Anion binding of 3,4-dichloro-2,5-diamidopyrrole and anionic self-assembly dimerization of its deprotonated species

The molecular structures of 3,4-dichloro-2,5-diamidopyrrole LH, its deprotonated species L−, self-assembly dimeric species and its complexes with fluoride, chloride and hydroxide ions were obtained using the B3LYP/6-31G(d) calculations. The optimized structures at the B3LYP/6-31G(d) and ONIOM(B3LYP/6-31G(d):PM3) levels of the self-assembly dimer co-existing with TBA (tetrabutylammonium) as [L2.2TBA] were obtained and their geometrical data show good agreement with the X-ray crystallographic structure. In the presence of hydroxide (as TBA.OH), deprotonation of LH and dimerization of L− are the most favorable reaction as compared to systems in the presence of fluoride and chloride ions. The hydroxide ion is able to draw a pyrrole proton from the LH and afford one water molecule via proton-transfer process.