High Affinity Macrocycle Threading by a Near-Infrared Croconaine Dye with Flanking Polymer Chains

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• 作者：Wenqi Liu ; Evan M. Peck ; Bradley D. Smith
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：February 11, 2016
• 年：2016
• 卷：120
• 期：5
• 页码：995-1001
• 全文大小：362K
• ISSN：1520-5207

文摘

Croconaine dyes have narrow and intense absorption bands at ～800 nm, very weak fluorescence, and high photostabilities, which combine to make them very attractive chromophores for absorption-based imaging or laser heating technologies. The physical supramolecular properties of croconaine dyes have rarely been investigated, especially in water. This study focuses on a molecular threading process that encapsulates a croconaine dye inside a tetralactam macrocycle in organic or aqueous solvent. Macrocycle association and rate constant data are reported for a series of croconaine structures with different substituents attached to the ends of the dye. The association constants were highest in water (Kb>ab> ～ 10⁹ M^–1), and the threading rate constants (kb>onb>) increased in the solvent order Hb>2b>O > MeOH > CHClb>3b>. Systematic variation of croconaine substituents located just outside the croconaine/macrocycle complexation interface hardly changed Kb>ab> but had a strong influence on kb>onb>. A croconaine dye with N-propyl groups at each end of the structure exhibited a desirable mixture of macrocycle threading properties; that is, there was rapid and quantitative croconaine/macrocycle complexation at relatively high concentrations in water, and no dissociation of the preassembled complex when it was diluted into a solution of fetal bovine serum, even after laser-induced photothermal heating of the solution. The combination of favorable near-infrared absorption properties and tunable mechanical stability makes threaded croconaine/macrocycle complexes very attractive as molecular probes or as supramolecular composites for various applications in absorption-based imaging or photothermal therapy.