Two‐Step Spin Transition in a 1D FeII 1,2,4‐Triazole Chain Compound |
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| Authors: | Dr Marinela M Dîrtu France Schmit Dr Anil D Naik Dr Ionela Rusu Prof?Dr Aurelian Rotaru Sergej Rackwitz Dr Juliusz A Wolny Prof?Dr Volker Schünemann Prof?Dr Leonard Spinu Prof?Dr Yann Garcia |
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| Institution: | 1. Institute of Condensed Matter and Nanosciences, Molecules, Solids, Reactivity (IMCN/MOST), Université Catholique de Louvain, Place Louis Pasteur 1, 1348, Louvain‐la‐Neuve (Belgium);2. Faculty of Electrical Engineering and Computer Science, and AMNOL, Stefan cel Mare University, Str. Universitatii, No. 13, Suceava 720229 (Romania);3. Faculty of Physics, University of Kaiserslautern, 67663 Kaiserslautern (Germany);4. Advanced Materials Research Institute, and Department of Physics, University of New Orleans, New Orleans, Louisiana 70148 (USA) |
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| Abstract: | A thermochromic 1D spin crossover coordination (SCO) polymer Fe(βAlatrz)3](BF4)2 ? 2 H2O ( 1? 2 H2O), whose precursor βAlatrz, (1,2,4‐triazol‐4‐yl‐propionate) has been tailored from a β‐amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), 57Fe Mössbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two‐step spin crossover (T1/2↓=230 K and T1/2↑=235 K, and T1/2↓=172 K and T1/2↑=188 K, respectively) is registered for the first time for a 1,2,4‐triazole‐based FeII 1D coordination polymer. The two‐step SCO configuration is observed in a 1:2 ratio of low‐spin/high‐spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1? 2 H2O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low‐spin and high‐spin states of 1? 2 H2O. Vibrational spectra of 1? 2 H2O reveal that the BF4? anions and water molecules play no significant role on the vibrational properties of the Fe(βAlatrz)3]2+ polymeric chains, although non‐coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material Fe(βAlatrz)3](BF4)2 ( 1 ) reveals indeed a significantly different magnetic behavior with a one‐step SCO which was also investigated. |
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| Keywords: | coordination polymers density functional calculations magnetic properties spin crossover vibrational spectroscopy |
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