Multifunctional Properties of a 1D Helical Co(II) Coordination Polymer: Toward Single-Ion Magnetic Behavior and Efficient Dye Degradation

This contribution deals with the synthesis and utilization of a new pyrazole-based unsymmetrical ligand, 3-(3-carboxyphenyl)-1H-pyrazole-5-carboxylic acid (H2CPCA), for generating multifunctional materials. The reaction with the Co­(II) salt in the presence of a co-ligand 2,9-dimethyl phenanthroline (dmphen) results in the formation of the helical compound {[Co2(dmphen)2(CPCA)2]­DMF}n (1). However, two isostructural monomeric complexes are formed {[M­(HCPCA)2(H2O)2], M = Co­(II), (2) and Mn­(II) (3)} when reactions were carried out in the absence of dmphen. Compound 1 shows some highly encouraging single-ion magnetic (SIM) properties. Detailed magnetic studies unveil slow relaxation of magnetization of compound 1, driven by the higher magnetic anisotropy of the cobalt ion, with the energy barrier of ∼9.2 K and relaxation time of 9.1 × 10–5 s, suggesting a SIM behavior. Moreover, UV–vis and fluorescence studies confirm the selective dye degradation of compound 1 with methylene blue both in the presence and absence of H2O2, with the remarkable degradation efficiency of ∼98 and ∼82%, respectively.