Metal Complexes with Macrocyclic Ligands. Part XLI. Nickel(II) and copper(II) complexes with mono-N-functionalized dithiadiazamacrocycles

Three N₂S₂ macrocycles ( 3, 10, 12 ) carrying an amino group as a pendant arm have been synthesized and their complexation properties towards Ni²⁺ and Cu²⁺ studied. The crystal structures of the Cu²⁺ complexes with 10-methyl-1,4-dithia-7,10-diazacyclododecane-7-ethanamine ( 3 ) and 11-methyl-1,4-dithia-8,11-diazacyclotetradecane-8-ethanamine ( 10 ) show that, in both cases, the Cu²⁺ is pentacoordinated by the four donor atoms of the macrocycle and the amino group of the side chain. In aqueous solution, however, two forms of the complexes with stoichiometries [MLH] and [ML] (M = Cu²⁺ or Ni²⁺) have been observed. In [MLH], the amino group is protonated and does not bind to the metal ion, whereas in [ML] the amino group is bound, and a pentacoordinated geometry results. The pK_a values for the equilibrium [ML] + H⁺?[MLH]⁺ decrease in the order 12 > 10 > 3 , indicating that the 2-aminoethyl side chain binds better to the Cu²⁺ than the 3-aminopropyl side chain. Cyclic voltammetry for the Cu²⁺/Cu⁺ pair shows that the 2-aminoethyl pendant arm stabilizes the Cu²⁺ oxidation state, when the metal ion is in the 14-membered ring ( 10 ), whereas it stabilizes Cu⁺ for the 12-membered macrocycle ( 3 ).     

Metal Complexes with Macrocyclic Ligands. Part XLIII. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio- and methoxy-substituted pendant chains

The 14-membered tetraazamacrocyclic Ni²⁺ and Cu²⁺ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5 . (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni²⁺ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H₂O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni( 5 )](ClO₄)₂, [Cu( 5 )](ClO₄)₂, and [Cu( 7 )](ClO₄)₂ show a coordination number of 5, whereas that of [Ni( 6 )](ClO₄)₂ with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni²⁺ is reversibly reduced to Ni⁺ between ?0.64 and ?0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni( 6 )](ClO₄)₂ is observed under similar conditions.     

Metal Complexes with Macrocyclic Ligands. Part XXXVIII. Steric effects in the copper(II) and nickel(II) complexes with tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes

A series of tetra-N-alkylated 1,4,8,11-tetraazacyclotetradecanes have been synthesized and their complexation potential towards Ni²⁺ and Cu²⁺ studied. In the case of sterically demanding alkyl substituents, such as i-Pr, PhCH₂, or 2-MeC₆H₄CH₂, no metal complexes are formed, whereas for substituents such as Me, Et, and Pr, the metal ion is incorporated into the macrocycle. The spectroscopic properties of the Ni²⁺ and Cu²⁺ complexes in aqueous solution indicate that, depending on the sterical hindrance of the N-substituents, the complexes are either square planar or pentacoordinated. All these Ni²⁺ and Cu²⁺ complexes react with N to give ternary species, the stability of which have been determined by spectrophotometric titrations. The tendency to bind N decreases with increasing steric hindrance of the alkyl substituents. The X-ray studies of the Ni²⁺ complex with the macrocycle 11 , substituted by two Me and two Pr groups, and that of the Cu²⁺ complex with the tetraethyl derivative 8 show that in the solid state, the metal ions exhibit square planar coordination with a small distortion towards tetrahedral geometry.     

Metal Complexes with Macrocyclic Ligands. PartXLV Axial coordination tendency in reinforced tetraazamacrocyclic complexes

The Cu²⁺ and Ni²⁺ complexes of three reinforced tetraazamacrocycles, containing a piperazine subunit and one or two alkyl substituents at the other two N-atoms have been prepared and their structural properties studied. In solution, the Ni²⁺ complexes are square-planar and show no tendency to axially coordinate a solvent molecule or an N ion. In contrast, the Cu²⁺ complexes change their geometry depending upon the donor properties of the solvent, being square-planar in MeNO₂ and pentacoordinate in DMF. They also easily react in aqueous solution with N to give ternary species with pentacoordinate geometry, the stabilities of which have been determined. In the solid state, the X-ray crystal structures of three Cu²⁺ complexes also show both geometrical arrangements, two having a square-planar, the other one a distorted square pyramidal geometry. The difference behavior of Ni²⁺ and Cu²⁺ stems from the fact that the structural change from square-planar to square-pyramidal can easily be accomplished for Cu²⁺, whereas, for Ni²⁺, it is accompanied by an electronic rearrangement from the low-spin to the high-spin configuration. The relatively rigid ligands cannot Adapt to the somewhat larger high-spin Ni²⁺ion.     

