David J Harding

David J Harding
Walailak University · School of Science

Ph.D., B.Sc. (Hons.)
Currently working on spin crossover devices and supramolecular systems.

About

130
Publications
29,481
Reads
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1,378
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Introduction
My research is concerned with the discovery of molecular materials with interesting structural, magnetic, redox and optical properties. We have a particular interest in spin crossover and single molecule magnetic materials. For more information please go to: www.funtechwu.com/david-j-harding.
Additional affiliations
November 2012 - present
Position
  • Complex Metal-an Open Access Journal
Description
  • Co-Editor in Chief of Complex Metals-an Open Access Journal from Taylor & Francis, www.tandfonline.com/loi/tcme.
June 2004 - present
Walailak University
Position
  • Associate Professor of Inorganic Chemistry
December 2000 - November 2001
University of Ottawa
Position
  • PostDoc Position
Education
October 1997 - December 2000
University of Bristol
Field of study
  • Chemistry
October 1993 - July 1997
The University of Edinburgh
Field of study
  • Chemistry

Publications

Publications (130)
Article
Molecular magnetic switches are expected to form the functional components of future nanodevices. Herein we combine detailed (photo‐) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states. On cooling, it exhibits a partial thermal conversion associated wit...
Article
Full-text available
Herein, we report the first room temperature switchable Fe(III) molecular spin crossover (SCO) tunnel junction. The junction is constructed from [Fe III (qsal-I) 2 ]NTf 2 (qsal-I = 4-iodo-2-[(8-quinolylimino)methyl]phenolate) molecules self-assembled on graphene surfaces with conductance switching of one order of magnitude associated with the high...
Article
The Fe(III) spin-switching complexes [Fe(qsal-5-Y)2]X (where Y = F, Cl, Br, I or OMe; X = NCS−, Cl−, OTf−, NO3−, BF4−, PF6−, or BPh4−) display a variety of thermal spin transition profiles, including abrupt, stepped, and hysteretic, with potential applications as temperature-or gas-dependent switches or memory/ storage devices. Here, the complex [F...
Article
OctaDist is an interactive and visual program for determination of structural distortion in octahedral coordination complexes such as spin crossover complexes, single-ion magnets, perovskites or metal-organic frameworks. OctaDist computes the octahedral distortion parameters initially designed in the context of the spin-crossover phenomenon and den...
Article
Crystal packing is known to strongly influence spin crossover (SCO) behavior. The influence of the halogen substituent on the crystal structure and magnetic behavior is investigated in the series, [Fe(qsal-X) 2 ]NTf 2 (qsal-X = 4-X-2-[(8-quinolylimino)methyl]phenolate; X = Cl 1, Br 2, and I 3; NTf 2 = CF3SO2NSO2CF3). Compounds 1 and 2 are stabilize...
Article
Molecular devices based on spin-crossover (SCO) compounds are important targets for molecular electronics. In this study, six air-stable Fe III complexes have been prepared: [Fe(naphBzen)2]Cl (1), [Fe(naphBzen)2]Cl·0.5hexane (1·0.5hexane); [Fe(naphBzen)2]Cl·2CHCl3·1.15hexane (1·2CHCl3 ·1.15hexane), [Fe(naphBzen)2]Br (2), [Fe(naphBzen)2]Br·0.5hexane...
Article
Unprecedented pillar[5]arene-isocyanide pseudorotaxane complexes are reported. Extensive 1H-NMR experiments reveal remarkably strong binding affinities of alkyl diisocyanide guests (Ka > 105 M-1 in CDCl3) by pillar[5]arenes. Characterised by multinuclear 1H and 13C-NMR spectroscopy and single-crystal X-ray diffraction, it is demonstrated that pilla...
Article
Phytochemical investigation of the fruit extract of Clausena excavata Burm. f. resulted in the isolation and identification of 16 compounds, including seven coumarins (1–7), four phenylpropanoids (8–10 and 14), two benzaldehyde derivatives (11 and 12), one carbazole alkaloid (13), and two limonoids (15 and 16). Of these, nine compounds (1, 3, 5, 6,...
Article
Three previously undescribed isoflavones, derrisrobustones A–C, and a previously undescribed natural isoflavone, derrisrobustone D, along with eight known isoflavones, were isolated from the twig extract of Derris robusta (DC.) Benth. All structures were identified by extensive spectroscopic analysis. Derrisrobustones A–C were obtained as scalemic...
Article
In anatase TiO2, various passivated co-dopants such as (V–N), (Mo–C), (Nb–N), (Ta–N), and (F–N) are of significant interest due to their enhanced photocatalytic activities under visible light. Unlike the bulk phase, the effect of co-dopants in TiO2 nanoparticles still lacks fundamental exploration. To understand this, we perform density-functional-...
