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Ag4L2 Nanocage as a Building Unit toward the Construction of Silver Metal Strings

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posted on 17.11.2008, 00:00 by Jing-Yun Wu, Yu-Fang Lin, Chuan-Hung Chuang, Tien-Wen Tseng, Yuh-Sheng Wen, Kuang-Lieh Lu
Self-assembly of AgNO3 with the semirigid tetratopic ligands 1,2,4,5-tetrakis(benzoimidazol-1-ylmethyl)benzene (TBim) and 1,2,4,5-tetrakis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene (TDMBim) afforded compounds [Ag44-TBim)222-NO3)2](NO3)2·1/2CH2Cl2·2CH3OH (1μ1/2CH2Cl2·2CH3OH) and [(NO3)⊂{Ag44-TDMBim)2}][Ag(NO3)2](NO3)2·CH2Cl2·CH3OH·4H2O (2·CH2Cl2·CH3OH·4H2O), respectively. The structures of 1 and 2 were characterized by single-crystal X-ray diffraction analysis. Both compounds adopt a M4L2-type tetragonal metalloprismatic cage structure, [Ag44-L)2]4+, with strong intramolecular silver−silver contacts. Compound 1 is a discrete species, while compound 2 is a novel infinite chainlike supramolecular array involving silver metal strings assembled from a [Ag44-L)2]4+ nanocage and silver linkages. Thermogravimetric analyses of 1·1/2CH2Cl2·2CH3OH and 2·CH3OH·4H2O indicate that the Ag4L2-cage structures of 1 and 2 both are thermally stable up to 330 °C. Results from an in situ 1H NMR study of AgNO3 and TDMBim in different molar ratios unambiguously revealed the successive self-organization process, in which self-organization of the molecular cage takes place initially followed by crystallization of the corresponding supramolecular arrays with silver metal strings.