Polyol‐Metall‐Komplexe. 491) μ‐Dulcitolato‐O2, 3;4, 5‐Komplexe mit Amin‐Kupfer(II)‐ und ‐Nickel(II)‐Metallfragmenten

Polyol Metal Complexes. 49¹⁾ μ‐Dulcitolato‐O^{2, 3;4, 5} Complexes with Cu^II(en) and Ni^II(tren) Metal Fragments The dinuclear ethylenediamine‐copper(II) complex of the tetra‐anion of the achiral alditol dulcitol (galactitol) is remarkable, since it was the first crystalline carbohydrate—metal complex ever reported (W. Traube, G. Glaubitt, V. Schenck, Ber. Dtsch. Chem. Ges. 1930 , 63, 2083—2093). Although its existence is recognized for many decades, its structure remained unknown due to a kind of crystal packing that promotes twinning. Crystal growth at low temperatures now yielded crystalline specimens of [(en)₂Cu₂(Dulc2, 3, 4, 5H_—4)] · 7 H₂O ( 1 ) that have allowed us to unravel both the crystal structure and the twinning law. Closely related molecular structures are adopted by [(tren)₂Ni₂(Dulc2, 3, 4, 5H_—4)] · 20 H₂O ( 2 ) and [(Me₃tren)₂Ni₂(Dulc2, 3, 4, 5H_—4)] · 16 H₂O ( 3 ), the latter showing the shortest hydrogen bond towards a polyolate acceptor ever found (O···O distance: 2.422Å).     

Methyl 4‐O‐β‐d‐galactopyranosyl α‐d‐mannopyranoside methanol 0.375‐solvate

Methyl β‐d ‐galactopyranosyl‐(1→4)‐α‐d ‐mannopyranoside methanol 0.375‐solvate, C₁₃H₂₄O₁₁·0.375CH₃OH, (I), was crystallized from a methanol–ethanol solvent system in a glycosidic linkage conformation, with ϕ′ (O5_Gal—C1_Gal—O1_Gal—C4_Man) = −68.2 (3)° and ψ′ (C1_Gal—O1_Gal—C4_Man—C5_Man) = −123.9 (2)°, where the ring is defined by atoms O5/C1–C5 (monosaccharide numbering); C1 denotes the anomeric C atom and C6 the exocyclic hydroxymethyl C atom in the βGalp and αManp residues, respectively. The linkage conformation in (I) differs from that in crystalline methyl α‐lactoside [methyl β‐d ‐galactopyranosyl‐(1→4)‐α‐d ‐glucopyranoside], (II) [Pan, Noll & Serianni (2005). Acta Cryst. C 61 , o674–o677], where ϕ′ is −93.6° and ψ′ is −144.8°. An intermolecular hydrogen bond exists between O3_Man and O5_Gal in (I), similar to that between O3_Glc and O5_Gal in (II). The structures of (I) and (II) are also compared with those of their constituent residues, viz. methyl α‐d ‐mannopyranoside, methyl α‐d ‐glucopyranoside and methyl β‐d ‐galactopyranoside, revealing significant differences in the Cremer–Pople puckering parameters, exocyclic hydroxymethyl group conformations and intermolecular hydrogen‐bonding patterns.     

Synthesis of 5′‐O‐(2‐Azido‐2‐deoxy‐α‐D‐glycosyl)nucleosides and Their Antitumor Activities

The 1,3,4,6‐tetra‐O‐acetyl‐2‐azido‐2‐deoxy‐β‐D ‐mannopyranose ( 4 ) or the mixture of 1,3,6‐tri‐O‐acetyl‐2‐azido‐2‐deoxy‐4‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐galactopyranosyl)‐β‐D ‐mannopyranose ( 10 ) and the corresponding α‐D ‐glucopyranose‐type glycosyl donor 9 / 10 reacted at room temperature with protected nucleosides 12 – 15 in CH₂Cl₂ solution in the presence of BF₃?OEt₂ as promoter to give 5′‐O‐(2‐azido‐2‐deoxy‐α‐D ‐glycosyl)nucleosides in reasonable yields (Schemes 2 and 3). Only the 5′‐O‐(α‐D ‐mannopyranosyl)nucleosides were obtained. Compounds 21, 28, 30 , and 31 showed growth inhibition of HeLa cells and hepatoma Bel‐7402 cells at a concentration of 10 μM in vitro.     

