Synthesis of Cytotoxic Sinapyl Alcohol Derivatives fromLigularia nelumbifolia

Total synthesis of two cytotoxic natural products, nelumol A(1) and nelumal A(2), were carried out by two different paths. 4-O-Benzyl substitute analogues 26 and 27, as well as the 4-O-(2-methyl-butenyl) derivatives 29 and 30 were also synthesized for a SAR invesigation. 1 and 2 were also measured on different tumor cell line.     

Zeolite structure direction by simple bis(methylimidazolium) cations: the effect of the spacer length on structure direction and of the imidazolium ring orientation on the 19F NMR resonances

A series of doubly charged structure-directing agents based on two methylimidazolium moieties linked by a linear bridge of n = 3,4,5, or 6 methylene groups has been used in the synthesis of pure silica zeolites in the presence of fluoride. All of them yielded zeolite TON while only the one with n = 4 was able to produce also zeolite MFI at highly concentrated conditions. In this MFI zeolite, two distinct (19)F MAS NMR resonances with about equal intensity were observed, indicating two different chemical environments for occluded fluoride. With the singly charged 1-ethyl-3-methylimidazolium cation, which can be formally considered as the "monomer" of the bis-imidazolium cation with n = 4, TON and MFI were also obtained, and again two (19)F MAS NMR resonances now with largely dissimilar intensities were observed in MFI. Molecular mechanics simulations support a commensurate structure-direction effect for n = 4 in MFI, with each imidazolium ring, in two different orientations, sitting close to the [4(1)5(2)6(2)] cage. Periodic DFT calculations suggest that F in MFI resides always in the [4(1)5(2)6(2)] cages, with the different (19)F resonances observed being due to the different orientation of the closest imidazolium ring.     

Supramolecular isomerism within three-dimensional 3-connected nets: unusual synthesis and characterization of trimorphic copper(I) 3,5-dimethyl-1,2,4-triazolate

Solvothermal treatments of acetonitrile, aqueous ammonia and copper(II) salts frequently yielded alpha-[Cu(mtz)](1)(Hmtz = 3,5-dimethyl-1,2,4-triazole) under different reaction conditions. However, two new supramolecular isomers of 1, namely beta-[Cu(mtz)](2) and gamma-[Cu(mtz)](3) were successfully isolated upon introducing 4,4'-bipyridine or nitrate as an additive. 1-3 represent the first example of true supramolecular isomerism within 3D 3-connected nets. Besides the 4.8.10 net for the tetragonal phase 1 (P4(2)/n, a= 13.470(2), c= 6.142(2)A), two novel 3-connected nets, 8(2)10-a and 6.10(2), were observed in the new tetragonal phase 2 (I42d, a= 14.0247(5), c= 5.2884(4)A) and orthorhombic phase 3 (Iba2, a= 8.0423(7), b= 11.5310(10), c= 17.3505(16)A), respectively. The three isomers also displayed distinct physical properties related to their different supramolecular structures.     

Acetic acid induced self-assembly of supramolecular compounds [Et4N]3[(WS4Cu2)2(mu-CN)3].2MeCN and [PPh4][WS4Cu3(mu-CN)2].MeCN from preformed clusters [A]2[WS4(CuCN)2] (A = Et4N, PPh4)

Reactions of two preformed trinuclear W/Cu/S clusters, [A](2)[WS(4)(CuCN)(2)] (1: A = Et(4)N; 2: A = PPh(4)), with different concentrations of acetic acid in MeCN generate two interesting 2D polymeric clusters [Et(4)N](3)[(WS(4)Cu(2))(2)(mu-CN)(3)].2MeCN (3), and [PPh(4)][WS(4)Cu(3)(mu-CN)(2)].MeCN (4), respectively. Compound 4 can also be readily obtained in a high yield from the reaction of 2 with equimolar [Cu(MeCN)(4)]PF(6) in MeCN. These compounds have been characterized by elemental analysis, IR spectra, thermal analysis, and single-crystal X-ray diffraction. An X-ray analysis reveals that compound 3 retains the WS(4)Cu(2) cluster core, which serves as a 3-connecting node to link equivalent nodes via single cyanide bridges, forming an anionic 2D (6,3) net. Compound 4 consists of a T-shaped WS(4)Cu(3) core, which also acts as a 3-connecting node, with links to 3 equivalent clusters either through single or double cyanide bridges, affording a different anionic 2D (6,3) network. The acetic acid induced aggregation of 3 and 4 from the two cluster precursors 1 and 2 suggests that this simple synthetic strategy is likely to be applicable to many related systems.     

