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2. A noble nexus: a phosphino-phen ligand for tethering precious metals.

Author

Newman, Paul D., Platts, James A., Alrashidi, Basheer, Pope, Simon J. A., and Kariuki, Benson M.

Subjects
PRECIOUS metals, GOLD compounds, LIGANDS (Chemistry), IRIDIUM, RHENIUM
Abstract

Controlled formation of mixed-metal bimetallics was achieved via two derivatised 1,10-phenanthroline ligands bearing an imino- or amino-phosphine appendage at the 5-position. Selective coordination of the phen group to the [Re(CO)3Cl] core was achieved enabling precise construction of bimetallic complexes with a second rhenium centre or with gold. The mixed Ru/Au complex was similarly obtained with the imino-phosphine but access to the heterobimetallic iridium systems required prior formation of the P-bound gold complexes subsequent to the introduction of the [Ir(Ppy)2]+ fragment. The Re/Pd, Re/Pt, Ir/Pd and Ir/Pt compounds were prepared from the combination of κ-N′′,P-Pd(Pt)Cl2 and the appropriate rhenium or iridium precursors. Spectroscopic and theoretical analyses have been employed to investigate the structural and electronic impact of the second metal. [ABSTRACT FROM AUTHOR]

Published
2024
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7. 2-(Thienyl)quinoxaline derivatives and their application in Ir(III) complexes yielding tuneable deep red emitters.

Author

Fitzgerald, Sophie A., Payce, Ellie N., Horton, Peter N., Coles, Simon J., and Pope, Simon J. A.

Subjects
QUINOXALINES, MOLECULAR structure, SINGLE crystals, X-ray diffraction, THIOPHENES
Abstract

The synthesis and characterisation of eleven different 2-(thienyl)quinoxaline species that incorporate different points of functionality, including at the thiophene or quinoxaline rings, are described. These species display variable fluorescence properties in the visible region (λem = 401–491 nm) depending upon the molecular structures and extent of conjugation. The series of 2-(thienyl)quinoxaline species were then investigated as cyclometalating agents for Ir(III) to yield [Ir(C^N)2(bipy)]PF6 (where C^N = the cyclometalated ligand; bipy = 2,2′-bipyridine). Eight complexes were successfully isolated and fully characterised by an array of spectroscopic and analytical techniques. Two Ir(III) examples were structurally characterised in the solid state using single crystal X-ray diffraction; both structures confirmed the proposed formulations and coordination spheres in each case showing that the thiophene coordinates via a Ir–C bond. The photophysical properties of the complexes revealed that each complex is luminescent under ambient conditions with a range of emission wavelengths observed (665–751 nm) indicating that electronic tuning can be achieved via both the thienyl and quinoxaline moieties. [ABSTRACT FROM AUTHOR]

Published
2023
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13. Organometallic Platinum(II) Photosensitisers that Demonstrate Ligand‐Modulated Triplet‐Triplet Annihilation Energy Upconversion Efficiencies.

Author

Fitzgerald, Sophie A., Xiao, Xiao, Zhao, Jianzhang, Horton, Peter N., Coles, Simon J., Knighton, Richard C., Ward, Benjamin D., and Pope, Simon J. A.

Subjects
ENERGY consumption, PLATINUM, REACTIVE oxygen species, QUANTUM efficiency, PHOTON upconversion
Abstract

A series of 2‐phenylquinoxaline ligands have been synthesised that introduce either CF3 or OCF3 electron‐withdrawing groups at different positions of the phenyl ring. These ligands were investigated as cyclometalating reagents for platinum(II) to give neutral complexes of the form [Pt(C^N)(acac)] (in which C^N=cyclometalating ligand; acac=acetyl acetonate). X‐ray crystallographic studies on three examples showed that the complexes adopt an approximate square planar geometry. All examples revealed strong Pt−Pt linear contacts of 3.2041(6), 3.2199(3) and 3.2586(2) Å. The highly coloured complexes display efficient visible absorption at 400–500 nm (ϵ ≈5000 M−1 cm−1) and orange red photoluminescent characteristics (λem=603–620 nm; Φem ≤37 %), which were subtly tuned by the ligand. Triplet emitting character was confirmed by microsecond luminescence lifetimes and the photogeneration of singlet oxygen with quantum efficiencies up to 57 %. Each complex was investigated as a photosensitiser for triplet–triplet annihilation energy upconversion using 9,10‐diphenylanthracene as the annihilator species: a range of good upconversion efficiencies (ΦUC 5.9–14.1 %) were observed and shown to be strongly influenced by the ligand structure in each case. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Interplay of light antenna and excitation 'energy reservoir' effects in a bichromophoric system based on ruthenium-polypyridine and pyrene units linked by a long and flexible poly(ethylene glycol) chain

Author

Morales, Angeles Farran, Accorsi, Gianluca, Armaroli, Nicola, Barigelletti, Francesco, Pope, Simon J. A., and Ward, Michael D.

