Fe-TPP Coordination Network with Metalloporphyrinic Neutral Radicals and Face-to-Face and Edge-to-Face pi-pi Stacking

Compound ([FeTPPbipy](center dot))(n) (TPP = meso-tetraphenylporphyrin and bipy = 4,4'-bipyridine) is the first example of a Fe-TPP-bipy coordination network, and it consists of 1D polymers packed through face-to-face and edge-to-face pi-pi interactions. The compound has been investigated by means of X-ray diffraction, IR, Mossbauer, UV-visible, and EPR spectroscopies, thermogravimetry, magnetic susceptibility measurements, and quantum-mechanical density functional theory (DFT) and time-dependent DFT calculations. The chemical formula for this compound can be confusing because it is compatible with Fe-II and TPP2- anions. However, the spectroscopic and magnetic properties of this compound are consistent with the presence of low-spin Fe-III ions and [FeTPPbipy](center dot) neutral radicals. These radicals are proposed to be formed by the reduction of metalloporphyrin, and the quantum-mechanical calculations are consistent with the fact that the acquired electrons are located on the phenyl groups of TPP.