Luminescent liquid crystalline hybrid materials by embedding octahedral molybdenum cluster anions with soft organic shells derived from tribenzo[18]crown-6

Abstract

Crown ethers and their derivatives are versatile building blocks for the design of supramolecular materials. They can be functionalized at will and are well known for their abilities to complex with alkali cations. Here, we show that emissive lanthanide free hybrid materials can be generated by using such building blocks. The organic tribenzo[18]crown-6 central core was functionalized via six-fold Suzuki cross-coupling as a key reaction with three o-terphenyl units which could be converted into their corresponding triphenylenes by the Scholl reaction, leading to novel liquid-crystalline columnar materials. Selected tribenzo[18]crown-6 o-terphenyls could interact with emissive ternary metal cluster compound salts to generate hybrid materials combining the properties of both moieties. Due to synergistic effects and despite the anisometry of the cluster compounds, individual properties such as liquid-crystalline phase stability of the organic part and emission abilities of its inorganic counter-part are enhanced in the hybrid compounds.

Game of Crowns: Na+Is Coming! Red NIR-Emissive Hybrid Liquid Crystals Containing Discotic Crown Ethers and Na2Mo6X8iCl6(Xi= Cl or Br)

“…27,38,42 In addition, previous work on tribenzo [18]crown-6 derivatives revealed that the tribenzo [18]crown-6 triphenylenes decomposed upon attempted complexation with the cluster salts, whereas the corresponding o-terphenyls formed stable clustomesogens. 28 Sodium salts of metal clusters were synthesized in solution starting from (H 3 O) 2 Mo 6 Cl 14 •7H 2 O or Mo 6 Br 12 as described in the Experimental Section. The identity and purity of the cluster salts were assessed by X-ray diffraction (XRD), powder diffraction, and energy-dispersive spectroscopy (EDS) analyses.…”

Original Synthesis of Molybdenum Nitrides Using Metal Cluster Compounds as Precursors: Applications in Heterogeneous Catalysis

“…As defined by Cotton et al cluster compounds are aggregates of finite dimensions of metal atoms connected to each other by metal–metal bonding. Transition metal cluster compounds are widely used for their luminescence or UV–NIR absorption properties. − In this work, the true nanoscale aspect (∼1 nm) of these compounds is used to form nanostructured molybdenum nitrides. Several molybdenum cluster compounds are treated at different temperatures under a fixed ammonia flow of 30L/h.…”

“…• RESULTS AND DISCUSSION Choice of the precursor As defined by Cotton et al 35 cluster compounds are aggregates of finite dimensions of metal atoms connected to each other by metal-metal bonding. Transition metal cluster compounds are widely used for their luminescence or UV-NIR absorption properties [36][37][38][39][40] . In this work, the true nanoscale aspect (≈1 nm) of these compounds is used in order to form nanostructured molybdenum nitrides.…”

Designing Functional Polyoxometalate‐Based Ionic Liquid Crystals and Ionic Liquids

“…In addition to the two previous approaches, Molard and coworkers developed another strategy with hexametallic clusters which consisted in trapping the alkali counter cations, especially K + and Cs + , within functionalized 15C5 or 18C6 crown ethers (see Figure 10). [91,92] Following this idea, they succeeded to design columnar hexagonal arrangements mainly due to discotic-like complex formed between the crown ethers and the alkali, while the metallic clusters, well known for their strong luminescence properties, were localized between the columns (see Figure 11). Even if this family of clusters does not formally belong to POM's family, this strategy constitutes a very interesting perspective for developing new POM-based ionic liquid crystals with new arrangements.…”

“…Figure 10. Representation of 15C5 and 18C6 crown ethers derivatives used by Molard and coworkers to coordinate K + and Cs + counter cations paired with hexametallic clusters [Mo 6 X 14 ] 2-(X = Cl, Br, I) and [Mo 6 I 8 (C 2 F 5 COO) 6 ] 2- [91,92]. …”