Rational design of efficient nanosensor for glyphosate and temperature out of terbium complexes with 1,3-diketone calix[4]arenes

The temperature and substrate dependent luminescence of terbium complexes with calix[4]arene derivatives makes them promising building blocks of nanosensors. Thus, calix[4]arene 1,3-diketones in 1,3-alternate and cone isomeric forms bearing buthyl, dodecyl, nonyl and bromine substituents are introduced as ligands forming luminescent Tb3+ complexes in basified DMF solutions. The structure variation of the ligands allows to highlight buthyl-substituted derivative of calix[4]arene 1,3-diketone in 1,3-alternate isomeric form as the optimal structure. The detailed studies of the complex stoichiometry by means of UV-Vis and H1 NMR diffusion spectroscopy methods reveal 2:2 stoichiometry as the main for the calix[4]arene 1,3-diketones in 1,3-alternate isomeric form. The predominance of 2:2 over 1:1 and 1:2 (Tb:L) complex stoichiometries for the buthyl-substituted ligand was confirmed by comparison of the quantum chemically calculated thermochemical parameters of their complex formation. However, the 2:2 complex formation is either restricted for their dodecyl-substituted derivative or interferes with the 1:2 stoichiometry for the bromo-substituted counterpart. The conversion of the Tb3+ complexes from the DMF solutions to the PSS-stabilized colloids through the solvent-exchange procedure reveals the unfavorable effect of the nonyl- and dodecyl-substituted ligands on aggregation behavior of the colloids. Thus, 2:2 terbium complex with buthyl-substituted ligand in 1,3-alternate isomeric form is the optimal basis for production of the luminescent PSS-colloids with high colloid stability. The Tb3+- luminescence of the colloids exhibit the enhanced sensitivity to both environmental pollutant glyphosate with LOD = 1.97 nM and temperature changes within the physiological temperature range with SI = −4.67 K-% at 323 K.