Self-Assembling Synthesis of Cyclic Tri- and Tetranuclear Cobalt(III) Complexes Bridged by Purine-6-thione and Their Characterization by Electrospray Mass Spectrometry and X-ray Crystal Analysis

• Published in: Inorganic chemistry 1998-10, Vol.37 (21), p.5611-5618
• Main Authors: Yamanari, Kazuaki, Fukuda, Ito, Kawamoto, Tatsuya, Kushi, Yoshihiko, Fuyuhiro, Akira, Kubota, Naoko, Fukuo, Tsuyoshi, Arakawa, Ryuichi
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic9802146

The cyclic multinuclear complexes [Co n (L-N,S,N‘) n (tacn) n ] n + (L = purine-6-thiones; tacn = 1,4,7-triazacyclononane) were synthesized through self-assembly of the mononuclear complex [Co(HL-N,S)Cl(tacn)]+ based on the multidentate bridging ability of purine-6-thione. Three kinds of purine-6-thione ligands were used:  9H-purine-6(1H)-thione (H2put), 2-amino-9H-purine-6(1H)-thione (H2aput), and 3,6-dihydro-6-thioxo-9H-purin-2(1H)-one (H3tpuo). The complexes [Co n (L-N,S,N‘) n (tacn) n ] n +, n = 3 and 4 for put and n = 4 for aput and Htpuo, were characterized by NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), and X-ray crystal structure analysis. ESI-MS proved to be a very powerful tool for determining the nuclearity (n value) unambiguously. X-ray crystal structure analyses of [Co4(put)4(tacn)4](CF3SO3)4·12H2O [triclinic, P1̄ (No. 2)] and [Co4(aput)4(tacn)4]Cl4·16H2O [monoclinic, C2/c (No. 15)] reveal that all purinethione ligands act as tridentate ligands via S6/N(7) chelation and the N(9) bridge and both tetranuclear complexes adopt the cyclic S 4 structure which is stabilized by four intramolecular hydrogen bonds between N(3) and H−N(tacn). The trinuclear complex [Co3(put)3(tacn)3]3+ having the C 1 structure was optically resolved. Stereochemistry for the cyclic molecular boxes containing chiral octahedral ions is developed.