A Homochiral Metal‐Dipeptide Supramolecular Framework Including a Hydrogen‐bonded Guest Network of Water and Uncoordinated 4, 4′‐Bipyridine

Abstract. The self‐assembly of glycyl‐L ‐leucine, Cu(NO₃)₂ · 3H₂O and 4, 4′‐bipyridine resulted in the tetranuclear‐based metal‐dipeptide supramolecular framework [Cu₄(C₈H₁₄N₂O₃)₄(H₂O)₂(C₁₀H₈N₂)₂] · (C₁₀H₈N₂) · 13H₂O ( 1 ). In the structure, the 4, 4′‐bipyridine‐bridged tetranuclear complex of Cu^II‐glycyl‐L ‐leucine interacts with each other to form a 1D hydrogen‐bonded chain including uncoordinated 4, 4′‐bipyridine and an interesting water chain in different channels. Under similar reaction conditions, racemic glycyl‐D ,L ‐leucine gave rise to the centrosymmetric dinuclear complex [Cu₂(C₈H₁₄N₂O₃)₂(C₁₀H₈N₂)] · 2H₂O ( 2 ), which is linked into a 2D hydrogen‐bonded structure without 4, 4′‐bipyridine included.     

Methyl 4‐O‐β‐D‐mannopyranosyl β‐D‐xylopyranoside

Methyl β‐D‐mannopyranosyl‐(1→4)‐β‐D‐xylopyranoside, C₁₂H₂₂O₁₀, (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a ϕ′ torsion angle (O5′_Man—C1′_Man—O1′_Man—C4_Xyl; Man is mannose and Xyl is xylose) of −88.38 (17)° and a ψ′ torsion angle (C1′_Man—O1′_Man—C4_Xyl—C5_Xyl) of −149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are −89.82 (17) and −159.98 (14)°, respectively. Ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH₂OH) C atom in the β‐Xylp and β‐Manp residues, respectively. By comparison, the internal glycosidic linkage in the major disorder component of the structurally related disaccharide, methyl β‐D‐galactopyranosyl‐(1→4)‐β‐D‐xylopyranoside), (II) [Zhang, Oliver & Serriani (2012). Acta Cryst. C 68 , o7–o11], is characterized by ϕ′ = −85.7 (6)° and ψ′ = −141.6 (8)°. Inter‐residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Man in both (IA) and (IB) [O3_Xyl...O5′_Man internuclear distances = 2.7268 (16) and 2.6920 (17) Å, respectively], analogous to the inter‐residue hydrogen bond detected between atoms O3_Xyl and O5′_Gal in (II). Exocyclic hydroxymethyl group conformation in the β‐Manp residue of (IA) is gauche–gauche, whereas that in the β‐Manp residue of (IB) is gauche–trans.     

A New Route for Preparation of 5‐Deoxy‐5‐(hydroxyphosphinyl)‐ D‐mannopyranose and ‐L‐gulopyranose Derivatives

