resumo
Two germanium-hedp(4-) solids with heteroaromatic amines 8-hydroxyquinoline (hqn) and 1,10-phenanthroline (phen), (HL)(6)[Ge-6(OH)(6)(hedp)(6)]center dot 2(L)-nH(2)O (L = hqn or phen), in I and II respectively, have been prepared and characterised by single-crystal XRD, thermogravimetry, FTIR and UV/Vis spectroscopy. The complex hydrogen-bond networks, particularly in compound I, have been studied by advanced high-resolution solid-state NMR spectroscopy that combines homonuclear recoupling techniques (two-dimensional H-1-H-1 DQF and H-1-H-1 RFDR MAS NMR) and combined rotation and multiple-pulse spectroscopy (two-dimensional H-1-H-1 FSLG, H-1-P-31 FS-LG). The fine details of the crystal structure of I have been elucidated, mainly those involving the pi-pi stacking of 8-hydroxyquinoline and the relative orientation of adjacent such molecules. Compound II exhibits an emission from the lowest triplet-state energy (pi-pi* 0-phonon transition) of the aromatic rings at 320 nm (31250 cm(-1)) from 14 K to room temperature. In contrast, the triplet emission of I at 530 nm (18868 cm(-1)) is only detected at low temperature, because of thermally activated non-radiative mechanisms. The emission spectra of I and II display a lower-energy component with a larger life time, which results from the formation of an excimer state that originated from the pi-pi phenanthroline and hydroxyquinoline interactions, respectively. (c) Wiley-VCH Verlag GmbH & Co.
palavras-chave
NUCLEAR-MAGNETIC-RESONANCE; SECONDARY BUILDING UNITS; H-1-NMR SPECTROSCOPY; MOLECULAR-STRUCTURE; ROTATING SOLIDS; FRAMEWORKS; COMPLEXES; EXCHANGE; ACID; DIFFRACTION
categoria
Chemistry
autores
Mafra, L; Paz, FAA; Shi, FN; Ferreira, RAS; Carlos, LD; Trindade, T; Fernandez, C; Klinowski, J; Rocha, J
nossos autores
Fa-Nian Shi
Investigador
Filipe Alexandre Almeida Paz
Investigador Principal
João Rocha
Prof. Catedrático
Luís Carlos
Professor Catedrático
Luís Mafra
Investigador Principal
Maria Rute de Amorim e Sá Ferreira André
Professor Catedrático