Bioorthogonal chemistry of polyoxometalates - challenges and prospects.

Bioorthogonal chemistry has enabled scientists to carry out controlled chemical processes in high yields while minimizing hazardous effects. Its extension to the field of polyoxometalates (POMs) could open up new possibilities and new applications in molecular electronics, sensing and catalysis, including inside living cells. However, this comes with many challenges that need to be addressed to effectively implement and exploit bioorthogonal reactions in the chemistry of POMs.

Increasing the redox switching capacity of Lindqvist-type hexavanadates by organogold post-functionalisation.

The covalent attachment of organogold(I) moieties to the Lindqvist-type polyoxovanadate results in a measurable charge re-distribution across the formed Au-{V6}-Au linkages. Scanning probe microscopy studies of these hybrid compounds on the Au(111) surface demonstrate the increase in the number of switching states with stepwise increase in molecular conductance, compared with unfunctionalised hexavanadates.

Controllable Synthesis and Luminescence Behavior of Tetrahedral Au@Cu and Au@Ag Clusters Supported by tris(2-Pyridyl)phosphine.

We report herein a family of polynuclear complexes, [Au@Ag(PyP)]X and [Au@Cu(PyP)]X [X = NO, ClO, OTf, BF, SbF], containing unprecedented Au-centered Ag and Cu tetrahedral cores supported by tris(2-pyridyl)phosphine (PyP) ligands. The [Au@Ag] clusters are synthesized controlled substitution of the central Ag(I) ion in all-silver [Ag@Ag] precursors by the reaction with Au()Cl, while the [Au@Cu] cluster is assembled through the treatment of a pre-organized [Au(PyP)] metallo-ligand with 4 equiv of a Cu(I) source. The structure of the Au@M clusters has been experimentally and theoretically investigated to reveal very weak intermolecular Au-M metallophilic interactions.

Re(I) Complexes as Backbone Substituents and Cross-Linking Agents for Hybrid Luminescent Polysiloxanes and Silicone Rubbers.

This study focuses on the synthesis of hybrid luminescent polysiloxanes and silicone rubbers grafted by organometallic rhenium(I) complexes using Cu(I)-catalyzed azido-alkyne cycloaddition (CuAAC). The design of the rhenium(I) complexes includes using a diimine ligand to create an MLCT luminescent center and the introduction of a triple C≡C bond on the periphery of the ligand environment to provide click-reaction capability. Poly(3-azidopropylmethylsiloxane--dimethylsiloxane) (N-PDMS) was synthesized for incorporation of azide function in polysiloxane chain.

Just Add the Gold: Aggregation-Induced-Emission Properties of Alkynylphosphinegold(I) Complexes Functionalized with Phenylene-Terpyridine Subunits.

A series of organometallic complexes containing an alkynylphosphinegold(I) fragment and a phenylene-terpyridine moiety connected together by flexible linker have been prepared using the specially designed terpyridine ligands. The compounds were studied crystallographically to reveal that all of them contain a linearly coordinated Au(I) atom and a free terpyridine moiety. The different orientations of the molecules relative to each other in the solid state determine the multiple noncovalent interactions such as antiparallel ππ stacking, CH-π, and CH-Au, but no aurophilic interactions are realized.

Functionalizing Collagen with Vessel-Penetrating Two-Photon Phosphorescence Probes: A New In Vivo Strategy to Map Oxygen Concentration in Tumor Microenvironment and Tissue Ischemia.

The encapsulation and/or surface modification can stabilize and protect the phosphorescence bio-probes but impede their intravenous delivery across biological barriers. Here, a new class of biocompatible rhenium (Re ) diimine carbonyl complexes is developed, which can efficaciously permeate normal vessel walls and then functionalize the extravascular collagen matrixes as in situ oxygen sensor. Without protective agents, Re -diimine complex already exhibits excellent emission yield (34%, λ   = 583 nm) and large two-photon absorption cross-sections (σ   = 300 GM @ 800 nm) in water (pH 7.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes.

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior.

Hexavanadate-Organogold(I) Hybrid Compounds: Synthesis by the Azide-Alkyne Cycloaddition and Density Functional Theory Study of an Intriguing Electron Density Distribution.

The fully oxidized Lindqvist-type hexavanadate compounds decorated by phosphine-derivatized Au(I) moieties oriented in a fashion (-BuN)[VO{(OCH)CCH(NCCH)AuP(CHOMe)}] () and (-BuN)[VO{(OCH)CCHOCH(CNH)AuP(CHOMe)}] () have been prepared by azide-alkyne cycloaddition reactions and characterized by various techniques, including NMR, IR, and UV/vis spectroscopy and electrospray ionization mass spectrometry. Electronic structure calculations unveil the potential of these model hybrid junctions for application in controlled charge-transport experiments on substrate surfaces.

Modulation of Metallophilic and π-π Interactions in Platinum Cyclometalated Luminophores with Halogen Bonding.

