COORDINATION CHEMISTRY IN PYRIDINE AND IMIDAZOLE COMPOUNDS CONTAINING GEM-DIOL MOIETIES: SOLID-STATE NMR AND X-RAY STUDIES

GARRO-LINCK, YAMILA; LÁZARO MARTÍNEZ, JUAN MANUEL; VEGA, DANIEL; CRESPI, AYELÉN FLORENCIA; CAMPO DALL'ORTO, VIVIANA

Edimburgo

Conferencia; 5th International Conference on Physical and Theoretical Chemistry; 2018

J. Phys Chem Biophys

The need for clean technology either for fine chemistry or for wastetreatment leads to the replacement of traditional inorganic oxidantssuch as K2Cr2O7 and KMnO4 by benign, easy-to-handle oxidants, suchas H2O2 and O2. The activation of H2O2 can be achieved by transitionmetalion complexes with organic ligands. Particularly, H2O2 canproduce OH? via the Cu(II)/Cu(I) cycle involving different reactionpathways.1-3 Understanding the chemistry of gem-diols is crucial for thedevelopment of synthetic methods to obtain new organic ligands, whichare often used for the design of metal complexes with catalyticactivity.4-6 A high number of metal complexes bearing gem-diols hasbeen reported, in which the presence of these moieties is generallydemonstrated by single-crystal X-ray diffraction. As a rule, the stabilityof this functional group is not studied in the free ligand before thepreparation of the metal complex. In this context, solid-state NMR (ss-NMR) is a useful methodology to elucidate the chemical composition ofmixtures in which both gem-diol and carbonyl forms are present incases where the single-crystal X-ray cannot be obtained (Fig. 1).Additionally, the 1H-MAS ss-NMR spectra (@60 kHz) can also bringstructural information about the ligands surrounding the paramagneticcenter (Fig .1).To have an insight into the chemistry of gem?diol compounds, the aimof this work was to study the gem-diol generation and coppercoordination properties in imidazole- and pyridinecarboxaldehydesthrough the combination of ss-NMR and single-crystal X-ray diffractiontechniques.5,6 Complementary analyses were performed by solutionstateNMR, high-resolution mass spectrometry (HRMS), and 1H ss-NMR.These studies allow us to expand the chemistry in metal complexes interms of structural diversity of the ligands at the same time that newCu(II)-homogenous catalyst towards the activation of H2O2 will beexplored.