2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil,a cyclouridine nucleoside with a C4′‐endo furanosyl conformation

2,2′‐Anhydro‐1‐(3′,5′‐di‐O‐acetyl‐β‐D‐arabinofuranosyl)uracil, C₁₃H₁₄N₂O₇, was obtained by refluxing 2′,3′‐O‐(methoxymethylene)uridine in acetic anhydride. The structure exhibits a nearly perfect C4′‐endo (⁴E) conformation. The best four‐atom plane of the five‐membered furanose ring is O—C—C—C, involving the C atoms of the fused five‐membered oxazolidine ring, and the torsion angle is only −0.4 (2)°. The oxazolidine ring is essentially coplanar with the six‐membered uracil ring [r.m.s. deviation = 0.012 (5) Å and dihedral angle = −3.2 (3)°]. The conformation at the exocyclic C—C bond is gauche–trans which is stabilized by various C—H...π and C—O...π interactions.     

A chloro(2‐pyridinecarboxaldehyde)(2,2′:6′,2′′‐ter­pyridine)­ruthenium(II) complex

The aldehyde moiety in the title complex, chloro(2‐pyridinecarboxaldehyde‐N,O)(2,2′:6′,2′′‐terpyridine‐κ³N)ruthenium(II)–chloro­(2‐pyridine­carboxyl­ic acid‐N,O)(2,2′:6′,2′′‐ter­pyridine‐κ³N)­ruthenium(II)–perchlorate–chloro­form–water (1.8/0.2/2/1/1), [RuCl­(C₆H₅NO)­(C₁₅H₁₁N₃)]_1.8[RuCl­(C₆H₅­NO₂)(C₁₅H₁₁N₃)]_0.2­(ClO₄)₂·­CHCl₃·­H₂O, is a structural model of substrate coordination to a transfer hydrogenation catalyst. The title complex features two independent Ru^II complex cations that display very similar distorted octahedral coordination provided by the three N atoms of the 2,2′:6′,2′′‐ter­pyridine ligand, the N and O atoms of the 2‐pyridine­carbox­aldehyde (pyCHO) ligand and a chloride ligand. One of the cation sites is disordered such that the aldehyde group is replaced by a 20 (1)% contribution from a carboxyl­ic acid group (aldehyde H replaced by carboxyl O—H). Notable dimensions in the non‐disordered complex cation are Ru—N 2.034 (2) Å and Ru—O 2.079 (2) Å to the pyCHO ligand and O—C 1.239 (4) Å for the pyCHO carbonyl group.     

Theoretical study on the deglycosylation mechanism of rice BGlu1 β‐glucosidase

It is proposed that the catalysis of GH1 enzymes follows a double‐displacement mechanism involving a glycosylation and a deglycosylation steps. In this article, the deglycosylation step was studied using quantum mechanical/molecular mechanical (QM/MM) approach. The calculation results reveal that the nucleophilic water (Wat1) attacks to the anomeric C₁, and the deglycosylation step experiences a barrier of 21.4 kcal/mol from the glycosyl‐enzyme intermediate to the hydrolysis product, in which an oxocarbenium cation‐like transition state (TS) is formed. At the TS, the covalent glycosyl‐enzyme bond is almost broken (distance of 2.45 Å), and the new covalent bond between the attacking oxygen of the water molecule and C₁ is basically established (length of 2.14 Å). In addition, a short hydrogen bridge is observed between the nucleophilic E386 and the C₂? OH of sugar ring (distance of 1.94 Å) at the TS, which facilitates the ring changing from a chair form to half‐chair form, and stabilizes the oxocarbenium cation‐like TS. © 2013 Wiley Periodicals, Inc.     

5‐Methyl‐2‐thiouracil

The molecular structure of the title compound, also known as 2‐thio­thymine [systematic name: 2,3‐di­hydro‐5‐methyl‐2‐thioxopyrimidin‐4(1H)‐one], C₅H₆N₂OS, is similar to that of thymine, with only small changes in the ring structure, apart from a significant difference at the substitution site [S=C = 1.674 (1) Å]. The mol­ecules are connected by hydrogen bonds, with N—H?O = 2.755 (2) Å and N—H?S = 3.352 (1) Å. The hydrogen‐bond network is different from that in thymine, since it involves all the donor and acceptor atoms.     