Luminescent cyclometalated complexes [M(C^N^N)CN] (M=Pt, Pd; HC^N^N=pyridinyl- (M=Pt 1, Pd 5), benzyltriazolyl- (M=Pt 2), indazolyl- (M=Pt 3, Pd 6), pyrazolyl-phenylpyridine (M=Pt 4)) decorated with cyanide ligand, have been explored as nucleophilic building blocks for the construction of halogen-bonded (XB) adducts using IC F as an XB donor. The negative electrostatic potential of the CN group afforded CN⋅⋅⋅I noncovalent interactions for platinum complexes 1-3; the energies of XB contacts are comparable to those of metallophilic bonding according to QTAIM analysis. Embedding the chromophore units into XB adducts 1-3⋅⋅⋅IC F has little effect on the charge distribution, but strongly affects Pt⋅⋅⋅Pt bonding and π-stacking, which lead to excited states of MMLCT (metal-metal-to-ligand charge transfer) origin.

Silver-Decorated TiO Inverse Opal Structure for Visible Light-Induced Photocatalytic Degradation of Organic Pollutants and Hydrogen Evolution.

TiO inverse opal (TIO) structures were prepared by the conventional wet chemical method, resulting in well-formed structures for photocatalytic activity. The obtained structures were functionalized with liquid flame spray-deposited silver nanoparticles (AgNPs). The nanocomposites of TIO and AgNPs were extensively characterized by various spectroscopies such as UV, Raman, X-ray diffraction, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy combined with microscopic methods such as scanning electron microscopy, transmission electron microscopy (TEM), and high-resolution TEM.

Binuclear Gold(I) Phosphine Alkynyl Complexes Templated on a Flexible Cyclic Phosphine Ligand: Synthesis and Some Features of Solid-State Luminescence.

A flexible bidentate cyclic phosphine, namely, 1,5-bis(-tolyl)-3,7-bis(pyridin-2-yl)-1,5-diaza-3,7-diphosphacyclooctane (), was used as a template to construct a family of binuclear heteroleptic phosphine alkynyl complexes [(AuCR)], with R = Ph, CHOH, CHOH, (CH)COH, PhCOH. All complexes obtained were characterized by CHN elemental analysis, NMR spectroscopy, and single-crystal X-ray analysis. It was found that the gold(I) complexes demonstrate a different organization of the crystal structure depending on the nature of the cocrystallized solvent (dichloromethane, acetone, and acetonitrile) because of formation of the supramolecular complexes through hydrogen bonding.

Oligophosphine-thiocyanate Copper(I) and Silver(I) Complexes and Their Borane Derivatives Showing Delayed Fluorescence.

The series of chelating phosphine ligands, which contain bidentate P (bis[(2-diphenylphosphino)phenyl] ether, DPEphos; 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, Xantphos; 1,2-bis(diphenylphosphino)benzene, dppb), tridentate P (bis(2-diphenylphosphinophenyl)phenylphosphine), and tetradentate P (tris(2-diphenylphosphino)phenylphosphine) ligands, was used for the preparation of the corresponding dinuclear [M(μ-SCN)P] (M = Cu, 1, 3, 5; M = Ag, 2, 4, 6) and mononuclear [CuNCS(P/P)] (7, 9) and [AgSCN(P/P)] (8, 10) complexes. The reactions of P with silver salts in a 1:2 molar ratio produce tetranuclear clusters [Ag(μ-SCN)(t-SCN)(P)] (11) and [Ag(μ-SCN)(P)] (12). Complexes 7-11 bearing terminally coordinated SCN ligands were efficiently converted into derivatives 13-17 with the weakly coordinating SCN:B(CF) isothiocyanatoborate ligand.

Supramolecular Construction of Cyanide-Bridged Re Diimine Multichromophores.

The reactions of labile [Re(diimine)(CO)(HO)] precursors (diimine = 2,2'-bipyridine, bpy; 1,10-phenanthroline, phen) with dicyanoargentate anion produce the dirhenium cyanide-bridged compounds [{Re(diimine)(CO)}CN)] (1 and 2). Substitution of the axial carbonyl ligands in 2 for triphenylphosphine gives the derivative [{Re(phen)(CO)(PPh)}CN] (3), while the employment of a neutral metalloligand [Au(PPh)(CN)] affords heterobimetallic complex [{Re(phen)(CO)}NCAu(PPh)] (4). Furthermore, the utilization of [Au(CN)], [Pt(CN)], and [Fe(CN)] cyanometallates leads to the higher nuclearity aggregates [{Re(diimine)(CO)NC} M] (M = Au, x = 2, 5 and 6; Pt, x = 4, 7 and 8; Fe, x = 6, 9 and 10).

Heterometallic Cluster-Capped Tetrahedral Assemblies with Postsynthetic Modification of the Metal Cores.

