Synthesis and characterization of Mg(II), Mn(II), Zn(II) and Cd(II) complexes with a new heptaaza Schiff base pendant-armed macrocycle: X-ray crystal structure, NMR and computational study

New 2-aminoethyl pendant-armed Schiff base macrocyclic complexes, [ML⁷]²⁺ (M = Mn(II), Mg(II), Zn(II) and Cd(II)), have been prepared via M(II) templated [1 + 1] cyclocondensation of 2,6-diacetylpyridine with a new branched hexamine, N,N,N′,N′-tetrakis(2-aminoethyl)-2,2-dimethylpropane-1,3-diamine. The ligand is a 16-membered pentaaza macrocycle having two 2-aminoethyl pendant arms [L⁷ is 2,14-dimethyl-6,10-bis(2-aminoethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]8,8-dimethylnonadeca-1(19),2,13,15,17-pentaene]. The crystal structures of [MnL⁷]²⁺ and [MgL⁷]²⁺ were determined from X-ray diffraction data. The geometry of the coordination sphere of complexes is a slightly distorted pentagonal bipyramid with the metal ion located within a pentaaza macrocycle and two pendant amines coordinating on opposite sides. All complexes were characterized by IR, microanalysis and except of [MnL⁷]²⁺ by ¹H NMR, ¹³C NMR, DEPT135, COSY(H, H) and HMQC spectroscopy. The data indicate that the structure is pentagonal bipyramidal in each case. The structure of all complexes has also been theoretically studied by ab initio Hartree-Fock and density functional theory methods.     

New macrocyclic Schiff-base complexes incorporating a phenanthroline unit. Part 2: Template synthesis of some manganese(II) complexes and crystal structure studies

A series of Mn(II) macrocyclic Schiff-base complexes [MnLⁿ]²⁺ have been prepared via the Mn(II) templated [1+1] cyclocondensation of 2,9-dicarboxaldehyde-1,10-phenanthroline with appropriate linear and branched amines. In this way ligands the pentaaza macrocycle L¹ which is 15-membered and L² which is 16-membered possessing no pendant arm, L⁶ is 15-membered with one 2-aminoethyl pendant arm and L⁸ which is 18-membered hexaaza macrocycle with two 2-aminoethyl pendant arms are formed. All the complexes have been characterized using spectroscopic methods. The crystal structures of [MnL⁸](ClO₄)₂ · EtOH were determined and indicate that in the solid state the complex adopts a slightly distorted hexagonal bipyramid geometry with the Mn(II) ion located within a hexaaza macrocycle with the two pendant amines coordinating in the axial positions.     

Synthesis, crystal structure, NMR and ab initio molecular-orbital studies of some magnesium(II) macrocyclic Schiff-base complexes, with two 2-aminoethyl pendant arms

Three new Mg(II) bis(pendant arm) macrocyclic Schiff-base complexes, [MgLⁿ]²⁺(n=5, 6, 7), have been prepared via cyclocondensation of 2,6-diacetylpyridine with branched hexaamines and characterised spectroscopically. In addition, for [MgL⁵](ClO₄)₂ the crystal structure is reported. This is the first X-ray structural determination of an Mg(II) complex coordinated by seven nitrogen atoms. The ligands, L, are 15-, 16- and 17-membered pentaaza macrocycles having two 2-aminoethyl pendant arms [L⁵; 2,13-dimethyl-6,9-bis(aminoethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18), 2, 12, 14, 16-pentaene, L⁶; 2,14-dimethyl-6,10-bis(aminoethyl)-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19), 2, 13, 15, 17-pentaene and L⁷; 2,15-dimethyl-6,11-bis(aminoethyl)-3,6,11,14,20-pentaazabicyclo[14.3.1]eicosa-1(20),2,14,16,18-pentaene]. The crystal structure of [MgL⁵](ClO₄)₂, was determined by X-ray diffraction and showed that the complex cation that had formed consisted of a pentagonal bipyramidally coordinated Mg(II) ion. All complexes were characterised by IR, ¹H NMR,¹³C NMR, COSY(H,H) and HETCOR(H,C) spectroscopy, and the data indicate that the structure is approximately pentagonal bipyramidal in each case. This structural assignment is also supported by ab initio HF-MO calculations made using the standard 3-21G* basis set.     

