Diverse anion exchange of pliable [X@PdL] double cages: a molecular ruler for recognition of polyatomic anions

Reaction of Pd(BF 4 ) 2 with L (L = bis(pyridin-3-yl-propyl)pyridine-3,5-dicarboxylate) in the 1 : 2 mole ratio gives rise to a spiro-type [PdL 2 ]·(BF 4 ) 2 ·2C 6 H 6 ·2CH 3 CN, and further self-assembly of [PdL 2 ]·(BF 4 ) 2 ·2C 6 H 6 ·2CH 3 CN with Pd(NO 3 ) 2 in the 2 : 1 mole ratio in Me 2 SO at 90 °C produces a uniquely pliable double cage of [(NO 3 ) 2 (H 2 O) 2 @Pd 3 L 4 ](BF 4 ) 4 ·6C 3 H 7 NO. Both the encapsulated NO 3 − and the outside BF 4 − anions are exchanged by X − to form [(X) 2 @Pd 3 L 4 ](X′) 4 (X − = PF 6 − , ClO 4 − , and/or NO 3 − ; X' − = BF 4 − , PF 6 − , ClO 4 − , and NO 3 − ) with all-inclusive pure or mixed anions. The pliable and characteristic properties of the double cages were confirmed by anion exchange of the nestled or outside anions in the present study. This system can be used as a ruler for recognition of ubiquitous polyatomic anions. This pliable double cage is an efficient, tolerant, and reproducible porous matrix for diverse anion exchange, which is as a ruler for recognition of ubiquitous polyatomic anions.