Photoinduced charge separation of a phenothiazine–anthraquinone dyad 1 with a rigid bicyclo[2.2.2]octane spacer was investigated by means of picosecond and nanosecond transient absorption and time-resolved ESR spectroscopies. Irradiation of the anthraquinone chromophore in 1 produced the charge-separated (CS) state in THF. Time constants of the formation and the decay of the CS state were determined to be 1.3 ns and 1.0 µs, respectively. Time-resolved ESR showed spin-polarized all-emission signals due to the formation of the CS state via the triplet mechanism.

Photoinduced intramolecular electron transfer of dyad PTZ3-PTZ2-PTZ1-B-AQ consisting of phenothiazine trimer (PTZ3-PTZ2-PTZ1), bicyclo[2.2.2]octane (B), and anthraquinone (AQ) was investigated. After excitation (∼20 ps) of the AQ moiety in THF, a metastable radical ion pair (RIP) PTZ3-PTZ2-PTZ1(+)-B-AQ(-) appeared at ∼620 nm. From 500 ps to 6 ns the spectrum changed to a new absorption (∼950 nm), which was assigned to the hole-shifted stable RIP state PTZ3-PTZ2(+)-PTZ1-B-AQ(-). The time constant of the hole-shift process was determined to be 6.0 ns. The hole-shifted RIP state had a lifetime (τ) of 250 ns and was characterized by spin-polarized signals as a spin-correlated radical pair (SCRP) by means of time-resolved ESR. These results were compared with those for the phenothiazine monomer analog PTZ-B-AQ, which also produced the RIP state PTZ(+)-B-AQ(-) with τ = 1.9 μs. Time-resolved ESR showed an all emission signal pattern showing the triplet mechanism of PTZ-B-(3)AQ* → (3)[PTZ(+)-B-AQ(-)]. The origin of the difference in the lifetimes between the trimer and the monomer RIP states was discussed from various points of view, including free energy difference in the RIP states, reorganization energy difference in the charge recombination process, and the spin-state difference. Of these, the spin-state difference effect provided the most reasonable explanation.

C−X bond reductive elimination and oxidative addition are key steps in many catalytic cycles for C−H functionalization catalyzed by precious metals; however, engaging first row transition metals in these overall 2e − processes remains a challenge. Although high-valent Mn aryl species have been implicated in Mn-catalyzed C−H functionalization, the nature and reactivity of such species remain unelucidated. In this work, we report rare examples of stable, cyclometalated monoaryl Mn III complexes obtained through clean oxidative addition of Ar−Br to Mn I (CO) 5 Br. These isolated Mn III −Ar complexes undergo unprecedented 2e − reductive elimination of the Ar−X (X = Br, I, and CN) bond and Mn II induced by 1e − oxidation, presumably via transient reactive Mn IV species. Mechanistic studies suggest a nonradical pathway.

We found a unique stereoelectronic-substituent effect on the oxidation potentials of bis(diarylamino)phenothiazines through large conformational changes during the oxidation process.

Triboluminescent compounds that generate emission of light in response to mechanical stimulus are promising targets in the development of “smart materials” and damage sensors. Among triboluminescent metal complexes, rare-earth europium...