期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 143, 期 9, 页码 3466-3480出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.0c12568
关键词
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资金
- Fonds der Chemischen Industrie (Kekule-Stipendium)
- MINT Lehramt Plus
- German Research foundation [SFB840]
- BayNAT program
- ENB Elite Network of Bavaria
- University of Bayreuth
- German National Science Foundation [KO 3973/2-1, GRK 1640]
- Solar Technologies Go Hybrid (SolTech), an initiative of the Bavarian State Ministry for Science, Research, and Art
The study presents a family of planar nickel(II) complexes with sensitive CISSS tracked by fluorescence detection. These complexes fluoresce in noncoordinating solvents but are fluorescence-silent in the presence of axial ligands. FD-CISSS shows higher sensitivity compared to absorption-based CISSS.
The response of the spin state to in situ variation of the coordination number (CISSS) is a promising and viable approach to smart sensor materials, yet it suffers to date from insensitive detection. Herein, we present the synthetic access to a family of planar nickel(II) complexes, whose CISSS is sensitively followed by means of fluorescence detection. For this purpose, nickel(II) complexes with four phenazine-based Schiff base-like ligands were synthesized and characterized through solution-phase spectroscopy (NMR and UV-vis), solid-state structure analysis (single-crystal XRD), and extended theoretical modeling. All of them reveal CISSS in solution through axial ligating a range of N- and O-donors. CISSS correlates nicely with the basicity of the axial ligand and the substitution-dependent acidity of the nickel(II) coordination site. Remarkably, three out of the four nickel(II) complexes are fluorescent in noncoordinating solvents but are fluorescence-silent in the presence of axial ligands such as pyridine. As these complexes are rare examples of fluorescent nickel(II) complexes, the photophysical properties with a coordination number of 4 were studied in detail, including temperature-dependent lifetime and quantum yield determinations. Most importantly, fluorescence quenching upon adding axial ligands allows a black or white, i.e. digital, sensoring of spin state alternation. Our studies of fluorescence-detected CISSS (FD-CISSS) revealed that absorption-based CISSS and FD-CISSS are super proportional with respect to the pyridine concentration: FD-CISSS features a higher sensitivity. Overall, our findings indicate a favored ligation of these nickel(II) complexes in the excited state in comparison to the ground state.
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