Inversion of DNA helicity induced by zinc (II)-macrocyclic polyamine complexes

Abstract

Exposure of synthetic polynucleotide poly(dG-dC)·poly(dG-dC) to Zn^II cyclen, 2 (cyclen = 1,4,7,10-tetraazacyclododecane), produces a dramatic change in its circular dichroism (CD) spectrum in H₂O at pH 7.2, 24°C: the CD spectrum of the initial B form changes to that of the Z form (or a non-Z structure with a left-handed helix) at very low concentrations ([Zn^II]/[base pair] in molar basis ≤ 1). By contrast, Zn^II-[12]aneN₃, 1 ([12]aneN₃ = 1,5,9-triazacyclododecane), and Zn^II-cyclam, 3 (cyclam = 1,4,8,11-tetraazacyclo-tetradecane), do not significantly have such a topological affect on the polynucleotide even at much higher concentrations. An increase in Na⁺ ionic strength nullified the effect of 2 on the CD spectrum, indicating an outside interaction (electrostatic and/or hydrogen bonding) of the DNA model. This study illustrates the significance of the macrocyclic ligand structure around the Zn^II ion for specific interaction with DNA.     

Influence of the Coordination of Donor Solvent Molecules to 1,4,7,10-Tetramethyl-1,4,7,10- tetraazacyclododecanenickel(II) and Analogous Nickel(II) Complexes on Their Steric Factors

Coordination equilibrium constants (K _NiS) of some donor solvent molecules to 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecanenickel(II) ([Ni(Me₄[12]aneN₄)]²⁺) were determined in nitrobenzene (a noncoordinating bulk solvent). The first (K _NiS1) and second stepwise coordination equilibrium constants (K _NiS2) for 1,4,7,10-tetraazacyclododecanenickel(II) ([Ni([12]aneN₄)]²⁺), 1,4,8,11-tetraazac yclotetradecane- nickel(II) ([Ni([14] aneN₄)]²⁺), 1,4,8,11-tetrathiacyclotetra-decanenickel(II) ([Ni([14]aneS₄)]²⁺) were also reinvestigated. The K _NiS values for [Ni(Me₄[12]aneN₄)]²⁺ were compared to those of [Ni([12]aneN₄)]²⁺, (1R,4S, 8R,11S)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecanenickel(II) (R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺), R,R,S,S-[Ni(Me₄[14]aneN₄)]²⁺, [Ni([14]aneN₄)]²⁺, and [Ni([14]aneS₄)]²⁺. Coordination of pyridine (Py), N,N,N′,N′-tetramethylurea (TMU), and N,N-dimethylacetamide (DMA) to [Ni(Me₄[12]aneN₄)]²⁺ was observed, although these donor solvent molecules did not coordinate to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺. The K _NiS values for Py, TMU, and DMA are 7.9, 2.8, and 9.0 dm³⋅mol⁻¹, respectively. Some hydrogen-bonding waters were coordinated to R,S,R,S-[Ni(Me₄[14]aneN₄)]²⁺, but such waters did not coordinate to [Ni(Me₄[12] aneN₄)]²⁺. Also, the K _NiS2 values were larger than the corresponding K _NiS1 values for [Ni([14]aneS₄)]²⁺. Furthermore, the K _NiS1 values for [Ni([12]aneN₄)]²⁺ were the largest among these nickel(II) complex cations. The K _NiS, K _NiS1, and K _NiS2 values are discussed in terms of properties of the donor solvents and steric strains of these nickel(II) complex cations.     

Uridine binding by Zn(II) macrocyclic complexes: diversion of RNA cleavage catalysts

