Extended Physicochemical Characterization of the Synthetic Anticoagulant Pentasaccharide Fondaparinux Sodium by Quantitative NMR and Single Crystal X-ray Analysis.

Fondaparinux sodium is a synthetic pentasaccharide representing the high affinity antithrombin III binding site in heparin. It is the active pharmaceutical ingredient of the anticoagulant drug Arixtra®. The single crystal X-ray structure of Fondaparinux sodium is reported, unequivocally confirming both structure and absolute configuration. The iduronic acid adopts a somewhat distorted chair conformation. Due to the presence of many sulfur atoms in the highly sulfated pentasaccharide, anomalous dispersion could be applied to determine the absolute configuration. A comparison with the conformation of Fondaparinux in solution, as well as complexed with proteins is presented. The content of the solution reference standard was determined by quantitative NMR using an internal standard both in 1999 and in 2016. A comparison of the results allows the conclusion that this method shows remarkable precision over time, instrumentation and analysts.

The conformation of the idopyranose ring revisited: How subtle O-substituent induced changes can be deduced from vicinal 1H-NMR coupling constants.

The idopyranose ring plays a pivotal role in the conformational, dynamical, and intermolecular binding aspects of glycosaminoglycans like heparin and dermatan sulfate and it was early on assigned a role in the Sugar Code governing biological recognition processes. There is consensus that next to the two canonical 1C4 and 4C1 chair conformations, the conformational space accessible to the idopyranose ring entails a 2SO skew-boat conformation, but the equilibrium between these three ring puckers has evaded satisfactory quantification. In this study a meta-analysis of X-ray solid-state data and vicinal NMR coupling constants is presented, based on the Truncated Fourier Puckering (TFP) formalism and the generalized Karplus (CAGPLUS) equation. This approach yields a model-free, granular and consistent reckoning of 159 idopyranose solution puckering equilibria studied by NMR and allows us to reproduce the involved 636 NMR vicinal couplings with an overall residual RMS(Jobs-Jcalc) of 0.184 Hz. Our analyses show that for all ring systems examined, the idopyranosyl chair conformations take up the same ring pucker irrespective of the ring substituent pattern or a vast variety in experimental conditions. Instead, it is the (skew-)boat conformation that adapts to the substitution pattern of the idopyranose ring or a specific sulfation pattern of neighboring saccharides. All idopyranose rings are involved in conformational equilibria that subsume the aforementioned conformers which turn out to differ only a few kJ/mole in conformational energy. Thus, the plasticity and flexibility of idopyranose remains intact under practically all circumstances and, as the glycosidic linkages in heparin are considered to be relatively stiff, the iduronic moiety functions as the linchpin of heparin flexibility thereby being rather a "space(r)" than a "letter" in the alleged Sugar Code alphabet.

Synthesis, crystal structure, studies in solution and cytotoxicity of two new fluorescent platinum(II) compounds containing anthracene derivatives as a carrier ligand.

Two new cytotoxic fluorescent platinum(II) compounds, cis-[Pt(A9opy)Cl2] (1) and cis-[Pt(A9pyp)(DMSO)Cl2] (2),have been designed, synthesized, and characterized by IR, 1H NMR, and 195Pt NMR spectroscopy; electrospray ionization mass spectrometry (ESI-MS); and single-crystal X-ray diffraction. The carrier ligands selected for thesynthesis of these fluorescent platinum(II) compounds are E-2-[1-(9-anthryl)-3-oxo-3-prop-2-enylpyridine] (abbreviatedas A9opy) and E-1-(9-anthryl)-3-(2-pyridyl)-2-propenone (abbreviated as A9pyp). The compound cis-[Pt(A9opy)Cl2](1) comprises a peculiar cis-platinum(II) organometallic compound, in which the platinum(II) ion is bound to the photoisomerizable carbon-carbon double bond of the carrier ligand. The effects of the metal-ion coordination on the photoisomerization of the carbon-carbon double bond of the ligand have been studied. In contrast, the carrier ligand A9pyp used for the synthesis of the cis-[Pt(A9pyp)(DMSO)Cl2] compound (2) does not undergo such anisomerization process and remains in the E conformation, while coordinated to the platinum(II) ion through the nitrogen of the pyridine ring. In addition to the synthesis and characterization, solution studies of both compounds have also been performed in detail, including NMR and ESI-MS spectroscopy. Moreover, a high degree of cytotoxicactivity of compound 1 was found, as compared to cisplatin and its corresponding platinum-free molecule, in a series of human tumor cell lines. Compound 2 was also found to be highly active against these cell lines but appeared less active compared to the platinum-free molecule.

