Vanadium complexes with mixed O,S anionic ligands derived from maltol: synthesis, characterization, and biological studies

Four mixed O,S binding bidentate ligand precursors derived from maltol (3-hydroxy-2-methyl-4-pyrone) have been chelated to vanadium to yield new bis(ligand)oxovanadium(IV) and tris(ligand)vanadium(III) complexes. The four ligand precursors include two pyranthiones, 3-hydroxy-2-methyl-4-pyranthione, commonly known as thiomaltol (Htma), and 2-ethyl-3-hydroxy-4-pyranthione, commonly known as ethylthiomaltol (Hetma), as well as two pyridinethiones, 3-hydroxy-2-methyl-4(H)-pyridinethione (Hmppt) and 3-hydroxy-1,2-dimethyl-4-pyridinethione (Hdppt). Vanadium complex formation was confirmed by elemental analysis, mass spectrometry, and IR and EPR (where possible) spectroscopies. The X-ray structure of oxobis(thiomaltolato)vanadium(IV),VO(tma)(2), was also determined; both cis and trans isomers were isolated in the same asymmetric unit. In both isomers, the two thiomaltolato ligands are arranged around the base of the square pyramid with the V=O linkage perpendicular; the vanadium atom is slightly displaced from the basal plane [V(1) = 0.656(3) A, V(2) = 0.664(2) A]. All of the new complexes were screened for insulin-enhancing effectiveness in streptozotocin-induced diabetes in rats, and VO(tma)(2) was profiled metabolically for urinary vanadium and ligand clearance by GFAAS and ESIMS, respectively. The new vanadium complexes did not lower blood glucose levels acutely, possibly because of rapid dissociation and excretion.     

Metal complexes of the trans-influencing ligand thiomaltol

The wide use of the ligand 3-hydroxy-2-methyl-4-pyrone (maltol) in bioinorganic chemistry has prompted an effort to further exploit this ligand class by achieving an efficient, one-step synthesis of the chelator 3-hydroxy-2-methyl-4-thiopyrone (thiomaltol). Complexes of thiomaltol with nickel(II) and iron(III) have been prepared and studied by using UV-visible spectroscopy and electrochemical methods. In addition, both complexes as well as the free thiomaltol ligand have been structurally characterized by using single-crystal X-ray diffraction methods. The ligand is found to exert a strong trans influence on the structure of the complexes in the solid state with the nickel(II) and iron(III) complexes demonstrating a cis and fac geometry, respectively. The compounds described here should significantly expand the scope and utility of O,S-donor ligands derived from maltol and related precursors.     

New lipophilic 3-hydroxy-4-pyridinonate iron(III) complexes: synthesis and EXAFS structural characterisation

New tris-iron(III) chelates of 3-hydroxy-4-pyridinone ligands derived from maltol (3-hydroxy-2-methyl-4-pyrone) or ethylmaltol (2-ethyl-3-hydroxy-4-pyrone), including a variety of N-aryl (phenyl, 4'-tolyl, 4'-(n-butyl)phenyl, 4'-(n-hexyl)phenyl) and N-benzyl (4'-methylbenzyl, 4'-fluorobenzyl and 4'-(trifluoromethyl)benzylamine) substituents on the nitrogen atom of the pyridinone ring, have been prepared. Characterization by C,H,N elemental analysis and thermogravimetric measurements indicates that most of the complexes are obtained as hydrates of general formula ML3.xH2O. Structural characterization of these difficult to crystallize lipophilic complexes has been achieved by EXAFS spectroscopy. Solutions of iron(III) complexes of maltol, ethylmaltol, 1,2-dimethyl-3-hydroxy-4-pyridinone and 1-phenyl-2-methyl-3-hydroxy-4-pyridinone in methanol-water mixtures were also examined by EXAFS. Distances from the central atom to ligand atoms, within 6 A of the metal, have been determined in the solid and solution samples and the results show that the structure observed in the powder is maintained in solution. The local structure around the metal centre, bond distances and bond angles, does not change significantly with variable lipophilicity, thus indicating that ligands may be tailored according to specific needs without altering their chelation properties. EXAFS data analysis for this set of tris-iron(III) compounds illustrates the important contribution of both intra-ligand and inter-ligand multiple scattering pathways through the metal centre to a peak observed in the FT spectrum at twice the metal ligand distance (approximately 4 A). The present results demonstrate that EXAFS features at twice the metal-ligand distance are valuable in the assignment of molecular geometry and that location of hydration water molecules, by EXAFS analysis, is limited by the geometry of the complexes, in particular for those in which ligands containing phenyl rings are present.     

