Oxidative catalytic evolution of redox- and spin-states of a Fe-phthalocyanine studied by EPR

Molecular catalysts with electronic axial stretching for high-performance lean-oxygen seawater batteries

A dissolved-oxygen seawater battery (SWB) can generate electricity by reducing dissolved oxygen and sacrificing the metal anode at different depths and temperatures in the ocean, acting as the basic unit of spatially underwater energy networks for future maritime exploration. However, most traditional oxygen reduction reaction (ORR) catalysts are out of work at such ultralow dissolved oxygen concentration. Here, we proposed that the electronic axial stretching of the catalyst is essentially responsible for enhancing the catalyst's sensitivity to dissolved oxygen. By modulating the lattice of iron phthalocyanine (FePc) as a model catalyst, the unique electronic axial stretching in the z-direction of planar FePc molecules was realized to achieve a boosted adsorption and electron transfer and result in a much improved ORR activity in lean-oxygen seawater environment. The peak power density of a homemade SWB using a practical carbon brush electrode decorated by the FePc is estimated to be as high as 3 W L-1. These results provide inspiring insights into the interaction between the catalyst and complicated seawater environment, and propose the electronic axial stretching as an effective indicator for the rational design of catalysts to be used in extremely lean-oxygen environment.

Guest-Stimulated Nonplanar Porphyrins in Flexible Metal-Organic Frameworks

Nonplanar porphyrins with out-of-plane distortions play crucial roles in many biological functions and chemical applications. The artificial construction of nonplanar porphyrins usually involves organic synthesis and modification, which is a highly comprehensive approach. However, incorporating porphyrins into guest-stimulated flexible systems allows to manipulate the porphyrin distortion through simple ad/desorption of guest molecules. Here, a series of porphyrinic zirconium metal-organic frameworks (MOFs) is reported that exhibit guest-stimulated breathing behavior. X-Ray diffraction analysis and skeleton deviation plots confirm that the material suffers from porphyrin distortion to form a ruffled geometry under the desorption of guest molecules. Further investigation reveals that not only the degree of nonplanarity can be precisely manipulated but also the partial distortion of porphyrin in a single crystal grain can be readily achieved. As Lewis acidic catalyst, the MOF with nonplanar Co-porphyrin exhibits active properties in catalyzing CO2 /propylene oxide coupling reactions. This porphyrin distortion system provides a powerful tool for manipulating nonplanar porphyrins in MOFs with individual distortion profiles for various advanced applications.

Tailoring the d-Orbital Splitting Manner of Single Atomic Sites for Enhanced Oxygen Reduction

Regulating the electronic states of single atomic sites around the Fermi level remains a major concern for boosting the electrocatalytic oxygen reduction reaction (ORR). Herein, a Fe d-orbital splitting manner modulation strategy by constructing axial coordination on FeN₄ sites is presented. Experimental investigations and theoretical calculations reveal that the axial tractions induce the distortion of square-planar field (FeN₄ SP), up to the quasi-octahedral coordination (FeN₄ O₁ OC_quasi ), thus leading to the electron rearrangement with a diluted spin polarization. The declined population of unpaired electrons in d_z ² , d_{x z} and d_yz states engenders a moderate adsorption of ORR intermediates, thereby reinforcing the intrinsic reaction activity. In situ infrared spectroscopy further demonstrates that the reordering of d-orbital splitting and occupation facilitates the desorption of *OH. The FeN₄ O₁ OC_quasi exhibits a dramatic improvement of kinetic current density and turnover frequency, which are fivefold and tenfold higher than those of FeN₄ SP. This work presents a novel understanding on improving the electrocatalytic performance through the orbital-scale manipulation.

Continuous Modulation of Electrocatalytic Oxygen Reduction Activities of Single-Atom Catalysts through p-n Junction Rectification

Fine-tuning single-atom catalysts (SACs) to surpass their activity limit remains challenging at their atomic scale. Herein, we exploit p-type semiconducting character of SACs having a metal center coordinated to nitrogen donors (MeN_x ) and rectify their local charge density by an n-type semiconductor support. With iron phthalocyanine (FePc) as a model SAC, introducing an n-type gallium monosulfide that features a low work function generates a space-charged region across the junction interface, and causes distortion of the FeN₄ moiety and spin-state transition in the Fe^II center. This catalyst shows an over two-fold higher specific oxygen-reduction activity than that of pristine FePc. We further employ three other n-type metal chalcogenides of varying work function as supports, and discover a linear correlation between the activities of the supported FeN₄ and the rectification degrees, which clearly indicates that SACs can be continuously tuned by this rectification strategy.

An anionic phthalocyanine decreases NRAS expression by breaking down its RNA G-quadruplex

Aberrant activation of RAS signalling pathways contributes to aggressive phenotypes of cancer cells. The RAS-targeted therapies for cancer, therefore, have been recognised to be effective; however, current developments on targeting RAS have not advanced due to structural features of the RAS protein. Here, we show that expression of NRAS, a major isoform of RAS, can be controlled by photo-irradiation with an anionic phthalocyanine, ZnAPC, targeting NRAS mRNA. In vitro experiments reveal that ZnAPC binds to a G-quadruplex-forming oligonucleotide derived from the 5'-untranslated region of NRAS mRNA even in the presence of excess double-stranded RNA, which is abundant in cells, resulting in selective cleavage of the target RNA's G-quadruplex upon photo-irradiation. In line with these results, upon photo-irradiation, ZnAPC decreases NRAS mRNA and NRAS expression and thus viability of cancer cells. These results indicate that ZnAPC may be a prominent photosensitiser for a molecularly targeted photodynamic therapy for cancer.