Theoretical Study on the Spectroscopic Properties of CO3.−.nH2O Clusters: Extrapolation to Bulk

Vertical detachment energies (VDE) and UV/Vis absorption spectra of hydrated carbonate radical anion clusters, CO₃^.?.n H₂O (n=1–8), are determined by means of ab initio electronic structure theory. The VDE values of the hydrated clusters are calculated with second‐order Moller–Plesset perturbation (MP2) and coupled cluster theory using the 6‐311++G(d,p) set of basis functions. The bulk VDE value of an aqueous carbonate radical anion solution is predicted to be 10.6 eV from the calculated weighted average VDE values of the CO₃^.?.n H₂O clusters. UV/Vis absorption spectra of the hydrated clusters are calculated by means of time‐dependent density functional theory using the Becke three‐parameter nonlocal exchange and the Lee–Yang–Parr nonlocal correlation functional (B3LYP). The simulated UV/Vis spectrum of the CO₃^.?.8 H₂O cluster is in excellent agreement with the reported experimental spectrum for CO₃^.? (aq), obtained based on pulse radiolysis experiments.     

Carbon Dioxide Activation at Metal Centers: Evolution of Charge Transfer from Mg .+ to CO2 in [MgCO2(H2O)n].+, n=0–8

We investigate activation of carbon dioxide by singly charged hydrated magnesium cations Mg ^.+(H₂O)_n, through infrared multiple photon dissociation (IRMPD) spectroscopy combined with quantum chemical calculations. The spectra of [MgCO₂(H₂O)_n]^.+ in the 1250–4000 cm^?1 region show a sharp transition from n=2 to n=3 for the position of the CO₂ antisymmetric stretching mode. This is evidence for the activation of CO₂ via charge transfer from Mg ^.+ to CO₂ for n≥3, while smaller clusters feature linear CO₂ coordinated end‐on to the metal center. Starting with n=5, we see a further conformational change, with CO₂^.? coordination to Mg²⁺ gradually shifting from bidentate to monodentate, consistent with preferential hexa‐coordination of Mg²⁺. Our results reveal in detail how hydration promotes CO₂ activation by charge transfer at metal centers.     

Four‐Center Oxidation State Combinations and Near‐Infrared Absorption in [Ru(pap)(Q)2]n (Q=3,5‐Di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine,pap=2‐Phenylazopyridine)

The complex series [Ru(pap)(Q)₂]ⁿ ([ 1 ]ⁿ–[ 4 ]ⁿ; n=+2, +1, 0, ?1, ?2) contains four redox non‐innocent entities: one ruthenium ion, 2‐phenylazopyridine (pap), and two o‐iminoquinone moieties, Q=3,5‐di‐tert‐butyl‐N‐aryl‐1,2‐benzoquinonemonoimine (aryl=C₆H₅ ( 1⁺ ); m‐(Cl)₂C₆H₃ ( 2⁺ ); m‐(OCH₃)₂C₆H₃ ( 3⁺ ); m‐(tBu)₂C₆H₃ ( 4 ⁺)). A crystal structure determination of the representative compound, [ 1 ]ClO₄, established the crystallization of the ctt‐isomeric form, that is, cis and trans with respect to the mutual orientations of O and N donors of two Q ligands, and the coordinating azo N atom trans to the O donor of Q. The sensitive C? O (average: 1.299(3) Å), C? N (average: 1.346(4) Å) and intra‐ring C? C (meta; average: 1.373(4) Å) bond lengths of the coordinated iminoquinone moieties in corroboration with the N?N length (1.292(3) Å) of pap in 1 ⁺ establish [Ru^III(pap⁰)(Q^.?)₂]⁺ as the most appropriate electronic structural form. The coupling of three spins from one low‐spin ruthenium(III) (t_2g⁵) and two Q^.? radicals in 1 ⁺– 4 ⁺ gives a ground state with one unpaired electron on Q^.?, as evident from g=1.995 radical‐type EPR signals for 1 ⁺– 4 ⁺. Accordingly, the DFT‐calculated Mulliken spin densities of 1 ⁺ (1.152 for two Q, Ru: ?0.179, pap: 0.031) confirm Q‐based spin. Complex ions 1 ⁺– 4 ⁺ exhibit two near‐IR absorption bands at about λ=2000 and 920 nm in addition to intense multiple transitions covering the visible to UV regions; compounds [ 1 ]ClO₄–[ 4 ]ClO₄ undergo one oxidation and three separate reduction processes within ±2.0 V versus SCE. The crystal structure of the neutral (one‐electron reduced) state ( 2 ) was determined to show metal‐based reduction and an EPR signal at g=1.996. The electronic transitions of the complexes 1 ⁿ– 4 ⁿ (n=+2, +1, 0, ?1, ?2) in the UV, visible, and NIR regions, as determined by using spectroelectrochemistry, have been analyzed by TD‐DFT calculations and reveal significant low‐energy absorbance (λ_max>1000 nm) for cations, anions, and neutral forms. The experimental studies in combination with DFT calculations suggest the dominant valence configurations of 1 ⁿ– 4 ⁿ in the accessible redox states to be [Ru^III(pap⁰)(Q^.?)(Q⁰)]²⁺ ( 1 ²⁺– 4 ²⁺)→[Ru^III(pap⁰)(Q^.?)₂]⁺ ( 1 ⁺– 4 ⁺)→[Ru^II(pap⁰)(Q^.?)₂] ( 1 – 4 )→[Ru^II(pap^.?)(Q^.?)₂]^? ( 1 ^?– 4 ^?)→[Ru^III(pap^.?)(Q^2?)₂]^2? ( 1 ^2?– 4 ^2?).     