Bis(μ‐succinato‐O,O′:O′′,O′′′)bis[bis(2‐amino‐1,3‐benzothiazole‐N3)copper(II)]

In the title dimeric complex, [Cu₂(C₄H₄O₄)₂(C₇H₆N₂S)₄], which possesses a centre of symmetry, the Cu atoms are enclosed in a 14‐membered ring. They adopt a distorted square‐bipyramidal (4+2) coordination. The four closest donor atoms are two N atoms of 2‐amino­benzo­thiazole ligands and two O atoms of the succinate carboxylate groups. They form a square‐planar cis arrangement, with an average Cu—N distance of 2.003 (3) Å and Cu—O distances of 1.949 (3) and 1.965 (3) Å. Two longer Cu—O bonds of 2.709 (3) and 2.613 (3) Å involving the remaining O atoms of the carboxylate groups complete the sixfold coordination of the Cu atoms. The H atoms of each amino group of the 2‐amino­benzo­thiazole molecules form intra‐ and inter­molecular N—H?O hydrogen bonds. A nearly perpendicular inter­molecular C—H?Cg interaction (Cg is the centroid of the imidazole ring) is observed. The intramolecular Cu?Cu distance is 6.384 (2) Å.     

New organic–inorganic frameworks incorporating iso‐ and heteropolymolybdate units and a 3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium multiple hydrogen‐bond donor

Poly[bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) γ‐octamolybdate(VI) dihydrate], {(C₁₀H₁₆N₄)₂[Mo₈O₂₆]·2H₂O}_n, (I), and bis(3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium) α‐dodecamolybdo(VI)silicate tetrahydrate, (C₁₀H₁₆N₄)₂[SiMo₁₂O₄₀]·4H₂O, (II), display intense hydrogen bonding between the cationic pyrazolium species and the metal oxide anions. In (I), the asymmetric unit contains half a centrosymmetric γ‐type [Mo₈O₂₆]⁴⁻ anion, which produces a one‐dimensional polymeric chain by corner‐sharing, one cation and one water molecule. Three‐centre bonding with 3,3′,5,5′‐tetramethyl‐4,4′‐bi‐1H‐pyrazole‐2,2′‐diium, denoted [H₂Me₄bpz]²⁺ [N...O = 2.770 (4)–3.146 (4) Å], generates two‐dimensional layers that are further linked by hydrogen bonds involving water molecules [O...O = 2.902 (4) and 3.010 (4) Å]. In (II), each of the four independent [H₂Me₄bpz]²⁺ cations lies across a twofold axis. They link layers of [SiMo₁₂O₄₀]⁴⁻ anions into a three‐dimensional framework, and the preferred sites for pyrazolium/anion hydrogen bonding are the terminal oxide atoms [N...O = 2.866 (6)–2.999 (6) Å], while anion/aqua interactions occur preferentially viaμ₂‐O sites [O...O = 2.910 (6)–3.151 (6) Å].     

Hexa‐μ2‐chloro‐μ4‐oxo‐tetrakis[(2‐ethyl­tetrazole‐κN4)copper(II)]

In the title molecular complex, [Cu₄Cl₆O(2‐EtTz)₄], where 2‐EtTz is 2‐ethyl­tetrazole (C₃H₆N₄), the central O atom is located on the symmetry site and is tetrahedrally coordinated to four Cu atoms, with Cu—O distances of 1.8966 (4) Å. A very slight distortion of Cu₄O from a regular tetrahedron is observed [two Cu—O—Cu angles are 108.76 (3)° and four others are 109.828 (13)°]. Each Cu atom is connected to three others via the Cl atoms, forming a slightly distorted Cl octahedron around the O atom, with O⋯Cl distances of 2.9265 (7) Å for Cl atoms lying on the twofold axis and 2.9441 (13) Å for those in general positions. The Cu atom has a distorted trigonal–bipyramidal environment, with three Cl atoms in the equatorial plane, and with the N atom of the 2‐ethyl­tetrazole ligand and the μ₄‐O atom in axial positions. The Cu atom is displaced out of the equatorial plane by ca 0.91 Å towards the coordinated N atom of the 2‐­ethyl­tetrazole ligand.     

