The high element abundance and d10 electron configuration make ZnII‐based compounds attractive candidates for the development of novel photoactive molecules. Although a large library of purely fluorescent compounds exists, emission involving triplet excited states is a rare phenomenon for zinc complexes. We have investigated the photophysical and ‐chemical properties of a series of dimeric and monomeric ZnII halide complexes bearing a cyclic (alkyl)(amino)carbene (cAAC) as chromophore unit. Specifically, [(cAAC)XZn(μ‐X)2ZnX(cAAC)] (X=Cl (1), Br (2), I (3)) and [ZnX2(cAAC)(NCMe)] (X=Br (4), I (5)) were isolated and fully characterized, showing intense visible light photoluminescence under UV irradiation at 297 K and fast photo‐induced transformation. At 77 K, the compounds exhibit improved stability allowing to record ultra‐long lifetimes in the millisecond regime. DFT/MRCI calculations confirm that the emission stems from 3XCT/LEcAAC states and indicate the phototransformation to be related to asymmetric distortion of the complexes by cAAC ligand rotation. This study enhances our understanding of the excited state properties for future development and application of new classes of ZnII phosphorescent complexes.

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Synthesis of pharmaceutically active heterocycles is always appealing as the majority of the widely used drugs contain heterocyclic moieties as their core structure. So, the straightforward construction of heterocycles from readily available/accessible reagents is one of the prime targets of the synthetic chemists. In this context, CÀ H functionalization has emerged as an effective tool for the designing and synthesis of various heterocyclic moieties as it offers a straightforward and step-economic pathway. On the other hand, the readily available/accessible conjugated carbonyls are well-known reagents for the construction of carbocycles and heterocycles over the years. However, the employment of CÀ H functionalization of the two CÀ H bonds of the conjugated alkene in carbocycle/heterocycle synthesis was not so explored. In the last decade, much focus has been paid on the synthesis of various pharmaceutically active heterocycles through CÀ H bond functionalization of α,β-unsaturated aldehydes/ketones. These protocols have been developed through either oxida-tive coupling of conjugated carbonyls with suitable coupling partners or intramolecular CÀ H bond functionalization of conjugated carbonyls. In this review, we will discuss all the methodologies developed for the synthesis of heterocycles employing intermolecular CÀ H bond functionalization of conjugated carbonyls. The mechanistic pathways and usefulness of the methodologies will be also highlighted.

A dimeric ZnII carbene complex featuring bridging and chelating benzene-1,2-dithiolate ligands is highly stable towards air and water. The donor-Zn-acceptor structure leads to visible light emission in the solid state, solution and polymer matrices with max between 577-657 nm and, for zinc(II) complexes, unusually high radiative rate constants for triplet exciton decay of up to kr = 1.5105 s-1 at room temperature. Variable temperature and DFT/MRCI studies show that a small energy gap between the 1/3LL/LMCT states of only 79 meV is responsible for efficient TADF. Time-resolved luminescence and transient absorption studies confirm the occurrence of long-lived, dominantly ligand-to-ligand charge transfer excited states in solution, allowing for application in Dexter energy transfer photocatalysis.

Carbene coinage metal carbazolates are currently the most efficient organometallic TADF emitters. Herein we report on the photophysical influence of introducing a [2.2]paracyclophane moiety via a carbazolophane ligand instead of carbazolate, which greatly enhances the radiative rate constants by a factor of three to 1-3·106 s-1 for triplet exciton emission.