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Dr Max Julian David Attwood


Postgraduate Research Student

Academic and research departments

Department of Chemistry.

My publications

Publications

2,6-Bis(pyrazol-1-yl)pyridine (L1) and 2,2:62,23-terpyridine (L2) are popular ligands for use in a wide range of applications in coordination chemistry. Both ligands are capable of forming metal complexes with highly interesting and potentially exploitable properties: luminescence, catalytic redox activity and magnetic spin crossover (SCO). SCO materials have received attention because of the potential for incorporation into commercially relevant technologies such as sensors and information storage media. This review explores the potential of ?back to back? L1 SCO polymers using reported examples, and looks towards the larger L2 chemical library, covering the coordination chemistry with a focus on magnetic properties. In principle, polymeric coordination materials are easier to process and may offer an easier route to tuning properties that are dependent on the electronic environment. It is the intention of this review to highlight the potential of these materials, with the goal of promoting the development of multifunctional SCO hybrids.
Attwood Max Julian David, Akutsu Hiroki, Martin Lee, Cruickshank Dyanne, Turner Scott S (2018) Above Room Temperature Spin Crossover in Thioamide-Functionalised 2,6-bis(pyrazol-1-yl)pyridine Iron(II) Complexes,Dalton Transactions (48) pp. 90-98 Royal Society of Chemistry
This work describes the synthesis of two novel functionalised 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands, namely 2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNH2) and N-methyl-2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNHMe). The corresponding solvated or non-solvated Fe(II) salts, [Fe(bppCSNH2)2]X2 and [Fe(bppCSNHMe)2]X2 (X = BF4- or ClO4-) were synthesised and their properties measured by SQUID magnetometry, Evans NMR, differential scanning calorimetry and single crystal X-ray diffraction. In the solid state [Fe(bppCSNH2)2]2+ salts persist in the low spin state below 350 K. The structure of [Fe(bppCSNH2)2](BF4)2.2MeNO2 shows a network of intermolecular interactions responsible for the low spin state stabilisation, relative to the prototypical [Fe(bpp)2]2+ spin crossover (SCO) salts. By contrast the complexes of bppCSNHMe both display abrupt SCO above 300 K. [Fe(bppCSNHMe)2](BF4)2.MeNO2 requires solvent loss before SCO can be observed centred at 332 K. The non-solvated [Fe(bppCSNHMe)2](ClO4)2 shows SCO centred at 325 K. Analysis of solvated and non-solvated crystal structures suggests that cooperativity is facilitated by thioamide-group interactions with neighbouring pyrazolyl and pyridyl moieties.
Attwood Max, Akutsu Hiroki, Martin Lee, Cruickshank Dyanne, Turner Scott S. (2019) Above room temperature spin crossover in thioamide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complexes,Dalton Transactions 48 (1) pp. 90-98 Royal Society of Chemistry
This work describes the synthesis of two novel functionalised 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands, namely 2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNH2) and N-methyl-2,6-bis(pyrazol-1-yl)pyridine-4-carbothioamide (bppCSNHMe). The corresponding solvated or non-solvated Fe(II) salts, [Fe(bppCSNH2)2]X2 and [Fe(bppCSNHMe)2]X2 (X = BF4? or ClO4?) were synthesised and their properties measured by SQUID magnetometry, Evans NMR, differential scanning calorimetry and single crystal X-ray diffraction. In the solid state [Fe(bppCSNH2)2]2+ salts persist in the low spin state below 350 K. The structure of [Fe(bppCSNH2)2](BF4)2·2MeNO2 shows a network of intermolecular interactions responsible for the low spin state stabilisation, relative to the prototypical [Fe(bpp)2]2+ spin crossover (SCO) salts. By contrast the complexes of bppCSNHMe both display abrupt SCO above 300 K. [Fe(bppCSNHMe)2](BF4)2·MeNO2 requires solvent loss before SCO can be observed centred at 332 K. The non-solvated [Fe(bppCSNHMe)2](ClO4)2 shows SCO centred at 325 K. Analysis of solvated and non-solvated crystal structures suggests that cooperativity is facilitated by thioamide-group interactions with neighbouring pyrazolyl and pyridyl moieties.
The following work regards the synthesis and characterisation of compounds with the potential to
undergo a spin crossover (SCO). A SCO describes an electronic transition between the LS and HS states
in response to perturbation by light, pressure, magnetic-field or thermal stimuli. These materials consist of d4 ? d7 first row transition metal ions chelated to a suitable organic ligand system. By
inducing a SCO transition, a compound exhibits exploitable changes in magnetism, colour and
conductivity, making them candidates for use in information storage media. For conventional systems,
the SCO must occur around room temperature with a practical hysteresis. Here, the LS state and HS
state can correspond to, for instance, the binary states used in computational memory. Currently, a
suitable compound remains elusive. To this end, this thesis challenges the design and development of
cationic Fe(II) and Co(II) complexes by intelligent ligand modification.
Amide- and thioamide-functionalisation of Fe(II) 2,6-bis(pyrazol-1-yl)pyridine (bpp) complexes, of the form [Fe(ligand)2](X)2, where X = BF4- or ClO4-, has been used to modulate the SCO properties.
Complexes were found to exhibit a range of magnetic, from being locked in the LS or HS state, to
abrupt SCO with hysteresis up to 96 K. Crystallisation of several compounds was achieved by slow
vapour diffusion. Intermolecular hydrogen bonding between NH-groups and anions were responsible
for isostructural packing between salts, which led to similar SCO properties. In addition, amide-linked
homo- and heterobimetallic coordination polymers were synthesised and found to exhibit gradual
SCO, attributed to their amorphous nature. Finally, an attempt was made to establish a more ?green?
and efficient synthesis of bpp and related ligands. As a result, several novel ligand species and their
Fe(II) and Co(II) complexes were synthesised. Amide-functionalised 2,6-bis(benzimidazol-2-yl)pyridine
(bbip) Fe(II) complexes were found to exhibit SCO behaviour, while ester functionalised versions
persisted in the LS state. Compounds were analysed by TGA, DSC, Evan?s method NMR spectroscopy,
SQUID magnetometry, UV/Vis, Raman spectroscopy, single crystal and powder X-ray diffraction.
Surface deposits of coordination polymers were also characterised by SEM and AFM following drop
casting and spin coating onto silicon wafers.
Overall, this has been a highly fruitful investigation leading to a total of 33 novel organic compounds
and 46 novel complexes, 26 of which displayed some form of SCO.