Metal Complexes of Ditopic and Polytopic Macrocyclic Ligands

Soft Supramolecular Materials (SSM) are multicomponent materials formed bythe bulk supramolecular assembly/aggregation of building units into a regularstructure, with stronger bonding within building units and weaker bondingbetween them. The nature of the building units may vary from simple moleculesto nanoparticles, and the forces linking the units together may vary from coordinativeto van der Waals. Recently SSM have attracted a great deal of attention due to theirwide variability, easy conversion from one structure to another, and active responseto external stimuli. It seems evident that the progress in the chemistry of SSMpredestines the appearance of a new generation of functional and ``smart'' materials.     

Metal Complexes with Macrocyclic Ligands. Part XLVI. Synthesis and structures of dinuclear metal complexes of bis-macrocycles having a pyrazole bridging unit

Three bis-macrocyclic ligands consisting of two N₃-, N₂S-, or NS₂-cyclononane rings, i.e., of two octahydro-1H-1,4,7-triazonine, octahydro-1,4,7-thiadiazonine, or hexahydro-5H-1,4-7-dithiazonine rings, connected by a 1H-pyrazolediyl unit were prepared. They form dinuclear Cu^II and Ni^II complexes which are able to bind one additional exogenous bridging molecule such as Cl^?, Br^?, N, SO, and 1H-pyrazol-1-ide. The structures determined by X-ray diffraction show that each Cu²⁺ is coordinated by the three donor atoms of the macrocyclic ring, by a pyrazolidodiyl N-atom, by an atom of the exogenous bridging ligand, and sometimes by a solvent molecule. In the majority of the Cu²⁺ cases, the metal ion exhibits square-pyramidal or trigonal-bipyramidal coordination geometry, except in the sulfato-bridged complex, in which one Cu²⁺ is hexacoordinated with the participation of a water molecule. The X-ray structure of the azide-bridged dinuclear Ni²⁺ complex was also solved and shows that both Ni²⁺ centres have octahedral coordination geometries. In all complexes, the 1H-pyrazolediyl group connecting the macrocycles is deprotonated and bridges the two metal centres, which, depending on the exogenous ligand, have distances between 3.6 and 4.5 Å. In the dinuclear Cu²⁺ complexes, antiferromagnetic coupling is present. The azido-bridged complex shows a very strong interaction with ?2J ≥ 1040 cm^?1; in contrast, the H-pyrazol-1-ide and chloride bridged species have ?2J values of 300 and 272cm^?1, respectively. Cyclic voltammetry of the Cu²⁺ complexes in MeCN reveals a strong dependence of the potentials Cu^II/Cu-^II → Cu^II/Cu^I → Cu^I/Cu^I on the nature of the donor atoms of the macrocycle as well as on the type of bridging molecule. The more S-donors are present in the macrocycle, the higher is the potential, indicating a stabilization of the Cu¹ oxidation state.     

Metal Complexes with Macrocyclic Ligands. Part XXVI. Synthesis and spectral properties of Cu2+ complexes with mono-N-functionalized 1,4,8-trimethyl-1,4,8,11-tetraazacyclotetradecanes

A series of mono-N-functionalized 1,4,8-trimethyl-1,4,8,11-tetraazacyclotetradecanes 3 – 14 were synthesized by alkylating the secondary N-atom of the macrocycle 1 . The spectral properties of the Cu²⁺ complexes, studied under different pH conditions, are discussed in relation to the possibility of coordination of the donor group of the side chain to the axial position of the metal ion and to the effect of the length of the side chain.     