(S)-6-Methyl-∊-caprolactone.

The chiral title compound, C(7)H(12)O(2), a lactone derivative, features a seven-membered ring that adopts a chair conformation. The crystal structure is stabilized by weak C-H⋯O inter-actions occurring in the (100) plane. The absolute configuration was assigned on the basis of the enantioselective synthesis.

The synthesis, chemical and biological properties of dichlorido(azpy)gold(III) chloride (azpy=2-(phenylazo)pyridine) and the gold-induced conversion of the azpy ligand to the chloride of the novel tricyclic pyrido[2,1-c][1,2,4]benzotriazin-11-ium cation.

A new Au(III) coordination compound with the ligand 2-(phenylazo)pyridine has been synthesized and fully characterized by means of elemental analysis, IR, UV-visible, conductivity measurements, NMR, electrospray ionization (ESI-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The chemical stability of the cation in this compound, [Au(azpy)Cl(2)](+) (abbreviated: Au-azpy), was analyzed by means of several physicochemical methods. While stable in the solid state, stability studies performed with the gold compound in solution showed an unexpected and unprecedented reactivity. A cationic organic derivative of 2-(phenylazo)pyridine, (abbreviated: pyrium), was produced from the solution and has been isolated as its chloride salt and characterized by crystal structure determination, elemental analysis, NMR, ESI-MS and conductivity studies in solution. This cyclization reaction is reported for the first time in the case of gold coordination compounds. The Au adduct and the pyrium cation were investigated as potential cytotoxic and anticancer agents, and both show moderate to high cytotoxic properties in cisplatin-sensitive and cisplatin-resistant ovarian carcinoma cell lines, A2780; and cisplatin-sensitive and cisplatin-resistant murine lymphocytic leukemia cell lines, L1210. Significant anticancer activity against the cisplatin resistant cell lines was found for the pyrium salt, ruling out the occurrence of cross resistance phenomena.

Study on the isomerism in meso-amavadin and an amavadin analogue.

An X-ray crystallographic study of 'meso-amavadin' revealed that in the crystal the negatively charged anionic species of the title compound join into infinite hydrogen-bonded chains, counterbalanced by cationic hydronium species. Along with water of crystallization a three-dimensional hydrogen-bonded network is formed. Based on NMR- and X-ray data of amavadin and 'meso-amavadin', a model was developed that accounts for the structure of amavadin-type complexes, i.e. vanadium(IV) non-oxo complexes that contain two ligands with a tridentate N-hydroxyiminodiacetate backbone. The model describes the different arrangements of the two ligands around the vanadium and it accounts for eventual symmetry in the complex. The model was used for the interpretation of NMR-data of an amavadin analogue with a benzyl group at the ligand backbone.

(4aS,5R,7R,8S,8aR)-8-(1,3-Dioxolan-2-yl)-7,8-dimethyl-5-(1-methyl-ethen-yl)perhydro-naphthalen-2-one.

In the chiral title compound, C(18)H(28)O(3), the two six-membered rings of the perhydronaphthalenone adopt a rigid chair-chair conformation and the five-membered dioxolanyl ring adopts an envelope conformation. The crystal structure is stabilized only by weak inter-actions.

New routes to manganese higher-nuclearity topologies: synthesis of the cluster [Mn8(mu4-O)4(phpz)8(thf)4].

