Applications in near‐infrared (NIR) have been explored significantly in many fields, including bioimaging, night vision, plant growth, and chemical analysis. Different emission profiles are required within the same industry. Developing luminescent materials with different tuning methods is reliable for controlling the NIR regions (NIR‐I, 700–1000 nm; NIR‐II, 1000–1700 nm). Spinel phosphors are promising candidates due to their ability to modulate the crystal field. Understanding the parameters that influence the degree of inversion in spinel compounds is crucial to harness the variability of the spinel structure. Cr3+ and Ni2+ are ideal activators for NIR‐I and NIR‐II emissions, respectively. However, there is a need for phosphors that emit in the NIR‐II region when excited by visible light. Although the energy transfer method combining two activators is considered, this review focuses on different types of spinel structures, discussing their types and common strategies to tune the host structure. The goal is to achieve desired shift and broadness of the entire NIR spectrum, highlighting the importance of spectrum tuning for practical applications.
The framework of 4-pyrimidinones is prevalent in biologically and medicinally important molecules. Here we report that chiral N-substituted 4-pyrimidinones were prepared by an enantioselective, organocatalytic aza-Michael addition of 4 (3H)-pyrimidinone (4-hydroxypyrimidine) to α,β-unsaturated 1,4-dicarbonyl compounds for the first time. The reactions were optimized by the choice of solvents, screening Cinchona alkaloid-based bifunctional catalysts, and Michael acceptors to achieve good yields and enantioselectivities.
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