Aggregation in nanobundles and the effect of diverse environments on the solution-phase photochemistry and photophysics of -Re(CO)3L+ (L = 1,10-phenanthroline, 2,2'-bipyridine) pendants bonded to poly(4-vinylpyridine).

The UV-vis spectroscopy and photochemical properties of {(vpy-[Re(CO)3(2,2'-bpy)])m(vpy-[Re(CO)3(phen)])n(vpy)p}(CF3SO3)(m+n)}, vpy = 4-vinylpyridine, m = 131, n = 131 or m = 200, n = 150, and m + n + p = 600, were investigated in solution phase. The polymers exist in solution as aggregates of polymer strands with radii as large as approximately 10(2) nm. Given the size of the poly-vpy backbone, the aggregates must contain a large number of strands. The luminescence spectrum exhibits a strong resemblance to the emission spectrum of {(vpy-[Re(CO)3(phen)])200(vpy)400}(CF3SO3)200. The existence of Re(I) chromophores in diverse environments was shown by the intrinsic kinetics of the luminescence, the decay kinetics of the MLCT excited states observed by time resolved-absorption spectroscopy, and the quenching of the luminescence by various quenchers. Redox reactions of the MLCT excited states with the quenchers were responsible for the luminescence quenching. While static quenching resulted when Cu(II) and Fe(III) EDTA complexes were the quenchers, a dynamic quenching resulted with Fe(CN)6(4-) or 2,2',2' '-triethanolamine, TEOA. The photochemical and photophysical properties of the mixed-pendant polymers have been discussed in terms of arrays of MLCT excited states whose energies are determined by the diverse environments of the Re(I) chromophores. Conversions (with and without radiation) of the upper-energy MLCT excited states to the ground state and lower-energy MLCT excited states and the latter excited state to the ground state account for the experimental results.

On the quenching of MLCT(Re-->bpy) luminescence by Cu(II) species in Re(I) polymer micelles.

Transmission electron microscopy (TEM) and dynamic light scattering (DLS) studies on acetonitrile solutions of the polymer {[(vpy)2-vpyRe(CO)3bpy] CF3SO3}200 demonstrated that the Re(I) polymer molecules aggregate to form spherical micelles of radius R = 156 nm. Coordination of Cu(II) species to the Re (I) polymer causes a decrease in the micelle radius and a distortion from the spherical shape. Besides, the coordination of Cu(II) species to the {[(vpy)2-vpyRe(CO)3bpy] CF3SO3}200 polymer produces the quenching of the metal to ligand charge transfer (MLCT) excited state by energy transfer processes that are more efficient than those in the quenching of the monomer pyRe(CO)3bpy+ luminescence by Cu(II). Moreover, the kinetics of the quenching by Cu(II) do not follow a Stern-Volmer behavior. Conversely, the quenching of the MLCT luminescence of the Re(I) polymer by the sacrificial electron donor 2,2',2' '-nitrilotriethanol, TEOA, follows a Stern-Volmer kinetics. A comparison is made between the quenching by CuX2 (X = Cl or CF3SO3) and TEOA.