Zn(II) complexes of 1-oxa-4,7,10-triazacyclododecane (12[ane]N3O), 1,5,9-triazacyclododecane (12[ane]N3), and 1-hydroxyethyl-1,4,7-triazacyclononane (9[ane]N3OH) promote cleavage of the RNA analogue, 2-hydroxypropyl-4-nitrophenyl phosphate (HpPNP) at pH 8.0, I=0.10 M (NaCl), 25 degrees C with second-order rate constants of 8.9x10(-3), 9.0x10(-3), and 3.3x10(-3) M-1 s-1, respectively. Cleavage of HpPNP by these catalysts is inhibited by uridine with inhibition constants (Ki) of 1.2, 0.46, and 45 mM, respectively, under these conditions. Binding constants derived from these inhibition constants are 2-200-fold larger than those for binding of related Zn(II) complexes to phosphate diesters under similar conditions, suggesting that uridine sequences in RNA will inhibit Zn(II)-catalyzed cleavage by competing with phosphate diester binding sites. Further studies are carried out that utilize pH-potentiometric titrations to monitor uridine binding to five Zn(II) macrocyclic complexes in aqueous solution at 25 degrees C, I=0.10 M (NaCl). The data are consistent with binding of the Zn(II) complexes to the N3-deprotonated form of uridine to give log KU.-values of 5.29, 4.57, 4.56, 3.47, and 2.65 for the Zn(II) complexes of 12[ane]N3, 12[ane]N4, 12[ane]N3O, 15[ane]N3O2, and 9[ane]N3OH, respectively (12[ane]N4=1,4,7,10-tetraazacyclododecane, 15[ane]N3O2=1,4-dioxa-7,10,13-triazacyclopentadecane). For the five Zn(II) complexes studied, there is a linear relationship between uridine anion binding constants and hydroxide binding constants.     

Template synthesis and characterization of host (nanopores of zeolite Y)/guest (Co(II)-tetraoxodithiatetraaza macrocyclic complexes) nanocomposite materials

A series of Co(II) tetraoxodithiatetraaza macrocyclic complexes ([18]aneN₄S₂, [20]aneN₄S₂, Bzo₂[18]aneN₄S₂ and Bzo₂[20]aneN₄S₂) have been encapsulated in the nanopores of zeolite Y by template condensation reaction. Co(II) complexes with tetraoxodithiatetraaza macrocyclic ligand were entrapped in the nanopores of zeolite Y by a two-steps process in the liquid phase: (i) ion-exchange of [bis(diamine)cobalt(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); [Co(N–N)₂]²⁺–NaY; in the nano-cavity of the zeolite, and (ii) in situ template condensation of the cobalt(II) precursor complex with thiodiglycolic acid. The mode of bonding and overall geometry of the complexes and new host/guest nanocomposite materials ([Co([18]aneN₄S₂)]²⁺–NaY, [Co([20]aneN₄S₂)]²⁺–NaY, [Co(Bzo₂[18]aneN₄S₂)]²⁺–NaY, [Co(Bzo₂[20]aneN₄S₂)²⁺–NaY) has been inferred through FT-IR, DRS and UV–Vis spectroscopic techniques, BET technique, molar conductance and magnetic moment data, XRD and elemental analysis, as well as nitrogen adsorption. The average number of encapsulated Co complexes per nano-cavity was determined to be 0.33 for the Co complexes–NaY. An octahedral geometry around the cobalt(II) ion is suggested for the complexes and new host/guest nanocomposite materials.     

Host (nanopores of zeolite-Y)/guest (Ni(II)-tetraoxo dithia tetraaza macrocyclic complexes) nanocomposite materials: template synthesis and characterization

Nickel(II) complexes with six co-ordinate tetraoxo dithia tetraaza macrocyclic ligands derived from diamine and which provide a N₄S₂ co-ordination sphere, [18]aneN₄S₂: 1,4,10,13-tetraaza-5,9,14,18-tetraoxo-7,16-dithia-cyclooctadecane, [20]aneN₄S₂: 1,5,11,15-tetraaza-6,10,16,20-tetraoxo-8,18-dithia-cyclocosane, Bzo₂[18]aneN₄S₂: dibenzo-1,4,10,13-tetraaza-5,9,14,18-tetraoxo-7,16-dithia-cyclooctadecane, Bzo₂[20]aneN₄S₂: dibenzo-1,5,11,15-tetraaza-6,10,16,20-tetraoxo-8,18-dithia-cyclocosane, were entrapped in the nanopores of zeolite NaY by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)nickel(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); [Ni(N–N)₂]²⁺-NaY; in the nanopores of the zeolite, and (ii) in situ template condensation of the nickel(II) precursor complex with thiodiglycolic acid. The mode of bonding and overall geometry of the complexes and new host/guest nanocomposite materials ([Ni([18]aneN₄S₂)]²⁺-NaY, [Ni([20]aneN₄S₂)]²⁺-NaY, [Ni(Bzo₂[18]aneN₄S₂)]²⁺-NaY, [Ni(Bzo₂[20]aneN₄S₂)²⁺-NaY) has been inferred through FT-IR, DRS and UV–vis spectroscopic techniques, molar conductance and magnetic moment data, XRD and elemental analysis, as well as nitrogen adsorption. An octahedral geometry around the nickel(II) ion is suggested for the complexes and new host/guest nanocomposite materials.     

