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.     

Synthesis, Structure, and Reactivity of Enediyne Macrocycles

The reaction of bis-propargyl bromide enediyne 4 with weakly basic nucleophiles allows the facile synthesis of acyclic and macrocyclic enediynes. Depending on the bis-nucleophile employed, 12- to 16-membered enediyne macrocycles were obtained. The thermal stability of the new cyclic enediynes was investigated by differential scanning calorimetry. Upon coordination of the macrocycle 5c with Hg(O(2)CCF(3))(2), a drop of the enediyne cyclization temperature of nearly 100 K was observed.     

Preparation and characterization of mononuclear Co, Ni, and Zn complexes of dinucleating macrocyclic hexaaza-dithiophenolate ligands and their open-chain derivatives

The preparation and characterization of mononuclear complexes of the dinucleating 24-membered hexazadithiophenolate macrocycles H2L2 and H2L3 and their open-chain N3S2 analogues H2L4 and H2L5 are reported. The highly crystalline compounds [Ni(L4)] (4), [Ni(L5)] (5), [Co(L5)] (6), [NiH2(L2)]2+ (7), [ZnH2(L2)]2+ (8), and [NiH2(L3)]2+ (9) could be readily prepared by stoichiometric complexation reactions of the hydrochlorides of the free ligands with the corresponding metal(II) dichlorides and NEt3 in methanolic solution. All complexes were characterized by X-ray crystallography. Monometallic complexes 4-6 of the pentadentate ligands H2L4 and H2L5 feature distorted square pyramidal MN3S2 structures (tau = 0.01 to 0.44). Similar coordination geometries are observed for the macrocyclic complexes 7-9 of the octadentate ligands H2L2 and H2L3. The two hydrogen atoms in 7-9 are attached to the noncoordinating benzylic amine functions and are hydrogen bonded to the metal-bound thiophenolate functions. A comparison of the structures of 4-9 reveals that the macrocycles L2 and L3 have a rather flexible ligand backbone that do not confer unusual coordination geometries on the metal ions. We also report on the ability of the monometallic complexes 7 and 8 to serve as starting materials for the preparation of dinuclear complexes.     

Conformational and stereochemical flexibility in cadmium(II) complexes of aza-thioether macrocycles

The synthesis and crystal structures of four CdII macrocyclic complexes containing mixed N-, O- and S-donors, [Cd(NO3)2([12]aneN2S2)] (1), [Cd(NO3)2([12]aneNS3)] (2), [Cd(NO3)2([15]aneNO2S2)] (3) and [Cd(NO3)([15]aneN2O2S)]NO3 (4), are presented. The metal ion is coordinated outside of the macrocyclic cavity in the complexes of the smaller macrocycles ([12]aneN2S2 and [12]aneNS3) while the flexibility of the larger macrocycles in and allows very different conformations to be adopted with a 'butterfly' geometry in and a flattened geometry in. No correlation between the number of sulfur donors and Cd-S bond distance in these types of complexes is observed, although the number and binding mode of the nitrato ligands is determined by the conformation and binding mode of the macrocycle. The position of the nitrato ligand also influences, through steric conflicts with the macrocyclic donor atoms, the bond distances in both ligand systems.     

Interaction of Co(II), Ni(II) and Cu(II) with dibenzo-substituted macrocyclic ligands incorporating both symmetrically and unsymmetrically arranged N, O and S donors

The synthesis and characterisation of four 17-membered, dibenzo-substituted macrocyclic ligands incorporating unsymmetrical arrangements of their N(3)S(2), N(3)O(2) and N(3)OS (two ligands) donor atoms are described; these rings complete the matrix of related macrocyclic systems incorporating both symmetric and unsymmetric donor sets reported previously. The X-ray structures of three of the new macrocycles are reported. In two of the Cu(II) structures only three of the possible five donor atoms present in the corresponding macrocyclic ligand bind to the Cu(II) site, whereas all five donors are coordinated in each of the remaining complexes. The interaction of Co(II), Ni(II) and Cu(II) with the unsymmetric macrocycle series has been investigated by potentiometric (pH) titration in 95% methanol; X-ray structures of two nickel and three copper complexes of these ligands, each exhibiting 1:1 (M:L) ratios, have been obtained. The results are discussed in the context of previous results for these metals with the analogous 17-membered ring systems incorporating symmetrical arrangements of their donor atoms, with emphasis being given to both the influence of the donor atom set, as well as the donor atom sequence, on the nature of the resulting complexes.     