Effect of alkyl substitueras in hydrophobic 8-quinolinol on the extraction of gallium(III) and applications to the separation of gallium(III) from aluminum(III)

The extraction of gallium(III) with newly prepared 5-alkyloxymethyl-8-quinolinol derivatives with alkyl substituent at the 2-position in 8-quinolinol moiety has been studied. The Ga(III)-5-octyloxymethyl-8-quinolinol (HO(8)Q), Ga(III)-2-methyl-5-octyloxymethyl-8-quinolinol (HMO(8)Q), Ga(III)-2-methyl-5-hexyloxymethyl-8-quinolinol (HM-O(6)Q), and Ga(HI)-2-n-butyl-5-hexyloxymethyl-8-quinolinol (HNBO(6)Q) complexes extracted in heptane from a perchloric acid medium were Ga(O(8)Q)(3), Ga(OH)(H(2)O)(MO(8)Q)(2), Ga(OH)(H(2)O)(MO(6)Q)(2) and Ga(OH)H(2)O)(NBO(6)Q)(2), respectively. The 2-tert-butyl-5-hexyloxymethyl-8-quinolinol did not exhibit any reactivity toward gallium(III). The extraction constants for Ga(O(8)Q)(3) (K(ex) = [Ga(O(8)Q)(3)](org) [H(+)](3)/[Ga(3+)][HO(8)Q](org)(3)), Ga(OH)(H(2)O)(MO(8)Q)(2) (K(ex) = [Ga(OH) (H(2)O)(MO(8)Q)(2)](org) [H(+)](3)/[Ga(3+)][HMO(8)Q](org)(2)), Ga(OH)(H(2)O)(2)(MO(6)Q)(2) and Ga(OH)(H(2)O)(NBO(6)Q)(2), which were extracted in heptane from an acidic solution, are 10(3.21 +/- 0.12), 10(-4.24 +/- 0.16), 10(-3.84 +/- 0.16) and 10(-4.07 +/- 0.07), respectively at I = 0.1 M and 25 degrees C. HNBO(6)Q exhibited very high selectivity toward gallium(III) in the presence of aluminum(III). Even in the presence of a 100 fold excess of aluminum(III) to gallium(III) (1.43 x 10(-5) M), gallium(III) was completely extracted and the distribution ratio of aluminum(III) was found to be less than 2.0 x 10(-3).     

Spectroscopic, thermal and biological studies of the coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes

The complexations of sulfasalazine (H3Suz) with some of transition metals have been investigated. Three types of complexes, [Mn(HSuz)-2(H2O)4] x 2H2O, [M(HSuz)-2(H2O)2] x xH2O (M=Hg(II), ZrO(II) and VO(II), x=4, 8 and 6, respectively) and [M(HSuz)-2(Cl)(H2O)3] x xH2O (M=Cr(III) and Y(III), x=5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the H3Suz behaves as a bidentate ligand. The thermal decomposition of the complexes as well as thermodynamic parameters (DeltaE*, DeltaH*, DeltaS* and DeltaG*) were estimated using Coats-Redfern and Horowitz-Metzger equations. In vitro antimicrobial activities of the H3Suz and the complexes were tested.     

Synthesis, structure, and electronic properties of RuN6 dinuclear Ru-Hbpp complexes

A series of RuN(6) dinuclear Ru-Hbpp complexes (Hbpp is the dinucleating tetraaza ligand 3,5-bis(pyridyl)pyrazole) of general formula {[Ru(II)(R(2)-trpy)(MeCN)](2)(μ-R(1)-bpp)}(3+), 10(3+)-14(3+), (R(1) = H, Me, or NO(2). and R(2) = H, Me, MeO; see Scheme 1) has been prepared from their Cl(-) or AcO(-) bridged precursors. The complexes have been characterized by UV-vis, NMR, CV, and some by X-ray. Complexes 10(3+)-14(3+), Ru(2)(II,II), were oxidized by 1 equiv in solution, leading to the mixed valence Ru(2)(II,III) complexes 10(4+)-14(4+) containing one unpaired electron and were characterized by EPR and UV-vis-near-IR, which showed metal-centered spin and the presence of low-energy IVCT bands. The H(ab) parameter indicates a relatively strong electronic coupling between the two ruthenium centers (class II). Further two electron oxidation in solution of the 10(3+)-14(3+) led to the formation of EPR silent Ru(2)(III,III) complexes 10(5+)-14(5+), that were further characterized by UV-vis-NIR. TD-DFT calculations are employed to assign the nature of the UV-vis transitions for the complexes in the various oxidation states, which are of metal to ligand charge transfer (MLCT) type for Ru(2)(II,II) and ligand to metal charge transfer (LMCT) type for Ru(2)(III,II) and Ru(2)(III,III).     