Two macrocyclic pentaaza compounds containing pyridine evaluated as novel chelating agents in copper(II) and nickel(II) overload

Two pentaaza macrocycles containing pyridine in the backbone, namely 3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),14,16-triene ([15]pyN₅), and 3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),15,17-triene ([16]pyN₅), were synthesized in good yields. The acid-base behaviour of these compounds was studied by potentiometry at 298.2 K in aqueous solution and ionic strength 0.10 M in KNO₃. The protonation sequence of [15]pyN₅ was investigated by ¹H NMR titration that also allowed the determination of protonation constants in D₂O. Binding studies of the two ligands with Ca²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ metal ions were performed under the same experimental conditions. The results showed that all the complexes formed with the 15-membered ligand, particularly those of Cu²⁺ and especially Ni²⁺, are thermodynamically more stable than with the larger macrocycle. Cyclic voltammetric data showed that the copper(II) complexes of the two macrocycles exhibited analogous behaviour, with a single quasi-reversible one-electron transfer reduction process assigned to the Cu(II)/Cu(I) couple. The UV-visible-near IR spectroscopic and magnetic moment data of the nickel(II) complexes in solution indicated a tetragonal distorted coordination geometry for the metal centre. X-band EPR spectra of the copper(II) complexes are consistent with distorted square pyramidal geometries. The crystal structure of [Cu([15]pyN₅)]²⁺ determined by X-ray diffraction showed the copper(II) centre coordinated to all five macrocyclic nitrogen donors in a distorted square pyramidal environment.     

Palladium(II) as a versatile template for the formation of tetraaza macrocycles via Mannich-type reactions

The versatility of palladium(II) as a template for Mannich-type macrocyclization is illustrated. Reaction of (bis(3-aminopropyl)piperazine)palladium(II) with formaldehyde and nitroethane in basic aqueous solution yields the ‘reinforced’ macrocycle 7-methyl-7-nitro-1,5,9,13-tetraazabicyclo[11.2.2]heptadecane as its palladium(II) complex. The crystal structure shows the palladium ion lies in a slightly tetrahedrally distorted square plane of four nitrogen donors, with distances to the two tertiary donors [av. 2.059(3) Å] slightly shorter than those to the secondary amines [av. 2.066(3) Å]. The 3-methyl-3-nitro-1,5,9,13-tetraazacyclohexadecane as its palladium(II) complex was prepared by an analogous route. In a separate reaction based on the [Pd(en)(chxn)]²⁺ (en = ethane-1,2-diamine; chxn = cyclohexane-1,2-diamine) intermediate, an unsymmetrical macrocycle with a fused cyclohexane ring, 4,11-dimethyl-4,11-dinitro-2,6,9,13-tetraazabicyclo[12.4.0]octadecane was isolated as its palladium(II) complex. Accessibility to an isolable mixed-ligand precursor is a key to this reaction, provided by using palladium(II) as the templating metal. Reaction of (4,8-diazaundecane-1,11-diamine)palladium(II) with formaldehyde and diethyl malonate in basic aqueous solution yields, with ester hydrolysis and decarboxylation, the carboxylate-pendant macrocycle 1,5,9,13-tetraazacyclohexadecane-3-carboxylic acid as its palladium(II) complex. The crystal structure is comprised of hydrogen-bonded dimers {[Pd(L)][Pd(L-H)]}³⁺ where the pair of inversion related square-planar complexes share a single proton between their pendant carboxylates. Bis(3-aminopropyl)(piperazine)palladium(II) yields the macrocyclic complex ion (1,5,9,13-tetraazabicyclo[11.2.2]heptadecane-7-carboxylic acid)palladium(II), in a similar reaction.     

