Polyazamacrocycles VI. Homo-trimetallic copper(II) and nickel(II) complexes with a new tri-cavity macrocycle

Summary A new tri-cavity decaaza macrocycle (TCM) has been synthesised by the condensation of tetra(aminopropyl)-cyclam with diethanolamine. The new macrocyclic ligand forms tri-nuclear complexes, [Cu₃(TCM)(H₂O)₂]-(ClO₄)₆ and [Ni₃(TCM)(H₂O)₂](ClO₄)₆.     

Synthesis and characterization of a novel unsymmetrical metal-free phthalocyanine with donor-acceptor substituents

A novel unsymmetrical metal-free phthalocyanine with a nitro group as an acceptor substituent and three t-butyl groups as donor groups, namely nitro-tri-t-butylphthalocyanine (NtBuPc) was synthesized for the first time by mixed condensation of two corresponding diiminoisoindolines. The NtBuPc can be separated by common column chromatography on silica gel using chloroform-hexane as the elution solvent. The structure was confirmed by elemental analysis, nmr, uv-vis, ir and mass spectroscopy. No contamination of either symmetrical or other related phthalocyanines was observed.     

Polymeric copper(II) and nickel(II) complexes of a tetraoxime containing a binucleating macrocycle ligand

Polymeric copper(II) and nickel(II) complexes of a binucleating tetraoxime macrocycle, 6,6-methylene-bis[1,12-di(hydroximino)- 2,3;9,10-dibenzo-1,11-diaza-4,8-dithiacyclotridecane] (H4L), have been prepared and characterised by elemental analysis, magnetic moments, i.r., uv/vis., and e.p.r. spectral studies. I.r. spectra show that the ligand acts in a tetradentate manner and coordinates via N, S and O donor atoms. The geometry of the resulting metal chelates is discussed with the help of magnetic and spectroscopic measurements. The elemental analyses, stoichiometry and the spectroscopic data of the complexes indicate that the copper(II) and nickel(II) ions are coordinated by the coordination environment of the ligand. The spectral data suggest a distorted tetragonal geometry for polymeric copper(II), and nickel(II) ions in the complexes. The stoichiometry of the metal-to- H4L ratio of complexes (2) and (3), prepared from CuCl2 and NiCl2 respectively, was 3:1, suggesting the formation of polymeric species.     

Synthesis and properties of nickel(II) and copper(II) complexes of a di-N-acetamide tetraaza macrocycle

The syntheses of the hexadentate ligand 2,13-bis(acetamido)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane (L²) and its complexes with Ni(II) and Cu(II) are described. Crystal structures of H₂L²·2HClO₄ (1), [Ni(L²)](ClO₄)₂ (2) and [Cu(L²)](ClO₄)₂ (3) are reported. The two pendant acetamide groups of the macrocyclic ligand 1 are trans to each other and the absolute configuration is a trans-IV in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant acetamide groups at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.     

Synthesis and characterization of copper(II) and nickel(II) complexes of a di-N-carboxymethylated tetraaza macrocycle

The reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane (L¹) with bromoacetic acid produced the macrocycle (L²=2,13-bis(2-carboxymethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) in which two carboxymethyl groups are appended. The complexes [NiL²]·4H₂O (2) and [CuL²]·4H₂O (3) have been prepared and characterized. The two pendant carboxymethyl groups of the macrocyclic ligand are trans to each other, and the absolute configuration is a trans-III in the solid state. The crystal structures of 2 and 3 revealed an axially elongated octahedral geometry with four nitrogen atoms of the macrocycle and two oxygen atoms of the pendant arms at the axial positions. The nickel(II) and copper(II) ions are located at an inversion center. Macrocycle L² reacts more rapidly with metal (II) ions than does L¹. Spectra and electrochemical behaviors of the complexes are also discussed.     

