Porous polymer networks cross-linked by novel copper Schiff base complex: From synthesis to catalytic activity

Abstract

A new ethynylated Schiff base complex, [Cu(SALANI)2], in which two N-salicylidene(3-ethynylaniline) (SALANI) ligands coordinated one Cu2+ ion, was prepared and characterized by single-crystal X-ray diffraction, FTIR and 1H NMR spectroscopy. The 1H NMR spectra were obtained and interpreted (with the help of DFT calculation) despite the paramagnetic character of the [Cu(SALANI)2] complex. Chain-growth copolymerization of [Cu(SALANI)2] with 4,4′-diethynylbiphenyl and 1,4-diethynylbenzene provided polyacetylene-type micro/mesoporous organometallic networks with [Cu(N-salicylideneaniline)2] segments as network knots. Networks of this type were also prepared by postpolymerization metalation of polyacetylene networks containing N-salicylideneaniline segments as pendant groups. Postpolymerization metalation (leading to further cross-linking) enabled to transform nonporous parent networks into organometallic networks with permanent porosity. The new porous organometallic networks showed a specific surface area from 400 to 700 m2/g and a Cu2+ content of about 6 wt%. The networks prepared by both prepolymerization and postpolymerization metalation were active as heterogeneous catalysts of oxidation of linalool to linalool oxide.