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 Na ₂(L¹)(ClO₄)(H₂O) _n ](ClO₄) _n (1), Na ₃(L²)(ClO₄)₃(H₂O)_{2 n} ] (2), and Na(L ³)(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, namely ₃-O andhapto-3-O plushapto-2-O in (1) and (2), respectively.