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Browsing by Author "Li, F"

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18O isotope substitution on the multiferroic compound DyMnO3
(Australian Institute of Physics, 2013-02-06) Narayanan, N; Li, F; Hutchison, WD; Reynolds, NM; Rovillain, P; Ulrich, C; Hester, JR; McIntyre, GJ; Mulders, AM
Not available
3d transition metal complexes with a julolidine–quinoline based ligand: structures, spectroscopy and optical properties
(Royal Society of Chemistry, 2015-12-07) Fanna, DJ; Zhang, YJ; Li, L; Karatchevtseva, I; Shepherd, ND; Azim, A; Price, JR; Aldrich-Wright, JR; Reynolds, JK; Li, F
A Schiff base type ligand with the combination of the julolidine and the quinoline groups has been reported as a potential chemosensor in detecting the cobalt(II) ion among other heavy and transition metal ions in solution. However, no crystal structure of such a ligand with any metal ions has been reported. In this work, its complexation with 3d transition metal ions (Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) has been investigated with five new complexes being synthesised, and spectroscopically and structurally characterised. [Mn2L2(CH3OH)2(CH3COO)2]•CH3OH (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} shows a dinuclear structure with two Mn : L : acetate (1 : 1 : 1) units bridged by two methanol molecules. [CoL2(NO3)]•CH3OH•H2O (2) and [NiL2]•H2O (3) exhibit mononuclear structures with a Co : L or Ni : L ratio of 1 : 2. [CuL(CH3COO)]•1/3CH3OH (4) demonstrates a mononuclear structure and the Cu ion has a square planar coordination polyhedron with a L ligand and a highly non-symmetrical acetate anion. [Zn2L2(CH3COO)2]•CH3OH (5) has two types of dinuclear units, both with two ZnL units bridged by two acetate anions but in three different bridging coordination modes. Their vibrational modes, absorption and photoluminescence properties have also been investigated. © 2016 The Partner Organisations
Cytotoxicity and structural analyses of 2,2′‐bipyridine‐, 4,4′‐dimethyl‐2,2′‐bipyridine‐ and 2‐(2′‐pyridyl)quinoxalineplatinum(II) complexes
(John Wiley and Sons, 2015-08-07) Pages, BJ; Zhang, YJ; Li, F; Sakoff, J; Gilbert, J; Aldrich-Wright, JR
Platinum anticancer complexes incorporating 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (44Me2bpy) or 2-(2′-pyridyl)quinoxaline (2pq) as polyaromatic ligands and the S,S or R,R isomer of 1,2-diaminocyclohexane as ancillary ligands in the form [Pt(PL)(AL)]2+ have been synthesised and characterised. X-ray diffraction was used to elucidate the structure and stacking behaviour of the complexes, revealing interesting properties that may impact their biological activity. Pulsed gradient spin-echo NMR experiments elucidated the aggregation behaviour of these complexes in solution. The cytotoxicity of each complex was assessed against the L1210 murine leukaemia, HT29 human colon carcinoma and U87 human glioblastoma cell lines and compared to other complexes within this class. The complexes incorporating 44Me2bpy were found to be the most potent at inhibiting cell growth with IC50 values for the S,S isomer (0.13–0.5 μM) less than that for cisplatin (0.36–11 μM), oxaliplatin (0.9–1.8 μM) or carboplatin (>50 μM). Most complexes were found to be very effective against HT29 colon carcinoma cells. © 1999-2020 John Wiley & Sons, Inc.
