Experimental and Theoretical Studies of Magnetic Exchange in Silole-Bridged Diradicals
作者:Nans Roques、Philippe Gerbier、Ulrich Schatzschneider、Jean-Pascal Sutter、Philippe Guionneau、José Vidal-Gancedo、Jaume Veciana、Eva Rentschler、Christian Guérin
DOI:10.1002/chem.200501280
日期:2006.7.17
DeltaE(T-S) and J values (DeltaE(T-S) = -2 J) clearly show the intramolecular origin of the observed antiferromagnetic interaction. Analyses of the data with a "Karplus-Conroy"-type equation enabled us to establish that the silole ring, as a whole, allows a more efficient magnetic coupling of the two nitroxide radicals attached to its 2,5-positions than the thiophene ring. This superiority probably
研究了通过甲硅烷(7 ad)或噻吩(12)环作为成色剂连接的五个双(叔丁基硝基氧)双自由基。化合物12在正交晶体空间群Pna2(1)中结晶,其a = 20.752(5),b = 5.826(5)和c = 34.309(5)A。X射线晶体结构测定,电子光谱,可变温度EPR光谱学,SQUID测量和DFT计算(UB3LYP / 6-31 + G *)用于研究该系列分子的分子构象和电子自旋耦合。化合物7b,7c和7d在溶液和固态下都非常稳定,而化合物7b和7d则部分地电子重排为反磁性喹诺酮形式和单自由基物质,这是因为它们对应于π共轭Kekule结构的开放形式。在固态下 磁测量表明,双基自由基都是反铁磁耦合的,正如其拓扑结构所预期的那样。这些交互作用最好通过“ Bleaney-Bowers”模型重现,该模型给出7 a的J = -142.0 cm(-1),7 b的-1.8 cm(-1),-1.3 cm(-1)的值7