A Halomanganates(II) with P,P’-Diprotonated Bis(2-Diphenylphosphinophenyl)ether: Wavelength-Excitation Dependence of the Quantum Yield and Role of the Non-Covalent Interactions

• Main Author: Alexey S. Berezin
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: International Journal of Molecular Sciences
• Subjects: manganese(II); luminescence; EPR; non-covalent interaction; DFT
• Online Access: https://www.mdpi.com/1422-0067/22/13/6873
• ISSN: 1661-6596; 1422-0067

A [H₂DPEphos][MnX₄] [X = Br, Cl] tetrahalomanganates(II) with P,P’-diprotonated bis[2-(diphenylphosphino)phenyl]ether cation has been designed and investigated in photophysics and EPR terms. The complexes exhibit a green luminescence resulted from the Mn(II) <i>d</i>–<i>d</i> transitions (⁴<i>T</i>₁→⁶<i>A</i>₁) with the wavelength-excitation dependence of the quantum yield. The solid [H₂DPEphos][MnBr₄] complex exhibits a bright green phosphorescence (λ_max = 515 nm) with the high luminescence quantum yield depending on the excitation energy whereas the solid [H₂DPEphos][MnCl₄] complex exhibits a very weak phosphorescence (λ_max = 523 nm). The unexpected shorter luminescence lifetime for the [H₂DPEphos][MnCl₄] than for the [H₂DPEphos][MnBr₄] at 300 K can be a result of the higher non-radiative relaxation contribution. On the one hand, the non-covalent PH…X(Mn) interactions quench the manganese(II) luminescence. On the other hand, the PH…X(Mn) interactions are a pathway of the excitation transfer from [H₂DPEphos]²⁺ to [MnX₄]²⁻.