Heteroleptic Copper Dipyrromethene Complexes: Synthesis, Structure, and Coordination Polymers

The synthesis of neutral [Cu(dpm)2] and [Cu(dpm)(acac)] (dpm = dipyrromethene, acac = acetylacetonato) complexes
is presented. The formation of the asymmetric metal complexes was monitored by electronic absorption and infrared
spectroscopy. Two of the complexes investigated, containing pyrdpm ligands (pyrdpm = pyridyldipyrromethene),
form 1-dimensional coordination polymers. The coordination polymers formed by these complexes have been
characterized by single-crystal X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis.
The complexes possess square pyramidal coordination geometries with the apical position occupied by the meso-pyridyl donor of a neighboring complex in the crystal lattice. The features of these coordination complexes that
facilitate formation of extended solids have been probed. Symmetric [Cu(pyrdpm)2] complexes are unable to form
coordination solids due to steric hindrance at the metal center. Use of cyano donors in complexes such as
[Cu(cydpm)(acac)] (cydpm = cyanodipyrromethene) in lieu of pyridyl donors also fail to form network solids. Through
these systematic studies, both the basic coordination chemistry of these complexes and the fundamental design
requirements for synthesizing this novel class of coordination polymers have been defined.