Polymorphism of mer‐μ‐oxalato‐bis[chloridotripyridinecobalt(II)] pyridine disolvate

Single crystals of a triclinic polymorphic form of mer‐μ‐oxalato‐bis[chloridotripyridinecobalt(II)] pyridine disolvate, [Co₂(C₂O₄)Cl₂(C₅H₅N)₆]·2C₅H₅N, have been prepared by solvothermal methods. The structure and geometric parameters strongly resemble those of the previously reported monoclinic polymorph [Bolte (2006). Acta Cryst. E 62 , m597–m598]. In both polymorphic forms, the dinuclear complex molecules are located on a crystallographic centre of inversion, with the Co^II cations in a distorted octahedral environment consisting of a chloride ligand, three pyridine ligands and a chelating bis‐bidentate oxalate ligand. This last serves as a bridging ligand between two Co^II cations. The polymorphs differ in the mutual orientation of their pyridine ligands in the dinuclear molecules and in their intermolecular connectivity. In the triclinic polymorph, C—H...O, C—H...Cl, C—H...π and π–π interactions link the dinuclear molecules into a three‐dimensional structure. Pyridine solvent molecules are attached to this structure via weak interactions.     

Rational Design of a Lanthanide‐Based Complex Featuring Different Single‐Molecule Magnets

The rational synthesis of the 2‐{1‐methylpyridine‐N‐oxide‐4,5‐[4,5‐bis(propylthio)tetrathiafulvalenyl]‐1H‐benzimidazol‐2‐yl}pyridine ligand ( L ) is described. It led to the tetranuclear complex [Dy₄(tta)₁₂( L )₂] ( Dy‐Dy₂‐Dy ) after coordination reaction with the precursor Dy(tta)₃?2 H₂O (tta^?=2‐thenoyltrifluoroacetonate). The X‐ray structure of Dy‐Dy₂‐Dy can be described as two terminal mononuclear units bridged by a central antiferromagnetically coupled dinuclear complex. The terminal N₂O₆ and central O₈ environments are described as distorted square antiprisms. The ac magnetism measurements revealed a strong out‐of‐phase signal of the magnetic susceptibility with two distinct sets of data. The high‐ and low‐frequency components were attributed to the two terminal mononuclear single‐molecule magnets (SMMs) and the central dinuclear SMM, respectively. A magnetic hysteresis loop was detected at very low temperature. From both structural and magnetic points of view, the tetranuclear SMM Dy‐Dy₂‐Dy is a self‐assembly of two known mononuclear SMMs bridged by a known dinuclear SMM.     

Synthesis,Structures, and Reactivities of Pincer‐Type Ruthenium Complexes Bearing Two Proton‐Responsive Pyrazole Arms

A new metal–ligand bifunctional, pincer‐type ruthenium complex [RuCl( L1‐H2 )(PPh₃)₂]Cl ( 1 ; L1‐H2 =2,6‐bis(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)pyridine) featuring two proton‐delivering pyrazole arms has been synthesized. Complex 1 , derived from [RuCl₂(PPh₃)₃] with L1‐H2 , underwent reversible deprotonation with potassium carbonate to afford the pyrazolato–pyrazole complex [RuCl(L1‐H)(PPh₃)₂] ( 2 ). Further deprotonation of 1 and 2 with potassium hexamethyldisilazide in methanol resulted in the formation of the bis(pyrazolato) complex [Ru(L1)(MeOH)(PPh₃)₂] ( 3 ). Complex 3 smoothly reacted with dioxygen and dinitrogen to give the side‐on peroxo complex [Ru(L1)(O₂)(PPh₃)₂] ( 4 ) and end‐on dinitrogen complex [Ru(L1)(N₂)(PPh₃)₂] ( 5 ), respectively. On the other hand, the reaction of [RuCl₂(PPh₃)₃] with less hindered 2,6‐di(1H‐pyrazol‐3‐yl)pyridine ( L3‐H2 ) led to the formation of the dinuclear complex [{RuCl₂(PPh₃)₂}₂(μ₂‐ L3‐H2 )₂] ( 6 ), in which the pyrazole‐based ligand adopted a tautomeric form different from L1‐H2 in 1 and the central pyridine remained uncoordinated. The detailed structures of 1 , 2 , 3 , 3.MeOH , 4 , 5 , 6 were determined by X‐ray crystallography.     