1,3-双(偶氮介晶基)-1,1,3,3-四甲基二硅氧烷的 合成、2D NMR结构分析和液晶性能

合成了2个(CH3(C6H4)N2(C6H3A)COO(C6H4)OCH2-Si(CH3)2)2O化合物,其中A = H为1,A = CH3为2。经IR、1H NMR和元素分析表征,并用2D NMR1H-1H COSY记录了2个化合物中不同取代基苯环上所有质子的化学位移和相关-自旋偶合常数,对谱线的归属作了指认。通过偏光显微镜和DSC分析,1具有液晶性能,而2没有液晶性能。同时,用AM1方法计算了它们的电子结构,讨论了它们的结构与性能之间的关系。     

Linking two distinct layered networks of nanosized {Ln18} and {Cu24} wheels through isonicotinate ligands

A new series of heterolanthanide(III)-copper(I) wheel-cluster complexes [Ln6(micro3-O)2](IN)18-[Cu8(micro4-I)2(micro2-I)3].H3O (IN=isonicotinate; Ln=Y 1, Nd 2, Dy 3, Gd 4, Sm 5, Eu 6, Tb 7) were prepared by hydrothermal reaction at low pH. X-ray crystallographic studies reveal that two unusual trinuclear [Ln3(micro3-O)] and tetranuclear [Cu4(micro4-I)] cores are successfully used as secondary building units to make two different nanosized wheels [Ln18(micro3-O)6(CO2)48](6-), {Ln18}, and [Cu24(micro4-I)6(micro2-I)12]6+, {Cu24}, with 12-rings and a diameter of 26.7 and 26.4 A, respectively. The wheels are further assembled into two-dimensional (2D) {Ln18} and {Cu24} networks, the linkages between two distinct layered networks of {Ln18} and {Cu24} wheels by IN pillars along the c axis giving a series of unprecedented three-dimensional (3D) sandwich frameworks. To our knowledge, compounds 1-7 are the first examples containing two different layered networks of nanosized Ln and transition metal (TM) wheels in wheel-cluster chemistry. The IR, UV/Vis, thermogravimetric analysis (TGA), luminescent, and magnetic properties of these complexes were also studied.     

Disordered CuN(6) Jahn-Teller Centers in Hexakis(1-methyltetrazole)copper(II) Tetrafluoroborate: A Temperature-Dependent X-ray Diffraction and EPR Study

The influence of the molecular crystalline arrangement upon the state of a Jahn-Teller-active center has been investigated in crystals of the complex Cu(mtz)(6)(BF(4))(2), where mtz = 1-methyltetrazole. Crystal structures at 293, 123, and 93 K were determined by X-ray diffraction for the copper complex and at 293 and 100 K also for the analogous zinc complex, Zn(mtz)(6)(BF(4))(2). The respective lattice parameters for the copper complex at 293, 123, and 93 K are as follows: a = 18.137(4), 17.597(4), 17.575(4) ?; b = 10.247(4), 10.131(4), 10.133(4); c = 18.446(5), 18.531(4), 18.535(4) ?; beta = 112.62(2), 113.55(2), 113.61(2) degrees. Those for the zinc complexes at 293 and 100 K, respectively, are as follows: a = 18.153(2), 17.663(2) ?; b = 10.289(1), 10.159(2) ?; c = 18.506(3), 18.578(3) ?; beta = 113.21(1), 114.15(2) degrees. The crystal system is monoclinic, space group P2(1)/n (Z = 4), for all crystals with two crystallographically inequivalent pairs of centrosymmetric molecules, M(mtz)(6)(BF(4))(2), in the unit cell. The two inequivalent Cu(mtz)(6)(2+) complexes, Cu(A) and Cu(B), both exhibit Jahn-Teller distortions, but in different ways, the Cu-N distances for the unit on site A being 2.015(4), 2.031(5), and 2.384(5) ? at 93 K, while those for the unit on site B are 2.053(5), 2.126(5), and 2.204(5) ?. However, the Jahn-Teller radii of the two complexes, as calculated from the metal-ligand distances and the U tensors of the two CuN(6) units, were both found to be 0.41(3) ?. EPR experiments at room temperature on polycrystalline samples of the pure copper compound and of the copper-doped zinc compound confirm the presence of two different Jahn-Teller centers; both complexes are rapidly pulsating, but the CuN(6) units on site A are confined predominantly to one potential well of the warped Mexican hat potential, whereas the CuN(6) units on site B have density in all three wells. At 78 K, however, the spectrum of the polycrystalline material is consistent with a single site having an axial g tensor with maximum anisotropy (g( parallel) = 2.300(5), g( perpendicular) = 2.068(5)). While the low-temperature X-ray results also indicate a structure in which the Cu(A) center is exclusively populated in one potential well, the U tensor and potential well population data for the Cu(B) centers indicate that at 93 K a nonpulsating averaged structure based on tetragonally elongated CuN(6) units is being observed. The more pronounced preference for the CuN(6) octahedron on site A to show elongation in one specific direction, in contrast to that on the B site, appears to be due to the differing impacts of the local-site strains at the two distinct centers of symmetry, and a simple model for evaluating a crystal "packing" strain from the bond length data for the isomorphous zinc complex is described.     