Synthesis,crystal structure and properties of a 1D copper(II) complex with 1,5,9-triazacyclododecane bridged by p -benzenebicarboxylate

A 1D complex [{[Cu₂([12]aneN₃)₂(p-paa)(H₂O)₂](ClO₄)₂}[Cu₂([12]aneN₃)₂(p-paa)₂]] _n ([12]aneN₃ = 1,5,9-triazacyclododecane, p-paa = p-benzenebicarboxylate) has been synthesized and structurally characterized. The complex contains two different binuclear copper(II) moieties. One part includes a binuclear copper(II) unit and non-coordinated perchlorate anions. A neutral binuclear copper(II) part which forms a zigzag chain structure via the bridging p-paa ligand completes the unit-cell. Elemental analysis, IR, UV-Vis spectra and magnetic properties for the complex have also been determined. Magnetic susceptibilities in the solid state are measured over the temperature range from 77 to 300 K, showing a weak antiferromagnetic coupling with a best fit J ₁ = ?3.09 cm^?1, J ₂ = ?5.279 cm^?1, g = 2.099 and R = 1.226 × 10^?5.     

Formation and isomerisation of theO-sulphito complex of 1,4,7,10,13-penta-azacyclohexadecanecobalt(III)

Summary Dissolved SO₂ reacts rapidly with [Co([16]aneN₅)OH]²⁺ to give [Co([16]aneN₅OSO₂]⁺([16]aneN₅=1,4,7,10, 13-penta-azacyclohexadecane), which on immediate acidification loses SO₂ to give [Co([16]aneN₅)OH₂]³⁺. The O-bonded sulphito complex (_max 526 nm) undergoes a slow linkage isomerisation to give the S-bonded species [Co([16]aneN₅)SO₃]⁺ (_max 466 nm), rather than an internal redox reaction. The S-bonded complex has been isolated and characterised as the perchlorate salt [Co([16]aneN₅) (SO₃H)](ClO₄)₂.     

Complexation of Cu2+ by Binucleating Macrocycles Containing the N6 Donor Set

The hexadentate ligands 1,4,7,12,15,18-hexaazacyclododecosane ([2]aneN₆) and 1,4,7,14,17,20-hexaazacyclohexacosane ([26]aneN₆) both form eight complexes with Cu²⁺, three of them being binuclear. The corresponding stability constants have been determined potentiometrically, and the electronic absorption spectra have been obtained from spectrophotometric data. Possible interactions of the Cu²⁺ pairs in the three binuclear complexes have, in addition, been investigated by ESR and and linear -sweep voltammetry (LSV). The binuclear complex of [22]aneN₆ with one addditional OH group is exceptionally stable, ESR-silent, and the results of the LSV-experiments are characteristically different from those of the other binuclear complexes with both ligands. This indicates that [22]aneN₆ forms a very stable hydroxo-bridged binuclear Cu²⁺ complex Cu₂L(OH)³⁺, whereas in the case of [26]andN₆ no bridged Cu²⁺ pair exists.     

Chemical mechanism of controlled nitric oxide release from trans-[RuCl([15]aneN4)NO](PF6)2 as a vasorelaxant agent

The nitrosyl ruthenium complex, trans-[RuCl([15]aneN₄)NO](PF₆)₂, ([15]aneN₄?=?1,4,8,12-tetraazacyclopentadecane), exhibits vasorelaxation characteristics attributed to its nitric oxide release properties. The observed in vitro and in vivo vasodilation is dependent on noradrenaline concentration. We report here the chemical mechanism of the reaction between noradrenaline and trans-[RuCl([15]aneN₄)NO](PF₆)₂ in aqueous phosphate buffer solution at pH 7.40. NO measurement by NO-sensor electrode, cyclic voltammetry, ³¹PNMR and HPLC analysis were used to investigate the reduction process as the fundamental step for NO release characteristic of trans-[RuCl([15]aneN₄)NO](PF₆)₂. A supramolecular species containing HPO₄ ^2? as a bridging group between noradrenaline and trans-[RuCl([15]aneN₄)NO](PF₆)₂ is suggested as an intermediate prior to the reduction of the nitrosyl ruthenium complex.     

