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

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) (), Mn3Br6(18-crown-6)2 () and Mn3Br6(18-crown-6) (). 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. Mn3Br6(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. Mn3Br6(18-crown-6), finally, forms an infinite, non-charged [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% (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.

2-[2-(Benzyl-sulfan-yl)phen-yl]-1,1,3,3-tetra-methyl-guanidine

The mol-ecular structure of the title compound, C(18)H(23)N(3)S, shows it to be a derivative of an amino-thio-phenol possessing a tetra-methyl-guanidine group with a localized C=N double bond of 1.304 (2) Å and a protected thiol functional group as an S-benzyl thio-ether. The two aromatic ring planes make a dihedral angle of 67.69 (6)°.

N-[Bis(dimethyl-amino)-methyl-idene]-2-[(triphenyl-meth-yl)sulfan-yl]ethanaminium hexa-fluoro-phosphate

The mol-ecular structure of the title compound, C(26)H(32)N(3)S(+)·PF(6) (-), shows a protonated guanidyl group bridged by an ethyl-ene linker with a tritylsulfanyl unit. The guanidinium (gua) unit displays charge delocalization over the three N-C(gua) bonds. The N-C-C-S group shows a folded nonplanar conformation with a torsion angle of 158.4 (1)°. In the crystal, the cation and anion are linked by an N-H⋯F inter-action.