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71.
Jenkins DM Senn JF Bernhard S 《Dalton transactions (Cambridge, England : 2003)》2012,41(26):8077-8085
Presented is the synthesis of an array of 16 heteroleptic phosphorescent diimine complexes of platinum(II) with electronically diverse ligand spheres and their full spectroscopic, photophysical, and electrochemical characterization. The complexes were found to exhibit luminescence (480-500 nm) in deaerated solutions at room temperature from a long-lived (3)LC state (τ = 2-3 μs) that exhibits significant metal character perturbed by a low-lying (1)MLCT state. Interestingly, emission from a (3)MLCT state was not observed as is the case with many other polypyridine-based d-block complexes. Electrochemical intermediates proved stable as multiple reversible reductions between -1 and -2 V vs. SCE were noted during cyclic voltammetry experiments unveiling the potential of these luminophores for use in a variety of optoelectronic and solar energy conversion applications. 相似文献
72.
The synthesis of squaric acid N-hydroxylamide esters 5 and amides 6 from dimethyl squarate 2a is described. These derivatives are analogues of the naturally occurring iron(III) chelator hydroxamic acid. On the basis of a comparative reactivity study, a concerted retro-Cope mechanism for the formation of the N-hydroxylamide esters 5 by reaction of dimethyl squarate with hydroxylamines is proposed. A preliminary iron(III) binding study of these hydroxamic acid analogues is presented, demonstrating binding of iron(III) to amides 6 in aqueous solutions, while the esters 5 did not show any sign of metal ion binding. 13C NMR spectroscopic data (chemical shift and spin-lattice relaxation time determination) of these and related derivatives delineate the resonance structures predominant in these molecules. The resonance structures of the derivatives rationalize their spectroscopic data, chemical reactivity, and iron(III) binding properties. Single-crystal X-ray structure analyses of squaric acid N-hydroxylamide ester 5b and squaric acid N-hydroxylamide amide 6c confirm their connectivity and provide structural evidence supporting the spectroscopically derived conclusions. The squaric acid N-hydroxylamides are potentially useful in the construction of chemosensors for iron(III). 相似文献
73.
Vidjayacoumar B Ilango S Ray MJ Chu T Kolpin KB Andreychuk NR Cruz CA Emslie DJ Jenkins HA Britten JF 《Dalton transactions (Cambridge, England : 2003)》2012,41(26):8175-8189
A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H(2)[TXA(2)], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using (n)BuLi provided Li(2)(DME)(2)[TXA(2)] (2), and subsequent reaction with UCl(4) afforded [Li(DME)(3)][(TXA(2))UCl(3)] (4). The analogous NON-donor ligated complex [(XA(2))UCl(3)K(DME)(3)] [3; XA(2) = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K(2)(DME)(x)[XA(2)] with UCl(4). A cyclic voltammogram (CV) of 3 in THF/[NBu(4)][B(C(6)F(5))(4)] at 200 mV s(-1) showed an irreversible reduction to uranium(III) at E(pc) = -2.46 V versus FeCp(2)(0/+1), followed by a product wave at E(1/2) = -1.83 V. Complex 4 also underwent irreversible reduction to uranium(iii) [E(pc) = -2.56 V], resulting in an irreversible product peak at E(pa) = -1.83 V. One-electron reduction of complexes 3 and 4 using K(naphthalenide) under an argon atmosphere in DME yielded 6-coordinate [(XA(2))UCl(DME)] (5) and the thermally unstable 7-coordinate [(TXA(2))U(DME)Cl(2)Li(DME)(2)] (6), respectively. The U-S distances in 4 and 6 are uncommonly short, the C-S-U angles are unusually acute, and the thioxanthene backbone of the TXA(2) ligand is significantly bent. By contrast, the xanthene backbone in XA(2) complexes 3 and 5 is planar. However, κ(3)-coordination and an approximately meridional arrangement of the ancillary ligand donor atoms is maintained in all complexes. DFT and Atoms in Molecules (AIM) calculations were carried out on 3, 4, 5, 6, [(XA(2))UCl(3)](-) (3B), [(TXA(2))UCl(2)(DME)](-) (6B) and [(TXA(2))UCl(DME)] (6C) to probe the extent of covalency in U-SAr(2) bonding relative to U-OAr(2) bonding. 相似文献
74.