Poly[μ2‐(N‐hydroxypyridine‐2‐carboxamidine)‐μ2‐nitrato‐silver(I)]

In the title complex, [Ag(NO₃)(C₆H₇N₃O)]_n or [Ag(NO₃)(pyaoxH₂)] (pyaoxH₂ is N‐hydroxypyridine‐2‐carboxamidine), the Ag⁺ ion is bridged by the pyaoxH₂ ligands and nitrate anions, giving rise to a two‐dimensional molecular structure. Each pyaoxH₂ ligand coordinates to two Ag⁺ ions using its pyridyl and carboxamidine N atoms, and the OH and the NH₂ groups are uncoordinated. Each nitrate anion uses two O atoms to coordinate to two Ag⁺ ions. The Ag...Ag separation via the pyaoxH₂ bridge is 2.869 (1) Å, markedly shorter than that of 6.452 (1) Åvia the nitrate bridge. The two‐dimensional structure is fishscale‐like, and can be described as pyaoxH₂‐bridged Ag₂ nodes that are further linked by nitrate anions. Hydrogen bonding between the amidine groups and the nitrate O atoms connects adjacent layers into a three‐dimensional network.     

Crystal‐to‐crystal transformation upon dehydration of a copper(II) 2,2′:6′,2′′‐terpyridine complex

The reaction of 2,2′:6′,2′′‐terpyridine (terpy) with CuCl₂ in the presence of sodium sulfite led to the synthesis of the ionic complex aquachlorido(2,2′:6′,2′′‐terpyridyl‐κ³N,N′,N′′)copper(II) chlorido(dithionato‐κO)(2,2′:6′,2′′‐terpyridyl‐κ³N,N′,N′′)cuprate(II) dihydrate, [CuCl(C₁₅H₁₁N₃)(H₂O)][CuCl(S₂O₆)(C₁₅H₁₁N₃)]·2H₂O, (I), and the in situ synthesis of the S₂O₆²⁻ dianion. Compound (I) is composed of a [CuCl(terpy)(H₂O)]⁺ cation, a [Cu(S₂O₆)(terpy)]⁻ anion and two solvent water molecules. Thermogravimetric analysis indicated the loss of two water molecules at ca 363 K, and at 433 K the weight loss indicated a total loss of 2.5 water molecules. The crystal structure analysis of the resulting pale‐green dried crystals, μ‐dithionato‐κ²O:O′‐bis[chlorido(2,2′:6′,2′′‐terpyridyl‐κ³N,N′,N′′)copper(II)] monohydrate, [Cu₂Cl₂(S₂O₆)(C₁₅H₁₁N₃)₂]·H₂O, (II), revealed a net loss of 1.5 water molecules and the formation of a binuclear complex with two [CuCl(terpy)]⁺ cations bridged by a dithionate dianion. The crystal‐to‐crystal transformation involved an effective reduction in the unit‐cell volume of ca 7.6%. In (I), the ions are linked by O—H...O hydrogen bonds involving the coordinated and solvent water molecules and O atoms of the dithionate unit, to form ribbon‐like polymer chains propagating in [100]. These chains are linked by Cu...Cl interactions [3.2626 (7) Å in the cation and 3.3492 (7) Å in the anion] centred about inversion centres, to form two‐dimensional networks lying in and parallel to (01). In (II), symmetry‐related molecules are linked by O—H...O hydrogen bonds involving the partially occupied disordered water molecule and an O atom of the bridging thiosulfite anion, to form ribbon‐like polymer chains propagating in [100]. These chains are also linked by Cu...Cl interactions [3.3765 (12) Å] centred about inversion centres to form similar two‐dimensional networks to (I) lying in and parallel to (02), crosslinked into three dimensions by C—H...O=S and C—H...O(water) interactions.     

catena‐Poly­[[(di‐2‐pyridyl­amine)­silver(I)]‐μ‐nicotinato] and catena‐poly­[[(di‐2‐pyridyl­amine)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato]