Reaction of Mn(ClO4)2.6H2O with 3(5)-methyl-5(3)-(2-hydroxyphenyl)pyrazole (H2phpz) affords a highly asymmetric octanuclear manganese(III) cluster resulting from the different bridging coordination modes of the ligand H2phpz.

A novel octanuclear Mn(III) aggregate as a single-molecule magnet.

The novel octanuclear cluster [Mn8O2(OH)2(OMe)12(OAc)2(Mesalim)4] (1) presents SMM behaviour with a relatively high experimental energy barrier (eff/kB= 36.0 K) as shown by its dc and ac magnetic properties.

New cytotoxic and water-soluble bis(2-phenylazopyridine)ruthenium(II) complexes.

New water-soluble bis(2-phenylazopyridine)ruthenium(II) complexes, all derivatives of the highly cytotoxic alpha-[Ru(azpy)(2)Cl(2)] (alpha denoting the coordinating pairs Cl, N(py), and N(azo) as cis, trans, cis, respectively) have been developed. The compounds 1,1-cyclobutanedicarboxylatobis(2-phenylazopyridine)ruthenium(II), alpha-[Ru(azpy)(2)(cbdca-O,O')] (1), oxalatobis(2-phenylazopyridine)ruthenium(II), alpha-[Ru(azpy)(2)(ox)] (2), and malonatobis(2-phenylazopyridine)ruthenium(II), alpha-[Ru(azpy)(2)(mal)] (3), have been synthesized and fully characterized. X-ray analyses of 1 and 2 are reported, and compound 1 is the first example in which the cbdca ligand is coordinated to a ruthenium center. The cytotoxicity of this series of water-soluble bis(2-phenylazopyridine) complexes has been determined in A2780 human ovarian carcinoma and A2780cisR, the corresponding cisplatin-resistant cell line. For comparison reasons, the cytotoxicity of the complexes alpha-[Ru(azpy)(2)Cl(2)], alpha-[Ru(azpy)(2)(NO(3))(2)], beta-[Ru(azpy)(2)Cl(2)] (beta indicating the coordinating pairs Cl, N(py), and N(azo) as cis, cis, cis, respectively), and beta-[Ru(azpy)(2)(NO(3))(2)] have been determined in this cell line. All the bis(2-phenylazopyridine)ruthenium(II) compounds display a promising cytotoxicity in the A2780 cell line (IC(50) = 0.9-10 microM), with an activity comparable to that of cisplatin and even higher than the activity of carboplatin. Interestingly, the IC(50) values of this series of ruthenium compounds (except the beta isomeric compounds) are similar in the cisplatin-resistant A2780cisR cell line compared to the normal cell line A2780, suggesting that the activity of these compounds might not be influenced by the multifactorial resistance mechanism that affect platinum anticancer agents.

Hydrogen-Bonded Complexes of Diaminopyridines and Diaminotriazines: Opposite Effect of Acylation on Complex Stabilities.

The association behavior of several 2,4-diamino-s-triazines, 2,6-diaminopyridines, and their acylated derivatives with uracil derivatives was studied. In solution (1)H-NMR and IR spectroscopy were used, and in the solid state as (co)crystals X-ray diffraction was used. Acylation of 2,6-diaminopyridine leads to an increase of the association constant in CDCl(3) of the complexes with N-propylthymine from 84 to 440-920 M(-)(1), whereas acylation of diamino-s-triazines leads to a dramatic fall in the association constant of the complexes with N-propylthymine from 890 to ca. 6 M(-)(1). This phenomenon is related to different conformational preferences of these compounds. The amide groups in bis(acylamino)pyridines prefer a trans conformation, with the carbonyl group anti with respect to the ring nitrogen and coplanar with the aromatic ring. The amides of bis(acylamino)triazines, however, reside predominantly in a cis conformation. Repulsive secondary electrostatic interactions between the cis-amide and uracil carbonyl groups are thought to be responsible for the low association constant of complexes of bis(acylamino)triazines with uracils. The relatively high dimerization constants of bis(acylamino)triazines have been rationalized by the strong tendency to dimerize via quadruple hydrogen bonding.

