Tetraamine Complexes Research Articles

The π-donor/acceptor trans effect on NO release in ruthenium nitrosyl complexes: a computational insight

The NO release using ruthenium tetraamine complexes was finally elucidated from DFT calculations, highlighting the influence of the acidic medium.

Tracking the role oftrans-ligands in ruthenium–NO bond lability: computational insight

Ruthenium–NO tetraamine structures control the nitric oxide bioavailability. The ligandtransto NO modulates the Ru–NO bond stability.

Precious metals recovery from waste printed circuit boards using thiosulfate leaching and ion exchange resin

Precious metals recovery from secondary sources is a novel alternative since they hold higher contents of several metals than average ores. In this research gold and silver were recovered from Waste Printed Circuit Boards (WPCBs) with the use of ammonia-thiosulfate solutions and the MTA 5011 ion exchange resin. First, it was necessary to remove the excess of copper from WPCBs since it could be detrimental for precious metals dissolution during leaching with thiosulfate. Nitric acid was the best reagent for decreasing copper concentration within WPCBs from 27% to 1.5%. Then, precious metals were dissolved with ammonia-thiosulfate solutions during 6 h at room temperature. Since copper was still within WPCBs, there was no need to add copper salts in order to form the copper tetramine complex required for accelerating precious metals dissolution. MTA 5011 ion exchange resin was used for precious metals recovery from leachates. It was determined that at higher resin: solution ratios, gold and silver recovery on the resin increased whereas selectivity towards gold diminished. The 87% of the gold was recovered and only 29% of copper was adsorbed too. Afterwards, a pre-elution stage was performed with sodium thiosulfate for a selective elution of copper. The 83% of the copper was desorbed while 28% of gold was eluted as well. For precious metals elution, several reagents were tested and KSCN was the most efficient of all since it desorbed the 98% of gold and only the 15% of the remaining copper. A combined solution of NaCl and Na2SO3 was assessed as well since they can regenerate the resin during the elution process. Finally, electrodeposition was better with solutions coming from elution with NaCl and NaSO3 (82% of Au and 94% of Ag recovery on cathodes surface) compared to those from thiocyanate elution (62% of Au and 87% of Ag).

Electrocatalytic Water Oxidation by Mononuclear Cu(II) Aliphatic Tetraamine Complexes

AbstractWe report here electrocatalytic water oxidation by a series of mononuclear Cu(II) aliphatic tetraamine complexes at various pH. In phosphate buffer solution of pH 12, the Cu(II)‐Tren (Tren is tris‐(2‐aminoethyl)amine) complex is decomposed to generate a Cu oxide/hydroxide film with phosphate incorporated on the electrode surface which can catalyze water oxidation with a small onset overpotential of 420 mV and a low Tafel slope of 48 mV dec−1. By contrast, the other two Cu(II) complexes, Cu(II)‐Me3(Tren) (Me3(Tren) is (tris‐(2‐(methylamino)ethyl)amine)) and Cu(II)‐Me6(Tren) (Me6(Tren) is tris‐(3‐methyl‐3‐azabuty)amine), having the ligands that sharing the same molecular skeleton of Tren but with methyl group substituents, are noneffective to form the surface‐bound active species. The experimental results indicate that the Cu(II)‐Tren complex decomposes by intra‐complex proton‐coupled electron transfer (PCET) from the amine ligand to the higher‐oxidation‐state Cu with significant pH/buffer base effects. At pH 9, water oxidation with Cu(II)‐Tren transforms from heterogeneous to homogeneous featuring a single‐site catalysis mechanism. Moreover, the comparison of the three Cu(II) complexes at this pH also suggests a steric effect of methyl groups on the catalysis performance. As pH decreases further to 7, Tren, with pKb ∼5.9, becomes less coordinating and precipitation of a Cu3(PO4)2 film during electrolysis leads to electrode passivation, which inhibits the homogeneous water oxidation at this pH.

