Colette Boskovic | University of Melbourne (original) (raw)
Papers by Colette Boskovic
Dalton Transactions, 2019
Variation of alkyl substituents on pyridinophane ancillary ligands governs temperature-dependent ... more Variation of alkyl substituents on pyridinophane ancillary ligands governs temperature-dependent valence tautomeric or spin crossover equilibria in a family of cobalt–dioxolene complexes.
Crystal Growth & Design
The combination of the divergent tetrakis-pyridyl linking ligand 1,2,4,5-tetra(4pyridyl)benzene (... more The combination of the divergent tetrakis-pyridyl linking ligand 1,2,4,5-tetra(4pyridyl)benzene (tpb) with cobalt and 3,5-di-tert-butyldioxolene (3,5-dbdiox) ligands has afforded the complexes [Co(3,5-dbdiox)2(tpb)]∞ (1) and [Co(3,5-dbdiox)2(tpb)0.5]∞ (2). Both species are 1D coordination polymers that crystallize as the hydrated compounds 1•3H2O and 2•9H2O. While the tpb in complex 1 is a 2-connecting linker, affording a conventional 1D chain, the tpb in 2 is a 4-connecting linker, giving rise to a ribbon topology. Single crystal X-ray 2 structural analysis indicates that 1•3H2O and 2•9H2O both possess the {Co III (3,5-dbcat)(3,5dbsq)} (3,5-dbcat = 3,5-di-tert-butylcatecholate; 3,5-dbsq = 3,5-di-tert-butyl-semiquinonate) charge distribution at 100 or 130 K, respectively. Variable temperature magnetic susceptibility studies of partially dehydrated 1•H2O indicate a thermally induced valence tautomeric (VT) transition above 300 K. 19 obtained are instead 1D coordination polymers with chain (1) and ribbon (2) topologies. To our knowledge complex 1 is the first example of tpb acting as 2-connecting ligand, while complex 2 is a rare example of a 4-connecting tbp with a staggered conformation of the pyridyl groups. Magnetochemical, structural and spectroscopic studies suggest that compound 1•H2O can be formulated as {ls-Co III (3,5-dbcat)(3,5-dbsq)} below 300 K, with an incomplete thermallyinduced VT transition to a {hs-Co II (3,5-dbsq)2} species commencing above 300 K. ASSOCIATED CONTENT Supporting information. The Supporting Information is available free of charge on the ACS Publication website. Additional structural figures, thermogravimetric analysis data and infrared spectra (PDF). Accession Codes CCDC 1522817 and 1522818 contain the supplementary crystallographic data for 1•3H2O and 2•9H2O, respectively. These data can be obtained free of charge via
European Journal of Inorganic Chemistry
The study of four different salts of a hybrid glycinepolyoxotungstate has revealed photocoloratio... more The study of four different salts of a hybrid glycinepolyoxotungstate has revealed photocoloration that is dependent on the intramolecular hydrogen bonding between the glycine ammonium groups and the polyoxotungstate. Four compounds comprised of the hybrid polyoxometalate [As 4 {W 3 Y}W 44 Y 4 O 160 (Gly) 8 (H 2 O) 12 ] 9-(Gly = glycine) with glycinium, benzylammonium, 4-methylbenzylammonium or benzyltriethylammonium countercations have been synthesized and structurally characterized. In the solid state, two of the compounds exhibit reversible coloration associated with photoreduction, cycling from white to blue under UV irradiation and bleaching back to white following re-oxidation in air. The ability of the hybrid POM to undergo photoreduction correlates with the orientation of the zwitterionic ammonium groups of the glycine ligands and the intramolecular hydrogen bonding to POM oxo ligands. The kinetics of coloration of these POMs follows a pseudo second-order rate law.
Chemistry – A European Journal
Inorganic Chemistry Frontiers
Solvent-induced color-changing phenomena exhibited by some metal complexes can illuminate key asp... more Solvent-induced color-changing phenomena exhibited by some metal complexes can illuminate key aspects of their switchable behavior.
European Journal of Inorganic Chemistry
Inorganic chemistry, Jan 5, 2016
Eight new members of a family of mixed-metal (Mo,W) polyoxometalates (POMs) with amino acid ligan... more Eight new members of a family of mixed-metal (Mo,W) polyoxometalates (POMs) with amino acid ligands have been synthesized and investigated in the solid state and solution using multiple physical techniques. While the peripheral POM structural framework is conserved, the different analogues vary in nuclearity of the central metal-oxo core, overall redox state, metal composition, and identity of the zwitterionic α-amino acid ligands. Structural investigations reveal site-selective substitution of Mo for W, with a strong preference for Mo to occupy the central metal-oxo core. This core structural unit is a closed tetrametallic loop in the blue reduced species and an open trimetallic loop in the colorless oxidized analogues. Density functional theory calculations suggest the core as the favored site of reduction and reveal that the corresponding molecular orbital is much lower in energy for a tetra- versus trimetallic core. The reduced species are diamagnetic, each with a pair of strong...
