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Title: | Bistability in organic magnetic materials: a comparative study of the key differences between hysteretic and non-hysteretic spin transitions in dithiazolyl radicals |
Author: | Vela Llausí, Sergi Reardon, Michael B. Jakobsche, Charles E. Turnbull, Mark M. Ribas Ariño, Jordi Novoa Vide, Juan J. |
Keywords: | Transformacions de fase (Física estadística) Radicals (Química) Phase transformations (Statistical physics) Radicals (Chemistry) |
Issue Date: | 1-Mar-2017 |
Publisher: | Wiley-VCH |
Abstract: | Dithiazolyl (DTA)- based radicals have furnished many examples of organic spin- transition materials, some of them occurring with hysteresis and some others without. Herein, we present a combined computational and experimental study aimed at deciphering the factors controlling the existence or absence of hysteresis by comparing the phase transitions of 4- cyanobenzo- 1,3,2- dithiazolyl and 1,3,5trithia- 2,4,6- triazapentalenyl radicals, which are prototypical examples of non- bistable and bistable spin transitions, respectively. Both materials present low- temperature diamagnetic and high- temperature paramagnetic structures, characterized by dimerized (center dot center dot center dot A-A center dot center dot center dot A-A center dot center dot center dot) n and regular (center dot center dot center dot A center dot center dot center dot A center dot center dot center dot A center dot center dot center dot A center dot center dot center dot) n pi- stacks of radicals, respectively. We show that the regular pi-stacks are not potential energy minima but average structures arising from a dynamic inter-conversion between two degenerate dimerized configurations: (center dot center dot center dot A-A center dot center dot center dot A-A center dot center dot center dot)n <->(-A center dot center dot center dot A-A center dot center dot center dot A-)n. The emergence of this intrastack dynamics upon heating gives rise to a second-order phase transition that is responsible for the change in the dominant magnetic interactions of the system. This suggests that the promotion of a (center dot center dot center dot A-A center dot center dot center dot A-A center dot center dot center dot)n <->(-A center dot center dot center dot A-A center dot center dot center dot A-) n dynamics is a general mechanism for triggering spin transitions in DTA-based materials. Yet, this intra-stack dynamics does not suffice to generate bistability, which also requires a rearrangement of the intermolecular bonds between the pstacks via a first-order phase transition. |
Note: | Versió postprint del document publicat a: https://doi.org/10.1002/chem.201700021 |
It is part of: | Chemistry-A European Journal, 2017, vol. 23, num. 14, p. 3479-3489 |
URI: | http://hdl.handle.net/2445/154513 |
Related resource: | https://doi.org/10.1002/chem.201700021 |
ISSN: | 0947-6539 |
Appears in Collections: | Articles publicats en revistes (Ciència dels Materials i Química Física) |
Files in This Item:
File | Description | Size | Format | |
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678271.pdf | 8.97 MB | Adobe PDF | View/Open |
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