Tunable Thermochromism of Multifunctional Charge-Transfer-Based Supramolecular Materials Assembled in Water (original) (raw)
Related papers
Peptide-Based Low Molecular Weight Photosensitive Supramolecular Gelators
Gels
Over the last couple of decades, stimuli-responsive supramolecular gels comprising synthetic short peptides as building blocks have been explored for various biological and material applications. Though a wide range of stimuli has been tested depending on the structure of the peptides, light as a stimulus has attracted extensive attention due to its non-invasive, non-contaminant, and remotely controllable nature, precise spatial and temporal resolution, and wavelength tunability. The integration of molecular photo-switch and low-molecular-weight synthetic peptides may thus provide access to supramolecular self-assembled systems, notably supramolecular gels, which may be used to create dynamic, light-responsive “smart” materials with a variety of structures and functions. This short review summarizes the recent advancement in the area of light-sensitive peptide gelation. At first, a glimpse of commonly used molecular photo-switches is given, followed by a detailed description of thei...
Cation-Tuned Stimuli Responsive and Optical Properties of Supramolecular Hydrogels
Chemistry, an Asian journal, 2015
Hierarchical self-assembly of an amphiphilic tris-urea in aqueous media is shown. A mixture of the amphiphilic tris-urea and an alkaline solution gave a viscous solution composed of fibrous aggregates. This viscous solution transformed into supramolecular hydrogels, which are capable of hierarchically organizing into higher-order aggregates, in response to several cationic triggers. The resulting supramolecular hydrogels were relatively stiff and their storage moduli attained over 103 Pa. Stimuli responsive and optical properties of the resulting hydrogels were influenced by the cationic trigger. Proton and calcium ion triggers gave pH and chemical stimuli responsive hydrogels, respectively. A terbium ion trigger also provided a highly luminescent hydrogel through energy transfer from the tris-urea to terbium.
Supramolecular Strategies To Construct Biocompatible and Photoswitchable Fluorescent Assemblies
Journal of the American Chemical Society, 2011
We designed and synthesized an amphiphilic copolymer with pendant hydrophobic decyl and hydrophilic poly(ethylene glycol) chains along a common poly(methacrylate) backbone. This macromolecular construct captures hydrophobic boron dipyrromethene fluorophores and hydrophobic spiropyran photochromes and transfers mixtures of both components in aqueous environments. Within the resulting hydrophilic supramolecular assemblies, the spiropyran components retain their photochemical properties and switch reversibly to the corresponding merocyanine isomers upon ultraviolet illumination. Their photoinduced transformations activate intermolecular electron and energy transfer pathways, which culminate in the quenching of the boron dipyrromethene fluorescence. As a result, the emission intensity of these supramolecular constructs can be modulated in aqueous environments under optical control. Furthermore, the macromolecular envelope around the fluorescent and photochromic components can cross the membrane of Chinese hamster ovarian cells and transport its cargo unaffected into the cytosol. Indeed, the fluorescence of these supramolecular constructs can be modulated also intracellularly by operating the photochromic component with optical inputs. In addition, cytotoxicity tests demonstrate that these supramolecular assemblies and the illumination conditions required for their operation have essentially no influence on cell viability. Thus, supramolecular events can be invoked to construct fluorescent and photoswitchable systems from separate components, while imposing aqueous solubility and biocompatibility on the resulting assemblies. In principle, this simple protocol can evolve into a general strategy to deliver and operate intracellularly functional molecular components under optical control.
