Syntheses and Properties of Cerium Diphthalocyanines in High Oxidation States ; Crystal Structure of

Ring oxidized green Cerium(IV)diphthalocyanines, [Ce(Pc)2]X (X = (poly)halide, N 0 3_) are prepared by chemical oxidation of ("Bu4N)[Ce(Pc2~)2] with the corresponding halogen in solution or of solid [Ce(Pc2_)2] with aqueous HNO> Electrochemical oxidation of ("Bu4N)[Ce(Pc2_)2] in solution in the presence of ("Bu4N)BF4 yields [Ce(Pc)2](BF4)0.;p, which crystallizes in the tetragonal space group P4/nnc (a, b = 19.643(3) A, c = 6.525(3) A, Z = 2). The CeIV ion is eightfold coordinated by the isoindole N atoms (Niso) of the two staggered (ca. 41°), slightly distorted Pc ligands. The “[Ce(Pc)2]<)33+” subunits are arranged in infinite columns along [001] with the Ce atoms statistically disordered over two positions and C e -N iso bond lengths of 2.45(1) and 2.69(1) A, respectively The UV-VIS spectrum is dominated by the transitions of the Pc2ligand at ca. 15,000 (B band), 30,000 and 36,000 cm-1 (Q, N region). A low energy (“metallic”) band at ca. 2800 cm-1 typical for partially oxidized systems is present. The UV-VIS-NIR spectrum of [Ce(Pc)2]N 0 3 indicates a cofacial Pc2“ -P c complex. In addition to the jt-jz' transitions of the Pc2moiety at ca. 14,000, 30,000 and 36,000 cm-1, the Ch transition of the Pcring is observed at ca. 19,200 cm -1 and the typical NIR band at 6380 cm -1. Oxidation of a thin film of (PNP)[Ce(Pc2_)2] with dry Br2/ N2 gas yields purple [Ce(Pc_)2]Brv, whose UV-VIS-NIR spectrum shows the diagnostic fea­ tures of dimeric Pc~ radicals with intense bands at ca. 14,000 and 18,000 cm-1 assigned as B and Qi bands, respectively. A t ca. 9000 cm 1 the typical Q D absorption is observed. The vibrational spectra are dominated by the transitions of the Pcligand at 1305/1445 cm-1 (IR) and 560/1120/1172/1591 cm-1 (resonance Raman). Excitation with 1064 nm strongly enhances the sym. C e -N stretch at 163 c m '1.