Multifunctional gels from polymeric spin-crossover metallo-gelators.

The gelation abilities toward organic solvents of a series of triazole-based coordination polymers of formula [M(C(n)trz)(3)]A(2) (M = Fe(II) or Zn(II); C(n)trz = 4-n-alkyl-1,2,4-triazole with n = 13, 16, 18; A = monovalent anions, abbreviated as MC(n)A) have been studied to form thermally responsive multifunctional metallogels, in particular for the iron polymers that present the spin-crossover phenomenon. Indeed thermo-reversible physical gels exhibiting thermally reversible magnetic and optical crossovers are formed in decane and toluene. The FeC(18)ptol/decane and FeC(18)ptol/toluene phase diagrams are described (ptol = p-toluene sulfonate anion), together with the rheological properties of the gels determined as a function of the solvent, the gelator concentration as well as temperature. Microscopic observations of the gel structure are correlated to the composition and rheological properties of the gels. Magnetic and thermal studies show that both the gel-liquid and spin-crossover phenomena can be adjusted through the composition of the gel mixture.