Supramolecular Materials for Optical and Electrochemical Biosensors
Biosensors - Micro and Nanoscale Applications, 2015
It is incontestable that the interactions and bonds that keep molecules united to generate unique supramolecular compounds, with individual properties, morphologies and behaviour, are of special dynamics and singular forces. Therefore, it is necessary to discuss and consider the types of interactions that may occur in a determined system, their dynamics and number, which directly act on the energetic balance that strengthen the union between participants and give rise to a supramolecule. In this chapter, a number of such supramolecular systems that find application as any component of a biosensor are presented and discussed, considering intermolecular interaction forces that confer them shape, function and unique properties. To better understand their structural dynamics and the mechanisms through which they can be used in biosensing, a brief explanation on the interaction thermodynamics, types of intermolecular interactions that compete against each other and the energetic equilibrium that originate and stabilize supramolecular systems is given. To explain how this balance of forces can be extensively exploited to develop methods to produce supramolecular compounds, an overview on supramolecular strategies is presented and their contribution is explored in each example presented in this text, to evidence the importance of planning and developing methodologies of preparation, based on
We report a multi-stimuli responsive polymeric sensor consisting of a pseudorotaxane-like architecture fabricated from a 1,5-diaminonaphthalene end-functionalized poly(N-isopropyl)acrylamide (Napht-N-PNIPAM) and cyclobis(paraquat-p-phenylene) (CBPQT 4+ , 4Cl À ). The coloured nature of the poly-pseudorotaxane provides a sensor for temperature and pH in water with an associated visible readout. To create this dual responsive polymeric sensor, a new chain transfer agent (Napht-N-CTA) incorporating a pH-responsive 1,5-diaminonaphthalene unit was synthesized and used for the polymerization of N-isopropylacrylamide via Reversible Addition-Fragmentation Chain Transfer (RAFT). The ability of Napht-N-PNIPAM to form a pseudorotaxane architecture with CBPQT 4+ , 4Cl À in aqueous media was studied by means of UV-Vis, NMR ( 1 H, 2D-ROESY, DOSY) and ITC experiments. Interestingly, the pseudorotaxane architecture can be reversibly dissociated upon either heating the sample above its cloud point or protonating the nitrogen atoms of the 1,5-diaminonaphthalene-based guest unit by adjusting the pH to around 1. In both cases a dramatic colour change occurs from intense blue-green to colourless.
A ligand-chirality controlled supramolecular hydrogel
Dalton Transactions, 2010
We report a novel example of ligand-chirality finely controlled in situ supramolecular hydrogel formation based on the coordination of phenylalanine (Phe) to Cu(II) with higher selectivity over other metal ions. As decreasing both enantiomeric excesses (ee%) of ligand Phe towards its D-and L-forms, the gelation ability of Phe-Cu(II) supramolecular metallogelator was found to be weakened and eventually disappeared, which likely resulted from the stereoselectivity of the ligand Phe. Intermolecular hydrogen bonding, hydrophobic and/or p-p stacking interactions were also found to be essential for forming the metallogel. We believe that the present work can open up a new entry for developing novel and promising chiral sensing and recognition platforms, i.e. visually sensing chiral molecules by naked eyes due to the feature of a sol-to-gel transition induced smartly by varying the ligand chirality.
Chemical Communications, 2006
Synthesis of bismelamines was reported previously. 4c Fluorescence quantum yields were estimated using Rhodamine 6G as a reference. Molecular modeling calculations were performed on MacroModel 9.0 using MMFF force-field method. Dynamic light scattering measurements were conducted on Beckmann Coulter N5 particle analyzer equipped with 25 mW He-Ne laser. Sample solutions were filtered with Millipore membrane filter (pore size = 0.2 µm) before measurements to remove dust. Complexation between 1 and M UV−vis titration experiment of monotopic melamine M (3 × 10 −4) with 1 (each addition is 3 × 10 −5 , from 3 × 10 −5 to 3 × 10 −4 M) was carried out in MCH (Fig. S1a). Two spectral transition stages were clearly observed. First stage is hypsochromic shift of 1 from 465 nm to 461.5 nm (solid arrow in Fig. S1a), indicating the fully-complexed 1 (because of excess amount of M) to partially complexed 1. This transition finished at the ratio of M:1 = 2:1 (Fig. S1b), which clearly matches well with the stoichiometry based on the binding sites. The second stage was observed at the ratio of M:1 above 2:1, where the absorption band of 1 gradually broadened (dashed arrow in Fig. S1a). This indicates the presence of interchromophoric interaction. The spectral transition from 2:1 ([1] = 1.5 × 10 −4 M) to 2:1.2 ratio ([1] = 1.8 × 10 −4 M) is remarkable, again highlighting the 2:1 binding stoichiometry between M and 1. At this stage, the stoichiometry of the binding sites mismatches (excess hydrogen-bonding sites in 1), and the nonspecific association of complexes possessing free hydrogen-bonding sites (upper structures in Fig, S2), which have low solubility in apolar solvents, would occur in MCH.