Crystallographic and structural characterization of heterometallic platinum complexes Part VI. Heterohexanuclear complexes

This review classifies and analyzes heterohexanuclear platinum clusters into seven types of metal combinations:Pt₅M, Pt₄M₂, Pt₃M₃, Pt₂M₄, PtM₅, Pt₂M₃M′, and Pt₂M₂M₂′. The crystals of these clusters generally belong to six crystal classes: monoclinic, triclinic, orthorhombic, tetragonal, trigonal and cubic. Among the wide range of stereochemistry adopted by these clusters, octahedral and capped square-pyramidal are the most common. Although platinum is classified as a soft metal atom, it bonds to a variety of soft, borderline and hard metals. Nineteen different heterometal ions are involved in hexanuclear platinum clusters. The shortest Pt-M bond distance in the case of M being a non-transition element is 2.395(4) Å for germanium and for M being a transition metal ion it is 2.402(2) Å for Cobalt. The shortest Pt-Pt bond distance observed in these clusters is 2.532 Å. Several relationships between the structural parameters are identified and discussed. Some clusters exist in two isomeric forms and some show crystallographically independent molecules within the same crystal. Such isomers and independent molecules are examples of distortion isomerism.      

Crystallographic and structural characterization of heterometallic platinum compounds part IV: heterotetranuclear clusters

This review includes over two hundred heterotetranuclear platinum clusters. The clusters are of the compositions Pt₃M, Pt₃M₂, PtM₃, Pt′₂MM′, PtM₂M′ and PtMM′M”. There are twenty five different M atoms (transition and non-transition) as a partner(s) of platinum. The four metal atoms are found in a tetrahedral, planar-rhombohedral, butterfly, spited-triangular, cubane, eight — and oligo-membered rings and a unique structures. There is wide variety of the ligands from uni to- undecadentate, with the most common P and C donor sites. The shortest Pt-M (transition) versus Pt-M (non-transition) bond distances are 2.4833(8)Å (M=Pd) vs. 2.4365(5)Å (Ge). Several relationships between the various structural parameters were found and are discussed.      

Crystalographic and structural characterization of heterometallic platinum compounds. Part III: heterotrinuclear compounds

This review article includes over three hundred and sixty heterotrinuclear platinum complexes of the composition Pt₂M (205 examples), PtM₂ (132 examples) and PtMM (24 examples). The heterometals include the non-transition and transition metals. Three metal atoms form a wide variability of frameworks: M₃ triangular, dicapped M₃ triangular, V shaped M₃, M₃ linear, five-, six- and seven- metallocycles and unique structures of which triangular and linear are the most common. This has led to a rich chemistry of platinum not only from variability of metals, but also from their framework and stereochemistry. The shortest Pt-M (non-transition) and Pt-M (transition) bonds are 2.315(1) Å for Pt-Ga and 2.4896(9) Å for Pt-Co. The shortest Pt-Pt bond distance is 2.581(1) Å. Two complexes exist in two isomeric forms and several others contain crystallographically independent molecules. All are typical examples of distortion isomerism. Correlations between structural parameters, heterometal and ligand donor atoms are developed and discussed.      

Crystal structures and spectral properties of new Cd(II) and Hg(II) complexes of monensic acid with different coordination modes of the ligand

The single crystal X-ray structures and the spectroscopic properties of complexes of monensic acid (C₃₆H₆₂O₁₁·H₂O) with toxic metal ions of Cd(II) and Hg(II) are discussed. The cadmium(II) complex (1) is of composition [Cd(C₃₆H₆₁O₁₁)₂(H₂O)₂] and crystallizes in the monoclinic system (space group P2(1), Z = 2) with a = 12.4090(8), b = 24.7688(16), c = 14.4358(11) Å, β = 91.979(7)°. Two ligand monoanions are bound in a bidentate coordination mode to Cd(II) via the carboxylate and the primary hydroxyl oxygens occupying the equatorial plane of the complex. The axial positions of the inner coordination sphere of Cd(II) are filled by two water molecules additionally engaged in intramolecular hydrogen bonds. The Hg(II) complex (2), [Hg(C₃₆H₆₀O₁₁)(H₂O)], crystallizes in the orthorhombic system (space group P2(1)2(1)2(1), Z = 4) with a = 12.7316(2), b = 16.4379(3), c = 18.7184(4) Å. The monensic acid reacts with Hg(II) in a tetradentate coordination manner via both oxygen atoms of the carboxylate function and oxygens of two hydroxyl groups. The twofold negative charge of the ligand is achieved by deprotonation of carboxylic and secondary hydroxyl groups located at the opposite ends of the molecule. Hg(II) is surrounded by five oxygen atoms in a distorted square pyramidal molecular geometry.

