Blanco Víctor, Abella Dolores, Pía Elena, Platas-Iglesias Carlos, Peinador Carlos, Quintela José M
Departamento de Química Fundamental, Facultad de Ciencias, Universidade da Coruña, Campus A Zapateira, 15071 A Coruña, Spain.
Inorg Chem. 2009 May 4;48(9):4098-107. doi: 10.1021/ic8022425.
Dinuclear metallocycles were assembled from an L-shaped bidentate ligand based on 4,4'-bipyridine and palladium or platinum square-planar cis complexes. The palladium (4a,b) or platinum (5a,b) square metallocycles were obtained as 1:1 regioisomeric mixtures depending on which pair of coordinative nitrogen atoms binds to the metal center. The squares display a pi-deficient cavity suitable to incorporate two pi-donor aromatic systems. Therefore, the reaction with macrocyclic polyethers (BPP34C10 or DN38C10) resulted in the regioselective self-assembly of the [3]catenanes 4a(BPP34C10 or DN38C10)(2) x 6 PF(6) and 5a(BPP34C10 or DN38C10)(2) x 6 PF(6) because only macrocycles 4a and 5a present the correct disposition of the pi-deficient aromatic systems to maximize the pi...pi stacking interactions. Single-crystal X-ray analyses of [3]catenanes revealed that the structures are additionally stabilized by [C-H...O], [N-H...O] bonds and [C-H...pi] interactions. The 1:2 inclusion complexes of metallocycles were prepared by self-assembly of three components: the ligand 1-(4-(pyridin-4-yl)benzyl)-4,4'-bipyridin-1-ium, a square planar complex M(en)(NO(3))(2) (M = Pd or Pt, en = ethylenediamine), and a dioxoaromatic guest in a 2:2:2 ratio. The comparative study of the formation of 1:2 inclusion complexes has allowed us to conclude that the pi...pi interactions between the host and guests are responsible for the observed regioselectivity.
双核金属环是由基于4,4'-联吡啶的L形双齿配体与钯或铂的平面正方形顺式配合物组装而成。根据哪一对配位氮原子与金属中心结合，钯（4a,b）或铂（5a,b）方形金属环以1:1区域异构体混合物的形式获得。这些正方形显示出一个缺π空腔，适合容纳两个π供体芳香体系。因此，与大环聚醚（BPP34C10或DN38C10）的反应导致了[3]索烃4a(BPP34C10或DN38C10)(2)×6 PF(6)和5a(BPP34C10或DN38C10)(2)×6 PF(6)的区域选择性自组装，因为只有大环4a和5a呈现出缺π芳香体系的正确排列，以最大化π…π堆积相互作用。[3]索烃的单晶X射线分析表明，这些结构还通过[C-H…O]、[N-H…O]键和[C-H…π]相互作用得到稳定。金属环的1:2包合物是通过三种组分的自组装制备的：配体1-(4-(吡啶-4-基)苄基)-4,4'-联吡啶鎓、平面正方形配合物M(en)(NO(3))(2)（M = Pd或Pt，en = 乙二胺）和二氧代芳香客体，比例为2:2:2。对1:2包合物形成的比较研究使我们能够得出结论，主体与客体之间的π…π相互作用是观察到的区域选择性的原因。