(μ‐2,11‐Dithia­[3.3]paracyclo­phane‐κ2S:S′)bis­[(6‐carboxy­pyridine‐2‐carboxylato‐κ2N,O6)silver(I)]: a mixed‐ligand silver‐based dinuclear compound

In the title complex, [Ag₂(C₇H₄NO₄)₂(C₁₆H₁₆S₂)], each Ag^I atom is trigonally coordinated by one S atom of a 2,11‐dithia­[3.3]paracyclo­phane (dtpcp) ligand, and by one N and one O atom of a 6‐carboxy­pyridine‐2‐carboxylate ligand. Dtpcp acts as a bidentate ligand, bridging two inversion‐related Ag^I atoms to give a dinuclear silver(I) compound. The dinuclear moieties are inter­connected via O—H·O hydrogen bonds to form a two‐dimensional zigzag sheet. Two such sheets are inter­woven viaπ–π inter­actions between pyridine rings, affording an inter­woven bilayer network.     

Synthesis,Spectroscopy, and Structures of Mono‐ and Dinuclear Copper(I) Halide Complexes with 1,3‐Imidazolidine‐2‐thiones

Copper(I) halides with triphenyl phosphine and imidaozlidine‐2‐thiones (L ‐NMe, L ‐NEt, and L ‐NPh) in acetonitrile/methanol (or dichloromethane) yielded copper(I) mixed‐ligand complexes: mononuclear, namely, [CuCl(κ¹‐S‐L ‐NMe)(PPh₃)₂] ( 1 ), [CuBr(κ¹‐S‐L ‐NMe)(PPh₃)₂] ( 2 ), [CuBr(κ¹‐S‐L ‐NEt)(PPh₃)₂] ( 5 ), [CuI(κ¹‐S‐L ‐NEt)(PPh₃)₂] ( 6 ), [CuCl(κ¹‐S‐L ‐NPh)(PPh₃)₂] ( 7 ), and [CuBr(κ¹‐S‐L ‐NPh)(PPh₃)₂] ( 8 ), and dinuclear, [Cu₂(κ¹‐I)₂(μ‐S‐L ‐NMe)₂(PPh₃)₂] ( 3 ) and [Cu₂(μ‐Cl)₂(κ¹‐S‐L ‐NEt)₂(PPh₃)₂] ( 4 ). All complexes were characterized with analytical data, IR and NMR spectroscopy, and X‐ray crystallography. Complexes 2 – 4 , 7 , and 8 each formed crystals in the triclinic system with P$\bar{1}$ space group, whereas complexes 1 , 5 , and 6 crystallized in the monoclinic crystal system with space groups P2₁/c, C2/c, and P2₁/n, respectively. Complex 2 has shown two independent molecules, [(CuBr(κ¹‐S‐L ‐NMe)(PPh₃)₂] and [CuBr(PPh₃)₂] in the unit cell. For X = Cl, the thio‐ligand bonded to metal as terminal in complex 4 , whereas for X = I it is sulfur‐bridged in complex 3 .     

Di‐μ‐acesulfamato‐κ3N,O:O;κ3O:N,O‐bis[(acesulfamato‐κ2N,O)bis(3‐methylpyridine)cadmium(II)]

In the structure of the title compound, [Cd₂(C₄H₄NO₄S)₂(C₆H₇N)₂], the dinuclear Cd^II complex is located on a twofold axis with two Cd²⁺ ions bridged by two oxide O atoms. Each Cd²⁺ ion is additionally coordinated in an equatorial plane by two N and three O atoms of the acesulfamate ligands and axially by two N atoms of the 3‐methylpyridine ligands, resulting in a distorted pentagonal bipyramidal coordination. We present here an example of a supramolecular assembly based on hydrogen bonds in a mixed‐ligand metal complex; intermolecular C—H...O hydrogen bonds give rise to R₄⁴(40) rings, which lead to one‐dimensional chains.     