Synthesis and reactivity of metal complexes supported by the tetradentate monoanionic ligand bis(2-picolyl)(2-hydroxy-3,5-di-tert-butylbenzyl)amide (BPPA)

Metal-halide complexes of Ti, V, Y, Zr, Al, Ga, and U supported by the tetradentate monoanionic (TDMA) ligand bis(2-picolyl)(2-hydroxy-3,5-di-tert-butylbenzyl)amine, H(BPPA), were synthesized and spectroscopically characterized. In addition, the complexes (BPPA)TiCl2, (BPPA)VBr2, [(BPPA)YCl2]2, (BPPA)AlCl2, (BPPA)GaCl2, and (BPPA)UI3 were characterized by single-crystal X-ray crystallography. In all cases the ligand is bound kappa4 to the metal center. All structurally characterized compounds are monomeric in the solid-state with the exception of [(BPPA)YCl2]2, which exists as a dimer in the solid-state. The metal-alkyl complexes (BPPA)AlMe2 and (BPPA)Zr(CH2Ph)3 were also synthesized and characterized, and an X-ray structure of (BPPA)Zr(CH2Ph)3 was obtained. The transformation of BPPA from a monoanionic to a dianionic ligand via proton abstraction was observed and monitored by NMR spectroscopy.     

Controllable assembly of metal-directed coordination polymers under diverse conditions: a case study of the M(II)-H3tma/Bpt mixed-ligand system

A series of new metal-organic polymeric complexes, [[Co(bpt)(Htma)(H2O)3].2.25H2O]n (1), [Co(bpt)(Htma)(H2O)]n (2), [Ni(bpt)(Htma)(H2O)]n (3), [Zn(bpt)2(H2tma)2].6H2O (4), [[Cd(bpt)(Htma)(H2O)].(C2H5OH)(H2O)1.5]n (5), and [[Cd(bpt)(Htma)(H2O)2].5.5H2O]n (6), was prepared from solution reactions of 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (bpt) and trimesic acid (H3tma) with different metal salts under diverse conditions. All these compounds were structurally determined by X-ray single-crystal diffraction, and the bulk new materials were further identified by X-ray powder diffraction. Complexes 1 and 6 show 1-D zigzag or linear Htma-bridged polymeric chains, with the terminal bpt ligands as pendants, which are extended to 2-D hydrogen-bonded arrays with 4.8(2) or (6,3) network topology. Coordination polymers 2 and 3, in which the 2-D corrugated metal-organic frameworks make the interdigitated 3-D packing, are isostructural. Complex 4 has a mononuclear structure, and its subunits are hydrogen-bonded to each other to give a 2-D grid-like net. For complex 5, the Cd(II) centers are linked by bpt/Htma ligands to form a 2-D (4,4) coordination layer, and these layers are interdigitated in pairs. Notably, secondary noncovalent forces, such as hydrogen bonds, play an important role in extending and stabilizing these structural topologies. Interestingly, distinct products are obtained for Co(II) (1 and 2) and Cd(II) (5 and 6) under ambient or hydrothermal conditions; however, for Ni(II) and Zn(II), single products, 3 and 4, are generated. The thermal stabilities of 1-6 were studied by thermogravimetric analysis of mass loss. The desorption/adsorption properties of the porous material 5 are also discussed. Solid-state luminescent spectra of the Zn(II) and Cd(II) complexes, 4-6, indicate intense fluorescent emissions at ca. 380 nm.     

Water oxidation by mononuclear ruthenium complexes with TPA-based ligands

The synthesis, characterization, and water oxidation activity of mononuclear ruthenium complexes with tris(2-pyridylmethyl)amine (TPA), tris(6-methyl-2-pyridylmethyl)amine (Me(3)TPA), and a new pentadentate ligand N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine (DPA-Bpy) have been described. The electrochemical properties of these mononuclear Ru complexes have been investigated by both experimental and computational methods. Using Ce(IV) as oxidant, stoichiometric oxidation of water by [Ru(TPA)(H(2)O)(2)](2+) was observed, while Ru(Me(3)TPA)(H(2)O)(2)](2+) has much less activity for water oxidation. Compared to [Ru(TPA)(H(2)O)(2)](2+) and [Ru(Me(3)TPA)(H(2)O)(2)](2+), [Ru(DPA-Bpy)(H(2)O)](2+) exhibited 20 times higher activity for water oxidation. This study demonstrates a new type of ligand scaffold to support water oxidation by mononuclear Ru complexes.     

