Synthesis and Characterization of Tb[N(CN)2]3·2H2O and Eu[N(CN)2]3·2H2O: Two New Luminescent Rare-Earth Dicyanamides
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- 作者：Abanti Nag ; Peter J. Schmidt ; Wolfgang Schnick
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：November 28, 2006
- 年：2006
- 卷：18
- 期：24
- 页码：5738 - 5745
- 全文大小：244K
- 年卷期：v.18,no.24(November 28, 2006)
- ISSN：1520-5002
文摘
Two new rare-earth dicyanamides, namely, Tb[N(CN)2]3·2H2O and Eu[N(CN)2]3·2H2O, have beenprepared by ion exchange in aqueous solution, followed by evaporation of the solvent at room temperature.The structures of both compounds have been solved and refined from single-crystal and powder X-raydiffraction data, respectively. The two compounds are isostructural and are built up from irregular quadraticantiprismatic LnN6O2 polyhedra connected to each other by three crystallographically independentdicyanamide ([N(CN)2]3-) ions (Tb[N(CN)2]3·2H2O, P21/n, Z = 4, a = 7.4632(15) Å, b = 11.523(2) Å,c = 13.944(3) Å, 
= 94.06(3)
, V = 1196.2(4) Å3; Eu[N(CN)2]3·2H2O, P21/n, Z = 4, a = 7.4780(3) Å,b = 11.5429(5) Å, c = 13.9756(7) Å, = 93.998(4), V = 1203.41(10) Å3). Annealing of the hydratedphases of Ln[N(CN)2]3·2H2O (Ln = Eu, Tb) at 150 C under an argon atmosphere leads to the formationof nonhydrated Ln[N(CN)2]3 (Ln = Eu, Tb). Both the hydrated (Eu[N(CN)2]3·2H2O) and nonhydrated(Eu[N(CN)2]3) europium(III) dicyanamides show red luminescence due to the dominant intensity of 5D0-7FJ (J = 1, 2, 4) emission lines by excitation at 365 nm. The broad excitation band of europium(III)dicyanamide (fwhm = 8000 cm-1) ranging between 260 and 420 nm with 
max 
30000 cm-1 is ascribedto a Eu-N charge-transfer transition, which is significantly shifted to lower energy compared to that ofoxo compounds due to the nephalauxetic effect. Similarly, both the hydrated (Tb[N(CN)2]3·2H2O) andnonhydrated (Tb[N(CN)2]3) terbium(III) dicyanamides show green emission at exc = 365 nm, arisingmainly from the dominant 5D0-7F4 transition. However, unlike europium(III) dicyanamide, the broadexcitation band of terbium(III) dicyanamide ranging between 250 and 400 nm with a maximum at 33000cm-1 can be assigned to the 4f8-4f75d1 transition of Tb3+.
= 94.06(3), V = 1196.2(4) Å3; Eu[N(CN)2]3·2H2O, P21/n, Z = 4, a = 7.4780(3) Å,b = 11.5429(5) Å, c = 13.9756(7) Å, = 93.998(4), V = 1203.41(10) Å3). Annealing of the hydratedphases of Ln[N(CN)2]3·2H2O (Ln = Eu, Tb) at 150 C under an argon atmosphere leads to the formationof nonhydrated Ln[N(CN)2]3 (Ln = Eu, Tb). Both the hydrated (Eu[N(CN)2]3·2H2O) and nonhydrated(Eu[N(CN)2]3) europium(III) dicyanamides show red luminescence due to the dominant intensity of 5D0-7FJ (J = 1, 2, 4) emission lines by excitation at 365 nm. The broad excitation band of europium(III)dicyanamide (fwhm = 8000 cm-1) ranging between 260 and 420 nm with max 30000 cm-1 is ascribedto a Eu-N charge-transfer transition, which is significantly shifted to lower energy compared to that ofoxo compounds due to the nephalauxetic effect. Similarly, both the hydrated (Tb[N(CN)2]3·2H2O) andnonhydrated (Tb[N(CN)2]3) terbium(III) dicyanamides show green emission at exc = 365 nm, arisingmainly from the dominant 5D0-7F4 transition. However, unlike europium(III) dicyanamide, the broadexcitation band of terbium(III) dicyanamide ranging between 250 and 400 nm with a maximum at 33000cm-1 can be assigned to the 4f8-4f75d1 transition of Tb3+.