Dinuclear complexes of europium(III) and gadolinium(III) ions with a julolidine–quinoline-based tridentate ligand
(Taylor and Francis Online, 2016-06-13) Fanna, DJ; Zhang, YJ; Salih, A; Reynolds, JK; Li, F
The reaction of europium(III) or gadolinium(III) acetates with a Schiff base ligand {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} in methanol affords two dinuclear complexes which have been characterized by powder X-ray diffraction, Raman spectroscopy, scanning electron microscope–electron dispersive spectroscopy, absorption and emission spectroscopies as well as single-crystal X-ray diffraction. [Eu2L2(CH3COO)4(CH3OH)2] (1) and [Gd2L2(CH3COO)4(CH3OH)2] (2) are iso-structures, each consisting of two M : L : CH3COO : CH3OH (1 : 1 : 1 : 1) units bridged by two acetate anions with the metal center in a distorted capped square antiprismatic coordination geometry. Their vibration modes, electronic structures, and photoluminescent properties are reported. © 2016 Taylor & Francis Group
The effect of oxygen isotopes substitution on magnetism in multiferroic CaMn7O12
(Australian Institute of Nuclear Science and Engineering, 2012-11-15) Li, F; Narayanan, N; Hutchison, WD; Ulrich, C; McIntyre, GJ
Multiferroic materials, where ferroelectricity and ferromagnetism coexist and interact and one property can be used to drive the other, can find potential applications in spintronics and information technology and form the basis for four-state memory. However the details of coupling between these two orders are not yet understood. Competing theories of inherent electronic structure and ionic displacement are proposed to explain this coupling, but no experimental evidence currently exists to differentiate these models. To investigate the interaction between magnetic moments and electric dipoles on a fundamental level, this study will extend the isotopic pure oxygen substitution, a widely used technique for the investigation of high temperature superconductors, to multiferroics. Single crystal CaMn{sub 7}0{sub 12} showing the largest magnetically induced electric polarization measured to date is chosen as a test material and synthesized by flux method. The preliminary results show that single crystals of a size —100x100x100 μm can be obtained however a small amount of CaMn 3 0 6 impurity phase is also detected in XRD. Efforts on growing a larger single crystal are under way.
Effects of 18O isotope substitution in multiferroic RMnO3 (R=Tb, Dy)
(Australian Institute of Physics, 2015-02-02) Graham, PJ; Narayanan, N; Reynolds, NM; Li, F; Rovillain, P; Bartkowiak, M; Hester, JR; Kimpton, JA; Yethiraj, M; Pomjakushina, E; Conder, K; Kenzelmann, M; McIntyre, GJ; Hutchison, WD; Ulrich, C
Multiferroic materials demonstrate desirable attributes for next-generation multifunctional devices as they exhibit coexisting ferroelectric and magnetic orders. In type-II multiferroics, coupling exists that allows ferroelectricity to be manipulated via magnetic order and vice versa, offering potential in high-density information storage and sensor applications. Despite extensive investigations into the subject, questions of the physics of magnetoelectric coupling in multiferroics remain, and competing theories propose different mechanisms. The aim of this investigation was to study changes in the statics and dynamics of structural, ferroelectric and magnetic orders with oxygen-18 isotope substitution to shine light into the coupling mechanism in multiferroic RMnO3 (R=Tb, Dy) systems. We have performed Raman spectroscopy on 16O and 18O-substituted TbMnO3 single crystals. Oxygen-18 isotope substitution reduces all phonon frequencies significantly. However, specific heat measurements determine no changes in Mn3+ (28 and 41 K) magnetic phase transition temperatures. Pronounced anomalies in peak position and linewidth at the magnetic and ferroelectric phase transitions are seen. While the anomalies at the sinusoidal magnetic phase transition (41 K) are in accordance to the theory of spin-phonon coupling, further deviations develop upon entering the ferroelectric phase (28 K). Furthermore, neutron diffraction measurements on 16O and 18O-substituted DyMnO3 powders show structural deviations at the ferroelectric phase transition (17 K) in the order of 100 fm. These results indicate that the structure is actively involved in the emergence of ferroelectricity in these materials.
Evaluation on nuclear emergency response strategies in the Asia-Pacific region
(Elsevier B. V., 2021-09) Li, F; Wang, J; Li, H; Hu, Q; Dan, WX; Ge, LQ; Cohen, DD
The safe use of nuclear energy has always been one of the vital factors hindering the development of nuclear energy. Especially after the Chernobyl Disaster in 1986 and the Fukushima nuclear power plant accident in 2011, the attitude of the government and the public towards the safe handling of nuclear power has become increasingly negative. International discussions on the emergency decision of nuclear accidents have never ceased, and the process of dealing with the accidents’ aftermath is still difficult. Therefore, it is worth researching on the trend, effectiveness and perfection of the nuclear emergency response strategies issued by the government. This article selected the Asia-Pacific region as the research object, deeply reviewed the optimization policy and management of Australia, China, Thailand, Russia and other countries since 1953. With the constantly innovation of nuclear technology, this work is of great significance to formulate relevant policies and to improve the global nuclear emergency response strategies in the future. © 2021 Elsevier B.V.