A review of factors affecting gold leaching in non-ammoniacal thiosulfate solutions including degradation and in-situ generation of thiosulfate

Cyanide has been used for more than a century as a preferred lixiviant for extracting gold from ores and concentrates. While cyanide is very effective in treating certain ores and concentrates, it is not suitable for carbonaceous and high copper-bearing ores. Research activities over many decades have indicated that thiosulfate has potential as an alternative lixiviant for extracting gold from problematic ores/concentrates which are not amenable for cyanidation. A number of studies have shown faster gold leaching kinetics with thiosulfate in the presence of ammonia and copper(II) in the form of a cupric tetraamine complex that acts as an oxidant for gold. However, ammonia is toxic and the lixiviant system is highly complex due to the presence of several ligands, which particularly affects speciation of the copper ions and their reactions in the system. For this reason, recent studies have been focusing on alternative oxidants that do not use ammonia. In this article, a comprehensive review of fundamental studies of leaching of gold from different ores in ammonia-free thiosulfate solutions is presented with special emphasis on factors that affect gold leaching kinetics including mineralogical composition of ores and concentrates. Important aspects of thiosulfate gold leaching such as thiosulfate stability, in-situ generation and consumption of thiosulfate and passivation of gold are reviewed.

Study of silver leaching with the thiosulfate–nitrite–copper alternative system: Effect of thiosulfate concentration and leaching temperature

Thiosulfate system is considered an interesting alternative leaching process for precious metals. Nevertheless, most of the literature published on these conventional thiosulfate leaching solutions has been focused on the use of ammonia and copper to generate the cupric tetraamine complex, which acts as a catalytic oxidant for silver. However, ammonia toxicity is also a detrimental issue in terms of the process sustainability. For that reason, thiosulfate–nitrite–copper solutions were studied as an alternative less toxic system for silver leaching.In this work, the effect of the thiosulfate concentration (0.07M, 0.1M and 0.15M) and temperature (room temperature, 30, 35, 40 and 45°C) on the metallic silver leaching kinetics is presented for the S2O3–NO2–Cu system. The results show that the thiosulfate concentration plays an important role in the S2O3–NO2–Cu–Ag system since it controls the silver leaching kinetics. On the other hand, an increase in temperature favors the silver recovery.Finally, the SEM–EDS analysis, the X-ray mapping and the X-ray diffractograms show that the solid silver particles are coated by a Cu, S and O layer for the 0.07M and 0.1M thiosulfate experiments, which is consistent with the formation of antlerite (Cu3(SO4)(OH)4); while the 0.15M thiosulfate scenario produced a layer composed only of Cu and S, revealing the formation of stromeyerite (CuAgS). The UV–Visible technique confirmed the in-situ generation of copper–ammonia complexes for the 0.07M leaching condition; however, these complexes are not formed at the 0.15M condition.

Synthesis of Platinum Catalysts over Thick Slurries of Oxide Supports by Strong Electrostatic Adsorption

AbstractPlatinum uptake by strong electrostatic adsorption on alumina, silica, and titania supports was studied at different slurry thicknesses (or surface loadings). For the anionic platinum chloride precursor, a high counterion concentration at high surface loadings hindered adsorption on the high point of zero charge alumina support, as predicted by the revised physical adsorption model. Owing to this adsorption retardation in thicker slurries, a highly dispersed Pt/Al2O3 catalyst could only be prepared with a lower weight fraction of Pt than that in thin slurries. However, for cationic platinum tetraamine complexes, the effect of counterions in retarding the adsorption at high surface loadings was unexpectedly diminished. As a result, it was possible to synthesize highly dispersed Pt/SiO2 even at a maximum slurry thickness (incipient wetness) without having to sacrifice the Pt loading.

Study of thiosulfate leaching of silver sulfide in the presence of EDTA and sodium citrate. Effect of NaOH and NH4OH

In this research, an analysis of the effect of NaOH and NH4OH on the silver sulfide leaching kinetics was performed using thiosulfate–copper solutions in the presence of EDTA and sodium citrate, in order to develop an alternative green hydrometallurgical process for the sustainable recovery of precious metals. For that purpose, silver sulfide leaching experiments were carried out with different thiosulfate–copper solutions at room temperature. The different copper species present in the leaching systems were elucidated with the aid of species distribution thermodynamic diagrams. The solid residues of all leaching experiments were morphologically and chemically characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive X Ray Spectroscopy (EDXS), in order to identify the solid products formed, and to elucidate the effect of the morphology of the solid and its composition on the silver sulfide leaching kinetics. The results of this study showed that the cupric tetraamine complex (Cu(NH3)42+), generated by the NH4OH presence in the leaching solutions containing EDTA or citrate, enhances the silver leaching kinetics. The ammoniacal–citrate and ammoniacal–EDTA system showed the formation of a porous layer composed by copper oxides and copper sulfides on the silver sulfide particle. The ammoniacal–citrate system presented a degradation of thiosulfate which inhibits the silver sulfide leaching kinetics. On the other hand, when the sodium hydroxide is employed, the complexes Cu(EDTA)OH3− and Cu2(cit)2OH3− are formed and play a similar role to that of the Cu(NH3)42+ in systems containing ammonium hydroxide. The solid residues presented a porous layer composed by copper oxides and copper sulfides through which the fluid reactants have to diffuse in order to leach the silver, with the NaOH–EDTA and NaOH–citrate systems. This research also reveals that the thiosulfate–copper–NaOH–citrate system could be a promising alternative process to leach silver from silver sulfide.