In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐nico­tinato‐κ²N:O], [Ag(C₆H₄NO₂)(C₁₀H₉N₃)]_n, the Ag^I atom is tetracoordinated by two N atoms from the di‐2‐pyridyl­amine (BPA) ligand [Ag—N = 2.3785 (18) and 2.3298 (18) Å] and by one N atom and one carboxyl­ate O atom from nicotinate ligands [Ag—N = 2.2827 (15) Å and Ag—O = 2.3636 (14) Å]. Bridging by nicotinate N and O atoms generates a polymeric chain structure, which extends along [100]. The carboxyl O atom not bonded to the Ag atom takes part in an intrachain C—H⋯O hydrogen bond, further stabilizing the chain. Pairs of chains are linked by N—H⋯O hydrogen bonds to generate ribbons. There are no π–π interactions in this complex. In catena‐poly­[[(di‐2‐pyridyl­amine‐κ²N,N′)silver(I)]‐μ‐2,6‐di­hydroxy­benzoato‐κ²O¹:O²], [Ag(C₇H₅O₄)(C₁₀H₉N₃)]_n, the Ag^I atom has a distorted tetrahedral coordination, with three strong bonds to two pyridine N atoms from the BPA ligand [Ag—N = 2.286 (5) and 2.320 (5) Å] and to one carboxyl­ate O atom from the 2,6‐di­hydroxy­benzoate ligand [Ag—O = 2.222 (4) Å]; the fourth, weaker, Ag‐atom coordination is to one of the phenol O atoms [Ag⋯O = 2.703 (4) Å] of an adjacent moiety, and this interaction generates a polymeric chain along [100]. Pairs of chains are linked about inversion centers by N—H⋯O hydrogen bonds to form ribbons, within which there are π–π interactions. The ribbons are linked about inversion centers by pairs of C—H⋯O hydrogen bonds and additional π–π interactions between inversion‐related pairs of 2,6‐di­hydroxy­benzoate ligands to generate a three‐dimensional network.     

catena‐Poly­[[di­aqua­cadmium(II)]‐μ‐5‐carboxyimidazole‐4‐carboxylato‐κ4N1,O5:O4,N3]

A new cadmium coordination polymer, [Cd(C₅H₂N₂O₄)(H₂O)₂]_n, possesses a one‐dimensional zigzag chain structure built from Cd^II centers bridged sequentially by pairs of O and N atoms of the 5‐carboxyimidazole‐4‐carboxylate ligand. The Cd^II center is in a distorted octahedral geometry, being coordinated by two O atoms from two coordinated water mol­ecules [Cd—O = 2.322 (7) and 2.364 (7) Å], and by two N atoms [Cd—N = 2.222 (6) and 2.232 (6) Å] and two carboxyl O atoms [Cd—O = 2.383 (6) and 2.414 (6) Å] from two 5‐carboxyimidazole‐4‐carboxylate ligands.     

A Novel Dinuclear Nickel(II) Complex with Three Bridges of Cl–, OAc– and (‐OCH2CH2O‐) Group of N,N, N′, N′‐Tetrakis(2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino) Glycol Ether

The novel dinuclear Ni²⁺ complex [Ni₂(μ‐Cl)(μ‐OAc) (EGTB)]·Cl·ClO₄·2CH₃OH, where EGTB is N, N, N′, N′‐tetrakis (2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino)glycol ether, crystallizes in the orthorhombic space group Pnma with a = 15.272(2), b = 14.768(2), c = 22.486(3) Å, V = 5071.4(12) ų, Z = 4, D_calc = 1.414 g cm^?3, and is bridged by triply bridging agents of a chloride ion, an acetate and an intra‐ligand (‐OCH₂CH₂O‐) group. The nickel coordination geometry is that of a slightly distorted octahedron with a NiN₃O₂Cl arrangement of the ligand donor atoms. The Ni–Cl distance is 2.361(2) Å, and two Ni–O distances are 1.996(5) and 2.279(6) Å. The three Ni–N distances are 2.033(7), 2.060(6), and 2.166(6) Å with the Ni–N bond trans to an ether oxygen the shortest, the Ni–N bond trans to an acetate oxygen the middle and the Ni–N bond trans to Cl the longest.     

(E)‐2‐Methyl‐5‐(1‐naphthyl­methyl)­cinnamic acid

The title compound, C₂₁H₁₈O₂, crystallized in the centrosymmetric space group P2₁/n with one mol­ecule in the asymmetric unit. There is a single hydrogen bond, with an O_donor?O_acceptor distance of 2.624 (2) Å, which forms a cyclic dimer about a center of symmetry. The carboxyl group O atoms are ordered, while the carboxyl‐H atom is disordered. A single leading intermolecular C—H?O interaction has an H?O distance of 2.68 Å and a C—H?O angle of 178°; this interaction forms chains. Taken together with the hydrogen bond, it generates chains and rings. Structural comparisons are made with trans‐cinnamic acid and with 4‐methyl‐trans‐cinnamic acid.     

