Heterometallic coordination polymers incorporating dipyrrin based heteroleptic copper and cobalt complexes: to Ag–π or not?

Abstract

Using ligands based on either an acetylacetonate or a dipyrrin moiety appended with pyridyl groups, a series of novel heteroleptic copper(II) and cobalt(III) complexes combining both chelate units such as (acacpy₂)Cu(dpm-py) and (acacpy₂)Co(dpm-py)₂ (acacpy₂ = 1,3-bis(4-pyridyl)-1,3-propanedionate; dpm-py = 5-(4-pyridyl)dipyrrin) have been prepared and fully characterized. These two complexes were obtained upon reaction of dpm-py with the (acacpy₂)M homoleptic species (M = Cu(II), Co(II)). In the solid state, the (acacpy₂)Cu(dpm-py) complex behaves as a self-complementary metallatecton and leads to the formation of a 1D coordination polymer (CP) through the coordination of a peripheral pyridyl group to the copper centre. Contrastingly, the octahedral (acacpy₂)Co(dpm-py)₂ complex featuring a coordinatively saturated Co(III) centre crystallizes as an isolated mononuclear species. In order to generate heterometallic CPs, both complexes have been used as metallatectons upon their combination with different silver(I) salts. Upon reaction of (acacpy₂)Cu(dpm-py) with Ag(BF₄) or Ag(TfO), 2- and 3-D heterometallic networks were obtained, respectively. In both cases, sheet type arrangements resulting from the binding of Ag⁺ cations by three peripheral pyridyl groups were observed. These 2D sheets are further interconnected through Ag–π interactions with the pyrrolic rings. Under the same conditions, the combination of (acacpy₂)Co(dpm-py)₂ with Ag(TfO) leads to two networks differing by their connectivity patterns and dimensionality. Interestingly, whereas no Ag–π interactions were observed for the 2D network, a combination of coordination bonding with the pyridyl moieties and Ag–π interactions was detected for the 1D architecture.