Poly[diaquabis(μ3‐hexamethylenetetramine)[μ2‐2,2′‐(piperazine‐1,4‐diyl)bis(ethanesulfonato)]disilver(I)]: a three‐dimensional pillared‐layer framework encapsulating a water chain of (H2O)12 clusters

The title compound, {[Ag₂(C₈H₁₆N₂O₆S₂)(C₆H₁₂N₄)₂(H₂O)₂]·12H₂O}_n, consists of a two‐dimensional Ag^I–hexamethylenetetramine (6,3) net pillared by the 2,2′‐(piperazine‐1,4‐diyl)bis(ethanesulfonate) ligand, which lies across a centre of inversion. This compound can also be viewed as a (3,4)‐connected topology by considering the hexamethylenetetramine ligand and the Ag^I ion as the three‐ and four‐connected nodes, respectively. There is a one‐dimensional channel along the a axis accommodating a water chain assembled by the (H₂O)₁₂ clusters.     

Neutral 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide and its salt forms with inorganic anions

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide, C₁₉H₁₆N₄O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C₁₉H₁₇N₄O⁺·Cl^?·2H₂O, (II), the nitrate dihydrate, C₁₉H₁₇N₄O⁺·NO₃^?·2H₂O, (III), and the thiocyanate 2.5‐hydrate, C₁₉H₁₇N₄O⁺·SCN^?·2.5H₂O, (IV), of 2‐[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H₂BzPyS]⁺·X^?·nH₂O, with X = Cl^? and n = 2 for (II), X = NO₃^? and n = 2 for (III), and X = SCN^? and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter‐ions (chloride or nitrate) are involved in the formation of a two‐dimensional arrangement by the establishment of hydrogen bonds with the N—H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π–π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H₂BzPyS]⁺ cation is in good agreement with the experimental results.     

Structures and Reactivity of Oxygen‐Rich Scandium Cluster Anions ScO3–5−

Oxygen‐rich scandium cluster anions ScO_3–5^? are prepared by laser ablation and allowed to react with n‐butane in a fast‐flow reactor. A time‐of‐flight mass spectrometer is used to detect the cluster distribution before and after the reactions. The ScO₃^? and ScO₄^? clusters can react with n‐butane to produce ScO₃H^?, ScO₃H₂^?, and ScO₄H^?, while the more oxygen‐rich cluster ScO₅^? is inert. The experiment suggests that unreactive cluster isomers of ScO₃^? and ScO₄^? are also present in the cluster source. Density functional theory and ab initio methods are used to calculate the structures and reaction mechanisms of the clusters. The theoretical results indicate that the unreactive and reactive cluster isomers of ScO_3,4^? contain peroxides (O₂^2?) and oxygen‐centered radicals (O^.?), respectively. The mechanisms and energetics for conversion of unreactive O₂^2? to reactive O^.? species are also theoretically studied.     

