Biomedical subjects
Publications and source records attributed to Song Gao.
A novel end-on azide-bridged homospin 1D chain, Co(bt)(N3)2 (1) (bt = 2,2'-bithiazoline), is constructed by sharing edges of Co(II) distorted octahedrons to form a helix, which shows magnetic hysteresis with steps and slow relaxation below 5-6 K, typical of single-chain magnet behavior.
Two new one-dimensional (1-D) 3d-5d cyano-bridged bimetallic assemblies, ([Co(3)(II)(DMF)(12)][W(V)(CN)(8)](2)])(infinity) (1) and ([Mn(3)(II)(bipy)(2)(DMF)(8)][W(V)(CN)(8)](2))(infinity) (2), have been synthesized and characterized, where bipy stands for 2,2'-bipyridine and DMF represents N,N-dimethylformamide. The X-ray analyses show that the two complexes belong to the P(-)1 space group with Z = 1 and C(52)H(84)N(28)O(12)Co(3)W(2), a = 11.690(3) A, b = 12.703(3) A, c = 13.712(3) A, alpha = 86.889(4) degrees, beta = 73.256(4) degrees, and gamma = 77.033(4) degrees for 1 and C(60)H(72)N(28)O(8)Mn(3)W(2), a = 10.672(2) A, b = 13.024(3) A, c = 16.000(3) A, alpha = 78.32(3) degrees, beta = 75.69(3) degrees, and gamma = 66.63(3) degrees for 2. The structures of the two complexes are similar and consist of 12-atom rhombic M(2)W(2)(CN)(4) (M = Co (1), Mn (2)) units, which act as a basic component to be repeatedly connected through W-C-N-M-N-C-W linkages to form a one-dimensional infinite 3,2-chain; these chains are well separated by the DMF molecules or 2,2'-bipyridines coordinated to the metal ions Co(2+) for 1 and Mn(2+) for 2. Magnetic studies, including linear and nonlinear ac susceptibility measurements, demonstrate that the long-range magnetic ordering and spin glass behavior coexist in the two 1-D compounds.
A series of cyano-bridged Ni(II)-Cr(I/III) complexes have been synthesized by the reactions of hexaazacyclic Ni(II) complexes with [Cr(CN)(6)](3-) or [Cr(CN)(5)(NO)](3-). Using the tetravalent Ni(II) complex [Ni(H(2)L(2))](4+) (L(2) = 3,10-bis(2-aminoethyl)-1,3,6,8,10,12-hexaazacyclotetradecane), one-dimensional chainlike complexes were produced and subject to magnetic studies, affording the intermetallic magnetic exchange constants of J(1) = +0.23 cm(-1) and J(2) = +8.4 cm(-1) for the complex [Ni(H(2)L(2))][Cr(CN)(5)(NO)]ClO(4).5H(2)O (1) and of J = +5.9 cm(-1) for the complex [Ni(H(2)L(2))](4)[Cr(CN)(6)](5)OH.15H(2)O (2). X-ray diffraction analysis shows that complex 1 has a zigzag chain structure, whereas complex 2 consists of a branched chain structure. Complex 2 exhibits antiferromagnetic ordering at 8.0 K (T(N)). When an octahedral Ni(II) complex cis-[NiL(3)(en)](2+) (en = 1,2-ethylenediamine, L(3) = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane) was used for the synthesis, the common 2D honeycomb-layered complex [NiL(3)](3)[Cr(CN)(5)(NO)](2).8H(2)O (3) was obtained, which has a T(N) value of 3.3 K. Below T(N), a metamagnetic behavior was observed in complexes 2 and 3.
A three-dimensional complex, [Mn(3)(4-aba)(6)](n) (1) (4-Haba = 4-aminobenzoic acid), consisting of manganese(II) chains and 4-aba bridging ligands, has been synthesized and characterized. Magnetic studies show that the compound behaves as a three-dimensional metamagnet built of homometallic ferrimagnetic chains. The required noncompensation in spin moments is achieved by alternating interactions in an AF-AF-F sequence (AF = antiferromagnetic; F = ferromagnetic) by considering intrachain magnetic interactions.
Two novel acentric hydrogen bonded two-dimensional sheet and three-dimensional 2-fold interpenetrating diamond-like networks have been designed and prepared based on a tetrahedral ammonium node and the O,O'-bifunctional linker molecules dipyridine dioxide (dpdo) and trans-bis(4-pyridyl)ethylene dioxide (bpedo).