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Synthesis and molecular and crystal structures of binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione

Binuclear complexes of Sm(III), Eu(III), Gd(III), Tb(III), and Dy(III) nitrates with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione (C₁₁H₂₀N₄O₂, SC)—[Sm(NO₃)₃(SC)(H₂O)]₂(I), [Eu(NO₃)₃(SC)(H₂O)]₂ (II), [Gd(NO₃)₂(SC)(H₂O)₃)]₂(NO₃)₂ (III), [Tb(NO₃)₃(SC)(H₂O)]₂ (IV), [Dy(NO₃)₃(SC)(H₂O)]₂ (V), are synthesized, and their X-ray diffraction analyses are carried out. The crystals of complexes I–V are monoclinic: space group P2₁/n for III and P2₁/c for I, II, IV, and V. In centrosymmetric coordination complexes II, III, IV, and V, the Ln atoms are coordinated by two O(1) and O(2) atoms of two molecules of the SC ligands bound by a symmetry procedure (1 ? x, ?y, 1 ? z), three bidentate nitrate anions, and a water molecule. The coordination numbers of the metal atoms are equal to 9, and the coordination polyhedra are considerably distorted three-capped trigonal prisms, whose bases include the O(1), O(2), O(12) and O(3), O(7), O(9) atoms. The dihedral angle between the bases of the prism is 18°, and that between the mean planes of the side faces is 55°–71° for I, 17° and 55°–71° for II, 16° and 55°–70° for IV, and 16° and 55°–70° for V. The Sm...Sm distance in complex I is 9.44 Å, Eu...Eu in II is 9.42 Å, Tb...Tb in IV is 9.36Å, and Dy...Dy in V is 9.36Å. The gadolinium atom in complex III is coordinated by two oxygen atoms of two ligand molecules bound by a symmetry procedure (?x, ?y + 1, ?z + 1), two bidentate nitrate anions, and three water molecules. One of the nitro groups in compound III is localized in the external coordination sphere of the metal. The coordination number of gadolinium is 9, and the coordination polyhedron is a significantly distorted three-capped trigonal prism, whose base includes the O(1), O(2), O(7) and O(4), O(5), O(9) atoms. The dihedral angle between the bases of the prism is 22.8°, and that between the mean planes of the side faces is 53°–72°. The Gd...Gd distance in complex III is 9.17 Å.     

The crystal structure of Sm4Ni11In20 and its relation to other indium-rich compounds

Polycrystalline Sm₄Ni₁₁In₂₀ was obtained by arc-melting of metal ingots. A subsequent high temperature treatment was used for single crystal growth. The Sm₄Ni₁₁In₂₀ crystal structure (U₄Ni₁₁Ga₂₀ type; C2/m, a = 22.5457(3) Å, b = 4.34929(5) Å, c = 16.5479(2) Å, β = 124.592(2)°, R1 = 0.0358, wR2 = 0.0934) was determined by single crystal synchrotron radiation X-ray diffraction from 2014 independent reflections with I > 2σ(I). Sm₄Ni₁₁In₂₀ extends the R ₄Ni₁₁In₂₀ (R = Y, Gd, Tb, Dy, Ho) series of phases. The R ₄Ni₁₁In₂₀ and RNi₃In₆ (LaNi₃In₆ type; R = La, Ce, Pr, Nd, Eu) series have similar compositions. Their structures share similar fragments; in particular the rare earth atom coordination polyhedra are pentagonal prisms with additional atoms.      