Synthesis and characterization of di‐n‐butyltin(IV) complexes with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids: X‐ray crystal structures of [{(n‐C4H9)2Sn(OCOC12H8NO2−4′)}2O]2 and (n‐C4H9)2Sn{OCOC12H8NO2−4′}2

Reactions of di‐n‐butyltin(IV) oxide with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids in 1 : 1 and 1 : 2 stoichiometry yield complexes [{(n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′/2′)}₂O]₂ ( 1 and 2 ) and (n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′/2′)₂ ( 3 and 4 ) respectively. These compounds were characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. The IR spectra of these compounds indicate the presence of anisobidentate carboxylate groups and non‐linear C? Sn? C bonds. From the chemical shifts δ (¹¹⁹Sn) and the coupling constants ¹J(¹³C, ¹¹⁹Sn), the coordination number of the tin atom and the geometry of its coordination sphere have been suggested. [{(n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′)}₂O]₂ ( 1 ) exhibits a dimeric structure containing distannoxane units with two types of tin atom with essentially identical geometry. To a first approximation, the tin atoms appear to be pentacoordinated with distorted trigonal bipyramidal geometry. However, each type of tin atom is further subjected to a sixth weaker interaction and may be described as having a capped trigonal bipyramidal structure. The diffraction study of the complex (n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′)₂ ( 3 ) shows a six–coordinate tin in a distorted octahedral frame containing bidentate asymmetric chelating carboxylate groups, with the n‐Bu groups trans to each other. The n‐Bu? Sn? n‐Bu angle is 152.8° and the Sn? O distances are 2.108(4) and 2.493(5) Å. The oxygen atom of the nitro group of the ligand does not participate in bonding to the tin atom in 1 and 3 . Crystals of 1 are triclinic with space group P1 and of that of 3 have orthorhombic space group Pnna. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of microhydration on the atmospherically important metastable carbonyl sulfide anion: Structure,energetic, and infrared study

Structure, energetics, and vibrational frequency of the microhydrated carbonyl sulfide anion [OCS^?? (H₂O)_n (n = 1–6)] have been explored by the systematic ab initio study to have a comprehensive understanding about the hydration‐induced stabilization phenomenon of OCS^?. Water binds with the OCS^? in single hydrogen‐bonded (SHB) or double hydrogen‐bonded (DHB) fashion with O? H S and O? H O contacts. Maximum five water molecules can stay in a cyclic water network of these hydrated clusters forming interwater hydrogen bonding (IHB) with each other and out of this, maximum of two water molecules can bind directly to the OCS^? in (DHB) arrangement. The stabilization energy values of OCS^?? (H₂O)_n depict that ion–water interaction is significant up to four water molecules and beyond that OCS^? is stabilized by IHB between the water molecules. The CO stretching frequency of OCS^? gets red shifted, whereas CS stretching frequency gets blue shifted on hydration. Charge analysis of hydrated clusters of OCS^? indicates that negative charge moves toward oxygen from sulfur on hydration. © 2015 Wiley Periodicals, Inc.     

A three‐dimensional polymeric potassium complex of 5‐sulfonobenzene‐1,2,4‐tricarboxylic acid: poly[μ‐aqua‐aqua‐μ9‐(2,4‐dicarboxy‐5‐sulfonatobenzoato)‐dipotassium(I)]

