Phosphorescent platinum(II) complexes bearing pentafluorosulfanyl substituted cyclometalating ligands

TY - JOUR

T1 - Phosphorescent platinum(II) complexes bearing pentafluorosulfanyl substituted cyclometalating ligands

AU - Henwood, Adam F.

AU - Webster, James

AU - Cordes, David

AU - Slawin, Alexandra M. Z.

AU - Jacquemin, Denis

AU - Zysman-Colman, Eli

N1 - Copyright: © 2017 The Royal Society of Chemistry.

PY - 2017

Y1 - 2017

N2 - The first examples of phosphorescent platinum(ii) complexes bearing pentafluorosulfanyl (-SF5) substituted cyclometalating ligands (C^N) are reported. These complexes are of the form [Pt(C^N)(pivacac)], where pivacac is 2,2′,6,6′-tetramethylheptane-3,5-dionate. Modifying the phenyl ring of the C^N ligand to incorporate one strongly electron-withdrawing -SF5 group has important effects on the photophysical and electrochemical properties of the complex that are dependent on the regiochemistry of the substituent. In a meta position with respect to the Pt-CC^N bond, the substituent exerts a predominantly stabilising effect on the lowest triplet excited state that red-shifts the emission of the complex compared to the reference [Pt(ppy)(pivacac)], 1, where ppy is 2-phenylpyridinato. When the -SF5 group is located para to the Pt-CC^N bond, it does not affect the triplet state directly, and the electron-withdrawing group stabilises the metal-based orbitals, resulting in a blue-shift of the emission. In the solid-state all three complexes are mechanochromic, and can display excimeric emission originating from intermolecular π-π∗ interactions, but the relative emission intensities of the monomeric and dimeric excited states correlate with the steric congestion of the metal centre, and in particular the regiochemistry of the -SF5 group. We relate these findings with observations in the crystal structures.

AB - The first examples of phosphorescent platinum(ii) complexes bearing pentafluorosulfanyl (-SF5) substituted cyclometalating ligands (C^N) are reported. These complexes are of the form [Pt(C^N)(pivacac)], where pivacac is 2,2′,6,6′-tetramethylheptane-3,5-dionate. Modifying the phenyl ring of the C^N ligand to incorporate one strongly electron-withdrawing -SF5 group has important effects on the photophysical and electrochemical properties of the complex that are dependent on the regiochemistry of the substituent. In a meta position with respect to the Pt-CC^N bond, the substituent exerts a predominantly stabilising effect on the lowest triplet excited state that red-shifts the emission of the complex compared to the reference [Pt(ppy)(pivacac)], 1, where ppy is 2-phenylpyridinato. When the -SF5 group is located para to the Pt-CC^N bond, it does not affect the triplet state directly, and the electron-withdrawing group stabilises the metal-based orbitals, resulting in a blue-shift of the emission. In the solid-state all three complexes are mechanochromic, and can display excimeric emission originating from intermolecular π-π∗ interactions, but the relative emission intensities of the monomeric and dimeric excited states correlate with the steric congestion of the metal centre, and in particular the regiochemistry of the -SF5 group. We relate these findings with observations in the crystal structures.

UR - https://www.scopus.com/pages/publications/85021633899

U2 - 10.1039/c7ra03190d

DO - 10.1039/c7ra03190d

M3 - Article

AN - SCOPUS:85021633899

SN - 2046-2069

VL - 7

SP - 25566

EP - 25574

JO - RSC Advances

JF - RSC Advances

IS - 41

ER -