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Articles by Malcolm Halcrow
Nanoindentation Reveals Drastic Elastic Softening in a Spin Crossover Molecular Crystal Click to copy article link Article link copied!
Abstract Click to copy section linkSection link copied! Spin-crossover molecular crystals exhibit a unique interplay between electronic and structural degrees of freedom, yet their mechanical response remains poorly understood. In this study, we employ variable-temperature nanoindentation to quantify elastic modulus and hardness of single crystals of the molecular complex [Fe0.89Zn0.11(bpp)2](BF4)2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine) across the thermally induced first-order spin transition.
Mix and Match - Controlling the Functionality of Spin-Crossover Materials Through Solid Solutions and Molecular Alloys
Mix and Match – Controlling the Functionality of Spin-Crossover Materials Through Solid Solutions and Molecular Alloys The influence of dopant molecules on the structure and functionality of spin-crossover (SCO) materials is surveyed. Two aspects of the topic are well established. Firstly, isomorphous inert metal ion dopants in SCO lattices are a useful probe of the energetics of SCO processes.
Structural Consequences of Different Metal Compositions in the Doped Spin‐Crossover Crystals [FezM1−z(bpp)2][BF4]2 (M=Ni, Zn; bpp=2,6‐Bis{Pyrazol‐1‐yl}Pyridine)
Introduction Iron(II) spin-crossover (SCO) materials1-6 have continued interest as switching components in nanoelectronics,7-9 and for micro- and macro-scale materials applications.10-15 They also have a fundamental role for the elucidation of dynamic processes in molecular and framework crystals.16-18 In the latter regard, doping spin-crossover materials with inert metal ion dopants has been an important method for probing the lattice contribution to SCO thermodynamics and kinetics.19, 20...
Introduction to the Dalton Transactions themed collection: recent progress and perspectives on spin transition compounds
Introduction to the Dalton Transactions themed collection: recent progress and perspectives on spin transition compounds A graphical abstract is available for this content You have access to this article Fetching data from CrossRef. This may take some time to load.
Recent progress and perspectives on spin transition compounds Home
The passing of Prof. Philipp Gütlich in September 2022, which is a great loss to the community of spin transition, has urged us to review the current status and development of this field. It was realized that, in many cases, the concept of spin transition is considered of secondary importance within the topics of molecule-based materials and molecular magnetism. Studies of spin transition, especially from the next generation of scientists, have yet to receive the attention they are due.
Activating a High-Spin Iron(II) Complex to Thermal Spin-Crossover with an Inert Non-Isomorphous Molecular Dopant
Activating a High-Spin Iron(II) Complex to Thermal Spin-Crossover with an Inert Non-Isomorphous Molecular Dopant [Fe(bpp)2][ClO4]2 (bpp = 2,6-bis{pyrazol-1-yl}pyridine; monoclinic, C2/c) is high-spin between 5-300 K, and crystallises with a highly distorted molecular geometry that lies along the octahedral−trigonal prismatic distortion pathway. In contrast, [Ni(bpp)2][ClO4]2 (monoclinic, P21) adopts a more regular, near-octahedral coordination geometry.
Iron(II) Complexes of 2,6-Bis(imidazo[1,2‑a]pyridin-2-yl)pyridine and Related Ligands with Annelated Distal Heterocyclic Donors
Iron(II) Complexes of 2,6-Bis(imidazo[1,2‑a]pyridin-2-yl)pyridine and Related Ligands with Annelated Distal Heterocyclic Donors Following a published synthesis of 2,6-bis(imidazo[1,2‑a]pyridin-2-yl)pyridine (L1), treatment of α,α’-dibromo-2,6-diacetyl-pyridine with 2 equiv 2-aminopyrimidine or 2-aminoquinoline in refluxing acetonitrile respectively gives 2,6-bis(imidazo[1,2‑a]pyrimidin-2-yl)pyridine (L2) and 2,6-bis(imidazo[1,2‑a]quinolin-2-yl)pyridine (L3).
Exploring the Influence of Counterions on a Hysteretic Spin-Transition in Isomorphous Iron(II) Complex Salts
Exploring the Influence of Counterions on a Hysteretic Spin-Transition in Isomorphous Iron(II) Complex Salts Thomas D Roberts, Christopher M. Pask, Izar Capel Berdiell, Floriana Tuna and Malcolm Halcrow Abstract [FeL2]X2·2H2O (L = 2,6-bis{5-methyl-1H-pyrazol-3-yl}pyridine; X‒ = BF4‒ or ClO4‒) are readily dehydrated upon mild heating. Anhydrous [FeL2][BF4]2 exhibits an abrupt spin-transition at T½ = 205 K, with a 65 K thermal hysteresis loop which narrows upon repeated scanning.