Monodentate sigma-N and Bidentate sigma-N,sigma-N' Coordination of 1,1-Bis((N-p-tolylimino)diphenylphosphoranyl)ethane, CHCH(3)(PPh(2)=NC(6)H(4)-4-CH(3))(2), to Platinum(II).

The new ligand, 1,1-bis((N-p-tolylimino)diphenylphosphoranyl)ethane (1,1-BIPE), 1, has been synthesized by means of a Staudinger reaction of 1,1-bis(diphenylphosphino)ethane (1,1-dppe) with 2 equiv of p-tolylazide. Bridge-splitting reactions of Pt(2)Cl(4)(PR(3))(2) with 1 readily afforded sigma-N monodentate complexes, [PtCl(2)(PR(3)){1,1-BIPE-sigmaN}] (2a, PR(3) = PEt(3); 2b, PR(3) = PMe(2)Ph). Conversion of 2 into the six-membered platinacycle [PtCl(PR(3)){1,1-BIPE-sigmaN,sigmaN'}](+)[X](-) (3) (X = Cl, PtCl(3)(PR(3)), BF(4)) took place after prolonged stirring, its reaction rate being strongly dependent on the type of phosphine (>5 days for 2ain the presence of NaBF(4), 1 h for 2b) and the metal-to-ligand ratio. The compounds 1, 2, and 3 have been fully characterized by (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR and IR spectroscopy, elemental analysis, or FAB mass spectroscopy. The molecular structures of CHCH(3)(PPh(2)=NC(6)H(4)-4-CH(3))(2) (1) and [PtCl(PMe(2)Ph){(N(pTol)=PPh(2))(2)CHCH(3)}](+)[Cl](-) (3b) have been determined by X-ray crystallography. Crystal data for 1: space group P2(1)/c with a = 8.9591(5) Å, b = 19.1961(12) Å, c = 21.9740(9) Å, beta = 105.069(4) degrees, V = 3649.1(3) Å(3), and Z = 4. The structure refinement converged to R = 0.080 and R(w) = 0.109. Crystal data for 3b: monoclinic, space group P2(1)/c with a = 12.4021(7) Å, b = 16.9705(11) Å, c = 23.760(2) Å, beta = 109.544(5) degrees, V = 4712.7(5) Å(3), and Z = 4. The structure refinement converged to R1 = 0.057, wR2 = 0.122. Variable temperature NMR spectroscopy has revealed that complexes 3 exclusively adopt a twisted boat conformation with the methyl group in equatorial position at low temperature, in agreement with the solid state structure of 3b as determined by X-ray crystallography. Boat-to-boat inversion is assumed to take place at temperatures above 293 K. Furthermore, for 3, hindered rotation of one of the p-tolyl substituents on nitrogen has been established at low temperatures.

Rhenium(V)-Salen Complexes: Configurational Control and Ligand Exchange.

