Fe–TPP Coordination Network with Metalloporphyrinic Neutral Radicals and <i>Face-to-Face</i> and <i>Edge-to-Face</i> π–π Stacking

Compound ([FeTPPbipy]•)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 π–π interactions. The compound has been investigated by means of X-ray diffraction, IR, Mössbauer, 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 FeII and TPP2– anions. However, the spectroscopic and magnetic properties of this compound are consistent with the presence of low-spin FeIII ions and [FeTPPbipy]• 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.