Synthesis and characterization of [PW11O39Ir(H2O)]4-: successful incorporation of Ir into polyoxometalate framework and study of the substitutional lability at the Ir(III) site

The first Keggin-type heteropolyanion, [PW(11)O(39)Ir(H(2)O)](4-) (1), was synthesized by hydrothermal reaction from two different polytungstate precursors and [IrF(6)](2-). It was isolated as (Bu(4)N)(4)[PW(11)O(39)Ir(H(2)O)] (1a), which was completely characterized by multinuclear (31)P and (183)W NMR, ESI-mass spectrometry and cyclic voltammetry. A rapid screening methodology to ascertain the intrinsic substitutional lability at the Ir site is also presented, based on ESI-MS.     

Electrochemical synthesis,characterisation and comparative study of new conducting polymers from amino-substituted naphthalene sulfonic acids

Conducting polymers have been synthesised electrochemically from 4-amino-3-hydroxynaphthalene-1-sulfonic acid (4A3HN1SA), 4-aminonaphthalene-1-sulfonic acid (4AN1SA) and 7-amino-4-hydroxynaphthalene-2-sulfonic acid (7A4HN2SA) on glassy carbon electrodes. The influence of the positive potential limit on the potential cycling polymerisation of 4A3HN1SA was studied, and a sufficiently high potential limit allowed better film growth. Under similar polymerisation conditions, the three monomers showed different radical formation potentials and different voltammetric peak profiles. The effects of scan rate and solution pH on the electrochemical properties of the polymers were investigated, in the range between 10 and 200 mV s^?1, all the modified electrodes showing a surface-confined electrode process. In the pH range from 2.0 to 9.0, the anodic peak potentials decreased linearly with increasing pH for all the three modified electrodes. The modified electrodes were characterised by electrochemical impedance spectroscopy in pH 4.0 and 7.0 buffer solutions. The results showed a more porous poly(7A4HN2SA) film, which is less affected by pH change than the other two films. Scanning electron microscopy of the polymer films also showed significant differences in their morphologies.     

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

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

Organoaluminium and -gallium compounds with N,N-diisopropylaminomethyl groups

The N,N-diisopropylaminomethyl aluminium compound [tBu2AlCH2NiPr2 x LiCl]2(1) and the gallium compounds Li[tBu2Ga(CH2NiPr2)2](2) and [tBu2GaCH2N(H)iPr2]Cl x tBu3Ga (3) were prepared by transmetallation of N,N-diisopropylaminomethyllithium LiCH2NiPr2 with di-tert-butylaluminium or -gallium chloride, and characterised by elemental analyses, multinuclear NMR spectroscopy (1H, 13C, 27Al, 7Li) and IR spectroscopy. The crystal structures have been determined by single crystal X-ray diffraction. Compound aggregates as a centrosymmetric dimer, with two Al-C-N units connected by a frame of two LiCl molecules [Al-Cl 2.367(1), Cl-Li 2.339(4) and 2.374(4), Li-N 1.977(4)A]. Compound 2 is a lithium organogallate with two weak LiN bonds [1.965(7) and 1.937(7)A]. Compound 3 contains two different moieties: tBu3Ga and a [tBu2GaCH2N(H)iPr2]+ cation, which are bridged by a Cl- anion [Ga-Cl 2.445(1) and 2.579(1), HCl 2.362(3)A].     