The asymmetric unit in the structure of the title compound, [K₂(C₉H₄O₉S)(H₂O)₂]_n, consists of two eight‐coordinated K^I cations, one 2,4‐dicarboxy‐5‐sulfonatobenzoate dianion (H₂SBTC²⁻), one bridging water molecule and one terminal coordinated water molecule. One K^I cation is coordinated by three carboxylate O atoms and three sulfonate O atoms from four H₂SBTC²⁻ ligands and by two bridging water molecules. The second K^I cation is coordinated by four sulfonate O atoms and three carboxylate O atoms from five H₂SBTC²⁻ ligands and by one terminal coordinated water molecule. The K^I cations are linked by sulfonate groups to give a one‐dimensional inorganic chain with cage‐like K₄(SO₃)₂ repeat units. These one‐dimensional chains are bridged by one of the carboxylic acid groups of the H₂SBTC²⁻ ligand to form a two‐dimensional layer, and these layers are further linked by the remaining carboxylate groups and the benzene rings of the H₂SBTC²⁻ ligands to generate a three‐dimensional framework. The compound displays a photoluminescent emission at 460 nm upon excitation at 358 nm. In addition, the thermal stability of the title compound has been studied.     

A one‐dimensional heterometallic coordination polymer with a three‐dimensional supramolecular framework: poly[μ2‐aqua‐diaqua(2,2′‐bipyridyl)(μ5‐2‐sulfonatobutanedioato)copper(II)sodium(I)]

The title compound, [CuNa(C₄H₃O₇S)(C₁₀H₈N₂)(H₂O)₃]_n, consists of one Cu^II cation, one Na^I cation, one 2‐sulfonatobutanedioate trianion (SSC³⁻), one 2,2′‐bipyridyl (bpy) ligand and three coordinated water molecules as the building unit. The coordination of the Cu^II cation is composed of two pyridyl N atoms, one water O atom and two carboxylate O atoms in a distorted square‐pyramidal coordination geometry with an axial elongation. The Na^I cation is six‐coordinated by three water molecules and three carboxylate O atoms from three SSC³⁻ ligands in a distorted octahedral geometry. Two SSC³⁻ ligands link two Cu^II cations to form a Cu₂(SSC)₂(bpy)₂ macrocyclic unit lying across an inversion centre, which is further linked by Na^I cations via Na—O bonds to give a one‐dimensional chain. Interchain hydrogen bonds link these chains to form a two‐dimensional layer, which is further extended into a three‐dimensional supramolecular framework through π–π stacking interactions. The thermal stability of the title compound has also been investigated.     

Self‐assembled hydrogen‐bonded bilayers in 1,4‐diazabicyclo[2.2.2]octane–N‐(phosphonomethyl)iminodiacetic acid–water (1/1/1.5)

The title compound is a hydrated salt, 1,4‐diazo­nia­bi­cyclo­[2.2.2]­octane–N‐[(hydroxy­phosphinato)­methyl]­iminiodi­acetate–water (1/1/1.5), C₆H₁₄N₂²⁺·C₅H₈NO₇P^2?·1.5H₂O, in which one of the water mol­ecules lies across a twofold rotation axis in space group P2/n. The ionic components are linked into sheets by a combination of a three‐centre N—H?(O)₂ hydrogen bond and two‐centre O—H?O and N—H?O hydrogen bonds, and these sheets are pairwise linked by the water mol­ecules into bilayers, by means of further O—H?O hydrogen bonds.     

catena‐Poly[[silver(I)‐μ‐1,3‐bis(4‐pyridyl)propane] hemi(naphthalene‐1,5‐disulfonate) dihydrate]: a three‐dimensional metallo‐supramolecular sandwich lamellar network

The title compound, {[Ag(C₁₃H₁₄N₂)](C₁₀H₆O₆S₂)_0.5·2H₂O}_n, (I), features a three‐dimensional supramolecular sandwich architecture that consists of two‐dimensional cationic layers composed of polymeric chains of silver(I) ions and 1,3‐bis(4‐pyridyl)propane (bpp) ligands, linked by Ag...Ag and π–π interactions, alternating with anionic layers in which uncoordinated naphthalene‐1,5‐disulfonate (nds²⁻) anions and solvent water molecules form a hydrogen‐bonded network. The asymmetric unit consists of one Ag^I cation linearly coordinated by N atoms from two bpp ligands, one bpp ligand, one half of an nds²⁻ anion lying on a centre of inversion and two solvent water molecules. The two‐dimensional {[Ag(bpp)]⁺}_n cationic and {[(nds)·2H₂O]²⁻}_n anionic layers are assembled into a three‐dimensional supramolecular framework through long secondary coordination Ag...O interactions between the sulfonate O atoms and Ag^I centres and through nonclassical C—H...O hydrogen bonds.     

