Modulation of Electronics and Thermal Stabilities of Photochromic Phosphino鈥揂minoazobenzene Derivatives in Weak-Link Approach Coordination Complexes

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• 作者：Jung Su Park ; Alejo M. Lifschitz ; Ryan M. Young ; Jose Mendez-Arroyo ; Michael R. Wasielewski ; Charlotte L. Stern ; Chad A. Mirkin
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：November 13, 2013
• 年：2013
• 卷：135
• 期：45
• 页码：16988-16996
• 全文大小：432K
• 年卷期：v.135,no.45(November 13, 2013)
• ISSN：1520-5126

文摘

A series of d⁸ transition-metal (Pt(II) and Pd(II)) coordination complexes incorporating phosphine-functionalized aminoazobenzene derivatives as hemilabile phosphino鈥揳mine (P,N) ligands were synthesized and studied as model weak-link approach (WLA) photoresponsive constructs. The optical and photochemical properties of these complexes were found to be highly influenced by various tunable parameters in WLA systems, which include type of metal, coordination mode, type of ancillary ligand, solvent, and outer-sphere counteranions. In dichloromethane, reversible chelation and partial displacement of the P,N coordinating moieties allow for toggling between aminoazobenzene- or pseudostilbene- and azobenzene-type derivatives. The reversible switching between electronic states of azobenzene can be controlled through either addition or extraction of chloride counterions and is readily visualized in the separation between 蟺鈥撓€* and n鈭捪€* bands in the complexes鈥?electronic spectra. In acetonitrile solution, the WLA variables inherent to semiopen complexes have a significant impact on the half-lives of the corresponding cis isomers, allowing one to tune their half-lives from 20 to 21000 s, while maintaining photoisomerization behaviors with visible light. Therefore, one can significantly increase the thermal stability of a cis-aminoazobenzene derivative to the extent that single crystals for X-ray diffraction analysis can be grown for the first time, uncovering an unprecedented edge-to-face arrangement of the phenyl rings in the cis isomer. Overall, the azobenzene-functionalized model complexes shed light on the design parameters relevant for photocontrolled WLA molecular switches, as well as offer new ways of tuning the properties of azobenzene-based, photoresponsive materials.