Metal Complexes of Macrocyclic Ligands. XII. A Complexone-like Tetraazamacrocycle

The complexone-like tetraazamacrocycle 1 (LH₄) forms a series of metal complexes with Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (M²⁺) of the type MLH₂, ML^2? and M₂L, which have been isolated and characterized by VIS., IR. and NMR. spectroscopy. Based on these results tentative structures for the different species are proposed.     

Metal Complexes with Macrocyclic Ligands. Part XXVIII.. Structures and stabilities of the Cu2+ complexes with 1,4,7-triazacyclononane-1-acetic acid

The potentiometric study of the complexation of 1,4,7-triazacyclononane-l-acetic acid ( 1 ) with Cu²⁺ (I = 0.5 (KNO₃), T = 25°) indicates the presence of the species [Cu( 1 )], [Cu( 1 )OH], [Cu( 1 )₂], and [(Cu( 1 ))₂OH], the stability constants of which are determined. The two complexes [Cu( 1 )]ClO₄ and [(Cu( 1 )₂)OH]ClO₄ were also characterized by X-ray structure analysis. In both cases, the Cu²⁺ ion is in a distorted square-pyramidal arrangement, penta-coordinated by the three N-atoms of the macrocycle, an O-atom of the carboxylate, and an additional O-atom either from a second carboxylate or from an OH^?, acting as a bridge between two metal centres.     

Metal Complexes with Macrocyclic Ligands. Part XXXI. Protonation studies and complexation properties of tetraazamacrocyclic methylenephosphonates with earth-alkali ions

The three ligands 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylenephosphonic acid) ( 1 ), 1,4,7,11-tetraazacyclotridecane-1,4,7,11-tetrakis(methylenephosphonic acid) ( 2 ), and 1,4,8,11-tetraazacyclotetradecane-1,4,8,1 1-tetrakis(methylenephosphonic acid) ( 3 ) have been synthesized by condensation of the corresponding macrocycles with formaldehyde and phosphorous acid. The protonation and stability constants with the earth-alkali ions have been determined at 25° and I = 0.1 M (Me₄)N(NO₃) by potentiometric titrations. Because of the high values of the first two protonation constants, ¹H-NMR measurements were necessary to determine them. Titrations in different supporting electrolytes (NaNO₃, KNO₃, RbNO₃, CsNO₃, and Me₄N(NO₃)) show that their choice is of paramount importance, as the above ligands can form complexes with alkali-metal ions. The potentiometric results for the earth-alkali ions show that beside mononuclear complexes of different degrees of protonation ([MLH_n], n = 0–4), also binuclear species are formed ([M₂LH_m], m = 0–2). It is interesting that 1 with the smallest macrocyclic ring has the greatest tendency to form binuclear complexes, which are so stable that they partially prevent the formation of the corresponding mononuclear species. For [ML], [MLH], [M₂L], and [M₂LH], the stability sequence is Mg²⁺ < Ca²⁺ > Sr²⁺ > Ba²⁺, whereas for [MLH₂], [MLH₃], and [MLH₄], the stability steadily decreases from Mg²⁺ to Ba²⁺.     

Metal Complexes with Macrocyclic Ligands. Part XXXIX. Mono- and binuclear copper(II) complexes of a bridging bis[1, 4, 7-triazacyclononane]

The new bis-macrocycle 1, 1′-[(1H-pyrazol-3], 5-diyl)bis(methylene)bis[1, 4, 7-triazacyclononane] ( 1 ) was synthesized and its complexation with Cu²⁺ studied. Potentiometric and spectrophotometric titrations indicate that, in addition to the mononuclear species [Cu(LH₂)]⁴⁺, [Cu(LH)]³⁺, [CuL]²⁺, and [Cu(LH_?1)]⁺, binuclear complexes such as [Cu₂L]⁴⁺, [Cu₂(LH_?1)]³⁺, and [Cu₂(LH_-2)]²⁺ are also formed in solution. The stability constants and spectral properties of these are reported. The binuclear species [Cu₂(LH_?1)]³⁺ specifically reacts with an azide ion to give a ternary complex [Cu₂(LH_?1)(N₃)]²⁺, the stability and structure of which were determined spectrophotometrically and by X-ray diffraction, respectively. The two Cu²⁺ ions are in a square-pyramidal coordination geometry. The axial ligand is one of the N-atoms of the 1, 4, 7-triazacyclononane ring, whereas at the base of the square pyramid, one finds the other two N-atoms of the macrocycle, one N-atom of the pyrazolide and one of the azide, both of which are bridging the two metal centres. In [Cu₂(LH_?1)(N₃)]²⁺, a strong antiferromagnetic coupling is present, thus resulting in a species with a low magnetic moment of 1.36 B.M. at room temperature.     