Coordination-driven self-assembly of ruthenium-based molecular-rectangles: synthesis, characterization, photo-physical and anticancer potency studies

A suite of eight cationic, tetra-metallic molecular rectangles (1-8) was generated via coordination-driven self-assembly using four dicarboxylate-bridged arene-Ru precursors (A1-A4) with one of two dipyridyl ligands (D1, D2). The high-yielding (84-92%) rectangles were characterized by (1)H NMR and HR-ESI-MS to support their structural assignments. The molecular structure of 5 was determined by single crystal X-ray analysis, which indicated that two D2 ligands bridge two A1 acceptors to form a rectangular construct. The photophysical properties of these metalla-rectangles and their molecular precursors were also investigated, as well as an MTT assay to evaluate the in vitro cytotoxicities relative to two chemotherapeutic agents, cisplatin and doxorubicin. MTT assays were conducted using SK-hep-1 (liver cancer) and HCT-15 (colon cancer) human cancer cell lines. Compounds 3, 4, 7 and 8 showed significant activity, with IC(50) values comparable to those of cisplatin and doxorubicin.     

Homoleptic rare earth dipyridylamides [Ln2(N(NC5H4)2)6], Ln = Ce, Nd, Sm, Ho, Er, Tm, Yb, and Sc: metal oxidation by the amine melt and in 1,2,3,4-tetrahydroquinoline with the focus of different metal activation by amalgams, liquid ammonia, and microwaves

Homoleptic dimeric dipyridylamide complexes of the rare earth elements are obtained by solvent-free oxidation reactions of the metals with melts of 2,2'-dipyridylamine. As the thermal stabilities of the ligand as well as the amide complexes are limiting factors in these high-temperature syntheses, several different metal activation procedures have been investigated: the formation of Ln amalgams and dissolution of the metals in liquid ammonia as well as coupling to microwaves. For comparison with a solvent that shows low solubility of the metals and products, reactions in 1,2,3,4-tetrahydroquinoline were also carried out. For all lanthanides and group 3 metals used homoleptic dimers of the formula [Ln(2)(Dpa)(6)], Ln = Ce (1), Nd (2), Sm (3), Ho (4), Er (5), Tm (6), Yb (7), and Sc (8) and Dpa- = (C5H4N)2N-, were obtained, all containing trivalent rare earth ions with a distorted square antiprismatic nitrogen coordination. Due to the large differences in the ionic radii of the metal ions, two different structure types are found that crystallize in the space groups P2(1)/c and P2(1)/n with the border of the two types being between Tm and Yb. The orientations of two 1,3/1,3-double chelating and linking dipyridylamide ligands (Dpa(-) = (C(5)H(4)N)(2)N(-)) result in different overall orientations of the dimers and thus two structure types. All compounds were identified by single-crystal X-ray analysis. Mid-IR, far IR, and Raman spectroscopy, microanalyses, and simultaneous DTA/TG as well as mass spectrometry regarding their thermal behavior were also carried out to characterize the products. Crystal data for the two types follow. Ce (1): P2(1)/n; T = 170(2) K; a = 1063.0(1), b = 1536.0(1), c = 1652.0(2) pm; beta = 101.60(1) degrees ; V = 2642.2(3) x 10(6) pm(3); R(1) for F(o) > 4sigma(F(o)) = 0.046, wR(2) = 0.120. Sc (8): P2(1)/c; T = 170(2) K; a = 1073.0(1), b = 1506.2(2), c = 1619.8(2) pm; beta = 103.16(9) degrees ; V = 2548.9(5) x 10(6) pm(3); R(1) for F(o) > 4sigma(F(o)) = 0.038, wR(2) = 0.091.     

