Clustomesogens: Liquid Crystal Materials Containing Transition-Metal Clusters

Joint Venture of Metal Cluster and Amphiphilic Cationic Minidendron Resulting in Near Infrared Emissive Lamellar Ionic Liquid Crystals

Inorganic red-NIR emissive materials are particularly relevant in many fields like optoelectronic, bioimaging or solar cells. Benefiting from their emission in devices implies their integration in easy-to-handle materials like liquid crystals, whose long-range ordering and self-healing abilities could be exploited and influence emission. Herein, we present red-NIR emissive hybrid materials obtained with phosphorescent octahedral molybdenum cluster anions electrostatically associated with amphiphilic guanidinium minidendrons. Polarized optical microscopy and X-ray analysis show that while the minidendron chloride salts self-organize into columnar phases, their association with the dianionic metal cluster leads to layered phases. Steady-state and time-resolved emission investigations demonstrate the influence of the minidendron alkyl chain length on the phosphorescence of the metal cluster core.

In Situ Generation of Active Molybdenum Octahedral Clusters for Photocatalytic Hydrogen Production from Water

The photocatalytic hydrogen evolution reaction (HER) from water under homogeneous and heterogeneous conditions is explored for the {Mo6 Br(i) 8 }(4+) cluster core based unit starting from (TBA)2 [Mo6 Br(i) 8 F(a) 6 ] (TBA=tetra-n-butylammonium; "i" and "a" refer to the face-capping inner and terminal apical ligand, respectively). The catalytic activity of {Mo6 Br(i) 8 }(4+) is enhanced by the in situ generation of [Mo6 Br(i) 8 F(a) 5 (OH)(a) ](2-) , [Mo6 Br(i) 8 F(a) 3 (OH)(a) 3 ](2-) , and [Mo6 Br(i) 8 (OH)(a) 6 ](2-) , which are identified by ESIMS, luminescence, and NMR techniques. Full substitution of F(-) by OH(-) leads to the formation of (H3 O)2 [Mo6 Br(i) 8 (OH)(a) 6 ]⋅10 H2 O; its structure was determined by single-crystal XRD. The immobilization of the active {Mo6 Br(i) 8 }(4+) onto graphene oxide (GO) surfaces enhances its stability under catalytic conditions. The catalytic activity of the resulting (TBA)2 Mo6 Br(i) 8 @GO material is improved with respect to GO, but is reduced compared to the activity under homogeneous conditions because of changes in the GO semiconducting properties as well as lower activity and/or accessibility of the anchored cluster.

Development of structural complexity by liquid-crystal self-assembly

Since the discovery of the liquid-crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self-assembly of liquid crystals. The focus is on new exciting soft-matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry-breaking. Comparisons are made with developments in related fields, such as self-assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.