Spatially Resolved Investigation and Control of the Bistability in Single Crystals of the [Fe(bbpya) (NCS)2] Spin Crossover Complex

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• 作者：Edna M. Hernández ; Sipeng Zheng ; Helena J. Shepherd ; Dmitry S. Yufit ; Karl Ridier ; Salma Bedoui ; William Nicolazzi ; Víctor Velázquez ; Sylvestre Bonnet ; Gábor Molnár ; Azzedine Bousseksou
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 8, 2016
• 年：2016
• 卷：120
• 期：48
• 页码：27608-27617
• 全文大小：523K
• ISSN：1932-7455

文摘

The spin transition in single crystals of the [Fe^II(bbpya) (NCS)₂] (bbpya = N,N-bis(2–2′-bipyrid-6-yl)amine) mononuclear complex was investigated by a combination of X-ray diffraction, Raman spectroscopy, as well as optical and atomic force microscopy (AFM) methods. These studies, performed around 440 K, revealed an extremely abrupt spin transition associated with a structural phase transition from a triclinic (low spin) to a monoclinic (mixed low spin/high spin) structure. Spatially resolved observations of this transition evidenced a clear phase separation associated with heterogeneous nucleation and the formation of a moving macroscopic interface whose velocity reached in some cases 300 μm s^–1. Using photothermal control it was possible to stabilize biphasic states of the crystal and then acquire AFM images of the phase boundary. A “sawtooth” like topography was repeatedly observed, which most likely emerges so as to minimize the elastic strain. Remarkably, a fine spatial control of the phase boundary could be also achieved using the AFM probe itself, through probe–sample convective heat exchange.