Combining the star-shaped alkynyl ligands with low-nuclearity gold-copper triphosphane clusters produces 3D metallocage aggregates, which demonstrate room temperature phosphorescence in solution (max Φ =0.6). Their luminescence mainly originates from cluster-localized metal-to-ligand charge transfer excited state.

Improvement of the Photophysical Performance of Platinum-Cyclometalated Complexes in Halogen-Bonded Adducts.

Three groups of luminescent platinum complexes [Pt(C^N)(L)(Y)] [C^N=benzothienyl-pyridine (1), bezofuryl-pyridine (2), phenyl-pyridine (3); L/Y=DMSO/Cl (a), PPh /Cl (b), PPh /CN (c)] have been probed as halogen-bond (XB) acceptors towards iodofluorobenzenes (IC F and I C F ). Compounds 1 a and 2 a (L/Y=DMSO/Cl) afford the adducts 1 a⋅⋅⋅I C F and 2 a⋅⋅⋅I C F , which feature I⋅⋅⋅S /I⋅⋅⋅π and I⋅⋅⋅O /I⋅⋅⋅Cl short contacts, respectively. The phosphane-cyanide derivatives 1 c and 2 c (L/Y=PPh /CN) co-crystallise with both IC F and I C F .

A rare example of a compact heteroleptic cyclometalated iridium(iii) complex demonstrating well-separated dual emission.

A series of [Ir(C^N)2(NN)][PF6] complexes in which NN is 5-(4-ethynylphenyl)-2,2'-bipyridine has been synthesized and characterized by spectroscopic methods. All novel complexes exhibit unique singlet-triplet dual emission in solution with two well-separated emission bands. The mechanism of dual emission has been elucidated on the basis of experimental data and confirmed by TDDFT calculations.

Chromophore-Functionalized Phenanthro-diimine Ligands and Their Re(I) Complexes.

A series of diimine ligands has been designed on the basis of 2-pyridyl-1 H-phenanthro[9,10- d]imidazole (L1, L2). Coupling the basic motif of L1 with anthracene-containing fragments affords the bichromophore compounds L3-L5, of which L4 and L5 adopt a donor-acceptor architecture. The latter allows intramolecular charge transfer with intense absorption bands in the visible spectrum (lowest λ 464 nm (ε = 1.

Luminescence Thermochromism of Gold(I) Phosphane-Iodide Complexes: A Rule or an Exception?

A series of gold(I) iodide complexes 1-11 have been prepared from di-, tri-, and tetraphosphane ligands. Crystallographic studies reveal that the di- (1-7) and tetrametallic (11) compounds feature linearly coordinated gold(I) ions with short aurophilic contacts. Their luminescence behavior is determined by the combined influence of the phosphane properties, metal-metal interaction, and intermolecular lattice-defined interactions.

Gold(I) Alkynyls Supported by Mono- and Bidentate NHC Ligands: Luminescence and Isolation of Unprecedented Ionic Complexes.

Reactions of NHC·HX (NHC = 1-benzyl-3-methylbenzimidazol-2-ylidene, X = Br, PF) and (AuC≡CR) (R = Ph, CHOH) in the presence of CsCO initially afford compounds of the general formula [(NHC)Au][(RC)Au]X, which can be isolated by crystallization. With increased reaction time, only the expected mononuclear complexes of the type [NHCAuC≡CR] are produced. The crystal structure of [(NHC)Au][(PhC)Au]PF reveals an unprecedented triple-decker array upheld by a remarkably short (2.

Linking Re and Pt Chromophores with Aminopyridines: A Simple Route to Achieve a Complicated Photophysical Behavior.

The bifunctional aminopyridine ligands H N-(CH ) -4-C H N (n=0, L1; 1, L2; 2, L3) have been utilized for the preparation of the rhenium complexes [Re(phen)(CO) (L1-L3)] (1-3; phen=phenanthroline). Complexes 2 and 3 with NH -coordinated L2 and L3, respectively, were coupled with cycloplatinated motifs {Pt(ppy)Cl} and {Pt(dpyb)} (ppy=2-phenylpyridine, dpyb=dipyridylbenzene) to give the bimetallic species [Re(phen)(CO) (μ-L2/L3)Pt(ppy)Cl] (4, 6) and [Re(phen)(CO) (μ-L2/L3)Pt(dpyb)] (5, 7). In solution, complexes 4 and 6 show MLCT {Re}-based emission at 298 K, which changes to the IL(ppy) state at 77 K.

A model electrode of well-defined geometry prepared by direct laser-induced decoration of nanoporous templates with Au-Ag@C nanoparticles.

We present an original type of model electrode system consisting of bimetallic Au-Ag nanoparticles embedded in an amorphous carbon matrix with an extremely well-defined geometry of parallel, straight, cylindrical macropores. The samples are prepared in one step by direct laser deposition of the metal/carbon composite onto the inner walls of a porous 'anodic' alumina matrix serving as a template. The coating is homogeneous from top to bottom of the pores, and the amount of material deposited can be tuned by the duration of the deposition procedure.