Substantial Non-linear Optical Response of New Polyads Based on Ru and Os Complexes of Modified Terpyridines

Abstract

The third-order non-linear optical behavior of two new series of multicomponent systems based on coordination compounds of transition metals is reported. These systems, soluble in acetonitrile, are made of a metal (Ru or Os) bis-terpyridyl (tpy) unit, as photosensitizer P, connected to one or two electron acceptor groups, or to both electron donor (D) and electron acceptor (A) groups to form polyads of D−P−A type. The non-linear absorption and non-linear refraction response was substantial and was examined using the z-scan technique. The results are presented for two different excitation conditions. For excitation under laser pulses of nanosecond duration the compounds with the Ru center exhibit reverse saturable absorption (RSA). The corresponding Os samples show saturable absorption (SA) for low incident intensities that turns to RSA above an intensity threshold that depends on the concentration of the solutions. In contrast, under sub-picosecond laser excitation the Ru and the Os samples each exhibit s...