The first example of generation and emission of divalent Sm2+* ion in a liquid-phase chemiluminescence in the system SmCl3·6H2O–THF–Bui2AlH–O2

• First SmCl2·THF2 complex were obtained, isolated and identified.
• First liquid-phase chemiluminescence (CL) of Sm2+ was found and studied.
• In contrast to the known blue Eu2+*–CL, Sm2+* ion emits near-infrared light.
• Sm2+ ion is excited by energy transfer from the triplet-excited isobutyric aldehyde.
• Sm2+–CL is less bright than Eu2+–CL due to less efficient energy transfer to Sm2+.

First it was found that the divalent Sm2+ ion can act as enhancer and emitter of a liquid-phase chemiluminescence (СL) on the example of the near-infrared emission of Sm2+* in the system SmCl3·6H2O–THF–Bui2AlH–O2. The Sm2+*–CL (λmax = 780 ± 20 nm) occurs upon adding the diisobutylaluminum hydride Bui2AlH to a suspension of the SmCl3·6H2O crystalline hydrate in THF. The Bui2AlH removes water molecules from the coordination sphere of Sm3+ and reduces Sm3+ to Sm2+ with formation of the SmCl2·(THF)2 complex. The excess of Bui2AlH is oxidized by oxygen with generating a primary emitter, the triplet-excited molecule of isobutyric aldehyde 3Me2CHC(H) = O*. The energy of the latter is transferred to the SmCl2·(THF)2 complex, leading to the formation of the excited state of the Sm2+ ion. The composition of SmCl2·(THF)2 complex, which are formed after the interaction in the system SmCl3·6H2O–THF–Bui2AlH–O2, was also determined. Moreover, its photoluminescence (PL), UV–vis IR, 1H and 13C NMR spectra were measured. The spectrum of Sm2+*–CL contains maxima both ions Sm2+ and Sm3+ due to incomplete reducing of Sm3+.