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Several Derivatives (several + derivative)

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Chemistry100%

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Tetracyanoquinodimethanido Derivatives of (Terpyridine)- and (Phenanthroline)metal Complexes , Structural and Magnetic Studies of Radical-Ion Salts

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2005
Cristina Alonso
Abstract Several derivatives of formulae [M(terpy)2](TCNQ)2 or [M(terpy)2](TCNQ)3 (M = Ni, Cu, Zn; terpy = 2,2,:6,,2"-terpyridine; TCNQ= 7,7,8,8-tetracyanoquinodimethane) and [M(phen)3](TCNQ)2 or [M(phen)3](TCNQ)4 (M = Fe, Ni; phen = 1,10-phenanthroline) have been obtained. The crystal structures of [M(terpy)2](TCNQ)2 (M = Ni, Cu) show that the metal is surrounded by the terpyridine nitrogen atoms in a closed octahedral environment and the TCNQ anions are dimerised by , overlap. The cationic [M(terpy)2]2+ and the anionic [TCNQ]22, groups alternate in the crystal. For the derivatives with three TCNQ groups, the existence of a stack of trimeric [TCNQ]32, ions having electronic delocalisation is proposed. The compound [Fe(phen)3](TCNQ)2, which shows a strong interaction between TCNQ anions, led to the formation of a , bond in the diamagnetic species [TCNQ,TCNQ], while the nickel analogue is expected to have a localised structure formed by alternation of cationic metal complexes and dimeric [TCNQ]22, anions similar to those observed in the analogous terpy derivatives. The derivatives having four TCNQ groups also show electronic delocalisation and a 1D stack based on the magnetic data is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Disaccharide Mimetics of the Aminoglycoside Antibiotic Neamine

CHEMBIOCHEM, Issue 9 2004
Andre Venot Dr.
Abstract A highly convergent approach has been employed for the facile synthesis of a library of 24 disaccharides that are ,(1,3), ,(1,3), ,(1,4), or ,(1,4) linked and contain 2,4 amino groups. Fourier-transformation ion cyclotron resonance mass spectrometry (FT-ICR MS) has been used to determine dissociation constant (Kd) values for the binding of the disaccharides to a prototypical fragment of 16S ribosomal RNA. Several derivatives bound with affinities similar to that of neamine. Structure,activity relationships have revealed the substitution pattern that is important for high-affinity binding. The compounds described here are unique lead compounds for the design of novel aminoglycoside antibiotics. [source]

Direct hydride transfer in the reaction mechanism of quinoprotein alcohol dehydrogenases: a quantum mechanical investigation

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2001
A. Jongejan
Abstract Oxidation of alcohols by direct hydride transfer to the pyrroloquinoline quinone (PQQ) cofactor of quinoprotein alcohol dehydrogenases has been studied using ab initio quantum mechanical methods. Energies and geometries were calculated at the 6-31G(d,p) level of theory. Comparison of the results obtained for PQQ and several derivatives with available structural and spectroscopic data served to judge the feasibility of the calculations. The role of calcium in the enzymatic reaction mechanism has been investigated. Transition state searches have been conducted at the semiempirical and STO-3G(d) level of theory. It is concluded that hydride transfer from the C,-position of the substrate alcohol (or aldehyde) directly to the C(5) carbon of PQQ is energetically feasible. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1732,1749, 2001 [source]

The addition reaction of diamides to 1,2,5-thiadiazole 1,1-dioxide derivatives,

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2004
José A. Caram
Abstract The reactions of several derivatives of 1,2,5-thiadiazole 1,1-dioxide [3,4-diphenyl-(1a), 3,4-bis(p -methoxyphenyl)-(1b), phenanthro[9,10- c]-(1c) and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide (1d), 3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2a) and 4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2b)], with reagents possessing two nucleophilic nitrogen atoms (urea, N,N,-dimethylurea, thiourea, N -methylthiourea, N -ethylthiourea, N -allylthiourea, N,N,-diethylthiourea, N,N,-diphenylthiourea, dithioxamide and sulfamide), were followed by cyclic voltammetry (CV) and UV,visible spectrophotometry in aprotic solvent solution. The products were isolated, characterized by IR, 1H NMR and 13C NMR methods and their structure was confirmed by single-crystal x-ray diffraction. Several substrate,nucleophile combinations (1a,d and 2a with some ureas and thioureas) reacted to give good yields of new compounds formed by the addition reaction of the two nitrogen atoms of the nucleophile to the two >CN, double bonds of the 1,2,5-thiadiazole 1,1-dioxide ring. Some systems (1a,dithioxamide and 2b,thiourea) did not react, whereas in others (e.g. 1a,sulfamide) a monoaddition equilibrium reaction was observed. Copyright © 2004 John Wiley & Sons, Ltd. [source]