TY - JOUR
T1 - Solid-State Photoluminescence Sensitization of Tb3+ by Novel Au2Pt2 and Au2Pt4 Cyanide Clusters
AU - Ladner, LeAnn
AU - Ngo, Tu
AU - Crawford, Carlos
AU - Assefa, Zerihun
AU - Sykora, Richard E
PY - 2011
Y1 - 2011
N2 - The syntheses are reported for two novel Tb heterotrimetallic cyanometallates, K2[Tb(H2O)4(Pt(CN) 4)2]-Au(CN)2· 2H2O (l) and [Tb(C10N2H8) (H2O) 4(Pt(CN)4)-(Au(CN)2)] · 1.5C 10N2H8· 2H2O(2) (C 10N2H8 = 2,2'-bipyridine). Both compounds have been isolated as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoKa, λ = 0.71073 Å, T = 290 K): 1, tetragonal, space group P4 2/nnm, a = 11.9706(2) Å, c = 17.8224(3) Å, V = 2553.85(7) Å3, Z = 4; 2, triclinic, space group P1̄, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) A, α = 101.410(2)°, β = 92.067(2)°, γ =91.196(2)°, V = 1874.14(6) A3, Z = 2. Fort he caseof 1,the structurecontainsAu2Pt4 hexameric noble metal clusters, while 2 includes Au2Pt2 tetrameric clusters. The clusters are alike in that they contain Au-Au and Au-Pt, but not Pt-Pt, metallophilic interactions. Also, the discrete clusters are directly coordinated to Tb3+ and sensitize its emission in both solidstate compounds, 1 and 2. The Photoluminescence (PL) spectra of 1 show broad excitation bands corresponding to donor groups when monitored at the Tb3+ ion f-f transitions, which is typical of donor/acceptor energy transfer (ET) behavior in the system. The compound also displays a broad emission band at ∼445 nm, assignable to a donor metal centered (MC) emission of the Au2Pt4 clusters. The PL properties of 2 show a similar Tb3+ emission in the visible region and a lack of donor-based emission at room temperature; however, at 77 K a weak, broad emission occurs at 400 nm, indicative of uncoordinated 2,2-bipyridine, along with strong Tb 3+ transitions. The absolute quantum yield (QY) for the Tb 3+ emission (5D4 → 7F j (J = 6-3)) in 1 is 16.3% with a lifetime of 616 μs when excited at 325 nm. In contrast the weak MC emission at 445 nm has a quantum yield of 0.9% with a significantly shorter lifetime of 0.61 μs. For 2 the QY value decreases to 9.3% with a slightly shorter lifetime of 562μs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donor-acceptor excited energy gap relative to the optimal gap suggested for Tb3+ and (2) Tb3+ emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.
AB - The syntheses are reported for two novel Tb heterotrimetallic cyanometallates, K2[Tb(H2O)4(Pt(CN) 4)2]-Au(CN)2· 2H2O (l) and [Tb(C10N2H8) (H2O) 4(Pt(CN)4)-(Au(CN)2)] · 1.5C 10N2H8· 2H2O(2) (C 10N2H8 = 2,2'-bipyridine). Both compounds have been isolated as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoKa, λ = 0.71073 Å, T = 290 K): 1, tetragonal, space group P4 2/nnm, a = 11.9706(2) Å, c = 17.8224(3) Å, V = 2553.85(7) Å3, Z = 4; 2, triclinic, space group P1̄, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) A, α = 101.410(2)°, β = 92.067(2)°, γ =91.196(2)°, V = 1874.14(6) A3, Z = 2. Fort he caseof 1,the structurecontainsAu2Pt4 hexameric noble metal clusters, while 2 includes Au2Pt2 tetrameric clusters. The clusters are alike in that they contain Au-Au and Au-Pt, but not Pt-Pt, metallophilic interactions. Also, the discrete clusters are directly coordinated to Tb3+ and sensitize its emission in both solidstate compounds, 1 and 2. The Photoluminescence (PL) spectra of 1 show broad excitation bands corresponding to donor groups when monitored at the Tb3+ ion f-f transitions, which is typical of donor/acceptor energy transfer (ET) behavior in the system. The compound also displays a broad emission band at ∼445 nm, assignable to a donor metal centered (MC) emission of the Au2Pt4 clusters. The PL properties of 2 show a similar Tb3+ emission in the visible region and a lack of donor-based emission at room temperature; however, at 77 K a weak, broad emission occurs at 400 nm, indicative of uncoordinated 2,2-bipyridine, along with strong Tb 3+ transitions. The absolute quantum yield (QY) for the Tb 3+ emission (5D4 → 7F j (J = 6-3)) in 1 is 16.3% with a lifetime of 616 μs when excited at 325 nm. In contrast the weak MC emission at 445 nm has a quantum yield of 0.9% with a significantly shorter lifetime of 0.61 μs. For 2 the QY value decreases to 9.3% with a slightly shorter lifetime of 562μs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donor-acceptor excited energy gap relative to the optimal gap suggested for Tb3+ and (2) Tb3+ emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.
M3 - Article
VL - 50
SP - 2199
EP - 2206
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 6
ER -