Abstract
Two new Rdpt ligands featuring long "tails"; padpt (N-4H-1,2,4-triazole-3,5-di(2-pyridyl)palmitamide) and hpdpt (4-(4-heptadecafluoroctylphenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole), were made and reacted with [Fe-II(py)(4)(NCS)(2)] to give pinkish-red [Fe-II(padpt)(2)(SCN)(2)] (1) and purple-red [Fe-II(hpdpt)(2)(SCN)(2)] (2) as solvent-free crystals. Magnetic measurements reveal that both 1 and 2 exhibit complete and reproducible spin crossovers, with a far lower T-1/2 for the amide-alkyl tailed 1 (182 K) than for the fluorocarbon tailed 2 (248 K), which in turn is far lower than the T-1/2 of 290 K previously reported for the nonamide-alkyl tailed analogue.[Fe-II(C(16)dpt)(2)(SCN)(2)]center dot 2/3H(2)O (3). Structure determinations for 1 and 2 in both the high spin (HS) and low spin (LS) states confirm the expected trans-NCS conformation and reveal that.(a) the "tails" interdigitate and (b) the LS forms are less distorted than the HS forms (Sigma = 58=70 degrees vs 47-54 degrees). DSC and Raman spectroscopy confirmed the high tail-dependence of the SCO events in 1 and 2, as well as in 3, with the Raman data giving T-1/2 values of 190, 243, and 285 K, respectively. Bright orange single crystals of the solvatomorph [Fe-II(hpdpt)(2)(SCN)(2)]center dot MeOH center dot H2O (2(solv)) were also structurally and magnetically characterized and, in Contrast to 2, found to remain HS down to 4 K, providing further evidence of the huge impact of crystal packing on SCO. Both 1 and 2 form stable Langmuir films at an air-water interface, a single layer of Which can be transferred to a solid support.