Preparation of new tetraaza macrocyclic nickel(II) and copper(II) complexes bearing N-propionic methyl ester groups

A 14-membered tetraaza macrocycle, 2,13-bis(2-carbomethoxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.^1.180^7.12]docosane (L²) bearing two N-CH₂CH₂COOMe groups, and its nickel(II) and copper(II) complexes have been prepared and characterized. The nickel(II) and copper(II) complexes of 2-(2-carbomethoxyethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.^1.180^7.12]docosane (L³) containing one N-CH₂CH₂COOMe group have also been prepared. The crystal structure of [NiL²](ClO₄)₂ shows that the complex has a slightly distorted trans-octahedral coordination geometry with two relatively short axial Ni-O (N-CH₂CH₂COOMe group) bonds (2.136(3) Å). In various solvents, however, a considerable proportion of [NiL²]²⁺ exists as a square-planar form, in which the functional pendant arms are not involved in coordination. The proportion of the square-planar isomer varies with solvents in the order of nitromethane ? acetonitrile < H₂O < DMF ? DMSO. In the case of [CuL²](ClO₄)₂, only one N-CH₂CH₂COOMe group is involved in coordination. The N-CH₂CH₂COOMe group of [NiL³](ClO₄)₂ is not directly involved in coordination even in the solid state, though the functional group of [CuL³](ClO₄)₂ is coordinated to the metal ion.     

Preparation and photophysical studies of copper(I) and ruthenium(II) complexes of 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine

We report the synthesis of a new ligand, 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine, optimised for binding to copper(I) and with pendant functionality that can eventually be developed into metallodendritic structures. The synthesis and photophysical properties of complexes with copper(I) and ruthenium(II) are reported. The solid state structure of the complex [Cu(1)₂][PF₆] · MeCN (1 = 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine) is also described.     

Synthesis, structures and properties of macrocyclic nickel(II) supramolecules with imidazole pendants

Two new nickel(II) complexes with the composition [Ni(L+H)(CH₃CN)₂](ClO₄)₃ (1) and [Ni(L)(tp)]·6H₂O (2), (L = 3,10-bis{3-(1-imidazolyl)propyl}-1,3,5,8,10,12-hexaazacyclotetradecane, tp = terephthalate) have been synthesized and structurally characterized by a combination of analytical, spectroscopic and X-ray diffraction methods. The structure of 1 consists of monomeric cations of the formula [Ni(L+H)(CH₃CN)₂]³⁺ and perchlorate ions. The nickel(II) ion is six-coordinate with bonds to the four nitrogen atoms of the macrocycle and two nitrogen atoms of the axial acetonitrile ligands. One of the protonated imidazole pendants of the macrocycle is hydrogen bonded to the imidazole group of the neighboring nickel(II) macrocycle, forming an undulated 1D supramolecule. Then, the two 1D supramolecular chains are further interconnected by C-H···π interactions between the methyl group of the acetonitrile ligand and one of the imidazole groups to form a 2D double stranded supramolecular polymer. In the structure of 2, the 1D coordination polymer is formed with nickel(II) macrocycles and bridging terephthalate ions, where each 1D chain is interconnected with π-π interactions of pendant imidazole moieties of the macrocycles, resulting in the formation of a 2D supramolecule.     

Synthesis and characterization of new adjacent-bridged tetraaza macrocyclic compounds with C-alkyl groups: crystal structure and spectral properties of a copper(II) complex

New structurally constrained tetraaza macrocycles 2,3-dimethyl-1,5,12,16-tetraazapentacyclo[14.6.3.3^5.12.0^6.11.0^17.22]octacosane (L⁶) and 2,2,4,10,12,18,20-octamethyl-1,5,9,13-tetraazatricyclo[11.3.2. 2^5.9]eicosane (L⁷) have been prepared in high yield by direct reaction of 1,3-dibromopropane with 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0^7.12]docosane (L³) or 2,5,5,7,9,12,12,14-octamethyl-1,4,8,11-tetraazacyclodecane (L⁵). The macrocycle L⁶ readily reacts with anhydrous copper(II) ion to yield [CuL⁶]²⁺ in dry methanol but does not react with nickel(II) ion, showing a high copper(II) ion selectivity. On the other hand, neither of the metal ions is inserted into the cavity of L⁷ in similar conditions. The copper(II) complex [CuL⁶](ClO₄)₂ has a severely distorted square-planar coordination polyhedron with a rarely observed trans-IV type N-conformation. The visible absorption spectrum of [CuL⁶]²⁺ shows the d-d transition band at 490 nm (ε=690 M⁻¹ cm⁻¹); the wavelength is quite similar to that of [CuL³]²⁺, but the molar absorption coefficient is extraordinarily larger than those of [CuL³]²⁺ and other related tetraaza macrocyclic copper(II) complexes.     