大环多胺配体BDBPH的设计合成及其晶体结构

用Pb(SN)₂作模板,2,6-二甲酰基对甲苯酚与二亚乙基三胺通过[2+2]缩合反应,经NaBH₄还原、脱Pb²⁺、酸化等操作,得晶体BDBPH·6HBr·4H₂O.晶体属单斜晶系,P2_1/c空间群,晶体学参数:a=1.4441(5)nm,b=1.1482(4)nm,c=1.2090(6)nm,α=90°,β=96.92°,γ=90°,V=1.9900nm³大环分子采取椅式构型,6个Br-和4个H₂O分子对称分布于大环两侧.该大环配体结构新颖,可用于多种金属配合物的研究,对进一步了解金属酶活性中心的结构及其催化作用机理具有重要价值.     

DOTP-manganese and -nickel complexes: from a tetrahedral network with 12-membered rings to an ionic phosphonate

DOTP (1,4,7,10-tetrakis(methylenephosphonic acid)-1,4,7,10-tetraazacyclododecane) was reacted hydrothermally with MnCl(2).2H(2)O and Ni(NO(3))(2).6H(2)O resulting in two structurally different compounds. Mn[C(3)NH(7)(PO(3)H(0.5))](4) crystallizes in the tetragonal space group P4/ncc, with a = 12.349(2) A, b = 12.349(2) A, c = 14.066(4) A, V = 2144.9(8) A(3), and Z = 4. Manganese atoms are tetrahedrally bonded by four phosphonate oxygen atoms from four equivalent ligands. All 12-membered macrocycles are connected in a "zigzag" manner by sharing manganese atoms and forming 22-membered cavities between each pair of two adjacent macrocycles. Ni[C(3)NH(6)(PO(3)H)](4)[Ni(H(2)O)(6)] crystallizes as an ion pair complex. Ni(1) is octahedrally coordinated to two pendent phosphonate oxygen atoms and four nitrogen atoms from the macrocyclic backbone. Ni(2) is surrounded by six coordinatedly bonded water molecules to form a hexaqua cation. The manganese complex shows ion exchange capability for Cs(+).     

Synthesis and Structure Elucidation of Large Phosphorus Macrocycles

The simple reaction between 1,ω-diamino derivatives and R-bis-(dimethylamino)-phosphane (R = CH₃, C₆H₅), followed by an oxidation step led to the formation of the expected macrocyclic phosphorus compounds. By this way 17- to 27-membered macrocycles were easily obtained. During the synthesis, the formation of dimeric (40- and 52-membered rings) and trimeric (78-membered rings) macrocyclic species were obtained from 3 and 5 and fully characterized by NMR and mass spectrometry. The P(III) phosphorus species exchange in solution and the macrocycle/oligomers ratio is temperature and concentration dependent. The crystal structure analysis of macrocycles 1, 5, 7 and 8 show that voids are minimized in the solid so that the macrocyclic cavity is filled up with part of the molecule itself or with a guest molecule, when the size of the macrocycle does not allow molecular folding for self-filling the cavity. Dedicated to the memory of Prof. Jean-Bernard Robert     

Exploring the interaction of mercury(II) by N(2)S(2) and NS(3) anthracene-containing macrocyclic ligands: photophysical, analytical, and structural studies

The complexation properties toward Hg(II) of six macrocyclic ligands, 3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1), 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L2), 7-(10-methyl-9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L3), 7,7'-[9,10-anthracenediylbis(methylene)]bis-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L4), 1,4,7-trithia-11-azacyclotetradecane (L5), and 11,-(anthracen-9-ylmethyl)-1,4,7-trithia-11-azacyclotetradecane (L6), were studied. The stoichiometries of the formed species were determined from absorption and fluorescence titrations. In these anthracene-containing macrocycles, a fluorescent quenching of the emission was found upon Hg(II) addition. The X-ray crystal structure of [HgCl2(L2)] x 1/2CH2Cl2 was determined. The asymmetric unit contains two independent [HgCl2(L2)] molecules and one dichloromethane molecule. Each Hg(II) ion is coordinated by the pyridine nitrogen, the two sulfur atoms of one L2 molecule, and two chloride ions. Analytical studies using solvent extraction separation of Hg(II) from aqueous solutions were performed to determine the Hg(II) extraction capability of ligands L1, L2, and L5.     