Luminescent complexes of silver(I) with pyridylbis(3-hexamethyleneiminyl thiosemicarbazone): effect of the counterion on the nuclearity

The reaction of pyridylbis(3-hexamethyleneiminyl thiosemicarbazone) (H(2)Plhexim) with various silver(I) salts and metal-ligand ratios led to the isolation of different complexes of the formulae [Ag(NO(3))(H(2)Plhexim)]·H(2)O (1), [Ag(2)(NO(3))(H(2)Plhexim)(CH(3)OH)](NO(3)) (2), [Ag(2)(ClO(4))(2)(H(2)Plhexim)] (3), [Ag(HPlhexim)]·xH(2)O (4), [Ag(HPlhexim)] (4a), [Ag(2)(Plhexim)(PPh(3))(4)]·2MeOH (5) and [Ag(4)(Plhexim)(2)]·DMF (6). The complexes were fully characterized by elemental analysis, ESI mass spectrometry, IR and NMR ((1)H, (31)P) spectroscopy. The structures of 4a, 5 and 6 were also identified by single crystal X-ray structure determination. The concentration dependence on the absorption spectra of the methanolic solutions indicates polymerization equilibria in the ground state in both the ligand and the complexes. While H(2)Plhexim is essentially non-fluorescent, complexes 1-5 fluoresce more strongly by comparison. This fluorescent behavior is consistent with the monomeric or dimeric nature of the complexes.     

Biomimetic aryl hydroxylation derived from alkyl hydroperoxide at a nonheme iron center. Evidence for an Fe(IV)=O oxidant

Many nonheme iron-dependent enzymes activate dioxygen to catalyze hydroxylations of arene substrates. Key features of this chemistry have been developed from complexes of a family of tetradentate tripodal ligands obtained by modification of tris(2-pyridylmethyl)amine (TPA) with single alpha-arene substituents. These included the following: -C(6)H(5) (i.e., 6-PhTPA), L(1); -o-C(6)H(4)D, o-d(1)-L(1); -C(6)D(5), d(5)-L(1); -m-C(6)H(4)NO(2), L(2); -m-C(6)H(4)CF(3), L(3); -m-C(6)H(4)Cl, L(4); -m-C(6)H(4)CH(3), L(5); -m-C(6)H(4)OCH(3), L(6); -p-C(6)H(4)OCH(3), L(7). Additionally, the corresponding ligand with one alpha-phenyl and two alpha-methyl substituents (6,6-Me(2)-6-PhTPA, L(8)) was also synthesized. Complexes of the formulas [(L(1))Fe(II)(NCCH(3))(2)](ClO(4))(2), [(L(n)())Fe(II)(OTf)(2)] (n = 1-7, OTf = (-)O(3)SCF(3)), and [(L(8))Fe(II)(OTf)(2)](2) were obtained and characterized by (1)H NMR and UV-visible spectroscopies and by X-ray diffraction in the cases of [(L(1))Fe(II)(NCCH(3))(2)](ClO(4))(2), [(L(6))Fe(II)(OTf)(2)], and [(L(8))Fe(II)(OTf)(2)](2). The complexes react with tert-butyl hydroperoxide ((t)()BuOOH) in CH(3)CN solutions to give iron(III) complexes of ortho-hydroxylated ligands. The product complex derived from L(1) was identified as the solvated monomeric complex [(L(1)O(-))Fe(III)](2+) in equilibrium with its oxo-bridged dimer [(L(1)O(-))(2)Fe(III)(2)(mu(2)-O)](2+), which was characterized by X-ray crystallography as the BPh(4)(-) salt. The L(8) product was also an oxo-bridged dimer, [(L(8)O(-))(2)Fe(III)(2)(mu(2)-O)](2+). Transient intermediates were observed at low temperature by UV-visible spectroscopy, and these were characterized as iron(III) alkylperoxo complexes by resonance Raman and EPR spectroscopies for L(1) and L(8). [(L(1))Fe(II)(OTf)(2)] gave rise to a mixture of high-spin (S = 5/2) and low-spin (S = 1/2) Fe(III)-OOR isomers in acetonitrile, whereas both [(L(1))Fe(OTf)(2)] in CH(2)Cl(2) and [(L(8))Fe(OTf)(2)](2) in acetonitrile afforded only high-spin intermediates. The L(1) and L(8) intermediates both decomposed to form respective phenolate complexes, but their reaction times differed by 3 orders of magnitude. In the case of L(1), (18)O isotope labeling indicated that the phenolate oxygen is derived from the terminal peroxide oxygen via a species that can undergo partial exchange with exogenous water. The iron(III) alkylperoxo intermediate is proposed to undergo homolytic O-O bond cleavage to yield an oxoiron(IV) species as an unobserved reactive intermediate in the hydroxylation of the pendant alpha-aryl substituents. The putative homolytic chemistry was confirmed by using 2-methyl-1-phenyl-2-propyl hydroperoxide (MPPH) as a probe, and the products obtained in the presence and in the absence of air were consistent with formation of alkoxy radical (RO(*)). Moreover, when one ortho position was labeled with deuterium, no selectivity was observed between hydroxylation of the deuterated and normal isotopomeric ortho sites, but a significant 1,2-deuterium shift ("NIH shift") occurred. These results provide strong mechanistic evidence for a metal-centered electrophilic oxidant, presumably an oxoiron(IV) complex, in these arene hydroxylations and support participation of such a species in the mechanisms of the nonheme iron- and pterin-dependent aryl amino acid hydroxylases.     

