Biomedical subjects
Publications and source records attributed to N Feeder.
The crystal structure of the widely used title fungicidal material, [Cu(C(5)H(4)NOS)(2)], has been determined at 150 (2) K from a microcrystalline fragment using synchrotron radiation. The molecule adopts a trans-square-planar configuration, with the Cu atom sited at a crystallographic centre of inversion.
Rh(III) porphyrin complexes with bridging hydrazine and substituted hydrazine ligands were characterized in solution by (1)H NMR spectroscopy and in the solid state by X-ray diffraction. Addition of further ligand to these species afforded 1:1 complexes in which methylhydrazine and N,N-dimethylhydrazine preferentially bound to the Rh center through the substituted nitrogen atom, as evidenced by (1)H NMR chemical shifts. An alkylated Rh(III) porphyrin was isolated as a decomposition product of the reaction of N,N-dimethylhydrazine with Rh(III) porphyrin in the presence of light and oxygen. Me(2)Se(2) and Me(2)S(2) formed bridging and nonbridging complexes with Rh(III) porphyrin, analogous to that observed with N,N'-dimethylhydrazine.
The coordination chemistry of a Rh(III) porphyrin building block was investigated with a view to the construction of heterometallic arrays of porphyrins. The Rh(III) porphyrin was found to coordinate methanol in the solid state and weakly in CDCl(3) solution. Crystallization afforded five coordinate pi stacked Rh(III) porphyrins. The distribution of products from reaction of Rh(III) porphyrin with DABCO, 4,4'-bipyridine, and 4,4'-bipyrimidine could be displaced toward dimeric species by silica gel column chromatography or recrystallization which served to remove excess ligand. Weak coordination to nitriles was observed, although it was sufficiently strong to organize a dimeric complex of 5,5'-dicyano-2,2'-bipyridine in the solid state. Complexes with 4,4'-bipyrimidine and 5,5'-dicyano-2,2'-bipyridine possess uncoordinated chelating nitrogen atoms. Larger heterometallic porphyrin arrays were assembled using a combination of Sn(IV) and Rh(III) porphyrin coordination chemistry. A Sn(IV) porphyrin acted as a core around which were coordinated two isonicotinate groups, carboxylic acid functionalized porphyrins, or porphyrin trimer dendrons. Rh(III) porphyrins were coordinated to pyridyl groups at the periphery of these entities. In this way an eleven porphyrin array, with four different porphyrin metalation states, was assembled. The diamagnetic nature of both the Rh(III) and Sn(IV) porphyrins, the slow ligand exchange kinetics on the NMR time scale, and tight ligand binding permitted the porphyrin arrays to be analyzed by two-dimensional (1)H NMR techniques.
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Two remarkable crystal structures are reported of a cyclic receptor 1, containing two metalloporphyrin units. The overall crystal structure of 1 provides the first direct evidence that pi-stacking between two metalloporphyrins reduces the Lewis acidity of the metal ion and thereby dramatically reduces the affinity of zinc for external ligands; this effect was previously suggested indirectly by solution state binding studies. In addition, crystallising 1 from a different combination of solvents and the ability of 1 to distort its structure leads to the remarkable observation of a supramolecular dimer of inter-penetrating macrocycles, 4, held together by clusters of hydrogen-bonded methanol molecules.
The equilibrium distribution of deoxycholate-based macrocyclic N-acyl hydrazones is dependent upon the nature of the substituents at the 3- and 12-position. These substituents can also influence the preferred conformation of the macrocycles. The conversion of pure cyclic dimer and trimer into a mixture of both components, in the presence of trifluoroacetic acid, has been demonstrated and an X-ray crystal structure obtained of a macrocyclic N-acyl hydrazone dimer.
[reaction: see text] A series of diimide-based macrocycles have been prepared using Mitsunobu-mediated alkylation as the macrocyclization step. These macrocycles could not be incorporated into [2]catenanes using previously established building blocks and coupling methodology. However, when one of the macrocycle syntheses was conducted in the presence of a dinaphtho crown ether, catenane formation was achieved. This result is discussed in terms of the ability of the components to establish intermolecular C-H...O hydrogen-bonding contacts.
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Two polymorphs, alpha and gamma, of the title compound, C(22)H(20)N(2)O(2), have been characterized by means of single-crystal synchrotron X-ray diffraction. In the alpha form, the molecules pack in a herring-bone fashion, linked via weak C-H.N intermolecular interactions (H.N 2.58 A). In the gamma form, the molecules are arranged in nearly planar sheets, which form a network held together by intermolecular hydrogen bonds of the type C-H.O (H. O 2.49 A) and C-H.N (H.N 2.50 A). The stacking distance between the sheets is 3.40 A.