A new ZnII metallocryptand with unprecedented diflexure helix induced by V-shaped diimidazole building blocks

Abstract

Taking advantage of V-shaped ligands, a ZnII metallocryptand, namely {[Zn2(didp)2(m-bdc)2]} n , (1) [didp = 2,8-di(1H-imidazol-1-yl)-dibenzothiophene and m-H2bdc = isophthalic acid], has been hydrothermally synthesized. Single-crystal X-ray diffraction analysis reveals a 26-membered butterfly-type metallomacrocycle [Zn2(didp)2]. One m-bdc2− ligand bridges [Zn2(didp)2] units to form a laterally non-symmetric [Zn2(didp)2(m-bdc)] metallocryptand with an exo–exo conformation. Another crystallographically independent m-bdc2− functions as a secondary synthon to bridge discrete metallocryptands into a 1D zigzag chain architecture. Undoubtedly, the choice of two matched ligands in this work is crucial for metallocryptand construction and structure expansion. Interestingly, a rare helical chain with two flexures in one single L and/or R strand is observed. Another important feature is the C—O...π interactions, by which the dimensionality extension of (1) can be induced. Fluorescence measurements and density functional theory (DFT) calculations illustrate that the emission of (1) can probably be attributed to ligand-to-ligand charge transfer (LLCT).