Novel 1D Copper(II) Helical Chain Formed by Weak Coordination‐driven Self‐assembly: Synthesis,Structure, and Magnetic Property

A novel 1D copper(II) helical chain is constructed through the connection of tetranuclear copper(II) units [Cu₄(L)(Py)₄] (H₈L=N,N′‐(BINOL‐3,3′‐dicarboxyl)‐disalicylhydrazide, where BINOL is 1,1′‐binaphthalenyl‐2,2′‐diol, py=pyridine) by weak coordination‐driven self‐assembly, and characterized by IR, single crystal X‐ray diffraction, thermogravimetric analysis, and X‐ray power diffraction analysis. Interestingly, the helical chains are packed in an alternating left‐(M) and right‐handed (P) chirality, the orientation of the helices was determined by the axial chirality of the ligand. The complex shows antiferromagnetic interactions between the copper centers.     

Dimeric copper(II) trimethylsilyl­acetate adducts with pyridine, 2‐­methylpyridine, 3‐methylpyridine and quinoline,and a polymeric copper(II) trimethylsilylacetate

In the crystals of bis(pyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₅H₅N)₂], (I), the dinuclear Cu^II complexes have cage structures with Cu?Cu distances of 2.632 (1) and 2.635 (1) Å. In the crystals of bis(2‐­methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (II), bis­(3‐methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (III), and bis(quinoline‐N)­tetrakis(μ‐­trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₉H₇N)₂], (IV), the centrosymmetric dinuclear Cu^II complexes have a cage structure with Cu?Cu distances of 2.664 (1), 2.638 (3) and 2.665 (1) Å, respectively. In the crystals of catena‐poly­[tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II)], [Cu₂(C₅H₁₁O₂Si)₄]_n, (V), the dinuclear Cu^II units of a cage structure are linked by the cyclic Cu—O bonds at the apical positions to form a linear chain by use of a glide translation.     

A new coordination mode of 6‐methylnicotinic acid in trans‐tetraaquabis(6‐methylpyridine‐3‐carboxylato‐κO)cobalt(II) tetrahydrate

The title compound, [Co(C₇H₆NO₂)₂(H₂O)₄]·4H₂O, contains a Co^II ion lying on a crystallographic inversion centre. The Co^II ion is octahedrally coordinated by two 6‐methylpyridine‐3‐carboxylate ligands in axial positions [Co—O = 2.0621 (9) Å] and by four water molecules in the equatorial plane [Co—O = 2.1169 (9) and 2.1223 (11) Å]. There are also four uncoordinated water molecules. The 6‐methylpyridine‐3‐carboxylate ligands are bound to the Co^II ion in a monodentate manner through a carboxylate O atom. There is one strong intramolecular O—H...O hydrogen bond, and six strong intermolecular hydrogen bonds of type O—H...O and one of type O—H...N in the packing, resulting in a complex three‐dimensional supramolecular structure.     

Elaboration of 1,8‐naphthyridine‐2,7‐dicarboxaldehyde into novel 2,7‐dimethylimine derivatives