Oxidative polymerization of 2,6‐dimethylphenol to form poly(2,6‐dimethyl‐1,4‐phenylene oxide) in water through one water‐soluble copper(II) complex of a zwitterionic calix[4]arene

In the presence of excess NaOH, reaction of Cu(OAc)₂·H₂O with equimolar ammonium calix[4]arene [H₄L]I₄ ( 1 , H₄L = [5,11,17,23‐tetrakis(trimethylammonium)‐25,26,27,28‐tetrahydroxycalix[4]arene]) resulted in the formation of a mononuclear cationic Cu(II) complex [Cu(II)L(H₂O)]I₂ ( 2 ) in 43% yield. Complex 2 was characterized by elemental analysis, infrared (IR), and single crystal X‐ray diffraction. The Cu(II) atom in 2 is coordinated by four oxygen atoms of one L^4? ligand and one O atom from one water molecule, forming a square pyramidal geometry. Complex 2 exhibited high catalytic activity in the oxidative polymerization of 2,6‐dimethylphenol using O₂ as oxidizing agent in water under mild conditions. The selective polymerization produced poly(2,6‐dimethyl‐1,4‐phenylene oxide) in high yields with almost no diphenoquinone. The influence of the polymerization temperature, the time interval, the molar ratio of 2,6‐dimethylphenol/ 2 , the concentrations of sodium hydroxide, and sodium n‐dodecyl sulfate were examined. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Construction of Four Coordination Polymers based on 2‐[4‐(Pyridine‐4‐yl)phenyl]‐1H‐imidazole‐4,5‐dicarboxylic Acid

The imidazole‐based dicarboxylate ligand 2‐(4‐(pyridin‐4‐yl)phenyl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PyPhIDC), was synthesized and its coordination chemistry was studied. Solvothermal reactions of Ca^II, Mn^II, Co^II, and Ni^II ions with H₃PyPhIDC produced four coordination polymers, [Ca(μ₃‐HPyPhIDC)(H₂O)₂]_n ( 1 ), {[M₃(μ₂‐H₂PyPhIDC)₂(μ₃‐HPyPhIDC)₂₆(H₂O)₂] · 6H₂O}_n [M = Mn ( 2 ), Co ( 3 )], and {[Ni(μ₃‐HPyPhIDC)(H₂O)] · H₂O}_n ( 4 ). Compounds 1 – 4 were analyzed by IR spectroscopy, elemental analyses, and single‐crystal and powder X‐ray diffraction. Compound 1 displays a one‐dimensional (1D) infinite chain. Compounds 2 and 3 are of similar structure, showing 2D network structures with a (4,4) topology based on trinuclear clusters. Compound 4 has another type of 2D network structure with a 3‐connected (4.8²) topology. The results revealed that the structural diversity is attributed to the coordination numbers and geometries of metal ions as well as the coordination modes and conformations of H₃PyPhIDC. Moreover, the thermogravimetric analyses of all the compounds as well as luminescence properties of the H₃PyPhIDC ligand and compound 1 were also studied.     

A novel three‐dimensional coordination polymer constructed from pyrazine and copper(I): poly[[copper(I)‐di‐μ2‐pyrazine‐κ4N:N′] 3,5‐dicarboxybenzenesulfonate monohydrate]

In the title metal–organic framework complex, {[Cu(C₄H₄N₂)₂](C₈H₅O₇S)·H₂O}_n or {[Cu^I(pyz)₂](H₂SIP)·H₂O}_n (pyz is pyrazine and H₃SIP is 5‐sulfoisophthalic acid or 3,5‐dicarboxybenzenesulfonic acid), the asymmetric unit is composed of one copper(I) center, one whole pyrazine ligand, two half pyrazine ligands lying about inversion centres, one H₂SIP⁻ anion and one lattice water molecule, wherein each Cu^I atom is in a slightly distorted tetrahedral coordination environment completed by four pyrazine N atoms, with the Cu—N bond lengths in the range 2.017 (3)–2.061 (3) Å. The structure features a three‐dimensional diamondoid network with one‐dimensional channels occupied by H₂SIP⁻ anions and lattice water molecules. Interestingly, the guest–water hydrogen‐bonded network is also a diamondoid network, which interpenetrates the metal–pyrazine network.     

