Metal-ligand Lability and Ligand Mobility Enables Framework Transformation via Ligand Release in a Family of Crystalline 2D Coordination Polymers.

A family of seven silver(I)-perfluorocarboxylate-quinoxaline coordination polymers, [Ag 4 (O 2 CR F ) 4 (quin) 4 ] 1-5 (R F =(CF 2 ) n-1 CF 3 ) 4 , n=1 to 5); [Ag 4 (O 2 C(CF 2 ) 2 CO 2 ) 2 (quin) 4 ] 6; [Ag 4 (O 2 CC 6 F 5 ) 4 (quin) 4 ] 7 (quin=quinoxaline), denoted by composition as 4 : 4 : 4 phases, was synthesised from reaction of the corresponding silver(I) perfluorocarboxylate with excess quinoxaline. Compounds 1-7 adopt a common 2D layered structure in which 1D silver-perfluorcarboxylate chains are crosslinked by ditopic quinoxaline ligands. Solid-state reaction upon heating, involving loss of one equivalent of quinoxaline, yielding new crystalline 4 : 4 : 3 phases [Ag 4 (O 2 C(CF 2 ) n-1 CF 3 ) 4 (quin) 3 ] n (8-10, n=1 to 3), was followed in situ by PXRD and TGA studies. Crystal structures were confirmed by direct syntheses and structure determination. The solid-state reaction converting 4 : 4 : 4 to 4 : 4 : 3 phase materials involves cleavage and formation of Ag-N and Ag-O bonds to enable the structural rearrangement. One of the 4 : 4 : 3 phase coordination polymers (10) shows the remarkably high dielectric constant in the low electric field frequency range.