The known 1,8‐naphthyridine‐2,7‐dicarboxaldehyde was prepared by SeO₂ oxidation of 2,7‐dimethyl‐1,8‐naphthyridine. The dimethylated naphthyridine molecule was assembled from an adaptation of the Skraup synthesis using 2‐amino‐6‐methylpyridine and crotonaldehyde to afford a reproducible 37% yield, and constitute a significant advance over the literature of this reaction. The condensation of 1,8‐naph‐thyridine‐2,7‐dicarboxaldehyde with various primary amines (R = ‐C₆H₁₁, ‐CH₂C₆H₅, ‐C(CH₃)₃, ‐C₁₀H₁₅, and CH₂CH₂SCH₂CH₃) in alcohol affords diimines 1(a‐e) . The inherent crystallinity of 1(a‐e) affords pure compounds in reasonable to excellent yields (ca. 70%) after evaporation of solvent and recrystallization. The anticipated spectroscopic features of (N=C‐H) ¹H nmr shift and v(C=N) in the ir spectrum appear around 8.50 δ and 1640 cm^?1, respectively, for the series 1(a‐e) . These novel naph‐thyridines typically display the signature ¹H nmr doublets at ca. 8.15‐8.30 δ ascribed to the 3 and 4 naphthyridine protons, consistent with a mirror plane (through the quaternary carbons) perpendicular to the naphthyridine plane, and syn, syn relationships of the naphthyridine moiety with each imine nitrogen lone pair. Complexation studies of 1(a‐e) with transition metals of biological relevance such as copper(I) and copper(II) will be reported elsewhere.     

Transformations of the chameleon ligand 1,10‐phenanthroline‐5,6‐dione/diol: cis‐dichlorido(1,10‐phenanthroline‐5,6‐dione‐κ2N,N′)‐trans‐dipyridinecobalt(II) pyridine disolvate prepared from the diol

The title compound, [CoCl₂(C₅H₅N)₂(C₁₂H₆N₂O₂)]·2C₅H₅N, is a neutral Co^II complex with two chloride anions coordinated in a cis fashion, two pyridine ligands in trans positions and a chelating 1,10‐phenanthroline‐5,6‐dione ligand that completes the octahedral coordination geometry. Two pyridine solvent molecules reside in channels (about 7 × 4 Å wide; the closest atom–atom distance within the channel is 10 Å). The three‐dimensional structure supporting these channels is held together by C—H...Cl [3.466 (8)–3.670 (9) Å] and C—H...O [3.014 (9)–3.285 (8) Å] hydrogen bonds, and can be viewed as a CsCl or bcu (body‐centred cubic) net.     

Synthesis,Characterization, Thermal Decomposition,and Kinetic Studies of Binuclear Sulfur‐Coordinated Tungsten(V) Complexes with Piperidine‐1‐carbodithioate

We describe the synthesis, characterization by IR and electronic spectra, magnetic susceptibility measurements, analytical data, kinetic study by differential‐scanning calorimetry, and thermogravimetric analysis of the thermal decomposition under N₂ of the adducts 2 – 7 with pyridine or substituted pyridines of bis(piperidine‐1‐carbodithioato‐κS,κS′)di‐μ‐thioxodithioxoditungsten(V) ( 1 ), to which the general formula [W₂B₂(pipCS₂)₂S₂(μ‐S)₂] is assigned (pipCS₂=piperidine‐1‐carbodithioato and B=pyridine (py), 3‐methylpyridine (3‐Mepy), 4‐methylpyridine (4‐Mepy), 3,5‐dimethylpyridine (3,5‐Me₂py), pyridin‐3‐amine (3‐pyNH₂), and pyridin‐4‐amine (4‐pyNH₂)). For the endothermic process of loss of the coordinated base B, we calculated activation energies with a method reported previously by us; the mechanism and pre‐exponential Arrhenius factor of this reaction were also determined. A relationship between the pyridines' basicity, IR and electronic spectral data, and activation energies was established.     

