Remarkably high-temperature spin transition exhibited by new 2D metal-organic frameworks

Highly stable two-dimensional metal-organic frameworks, (2)(infinity)[FeII (L) 2] (HL = 3-(2-pyridyl)-5-(3-pyridyl)- 1,2,4-triazole (1) and 3-(3-methyl-2-pyridyl)-5-(3-pyridyl)-1,2,4-triazole (2), display well defined two-step spin crossover properties at remarkably high temperatures, namely, T-c1 = 329 K, T-c2 = 501 K for 1 and T-c1 = 351 K, T-c2 = 520 K for 2, which are the highest critical temperatures reported so far.