Syntheses, crystal structures, and luminescence of two main-group metal complexes based on 3,4-pyrazoledicarboxylic acid

Abstract

Two new metal complexes, [Pb(H2pdc)2(H2O)] · 2H2O (1) and [Sr2(H2pdc)4(H2O)8] · 2H2O (2) (H3pdc = 3,4-pyrazoledicarboxylic acid), have been synthesized and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. In 1, the geometry of Pb(II) is hemidirected and the 6s2 lone electron pair on Pb(II) is stereochemically active, resulting in the formation of a secondary Pb ··· O bond. The weak Pb ··· O interactions, π–π stacking, and hydrogen-bonding interactions construct 1 into a 3-D framework with 1-D channels. Complex 2 is a dinuclear structure, which is further assembled to a 3-D supramolecular network through intermolecular hydrogen bonds and π–π stacking. Three coordination modes of 3,4-pyrazoledicarboxylic acid were observed. The thermal and photoluminescent properties of 1 and 2 in the solid state have also been investigated.