In this communication we report the synthesis and characterisation of a novel dianionic compound with aggregation‐induced emission properties. This compound was able to recognize spermine via a multivalent electrostatic interaction leading to a restriction of intramolecular rotation enhancing the fluorescence emission. This recognition was investigated in detail using UV‐Vis and fluorescence spectroscopy. Furthermore the binding stoichiometry was determined via isothermal titration calorimetry. Besides that the structure of the compound was confirmed by X‐ray crystallography. To proof the bivalent binding a singly negatively charged control compound was synthesized showing no specific interaction with the amines screened. Theoretical calculations were performed to get a deeper insight in the molecular structure and the electronic transitions.
We report a pH‐ and temperature‐controlled reversible self‐assembly of Au‐nanoparticles (AuNPs) in water, based on their surface modification with cationic guanidiniocarbonyl pyrrole (GCP) and zwitterionic guanidiniocarbonyl pyrrole carboxylate (GCPZ) binding motifs. When both binding motifs are installed in a carefully balanced ratio, the resulting functionalized AuNPs self‐assemble at pH 1, pH 7 and pH 13, whereas they disassemble at pH 3 and pH 11. Further disassembly can be achieved at elevated temperatures at pH 1 and pH 13. Thus, we were able to prepare functionalized nanoparticles that can be assembled/disassembled in seven alternating regimes, simply controlled by pH and temperature.
We present an in-depth investigation of cyclodextrin complexes with guest compounds featuring complexation-induced room temperature phosphorescence (RTP) in aqueous solution. Very interestingly, only the complexed regioisomers bearing lateral substituents on meta-position show RTP, whereas the stronger host-guest systems with para-substituted dyes show no RTP features. The reported systems were investigated regarding their complexation behavior in water using isothermal titration calorimetry and mass spectrometry. In the case of γ-CD very strong 1 : 1 inclusion complexes (K a up to 5.13 × 10 5 M À 1 ) were unexpectedly observed. It was found that not only a strong binding to the cyclodextrin cavity is needed to restrict motion, inducing the emission, but also the conformation inside the cavity plays a pivotal role -as supported by an extensive NMR study and MD simulations.
In this article, we present fluorescent guanidiniocarbonyl-indoles as versatile oxo-anion binders. Herein, the guanidiniocarbonyl-indole (GCI) and methoxy-guanidiniocarbonyl-indole (MGCI) were investigated as ethylamides and compared with the well-known guanidiniocarbonyl-pyrrole (GCP) concerning their photophysical properties as well as their binding behavior towards oxo-anions. Hence, a variety of anionic species, such as carboxylates, phosphonates and sulfonates, have been studied regarding their binding properties with GCP, GCI and MGCI using UV-Vis titrations, in combination with the determination of the complex stoichiometry using the Job method. The emission properties were studied in relation to the pH value using fluorescence spectroscopy as well as the determination of the photoluminescence quantum yields (PLQY). Density functional theory (DFT) calculations were undertaken to obtain a better understanding of the ground-lying electronic properties of the investigated oxo-anion binders. Additionally, X-ray diffraction of GCP and GCI was conducted. We found that GCI and MGCI efficiently bind carboxylates, phosphonates and sulfonates in buffered aqueous solution and in a similar range as GCP (Kass ≈ 1000–18,000 M−1, in bis-tris buffer, pH = 6); thus, they could be regarded as promising emissive oxo-anion binders. They also exhibit a visible fluorescence with a sufficient PLQY. Additionally, the excitation and emission wavelength of MGCI was successfully shifted closer to the visible region of the electromagnetic spectrum by introducing a methoxy-group into the core structure, which makes them interesting for biological applications.
In this contribution, three deoxyestrone-based emissive lipofection agents are reported. Because of a centrally incorporated terephthalonitrile motif, these ligands can be classified as solution and solid-state emitters (SSSEs). With the...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.