Zafra Stein

Crystalline complexes, coordination polymers and aggregation modes of tetra(4-pyridyl)porphyrin

Aggregation patterns of tetra(4-pyridyl)porphyrin and of its zinc(II) complex in seven new solid materials have been investigated by X-ray diffraction. The metalloporphyrin compound forms two types of coordination polymers through ligation of the porphyrin periphery on one molecule to the metal center of an adjacent porphyrin. These include one-dimensional chains with a zigzag conformation, as well as three-dimensional, extensively interlinked, polymeric structures. The non-metallated compound reveals a characteristic layered arrangement and interporphyrin stacking of the type which is commonly observed in the structures of tetraphenylporphyrin derivatives. In the absence of a metal center, the basic functionality of the pyridyl substituents is utilized for effective H-bond directed coordination and co-crystallization with solvent/guest components. The stoichiometry of the porphyrin solvation, and the consequent interporphyrin organization in the solid phase, are quite sensitive to the nature of the coordinating solvent.

Supramolecular architectures of functionalized tetraphenylmetalloporphyrins in crystalline solids. Studies of the 4-methoxyphenyl, 4-hydroxyphenyl and 4-chlorophenyl derivatives

Abstract A series of new ‘inclusion’ materials based on tetra-4-methoxyphenyl, tetra-4-hydroxyphenyl and tetra-4-chlorophenyl derivatives of the metalloporphyrin system, in combination with a wide variety of guest molecules and ligands, have been prepared, and their structural systematics analysed. Crystallographic investigations have confirmed that the supramolecular arrangement of the hydroxyphenylporphyrin species is dominated by interporphyrin directional hydrogen-bonding interactions, and consists of continuous networks of strongly coordinated entities with varying degrees of cross-linking and rigidity. Guest molecules can be absorbed in these solids in distinctly defined sites of the lattice: in the small interhost cages of fixed size between adjacent intercoordinated porphyrin hosts, or in extended one-dimensional channels formed between the hydrogen bonded host arrays running parallel or perpendicular to the porphyrin plane. For polar ligands with strong nucleophiles, their potential coordination ...

Phorbazoles AD, novel chlorinated phenylpyrrolyloxazoles from the marine sponge phorbas aff. clathrata

Abstract Four new chlorinated phenylpyrrolyloxazoles, phorbazoles AD (1a-4) have been isolated from the sponge Phorbas aff clathrata. The structure of phorbazole A was unambiguously determined by X-ray diffraction studies of its dimethyl derivative (1b). The structures of compounds 2–4 were determined by extensive use of 1D and 2D NMR techniques. Phorbazoles AD represent a new class of marine alkaloids embodying the previously unprecedented, chlorinated pyrrole moiety, from marine sources.

Supramolecular Assembly of Functionalized Metalloporphyrins. Porous Crystalline Networks of Zinc-Tetra(4-Carboxyphenyl)Porphyrin

Abstract Two crystalline compounds based on the Zn-tetra (4-carboxyphenyl)porphyrin building block have been prepared and structurally analysed by x-ray diffraction in order to ellucidate the characteristic supramolecular aggregation modes of this functionalized metalloporphyrin moiety. Crystals of the 1:1 complex with sec-phenethyl alcohol (1) are monoclinic, space group I2/a (No. 15), a = 14.420(1), b = 24.678(2), c = 33.688(2) A, β = 90.03(2)°, Dc = 1.082 g/cm3, Z = 8, R = 0.080 for 3053 data. Those of the 1:3 complex with dimethylsulphoxide (2) are monoclinic, space group P21/n (No. 14), a = 14.881(1), b = 8.986(2), c = 37.550(3) A, β = 94.21(1)°, Dc = 1.444 g/cm3, Z = 4, R = 0.093 for 4200 data. The two compounds consist of nearly square-pyramidal five-coordinate metalloporphyrin species, molecules of the sec-phenethyl alcohol (in 1) and dimethylsulphoxide (in 2) linking to the metal center at the axial site. In 2, two additional molecules of dimethylsulphoxide associate through H-bonds to the termin...

Optical resolution of amine N-oxide by diastereoisomeric complex formation with optically active host compound

Optical stereoisomers of various amine N-oxides with one or two chiral centers can effectively be resolved by selective crystalline complexation with an optically active host. Intermolecular interaction schemes and absolute configurations of the N-oxide guests are revealed by crystallographic analyses of the diastereoisomeric complexes.

Cyanthiwigin A-D, Novel Cytotoxic Diterpenes From The Sponge Epipolasis Reiswigi

Abstract Four Novel Diterpenes, Cyanthiwigin A-D (1–4) Have Been Isolated From The Marine Sponge E. Reiswigi And Their Structure Elucidated By Mass And Mainly Nmr Spectra. The Tricarbocyclic Structure Of 1 Was Confirmed By An X-Ray Analysis And Its Absolute Configuration Was Established To Be 4s, 5r, 6s, 9s By The Modified Moshers Method. The Four Compounds Have The Same Planar Skeleton As Cyanthin But Differ In Their Stereochemistry.