Crown compounds for anions. Sandwich complexes of cyclic trimeric perfluoro-o-phenylenemercury with hexacyanoferrate(III) and nitroprusside anions

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[(o-C₆F₄Hg)₃]₂[Fe(CN)₆]}³⁻ and {[(o-C₆F₄Hg)₃]₂[Fe(CN)₅NO]}²⁻, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe-C-N-Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host-guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.     

Copper(II) and nickel(II) complexes of binucleating macrocyclic bis(disulfide)tetramine ligands

Novel macrocyclic bis(disulfide)tetramine ligands and several Cu(II) and Ni(II) complexes of them with additional ligands have been synthesized by the oxidative coupling of linear tetradentate N2S2 tetramines with iodine. Facile demetalation of the Ni(II) oxidation products affords the free 20-membered macrocycles meso-9 and rac-9 and the 22-membered macrocycle 16, all of which are potentially octadentate N4S4 ligands. X-ray structure analyses reveal distinctly different conformations for the two isomers of 9; meso-9 shows a stepped conformation in profile with the disulfide groups corresponding to the rise of the step, whereas rac-9 exhibits a V conformation with the disulfide groups near the vertex of the V. No metal complexes of rac-9 have been isolated. Crystallographic studies of three Cu(II) complexes reveal that depending upon the size of the macrocyclic ligand and the nature of the additional ligands (I-, NCO-, and CH3CN), the Cu(II) coordination geometry shows considerable variation (plasticity), with substantial changes in the Cu(II)-disulfide bonding. Thus, a diiodide salt contains six-coordinate Cu(II) to which all four bridging disulfide sulfur atoms form strong equatorial bonds. In contrast, isocyanato complexes of the 20- and 22-membered macrocycles exhibit trigonal-bipyramidal Cu(II) and distorted cis-octahedral Cu(II) geometries, respectively, having only one and no short equatorially bound sulfur atoms. The coordination geometry of the latter complex can also be described as four-coordinate seesaw with two semicoordinated S(disulfide) ligands. Disulfide-->Cu(II) ligand-to-metal charge transfer absorptions of both isocyanato-containing Cu(II) species appear too weak to observe, probably because of poor overlap of the sulfur orbitals with the Cu(II) d-vacancy. The dual disulfide-bridged Ni(II) units of the crystallographically characterized octahedral Ni(II) complex of meso-9 with axial iodide and acetonitrile ligands promote substantial antiferromagnetic coupling (J = -13.0(2) cm-1).     

Bimetallic M(V)(2)Cu(II)(3) (M = Mo, W) coordination complexes based on octacyanometalates: structures and magnetic variations tuned by chelated tetradentate macrocyclic ligands

Four octacyanometalate-based bimetallic Cu-M (M = Mo, W) assemblies coordinated by tetradentate macrocyclic ligands were prepared via self-assembly process in a stoichiometric ratio of [M(CN)8]3- and Cu(macrocycle)2+ and characterized in terms of structures and magnetic properties. The crystal structures are varied depending on the macrocycles used. The employment of cyclam with no pendant groups produced a one-dimensional chain (1) with a rope-ladder pattern, whereas macrocycles with side groups allowed for the formation of two-dimensional honeycomb-like architectures (2-4). From the crystal structures, the variations in apical Cu-Nax lengths and Cu-Nax-Cax angles on the bridging pathways are observed, which arises from the existence of side groups on macrocyclic ligands. The magnetic results reveal that all of the prepared compounds show ferromagnetic couplings between magnetic centers transimitted through CN bridges under the present structural parameters. Comparing the magnetic strength of the Cu-Mo (3d-4d; 2) and Cu-W (3d-5d; 3) complexes supports that 3d-5d magnetic coupling is stronger than 3d-4d because the 5d orbital is more diffuse than 4d. The magnetic analyses for 1-4 and related complexes tentatively suggest that, when the Cu-Nax distances are long enough, the axial Cu-Nax bond length in the bridging route may be one of the major structural parameters to determine the magnitude of the ferromagnetic exchange coupling.     