Subjects
Chemistry, Inorganic -- Research, Excited state chemistry -- Research, Ruthenium, Polymers -- Composition, Pyridine, Ethylene glycol, Acetonitrile, Solvents, Chemistry
Abstract

Research has been conducted on bichromophoric species containing ruthenium-polypyridine and pyrene units. The time-resolved and steady-state spectroscopic properties of these compounds linked by flexible poly(ethylene glycol) chains have been studied in acetonitrile solvent, and the details are reported.

Published
2002

29. Towards dual SPECT/optical bioimaging with a mitochondrial targeting, 99mTc(i) radiolabelled 1,8-naphthalimide conjugate

Author

Day, Adam H., primary, Domarkas, Juozas, additional, Nigam, Shubhanchi, additional, Renard, Isaline, additional, Cawthorne, Christopher, additional, Burke, Benjamin P., additional, Bahra, Gurmit S., additional, Oyston, Petra C. F., additional, Fallis, Ian A., additional, Archibald, Stephen J., additional, and Pope, Simon J. A., additional

Published
2020
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31. Targeted cell imaging properties of a deep red luminescent iridium(iii) complex conjugated with a c-Myc signal peptide

Author

Day, Adam H., primary, Übler, Martin H., additional, Best, Hannah L., additional, Lloyd-Evans, Emyr, additional, Mart, Robert J., additional, Fallis, Ian A., additional, Allemann, Rudolf K., additional, Al-Wattar, Eman A. H., additional, Keymer, Nathaniel I., additional, Buurma, Niklaas J., additional, and Pope, Simon J. A., additional

Published
2020
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32. Fluorescent functionalised naphthalimides and their Au(I)–NHC complexes for potential use in cellular bioimaging

Author

Groves, Lara M., Williams, Catrin F., Hayes, Anthony J., Ward, Benjamin D., Isaacs, Marc D., Symonds, Nadine O., Lloyd, David, Horton, Peter N., Coles, Simon J., and Pope, Simon J. A.

Abstract

A series of cationic, dihydroimidazolinium-functionalized 1,8-naphthalimide fluorophores have been isolated as their hexafluorophosphate salts, [HL]PF6. These pro-ligands react with [AuCl(tht)] in the presence of base to form N-heterocyclic carbene (NHC) complexes, [AuCl(L)]. Two X-ray structures represent a pro-ligand and complex pairing: the latter reveals the two-coordinate linear geometry of the NHC–Au(I) species, as well as intermolecular interactions supported by both ligand π–π stacking and a weak aurophilic interaction of 3.3205(6) Å. The luminescence properties of the pro-ligands and complexes are dominated by the ICT character of the substituted fluorophore at ca. 500 nm, which is further modulated via functionalization at the 4-position of the naphthalimide. Cytotoxicity assessments were performed for all [HL]PF6 and [AuCl(L)] species against LOVO, MCF-7, A549 and PC3 cell lines; added lipophilicity seems to correlate with increased cytotoxicity. Confocal fluorescence microscopy was undertaken on a selected [HL]PF6 and [AuCl(L)] species and showed that the intracellular distribution is dependent upon the specific ligand structure. More detailed co-localisation studies show that selected examples present a predominant lysosomal staining pattern. FLIM studies exemplified the applicability of these probes, and secondly suggest that fluorescence lifetime could be used to provide information on the integrity of the complex and thus liberation of gold in a biological environment.

Published
2018

33. Synthesis and characterisation of phosphorescent rhenium(I) complexes of hydroxy- and methoxy-substituted imidazo[4,5- f ]-1,10-phenanthroline ligands

Author

Bonello, R. Owen, Pitak, Mateusz B., Coles, Simon J., Hallett, Andrew J., Fallis, Ian Andrew, and Pope, Simon J. A.

