Solid-state NMR applied to the characterization of chemical compounds and polymer materials

JUAN MANUEL LÁZARO MARTÍNEZ; ANA KARINA CHATTAH; GUSTAVO ALBERTO MONTI; VIVIANA CAMPO DALL´ORTO; GRACIELA YOLANDA BULDAIN

Córdoba, Argentina

Workshop; Bruker Solid State NMR Workshop 2009; 2009

Bruker BioSpin GmbH y la Facultad de Matemática, Astronomía y Física (UNC)

New 2-substituted imidazole derivates bearing coordination groups have been synthesized from the imidazole-2-carboxaldehyde (1) as started material, prepared from inexpensive and commercially available bulk chemicals following an improvement of the synthetic route reported by Godefroid et al [1]. The structure of 1 was studied using solution (13C) and solid-state Nuclear Magnetic Resonance experiments. In particular high resolution 13C spectrum obtained with cross-polarization and magic angle spinning (CP-MAS), a quaternary carbon edition technique (NQS) and 1H-13C heteronuclear correlation spectrum (HETCOR) were used. The results allowed to concluded that at pH = 8.0 the hydrate-form (2a) was stable and precipitated, however, the aldehyde-form 2 was isolated at 6.5 > pH > 9.0. FTIR experiments supported our conclusions. The tautomeric forms of the 2-substituted imidazole compounds were also analyzed by 13C NMR using liquid- and solid-state spectra. Moreover, novel solid copper (II) complexes were obtained from the polyampholyte Poly(EGDE-MAA-IM) and the polyelectrolyte Poly(EGDE-MAA) polymers with copper salts at different concentration levels [2]. The coordination behavior of the carboxylic acid of the MAA, compared to that provided by the imidazole ring, was studied through solid-state 13C NMR and changes in the FTIR spectra. The non-homogenous character of the doped and undoped materials was analyzed by the glass transition temperature (Tg), 2D 1H-13C WISE NMR and proton spin-lattice relaxation time in the rotating frame (TH1rho). In particular, the TH1rho and TH1 values in the complexes decreased with the Cu(II) concentration, showing the high sensitivity of both parameters to the presence of a paramagnetic ion. References: [1] L. A. M. Bastiaansen, P. M. Van Lier, E. F. Godefroi. Organic Synthesis 7 (1990) 287-290. [2] J.M. Lázaro Martínez, A.K. Chattah, G.A. Monti, M.F. Leal Denis, G.Y. Buldain, V. Campo Dall´Orto. Polymer 49 (2008) 5482-5489.