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Long‐Lived Room‐Temperature Near‐IR Phosphorescence of BODIPY in a Visible‐Light‐Harvesting N^C^N Pt II –Acetylide Complex with a Directly Metalated BODIPY Chromophore
Author(s) -
Wu Wanhua,
Zhao Jianzhang,
Guo Huimin,
Sun Jifu,
Ji Shaomin,
Wang Zilong
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102634
Subject(s) - bodipy , phosphorescence , photochemistry , excited state , acetylide , photon upconversion , chemistry , intersystem crossing , quantum yield , chromophore , fluorescence , singlet state , atomic physics , organic chemistry , physics , optics , ion
Room‐temperature long‐lived near‐IR phosphorescence of boron‐dipyrromethene (BODIPY) was observed ( λ em =770 nm, Φ P =3.5 %, τ P =128.4 μs). Our molecular‐design strategy is to attach Pt II coordination centers directly onto the BODIPY π‐core using acetylide bonds, rather than on the periphery of the BODIPY core, thus maximizing the heavy‐atom effect of Pt II . In this case, the intersystem crossing (ISC) is facilitated and the radiative decay of the T 1 excited state of BODIPY is observed, that is, the phosphorescence of BODIPY. The complex shows strong absorption in the visible range ( ε =53800 M −1 cm −1 at 574 nm), which is rare for Pt II –acetylide complexes. The complex is dual emissive with 3 M LCT emission at 660 nm and the 3 IL emission at 770 nm. The T 1 excited state of the complex is mainly localized on the BODIPY moiety (i.e. 3 IL state, as determined by steady‐state and time‐resolved spectroscopy, 77 K emission spectra, and spin‐density analysis). The strong visible‐light‐harvesting ability and long‐lived T 1 excite state of the complex were used for triplet‐triplet annihilation based upconversion and an upconversion quantum yield of 5.2 % was observed. The overall upconversion capability ( η = ε × Φ UC ) of this complex is remarkable considering its strong absorption. The model complex, without the BODIPY moiety, gives no upconversion under the same experimental conditions. Our work paves the way for access to transition‐metal complexes that show strong absorption of visible light and long‐lived 3 IL excited states, which are important for applications in photovoltaics, photocatalysis, and upconversions, etc.