuation is intensified, not only in the shear layer between the jetlike flow and the recirculating flow regions but also in the near wall region. These intensifications result in the effective augmentation of heat transfer in this case. Therefore, it is concluded that the mounting of a cylinder is effective if it is mounted in the proper position.

The reaction of [N,N′-ethylene- or [N,N′-propane-1,3-diylbis(3-formyl-5-methylsalicylideneiminato)]-metal(II)(M = Cu or Ni) and a diamine (ethylenediamine, propane-1,3-diamine, butane-1,4-diamine or pentane-1,5-diamine) in the presence of lead(II) ion gives macrocyclic complexes [Pb(MLm,n)2]X2[H2Lm,n= macrocycle formed by the condensation of two molecules of 2,6-diformyl-4-methylphenol and two diamines H2N(CH2)mNH2 and H2N(CH2)nNH2; m= 2 or 3 and n= 2–5; M = Cu or Ni; X = CIO4, PF6, BPh4 or BF4]. They were characterized by elemental analyses, single-crystal X-ray analysis, fast atom bombardment mass, IR, electronic and ESR spectra and magnetic measurements. The crystal structure of [Pb(CuL3,3)2][CIO4]2 has revealed that the copper(II) ion in each CuL3,3 is bound at one of the N2O2 donor sites and the lead ion is sandwiched by the vacant N2O2 sites of two CuL3,3 entities, providing a square-antiprismatic environment.

A new binucleating pyrazole ligand, 3,5-bis{N,N-bis[2-(diethylamino)ethyl]aminomethyl}pyrazole (HL), has been synthesized. It forms cobalt(II) and copper(II) complexes of the general formula [M2(L)(X)](BPh4)2·n(acetone) (M=Co, Cu; X=CH3COO−, N3−; n=0–3), where two metal ions are bridged by the endogenous pyrazolate group and the exogenous X group. Electronic spectra of the cobalt(II) and copper(II) complexes suggest a trigonal-bipyramidal configuration around each metal ion. Magnetic properties have been examined over the temperature range 75–300 K. The cobalt(II) complexes [Co2(L)(CH3COO)](BPh4)2·acetone and [Co2(L)(N3)](BPh4)2·2acetone both show a slight increase of magnetic moment with lowering of temperature (from 4.03 and 3.94 μB, respectively, at 300 K to 4.16 and 4.08 μB, respectively, at 85 K). [Cu2(L)(CH3COO)](BPh4)2 shows a weak antiferromagnetic spin-coupling (J = −7.02 cm−1 based on spin Hamiltonian H = −2JŜ1·Ŝ2). [Cu(L)(N3)](BPh4)2·acetone exhibits a much lowered magnetic moment (1.10 μB at 300 K) owing to a strong antiferromagnetic spin coupling but its cryomagnetic property could not be simulated based on the Heisenberg model.

Binuclear complexes, [Cu(L)Cu(L′)(H2O)2]X2 (H2L=3,3′-trimethylenedinitrilobis(2-butanoneoxime) (H2dopn) or 3,3′-ethylenedinitrilobis(2-butanoneoxime) (H2doen); L′=2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen); X=ClO4 or NO3), [Ni(dopn)Cu(bpy)(H2O)](ClO4)2, and [Ni(dopn)Ni(bpy)2](ClO4)2, have been prepared and characterized. The structure of [Cu(dopn)Cu(phen)(CH3OH)2](ClO4)2 (di-methanol adduct) has been determined by single crystal X-ray method. The Cu(dopn) molecule coordinates to the second copper(II) ion through the deprotonated oximate oxygens to afford a binuclear structure doubly bridged by the oximate groups in the cis arrangement. The binuclear cation is bent at the oxymate oxygens with a dihedral angle of 26.7(2)°. The binuclear copper(II) complexes show a characteristic visible band of significant intensity (e 2700–2900 dm3 mol−1cm−1) near 22000 cm−1 and a strong intramolecular antiferromagnetic spin-exchange interaction. The exchange integrals (J) are evaluated to be −413.3–−433.0 cm−1. Th...

