Synthesis of a fluorescent BODIPY-tagged ROMP catalyst and initial polymerization-propelled diffusion studies

Water-soluble chitosan-g-PMAm (PMAA)-Bodipy probes prepared by RAFT methods for the detection of Fe3+ ion

It is a challenge to achieve the fully water-soluble chitosan. In this work, water-soluble chitosan-based probes were obtained by the following steps: boron-dipyrrolemethene (BODIPY)-OH was synthesized, and then BODIPY-OH was halogenated to BODIPY-Br. Afterwards, BODIPY-Br reacted with carbon disulfide and mercaptopropionic acid to obtain BODIPY-disulfide. BODIPY-disulfide was introduced to chitosan via amidation reaction to obtain fluorescent chitosan-thioester (CS-CTA); it is employed as the macro-initiator. Methacrylamide (MAm) was grafted onto chitosan fluorescent thioester through reversible addition-fragmentation chain transfer (RAFT) polymerization method. Thus, a water-soluble macromolecular probe (CS-g-PMAm) with chitosan as the main chain and PMAm as long-branched chains was obtained. It greatly improved the solubility in pure water. The thermal stability was reduced slightly, and the stickiness was greatly reduced and the samples displayed the characteristics of liquid. CS-g-PMAm could detect Fe³⁺ in pure water. By the same method, CS-g-PMAA (CS-g-Polymethylacrylic acid) was synthesized and investigated as well.

In Vivo Olefin Metathesis in Microalgae Upgrades Lipids to Building Blocks for Polymers and Chemicals

Sustainable sources are key to future chemicals production. Microalgae are promising resources as they fixate carbon dioxide to organic molecules by photosynthesis. Thereby they produce unsaturated fatty acids as established raw materials for the industrial production of chemical building blocks. Although these renewable feedstocks are generated inside cells, their catalytic upgrading to useful products requires in vitro transformations. A synthetic catalysis inside photoautotrophic cells has remained elusive. Here we show that a catalytic conversion of renewable substrates can be realized directly inside living microalgae. Organometallic catalysts remain active inside the cells, enabling in vivo catalytic olefin metathesis as new-to-nature transformation. Stored lipids are converted to long-chain dicarboxylates as valuable building blocks for polymers. This is a key step towards the long-term goal of producing desired renewable chemicals in microalgae as living "cellular factories".

Tuning the Photonic Behavior of Symmetrical bis-BODIPY Architectures: The Key Role of the Spacer Moiety

Herein we describe the synthesis, computationally assisted spectroscopy, and lasing properties of a new library of symmetric bridged bis-BODIPYs that differ in the nature of the spacer. Access to a series of BODIPY dimers is straightforward through synthetic modifications of the pending ortho-hydroxymethyl group of readily available C-8 (meso) ortho-hydroxymethyl phenyl BODIPYs. In this way, we have carried out the first systematic study of the photonic behavior of symmetric bridged bis-BODIPYs, which is effectively modulated by the length and/or stereoelectronic properties of the spacer unit. The designed bis-BODIPYs display bright fluorescence and laser emission in non-polar media. The fluorescence response is governed by the induction of a non-emissive intramolecular charge transfer (ICT) process, which is significantly enhanced in polar media. The effectiveness of the fluorescence quenching and also the prevailing charge transfer mechanism (from the spacer itself or between the BODIPY units) rely directly on the electron-releasing ability of the spacer. Moreover, the linker moiety can also promote intramolecular excitonic interactions, leading to excimer-like emission characterized by new spectral bands and the lengthening of lifetimes. The substantial influence of the bridging moiety on the emission behavior of these BODIPY dyads and their solvent-sensitivity highlight the intricate molecular dynamics upon excitation in multichromophoric systems. In this regard, the present work represents a breakthrough in the complex relationship between the molecular structure of the chromophores and their photophysical signatures, thus providing key guidelines for rationalizing the design of tailored bis-BODIPYs with potential advanced applications.

Synthesis and Photostability of Unimolecular Submersible Nanomachines: Toward Single-Molecule Tracking in Solution

The synthesis and photophysical properties of a series of photostable unimolecular submersible nanomachines (USNs) are reported as a first step toward the analysis of their trajectories in solution. The USNs have a light-driven rotatory motor for propulsion in solution and photostable cy5-COT fluorophores for their tracking. These cy5-COT fluorophores are found to provide an almost 2-fold increase in photostability compared to the previous USN versions and do not affect the rotation of the motor.

Profluorescent substrates for the screening of olefin metathesis catalysts

Herein we report on a 96-well plate assay based on the fluorescence resulting from the ring-closing metathesis of two profluorophoric substrates. To demonstrate the validity of the approach, four commercially available ruthenium-metathesis catalysts were evaluated in six different solvents. The results from the fluorescent assay agree well with HPLC conversions, validating the usefulness of the approach.

Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring

Unimolecular submersible nanomachines (USNs) bearing light-driven motors and fluorophores are synthesized. NMR experiments demonstrate that the rotation of the motor is not quenched by the fluorophore and that the motor behaves in the same manner as the corresponding motor without attached fluorophores. No photo or thermal decomposition is observed. Through careful design of control molecules with no motor and with a slow motor, we found using single molecule fluorescence correlation spectroscopy that only the molecules with fast rotating speed (MHz range) show an enhancement in diffusion by 26% when the motor is fully activated by UV light. This suggests that the USN molecules give ∼9 nm steps upon each motor actuation. A non-unidirectional rotating motor also results in a smaller, 10%, increase in diffusion. This study gives new insight into the light actuation of motorized molecules in solution.