Defects and Luminescence Behavior of Cubic F23 [(NH4(18-Crown-6))4MnX4] [TlX4]2 (X=Cl, Br) Crystals |
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| Authors: | Nicolette S Fender Ishenkumba A Kahwa Frank R Fronczek |
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| Affiliation: | a Department of Chemistry, University of the West Indies Mona Campus, Kingston 7, Jamaica, West Indiesb Department of Chemistry, Louisiana State University Baton Rouge, Louisiana, 70803 |
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| Abstract: | Luminescence from [(NH4(18-Crown-6))4MnBr4][TlBr4]2 (1), [(NH4(18-Crown-6))4MnCl4][TlCl4]2 (2), [(NH4(18-Crown-6))2MnBr4] (3), and [(NH4(18-Crown-6))2MnCl4] (4) was studied in search of new insights regarding crystal defects in 2. Emission from 3 and 4 is normal Mn2+(4T1(4G)→6A1); that of 2 (λmax≈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<150 K (1-2, NH+4 rotations), 150<T<250 K (7-14, energy migration among [MnX4]2−), 250<T<300 K (26-35, rotations of 18-Crown-6)); yellow emission of 2: T;<250 K (7-8, energy migration among [MnX4]2−), T>250 K (29 kJ/mol, defect-to-Mn2+(4T1(4G)) back energy transfer). Crystal data for 4: Space group P21/c; Z=4; a=20.173(1) Å; b=9.0144(8) Å; c=20.821(1) Å; β=98.782(5)°; V=3741.9(8) Å3; Rw=0.059; R=0.054. |
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| Keywords: | supramolecular aggregations manganese(II) luminescence tetrahalomanganate(II) energy transfer 18-Crown-6 crystal defects. |
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