Hydrolytic cleavage of DNA promoted by cobalt(III)–tetraamine complexes: Synthesis and characterization of carbonatobis[2-(2-pyridylethyl)]-(2-pyridylmethyl)aminecobalt(III) perchlorate

cis-Aquahydroxo–tetraamine–cobalt(III) complexes of the general formula [Co(N 4)(OH)(H 2O)] 2+ have been prepared (pH ∼ 7) from their corresponding well characterized carbonato or dichloro compounds, where N 4 = TPA {tris(2-pyridylmethyl)amine}, 1; pmap {bis[2-(2-pyridylethyl)]-(2-pyridylmethyl)amine}, 2; 2,2,2-tet {triethylenetetraamine}, 3; 3,2,3-tet {4,7-diaza-1,10-decanediamine}, 4; tren {tris(2-aminoethyl)amine}, 5; and abap {N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine}, 6. The carbonato complex [Co(pmap)(CO 3)]ClO 4 was structurally characterized by X-ray crystal analysis. The interactions of the complexes 1– 6 with DNA have been investigated (pH 7.0, I = 0.1 M, 37 °C). The complexes 4– 6 did not show any detectable hydrolytic cleavage for DNA, whereas significant cleavages were obtained with the rest of the studied complexes ( 1– 3). Under pseudo-Michaelis–Menten kinetic conditions, the reactivity of the complexes in promoting the hydrolytic cleavage of DNA decreases in the order 1 > 3 ≫ 2 (rates were compared at the saturation levels, i.e. V max ′ ) and the kinetic parameters k cat ′ and K M were determined: k cat ′ = 3.49 × 10 −4 s −1 and K M = 159 μM for 1 and k cat ″ = 5.08 × 10 −5 s −1 and K M = 296 μM for 3. The calculated values of k cat ″ correspond to an enhancement of 3.5 × 10 7 and 5.1 × 10 6 for 1 and 3, respectively, over the uncatalyzed DNA. The DNA cleavage with these two complexes was also monitored under ‘true’ Michaelis–Menten kinetic conditions using constant catalyst concentration (Co(III)) and varying substrate concentrations (DNA) but no kinetic fits were observed between k obs and [DNA] and hence the parameters k cat and K M were not calculated in this case. The reactivity of the complexes is discussed based on the structural skeletons of the tetraamine blocking ligands.

Destruction of the propylenediamine ring upon the chlorination of the platinum(IV) tetramine complex [PtpnPy2Cl2]Cl2

The chlorination of an aqueous solution of [PtpnPy2Cl2]Cl2 affords the platinum(IV) dichloroamine complex [PtPy2(NCl2)2Cl2](I), as the major reaction product formed due to the complete destruction of the five-membered chelate ring. Complex I is obtained in the pure state from acetonitrile. In addition, the [PtPy(NH2-CH(CH3)-CH(CH3)-NH2)Cl3]Cl · 1/2 H2O complex (II) is isolated from the mother liquor upon chlorination. Complex I reacts rapidly with concentrated HCl to form the tetramine complex [PtPy2(NH3)2Cl2](CF3SO3)2 · 1/2 H2O(III). The X-ray diffraction study is carried out for complexes I, II, and III. Complex I crystallizes in the monoclinic crystal system: space group C2/c, a = 7.4529(4), b = 15.2143(9), c = 14.9965(8) A, β = 99.866(1)°, V = 1675.3(2) A3, Z = 4; Rhkl = 0.040. The crystals of complex II are triclinic: space group P\( \bar 1 \) , a = 8.163(2), b = 8.656(2), c = 10.638(2) A, α = 78.30(3)°, β = 83.95(3)°, γ = 84.68(3)°, V = 730.0(3) A3, Z = 2; Rhkl = 0.026. The crystals of complex III are monoclinic: space group C2/c, a = 11.946(2), b = 19.624(4), c = 10.034(2) A, β = 95.96(3)°, V = 2339.5(8) A3, Z = 4; Rhkl = 0.043. The IR spectra of all the compounds synthesized are studied.

