Access to functionalized luminescent Pt(ii) complexes by photoredox-catalyzed Minisci alkylation of 6-aryl-2,2'-bipyridines

Synthesis and Biological Activities of Luminescent 5,6-Membered Bis(Metallacyclic) Platinum(II) Complexes

Four couples of 5,6-membered bis(metallacyclic) Pt(II) complexes with acetylide and isocyanide auxiliary ligands have been prepared and characterized. The structures of (-)-2 and (-)-3 are confirmed by single-crystal X-ray diffraction, showing a distorted square-planar coordination environment around the Pt(II) nucleus. Both solutions and solid samples of all complexes are emissive at RT. Acetylide-coordinated Pt(II) complexes have a lower energy emission than those isocyanide-coordinated ones. The emission spectra of N^N'*C-coordinated Pt(II) derivatives show a lower energy emission maximum relative to N^C*N'-coordinated complexes with the same auxiliary ligand. Moreover, the difference between cyclometalated N^N'*C and N^C*N' ligands exerts a more remarkable effect on the emission than the auxiliary ligands acetylide and isocyanide. Cytotoxicity and cell imaging of luminescent 5,6-membered bis(metallacyclic) Pt(II) complexes have been evaluated.

Circularly polarized luminescence of pinene-modified tetradentate platinum(II) enantiomers containing fused 5/6/6 metallocycles

In this study, a couple of tetradentate Pt(II) enantiomers ((−)-1 and (+)-1) and a couple of tetradentate Pt(IV) enantiomers ((−)-2 and (+)-2) containing fused 5/6/6 metallocycles have been synthesized by controlling reaction conditions. Two valence forms could transform into each other through mild chemical oxidants and reductants. Single-crystal X-ray diffraction confirms the structures of (−)-1 and (−)-2. The coordination sphere of the Pt(II) cation in (−)-1 displays a distorted square-planar geometry and a platinum centroid helix chirality. In contrast, the structure of (−)-2 reveals a distorted octahedral geometry. The solution and the solid of (−)-1 are highly luminescent. Complex (−)-1 shows a prominent aggregation-induced emission enhancement (AIEE) behavior in DMSO/water solution with emission quantum yield (Φ_em) up to 73.2%. Furthermore, highly phosphorescent Pt(II) enantiomers exhibit significant circularly polarized luminescence (CPL) with a dissymmetry factor (g_lum) of order 10⁻³ in CH₂Cl₂ solutions at room temperature. Symmetrically appreciable CPL signals are observed for the enantiomers (−)-1 and (+)-1.

General electrochemical Minisci alkylation of N-heteroarenes with alkyl halides

Herein, we report, a general, facile and environmentally friendly Minisci-type alkylation of N-heteroarenes under simple and straightforward electrochemical conditions using widely available alkyl halides as radical precursors. Primary, secondary and tertiary alkyl radicals have been shown to be efficiently generated and coupled with a large variety of N-heteroarenes. The method presents a very high functional group tolerance, including various heterocyclic-based natural products, which highlights the robustness of the methodology. This applicability has been further proved in the synthesis of various interesting biologically valuable building blocks. In addition, we have proposed a mechanism based on different proofs and pieces of electrochemical evidence.

Visible-Light-Driven Site-selective Alkylation of Benzo Core of Coumarins

An unprecedented, straightforward photochemical platform for efficient site-selective C-H alkylation of C7 position of benzocore via the cross coupling between coumarins and NHPI ester, employing Ru(II) as photocatalyst in visible...