Copper and manganese diazacalix[4]arene complexes: structural and cytotoxicity studies and use in ring opening polymerization of ε-caprolactone and δ-valerolactone

From reactions of M(OAc)2·nH2O (M = Cu, Mn) or Cu(NO3)2·3H2O with p-methyl-N,N’-dimethyldiazacalix[4]areneH4 (p-MeLH4) under aerobic conditions, rare examples of azacalixarene-3d-metal complexes were isolated. These, thermally stable non-toxic compounds (≤ µM IC50 values) were screened as catalysts for the ring opening polymerization of the cyclic esters ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) affording low molecular weight cyclic or linear (H/OH end group) polymers. The Mn-based system exhibited the higher activity.