Starting from methyl 2,3‐O‐isopropylidene‐α‐D ‐mannofuranoside ( 5 ), methyl 6‐O‐benzyl‐2,3‐O‐isopropylidene‐α‐D ‐lyxo‐hexofuranosid‐5‐ulose ( 12 ) was prepared in three steps. The addition reaction of dimethyl phosphonate to 12 , followed by deoxygenation of 5‐OH group, provided the 5‐deoxy‐5‐dimethoxyphosphinyl‐α‐D ‐mannofuranoside derivative 15a and the β‐L ‐gulofuranoside isomer 15b . Reduction of 15a and 15b with sodium dihydrobis(2‐methoxyethoxy)aluminate, followed by the action of HCl and then H₂O₂, afforded the D ‐mannopyranose ( 17 ) and L ‐gulopyranose analog 21 , each having a phosphinyl group in the hemiacetal ring. These were converted to the corresponding 1,2,3,4,6‐penta‐O‐acetyl‐5‐methoxyphosphinyl derivatives 19 and 23 , respectively, structures and conformations (⁴C₁ or ¹C₄, resp.) of which were established by ¹H‐NMR spectroscopy.     

Structural properties of D‐mannopyranosyl rings containing O‐acetyl side‐chains

The crystal structures of 1,2,3,4,6‐penta‐O‐acetyl‐α‐d ‐mannopyranose, C₁₆H₂₂O₁₁, and 2,3,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranosyl‐(1→2)‐3,4,6‐tri‐O‐acetyl‐α‐d ‐mannopyranosyl‐(1→3)‐1,2,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranose, C₄₀H₅₄O₂₇, were determined and compared to those of methyl 2,3,4,6‐tetra‐O‐acetyl‐α‐d ‐mannopyranoside, methyl α‐d ‐mannopyranoside and methyl α‐d ‐mannopyranosyl‐(1→2)‐α‐d ‐mannopyranoside to evaluate the effects of O‐acetylation on bond lengths, bond angles and torsion angles. In general, O‐acetylation exerts little effect on the exo‐ and endocyclic C—C and endocyclic C—O bond lengths, but the exocyclic C—O bonds involved in O‐acetylation are lengthened by ～0.02 Å. The conformation of the O‐acetyl side‐chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°‐alcoholic C atom or bisecting the H—C—H bond angle of a 1°‐alcoholic C atom. Of the two C—O bonds that determine O‐acetyl side‐chain conformation, that involving the alcoholic C atom exhibits greater rotational variability than that involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of O‐acetyl side‐chain conformations in saccharides. Experimental evidence was also obtained to confirm density functional theory (DFT) predictions of C—O and O—H bond‐length behavior in a C—O—H fragment involved in hydrogen bonding.     

Facile Synthesis of the Pentasaccharide Repeating Unit of the Exopolysaccharide from Cryptococcus neoformans Serotype D

β‐D ‐GlcpA‐(1→2)‐[β‐D ‐Xylp‐(1→2)‐α‐D ‐Manp‐(1→3)]‐α‐D ‐Manp‐(1→3)‐α‐D ‐Manp, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serotype D, was synthesized as its 4‐methoxyphenyl glycoside. The approach presented here also provides a route to the synthesis of more complex repeating units of glucuconoxylomannan (GXM) of C. neoformans serotypes A–C.     

Two 3d‐4f Heterometallic Coordination Polymers of Macrocyclic Oxamide with Benzotriazole‐5‐carboxylate Co‐ligand: Syntheses,Crystal Structures and Magnetic Properties

Two heterometallic 3d–4f coordination polymers, [Gd(CuL)₂(Hbtca)(btca)(H₂O)] · 2H₂O ( 1 ) and [Er(CuL)₂(Hbtca)(btca)(H₂O)] · H₂O · CH₃OH ( 2 ) (CuL, H₂L = 2,3‐dioxo‐5,6,14,15‐dibenzo‐1,4,8,12‐tetraazacyclo‐pentadeca‐7,13‐dien; H₂btca = benzotriazole‐5‐carboxylic acid) were synthesized by solvothermal methods and characterized by single‐crystal X‐ray diffraction. Complexes 1 and 2 exhibit a double‐strand meso‐helical chain structures formed by [Ln^IIICu^II₂] (Ln^III = Gd, Er) units by oxamide and benzotriazole‐5‐carboxylate bridges. They are isomorphic except that one free water molecule of 1 is replaced by a methanol molecule. All 1D chains are further interlinked by hydrogen bonds resulting in a 3D supramolecular architecture. The magnetic properties of the compound 1 and 2 are also discussed.     