Nickel(II) cyclidenes with appended ethylpyridine receptor centers as molecular tweezers for dicarboxylic acids

A series of 14-, 15-, and 16-membered nickel(II) cyclidene macrocycles appended with 2-aminoethyl(2-pyridine) receptors I-III, respectively, were prepared and characterized by X-ray crystallography and NMR techniques. The 14- and 15-membered macrocycles I and II exist in a planar or extended Z-configuration, whereas the 16-membered macrocycle III was saddle shaped and had two asymmetric configurations in the unit cell (IIIa in a "capped" configuration and IIIb in an "open" configuration). Variable-temperature (1)H NMR studies of III in CD(3)CN were conducted (25-65 degrees C), and at room temperature, the interconversion between capping and uncapping is slow on the NMR time scale, resulting in a broad spectrum, whereas at 65 degrees C, interconversion was fast. (1)H NMR binding studies indicated I-III bind unsaturated dicarboxylic acids in a 1:1 stoichiometry with binding constants approaching 400 M(-)(1) in CD(3)CN, and the binding strength was dependent on the shape of the macrocyclic cyclidene platforms, whereas monocarboxylic acids were not bound. Generally, the planar 14-membered cyclidene I bound diacids the weakest and the 16-membered cyclidene III bound diacids the strongest. The presence of nuclear Overhauser effect spectrometry cross peaks in a 20 mM solution of 1:1 II-maleic acid indicates that the binding mode is ditopic with the guest being encapsulated by the aminoethylpyridine arms above the macrocyclic framework.     

Syntheses and structural characterizations of 24-membered dimetal (Mn, Ni, Fe) macrocyclic complexes and the C-S bond formation between acetylacetone and a mercapto N-heterocycle

An organic ligand 2,5-di(3-pentanedionylthio)-1,3,4-thiadiazole (H2L) reacts with metal (Mn, Ni, Fe) salts, resulting in 24-membered dimetal macrocyclic complexes [MnL(H2O)(dmso)](2).2dmso, [NiL(H2O)(dmf)](2).2dmf, [MnL(dmf)2]2 and [Fe2L2(solvent)2(SO4)] (solvent=dmso; H2O ; dmf). Di-manganese macrocyclic complexes [MnL(dmf)(dmso)]2 and [MnL(H2O)2](2).6H2O can also be obtained directly by aerobic assembly reaction of MnCl2, dipotassium 1,3,4-thiadiazole-2,5-dithiolate (K2tdadt) and acetylacetone (H2acac) in various solvents, accompanying a C-S bond formation between acetylacetone and the mercapto N-heterocycle. Disulfide has been considered as the intermediate in the assembly reaction. Meanwhile an assembly reaction including MnCl2, 2-mercaptobenzimidazole and H2acac has produced an organic compound 2-(3-pentanedionylthio)benzimidazole with a new C-S bond. These dimetal complexes have similar macrocyclic structures, in which solvent molecules and sulfate coordinate to the octahedral metal in trans-configuration, whereas a pair of water molecules are located in octahedral cis-positions for owing to a small steric effect. A host cavity of sufficiently large size exists in the macrocyclic structure to trap the solvent molecules and the sulfate anion. The IR spectra have been used to assign the solvent molecules trapped and the sulfate anion which is shown as a bridged bidentate ligand. Thermal analyses show the stability of the macrocyclic backbone below 200 degrees C and gradual release processes of the trapped solvent molecules. Decomposition and oxidation of the dimetal macrocycle backbone occur at 300-500 degrees C, resulting in a metal sulfate. Further decomposition led to metal oxide at 500-600 degrees C.     

Synthesis, characterization, and structure of macrocyclic mono- and C2-symmetric, binuclear nickel calixsalen complexes

