Crystal Structure, Solid‐State NMR Spectroscopic and Photoluminescence Studies of Organic‐Inorganic Hybrid Materials (HL) 6 [Ge 6 (OH) 6 (hedp) 6 ]·2(L)· n H 2 O, L = hqn or phen

Two germanium–hedp 4– solids with heteroaromatic amines 8‐hydroxyquinoline (hqn) and 1,10‐phenanthroline (phen), (HL) 6 [Ge 6 (OH) 6 (hedp) 6 ] · 2(L) · n H 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 1 H‐ 1 H DQF and 1 H‐ 1 H RFDR MAS NMR) and combined rotation and multiple‐pulse spectroscopy (two‐dimensional 1 H‐ 1 H FS‐LG, 1 H‐ 31 P FS‐LG). The fine details of the crystal structure of I have been elucidated, mainly those involving the π–π stacking of 8‐hydroxyquinoline and the relative orientation of adjacent such molecules. Compound II exhibits an emission from the lowest triplet‐state energy (π–π* 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 π–π phenanthroline and hydroxyquinoline interactions, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)