Crystal structures and solid-state CPMAS 13C NMR correlations in luminescent zinc(II) and cadmium(II) mixed-ligand coordination polymers constructed from 1,2-bis(1,2,4-triazol-4-yl)ethane and benzenedicarboxylate

The hydrothermal reaction of M(NO3)(2)center dot 4H(2)O (M = Zn and Cd) with benzene-1,4-dicarboxylic acid (H(2)bdc) or benzene-1,3-dicarboxylic acid (H(2)ip) and 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) produced the mixed-ligand coordination polymers (MOFs) (3)(infinity){[Zn-2(mu(2)-bdc)(2)(mu(4)-btre)]} (1), (3)(infinity){[Cd-2(mu(4)-bdc)(mu(4)-btre)(2)](NO3)(2)center dot H2O} (2) and (2)(infinity){[Zn-2(mu(3)-ip)(2)(mu(2)-btre)(H2O)(2)]center dot 2H(2)O} (3). The compounds, characterized by single-crystal X-ray diffraction, X-ray powder diffraction, solid-state cross-polarization (CP) magic-angle-spinning (MAS) C-13 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 C-13 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).