Poly[[diaqua‐μ‐4,4′‐bipyridine‐dinitratodi‐μ‐l‐tyrosinato‐dicopper(II)]: a chiral two‐dimensional coordination polymer

The title compound, [Cu₂(C₉H₁₀NO₃)₂(NO₃)₂(C₁₀H₈N₂)(H₂O)₂]_n, contains Cu^II atoms and l ‐tyrosinate (l ‐tyr) and 4,4′‐bipyridine (4,4′‐bipy) ligands in a 2:2:1 ratio. Each Cu atom is coordinated by one amino N atom and two carboxylate O atoms from two l ‐tyr ligands, one N atom from a 4,4′‐bipy ligand, a monodentate nitrate ion and a water molecule in an elongated octahedral geometry. Adjacent Cu atoms are bridged by the bidentate carboxylate groups into a chain. These chains are further linked by the bridging 4,4′‐bipy ligands, forming an undulated chiral two‐dimensional sheet. O—H...O and N—H...O hydrogen bonds connect the sheets in the [100] direction. This study offers useful information for the engineering of chiral coordination polymers with amino acids and 4,4′‐bipy ligands by considering the ratios of the metal ion and organic components.     

Synthesis of Stable Dolichylphosphomannose Analogues

Four oleyl or dolichyl thiophosphate esters 16, 17, 21 , and 22 , analogues of Dol‐P‐Man possessing C(1)? S and/or P? S bonds, were synthesized as potential inhibitors of mannosyl transferases operating in the endoplasmic reticulum (ER). The β‐mannosyl derivatives were prepared by a Mitsunobu reaction of 2,3,4,6‐tetra‐O‐acetyl‐α‐D ‐mannopyranose ( 1 ) with the thiophosphate 2 that provided O‐ and S‐glycosides with good‐to‐excellent diastereoselectivity. A second route to β‐mannosyl derivatives is based on the phosphitylation of the β‐D ‐mannopyranosyl thiol 3 with the phosphoramidites 4a and 4b . Oxidation of the intermediate oleyl thiophosphite with t‐BuOOH led to mono‐ and dithiophosphates. The thiophospholipids 16, 21 , and 22 were inactive as inhibitors of the Man₆(GlcNAc)₂‐PP‐Dol glycolipid elongation.     

Koordinationspolymere 1, 2‐Dithiooxalato‐ und 1, 2‐Dithioquadratato‐Komplexe. Synthese und Strukturen von [BaCr2(bipy)2(1, 2‐dtox)4(H2O)2], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)2(H2O)2]·2H2O und [H3O][H5O2][Cu(cyclam)]3[Cu2(1, 2‐dtsq)3]2

Coordination Polymeric 1, 2‐Dithiooxalato and 1, 2‐Dithiosquarato Complexes. Syntheses and Structures of [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H2₂, and [H₃O][H₅O₂][Cu(cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ 1, 2‐Dithioxalate and 1, 2‐dithiosquarate ions have a pair of soft and hard donor centers and thus are suited for the formation of coordination polymeric complexes containing soft and hard metal ions. The structures of four compounds with building blocks containing these ligands are reported: In [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂] Barium ions and pairs of Cr(bipy)(1, 2‐dtox)₂ complexes form linear chains by the bisbidentate coordination of the dithiooxalate ligands towards Ba²⁺ and Cr³⁺. In [Ni(cyclam)(1, 2‐dtsq)]·2DMF short NÖH···O hydrogen bonds link the NiS₂N₄‐octahedra with C_2v‐symmetry to an infinite chain. In [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H₂O the 1, 2‐dithiosquarato ligand shows a rare example of S‐coordination towards manganese(II). The sulfur atoms of cis‐MnO₂S₄‐polyedra are weakly coordinated towards the axial sites of square‐planar NiN₄‐centers, thus forming a zig‐zag‐chain of Mn···Ni···Mn···Ni polyhedra. [H₃O][H₅O₂][Cu (cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ contains square planar [Cu^II(cyclam)]²⁺ ions and dinuclear [Cu^I₂(1, 2‐dtsq)₃]^4— ions. Here each copper atom is trigonally planar coordinated by S‐donor atoms of the ligands. The Cu…Cu distance is 2.861(4)Å.     

