Complex structures arising from the self-assembly of a simple organic salt.

Molecular self-assembly is the spontaneous association of simple molecules into larger and ordered structures1. It is the basis of several natural processes, such as the formation of colloids, crystals, proteins, viruses and double-helical DNA2. Molecular self-assembly has inspired strategies for the rational design of materials with specific chemical and physical properties3, and is one of the most important concepts in supramolecular chemistry. Although molecular self-assembly has been extensively investigated, understanding the rules governing this phenomenon remains challenging. Here we report on a simple hydrochloride salt of fampridine that crystallizes as four different structures, two of which adopt unusual self-assemblies consisting of polyhedral clusters of chloride and pyridinium ions. These two structures represent Frank-Kasper (FK) phases of a small and rigid organic molecule. Although discovered in metal alloys4,5 more than 60 years ago, FK phases have recently been observed in several classes of supramolecular soft matter6-11 and in gold nanocrystal superlattices12 and remain the object of recent discoveries13. In these systems, atoms or spherical assemblies of molecules are packed to form polyhedra with coordination numbers 12, 14, 15 or 16. The two FK structures reported here crystallize from a dense liquid phase and show a complexity that is generally not observed in small rigid organic molecules. Investigation of the precursor dense liquid phase by cryogenic electron microscopy reveals the presence of spherical aggregates with sizes ranging between 1.5 and 4.6 nanometres. These structures, together with the experimental procedure used for their preparation, invite interesting speculation about their formation and open different perspectives for the design of organic crystalline materials.

Synthesis and Thermal Studies of Two Phosphonium Tetrahydroxidohexaoxidopentaborate(1-) Salts: Single-Crystal XRD Characterization of [iPrPPh3][B5O6(OH)4]·3.5H2O and [MePPh3][B5O6(OH)4]·B(OH)3·0.5H2O.

Two substituted phosphonium tetrahydoxidohexaoxidopentaborate(1-) salts, [iPrPPh3][B5O6(OH)4]·3.5H2O (1) and [MePPh3][B5O6(OH)4]·B(OH)3·0.5H2O (2), were prepared by templated self-assembly processes with good yields by crystallization from basic methanolic aqueous solutions primed with B(OH)3 and the appropriate phosphonium cation. Salts 1 and 2 were characterized by spectroscopic (NMR and IR) and thermal (TGA/DSC) analysis. Salts 1 and 2 were thermally decomposed in air at 800 °C to glassy solids via the anhydrous phosphonium polyborates that are formed at lower temperatures (<300 °C). BET analysis of the anhydrous and pyrolysed materials indicated they were non-porous with surface areas of 0.2-2.75 m2/g. Rhe recrystallization of 1 and 2 from aqueous solution afforded crystals suitable for single-crystal XRD analyses. The structure of 1 comprises alternating cationic/anionic layers with the H2O/pentaborate(1-) planes held together by H-bonds. The cationic planes have offset face-to-face (off) and vertex-to-face (vf) aromatic ring interactions with the iPr groups oriented towards the pentaborate(1-)/H2O layers. The anionic lattice in 2 is expanded by the inclusion of B(OH)3 molecules to accommodate the large cations; this results in the formation of a stacked pentaborate(1-)/B(OH)3 structure with channels occupied by the cations. The cations within the channels have vf, ef (edge-to-face), and off phenyl embraces. Both H-bonding and phenyl embrace interactions are important in stabilizing these two solid-state structures.

Photoconducting Devices with Response in the Visible-Near-Infrared Region Based on Neutral Ni Complexes of Aryl-1,2-dithiolene Ligands.