The Effect of Tether Groups on the Spin States of Iron(II)/Bis[2,6-Di(pyrazol-1-yl)pyridine] Complexes
The Effect of Tether Groups on the Spin States of Iron(II)/Bis[2,6-Di(pyrazol-1-yl)pyridine] Complexes The synthesis of six 2,6-di(pyrazol-1-yl)pyridine derivatives bearing dithiolane or carboxylic acid tether groups is described: [2,6-di(pyrazol-1-yl)pyrid-4-yl]methyl (R)-lipoate (L1), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]ethyl (R)-lipoate (L2), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxy]ethyl (R)-lipoate (L3), N-([2,6-di(pyrazol-1-yl)pyrid-4-ylsulfanyl]-2-aminoethyl...
Influence of Ligand Substituent Conformation on the Spin State of an Iron(II)/Di(pyrazol-1-yl)pyridine Complex
Influence of Ligand Substituent Conformation on the Spin State of an Iron(II)/Di(pyrazol-1-yl)pyridine Complex The temperature of the solution-phase spin-crossover equilibrium in iron(II) complexes of 4-alkylsulfanyl-2,6-di{pyrazol-1-yl}pyridine (bppSR) complexes depends strongly on the alkylsulfanyl substituent.
Manipulating Metal Spin States for Biomimetic, Catalytic and Molecular Materials Chemistry
Manipulating Metal Spin States for Biomimetic, Catalytic and Molecular Materials Chemistry This article surveys the relationship between ligand type, coordination geometry and metal spin state in complexes of iron and other metal ions. Compounds and materials containing high-, intermediate- and low-spin metal ions differ in their molecular structures, their physical properties and their chemical reactivity.
Molecular Squares, Coordination Polymers and Mononuclear Complexes Supported by 2,4-Dipyrazolyl-6H-1,3,5-triazine and 4,6-Dipyrazolylpyrimidine Ligands
Molecular Squares, Coordination Polymers and Mononuclear Complexes Supported by 2,4-Dipyrazolyl-6H-1,3,5-triazine and 4,6-Dipyrazolylpyrimidine Ligands Izar Capel Berdiell, Sarah E Farmiloe, Rafal Kulmaczewski and Malcolm Halcrow Abstract The Fe[BF4]2 complex of 2,4-di(pyrazol-1-yl)-6H-1,3,5-triazine (L1) is a high-spin molecular square, [{Fe(L1)}4(μ-L1)4][BF4]8, whose crystals also contain the unusual HPzBF3 (HPz = pyrazole) adduct.
An iron(II) coordination polymer of a triazolyl tris-heterocycle showing a spin state conversion triggered by loss of lattice solvent
An iron(ii) coordination polymer of a triazolyl tris-heterocycle showing a spin state conversion triggered by loss of lattice solvent†‡ Solvated crystals of “[FeL2][BF4]2·H2O” (L = 2-(1,2,4-triazol-1-yl)-6-(pyrazol-1-yl)pyridine) contain a 1D coordination polymer, [Fe(μ-L)2{Fe(OH2)2L2}][BF4]4. Two iron environments linked by κ1:κ3,μ-L ligands alternate in the chains, Fe(1) being coordinated by two tridentate L ligands and Fe(2) by four monodentate L and two water molecules.
Silver(I) Complexes of Bis- and Tris-(pyrazolyl)azine Derivatives - Dimers, Coordination Polymers and a Pentametallic Assembly
Silver(I) complexes of 2,4,6-tri(pyrazol-1-yl)pyridine (tpp), 2,4,6-tri(pyrazol-1-yl)pyrimidine (tpym), 2,4,6-tri(pyrazol-1-yl)-1,3,5-triazine (tpt) and 2,4-di(pyrazol-1-yl)-1,3,5-triazine (bpt) are reported. Dinuclear [Ag (μ-tpp) (MeCN) ][BF ] ·2MeCN and [Ag (μ-tpym) (MeCN) ][BF ] are formed from approximately planar [AgL(NCMe)] (L = tpp or bpym) centres, which dimerise via apical interactions to the pendant pyrazolyl donor on each ligand.
Transition metals and orbitals overlap
Molecular orbitals of transition metal complexes Yves Jean Oxford, UK; Oxford University Press | ISBN 0198530935 | 2005 | 275pp | ?39.95 Reviewed by Malcolm Halcrow The most important single influence on the shape, spectroscopy and reactivity of a transition metal compound is the distribution of electrons within its frontier d-orbitals.
Transition metals and orbitals overlap
Molecular orbitals of transition metal complexes Molecular orbitals of transition metal complexes Yves Jean Oxford, UK; Oxford University Press | ISBN 0198530935 | 2005 | 275pp | ?39.95 Reviewed by Malcolm Halcrow The most important single influence on the shape, spectroscopy and reactivity of a transition metal compound is the distribution of electrons within its frontier d-orbitals.
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