Utilization of a Pt(ii) di-yne chromophore incorporating a 2,2′-bipyridine-5,5′-diyl spacer as a chelate to synthesize a green and red emitting d–f–d heterotrinuclear complex

Abstract

A new heterotrinuclear (d–f–d) complex [Eu(btfa)₃1c] (btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1c = [(Ph)(Et₃P)₂Pt–CC–R–CC–Pt(Et₃P)₂(Ph)] (R = 2,2′-bipyridine-5,5′-diyl) has been synthesized by utilizing the N,N-donor sites of the organometallic chromophore. The complex was characterized by analytical and spectroscopic methods. Photophysical properties of the complex were analysed in detail using both steady-state and time-resolved emission and excitation spectroscopy. The optical absorption spectrum of the complex is dominated by the spin allowed π–π* transitions of the btfa and 1c units in the UV–visible region (200–418 nm) and thus is excitable over a wide range of wavelengths across the UV into the visible region of the electromagnetic spectrum. The complex displays typical red Eu(III) emission when excited at 345 nm. However, it also shows green emission when excited at 464 nm and, thus could be an interesting candidate for full colour display applications. The change in the colour could be a result of the high value of the energy back-transfer rate (6.73 × 10⁵ s⁻¹) from the triplet state of the organometallic chromophore to the ⁵D₁ state of Eu(III). Judd–Ofelt (J–O) intensity parameters (Ω₂ and Ω₄), radiative (A_R), non-radiative (A_R) decay rates and intrinsic quantum yield (Q^Eu_Eu) have been calculated.