Simultaneous determination of Pt and Rh by catalytic adsorptive stripping voltammetry, using hexamethylene tetramine (HMTA) as complexing agent

Characteristics of the adsorption/electro-reduction of Pt/Rh hexamethylene tetramine (HMTA) complex on static mercury drop electrode surface were studied. Cyclic voltammetry was carried out to get the insight about the mechanistic behaviour of the catalytic current obtained in the voltammetric scan of Pt/Rh HMTA complex in acidic solution. Adsorptive stripping voltammetry using HMTA as the complexing agent was found to be highly sensitive method for the determination of Pt/Rh. Voltammetric measurements were carried out using hanging mercury drop electrode (HMDE) as the working electrode, a glassy carbon rod as the counter and an Ag/AgCl/KCl saturated as the reference electrode. Various electrochemical parameters like deposition potential, deposition time, concentration of the ligand, supporting electrolyte etc. were optimized. The detection limit of Pt and Rh was found to be 4.38 pML −1 and 2.80 pML −1, respectively for the deposition time of 30 s. Simultaneous determination of Pt(II) and Rh(III) in water samples was possible. The method was found to be free from the commonly occurring interfering ions such as Cu(II), Cd(II), Zn(II), Pb(II), Cr(III), Cr(VI), Fe(III), Fe(II), Ni(II) and Co(II). Spike recovery tests for both Pt and Rh in tap water and sea water samples were also carried out. The method has been verified by analyzing certified reference material (WMG-1).

Conformational Changes of DNA by Photoirradiation of DNA-Bis(ZnII-Cyclen)-Azobenzene Complex

Bis(ZnII-cyclen)-azobenzene derivative, which has two ZnII-macrocyclic tetraamine complexes connected through azobenzene spacer, has been synthesized as a cross-linking agent for double stranded DNA in aqueous solution. The ZnII-cyclen derivative selectively binds to A-T base pairs producing complexes between the ZnII-cyclen moiety and the imide-deprotonated thymine with breaking A-T base pairs. The azobenzene spacer undergoes cis/trans photoisomerization in the complex between the ZnII-cyclen derivative and the DNA duplex. The conformation of the DNA remarkably changed by photoisomerization of the azobenzene linker, when the ZnII-cyclen derivative binds to the DNA duplex with an interstrand cross-linking manner.

Compounds of nickel(II) with 5 SR,7 RS,12 SR,14 SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rmL 2: The structures of [Ni(rmL 2)](ClO 4) 2 · 0.5H 2O and cis-[Ni(rmL 2)(acac)]ClO 4

The imine functions of [Ni(mL 1)](ClO 4) 2 (mL 1 = meso-7 RS,14 SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) are reduced by using NaBH 4 in acetonitrile/methanol to form the meso–meso and rac–meso isomeric cyclic tetramine complex cations [Ni(mmL 2)] 2+ and [Ni(rmL 2)] 2+ (mml 2 = 5 RS,7 RS,12 SR,14 SR- and rmL 2 = 5 SR,7 RS,12 SR,14 SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) in ca. 8:1 proportions. [Ni(rmL 2)] 2+ is also prepared from rmL 2, formed in <1% yield by the reduction of mL 1 by NaBH 4 in ethanol. Square planar singlet ground state ( S = 1) salts [Ni(rmL 2)](ClO 4) 2 and [Ni(rmL 2)][ZnCl 4] and triplet ground state ( S = 3) trans-di-ligand octahedral compounds trans-[Ni(rmL 2)X 2] ( X - = Cl - , Br - , NCS - , N 3 - , NO 3 - , NO 2 - and HCO 3 - ) ,μ-Y- trans-[Ni(rmL 2)Y] ( Y 2 - = C 2 O 4 2 - and [ Ni ( CN ) 4 ] 2 - ) and folded macrocycle compounds cis-[Ni(rmL 2)(acac)]CIO 4 (acac − = pentane-2,4-dionato), cis-[{Ni(rmL 2)} 2(C 2O 4)](ClO 4) 2, cis-[Ni(rmL 2)(H 2O) 2](ClO 4) 2 and cis-[Ni(rmL 2)X 2], X − = Cl −, Br −, are described. The S = 1 salt 1 SR,4 SR,5 SR,7 RS,8 RS,11 RS,12 SR,14 SR-[Ni(rmL 2)](ClO 4) 2 · 0.5H 2O has a disordered structure with Ni(II) in square planar coordination by the nitrogen atoms of the macrocycle, in N-configuration III, with Ni–N mean = 1.96(2) Å. The six-membered chelate rings both have chair conformations, with the phenyl substituents equatorially oriented and with the methyl substituents disordered over axial and equatorial orientations. The S = 3 compound cis-1 SR,4 SR,5 SR,7 RS,8 SR,11 SR,12 SR,14 SR-[Ni(rmL 2)(acac)]ClO 4 has N-configuration V. The macrocycle is folded along N 1–Ni–N 8, adjacent to the phenyl substituents {N1–Ni–N8 = 176.45(6), N4–Ni–N11 = 98.16(6)°}, with mean Ni–N = 2.09(2) Å and mean Ni–O = 2.121(5) Å. Both six-membered chelate rings have chair conformations with the methyl substituents equatorially oriented, while one has the phenyl substituent equatorially and the other has it axially oriented. The structures of the isomeric [M(rmL 2)(acac)]ClO 4, [M(rrL 2)(acac)]CIO 4 and [M(mmL 2)(acac)]ClO 4 compounds are compared.