The high temperature gas-cooled reactor
(Elsevier, 2021) Fütterer, MA; Strydom, G; Sato, H; Li, F; Abonneau, E; Abram, T; Davies, MW; Kim, MW; Edwards, L; Muránsky, O; Pouchon, MA; Yetisir, M
Starting from historical developments in the area of High Temperature Gas-cooled Reactors (HTR or HTGR) this article highlights the most significant recent achievements of this technology internationally and explains its potential value in a modern energy economy beyond pure electricity generation. The HTR is a relatively simple Small Modular Reactor design featuring demonstrated robust passive and inherent safety. It responds to the needs of a very large and growing process heat market in most industrialized countries many of which pursue a stringent policy of reducing fossil fuel burn. The article concludes with an outlook on work towards building demonstration plants, which are required to de-risk private investments and to incentivize deployment. The authors are members of the VHTR System Steering Committee of the Generation IV International Forum. © 2021 Elsevier Inc.
Investigating the cytotoxicity of platinum(II) complexes incorporating bidentate pyridyl-1,2,3-triazole “click” ligands
(Elsevier B.V., 2016-12-01) Pages, BJ; Sakoff, J; Gilbert, J; Zhang, Y; Li, F; Preston, D; Crowley, JD; Aldrich-Wright, JR
Six platinum(II) complexes of the type [Pt(PL)(AL)]2 +, where PL is a bidentate pyridyl-1,2,3-triazole “click” ligand and AL is the R,R or S,S isomer of 1.2-diaminocyclohexane, have been synthesised and characterised by several methods including elemental microanalysis, proton NMR spectroscopy and X-ray crystallography. The in vitro cytotoxicity of each complex was assessed in eleven cell lines, revealing moderate to good activity for complexes incorporating 2-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridine. © 2016 Elsevier B.V.
A large spin-crossover [Fe4L4]8+ tetrahedral cage
(Royal Society of Chemistry, 2015-05-20) Li, L; Saigo, N; Zhang, YJ; Fanna, DJ; Shepherd, ND; Clegg, JK; Zheng, RK; Hayami, S; Lindoy, LF; Aldrich-Wright, JR; Li, CG; Reynolds, JK; Harman, DG; Li, F
A large discrete face-capped tetranuclear iron(II) cage, [Fe4L4](BF4)8·n(solvent), was synthesised via metal-ion directed self-assembly. The cage is formed from a rigid tritopic ligand that incorporates chelating imidazole-imine functional groups. The cage displays temperature induced spin-crossover and LIESST effects and is amongst the largest iron(II) tetrahedral cages with such properties reported. The synthesis, structure and magnetic properties of this new metallo-cage are presented. © 2015 The Royal Society of Chemistry
Magnetically driven electric polarization in frustrated magnetic oxide multiferroics
(Australian Institute of Physics, 2014-02-06) Narayanan, N; Reynolds, NM; Li, F; Mulders, AM; Rovillain, P; Ulrich, C; Bartkowiak, M; Hester, JR; McIntyre, GJ; Hutchison, WD
In multiferroics more than one ferroic order can coexist and in the present case we are interested in systems which exhibit simultaneous magnetic ordering and electric polarization (EP). Of particular interest are frustrated magnetic materials that exhibit an electric polarization that is strongly coupled to the magnetism [1]. Examples of such multiferroics are RMnO3 (R= Tb, Dy), Ni3V2O8, and RbFe(MoO4)2 [2-4]. This coupling can be utilized in applications such as magnetoelectric random access memory. Although technically relevant, the coupling mechanism between these two orders is complicated [1]. Whereas the magnetic ordering results from exchange interaction of unpaired spins, origins of EP coupled to the magnetic ordering depends on the interplay between lattice, orbital, spin and charge degrees of freedom. Several mechanisms such as the inverse Dzyaloshinskii - Moriya interaction, magnetostriction and coupling of the chirality to the crystal structure or a