Photo-physical properties and OPL of some novel thiophenyl Pt(II)-ethynyl derivatives

Abstract

The multi-photon absorption and optical power limiting (OPL) properties of two new thiophenyl-containing bis(ethynylaryl)bis(tributylphosphine) platinum(II) complexes (ATP1, ATP2) were studied. Thiophene units were introduced into the structure as an attempt to enhance the OPL properties. The two compounds have the thiophene rings either close to the Pt-atom (ATP1) or at the terminal ends (APT2). The measurement results were compared with those of Pt1 capped with a 2,2-bis(methylol)propionic acid (bis-MPA) dendrimer (Pt1-G1). As for Pt1-G1, both thiophenyl derivatives showed large inter-system crossing capabilities and triplet phosphorescence, indicating that these compounds have potential of enhancing the nonlinear absorption and specifically the OPL properties. The two-photon absorption cross sections of ATP1 and ATP2 was found to be in the same order of magnitude as that of Pt1-G1, i.e. between 10-20 GM, but is slightly larger for ATP1 than for ATP2. The fluorescence decay time of all compounds was found to be very short (sub nanosecond) and with quantum yields in the order of 10^-3. The multi-photon induced phosphorescence was reduced with decreased pulse repetition frequency (prf) showing a population dependence of the triplet state with prf, correlating with the relatively long phosphorescence decay lifetime around 200 μs. OPL measurements at 532, 550 and 610 nm show that ATP1 has the same clamping level as Pt1-G1 at 532 nm and ATP2 has somewhat weaker OPL response than the other two.