Iridium Complexes Containing Bis(imidazoline thione) and Bis(imidazoline selone) Ligands for Visible-Light-Induced Oxidative Coupling of Benzylamines to Imines

Abstract

Novel iridium(III) complexes containing bis(N-heterocyclic carbene), bis(imidazoline thione) L2, and bis(imidazoline selone) L3 were prepared. The iridium complexes bearing L2 and L3 showed the significant absorption of visible light with maximum intensity at ∼460 nm. Bis(2-(2′-benzothienyl)pyridinato)iridium(III) complexes (Ir-6) with L3 showed excellent ability as a photosensitizer of visible light. Under blue LED irradiation with maximum emission at 460 nm, 0.25 mol % Ir-6 showed 94% conversion of benzylamine for 5 h at room temperature. Through mechanistic studies, it was suggested that the photoinduced oxidative coupling of benzylamine by Ir-6 follows a singlet oxygen pathway. The excellent performance of Ir-6 originated from the efficient visible light absorption at 460 nm and the enhanced triplet state due to the heavy-atom effect of L3. This work shows that bis(imidazoline thione) and bis(imidazoline selone) can be efficient ligands for tuning the optical properties of iridium(III) complexes.

Retraction: Synthesis and Characterization of Sterically Congested Mesityltris(imidazolium) Salts and the Corresponding Highly Crystalline Tris‐selone Derivatives

“…[13,25] Imidazole selones, as pecial class of heteroketones, have gained increasing interest in recenty ears as efficient ligating agents in lieu of traditional N-heterocyclic carbenes. In fact, mono-and bis-imidazole selones have been extensively used to generate transitionmetal-based complexes [26][27][28][29][30][31][32][33][34][35][36][37][38] and have furtherb een employed in versatile catalytic applications, such as polymerization [39] and the reduction of nitrobenzenes. [40] Moreover,s uch selenoketones have been used as inhibitors of lactoperoxidase-catalyzed oxidation and tyrosine nitration, [41][42][43] as an analogue of the antithyroidd rug methimazole, [44][45][46] in optoelectronics, [47] as chemicals ensors, [48] and also as ac hemical tool for Pd II extraction from water.…”

Synthesis and Characterization of Sterically Congested Mesityltris(imidazolium) Salts and the Corresponding Highly Crystalline Tris-selone Derivatives

“…[13,25] Imidazole selones, as pecial class of heteroketones, have gained increasing interest in recenty ears as efficient ligating agents in lieu of traditional N-heterocyclic carbenes. In fact, mono-and bis-imidazole selones have been extensively used to generate transitionmetal-based complexes [26][27][28][29][30][31][32][33][34][35][36][37][38] and have furtherb een employed in versatile catalytic applications, such as polymerization [39] and the reduction of nitrobenzenes. [40] Moreover,s uch selenoketones have been used as inhibitors of lactoperoxidase-catalyzed oxidation and tyrosine nitration, [41][42][43] as an analogue of the antithyroidd rug methimazole, [44][45][46] in optoelectronics, [47] as chemicals ensors, [48] and also as ac hemical tool for Pd II extraction from water.…”

Singlet Oxygen Generation by Cyclometalated Complexes and Applications

“…The calculated excited‐state energy levels of 21 suggest that electron transfer from the benzylamine to oxidized 21 is unlikely, thus disfavoring the Type I photoredox pathway. Furthermore, the singlet oxygen emission signal from the diselone complex 21 was 2.4 times high than that of the dithione complex 20 , consistent with a singlet oxygen pathway, as 21 leads to a considerably higher yields in the coupling reaction .…”

“…Son et al . prepared two interesting biscyclometalated complexes bearing an S‐bound dithione ( 20 ) and a Se‐bound di‐selenone ( 21 , Scheme ; (btpy = bis(2‐(2′‐benzothienyl)pyridine; biS = bis(imidazoline thione; biSe = bis(imidazoline selone), 20 ) . The authors were able to detect singlet oxygen by its near‐infrared emission signal.…”