A family of π-extended platinum(II) porphyrins has been synthesized and incorporated into solution processed polymer light emitting diodes (PLEDs) and vapor deposited multilayer organic light emitting diodes (OLEDs), giving rise to devices with peak emission ranging from 771 to 1005 nm. The longest wavelength emitter, platinum(II)-5,10,15,20-(3,5di-tert-butylphenyl)tetraanthroporphyrin (Pt-Ar 4 TAP), shows an emission maximum at 1005 nm, an external quantum efficiency (EQE) of 0.12%, and a maximum radiant emittance (R max ) of 0.23 mW/cm 2 in single layer PLED architectures, which is enhanced to an EQE of 0.20% with an R max of 0.57 mW/cm 2 upon vapor deposition of an electron transport layer. In an effort to understand substituent effects and enhance the performance of π-extended Pt-porphyrins in PLEDs and OLEDs, a family of Pt-tetrabenzoporphyrins (Pt-TBPs) with varying functionality was investigated. The luminescent lifetimes of the Pt-TBPs in solution and in films were measured, and a strong correlation was demonstrated between the film lifetimes and the PLED and OLED efficiencies. An improvement in external quantum efficiency (EQE) from 2.07 to 2.49% for PLEDs and from 8.0 to 9.2% for OLEDs was observed between the less substituted Pt-tetraphenyltetrabenzoporphyrin and the more substituted 10,15,tetrabenzoporphyrin. The PLED EQEs were further enhanced to 3.02% with the disubstituted Pt-5,15-(3,5-di-tert-butylphenyl)tetrabenzoporphyrin; however, this increase was not observed for the OLEDs where an EQE of 7.8% was measured.

A comprehensive photophysical study is reported on a family of π-extended platinum(II) porphyrin complexes. The platinum(II) complexes are synthesized from the corresponding free base porphyrins by treatment with platinum(II) acetate in hot benzonitrile, affording the complexes in considerably higher yield than by reaction with platinum(II) chloride. A quantitative study of the absorption and luminescence properties of the metalloporphyrins is presented. A series including tetraarylbenzo-, tetraarylnaphtho-, and tetraarylanthroporphyrin exhibits efficient phosphorescence at 773, 890, and 1020 nm in the near-infrared region, with quantum yields of 0.35, 0.15, and 0.08, respectively. The triplet lifetimes and phosphorescence yields decrease with increasing emission wavelength, consistent with energy gap law behavior. A set of six Pt-tetrabenzoporphyrins (TBPs) with different meso-substituents were examined. The Pt-TBPs exhibit efficient phosphorescence with λ max ∼ 770 nm and with a quantum yield ranging from 0.26−0.49, depending on the substitution pattern. The results show that the 5,15-diarylbenzoporphyrins feature 50−60% higher phosphorescence emission yield compared to the 5,10,15,20-tetraarylbenzoporphyrins. The highest phosphorescence quantum efficiency is observed for a platinum(II) 5,15-diarylbenzoporphyin which emits at 770 nm with a quantum yield of 49%.

Chromophores and materials that exhibit nonlinear absorption over a broad spectrum and with high temporal dynamic range are of interest for application in materials engineering and biology. Recent work by a number of research groups has led to the development of a new family of organometallic chromophores and materials featuring interesting and useful nonlinear absorption properties. These systems contain the platinum acetylide moiety as a fundamental molecular unit, combined with delocalized, π-conjugated electron systems. These organometallic chromophores provide a unique combination of properties, such as negligible ground state absorption in the visible region, large spin-orbit coupling giving rise to high triplet excited state yield, triplet lifetime in the microsecond domain, high two-photon cross-section in the visible and near-infrared regions, and high triplet-triplet absorption cross-section in the visible and near-infrared region. This Spotlight on Application highlights recent developments in this area, combining background and review on nonlinear absorption in platinum acetylide chromophores and describing significant recent results from our own laboratory.

A series of platinum-containing organometallic dimer complexes has been synthesized and the photophysical properties have been investigated under one- and two-photon (2PA) absorption conditions. The complexes have the general structure [DPAF-C[triple bond]C-Pt(PBu(3))(2)-C[triple bond]C-Ar-C[triple bond]C-Pt(PBu(3))(2)-C[triple bond]C-DPAF], where Ar is a pi-conjugated unit, Bu = n-butyl, and DPAF = diphenylamino-2,7-fluorenylene. The core Ar units include 1,4-phenylene, 2,5-thienylene, 5,5'-(2,2'-bithienylene), 2,5-(3,4-ethylenedioxythiophene, 2,1,3-benzothiadiazole, and 4,7-dithien-2-yl-2,1,3-benzothiadiazole. Absorption and photoluminescence spectroscopy indicates that the complexes feature low-lying excited states based on both the core [-Pt(PBu(3))(2)-C[triple bond]C-Ar-C[triple bond]C-Pt(PBu(3))(2)-] chromophore as well as the DPAF units. Photoexcitation of the complexes produces a singlet state excited state, which rapidly undergoes intersystem crossing to afford a triplet state that has a lifetime in the microsecond time domain. In most cases, the lowest energy triplet state is localized on the core chromophore. Femtosecond 2PA spectra are measured along with triplet-triplet absorption spectra and nanosecond intensity-dependent transmission for solutions of the complexes. Each of the complexes features a 2PA absorption band in the near-infrared region (lambda approximately 700-750 nm) with a cross section 50-200 GM that is ascribed to the DPAF chromophore. The complexes also feature broad triplet-triplet absorption throughout the visible and near-infrared regions (lambda approximately 500-800 nm, (TT) approximately 5-10 x 10(4) M(-1) cm(-1)). Each of the complexes exhibits efficient nonlinear absorption of nanosecond pulses in the near-infrared region (600-800 nm), and we demonstrate that effect is most efficient in the chromophores where the 2PA cross section maxima coincides spectrally with the excited triplet state absorption.