异相Ziegler-Natta催化剂的活性中心多分散性(Ⅰ)——钛催化体系聚合物分子量分布的研究

对TiCl₃及TiCl₄/MgCl₂-Al(C₂H₅)₃(或Al(i-C₄H₉)₃、Al(C₂H₅)₂Cl)催化体系合成的聚辛烯的分子量分布用SchulzeFlory"最可几分布"函数作拟合处理,将各种聚合条件下的实测分布分成了3～5个"最可几分布"的叠加,催化剂结构及聚合条件对这些"最可几分布"峰的位置、大小的影响较有规律,表明每个峰对应于一种活性中心。还测定了聚辛烯各级分的活性中心浓度。对各活性中心的差异作了分析。     

RE(AuAl2)nAl2(AuxSi1-x)2: a new homologous series of quaternary intermetallics grown from aluminum flux

The combination of early rare earth metals (La- to Gd and Yb), gold, and silicon in molten aluminum results in the formation of intermetallic compounds with four related structures, forming a new homologous series: RE[AuAl2]nAl2(AuxSi(1-x))2, with x approximately 0.5 for most of the compound and n = 0, 1, 2, and 3. Because of the highly reducing nature of the Al flux, rare earth oxides instead of metals can also be used in these reactions. These compounds grow as large plate-like crystals and have tetragonal structure types that can be viewed as intergrowths of the BaAl4 structure and antifluorite-type AuAl2 layers. REAuAl2Si materials form with the BaAl4 structure type in space group I4/mmm (cell parameters for the La analogue are a = 4.322(2) A, c = 10.750(4) A, and Z = 2). REAu2Al4Si forms in a new ordered superstructure of the KCu4S3 structure type, with space group P4/nmm and cell parameters of the La analogue of a = 6.0973(6) A, c = 8.206(1) A, and Z = 2. REAu3Al6Si forms in a new I4/mmm symmetry structure type with cell parameters of a = 4.2733(7) A, c = 22.582(5) A, and Z = 2 for RE = Eu. The end member of the series, REAu4Al8Si, forms in space group P4/mmm with cell parameters for the Yb analogue of a = 4.2294(4) A, c = 14.422(2) A, and Z = 1. New intergrowth structures containing two different kinds of AuAl2 layers were also observed. The magnetic behavior of all these compounds is derived from the RE ions. Comparison of the susceptibility data for the europium compounds indicates a switch from 3-D magnetic interactions to 2-D interactions as the size of the AuAl2 layer increases. The Yb ions in YbAu(2.91)Al(6)Si(1.09) and YbAu(3.86)Al(8)Si(1.14) are divalent at high temperatures.     

Synthesis, characterization, and magnetic properties of self-assembled compounds based on discrete homotrinuclear complexes of Cu(II)

Three new supramolecular entities of Cu(II) were synthesized and characterized: [(Cu(H(2)O)(tmen))(2)(mu-Cu(H(2)O)(opba))](2)[(ClO(4))(2)](2).2H(2)O (1), [(Cu(H(2)O)(tmen))(2) (mu-Cu(H(2)O) (Me(2)pba))](2)[(ClO(4))(2)](2) (2), and [(Cu(H(2)O)(tmen))(Cu(tmen))(mu-Cu(OHpba))](n)() ((ClO(4))(2))(n)().nH(2)O (3), where opba = o-phenylenbis(oxamato), Me(2)pba = 2,2-dimethyl-1,3-propylenbis(oxamato), OHpba = 2-hydroxy-1,3-propylenbis(oxamato), and tmen = N,N,N'N'-tetramethylethylenediamine. The crystal structures of 1, 2, and 3 were solved. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 20.572(4) A, b = 17.279(6) A, c = 22.023(19) A, beta = 103.13(4) degrees, and Z = 8. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 16.7555(7) A, b = 13.5173(5) A, c = 17.1240(7) A, beta = 104.9840(10) degrees, and Z = 4. Complex 3 crystallizes in the orthorhombic system, space group Pca2(1) with a = 21.2859(4) A, b = 12.8286(10) A, c = 12.6456(2) A, and Z = 4. The three complexes are very similar in structure: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine, but with a different environment in the Cu(II) central ion. In the case of complex 1, two of these trinuclear entities are packed with a short distance between the central Cu(II) ions of two separate entities forming a hexanuclear-type compound. In the case of 2, two of these trinuclear entities are linked by a hydrogen bond between a water molecule of one terminal Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, also forming a hexanuclear complex. In the case of complex 3, the intermolecular linkages give a one-dimensional system where the OH groups of the OHpba entities are linked to the terminal Cu(II) of the neighboring entities. The magnetic properties of the three complexes were studied by susceptibility measurements vs temperature. For complex 1, an intramolecular J value of -312.1 cm(-)(1) and a contact dipolar interaction of -0.44K were found. For complex 2 and 3 the fit was made by the irreducible tensor operator formalism (ITO). The values obtained were as follows: J(1) = -333.9 cm(-)(1) and J(2) = 0.67 cm(-)(1) for 2 and J(1) = -335.9 cm(-)(1) and J(2) = 3.5 cm(-)(1) for 3.     