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.

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.

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.

The stereoselectivity of bis[N-(R)-1-phenylethylsalicylideneiminato]zinc(II) has been studied by means of single-crystal X-ray analysis and circular dichroism (c.d.) spectra. The complex crystallizes in space group P212121 with a= 17.738(4), b= 29.632(9), c= 9.968(2)A, and Z= 4. The unit cell is comprised of four units each containing two complex molecules (A and B). Each molecule adopts a nearly tetrahedral structure with two bidentate ligands; the dihedral angle defined by the two chelate rings is 81.7° for molecule A and 84.9° for molecule B. The absolute configuration along the pseudo-C2 axis is Λ for both molecules. Based on the X-ray analysis it is suggested that intramolecular non-covalent interactions between the chiral N-substituent and the adjacent chelate ring give rise to stereoselectivity and the Λ configuration around the metal ion. The c.d. couplet (+and – signs) induced at the azomethine π–π* transition at around 27 000 cm–1 is discussed with respect to the absolute configuration and in comparison with the spectra of related Schiff-base complexes.

The preparation of new dinucleating pyrazole ligands, 3,5-bis[(2-diethylamino)ethylaminomethyl]pyrazole (HL1) and 3,5-bis[(3-dimethylamino)propylaminomethyl]pyrazole (HL2), has been accomplished. They afford binuclear copper(II) complexes of the formula [Cu2L2][BPh4]2(L = L1 or L2). The structure of [Cu2L12][BPh4]2 was determined by single-crystal X-ray analysis. It crystallizes in the triclinic space group P with a= 13.437(4), b= 15.192(5), c= 12.364(4)A, α= 116.38(3), β= 113.71(3), γ= 60.48(2)°, and Z= 1. The complex has a binuclear structure doubly bridged by the pyrazolate groups with the Cu ⋯ Cu separation 3.903(2)A. The configuration geometry of each copper is a square pyramid, whose basal plane is formed by the two pyrazolate nitrogens and the ‘articular’ nitrogens [Cu–N 1.906(3)–2.028(3)A] and the apical site by one of the ‘terminal’ nitrogens [Cu–N 2.496(5)A]. The other terminal nitrogen is free from co-ordination. Cryomagnetic investigations over the temperature range 100–300 K revealed a strong antiferromagnetic spin exchange in both complexes. The exchange integral (J) based on the Heisenberg model, was evaluated as – 214 cm–1 for [Cu2L12][BPh4]2 and –181 cm–1 for [Cu2L22][BPh4]2.

Two types of hetero–metal assemblies {NBu4CuCr(ox)3]}x (1) and {[{Cu(bpy)}2Cr(ox)3]NO3}x (2)(NBu4 = tetrabutylammonium ion, ox = oxalate ion, bpy = 2,2′-bipyridine, x = infinite number) have been synthesized and their cryomagnetic properties (4.2–300 K) have been examined. The compound 1 has an oxalate-bridged three-dimensional lattice and show a ferromagnet-like property (Curie point 7 K): the moment (per CrCu) increases from 4.37 μB at 300 K to 14.80 μB at 9 K and diverges below 9 K. The compound 2 also shows a ferromagnetic interaction and its moment (per CrCu2) increases from 4.82 μB at 300 K to 8.78 μB at 5 K.

