Heterocalixarene Inclusion Chemistry. Structure of a Crystalline Host-Guest Complex Including endo-Calix Ethyl Acetate and exo-Calix Clustering of Water

The X-ray crystal structure of the solvent inclusion compound formed between heterocalix[8]arene 1, ethyl acetate and water (1 : 1 : 4.5) has been studied. The compound crystallized in tetragonal space group I4₁/a, a = b = 21.278(3), c = 31.290(4) Å, V = 14167(4) ų, Z = 8. The host molecule, incorporating benzimidazol-2-one and 2,5-dimethoxy-1,3-phenylene subunits in an alternate cyclic arrangement, forms an almost perfectly closed cavity which encapsulates one solvent ethyl acetate guest molecule. Water molecules being entrapped in the lattice cages in the form of cyclic and linear clusters bind the bulky inclusion complexes via H-bonds in infinite layers. Two symmetry center related benzimidazole-2-one moieties of two hosts from neighbouring layers in the crystal lattice are arranged such that they partially overlap exhibiting stacking interaction.     

A Characterization of Association Schemes from Affine Spaces

We characterize theassociation schemes from affine spaces as the association schemesin which all relations are equivalence relations (when unitedwith the identity relation). The schemes from affine spaces ofdimension at least three are counterexamples of a conjectureof A. V. Ivanov [Problem 1.3]I on amorphic schemes.     

Quantum-well states and spin polarization in thin Ni films on Cu(0 0 1)

The unoccupied quantum-well states in thin Ni films on Cu(0 0 1) have been studied by spin- and angle-resolved inverse photoemission. Three quantum-well features are clearly resolved with exchange splittings of up to 70 meV. As a function of the wave vector parallel to the surface, the quantum-well states follow the corresponding sp band dispersion and evolve into surface resonances upon approaching the band-gap boundary.     

BOPHY-Fullerene C60 Dyad as a Photosensitizer for Antimicrobial Photodynamic Therapy

A novel BOPHY–fullerene C₆₀ dyad ( BP-C₆₀ ) was designed as a heavy-atom-free photosensitizer (PS) with potential uses in photodynamic treatment and reactive oxygen species (ROS)-mediated applications. BP-C₆₀ consists of a BOPHY fluorophore covalently attached to a C₆₀ moiety through a pyrrolidine ring. The BOPHY core works as a visible-light-harvesting antenna, while the fullerene C₆₀ subunit elicits the photodynamic action. This fluorophore–fullerene cycloadduct, obtained by a straightforward synthetic route, was fully characterized and compared with its individual counterparts. The restricted rotation around the single bond connecting the BOPHY and pyrrolidine moieties led to the formation of two atropisomers. Spectroscopic, electrochemical, and computational studies disclose an efficient photoinduced energy/electron transfer process from BOPHY to fullerene C₆₀. Photodynamic studies indicate that BP-C₆₀ produces ROS by both photomechanisms (type I and type II). Moreover, the dyad exhibits higher ROS production efficiency than its individual constitutional components. Preliminary screening of photodynamic inactivation on bacteria models (Staphylococcus aureus and Escherichia coli) demonstrated the ability of this dyad to be used as a heavy-atom-free PS. To the best of our knowledge, this is the first time that not only a BOPHY–fullerene C₆₀ dyad is reported, but also that a BOPHY derivative is applied to photoinactivate microorganisms. This study lays the foundations for the development of new BOPHY-based PSs with plausible applications in the medical field.     

Nitroxide‐mediated radical copolymerization of methyl methacrylate controlled with a minimal amount of 9‐(4‐vinylbenzyl)‐9H‐carbazole

The controlled nitroxide‐mediated homopolymerization of 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) and the copolymerization of methyl methacrylate (MMA) with varying amounts of VBK were accomplished by using 10 mol % {tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino} nitroxide relative to 2‐({tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino}oxy)‐2‐methylpropionic acid (BlocBuilder?) in dimethylformamide at temperatures from 80 to 125 °C. As little as 1 mol % of VBK in the feed was required to obtain a controlled copolymerization of an MMA/VBK mixture, resulting in a linear increase in molecular weight versus conversion with a narrow molecular weight distribution (M_w /M_n ≈ 1.3). Preferential incorporation of VBK into the copolymer was indicated by the MMA/VBK reactivity ratios determined: r_VBK = 2.7 ± 1.5 and r_MMA = 0.24 ± 0.14. The copolymers were found significantly “living” by performing subsequent chain extensions with a fresh batch of VBK and by ³¹P NMR spectroscopy analysis. VBK was found to be an effective controlling comonomer for NMP of MMA, and such low levels of VBK comonomer ensured transparency in the final copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

X-ray crystal structures of <Emphasis Type="Italic">p</Emphasis>-halogenated 6,6-diphenylfulvenes

Crystal structures of a series of p-halogenated 6,6-diphenylfulvenes 2–5 are reported and comparatively discussed including the known structure of the non-halogenate parent compound 1. The molecular structures show twisted conformations of the plane aryl and fulvene subunits against each other, rather unaffected by the different halogen substituents. The packing structures exclusively involve C–H···X (X = F, Cl, π) contacts while Hal···Hal and π-stacking interactions do not occur.     

25‐Allyloxy‐5,11,17,23‐tetra‐tert‐butyl‐26,27,28‐trihydroxycalix[4]arene chloroform disolvate

In the title solvated calixarene, C₄₇H₆₀O₄·2CHCl₃, the host chalice displays an almost undistorted cone conformation, stabilized by three strong O—H...O hydrogen bonds at the calixarene's lower rim. One chloroform solvent molecule is fixed in the calixarene cavity by C—H...π interactions, while the second is accommodated in a clathrate‐like mode in elliptical packing voids. These voids are spanned by six host molecules connected via C—H...π contacts and van der Waals interactions. Within the crystal structure, one tert‐butyl group of the calixarene host is disordered over two orientations, with occupancies of 0.884 (4) and 0.116 (4). Furthermore, both solvent molecules show disorder, with occupancies of 0.857 (2) and 0.143 (2) for the cavitate‐type, and 0.9359 (17) and 0.0641 (17) for the clathrate‐type chloroform solvent molecules.     

6,6′-Dimethoxygossypol: molecular structure,crystal polymorphism,and solvate formation

6,6′-Dimethoxygossypol (DMG) is a naturally occurring derivative of gossypol that is found in relatively high concentration in some Gossypium barbadense cotton varieties. Like gossypol, DMG forms an equimolar solvate with acetic acid, but it was not known if, like gossypol, the compound would also form clathrates with other molecules. To test for this, the compound was crystallized from different solvents. Four new structures of DMG were found that include two polymorphic and two solvated forms. The polymorphs include two monoclinic structures with P2₁/c and C2/c space groups (P1 and P2, respectively). Packing of the DMG molecules P1 is similar to packing of the gossypol molecules in the P1 polymorphic form of gossypol. The DMG molecules in P2 pack in a highly ordered arrangement that has not been previously observed among gossypol structures. DMG forms equimolar solvates with water (S1) and cyclohexanone (S2). Both structures are triclinic with P [`1]P \bar {1} space groups. The DMG molecules in S2 assemble in a manner that is similar to the gossypol molecules of gossypol–cyclohexanone (1:1), and the DMG molecules in S1 pack in a manner that is similar to the DMG molecules in DMG–acetic acid (1:1) as well as the gossypol molecules in gossypol–acetic acid (1:1). Although DMG is not as versatile a host compound as gossypol, it still forms solvates under many crystallization conditions. Consequently, some care is needed to be sure that one understands exactly which form is recovered when the compound is isolated.