Terpyridine and 2,6-di(1H-pyrazol-1-yl)pyridine substituted cyclotri- and polyphosphazene ruthenium(II) complexes: Chemical and physical behaviour

Synthesis and Characterization of a One-Dimensional Malleable Spin-Crossover Polymer Complex Modified by Methoxy Polyethylene Glycol

A novel one-dimensional malleable spin-crossover (SCO) complex {[Fe(MPEG-trz)₃](BF₄)₂} has been successfully synthesized by molecular self-assembly between 4-amino-1,2,4-triazoles (MPEG-trz) grafted with a long flexible chain methoxy polyethylene glycol (MPEG) and metallic complex Fe(BF₄)₂•6H₂O. The detailed structure information was illustrated by using FT-IR and ¹H NMR measurements, while the physical behaviors of the malleable SCO complexes were systematically investigated by using magnetic susceptibility measurements using superconductivity quantum interference device (SQUID) and differential scanning calorimetry (DSC). This new metallopolymer exhibits a remarkable spin crossover transition behavior, between two spin quantum states (Fe²⁺ ions): high spin (HS) state (quintet state) and low spin (LS) state (singlet state), at a specific critical temperature with a slender hysteresis loop of 1 K. DFT computations revealed the partial rules of HOMO-LUMO energy levels and spin density distributions of different four-position substituted [Fe(1,2,4-triazole)₃]²⁺ derivatives with different length of repeat units in polymer complexes. This can go a step further to depict the spin and magnetic transition behaviors of SCO polymer complexes. Furthermore, the coordination polymers possess an excellent processability due to an outstanding malleability, which can be easily shaped into a polymer film with spin magnetic switching properties.

Polyphosphazenes: Phosphorus in Inorganic-Organic Polymers

Although the best-known examples of synthetic polymers are derived from carbon-based monomers, there exists another large and growing family of macromolecules based on the chemistry of phosphorus. These are the poly(organophosphazenes): polymers with a backbone of alternating phosphorus and nitrogen atoms and with two organic side groups attached to each phosphorus. The methods of synthesis of these polymers allow access to property combinations not found in all-organic counterparts, and this provides pathways to new materials that are important in biomedical research, energy generation and storage, aerospace materials, and numerous other specialized applications.

The expanding field of polyphosphazene high polymers

The wide variety of accessible poly(organophosphazenes) is a consequence of the unusual macromolecular substitution approach to their synthesis.