Extended rodlike polyaromatic receptors with bent tridentate units complexed to lanthanide metal ions

A synthetic strategy is developed to attach semirigid lipophilic sidearms to the 6-positions of bent aromatic tridentate 2,6-bis(benzimidazol-2-yl)pyridine cores to produce U-shaped ligands, L6,7. Differential scanning calorimetry (DSC) reveals that entropic contributions severely affect the isotropization processes of these flexible receptors, but no mesomorphism is detected. The attachment of oxygen linkers to the 5- or 6-positions of the benzimidazole sidearms lowers the ligand-centered 1 pi pi* and 3 pi pi* excited states, and the semiempirical ZINDO method assigns this effect to a destabilization of the HOMO orbitals resulting from pi-interactions. Reactions of L6 with Ln(NO3)3.xH2O provide the rodlike 1:1 complexes [Ln(L6)(NO3)3] (Ln = La-Lu), which are stable in the solid state but partially dissociate in acetonitrile. The crystal structure of [Lu(L6)(NO3)3].CH3CN (18a, LuC63H84N9O13, monoclinic, P2(1)/n, Z = 4) reveals an I-shaped arrangement of the ligand strand arising from the meridional complexation of the bent tridentate unit to nine-coordinate Lu(III). The replacement of nitrate anions with trifluoroacetate anions gives the centrosymmetric dimer [Lu(L6)(CF3CO2)3]2 (23, Lu2C134H162N10O20F18, triclinic, P1, Z = 1), in which the symmetry-related Lu atoms are connected by two bridging carboxylates, leading to an H-shaped dimetallic edifice. These complexes [Ln(L6)(NO3)3] and [Ln(L6)(CF3CO2)3]2 fulfill the geometrical criteria required by precursors of calamitic metallomesogens, but no mesomorphism can be detected, while photophysical studies indicate that the low energies of ligand-centered 3 pi pi* excited states drastically limit the luminescence of Eu(III) complexes. The relationships between structural and electronic properties resulting from 5- or 6-substitutions of the benzimidazole rings and the effects of these substitutions on photophysical and thermal properties are discussed.     

Complexes of aminosquarate ligands with first-row transition metals and lanthanides: new insights into their hydrolysis

Attempts at synthesizing first-row transition-metal complexes of the 3-hydroxy-4-[(1'S,2'R)-(2-hydroxy-1',2'-diphenylethyl)amino]-3-cyclobutene-1,2-dione ligand in alcoholic solutions resulted in the formation of the monomers [M(NH(2)C(4)O(3))(2)(H(2)O)(4)] [M = Mn (1), Co (2), Ni (3), Cu (4), Zn (5)] instead, as a result of the hydrolysis of the ligand. 1, 2, and 3 are isomorphous (C2/c), with the metal atoms octahedrally coordinated to four aqua and two cis aminosquarate ligands. The copper and zinc complexes (4 and 5) have the same molecular formula as 1-3 but belong to the C2/m and P2(1)/c space groups respectively. 4 has square-pyramidal geometry with trans-oriented aminosquarate ligands in the basal plane; aqua ligands complete the coordination sphere. 5 has octahedral geometry, with four aqua and two trans-oriented aminosquarate ligands. Reaction of aqueous solutions of the anilinosquarate ligand with Ln(NO(3))(3) x xH(2)O produced the eight-coordinate complexes {Sm(mu-C(6)H(5)NHC(4)O(3))(3)(H(2)O)(4) x 3H(2)O}n (6), {[M(mu(2)-C(4)O(4))(H(2)O)(6)][C(6)H(5)NHC(4)O(3)] x 4H(2)O}n [M = Er (7), Yb (8)], {Sm(C(6)H(5)NHC(4)O(3)) (mu(3)-C(4)O(4))(H(2)O)(4) x H(2)O}(n) (9), and {[{(C(6)H(5)NHC(4)O(3))(2)(H(2)O)(5)Yb}(2)(mu-C(4)O(4))] x 4H(2)O}n (10). 7 and 8 are isomorphous with the previously reported analogues Eu, Gd, and Tb ionic polymers. The presence of the squarate ligand in 7-10 is indicative of some form of hydrolysis of the anilinosquarate ligand during their syntheses. However, hydrolysis was not evident in the synthesis of 6. The mechanism for the hydrolysis in the syntheses of 1-5 is apparently different from that for 7-10.     

