RESUMO
The infrared spectra, elemental and thermal (TG/DTG and DTA) analyses of novel [Zn(cyclen-κ4N1,4,7,10)(HGly-κ2O,O')](ClO4)2 (1), and [Zn2(cyclen-κ4N1,4,7,10)2(µ-S-Ala-κ2N,O)](ClO4)(3)·2H2O (2) complexes (cyclen - 1,4,7,10-tetraazacyclododecane) were recorded and analyzed in the relation to their structural peculiarities. IR spectral data indicate both mono- or bidentate coordination mode of a carboxylate group in the prepared complexes (at pH≈9). The results indicate unusual bidentate carboxylate coordination mode (in complex (1)) toward to Zn2+-cyclen unit. Therefore the crystal structure determination of the crystalline complex [Zn(cyclen-κ4N1,4,7,10)(NO3-κ2O,O')](NO3) was attached in order to support the coordination mode assignment in complex (1).
Assuntos
Alanina/química , Glicina/química , Compostos Heterocíclicos/química , Zinco/química , Absorção , Ciclamos , Modelos Moleculares , Espectrofotometria Infravermelho , TemperaturaRESUMO
Potentiometric titrations and (1) H NMR spectroscopic studies of amino acids binding to the [ZnL](2+) -complex where L=cyclen in aqueous solution provide information concerning complexing species identity, their stability, and coordination mode declaration. The amino acids form stable ternary [ZnL(HL(n))](2+) and [ZnL(L(n))](+) complexes. The observations indicate bidentate coordination mode of the deprotonated amino acids, involving both the amine and the carboxylate functions to the [ZnL](2+) complex in pH region of about 7.5-9.5. The determined stability constants indicate that [ZnL](2+) complex is a very efficient receptor for simple amino acids such as glycine and alanine.