Reactions of ReO(PPh(3))(2)Cl(3) with tetradentate bis(salicylideneamine) ligands, H(2)salpd (1) and H(2)salbd (2), in different alcohols gave the novel mixed-ligand rhenium complexes ReO(sal)OAlk (OAlk = variety of alkoxy ligands). Configurational studies show that the rhenium complexes ReO(salpd)OAlk (1a-f) display either a symmetrical or a nonsymmetrical configuration, depending on the size of the alcohol and its boiling point. The rhenium complexes ReO(salbd)OAlk (2a-d) are all nonsymmetrical due to the number of carbons that bridge the imine nitrogens. In the case of the symmetrical ReO(salpd)OMe (1a) complex the methoxy ligand can be exchanged for a number of ligands of different types (OAlk, OPh, SAlk, OC(O)Alk). In the newly formed complexes the original configuration was retained except for the ReO(salpd)SAlk (1i,j) complexes which were isolated in the nonsymmetrical configuration. Starting from the nonsymmetrical ReO(salpd)OPr (2c) complex, ligand exchange led to a mixture of the symmetrical and nonsymmetrical complexes, with ratios depending on the reaction time. The crystal structures of ReO(salbd)OPr (2c), and ReO(salpd)OPhOMe (1g) have been determined. ReO(salbd)OPr crystallizes in the triclinic space group P&onemacr;, Z = 2, with a = 10.0344(16) Å, b = 10.647(2) Å, c = 11.481(2) Å, alpha = 86.551(15) degrees, beta = 86.998(14) degrees, gamma = 80.112(15) degrees, V = 1205.1(4) Å(3), and final R = 0.0460. Crystals of ReO(salpd)OPhOMe are orthorhombic, space group P2(1)2(1)2(1), Z = 4, with a = 10.6222(15) Å, b = 12.442(3) Å, c = 16.354(3) Å, V = 2161.4(7) Å(3), and final R = 0.0371. Under the influence of traces of water a number of symmetrical complexes react to a "dimeric" structure, consisting of two ReO(salpd) moieties bridged by an oxygen atom with the bridging Re-O-Re angle symmetrically imposed at 180 degrees. [ReO(salpd)](2)O (3) crystallizes in the monoclinic, space group P2(1)/c, Z = 4, with a = 14.860(2) Å, b = 12.545(2) Å, c = 16.5111(17) Å, beta = 95.030(10) degrees, V = 3066.1(7) Å(3), and final R = 0.0439.

Chemistry of Bis(aryloxo)palladium(II) Complexes with N-Donor Ligands: Structural Features of the Palladium-to-Oxygen Bond and Formation of O-H.O Bonds.

Reaction of palladium acetate with 2 equiv of sodium phenoxide in the presence of a chelate diamine ligand affords the complexes [Pd(OPh)(2)(N approximately N)] (N approximately N = bpy (1), tmeda (2), teeda (3), dpe (4), dmap (5)). These yellow to orange bis(phenoxo)palladium(II) complexes are thermally stable at room temperature in the solid state as well as in solution. Addition of an excess of pentafluorophenol to 1, 2, 4, and 5 affords crystalline complexes [Pd(OC(6)F(5))(2)(N approximately N)] (N approximately N = bpy (6), tmeda (7), dpe (8), dmap (9)). Crystals of 1 and 6 have been subjected to X-ray diffraction studies. Crystals of 1 are orthorhombic, space group P2(1)2(1)2(1) (no. 19), with a = 6.7655(6) Å, b = 16.0585(10) Å, c = 16.7275(13) Å, and Z = 4. Crystals of 6 are triclinic, space group P&onemacr; (no. 2), with a = 7.567(4) Å, b = 12.708(3) Å, c = 12.912(5) Å, alpha = 61.51(3) degrees, beta = 74.74(4) degrees, gamma = 88.78(4) degrees, and Z = 2. The molecular structures of 1 and 6 show them to be square-planar complexes, and the main structural difference between these complexes is the orientation of the aromatic rings. In 6 the OC(6)F(5) ligands are almost parallel in a face-to-face orientation (pi-pi stacking interactions), whereas in 1 the OC(6)H(5) units are skewed away from each other. An unexpected "mixed" alkoxo(aryloxo) complex [Pd(OCH(CF(3))(2))(OPh)(bpy)].HOPh (10) is formed when 1 is reacted with 1,1,1,3,3,3-hexafluoro-2-propanol. The molecular structure of 10 shows O-H.O hydrogen bonding (O.O = 2.642(8) Å) between the hydroxyl hydrogen of phenol and the oxygen atom of the phenoxide ligand as well as an additional C-H.O contact (C.O) = 2.95(1) Å), which can be regarded as the initial stage of a base-assisted beta-hydrogen elimination. Crystals of 10 are monoclinic, space group P2(1)/c, with a = 8.3241(14) Å, b = 11.0316(17) Å, c = 26.376(3) Å, alpha = 93.01(1) degrees, Z = 4. Spectroscopic data of complexes 1-10 indicate that the oxygen atom of the aryloxide or alkoxide ligand is extremely electron-rich, leading to high polarization of the palladium-to-oxygen bond. The bis(phenoxide) complexes 1, 2, and 4 associate with two molecules of phenol through O-H.O hydrogen bonds to form adducts [Pd(OPh)(2)(N approximately N)].2HOPh (N approximately N = bpy (11), tmeda (12), dpe (13)). The palladium complexes 6-9 with OC(6)F(5) groups show no tendency to form adducts with alcohols.