Anal Chem, 1999
Quantitative analysis of the complex problem of coupled electron- and proton-transfer steps durin... more Quantitative analysis of the complex problem of coupled electron- and proton-transfer steps during reduction of the polyoxo anions α-[P(2)W(18)O(62)](6)(-) and α-[H(2)W(12)O(40)](6)(-) in aqueous NaCl (0.5 M) has been achieved by simulation of cyclic voltammograms (Rudolph, M.; Reddy, D. P.; Feldberg, S. W. Anal. Chem. 1994, 66, 589A) over wide ranges of anion concentration, pH, and scan rate. Since there are too many unknown parameters to attempt a one-step global form of simulation, a systematic, stepwise approach has been adopted by progressively accessing regimes of increasing voltammetric complexity. This protocol allows experimental behavior in each system over 5 orders of magnitude in proton concentration to be simulated by estimation of three protonation constants combined with experimentally determined reversible half-wave potentials for the two one-electron processes involved. Fast electron transfer and protonation kinetics are assumed. The importance of the values chosen for the diffusion coefficients of the proton and polyoxo anion species is considered. The simulations account for the fact that pairs of one-electron processes coalesce to give an apparent two-electron process in the pH range 1-6 for reduction of both anions.
Inorganic Syntheses, 2002
Inorganic chemistry, Jun 6, 2016
Optimization of literature synthetic procedures has afforded, in moderate yield, homogeneous and ... more Optimization of literature synthetic procedures has afforded, in moderate yield, homogeneous and crystalline samples of the five analogues Na11[{RE(OH2)}3CO3(PW9O34)2] (1-RE; RE = Y, Tb, Dy, Ho, and Er). Phase-transfer methods have allowed isolation of the mixed salts (Et4N)9Na2[{RE(OH2)}3CO3(PW9O34)2] (2-RE; RE = Y and Er). The isostructural polyanions in these compounds are comprised of a triangular arrangement of trivalent rare-earth ions bridged by a μ3-carbonate ligand and sandwiched between two trilacunary Keggin {PW9O34} polyoxometalate ligands. Alternating-current (ac) magnetic susceptibility studies of 1-Dy, 1-Er, and 2-Er reveal the onset of frequency dependence for the out-of-phase susceptibility in the presence of an applied magnetic field at the lowest measured temperatures. Inelastic neutron scattering (INS) spectra of 1-Ho and 1-Er exhibit transitions between the lowest-lying crystal-field (CF) split states of the respective J = 8 and (15)/2 ground-state spin-orbit mu...
Chem. Commun., 2015
Ab initio calculations of the electronic structure of Na9[Tb(W5O18)2] have allowed interpretation... more Ab initio calculations of the electronic structure of Na9[Tb(W5O18)2] have allowed interpretation of the inelastic neutron scattering spectra, revealing the subtle relationship between molecular geometry and magnetic properties of two isostructural species.
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Cited By (since 1996): 9, Export Date: 30 July 2012, Source: Scopus, CODEN: INOCA, doi: 10.1021/i... more Cited By (since 1996): 9, Export Date: 30 July 2012, Source: Scopus, CODEN: INOCA, doi: 10.1021/ic200366a, Language of Original Document: English, Correspondence Address: Boskovic, C.; School of Chemistry, University of Melbourne, VIC 3010, Australia; email: c.boskovic@unimelb.edu.au, References: Pope, M.T., (1983) Heteropoly and Isopoly Oxometalates, , Springer-Verlag: Berlin;
Australian Journal of Chemistry, 2014
Polyoxometalates are robust and versatile multidentate oxygen-donor ligands, eminently suitable f... more Polyoxometalates are robust and versatile multidentate oxygen-donor ligands, eminently suitable for coordination to trivalent lanthanoid ions. To date, 10 very different structural families of such complexes have been found to exhibit slow magnetic relaxation due to single-molecule magnet (SMM) behaviour associated with the lanthanoid ions. These families encompass complexes with between one and four of the later lanthanoid ions: Tb, Dy, Ho, Er, and Yb. The lanthanoid coordination numbers vary between six and eleven and a range of coordination geometries are evident. The highest energy barrier to magnetisation reversal measured to date for a lanthanoid–polyoxometalate SMM is Ueff/kB = 73 K for the heterodinuclear Dy–Eu compound (Bu4N)8H4[DyEu(OH)2(γ-SiW10O36)2].