The trinuclear copper(II) complex [Cu(CuL)2][ClO4]2[H2L = 3,3′-(trimethylenedinitrilo)bis-(2-butanone oxime)] has been synthesized. It crystallizes in monoclinic space group C2/c, with Z= 4, a= 14.253(1), b= 18.798(2), c= 12.675(1)A, and β= 106.92(1)°. The structure consists of trinuclear cations [Cu(CuL)2]2+ and perchlorate ions. The central copper is co-ordinated by oximate oxygens of two CuL entities and the configuration around the metal is significantly distorted from tetrahedral with a dihedral angle of 33.31 (6)°. Each terminal copper adopts an essentially planar configuration with the nitrogen atoms of L2–. The three chromophores in the cation are bent at the edges of the bridging oximate oxygens, with a dihedral angle of 55.88(9)°, to afford a butterfly shape for the cation. In the crystal the trinuclear cations interact with each other at the terminal copper, in the so-called out-of-plane mode, through oximate oxygen to form an infinite chain along the c axis. Cryomagnetic investigations in the range 80–300 K revealed a strong antiferromagnetic spin-exchange interaction within the molecule; the magnetic moment per cation is 2.00 µB at room temperature but converges to 1.80 ± 0.01 µB at 170 K. The exchange integral J, based on the isotropic exchange model ℋ=–2∑jijŜiŜj, is –290.8 cm–1.

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.

Trinuclear complexes of general formulas [MCu2(CH3CO2)2(salpd)2](M = MgII, MnII, CoII, NiII, CuII, or ZnII) and [MNi2(CH3CO2)2(salpd)2](M = MgII, MnII, CoII, or NiII) were prepared, where H2salpd represents propene-1,3-diylbis(salicylideneimine). Further reactions of the complexes of the former series with sulphur dioxide yielded [MCu2(CH3CO2SO2)2(salpd)2](M = MgII, MnII, CoII, or NiII) and [Cu3(HSO3)2(salpd)2(H2O)2]. Cryomagnetic measurements (77.4–295 K) have shown that a weak or negligible antiferromagnetic spin coupling (J=–46 to 0 cm–1) is operating between the terminal and central metal ions in the complexes except for [Cu3(HSO3)(salpd)2(H2O)2] which showed a strong antiferromagnetic coupling (J=–186 cm–1) between neighbouring copper(II) ions. X-Ray crystal analysis was carried out for [Zn{(µ-CH3CO2)(salpd-µ-O,O′)Cu}2]. It crystallizes in the monoclinic space group P21/a with a= 16.228(5), b= 11.971 (2), c= 9.239(3)A, β= 100.15(3)°Z= 2, and R=–0.0887. The complex consists of a linear CuII–ZnII–CuII trinuclear unit which has an inversion centre. The CuII and ZnII are bridged by the two phenolate oxygens of the salpd and the oxygens of the acetate ion.

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.

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.

A series of imidazolate-bridged trinuclear complexes [Cu(A)M(hfac)2Cu(A)] (M = Zn2+, Cu2+, Ni2+, Co2+, Mn2+) have been prepared, where H2A = 4-(6-methyl-8-hydroxy-2,5-diazanonane-1,5,7-trienyl)imidazole and Hhfac = hexafluoroacetylacetone. The magnetic susceptibility data (4.2–300 K) were well reproduced by the equation based on the spin-Hamiltonian H = −2JCuM (SCu1·SM+SM·SCu2) to give the coupling parameters of JCuCu = −52.5 cm−1 (SCu = 1⁄2), JCuNi = −20.3 cm−1 (SNi = 1), JCuCo = −13.2 cm−1 (SCo = 3⁄2), and JCuMn = −4.5 cm−1 (SMn = 5⁄2).

The reaction of 2,6-difomyl-4-methylphenol and 1,9-diamino-3,7-diazanonane in methanol in the presence of lead(II) ion forms a dinuclear lead(II) complex of a very rare macrocycle containing hexahydropyrimidine rings. The structure of the complex is determined by single crystal X-ray method.

A dilead(II) complex of a binucleating macrocycle formed by the condensation of two molecules of 2,6-diformyl-4-methylphenol and two molecules of 1,3-diaminopropane has been obtained by template reaction. The crystal structure of this complex was analyzed by single-crystal X-ray method.