Synthesis and characterization of new unsaturated macrobicyclic and bis(macrocyclic) copper(II) complexes containing N-CH2-N linkages

New copper(II) complexes [CuL²]²⁺ (L²=7,7,9-trimethyl-1,3,6,10,13-pentaazabicyclo[11,2,1^1.13]hexadec-9-ene) and [Cu₂(L³)(H₂O)₂]⁴⁺ have been prepared by the reaction of [CuL¹]²⁺ (L¹=5,5,7-trimethyl-1,4,8,11,14-pentaazatetradce-7-ene) and formaldehyde. The mononuclear complex [CuL²]²⁺ has a square-planar coordination geometry with a 5-6-5-6 chelate ring sequence and is relatively stable even in low pH at room temperature. The dinuclear complex [Cu₂(L³)(H₂O)₂]⁴⁺ consists of two unsaturated 15-membered pentaaza macrocyclic units (7,7,9-trimethyl-1,3,6,10,13-pentaazacyclopentadec-9-ene) that are linked together by a methylene group in a tilted face-to-face arrangement [Cu?Cu distance: 7.413(2) Å ]. Each macrocyclic unit of [Cu₂(L³)(H₂O)₂]⁴⁺ contains one four-membered chelate ring and has a severely distorted octahedral coordination polyhedron. The dinuclear complex is quite stable in aqueous solutions containing an excess of formaldehyde or in dry acetonitrile but is decomposed to [CuL¹]²⁺ and [CuL²]²⁺ in pure water.     

Synthesis and characterization of Os(II)(dpop′) (dpop′ = dipyrido(2,3-a;3′,2′-j)phenazine) complexes with 2,2′-bipyridine(bpy); 2,2′-bipyrimidine(bpm) and 2,3-bis(2-pyridyl)pyrazine(dpp)

New Os(II) complexes including [Os(dpop′)₂](PF₆)₂ (dpop′= dipyrido(2,3-a;3′,2′-j)phenazine) and a series of mixed ligand [Os(dpop′)(N-N)Cl]PF₆ (N-N = 2,2′-bipyridine(bpy); 2,2′-bipyrimidine(bpm) and 2,3-bis(2-pyridyl)pyrazine(dpp)) were synthesized. The Os dπ → dpop′ π^∗ MLCT transitions for [Os(dpop′)₂]²⁺ are observed at lower energy than for Os dπ → tpy π^∗ (tpy = 2,2′:6′,2″-terpyridine) and Os dπ → tppz π^∗ (tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) (The ligand abbreviations tpd, tpp and tpypz have also appeared in the literature for 2,3,5,6- tetrakis(2-pyridyl)pyrazine in addition to tppz.) MLCT transitions in the comparative [Os(tpy)₂]²⁺ and [Os(tppz)₂]²⁺ complexes. The Os dπ → dpop′ π^∗ MLCT transitions are observed at lower energy in mixed bidentate ligand N-N systems compared with [Os(dpop′)₂]²⁺. Cyclic voltammetry shows more positive osmium oxidation, and less negative ligand reduction potentials for [Os(dpop′)₂]²⁺ as compared to [Os(tpy)₂]²⁺ and [Os(tppz)₂]²⁺ complexes. The osmium oxidation potentials in mixed ligand [Os(dpop′)(N-N)Cl]⁺ complexes are at less positive potential than for the [Os(dpop′)₂]²⁺ ion. NMR results show different chemical shifts for ring protons either trans or cis to dpop′ in mixed ligand systems, and also show two geometrical isomers for the [Os(dpop′)(dpp)Cl]⁺ complex. The [Os(dpop′)(dpp)Cl]⁺ geometric isomer with the pyrazine ring of dpp trans to dpop′ is found more predominate by 1.0/0.7 over the isomer with the pyrazine ring of dpp cis to dpop′ and that inter-conversion of geometric isomers does not occur in room temperature solution on the NMR timescale.     