combination of them are currently discussed depending on the compound [2-5]. Additionally EP has ionic and electronic contributions. In the present work we investigate the coupling of magnetism to EP involving all three above mechanisms, in orthorhombic DyMnO3 (DMO), Cu3Nb2O8 and Ba3NiNb2O9 with neutron powder diffraction (NPD), magnetization and heat capacity measurements focusing on the magnetic and multiferroic phase transitions. In order to investigate the role of the lattice distortion or equivalently the role of oxygen, isotope substitution of 16O with 18O was performed on DMO. All samples are prepared as single phases via the solid state route and NPD experiments are carried out at Wombat and at Echidna at OPAL
Magnetically driven electric polarization in frustrated magnetic oxide multiferroics
(Australian Institute of Physics, 2014-02-04) Narayanan, N; Reynolds, NM; Li, F; Mulders, AM; Rovillian, P; Ulrich, C; Bartkowiak, M; Hester, JR; McIntyre, GJ; Hutchinson, WD
In multiferroics more than one ferroic order can coexist and in the present case we are interested in systems which exhibit simultaneous magnetic ordering and electric polarization (EP). Of particular interest are frustrated magnetic materials that exhibit an electric polarization that is strongly coupled to the magnetism [1]. Examples of such multiferroics are RMnO3 (R= Tb, Dy), Ni3V2O8, and RbFe(MoO4)2 [2-4]. This coupling can be utilized in applications such as magnetoelectric random access memory. Although technically relevant, the coupling mechanism between these two orders is complicated [1]. Whereas the magnetic ordering results from exchange interaction of unpaired spins, origins of EP coupled to the magnetic ordering depends on the interplay between lattice, orbital, spin and charge degrees of freedom. Several mechanisms such as the inverse Dzyaloshinskii-Moriya interaction, magnetostriction and coupling of the chirality to the crystal structure or a combination of them are currently discussed depending on the compound [2-5]. Additionally EP has ionic and electronic contributions. In the present work we investigate the coupling of magnetism to EP involving all three above mechanisms, in orthorhombic DyMnO3 (DMO), Cu3Nb2O8 and Ba3NiNb2O9 with neutron powder diffraction (NPD), magnetization and heat capacity measurements focusing on the magnetic and multiferroic phase transitions. In order to investigate the role of the lattice distortion or equivalently the role of oxygen, isotope substitution of 16O with 18O was performed on DMO. All samples are prepared as single phases via the solid state route and NPD experiments are carried out at Wombat and at Echidna at OPAL.
Neodymium coordination polymers with propionate, succinate and mixed succinate–oxalate ligands: synthesis, structures and spectroscopic characterization
(Elsevier, 2015-12-14) Scales, N; Zhang, YJ; Bhadbhade, MM; Karatchevtseva, I; Kong, L; Lumpkin, GR; Li, F
Three neodymium (Nd) coordination polymers with propionate, succinate and mixed succinate–oxalate ligands have been synthesized and structurally characterized. Nd2(C3H5O2)6(H2O)3·3H2O (1) has a 1D polymeric structure built with both ninefold and ten-fold coordinated neodymium polyhedra linked through μ2-bridging propionate ligands. Nd2(C4H4O4)3(H2O)2 (2) has a 3D polymeric structure constructed with two distinct ninefold coordinated neodymium polyhedra linked through three types of succinate ligands, two in μ4- and one in μ3-coordination modes. Nd2(C4H4O4)2(C2O4)(H2O)4·3H2O (3) is built with two types of ten-fold coordinated neodymium polyhedra linked through μ4-succinate ligands into 2D undulating layers which are further connected through μ2-oxalate ligands forming a 3D network with channels. Their vibrational modes and thermal stabilities have been further investigated. Crown Copyright © 2015 Published by Elsevier Ltd.
