Syntheses and Crystal Structures of Two Coordination Polymers with Aromatic Dioxide as Bridge Ligands

Two coordination polymers, namely, two-dimensional complex 1 {[Cu(μ- L)1.5(ClO4)2(H2O)].(H2O)0.5}n (L = pyrazine-1,4-dioxide) and one-dimensional complex 2 [Co(μ-L)Br2(H2O)2]n, have been synthesized with pyrazine-1,4-dioxide as bridging ligands, and their crystal structures were determined by X-ray crystallography. Crystal data for complex 1: monoclinic system, space group C2/c, with a = 23.310(3), b = 12.2338(17), c = 10.6075(15) , β = 110.487(2)°, V = 2833.6(7) 3, Z = 8, C6H9Cl2CuN3O12.5, Mr = 457.60, Dc = 2.145 g/cm3, F(000) = 1832 and μ = 1.998 mm-1; and those for 2: monoclinic system, space group C2/c, with a = 11.012(3), b = 7.483(2), c = 11.451(3) , β = 101.654(4)°, V = 924.2(4) 3, Z = 4, C4H8Br2CoN2O4, Mr = 366.87, Dc = 2.637 g/cm3, F(000) = 700 and μ = 10.487 mm-1. 1 shows a two-dimensional sheet structure on the ac plane through the coordination of μ-L bridging ligands with Cu(II) ions, while 2 displays a zigzag one-dimensional chain along the c axis via the coordination of μ-L bridging ligand with Co(II) ions. Hydrogen bonds in 1 and 2 make the sheets (or chains) connect each other to form a three-dimensional structure.     

Magnetic study on a two-dimensional coordination polymer with mixed bridging ligands

A two-dimensional coordination polymer, [Co(mu(1,3)-SCN)(2)(mu(1,6)-dmpzdo)](n)() (where dmpzdo = 2,5-dimethylpyrazine-1,4-dioxide), has been synthesized and its crystal structure determined by X-ray crystallography. In the complex, the adjacent Co(II) ions are coordinated by mu(1,3)-SCN(-) bridging ligands which forms a one-dimensional chain along the a axis; the one-dimensional chains are further connected by mu(1,6)-dmpzdo bridging ligands which leads to the formation of a two-dimensional layer on the ac plane. The theoretical calculations reveal that a ferromagnetic coupling exists between the mu(1,3)-SCN(-) bridging Co(II) ions and an anti-ferromagnetic interaction between the mu(1,6)-dmpzdo bridging Co(II) ions, and the anti-ferromagnetic interaction is stronger than the ferromagnetic interaction. The fitting of the variable-temperature (34-300 K) magnetic susceptibilities reveals that there is an anti-ferromagnetic coupling between the bridging Co(II) ions with the magnetic coupling constant J = -3.52 cm(-1).     

Synthesis and Crystal Structure of a Three-dimensional Cd(Ⅱ) Coordination Polymer [Cd(μ1,3-SCN)(μ3-pco)]n (pco = Pyrazine-2-carboxylate 4-oxide Anion)

The three-dimensional complex [Cd(μ1,3-SCN)(μ3-pco)]n has been synthesized with μ1,3-SCN- and pco as mixed bridged ligands. The crystal belongs to monoclinic, space group P21/n with a = 10.3777(16), b = 6.2592(9), c = 13.150(2) (A), β= 97.317(2)°, V=847.2(2) (A)3, Z= 4,C6H3CdN3O3S, Mr = 309.575, Dc = 2.427 g/cm3, F(000) = 592 and μ = 2.804 mm-1. The structure was refined to R = 0.0255 and wR = 0.0550 for 1712 observed reflections (I＞2σ(I)). In the crystal the Cd(Ⅱ) ions are coordinated by μ1,3-SCN- and μ3-pco bridge ligands to form a three-dimensional structure.     

聚乙二醇甲醚-聚(D,L-乳酸)嵌段共聚物纳米胶束的制备

聚乙二醇甲醚-聚(D;L-乳酸)嵌段共聚物纳米胶束的制备;聚乙二醇单甲醚;两亲性二嵌段共聚物;纳米沉淀技术     

The absolute configuration of anti-Vibrio citrinin dimeric derivative by VCD,ECD and NMR methods

Citrinin dimeric derivatives are bioactive polyketides previously reported from Penicillium, Aspergillus and Monascus fungi species. Due to the large distance between the stereogenic centers of the two monomer units, it was difficult to determine the absolute configuration of the whole molecule (1). In previous work, the absolute configuration of 1 was just proposed by biogenetic considerations. To address this problem, the experimental VCD of 1 was compared with the corresponding DFT calculations for two diastereomers (1a and 1b). Also, the experimental ECD and NMR spectra of 1 were combined for analysis with the corresponding theoretical predictions for different diastereomers. Additionally, compound 1 showed promising anti-Vibrio activity against pathogenic Vibrio spp. with MIC values ranging from 0.4 to 0.8?μM.

