Issue 15, 2016

MnBr2/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield

Abstract

The reaction of manganese(II) bromide and the crown ether 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] under mild conditions (80–130 °C) resulted in the formation of three different coordination compounds: MnBr2(18-crown-6) (1), Mn3Br6(18-crown-6)2 (2) and Mn3Br6(18-crown-6) (3). In general, the local coordination and the crystal structure of all compounds are driven by the mismatch between the small radius of the Mn2+ cation (83 pm) and the ring opening of 18-crown-6 as a chelating ligand (about 300 pm). This improper situation leads to different types of coordination and bonding. MnBr2(18-crown-6) represents a molecular compound with Mn2+ coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3Br6(18-crown-6)2 falls into a [MnBr(18-crown-6)]+ cation – with Mn2+ coordinated by six oxygen atoms and Br – and a [MnBr(18-crown-6)MnBr4] anion. In this anion, Mn2+ is coordinated by five oxygen atoms of the crown ether as well as by two bromine atoms, one of them bridging to an isolated (MnBr4) tetrahedron. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged 1[Mn2(18-crown-6)(MnBr6)] chain. Herein, 18-crown-6 is exocyclically coordinated by two Mn2+ cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3Br6(18-crown-6)) and 98% (Mn3Br6(18-crown-6)2). The excellent quantum yield of Mn3Br6(18-crown-6)2 and its differentiation from MnBr2(18-crown-6) and Mn3Br6(18-crown-6) can be directly correlated to the local coordination.

Graphical abstract: MnBr2/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield

Supplementary files

Article information

Article type
Paper
Submitted
01 Feb 2016
Accepted
24 Feb 2016
First published
24 Feb 2016

Dalton Trans., 2016,45, 6541-6547

MnBr2/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield

D. Hausmann, A. Kuzmanoski and C. Feldmann, Dalton Trans., 2016, 45, 6541 DOI: 10.1039/C6DT00458J

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