Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore

Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore

Photophysics of organometallic platinum(II) derivatives of the diketopyrrolopyrrole chromophore
Subhadip Goswami, Russell W Winkel, Erkki Alarousu, Ion Ghiviriga, Omar F. Mohammed, and Kirk S. Schanze.
J. Phys. Chem. A, 118 (50), pp 11735–11743, (2014)
Subhadip Goswami, Russell W Winkel, Erkki Alarousu, Ion Ghiviriga, Omar F. Mohammed, and Kirk S. Schanze
Diketopyrrolopyrrole (DPP) chromophores, Photophysics
2014
A pair of diketopyrrolopyrrole (DPP) chromophores that are end-functionalized with platinum containing “auxochromes” were subjected to electrochemical and photophysical study. The chromophores contain either platinum acetylide or ortho-metallated 2-thienylpyridinyl(platinum) end-groups (DPP-Pt(CC) and DPP-Pt(acac), respectively). The ground state redox potentials of the chromophores were determined by solution electrochemistry, and the HOMO and LUMO levels were estimated. The chromophores’ photophysical properties were characterized by absorption, photoluminescence and time-resolved absorption spectroscopy on timescales from sub-picoseconds to microseconds. Density functional theory (DFT) computations were performed to understand the molecular orbitals involved in both the singlet and triplet excited state photophysics. The results reveal that in both platinum DPP derivatives the organometallic auxochromes have a significant effect on the chromophores’ photophysics. The most profound effect is a reduction in the fluorescence yields accompanied by enhanced triplet yields due to spin-orbit coupling induced by the metal centers. The effects are most pronounced in DPP-Pt(acac) indicating that the orthometallated platinum auxochrome is able to induce spin-orbital coupling to a greater extent compared to the platinum acetylide units.


DOI: 10.1021/jp509987p