Supramolecular framework in catena‐poly[[(nitrato‐κO)silver(I)]‐μ‐(R,S)‐2‐(pyridin‐4‐ylsulfinyl)pyrimidine‐κ3N,O:N′]

In the title complex, [Ag(NO₃)(C₉H₇N₃OS)]_n, η¹:η¹:η¹:μ₂‐bridging 2‐(pyridin‐4‐ylsulfinyl)pyrimidine (pypmSO) ligands with opposite chiralities are alternately arranged to link the Ag^I cations through two N atoms and one sulfinyl O atom of each ligand, leading to an extended zigzag coordination chain structure along the [01] direction. An FT–IR spectroscopic study shows a decreased stretching frequency for the η¹‐O‐bonded S=O group compared with that of the free ligand. The parallel chains are arranged and interconnected via O(S=O)...π(pyridine/pyrimidine) and C—H(pyridine)...O(NO₃⁻) interactions to furnish a layer almost parallel to the ac plane. Along the b axis, the layers are stacked and stabilized through anion(NO₃⁻)...π(pyrimidine) interactions to form a three‐dimensional supramolecular framework. The ligand behaviour of the new diheterocyclic sulfoxide and the unconventional O(S=O)...π(pyridine/pyrimidine) and anion(NO₃⁻)...π(pyrimidine) interactions in the supramolecular assembly of the title complex are presented.     

Three AgI,CuI and CdII coordination polymers based on the new asymmetrical ligand 2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole: syntheses,characterization and emission properties

The new asymmetrical organic ligand 2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole ( L , C₁₇H₁₃N₅O), containing pyridine and imidazole terminal groups, as well as potential oxdiazole coordination sites, was designed and synthesized. The coordination chemistry of L with soft Ag^I, Cu^I and Cd^II metal ions was investigated and three new coordination polymers (CPs), namely, catena‐poly[[silver(I)‐μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole] hexafluoridophosphate], {[Ag( L )]PF₆}_n, catena‐poly[[copper(I)‐di‐μ‐iodido‐copper(I)‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)] 1,4‐dioxane monosolvate], {[Cu₂I₂( L )₂]·C₄H₈O₂}_n, and catena‐poly[[[dinitratocopper(II)]‐bis(μ‐2‐{4‐[(1H‐imidazol‐1‐yl)methyl]phenyl}‐5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazole)]–methanol–water (1/1/0.65)], {[Cd( L )₂(NO₃)₂]·2CH₄O·0.65H₂O}_n, were obtained. The experimental results show that ligand L coordinates easily with linear Ag^I, tetrahedral Cu^I and octahedral Cd^II metal atoms to form one‐dimensional polymeric structures. The intermediate oxadiazole ring does not participate in the coordination interactions with the metal ions. In all three CPs, weak π–π interactions between the nearly coplanar pyridine, oxadiazole and benzene rings play an important role in the packing of the polymeric chains.     

catena‐Poly[[di‐μ2‐aqua‐hexaaquabis(μ3‐4‐oxidopyridine‐2,6‐dicarboxylato)trimanganese(II)] trihydrate]: a new one‐dimensional coordination polymer based on a trinuclear MnII complex of chelidamic acid

