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.

Keywords:

• Lead(II)
• Strontium(II)
• 3,4-pyrazoledicarboxylic acid
• Crystal structure
• Photoluminescence

Acknowledgments

The authors thank the Natural Science Foundation of China (Nos 20671045, 20971060, and 21101018), the Natural Science Foundation of State Key Laboratory of Coordination Chemistry, and the International Science and Technology Cooperation Project of Changzhou city (CZ20110023) for the financial support.