A Two‐Dimensional Iron(II) Coordination Polymer with Synergetic Spin‐Crossover and Luminescent Properties

• Published in: Angewandte Chemie International Edition Vol. 58; no. 26; pp. 8789 - 8793
• Main Authors: Ge, Jing‐Yuan, Chen, Zhongyan, Zhang, Li, Liang, Xiao, Su, Jian, Kurmoo, Mohamedally, Zuo, Jing‐Lin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 24.06.2019
• Edition: International ed. in English
• Subjects: Composite materials; Coordination polymers; Crossovers; Crystal structure; Crystals; Energy transfer; Ethene; Ethylene; Fluorescence; Hysteresis; Iron; luminescence; multifunctional materials; Optical properties; Polymer matrix composites; spin crossover; coordination polymers; iron; luminescence; multifunctional materials; spin crossover
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201903281

A composite material, {[Fe(L)(TPPE)0.5]⋅3 CH3OH}n, has been constructed by integrating the spin‐crossover (SCO) subunit FeII{diethyl(E,E)‐2,2′‐[1,2‐phenyl‐bis(iminomethylidyne)]bis(3‐oxobutanoate)‐(2‐)‐N,N′,O3,O3′} and the highly luminescent connector 1,1,2,2‐tetrakis(4‐(pyridin‐4‐yl)phenyl)‐ethene. Its structure contains four staggered 4×4 layers and intercalated methanol. The packing is dominated by considerable H‐bonds either between adjacent layers and between layers and guests. A crystal‐structure transformation was detected upon removal of the guest molecules. The SCO transition of the solvated crystals is centered at ca. 215 K with a non‐symmetrical hysteresis of 25 K wide, and the desolvated [Fe(L)(TPPE)0.5]n exhibits gradual SCO without hysteresis. Intriguingly, the intensity of the fluorescence at 460 nm for the latter is maximized at the SCO transition. The energy transfer between luminescent and SCO entities is achievable as confirmed by theoretical calculations. A square‐grid layered FeII coordination polymer based on a luminophore connector TPPE was studied. This framework not only features a solvent‐dependent structure and spin crossover (SCO) behavior, but also exhibits a switch between spin transition and fluorescence for the guest‐free species. Theoretical calculation reveals an energy‐transfer mechanism.