Structural disruption of melanin-like polymers with boosted UV protection

Manipulating the energy structure of materials represents an efficient way to regulate their light absorption behaviors. For example, constructing donor-acceptor(D-A) structures to increase the polarizability and reduce the energy bandgap of local molecules has been widely used in the field of organic photovoltaics with ordered structures. Remarkably, even in disordered and chaotic systems such as melanin-like polydopamine(PDA), visible and near-infrared light absorption can be significantly improved using this strategy. However, there has been a noticeable dearth of research on the ultraviolet(UV) light absorption regulation of bioinspired polymers with disordered and chaotic architectures by tailoring the D-A microstructures. In this study, a series of benzoheterocyclic molecules with strong electron-donating features screened by molecular simulation calculations were involved in disrupting the D-A structures within PDA. The destruction of D-A structures promoted the increase of the energy band gap and finally boosted the UV absorption of PDA. The resulting PDA nanoparticles with enhanced UV absorption were further employed to fabricate UV shielding composite films to protect the growth of plants from harmful UV radiation. This research may open up new avenues for structural disruption of bioinspired polymers for enhanced photoprotection applications.

Difluorocarbene-derived rapid late-stage trifluoromethylation of 5-iodotriazoles for the synthesis of^(18)F-labeled radiotracers

Difluorocarbene has emerged as a valuable intermediate to synthesize fluorides.However,difluorocarbene-derived synthesis of^(19)F/^(18)F-trifluoromethyl triazoles has not been explored.Herein,we reported the Cu(I)-promoted difluorocarbene-derived^(19)F/^(18)F-trifluoromethylation of iodotriazoles using KF/K^(18)F as the fluorine source.This approach rapidly generated a wide range of 5-trifluoromethyl-1,2,3-triazoles in good yields showing high functional group compatibility.The reaction was effective for late-stage functionalization of bioactive molecules and^(18)F-trifluoromethylation of iodotriazoles.This work provides a practical synthetic methodology for the development of triazole drugs and^(18)F-radiotracers for positron emission tomography.

Derivatization based on tetrazine scaffolds:synthesis of tetrazine derivatives and their biomedical applications

Bioorthogonal chemistry is widely used in biological systems and has been trialed in patients,attracting a lot of attention in this century.Tetrazine-based bioorthogonal reactions are essential in chemical biology applications,including cellular labeling,live-cell imaging,diagnosis,drug release,and oncotherapy,due to their tunable rapid reaction kinetics and unique fluorogenic characteristics.However,the scope of de novo tetrazine synthesis is restricted due to the limited supply of commercial starting materials.Therefore,derivatization based on tetrazine scaffolds has been used to synthesize various tetrazine derivatives to enhance the applications of tetrazine bioorthogonal reactions.Herein,the recent advances in tetrazine scaffold-based derivatizations,including tetrazine skeletons,aromatic substituents and alkyl substituents of tetrazines,have been summarized.The advantages and limitations of the derivatization methods and applications of the developed tetrazine derivatives in bioorthogonal chemistry have also been highlighted.