Highly Luminescent Divalent Tin(II) Imide Complexes [ArNSn]₂

Abstract

Herein, we describe low-valent tin imides bearing a planar Sn₂N₂ core that serve as highly tunable platforms, exhibiting robust phosphorescence, redox responsiveness, and promise for advanced optoelectronic applications, including luminescent thermometry. Synthesis via transamination furnishes orange crystals of [R1,R2ArNSn]2 (R1,R2Ar = 2,6-((4-R1-С6H4)2CH)2-4-R2-C6H2) (1-4) with notably bright phosphorescence (quantum yields up to 80 % and microsecond-scale lifetimes). Temperature-dependent luminescence measurements reveal promising thermometric performance over the 298–405 K range. Detailed NMR, X-ray crystallographic, and theoretical (TD-DFT) analyses suggest a dual ligand-to-metal charge transfer and metal-centered phosphorescence mechanism, facilitated by significant spin-orbit coupling that promotes intersystem crossing to the triplet state. Notably, these complexes also undergo selective two-electron oxidation to form mixed-valence Sn(II)/Sn(IV) dimers, illustrating the antiaromatic character of the Sn₂N₂ core and its capacity for controlled redox transformations.