Structures and magnetism of {Ni2Na2}, {Ni4} and {Ni6(II)Ni(III)} 2-hydroxy-3-alkoxy-benzaldehyde clusters

Three polynuclear complexes, [NiNa(μ(1,1,1)-N(3))(μ-hmb)(2)(DMF)](2), (1), [Ni(4)(μ(3)-OMe)(4)(heb)(4)(MeOH)(1.05)(H(2)O)(2.95)], (2) and [Ni(III)(OH)(6)(hmb)(6)Ni(II)(6)]·(ClO(4))(3) (3) (Hhmb = 2-hydroxy-3-methoxy-benzaldehyde; Hheb = 2-hydroxy-3-ethoxy-benzaldehyde), were prepared by reaction of the appropriate ligand with nickel(II) perchloride hexahydrate under solvothermal conditions. All compounds were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 exhibits a centrosymmetric heterotetranuclear cluster which represents the first nickel complex to possess two connected face-sharing cubes structure {Ni(2)Na(2)N(2)O(4)}. Compound 2 has a tetranuclear Ni cluster with a cubane topology in which the Ni(II) and the oxygen atoms from the methanol ligands occupying alternate vertices of the cube. Compound 3 consisits of a mixed-valence [Ni(III)(OH)(6)(hmb)(6)Ni(II)(6)](3+) subunits and it represents the first nickel {Ni(II)(6)Ni(III)} complex to possess a planar hexagonal disc-like structure. The results show that the minor ligand modifications or solvent change have a key role in the structural control of the self-assembly process. Magnetic properties of 1-3 in the 300-2 K have been discussed. The {Ni(2)Na(2)} (1) and {Ni(4)} (2) core display dominant ferromagnetic interactions from the nature of the binding modes through μ(3)-N(3)(-) or μ(3)-OCH(3)(-), while {Ni(II)(6)Ni(III)} core (3) displays dominant anti-ferromagnetic interactions from the nature of the binding modes through μ(3)-OH(-).     

具有生物活性的金属配合物的研究 II: 3,6-二(二甲氨基)-二苯并碘六环稀土乙二胺四乙酸配合物的合成, 性质及抗肿瘤活性

合成了十四种新的3,6-二(二甲氨基)-二苯并碘六环稀土乙二胺四乙酸(EDTA)配合物, 其化学式为[C17H20N2I][RE(EDTA)].xH2O(RE=Ce, x=2; Pr, x=3; Nd-Lu, Y,x=4). 利用热重-差热分析, X射线粉末衍射, 摩尔电导,红外及紫外光谱等对这些配合物进行了表征. 试验表明, 配合物对体外癌(L7712)细胞DNA合成的抑制率较其前体为高.     

Synthesis, structure, and reactivity of rhodium and iridium complexes of the chelating bis-sulfoxide tBuSOC2H4SOtBu. Selective O-H activation of 2-hydroxy-isopropyl-pyridine

