Toppled Molecular-Domino Sets by Self-Assembly of Self-assembly: The π-Polymers

Abstract

A series of designed binuclear palladium(II)based self-assemblies, [Pd 2 (en) 2 (L) 2 ](NO 3 ) 4 , 1a; [Pd 2 -(tmeda) 2 (L) 2 ](NO 3 ) 4 , 2a; [Pd 2 (bpy) 2 (L) 2 ](NO 3 ) 4 , 3a; and [Pd 2 (phen) 2 (L) 2 ](NO 3 ) 4 , 4a, are synthesized. These complexes are obtained in good to excellent yields by equimolar combination of the nonchelating bidentate ligand bis(4pyridylmethyl)piperazine, L, with the corresponding cis-protected palladium(II) component, that is, Pd(N-N)(NO 3 ) 2 , under suitable reaction conditions. The cis-protecting N-N units used are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridyl (bpy), and 1,10-phenanthroline (phen). The complexes 1a−4a are well-characterized by 1 H NMR, H−H COSY, and HSQC, and the molecular compositions have been established by ESI-MS. The molecular structures are confirmed for the complexes [Pd 2 (tmeda) 2 (L) 2 ](ClO 4 ) 4 , 2b; [Pd 2 (bpy) 2 (L) 2 ](ClO 4 ) 4 , 3b; and [Pd 2 (phen) 2 (L) 2 ](NO 3 ) 4 , 4a, by the single-crystal X-ray diffraction technique. In the cases of the complexes 3b and 4a, the crystal packing diagrams display a unique onedimensional predefined organization of molecules by intermolecular π−π interactions using the strategically located π-surfaces of the cis-protecting units. This organization resembles a set of toppled dominos. A given set exhibits further interactions with the neighboring sets in the packing pattern that are influenced by the nature of the N-N moiety, for example, bpy or phen. However, no such arrangement is observed in the case of the complex 2b due to the lack of a π-surface at the cis-protecting moiety.

Thermodynamic, energetic, and topological properties of crystal packing of pyrazolo[1,5-a]pyrimidines governed by weak electrostatic intermolecular interactions

“…This interaction has been shown to be essential to stabilize and drive the crystal packing of organic molecules 50 as well as more complex systems such as polymers 51 and proteins. 52 The supramolecular approach also led to the observation that crystallization can be governed by the complementarity of surfaces. Thus, the results described here corroborate with the hypothesis that the contact surface between the molecules leads to the approximation of molecules during crystallization and it may be the driving force for the crystalline arrangement of pyrazoloij1,5-a]pyrimidines.…”

Structural and Dynamic Aspects of Palladium(II)‐Based Self‐Assembled Binuclear Coordination Complexes

“…Inspired by our previous progress on synthesis of self‐assembled binuclear complexes,–,,,,, we envisioned that the introduction of the 4,4′‐diphenylmethane moiety as spacer into a ligand back‐bone would end up self‐assembled complexes with large cavities. For this purpose, we considered a “C‐shaped” lengthy bidentate pyridine appended ligand, L containing two urea functionalities and a central 4,4′‐diphenylmethane spacer, (Scheme ).…”

Octadecanuclear Gear Wheels by Self‐Assembly of Self‐Assembled “Double Saddle”‐Type Coordination Entities: Molecular “Rangoli”

“…[1] In order to describe the composition of the core of the architectures, such complexes could be classified under [Pd x L' x L y ] families. A large number of binuclear [Pd 2 L' 2 L 2 ]-type complexes have been prepared, [1][2][3][4][5][6] mostly from selected "bow-shaped" non-chelating bidentate ligands and a variety of cis-protected palladium(II) compounds. Well-explored functional and structural aspects of these binuclear complexes include guest encapsulation, [2] interlocking to form [2]-catenanes, [3] and solid-state packing.…”

“…Well-explored functional and structural aspects of these binuclear complexes include guest encapsulation, [2] interlocking to form [2]-catenanes, [3] and solid-state packing. [4,5] In such binuclear complexes, there are two square-planar palladium(II) centers, in which both of the coordination square planes are usually located almost in the same plane, in a "plateau"-type overall disposition. [5] Considerably fewer [Pd 2 L' 2 L 2 ]-type compounds prepared from slightly divergent "U-shaped" ligands have been reported, in which one of the square planes is radially displaced from the plateau position and located almost above the other in an "opened jaws" manner ( Figure 1 a).…”

“…[4,5] In such binuclear complexes, there are two square-planar palladium(II) centers, in which both of the coordination square planes are usually located almost in the same plane, in a "plateau"-type overall disposition. [5] Considerably fewer [Pd 2 L' 2 L 2 ]-type compounds prepared from slightly divergent "U-shaped" ligands have been reported, in which one of the square planes is radially displaced from the plateau position and located almost above the other in an "opened jaws" manner ( Figure 1 a). [4,6] A series of self-assembled "opened jaws"-shaped compounds have been studied in our group to evaluate their packing in the solid state and to effect targeted self-assembly of the self-assembled complexes.…”