SYNTHESIS, CHARACTERIZATION, AND X-RAY STRUCTURE OF THE ZIRCONIUM BIS(PORPHYRINATE) DI(PI-RADICAL-CATION) COMPLEX [ZR(TPP)2][SBCL6]2 AND X-RAY STRUCTURE OF THE MONO(PI-RADICAL-CATION) COMPLEX [ZR(TPP)2][SBCL6]

Abstract

The di(pi-radical-cation) complex [Zr(TPP)2][SbCl6]2 (TPP = meso-tetraphenylporphyrin dianion) was synthesized and fully characterized. Spectroscopic and magnetic susceptibility data of the dication complex indicate a strong antiferromagnetic coupling between the unpaired electrons residing on the two porphyrin rings. One notable feature of the dication complex is the high-energy near-IR absorption band which appears at 780 nm in the visible region. X-ray structures of [Zr(TPP)2][SbCl6] and [Zr(TPP)2][SbCl6]2 reveal that the interporphyrin distances shorten progressively as one proceeds from the neutral to the dication species. These structural features are consistent with the spectroscopic data and confirm that the pi-pi interaction between the two porphyrin rings is enhanced by oxidation. Crystallographic data for [Zr(TPP)2][SbCl6].3CH2Cl2 (2): tetragonal, P4/ncc, a = 21.260 (3) angstrom, c = 18.042 (5) angstrom, V = 8155 (2) angstrom3, Z = 4, d(calc) = 1.551 g cm-3, T = 23-degrees-C, R = 0.054 and R(w) = 0.063 for 1333 absorption-corrected reflections with I > 3-sigma(I). [Zr(TPP)2][SbCl6]2.3CH2Cl2 (3): monoclinic, P2(1)/c, a = 18.555 (3) angstrom, b = 18.037 (2) angstrom, c = 27.468 (5) angstrom, beta = 102.95 (2)-degrees, V = 8959 (2) angstrom3, Z = 4, d(calc) = 1.661 g cm-3, T = -100-degrees-C, R = 0.079 and R(w) = 0.090 for 3196 absorption-corrected reflections with I > 3-sigma(I).