Three-Way Crystal-to-Crystal Reversible Transformation and Controlled Spin Switching by a Nonporous Molecular Material

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• 作者：Jos茅 S谩nchez Costa ; Santiago Rodr铆guez-Jim茅nez ; Gavin A. Craig ; Benjamin Barth ; Christine M. Beavers ; Simon J. Teat ; Guillem Arom铆
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：March 12, 2014
• 年：2014
• 卷：136
• 期：10
• 页码：3869-3874
• 全文大小：322K
• 年卷期：v.136,no.10(March 12, 2014)
• ISSN：1520-5126

文摘

Porous materials capable of hosting external molecules are paramount in basic and applied research. Nonporous materials able to incorporate molecules via internal lattice reorganization are however extremely rare since their structural integrity usually does not resist the guest exchange processes. The novel heteroleptic low-spin Fe(II) complex [Fe(bpp)(H₂L)](ClO₄)₂路1.5C₃H₆O (1; bpp = 2,6-bis(pyrazol-3-yl)pyridine, H₂L = 2,6-bis(5-(2-methoxyphenyl)pyrazol-3-yl)pyridine) crystallizes as a compact discrete, nonporous material hosting solvate molecules of acetone. The system is able to extrude one-third of these molecules to lead to [Fe(bpp)(H₂L)](ClO₄)₂路C₃H₆O (2), switching to the high-spin state while experiencing a profound crystallographic change. Compound 2 can be reversed to the original material upon reabsorption of acetone. Single crystal X-ray diffraction experiments on the latter system (1鈥? and on 2 show that these are reversible single-crystal-to-single-crystal (SCSC) transformations. Likewise, complex 2 can replace acetone by MeOH and H₂O to form [Fe(bpp)(H₂L)](ClO₄)₂路1.25MeOH路0.5H₂O (3) through a SCSC process that also implies a switch to the spin state. The 3鈫?b>1 transformation through acetone reabsorption is also demonstrated. Besides the spin switching at room temperature, this series of SCSC transformations causes macroscopic changes in color that can be followed by the naked eye. The reversible exchanges of chemicals are therefore easily sensed at the temperature at which these occur, contrary to what is the case for most of the few existing nonporous spin-based sensors, which feature a large temperature gap between the process monitored and the mechanism of detection.