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Synthesis, Mesomorphism, and Photophysics of 2,5‐Bis(dodecyloxyphenyl)pyridine Complexes of Platinum(IV)
Author(s) -
Parker Rachel R.,
Sarju Julia P.,
Whitwood Adrian C.,
Williams J. A. Gareth,
Lynam Jason M.,
Bruce Duncan W.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201804026
Subject(s) - pyridine , excited state , luminescence , chemistry , crystallography , quantum yield , platinum , ligand (biochemistry) , mesophase , lamellar structure , metal , stereochemistry , photochemistry , medicinal chemistry , fluorescence , materials science , catalysis , organic chemistry , receptor , quantum mechanics , nuclear physics , phase (matter) , biochemistry , physics , optoelectronics
It has been shown for the first time that the Pt IV complex cis ‐[Pt(N^C‐tolpy) 2 Cl 2 ] (tolpy=2‐(4‐tolyl)pyridinyl) can be prepared in a one‐pot reaction from K 2 [PtCl 4 ], 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) 2 Cl 2 ] are liquid crystals and small‐angle X‐ray scattering suggests formation of a lamellar mesophase. Surprisingly, heating [Pt(κ 2 ‐N^C‐L) 2 Cl(κ 1 ‐N^C‐LH)] also leads to a mesomorphic compound, which results from thermally induced oxidation to cis ‐[Pt(N^C‐L) 2 Cl 2 ] and what is presumed to be another geometric isomer of the same formula. The Pt IV complexes are quite strongly luminescent in deoxygenated solution, with φ ≈10 % and show vibrationally structured emission spectra, λ max (0,0)=532 nm, strongly displaced to the red compared to cis ‐[Pt(N^C‐tolpy)Cl 2 ]. 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)X 2 ], 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.