Metal bis(1,2-dithiolene) complexes belonging to the class [Ni(Ar-edt)2]x- [Ar-edt2- = arylethylene-1,2-dithiolate; Ar = phenyl, (1x-), 2-naphthyl (2x-); x = 0 and 1] were fully characterized by NMR, UV-visible-near-infrared (UV-vis-NIR), diffuse reflectance, and FT-IR spectroscopy, as well as cyclic voltammetry and single-crystal X-ray diffraction analysis. These complexes have emerged as new photoconducting materials that allowed for the development of a prototype of photodetectors with response in the vis-NIR region. The photodetecting devices showed in some cases quantum efficiencies orders of magnitude higher than those of previously reported 1,2-dithiolene systems.

A racemic and enantiopure unsymmetric diiron(III) complex with a chiral o-carborane-based pyridylalcohol ligand: combined chiroptical, magnetic, and nonlinear optical properties.

The design of molecule-based systems combining magnetic, chiroptical and second-order optical nonlinear properties is still very rare. We report an unusually unsymmetric diiron(III) complex 1, in which three bulky chiral carboranylpyridinealkoxide ligands (oCBhmp(-)) bridge both metal ions and the complex shows the above-mentioned properties. The introduction of o-carborane into the 2-(hydroxymethyl)pyridine (hmpH) architecture significantly alters the coordination of the simple or aryl-substituted 2-hmpH. The unusual architecture observed in 1 seems to be triggered by the poor nucleophilicity of our alkoxide ligand (oCBhmp(-)). A very rare case of spontaneous resolution takes place on precipitation or exposure to solvent vapor for the bulk compound, as confirmed by a combination of single-crystal and powder X-ray diffraction, second-harmonic generation, and circular dichroism. The corresponding enantiopure complexes (+)1 and (-)1 have also been synthesized and fully characterized. This research provides a new building block with unique geometry and electronics to construct coordination complexes with multifunctional properties.

Eight isostructural 4,4'-disubstituted N-phenylbenzenesulfonamides.

The isostructural crystals of 4-cyano-N-(4-methoxyphenyl)benzenesulfonamide, C(14)H(12)N(2)O(3)S, (I), N-(4-methoxyphenyl)-4-(trifluoromethyl)benzenesulfonamide, C(14)H(12)F(3)NO(3)S, (II), 4-iodo-N-(4-methoxyphenyl)benzenesulfonamide, C(13)H(12)INO(3)S, (III), 4-bromo-N-(4-methoxyphenyl)benzenesulfonamide, C(13)H(12)BrNO(3)S, (IV), 4-chloro-N-(4-methoxyphenyl)benzenesulfonamide, C(13)H(12)ClNO(3)S, (V), 4-fluoro-N-(4-methoxyphenyl)benzenesulfonamide, C(13)H(12)FNO(3)S, (VI), N-(4-chlorophenyl)-4-methoxybenzenesulfonamide, C(13)H(12)ClNO(3)S, (VII), and 4-cyano-N-phenylbenzenesulfonamide, C(13)H(10)N(2)O(2)S, (VIII), contain infinite chains composed of N-H···O(sulfonyl) hydrogen-bonded molecules. The crystal structures of (I)-(VIII) have been compared using the XPac software and quantitative descriptors of isostructurality were generated [Gelbrich, Threlfall & Hursthouse (2012). CrystEngComm, 14, 5454-5464]. Certain isostructural relationships in this series involve molecules with substantially different spatial demands, e.g. (VI) and (VIII) are related by the simultaneous interchange of F→CN on the benzenesulfonamide ring and OMe→H on the N-phenyl ring, which indicates that the geometry of the three-dimensional crystal-packing mode of (I)-(VIII) is unusually adaptable to different molecular shapes.

Dynamic and static behaviors of N-Z-N σ(3c-4e) (Z = S, Se, and Te) interactions: atoms-in-molecules dual functional analysis with high-resolution X-ray diffraction determination of electron densities for 2-(2-pyridylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyridine.