Bis{μ‐3‐[3‐(2‐pyridyl)pyrazol‐1‐ylmethyl]pyridine}disilver(I) bis(trifluoromethanesulfonate): effect of counter‐anions on the self‐assembly of coordination complexes

As part of a study on the effect of different counter‐anions on the self‐assembly of coordination complexes, a new dinuclear Ag^I complex, [Ag₂(C₁₄H₁₂N₄)₂](CF₃SO₃)₂, with the 3‐[3‐(2‐pyridyl)pyrazol‐1‐ylmethyl]pyridine (L) ligand was obtained through the reaction of L with AgCF₃SO₃. In this complex, each Ag^I center in the centrosymmetric dinuclear complex cation is coordinated by two pyridine and one pyrazole N‐atom donor of two inversion‐related L ligands in a trigonal planar geometry. This forms a unique box‐like cyclic dimer with an intramolecular nonbonding Ag...Ag separation of 6.379 (7) Å. Weak Ag...CF₃SO₃ and C—H...X (X = O and F) hydrogen‐bonding interactions, together with π–π stacking interactions, link the complex cations along the [001] and [10] directions, respectively, generating two different one‐dimensional chains and then an overall two‐dimensional network of the complex running parallel to the (110) plane. Comparison of the structural differences with previous findings suggests that the presence of different counter‐anions plays an important role in the construction of such supramolecular frameworks.     

The versatile, efficient, and stereoselective self-assembly of transition-metal helicates by using hydrogen-bonds

A diverse range of dinuclear double-stranded helicates in which the ligand strand is built up by using hydrogen-bonding has been synthesized. The helicates, formulated as [Co(2)(L)(2)(L-H)(2)X(2)], readily self-assemble from a mixture of a suitable pyridine-alcohol compound (L; for example, 6-methylpyridine-2-methanol, 1), and a CoX(2) salt in the presence of base. Nine such helicates have been characterized by X-ray crystallography. For helicates derived from the same pyridine-alcohol precursor, a remarkable regularity was found for both the molecular structure and the crystal packing arrangements, regardless of the nature of the ancillary ligand (X). A notable exception was observed in the solid-state structure of [Co(2)(1)(2)(1-H)(2)(NCS)(2)] for which intermolecular nonbonded contacts between the sulfur atoms (SS=3.21 A) lead to the formation of 1D chains. Helicates derived from (R)-6-methylpyridine-2-methanol (2) are soluble in solvents such as CH(3)CN and CH(2)Cl(2), and their self-assembly could be monitored in solution by (1)H NMR, UV/Vis, and CD titrations. No intermediate complexes were observed to form in a significant concentration at any point throughout these titrations. The global thermodynamic stability constant of [Co(2)(2)(2)(2-H)(2)(NO(3))(2)] was calculated from spectrophotometric data to be logbeta=8.9(8). The stereoisomerism of these helicates was studied in some detail and the self-assembly process was found to be highly stereoselective. The chirality of the ligand precursors can control the absolute configuration of the metal centers and thus the overall helicity of the dinuclear assemblies. Furthermore, the enantiomers of rac-6-methylpyridine-2-methanol (3) undergo a self-recognition process to form exclusively homochiral helicates in which the four pyridine-alcohol units possess the same chirality.     

Synthesis,Characterization, Catalytic and Antibacterial Activity of Two Series of Dinuclear Ruthenium Sulphoxide Complexes Using 5,5¢‐Methylenebis(pyridine) as Bis‐chelating Bridging Ligand

The reaction of a new heterocyclic bidentate N containing spacer, (ligand) 5,5′‐methylenebis(pyridine) with ruthenium sulphoxide precursors resulted, dinuclear complexes. We herein report three formulations; [{cis,fac‐RuCl₂(so)₃}₂(μ‐mbp)].3so; [{trans,mer‐RuCl₂(so)₃₂}₂(μ‐mbp)].3so and [{trans‐RuCl₄(so)}₂(μ‐mbp)]^2?[X]₂⁺; where so = dimethyl‐sulfoxide/tetramethylenesulfoxide; mbp = 5,5′‐methylenebis(pyridine) and [X]⁺ = [(dmso)₂H]⁺, Na⁺ or [(tmso)H]⁺. These complexes were characterized on the basis of elemental analyses, molar conductance measurement, magnetic susceptibility, FT‐IR, ¹H‐NMR, ¹³C{¹H}‐NMR, electronic spectroscopy and FAB‐Mass spectrometry. Catalytic activity of these complexes has been investigated in hydrolysis of benzonitrile. All the complexes exhibit good antibacterial activity against gram‐negative bacteria Escherichia coli in comparison to Chloramphenicol.     

