Formation of various polymeric frameworks by dicarboxylate-like ligands: Synthesis and crystal structures of polymeric complexes of sodium perchlorate with flexible double betaines

Three crystalline complexes of sodium perchlorate with different flexible double betaines [Na₂(L¹)(ClO₄)(H₂O)_n](ClO₄)_n (1), [Na₃(L²)(ClO₄)₃(H₂O)_2n] (2), and [Na(L³)(CH₃OH)_n]-(ClO₄)_n·xnH₂O (x=0.25) (3) [^–O₂CCH₂N⁺Me₂–(CH₂)_n-N⁺Me₂CH₂CO₂^–,n=2 L¹;n=3 L²;n=4 L³] have been synthesized and characterized by single-crystal X-ray structure analysis. Complex (1) comprises tetranuclear sodium units consolidated by betaine and aqua ligands, which are bridged by half of the ClO₄^– anions to form layers matching the (200) planes, the remaining uncoordinated ClO₄^– anions being accommodated between adjacent layers. Complex (2) possesses a double-layer polymeric structure with the sodium atoms bridged by ligand oxygen atoms to form columns running parallel to thea axis, which are interconnected by double-betaine ligands lying parallel to theac plane. All of the ClO₄^– groups and water molecules are coordinated to the metal atoms. In complex (3) the chains composed of alternating eight-membered and four-membered metallocycles are cross-linked by the betaine ligands, which lie in the (020) and (01/1) families of planes, to yield a three-dimensional network. All of the ClO₄^– groups and water molcules fill the resulting infinite channels running parallel to thea axis. Two unusual carboxylate coordination modes are identified, namely₃-O andhapto-3-O plushapto-2-O in (1) and (2), respectively.