Solid state photochemistry of novel composites containing luminescent metal centers and Poly(2-methoxyaniline-5-sulfonic acid)
Steady state luminescence and measurements of the luminescent lifetime as well as cyclic voltammetry have been used to elucidate the mechanism and dynamics of interaction between a luminescent ruthenium metal center and two different fractions of poly(2-methoxyaniline-5-sulfonic acid) (PMAS). The two fractions, high molecular weight (HMWT) PMAS and low molecular weight (LMWT) PMAS oligomer, showed significantly distinctive influences on the luminophore. The HMWT PMAS, confirmed to be an emeraldine salt by its characteristic redox chemistry, greatly impacted the diffusion coefficient of the Ru2+/3+ within the composite film, increasing the diffusion coefficient, DCT, by 2 orders of magnitude. The HMWT PMAS also resulted in quenching of the ruthenium-based emission. Significantly, these results indicate that quenching involves both static and dynamic processes, with the static quenching being the dominant process, suggesting that the metal center and polymer backbone were strongly associated. In stark contrast, the LMWT PMAS did not influence the electrochemical properties of the ruthenium metal center; however, it did double the emission observed from the ruthenium metal center. The insensitivity of the luminescence lifetime does suggest that, as with the HMWT PMAS, LWMT PMAS is strongly associated with the ruthenium metal center. The enhanced luminescence may allow for many potential sensor developments based on the luminescent ruthenium metal center, while the HMWT PMAS quenching could be utilized within quenching-based strategies or electrochemical devices.
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