Journal of the American Chemical Society, 2002
The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyrid... more The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyridine (hmpH) or 2-(hydroxyethyl)pyridine (hepH) gives the Mn(II)(2)Mn(III)(10) title compounds [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hmp)(6)] (2) and [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hep)(6)] (3), respectively, with X = Cl. Subsequent reaction of 3 with HBr affords the Br(-) analogue [Mn(12)O(8)Br(4)(O(2)CPh)(8)(hep)(6)] (4). Complexes 2.2Et(2)O.4CH(2)Cl(2), 3.7CH(2)Cl(2), and 4.2Et(2)O.1.4CH(2)Cl(2) crystallize in the triclinic space group P1, monoclinic space group C2/c, and tetragonal space group I4(1)/a, respectively. Complexes 2 and 3 represent a new structural type, possessing isomeric [Mn(III)(10)Mn(II)(2)O(16)Cl(2)] cores but with differing peripheral ligation. Complex 4 is essentially isostructural with 3. A magnetochemical investigation of complex 2 reveals an S = 6 or 7 ground state and frequency-dependent out-of-phase signals in ac susceptibility studies that establish it as a new class of single-molecule magnet. These signals occur at temperatures higher than those observed for all previously reported single-molecule magnets that are not derived from [Mn(12)O(12)(O(2)CR)(16)(H(2)O)(x)]. A detailed investigation of forms of complex 2 with different solvation levels reveals that the magnetic properties of 2 are extremely sensitive to the latter, emphasizing the importance to the single-molecule magnet properties of interstitial solvent molecules in the samples. In contrast, complexes 3 and 4 are low-spin molecules with an S = 0 ground state.
Journal of the …, 2002
In an effort to obtain new high-spin molecules and possibly SMMs, we have been continuing our inv... more In an effort to obtain new high-spin molecules and possibly SMMs, we have been continuing our investigation into the usefulness of the chelating ligand hmp - and the related ligand hep - [where hepH is 2-(hydroxyethyl)pyridine] in Mn chemistry. In addition to the tetranuclear ...
Dalton Transactions, 2019
Variation of alkyl substituents on pyridinophane ancillary ligands governs temperature-dependent ... more Variation of alkyl substituents on pyridinophane ancillary ligands governs temperature-dependent valence tautomeric or spin crossover equilibria in a family of cobalt–dioxolene complexes.
Crystal Growth & Design
The combination of the divergent tetrakis-pyridyl linking ligand 1,2,4,5-tetra(4pyridyl)benzene (... more The combination of the divergent tetrakis-pyridyl linking ligand 1,2,4,5-tetra(4pyridyl)benzene (tpb) with cobalt and 3,5-di-tert-butyldioxolene (3,5-dbdiox) ligands has afforded the complexes [Co(3,5-dbdiox)2(tpb)]∞ (1) and [Co(3,5-dbdiox)2(tpb)0.5]∞ (2). Both species are 1D coordination polymers that crystallize as the hydrated compounds 1•3H2O and 2•9H2O. While the tpb in complex 1 is a 2-connecting linker, affording a conventional 1D chain, the tpb in 2 is a 4-connecting linker, giving rise to a ribbon topology. Single crystal X-ray 2 structural analysis indicates that 1•3H2O and 2•9H2O both possess the {Co III (3,5-dbcat)(3,5dbsq)} (3,5-dbcat = 3,5-di-tert-butylcatecholate; 3,5-dbsq = 3,5-di-tert-butyl-semiquinonate) charge distribution at 100 or 130 K, respectively. Variable temperature magnetic susceptibility studies of partially dehydrated 1•H2O indicate a thermally induced valence tautomeric (VT) transition above 300 K. 19 obtained are instead 1D coordination polymers with chain (1) and ribbon (2) topologies. To our knowledge complex 1 is the first example of tpb acting as 2-connecting ligand, while complex 2 is a rare example of a 4-connecting tbp with a staggered conformation of the pyridyl groups. Magnetochemical, structural and spectroscopic studies suggest that compound 1•H2O can be formulated as {ls-Co III (3,5-dbcat)(3,5-dbsq)} below 300 K, with an incomplete thermallyinduced VT transition to a {hs-Co II (3,5-dbsq)2} species commencing above 300 K. ASSOCIATED CONTENT Supporting information. The Supporting Information is available free of charge on the ACS Publication website. Additional structural figures, thermogravimetric analysis data and infrared spectra (PDF). Accession Codes CCDC 1522817 and 1522818 contain the supplementary crystallographic data for 1•3H2O and 2•9H2O, respectively. These data can be obtained free of charge via
European Journal of Inorganic Chemistry
The study of four different salts of a hybrid glycinepolyoxotungstate has revealed photocoloratio... more The study of four different salts of a hybrid glycinepolyoxotungstate has revealed photocoloration that is dependent on the intramolecular hydrogen bonding between the glycine ammonium groups and the polyoxotungstate. Four compounds comprised of the hybrid polyoxometalate [As 4 {W 3 Y}W 44 Y 4 O 160 (Gly) 8 (H 2 O) 12 ] 9-(Gly = glycine) with glycinium, benzylammonium, 4-methylbenzylammonium or benzyltriethylammonium countercations have been synthesized and structurally characterized. In the solid state, two of the compounds exhibit reversible coloration associated with photoreduction, cycling from white to blue under UV irradiation and bleaching back to white following re-oxidation in air. The ability of the hybrid POM to undergo photoreduction correlates with the orientation of the zwitterionic ammonium groups of the glycine ligands and the intramolecular hydrogen bonding to POM oxo ligands. The kinetics of coloration of these POMs follows a pseudo second-order rate law.