Two Spectrophotometric Assays for Dopamine Derivatives in Pharmaceutical Products and in Biological Samples of Schizophrenic Patients Using Copper Tetramine Complex and Triiodide Reagent

Two simple, rapid, and sensitive spectrophotometric methods are proposed for the determination of levodopa (LD). The first method is based on coupling of 4-aminoantipyrine (4-AAP) with one of the dopamine derivatives (LD, CD) to give a new ligand that reacts with copper tetramine complex to give intensely colored chelates. The colored products are quantified spectrophotometrically at 525 and 520 nm for LD and CD, respectively. The optimization of the experimental conditions is described. The method has been used for the determination of 19.7–69.0 and 18.1–54.3 μg mL−1 of LD and CD, respectively. The accuracy of the method is achieved by the values of recovery (100 ± 0.2%) and the precision is supported by the low standard deviation (SD = 0.17–0.59) and relative standard deviation (CV = 0.4%–1.54%) values. The second method is based on the formation of ion-pair iodinated inner sphere or outer sphere colored complexes between the LD and triiodide ions at pH 5 and room temperature (23 ± 3°C). This method has been used for the determination of LD within the concentration range 39.44–78.88 μg mL−1 with SD = 0.22–0.24 and recovery percent = 100 ± 0.3%. The sensitivity of the two methods is indicated by Sandell's sensitivity of 0.014–0.019 g cm−2. The results of the two methods are compared with those of the official method. The interference of common drug additives, degradation products, and excipients was also studied. The proposed methods were applied successfully to the determination of the LD-CD synthetic mixture and Levocare drug. The determination of LD in urine of some schizophrenic patients was applied with good precision and accuracy. The reliability of the methods was established by parallel determinations against the official British pharmacopoeia method.

Further insights on the high–low spin interconversion in nickel(ii) tetramine complexes. Solvent and temperature effects

The spin interconversion equilibrium involving the [Ni(II)(cyclam)]2+ complex has been investigated in a variety of polar solvents, at varying temperatures. The greater the donor tendencies of the solvent, the higher the endothermicity of the high-to-low-spin conversion. In particular, a positive linear relationship exists between DeltaHdegrees and Gutmann's Donor Number (DN). In the same way, higher donor tendencies of the solvent favour the occurrence of the Ni(II)-to-Ni(III) oxidation process and negative linear relationship has been found between the E1/2(Ni(III)/Ni(II)) and DN. General behaviour is related to the intensity of the metal-solvent axial bonds in the octahedrally elongated cyclam complexes (of both Ni(II) and Ni(III)).