The synthesis of metal-free octaazaphthalocyanine derivatives containing bulky phenoxy substituents to prevent self-association

Octaazaphthalocyanines with eight phenoxy groups in the peripheral sites are prepared for the first time using the simple synthetic procedure of heating their pyrazine-2,3-dicarbonitrile precursor in quinoline. This process avoids transetherification, which has hindered previous attempts at preparing metal-free octaazaphthalocyanines. Metal-containing derivatives were also prepared by adding the appropriate metal salt to the reaction mixture. Bulky iso-propyl or phenyl groups at the 2,6-positions of the phenoxy substituents prevent self-association of the octaazaphthalocyanine cores even in the solid state.     

Alkyne haloallylation [with Pd(II)] as a core strategy for macrocycle synthesis: a total synthesis of (-)-haterumalide NA/(-)-oocydin A

The rarely used haloallylation reaction, first described by Kaneda and Teranishi in 1974, employs a Pd(II) catalyst to join an alkyne with an allylic halide to produce a 1-halo-1,4-diene subunit. It is shown here that functionalized and tertiary allylic chlorides perform well as substrates in this reaction under the action of PdCl2(PhCN)2 in THF solution. When the alkyne is added slowly to the reaction mixture, the two reactants can be used in a nearly equimolar ratio. This fact means (i) that reasonably complex pairs of alkyne and allylic halide substrates are tolerated and, therefore, (ii) that an intramolecular version of the reaction is suitable as a core strategy for complex molecule construction. The latter is demonstrated in the macrocyclization of 2b to 17b, which is the central step in the total synthesis of (-)-haterumalide NA/(-)-oocydin A (1) that is reported. The final key to the completion of the synthesis was the choice of the acid-labile PMB ester of 1 as the penultimate intermediate.     

Protonation and coordination properties towards Zn(II), Cd(II) and Hg(II) of a phenanthroline-containing macrocycle with an ethylamino pendant arm

Protonation and Zn(II), Cd(II) and Hg(II) coordination with the ligand 5-aminoethyl-2,5,8-triaza-[9]-10,23-phenanthrolinophane (L2), which contains an aminoethyl pendant attached to a phenanthroline-containing macrocycle, have been investigated by means of potentiometric, 1H NMR and spectrofluorimetric titrations in aqueous solutions. The coordination properties of L2 are compared with those of the ligand 2,5,8-triaza-[9]-10,23-phenanthrolinophane (L1). Ligand protonation occurs on the aliphatic amine groups and does not involve directly the heteroaromatic nitrogens. The fluorescence emission properties of L2 are controlled by the protonation state of the benzylic nitrogens: when not protonated, their lone pairs are available for an electron transfer process to the excited phenanthroline, quenching the emission. As a consequence, the ligand is emissive only in the highly charged [H3L2]3+ and [H4L2]4+ species, where the benzylic nitrogens are protonated. Considering metal complexation, both [ML1]2+ and [ML2]2+ complexes (M = Zn(II) and Cd(II)) are not emissive, since the benzylic nitrogens are weakly involved in metal coordination, and, once again, they are available for quenching the fluorescence emission. Protonation of the L2 complexes to give [MHL2]3+ species, instead, leads to a recovery of the fluorescence emission. Complex protonation, in fact, occurs on the ethylamino group and gives a marked change of the coordination sphere of the metals, with a stronger involvement in metal coordination of the benzylic nitrogens; consequently, their lone pairs are not available for the process of emission quenching.     

Copper(II) template synthesis of a new N2S2-donor macrocycle incorporating a pendent pyridyl substituent

