Use of chelating ligands in the synthesis of paramagnetic frameworks

Chapter 1 of this thesis contains an extensive literature review of magneto-structural correlations (MSCs) of a range of transition metal dimers. Different structural parameters are considered and a critical assessment is given of the principal factors influencing the exchange interactions in each case. Following this, two different synthetic strategies for the synthesis of polymetallic systems are compared and contrasted. Their role in the formation of paramagnetic frameworks is also considered. Chapter 2 describes the synthesis of a family of MnIII dimers and highlights the importance of chelating ligands in their formation and magnetic properties. A family of MnIII dimers of general formula of [MnIII2(R-sao)2(dpa)2](ClO4)2 (1-5) has been synthesised using derivatised phenolic oximes (R-saoH2, where R=H, Me, Et, Ph) in combination with di-(2-picolyl)-amine (dpa). The structures reveal a double-oxime bridged [MnIII(NO)]2 magnetic core in which the Jahn-Teller axes lie perpendicular to the bridging plane, in contrast to two previously reported family members (6 and 7). The switch in the orientation of the Jahn-Teller axes is enforced through the use of the chelating ligand which is present in 1-5 and absent in 6-7. Dc magnetic susceptibility measurements reveal that the exchange interactions between the MnIII metal centres in 1-5 are antiferromagnetic in contrast to that observed for 6 and 7 which are ferromagnetic. DFT calculations have also been undertaken in order to confirm these findings. Chapter 3 describes the synthesis of a family of novel cages from the metalloligand [FeIIIL3], where HL = 1-(4-pyridyl)butane-1,3-dione and metal salts CuBr2, Cu(NO3)2, NiCl2, CoCl2 Co(SCN)2, ZnBr2 and Pd(OTf)2 (where OTf = triflate anion). The flexibility in the design of these structures offers huge potential to tune their physical properties as the constituent parts of the cage can be altered without any change to the structure. Due to the large size of the internal cavity, it is possible that the cage could play host to different species, such as magnetic guests, which would then exert control over the exchange interaction between the metal ions in the host framework and between the host and guest(s). Chapter 4 presents the synthesis and crystallographic studies of two novel metal organic framework (MOF) [CuIIL2]n and HL = 1-(4-pyridyl)butane-1,3-dione. An in-depth high-pressure crystallographic study of structure shows that the framework undergoes a single-crystal phase transition as well as a switching of the orientation of the Jahn-Teller axis, which is dependent on the hydrostatic media and also the presence of negative linear compressibility (NLC) behaviour

Pressure-and temperature induced phase transitions, piezochromism, NLC behaviour and pressure controlled Jahn–Teller switching in a Cu-based framework

In situ single-crystal diffraction and spectroscopic techniques have been used to study a previously unreported Cu-framework bis[1-(4-pyridyl)butane-1,3-dione]copper(II) (CuPyr-I). CuPyr-I was found to exhibit high-pressure and low-temperature phase transitions, piezochromism, negative linear compressibility, and a pressure induced Jahn?Teller switch, where the switching pressure was hydrostatic media dependent.The support by the Spanish Ministerio de Econom´ıa, Industria y Competitividad (PGC2018-101464-B-I00), and INNVAL 18/28 is also acknowledged

Switching the orientation of Jahn-Teller axes in oxime-based Mn(III) dimers and its effect upon magnetic exchange:a combined experimental and theoretical study

A family of Mn-III dimers of general formula [Mn-2(III)(R-sao)(2)(dpa)(2)](ClO4)(2) (1-5) has been synthesised using derivatised phenolic oximes (R-saoH(2), where R = H, Me, Et, Ph) in combination with di-(2-picolyl)-amine (dpa). Their structures reveal a double-oxime bridged [Mn-III(NO)](2) magnetic core in which the Jahn-Teller axes lie perpendicular to the bridging plane, in contrast to two previously reported family members (6, 7). The switch in the orientation of the Jahn-Teller axes is enforced through the use of the chelating ligand which is present in 1-5 and absent in 6-7. Dc magnetic susceptibility measurements reveal that the exchange interactions between the MnIII metal centres in 1-5 are antiferromagnetic in contrast to that observed for 6 and 7 which are ferromagnetic. DFT calculations performed on complexes 1-6 reproduce both the sign and strength of the J values found experimentally. Molecular orbital analysis unlocks a common mechanism of magnetic coupling based upon the orientation of the Jahn-Teller axis, with the magneto-structural correlation also dependent upon the Mn-N-O-Mn angles - with ferromagnetic interactions at smaller dihedral angles

