Nuclearity control in calix[4]arene-based zinc() coordination complexes

Three zinc-based coordination complexes were selectively generated in the crystalline phase using a new flexible molecular "tweezers" calix[4]arene derivative ligand decorated with two appended carboxylic moieties and benzyl spacers ( 3 -4H). Through the control of the metal/ligand ratio and the synthetic conditions, the coordination sphere around the zinc cations was found to be different, which influenced the nuclearity of the obtained complexes. The mononuclear complex ( 3 -3H) 2 -Zn(DMF) 2 was obtained, while two partially deprotonated ligands ( 3 -3H) − cap the metallic cation, leading to a nontubular "8"-shaped structure with a metal/ligand ratio equal to 1/2. The dinuclear ( 3 -2H) 2 -Zn 2 py 4 complex displays a tubular structure with a metal/ligand ratio equal to 1/1, where two zinc cations act as a linear metal linker between two ( 3 -2H) 2− species, which adopts a cone conformation. Finally, the third trinuclear coordination complex ( 3 -2H) 4 -Zn 3 (OH 2 ) was obtained using ( 3 -4H) and the highly coordinating sulfonylcalix[4]arene ( 4 -4H), exhibiting a 3/1/1 metal/ 3 / 4 ratio. Thus, it has been demonstrated that under self-assembly conditions, the nuclearity of the new complexes based on zinc cations and calix[4]arene dicarboxylate ( 3 -4H) can be tuned using different synthetic conditions: nature of solvent, crystallization method, use of a highly coordinating ligand ( 4 -4H). Three zinc-based coordination complexes were selectively generated in the crystalline phase using a new flexible molecular "tweezers" calix[4]arene derivative ligand decorated with two appended carboxylic moieties and benzyl spacers (( 3 -4H)).