Unusual Luminescence Spectra and Decay Dynamics in Crystalline Supramolecular [(A18C6) 4 MBr 4 ][TlBr 4 ] 2 (A = Rb, K; M = 3d Element) Complexes
1997; American Chemical Society; Volume: 36; Issue: 24 Linguagem: Inglês
10.1021/ic9601753
ISSN1520-510X
AutoresNicolette Fender, Frank R. Fronczek, Vijay T. John, Ishenkumba A. Kahwa, Gary L. McPherson,
Tópico(s)Synthesis and characterization of novel inorganic/organometallic compounds
ResumoLuminescence and electronic energy transport characteristics of supramolecular cubic F23 [(A18C6)4MnBr4][TlBr4]2 complexes (A = Rb, 1; A = K, 2) were studied with the expectation that MnBr42- ions would be effective luminescent probes for solid state 18-crown-6 rotation-conformational reorientation motion frequently revealed by NMR methods. Luminescence and excitation spectra of 1 are normal for complexes of MnBr42-, but complex 2 features an unusual orange emission (due to crystal defects) with λmax ≈ 570 nm which is sensitized by MnBr42- ions. Thermal barriers of 8 and 14 kJ mol-1 (T < 210 K and T > 240 K, respectively) for 1 (MnBr42- λem = 511 nm) and 2 (crystal defect λem = 610 nm) are attributed to the energy required to bridge the Stokes shifted 4T1(4G) emission of the donor MnBr42- ions with the electronic origin of the 4T1(4G) state on the acceptor MnBr42- during energy migration. That of 26 kJ mol-1 (210 < T < 240 K) exhibited by 1 is attributed to the activation energy for the 18C6 solid state motion inferable from the single, broad, featureless solid state 13C NMR band of [(K18C6)4ZnBr4][TlBr4]2 (3). Crystal data for [(K18C6)4MBr4][TlBr4]2, where M = Mn (Zn): space group F23 and Z = 4 for both complexes; a = 20.986(7) (20.9682(7)) Å, V = 9242.8(3) (9219.0(3)) Å3, number of observed data = 672 (668), Rw = 0.037 (0.039), R = 0.062 (0.036).
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