Spin-Crossover Dendrimers: Generation Number-Dependent Cooperativity for Thermal Spin Transition
- 26 March 2005
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 127 (15), 5484-5489
- https://doi.org/10.1021/ja050275k
Abstract
Poly(benzyl ether) dendrons having a focal triazole unit (Gntrz: trz = triazole; n = generation number = 0−2) were found to react with (MeSO3)2Fe to form dendritic coordination polymers ([Fe(Gntrz)3](MeSO3)2·2H2O) that undergo the thermal spin transition. When the generation number of the dendritic unit was larger (n = 0 → 1 → 2), the average degree of polymerization (Dp = 20 → 10 → 3) and spin-crossover temperature (Tc = 335 → 315 → 300 K) of the resulting polymer were lower. However, the abruptness of the spin transition was not monotonically dependent on the generation number; (G1trz)Fe exhibited an abrupt spin transition with a temperature width of only 10 K, while the smallest and largest members of the (Gntrz)Fe family both displayed a rather broad spin-transition temperature width (30 (n = 0) and 50 K (n = 2)). X-ray diffraction and calorimetric analyses indicated the presence of a discotic columnar core−shell assembly with a crystal lattice best occupied by a C3v symmetric array of medium-sized (G1trz)Fe.Keywords
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