The structure of 2-(2-pyridylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyridine (NSN) indicates that the molecule has a planar geometry with a linear N···S···N linkage, creating a tetracyclic structure of the formal C(2v) symmetry. To clarify the nature of the NSN σ(3c-4e) bonding, together with the related NSeN and NTeN, the dynamic and static behaviors are investigated by applying atoms-in-molecules (AIM) dual functional analysis to both the fully optimized and perturbed structures. The structures were optimized computationally, retaining C(2v) symmetry. All bond critical points are detected as expected and exhibited on both sides of the N···Z···N moiety which supports the formation of NZN σ(3c-4e). It is confirmed that N···S···N is of the covalent nature close to Me(2)S(+)-∗-Cl or Me(2)Se(+)-∗-Br, whereas N···Se···N and N···Te···N have the (regular) CS nature close to the CT adducts of Me(2)S(-∗-Cl)(2) (TBP) and Me(2)Se-∗-Br(2) (MC), respectively. An experimental high-resolution charge density determination has been performed on NSN, which thoroughly supports the theoretical results. Very similar results are obtained in the analogous pyrimidyl derivatives for N···S···N, N···Se···N, and N···Te···N. AIM dual functional analysis, as validated by experimental high-resolution charge densities, is thus confirmed to be an excellent method to elucidate the nature of these interactions.

cis-Bis(L-DOPA-κ2N,O)copper(II) monohydrate: synthesis, crystal structure, and approaches to the analysis of pseudosymmetry.

The crystal structure of the cis isomer of cis-bis(L-DOPA-κ2N,O)copper(II) monohydrate (L-DOPA is 3,4-dihydroxy-L-phenylalanine) (CuLD), [Cu(C9H10NO4)2]·H2O, is a singular example of a structurally characterized, homoleptic, crystalline metal L-DOPA complex. CuLD crystallizes in the space group P21, with Z' = 2. The two independent molecules are square planar, and are interconnected by a linear hydrogen-bonded chain containing 12 independent hydrogen bonds. The copper ions in both molecules have weak apical intermolecular Cu...O interactions [2.739 (2) and 2.973 (2) Å] with catechol -OH groups. A survey of the Cambridge Structural Database suggested that cis and trans isomers of Cu(NH2-C-CO2)2 amino acid complexes are equally likely to occur. 12 strong O-H...O and N-H...O hydrogen bonds stabilize an unusual linear arrangement of the Cu complexes. The Cu...Cu' distances along the chain are nearly equal [5.0739 (3) and 5.1107 (3) Å] and the Cu...Cu'...Cu angles are nearly linear [176.75 (1)°]. The MATCH procedure available in the Oxford University Crystals for Windows package was used to carry out a detailed analysis of the relationship between the two independent molecules. MATCH has some particular advantages in studying the details of pseudosymmetry, which include: (i) no atomic-order requirements; (ii) the pseudosymmetry matrix is readily available, which allows quick insight into the symmetry elements involved and their location; and (iii) the differences between molecular centroids, as well as between all atomic positions and torsion angles, are listed. A tutorial presentation is designed to attract new users to the technique. In the present case, a search for a pseudosymmetric relationship between the two independent molecules showed that they are related by a pseudo-42 axis along the crystallographic c direction. A detailed analysis shows that the pseudo-42 symmetry is disrupted by torsions about the CH2-C(ipso) bonds, and that there is no supergroup that can be used to describe the crystal structure.

Evolution of linear absorption and nonlinear optical properties in V-shaped ruthenium(II)-based chromophores.

In this article, we describe a series of complexes with electron-rich cis-{Ru(II)(NH(3))(4)}(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF(6)(-) salts and characterized by using various techniques including (1)H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities beta have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) and pi --> pi* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant beta(0) responses as high as ca. 600 x 10(-30) esu. These pseudo-C(2v) chromophores show two substantial components of the beta tensor, beta(zzz) and beta(zyy), although the relative significance of these varies with the physical method applied. According to HRS, beta(zzz) dominates in all cases, whereas the Stark analyses indicate that beta(zyy) is dominant in the shorter chromophores, but beta(zzz) and beta(zyy) are similar for the extended species. In contrast, finite field calculations predict that beta(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand pi-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880-3891).