Article
Self-standing electrocatalysts for water splitting have been intensively exploited. Herein, 3D binder-free bimetallic nickel-cobalt selenides nanosheets anchored on a macroporous conducting carbon membrane (NiCoSe2@PCM) have been developed. A unique interconnected macropores PCM was prepared via cryogelation, freeze-drying, and subsequent carboniza...
Article
A series of Ni(II) trinuclear complexes, [Ni3(sala-X)6] (sala-X = o-[(p-X-phenylimino)methyl]phenol; X = Br 1-Br, Me 1-Me and OMe 1-OMe), have been prepared and fully characterised. X-ray crystallographic studies reveal that the complexes are composed of three face-sharing octahedral Ni(II) metal ions bridged by the phenoxide oxygens of the sala-X...
Article
Three undescribed abyssomicin derivatives, including microbimisin, abyssomicins Z1, and Z2, were isolated from the soil actinomycete Microbispora rhizosphaerae sp. nov. TBRC6028. Chemical structures were determined by NMR spectroscopic data (¹H, ¹³C, COSY, HSQC, HMBC, and NOESY spectra) and the absolute configurations were verified by single-crysta...
Preprint
A series of Ni(II) trinuclear complexes, [Ni<sub>3</sub>(sala-X)<sub>6</sub>] (sala-X = o -[( p -X-phenylimino)methyl]phenol; X = Br 1-Br , Me 1-Me and OMe 1-OMe ), have been prepared and fully characterised. X-ray crystallographic studies reveal that the complexes are composed of three face-sharing octahedral Ni(II) metal ions bridged by the pheno...
Preprint
div>The influence of the halogen substituent on crystal packing and redox properties is investigated in a series of heteroleptic complexes [Fe(qsal-X)(dipic)]MeOH (qsal-X = 4-halogen-2-[(8-quinolylimino)methyl]phenolate; dipic = 2,6-pyridinedicarboxylate; X = F 1, Cl 2, Br 3 and I 4). Compounds 1 and 2 exhibit triclinic symmetry (P1̅), whereas 3...
Article
Metal thiocyanates, such as copper(I) thiocyanate (CuSCN) and tin(II) thiocyanate [Sn(SCN)2], are emerging as novel semiconductors for electronic applications, and while other thiocyanate coordination polymers are known, their electronic structures and properties have not been investigated. In this work, we employed density functional theory (DFT)...
Cover Page
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Visual representation of switching of a molecular magnet for use in molecular electronics.
Article
Full-text available
A series of Fe(II) complexes (1–4) and Fe(III) complexes (5–8) from Fe(II)/(III) chloride and N-(8-quinolyl)-X-salicylaldimine Schiff base ligands (Hqsal-X2/X: X = Br, Cl) were successfully synthesized and characterized by spectroscopic (FT-IR, 1H-NMR), mass spectrometry, thermogravimetric analysis (TGA), and single crystal X-ray crystallographic t...
Article
The influence of the halogen substituent on crystal packing and redox properties is investigated in a series of heteroleptic complexes [Fe(qsal-X)(dipic)]·MeOH (qsal-X = 4-halogen-2-[(8-quinolylimino)methyl]phenolate; dipic = 2,6-pyridinedicarboxylate; X = F...
Article
Highly water-soluble fluorescent polyaromatic-based imidazolium compounds capable of detecting a wide-range of nitroaromatics, e.g., nitrophenols and picric acid in aqueous solution with fully quenched fluorescence are reported. The two probes contained an anthracene and pyrene group with the increased size and angularity of the pyrene ring in pyre...
Article
A family of iron(III) spin crossover complexes with different counteranions, [Fe(qsal-F)2]A (qsal-F = 4-fluoro-2-[(8-quinolylimino)-methyl]phenolate; A = PF6− 1, OTf− 2, NO3− 3, ClO4− 4, BF4− 5, or NCS− 6) have been prepared. All compounds are isostructural and crystallize (triclinic P1̅ space group) with two independent iron(III) centers (Fe1 and...
Article
The structural changes that occur in the strongly hysteretic spin crossover complex, [Fe(qsal-I)2]NTf2 1 have determined for the full width of the hysteresis. In the cooling mode, structural changes are abrupt while those in the warming mode are more gradual mirroring the magnetic profile of 1. The anion conformational change previously observed in...
Article
Full-text available
Copper(I) thiocyanate (CuSCN) is rising to prominence as a hole‐transporting semiconductor in various opto/electronic applications. Its unique combination of good hole mobility, high optical transparency, and solution‐processability renders it a promising hole‐transport layer for solar cells and p‐type channel in thin‐film transistors. CuSCN is typ...