Crystal Structures,Magnetic Properties and Catecholase‐Like Activities of μ‐Alkoxo‐μ‐Carboxylato Double Bridged Dinuclear and Tetranuclear Copper(II) Complexes

One μ‐alkoxo‐μ‐carboxylato bridged dinuclear copper(II) complex, [Cu₂(L¹)(μ‐C₆H₅CO₂)] ( 1 )(H₃L¹ = 1,3‐bis(salicylideneamino)‐2‐propanol)), and two μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear copper(II) complexes, [Cu₄(L¹)₂(μ‐C₈H₁₀O₄)(DMF)₂]·H₂O ( 2 ) and [Cu₄(L²)₂(μ‐C₅H₆O₄]·2H₂O·2CH₃CN ( 3 ) (H₃L² = 1,3‐bis(5‐bromo‐salicylideneamino)‐2‐propanol)) have been prepared and characterized. The single crystal X‐ray analysis shows that the structure of complex 1 is dimeric with two adjacent copper(II) atoms bridged by μ‐alkoxo‐μ‐carboxylato ligands where the Cu···Cu distances and Cu‐O(alkoxo)‐Cu angles are 3.5 11 Å and 132.8°, respectively. Complexes 2 and 3 consist of a μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear Cu(II) complex with mean Cu‐Cu distances and Cu‐O‐Cu angles of 3.092 Å and 104.2° for 2 and 3.486 Å and 129.9° for 3 , respectively. Magnetic measurements reveal that 1 is strong antiferromagnetically coupled with 2J =‐210 cm^?1 while 2 and 3 exhibit ferromagnetic coupling with 2J = 126 cm^?1 and 82 cm^?1 (averaged), respectively. The 2J values of 1–3 are correlated to dihedral angles and the Cu‐O‐Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ) catalyzed by 1–3 was studied. Complexes 1–3 exhibit catecholase‐like active at above pH 8 and 25 °C for oxidation of 3,5‐di‐tert‐butylcatechol.     

Phosphanimin‐Komplexe des Berylliums und Phosphaniminato‐Komplexe mit Heterokubanstruktur

Phosphaneimine Complexes of Beryllium and Phosphoraneiminato Complexes with Heterocubane Structure Beryllium dichloride reacts with the silylated phosphaneimine Me₃SiNPEt₃ in dichloromethane solution to give the monomeric donor‐acceptor complex [BeCl₂(Me₃SiNPEt₃)] ( 1 ). Under cleavage of trimethylchlorosilane the thermolysis of 1 at 160 °C leads to the formation of the phosphoraneiminato complex [BeCl(μ₃‐NPEt₃)]₄ ( 2 ) with heterocubane structure. In the presence of BeCl₂ 1 reacts in the melt to give the phosphoraneiminato complex [Be₄Cl₄(μ₃‐Cl)(μ₃‐NPEt₃)₃] ( 3 ), the structure of which corresponds with the structure of 2 by substitution of a ligand (μ₃‐NPEt₃)^— by a μ₃‐chloro ligand. As a by‐product from the synthesis of 2 in dichloromethane solution the phosphaneimine complex [BeCl₂(μ‐HNPEt₃)]₂·CH₂Cl₂ ( 4 ·CH₂Cl₂) can be obtained. Its dimeric units form dimers [{BeCl₂(μ‐HNPEt₃)}₂]₂ with symmetry D₂ via Cl···H‐N hydrogen bridges. The compounds 1 — 4 ·CH₂Cl₂ are characterized by X‐ray structure determinations, 1 — 3 additionally by IR spectroscopy. 1 : Space group C2/c, Z = 8, lattice dimensions at 193 K: a = 1502.5(1), b = 801.8(1), c = 2609.6(2) pm, β = 96.15(1)°, R₁ = 0.0523. 2 : Space group C2/c, Z = 4, lattice dimensions at 193 K: a = 1992.2(2), b = 1054.8(1), c = 1950.6(2) pm, β = 114.82(1)°, R₁ = 0.0275. 3 : Space group P2₁2₁2₁, Z = 4, lattice dimensions at 193 K: a = 1159.5(1), b = 1199.0(1), c = 2251.1(2) pm, R₁ = 0.0399. 4 ·CH₂Cl₂: Space group Ccca, Z = 8, lattice dimensions at 193 K: a = 1454.6(1), b = 2795.7(3), c = 1235.6(1) pm, R₁ = 0.0349.     

