Synthesis, crystal structure and photophysical properties of a dinuclear MnII complex with 6-(diethylamino)-4-phenyl-2-(pyridin-2-yl)quinoline

Abstract

A new quinoline derivative, namely, 6-(diethylamino)-4-phenyl-2-(pyridin-2-yl)quinoline, C24H23N3 (QP), and its MnII complex aqua-1κO-di-μ-chlorido-1:2κ4Cl:Cl-dichlorido-1κCl,2κCl-bis[6-(diethylamino)-4-phenyl-2-(pyridin-2-yl)quinoline]-1κ2N1,N2;2κ2N1,N2-dimanganese(II), [Mn2Cl4(C24H23N3)2(H2O)] (MnQP), were synthesized. Their compositions have been determined with ESI-MS, IR, and 1H NMR spectroscopy. The crystal-structure determination of MnQP revealed a dinuclear complex with a central four-membered Mn2Cl2 ring. Both MnII atoms bind to an additional Cl atom and to two N atoms of the QP ligand. One MnII atom expands its coordination sphere with an extra water molecule, resulting in a distorted octahedral shape. The second MnII atom shows a distorted trigonal–bipyramidal shape. The UV–vis absorption and emission spectra of the examined compounds were studied. Furthermore, when investigating the aggregation-induced emission (AIE) properties, it was found that the fluorescent color changes from blue to green and eventually becomes yellow as the fraction of water in the THF/water mixture increases from 0% to 99%. In particular, these color and intensity changes are most pronounced at a water fraction of 60%. The crystal structure contains disordered solvent molecules, which could not be modeled. The SQUEEZE procedure [Spek (2015). Acta Cryst. C71, 9–18] was used to obtain information on the type and quantity of solvent molecules, which resulted in 44 electrons in a void volume of 274 Å3, corresponding to approximately 1.7 molecules of ethanol in the unit cell. These ethanol molecules are not considered in the given chemical formula and other crystal data.

Keywords

• crystal structure
• mnii complex
• dinuclear complex
• aggregation-induced emission