Allylation of aldehydes catalyzed by chiral N,N'-bis(N-methyl-2-methylene-4,5-bisphenyl-imidazole)-1,2-cyclohexane diamine rhodium(III) complexes

Chiral bis-imidazole rhodium(III) complexes catalyze the allylation of aldehydes by allyltributyltin. The pre-catalyst was readily prepared from chiral N,N'-bis(N-methyl-2-methylene-4,5-bisphenylimidazole)-1,2-cyclohexanediamine, potassium carbonate, and rhodium(III) chloride trihydrate. The rhodium(III) complex produced showed no activity in an allyl transfer process in the presence of the allyltin reagent. However, when silver tetrafluoroborate was added to the pre-catalyst and stirred for 1 h, the resulting system became an efficient catalyst for the allyl transfer process. The reductions produced homo-allyl alcohols with good to excellent yield, although generally with poor facial selectivity (8–10% ee, aryl aldehydes, 4 examples; 99% ee, aliphatic aldehyde, 1 example).Key words: allylation, aldehydes, enantioselectivity, rhodium(III) tetramine complex.

Supramolecular Chemistry of Multinuclear Zinc(II) Complexes in Aqueous Solution

AbstractFor Abstract see ChemInform Abstract in Full Text.

SYNTHESIS, CHARACTERIZATION, AND STUDY OF MESOGENIC PROPERTIES OF Cu(II) AND Ni(II) COMPLEXES OF Bis- and TETRADENTATE SCHIFF'S BASES DERIVED FROM 2-HYDROXY-4-(n-ALKOXY) BENZALDEHYDES

Bis-(2-hydroxy-4-(n-alkoxy) benzaldimino) copper (II) and bis-(2-hydroxy-4 (n-alkoxy) benzaldimino) nickel (II) complexes have been synthesized by the reaction of 2-hydroxy-4-(n-alkoxy) benzaldehyde with tetraamine complexes of Cu(II) and Ni(II) under template condition. Cu(II) and Ni(II) complexes of 1,2-bis-(2-hydroxy-4-(n-alkoxy) benzaldimino) ethane and 1,3-bis-(2-hydroxy-4-(n-alkoxy) benzaldimino) propane have been synthesized from the imine complexes by amine exchange with 1,2-diaminoethane and 1,3-diaminopropane, respectively. The complexes have been characterized by spectral and magnetic studies. Some of these complexes exhibit mesogenic properties. This has been correlated to the structures of the complexes.

Sol-Gel Synthesis of Complex Titanates in Micro-Emulsions

Amorphous precursor nanopowders of zirconolite (CaZrTi 2 O 7 ) were prepared using a water-in-oil micro-emulsion synthesis, with Ti(O i C 3 H 7 ) 4 , Zr(O n C 3 H 7 ) 4 and either Ca(OC 2 H 5 ) 2 or an aqueous Ca(NO 3 ) 2 solution as precursors. The stoichiometry and structural evolution of the nanoparticles were investigated using a range of techniques, including ICP-MS, TEM, gas adsorption and vibrational spectroscopy. The use of Ca(OC 2 H 5 ) 2 led to slightly sub-stoichiometric nanopowders (Ca x ZrTi 2 O 6+x , x = 0.8), following washing. Lower values of x were obtained in the washed nanopowders when using Ca(NO 3 ) 2 , with x = 0.004, 0.022 or 0.52 at pH 2, 7 or 13, respectively. In the latter system, a comparison between the washed and unwashed nanopowders revealed that 25% of the calcium was lost during washing. The Ca(NO 3 ) 2 was found to form unstable tetraamine complexes within the reverse micelles at high pH, which transformed into Ca(OH) 2 on ageing. The Ca(OH) 2 can then interact with the hydrolysed titanium/zirconium alkoxides, and thus be integrated chemically into the final nanoparticle structure.

Macrocyclic Melamine‐Based Ligand Complexes as Building Blocks for the Metal‐Directed Synthesis of Heterometallic Di‐ and Trinuclear Compounds

AbstractHeterodi‐ and heterotrimetallic NiII/CuII, Ni2II/CuII and NiII/Cu2II complexes of bis‐ and tris‐macrocyclic ligands, linked by a 1,3,5‐triazine spacer group, are obtained as products of copper(II)‐ or nickel(II)‐assisted condensations of the open‐chain tetraamine complexes [M2(2,3,2‐tet)]2+ [2,3,2‐tet= bis‐N,N′‐(2‐aminoethyl)propane‐1,3‐diamine, M2 = NiII or CuII] with formaldehyde and the monomacrocyclic ligand complexes [M1(L1)]2+, where L1 is a cyclam‐type macrocycle with a pendent melamine group (M1 = CuII or NiII). The spectroscopic (UV/Vis and EPR) and electrochemical properties of the oligonuclear heterometallic compounds in comparison with those of the homometallic analogues indicate small, but significant, intramolecular metal‐metal interactions. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)