The synthesis of the new potentially pentadentate ligand, 2,2??-(2-methyl-2-(pyridin-2-yl)propane-1,3-diyl)bis(sulfanediyl)diethanamine (L ¹ ), containing two thioether sulfurs, two ?CNH₂ amines and a pyridyl nitrogen heteroatom is described. Reaction of L ¹ with copper(II) chloride and addition of hexafluorophosphate anion has led to isolation of the mixed anion complex Cu₂(L ¹ )₂Cl(PF₆)₃. The synthesis and X-ray structure of cobalt(III) species, [Co(L ¹ )Cl](PF₆)₂, is also reported. In situ reaction of L ¹ with copper(II) as a metal template in the presence of formaldehyde and the carbon acid nitroethane together with triethylamine (as base) led to macrocycle ring closure to yield [Cu(L ² )Cl]PF₆ (where L ²  = 6,13-dimethyl-6-nitro-13-(pyridin-2-yl)-1,11-dithia-4,8-diazacyclotetradecane) whose X-ray structure shows that the copper centre has a distorted square pyramidal coordination geometry being bound by both ?CNH₂ nitrogens and both sulfurs of L ² while the pyridyl nitrogen remains uncoordinated.     

Synthesis of (η-arene)(η-cyclopentadienyl) iron (II) complexes with heteroatom and carbonyl substituents Part II, Amino substituents

A variety of methods have been used in the synthesis of amino-substituted (η⁶-arene)(η⁵-cyclopentadienyl) iron(II) complexes. Conventional thermal ligand exchange of 2-fluoroaniline with ferrocene in the presence of Devarda’s alloy gave an Ullmann coupling product, 2,2′ diaminobiphenyl complex, whereas omitting metal powder gave the 2-fluorobenzene complex. Double S_NAr substitution of the 1,2-dichlorobenzene complex by dimethylamine is reported. Microwave-assisted S_NAr reactions have led to the development of a one-pot synthesis of N-arylaminoacids. Acetylation of amino-complexes is described and the product anilide complexes used in S_NAr displacements to form aminoanilide analogues. Hexamethyldisilazane was found to be an efficient aminating agent in the presence of alcohols or phenols in DMSO, leading to the synthesis of the (η⁶-1,2-diaminobenzene)(η⁵-Cp) iron(II) complex, the first (ArFeCp)⁺ species reported containing two primary amino groups.     

Carboxyester hydrolysis catalyzed by a novel dicopper(II) complex with an alcohol-pendant macrocycle

A novel hexaaza macrocycle bearing two hydroxyethyl pendants (L), 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2(11,14)]triaconta-1,11,13,24,27,29-hexaene, was synthesized as a potential binucleating ligand. The corresponding Cu(II) complex [Cu(2)LCl(2)]Cl(2) small middle dot5.5H(2)O was isolated as a blue crystal, triclinic, space group P with a= 9.4920(19) A, b = 4.783(3) A, c = 16.553(3) A, alpha = 63.87(3) degrees, beta = 86.10(3) degrees, gamma = 83.8(3) degrees, V = 2072.8(7) A(-3), Z = 2, R1 = 0.0658, and wR2 = 0.1839. Both Cu ions adopt the geometry of a distorted trigonal bipyramid in a pentacoordinated environment. A complexation study on the novel title complex has revealed that the alcoholic OH groups of the complex Cu(2)L exhibit an obvious acidity with rather low pK(a) values at 25 degrees C. The Cu(II)-bound alkoxides, which act as reactive nucleophiles toward the hydrolysis of 4-nitrophenyl acetate in 10% (v/v) CH(3)CN at 25 degrees C, with I = 0.10 (NaNO(3)) and pH 9.3, have shown a second-order rate constant, 0.41 +/- 0.02 M(-1) s(-1), a value that is approximately 10 times greater than the corresponding value for the mononuclear Cu(II) complex formed by a relatively simple tripodal ligand (L1). The pH-rate profile gave a sigmoidal curve. The possible catalytic mechanism has been proposed, and the reason for the high catalytic activity of the title complex has been discussed.     

Azamacrocyclic nickel(II) and copper(II) complexes bearing aryl substituents: synthesis,properties, and crystal structures

A synthetic procedure for preparation of new amphiphilic copper(II) and nickel(II) azamacrocyclic complexes bearing aromatic substituents is developed. The nature of substituents is shown to exert a negligible influence on spectral and electrochemical characteristics of the prepared compounds. The X-ray diffraction analysis of three copper complexes revealed the formation of the dimers of macrocyclic cations associated by noncovalent interactions, nature of which is determined by the structure of the substituent in the macrocyclic ligand.     