7‐Phenyl‐1‐oxa‐4‐thiaspiro[4.5]decan‐7‐ol stereoisomers

The stereoisomers of 7‐phenyl‐1‐oxa‐4‐thia­spiro­[4.5]­decan‐7‐ol, C₁₄H₁₈O₂S, have the same stereochemistry at the C atom bearing an OH group, i.e. axial OH and equatorial phenyl groups. However, the acetal S and O atoms are axial and equatorial, respectively, in one isomer and reversed in the second. Furthermore, the crystals of one isomer are composed of hydrogen‐bonded mol­ecules involving the hydroxyl H atom and the O atom of the five‐membered heterocyclic ring, with an O?O distance of 2.962 (3) Å, forming a polymeric chain along the b axis. The asymmetric unit of the other isomer is composed of two mol­ecules, wherein hydroxyl H atoms and the O atoms of the five‐membered heterocyclic rings display intramolecular O—H?O hydrogen bonds with O?O separations of 2.820 (2) and 2.834 (2) Å.     

Polymeric tris(μ2‐acetone‐κ2O:O)sodium polyiodide at 120 K

In the title compound, [Na(C₃H₆O)₃]_n(I₂)_n, all non‐H atoms are in special positions of the space group P6₃/mcm, with the Na atom in 2b, the I atom in 4c, the carbonyl O atom and the C atom attached to it both in 6g, and the methyl C atom in 12k. The H atoms of the rotationally disordered methyl groups are in 24l general positions but with occupancies of 0.5, because they occur in two sets related by a crystallographic mirror plane. Infinite chains are created by face‐sharing octahedral Na‐coordination polyhedra, with Na—O and Na⋯Na distances of 2.439 (5) and 3.2237 (4) Å, respectively. I atoms form infinite linear chains, in which the I‐atom separation is 3.2237 (4) Å.     

Synthesis,Crystal Structure and Hydrolysis of a Novel Anhydrogalactosucrose: 2′‐Methoxyl‐O‐1′,4′:3′,6′‐dianhydro‐β‐D‐fructofuranosyl 3,6‐anhydro‐4‐chloro‐4‐deoxy‐α‐D‐galactopyranoside

A novel anhydrogalactosucrose derivative 2′‐methoxyl‐O‐1′,4′:3′,6′‐dianhydro‐β‐D‐fructofuranosyl 3,6‐anhydro‐4‐chloro‐4‐deoxy‐α‐D‐galactopyranoside ( 4 ) was prepared from 3,6:1′,4′:3′,6′‐trianhydro‐4‐chloro‐4‐deoxy‐galactosucrose ( 3 ) via a facile method and characterized by ¹H NMR, ¹³C NMR and 2D NMR spectra. The single crystal X‐ray diffraction analysis shows that the title molecule forms a two thee‐dimensional network structure by two kinds of hydrogen bond interactions [O(2) H(2)···O(7), O(5) H(5)···O(8)]. Its stability was investigated by acid hydrolysis reaction treated with sulfuric acid, together with the formation of 1,6‐Di‐O‐methoxy‐4‐chloro‐4‐deoxy‐β‐D‐galactopyranose ( 5 ) and 2,2‐Di‐C‐methoxy‐1,4:3,6‐dianhydromannitol ( 6 ). According to the result, the relative stability of the ether bonds in the structure is in the order: C(1) O C(5)≈C(3′) O C(6′)≈C(1′) O C(4′)>C(3) O C(6)≈C(1) O C(2′)>C(2′) O C(5′).     

Poly­[[bis­(pyridine‐κN)copper(II)]‐μ3‐5‐hydroxy­isophthalato‐κ3O:O′:O′′]

In the title compound, [Cu(C₈H₄O₅)(C₅H₅N)₂]_n or [Cu(OH‐BDC)(py)₂]_n (where OH‐H₂BDC is 5‐hydroxy­isophthalic acid and py is pyridine), the Cu atoms are coordinated by two N atoms from the pyridine ligands and by three O atoms from hydroxy­isophthalate ligands in a highly distorted triangular bipyramidal environment, with Cu—O distances in the range 1.941 (4)–2.225 (5) Å and Cu—N distances of 2.014 (6) and 2.046 (6) Å. The [Cu(OH‐BDC)]_n two‐dimensional network is built up from interlocking 22‐, 15‐ and eight‐membered rings via sharing of Cu atoms and O—H⋯O hydrogen bonds. Consolidation of the packing structure is achieved by edge‐ or point‐to‐face C—H⋯π interactions and offset or slipped π–π stacking interactions.     

