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O: Fachverband Oberflächenphysik
O 91: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales III
O 91.5: Talk
Thursday, March 21, 2024, 16:15–16:30, MA 041
Activating the fluorescence of a Ni(II) complex by energy transfer — Tzu-Chao Hung1,2, Yokari Godinez-Loyola3, Manuel Steinbrecher1, Brian Kiraly1, Alexander A. Khajetoorians1, Nikos L. Doltsinis3, Cristian A. Strassert3, and •Daniel Wegner1 — 1Radboud University, Nijmegen, The Netherlands — 2University of Regensburg — 3University of Münster
Luminescence of open-shell 3d metal complexes is often quenched due to ultrafast intersystem crossing (ISC) and cooling into a dark metal-centered excited state. We demonstrate successful activation of fluorescence from individual nickel phthalocyanine (NiPc) molecules in the junction of a scanning tunneling microscope (STM) by resonant energy transfer from other metal phthalocyanines at low temperature. By combining STM, STS, STM-induced luminescence and time-dependent density functional theory, we provide evidence that there is an activation barrier for the ISC, which in most experimental conditions is overcome. We demonstrate that, when placing a donor MPc (M = Zn, Pd, Pt) molecule close to NiPc by means of STM atomic manipulation, resonant energy transfer can excite the acceptor NiPc without overcoming the ISC activation barrier, leading to Q-band fluorescence. This work demonstrates that the thermally activated population of dark metal-centered states can be avoided by a designed local environment at low temperatures paired with a directed molecular excitation into vibrationally cold electronic states.
Keywords: STM-induced luminescence; scanning tunneling microscopy; fluorescence; resonant energy transfer; intersystem crossing