Reaction of naphthoquinones with substituted nitromethanes. Facile synthesis and antifungal activity of naphtho[2,3-d]isoxazole-4,9-diones.

We report here a simple entry into naphtho[2,3-d]isoxazole-4,9-dione system containing a EWG in position 3 using the readily available 2,3-dichloro-1,4-naphthoquinone and nitromethyl derivatives in the presence of base. Antifungal activity of synthesised naphthoquinones was evaluated against ATCC and PYCC reference strains of Candida. The results suggest that the naphtho[2,3-d]isoxazole-4,9-dione scaffold has the potential to be developed into novel and safe therapeutic antifungal agents.

X-ray structural characterization of the bis-guanine derivative of a cisplatin analogue having just one proton on each coordinated nitrogen and a head-to-head conformation: [Pt{(+/-)-N,N'-dimethyl-2,3-diaminobutane}(9-ethyl-guanine)2]dinitrate.

The X-ray structural and NMR characterization of a bis-guanine derivative of a cisplatin analogue designed to reduce the rate of the Pt-N7 rotation of the coordinated guanine nucleobases by more than 1-million-fold is reported. The [Pt{(+/-)-Me(2)dab}(9-EtG)(2)](NO(3))(2) (Me(2)dab = N,N'-dimethyl-2,3-diaminobutane, 9-EtG = 9-ethyl-guanine) complex crystallizes in the P2(1)/n space group, and the crystal contains a racemic mixture of complex molecules. The data were collected at 120 +/- 2 K, and the crystal and molecular structure (comprising one disordered nitrate) were resolved and refined to conventional agreement factors of R1 = 0.0270 and wR2 = 0.0565. The guanine ligands assume the less common head-to-head (HH) orientation, disclosing full details of the intramolecular relationships between cis guanines and between guanine and cis amine. Moreover, an understanding has been gained of the steric factors determining induction of asymmetry (from carbons to adjacent nitrogen atoms) and puckering of the chelate ring (delta or lambda for R,S,S,R or S,R,R,S configurations at the N,C,C,N chelate-ring atoms, respectively) within the Me(2)dab ligand. The chemical shift separation between H8 signals of the two HT atropisomers and between the two H8 signals of the single HH atropisomer can be explained in terms of canting of the nucleobases relative to the coordination plane and in terms of the different relationships between the H8 proton of one guanine and the shielding zone of the cis guanine. Furthermore, for each configuration of the Me(2)dab ligand (R,S,S,R or S,R,R,S), the NMR data indicate that the handedness of canting is similar for the two guanines in all three (two HT and one HH) conformers (R canting for R,S,S,R and L canting for S,R,R,S configuration).

Synthesis and structure of pillared molybdates and tungstates with framework layers.

Six new layered lanthanide molybdate and tungstate phases pillared by either naphthalenedisulfonate (NDS) or fumarate anions have been synthesized hydrothermally and structurally characterized. Five of these materials, [Nd(H(2)O)MoO(4)](2)[2,6-NDS] (1), [Nd(H(2)O)MoO(4)](2)[1,5-NDS] (2), [La(H(2)O)WO(4)](2)[1,5-NDS] (3), [La(H(2)O)WO(4)](2)[2,6-NDS] (4), and [Ce(H(2)O)MoO(4)](2)[fumarate] (6), have a closely related cationic inorganic layer structure which comprises a bilayer of polyhedra leading to the formation of a framework layer containing small, inaccessible pores. These layers are pillared by the organic anions which also bridge between the lanthanide cations within the layers. In the La/WO(4)/2,6-NDS system, a second polymorph, [La(2)(H(2)O)(2)W(2)O(8)][2,6-NDS] (5), is observed. In this compound, the tungstate anions have dimerized, forming W(2)O(8)(4-). This dimer is unique and comprises two square-based pyramidal tungsten centers which are opposed to each other.

