MnBr2/18-crown-6 coordination complexes showing high room temperature luminescence and quantum yield. Issue 15 (9th March 2016)

• Record Type: Journal Article
• Authors: Hausmann, David; Kuzmanoski, Ana; Feldmann, Claus
• Is Part Of: Dalton transactions. Volume 45:Issue 15(2016)
• Page Start: 6541
• Page End: 6547
• Publication Date: 2016-03-09
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt00458j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The reaction of MnBr2 and 18-crown-6 in [( n -Bu)3 MeN][N(Tf)2 ] under mild conditions (80–130 °C) resulted in the formation of the coordination compounds MnBr2 (18-crown-6) (1 ), Mn3 Br6 (18-crown-6)2 (2 ) and Mn3 Br6 (18-crown-6) (3 ). Abstract : The reaction of manganese(ii ) bromide and the crown ether 18-crown-6 in the ionic liquid [( n -Bu)3 MeN][N(Tf)2 ] under mild conditions (80–130 °C) resulted in the formation of three different coordination compounds: MnBr2 (18-crown-6) (1 ), Mn3 Br6 (18-crown-6)2 (2 ) and Mn3 Br6 (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 Mn 2+ 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 Mn 2+ coordinated by two bromine atoms and only five oxygen atoms of 18-crown-6. Mn3 Br6 (18-crown-6)2 falls into a [MnBr(18-crown-6)] + cation – with Mn 2+ coordinated by six oxygen atoms and Br – and a [MnBr(18-crown-6)MnBr4 ] − anion. In this anion, Mn 2+ 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. Mn3 Br6 (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 Mn 2+ cations. All compounds show intense luminescence in the yellow to red spectral range and exhibit remarkable quantum yields of 70% (Mn3 Br6 (18-crown-6)) and 98% (Mn3 Br6 (18-crown-6)2 ). The excellent quantum yield of Mn3 Br6 (18-crown-6)2 and its differentiation from MnBr2 (18-crown-6) and Mn3 Br6 (18-crown-6) can be directly correlated to the local coordination.