     

Syntheses and Crystal Structures of Two Two-dimensional Coordination Polymers with 2,3-Dimethylpyrazine-1,4-dioxide and Thiocyanate as Mixed Bridge Ligands

Two two-dimensional coordination polymers,[Cd(μ1,3-SCN-)2(μ1,6-L)]n 1 and [Co(μ1,3-SCN-)2(μ1,6-L)]n 2,have been synthesized with 2,3-dimethylpyrazine-1,4-dioxide (L) and thiocyanate as mixed bridging ligands,and their crystal structures were determined by X-ray crystallography.Both crystals belong to monoclinic system,space group C2/c.The other crystal parameters are as follows:for complex 1:a = 9.732(3),b = 14.658(5),c = 8.811(3) (A),β =102.935(4)°,Z = 4,V = 1225.1(7)(A)3,CsHsCdN4O2S2,Mr = 368.71,Dc.-- 1.999 g/cm3,F(000) =720 andμ = 2.117 mm-1;for complex 2:a = 9.528(7),b = 14.563(11),c = 8.415(6) (A),β =102.195(9)°,V= 1141.3(14) (A)3,Z = 4,C8H8CoN4O2S2,Mr = 315.23,Dc = 1.835 g/cm3,F(000) =636 andμ = 1.863 mm-1.The two complexes show similar two-dimensional sheet structures.Along the c axis one-dimensional chains are constructed by the coordination of Cd(Ⅱ) (or Co(Ⅱ))ions with μ1,6-L bridging ligand,and the μ1,3-SCN- bridging ligands make the chains connect to each other,resulting in the formation of a two-dimensional sheet on the ac plane.     

Synthesis, crystal structure and magnetism study on novel one-dimensional Cu(II) coordination polymers with 2,5-dimethylpyrazine-1,4-dioxide as bridging ligand

A novel one-dimensional coordination polymer [Cu(μ _1,6-dmpzdo)(dmpzdo)₂]·(ClO₄)₂ (dmpzdo = 2,5-dimethylpyrazine-1,4-dioxide) has been synthesized and its crystal structure determined by X-ray crystallography. In the complex each Cu1 atom is located in a square planar coordination environment with two oxygen atoms O2 and O2A from two dmpzdo terminal ligands, and two other oxygen atoms O3 and O3A from two μ _1,6-dmpzdo bridging ligands. The one-dimensional chain is constructed by the coordination of a μ _1,6-dmpzdo bridging ligand and Cu(II) ions. The data of the variable temperature (4–300 K) magnetic susceptibilities were fitted by using the one-dimensional chain fitting formula, which gave the magnetic coupling constants 2J = −98.88 cm⁻¹.     

Bent π-Conjugation within a Macrocycle: Asymmetric Total Syntheses of Spirohexenolides A and B

Macrocycles with bent π-conjugation motif are extremely rare in nature and synthetically daunting and anticancer haouamines and spirohexenolides were representative of such rare natural products with synthetically challenging bent π-conjugation within a macrocycle. While the total synthesis of haouamines has been elegantly achieved, spirohexenolides remains an unmet synthetic challenge due to the highly strained bent 1,3,5-triene conjugation within C15 macrocycle. Inspired by the chemical synthesis of cycloparaphenylenes (CPPs) and haouamines, herein we devise a synthetic strategy to overcome the highly strained bent 1,3,5-triene conjugation within the macrocycle and achieve the first, asymmetric total synthesis of spirohexenolides A (>20 mg) and B (>50 mg). Our synthesis features strategic design of ring-closing metathesis (RCM) macrocyclization followed by double dehydration to achieve the C15 macrocycle with the deformed nonplanar 1,3,5-triene conjugation. In addition, we have developed a new enantioselective construction of highly functionalized spirotetronate fragment (northeast moiety) through RCM and Ireland–Claisen rearrangement. Our in vitro bioassay studies reveal that both spirohexenolides are cytotoxic against a panel of human cancer cells with IC₅₀ 1.2–13.3 μM and spirohexenolide A is consistently more potent (up to 3 times) than spirohexenolide B, suggesting the importance of alcohol for their bioactivity and for medicinal chemistry development.