Redox-induced magnetic transformation in organic diradicals is an appealing phenomenon. In this study, we theoretically designed twelve couples of diradicals in which two nitroxide (NO) radical groups are connected to the redox-active couplers including p-benzoquinonyl, 1,4-naphthoquinyl, 9,10-anthraquinonyl, naphthacene-5,12-dione, pentacene-6,13-dione, hexacene-6,15-dione, pyrazinyl, quinoxalinyl, phenazinyl, 5,12-diazanaphthacene, 6,13-diazapentacene, and 6,15-diazahexacene. As evidenced at both the B3LYP and M06-2X levels of theory, the calculations reveal that the magnetic reversal can take place from ferromagnetism to antiferromagnetism, or vice versa, by means of redox method in these designed organic magnetic molecules. It was observed that p-benzoquinonyl, 1,4-naphthoquinyl, 9,10-anthraquinonyl, naphthacene-5,12-dione, pentacene-6,13-dione, and hexacene-6,15-dione-bridged NO diradicals produce antiferromagnetism while their dihydrogenated counterparts exhibit ferromagnetism. Similarly, pyrazinyl, quinoxalinyl, phenazinyl, 5,12-diazanaphthacene, 6,13-diazapentacene, and 6,15-diazahexacene-bridged NO diradicals present ferromagnetism while their dihydrogenated counterparts show antiferromagnetism. The differences in the magnetic behaviors and magnetic magnitudes of each of the twelve couples of diradicals could be attributed to their distinctly different spin-interacting pathways. It was found that the nature of the coupler and the length of the coupling path are important factors in controlling the magnitude of the magnetic exchange coupling constant J. Specifically, smaller HOMO-LUMO (HOMO: highest occupied molecular orbital, LUMO: lowest unoccupied molecular orbital) gaps of the couplers and shorter coupler lengths, as well as shorter linking bond lengths, can attain stronger magnetic interactions. In addition, a diradical with an extensively π-conjugated structure is beneficial to spin transport and can effectively promote magnetic coupling, yielding a large |J| accordingly. That is, a larger spin polarization can give rise to a stronger magnetic interaction. The sign of J for these studied diradicals can be predicted from the spin alternation rule, the shape of the singly occupied molecular orbitals (SOMOs), and the SOMO-SOMO energy gaps of the triplet state. This study paves the way for the rational design of magnetic molecular switches.

The solar-driven water splitting for the production of renewable green hydrogen fundamentally relies on the exploration of efficient photocatalysts. Nanostructured TiO₂ is widely recognized as a promising material for photocatalysis, yet it remains hindered by inadequate light harvesting and fast photogenerated carrier recombination. Herein, calcined C/TiO₂ xerogels with yolk–shell and core–shell nanostructures (denoted as YS-C/TiO₂ and CS-C/TiO₂) were designed and fabricated via a typical sol–gel–calcination assisted approach. Thanks to the encapsulation of carbon nanospheres into TiO₂, it effectively enhances light absorption, improves carrier separation, and lessens carrier recombination, making the well-designed YS-C/TiO₂ composite display a remarkable hydrogen evolution rate of 975 µmol g⁻¹ h⁻¹ under simulated solar light irradiation and without the use of any co-catalyst, which is approximately 21.7 times that of the commercial TiO₂. The work provides an efficacious design concept in developing nanostructured TiO₂-based photocatalysts and in boosting broad photocatalytic applications.