Syntheses, structures, and properties of two new hybrid Dawson-based polyoxotungstates [Mn(2,2′-bipy)₃]H₂ [Mn(2,2′-bipy)₂][P₂W₁₈O₆₂] and [Co(H₂biim)₃)]₂H₂[P₂W₁₈O₆₂] · 8H₂O

Abstract

Two new hybrid Dawson-based polyoxotungstates, [Mn(2,2′-bipy)₃]H₂[Mn(2,2′-bipy)₂][P₂W₁₈O₆₂] (1) and [Co(H₂biim)₃)]₂H₂[P₂W₁₈O₆₂] · 8H₂O (2) (2,2′-bipy = 2,2′-bipyridine, H₂biim = 2,2′-biimdazole), have been prepared under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric analyses (TGA), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectra. Compound 1 is a 1-D zigzag chain constructed from alternate Dawson-type heteropolyanions [α-P₂W₁₈O₆₂]⁶⁻ and metal coordination cations [Mn(2,2′-bipy)₂]²⁺, in which the 1-D chains are extended into a 3-D framework through C–H ··· π and π–π stacking interactions. Compound 2 is a discrete structure consisting of [α-P₂W₁₈O₆₂]⁶⁻ and two [Co(H₂biim)₃)]²⁺ cations, forming a 3-D supramolecular framework via N–H ··· O hydrogen bonds and C–H ··· π interactions. Photoluminescence properties of 1 and 2 have been investigated at room temperature.

Keywords:

• Polyoxometalates
• Biimdazole
• Polyoxotungstate
• Dawson structure

Acknowledgments

We thank the National Natural Science Foundation of China, the Natural Science Foundation of Henan Province and Foundation of Education Department of Henan Province for financial support.