Metal Complexes with Macrocyclic Ligands. Part XLII. Tetraazamacrocyclic nickel(II) complexes with a methylthio or a methoxy pendant chain as model for cofactor F430

The 14-membered macrocyclic Ni²⁺ complexes of 1 and 2 , with a methylthio pendant chain, and those of 3 and 4 , with a methoxy pendant chain, have been synthesized and their chemistry has been studied. Solution spectra in H₂O, MeCN, and DMF indicate no participation of the side-chain donor group in metal coordination. This is also the case in the solid state as shown by the X-ray structures of the Ni²⁺ complexes with 1 and 2 , in which a tetrahedrally distorted square-planar geometry around the Ni²⁺ results by the coordination of the four N-atoms of the macrocycle. Cyclic voltammetry of these complexes in MeCN reveals that Ni²⁺ is reversibly reduced to Ni⁺ between ?0.7 and ?0.8 V vs. SCE. For the complexes with 1 and 2 , the thioether bond is cleaved at more negative potentials, whereby a thiol group is formed. This thiol group is then oxidized at ca. +0.7 V vs. SCE, when a glassy C electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in the complexes with 3 and 4 is observed under similar conditions. Reduction of the Ni²⁺ complexes of 1 and 2 with Na-amalgam in DMF produces small amounts of methane only in the case of 1 , indicating the importance of the proximity between the Ni^I centre and the MeS group.     

Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L¹ , L² and L³ , has been investigated.The Schiff base macrocycle L¹ and its corresponding reduced ligand L² arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L³ is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L¹ and L² have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L¹ give the expected [1:1, Ln:L¹ ] stoichiometry; however, complexes obtained with L² show a [2:1, Ln:L² ] stoichiometry. Finally, complexation reactions with L³ have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.     

Metal Complexes with Macrocyclic Ligands. Part XXI. A nonlinear relationship between the stability of Cu2+ complexes and their complexation rate with 1,4,8,11-tetraazacyclotetradecane

The kinetics of the reaction (1) between 1,4,8,11-tetraazacyclotetradecane (Cy) and a series of Cu(II) complexes CuL (L) = glycolate, malonate, succinate, picolinate, glycinate, iminodiacetate, nitrilotriacetate, N-(2-hydroxyethyl)ethylenediaminetriacetate, ethyienediamine, 1,3-diaminopropane, diethylenetriamine and N,N-bis(3-aminopropylamine) were studied spectrophotometrically at 25° and I = 0.5 (KNO₃). From the analysis of the log k_obs/log [L] profiles obtained at different pH values the resolved bimolecular rate constants k (Table 3) were obtained by a nonlinear curve-fitting procedure. For nearly all systems studied, the rate constant k, describing the reaction between the 1:1 complex CuL and the monoprotonated form of the macrocycle CyH, was obtained. The nonlinear relationship between log k and log K_CuL and its nature is discussed. It is shown that the inverse relationship between reactivity and stability described by others is only a special case of the more general Eqn. 3 described here.     

Syntheses,Structural, and Spectroscopic Properties of Copper(II) Complexes of Constrained Macrocyclic Ligands

The complexes [Cu(L¹)(H₂O)₂](BF₄)₂ · 2H₂O ( 1 ) [L¹ = 5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] and 0.5[Cu(L²)(NO₃)₂][Cu(L²)](NO₃)₂ ( 2 ) [L² = dibenzyl‐5, 16‐dimethyl‐2, 6, 13, 17‐tetraazatricyclo(14, 4, 0^1.18,0^7.12)docosane] were synthesized and characterized by single crystal X‐ray analyses. In these constrained macrocycles, the central copper(II) atoms are in a tetragonally distorted octahedral environment with four nitrogen atoms of the macrocyclic ligands in equatorial positions and oxygen atoms from either water molecules or nitrato groups in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans‐III conformation. The Cu–N distances [1.999(7)–2.095(7) Å] are typical for such complexes, but the axial ligands are weakly coordinating Cu–OH₂ bonds [2.693(3) Å] and Cu–ONO₂ bonds [2.873(7) Å] due to the combination of the pseudo Jahn–Teller effect and strong in‐plane ligand field. The crystals are stabilized by a three‐dimensional network by hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms, oxygen atoms of water molecules, fluorine atoms of BF₄^–, and oxygen atoms of NO₃^–. The electronic absorption and IR spectroscopic properties are also discussed.     