Synthetic use of the primary kinetic isotope effect in hydrogen atom transfer: generation of α-aminoalkyl radicals.

The extent to which deuterium can act as a protecting group to prevent unwanted 1,5-hydrogen atom transfer to aryl and vinyl radical intermediates was examined in the context of the generation of α-aminoalkyl radicals in a pyrrolidine ring. Intra- and intermolecular radical trapping following hydrogen atom transfer provides an illustration of the use of the primary kinetic isotope effect in directing the outcome of synthetic C-C bond-forming processes.

2-Cyano-N-(2,6-dimethoxypyrimidin-4-yl)-3-[4-(dimethylamino)phenyl]acrylamide and dimethylammonium 6-cyano-1,3-dimethyl-2,4,5-trioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidin-8-ide: a pi-stacked dimer and a hydrogen-bonded ribbon containing three types of ring.

The bond distances in 2-cyano-N-(2,6-dimethoxypyrimidin-4-yl)-3-[4-(dimethylamino)phenyl]acrylamide, C(18)H(19)N(5)O(3), (I), and in the anionic component of the salt dimethylammonium 6-cyano-1,3-dimethyl-2,4,5-trioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidin-8-ide, C(2)H(8)N(2)(+).C(10)H(7)N(4)O(3)(-), (II), provide evidence for the occurrence of electronic polarization. There are no hydrogen bonds in the structure of (I), instead pairs of molecules are linked into centrosymmetric dimers by a single pi-pi stacking interaction. In (II), a combination of a two-centre N-H...O hydrogen bond, a three-centre N-H...(O)(2) hydrogen bond, together utilizing all three O atoms, and a two-centre C-H...N hydrogen bond, link the components into a ribbon containing R(1)(2)(6), R(2)(2)(10) and R(6)(6)(30) rings.

1-(6-Amino-1,3-benzodioxol-5-yl)-3-(2-oxo-1,2-dihydroquinolin-3-yl)prop-2-enone: a sheet built by pi-stacking of hydrogen-bonded chains of rings.

The bond distances in the molecule of the title compound, C(19)H(14)N(2)O(4), provide evidence for electronic polarization in the aminoarylpropenone fragment and for bond fixation in the quinolinone unit. Molecules are linked by N-H...O and C-H...O hydrogen bonds into chains in which centrosymmetric rings of R(2)(2)(8) and R(2)(2)(18) types alternate, and these chains are linked into sheets by a single aromatic pi-pi stacking interaction.

N-(3-tert-Butyl-1-phenyl-1H-pyrazol-5-yl)-N-(4-methoxybenzyl)acetamide: a hydrogen-bonded chain of centrosymmetric rings.

The molecule of the title compound, C(23)H(27)N(3)O(2), adopts a conformation having no internal symmetry so that the compound exhibits conformational chirality. The molecules are linked by a combination of C-H...O and C-H...pi(arene) hydrogen bonds into a chain of rings in which two types of centrosymmetric ring alternate.

(E)-N2-{4-[(E)-2-(4-Chlorobenzoyl)ethenyl]-3-methyl-1-phenyl-1H-pyrazol-5-yl}-N1,N1-dimethylformamidine: polarized molecules within sheets of pi-stacked hydrogen-bonded chains.

The molecules of the title compound, C(22)H(21)ClN(4)O, are conformationally chiral, and in the space group P2(1)2(1)2(1) each crystal contains only one conformational enantiomer. The intramolecular dimensions provide evidence for polarization of the electronic structure. Molecules are linked by a single C-H...pi(arene) hydrogen bond into chains, which are themselves weakly linked into sheets by an aromatic pi-pi stacking interaction.

A hydrogen-bonded dimer in 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine and a chain of rings built from N-H...N and C-H...pi(pyridine) hydrogen bonds in 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine.

