Defects and Luminescence Behavior of Cubic F23 [(NH4(18-Crown-6))4MnX4] [TlX4]2 (X=Cl, Br) Crystals

Abstract Luminescence from [(NH 4 (18-Crown-6)) 4 MnBr 4 ][TlBr 4 ] 2 (1), [(NH 4 (18-Crown-6)) 4 MnCl 4 ][TlCl 4 ] 2 (2), [(NH 4 (18-Crown-6)) 2 MnBr 4 ] (3), and [(NH 4 (18-Crown-6)) 2 MnCl 4 ] (4) was studied in search of new insights regarding crystal defects in 2. Emission from 3 and 4 is normal Mn 2+ ( 4 T 1 ( 4 G)→ 6 A 1 ); that of 2 ( λ max ≈520 nm at ca. 300 K and 560 nm at 77 K) is unusual and temperature dependent. Thermal barriers (kJ/mol, assignment): green emission of 1 and 2, T + 4 rotations), 150 T X 4 ] 2− ), 250 T T; X 4 ] 2− ), T >250 K (29 kJ/mol, defect-to-Mn 2+ ( 4 T 1 ( 4 G)) back energy transfer). Crystal data for 4: Space group P 2 1 / c ; Z =4; a =20.173(1) A; b =9.0144(8) A; c =20.821(1) A; β =98.782(5)°; V =3741.9(8) A 3 ; R w =0.059; R =0.054.