The manipulation of carbon nitride (CN) structures is one main avenue to enhance the activity of CN‐based photocatalysts. Increasing the efficiency of photocatalytic heterogeneous materials is a critical step toward the realistic implementation of sustainable schemes for organic synthesis. However, limited knowledge of the structure/activity relationship in relation to subtle structural variations prevents a fully rational design of new photocatalytic materials, limiting practical applications. Here, the CN structure is engineered by means of a microwave treatment, and the structure of the material is shaped around its suitable functionality for Ni dual photocatalysis, with a resulting boosting of the reaction efficiency toward many CX (X = N, S, O) couplings. The combination of advanced characterization techniques and first‐principle simulations reveals that this enhanced reactivity is due to the formation of carbon vacancies that evolve into triazole and imine N species able to suitably bind Ni complexes and harness highly efficient dual catalysis. The cost‐effective microwave treatment proposed here appears as a versatile and sustainable approach to the design of CN‐based photocatalysts for a wide range of industrially relevant organic synthetic reactions.
The already known di(2-pyridyl)dihydropyrazine (dhdpp) was prepared and isolated also in the form of a bishydrated species, i.e., dhdpp•2H 2 O. As established by X-ray work, a small amount of single crystals of di(2-pyridyl)-pyrazine (dpp) was also obtained from the mother liquors, this testifying the possibility of a dehydrogenation process dhdpp → dpp in the absence of a catalyst. Using dhdpp as a ligand, mononuclear metal derivatives of formula [(dhdpp)MCl 2 ]•xH 2 O (M = Pd II , Pt II ) were obtained as stable-to-air solids, studied by X-ray powder, IR, UV−visible, and 1 H NMR spectra, and proved to exhibit a N 2 MCl 2 coordination site involving one pyridine and one pyrazine N atom ("py-pyz" coordination). An interesting relationship has been established in terms of the observed types of coordination with the analogs of di(2-pyridyl)-pyrazine (dpp) formulated as [(dpp)MCl 2 ]•3H 2 O, proved also by 1 H NMR spectra to exhibit the "py-pyz" mode of coordination. Attempts to isolate from the reaction of dhdpp with Pd(OAc) 2 the corresponding mononuclear derivatives were shown to lead, as definitely supported by 1 H NMR spectral data and crystallographic work, to the exclusive formation of the corresponding dpp complex [(dpp)Pd(OAc) 2 ]•5H 2 O ("py-pyz" coordination site), this proving the tendency of dhdpp to generate dpp under different reaction conditions. The promoted conversion of dhdpp into dpp in the complex was examined by sequential NMR analysis and established to be determined by Pd(OAc) 2 which plays the role of catalyst. The new salt-like species [(CH 3 )(dhdpp)PdI 2 ](I)•7H 2 O, prepared starting from [(dhdpp)PdCl 2 ] in its reaction with CH 3 I, allowed the separation from the mother liquors of small brown crystals identified on the basis of X-ray analysis as the already known complex of formula [(dpp)PdI 2 ] ("py-py" coordination), this result once again outlining the tendency of dhdpp to be dehydrogenated to dpp.
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