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 and metal-ion binding properties of new N2S4- and N2S5-donor macrocycles

Synthetic procedures for new N₂S₄- and N₂S₅-donor macrocycles (2 and 4) were given. The ligands were prepared by the reaction of NaBH₄ with the appropriate macrocyclic diamide in the presence of boron trifluoride ethyl etherate in dry tetrahydrofuran (THF). Solvent extraction method was used to evaluate metal-ion binding properties of the new ligands. The solvent extraction experiments suggested that the reduced macrocycles have Ag⁺ and Hg²⁺ selectivities compared to Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺, Cu²⁺, Mn²⁺ and Cd²⁺ ions. The extraction constants (log K _ex) and complex compositions were determined for Ag⁺ and Hg²⁺ complex of compound (4).     

Ligand- and anion-directed assembly of exo-coordinated mercury(II) halide complexes with O2S2-donor macrocycles

Assembly reactions of mercury(II) halides (Cl, Br, and I) with two O2S2 macrocycles (L(1) and L(2)) having different interdonor (S...S) distances were investigated, and four types of supramolecular complexes (1-4b) were obtained depending on the S...S distances as well as the size of the halide anions. Photoluminescence of these compounds was also studied.     

A study of the complexation and extraction of Cu(II) sulfate and Ni(II) sulfate by N3O2-donor macrocycles

Comparative solvent extraction (water/chloroform) studies of Ni(II) and Cu(II) employing a dinonyl-substituted N3O2-donor macrocycle (L2) as extractant have been undertaken from sulfate, chloride, nitrate and acetate-containing aqueous media. Contrary to expectations, efficient extraction of both metal sulfates was observed, the degree of extraction being comparable (or slightly enhanced) relative to that observed for each of the other anionic systems. X-Ray diffraction studies of [NiL1(H2O)3]SO4 x 4H2O and [CuL1(H2O)]SO4 x 6.67 H2O (where L1 is the unsubstituted derivative of L2) show that each complex occurs as a hydrogen-bonded 'cluster', with the sulfate anions involved in hydrogen bonded networks that incorporate ligand amine protons and water molecules; in the copper complex, which adopts a dimeric arrangement, simultaneous sulfate binding to a copper site is also present. In each complex the macrocyclic ligand fails to coordinate via its ether oxygen donors but instead is arranged so that the metal ion and sulfate anions are somewhat shielded hydrophobically from the exterior of the complex cluster assembly.     

Cadmium(II) and mercury(II) complexes of an NO2S2-donor macrocycle and its ditopic xylyl-bridged analogue

The NO2S2-donor macrocycle (L1) was synthesised from the ring closure reaction between Boc-N-protected 2,2'-iminobis(ethanethiol) (3) and 2,2'-(ethylenedioxy)bis(benzyl chloride) (4) followed by deprotection of the Boc-group. alpha,alpha'-Dibromo-p-xylene was employed as a dialkylating agent to bridge two L1 to yield the corresponding N-linked product (L2). The X-ray structure of L2 (as its HBr salt) is described. A range of Cd(II) and Hg(II) complexes of L1 (6-9) and L2 (10-12) were prepared and characterised. Reaction of HgX2 (X = Br or I) with L1 afforded [Hg(L1)Br]2[Hg2Br6].2CH2Cl2 6 and [Hg(L1)I(2)] 7, respectively. For 6, the Hg(II) ion in the complex cation has a distorted tetrahedral coordination environment composed of S2N donor atoms from L1 and a bromo ligand. In 7 the coordination geometry is highly distorted tetrahedral, with the macrocycle coordinating in an exodentate manner via one S and one N atom. The remaining two coordination sites are occupied by iodide ions. [Hg(L1)(ClO4)]ClO4 8 was isolated from the reaction of Hg(ClO4)2 and L1. The X-ray structure reveals that all macrocyclic ring donors bind to the central mercury ion in this case, with the latter exhibiting a highly distorted octahedral coordination geometry. The O2S2-donors from the macrocyclic ring define the equatorial plane while the axial positions are occupied by the ring nitrogen as well as by an oxygen from a monodentate perchlorato ion. Reaction of Cd(NO3)(2).4H2O with L1 afforded [Cd(L1)(NO3)2](.)0.5CH2Cl2 9 in which L1 acts as a tridentate ligand, binding exo-fashion via its S2N donors. The remaining coordination positions are filled by two bidentate nitrate ions such that, overall, the cadmium is seven-coordinate. Reactions of HgX2(X = Br or I) with L2 yielded the isostructural 2 : 1 (metal : ligand) complexes, [Hg2(L2)Br4] 10 and [Hg2(L2)I(4)] 11. Each mercury ion has a distorted tetrahedral environment made up of S and N donors from an exodentate L2 and two coordinated halides. Contrasting with this, the reaction of L2 with Cd(NO3)(2).4H2O yielded a 1-D coordination network, {[Cd2(L2)(NO3)4].2CH2Cl2}n 12 in which each ring of L2 is exo-coordinated via two S atoms and one N atom to a cadmium ion which is also bound to one monodentate and one bidentate nitrate anion. The latter also has one of its oxygen atom attached to a neighboring cadmium via a nitroso (mu2-O) bridge such that the overall coordination geometry about each cadmium is seven-coordinate. The [Cd(L2)0.5(NO3)2] units are linked by an inversion to yield the polymeric arrangement.     

