ORCID Profile
0000-0001-7491-9034
Current Organisation
University of Leeds
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Publisher: American Chemical Society (ACS)
Date: 06-06-2023
Publisher: Wiley
Date: 05-12-2011
Publisher: International Union of Crystallography (IUCr)
Date: 20-03-2004
Publisher: Wiley
Date: 16-05-2007
Publisher: Informa UK Limited
Date: 07-10-2012
Publisher: Wiley
Date: 17-04-2009
Abstract: Two bowl-shaped cavities, each having three OH(-) hydrogen-bond donors at its base, are present in double-cone-shaped metallacrown anion host [Co(6)(mu-OH)(6)(mu-L)(6)](m+) (1(m+) HL=3{5}-(pyrid-2-yl)-5{3}-(tert-butyl)pyrazole). Depending on its affinity for the anions present, it can be isolated in its Co(III) (3)Co(II) (3) (m=3 e.g., 1(ClO(4))(3)) and Co(III) (2)Co(II) (4) (m=2 e.g., 1(BF(4))(2)n H(2)O) oxidation states. See picture for photographs of isolated salts.Reaction of cobalt(II) salts with one equivalent of 3{5}-(pyrid-2-yl)-5{3}-(tert-butyl)pyrazole (HL) and NaOH in EtOH affords salts of [Co(6)(mu-OH)(6)(mu-L)(6)](m+) (2(m+), m=2 or 3). This is formed from alternating tetrahedral and octahedral cobalt centers, giving a double-cone-shaped molecule with two bowl-shaped cavities. Each cavity has three OH(-) hydrogen-bond donors at its base, giving them an affinity for inorganic anions. Reactions with CoX(2) (X(-)=ClO(4) (-) or CF(3)SO(3) (-)) afford products with the stoichiometry 2X(3). In contrast, when salts of fluorinated anions are used, the products have the formulae 2Y(2)n H(2)O (Y(-)=BF(4) (-), PF(6) (-), or SbF(6) (-) n approximately 2). The connectivity and topology of the metallacrown were confirmed by crystal structures of three of these salts. Magnetic measurements imply that the tricationic products have the oxidation state Co(III) (3)Co(II) (3), while the dications are formulated as Co(III) (2)Co(II) (4). Solutions of 2X(3) contain purely 2(3+) according to NMR spectroscopy, ES mass spectrometry, and UV/Vis/NIR spectroscopy, but solutions of 2Y(2)n H(2)O contain more than one significant component. The 2(3+)/2(2+) couple in MeCN is irreversible at room temperature by cyclic voltammetry, occurring near -1.1 V versus ferrocene/ferrocenium. Importantly, the 2Y(2)n H(2)O compounds do not exhibit this process in the presence of 0.1 M [NBu(4)][BPh(4)] as base electrolyte, but they do show it when the appropriate [NBu(4)]Y salt is used (where the Y(-) ions are present in 10(3)-fold excess). Conversely, the 2X(3) complexes exhibit a strong 2(3+)/2(2+) reduction under both experimental conditions. Hence, the isolation of 2(3+) or 2(2+) in the presence of different anions appears to be controlled by the affinity of those anions for the metallacrown.
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B700987A
Publisher: American Chemical Society (ACS)
Date: 23-09-2010
DOI: 10.1021/IC101211N
Abstract: Tris-allyl-cyclotriguaiacylene combines with silver salts to give a range of crystalline network structures and one discrete complex. A number of different coordination modes are found within the complexes including η(2)-allyl, aryl, and OR groups binding to Ag(I). AgSbF(6) gives two types of three-dimensional (3-D) coordination polymer with unusual topologies, along with a discrete Ag(2)L(2) capsule dependent on reaction stoichiometry and reaction conditions. Isostructural coordination chain structures are found with AgBF(4) and AgClO(4), while use of Ag(CF(3)SO(3)) gives two-dimensional (2-D) and 3-D coordination polymers through bridging triflate anions.
Publisher: Springer Science and Business Media LLC
Date: 18-02-2010
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC38768B
Abstract: A new bis(disulfide)-linked offset dimer is formed from a dithiolated analogue of cyclotriguaiacylene. Unlike a similar tris(disulfide)-linked ex le, this is not a true cryptophane as the offset nature of the dimerisation and intramolecular host-guest interactions preclude its use as a host.
Publisher: Royal Society of Chemistry (RSC)
Date: 2006
DOI: 10.1039/B609424D
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5SC02776D
Abstract: The redox series [1]0/1+/2+/3+ has been characterised by UV/vis/NIR spectroelectrochemistry, cw EPR, ENDOR and HYSCORE spectroscopies and DF calculations.
Publisher: Wiley
Date: 03-2016
Publisher: Wiley
Date: 02-02-2014
Abstract: Three diplatinum(II) complexes [{PtL} 2 (μ‐thea)] (H 4 thea=2,3,6,7‐tetrahydroxy‐9,10‐dimethyl‐9,10‐dihydro‐9,10‐ethanoanthracene) have been prepared, with diphosphine or bipyridyl “L” co‐ligands. One‐electron oxidation of these complexes gave radical cations containing a mixed‐valent [thea ] 3− ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin–Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal‐structure determinations and a DFT calculation imply that oxidation of the thea 4− ligand may lead to an increased through‐space interaction between the dioxolene π systems.
