Crystal Structure and Nontypical Deep-Red Luminescence of Ca3Mg[Li2Si2N6]:Eu2+

Rare-earth-doped nitridosilicates exhibit outstanding luminescence properties and have been intensively studied for solid-state lighting. Here, we describe the new nitridolithosilicate Ca3Mg­[Li2Si2N6]:Eu2+ with extraordinary luminescence characteristics. The compound was synthesized by the solid-state metathesis reaction in sealed Ta ampules. The crystal structure was solved and refined on the basis of single-crystal X-ray diffraction data. Ca3Mg­[Li2Si2N6]:Eu2+ crystallizes in the monoclinic space group C2/m (no. 12) [Z = 4, a = 5.966(1), b = 9.806(2), c = 11.721(2) Å, β = 99.67(3)°, V = 675.9(2) Å3] and exhibits a layered anionic network made up of edge- and corner-sharing LiN4 tetrahedra and [Si2N6]10– bow-tie units. The network charge is compensated by Ca2+ and Mg2+ ions. Upon irradiation with UV to blue light, red emission at exceptionally long wavelengths (λem = 734 nm, fwhm ≈2293 cm–1) is observed. According to emission in the near-infrared, application in LEDs for horticultural lighting appears promising.