Thermodynamic properties of second generation poly(phenylene-pyridyl) dendrimer

The temperature dependence of heat capacity C _p ^o = f (T) of second generation hard poly(phenylene-pyridyl) dendrimer (G2-24Py) was measured by a adiabatic vacuum calorimeter over the temperature range 6–320 K for the first time. The experimental results were used to calculate the standard thermodynamic functions: heat capacity C _p ^o (T), enthalpy H ^o(T)–H ^o(0), entropy S ^o(T)–S ^o(0) and Gibbs function G ^o(T)–H ^o(0) over the range from T → 0 K to 320 K. The standard entropy of formation at T = 298.15 K of G2-24Py was calculated. The low-temperature heat capacity was analyzed based on Debye’s heat capacity theory of solids. Fractal treatment of the heat capacity was performed and the values of the temperature characteristics and fractal dimension D were determined. Some conclusions regarding structure topology are given.     

C-取代二氧三胺大环配体合成及其Cu(II)配合物性质研究

本文合成了1, 4, 7-三氮杂环十烷-8, 10-二酮(td)和9-(2'-羟基苄基)-1, 4, 7-三氮杂环十烷-8, 10-二酮(btd)两个新型二氧三胺大环配体, 经元素分析, IR, 1H NMR以及MS等方法表征。采用分子力学方法探讨了取代基对配体合成的影响。利用pH法, 在25.0±0.1℃,I=0.1mol/L KNO3条件下, 测定了配体btd的质子化常数及其与Cu(II)配位的平衡常数。结合光谱滴定及配合物EPR结果, 讨论了二氧三胺大环配体与Cu(II)离子的配位方式。     

Planar Ni(II) 1,2-dithiolenes involving bidentate N -donor ligands

A series of planar Ni(II) dithiolenes derived from maleonitriledithiole (mnt), benzene-1,2-dithiole (bdt) and 1-toluene-3,4-dithiole (tdt) with bidentate N,N-ligands (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline, nphen = 5-nitro-1,10-phenanthroline) of the [Ni(N,N)(dithiol)] type have been synthesized. The compounds have been characterized by elemental analysis, IR and electronic spectroscopies, magnetochemical and conductivity measurements. Single crystal X-ray analysis of [Ni(phen)(bdt)] confirmed a planar geometry of NiN₂S₂. Possible practical applications such as use for vulcanization catalytic agents and for their anticholinesterase activity were evaluated.     

Metal complexes of sulfur-nitrogen chelating agents. Part 12. The chemistry of nickel(II), palladium(II), cobalt(II) and copper(II) complexes of N2S2 and N3S2 donor systems

Summary Nickel(II), palladium(II), cobalt(II) and copper(II) complexes of the ligandN,N-1,2-propane-bis(methyl 2-amino-cyclopent-1-ene-dithiocarboxylate) (H₂L¹),N,N-1,3-propane-bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate) (H₂L²) andN,N-[bis(methyl 2-aminocyclopent-1-ene-dithiocarboxylate)] diethylenetriamine (H₂L³) have been synthesised. Both H₂L¹ and H₂L² form complexes of the type ML, and all but the copper(II) complexes, are square planar. In the copper(II) complexes tetrahedral distortion is significantly more with CuL². From H₂L³ square planar complexes of the type [M(HL³)X] (M=Ni, X=Cl, Br, I or SCN; M=Pd, X=Cl or Br) have been obtained in which the donor unit involved is N₂SX. The composition of the cobalt(II) and copper(II) complexes is [M(H₂L³)X₂] (X=Cl or Br) which contain the chromophore [MN₃X₂].     

