Iron(II) Spin-Transition Complexes with Dendritic Ligands, Part II

The dendritic triazole-based complexes [Fe(G1-BOC)(3)](triflate)(2)center dot xH(2)O (1; G1-BOC = tert-butyl P{3-[3-(3-tert-butoxycarbonylaminopropyl)-5-{[1,2,4]triazol-4-ylcarbamoyl)- phenyl]propyl}carbamate, triflate = CF3SO3-), [Fe(G1-BOC)(3)]-(tosylate)(2)center dot xH(2)O (2; tosylate= p-CH3PhSO3-), [Fe(G1-DPBE)(3)]-(triflate)(2)center dot xH(2)O (3; G1-DPBE = 3,5-bis(3,5-didodecaoxy-benzyloxy)-N-[1,2,4]triazol-4-ylbenzamide}, [Fe(G1-DPBE)(3)]-(tosylate)(2)center dot xH(2)O (4) and [Fe(G1-DPBE)(3)](BF4)(2)center dot xH(2)O (5) were designed and synthesized. Magnetic and thermal properties of these novel complexes were characterized by magnetic susceptibility measurements, Fe-57 Mossbauer spectroscopy and thermogravimetric analysis or differential scanning calorimetry, respectively. All dendritic complexes under study show different spin-transition behaviour with respect to the nature of different dendritic ligands and counteranions. Complexes 1 and 2 have pronounced effects of a spin-state change during the first heating process and gradual spin-transition properties for further temperature treatments, whereas 3 and 4 exhibited a very sharp spin-state change in the first heating procedures. Complex 5 showed a gradual spin-transition curve. In this paper, we report how the magnetic properties of these complexes are correlated with noncoordinated water molecules and their effects on spin states.