Two novel coordination polymers of Co(II) with dicyanamide (dca) were obtained by the addition of ancillary ligands of pyrazine dioxide (pzdo) and 2-methyl pyrazine dioxide (mpdo) into the Co-dca binary system, respectively. Co[N(CN)(2)](2)(pzdo) (1) crystallizes in the orthorhombic space group of Pnnm (No. 58) with a = 9.4699(5) A, b = 14.9984(3) A, c = 7.4313(7) A, and Z = 4, while Co[N(CN)(2)](2)(mpdo) (2) is in the monoclinic space group C2 (No. 5) with a = 16.5391(4) A, b = 9.6065(2) A, c = 7.5001(2) A, beta = 105.779(1) degrees, and Z = 4. Both complexes contain similar two-dimensional triangular Co-dca layers, which offer rare examples of mixed 1,5-mu- and mu(3)-dca bridging coordination polymers with long-range ferromagnetic ordering below ca. 2.5 K.
Six new coordination polymers, [Eu(1,2-BDC)(1,2-HBDC)(phen)(H(2)O)](n) (1), [Eu(2)(1,3-BDC)(3)(phen)(2)(H(2)O)(2)](n).4nH(2)O (2), [Eu(1,4-BDC)(3/2)(phen)(H(2)O)](n) (3), [Yb(2)(1,2-BDC)(3)(phen)(H(2)O)(2)](n).3.5nH(2)O (4), [Yb(2)(1,3-BDC)(3)(phen)(1/2)](n) (5), and [Yb(2)(1,4-BDC)(3)(phen)(2)(H(2)O)](n) (6), were synthesized by hydrothermal reactions of lanthanide chlorides with three isomers of benzenedicarboxylic acid (H(2)BDC) and 1,10-phenanthroline (phen), and characterized by single-crystal X-ray diffraction. 1 has a 2-D herringbone architecture with a Z-shaped cavity. 2 and 5 have different 3-D networks, but both are formed by 1,3-BDC anions bridging metal centers (Eu or Yb) via carboxylate groups. 3 and 6 possess similar layer structures which are further constructed to form 3-D networks by hydrogen bonds and/or pi-pi aromatic interactions. 4 comprises 1-D chains that are further interlinked via hydrogen bonds, resulting in a 3-D network. In the three europium complexes, all the europium ions are eight-coordinated, while the coordination numbers of the ytterbium ions in other three-coordination polymers range from six to eight. Crystal data: for 1, monoclinic, space group P2(1)/c, with a = 12.565(6) A, b = 16.005(8) A, c = 12.891(6) A, beta = 102.173(8) degrees, and Z = 4; for 2, monoclinic, space group P2(1)/c, with a = 20.979(4) A, b = 11.5989(19) A, c = 20.810(3) A, beta = 110.391(3) degrees, and Z = 4; for 3, triclinic, space group P1, with a = 10.331(5) A, b = 10.887(5) A, c = 11.404(5) A, alpha = 107.660(7) degrees, beta = 91.787(7) degrees, gamma = 112.946(6) degrees, and Z = 2; for 4, triclinic, space group P1, with a = 11.517(5) A, b = 13.339(5) A, c = 13.595(6) A, alpha = 87.888(7) degrees, beta = 67.759(6) degrees, gamma = 68.070(6) degrees, and Z = 2; for 5, orthorhombic, space group C222(1), with a = 8.174(2) A, b = 24.497(7) A, c = 29.161(8) A, and Z = 8; for 6, triclinic, space group P1, with a = 10.349(3) A, b = 11.052(3) A, c = 19.431(6) A, alpha = 105.464(4) degrees, beta = 91.300(5) degrees, gamma = 93.655(5) degrees, and Z = 2. The magnetic properties of 1 and 4 were investigated. The photophysical properties of 1 were also studied.
Two three-dimensional (3D) malonate bridged networks, [Cu(mal)(DMF)](n) (1) and [[Cu(mal)(0.5pyz)].H(2)O](n) (2), have been synthesized in H(2)O-DMF solution. Compound 1 exhibits ferromagnetic ordering below 2.6 K (T(c)), and 2 displays a metamagnetic behavior below 3.2 K (T(N)).
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Compound Na6Co7(hedp)2(hedpH)4(H2O)4 x 8H2O (hedp = 1-hydroxyethylidenediphosphonate) with a novel layer structure is reported in this paper. The layer maybe viewed as made up from two types of chains each of composition Co3(hedp)2 and Co2(hedpH)2. Magnetic measurements at 1.8 K reveal a metamagnetic transition at ca. 6.5 kOe, followed by a second transition to a ferromagnetic state at ca. 30 kOe.
A novel (mu-nitrido-diruthenium)-bridged 1-D coordination polymer was formed from reaction of K5[Ru2N(CN)10] with [Cu(en)2](ClO4)2; a similar reaction with [Cu(pn)2][(ClO4)2] (pn = 1,3-diaminopropane) gave ([Cu(pn)2]5[Ru2N(CN)10]2) as a discrete molecular compound; variable temperature susceptibility measurements show that there is a weak ferromagnetic interaction between the Cu(II) ions in 1-D polymer.
