Dy(III) complexes of metformin Schiff-bases as glucose probe: synthesis, spectral, and thermal properties

Complexes of Dy3+ with metformin-Schiff-bases of salicylaldehyde (HL1); 2,3-dihydroxybenzaldehyde (H2L2); 2,4-dihydroxybenzaldehyde (H2L3); 2,5-dihydroxybenzaldehyde (H2L4); 3,4-dihydroxybenzaldehyde (H2L5); and 2-hydroxynaphthaldehyde (HL6) were synthesized by template reactions. The new compounds were characterized through elemental analysis, conductivity and magnetic moment measurements, IR, UV–vis, fluorescence, GC–MS, and XRD spectroscopies. The complexes are seven coordinate with formulas [DyL1–4,6(NO3)2(H2O)2]·nH2O where n = 2, 2½, 4, 2, 2 and [DyL5(NO3)(H2O)4]·2H2O. TGA, DTG, and DTA analyses confirmed the suggested stereochemistry and subsequently the proposed mechanism of thermal decomposition. Kinetic and thermodynamic parameters were calculated for the second decomposition step. Thus, we report the ability of using the prepared complexes in the detection of glucose at physiological conditions using UV–vis and fluorescence spectroscopy as well as viscosity measurements, where the association constants were calculated.