Solid-state NMR and EPR studies applied to the coordination behavior of Cu(II) ions in polymeric materials containing carboxylic acid and imidazole, triazole or pyrazole

JUAN MANUEL LÁZARO MARTÍNEZ; GRACIELA YOLANDA BULDAIN; GUSTAVO ALBERTO MONTI; ANA KARINA CHATTAH

Copper Mountain, Colorado

Conferencia; 54th Rocky Mountain Conference on Analytical Chemistry; 2012

Amercian Chemical Society

The development of polymers containing nitrogen as donor atoms is particularly important due to the generation of transition metal coordination polymers with relevance in the coordination chemistry of materials1 and environmental applications.2 In the present study, the copper ion coordination behavior of the carboxylic acid units, compared to that provided by the azole ligands (imidazole, triazole and pyrazole units) attached to the same polymer backbone, was studied through solid-state NMR and EPR techniques. From the comparison of the different 13C CP-MAS spectra of each material at different levels of Cu(II) ion adsorbed, we concluded that a competence for the complexation through the azole and carboxylic acid ligands occurs. Then, when the azole units are saturated, the complexation takes place preferentially through the carboxylic acid ligands, in the case of the triazole and imidazole. However, in the materials bearing pyrazole units, the coordination of copper ions is preferentially through the carboxylic acid ligands. In addition, the EPR results showed that in Cu(II)-polymer complexes containing only carboxylic acid or imidazole units as ligands the A// and g// values were 132 G/2.354 and 158 G/2.317 respectively. In the Cu(II)-polymer complexes containing both carboxylic acid and azole units (imidazole and triazole) the g// values increased and the A// values decreased when oxygen replace nitrogen in the coordination process as the level of the copper ion adsorbed increase. Finally, the non-homogenous character of the dopped and undopped materials was analyzed by the 2D 1H-13C WISE NMR, proton and carbon spin-lattice relaxation times in the rotating frame (T1_rho_H and T1_rho_C). 1.Lázaro-Martínez et al., Polymer, 2008, 49, 5485; Polymer, 2012, 53, 1288. 2.Lázaro-Martínez et al., Appl. Catal., B, 2008, 82, 273; J. Mol. Catal. A: Chem., 2010, 328, 88.