Abstract

Eight new fluorescent ligands (L1-L8) derived from the fused imidazo[4,5-f]-1,10-phenanthroline core, have been synthesised utilising a one-pot methodology. The ligands include two points of structural variety, allowing multiply-substituted aryl groups (including hydroxy and methoxy moieties) to be attached to the ligand core. The ligands L1-L8 are fluorescent (λem = 399–426 nm) and react with pentacarbonylbromorhenium to give coordination complexes of the form fac-[ReBr(CO)3(NˆN)] (where NˆN = L1-L8). The complexes were characterised using a variety of spectroscopic and analytical techniques, including single crystal X-ray diffraction studies on two examples. The rhenium complexes were all found to be luminescent, revealing classical 3MLCT emission at 579–587 nm in aerated solution with corresponding lifetimes in the range 149–166 ns.

Published
2017

34. Closely-Related ZnII2LnIII2 Complexes (LnIII = Gd, Yb) with Either Magnetic Refrigerant or Luminescent Single-Molecule Magnet Properties

Author

Ruiz, José, Lorusso, Giulia, Evangelisti, Marco, Herrera, Juan Manuel, Brechin, Euan K., Pope, Simon J. A., Colacio, Enrique, European Commission, Ministerio de Economía y Competitividad (España), Junta de Andalucía, Universidad de Granada, Engineering and Physical Sciences Research Council (UK), and Cardiff University

Subjects
Ligand field theory, Denticity, ION MAGNETS, Inorganic chemistry, 010402 general chemistry, 01 natural sciences, Inorganic Chemistry, Magnetization, chemistry.chemical_compound, METAL-ORGANIC FRAMEWORK, LANTHANIDE COMPLEXES, Molecule, Single-molecule magnet, FIELD, Physical and Theoretical Chemistry, ANISOTROPY, BRIDGING LIGANDS, SCHIFF-BASE LIGANDS, 010405 organic chemistry, Chemistry, Ligand, SMM BEHAVIOR, 3. Good health, 0104 chemical sciences, YTTERBIUM, Crystallography, Diethylenetriamine, EMISSION, Luminescence
Abstract

The reaction of the compartmental ligand N,N′,N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L) with Zn(NO3)2·6H2O and subsequently with Ln(NO3)3·5H2O (LnIII = Gd and Yb) and triethylamine in MeOH using a 1:1:1:1 molar ratio leads to the formation of the tetranuclear complexes {(μ3-CO3)2[Zn(μ-L)Gd(NO3)]2}·4CH3OH (1) and{(μ3-CO3)2[Zn(μ-L)Yb(H2O)]2}(NO3)2·4CH3OH (2). When the reaction was performed in the absence of triethylamine, the dinuclear compound [Zn(μ-L)(μ-NO3)Yb(NO3)2] (3) is obtained. The structures of 1 and 2 consist of two diphenoxo-bridged ZnII–LnIII units connected by two carbonate bridging ligands. Within the dinuclear units, ZnII and LnIII ions occupy the N3O2 inner and the O4 outer sites of the compartmental ligand, respectively. The remaining positions on the LnIII ions are occupied by oxygen atoms belonging to the carbonate bridging groups, by a bidentate nitrate ion in 1, and by a coordinated water molecule in 2, leading to rather asymmetric GdO9 and trigonal dodecahedron YbO8 coordination spheres, respectively. Complex 3 is made of acetate–diphenoxo triply bridged ZnIIYbIII dinuclear units, where the YbIII exhibits a YbO9 coordination environment. Variable-temperature magnetization measurements and heat capacity data demonstrate that 1 has a significant magneto–caloric effect, with a maximum value of −ΔSm = 18.5 J kg–1 K–1 at T = 1.9 K and B = 7 T. Complexes 2 and 3 show slow relaxation of the magnetization and single-molecule magnet (SMM) behavior under an applied direct-current field of 1000 Oe. The fit of the high-temperature data to the Arrhenius equation affords an effective energy barrier for the reversal of the magnetization of 19.4(7) K with τo = 3.1 × 10–6 s and 27.0(9) K with τo = 8.8 × 10–7 s for 2 and 3, respectively. However, the fit of the full range of temperature data indicates that the relaxation process could take place through a Raman-like process rather than through an activated Orbach process. The chromophoric L2– ligand is able to act as an “antenna” group, sensitizing the near-infrared (NIR) YbIII-based luminescence in complexes 2 and 3 through an intramolecular energy transfer to the excited states of the accepting YbIII ion. These complexes show several bands in the 945–1050 nm region, corresponding to 2F5/2→2F7/2 transitions arising from the ligand field splitting of both multiplets. The observed luminescence lifetimes τobs are 0.515 and 10 μs for 2 and 3, respectively. The shorter lifetime for 2 is due to the presence of one coordinated water molecule on the YbIII center (and to a lesser extent noncoordinated water molecules), facilitating vibrational quenching via O–H oscillators. Therefore, complexes 2 and 3, combining field-induced SMM behavior., Financial support from Ministerio de Economíay Competitividad (MINECO) for Projects CTQ-2011-24478 and MAT2012-38318-C03-01, the Junta de Andalucía (FQM-195 and the Project of Excellence P11-FQM-7756), and the University of Granada is acknowledged. E.K.B. thanks the EPSRC for funding. S.J.A.P. thanks Cardiff University and the EPSRC. G.L. acknowledges EU for a Marie Curie IEF (PIEFGA- 2011-299356).