A family of polyamino phenolic macrocyclic ligands. Acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions

The acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) of four polyamino-phenol macrocycles 15-hydroxy-3,6,9-triazabicyclo[9.3.1]pentadeca-11,13,1¹⁵-triene L1, 18-hydroxy-3,6,9,12-tetraazabicyclo[12.3.1]octadeca-14,16,1¹⁸-triene L2, 21-hydroxy-3,6,9,12,15-pentaazabicyclo[15.3.1]enaicosa-17,19,1²¹-triene L3 and 24-hydroxy-3,6,9,12,15,18-hexaazabicyclo[18.3.1]tetraicosa-20,22,1²⁴-triene L4 are reported. The protonation and stability constants were determined by means of potentiometric measurements in 0.15 mol dm⁻³ NMe₄Cl aqueous solution at 298.1 K. L1 forms highly unsaturated Co(II), Cu(II), Zn(II) and Cd(II) mononuclear complexes that are prone to give dimeric dinuclear species with [(MH₋₁L1)₂]²⁺ stoichiometry, in solution. L2 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes that can coordinate external species as OH⁻ anion, giving hydroxylated complexes at alkaline pH. L3 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes and Co(II), Ni(II), Cu(II) and Zn(II) dinuclear [M₂H₋₁L3]³⁺ species. L4 forms stable mono- and dinuclear Co(II), Cu(II), Zn(II) and Cd(II) complexes, but only mononuclear species with Pb(II). The effect of macrocyclic size is considered in the discussion of results.     

Synthesis and coordination behaviors of 14-membered tetraaza macrocyclic copper(II) complexes bearing two N-propionic acid or N-propionic methyl ester groups

A di-N-functionalized 14-membered tetraaza macrocycle, [H₄L³](ClO₄)₂ (L³ = 1,8-bis(2-carboxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane), has been synthesized by acid hydrolysis of 1,8-bis(2-cyanoethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L²). The copper(II) complexes [CuL²](ClO₄)₂ and [Cu(H₂L³)](ClO₄)₂ were prepared and characterized. The complex [Cu(H₂L³)]²⁺ readily reacts with methanol to yield [CuL⁴]²⁺ (L⁴ = 1,8-bis(2-carbomethoxyethyl)-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane). The N-CH₂CH₂COOH groups of [Cu(H₂L³)](ClO₄)₂ are not coordinated to the metal ion in the solid state but are involved in coordination in various non-aqueous solvents or in aqueous solutions of pH ? 1.0. Interestingly, [CuL⁴](ClO₄)₂ exists as two stable structural isomers, 1 (the pendant ester groups are not involved in coordination) and 2 (one of the two ester groups is coordinated to the metal ion), in the solid state; the two isomers can be prepared selectively by controlling ionic strength of a methanol solution of the complex. Crystal structures and coordination behaviors of the two isomers are described. The di-N-cyanoethylated macrocyclic complex [CuL²](ClO₄)₂ is rapidly decomposed in 0.1 M NaOH solution even at room temperature. On the other hand, [Cu(H₂L³)](ClO₄)₂ and [CuL⁴](ClO₄)₂ are quite inert against decomposition under similar basic conditions. In acidic or basic aqueous solutions, [CuL⁴]²⁺ is hydrolyzed to [Cu(H₂L³)]²⁺ or [CuL³].     