W. Ken Busfield Ian D. Jenkins Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》1997,35(2):263-270
The radical trapping technique employing 1,1,3,3-tetramethyl-1,3-dihydro-1H-isoindol-2-yloxyl as a scavenger has been used to investigate the reaction of t-butoxyl radicals with mixtures of ethyl vinyl ether and methyl methacrylate. The range of identified products includes those from both addition and hydrogen abstraction with both monomers, head addition with ethyl vinyl ether, and some second monomer addition products. Relative rate constants have been obtained for various pairs of constituent reactions. t-Butoxyl radicals add to ethyl vinyl ether one to two times faster than to methyl methacrylate, depending on which monomer is in excess. The ratio is less than 1 in nonolefinic solvents and as high as 6 in t-butanol. This solvent effect is thought to be due to the radicals complexing to either methyl methacrylate or t-butanol (H-bonding), thereby increasing its electrophilic character. © 1997 John Wiley & Sons, Inc. 相似文献
75.
Experimental Techniques - 相似文献
76.
77.
S.J. Jenkins 《Surface science》2010,604(19-20):1688-1693
The surfaces of hcp crystals can show a variety of structural features and classes of symmetry that differ markedly from those of simpler fcc or bcc crystals. The hcp-{213?1} surface, for example, can occur in four distinct stereomorphs, interconverted by a combination of mirror operations (linking degenerate enantiomorphically related surfaces) and/or the removal of the outermost atomic layer (linking non-degenerate diamorphically related surfaces). The strict pattern of degeneracy amongst these stereomorphs is analogous to that found for molecules with two chiral centres, and hence it is possible to view this system as doubly-chiral. Simple nearest-neighbour bond-counting arguments, however, suggest that for {213?1} even the diamorphically related cases should be near-degenerate, despite the fact that they differ in having either a notably short or notably long interlayer spacing between the outermost layers (ideal spacing ratio 1:5). In the present work, this counterintuitive result is confirmed at the level of density functional theory, both for the ideal and relaxed {213?1} surfaces of Co, Ru and Re. 相似文献
78.
Groups of structurally related materials, including the alkali halides, exhibit a proportionality of isothermal compressibility to formula-unit volume. The relationship has recently been explored by Glasser and by Recio et al. In this paper, we present the consequences of such proportionality on the relationships of Born-Lande? and Born-Mayer parameters to the formula-unit volume. These relationships have then been tested separately on (i) alkali (excluding cesium) halides and (ii) cesium halides. We conclude that the equations fit the NaCl-type materials satisfactorily, but less well for the CsCl-type materials, and that the Born-Mayer equation is more applicable. These results confirm the conclusion that volume is intimately linked to thermodynamic quantities, as already demonstrated by our development of volume-based thermodynamics (VBT). 相似文献
79.
Presented is the synthesis and characterization of a series of luminescent heteroleptic bis-cyclometalated platinum(IV) complexes. An oxidation-facilitated cyclometalation is employed to convert platinum(II) pendant species into bis-cyclometalated platinum(IV) dichlorides, which are transformed into the tris-chelated diimine complexes through ligand substitution. The structure-property relationship is probed by judiciously varying substituents on both the C(∧)N and the N(∧)N ligands resulting in a family of complexes exhibiting blue emission, long excited-state lifetimes, and highly efficient oxygen quenching. Excited-state properties are corroborated by static and time-dependent density-functional theory calculations of both the singlet and the triplet state. 相似文献
80.
Philip J. Burke William Clegg Terence C. Jenkins Ian T. Meikle 《Tetrahedron letters》2010,51(30):3918-7450
Treatment of the N-nitroaryl-3-hydroxypiperidine derivatives 12 and 13 with thionyl chloride afforded the corresponding N-aryl-2-chloromethylpyrrolidines 5 and 15 via a ring-contraction process involving an intermediate aziridinium ion. 相似文献