resumo
A new synthesis of a tetrahedral tecton, tetrakis(4-methoxyphenyl)methane, is reported. This compound exhibits a strong fluorescence around 340 nm at room temperature, both in solution and in the solid state. Upon crystallization, another luminescence band can be observed around 500 nm, attributed to phosphorescence. A study of the single-crystal structure of the compound provided a rationalization of this crystallization induced phosphorescence. The crystal of tetrakis(4-methoxyphenyl)methane belongs to the tetragonal space group P (4) over bar2(1)c, and the structural analysis revealed a close packing of the molecules, with no void space and no solvent molecules in the crystal. The molecules are held together in a columnar array via multiple C-H center dot center dot center dot pi it hydrogen bonds. The hydrogen bonds between the molecules impede the torsional vibrations of the aromatic rings, preventing thermal relaxation from the triplet state, and hence promoting phosphorescence at room temperature. (C) 2013 Elsevier Ltd. All rights reserved.
palavras-chave
HYDROGEN-BONDED NETWORKS; MOLECULAR TECTONICS; TETRAPHENYLMETHANE; TETRAPHENYLSILANE; EMISSION; SYMMETRY; SYNTHON
categoria
Chemistry
autores
Guieu, S; Rocha, J; Silva, AMS
nossos autores
João Rocha
Prof. Catedrático
Samuel Jacques André Guieu
Investigador Júnioragradecimentos
Thanks are due to the University of Aveiro and the Portuguese Fundacao para a Ciencia e a Tecnologia (FCT) for funding the Organic Chemistry Research Unit (project PEst-C/QUI/UI0062/2011), the CICECO Associate Laboratory (PEst-C/CTM/LA0011/2011) and the Portuguese National NMR Network (RNRMN). The authors thank R. A. S. Ferreira for the PL measurements and P. Brandao for her help for the XRD. S.G. also thanks the FCT for a postdoctoral grant (SFRH/BPD/70702/2010).