Fluorescence signaling of aromatic oxoanion inclusion within metal-ion activated molecular receptor complexes formed from 2-(9-anthracenylmethylamino)ethyl-appended cyclen

Our observations that 1-[2-[(9-anthracenylmethylamino)ethyl)-4,7,10-tris[(2S)-2-hydroxy-3-phenoxypropyl]-1,4,7,10-tetraazacyclododecane, L¹, complexes Cd(II) to form fluorescent [CdL¹]²⁺ which undergoes a fluorescence change when it acts as an aromatic anion receptor complex has caused us to explore further the potential development of an interesting sequestration/sensor system. Accordingly, three new, octadentate, fluorescent, macrocyclic ligands, 1-[2-[(9-anthracenylmethyl)((2S)-2-hydroxy-3-phenoxypropyl)amino]ethyl]-4,7,10-tris[(2S)-2-hydroxy-3-phenoxypropyl]-1,4,7,10-tetraazacyclododecane, (L²), 1-[2-[(9-anthracenyl-methyl)((2S)-2-hydroxy-3-(4??-methyl)phenoxypropyl)amino]ethyl]-4,7,10-tris[(2S)-2-hydroxy-3-(4??-methyl)phenoxypropyl]-1,4,7,10-tetraazacyclododecane, (L³), and 1-[2-[(9-anthracenylmethyl)((2S)-2-hydroxy-3-(4??-t-butyl)phenoxypropyl)amino]ethyl]-4,7,10-tris[(2S)-2-hydroxy-3-(4??-t-butyl)phenoxypropyl]-1,4,7,10-tetraazacyclododecane, (L⁴), have been prepared with a view to using their metal complexes to study aromatic anion sequestration. The eight-coordinate Cd(II) complexes of L² and L³, [CdL²](ClO₄)₂·5H₂O and [CdL³](ClO₄)₂·2H₂O·2Et₂O are both capable of acting as receptors for a range of aromatic oxoanions. This is demonstrated by perturbation of the anthracene derived fluorescence emission intensity as the guest aromatic oxoanion and the receptor complex combine. In 20% aqueous 1,4-dioxane the receptor complex/aromatic oxoanion association constants are in the range of 10^3.2 M^?1 (guest = p-hydroxybenzoate) to 10^7.3 M^?1 (guest = 3,4,5-trihydroxybenzoate).     

Coordination chemistry of N-aminopropyl pendant arm derivatives of mixed N/S-, and N/S/O-donor macrocycles, and construction of selective fluorimetric chemosensors for heavy metal ions

The coordination chemistry of the N-aminopropyl pendant arm derivatives (L1c-4c) of the mixed donor macrocyclic ligands [12]aneNS2O, [12]aneNS3, [12]aneN2SO, and [15]aneNS2O2(L1a-4a) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in aqueous solution has been investigated. The protonation and stability constants with the aforementioned metal ions were determined potentiometrically and compared, where possible, with those of the unfunctionalised macrocycles. The measured values show that Hg(II) and Cu(II) in water have the highest affinity for all ligands considered, with the N-aminopropyl pendant arm weakly coordinating the metal centres. Crystals suitable for X-ray diffraction analysis were grown for the perchlorate salt (H2L1c)(ClO4)2.dmf, and for the 1 : 1 complexes [Cd(L3a)(NO3)2](1), [Cu(L4a)dmf](ClO4)2(2), [Zn(L1c)(ClO4)]ClO4(3), [Cd(L1c)(NO3)]NO3(4), and [Hg(L2c)](ClO4)2(5). Their structures show the macrocyclic ligands adopting a folded conformation, which for the 12-membered systems can be either [2424] or [3333] depending on the nature of the metal ion. L1c-4c were also functionalised at the primary amino pendant group with different fluorogenic subunits. In particular the N-dansylamidopropyl (Lnd, n= 1-4), and the N-(9-anthracenylmethyl)aminopropyl (Lne, n= 1, 2, 4, ) pendant arm derivatives of L1a-4a were synthesised and their optical responses to the above mentioned metal ions were investigated in MeCN/H2O (4 : 1 v/v) solutions.     

