Palladium-Mediated Approach to Coumarin-Functionalized Amino Acids

Incorporation of the fluorogenic l-(7-hydroxycoumarin-4-yl)­ethylglycine into proteins is a valuable biological tool. Coumarins are typically accessed via the Pechmann reaction, which requires acidic conditions and lacks substrate flexibility. A Pd-mediated coupling is described between <i>o</i>-methoxyboronic acids and a glutamic acid derived (<i>Z</i>)-vinyl triflate, forming latent coumarins. Global deprotection with BBr₃ forms the coumarin scaffold in a single step. This mild and scalable route yielded five analogues, including a probe suitable for use at lower pH

Photophysical and DFT Characterization of Novel Pt(II)-Coupled 2,5-Diaryloxazoles for Nonlinear Optical Absorption

Several new bis-phosphine platinum­(II) complexes with 2,5-diaryl-substituted oxazole-containing alkyne ligands have been synthesized and optically characterized in solution. Measurements of nonlinear absorption showed strong attenuation of laser light at 532 and 600 nm. The light absorption of the Pt complexes was shifted from the near-UV region for the ground state to the red region for the excited triplet state, and was associated with large extinction coefficients. The optical limiting effect can be explained by triplet–triplet excited state absorption in conjunction with fast excited singlet–to-triplet intersystem crossing and slow triplet–to-ground-state decay, in comparison with the pulse length of the laser. DFT calculations show good predictability of the S₀–S₁ and S₀–T₁ energy gaps and offer insight into the interaction strength between Pt and the alkyne ligands. The use of this type of ligand, with weak absorption for the Pt­(II) complexes in the visual wavelength range as a key feature, enables the possibility to further improve these molecular systems for nonlinear absorption applications

Structure-activity relationships reveal beneficial selectivity profiles of inhibitors targeting acetylcholinesterase of disease-transmitting mosquitoes

Insecticide resistance jeopardizes the prevention of infectious diseases such as malaria and dengue fever by vector control of disease-transmitting mosquitoes. Effective new insecticidal compounds with minimal adverse effects on humans and the environment are therefore urgently needed. Here, we explore noncovalent inhibitors of the well-validated insecticidal target acetylcholinesterase (AChE) based on a 4-thiazolidinone scaffold. The 4-thiazolidinones inhibit AChE1 from the mosquitoes Anopheles gambiae and Aedes aegypti at low micromolar concentrations. Their selectivity depends primarily on the substitution pattern of the phenyl ring; halogen substituents have complex effects. The compounds also feature a pendant aliphatic amine that was important for activity; little variation of this group is tolerated. Molecular docking studies suggested that the tight selectivity profiles of these compounds are due to competition between two binding sites. Three 4-thiazolidinones tested for in vivo insecticidal activity had similar effects on disease-transmitting mosquitoes despite a 10-fold difference in their in vitro activity

Silica Hybrid Sol–Gel Materials with Unusually High Concentration of Pt–Organic Molecular Guests: Studies of Luminescence and Nonlinear Absorption of Light

The development of new photonic materials is a key step toward improvement of existing optical devices and for the preparation of a new generation of systems. Therefore synthesis of photonic hybrid materials with a thorough understanding and control of the microstructure-to-properties relationships is crucial. In this perspective, a new preparation method based on fast gelation reactions using simple dispersion of dyes without strong covalent bonding between dye and matrix has been developed. This new sol–gel method is demonstrated through synthesis of monolithic siloxane-based hybrid materials highly doped by various platinum­(II) acetylide derivatives. Concentrations of the chromophores as high as 400 mM were obtained and resulted in unprecedented optical power limiting (OPL) performance at 532 nm of the surface-polished solids. Static and time-resolved photoluminescence of the prepared hybrid materials were consistent with both OPL data and previous studies of similar Pt­(II) compounds in solution. The impacts of the microstructure and the chemical composition of the matrix on the spectroscopic properties, are discussed