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In article number 2002355, Pichaya Pattanasattayavong and co‐workers demonstrate how the coordination of diethyl sulfide solvent molecules influences copper(I) thiocyanate nanoscale crystallites. A simple antisolvent treatment improves the crystallinity and film uniformity, leading to a fivefold increase in the hole mobility, presenting an effectiv...
Article
Two conformational polymorphs of (N,N-dibutyldithiocarbamato-2 S,S')[tris(3,5-diphenylpyrazol-1-yl-N2)hydroborato]cobalt(II), [Co(C45H34BN6)(C9H18NS2)] or [Tp Ph2Co(S2CNBu2)], 1, are accessible by recrystallization from dichloromethane-methanol to give orthorhombic polymorph 1a, while slow evaporation from acetonitrile produces triclinic polymorph...
Article
A facile synthesis of decatosylate pillar[5]arene 1 is reported in excellent yield (>70%). The high yield is attributed to a self-template effect of the pendant tosylate arms. The X-ray crystal...
Article
To make electrochemical water splitting to produce hydrogen realistic, earth-abundant and low-cost electrocatalysts need to be developed. In this work, we demonstrate a facile strategy to synthesize decorated molybdenum oxide (MoO2) nanoparticles on graphene oxide (GO) layers. With GO sheets, hollow spheres of MoO2-G are formed. Incorporation of th...
Article
Three iron(III) complexes, [Fe(qnal)2]Y (qnal = 1‐[(8‐quinolinylimino)methyl]‐2‐naphthalenolate; Y = NO31, BPh4⋅CH2Cl2 2, NCS 3) have been prepared to explore anion effects in spin crossover systems. Structural studies on 2 reveal supramolecular chains formed by π‐π and C‐H⋅⋅⋅π interactions between the [Fe(qnal)2]+ cations. Magnetic susceptibility...
Article
Five new compounds, iranginins A-E (1-5), together with sixteen known compounds were isolated from the insect pathogenic fungus Ophiocordyceps irangiensis BCC 2728. The structures and the absolute configurations of the new compounds were established by spectroscopic analyses, the application of modified Mosher's method (for 2), ECD calculation (for...
Article
Copper(I) thiocyanate (CuSCN) is a promising semiconductor with an expansive range of applications already demonstrated. Belonging to the group of coordination polymers, its structure can be easily modified, for example via ligand (L) coordination. In this work, we have analyzed in detail the crystal structures of 26 CuSCN-L complexes that exhibit...
Article
Two iron(III) spin crossover complexes, [Fe(qsal-X)2]OTs·nH2O, (Br 1·H2O; I, 2·2H2O or non-solvated 1, 2) have been prepared and fully characterized. Structural studies of 1·H2O and 2·2H2O reveal the presence of 1D π-π chains linking the Fe(III) centres and a strong X···O halogen bond. In both complexes the 1D π-π chains are angled relative to each...
Article
Molecular magnetic switches are expected to form the functional components of future nanodevices. Herein we combine detailed (photo‐) crystallography and magnetic studies to reveal the unusual switching properties of an iron(III) complex, between low (LS) and high (HS) spin states. On cooling, it exhibits a partial thermal conversion associated wit...
Article
Full-text available
A series of Fe(II) complexes, fac-[Fe(4-ima-Bp) 3 ](Y) 2 ·sol (Y = ClO 4 ; sol = 3EtOH 1, 3MeOH 2; Y= BF 4 ; sol = EtOH·4H 2 O 3, 4H 2 O 4 and 3.5MeCN 5) have been prepared and structurally and magnetically characterized. The low temperature structures of 1, 2 and 5 have been determined by X-ray crystallography with LS Fe(II) centres found in all c...
Article
Semiconductors based on tin(II) show promising hole-transport characteristics due to the 5s electrons that form the valence band. In this paper, we report the synthesis and comprehensive characterization of tin(II) thiocyanate [Sn(NCS)2] and identify it as a novel transparent coordination polymer semiconductor. The single crystal X-ray analysis rev...
Article
A series of iron(III) complexes [Fe(naphEen)2]halide·sol (naphEen = 1-{[2-(ethylamino)-ethylimino]methyl}-2-naphtholate; X = F, sol = 0.5CH2Cl2·H2O 1; sol = H2O, X = Cl, 2 and X = Br 3) and [Fe(naphEen)2]I 4 has been prepared. The UV-Vis spectra reveal clear differences for 1 which DFT/TDDFT calculations suggest are due to an equilibrium between [F...
Article
The use of natural reagents from plant extracts for chemical analysis is one approach in the development of green analytical chemistry methodology. In this work, a natural reagent extracted from Phyllanthus emblica Linn. has been applied for the determination of iron(III) using a simple flow injection spectrophotometric method. The method was based...