Crystal and molecular structures of bis(2,2,6,6-tetramethyl-3-methylaminoheptan-5-onate) copper(II) and nickel(II)

Two bis-chelates M(tmih)₂ (M = Cu(II), Ni(II), tmih = (CH₃)₃C(NCH₃)CHCOC(CH₃)₃)^? are synthesized and their crystal structures are determined using XRD (Bruker APEX-II diffractometer with a CCD detector, λMoK _α, λCuK _α, graphite monochromator, T = 240(2) K and 296(2) K): Cu(tmih)₂ (I) (space group P2₁/c, a = 12.9670(8) Å, b = 18.4921(9) Å, c = 11.0422(6) Å, β = 93.408(4)°, V = 2643.1(3) ų, Z = 4) and Ni(tmih)₂ (II) (space group P2₁/c, a = 12.810(2) Å, b = 18.529(2) Å, c = 11.243(2) Å, β = 91.959(7)°, V = 2667.1(6) ų, Z = 4). The complexes are isostructural; the coordination polyhedron of metal atoms is a flattened tetrahedron formed from two O atoms (Cu-O of 1.901(2) Å, 1.892(2) Å, Ni-O of 1.845(2) Å, 1.833(2) Å) and two N atoms (Cu-N of 1.976(3) Å, 1.972(3) Å, Ni-N of 1.911(2) Å, 1.920(2) Å) of the ligand; the chelate OMN angles (M = Cu(II), Ni(II)) are in the 87.4–93.1° range; the OMO and NMN angles are 162.2° and 167.2° in I, 171.1° and 173.2° in II. The complexes have the molecular structures formed from isolated molecules bonded by van der Waals interactions. Using a quantum chemical hybrid M06 method, the structures of copper(II) chelates with the H, CH₃, CH₂CH₃, CH(CH₃)₂, and C(CH₃)₃ substituents at the nitrogen atom are calculated. Found that with a bulky substituent at the nitrogen atom, the formation of chelates is hindered due to the intraligand repulsion between the atoms of this substituent and the tert-butyl group.     

Comparative study of layered tetravalent metal phosphates containing various first-row divalent metals. Synthesis, crystalline structure

The transition metal forms of α-zirconium-. titanium-, and hafnium phosphates were prepared by ion exchange method. Their structure was investigated by X-ray powder diffraction (XRPD) method. It was found that the transition metal containing phosphates have the same layered structure as the pristine tetravalent metal phosphates, except for the increase of interlayer distance from 7.6 Å to ～9.5 Å. As a result of the incorporation of transition metals in the layers, the c-axis is increased from ～15 Å to ～20 Å (in the case of titanium phosphate to ～25 Å). All other parameters (a, b and β °) are practically unchanged.      

Crystal structures of 3-phenylpropenal thiosemicarbazone and its nickel and zinc chelates

3-Phenylpropenal thiosemicarbazone hydrate C₆H₅-HC=CH-CH=N-NH-C(S)-NH₂ · H₂O (HL · H₂O, I) and two chelates [Ni(L)₂] · nCH₃OH (II) and [Zn(L)₂] (III) are studied by X-ray diffraction. The crystals of I are orthorhombic: a = 6.227(1) Å, b = 7.763(2) Å, c = 25.585(5) Å, β = 90°, space group P2₁2₁2₁, Z = 4, R = 0.0426. A nonplanar molecule of I has an E conformation. The crystals of II are triclinic: a = 6.551(2) Å, b = 10.752(3) Å, c = 10.885(3) Å, α = 64.751(5)°, β = 82.753(5)°, γ = 89.857(5)°, space group, Z = 1, R = 0.0661. In a centrosymmetric molecule of II, the central atom coordinates two deprotonated ligands L through the immine nitrogen atom and thioamide sulfur atom at the vertices of a distorted square. The crystals of III are monoclinic: a = 25.342(2) Å, b = 9.150(2) Å, c = 21.340(3) Å, α = 90°, β = 111.84(2)°, γ = 90°, space group C2/c, Z = 8, R = 0.0556. In a molecule of complex III, two deprotonated bidentate ligands L are coordinated by the zinc ion through the immine nitrogen atoms and thioamide sulfur atoms to form a distorted tetrahedron at the central atom. In both II and III, ligand L after coordination by the metal ion changes the E conformation with respect to the N(1)-C(2) bond for the Z conformation. In crystals I-III, molecules are packed to form infinite layers parallel to the planes (001) and (010).     

Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex

Electrocatalytic oxidation of sulfide ion on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNTs) and a copper (II) complex was investigated. The Cu(II) complex was used due to the reversibility of the Cu(II)/Cu(III) redox couple. The MWCNTs are evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on Cu(II) complex adsorbed on MWCNTs immobilized on the surface of GCE. The modified GCE was applied to the selective amperometric detection of sulfide at a potential of 0.47 V (vs. Ag/AgCl) at pH 8.0. The calibration graph was linear in the concentration range of 5 µM–400 µM; while the limit of detection was 1.2 µM, the sensitivity was 34 nA µM^?1. The interference effects of SO₃ ^2?, SO₄ ^2?, S₂O₃ ^2?, S₄O₆ ^2?, Cysteine, and Cystein were negligible at the concentration ratios more than 40 times. The modified electrode is more stable with time and more easily restorable than unmodified electrode surface. Also, modified electrode permits detection of sulfide ion by its oxidation at lower anodic potentials.      

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M₃(CF₃COO)₆(CF₃COOH)₆)](CF₃COOH) and [M₃(CF₃COO)₆(CF₃COOH)₂(H₂O)₄)](CF₃COOH)₂, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF₃COO)₂ · 4H₂O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $P\bar 1$ , a = 13.199(6) Å, b = 14.649(6) Å, c = 15.818(6) Å, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) ų, Z = 2, R = 0.0480. Crystals II are trigonal: space group $R\bar 3$ , a = 13.307(2) Å, c = 53.13(1) Å, V = 8148(2) ų, Z = 6, R = 0.1112. Crystals III are triclinic: space group $P\bar 1$ , a = 9.001(8) Å, b = 10.379(9) Å, c = 12.119(9) Å, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) ų, Z = 1 Å, R = 0.1031. Crystals IV are triclinic: space group $P\bar 1$ , a = 9.121(18) Å, b = 10.379(2) Å, c = 12.109(2) Å, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) ų, Z = 1, R = 0.0334.     

Synthesis,spectroscopic characterization,crystal structure and antifungal activity of thiourea derivatives containing a thiazole moiety

Four novel thiourea derivatives containing a thiazole moiety were synthesized and characterized by IR, ¹H and ¹³C NMR, mass spectrometry and elemental analysis. The crystal structure of 1a was determined from single crystal X-ray diffraction data. It crystallizes in monoclinic space group P2₁/n with unit cell dimensions a = 11.7752(6) Å, b= 3.8677(2) Å, c= 27.4126(13) Å and β = 92.734(5) Å. There is a strong intramolecular hydrogen bond of the type N-H?O, with H?O distance of 2.5869(19) Å. The mass fragmentation pattern has also been discussed. The antifungal activity of the synthesized compounds was studied by broth micro-dilution method and poisoned food technique. The compounds 1b and 1c possessed a broad spectrum of antifungal activity.

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Complexes of platinum and palladium with 4-nitrobenzoic hydrazide: synthesis and cytotoxic activity

New complexes of platinum and palladium were isolated with 4-nitrobenzoic hydrazide (4-NH) and characterized by spectroscopic techniques. Results show that the ligand is coordinated to metallic ions by the basic nitrogen of NH₂ group and have the general structure cis-[M(4-NH)₂X₂] where M= Pt or Pd and x = Cl or I. The compound III, [Pt(4-NH)₂I₂], was found to display cytotoxicity (IC₅₀ = 0.96 μmol L^?1) against the K562 tumoral cell line. This complex is significantly more cytotoxic than cisplatin.      

A complex of cadmium(II) iodide with 4-cyanopyridine: Synthesis,crystal structure,and luminescent properties

The complex [CdI₂(4-CNPy)₂] (I) was obtained by a reaction of CdI₂ with 4-cyanopyridine (4-CNPy, C₆H₄N₂) and structurally characterized (CIF file CCDC no. 983377). The crystals of complex I are monoclinic, space group C2, a = 24.698(5) Å, b = 4.127(1) Å, c = 7.597(2) Å, β = 96.05(1)°, V = 770.0(3) ų, ρ_calcd = 2.477 g/cm³, Z = 2. In structure I, iodine atoms serve to unite complex molecules into the polymer chains [CdI₂(4-CNPy)₂]_∞ along the direction [010]. The Cd(1) atom lying on a twofold axis has a slightly distorted octahedral environment made up of four bridging iodine atoms and two nitrogen atoms of two ligands 4-CNPy (Cd-I_av, 2.947(2) and Cd-N(1), 2.410(6) Å). Within each chain, cadmium atoms are spaced apart at 4.13 Å. Complex I exhibits photoluminescence.     