Syntheses of bifunctional molecules containing [12]aneN3 and carbazol moieties as effective DNA condensation agents

Bifunctional molecules containing macrocyclic polyamine[12]aneN3 and carbazol units,1 4,have been efficiently synthesized and fully characterized.Through gel electrophoresis,atomic force microscopy,and dynamic light scattering experiments,compounds 3 and 4b bearing both[12]aneN3and carbazol moieties showed effective DNA condensation ability at the concentration of 80μM.Investigations from EB displacement fluorescence spectra,viscosity titration,and ionic strength effects revealed that the effective DNA condensation comes from the appropriate combination of carbazol and[12]aneN3units in the bifunctional molecules,and the DNA condensation process is reversible.The incorporation of triazole units in the molecules clearly reduced the cytotoxicity.     

Host (nanocavity of zeolite-Y)/guest (12- and 14-membered azamacrocyclic Ni(II) complexes) nanocatalyst: synthesis, characterization and catalytic oxidation of cyclohexene with molecular oxygen

Ni(II) complexes of [12]aneN₄: 1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone; [14]aneN₄: 1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone; Bzo₂[12]aneN₄: dibenzo-1,4,7,10-tetraazacyclododecane-2,3,8,9-tetraone and Bzo₂[14]aneN₄: dibenzo-1,4,8,11-tetraazacyclotetradecane-2,3,9,10-tetraone have been encapsulated in the nanopores of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)nickel(II)]; [Ni(N–N)₂]–NaY; in the supercages of the zeolite, and (ii) in situ condensation of the nickel(II) precursor complex with diethyloxalate. The new host-guest nanocatalyst (HGN) were characterized by several techniques: chemical analysis and spectroscopic methods (FT-IR, UV/Vis, XRD, BET, DRS) and then were used for oxidation of cyclohexene with molecular oxygen.     

Macrocyclic effect of auxiliary ligand on the gas‐phase dissociation of ternary copper(II)–GGX complexes

Previous studies into the dissociation of [Cu^II(dien)peptide] ^{. 2+} ions (dien = diethylenetriamine) have shown that NH‐containing auxiliary ligands do not favor the formation of [peptide] ^{. +} species; instead, they promote proton‐transfer reactions, especially for peptides containing basic amino residues. Formation of radical cationic tripeptides of the form GGX ^{. +} [GGX = glycylglycyl(residue X)] becomes feasible upon substituting the open‐chain tridentate ligand dien with its analogous cyclic ligand, 1,4,7‐triazacyclononane (9‐aneN₃); i.e., from [Cu^II(9‐aneN₃)GGX] ^{. 2+} ions. Similar enhancements occur when using 1,4,7,10‐tetraoxacyclododecane (12‐crown‐4) in place of its open‐chain analog, 2,5,8,11‐tetraoxadecane (triglyme). We have demonstrated that a sterically encumbered auxiliary macrocyclic ligand within [Cu^II(L)GGX] ^{. 2+} complex ions [where L = 9‐aneN₃ or 12‐crown‐4] facilitates the formation of radical cationic peptides through gas‐phase fragmentation. We verified our experimental observations by examining the reactivities of a series of 19 tripeptides of the type GGX that differ only in the identity of their C‐terminal residue. The energy of the electron‐transfer reaction correlates well with the bond‐dissociation energy of the peptide–Cu(II) interaction; the presence of a constrained macrocyclic ligand weakens metal–peptide chelation through steric repulsion between the ligand and the peptide, and this situation may lead to more favorable radical cationic peptide formation. Copyright © 2006 John Wiley & Sons, Ltd.     

Copper(II) complexes with 18-membered decaaza macrocycles: synthesis,characterization and catalytic activity

New square-planar copper(II) complexes of 18-membered decaaza macrocyclic ligands: 5,6,14,15-tetramethyl-1,3,4,7,8,10,12,13,16,17-decaazacyclooctadecane (Me₄[18]aneN₁₀); 1,10-dimethyl-(Me₂Me₄[18]aneN₁₀); 1,10-diethyl-(Et₂Me₄[18]aneN₁₀); 1,10-dipropyl-(Pr₂Me₄[18]aneN₁₀); 1,10-dibutyliso-(Bu₂Me₄[18]aneN₁₀) and 1,10-dibenzyl-5,6,14,15-tetramethyl-1,3,4,7,8,10,12,13,16,17-decaazacylooctadecane [(Benzyl)₂Me₄[18]aneN₁₀)] have been prepared by a one-pot template condensation of formaldehyde and 2,3-butanedihydrazone with alkyl and benzylamine in the presence of copper(II) ion. The complexes of the decaaza macrocycle have been characterized by elemental analyses, i.r., u.v.–vis., conductometric and magnetic measurements. The spectra of [Cu(R₂Me₄[18]ane N₁₀)](ClO₄)₂shows that the four nitrogen (α-diimine) atoms are coordinated to the copper(II) ion. These complexes are found to be effective catalysts for the selective oxidation of tetrahydrofuran to yield the corresponding tetrahydrofuran-2-one and a small amount of tetrahydrofuran-2-ol and 4-hydroxybutyraldehyde, using diluted H₂O₂ as the oxidant.     

