Intriguing Indium-salen Complexes as Multicolor Luminophores

The series of novel salen-based indium complexes (3-^tBu-5-R-salen)In-Me (3-^tBu-5-R-salen = N,N′-bis(2-oxy-3-tert-butyl-5-R-salicylidene)-1,2-diaminoethane, R = H (1), ^tBu (2), Br (3), Ph (4), OMe (5), NMe₂ (6)) and [(3-^tBu-5-NMe₃-salen)In-Me](OTf)₂ (7; OTf = CF₃SO₃^-) have been synthesized and fully characterized by NMR spectroscopy and elemental analysis. All indium complexes 1-7 are highly stable in air and even aqueous solutions. The solid-state structures for 3-5, which were confirmed by single-crystal X-ray analysis, exhibit square-pyramidal geometries around the indium center. Both the UV/vis absorption and PL spectra of 1-7 exhibit significant intramolecular charge transfer (ICT) transitions based on the salen moieties with systematically bathochromic shifts, which depend on the introduction of various kinds of substituents. Consequently, the emission spectra of these complexes cover almost the entire visible region (λ_em = 455-622 nm).