Chemistry – A European Journal
Inorganic Chemistry Frontiers
Solvent-induced color-changing phenomena exhibited by some metal complexes can illuminate key asp... more Solvent-induced color-changing phenomena exhibited by some metal complexes can illuminate key aspects of their switchable behavior.
European Journal of Inorganic Chemistry
Inorganic chemistry, Jan 5, 2016
Eight new members of a family of mixed-metal (Mo,W) polyoxometalates (POMs) with amino acid ligan... more Eight new members of a family of mixed-metal (Mo,W) polyoxometalates (POMs) with amino acid ligands have been synthesized and investigated in the solid state and solution using multiple physical techniques. While the peripheral POM structural framework is conserved, the different analogues vary in nuclearity of the central metal-oxo core, overall redox state, metal composition, and identity of the zwitterionic α-amino acid ligands. Structural investigations reveal site-selective substitution of Mo for W, with a strong preference for Mo to occupy the central metal-oxo core. This core structural unit is a closed tetrametallic loop in the blue reduced species and an open trimetallic loop in the colorless oxidized analogues. Density functional theory calculations suggest the core as the favored site of reduction and reveal that the corresponding molecular orbital is much lower in energy for a tetra- versus trimetallic core. The reduced species are diamagnetic, each with a pair of strong...
Anal Chem, 1999
Quantitative analysis of the complex problem of coupled electron- and proton-transfer steps durin... more Quantitative analysis of the complex problem of coupled electron- and proton-transfer steps during reduction of the polyoxo anions α-[P(2)W(18)O(62)](6)(-) and α-[H(2)W(12)O(40)](6)(-) in aqueous NaCl (0.5 M) has been achieved by simulation of cyclic voltammograms (Rudolph, M.; Reddy, D. P.; Feldberg, S. W. Anal. Chem. 1994, 66, 589A) over wide ranges of anion concentration, pH, and scan rate. Since there are too many unknown parameters to attempt a one-step global form of simulation, a systematic, stepwise approach has been adopted by progressively accessing regimes of increasing voltammetric complexity. This protocol allows experimental behavior in each system over 5 orders of magnitude in proton concentration to be simulated by estimation of three protonation constants combined with experimentally determined reversible half-wave potentials for the two one-electron processes involved. Fast electron transfer and protonation kinetics are assumed. The importance of the values chosen for the diffusion coefficients of the proton and polyoxo anion species is considered. The simulations account for the fact that pairs of one-electron processes coalesce to give an apparent two-electron process in the pH range 1-6 for reduction of both anions.
Inorganic Syntheses, 2002
Inorganic chemistry, Jun 6, 2016
Optimization of literature synthetic procedures has afforded, in moderate yield, homogeneous and ... more Optimization of literature synthetic procedures has afforded, in moderate yield, homogeneous and crystalline samples of the five analogues Na11[{RE(OH2)}3CO3(PW9O34)2] (1-RE; RE = Y, Tb, Dy, Ho, and Er). Phase-transfer methods have allowed isolation of the mixed salts (Et4N)9Na2[{RE(OH2)}3CO3(PW9O34)2] (2-RE; RE = Y and Er). The isostructural polyanions in these compounds are comprised of a triangular arrangement of trivalent rare-earth ions bridged by a μ3-carbonate ligand and sandwiched between two trilacunary Keggin {PW9O34} polyoxometalate ligands. Alternating-current (ac) magnetic susceptibility studies of 1-Dy, 1-Er, and 2-Er reveal the onset of frequency dependence for the out-of-phase susceptibility in the presence of an applied magnetic field at the lowest measured temperatures. Inelastic neutron scattering (INS) spectra of 1-Ho and 1-Er exhibit transitions between the lowest-lying crystal-field (CF) split states of the respective J = 8 and (15)/2 ground-state spin-orbit mu...
