COMBINING DIFFERENT HYDROGEN-BONDING MOTIFS TO SELF-ASSEMBLE INTERWOVEN SUPERSTRUCTURES

A series of carboxyl-substituted dibenzylammonium salts have been cocr ystallized with the macrocyclic polyethers dibenzo[24]crown-8 (DB24C8) and bis-p-phenylene[34]crown-10 (BPP34C10) to effect the noncovalent syntheses of a wide range of interwoven superstructures in the solid s tate. In all cases, the dibenzylammonium cations thread through the ca vities of the macrocyclic polyethers-primarily as a result of N+-H ... O hydrogen bonds, with occasional secondary stabilization from C-H .. . O and aryl-aryl interactions-to form pseudorotaxane complexes posses sing supplementary recognition sites (specifically, carboxyl groups) f or further intercomplex association through hydrogen bonding. One unit of each of the dibenzylammonium cations threads through the DB24C8 ma crocycle to make single-stranded, carboxyl-containing [2]pseudorotaxan es that interact further with one another to produce novel supramolecu lar architectures as a result of hydrogen bonding between their carbox yl groups (the carboxyl dimer supramolecular synthon), or between carb oxyl groups and polyether oxygen atoms. Elaborate architectures, such as side-/main-chain pseudopolyrotaxanes and a daisy-chain-like supramo lecular array, were thus synthesized noncovalently. BPP34C10 can accom modate two cations within its macrocyclic interior to form carboxyl-co ntaining [3]pseudorotaxanes in which BPP34C10 acts as a girdle that he lps to control the spatial orientation of the carboxylic acid-containi ng recognition sites for additional intersupramolecular association th rough the carboxyl dimer, PF6- anions were also found to play a role i n the self-assembly processes. When the anions interact with the [3]ps eudorotaxanes, these recognition sites are oriented in the same direct ion. This leads to the formation of doubly-encircled multicomponent su permolecules when BPP34C10 is cocrystallized with dibenzylammonium cat ions bearing only one carboxyl substituent. On the other hand, when BP P34C10 is cocrystallized with an isophthalic acid-substituted ammonium cation, there is no evidence of any anion assistance to self-assembly ; the isophthalic acid units are aligned in opposite directions, creat ing an interwoven supramolecular cross-linked polymer.