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Durham University

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Publication details for Prof. J.A. Gareth Williams

Parker, Rachel R., Sarju, Julia P., Whitwood, Adrian C., Williams, J. A. Gareth, Lynam, Jason M. & Bruce, Duncan W. (2018). Synthesis, Mesomorphism, and Photophysics of 2,5-Bis(dodecyloxyphenyl)pyridine Complexes of Platinum(IV). Chemistry - A European Journal 24(71): 19010-19023.

Author(s) from Durham

Abstract

It has been shown for the first time that the PtIV complex cis‐[Pt(N^C‐tolpy)2Cl2] (tolpy=2‐(4‐tolyl)pyridinyl) can be prepared in a one‐pot reaction from K2[PtCl4], although analogous complexes containing 2,5‐bis(4‐dodecyloxyphenyl)pyridine (=HL) could be prepared using existing routes. The resulting complexes cis‐[Pt(N^C‐L)2Cl2] are liquid crystals and small‐angle X‐ray scattering suggests formation of a lamellar mesophase. Surprisingly, heating [Pt(κ2‐N^C‐L)2Cl(κ1‐N^C‐LH)] also leads to a mesomorphic compound, which results from thermally induced oxidation to cis‐[Pt(N^C‐L)2Cl2] and what is presumed to be another geometric isomer of the same formula. The PtIV complexes are quite strongly luminescent in deoxygenated solution, with φ≈10 % and show vibrationally structured emission spectra, λmax(0,0)=532 nm, strongly displaced to the red compared to cis‐[Pt(N^C‐tolpy)Cl2]. Long luminescence lifetimes of 230 μs are attributed to a lower degree of metal character in the excited state accompanying the extension of conjugation in the ligand. There is no significant difference between the emission properties of the bromo‐ and chloro‐complexes, in contrast with the known complexes cis‐[Pt(N^C‐ppy)X2], where the quantum yield for X=Br is some 30 times lower than for X=Cl (ppyH=2‐phenylpyridine). The lower energy of the excited state in the new complexes probably ensures that deactivating LLCT/LMCT states remain thermally inaccessible, even when X=Br.