Synthesis And Photophysical Property Of Transbis(Alkylphosphine) Platinum(â…¡)-alkynyl Complexes

Pt(Ⅱ) complexes which contain visible light-harvesting ligands such as Bodipy, coumarin, naphthalenediimide, perylene bisimide, etc, show strong visible light absorption and long-lived triplet excited states, and have been used in triplet-triplet annihilation (TTA) upconversion, photoredox catalytic organic reactions and photosensitizing of 1O2.But there is a common disadvantage of these complexes is left to overcome, that is, there is usually only a single visible light-harvesting ligand in these complexes, as a result, these is only one major absorption band in visible spectral region. This is a drawback if a panchromatic light source was used, such as solar light. Therefore, it is important to prepare Pt(Ⅱ) complexes that show broadband absorption of visible light. This goal is unable to be achieved by using the conventional molecular structural protocol based on using single kind of visible light-harvesting ligand.On the other hand, the trans bis(alkylphosphine) platinum(Ⅱ)-alkynyl complexes has attracted much attention. The molecular structure of these compounds can be easily altered by variation of the acetylides ligands, providing tuneability of both photophysical and redox properties. However, trans bis(alkylphosphine) platinum(Ⅱ)-alkynyl complexes showing strong visible light absorption were rarely reported. In organic molecular dyads, fluorescent resonance energy transfer (FRET) was very often used to achieve a broadband visible light absorption. However, to the best of our knowledge, this strategy was never used to achieve broadband visible light absorption in transition metal complexes. In this paper we propose a strategy to achieve broadband visible light-absorption in transitional metal complexes. A series of Pt(Ⅱ) complexes that show broadband absorption of visible light were synthesized. The electronic absorption, emission, nanosecond transient absorption and electrochemical properties of these complexes were studied, and the Pt(Ⅱ) complexes were applied in TTA upconvertion.1.Two Pt(Ⅱ) complexes Pt-1 and Pt-2 with two different Bodipy ligands in these complexes were synthesized. They showed a broadband visible light-absorption (450 nm to 700 nm), molar extinction coefficient (ε) is up to 1.85×105 M-1 cm-1. The triplet lifetime of Pt-1 and Pt-2 were 63.13μs and 94.18 μs, on the other hand, with nanosecond pulsed laser excitation, delayed fluorescence was observed for the complexes,43.8μs and 111.0 μs. The complexes were used as efficient multi-wave length excitable triplet photosensitizers for triplet-trip let annihilation assisted upconversion. With PBI as the acceptor,589 nm exciting light stimulate, TTA upconversion quantum yield of Pt-1 and Pt-2 is 9.72% and 4.89%, respectively.2. Three Pt(II) complexes Pt-NI, Pt-Py2 and NI-Pt-Py, with pyrene or naphthalimides ligands in these complexes were synthesized. They showed a broadband visible light-absorption (350 nm to 450 nm), molar extinction coefficient(ε)is up to 47100 M-1 cm-1. The triplet lifetime of Pt-Py2 and NI-Pt-Py were 47.7 μs and 82.7μs.