Syntheses and structural determination of mononuclear nine-coordinate (MnH)[GdIII(EDTA)(H2O)3] · 4H2O and 2D ladder-like binuclear nine-coordinate (MnH)2[Gd 2 III (H2TTHA)2] · 4H2O

Two title rare earth metal coordination compounds, (MnH)[Gd^III(Edta)(H₂O)₃] · 4H₂O (I) and (MnH)₂[Gd ₂ ^III (H₂Ttha)₂] · 4H₂O (II), where Mn = methylamine, H₄Edta = ethylenediamine-N,N,N′,N′-tetraacetic acid, H₆Ttha = triethylenetetramine-N,N,N′,N″,N′″,N′″-hexaacetic acid), have been successfully synthesized through direct heating reflux and characterized by FT-IR spectroscopy, thermal analysis and single-crystal X-ray diffraction techniques. In complex I, the Gd³⁺ ion is nine-coordinated by an Edta ligand and three water molecules, yielding a pseudo-monocapped square antiprismatic (MC-SAP) conformation. Complex I crystallizes in the orthorhombic crystal system with space group Fdd2. The cell dimensions are as follows: a = 19.5207(17), b = 35.387(3), c = 12.5118(11) Å, and V = 8642.8(13) ų. The central Gd³⁺ ion of II is also ninecoordinate, forming tricapped trigonal prismatic (TC-TP) conformation with three amine nitrogen atoms and six oxygen atoms. Complex II crystallizes in the monoclinic crystal system with P2/c space group. The crystal data are as follows: a = 14.4301(13), b = 11.2400(11), c = 17.7102(16) Å, β = 112.606(2)°, and V = 2651.8(4) ų. There retain outer-protonated and inner-protonated carboxyl oxygen atoms in the [Gd ₂ ^III (H₂Ttha)₂]^2? complex anion. In II, there are only one type of methylamine cation (MnH⁺) as the counter ion, which connects [Gd ₂ ^III (H₂Ttha)₂]^2? complex anions and lattice water molecules through hydrogen bonds, leading to the formation of 2D ladder-like layer structure.     

Coordination molecular compounds of cadmium(II) iodide with dimethylpyridines

The reactions of CdI₂ with dimethylpyridines (Me₂Py is C₇H₉N) afford complexes CdI₂(2,3-Me₂Py)₂] (I), [CdI₂(2,6-Me₂Py) (II), and CdI₂(3,5-Me₂Py)₂ (III). The structures of compounds I and II are determined. The crystals of complex I are orthorhombic, space group Pbca, a = 7.930(1) Å, b = 15.537(1) Å, c = 29.943(1) Å, V = 3689.1(5) ų, ρ_calcd = 2.090 g/cm³, Z = 8. The crystals of complex II are monoclinic, space group C2/c, a = 14.784(1), b = 11.991(1), c = 17.711(1) Å, β = 90.39(1)°, V = 1081.1(2) ų, ρ_calcd = 2.908 g/cm³, Z = 4. The structure of compound I is built of discrete neutral complexes [CdI₂(2,3-Me₂Py)₂]. The Cd polyhedron is a distorted tetrahedron (Cd-I 2.289–2.295, Cd-N 2.708–2.734 Å, angles N(I)CdN(I) 103.1°-114.8°). Polymer chains [CdI₂(2,6-Me₂Py)]_∞ extended along the direction [100] are observed due to the bridging iodine atoms in structure II. The Cd polyhedron is a trigonal bipyramid containing iodine atoms at the axial vertices (Cd-I_aks 3.040 Å) and two iodine atoms and the nitrogen atom of the Me₂Py ligand in the equatorial plane Me₂Py (Cd-I_eq 2.840 Å, Cd-N 2.309 Å). The compounds in the solid state are photoluminescent.     

