Timothy U. Connell

Understanding electrogenerated chemiluminescence efficiency in blue-shifted iridium(III)-complexes: an experimental and theoretical study.

Compared to tris(2-phenylpyridine)iridium(III) ([Ir(ppy)3 ]), iridium(III) complexes containing difluorophenylpyridine (df-ppy) and/or an ancillary triazolylpyridine ligand [3-phenyl-1,2,4-triazol-5-ylpyridinato (ptp) or 1-benzyl-1,2,3-triazol-4-ylpyridine (ptb)] exhibit considerable hypsochromic shifts (ca. 25-60 nm), due to the significant stabilising effect of these ligands on the HOMO energy, whilst having relatively little effect on the LUMO. Despite their lower photoluminescence quantum yields compared with [Ir(ppy)3 ] and [Ir(df-ppy)3 ], the iridium(III) complexes containing triazolylpyridine ligands gave greater electrogenerated chemiluminescence (ECL) intensities (using tri-n-propylamine (TPA) as a co-reactant), which can in part be ascribed to the more energetically favourable reactions of the oxidised complex (M(+) ) with both TPA and its neutral radical oxidation product. The calculated iridium(III) complex LUMO energies were shown to be a good predictor of the corresponding M(+) LUMO energies, and both HOMO and LUMO levels are related to ECL efficiency. The theoretical and experimental data together show that the best strategy for the design of efficient new blue-shifted electrochemiluminophores is to aim to stabilise the HOMO, while only moderately stabilising the LUMO, thereby increasing the energy gap but ensuring favourable thermodynamics and kinetics for the ECL reaction. Of the iridium(III) complexes examined, [Ir(df-ppy)2 (ptb)](+) was most attractive as a blue-emitter for ECL detection, featuring a large hypsochromic shift (λmax =454 and 484 nm), superior co-reactant ECL intensity than the archetypal homoleptic green and blue emitters: [Ir(ppy)3 ] and [Ir(df-ppy)3 ] (by over 16-fold and threefold, respectively), and greater solubility in polar solvents.

Synthesis, Structure and Gas-Phase Reactivity of a Silver Hydride Complex [Ag3{(PPh2)2CH2}3(μ3-H)(μ3-Cl)]BF4†

Coinage metal hydrides continue to attract attention because of their interesting structural and physical properties, as well as for their role as reagents or intermediates in the transformation of organic substrates. For example, several copper hydride compounds have been structurally characterized and developed as catalysts for 1,4 reduction reactions of enones and for hydrocupration of alkynes. In contrast, whereas their heavier congeners have been implicated as reactive intermediates in oxidation and other reactions, and have been characterized in the gas phase, as well as by matrix isolation experiments, few silver and gold hydride compounds have been synthesized and structurally characterized by X-ray crystallography. We have been examining the role of coinage-metal cluster compounds in C C bond coupling reactions, click chemistry, and C X bond activation 8] of organic substrates. In our work, methods based on mass spectrometry (MS) are employed to explore cluster formation and reactivity, and to direct condensed phase synthesis and characterization of novel clusters. As part of this cluster chemistry program, we became interested in extending the method of generating bis(phosphino)-protected gold nanoclusters by sodium borohydride reduction of gold salts to generate related silver nanoclusters. Herein, we report on the serendipitous MSbased discovery of a novel silver hydride cluster, [Ag3HClL3] + (L = bis(phosphino) ligand), which has prompted its massspectrometry-directed synthesis and X-ray and neutron crystallographic structural characterization, which reveal a {Ag3(m3-H)(m3-Cl)} + core structure. 14] The gas-phase reactivity of this cluster is also explored. Electrospray ionization mass spectrometry (ESI-MS) analysis of methanol/chloroform solutions of silver(I) trifluoroacetate [Ag(tfa)] that had been treated with sodium borohydride in the presence of 1,1-bis(diphenylphosphino)methane (designated hereafter as L) showed evidence of the formation of silver hydride cluster cations (Figure 1; see also the Supporting Information, Figure S1), which, based on isotope patterns (Figures S2 and S3) and high resolution accurate mass measurements (Table S1), are formulated as: [Ag3HL3] , [Ag3HClL3] , [Ag3Cl2L3] + and [Ag10H8L6] . The species [Ag3H2L3] + was not observed in any of the spectra recorded. Replacing NaBH4 with sodium borodeuteride confirmed that NaBH4 is the source of the hydride in the clusters (for example, formation of [Ag3DL3] 2+ and not [Ag3HL3] ; Figures S4 and S5). The observation of abundant silver hydride cluster cations by ESI-MS encouraged us to refine the condensed-phase synthetic route (Supporting Information, Method A) to allow the isolation of a crystalline salt suitable for characterization by IR and H NMR spectroscopy (Figures S6 and S7, as well as supporting text), as well as structural determination by single-crystal X-ray diffraction and neutron diffraction. The presence of the abundant trinuclear silver hydride cluster ligated by the trifluoroacetate (tfa) anion, [Ag3H(tfa)L3] +

