Fluorescence emission was investigated in a series of Ba2−xEuxSi5N8 compounds. Two maxima corresponding to the two crystallographic Eu2+ sites are observed. Excitation with intense laser light at 1.047μm reveals strong fluorescence emission at ∼600nm due to two-photon-excitation. In Ba1.89Eu0.11Si5N8 the long lasting luminescence was studied. The emission peaking at about 590nm has been observed in the dark with the naked eye even 15min after removal of the activating lamp. This effect is due to the recombination of holes and traps consisting of nitrogen vacancies formed by reducing synthesis conditions. The maximum emission was observed at −7°C

The hydrothermal reaction of M(NO₃)₂·4H₂O (M = Zn and Cd) with benzene-1,4-dicarboxylic acid (H₂bdc) or benzene-1,3-dicarboxylic acid (H₂ip) and 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) produced the mixed-ligand coordination polymers (MOFs) ³ _∞{[Zn₂(μ₂-bdc)₂(μ₄-btre)]} (1), ³ _∞{[Cd₂(μ₄-bdc)(μ₄-btre)₂](NO₃)₂·H₂O} (2) and ² _∞{[Zn₂(μ₃-ip)₂(μ₂-btre)(H₂O)₂]·2H₂O} (3). The compounds, characterized by single-crystal X-ray diffraction, X-ray powder diffraction, solid-state cross-polarization (CP) magic-angle-spinning (MAS) ¹³C NMR and thermoanalysis, feature 3D metal–organic frameworks for 1 and 2 and 2D double layers which are connected through hydrogen bonds from the aqua ligands for 3. The CPMAS ¹³C NMR spectra picture the symmetry-independent (unique) C atoms and the bdc/ip-to-btre ligand ratio in agreement with the crystal structures. The zinc and cadmium coordination polymers 1–3 show a strong bluish fluorescence upon excitation with UV light (the free btre ligand is non-luminescent).