Hydrothermal synthesis and characterization of two cobalt phosphates based on double-four-ring units with fluorine-occlusion and phosphite-substitution modifications

Two new fluorinated microporous cobalt phosphates, (H2en)0.5[F(0.25)Co(H(0.5)PO4)0.5(PO4)0.5].0.25H2O (1) and (H2en)0.5[Fx(H2O)0.25(-x)Co(HPO3)x(PO4)1-x].0.25H2O (x = 0.17; 2), have been synthesized from different P sources, H3PO4 and H3PO3, in the presence of ethylenediamine and F ions. Both structures of 1 and 2 are based on the similar secondary building unit of a double four ring (D4R). 1 crystallizes in the orthorhombic space group Cmcm with a = 14.895(1) A, b = 9.7133(9) A, c = 13.688(1) A, V = 1980.4(3) A(3), and Z = 16 and is built up from fully F-occluded double-four-ring units via corner-sharing Co and P polyhedra and edge-sharing Co polyhedra. 2 crystallizes in the tetragonal space group /42m with a = 10.2033(4) A, c = 9.5545(9) A, V = 994.7(1) A(3), and Z = 8 and adopts an ACO-type framework with strict alternation of corner-sharing Co and P polyhedra. On the basis of the evidence from ion chromatography studies and elemental analyses, 2 contains both phosphate and phosphite ions, and the amount of F ions in 2 is the same as the amount of phosphite ions. This implies that some PO4(3-) groups in 2 are substituted by HPO3(2-) groups with the same amount of F(-) occlusion in the center of D4R as charge compensation. Magnetic susceptibility measurements of both 1 and 2 appear that they contain mainly antiferromagnetic interaction (theta = -27.8 K for 1 and -35.0 K for 2). However, the magnetic coupling is much more complicated in compound 1 because of the Co-O-Co linkages in it. Low-field temperature-dependent magnetization curves of 1 showed spontaneous magnetization in the form of two continuous bumps, one sharp and one broad. This may be related to the temperature dependence of two related but different types of spin canting. At 2 K, 1 also showed a large coercive field of about 5000 Oe.     

Syntheses, crystal structures and properties of novel copper(II) complexes obtained by reactions of copper(II) sulfate pentahydrate with tripodal ligands

Three novel metal-organic frameworks (MOFs), [Cu(1)SO4].H2O (4), [Cu2(2)2(SO4)2].4H2O (5) and [Cu(3)(H2O)]SO4.5.5H2O (6), were obtained by hydrothermal reactions of CuSO4.5H2O with the corresponding ligands, which have different flexibility. The structures of the synthesized complexes were determined by single-crystal X-ray diffraction analyses. Complex 4 has a 2D network structure with two types of metallacycles. Complex 5 also has a 2D network structure in which each independent 2D sheet contains two sub-layers bridged by oxygen atoms of the sulfate anions. Complex 6 has a 2D puckered structure in which the sulfate anions serve as counter anions, which are different from those in complexes 4 (terminators) and 5 (bridges). The different structures of complexes 4, 5 and 6 indicate that the nature of organic ligands affected the structures of the assemblies greatly. The magnetic behavior of complex 5 and anion-exchange properties of complex 6 were investigated.     

