Access to lanthanide acetate coordination compounds is challenged by the tendency of lanthanides to coordinate water and the plethora of acetate coordination modes. A straightforward, reproducible synthetic procedure by treating lanthanide chloride hydrates with defined ratios of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C 2 mim][OAc]) has been developed. This reaction pathway leads to two isostructural crystalline anhydrous coordination complexes, the polymeric [C 2 mim] n [{Ln 2 (OAc) 7 } n ] and the dimeric [C 2 mim] 2 [Ln 2 (OAc) 8 ], based on the ion size and the ratio of IL used. A reaction with an IL : Ln-salt ratio of 5 : 1, where Ln = Nd, Sm, and Gd, led exclusively to the polymer, whilst for the heaviest lanthanides (DyÀ Lu) the dimer was observed. Reaction with Eu and Tb resulted in a mixture of both polymeric and dimeric forms. When the amount of IL and/or the size of the cation was increased, the reaction led to only the dimeric compound for all the lanthanide series. Crystallographic analyses of the resulting salts revealed three different types of metal-acetate coordination modes where η 2 μk 2 is the most represented in both structure types.

A series of asymmetric and symmetric 1,3-dialkyltriazolium iodides were studied with hindsight to their application as electrolytes and redox mediators in dye-sensitized solar cells (DSSCs). Compounds with an alkyl chain length from C4 to C10 present the characteristics of ionic liquids (ILs), whilst those with longer chains exhibit liquid crystallinity. All compounds show an appreciable chemical and thermal stability with decomposition temperatures around 185–195 °C. Testing these compounds as electrolytes and redox mediators in DSSCs reveals significant changes in the properties of the electrolyte upon addition of the redox couple. Addition of iodine generally leads to a depression of the melting point and an enhancement of conductivity. These changes in the electrolyte, which are significant, have so far been largely overlooked in DSSC optimization. Furthermore, in comparison to frequently employed imidazolium iodides, 1-alkyl-3-methyltriazolium iodides show both an improved superior efficiency and an extended cell lifetime. This is attributed to the fact that, unlike the imidazolium salts, the triazolium counterparts are not hygroscopic. The nonhygroscopic nature of the salts also renders device fabrication easier. In addition, electrode passivation, which is commonly observed with imidazolium iodides, could not be noticed for the triazolium analogues, making these materials overall extremely attractive.

Emerging organic light‐emitting devices, such as light‐emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal‐free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal‐free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric‐field‐driven structural transformation of the original green‐light emitter structure into a red‐emitting structure.

Ionic liquids present a versatile, highly tunable class of soft functional materials. Aside from being low melting salts, they can be endowed with additional functionalities. In N-alkylimidazolium halides, which are a prominent class of ionic liquids (ILs), the imidazolium cation was linked via an ether-bridge to an azobenzene unit in order to obtain photoresponsive materials through photoinduced trans-cis isomerization. The azobenzene unit, in turn, was modified with electron-donating or -withdrawing groups such as methyl-, tert-butyl-, methoxy-, N,N-dimethylamino, and nitro groups to study their influence on the photoisomerization and phase behavior. Endowing the imidazolium additionally with a long alkyl chain allows the materials to potentially form liquid crystalline (LC) mesophases before melting into the isotropic liquid. All studied compounds qualify as ionic liquids, and all, except for the nitro-compound, show the formation of smectic mesophases melting to the isotropic liquid. The compounds with the bulkiest aliphatic substituent, the tert-butyl, shows the lowest melting point, the largest mesophase window, and an efficient photochemical trans–cis conversion (>90%). In summary, by tuning sterically and electronically the cationic part of ILs, a photoswitchable room temperature liquid crystal could be developed and design guidelines for photoresponsive ionic liquids could be obtained.

Light-emitting materials based on earth-abundant metals such as manganese hold great promises as emitters for organic lighting devices. In order to bring such emitter materials to application and in particular...