4‐Hydroxypyridine‐2,6‐dicarboxylic acid (chelidamic acid, hypydc_[H]H₂) reacts with MnCl₂·2H₂O in the presence of piperazine in water to afford the title complex, {[Mn₃(C₇H₂NO₅)₂(H₂O)₈]·3H₂O}_n or {[Mn₃(hypydc)₂(H₂O)₈]·3H₂O}_n. This compound is a one‐dimensional coordination polymer, with the twofold symmetric repeat unit containing three metal centres. Two different coordination geometries are observed for the two independent Mn^II metal centres, viz. a distorted pentagonal bipyramid and a distorted octahedron. The 4‐oxidopyridine‐2,6‐dicarboxylate anions and two of the water molecules act as bridging ligands. The zigzag‐like geometry of the coordination polymer is stabilized by hydrogen bonds. O—H...O and C—H...O hydrogen bonds and water clusters consolidate the three‐dimensional network structure.     

Methyl 2‐acetamido‐2‐deoxy‐β‐d‐glucopyranoside dihydrate and methyl 2‐formamido‐2‐deoxy‐β‐d‐glucopyranoside

Methyl 2‐acetamido‐2‐deoxy‐β‐d ‐glucopyranoside (β‐GlcNAcOCH₃), (I), crystallizes from water as a dihydrate, C₉H₁₇NO₆·H₂O, containing two independent molecules [denoted (IA) and (IB)] in the asymmetric unit, whereas the crystal structure of methyl 2‐formamido‐2‐deoxy‐β‐d ‐glucopyranoside (β‐GlcNFmOCH₃), (II), C₈H₁₅NO₆, also obtained from water, is devoid of solvent water molecules. The two molecules of (I) assume distorted ⁴C₁ chair conformations. Values of ϕ for (IA) and (IB) indicate ring distortions towards B_C2,C5 and ^C3,O5B, respectively. By comparison, (II) shows considerably more ring distortion than molecules (IA) and (IB), despite the less bulky N‐acyl side chain. Distortion towards B_C2,C5 was observed for (II), similar to the findings for (IA). The amide bond conformation in each of (IA), (IB) and (II) is trans, and the conformation about the C—N bond is anti (C—H is approximately anti to N—H), although the conformation about the latter bond within this group varies by ∼16°. The conformation of the exocyclic hydroxymethyl group was found to be gt in each of (IA), (IB) and (II). Comparison of the X‐ray structures of (I) and (II) with those of other GlcNAc mono‐ and disaccharides shows that GlcNAc aldohexopyranosyl rings can be distorted over a wide range of geometries in the solid state.     

Bridging behaviour of the 2‐thiobarbiturate anion in its complexes with LiI and NaI

The structures of the Li^I and Na^I salts of 2‐thiobarbituric acid (2‐sulfanylidene‐1‐3‐diazinane‐4,6‐dione, H₂TBA) have been studied. μ‐Aqua‐octaaquabis(μ‐2‐thiobarbiturato‐κ²O:O′)bis(2‐thiobarbiturato‐κO)tetralithium(I) dihydrate, [Li₄(C₄H₃N₂O₂S)₄(H₂O)₉]·2H₂O, (I), crystallizes with four symmetry‐independent four‐coordinated Li^I cations and four independent HTBA⁻ anions. The structure contains two structurally non‐equivalent Li^I cations and two non‐equivalent HTBA⁻ anions (bridging and terminal). Eight of the coordinated water ligands are terminal and the ninth acts as a bridge between Li^I cations. Discrete [Li₄(HTBA)₄(H₂O)₉]·2H₂O complexes form two‐dimensional layers. Neighbouring layers are connected via hydrogen‐bonding interactions, resulting in a three‐dimensional network. Poly[μ₂‐aqua‐tetraaqua(μ₄‐2‐thiobarbiturato‐κ⁴O:O:S:S)(μ₂‐thiobarbiturato‐κ²O:S)disodium(I)], [Na₂(C₄H₃N₂O₂S)₂(H₂O)₅]_n, (II), crystallizes with six‐coordinated Na^I cations. The octahedra are pairwise connected through edge‐sharing by a water O atom and an O atom from the μ₄‐HTBA⁻ ligand, and these pairs are further top‐shared by the S atoms to form continuous chains along the a direction. Two independent HTBA⁻ ligands integrate the chains to give a three‐dimensional network.