Acridine-viologen dyads: selective recognition of single-strand DNA through fluorescence enhancement

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Study of cavity size and nature of bridging units on recognition of nucleotides by cyclophanes

We synthesized a few novel cyclophanes CP-1 to CP-4 containing anthracene units linked together through different bridging and spacer groups and have investigated their interactions with various nucleosides and nucleotides. Of these systems, CP-1 and CP-3 showed selectivity for 5'-GTP and 5'-ATP as compared to other nucleotides and nucleosides, whereas negligible selectivity was observed with CP-2 and CP-4. Interestingly, CP-1, CP-2 and CP-3 exhibited significant binding interactions with the fluorescent indicator, 8-hydroxy-1,3,6-pyrene trisulfonate (HPTS), resulting in the formation of non-fluorescent complexes. Titration of these complexes with nucleosides and nucleotides resulted in the displacement of HPTS, leading to the revival of its fluorescence intensity. It was observed that 5'-GTP induced the maximum displacement of HPTS from the complex [CP-1.HPTS] with an overall fluorescence enhancement of ca. 150-fold, while 5'-ATP induced ca. 45-fold. Although the displacement of HPTS from the complexes [CP-2.HPTS] and [CP-3.HPTS] was found to be similar to that of [CP-1.HPTS], these complexes showed lesser selectivity and sensitivity. In contrast, negligible displacement of HPTS was observed from the complex [CP-4.HPTS] under similar conditions. These results indicate that CP-1, having a well-defined cavity and good electron acceptor (viologen), is capable of forming selective and stable complexes. Though CP-2 and CP-3 retain the good electron acceptor (viologen), their reduced aromatic surface and larger cavity, respectively, resulted in lesser sensitivity. In contrast, CP-4 having a large cavity and a poor acceptor (1,2-bis(pyridin-4-yl)ethene) showed negligible selectivity, thereby indicating the importance of cavity size, bridging unit and aromatic surface on biomolecular recognition properties of cyclophanes

Insight into Water-Soluble Highly Fluorescent Low-Dimensional Host–Guest Supramolecular Polymers: Structure and Energy-Transfer Dynamics Revealed by Polarized Fluorescence Spectroscopy

Water-soluble, highly fluorescent host–guest chromophore-cucurbit[8]­uril supramolecular polymer bundles are investigated by polarized time-resolved photoluminescence spectroscopy, structural methods, and quantum chemistry to fully reveal structural organization and heterogeneity but, in particular, energy-transfer dynamics, being of crucial importance for the design of supramolecular artificial light-harvesting systems

Self-Assembled Amphiphilic Molecules for Highly Efficient Photocatalytic Hydrogen Evolution from Water

Self-assembled molecules for outstanding hydrogen evolution rate and durability should promise practical water splitting due to the versatile visible light absorption, low production cost, and ease of control. Here, we adapted an amphiphilic molecule as a building block for efficient small molecule based self-assembled photocatalyst for hydrogen evolution from water. The self-assembled molecules with platinum cocatalyst showed outstanding performance (turnover number similar to 27000) virtually comparable to the state-of-the-art metal oxide based photocatalysts with catalytic activity extending over days. Transient absorption studies in combination with quantum chemical calculations revealed that elaborate excited state engineering of the molecules resulted in such high performance of hydrogen evolution from water. This study shows that the self-assembled amphiphilic molecules could pave the way to more economical and reproducible production of hydrogen from water.N