The application of solvent-assisted mechanochemical synthesis to the study of metal complex formation is illustrated by examples involving complexes of silver halides with ethylenethiourea.
Investigation of the EtOAc extract from the Thai sea hare, Bursatella leachii, resulted in the isolation of a potent stimulator of actin assembly, hectochlorin (1), and its new derivative, deacetylhectochlorin (2). Compound 2 exhibited more potent cytotoxicity than 1 against different human carcinoma cell lines. In addition, a new morpholine-2,5-dione analogue, syn-3-isopropyl-6-(4-methoxybenzyl)-4-methylmorpholine-2,5-dione (3), was co-isolated.
A new furoclerodane, croblongifolin, together with one known clerodane, crovatin and one known labdane, nidorellol, were isolated from the stem bark of Croton oblongifolius. Structures were established based on spectroscopic and X-ray analysis. Croblongifolin showed a significant cytotoxicity against various human tumor cell lines including HEP-G2, SW620, CHAGO, KATO3 and BT474.
Two novel benzoquinone metabolites, 2-chloro-5-methoxy-3-methylcyclohexa-2,5-diene-1,4-dione ( 1) and xylariaquinone A ( 2) together with two known compounds were isolated from an endophytic fungus, Xylaria sp. Their structures were assigned by analysis of spectroscopic data, and the structures of 1 and 3 were also confirmed by single-crystal X-ray data. Compounds 1 and 2 showed in vitro activity against Plasmodium falciparum, K1 strain, with IC 50 values of 1.84 and 6.68 microM and cytotoxicity against African green monkey kidney fibroblasts (Vero cells) with IC 50 values of 1.35 and >184 microM, respectively.
Syntheses, single crystal X-ray structural and spectroscopic characterizations are described for a variety of adducts of silver salts with ethylenethiourea (etu). Ag2SO4/etu (1:6) is isomorphous with its previously studied copper(I) counterpart, the [Ag(S-etu)3]+ species disposed with their silver atoms on crystallographic 3-axes, one of the two independent cations being slightly perturbed by a distant O-sulfate approach along that axis. In AgCl/etu (1:3), the silver atom is in a four-coordinate ClAgS3 environment, while AgNO3/etu (1:3) takes the form [(etu)2Ag(µ-S-etu)2Ag(etu)2](NO3)2. AgBr/etu (1:2) is binuclear [(etu)2Ag(µ-Br)2Ag(etu)2)], unlike its previously studied copper counterpart, which is [(etu)BrCu(µ-S-etu)2CuBr(etu)]. AgCl/etu (4:6) is an interesting ionic polymer [ClAg4(etu)6](∞|∞)Cl3, containing a novel one-dimensional polymeric cation. Bands in the far IR spectra of these compounds are assigned to v(AgS) and v(AgX) (X = halogen) modes, and a correlation between v(AgS) and the Ag–S bond length d(AgS) is established for silver complexes involving the etu ligand.Key words: silver, sulfur ligands, X-ray crystal structure, coordination chemistry, complexes.
Five new triply bridged dinuclear Cu(II) compounds have been synthesized, and their magnetic properties have been measured and characterized. The magnetic coupling constants (J) of these compounds plus a previously structurally characterized compound of the same type have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. Two of the compounds are ferromagnetically coupled, and three are antiferromagnetically coupled with J values in the [+150, -40] cm(-1) range. The validity of the structural aggregate Addison's parameter as a qualitative magneto-structural correlation is confirmed. The origin of the magnetic interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory-based calculations using a variety of state of the art exchange-correlation potentials. It is shown that the long-range separated LC-ωPBE provides the overall best agreement with experiment for this family as well as for a set of previously reported hetero triply bridged dinuclear Cu(II) compounds, especially for ferromagnetic systems.
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