Self-Association and Nitroaromatic-Induced Deaggregation of Pyrene Substituted Pyridine Amides
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- 作者：Sung Kuk Kim ; Jong Min Lim ; Tuhin Pradhan ; Hyo Sung Jung ; Vincent M. Lynch ; Jong Seung Kim ; Dongho Kim ; Jonathan L. Sessler
- 刊名：Journal of the American Chemical Society
- 出版年：2014
- 出版时间：January 8, 2014
- 年：2014
- 卷：136
- 期：1
- 页码：495-505
- 全文大小：705K
- ISSN：1520-5126
文摘
The self-assembly features of the bis-pyrene methyl amide functionalized pyridine and benzene 鈥渢weezers鈥?1 and 2 were studied in organic solution and in the solid state. These systems were found to display remarkably different self-association features and optical properties, which was rationalized by control experiments using compounds bearing pyrenemethyl esters, alkyl groups, or a single pyrene substituent (3鈥?b>6). As dilute solutions in chloroform, tweezers 1 displays both pyrene monomer and excimer emission features reflecting intramolecular contacts between the pyrene subunits. At higher concentrations in chloroform, as well as in the solid state, tweezers 1 self-assembles to form a linear supramolecular polymer. In contrast, tweezers 2 does not interact in an intermolecular fashion and photoexcitation produces emission features characteristic of a pyrene monomer. DFT (density functional theory) and TDDFT (time dependent density functional theory) calculations revealed that the lowest vertical transitions are forbidden and that S1 of 1 is an emissive state. In contrast to 1 and 2, both pyrene-free control systems 5 and 6 were found to form linearly self-assembled supramolecular arrays in the solid state, albeit of differing structure. Upon exposure to trinitrobenzene (TNB), the self-assembled structures formed from 1 undergo deaggregation to form TNB complexes. This change is reflected in both an easily discernible color change and a quenching of the fluorescence emission intensity. Changes in the optical features were also seen in the case of 2. However, notable differences between these two ostensibly similar systems were seen.