期刊
SCIENTIFIC REPORTS
卷 11, 期 1, 页码 -出版社
NATURE RESEARCH
DOI: 10.1038/s41598-021-85940-w
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资金
- University of Kurdistan [4/7224]
In this study, the acidity constants of methylthymol blue (MTB) and the association constants of its complexes with Zn-II, Cu-II, and Fe-II metal ions (MIs) were determined through theoretical and experimental methods. The results showed a mixed n->pi* and pi->pi* electronic transitions in the UV-Visible spectra of MTB, as well as the formation of 1:2 and 1:1 complexes for Zn-II and Cu-II, and 1:1 and 2:1 complexes for Fe-II. The UV-Visible spectra of the Zn(MTB) and Cu(MTB) complexes exhibited ligand-to-ligand charge transfer (LLCT) characters, while the Fe(MTB) complex showed LLCT and metal-to-ligand charge transfer (MLCT) characters.
In this study, we determine the acidity constants of methylthymol blue (MTB) and association constants of its complexes with the Zn-II, Cu-II, and Fe-II metal ions (MIs), through theoretical and experimental means. The complexes were characterized using UV-Visible absorption spectroscopy combined with soft/hard chemometrics methods and quantum chemical calculations. Quantum chemical calculations revealed that electronic transitions in the UV-Visible spectra of MTB have mixed n ->pi* and pi ->pi* characters. The results of molar ratio and multivariate curve resolution alternating least squares (MCR-ALS) revealed the formation of successive 1:2 and 1:1 complexes (MI:MTB) for the Zn-II and Cu-II systems. However, the formation of successive 1:1 and 2:1 complexes are suggested for Fe-II by the molar ratio and MCR-ALS. The majority of transitions observed in the UV-Visible spectra of the Zn(MTB) and Cu(MTB) complexes have ligand-to-ligand charge transfer (LLCT) characters. However, the transitions in the UV-Visible spectrum of the Fe(MTB) complex have LLCT and metal-toligand charge transfer (MLCT) characters. For the Fe-2(MTB) complex, the lowest energy transition of has an LLCT character. However, its higher energy transitions are a mixture of LLCT, MLCT, and metalto-metal charge transfer (MMCT) characters. The correlation between experimental and computed wavelengths revealed that the 1:1 complexes of Zn-II and Cu-II prefer square pyramidal geometries. However, the Fe-II complexes always show octahedral geometry.
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