One‐Dimensional Channels Encapsulated in Supramolecular Networks Constructed of Zinc(II), Manganese(II), or ­Nickel(II) Atoms with 3‐(Carboxymethyl)‐2, 7‐dimethyl‐3H‐benzo[d]imidazole‐5‐carboxylic Acid

Four complexes with supramolecular architectures, namely, MZCA · 3H₂O ( 1 ), [Zn(H₂O)₆]²⁺ · [MZCA]₂ · [H₂O]₆ ( 2 ), [Mn(MZCA)₂(H₂O)₄] · 2H₂O ( 3 ), and [Ni(MZCA)₂(H₂O)₄] · 2H₂O ( 4 ) [MZCA = 3‐(carboxymethyl)‐2, 7‐dimethyl‐3H‐benzo[d]imidazole‐5‐carboxylic acid], were synthesized and characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. Complexes 1 and 2 display a remarkable 3D network with 1D hydrophilic channels. Complexes 3 and 4 are isostructural and exhibit a 3D structure encapsulating 1D 24‐membered ring microporous channels. The UV/Vis and fluorescent spectra were measured to characterize complexes 1 – 4 . The thermal stability of complexes 2 – 4 were also examined.     

A copper(I) coordination polymer incorporation the corrosion inhibitor 1H‐benzotriazole: poly[μ3‐benzotriazolato‐κ3N1:N2:N3‐copper(I)]

The title complex, [Cu(C₆H₄N₃)]_n, was synthesized by the reaction of cupric nitrate, 1H‐benzotriazole (BTAH) and aqueous ammonia under hydrothermal conditions. The asymmetric unit contains three crystallographically independent Cu^I cations and two 1H‐benzotriazolate ligands. Two of the Cu^I cations, one with a linear two‐coordinated geometry and one with a four‐coordinated tetrahedral geometry, are located on sites with crystallographically imposed twofold symmetry. The third Cu^I cation, with a planar three‐coordinated geometry, is on a general position. Two Cu^I cations are doubly bridged by two BTA⁻ ligands to afford a noncentrosymmetric planar [Cu₂(BTA)₂] subunit, and two [Cu₂(BTA)₂] subunits are arranged in an antiparallel manner to form a centrosymmetric [Cu₂(BTA)₂]₂ secondary building unit (SBU). The SBUs are connected in a crosswise manner via the sharing of four‐coordinated Cu^I cations, Cu—N bonding and bridging by two‐coordinate Cu^I cations, resulting in a one‐dimensional chain along the c axis. These one‐dimensional chains are further linked by C—H...π and weak van der Waals interactions to form a three‐dimensional supramolecular architecture.     