Publisher: American Chemical Society (ACS)
Date: 10-11-2010
DOI: 10.1021/IC1020093
Abstract: The reaction of CuX(2) (X(-) ≠ F(-)) salts with 1 equiv of 3-pyridyl-5-tert-butylpyrazole (HL) in basic methanol yields blue solids, from which disk complexes of the type [Cu(7)(μ(3)-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) and/or the cubane [Cu(4)(μ(3)-OH)(4)(HL)(4)](4+) can be isolated by recrystallization under the appropriate conditions. Two of the disk complexes have been prepared in crystalline form: [Cu(7)(μ(3)-OH)(4)(μ-OCH(2)CF(3))(2)(μ-L)(6)][BF(4)](2) (2) and [Cu(7)(μ(3)-OH)(4)(μ-OCH(3))(2)(μ-L)(6)]Cl(2)·xCH(2)Cl(2) (3·xCH(2)Cl(2)). The molecular structures of both compounds as solvated crystals can be described as [Cu⊂Cu(6)(μ-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) (R = CH(2)CF(3) or CH(3)) adducts. The [Cu(6)(μ-OH)(4)(μ-OR)(2)(μ-L)(6)] ring is constructed of six square-pyramidal Cu ions, linked by 1,2-pyrazolido bridges from the L(-) ligands and by basal, apical-bridging hydroxy or alkoxy groups, while the central Cu ion is bound to the four metallamacrocyclic hydroxy donors in a near-regular square-planar geometry. The L(-) ligands project above and below the metal ion core, forming two bowl-shaped cavities that are fully (R = CH(2)CF(3)) or partially (R = CH(3)) occupied by the alkoxy R substituents. Variable-temperature magnetic susceptibility measurements on 2 demonstrated antiferromagnetic interactions between the Cu ions, yielding a spin-frustrated S = (1)/(2) magnetic ground state that is fully populated below around 15 K. Electrospray ionization mass spectrometry, UV/vis/near-IR, and electron paramagnetic resonance measurements imply that the heptacopper(II) disk motif is robust in organic solvents.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4TC02923B
Abstract: Cobalt complexes of alkylated N 3 -Schiff bases show mesomorphic and spin-crossover behaviours, and high S e values.
Publisher: Elsevier BV
Date: 04-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B618780C
Abstract: Treatment of CuF(2) with 2 equiv of 3{5}-[pyrid-2-yl]pyrazole (Hpz(Py)), 3{5}-phenylpyrazole (Hpz(Ph)) or 3{5}-[4-fluorophenyl]pyrazole (Hpz(PhF)) in MeOH, followed by evaporation to dryness and recrystallisation of the solid residues, allows solvated crystals of [{Cu(micro-pz(Py))(pz(Py))}(2)] (1), [{Cu(micro-pz(Ph))(2)}(4)] (2) and [Cu(4)F(2)(micro(4)-F)(micro-pz(PhF))(5)(Hpz(PhF))(4)] (3) to be isolated in moderate-to-good yields. Similar reactions of these three pyrazoles with Cu(OH)(2) in refluxing MeOH respectively afford 1, 2 and [Cu(pz(PhF))(2)(Hpz(PhF))(2)] (4) in ca. 10% yield. Crystalline 1 x 1/2H(2)O x 2CHCl(3) contains two independent dinuclear molecules with a puckered di-(1,2-pyrazolido) bridge motif, linked by a bridging, hydrogen-bonding water molecule. Compound 2 x 1/2C(5)H(12), containing cyclic, square tetranuclear complex molecules, is the first homoleptic alent metal pyrazolide to have a discrete molecular rather than polymeric structure, for a metal other than Pd or Pt. The two independent complex molecules in 3 x 3/4CH(2)Cl(2) x Hpz(PhF) contain a unique tetrahedral [Cu(4)(micro(4)-F)](7+) core, three of whose edges are spanned by bridging pyrazolido groups. Magnetic data show that the copper centres in 1 and 3 are antiferromagnetically coupled, but that dried bulk s les of 2 do not retain their molecular structure.
Publisher: Elsevier BV
Date: 06-2007
Publisher: Wiley
Date: 11-12-2017
Abstract: A ligand field molecular mechanics (LFMM) force field has been constructed for the spin states of [Fe(bpp)
Publisher: Wiley
Date: 17-12-2008
Abstract: Reaction of CuF2 with one equivalent of 3{5}-(pyrid-2-yl)-5{3}-(tertbutyl)pyrazole (HL) and excess NH4OH in MeOH affords crystalline [NH4{Cu(micro-F)(microL)}6(CH2Cl2)2]HF2 in moderate yield. This compound contains the 12-MC-6 metallacrown [{Cu(micro-F)(micro-L)}6] (1) with a NH4 + ion at its center, and CH2Cl2 molecules complexed in bowl-shaped cavities above and below the Cu6F6 ring. Similar reactions using the bases MeNH2, glycine, l-alanine or beta-alanine afforded solvated crystals of [1(H3NMe)2]Cl2, [1(gly)2], [1(l-ala)2], and [1(beta-ala)2], respectively. The metallacrown 1 in these products contains methylammonium and zwitterionic amino-acid guests in its two bowl-shaped cavities each of the amino acids hydrogen-bonds to three F atoms. A related reaction using 1,6-diaminohexane resulted in fixation of CO2 from the air to give solvated [1(H3NC6H12NHCO2)2], again with a zwitterionic guest. NMR, ESI-MS and UV/vis measurements suggest that the metallacrown 1 retains its integrity in several organic solvents, although it is unclear to what extent guest binding takes place in solution.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2002
End Date: 2006
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2008
End Date: 2012
Funder: Engineering and Physical Sciences Research Council
View Funded Activity