Hydrogen-bond architectures of protonated 4,4′-biimidazolium derivatives and oligo(imidazolium)s in charge-transfer salts with tetracyanoquinodimethane

Charge-transfer salts of protonated cations of 2,2'-disubstituted-4,4'-biimidazoles and oligo(imidazole)s with tetracyanoquinodimethane (TCNQ) were investigated to demonstrate the high potential of these systems for the regulation of molecular arrangement and electronic structure of charge-transfer salts. 4,4'-Biimidazole derivatives afforded six kinds of mixed-valent TCNQ salts exhibiting semiconducting behaviors. Structural analyses revealed that the protonated 4,4'-biimidazolium derivatives formed multidirectional and multidimensional hydrogen bonds with TCNQ, and constructed two kinds of self-assembled architectures: one-dimensional chainlike motifs involving TCNQ molecules and two-dimensional sheet structures composed of the alternation of segregated columns of 4,4'-biimidazolium and TCNQ. Furthermore, the hydrogen-bonding patterns regulated the electronic structures in TCNQ columns by strong cation-anion interaction, causing the nonuniform charge-distribution and semiconducting behaviors.