Toxic metal complexes of macrocyclic cyclen molecule – synthesis,structure and complexing properties

Toxic metal (Cd²⁺, Hg²⁺, Pb²⁺, and Ag⁺) complexes with the tetradentate macrocyclic ligand - cyclen (1,4,7,10-tetraazacyclododecane, [12]aneN₄, L) were prepared and studied in the solid state by IR, X-ray diffraction, elemental and thermal analysis. Diffraction results have yielded three molecular structures, [Cd([12]ane-κ⁴N^1,4,7,10)(NO₃)₂)] (1), [Hg([12]ane-κ⁴N^1,4,7,10)(NO₃-κ²O,O`)]NO₃ (2), [Pb₂([12]ane-κ⁴N^1,4,7,10)₂][Pb(NO₃)₆] (3) and one polymeric structure {[Ag₂([12]ane-κ³N^1,4,7)(μ₂-[12]aneN¹⁰)](NO₃)₂?2H₂O)}_n (4) featuring a unique coordination mode not observed before with cyclen as a ligand. The monodentate (1) and chelate (with small bite angle 50.3(3)°, (2) coordination modes of nitrate ligands were confirmed. Stereochemically active 6s² lone pair was suggested in 3 and DFT results confirmed no significant metal–metal covalent bond. The stability constants of the complexes with Cd²⁺ and Pb²⁺ ions were determined by potentiometric methods in aqueous solutions. Additionally, the structures of complexes in solution were observed by ¹H NMR. Both methods confirm similar cyclen complexing properties toward Zn²⁺ biometal and Cd²⁺, Pb²⁺ toxic metals.     

Characterization and properties of the copper(II/I) complexes of macrocyclic hexathiaether ligand [21]aneS6

The copper(II/I) complexes of hexathiaether macrocyclic ligand, 1,4,8,11,15,18-hexathiacyclohenicosane ([21]aneS₆), were synthesized, and characterized by electrochemical and spectroscopic techniques. Cyclic voltammetric studies indicate that Cu([21]aneS₆)^2+/+ forms a reversible one-electron redox couple. The electrochemical potential obtained for Cu([21]aneS₆)^2+/+ (E^f = 0.89 V, against SHE) was found to be the highest potential reported to date for a Cu^2+/+ macrocyclic system in aqueous solution. By employing the Nernst equation, we can infer that the practical upper limit for formal potential of Cu(II/I)L systems maybe close to this high value. Stability constant data obtained for these complexes indicate that Cu([21]aneS₆)⁺is 12 orders of magnitude greater in stability than that of Cu([21]aneS₆)²⁺ indicating the favorable nature of this large macrocyclic ligand towards formation of Cu(I) complexes over Cu(II) complexes. Crystal structure of Cu([21]aneS₆)⁺ ( Fig. 2) shows that four sulfurs adjacent to one another are coordinated to Cu⁺ ion in this complex. Bond angles and distances calculated for the crystal indicate that it is a distorted tetrahedron, a geometry commonly encountered by Cu(I) complexes. This is the first report of synthesis and characterization of a metal coordinated [21]aneS₆ complex.     

Synthesis and Characterization of the Mn(II) Complex of [15]aneN5

The complex Mn[15]aneN₅CIPF₆ has been prepared by the reaction of MnCI₂ [15]aneN₅.3HPF₆, and NaOH in water ([15]aneN₅ is 1,4,7,10,13-pentaazacyclopentadecane). The complex is obtained as a white solid formulated as [Mn(C₁₀H₂₅N₅)Cl](PF₆).3/2H₂O. It is a 2: 1 electrolyte in H₂O and a 1:1 electrolyte in CH₃CN, The complex contains high spin Mn(II), μ_eff = 5.83 B.M., and the EPR spectrum of the polycrystalline solid is indicative of rhombic symmetry at the metal site. The proton NMR relaxation enhancement of aqueous solvent by the complex is 2.3 mM^?1S ^?1 at 24 MHz and 25°C and is indicative of one rapidly exchanging water molecule in the coordination sphere of the solvated complex. The stability constant for the formation of the complex in aqueous solution as measured by potentiometric titration (IogK = 10.7) is four orders of magnitude greater than the comparable linear polyamine. In all, the characterization data are consistent with Mn(lI) strongly bound to a distorted or folded ligand and able to accommodate only one additional ligand.     

