Modified p-phenylene vinylene platinum (II) acetylides with enhanced two-photon absorption in solid host

Organometallic complexes comprising of a platinum (II) acetylide core linked with different -conjugated chromophores are promising materials for applications requiring strong nonlinear-optical response. In dual-mode optical power limiting, the chromophore first undergoes ultrafast two-photon absorption (2PA) in singlet manifold, followed by efficient intersystem crossing (ISC) and subsequent T-T absorption. While the heavy atom facilitates efficient T-T absorption, achieving sufficiently high intrinsic 2PA cross-section value has remained an issue. Here we present a series of linear- and cross-conjugated p-phenylene vinylene platinum (II) acetylides (TPV1-Ph, TP01-TPV2, crossTPV1, crossTPV1-DPAF, crossTPV3) with extended π-conjugated chains and discuss their linear- and nonlinear photophysical properties, including comparison to the properties of the constituting ligand chromophores. Remarkably high femtosecond 2PA cross-section values (up to 10,000 GM) were obtained for several of the new complexes by both nonlinear transmission (NLT) and two-photon excited fluorescence (2PEF) method. The large 2PA values, especially in crossTPV1 and crossTPV3, span a broad range of wavelengths, 570 – 810 nm, which overlaps with maximum wavelength of strong T-T excited state absorption measured by nanosecond transient absorption method. This combination of properties renders these compounds efficient dual-mode nonlinear absorbers in the visible to near-IR region. Examination of the photophysical properties allows us to elucidate the structure-property relationships both in the solutions as well as in solid samples where the chromophores are incorporated into a polymer host.