Supramolecular architectures in CoII and CuII complexes with thiophene‐2‐carboxylate and 2‐amino‐4,6‐dimethoxypyrimidine ligands

The coordination chemistry of mixed‐ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal–organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic–inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene‐2‐carboxylate (2‐TPC) and 2‐amino‐4,6‐dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X‐ray diffraction studies, namely (2‐amino‐4,6‐dimethoxypyrimidine‐κN)aquachlorido(thiophene‐2‐carboxylato‐κO)cobalt(II) monohydrate, [Co(C₅H₃O₂S)Cl(C₆H₉N₃O₂)(H₂O)]·H₂O, (I), and catena‐poly[copper(II)‐tetrakis(μ‐thiophene‐2‐carboxylato‐κ²O:O′)‐copper(II)‐(μ‐2‐amino‐4,6‐dimethoxypyrimidine‐κ²N¹:N³)], [Cu₂(C₅H₃O₂S)₄(C₆H₉N₃O₂)]_n, (II). In (I), the Co^II ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2‐TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2‐TPC ligand form an interligand N—H…O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R₂²(8) motif] via a pair of N—H…N hydrogen bonds. These interactions, together with O—H…O and O—H…Cl hydrogen bonds and π–π stacking interactions, generate a three‐dimensional supramolecular architecture. The one‐dimensional coordination polymer (II) contains the classical paddle‐wheel [Cu₂(CH₃COO)₄(H₂O)₂] unit, where each carboxylate group of four 2‐TPC ligands bridges two square‐pyramidally coordinated Cu^II ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one‐dimensional polymeric chains self‐assemble via N—H…O, π–π and C—H…π interactions, generating a three‐dimensional supramolecular architecture.     

Two different one‐dimensional supramolecular chains formed from the reaction of 2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline with two different precursors,Co(NO3)2 and CoCl2

Two different one‐dimensional supramolecular chains with Co^II cations have been synthesized based on the semi‐rigid ligand 2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline (L), obtained by condensation of 2‐(1H‐benzimidazol‐2‐yl)quinoline and 4‐(chloromethyl)pyridine hydrochloride. Starting from different Co^II salts, two new compounds have been obtained, viz. catena‐poly[[[dinitratocobalt(II)]‐μ‐2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline] dichloromethane monosolvate acetonitrile monosolvate], {[Co(NO₃)₂(C₂₂H₁₆N₄)]·CH₂Cl₂·CH₃CN}_n, (I) and catena‐poly[[[dichloridocobalt(II)]‐μ‐2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline] methanol disolvate], {[CoCl₂(C₂₂H₁₆N₄)]·2CH₃OH}_n, (II). In (I), the Co^II centres lie in a distorted octahedral [CoN₃O₃] coordination environment. {Co(NO₃)₂L}_n units form one‐dimensional helical chains, where the L ligand has different directions of twist. The helical chains stack together via interchain π–π interactions to form a two‐dimensional sheet, and another type of π–π interaction further connects neighbouring sheets into a three‐dimensional framework with hexagonal channels, in which the acetonitrile molecules and disordered dichloromethane molecules are located. In (II), the Co^II centres lie in a distorted trigonal–bipyramidal [CoCl₂N₃] coordination environment. {CoCl₂L}_n units form one‐dimensional chains. The chains interact via C—H...π and C—H...Cl interactions. The result is that two‐dimensional sheets are generated, which are further linked into a three‐dimensional framework via interlayer C—H...Cl interactions. When viewed down the crystallographic b axis, the methanol solvent molecules are located in an orderly manner in wave‐like channels.     