The chloro-bridged rhodium and iridium complexes [M2(BTSE)2Cl2] (M = Rh 1, Ir 2) bearing the chelating bis-sulfoxide tBuSOC2H4SOtBu (BTSE) were prepared by the reaction of [M2(COE)4Cl2] (M = Rh, Ir; COE = cyclooctene) with an excess of a racemic mixture of the ligand. The cationic compounds [M(BTSE)2][PF6] (M = Rh 3, Ir 4), bearing one S- and one O-bonded sulfoxide, were also obtained in good yields. The chloro-bridges in 2 can be cleaved with 2-methyl-6-pyridinemethanol and 2-aminomethyl pyridine, resulting in the iridium(I) complexes [Ir(BTSE)(Py)(Cl)] (Py = 2-methyl-6-pyridinemethanol 5, 2-aminomethyl-pyridine 6). In case of the bulky 2-hydroxy- isopropyl-pyridine, selective OH oxidative addition took place, forming the Ir(III)-hydride [Ir(BTSE)(2-isopropoxy-pyridine)(H)(Cl)] 7, with no competition from the six properly oriented C-H bonds. The cationic rhodium(I) and iridium(I) compounds [M(BTSE)(2-aminomethyl-pyridine)][X] (M = Rh 8, Ir 10), [Rh(BTSE)(2-hydroxy- isopropyl-pyridine)][X] 9(stabilized by intramolecular hydrogen bonding), [Ir(BTSE)(pyridine)2][PF6] 12, [Ir(BTSE)(alpha-picoline)2][PF6] 13, and [Rh(BTSE)(1,10-phenanthroline)][PF6] 14 were prepared either by chloride abstraction from the dimeric precursors or by replacement of the labile oxygen bonded sulfoxide in 3 or 4. Complex 14 exhibits a dimeric structure in the solid state by pi-pi stacking of the phenanthroline ligands.     

Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 4. UV-visible spectral and electrochemical evidence of the remarkable electron-deficient properties of the new tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazinatometal octacations, [(2-Mepy)8TPyzPzM]8+ (M = MgII(H2O), CoII, CuII, ZnII)

Metal derivatives of the octacationic tetrakis-2,3-[5,6-di{2-(N-methyl)pyridiniumyl}pyrazino]porphyrazine macrocycle [(2-Mepy)(8)TPyzPzH(2)](8+) (2-Mepy = 2-(N-methyl)pyridiniumyl ring) isolated as water-soluble hydrated iodide salts of the general formula [(2-Mepy)(8)TPyzPzM](I(8)).xH(2)O, (M = Mg(II)(H(2)O), Co(II), Cu(II), Zn(II); x = 2-5) were prepared from the corresponding neutral complexes [Py(8)TPyzPzM].xH(2)O previously reported. Reaction of these complexes with CH(3)I in N,N-dimethylformamide under mild conditions led to full quaternization of all eight pyridine N atoms and formation of the octacations [(2-Mepy)(8)TPyzPzM](8+). Clathrated water molecules could be eliminated from the species [(2-Mepy)(8)TPyzPzM](I(8)).xH(2)O by mild heating ( Co(I) process, but the site of electron transfer is reversed and the final product upon a further one-electron reduction is formulated as a Co(II) dianion as opposed to a Co(I) pi-anion radical. This sequence is similar to what was earlier reported for reduction of the same compound in pyridine. Reversible one-electron oxidations are also observed for the unmethylated species [Py(8)TPyzPzM].xH(2)O where M = Co(II) and Mn(II) in DMSO. Remarkably, the octacationic macrocycles [(2-Mepy)(8)TPyzPzM](I(8)).xH(2)O, (M = Mg(II)(H(2)O), Co(II), Cu(II), and Zn(II); x = 2-5) are more easily reduced at any step of the reduction than the corresponding unquaternized species with the same metal ion. This indicates a higher tendency to stepwise electron uptake after the quaternization process, which enhances the charge redistribution capability within the species formed by the electroreduction.     

Study of the ligand substitution reactions of cis,cis-[(bpy)(2)(L)RuORu(L')(bpy)(2)](n+) (L,L' = H(2)O,OH(-), NH(3)) using electrospray ionization mass spectrometry and (1)H NMR

We have successfully applied electrospray ionization mass spectrometry (ESI-MS) and (1)H NMR analyses to study ligand substitution reactions of mu-oxo ruthenium bipyridine dimers cis,cis-[(bpy)(2)(L)RuORu(L')(bpy)(2)](n+) (bpy = 2,2'-bipyridine; L and L' = NH(3), H(2)O, and HO(-)) with solvent molecules, that is, acetonitrile, methanol, and acetone. The results clearly show that the ammine ligand is very stable and was not substituted by any solvents, while the aqua ligand was rapidly substituted by all the solvents. In acetonitrile and acetone solutions, the substitution reaction of the aqua ligand(s) competed with a deprotonation reaction from the ligand. The hydroxyl ligand was not substituted by acetonitrile or acetone, but it exchanged slowly with CH(3)O(-) in methanol. The substitution reaction of the aqua ligands in [(bpy)(2)(H(2)O)Ru(III)ORu(III)(H(2)O)(bpy)(2)](4+) was more rapid than that of the hydroxyl ligand in [(bpy)(2)(H(2)O)Ru(III)ORu(IV)(OH)(bpy)(2)](4+). In methanol, slow reduction of Ru(III) to Ru(II) was observed in all the mu-oxo dimers, and the Ru-O-Ru bridge was then cleaved to give mononuclear Ru(II) complexes.     