Crystal structures of three complexes structurally similar to KTbW(CN)8 · 7H2O

Three complexes that crystallize into structures like KTbW(CN)₈ · 7H₂O (triclinic crystal system, space group P $ \bar 1 $ ) were structurally characterized by X-ray diffraction: KYMo(CN)₈ · 7H₂O, a = 7.6371(5), b = 9.2569(6), c = 14.4976(2) Å, α = 80.782(6)°, β = 87.644(5)°, γ = 77.645(5)°, V = 988.23(11) ų, Z = 2, ρ_calcd = 1.876 g/cm³; KHoW(CN)₈ · 7H₂O, a = 7.5887(4), b = 9.2232(5), c = 14.4479(9) Å, α = 80.709(5)°, β = 87.525(5)°, γ = 77.457(5)°, V = 974.12(10) ų, Z = 2, ρ_calcd = 2.462 g/cm³; KErW(CN)₈ · 7H₂O, a = 7.6180(5), b = 9.2356(6), c = 14.4903(11) Å, α = 80.655(6)°, β = 87.492(6)°, γ = 77.557(6)°, V = 982.29(13) ų, Z = 2, ρ_calcd = 2.449 g/cm³. The coordination polyhedra of the d element atoms [M(CN)₈] (M⁴⁺ = Mo and W) are dodecahedra; the coordination polyhedra of the rare-earth metal atoms [RN₄(OH₂)₄] (R³⁺ = Y, Ho, and Er) are tetragonal antiprisms. Four bridging cyano groups are coordinated to the W/Mo and rare-earth metal atoms through the C and N atoms, respectively, to form a polymeric 3D structure involving potassium atoms. The coordination polymers can be formulated as {[K(H₂O)][R(H₂O)₄][M(CN)₈] · 2H₂O} _n (R³⁺ = Y, M⁴⁺ = Mo; R³⁺ = Ho and Er, M⁴⁺ = W).     

Synthesis and biological screening of octasubstituted-triphenodioxazines and its sulphur analogues with some novel intermediates

Attempts have been made to prepare for the first time the octasubstituted-triphenodioxazines and triphenodithiazines heterocycles by cyclisation of 3,6-dichloro-2,5-bis(2′,4′,5′-trichloroanilino)-1,4-benzoquinone and condensation. This wasfollowed by cyclisation of substituted 2-aminobenzenethiol respectively with chloranil and bromanil in ethanolic solution of fused sodium acetate in the presence of benzoyl chloride in nitrobenzene. Their structures were confirmed on the basis of their chemical and spectral analyses. Moreover, the biological activity of these compounds was evaluated against the test organisms viz — E.coli, S. aureus, B. subtilis, M.luteus and C. albicans. These compounds synthesized from 2,4,5-trichloroaniline appeared to possess significant antimicrobial activities and an explicit correlation between structure and biological activity was also observed.      

Supramolecular complexes of podand ligands with xenon

Formation of stable complexes between xenon and podand polyoxyethylene ligands was ascertained. The complexation process was studied by ¹²⁹Xe NMR titration, NMR diffusiometry and heteronuclear NOE measurements. The ligands studied form a 1:1 complexes with Xe(0). Their stability constants depend on the ligand structure, i.e., polyoxyethylene chain length, number of complexating polyether units and the topology of the anchoring centre.      

Crystal and molecular structures of binuclear complexes of salycilic acid {Cu-M} (M = Cu, Sr, Ba)

Heterometallic complexes [CuSr(SalH)₄(DMAA)₄(H₂O)] (II) and [CuBa(SalH)₄(DMAA)₄ (H₂O)] (III) were synthesized by interaction of salicylates of s elements with copper nitrate. A mixture of III and vanadyl sulfate yielded the crystals of a homonuclear complex [CuCu(SalH)₄(H₂O)₂]·2DMAA (I). According to single crystal X-ray data, all of the products are of lantern type and belong to two space groups: I is triclinic, space group P-1, unit cell parameters a = 9.9083(2) Å, b = 10.5077(3) Å, c = 10.9512(3) Å, α = 112.736(2)°, β = 114.0800(10)°, γ = 93.131°; II and III are tetragonal, space group P4/n, lattice parameters a = b = 16.3180(3) Å, c = 8.7838(2) Å for II and a = b = 16.362(3) Å, c = 8.920(1) Å III. The copper atoms have a square-pyramidal environment. The coordination number of Sr and Ba is 8, and the coordination polyhedron can be represented as a Thomson cube in both cases. The carboxylic groups are coordinated in a syn-syn bridging mode. The oxygen atom of the hydroxyl group of salicylic acid is not involved in coordination, but forms intramolecular hydrogen bonds to the carboxylic groups. The hydrogen bonds between water and DMAA solvate molecules, as well as — interactions between the aromatic fragments of the dimers, play a particularly important role in the molecular packing in crystal.