Published
2014
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36. Ligand-Tuneable, Red-Emitting Iridium(III) Complexes for Efficient Triplet-Triplet Annihilation Upconversion Performance

Author

Phillips, Kaitlin A., primary, Stonelake, Thomas M., additional, Chen, Kepeng, additional, Hou, Yuqi, additional, Zhao, Jianzhang, additional, Coles, Simon J., additional, Horton, Peter N., additional, Keane, Shannon J., additional, Stokes, Emily C., additional, Fallis, Ian A., additional, Hallett, Andrew J., additional, O'Kell, Sean P., additional, Beames, Joseph M., additional, and Pope, Simon J. A., additional

Published
2018
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37. Cover Feature: Ligand-Tuneable, Red-Emitting Iridium(III) Complexes for Efficient Triplet-Triplet Annihilation Upconversion Performance (Chem. Eur. J. 34/2018)

Author

Phillips, Kaitlin A., primary, Stonelake, Thomas M., additional, Chen, Kepeng, additional, Hou, Yuqi, additional, Zhao, Jianzhang, additional, Coles, Simon J., additional, Horton, Peter N., additional, Keane, Shannon J., additional, Stokes, Emily C., additional, Fallis, Ian A., additional, Hallett, Andrew J., additional, O'Kell, Sean P., additional, Beames, Joseph M., additional, and Pope, Simon J. A., additional

Published
2018
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38. Scandium complexes bearing bis(oxazolinylphenyl)amide ligands: an analysis of their reactivity, solution-state structures and photophysical properties

Author

Bennett, Stacey D., Pope, Simon J. A., Jenkins, Robert Leyshon, and Ward, Benjamin D.

Subjects
QD
Abstract

The coordination chemistry of scandium supported by bis(oxazolinylphenyl)amide (R-BOPA) ligands is reported. The R-BOPA ligand is too sterically demanding to afford bis(amide) complexes [Sc(R-BOPA){N(SiMe3)2}2], but reaction of the protio-ligand with [Sc{N(SiMe3)2}2Cl(THF)] (1) afforded the mixed amido-chloride complexes [Sc(R-BOPA){N(SiMe3)2}Cl] (2). The selective reaction of the amido and chloride co-ligands in 2 has been investigated; whilst the chloride ligand can be removed cleanly by metathesis, protonation of the N(SiMe3)2 ligand results in competitive protonation of the R-BOPA ligand. The complexes [Sc(R-BOPA)(CH2SiMe2Ph)2] (5) have been synthesised. Each R-BOPA-containing complex exists in two isomeric forms. The equilibrium has been investigated both experimentally and computationally, and the data suggest that a concerted rotation of the phenyl rings interconverts the two diastereomeric isomers. All of the R-BOPA complexes were found to be luminescent; an analysis of the photophysics, aided by TD-DFT calculations, suggests ligand-centred luminescence with distinct emission lifetimes for each isomer.

Published
2016

41. A Twisted Bay‐Substituted Quaterrylene Phosphorescing in the NIR Spectral Region

Author

Miletić, Tanja, primary, Fermi, Andrea, additional, Papadakis, Ioannis, additional, Orfanos, Ioannis, additional, Karampitsos, Nikolaos, additional, Avramopoulos, Aggelos, additional, Demitri, Nicola, additional, De Leo, Federica, additional, Pope, Simon J. A., additional, Papadopoulos, Manthos G., additional, Couris, Stelios, additional, and Bonifazi, Davide, additional

Published
2017
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47. Diimine-acetylide compounds of ruthenium: the structure and spectroscopic effects of oxidation

Author

Adams, Christopher J. and Pope, Simon J. A.

