A three-dimensional Pb-centered coordination framework: crystal structure and electrochemiluminescent property

Rigid, dicarboxylic acid ligand 5-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid (H₃L) has been synthesized and utilized for assembling a metal organic framework [Pb₂(HL)₂]_n through the hydrothermal technique. The target complex has been described by single-crystal X-ray diffraction, powder X-ray diffraction measurement, elemental analysis and infrared spectroscopy, and proved to be a structurally novel 3D complex. The central metal ions Pb(II) of complex 1 are coordinated to the carboxyl oxygen atoms, possessing two different coordination modes, heptacoordination and octacoordination. In the case of topology, complex 1 exhibits a net topological structure of 2,3,9-c with Schläfi symbol of {3·5²}{3²·4⁴·5¹²·6¹⁴·7²·8²}{5}. The optical properties have been undertaken at room temperature, showing attractive luminescence behavior. Moreover, the electrochemiluminescent intensity of complex 1 can reach up to 1056 a.u. and maintain relatively stable after eight cycles, which could further provide ideas for building organic light-emitting diodes (OLEDs) constructed with a more affordable metal center.