Syntheses, structures and properties of a series of non-heme alkoxide-Fe(III) complexes of a benzimidazolyl-rich ligand as models for lipoxygenase

The treatment of Fe(ClO(4))(2)·6H(2)O or Fe(ClO(4))(3)·9H(2)O with a benzimidazolyl-rich ligand, N,N,N',N'-tetrakis[(1-methyl-2-benzimidazolyl)methyl]-1,2-ethanediamine (medtb) in alcohol/MeCN gives a mononuclear ferrous complex, [Fe(II)(medtb)](ClO(4))(2)·?CH(3)CN·?CH(3)OH (1), and four non-heme alkoxide-iron(III) complexes, [Fe(III)(OMe)(medtb)](ClO(4))(2)·H(2)O (2, alcohol = MeOH), [Fe(III)(OEt)(Hmedtb)](ClO(4))(3)·CH(3)CN (3, alcohol = EtOH), [Fe(III)(O(n)Pr)(Hmedtb)](ClO(4))(3)·(n)PrOH·2CH(3)CN (4, alcohol = n-PrOH), and [Fe(III)(O(n)Bu)(Hmedtb)](ClO(4))(3)·3CH(3)CN·H(2)O (5, alcohol = n-BuOH), respectively. The alkoxide-iron(III) complexes all show 1) a Fe(III)-OR center (R = Me, 2; Et, 3; (n)Pr, 4; (n)Bu, 5) with the Fe-O bond distances in the range of 1.781-1.816 ?, and 2) a yellow color and an intense electronic transition around 370 nm. The alkoxide-iron(III) complexes can be reduced by organic compounds with a cis,cis-1,4-diene moiety via the hydrogen atom abstraction reaction.     

Attempted syntheses of lanthanide(III) complexes of the anisole- and anilinosquarate ligands

The polymeric lanthanide complexes (Ln(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2 (H2O)4.xH2O)n [Ln=La (1), Eu (2), Gd (3)], formed from the reaction of aqueous solutions of anisolesquarate and Ln(NO3)3.xH2O, are all structurally similar with only subtle differences between the lanthanum complex and the isomorphous pair of europium and gadolinium analogues. The lanthanum atom in 1 has a square antiprismatic coordination geometry comprising two pendant and two mu-1,3-bridging anisolesquarate groups and four aqua ligands. Complexes 2 and 3 have two independent metal atoms in their asymmetric units compared to one for the lanthanum complex. However, the gross structures of 1-3 are essentially the same. The asymmetric unit of the terbium complex ((CH3OC6H5C4O3)3Tb(H2O)4(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2Tb(H2O)5).H2O (4) contains two independent binuclear units which hydrogen bond to form an extended structure very similar to those of 1-3. The ionic polymers ([Ln(mu2-C4O4)(H2O)6][C6H5NHC4O3].4H2O)n [Ln=Eu (5), Gd (6), Tb (7)] result from the incomplete hydrolysis of the anilinosquarate ion during the attempted synthesis of Eu(III), Gd(III), and Tb(III) anilinosquarate complexes. However, complete hydrolysis of the substituent is accomplished by La(III) ions, and the neutral polymer (La2(mu2-C4O4)2(mu3-C4O4)(H2O)11.2H2O)n (8) is formed. In complexes 5-7, the central lanthanide atom has a square antiprismatic geometry, being bonded to two mu-1,2-bridging squarate and six aqua ligands. Two anilinosquarate counteranions participate in second-sphere coordination via direct hydrogen bonding to aqua ligands on each metal center. These counteranions, and the included waters of crystallization, serve to link neighboring cationic polymer chains via an extensive array of O-H...O hydrogen bonds to form a 3-dimensional network. The polymeric lanthanum complex 8 contains two different metal environments, each having distorted monocapped square antiprismatic geometry. For one lanthanum atom the coordination polyhedron comprises five aqua and four squarate ligands, while for the other the polyhedron consists of six aqua and three squarate ligands; in each case one of the aqua ligands occupies the capping position. The squarate ligand exhibits two coordination modes in 8 (mu-1,2- and mu-1,3-bridging), and neighboring polymer chains are cross-linked by hydrogen bonds to form a 3-dimensional network.