Mono- (3a,b) and binuclear (4a,b) tetradentate NiII complexes of a series of 26-membered macrocyclic salen dimers, [salen(CH2)]2, are prepared in good yield by solvent-controlled reaction with Ni(OAc)2. The mononuclear complex 3b crystallizes in the trigonal space group 3P1(#144), a = 18.2566(2) A, c = 15.9244(2) A, V = 4596.57(8) A3, and Z = 3. Refinement converged with R = 0.054 and Rw = 0.049 for 6852 reflections with I > 2.003 sigma(I). The NiII in complex 3b coordinates in an approximate square planar geometry to one of the two available tetradentate salen sites. Complex 4b crystallizes in the orthorhombic space group P2(1)2(1)2(1)(#19), a = 19.531(2) A, b = 22.891(3), c = 13.373(1) A, V = 5960(1) A3, and Z = 4. The refinement converged with R = 0.067 and Rw = 0.065 for 3752 reflections with I > 2.003 sigma(I). Complex 4b coordinates two distorted square planar, cofacially oriented NiII-salen units held 7.1 A apart by a rigid, syn-folded macrocyclic structure. The solution spectroscopic data and solid-state crystallographic data of 3b and 4b demonstrate the presence of a molecular-sized cavity which shows host-guest properties. Reaction of the flexible 32-membered disalen macrocycle [salen(OCH2CH2O)]2 with Ni(OAc)2 resulted in formation of a binuclear complex, 5. Complex 5 crystallizes in the triclinic space group P1(#1), a = 10.366(4) A, b = 12.170(3) A, c = 10.021(2) A, alpha = 106.29(2) degrees, beta = 91.69(2) degrees, gamma = 68.63(2) degrees, V = 1126.3(5) A3, and Z = 1. The refinement converged with R = 0.052 and Rw = 0.053 for 2385 reflections with I > 2.003 sigma(I). The binuclear complex 5 contains two cofacially oriented, square planar NiII-salen groups lying 3.5 A apart in an anti-folded macrocyclic structure.     

Protonation and Zn(II) coordination by dipyridine-containing macrocycles with different molecular architecture. A case of pH-controlled metal jumping outside-inside the macrocyclic cavity

The synthesis of the macrocyclic ligand 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridylophane (L3), which contains a pentaamine chain linking the 4,4'-positions of a 2,2'-dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6'-positions of 2,2'-dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens.     

Anion and carboxylic acid binding to monotopic and ditopic amidopyridine macrocycles

Binding of inorganic anions, carboxylic acids, and tetraalkylammonium carboxylates by macrocyclic compounds of different size was studied by NMR in DMSO-d6. It has been shown that at least a 15-membered ring is necessary for successful recognition of fluoride. Larger macrocycles were shown to bind HSO4(-), H2PO4(-), Cl(-), and carboxylic acid salts. Effects of binding topicity are discussed. The 30-membered macrocycles 4 and 4m selectively bind substrates that are size- and shape-complementary: maximum binding is observed for dicarboxylic acids and dicarboxylates with four-carbon chains, and the binding constant for association of fumaric acid and 4 is ca. 5 orders of magnitude higher than that of maleic acid. The 30-membered macrocycle 4m showed selectivity toward alpha-ketocarboxylic acids. Secondary amino groups were not crucial for binding of fluoride to the macrocycles; however, they proved to be very important for selectivity and strength of carboxylic acid binding. The X-ray structure of the adduct of 4 and nitrobenzoic acid confirmed the guest H-bonding with both the amide and the secondary amino groups of the 30-membered macrocyclic host.     

Efficient proton-templated synthesis of 18- to 38-membered tetraimino(amino)diphenol macrocyclic ligands: structural features and spectroscopic properties

A whole range of Robson-type tetraiminodiphenol macrocyclic ligands have been prepared as their perchlorate salts [H4L](ClO4)2 in high yield (ca. 90%) by a single-step [2 + 2] condensation reaction between 4-methyl(or tert-butyl)-2,6-diformyl(or diacyl)phenols and alpha,omega-diaminoalkanes (C2-C12) in the presence of acetic acid and NaClO4. The reduction of these 18- to 38-membered macrocyclic salts with NaBH4 have afforded corresponding tetraaminodiphenol macrocycles H2L'. The X-ray crystal structures of two of the tetraiminodiphenol macrocycles with the C2 and C4 lateral chains have been determined, and the optimized configurations for all of the macrocycles have been obtained by molecular mechanics calculations. The macrocycles have been characterized by elemental analysis and by IR, absorption, emission, and NMR spectroscopic study. The protonated tetraiminodiphenol macrocycles exhibit strong fluoroscence in methanol, acetonitrile, and nitromethane and undergo quenching when treated with triethylamine. The neutral macrocycles H2L, isolated by treating [H4L](ClO4)2 with excess of triethylamine, lack luminescence, as do the reduced tetraaminodiphenol macrocycles H2L'. The hydrolytic cleavage of [H4L](ClO4)2 has been studied.     