Neutron powder diffraction experiments on multiferroic DyMnO 3
(Australian Institute of Nuclear Science and Engineering, 2012-11-15) Narayanan, N; Li, F; Hutchison, WD; Mulders, AM; Reynolds, N; Rovillan, P; Ulrich, C; Hester, JR; McIntyre, GJ
Multiferroic materials of particular interest are the frustrated magnetic compounds that exhibit a strongly coupled electric polarization (EP). One such compound is DyMnO{sub 3} which exists in an orthorhombic (o-DMO) and hexagonal modification depending on the synthesis conditions. In the present work the o-DMO is investigated by means of neutron powder diffraction focusing on the magnetic phase transitions and the behavior of the structural parameters in different magnetic and multiferroic phases. Below T{sub n,mn} =39 K, the Mn moments order sinusoidally with no EP. Then T{sub l=}16 K the Mn moments order in a spin spiral structure with an induced Dy moment and EP and finally below T{sub N,DY}=9 K a collinear ordering of the Dy moments takes place that reduces the EP significantly. Single phase samples are prepared via the solid state route and neutron diffraction (ND) experiments are carried out at the high flux ND beamline Wombat and at the high resolution ND beamline Echidna at OPAL. 0-DMO crystallizes in the space group Pbnm. All three magnetic phase transitions are identified and are in good agreement with. Below T{sub N,MN} an increased rotation of the rigid Mn06 octahedra in the ab plane, likely due to the competition between nearest neighbour aid next nearest neighbour superexchange interactions takes place. However below T{sub l} the MnO{sub 6} octahedra are significantly distorted along the c axis, the direction of the EP. Therefore the correlation between significant changes in the Mn-O bonds and the spontaneous EP are evident below T{sub l}. The reduction of EP below T{sub N.DY} on the other hand correlates with the rapid increase in the orbital ordering angle towards the 120° corresponding to the 3x{sup 2}-r{sup 2}/3y{sup 2}-r{sup 2} character of the orbitals.
A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C
(Springer Nature, 2017-01-03) Li, MR; Zhao, MW; Li, F; Zhou, W; Peterson, VK; Xu, XY; Shao, ZP; Gentle, IR; Zhu, ZH
The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells. © 2017 Springer Nature Limited. Open Access. This work is licensed under a Creative Commons Attribution 4.0 International License.
Self-assembly of a unique 3d/4f heterometallic square prismatic box-like coordination cage
(Royal Society of Chemistry, 2016-05-23) Li, L; Zhang, Y; Avdeev, M; Lindoy, LF; Harman, DG; Zheng, RK; Cheng, Z; Aldrich-Wright, JR; Li, F
AbstractWe present the synthesis and characterization of a unique, slightly distorted square prismatic, box-like coordination cage of type [Cu6Dy8L8(MeOH)8(H2O)6](NO3)12·χsolvent obtained via the supramolecular assembly between a non-centrosymmetric Dy(III) metalloligand and Cu(II) nitrate. Magnetic susceptibility measurements indicate that the complex behaves as a single-molecule magnet. © 2016 Royal Society of Chemistry
Solvothermal synthesis of uranium(VI) phases with aromatic carboxylate ligands: a dinuclear complex with 4-hydroxybenzoic acid and a 3D framework with terephthalic acid
(Elsevier B.V., 2016-02-01) Zhang, YJ; Karatchevtseva, I; Bhadbhade, MM; Tran, TT; Aharonovich, I; Fanna, DJ; Shepherd, ND; Lu, KT; Li, F; Lumpkin, GR
With the coordination of dimethylformamide (DMF), two new uranium(VI) complexes with either 4-hydroxybenzoic acid (H2phb) or terephthalic acid (H2tph) have been synthesized under solvothermal conditions and structurally characterized. [(UO2)2(Hphb)2(phb)(DMF)(H2O)3]·4H2O (1) has a dinuclear structure constructed with both pentagonal and hexagonal bipyramidal uranium polyhedra linked through a µ2-bridging ligand via both chelating carboxylate arm and alcohol oxygen bonding, first observation of such a coordination mode of 4-hydroxybenzoate for 5 f ions. [(UO2)(tph)(DMF)] (2) has a three-dimensional (3D) framework built with pentagonal bipyramidal uranium polyhedra linked with µ4-terephthalate ligands. The 3D channeled structure is facilitated by the unique carboxylate bonding with nearly linear C–O–U angles and the coordination of DMF molecules. The presence of phb ligands in different coordination modes, uranyl ions in diverse environments and DMF in complex 1, and tph ligand, DMF and uranyl ion in complex 2 has been confirmed by Raman spectroscopy. In addition, their thermal stability and photoluminescence properties have been investigated. © 2015 Elsevier Inc.
