In situ hydrothermal synthesis of tetrazole coordination polymers with interesting physical properties

Tetrazole compounds have been studied for more than one hundred years and applied in various areas. Several years ago Sharpless and his co-workers reported an environmentally friendly process for the preparation of 5-substituted 1H-tetrazoles in water with zinc salt as catalysts. To reveal the exact role of the zinc salt in this reaction, a series of hydrothermal reactions aimed at trapping and characterizing the solid intermediates were investigated. This study allowed us to obtain a myriad interesting metal-organic coordination polymers that not only partially showed the role of the metal species in the synthesis of tetrazole compounds but also provided a class of complexes displaying interesting chemical and physical properties such as second harmonic generation (SHG), fluorescence, ferroelectric and dielectric behaviors. In this tutorial review, we will mainly focus on tetrazole coordination compounds synthesized by in situ hydrothermal methods. First, we will discuss the synthesis and crystal structures of these compounds. Their various properties will be mentioned and we will show the applications of tetrazole coordination compounds in organic synthesis. Finally, we will outline some expectations in this area of chemistry. The direct coordination chemistry of tetrazoles to metal ions and in situ synthesis of tetrazole through cycloaddition between organotin azide and organic cyano group will be not discussed in this review.