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L = 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L¹ (5,7-dimethyl-3-(2′,3′,5′-tri-O-benzoyl-β-d-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L² (5,7-dimethyl-3-β-d-ribofuranosyl-s-triazolo[4,3-a]pyrimidine) and L³ (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L¹)](NO₃)₂, [Pd(bpy)(L¹)](NO₃)₂, cis-Pd(L³)₂Cl₂, [Pd₂(L³)₂Cl₄] · H₂O, cis-Pd(L²)₂Cl₂ and [Pt₃(L¹)₂Cl₆] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd₂(L³)₂Cl₄] · H₂O complex was established by X-ray crystallography. The two L³ ligands are found in a head to tail orientation, with a Pd?Pd distance of 3.1254(17) Å. L¹ coordinates to Pd(II) through N8 and N1 forming polymeric structures. L² coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L² does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond.     

Preparation, crystal structures and spectroscopic properties of novel [MCl3 − n(P)3 + n] (M = Co, Rh; n = 0, 1, 2 or 3) series of complexes containing tripodal tridentate phosphine, 1,1,1-tris(dimethylphosphinomethyl)ethane

Cobalt(III) and rhodium(III) complexes of the series of [M^IIICl_3 − n(P)_3 + n]ⁿ⁺ (M = Co or Rh; n = 0, 1, 2 or 3) have been prepared with the use of 1,1,1-tris(dimethylphosphinomethyl)ethane (tdmme) and mono- or didentate phosphines. The single-crystal X-ray analyses of both series of complexes revealed that the M-P and M-Cl bond lengths were dependent primarily on the strong trans influence of the phosphines, and secondarily on the steric congestion around the metal center resulting from the coordination of several phosphine groups. In fact, the M-P(tdmme) bonds became longer in the order of [MCl₃(tdmme)] < [MCl₂(tdmme)(PMe₃)]⁺ < [MCl(tdmme)(dmpe)]²⁺ (dmpe = 1,2-bis(dimethylphosphino)ethane) < [M(tdmme)₂]³⁺ for both Co^III and Rh^III series of complexes, while the M-Cl bond lengths were shortened in this order (except for [M(tdmme)₂]³⁺). Such a steric congestion around the metal center can also account for the structural and spectroscopic characteristics of the series of complexes, [MCl(tdmme)(dmpm, dmpe or dmpp)]²⁺ (dmpm = bis(dimethylphosphino)methane, dmpp = 1,3-bis(dimethylphosphino)propane). The X-ray analysis for [CoCl(tdmme)(dmpm or dmpe)](BF₄)₂ showed that all Co-P bonds in the dmpm complex were shorter by 0.03-0.04 Å than those in the dmpe complex. Furthermore, the first d-d transition energy of the Co^III complexes and the ¹J_Rh-P(tdmme) coupling constants observed for the Rh^III complexes indicated an unusual order in the coordination bond strengths of the didentate diphosphines, i.e., dmpm > dmpe > dmpp.     

A preparative study of some coronands and their complexation of silver(I), zinc(II), cadmium(II) and lead(II)

A study of the complexation of heavy metal ions by the coronands 3,12,20,29-tetraoxa-35,36-diazapentacyclo[29.3.1.1.^14,18.0^5,10.0^22,27]-hexatriaconta-1(35),5(10),6,8,14,16,18(36),22(27),23,25,31,33-dodecaene (1); 2,3,11,12-bis (4^′-methylbenzo)-1,4,10,13-tetrathia-7,16-dioxacyclo-octadeca-2,11-diene (2); 7,16-diaza-1,4,10,13-tetraoxa-2,3,11,12-dibenzocyclooctadeca-2,11-diene (3); 2-[19-(2-hydroxy-2-phenylethyl)-7,8,9,10, 18,19,20,21-octahydro-6H,17H-dibenzo[b,k][1,4,10,13,7,16]tetraoxadiazacyclooctadecin-8-yl]-1-phenyl-1-ethanol (4); 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane (5); and 2-[16-(2-hydroxy-2-phenylethyl)-1,4,10,13-tetraoxa-7,16-diazacyclo-octadecanyl]-1-phenyl-1-ethanol (6) is described. Coronands 1 and 3 were prepared by literature methods, improved methods were used to prepare 2, and 4 and 6 were prepared from 3 and 5 (obtained commercially), respectively. Potentiometric studies in N,N-dimethylformamide yielded (logK/dm³ mol⁻¹)=5.50, 6.49, 9.42 and 7.52 for [Ag · 1]⁺, [Ag · 2]⁺, [Ag · 5]⁺ and [Ag · 6]⁺, respectively; <2, <2, 4.30 and <2 for [Zn · 1]²⁺, [Zn · 2]²⁺, [Zn · 5]²⁺ and [Zn · 6]²⁺, respectively, <2, <2, 5.92 and >7.52 for [Cd · 1]²⁺, [Cd · 2]²⁺, [Cd · 5]²⁺, and [Cd · 6]²⁺, respectively, and 2.62, 2.38, 6.71 and >7.52 for [Pb · 1]²⁺, [Pb · 2]²⁺, [Pb · 5]²⁺, and [Pb · 6]²⁺, respectively. ESI-MS studies of the interactions of 1-6 with Ag⁺, Zn²⁺, Cd²⁺ and Pb²⁺ are also reported.     

