Effects of Self—coiling of Organic Molecules on Intramolecular Exciplex Formation and Fluoresscence Quenching in DX—H2O Solvent System

Effects of self-coiling of organic molecules on intramolecular exciplex formation of compound I,in which the carbazole chromophore and terephthalic acid methylester acceptor group are linked by one (CH2)10 chain,and the decrease of the fluorescence intensities of compounds Ⅱ，Ⅲ，and Ⅳ,in which the carbazole chromophore and 3,5-dinitrobenzoate are connected by one aliphatic chain of (CH2)10 (Ⅱ），（CH2）12（Ⅲ）,or (CH2)4(Ⅳ）,have been studied in the dioxane (DX)-H2O binary system.The results show that self-coiling of organic molecules in DX-H2O facilitates intramolecular exciplex formation of I and induces the decrease of fluorescence intensities of Ⅱ,bacause of the proximity effect brought about by selfcoiling of organic molecules under hydrophobic-lipophilic interaction(HLI) between the excited carbazole chromophore and the acceptor.Since the similar effects are observed even when the concentration of the probes are less than their CAgCs(critical aggregate concentrations )in the DX-H2O mixture with the same φ values,formation of the intermolecular exciplex has been excluded.The effects are found to be strongly depended on φ values,indication that they are mainly driven by HLI.The properties of the acceptors can also affect the intramolecular exciplex formation.With terephthalic acid methylester moiety as the acceptor,the carbazole chromophore exhibits the fluorescence spectra of the exciplex,while with 3,5-dinitrobenzoate moiety as the acceptor,only the fluorescence spectra of excited carbazolyl chromophore are observed.

Effects of Self‐coiling of Organic Molecules on Intramolecular Exciplex Formation and Fluorescence Quenching in DX‐H2O Solvent System

Effects of self‐coiling of organic molecules on intramolecular exciplex formation of compound I, in which the carbazole chromophore and terephthalic acid methylester acceptor group are linked by one (CH₂)₁₀ chain, and the decrease of the fluorescence intensities of compounds II, III, and IV, in which the carbazole chromophore and 3,5‐dinitrobenzoate are connected by one aliphatic chain of (CH₂)₁₀ (II), (CH₂)₁₂ (III), or (CH₂)₄ (IV), have been studied in the dioxane(DX)‐H₂O binary system. The results show that self‐coiling of organic molecules in DX‐H₂O facilitates intramolecular exciplex formation of I and induces the decrease of fluorescence intensities of II, because of the proximity effect brought about by self‐coiling of organic molecules under hydrophobic‐lipophilic interaction (HLI) between the excited carbazole chromophore and the acceptor. Since the similar effects are observed even when the concentrations of the probes are less than their CAgCs (critical aggregate concentrations) in the DX‐H₂O mixture with the same ? values, formation of the intermolecular exciplex has been excluded. The effects are found to be strongly depended on ? values, indicating that they are mainly driven by HLI. The properties of the acceptors can also affect the intramolecular exciplex formation. With terephthalic add methylester moiety as the acceptor, the carbazole chromophore exhibits the fluorescence spectra of the exciplex, while with 3,5‐dinitrobenzoate moiety as the acceptor, only the fluorescence spectra of excited carbazolyl chromophore are observed.