In 6-(4-bromophenyl)-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-b]pyridine, C(19)H(16)BrN(3), the reduced pyridine ring adopts a conformation that is close to a screw-boat form. Molecules are linked by pairs of symmetry-related C-H...pi(arene) hydrogen bonds into cyclic centrosymmetric dimers. Molecules of 3-(4-nitrophenyl)-4-phenyl-1H-pyrazolo[3,4-b]pyridine, C(18)H(12)N(4)O(2), are linked into centrosymmetric R(2)(2)(8) dimers by pairs of symmetry-related N-H...N hydrogen bonds, and these dimers are linked by pairs of C-H...pi(pyridine) hydrogen bonds to form a chain of edge-fused rings, or a molecular ladder, along [100]. The molecular aggregation in this compound is completed by two weak C-H...O hydrogen bonds, one of which links the chains along [100] into sheets.

5-Amino-1-benzoyl-3-methylpyrazole: complex sheets built from N-H...N, C-H...O and C-H...pi(arene) hydrogen bonds.

Molecules of the title compound [systematic name: (5-amino-3-methylpyrazol-1-yl)(phenyl)methanone], C(11)H(11)N(3)O, contain an intramolecular hydrogen bond. The molecules are linked into sheets by a combination of N-H...N, C-H...O and C-H...pi(arene) hydrogen bonds. Comparisons are made with the hydrogen-bonded structures of some related compounds.

Seven 3-methylidene-1H-indol-2(3H)-ones related to the multiple-receptor tyrosine kinase inhibitor sunitinib.

The solid-state structures of a series of seven substituted 3-methylidene-1H-indol-2(3H)-one derivatives have been determined by single-crystal X-ray diffraction and are compared in detail. Six of the structures {(3Z)-3-(1H-pyrrol-2-ylmethylidene)-1H-indol-2(3H)-one, C(13)H(10)N(2)O, (2a); (3Z)-3-(2-thienylmethylidene)-1H-indol-2(3H)-one, C(13)H(9)NOS, (2b); (3E)-3-(2-furylmethylidene)-1H-indol-2(3H)-one monohydrate, C(13)H(9)NO(2).H(2)O, (3a); 3-(1-methylethylidene)-1H-indol-2(3H)-one, C(11)H(11)NO, (4a); 3-cyclohexylidene-1H-indol-2(3H)-one, C(14)H(15)NO, (4c); and spiro[1,3-dioxane-2,3'-indolin]-2'-one, C(11)H(11)NO(3), (5)} display, as expected, intermolecular hydrogen bonding (N-H...O=C) between the 1H-indol-2(3H)-one units. However, methyl 3-(1-methylethylidene)-2-oxo-2,3-dihydro-1H-indole-1-carboxylate, C(13)H(13)NO(3), (4b), a carbamate analogue of (4a) lacking an N-H bond, displays no intermolecular hydrogen bonding. The structure of (4a) contains three molecules in the asymmetric unit, while (4b) and (4c) both contain two independent molecules.

Ring conformations and intermolecular interactions in two fused dibenzoazocines.

5-Acetyl-2-chloro-8,11-dimethyl-5,6,11,12-tetrahydrodibenzo[b,f]azocine, C(19)H(20)ClNO, (I), crystallizes as a single fully ordered isomer, but 14-acetyl-8,11-dimethyl-7,8,13,14-tetrahydrobenzo[f]naphtho[1,2-b]azocine-14-acetyl-8,9-dimethyl-7,8,13,14-tetrahydrobenzo[f]naphtho[1,2-b]azocine (74/26), C(23)H(23)NO, (II), exhibits threefold whole-molecule disorder involving both configurational and structural isomers. In (I) and in the predominant form of (II), the azocine rings adopt very similar conformations, forming boat-shaped rings having approximate twofold rotational symmetry. There are no direction-specific intermolecular interactions in the crystal structure of (I), but the molecules of (II) are weakly linked into chains by an aromatic pi-pi stacking interaction. The compounds were made under green conditions using an acid-catalysed cyclization process having very high atom utilization.