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Dynamic Self‐Assembly of an M 3 L 6 Molecular Triangle and an M 4 L 8 Tetrahedron from Naked Pd II Ions and Bis(3‐pyridyl)‐Substituted Arenes
Author(s) -
Chand Dillip K.,
Biradha Kumar,
Kawano Masaki,
Sakamoto Shigeru,
Yamaguchi Kentaro,
Fujita Makoto
Publication year - 2006
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200600029
Subject(s) - chemistry , crystallography , ion , pyridine , denticity , aqueous solution , benzene , ligand (biochemistry) , stereochemistry , tetrahedron , palladium , crystal structure , medicinal chemistry , organic chemistry , catalysis , biochemistry , receptor
The pyridine‐appended nonchelating bidentate ligands 1,4‐bis(3‐pyridyl)benzene ( 1 ) and 4,4′‐bis(3‐pyridyl) biphenyl ( 2 ) were complexed with a naked Pd II ion for the construction of molecular cage compounds. Prior to these experiments, the complexation of the ligands with cis ‐[Pd(en)(NO 3 ) 2 ] was also examined, because self‐assemblies from the cis ‐protected Pd II ion were expected to be simple motifs that constitute the assemblies from naked Pd II ion. The structures of the self‐assembled compounds resulting from 1 and [Pd(en)(NO 3 ) 2 ] depended on the solvent employed. In aqueous solution, an M 2 L 2 trenchlike compound was obtained. In dimethyl sulfoxide, however, a mixture of the M 2 L 2 trench and an M 3 L 3 macrocycle was found in equilibrium, the dynamic nature of which was confirmed by the concentration‐dependent nature of the species. At higher concentration, an M 4 L 4 macrocycle was mostly observed. The complexation of 1 with naked Pd II ions was expected to produce novel structures that are combinations of the M n L n type frameworks. A peculiar tetrahedral M 4 L 8 assembly was obtained quantitatively from 1 and Pd(NO 3 ) 2 , rather than the smallest possible M 3 L 6 double‐walled triangle. Interestingly, the use of Pd(CF 3 SO 3 ) 2 resulted in the sole formation of the latter structure. Thus, the anion is important as a template in the formation of these assemblies. Ligand 2 , which contains an extra p ‐phenylene unit compared to 1 , behaved in a similar manner when treated with [Pd(en)(NO 3 ) 2 ], but showed subtle differences with naked Pd II ions. With Pd(NO 3 ) 2 , 2 gave mostly a tetrahedron along with a double‐walled triangle. With Pd(CF 3 SO 3 ) 2 , this longer ligand formed a double‐walled triangle with a negligible amount of tetrahedra. A single discrete assembly of a perfect tetrahedron was obtained from 2 and Pd II ions by choosing p ‐tosylate as a counterion.