Four novel polypyridine cobalt(II) complexes were developed based on a hexadentate ligand scaffold bearing either electron‐withdrawing (−CF3) or electron‐donating (−OCH3) groups in different positions of the ligand. Experiments and theoretical calculations were combined to perform a systematic investigation of the effect of the ligand modification on the hydrogen evolution reaction. The results indicated that the position, rather than the type of substituent, was the dominating factor in promoting catalysis. The best performances were observed upon introduction of substituents on the pyridine moiety of the hexadentate ligand, which promoted the formation of the Co(II)H intermediate via intramolecular proton transfer reactions with low activation energy. Quantum yields of 11.3 and 10.1 %, maximum turnover frequencies of 86.1 and 76.6 min−1, and maximum turnover numbers of 5520 and 4043 were obtained, respectively, with a −OCH3 and a −CF3 substituent.

Systemic toxicity and severe side effects are commonly associated with anticancer chemotherapies. New strategies based on enhanced drug selectivity and targeted delivery to cancer cells while leaving healthy tissue undamaged can reduce the global patient burden. Herein, we report the design, synthesis and characterization of a bio-inspired hybrid multifunctional drug delivery system based on diatom microalgae. The microalgae’s surface was chemically functionalized with hybrid vitamin B12-photoactivatable molecules and the materials further loaded with highly active rhenium(I) tricarbonyl anticancer complexes. The constructs showed enhanced adherence to colorectal cancer (CRC) cells and slow release of the chemotherapeutic drugs. The overall toxicity of the hybrid multifunctional drug delivery system was further enhanced by photoactivation of the microalgae surface. Depending on the construct and anticancer drug, a 2-fold increase in the cytotoxic efficacy of the drug was observed upon light irradiation. The use of this targeted drug delivery strategy, together with selective spatial–temporal light activation, may lead to lower effective concentration of anticancer drugs, thereby reducing medication doses, possible side effects and overall burden for the patient.

The Cover Feature shows the structure–activity relationship of a family of heptacoordinate CoII complexes for light‐triggered H2 evolution. The complexes present a ligand scaffold including bipyridines and pyridines moieties functionalized with either electron‐donating or electron‐withdrawing groups. Results show that position plays a predominant role with respect to the electronic effect of the substituents. More information can be found in the Full Paper by F. Lucarini et al.

Design, synthesis and characterization of a bio-inspired hybrid multifunctional drug delivery system based on diatom microalgae. The microalgae’s surface was chemically functionalized with hybrid vitamin B₁₂-photoactivable molecules and the materials further loaded with highly active rhenium(I) tricarbonyl anticancer complexes. The constructs showed enhanced adherence to colorectal cancer (CRC) cells via transcobalamin (II) receptors and slow release of the chemotherapeutic drugs. The overall toxicity of the hybrid multifunctional drug delivery system was further enhanced by photoactivation of the microalgae surface. Depending on the construct and anticancer drug, a 2-fold increase in the cytotoxic efficacy of the drug was observed upon light irradiation.

Design, synthesis and characterization of a bio-inspired hybrid multifunctional drug delivery system based on diatom microalgae. The microalgae’s surface was chemically functionalized with hybrid vitamin B₁₂-photoactivable molecules and the materials further loaded with highly active rhenium(I) tricarbonyl anticancer complexes. The constructs showed enhanced adherence to colorectal cancer (CRC) cells via transcobalamin (II) receptors and slow release of the chemotherapeutic drugs. The overall toxicity of the hybrid multifunctional drug delivery system was further enhanced by photoactivation of the microalgae surface. Depending on the construct and anticancer drug, a 2-fold increase in the cytotoxic efficacy of the drug was observed upon light irradiation.