Toward Understanding of the Lower Rim Binding Preferences of Calix[4]arene.

Calixarenes form polymetallic clusters with many first row transition metals and lanthanides via binding at the lower rim. A detailed theoretical study of the relative binding preferences for calix[4]arene (C[4]) toward the first row transition metals is presented. In order to do this, the binding energies of C[4] with transition metals displaying a range of common oxidation states, and a variety of potential spin states of the bound cations were investigated using density functional theory. A known diagnostic test, B1, is employed as a measure to gauge the multireference nature of each compound and is used as justification for the choice of different DFT functionals employed.