Reactions of Chelate Complexes with Macrocyclic Ligands. Tetra-tert-butylphthalocyanine

Complexation reactions of tetra-tert-butylphthalocyanine (I) with Cu(II) acetate, acetylacetonate, 8-hydroxyquinolate, glycinate, valinate or dithizonate, as well as with Zn(II), Co(II), and Ni(II) 8-hydroxy-quinolates, valinates, and dithizonates were studied. Unlike porphyrins themselves and porphyrins with planar distortions, compound I was found to form metal phthalocyanines with all indicated chelate salts in common solvents. It was established that compound I exhibits more equalized dependences of the coordination rate on the nature of the salt anion and cation as compared to the majority of the other porphyrins.     

Transition Metal Complexes with Pyrazole-based Ligands. Part 8. Characterization and thermal decomposition of zinc(II) complexes with di- and trisubstituted pyrazoles

We report the synthesis and the characterization (elemental analysis, FT-IR spectroscopy, thermal methods and molar conductivity measurements) of the mixed complexes of zinc with acetate and 3-amino-5-methylpyrazole, HL ¹, [Zn(OAc)₂(HL¹)₂], or 3-amino-5-phenylpyrazole, HL ² [Zn(OAc)₂(HL²)₂], or 4-acetyl-3-amino-5-methylpyrazole, HL ³, [Zn(OAc)(L³)(HL³)]₂, with isothiocyanate and HL ² [Zn(SCN)₂(HL²)₂], or HL ³ [Zn(SCN)₂(HL³)₂], and with nitrate, isothiocyanate and 3,5-dimethyl-1-carboxamidinepyrazole, HL ⁴ [Zn(NO₃)(NCS)(HL⁴)₂]. The thermal decomposition of the complexes is generally continuous resulting zinc oxide as end product,except [Zn(OAc)(L³)(HL³)]₂ in which case a well-defined intermediate was observed between 570–620 K. On the basis of the IR spectra and elemental analysis data of the intermediate a decomposition scheme is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

含吡啶环系西佛碱大环配合物和氮杂大环自由配体的合成

2,6-二羟甲基吡啶(1)经活性MnO_2氧化得到2,6-二甲酰基吡啶(2)。邻硝基苯酚与N-取代的二(氯乙基)胺在DMF溶液中反应,得到N-取代的1,5-二(邻硝基苯氧基)-3-氮杂戊烷(3a～3c),再经水合肼/Raney Ni还原,获得N-取代的1,5-二(邻氨基苯氧基)-3-氮杂戊烷(4a～4c)。利用Ba~(2 )作为模板离子,(2)分别与(4a～4c)反应,合成了一类新的含吡啶环系西佛碱大环配合物Ⅰ～Ⅲ,配合物Ⅰ、Ⅲ经与NaBH_4的乙醇溶液还原解络,得到氮杂大环自由配体Ⅳ和Ⅴ。所有西佛碱大环配合物和氮杂大环自由配体均经元素分析、IR、~1H NMR、MS等证实了它们的结构和组成。     

Silver(I) Complexes with Nitrogen-Containing Noncyclic, Macrocyclic, and Macrobicyclic Ligands in Propylene Carbonate

Stability constants and thermodynamic data for complex formation of silver(I) with noncyclic, macrocyclic, and macrobicyclic ligands have been measured in propylene carbonate using potentiometric and calorimetric methods. All ligands containing two nitrogen donor atoms form extremely stable complexes. Only if substituents reduce the basicity of the nitrogen donor atoms, the stability of the complexes decreases drastically. However, the cryptand (221) forms the most stable complex of all ligands examined. In this case, the dimensions of the ligand cavity and of the cation are nearly identical.