3,3′-[1,2-Phenyl­enebis(methyl­ene)]bis­(1-ethyl­benzimidazolium) dibromide

In the title mol­ecular salt, C26H28N4 2+·2Br−, the central benzene ring makes dihedral angles of 76.75 (11) and 82.40 (10)° with the pendant benzimidazole rings. The corresponding angle between the benzimidazole rings is 57.03 (9)°. In the crystal, the cations and anions are linked via C—H⋯Br hydrogen bonds, forming sheets lying parallel to the bc plane. The crystal structure also features weak C—H⋯π inter­actions

Synthesis, structures and photoluminescence properties of silver complexes of cyclic (alkyl)(amino)carbenes

Silver complexes of cyclic (alkyl)(amino)carbenes (CAACs), (RL)nAgX (n = 1, X = Cl, Br, I; n = 2, X = OTf; R = Me2, Et2, or adamantyl) are accessible in high yields by reacting free carbenes with silver salts. The smaller carbene ligand Me2L leads to the formation of a mixture of neutral (Me2L)AgCl and cationic [(Me2L)2Ag]+ products. The transmetallation of (AdL)AgCl with copper and gold halides gives the corresponding copper and gold compounds (AdL)MCl (M = Cu and Au) in a clean and quantitative reaction. Whereas (Me2L)AgCl is monomeric in the solid state, (Et2L)AgCl crystallizes as a Cl-bridged dimer. None of the compounds show metal-metal interactions. The complexes show blue photoluminescence, which consists of a fluorescence component with a lifetime of several nanoseconds, as well as a long-lived emission in the microsecond regime

Recent advances in organic synthesis using light-mediated n-heterocyclic carbene catalysis

The combination of photocatalysis with other ground state catalytic systems have attracted much attention recently due to the enormous synthetic potential offered by a dual activation mode. The use of N-heterocyclic carbene (NHC) as organocatalysts emerged as an important synthetic tool. Its ability to harness umpolung reactivity by the formation of the Breslow intermediate has been employed in the synthesis of thousands of biologically important compounds. However, the available coupling partners are relatively restricted, and its combination with other catalytic systems might improve its synthetic versatility. Thus, merging photoredox and N-heterocyclic carbene (NHC) catalysis has emerged recently as a powerful strategy to develop new transformations and give access to a whole new branch of synthetic possibilities. This review compiles the NHC catalyzed methods mediated by light, either in the presence or absence of an external photocatalyst, that have been described so far, and aims to give an accurate overview of the potential of this activation modeL.M. acknowledges the Autonomous Community of Madrid (CAM) for the financial support (PEJD-2019-PRE/AMB-16640 and SI1/PJI/ 2019-00237) and for an “Atracción de Talento Investigador” contract (2017-T2/AMB-5037

Olefin poly/oligomerizations by metal precatalysts bearing non–heterocyclic N–donor ligands

none4sinoneBudagumpi, Srinivasa; Keri, Rangappa S.; Biffis, Andrea; Patil, Siddappa A.Budagumpi, Srinivasa; Keri, Rangappa S.; Biffis, Andrea; Patil, Siddappa A

Biologically relevant silver(i)-n-heterocyclic carbene complexes: synthesis, structure, intramolecular interactions, and applications

N-Heterocyclic carbenes (NHCs) complexed with silver represent new, broad-spectrum antimicrobial and anticancer agents, normally with low toxicity profiles, and they provide a range of versatile structures for targeted biological applications. Most of these complexes have shown higher cytotoxicity than cisplatin, a potent anticancer drug. This study reviews the design, synthesis, structural characterization, and biological applications of silver complexes derived from both functionalized and nonfunctionalized NHC ligands. Specifically, silver complexes of functionalized and nonfunctionalized imidazole- and benzimidazole-based NHC systems employed in antimicrobial and anticancer applications are reviewed. Advancements achieved in the use of silver(I)-NHC complexes of miscellaneous azolium ligands, such as 1,2,4-triazole and the heterocycle-fused imidazolium derivative xanthene are also reviewed. Encapsulation of a series of silver-NHC complexes in a polymer-based carrier material represents a promising method for the targeted delivery of silver ions to the infected sites. The advances achieved in this particular area are systematically reviewed in this paper. In general, these preliminary achievements reveal the potential of silver(I)-NHC complexes as efficient antimicrobial and anticancer candidates. NHC ligand design for the formation of mono- and binuclear AgI complexes is reviewed. Particular attention is paid to AgI-NHC complexes that exhibit different biological activities. The effects of different substituents on the structures of the complexes are investigated. AgI complexes with functionalized and nonfunctionalized NHCs are compared