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 (λem = 455–622 nm).