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

A H₂DPEphos]MnX₄] X = Br, Cl] tetrahalomanganates(II) with P,P’-diprotonated bis2-(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) d–d transitions (⁴T₁→⁶A₁) 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⁻.