Synthesis, structural, and magnetic characterization of substituted benzoimidazole-l-yl N,N′-dioxides
作者:Alexander Zakrassov、Vitaly Shteiman、Yana Sheynin、Boris Tumanskii、Mark Botoshansky、Moshe Kapon、Amit Keren、Menahem Kaftory、Thomas E. Vos、Joel S. Miller
DOI:10.1039/b400299g
日期:——
The crystal structures, EPR spectra and magnetic properties of the novel halogen- and cyano-substituted nitronyl nitroxide radicals 2-(2,6-dichlorophenyl)benzimidazolyl N,Nâ²-dioxide, 6, 2-(2,6-difluorophenyl)benzimidazolyl N,Nâ²-dioxide, 7, 2-(2-chloro-6-fluorophenyl)benzimidazolyl N,Nâ²-dioxide, 8, 2-(2,3,6-trichlorophenyl)benzimidazolyl N,Nâ²-dioxide, 9, 2-(2,3,4,5,6-pentafluorophenyl)benzimidazolyl N,Nâ²-dioxide, 10, and 2-(3-cyanophenyl)benzimidazolyl N,Nâ²-dioxide, 11, are reported. Compound 6 crystallizes in the triclinic crystal system in space group P. The molecules of 6 are arranged in pairs with short intermolecular distances between the NO groups. 7 crystallizes in two different modifications: polymorph α is orthorhombic, space group Pbca; polymorph β is monoclinic, space group P21/c. 8 crystallizes in two modifications: the α polymorph is monoclinic, space group P21/c; and the β polymorph is monoclinic, space group P21/n. 9 crystallizes in the monoclinic system, space group P21/c. 10 crystallizes in the monoclinic system, space group C2/c. The molecules of 10 are packed in pairs of two types that form a chain perpendicular to the c-axis. 11 crystallizes in the monoclinic crystal system in space group P21/c. The rotation angle between the two rings in compounds 6â10 is 54.2â76.7°. The rotation angle between the two rings is only 21.0° in 11 and it strongly affects the packing of the molecules that adopt the stacking mode. The magnetic measurements show that 6, 7, 10 and 11 exhibit large magnetic coupling. The best fitting with the experimental data for 6 and 11 was obtained using the BleaneyâBowers singletâtriplet model plus the CurieâWeiss spin impurity (S
= 1/2; H
=
â2JS1·S2)
J/kB
=
â84.2 K and θimp
= 0.3 K and J/kB
=
â95.3 K, θimp
= 1.8 K, respectively. A Pade expression for 7 revealed Jintra/kB
= 66.0 K and zJinter/kB
=
â14.0 K. Compound 10 shows evidence for large antiferromagnetic spin coupling (θ
=
â37.0 K CurieâWeiss model).
报告了 2-(2-氯-6-氟苯基)苯并咪唑 N,N²-二氧化物、8、2-(2,3,6-三氯苯基)苯并咪唑 N,N²-二氧化物、9、2-(2,3,4,5,6-五氟苯基)苯并咪唑 N,N²-二氧化物、10 和 2-(3-氰基苯基)苯并咪唑 N,N²-二氧化物 11。6 的分子成对排列,NO 基团之间的分子间距很短。7 以两种不同的形态结晶:多晶体 δ±为正方晶系,空间群为 Pbca;多晶体 δ²为单斜晶系,空间群为 P21/c。8 以两种不同的形态结晶:δ 多晶体为单斜晶体,空间群为 P21/c;δ² 多晶体为单斜晶体,空间群为 P21/n。9 结晶为单斜晶系,空间群为 P21/c。10 结晶为单斜晶系,空间群为 C2/c。10 的分子成对排列,形成垂直于 c 轴的链状。11 在单斜晶系中结晶,空间群为 P21/c。化合物 6â10 中两个环之间的旋转角度为 54.2â76.7° 。而在 11 中,两个环之间的旋转角度仅为 21.0°,这对采用堆积模式的分子堆积产生了很大影响。磁性测量结果表明,6、7、10 和 11 具有较大的磁性耦合。使用 BleaneyâBowers 单三态模型加上居里魏斯自旋杂质(S = 1/2; H = â2JS1Â-S2) J/kB = â84.2 K and θimp = 0.3 K 和 J/kB = â95.3 K, θimp = 1.8 K,可分别获得 6 和 11 与实验数据的最佳拟合。7 的帕德表达式显示 Jintra/kB = 66.0 K,zJinter/kB = â14.0 K。化合物 10 显示了大量反铁磁自旋耦合的证据(δ = â37.0 K 居里魏斯模型)。