Four N7‐alkoxybenzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones: hydrogen‐bonded supramolecular structures in zero,one, two or three dimensions

3‐tert‐Butyl‐7‐(4‐methoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₇N₃O₃, (I), 3‐tert‐butyl‐7‐(2,3‐dimethoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₂H₃₉N₃O₄, (II), 3‐tert‐butyl‐4′,4′‐dimethyl‐7‐(3,4‐methylenedioxybenzyl)‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₅N₃O₄, (III), and 3‐tert‐butyl‐4′,4′‐dimethyl‐1‐phenyl‐7‐(3,4,5‐trimethoxybenzyl)‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol 0.67‐solvate, C₃₃H₄₁N₃O₅·0.67C₂H₆O, (IV), all contain reduced pyridine rings having half‐chair conformations. The molecules of (I) and (II) are linked into centrosymmetric dimers and simple chains, respectively, by C—H...O hydrogen bonds, augmented only in (I) by a C—H...π hydrogen bond. The molecules of (III) are linked by a combination of C—H...O and C—H...π hydrogen bonds into a chain of edge‐fused centrosymmetric rings, further linked by weak hydrogen bonds into supramolecular arrays in two or three dimensions. The heterocyclic molecules in (IV) are linked by two independent C—H...O hydrogen bonds into sheets, from which the partial‐occupancy ethanol molecules are pendent. The significance of this study lies in its finding of a very wide range of supramolecular aggregation modes dependent on rather modest changes in the peripheral substituents remote from the main hydrogen‐bond acceptor sites.     

Disorder and conformational analysis of methyl β‐d‐galactopyranosyl‐(1→4)‐β‐d‐xylopyranoside

Methyl β‐d ‐galactopyranosyl‐(1→4)‐β‐d ‐xylopyranoside, C₁₂H₂₂O₁₀, (II), crystallizes as colorless needles from water with positional disorder in the xylopyranosyl (Xyl) ring and no water molecules in the unit cell. The internal glycosidic linkage conformation in (II) is characterized by a ϕ′ torsion angle (C2′_Gal—C1′_Gal—O1′_Gal—C4_Xyl) of 156.4 (5)° and a ψ′ torsion angle (C1′_Gal—O1′_Gal—C4_Xyl—C3_Xyl) of 94.0 (11)°, where the ring atom numbering conforms to the convention in which C1 denotes the anomeric C atom, and C5 and C6 denote the hydroxymethyl (–CH₂OH) C atoms in the β‐Xyl and β‐Gal residues, respectively. By comparison, the internal linkage conformation in the crystal structure of the structurally related disaccharide, methyl β‐lactoside [methyl β‐d ‐galactopyranosyl‐(1→4)‐β‐d ‐glucopyranoside], (III) [Stenutz, Shang & Serianni (1999). Acta Cryst. C 55 , 1719–1721], is characterized by ϕ′ = 153.8 (2)° and ψ′ = 78.4 (2)°. A comparison of β‐(1→4)‐linked disaccharides shows considerable variability in both ϕ′ and ψ′, with the range in the latter (∼38°) greater than that in the former (∼28°). Inter‐residue hydrogen bonding is observed between atoms O3_Xyl and O5′_Gal in the crystal structure of (II), analogous to the inter‐residue hydrogen bond detected between atoms O3_Glc and O5′_Gal in (III). The exocyclic hydroxymethyl conformations in the Gal residues of (II) and (III) are identical (gauche–trans conformer).     

(2‐Methyl­quinolin‐8‐olato)­iron(III) and ‐copper(II) complexes

The crystal structures of tris(2‐methyl­quinolin‐8‐olato‐N,O)­iron(III), [Fe­(C₁₀­H₈­NO)₃], (I), and aqua­bis(2‐methyl­quinolin‐8‐olato‐N,O)­copper(II), [Cu­(C₁₀­H₈NO)₂­(H₂O)], (II), have been determined. Compound (I) has a distorted octahedral configuration, in which the central Fe atom is coordinated by three N atoms and three O atoms from three 2‐methylquinolin‐8‐olate ligands. The three Fe—O bond distances are in the range 1.934 (2)–1.947 (2) Å, while the three Fe—N bond distances range from 2.204 (2) to 2.405 (2) Å. In compound (II), the central Cu^II atom and H₂O group lie on the crystallographic twofold axis and the coordination geometry of the Cu^II atom is close to trigonal bipyramidal, with the three O atoms in the basal plane and the two N atoms in apical positions. The Cu—N bond length is 2.018 (5) Å. The Cu—O bond length in the basal positions is 1.991 (4) Å, while the Cu—O bond length in the apical position is 2.273 (6) Å. There is an intermolecular OW—H?O hydrogen bond which links the mol­ecules into a linear chain along the b axis.