TY - JOUR

T1 - Harnessing Fluorescence versus Phosphorescence Ratio via Ancillary Ligand Fine-Tuned MLCT Contribution

AU - Kondrasenko, Ilya

AU - Chung, Kun You

AU - Chen, Yi Ting

AU - Koivistoinen, Juha

AU - Grachova, Elena V.

AU - Karttunen, Antti J.

AU - Chou, Pi Tai

AU - Koshevoy, Igor O.

N1 - Funding Information: I.O.K.; grant 138560, A.J.K.), the Alfred Kordelin Foundation (A.J.K.), University of Eastern Finland (Spearhead project) and the Russian Foundation for Basic Research (grant 14-03-00970) is gratefully acknowledged. Computational resources were provided by CSC-the Finnish IT Center for Science (A.J.K.). Publisher Copyright: © 2016 American Chemical Society. Copyright: Copyright 2016 Elsevier B.V., All rights reserved.

PY - 2016/6/9

Y1 - 2016/6/9

N2 - 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).

AB - 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).

UR - http://www.scopus.com/inward/record.url?scp=84974663193&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.6b03064

DO - 10.1021/acs.jpcc.6b03064

M3 - Article

VL - 120

SP - 12196

EP - 12206

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 22

ER -