Synthesis and Properties of 5-Chloro-8-hydroxyquinoline-Substituted Azacrown Ethers: A New Family of Highly Metal Ion-Selective Lariat Ethers

New 5-chloro-8-hydroxyquinoline (CHQ)-substituted aza-18-crown-6 (4), diaza-18-crown-6 (1), diaza-21-crown-7 (2), and diaza-24-crown-8 (3) ligands, where CHQ was attached through the 7-position, and aza-18-crown-6 (11) and diaza-18-crown-6 (10) macrocycles, where CHQ was attached through the 2-position, were prepared. Thermodynamic quantities for complexation of these CHQ-substituted macrocycles with alkali, alkaline earth, and transition metal ions were determined in absolute methanol at 25.0 degrees C by calorimetric titration. Two isomers, 1 and 10, which are different only in the attachment positions of the CHQ to the parent macroring, exhibit remarkable differences in their affinities toward the metal ions. Compound 1 forms very stable complexes with Mg(2+), Ca(2+), Cu(2+), and Ni(2+) (log K = 6.82, 5.31, 10.1, and 11.4, respectively), but not with the alkali metal ions. Ligand 10 displays strong complexation with K(+) and Ba(2+) (log K = 6.61 and 12.2, respectively) but not with Mg(2+) or Cu(2+). The new macrocycles and their complexes have been characterized by means of UV-visible and (1)H NMR spectra and X-ray crystallography. New peaks in the UV spectrum of the Mg(2+)-1 complex could allow an analytical determination of Mg(2+) in very dilute solutions in the presence of other alkali and alkaline earth metal cations. (1)H NMR spectral and X-ray crystallographic studies indicate that ligand 10 forms a cryptate-like structure when coordinated with K(+) and Ba(2+), which induces an efficient overlap of the two hydroxyquinoline rings. Such overlapping forms a pseudo second macroring that results in a significant increase in both complex stability and cation selectivity.     

Macrocyclic diorganotin complexes of gamma-amino acid dithiocarbamates as hosts for ion-pair recognition

The dimethyl-, di-n-butyl-, and diphenyltin(IV) dithiocarbamate (dtc) complexes [{R2Sn(L-dtc)}x] 1-7 (1, L = L1, R = Me; 2, L = L1, R = n-Bu; 3, L = L2, R = Me, x = infinity; 4, L = L2, R = n-Bu; 5, L = L3, R = Me, x = 2; 6, L = L3, R = n-Bu, x = 2; 7, L = L3, R = Ph, x = 2) have been prepared from a series of secondary amino acid (AA) homologues as starting materials: N-benzylglycine (alpha-AA derivative = L1), N-benzyl-3-aminopropionic acid (beta-AA derivative = L2), and N-benzyl-4-aminobutyric acid (gamma-AA derivative = L3). The resulting compounds have been characterized by elemental analysis, mass spectrometry, IR and NMR ((1)H, (13)C, and (119)Sn) spectroscopy, thermogravimetric analysis, and X-ray crystallography, showing that in all complexes both functional groups of the heteroleptic ligands are coordinated to the tin atoms. By X-ray diffraction analysis, it could be shown that [{Me2Sn(L2-dtc)}x] (3) is polymeric in the solid state, while the complexes derived from L3 (5-7) have dinuclear 18-membered macrocyclic structures of the composition [{R2Sn(L3-dtc)}2]. For the remaining compounds, it could not be established with certainty whether the structures are macrocyclic or polymeric. A theoretical investigation at the B3LYP/SBKJC(d,p) level of theory indicated that the alpha-AA-dtc complexes might have trinuclear macrocyclic structures. The macrocyclic complexes 5-7 have a double-calix-shaped conformation with two cavities large enough for the inclusion of aliphatic and aromatic guest molecules. They are self-complementary for the formation of supramolecuar synthons that give rise to 1D molecular arrangements in the solid state. Preliminary recognition experiments with tetrabutylammonium acetate have shown that the [{R2Sn(L3-dtc)}2] macrocycles 6 and 7 might interact simultaneously with anions (AcO(-)), which coordinate to the tin atoms, and organic cations (TBA(+)), which accommodate within the hydrophobic cavity (ion-pair recognition).