Subjects
Ruthenium -- Composition, Ruthenium -- Atomic properties, Chemical structure -- Analysis, Oxidation-reduction reaction -- Analysis, Chemistry
Abstract

The first series of ruthenium compounds containing both acetylide and bipridyl ligands are prepared. The ruthenium(II)- acetylide compounds are readily oxidized to ruthenium-(III), changing color as a MLCT transition is replaced by a LMCT transition.

Published
2004

48. Towards dual SPECT/optical bioimaging with a mitochondrial targeting, 99mTc(I) radiolabelled 1,8-naphthalimide conjugate.

Author

Day, Adam H., Domarkas, Juozas, Nigam, Shubhanchi, Renard, Isaline, Cawthorne, Christopher, Burke, Benjamin P., Bahra, Gurmit S., Oyston, Petra C. F., Fallis, Ian A., Archibald, Stephen J., and Pope, Simon J. A.

Subjects
CARDIOGRAPHIC tomography, BIO-imaging sensors, INTRAMOLECULAR charge transfer, CONFOCAL fluorescence microscopy, SINGLE-photon emission computed tomography, RADIONUCLIDE imaging
Abstract

A series of six different 1,8-naphthalimide conjugated dipicolylamine ligands (L1–6) have been synthesised and characterised. The ligands possess a range of different linker units between the napthalimide fluorophore and dipcolylamine chelator which allow the overall lipophilicity to be tuned. A corresponding series of Re(I) complexes have been synthesised of the form fac-[Re(CO)3(L1–6)]BF4. The absorption and luminescence properties of the ligands and Re(I) complexes were dominated by the intramolecular charge transfer character of the substituted fluorophore (typically absorption ca. 425 nm and emission ca. 520 nm). Photophysical assessments show that some of the variants are moderately bright. Radiolabelling experiments using a water soluble ligand variant (L5) were successfully undertaken and optimised with fac-[99mTc(CO)3(H2O)3]+. Confocal fluorescence microscopy showed that fac-[Re(CO)3(L5)]+ localises in the mitochondria of MCF-7 cells. SPECT/CT imaging experiments on naïve mice showed that fac-[99mTc(CO)3(L5)]+ has a relatively high stability in vivo but did not show any cardiac uptake, demonstrating rapid clearance, predominantly via the biliary system along with a moderate amount cleared renally. [ABSTRACT FROM AUTHOR]

Published
2020
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49. Chapter Two - Functional imaging of a model unicell: Spironucleus vortens as an anaerobic but aerotolerant flagellated protist.

Author

Lloyd, David, Millet, Coralie O., Williams, Catrin F., Hayes, Anthony J., Pope, Simon J. A., Pope, Iestyn, Borri, Paola, Langbein, Wolfgang, Olsen, Lars Folk, Isaacs, Marc D., and Lunding, Anita

Abstract

Advances in optical microscopy are continually narrowing the chasm in our appreciation of biological organization between the molecular and cellular levels, but many practical problems are still limiting. Observation is always limited by the rapid dynamics of ultrastructural modifications of intracellular components, and often by cell motility: imaging of the unicellular protist parasite of ornamental fish, Spironucleus vortens, has proved challenging. Autofluorescence of nicotinamide nucleotides and flavins in the 400-580 nm region of the visible spectrum, is the most useful indicator of cellular redox state and hence vitality. Fluorophores emitting in the red or near-infrared (i.e., phosphors) are less damaging and more penetrative than many routinely employed fluors. Mountants containing free radical scavengers minimize fluorophore photobleaching. Two-photon excitation provides a small focal spot, increased penetration, minimizes photon scattering and enables extended observations. Use of quantum dots clarifies the competition between endosomal uptake and exosomal extrusion. Rapid motility (161 μm/s) of the organism makes high resolution of ultrastructure difficult even at high scan speeds. Use of voltage-sensitive dyes determining transmembrane potentials of plasma membrane and hydrogenosomes (modified mitochondria) is also hindered by intracellular motion and controlled anesthesia perturbs membrane organization. Specificity of luminophore binding is always questionable; e.g. cationic lipophilic species widely used to measure membrane potentials also enter membrane-bounded neutral lipid droplet-filled organelles. This appears to be the case in S. vortens, where Coherent Anti-Stokes Raman Scattering (CARS) micro-spectroscopy unequivocally images the latter and simultaneous provides spectral identification at 2840 cm-1. Secondary Harmonic Generation highlights the highly ordered structure of the flagella. [ABSTRACT FROM AUTHOR]

Published
2020
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