New heterospin chain-polymers based on Cu(hfac)2 complex with TEMPO derivatives bearing β-(oxy)acrylate moiety: Synthesis, structural and magnetic properties.

Hitherto unknown 4-substituted TEMPO derivatives bearing β-(oxy)acrylate moiety have been synthesized via nucleophilic addition of 4-hydroxy-TEMPO to methyl and ethyl propiolate, respectively. The reaction of these radicals (L) with Cu(hfac) 2 produces heterospin chain-polymers [Cu(hfac) 2 L] n , which contain alternating { N – · O–Cu–O – · N } and { C O–Cu–O C } fragments. The magnetic behavior of these coordination polymers have been studied using SQUID magnetometry to reveal that the complex based on 4-[ E -(3-methoxy-3-oxoprop-1-en-1-yl)oxy]-TEMPO does not show significant exchange interactions between the spins of the Cu 2+ ion and the nitroxides. By contrast, complex with 4-[ E -(3-ethoxy-3-oxoprop-1-en-1-yl)oxy]-TEMPO features ferromagnetic exchange interaction between the paramagnetic centers. [ABSTRACT FROM AUTHOR]