Solvothermal synthesis of discrete cages and extended networks comprising {Cr(iii)3O(O2CR)3(oxime)3}2?(R = H, CH3, C(CH3)3, C14H9) building blocks

The synthesis, structural and magnetic characterisation of a family of related Cr(III) cages are reported. Each member comprises {Cr(III)3O(O2CR1)3(R2-sao)3}2? (R1 = H, CH3, C(CH3)3, C14H9; R2 = Me, Ph, tBu, C10H8) triangles linked by Na+ cations, resulting in either the discrete complexes [H3O][NEt4]2[NaCr(III)6O2(O2C-C14H9)6(Naphth-sao)6] (1) and [Na4Cr(III)6O2(O2CC(CH3)3)6(3,5-di-tBu-sao)6(MeCN)6] (3); or the extended networks [H3O]2[Na2Cr(III)6O2(O2CH)6(Ph-sao)6(MeCN)2(H2O)2]n·4MeCN (2); [H3O][Na3Cr(III)6O2(O2CCH3)6(Me-sao)6(MeCN)]n (4) and [Na2Cr(III)3O(O2CCH3)3(Me-sao)3(H2O)6]n·3MeCN (5). Magnetic susceptibility data obtained for 2 and 4 reveal weak antiferromagnetic exchange between the Cr(III) ions in the triangles

Solvothermal synthesis of discrete cages and extended networks comprising {Cr(III)3O(O2CR)3(oxime)3}2- (R = H, CH3, C(CH3)3, C14H9) building blocks

The synthesis, structural and magnetic characterisation of a family of related Cr(III) cages are reported. Each member comprises {Cr(III)3O(O2CR1)3(R2-sao)3}2- (R1 = H, CH3, C(CH3)3, C14H9 ; R2 = Me, Ph, tBu, C10H8) triangles linked by Na+ cations, resulting in either the discrete complexes [H3O][NEt4]2[NaCr(III)6O2(O2C-C14H9)6(Naphth-sao)6] (1) and [Na4Cr(III)6O2(O2CC(CH3)3)6(3,5-di-tBu-sao)6(MeCN)6] (3); or the extended networks [H3O]2[Na2Cr(III)6O2(O2CH)6(Phsao) 6(MeCN)2(H2O)2]n·4MeCN (2); [H3O][Na3Cr(III)6O2(O2CCH3)6(Me-sao)6(MeCN)]n (4) and [Na2Cr(III)3O(O2CCH3)3(Mesao) 3(H2O)6]n·3MeCN (5). Magnetic susceptibility data obtained for 2 and 4 reveal weak antiferromagnetic exchange between the Cr(III) ions in the triangles.The author (LFJ) would like to thank the SFI Investigator Program for funding (Investigator Project Number: 12/IP/1322). We would also like to thank the IRCSET Embark Fellowship Program for funding EH

Solvothermal synthesis of discrete cages and extended networks comprising {cr(iii)3o(o2cr)3(oxime)3}2− (r = h, ch3, c(ch3)3, c14h9) building blocks

The synthesis, structural and magnetic characterisation of a family of related Cr(III) cages are reported. Each member comprises {Cr(III)(3)O(O2CR1)(3)(R-2-sao)(3)}(2-) (R-1 = H, CH3, C(CH3)(3), C14H9; R-2 = Me, Ph, Bu-t, C10H8) triangles linked by Na+ cations, resulting in either the discrete complexes [H3O][NEt4](2)[NaCr(III)(6)O-2(O2C-C14H9)(6)(Naphth-sao)(6)] (1) and [Na4Cr(III)(6)O-2(O2CC(CH3)(3))(6)(3,5-di-tBu-sao)(6)(MeCN)(6)] (3); or the extended networks [H3O](2)[Na2Cr(III)(6)O-2(O2CH)(6)(Ph-sao)(6)(MeCN)(2)(H2O)(2)](n)center dot 4MeCN (2); [H3O][Na3Cr(III)(6)O-2(O2CCH3)(6)(Mesao)(6)(MeCN)](n) (4) and [Na2Cr(III)(3)O(O2CCH3)(3)(Me-sao)(3)(H2O)(6)](n)center dot 3MeCN (5). Magnetic susceptibility data obtained for 2 and 4 reveal weak antiferromagnetic exchange between the Cr(III) ions in the triangles