Synthesis and characterization of a topologically constrained tetraaza macropolycycle and its copper(II) complex

A new macropolycycle, 2,13-dimethyl-1,5,12,16-tetraazapentacyclo[14.6.2.2^5.12.0^6.11.0^17.22]hexacosane (L³), has been prepared by the reaction of 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0^7.12]docosane (L¹) with 1-bromo-2-chloroethane. The macropolycycle readily reacts with anhydrous copper(II) ion to yield [CuL³]²⁺ in dry methanol but does not with nickel(II) ion, showing a high copper(II) ion selectivity. Crystal structure of [CuL³](ClO₄)₂ shows that the complex has a distorted square-planar coordination polyhedron with a trans-IV type N-conformation. The Cu-N distances [1.989(3) and 2.015(3) Å] of [CuL³](ClO₄)₂ are distinctly shorter than those of [CuL¹](ClO₄)₂ and other related macrocyclic copper(II) complexes. The d-d transition band for [CuL³](ClO₄)₂ is observed at 447 nm, which is ca. 40 nm shorter than that for [CuL¹](ClO₄)₂.     

Synthesis, characterization and properties of iron(II) complexes with a series of tripodal ligands based on the parent ligand tris(2-pyridylmethyl)amine

Iron(II) complexes of the type [Fe(L)(NCS)₂] with the tripodal ligand apme (apme = N¹-(2-aminoethyl)-N¹-(2-pyridyl-methyl)-1,2-ethanediamine) as well as with its derivatives were prepared and structurally characterized. The bond distances thus obtained showed that all complexes investigated were high-spin at the respective temperature. Furthermore [Fe(Me₄apme)(NCS)₂] was analyzed using Mößbauer spectroscopy that showed that this complex remains in its high-spin state over the entire temperature range.     

Heterobimetallic M/Zn (M = Cu, Ni) complexes with open-chain N- and N,O-ligands: Template synthesis from metal powders and supramolecular crystal structures

A series of new heterometallic Cu^IIZn^II and Ni^IIZn^II complexes with N- and N,O open-chain multidentate ligands (L¹ = 4,6,6-trimethyl-1,9-diamino-3,7-diazanon-3-ene; L² = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3.3.1]nonane; L³ = 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetraazapentadec-6-ene and L⁴ = 1-hydroxy-9-oxy-4,6,6-trimethyl-3,7-diazanon-3-ene) have been prepared through the “direct template synthesis” approach, which is a combination of classical template reactions of amines with acetone/formaldehyde and the “direct synthesis” method based on using elemental metals as starting materials. There is a significant decrease in the reaction time when the “direct synthesis” method is used compared to the conventional template condensation methods. X-ray crystallographic analyses of the complexes with the general formula M(L)ZnX₄ and [CuL⁴ZnCl₃]₂ (M = Cu²⁺, Ni²⁺; L = L¹-L³; X = Cl⁻, NCS⁻) reveal the presence of long intermolecular distance interactions, such as semi-coordination, S?S and H-bonding, in their crystal organization.