Two cyano-bridged Gd(III)-Cr(III) complexes [Gd(urea)(4)(H(2)O)(2)](2)[Cr(CN)(6)](2) (1) and ([Gd(capro)(2)(H(2)O)(4)Cr(CN)(6)].H(2)O)(n)(2) (capro represents caprolactam) have been synthesized and characterized structurally and magnetically. Complex 1 has a tetranuclear Gd(2)Cr(2) square structure, in which two cis-CN(-) ligands of each [Cr(CN)(6)] link two [Gd(urea)(4)(H(2)O)(2)] groups and in turn, two [Gd(urea)(4)(H(2)O)(2)] link two [Cr(CN)(6)] in a cis fashion. Complex 2 is composed of 1D chains with alternating [Gd(capro)(2)(H(2)O)(4)] and [Cr(CN)(6)] moieties connected by the trans-CN(-) ligands of [Cr(CN)(6)]. The dehydration of 2 at 120 degrees C generates a new complex, [Gd(capro)(2)(H(2)O)(2)Cr(CN)(6)] (2'). Magnetic studies show the existence of antiferromagnetic Gd(III)-Cr(III) interaction in these complexes. On the basis of the tetranuclear model, the magnetic susceptibilities of 1 have been analyzed giving the intermetallic magnetic coupling constant of -0.36 cm(-1). Complex 2' exhibits a ferrimagnetic order below 2.1 K. Interestingly, 2' is quite soluble in water, and slow evaporation of the solution gives the hydrated complex 2. Therefore, 2' is a soluble molecular magnet, and this significant behavior implies potential applications. Isothermal magnetization measurements of 2' and other cyano-bridged Gd(III)-Cr(III) molecular magnets show unusual field-induced metamagnetic behavior from the ferrimagnetic ground state to the ferromagnetic state. Field dependence of magnetization of the cyano-bridged Gd(III)-Cr(III) complexes shows unusual field-induced metamagnetic behavior from the ferrimagnetic ground state to the ferromagnetic state.
A cyano-bridged bimetallic 4f-3d complex, triaqua-1 kappa(3)O-mu-cyano-1:2 kappa(2)N:C-pentacyano-2 kappa(5)C-tetrakis(2-pyrrolidone-1 kappa O)chromium(III)dysprosium(III) dihydrate, [CrDy(C(4)H(7)NO)(4)(CN)(6)(H(2)O)(3)] x 2H(2)O, has been prepared and characterized by X-ray crystallographic analysis. The structure consists of a neutral cyano-bridged Dy-Cr dimer. A hydrogen-bonded three-dimensional architecture is formed through N[bond]H...O, O[bond]H...N and O[bond]H...O hydrogen bonds.
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Covalent hybrid conjugates consisting of streptavidin (STV) and a 24-mer single-stranded DNA oligonucleotide have been used as a starting material for the synthesis of supramolecular nanocircles. For this, the covalent hybrid conjugates were oligomerized by cross-linking with 5 ,5 -bis-biotinylated double-stranded DNA (dsDNA) fragments of various length. Heat denaturation of the resulting oligomeric conjugates and subsequent rapid cooling led to the formation of the nanocircles, in which the oligonucleotide-containing STV molecule is coupled with both ends of the circular bis-biotinylated dsDNA fragment. The circular structure of the bioconjugates was established by electrophoretic studies including Ferguson plot analysis as well as by scanning force microscopy (SFM) inspection. The formation process and the stability against degradation by ligand exchange with free D-biotin was compared for the nanocircles obtained from covalent oligonucleotide-STV hybrids and native STV. The former nanocircles revealed a decreased stability with respect to ring opening than the circles obtained from native STV. This suggested that the affinity of the covalent oligonucleotide-STV hybrid for binding biotinylated DNA is significantly decreased. Nevertheless, the single-stranded oligonucleotide moiety of the hybrid nanocircles can be used as a molecular handle for further functionalization. For instance, it was used for the selective DNA-directed immobilization at a surface, previously functionalized with complementary capture oligonucleotides. Moreover, we demonstrate that a pair of nanocircles, containing complementary oligonucleotide moieties, can be hybridized to form specific dimers, thereby generating a novel type of supramolecular DNA-protein nanostructures.
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The title compounds are isomorphous, comprised of neutral monomeric [M(phen)(2)(dca)(2)] [(I): M = Mn, (II): M = Zn; phen is 1,10-phenanthroline, C(12)H(8)N(2); dca is dicyanamide, C(2)N(3)] molecules. In the molecule, the divalent metal ion is in a distorted octahedral coordination environment formed by six N atoms from the phen and dca ligands. The Mn-N [2.144 (2)-2.319 (2) A] and Zn-N [2.075 (2)-2.245 (2) A] distances are in agreement with the difference in size of the two divalent ions.
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