Structural Aspects of Lithium Arenethiolate Complexes with Intramolecular Coordinating Amine Donors.

Reaction of aryllithium reagents LiR (R = C(6)H(4)((R)-CH(Me)NMe(2))-2 (1a), C(6)H(3)(CH(2)NMe(2))(2)-2,6 (1b), C(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2 (1c)) with 1 equiv of sulfur (1/8 S(8)) results in the quantitative formation of the corresponding lithium arenethiolates [Li{SC(6)H(4)((R)-CH(Me)NMe(2))-2}](6) (3), [Li{SC(6)H(3)(CH(2)NMe(2))(2)-2,6}](6) (4), and [Li{SC(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2}](2) (5). Alternatively, 3 can be prepared by reacting the corresponding arenethiol HSC(6)H(4)((R)-CH(Me)NMe(2))-2 (2) with (n)BuLi. X-ray crystal structures of lithium arenethiolates 3 and 4, reported in abbreviated form, show them to have hexanuclear prismatic and hexanuclear planar structures, respectively, that are unprecedented in lithium thiolate chemistry. The lithium arenethiolate [Li{SC(6)H(4)(CH(2)N(Me)CH(2)CH(2)OMe)-2}](2) (5) is dimeric in the solid state and in solution, and crystals of 5 are monoclinic, space group P2(1)/c, with a = 17.7963(9) Å, b = 8.1281(7) Å, c = 17.1340(10) Å, beta = 108.288(5) degrees, Z = 4, and final R = 0.047 for 4051 reflections with F > 4sigma(F). Hexameric 4 reacts with 1 equiv of lithium iodide and 2 equiv of tetrahydrofuran to form the dinuclear adduct [Li(2)(SAr)(I)(THF)(2)] (6). Crystals of 6 are monoclinic, space group P2(1)/c, with a = 13.0346(10) Å, b = 11.523(3) Å, c = 16.127(3) Å, beta = 94.682(10) degrees, Z = 4, and final R = 0.059 for 3190 reflections with F > 4sigma(F).

Synthesis, Structure, Magnetic Behavior, and Mössbauer Spectroscopy of Two New Iron(II) Spin-Transition Compounds with the Ligand 4-Isopropyl-1,2,4-triazole. X-ray Structure of [Fe(3)(4-isopropyl-1,2,4-triazole)(6)(H(2)O)(6)](tosylate)(6).2H(2)O.

Two new iron(II) compounds with the formula [Fe(3)(iptrz)(6)(H(2)O)(6)]X(6).xH(2)O (with iptrz = 4-isopropyl-1,2,4-triazole and X = p-toluenesulfonate (Tos) or trifluoromethanesulfonate (Trifl)) were synthesized. The crystal structure of [Fe(3)(iptrz)(6)(H(2)O)(6)](Tos)(6).2H(2)O (I) has been solved at room temperature. Crystals of I are triclinic, space group P&onemacr; with a = 12.8820(11) Å, b = 15.580(2) Å, c = 24.445(4) Å, alpha = 79.270(12) degrees, beta = 86.688(11) degrees, gamma = 83.007(8) degrees, Z = 2. The structure of I consists of linear trinuclear cations with a +6 charge and noncoordinated anions and lattice water molecules. The central iron ion is located on an inversion center and is coordinated by 6 nitrogen atoms of 6 iptrz molecules bridging via the nitrogen atoms in the 1,2-positions. Each external iron atom completes its coordination sphere with three coordinated water molecules. The temperature dependent magnetic measurements of compound I and [Fe(3)(iptrz)(6)(H(2)O)(6)](Trifl)(6) (II) show that both compounds exhibit a gradual spin conversion of the central iron ion centered at T(1/2) = 242 K for I and 187 K for II. Temperature dependent Mössbauer spectroscopy measurements on I show the behavior expected for a compound of this nature. The measurements on II indicate a strong influence of the spin conversion of the central iron ion on both external iron ions. The nature of this phenomenon is proposed to be connected to a very rigid lattice structure (ionic, H-bonding) connecting the trinuclear units.