Chemical and spectroscopic studies of a new palladium(II) complex with N -acetyl-L-cysteine

Chemical and spectroscopic studies of a new palladium(II) N-acetyl-L-cysteine complex are described. Elemental analyses for the solid complex are consistent with the formula [Pd(C₅H₈NO₃S)₂]?·?H₂O or [Pd(NAC)₂]?·?H₂O. Solid-state ¹³C nuclear magnetic resonance (NMR), UV–Visible (UV–Vis) and infrared (IR) spectroscopic analyses are consistent with coordination of the ligand to palladium(II) through the nitrogen and sulfur atoms in a square-planar geometry. Thermogravimetric and differential thermal analyses confirmed the composition; final residue was identified as metallic palladium.     

A new iso-amyl benzothiazolyl sulfoxide as an extractant for palladium and the crystal structure of its palladium (II) complex

A new iso-amyl benzothiazolyl sulfoxide (ABSO) was synthesized and used in the extraction of Pd(II) from hydrochloric acid media. Pd(II) was extracted quantitatively from 0.1 M HCl with ABSO in benzene (0.5 M). Ammonia solution (2.0 M) could be used as stripping agent. ABSO and Pd(II) form a 2:1 adduct [Pd (ABSO)2Cl2] in the extraction. X-ray crystal structure determination revealed PdCl2(ABSO)2 is a square-planar complex in which ABSO acts as a neutral unidentate ligand coordinated with palladium(II) via the thiazolyl N atom.     

Structurally characterized dinuclear zinc(II) and copper(II) coumarin-based N2O2-donor complexes: syntheses,Hirshfeld analyses and fluorescent properties

Transition Metal Chemistry - Two newly designed dinuclear ZnII and CoII complexes [Co2(L)2]·H2O (1) and [Zn2(L)2]·H2O (2) of a coumarin-based N2O2-donor ligand H2L...     

Coordination behavior of symmetrical hexadentate O2N2S2-donor Schiff bases toward zinc (II): synthesis,characterization, and crystal structure

Two series of zinc(II) complexes of two Schiff bases (H₂L¹ and H₂L²) formulated as [Zn(HL¹/HL²)]ClO₄ (1a and 1b) and [Zn(L¹/L²)] (2a and 2b), where H₂L¹ = 1,8-bis(salicylideneamino)-3,6-dithiaoctane and H₂L² = 1,9-bis(salicylideneamino)-3,7-dithianonane, have been prepared and isolated in pure form by changing the chemical environment. Elemental, spectral, and other physicochemical results characterize the complexes. A single crystal X-ray diffraction study confirms the structure of [Zn(HL¹)]ClO₄ (1a). In 1a, zinc(II) has a distorted octahedral environment with a ZnO₂N₂S₂ chromophore.     

Template effects in S(N)2 displacements for the preparation of pseudopeptidic macrocycles

Macrocyclisation reactions of C(2)-symmetric pseudopeptides containing central pyridine-derived spacers are affected by the presence of different anions. The selection of the proper anion gives excellent results for the preparation of the corresponding macrocyclic structures. Kinetic studies show that the presence of those anions enhances both the yield and the rate of the reaction. Computational studies at the B3LYP/6-31G* level have allowed us to rationalise the experimental results. The obtained transition states (TSs) show that the interaction between the anion and the open-chain pseudopeptidic chain has a stabilising effect. The anion stabilises the two TSs involved: the first one, which involves the formation of the initial bond between the two subunits and leads to an open-chain intermediate, and the second one, which precedes the formation of the cyclic structure. The optimum anion (Br(-) when the central spacer is derived from 2,6-bis(aminomethyl)pyridine, is able to act as a template, in that it forces the two ends of the open-chain intermediate to approach each other by forming hydrogen bonds with the two amino acid subunits present in the intermediate. This stabilises the second TS to a greater extent than the first one, and thus, favours macrocyclisation over the competing oligomerisation reactions. The computational calculations also allowed us to predict the outcome of new experiments. Accordingly, the synthesis of the pseudopeptidic macrocycle derived from 2,6-diaminopyridine was not successful under the optimised conditions previously used. Nevertheless, calculations predicted that in this case Cl(-) should be more efficient than Br(-), and this was subsequently experimentally confirmed. Interestingly, the presence of different substituents on the constituent amino acids seems to play a minor role in the overall process.