Polymorphism of the dinuclear CoIII–Schiff base complex [Co2(o‐van‐en)3]·4CH3CN (o‐van‐en is a salen‐type ligand)

Reactions of Co(OH)₂ with the Schiff base bis(2‐hydroxy‐3‐methoxybenzylidene)ethylenediamine, denoted H₂(o‐van‐en), under different conditions yielded the previously reported complex aqua[bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]cobalt(II), [Co(C₁₈H₁₈N₂O₄)(H₂O)], 1 , under anaerobic conditions and two polymorphs of [μ‐bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]bis{[bis(3‐methoxy‐2‐oxidobenzylidene)ethylenediamine]cobalt(III)} acetonitrile tetrasolvate, [Co₂(C₁₈H₁₈N₂O₄)₃]·4CH₃CN, i.e. monoclinic 2 and triclinic 3 , in the presence of air. Both novel polymorphs were chemically and spectroscopically characterized. Their crystal structures are built up of centrosymmetric dinuclear [Co₂(o‐van‐en)₃] complex molecules, in which each Co^III atom is coordinated by one tetradentate dianionic o‐van‐en ligand in an uncommon bent fashion. The pseudo‐octahedral coordination of the Co^III atom is completed by one phenolate O and one amidic N atom of the same arm of the bridging o‐van‐en ligand. In addition, the asymmetric units of both polymorphs contain two acetonitrile solvent molecules. The polymorphs differ in the packing orders of the dinuclear [Co₂(o‐van‐en)₃] complex molecules, i.e. alternating ABABAB in 2 and AAA in 3 . In addition, differences in the conformations, the positions of the acetonitrile solvent molecules and the pattern of intermolecular interactions were observed. Hirshfeld surface analysis permits a qualitative inspection of the differences in the intermolecular space in the two polymorphs. A knowledge‐based study employing Full Interaction Maps was used to elucidate possible reasons for the polymorphism.     

Bis(pyridine‐2,6‐dimethanol‐N,O,O′)cobalt(II) and ‐copper(II) disacchar­inate dihydrate: three‐dimensional structures with extensive hydrogen bonds and aromatic π–π‐stacking interactions

Bis­(pyridine‐2,6‐di­methanol‐N,O,O′)­cobalt(II) disaccharinate dihydrate, [Co(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (I), and bis­(pyridine‐2,6‐di­methanol‐N,O,O′)copper(II) disaccharinate dihydrate, [Cu(C₇H₉NO₂)₂](C₇H₄NO₃S)₂·2H₂O, (II), collectively [M(dmpy)₂](sac)₂·2H₂O (where M is Co^II or Cu^II, sac is the saccharinate anion and dmpy is pyridine‐2,6‐di­methanol), are isostructural. The [M(dmpy)₂]²⁺ cations exhibit distorted octahedral geometry in which the two neutral dmpy species act as tripodal N,O,O′‐tridentate ligands. The crystal packing is determined by hydrogen bonding, as well as by weak pyridine–saccharinate π–π‐stacking interactions.     

Self‐Assembled Cyclic Structures from Copper(II) Peptoids

Metal–ligand coordination is a key interaction in the self‐assembly of both biopolymers and synthetic oligomers. Although the binding of metal ions to synthetic proteins and peptides is known to yield high‐order structures, the self‐assembly of peptidomimetic molecules upon metal binding is still challenging. Herein we explore the self‐assembly of three peptoid trimers bearing a bipyridine ligand at their C‐terminus, a benzyl group at their N‐terminus, and a polar group (N‐ethyl‐R) in the middle position (R=OH, OCH₃, or NH₂) upon Cu²⁺ coordination. X‐ray diffraction analysis revealed unique, highly symmetric, dinuclear cyclic structure or aqua‐bridged dinuclear double‐stranded peptoid helicates, formed by the self‐assembly of two peptoid molecules with two Cu²⁺ ions. Only the macrocycle with the highest number of intermolecular hydrogen bonds is stable in solution, while the other two disassemble to their corresponding monometallic complexes.