An efficient synthesis of the tamandarin B macrocycle

A reliable, high yielding cyclization protocol for the macrocycle of tamandarin B is presented. This strategy will facilitate the synthesis of side chain analogs.     

Tetracyanoquinodimethane complexes of nickel(II) with an N,O-donor macrocycle

A nickel(II) chelate, NiL¹Cl₂, has been obtained by reaction of nickel(II) chloride with a 15-membered N,O-donor macrocyclic ligand. Single-crystal X-ray studies reveal an octahedral environment around nickel(II). 7,7′,8,8′-Tetracyanoquinodimethane (tcnq) derivatives of the nickel(II) chelate were prepared by reaction with Litcnq and Et₃N(tcnq)₂. Spectroscopic measurements show the presence of only anionic tcnq in [NiL₁(tcnq)₂]·4H₂O and a mixture of non-coordinating anionic and neutral tcnq species in [NiL₁](tcnq)₄·H₂O.     

Structure and properties of a 1D supramolecule self-assembled by a copper(II) macrocycle with bicarbonate ligands

A new complex of composition [Cu(L3)(HCO^– ₃)₂] _n (1) (L3 = 3, 14-dimethyl-2, 6, 13, 17-tetraazatricyclo [14.4.0^1.18.0^7.12]docosane) has been synthesized and structurally characterized by a combination of analytical, spectroscopic, and crystallographic methods. The copper(II) coordination geometry in (1) consists of an axially elongated octahedron with four nitrogen atoms from the macrocycle and two oxygen atoms from the bicarbonate ligands. The [Cu(L3)(HCO₃ ^–)₂] unit extends its structure to form a novel 1D supramolecule (1) through intermolecular hydrogen bonding interactions between the bicarbonate ligands. Thus, the [Cu(L3)( HCO₃ ^–)₂] motif works as a metal complex synthon for the formation of the supramolecule (1).     

Preparation and characterization of Cr(III), Mn(II), Fe(II), Co(II) and Ni(II) complexes of a hexaazadithiophenolate macrocycle

The ligating properties of the 24-membered macrocyclic dinucleating hexaazadithiophenolate ligand (L(Me))2- towards the transition metal ions Cr(II), Mn(II), Fe(II), Co(II), Ni(II) and Zn(II) have been examined. It is demonstrated that this ligand forms an isostructural series of bioctahedral [(L(Me))M(II)2(OAc)]+ complexes with Mn(II) (2), Fe(II) (3), Co(II) (4), Ni(II) (5) and Zn(II) (6). The reaction of (L(Me))2- with two equivalents of CrCl2 and NaOAc followed by air-oxidation produced the complex [(L(Me))Cr(III)H2(OAc)]2+ (1), which is the first example for a mononuclear complex of (L(Me))2-. Complexes 2-6 contain a central N3M(II)(mu-SR)2(mu-OAc)M(II)N3 core with an exogenous acetate bridge. The Cr(III) ion in is bonded to three N and two S atoms of (L(Me))2- and an O atom of a monodentate acetate coligand. In 2-6 there is a consistent decrease in the deviations of the bond angles from the ideal octahedral values such that the coordination polyhedra in the dinickel complex 5 are more regular than in the dimanganese compound 2. The temperature dependent magnetic susceptibility measurements reveal the magnetic exchange interactions in the [(L(Me))M(II)2(OAc)]+ cations to be relatively weak. Intramolecular antiferromagnetic exchange interactions are present in the Mn(II)2, Fe(II)2 and Co(II)2 complexes where J = -5.1, -10.6 and approximately -2.0 cm(-1) (H = -2JS1S2). In contrast, in the dinickel complex 5 a ferromagnetic exchange interaction is present with J = +6.4 cm(-1). An explanation for this difference is qualitatively discussed in terms of the bonding differences.