Poly[[aqua­tetra­imidazole­di‐μ‐phthalato‐dicopper(II)] monohydrate]

The title complex, {[Cu₂(C₈H₄O₄)₂(C₃H₄N₂)₄(H₂O)]·H₂O}_n, is a three‐dimensional polymer formed through bridging by phthalate dianions of two different Cu^II cations and a network of O(N)—H⋯O hydrogen bonds. The Cu—O and Cu—N inter­action distances are in the ranges 2.0020 (16)–2.4835 (17) and 1.968 (2)–1.9855 (19) Å, respectively. The structure is composed of alternating polymer chains parallel to the c axis, with a shortest Cu⋯Cu distance of 6.3000 (5) Å.     

Cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D‐glucopyranose as a convenient synthesis of dextran

For the convenient synthesis of (1→6)‐α‐D ‐glucopyranan, i. e., dextran ( 4 ), ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D ‐glucopyranose ( 1 ) has been carried out using BF₃·OEt₂. With a ratio of [BF₃·OEt₂]/[ 1 ] = 0.5 at 0 °C for 140 h, the yield and M_n of the obtained polymer are 84.0% and 21 700, respectively. The polymer consists of (1→6)‐α‐linked 2,3,4‐tri‐O‐allyl‐D ‐glucopyranose ( 2 ) which is similar to the results for the cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐methyl‐β‐D ‐glucopyranose and 1,6‐anhydro‐2,3,4‐tri‐O‐ethyl‐β‐D ‐glucopyranose. Polymer 2 was isomerized using tris(triphenylphosphine)‐chlororhodium as the catalyst in toluene/ethanol/water to yield polymeric 2,3,4‐tri‐O‐propenyl‐(1→6)‐α‐D ‐glucopyranan ( 3 ). Deprotection of the propenyl ether linkage of 3 was then performed using hydrochloric acid in acetone to give 4 .     

Four Complexes with the Rigid Ligand 1,4‐Bis(1H‐imidazol‐4‐yl)benzene and Varied Carboxylate Ligands

Four metal‐organic coordination polymers [Co₂(L)₃(nipa)₂]·6H₂O ( 1 ), [Cd(L)(nipa)]·3H₂O ( 2 ), [Co(L) (Hoxba)₂] ( 3 ) and [Ni₂(L)₂(oxba)₂(H₂O)]·1.5L·3H₂O ( 4 ) were synthesized by reactions of the corresponding metal(II) salts with the rigid ligand 1,4‐bis(1H‐imidazol‐4‐yl)benzene (L) and different derivatives of 5‐nitroisophthalic acid (H₂nipa) and 4,4′‐oxybis(benzoic acid) (H₂oxba), respectively. The structures of the complexes were characterized by elemental analysis, FT‐IR spectroscopy and single‐crystal X‐ray diffraction. Complexes 1 and 3 have the same one‐dimensional (1D) chain while 2 is a 6‐connected twofold interpenetrating three‐dimensional (3D) network with α ‐Po 4¹²·6³ topology based on the binuclear Cd^II subunits. Compound 4 features a puckered two‐dimensional (2D) (4,4) network, and the large voids of the packing 2D nets have accommodated the uncoordinated L guest molecules. An abundant of N–H···O, O–H···O and C–H···O hydrogen bonding interactions exist in complexes 1–4 , which contributes to stabilize the crystal structure and extend the low‐dimensional entities into high‐dimensional frameworks. Lastly, the photoluminiscent properties of compounds 2 were also investigated.     

Two Ala‐Gln Dipeptide‐based Supramolecular Layers Decorated with Amino Acid Residues

l‐Alanyl‐glutamine dipeptide assembles with Cu^II ions to give the 2D coordination framework [Cu₂(C₈H₁₃N₃O₄)₂·2H₂O]_n ( 1 ) in which amino acid residues result in specific void space. In presence of 4,4′‐bipyridine, framework 1 is turned into a binuclear complex [Cu₂(C₈H₁₃N₃O₄)₂(H₂O)₂(C₁₀H₈N₂)·8H₂O] ( 2 ), which is further linked into a 2D hydrogen‐bonded layer in which amino acid residues induce a hydrogen‐bonded water cluster containing eight water molecules in the void space.