Tú Ngô - Academia.edu (original) (raw)

Papers by Tú Ngô

Research paper thumbnail of Solid-State Photoluminescence Sensitization of Tb3+ by Novel Au2Pt2 and Au2Pt4 Cyanide Clusters

The syntheses are reported for two novel Tb 3þ heterotrimetallic cyanometallates, K 2 [Tb(H 2 O) ... more The syntheses are reported for two novel Tb 3þ heterotrimetallic cyanometallates, K 2 [Tb(H 2 O) 4 (Pt(CN) 4) 2 ]-Au(CN) 2 3 2H 2 O (1) and [Tb(C 10 N 2 H 8)(H 2 O) 4 (Pt(CN) 4)-(Au(CN) 2)] 3 1.5C 10 N 2 H 8 3 2H 2 O (2) (C 10 N 2 H 8 = 2,2 0-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 (MoKR, 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) Å 3 , Z = 4; 2, triclinic, space group P1, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) Å, R = 101.410(2)°, β = 92.067(2)°, γ = 91.196(2)°, V = 1874.14(6) Å 3 , Z = 2. For the case of 1, the structure contains Au 2 Pt 4 hexameric noble metal clusters, while 2 includes Au 2 Pt 2 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 Tb 3þ 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 Tb 3þ 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 Au 2 Pt 4 clusters. The PL properties of 2 show a similar Tb 3þ 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 0-bipyridine, along with strong Tb 3þ transitions. The absolute quantum yield (QY) for the Tb 3þ emission (5 D 4 f 7 F 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 562 μs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donoracceptor excited energy gap relative to the optimal gap suggested for Tb 3þ and (2) Tb 3þ emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.

Research paper thumbnail of Solid-State Photoluminescence Sensitization of Tb3+ by Novel Au2Pt2 and Au2Pt4 Cyanide Clusters

The syntheses are reported for two novel Tb 3þ heterotrimetallic cyanometallates, K 2 [Tb(H 2 O) ... more The syntheses are reported for two novel Tb 3þ heterotrimetallic cyanometallates, K 2 [Tb(H 2 O) 4 (Pt(CN) 4) 2 ]-Au(CN) 2 3 2H 2 O (1) and [Tb(C 10 N 2 H 8)(H 2 O) 4 (Pt(CN) 4)-(Au(CN) 2)] 3 1.5C 10 N 2 H 8 3 2H 2 O (2) (C 10 N 2 H 8 = 2,2 0-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 (MoKR, 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) Å 3 , Z = 4; 2, triclinic, space group P1, a = 10.0646(2) Å, b = 10.7649(2) Å, c = 17.6655(3) Å, R = 101.410(2)°, β = 92.067(2)°, γ = 91.196(2)°, V = 1874.14(6) Å 3 , Z = 2. For the case of 1, the structure contains Au 2 Pt 4 hexameric noble metal clusters, while 2 includes Au 2 Pt 2 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 Tb 3þ 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 Tb 3þ 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 Au 2 Pt 4 clusters. The PL properties of 2 show a similar Tb 3þ 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 0-bipyridine, along with strong Tb 3þ transitions. The absolute quantum yield (QY) for the Tb 3þ emission (5 D 4 f 7 F 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 562 μs. The reduced QY in 2 is considered to be a consequence of (1) the slightly increased donoracceptor excited energy gap relative to the optimal gap suggested for Tb 3þ and (2) Tb 3þ emission quenching via a bpy ligand-to-metal charge transfer (LMCT) excited state.