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

Abstract

A [H2 DPEphos][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) d–d transitions (4 T1 →6 A1) with the wavelength-excitation dependence of the quantum yield. The solid [H2 DPEphos][MnBr4 ] complex exhibits a bright green phosphorescence (λmax = 515 nm) with the high luminescence quantum yield depending on the excitation energy whereas the solid [H2 DPEphos][MnCl4 ] complex exhibits a very weak phosphorescence (λmax = 523 nm). The unexpected shorter luminescence lifetime for the [H2 DPEphos][MnCl4 ] than for the [H2 DPEphos][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 [H2 DPEphos]2+ to [MnX4 ]2−.