Synthesis, Structural Characterization, and Gas-Phase Unimolecular Reactivity of the Silver Hydride Nanocluster [Ag3((PPh2)2CH2)3(μ3-H)](BF4)2

A bis(diphenylphosphino)methane-ligated trinuclear silver hydride nanocluster, [Ag3((Ph2P)2CH2)3(μ3-H)](BF4)2, featuring three silver(I) ions coordinated to a μ3-hydride, and its deuteride analogue, [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2, have been isolated and structurally characterized using electrospray ionization mass spectrometry (ESI-MS), X-ray crystallography, NMR and IR spectroscopy. The position of the deuteride in [Ag3((Ph2P)2CH2)3(μ3-D)](BF4)2 was determined by neutron diffraction. ESI-MS of [Ag3L3(μ3-H/D)](BF4)2 [L = ((Ph2P)2CH2)2] produces [Ag3L3(μ3-H/D)](2+) and [Ag3L3(μ3-H/D)(BF4)](+). A rich gas-phase ion chemistry of [Ag3L3(μ3-H/D)](2+) is observed under conditions of collision-induced dissociation (CID) and electron-capture dissociation (ECD). CID gives rise to the following complementary ion pairs: [Ag3L2](+) and [L+(H/D)](+); [Ag2(H/D)L2](+) and [AgL](+); [Ag2(H/D)L](+) and [AgL2](+). ECD gives rise to a number of dissociation channels including loss of the bis(phosphine) ligand, fragmentation of a coordinated bis(phosphine) ligand via C-P bond activation, and loss of a hydrogen (deuterium) atom with concomitant formation of [Ag3L3](+). Under CID conditions, [Ag3L3(μ3-H/D)(BF4)](+) fragments via ligand loss, the combined loss of a ligand and [H,B,F4], and cluster fragmentation to give [Ag2(BF4)L2](+) and [Ag2(L-H)L](+) [where (L-H) = (Ph2P)2CH(-)].

Copper and silver complexes of tris(triazole)amine and tris(benzimidazole)amine ligands: evidence that catalysis of an azide-alkyne cycloaddition ("click") reaction by a silver tris(triazole)amine complex arises from copper impurities.

The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L(1)), that is used as promoter to enhance Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L(1) reveals a dinuclear cation, [Ag2(L(1))2](2+), that is essentially isostructural to the copper(I) analogue. While the [Ag2(L(1))2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L(2)), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the Cu(I) complex [Cu(I)3(L(2))2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction.

A Versatile Approach for the Site‐Specific Modification of Recombinant Antibodies Using a Combination of Enzyme‐Mediated Bioconjugation and Click Chemistry

A unique two-step modular system for site-specific antibody modification and conjugation is reported. The first step of this approach uses enzymatic bioconjugation with the transpeptidase Sortase A for incorporation of strained cyclooctyne functional groups. The second step of this modular approach involves the azide-alkyne cycloaddition click reaction. The versatility of the two-step approach has been exemplified by the selective incorporation of fluorescent dyes and a positron-emitting copper-64 radiotracer for fluorescence and positron-emission tomography imaging of activated platelets, platelet aggregates, and thrombi, respectively. This flexible and versatile approach could be readily adapted to incorporate a large array of tailor-made functional groups using reliable click chemistry whilst preserving the activity of the antibody or other sensitive biological macromolecules.

Rhenium and technetium tricarbonyl complexes of 1,4‐Substituted pyridyl‐1,2,3‐triazole bidentate ‘click’ ligands conjugated to a targeting RGD peptide

New 1,4-substituted pyridyl-1,2,3-triazole ligands with pendent phenyl isothiocyanate functional groups linked to the heterocycle through a short methylene or longer polyethylene glycol spacers were prepared and conjugated to a peptide containing the arginine-glycine-aspartic acid peptide motif. Rhenium and technetium carbonyl complexes, [M(CO)3 L(x) (py)](+) (where M = Re(I) or (99m) Tc(I) ; L(x)  = 1,4-substituted pyridyl-1,2,3-triazole ligands and py = pyridine) were prepared. One rhenium complex has been characterized by X-ray crystallography, and the luminescent properties of [M(CO)3 L(x) (py)](+) are reported.

Analytically useful blue chemiluminescence from a water-soluble iridium(III) complex containing a tetraethylene glycol functionalised triazolylpyridine ligand.

We examine [Ir(df-ppy)2(pt-TEG)](+) as the first highly water soluble, blue-luminescent iridium(III) complex for chemiluminescence detection. Marked differences in selectivity were observed between the new complex and the conventional [Ru(bpy)3](2+) reagent, which will enable this mode of detection to be extended to new areas of application.