Molecular pac-man and tacos: layered cu(ii) cages from ligands with high binding site concentrations

The in situ formation and subsequent Cu(II) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy3- methoxyphenyl) methylideneamino] benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl) methylideneamino] benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl) methylideneamino] benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(II)(10)(L-1)(4)(2-aph)(2)(H2O)(2)](ClO4)(4)center dot 5MeOH (1), [Cu(II)(14)(L-1)(8)(MeOH)(2.5)(H2O)(7.5)](NO3)(4)center dot 3MeOH center dot 7H(2)O (2), [Cu(II)(14)(L-2)(8)(MeOH)(4)(H2O)(6)](NO3)(4)center dot 6H(2)O (3), [Cu(II)(14)(L-3)(8)(MeOH)(6)(H2O)(2)](NO3)(4)center dot 4MeOH center dot 8H(2)O (4) and [Cu(II)(30)O(OH)(4)(OMe)(2)(L-1)(16)(MeOH)4(H2O)(2)](ClO4)(4)center dot 2MeOH center dot 30H(2)O (5). Each member comprises a highly unusual topology derived from off-set, stacked, near planar layers of polynuclear subunits connected through long Cu(II)-O contacts. The exact topology observed is dependent on the specific reaction conditions and methodologies employed. Dc magnetic susceptibility studies on 1, 2, 4 and 5 reveals strong antiferromagnetic exchange between the Cu(II) centres in all siblings. We also present the 1D coordination polymer {[Cu(II)(L-4)]center dot H2O}(n) (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxyphenyl) methyleneamino] benzoyl] amino] ethanimidate (L4H2), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L1H3

Molecular pac-man and tacos: layered cu(ii) cages from ligands with high binding site concentrations

The in situ formation and subsequent Cu(II) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy3- methoxyphenyl) methylideneamino] benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl) methylideneamino] benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl) methylideneamino] benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(II)(10)(L-1)(4)(2-aph)(2)(H2O)(2)](ClO4)(4)center dot 5MeOH (1), [Cu(II)(14)(L-1)(8)(MeOH)(2.5)(H2O)(7.5)](NO3)(4)center dot 3MeOH center dot 7H(2)O (2), [Cu(II)(14)(L-2)(8)(MeOH)(4)(H2O)(6)](NO3)(4)center dot 6H(2)O (3), [Cu(II)(14)(L-3)(8)(MeOH)(6)(H2O)(2)](NO3)(4)center dot 4MeOH center dot 8H(2)O (4) and [Cu(II)(30)O(OH)(4)(OMe)(2)(L-1)(16)(MeOH)4(H2O)(2)](ClO4)(4)center dot 2MeOH center dot 30H(2)O (5). Each member comprises a highly unusual topology derived from off-set, stacked, near planar layers of polynuclear subunits connected through long Cu(II)-O contacts. The exact topology observed is dependent on the specific reaction conditions and methodologies employed. Dc magnetic susceptibility studies on 1, 2, 4 and 5 reveals strong antiferromagnetic exchange between the Cu(II) centres in all siblings. We also present the 1D coordination polymer {[Cu(II)(L-4)]center dot H2O}(n) (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxyphenyl) methyleneamino] benzoyl] amino] ethanimidate (L4H2), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L1H3

Magnetic relaxation pathways in lanthanide single-molecule magnets

10.1038/NCHEM.1707NATURE CHEMISTRY58673-67

Trends in International Business Research

My purpose this morning is to discuss with you what appear to be some significant trends in international business research.An overview of these trends indicates that international business research is alive and well indeed. Some of the specific trends that lead to this conclusion are the following:© 1970 JIBS. Journal of International Business Studies (1970) 1, 109–123