Subpicometer-scale atomic displacements and magnetic properties in the oxygen-isotope substituted multiferroic DyMn O3
(American Physical Society, 2017-02-27) Narayanan, N; Graham, PJ; Reynolds, N; Li, F; Rovillain, P; Hester, JR; Kimpton, JA; Yethiraj, M; McIntyre, GJ; Hutchison, WD; Ulrich, C
We have investigated DyMn16O3 and its isotopically substituted counterpart DyMn18O3 by neutron powder diffraction, x-ray diffraction, and heat capacity measurements to investigate the mechanism leading to its magnetically induced electric polarization. 18O isotope substitution does not influence the magnetic ordering temperature of the Mn ions TN,Mn or the multiferroic ordering temperature Tl coinciding with the onset of the spin spiral phase; however, it does reduce the ordering temperature of Dy into its incommensurate magnetic state TN,Dy from 7.0(1) K to 5.9(1) K. The temperature dependence of the magnetic propagation vector, qIC, changes with 18O substitution, while Tl remains almost constant, independent of qIC. Pronounced changes in the lattice parameters occur at the various phase transitions. Furthermore, distinct subpicometer-scale distortions of the MnO6 octahedra and displacements of the Dy ions are observed below the ferroelectric phase transition at Tl in both samples, pointing toward the mechanism for electric polarization and its coupling to the orbital degrees of freedom. ©2017 American Physical Society
Synthesis and characterisation of new tripodal lanthanide complexes and investigation of their optical and magnetic properties
(Royal Society of Chemistry, 2017-08-21) Craze, AR; Huang, XD; Etchells, I; Zheng, LM; Bhadbhade, MM; Marjo, CE; Clegg, JK; Moore, EG; Avdeev, M; Lindoy, LF; Li, F
This paper presents the synthesis of a tripodal ligand (H3L) via the Schiff base condensation of N,N-diethylsalicylaldehyde and tris(2-aminoethyl)amine. The neutral complexes of type [EuL], [GdL] and [DyL] were synthesized and characterized by FT-IR, SEM-EDS, PXRD, single crystal X-ray diffraction, CHN analysis and high resolution ESI-MS. X-ray crystallographic studies demonstrated that the heptadentate ligand incorporating a cavity pre-organized by hydrogen bonding binds the Ln(III) ions to yield a face capped octahedral coordination geometry with three-fold symmetry. Photoluminescence studies show a typical Ln(III) absorption character for the three complexes, with [EuL] demonstrating considerably stronger lanthanide-based luminescence peaks, and a Eu(III) centered luminescence lifetime of 0.144 ± 0.01 ms. Temperature/field-dependent DC and temperature/frequency-dependent AC magnetic measurements carried out for the Dy(III) complex indicated obvious magnetic anisotropy and suggested slow relaxation behaviour with considerable quantum tunnelling of the magnetization contribution. © The Royal Society of Chemistry 2017
Synthesis and characterisation of two new tripodal metalloligands incorporating zinc(II)
(Springer Nature, 2015-05-06) Fanna, DJ; Smith, A; Zhang, Y; Li, L; Shepherd, ND; Harman, DG; Li, F
The in situ Schiff base condensation of 2-acetylpyrazine with tris(2-aminoethyl)amine in the presence of zinc(II) perchlorate was carried out in absolute ethanol and 95 % ethanol, respectively. Two new tripodal metalloligands, 1 and 2, were isolated. The formation of complexes 1 and 2 has been verified by NMR, mass spectral studies and X-ray (for 2), with the evidence indicating that a zinc ion is incorporated in the tripodal cavity defined by the tren backbone in each case. However the products differed in the number of Schiff base condensation reactions that had occurred. While the use of absolute ethanol resulted in condensation at all three primary amine sites of tris(2-aminoethyl)amine, employing 95 % ethanol yielded condensation at only one of the primary amine sites. These different outcomes can be ascribed, at least in part, to the effect of the different water contents in the respective reaction solvents resulting in a shift of the dynamic equilibrium involving imine formation towards the precursor amine and ketone reagents. In 1, steric considerations dictate that the three uncoordinated pyrazine nitrogen donors will have their coordination vectors oriented in a mutually divergent manner suitable for coordination to three different metal centres when acting as a metalloligand while for 2, the X-ray structure confirms that the single uncoordinated (pendent) pyrazine nitrogen is also oriented for ready coordination to a second metal centre. © 2015 Springer Science+Business Media Dordrecht

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