Synthesis, crystal structure and luminescence properties of novel microporous europium silicate НK6Eu3+[Si10O25] with a framework formed of nano-scale tubes

• A new K, Eu-silicate was synthesized using hydrothermal techniques.
• The X-ray structure analysis was performed using single crystal diffraction data.
• The new compound represents the new structure type.

Single crystals of new microporous europium and potassium silicate were synthesized using hydrothermal techniques and structure was determined. Monoclinic unit-cell values are: a = 27.6960(3), b = 7.0504(1), c = 14.2190(2) Å, β = 116.306(1)°, space group C2/c. Structure model was determined by direct methods and refined up to R = 4.4% in anisotropic approximation. The compound НK6Eu3+[Si10O25] crystallizes in a new structure type that is based on nano-scale oval tubes of eight-member rings [Si8О24] with inner diameters of 1.7 and 3.4 Å joint by additional Si-tetrahedra. Despite of the fact that the inner diameter of tubes is very small they are not empty. Symmetrical H-bonds are formed between oxygen atoms along short diameters of the corrugated eight-member rings.Spectral characteristics of luminescence were determined. Low quantum yield with high element content and long kinetic attenuation show that minor number of Eu atoms is in “luminescent” state. The wide weak resolved lines of 5D0 → 7F1 transition point to considerable disorder variation of Eu3+ surrounding.

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