Mikhalyova Elena A, Zeller Matthias, Jasinski Jerry P, Butcher Raymond J, Carrella Luca M, Sedykh Alexander E, Gavrilenko Konstantin S, Smola Sergey S, Frasso Michael, Cazorla Sebastian Calderon, Perera Kuluni, Shi Anni, Ranjbar Habib G, Smith Casey, Deac Alexandru, Liu Youlin, McGee Sean M, Dotsenko Vladimir P, Kumke Michael U, Müller-Buschbaum Klaus, Rentschler Eva, Addison Anthony W, Pavlishchuk Vitaly V
L. V. Pisarzhevskii Institute of Physical Chemistry of the National Academy of Sciences of the Ukraine, Prospekt Nauki 31, Kiev, 03028, Ukraine.
Dalton Trans. 2020 Jun 21;49(23):7774-7789. doi: 10.1039/d0dt00600a. Epub 2020 May 14.
A series of tris(pyrazolyl)borate mono-, di- and trinuclear complexes, [TpLn]X (Ln = Eu, Tb, Gd, Dy, X = various mono-, bis- and tris(β-diketonates) has been prepared. The Tb and Dy complexes are luminescent single molecular magnets (SMM) and exhibit luminescence quantum efficiencies up to 73% for the Tb and 4.4% for the Dy compounds. Similar Eu complexes display bright emission only at lower temperatures. The Dy and Tb complexes possess SMM behavior in a non-zero dc field at low temperatures, while the polynuclear Dy complexes also show slow magnetic relaxation even in zero dc field up to 8 K. U-values determined from dynamic magnetic measurements were up to 31 and 6 cm for the Dy and Tb complexes, respectively. It was found that within a series of Dy and Tb compounds, U and luminescence quantum yields decreased with increasing nuclearity of the compounds and a shortening of the intramolecular Ln-Ln distance. Δ-values estimated from low-temperature luminescence spectra were significantly higher than those obtained from ac magnetic data, which may be due to involvement of additional processes in the relaxation mechanism (quantum tunneling, Raman, direct) reducing the energy barrier. Some of the Tb-compounds also display metal-centred electroluminescence, giving them potential as emitting layers in LEDs.
已制备出一系列三（吡唑基）硼酸单核、双核和三核配合物，[TpLn]X（Ln = Eu、Tb、Gd、Dy，X = 各种单、双和三（β - 二酮））。Tb和Dy配合物是发光单分子磁体（SMM），Tb化合物的发光量子效率高达73%，Dy化合物的发光量子效率为4.4%。类似的Eu配合物仅在较低温度下显示明亮发射。Dy和Tb配合物在低温下的非零直流场中具有SMM行为，而多核Dy配合物即使在零直流场中直至8 K也显示出缓慢的磁弛豫。通过动态磁测量确定的Dy和Tb配合物的U值分别高达31和6 cm。研究发现，在一系列Dy和Tb化合物中，U值和发光量子产率随着化合物核数的增加以及分子内Ln - Ln距离的缩短而降低。从低温发光光谱估计的Δ值明显高于从交流磁数据获得的值，这可能是由于弛豫机制（量子隧穿、拉曼、直接）中涉及额外过程降低了能垒。一些Tb化合物还显示出以金属为中心的电致发光，使其具有作为发光二极管发光层的潜力。
