Harnessing Fluorescence versus Phosphorescence Ratio via Ancillary Ligand Fine-Tuned MLCT Contribution

Ilya Kondrasenko, Kun You Chung, Yi Ting Chen, Juha Koivistoinen, Elena V. Grachova, Antti J. Karttunen*, Pi Tai Chou, Igor O. Koshevoy

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    18 Citations (Scopus)

    Abstract

    A series of gold(I) alkynyl-diphosphine complexes (XC6H4C2Au)PPh2 - spacer - PPh2(AuC2C6H4X); spacer = - C2(C6H4)nC2 - (A1, n = 2, X = CF3; A2, n = 2, X = OMe; A3, n = 3, X = CF3; A4, n = 3, X = OMe), - (C6H4)n - (B5, n = 3, X = OMe; B6, n = 4, X = OMe) were prepared, and their photophysical properties were investigated. The luminescence behavior of the titled compounds is dominated by the diphosphine spacer, which serves as an emitting ππ∗ chromophore. The complexes exhibit dual emission, comprising low and high energy bands of triplet (phosphorescence) and singlet (fluorescence) origins, respectively. The electron-donating characteristics of ancillary groups X significantly affect the LLCT/MLCT contribution of both alkynyl ligand and the metal center into the lowest lying excited state. In turn, it substantially influences the rate of intersystem crossing kisc S1 → Tm (m ≥ 1) that allows for tuning the ratio fluorescence vs phosphorescence without alteration of the chromophore core. Quantum chemical analysis of the excited states at the CC2/TZVP level of theory supports the experimental observations. Crystalline complexes A2 and B5, which exhibit dominating phosphorescence emission, for the first time for the unsupported gold luminophores were probed as molecular oxygen sensors (max KSV1 = 63 atm-1).

    Original languageEnglish
    Pages (from-to)12196-12206
    Number of pages11
    JournalJournal of Physical Chemistry C
    Volume120
    Issue number22
    DOIs
    Publication statusPublished - 9 Jun 2016
    MoE publication typeA1 Journal article-refereed

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