Rhenium(I)-Pterin water-soluble complex: Synthesis and structural characterization. Two reversible protonation-deprotonation behavior in aqueous solutions.

F. RAGONE; G. T. RUIZ*; O. E. PIRO; G. A. ECHEVERRÍA; F. M. CABRERIZO; G. PETROSELLI; R. ERRA-BALSELLS; K. HIRAOKA; F. GARCÍA EINSCHLAG; E. WOLCAN*

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2012 p. 4801 - 4810

1434-1948

A new water soluble complex, Re(CO)3(pterin)(H2O), was synthesized and characterized by 1H NMR, FTIR, and by a combination of three mass spectrometry techniques: MALDI, PESI and ESI. Due to the fact that, unlike most of the metal-pterin complexes, the Re(I) complex is quite soluble in water, appropriate single crystals could be obtained for structural X-ray analysis. We report here the first solid state molecular structure containing a pterin ligand coordinated to the ‒Re(CO)3 core. This determination revealed that strong H-bonds between the hydrogen of the 2-amino group and crystallization water molecules give rise to a polymeric arrangement Re(CO)3(pterin)(H2O) complexes in the lattice. Protonation studies in aqueous solutions of the Re(I) complex showed two acid-base equilibriums with pKa1 = 3.9 and pKa2 = 8.8. pKa1 was assigned to the protonation equilibrium at N3 of pterin ligand in the complex and pKa2 could be ascribed to deprotonation of coordinated water molecule.