Crystal structures and magnetic properties of metal complexes bearing four nitronyl nitroxide moieties in the same coordination sphere

Mononuclear transition metal complexes of the type [M(2,6-NITpy)2](ClO4)2 x solvent (2,6-NITpy = 2,6-bis-(3'-oxide-1'-oxyl-4',4',5',5'-tetramethylimidazolin-2'-yl)pyridine; M = Ni (1), Co (2), Zn (3), Mn (4), Cu (5)) have been synthesized and characterized by single-crystal X-ray diffraction studies. Crystal data: 1, monoclinic, P2(1)/c, Z = 4, a = 20.946(2) A, b = 12.0633(2) A, c = 21.173(2) A, beta = 113.55(1) degrees; 2, monoclinic, P2(1)/c, Z = 4, a = 20.902(2) A, b = 12.0981(8) A, c = 21.215(2) A, beta = 113.130(9) degrees; 3, triclinic, P1, Z = 2, a = 11.410(1) A, b = 12.932(1) A, c = 21.609(2) A, alpha = 96.040(2) degrees, beta = 102.24(1) degrees, gamma = 114.98(1); 4, monoclinic, P2(1)/n, Z = 4, a = 11.5473(8) A, b = 19.212(1) A, c = 25.236(2) A, beta = 98.772(9) degrees; 5, triclinic, P1, Z = 2, a = 12.1604(9) A, b = 12.6961(9) A, c = 18.103(2) A, alpha = 84.191(8) degrees, beta = 73.392(8) degrees, gamma = 66.072(8). The two 2,6-NITpy biradicals behave as terdentate ligands and bind almost perpendicular to each other in meridional positions. In compounds 1-4, the pyridine rings are axially ligated and four different nitronyl nitroxide radicals bind to the metal center through their O(nitroxyl) atoms, forming the equatorial plane of a distorted octahedron. On the contrary, in the copper(II) complex (5), the two N(pyridyl) atoms are found in equatorial positions. Only two nitroxide groups are then bound to the copper(II) ion in the equatorial plane, the other two being axially ligated. The two axially bound nitronyl nitroxide radicals couple ferromagnetically to the copper center (JCu-rad(ax) = + 10 K), whereas a strong antiferromagnetic coupling between this metal ion and the equatorial nitroxide groups (JCu-rad(eq) = -460 K) is observed. The other complexes exhibit strong antiferromagnetic metal-radical interactions: JNi-rad = -240 K, for 1; JMn-rad = -120 K, for 4. Interestingly, the study of the diamagnetic zinc(II) compound (3) reveals a moderate intramolecular antiferromagnetic interaction between radicals coordinated to the same metal center (Jrad-rad = -27.7 K). This interaction is transmitted through space and is also present in the other complexes: Jrad-rad = -14 K, for 1; Jrad-rad = -10 K, for 4; Jrad-rad = -20.5 K, for 5. Antiferromagnetic intermolecular interactions are also present in all the complexes herein studied.     

Cu3C4-: a new sandwich molecule with two revolving C2(2-) units

A combined photoelectron spectroscopy (PES) and ab initio study was carried out on a novel copper carbide cluster in the gas phase: Cu(3)C(4)(-). It was generated in a laser vaporization cluster source and appeared to exhibit enhanced stability among the Cu(3)C(n)(-) series. Its PES spectra were obtained at several photon energies, showing numerous well-resolved bands. Extensive ab initio calculations were performed on Cu(3)C(4)(-), and two isomers were identified: a C(2) structure ((1)A) with a Cu(3)(3+) triangular group sandwiched by two C(2)(2-) units and a linear CuCCCuCCCu structure (D(infinity)(h), (1)Sigma(g)(+)). A comparison of ab initio PES spectra with experimental data showed that the sandwich Cu(3)C(4)(-) cluster was solely responsible for the observed spectra and the linear isomer was not present, suggesting that the C(2) structure is the global minimum in accordance with CCSD(T)/6-311+G predictions. Interestingly, a relatively low barrier (0.4-0.6 kcal/mol) was found for the internal rotation of the C(2)(2-) units in the sandwich Cu(3)C(4)(-). To test different levels of theory in describing the Cu(m)C(n)(-) systems and lay foundations for the validity of the theoretical methods, extensive calculations at a variety of levels were also carried out on a simpler copper carbide species CuC(2)(-), where two isomers were found to be close in energy: a linear one (C(infinity)(v), (1)Sigma(+)) and a triangular one (C(2)(v), (1)A(1)). The calculated electronic transitions for CuC(2)(-) were also compared with the PES data, in which both isomers were present.