Abstract

Three new guanylated cyclophosphazenes G1-G3 have been synthesized through the catalytic guanylation of three different bi, tetra and hexa (p-aminophenoxy)-cyclophosphazenes by using N,N'-diisopropylcarbodiimide as guanylating agent, ZnEt2 as catalyst and dry tetrahydrofuran as solvent. The resulting products have been characterized by H-1, C-13{H-1} and P-31{H-1} NMR spectroscopy. The hexaguanylated cyclophosphazenes exhibit a deep purple colour, unusual for this type of compounds. The electronic structure of these compounds was investigated by carrying out density functional calculations at PBE-D3(BJ)/TZP level of theory. The molecular structural analysis reveals that aromatic rings are stacked and time dependent density functional calculations show that a charge transfer electronic transition occurs between the aromatic rings which absorb light around 500-700 nm. Finally, the catalytic usefulness of guanylated cyclophosphazene compounds G1-G3 has been proven by the preparation of styrene carbonate from the reaction between styrene oxide and carbon dioxide.