Synthesis, structure, and luminescence properties of sodium and ytterbium complexes with 2-(benzothiazol-2-yl)selenophenolate ligands

With the aim of designing new heteroorganic ligands capable of sensitizing the metal-centered photoluminescence (PL) of Yb III through the redox mechanism, a new diselenide, 2,2 ′ -(diseleno-2,1-diphenylene)bis[benzothiazole] ((SeSN) 2 , 1 ), was synthesized and structurally characterized. The selenophenolate complexes Na(SeSN)(DME) 2 (2) and Yb(SeSN) 3 ·0.5 THF (3) were synthesized by the reactions of diselenide 1 with Na and Yb metals in liquid ammonia. Complex 2 showed intense PL at 77 K in a DME solution, which appears as a broad band with a maximum at 575 nm assigned to the phosphorescence of the organoselenide ligand. In the crystalline state, ytterbium complex 3 , which was isolated and structurally characterized as an adduct with THF, exhibited intense metal-centered PL in the 980–1100 nm region. This PL is observed upon direct excitation or upon excitation through SeSN ligands (250–380 nm), as well as through excitation of the ligand-to-metal charge transfer (LMCT) band in the 430–700 nm region. The presence of low-energy LMCT states capable of sensitizing the metal-centered PL of Yb III in complexes with organoselenide ligands is responsible for a significant reduction of the Stokes shift of luminescence and opens up new prospects for the development of lanthanide-containing infrared luminophores exhibiting luminescence under long-wavelength excitation.