Molecular recognition of nitrogen – containing bases by Zn[5,15-bis-(2,6-dodecyloxyphenyl)]porphyrin

By means of spectrophotometric titration and 1H NMR spectroscopy, the selective binding ability of the Zn-5,15-bis-(2,6-dodecyloxyphenyl)porphyrin towards nitrogen containing organic molecules of various nature has been studied. It has been found that the presence of long alkoxy substituents at the ortho-positions of the Zn-porphyrin phenyl rings prevents the axial coordination of tertiary amines and, conversely, creates favourable conditions for binding of a primary diamine due to the presence of additional binding sites, namely the oxygen atoms of the ortho–ortho′- dodecyloxy substituents of the meso phenyl groups. The formation of stable complexes with multiple binding sites has been confirmed by DFT quantum chemical calculations and two-dimensional NMR experiments.