Dithiacrown Ether Substituted Porphyrazines: Synthesis, Single-Crystal Structure, and Control of Aggregation in Solution by Complexation of Transition-Metal Ions.

The synthesis of novel magnesium, copper, and metal-free porphyrazines, peripherally substituted with dithia-7-crown-2 (MPz(7)), dithia-15-crown-5 (MPz(15)), and dithia-18-crown-6 (MPz(18)) macrocycles is reported. These compounds are prepared starting from dicyanoethylene containing crown ethers 3, 2(1), and 2(2), respectively, which contain sulfur as well as oxygen heteroatoms. The "crowned" porphyrazines bind silver(I) and mercury(II) perchlorates. UV/vis spectroscopy and electron paramagnetic resonance measurements reveal that addition of the transition-metal ions leads to dimerization of the porphyrazine complexes. In the case of the dithia-18-crown-6-substituted porphyrazines, the dimers break up to form monomeric 6:1 guest-host complexes when more than 2 equiv of the metal ion is added. The single-crystal structures of the crown ether 2(2) and the porphyrazine MgPz(18) are presented. Compound C(14)H(20)N(2)O(4)S(2) (2(2)) crystallizes in the monoclinic space group P2(1)/c with a = 10.9310(13) Å, b = 19.383(3) Å, c = 8.6976(14) Å, beta = 108.898(11) degrees, V = 1743.5(5) Å(3), and Z = 4. The structure refinement converged to R = 0.0366 and R(w) = 0.0504. Compound C(56)H(82)MgN(8)O(17)S(8) (MgPz(18)) crystallizes in the triclinic space group P&onemacr; with a = 9.584(3) Å, b = 17.672(2) Å, c = 19.620(4) Å, alpha = 84.904(14) degrees, beta = 85.21(2) degrees, gamma = 89.29(2) degrees, V = 3298.4(13) Å(3), and Z = 2. The structure refinement converged to R1 = 0.0839 and wR2 = 0.2196. The electrical properties of H(2)Pz(18) have been studied by complex impedance spectroscopy. The bulk electrical conductivity of this compound is approximately 1 order of magnitude higher than that of the corresponding 18-crown-6 phthalocyanine.

Synthesis, Characterization, and Single-Crystal EPR Studies of Three Dinuclear Copper(II) Complexes and One Mixed-Valence Tetranuclear Copper(I)-Copper(II) Cluster with an Asymmetric Imidazole-Containing Tripodal Ligand with Copper(II)-Copper(II) Distances between 3.35 and 3.63 Å