Solvolysis Products of the Types [RhMeL2(Me3[9]aneN3)]2+ and [RuCl3—XLX(Me3[9]aneN3)](x)+ (x = 1‐2) and Preparation and Structure of [Ru([9]aneS3)(Me3[9]aneN3)](CF3SO3)2

Solvolysis of [RhMe(CF₃SO₃)₂(Me₃[9]aneN₃)] ( 1 ) (Me₃[9]aneN₃ = 1, 4, 7‐trimethyl‐1, 4, 7‐triazacyclononane) in CH₃CN, DMSO or pyrazole (L) leads to substitution of both trifluoromethylsulfonate ligands and formation of the cationic complexes [RhMeL₂(Me₃[9]aneN₃)](CF₃SO₃)₂ 3—5 . In contrast, treatment of [RuCl₃(Me₃[9]aneN₃)] ( 2 ) with Ag(CF₃SO₃) in a 1:3 ratio for 2h in CH₃CN leads to formation of the tetranuclear complex [{RuCl₃(Me₃[9]aneN₃)}₂Ag₂(CF₃SO₃)(CH₃CN)](CF₃SO₃) · CH₃CN ( 6 ) with a novel [(RuCl₃)₂Ag₂] core. More forcing conditions enable the substitution of respectively one or two chloride ligands by CH₃CN (reflux 18h) or DMF (85°C, 1h) to afford [RuCl₂(CH₃CN)(Me₃[9]aneN₃)](CF₃SO₃) ( 7 ) and [RuCl(DMF)₂(Me₃[9]aneN₃)](CF₃SO₃)₂ ( 8 ). The heteroleptic sandwich complex [Ru([9]aneS₃)(Me₃[9]aneN₃)](CF₃SO₃)₂ ( 9 ) can be prepared by reduction of 2 with Zn powder in acetone in the presence of 3 equiv. of Ag(CF₃SO₃), followed by addition of [9]aneS₃ (1, 4, 7‐trithiacyclononane). The redox potential E°(Ru³⁺/Ru²⁺) of +1.87 V vs NHE for 9 is only —0.12 V lower than that of the homoleptic complex [Ru([9]aneS₃)₂]²⁺. Crystal structures are reported for 3 — 9 .     

Synthesis, characterization and catalytic oxidation of tetrahydrofuran with 16-membered pentaazabis(macrocyclic) copper(II) complexes; {[Cu([16]aneN5)]2R}4+ (R = aromatic nitrogen–nitrogen linkers)

New square-planar bis(macrocyclic)dicopper(II) complexes containing phenylene bridges between 16-membered pentaaza macrocyclic subunits have been synthesized via in-situ one pot template condensation reaction (IOPTCR) of aromatic nitrogen-nitrogen linker (R = 1,4-phenylenediamine; benzidine; 4,4′-diaminodiphenylmethane; 4,4′-diaminodiphenylether; 4,4′-diaminodiphenylsulfone), formaldehyde, bis(1,3-diaminopropane)copper(II) perchlorate and 1,3-dibromopropane in a 1:4:2:2 molar ratio results in the formation of new series of binuclear copper(II) complexes; 1-phenyl- (1); 1,1′-phenyl- (2); 1,1′-diphenylmethan- (3); 1,1′-diphenylether- (4); 1,1′-diphenylsulfone- (5) bis(1,3,7,11,15-pentaazacyclohexadecane)copper(II)), {[Cu([16]aneN₅)]₂R}(ClO₄)₄″. The formation of the macrocyclic framework and the mode of bonding of the complexes have been confirmed by data obtained from elemental analyses, UV-visible, FT-IR, ¹H-NMR, electronic spectral studies, conductivity and magnetic susceptibility measurements. These bis(macrocyclic) complexes catalyzed efficiently the selective oxidation of tetrahydrofuran into tetrahydrofuran-2-one and a small amount of tetrahydrofuran-2-ol and 4-hydroxybutyraldehyde using dil. H₂O₂ as the oxidant.