Asmarines A-C; Three novel cytotoxic metabolites from the marine sponge Raspailia sp.

Abstract Three novel nitrogen-containing metabolites, asmarines A-C (1 – 3) together with two known diterpenes, zaatirin and chelodane were isolated from the Red Sea sponge Raspailia sp. collected in the Dahlak archipelago, Eritrea. The structure of the three new compounds and the known zaatirin and chelodane were established by spectroscopic analysis including X-ray diffraction analysis for asmarine A. Asmarines A-C are cytotoxic to a few human cancer cells.

Extremely long C−C bonds in strained 1,1,2,2-tetraphenylcyclobutaarenes : 3,8-dichloro-1,1,2,2-tetraphenylcyclobuta-[b]naphthalene, C36H24Cl2, and 3,6,9,10-tetrachloro-4,5-dimethyl-1,1,2,2,7,7,8,8-octaphenyldicyclobuta[b,h]phenanthrene toluene solvate, C68H46Cl4.1.5C7H8

Cyclobutaarenes are highly strained compounds which exhibit unusual geometric features. Introduction of diphenyl substituents on the peripheral C atoms of the cyclobutene ring adds stereoelectronic effects and causes further distortion of the ring structure. The interatomic distances observed for the peripheral C-C bonds in the cyclobutene moiety of the two compounds are in the range 1.71-1.72A, among the longest of C sp3 -C sp3 bonds previously reported for similar compounds. The core structure of the phenanthrodicyclobutene derivative is severely twisted due to non-bonding interactions between the chlorine substituents.

Structural patterns in clathrates and crystalline complexes of zinc-tetra(4-chlorophenyl)porphyrin and zinc-tetra(4-fluorophenyl)porphyrin

Twelve new crystalline materials based on zinc-tetra(4-chlorophenyl)porphyrin (8 compounds) and zinc-tetra(4-fluorophenyl)prophyrin (4 compounds) building blocks have been prepared and characterized by X-ray diffraction analysis. Several different modes of guest solvent incorporation into the porphyrin lattice, including enclathration (of solvents of low polarity) and complex formation (with strong Lewis bases), and of intermolecular organization have been detected. Unique interporphyrin architectures, affected by directional Cl...Cl interactions, characterize most of the known solid structures of the chlorosubstituted materials. A small number of the latter, as well as the fluorosubstituted derivatives, exhibit interporphyrin arrangements of the type which are commonly observed in the clathrates of unsubstituted tetraphenylmetalloporphyrins. The pore structure of these compounds is affected to a large extent by the nature of the incorporated solvate and, consequently, the degree of coordination of the metal center. In crystals of four-coordinate porphyrins the solvent guest components are usually incorporated into channel-type cavities formed between columns and layers of densely stacked hosts. In five-coordinate and six-coordinate materials the guest sites coincide with the axial coordination sites of the porphyrin metal atoms. The latter structures reveal a tight fit between adjacent layers of the complexed entities, the axial ligands of one layer being incorporated into localized interporphyrin cavities of another layer. Dipolar forces play also an important role in the interporphyrin organization.

Crystal inclusion chemistry of zinc-tetra(4-bromophenyl)porphyrin

The structural patterns of Zn(II)-tetra(4-bromophenyl)porphyrin and several of its newly prepared complexes and clathrates in the solid phase were determined by X-ray crystallography. The molecular structure of the porphyrin compound is characterized by a nearly perfect planarity of the metalloporphyrin core due to effective Zn...;Br intermolecular interactions in the crystalline lattice. The composite materials show three different kinds of interporphyrin organization, dominated to a large extent by the molecular shape, often exhibited by related tetraphenylporphyrin derivatives. These include monoclinic ‘herringbone’ packing modes without any apparent involvement of the halogen atoms in specific interactions, chained interporphyrin arrangements exhibiting C-Br...;π close approach, and porous layered networks of the porphyrin species revealing direct Br...;Br contacts. The latter two forms are also affected by C-H...;Br attractions. Four-, five- and six-coordination of the central zinc ion was observed, but there is no apparent correlation between the coordination number and the crystal packing type. Thermal analysis revealed the relative strength of binding of the ligand and solvate species to the porphyrin lattice. The bromophenyl-substituted porphyrin building block forms only a small number of crystalline heteromolecular materials with other components, and occurrence of the uniquely structured porous porphyrin networks is not as dominant as in the analogous chlorophenyl derivatives. Estimates of interporphyrin packing stabilization energies suggest that the stability of these layered patterns is affected primarily by dipolar attractions, which are less significant in solids containing the Br, rather than Cl, groups.