Special Issue "Pincer Compounds"

Guest Editor
Prof. Dr. David Morales-Morales
Instituto de Quimica, Universidad Nacional Autonoma de Mexico, Circuito Exterior S/N. Ciudad Universitaria. Coyoacan, C. P. 04510 Mexico
E-Mail: damor@servidor.unam.mx
Interests: pincer compounds; organometallic chemistry; homogeneous catalysis

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Type of Paper: Review
Title: Pincer Molecules Based on Oligo Tröger's Bases
Authors: Bohumil Dolenský, Martin Havlík and Vladimír Král
Affiliations: Department of analytical chemistry, Institute of Chemical Technology, Prague, Czeck Republic;
E-Mail: bohumil.dolensky@vscht.cz (B.D.)
Abstract: Derivatives of Tröger's base (2,8-dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine) have rigid chiral V-shape, which makes them to be a useful building block for construction of receptors having a pincer molecule structural motive. This review is focused on to phenomenon of oligo Tröger's bases (derivatives containing aromatic part(s) sharing by two or more Tröger's base subunits), which represent molecular tweezers, clips and calixes, and on synthetic approaches to their preparation.

Type of Paper: Article
Title: Group 11 Metal Compounds with Tripodal Bis(imidazole) Thioether Ligands: Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents
Authors: Fangwei Liu ¹, Reema Anis ¹, Eunmi Hwang ¹, Rafael Ovalle ², Armando Varela-Ramírez ³, Renato J. Aguilera ³ and María Contel ^1
1 Department of Chemistry, Brooklyn College and The Graduate Center, The City University of New York, Brooklyn, NY, 11210, USA;
E-Mail: mariacontel@brooklyn.cuny.edu
² Department of Biology, Brooklyn College, The City University of New York, Brooklyn, NY, 11210, USA
³ Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, USA
Abstract: Group 11 metal complexes with previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) {BITOMe,StBu} 2, have been prepared. The ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states (Au(I), Au(III), Ag(I), Cu(I) and Cu(II)). Thus new compounds [Au{BITOMe,StBu}Cl][AuCl4]2  (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3- 5, PF6- 6) and [Cu{BITOMe,StBu}Cl2] (7) have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed Au(III)-Au(I) species [Au2{BITOMe,S}Cl3] (8) were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a gold(III) center coordinated to the ligand through one N and the S atom. The soft gold(I) center coordinates to the ligand through the same S atom that has lost the tert-butyl group thus becoming a thiolate ligand. There is a short distance (3.383 Å) between the Au(I)-Au(III) atoms that may indicate a weak metal-metal interaction. Complexes 2-7 and the previously described Cu(I) compound [Cu{BITOMe,StBu}]PF6  (9) have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP) as the oxidant. Results have shown that gold(I) 4 and silver(I) 6 complexes (10 mol%) are the more active catalysts in this oxidative cleavage. The antimicrobial activity of 2-5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has been evaluated. The new gold and silver compounds display moderate to high antibacterial activity while copper derivatives are mostly inactive. Gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds displayed a very low cytotoxicity on this cell line (5 to 10 times lower than cis-platin) and on normal primary cells derived from C57B6 mouse muscle explants, which may make them promising candidates as potential antimicrobial agents and safer catalysts due to low toxicity in human and other mammalian tissues.