Preparation and reactivity of pendent- --CO2RhIII(phthalocyanine) bound to a poly(acrylate) backbone. Effects of the hypercoiled backbone on the association, photochemical and thermal redox reactions of the pendant macrocycle

Poly(acrylate) was derivatized with RhIII(pc) (pc = phthalocyanine) and the morphology of the strands was established by AFM microscopy. The strands of the polymer, poly-RhIII(pc), were seen as the strings of spherules expected for an hypercoiled poly(acrylate) backbone. Phthalocyanine pendants in a polymer, poly-RhIII(pc), having a 1:8 stoichiometric relationship of - - -RhIII(pc) to - - -CH2CH(CO2-)- - - - exhibited chemical properties different from those communicated for RhIII(pc-tetrasulfonate)3- in aqueous medium or XRhIII(pc), X = Cl, Br, I, in nonaqueous media. Reactions of poly-RhIII(pc) with reducing radicals like a e-aq, (CH3)2C•OH, NiL+ (L = [14]aneN4, Me6[14]aneN4), or oxidants, i.e., N3•, Cl2•-, Br2•-, or NiL3+ were investigated with the pulse radiolysis technique. The phthalocyanine radicals formed in these redox reactions were characterized by means of the transient UV−vis spectrum, and the kinetics of the formation and decay of the radicals were followed at various wavelengths. The photophysical and photochemical processes of poly-RhIII(pc) were studied by laser flash photolysis. The lifetime of the excited state, t = 133 ns, correlates well with the slow component of the decay of the luminescence detected in the NIR region. This transient has been assigned to a ligand field, LF, excited-state not observed in previous works when XRhIII(pc) complexes were irradiated in homogeneous solution. The thermal and photochemical properties of poly-RhIII(pc) are discussed on the basis of environmental conditions affecting the pendent macrocycles in the strand of polymer.