The synthesis and characterization of three dinuclear copper(II) complexes and one mixed-valence tetranuclear cluster with the asymmetric imidazole-containing ligand bis(1,1'-imidazole-2-yl)(4-imidazole-4(5)-yl)-2-azabutane (biib) are described. X-ray crystallographic parameters for the copper complexes are as follows. [Cu(2)(biib)(2)(BF(4))(2)](BF(4))(2)(H(2)O)(4): triclinic, space group P&onemacr;, a = 10.178(1) Å, b = 9.4881(9) Å, c = 11.037(1) Å, alpha = 95.130(10) degrees, beta = 112.20(1) degrees, gamma = 92.142(9) degrees, and Z = 1. [Cu(2)(biib)(2)(NO(3))(2)](NO(3))(2)(H(2)O)(4): monoclinic, space group &Pmacr;2(1)/n, a = 9.207(6) Å, b = 17.0516(6) Å, c = 12.6107(7) Å, beta = 109.82(1) degrees, and Z = 2. [Cu(2)(biib)(2)(CuBr(3))(2)]: monoclinic, space group P2(1)/c, a = 11.583(2) Å, b = 11.864(2) Å, c = 16.070(2) Å, beta = 112.459(12) degrees, and Z = 2. The two Cu(II) ions in all four complexes are coordinated in a square-pyramidal geometry by three imidazole nitrogens and one amine nitrogen donor in the equatorial plane, and each copper ion is weakly coordinated at the axial position by respectively a tetrafluoroborate, a perchlorate, a nitrate, or a tribromocuprate(I) anion. By comparison of the structural data of the four complexes a relationship has been established between the donor strength of the anion and some structural features, like the Cu(II)-Cu(II) distance, of the dinuclear Cu(II)-Cu(II) unit in the four complexes. Single-crystal EPR spectra of [Cu(2)(biib)(2)(BF(4))(2)](BF(4))(2)(H(2)O)(4) were recorded at room temperature at X-band frequencies. The triplet spectra have been fit with nonparallel g and D tensors, whose principle values are as follows: g(xx)() = 2.022(8), g(yy)() = 2.060(7), g(zz)() = 2.211(8), D(x)()(')(x)()(') = -0.0182(9) cm(-)(1), D(y)()(')(y)()(') = -0.081(6) cm(-)(1), D(z)()(')(z)()(') = 0.0264(7) cm(-)(1). The compounds were further characterized and studied by ligand field and by frozen-solution and polycrystalline powder EPR spectroscopy. EPR spectra recorded at 77 K of frozen solutions of the perchlorate complex show that upon dilution in methanol the dinuclear complex reacts to form a mononuclear species.

Iron Chemistry of a Pentadentate Ligand That Generates a Metastable Fe(III)-OOH Intermediate.

In an effort to gain more insight into the factors controlling the formation of low-spin non-heme Fe(III)-peroxo intermediates in oxidation catalysis, such as activated bleomycin, we have synthesized a series of iron complexes based on the pentadentate ligand N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine). The following complexes have been prepared: [(N4Py)Fe(II)(CH(3)CN)](ClO(4))(2) (1), [(N4Py)Fe(II)Cl](ClO(4)) (2), [(N4Py)Fe(III)OMe](ClO(4))(2) (3), and [(N4Py)(2)Fe(2)O](ClO(4))(4) (4). Complexes 1 and 2 have low- and high-spin Fe(II) centers, respectively, whereas 3 is an Fe(III) complex that undergoes a temperature-dependent spin transition. The iron centers in the oxo-bridged dimer 4 are antiferromagnetically coupled (J = -104 cm(-)(1)). Comparison of the crystal structures of 1, 3, and 4 shows that the ligand is well suited to accommodate both Fe(II) and Fe(III) in either spin state. For the high-spin Fe(III) complexes 3 and 4 the iron atoms are positioned somewhat outside of the cavity formed by the ligand, while in the case of the low-spin Fe(II) complex 1 the iron atom is retained in the middle of the cavity with approximately equal bond lengths to all nitrogen atoms from the ligand. On the basis of UV/vis and EPR observations, it is shown that 1, 3, and 4 all react with H(2)O(2) to generate the purple low-spin [(N4Py)Fe(III)OOH](2+) intermediate (6). In the case of 1, titration experiments with H(2)O(2) monitored by UV/vis and (1)H NMR reveal the formation of [(N4Py)Fe(III)OH](2+) (5) and the oxo-bridged diiron(III) dimer (4) prior to the generation of the Fe(III)-OOH species (6). Raman spectra of 6 show distinctive Raman features, particularly a nu(O-O) at 790 cm(-)(1) that is the lowest observed for any iron-peroxo species. This observation may rationalize the reactivity of low-spin Fe(III)-OOH species such as "activated bleomycin".