Chiral Heteropoly Blues and Controllable Switching of Achiral Polyoxometalate Clusters

Abstract

Managing the blues: Chiral heteropoly blues of achiral polyoxometalate clusters were created through an intermolecular interaction with a chiral organic compound. Controllable chiroptical switching of the cluster complexes was possible through reversible photochromism of the polyoxometalates (see picture).

Modular Molecules: Site‐Selective Metal Substitution, Photoreduction, and Chirality in Polyoxometalate Hybrids

“…A Cotton effect associated with d–d transitions is well known for metal complexes with chiral ligands. However, it has also been reported in association with IVCT bands (620–780 nm) in a reduced achiral POM with chiral cations 5. In the case of 2 , ESI‐MS (the Supporting Information, Figure S8 and Table S1) data suggest that chiral norleucine moieties remain associated with the metal‐oxo framework of the polyanion as both Nle ligands and NleH + countercations in ion clusters.…”

“…Polyoxometalates are ideal as sturdy inorganic frameworks for functionalization,1 with their structural versatility arising in part from the inclusion of various heteroatoms and organic components 2. 3 This can facilitate the introduction of chirality,3, 4 while judicious choice of countercation/ligand combination enables tailoring properties associated with self‐assembly and solid‐state packing 5. 6 The reversible and multi‐electron redox chemistry that POMs can display gives access to multiple electronic states through chemical, electrochemical, or photophysical processes,7 which have afforded long‐standing applications in analytical chemistry and catalysis.…”

Addition of Metalated 3‐Alkyl‐Substituted Alkoxyallenes to Imines: Preparation of Tetrasubstituted 2,5‐Dihydropyrroles, Pyrrolidin‐3‐ones, and Pyrroles

“…As no hydrogen atoms could be located, it is not possible to determine N-H and H···O distances, nor N-H···O angles, for the observed hydrogen bonds, and so, only NH···O distances are reported. [11][12][13][14][15][16][17] Therefore, it is reasonable to consider that the intermolecular hydrogen bonding between the primary ammonium or glycinium countercations and the POM may contribute to the photochromism observed for the present compounds. For the glycine ligands that bridge the Y atoms, up to three types of intramolecular N-H···O hydrogen bonds to bridging oxo ligands are evident in all compounds (Figures S14 and S15), with NH···O distances in the range of 2.9-3.2 Å.…”

“…[1][2][3][4] Compounds based on polyoxometalates (POMs) of early transition metals, such as Mo or W, can be excellent candidates, due to their facile reduction and accompanying color changes. [11][12][13][14][15][16][17] Two mechanisms have been proposed, both of which involve UV-induced O→Mo/W ligand-to-metal charge-transfer (LMCT) transitions on the polyoxomolybdate or polyoxotungstate, affording a metastable charge-transfer state that contains Mo 5+ or W 5+ ions. [5][6][7][8] The conceptually simplest approach to photochromic POM-based compounds has been covalent grafting of organic photochromes, such as spiropyrans, to the POM framework, [9,10] which has not necessarily exploited the redox properties of the POM.…”

Hybrid Liquid Crystals from the Self‐Assembly of Surfactant‐Encapsulated Polyoxometalate Complexes

“…[42,43] Among them, polyoxometalates (PMs), acting as a large group of nano-sized metal oxide clusters, [44][45][46] are excellent candidates for the creation of nano-hybrid liquid crystals. In contrast to nanoparticles with polyhedral structures and poly-dispersed size, PMs have unique characteristics: [47][48][49] (1) PMs have exact constituent atoms and well-defined chemical structures, one can measure the size and the topology from their singlecrystal structures; (2) PMs have absolutely uniform and strictly mono-dispersed size, which induces a homogeneous ligand distribution at the surface of the nanoclusters. One thus can investigate the influence of nature of PMs on the LC property of nano-hybrid LCs; (3) the number of the surface binding site for each PM cluster is completely confirmable.…”