Chem. Commun., 2015
Ab initio calculations of the electronic structure of Na9[Tb(W5O18)2] have allowed interpretation... more Ab initio calculations of the electronic structure of Na9[Tb(W5O18)2] have allowed interpretation of the inelastic neutron scattering spectra, revealing the subtle relationship between molecular geometry and magnetic properties of two isostructural species.
[
Cited By (since 1996): 9, Export Date: 30 July 2012, Source: Scopus, CODEN: INOCA, doi: 10.1021/i... more Cited By (since 1996): 9, Export Date: 30 July 2012, Source: Scopus, CODEN: INOCA, doi: 10.1021/ic200366a, Language of Original Document: English, Correspondence Address: Boskovic, C.; School of Chemistry, University of Melbourne, VIC 3010, Australia; email: c.boskovic@unimelb.edu.au, References: Pope, M.T., (1983) Heteropoly and Isopoly Oxometalates, , Springer-Verlag: Berlin;
Australian Journal of Chemistry, 2014
Polyoxometalates are robust and versatile multidentate oxygen-donor ligands, eminently suitable f... more Polyoxometalates are robust and versatile multidentate oxygen-donor ligands, eminently suitable for coordination to trivalent lanthanoid ions. To date, 10 very different structural families of such complexes have been found to exhibit slow magnetic relaxation due to single-molecule magnet (SMM) behaviour associated with the lanthanoid ions. These families encompass complexes with between one and four of the later lanthanoid ions: Tb, Dy, Ho, Er, and Yb. The lanthanoid coordination numbers vary between six and eleven and a range of coordination geometries are evident. The highest energy barrier to magnetisation reversal measured to date for a lanthanoid–polyoxometalate SMM is Ueff/kB = 73 K for the heterodinuclear Dy–Eu compound (Bu4N)8H4[DyEu(OH)2(γ-SiW10O36)2].
Journal of the American Chemical Society, 2002
The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyrid... more The reaction of (NBu(n)(4))[Mn(8)O(6)Cl(6)(O(2)CPh)(7)(H(2)O)(2)] (1) with 2-(hydroxymethyl)pyridine (hmpH) or 2-(hydroxyethyl)pyridine (hepH) gives the Mn(II)(2)Mn(III)(10) title compounds [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hmp)(6)] (2) and [Mn(12)O(8)Cl(4)(O(2)CPh)(8)(hep)(6)] (3), respectively, with X = Cl. Subsequent reaction of 3 with HBr affords the Br(-) analogue [Mn(12)O(8)Br(4)(O(2)CPh)(8)(hep)(6)] (4). Complexes 2.2Et(2)O.4CH(2)Cl(2), 3.7CH(2)Cl(2), and 4.2Et(2)O.1.4CH(2)Cl(2) crystallize in the triclinic space group P1, monoclinic space group C2/c, and tetragonal space group I4(1)/a, respectively. Complexes 2 and 3 represent a new structural type, possessing isomeric [Mn(III)(10)Mn(II)(2)O(16)Cl(2)] cores but with differing peripheral ligation. Complex 4 is essentially isostructural with 3. A magnetochemical investigation of complex 2 reveals an S = 6 or 7 ground state and frequency-dependent out-of-phase signals in ac susceptibility studies that establish it as a new class of single-molecule magnet. These signals occur at temperatures higher than those observed for all previously reported single-molecule magnets that are not derived from [Mn(12)O(12)(O(2)CR)(16)(H(2)O)(x)]. A detailed investigation of forms of complex 2 with different solvation levels reveals that the magnetic properties of 2 are extremely sensitive to the latter, emphasizing the importance to the single-molecule magnet properties of interstitial solvent molecules in the samples. In contrast, complexes 3 and 4 are low-spin molecules with an S = 0 ground state.
Journal of the …, 2002
In an effort to obtain new high-spin molecules and possibly SMMs, we have been continuing our inv... more In an effort to obtain new high-spin molecules and possibly SMMs, we have been continuing our investigation into the usefulness of the chelating ligand hmp - and the related ligand hep - [where hepH is 2-(hydroxyethyl)pyridine] in Mn chemistry. In addition to the tetranuclear ...