Parker RR, Sarju JP, Whitwood AC, Williams JAG, Lynam JM, Bruce DW. Synthesis, Mesomorphism, and Photophysics of 2,5-Bis(dodecyloxyphenyl)pyridine Complexes of Platinum(IV).
Chemistry 2018;
24:19010-19023. [PMID:
30211455 DOI:
10.1002/chem.201804026]
[Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Indexed: 02/02/2023]
Abstract
It has been shown for the first time that the PtIV complex cis-[Pt(N^C-tolpy)2 Cl2 ] (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)2 Cl2 ] are liquid crystals and small-angle X-ray scattering suggests formation of a lamellar mesophase. Surprisingly, heating [Pt(κ2 -N^C-L)2 Cl(κ1 -N^C-LH)] also leads to a mesomorphic compound, which results from thermally induced oxidation to cis-[Pt(N^C-L)2 Cl2 ] 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.
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