Article
A unique self-assembled mixed-valence FeII-FeIII tetranuclear star has been comprehensively characterised showing a large magnetic anisotropy at the peripheral FeII centres, ferromagnetic coupling between the iron centres and field-induced SMM...
Article
Reaction of a rigid tridentate ligand o-[(1H-imidazol-2-yl)methylideneamino]phenol (2-H2imap) with Co(ClO4)2 in the presence of NaN3, or Co(NO3)2 without a base yields [CoII(2-Himap)2] 1 and [CoIII(2-Himap)2]NO3·MeOH 2, respectively. Both complexes exhibit a mer-octahedral geometry with the cobalt centre being distorted along an octahedral-trigonal...
Article
Mixed ligand complexes [Fe(qsal-Cl)(qsal-Br)]Ysol (Y = NCS, sol = MeOH 1; PF6 2; BPh4, sol = 2CH2Cl2 3; OTf, sol = 0.5MeOH 4) have been synthesized. X-ray crystallographic studies of 1, 2 and 4 at 123 K reveal that the Fe(III) centres are low spin in all cases. In 2 there are two independent Fe(III) centres in the asymmetric unit cell. The structu...
Article
A new air stable FeIII spin crossover (SCO) complex has been synthesized. The compound undergoes abrupt SCO near room temperature with T1/2 (↓) = 244 K and T1/2 (↑) =...
Article
Full-text available
Solvent effects in a series of Fe(III) spin crossover (SCO) complexes [Fe(qsal-I)2]OTf[middle dot]sol (sol = MeOH 1, EtOH 2, n-PrOH 3, i-PrOH 4, acetone 5 and MeCN 6) are explored. SCO is abrupt in 1 (following MeOH loss) and 2, gradual for 3 (T1/2 = 199 K) and 4 (T1/2 = 251 K) and incomplete, even up to 350 K, for 5 and 6. In [Fe(qsal-I)2]OTf SCO...
Article
Full-text available
A detailed investigation of the accuracy of different quantum mechanical methods for the study of iron(III) spin crossover complexes is presented. The energy spin state gap between the high and low spin states; ΔE(HS-LS) of nine iron(III) quinolylsalicylaldiminate complexes were calculated with nine different DFT functionals, then compared. DFT fun...
Article
Abstract Spin crossover compounds are a diverse class of switchable materials with applications ranging from data storage devices to sensors. Iron(III) spin crossover complexes have received renewed attention over the last 10 years with an increasing number of abrupt and hysteretic spin crossover systems discovered. This review provides a detailed...
Article
The new ligand Hqsal-4-OMe was synthesized, and four iron(III) complexes, [Fe(qsal-4-OMe)2]Y·CH2Cl2 [Hqsal-4-OMe = 4-methoxy-N-(8-quinolyl)salicylaldimine; Y = ClO4 (1), NO3 (2)] and [Fe(qsal-4-OMe)2]Y (Y = PF6 (3), OTf (4)] as well as the isomer [Fe(qsal-5-OMe)2]PF6·CH2Cl2 (5), were prepared. UV/Vis spectroscopic studies indicated that the complex...
Article
Two new MnII/III redox pairs, [Mn(qsal-Cl)2]0/+10/+ and [Mn(qsal-Br)2]0/+20/+ have been synthesized employing the tridentate Schiff base ligands, 5-X–N-(8-quinolyl)salicylaldimine (Hqsal-X, X = Cl and Br). The neutral MnII complexes 1 and 2 were prepared from MnCl2 and Hqsal-Cl and Hqsal-Br while oxidation of 1 or 2 with AgOTf yields the cationic M...
Article
Full-text available
Three novel copper hydrotris(3,5-diphenylpyrazolyl)borate (TpPh2) dithiocarbamate complexes, [TpPh2Cu(dtc)] (dtc = S2CNEt2 1, S2CNBz2 2 and S2CN(CH2)4 3) have been prepared in a simple one pot reaction by sequential addition of KTpPh2 and Na(dtc) to CuCl2[middle dot]2H2O. IR, UV-Vis and ESR spectroscopic studies suggest a mostly [small kappa]3 coor...
Article
Full-text available
[Fe(qsal-Br)2]NO3·2MeOH is reported which undergoes abrupt two step symmetry breaking spin crossover, T½(1st step) = 136 K and T½(2nd step) = 232 K with a hysteresis of 16 K and 5 K, respectively and an unprecedented [HS-LS] plateau of 96 K
Article
Full-text available
The reaction of Fe(NCS)3 prepared in situ in MeOH with Hqsal-X (Hqsal-X = 5-X-N-quinolylsalicylaldimine) in CH2Cl2 yields the FeIII complexes, [Fe(qsal-X)2]NCS·solvent (X = F 1; X = Cl, 2, Br, 3 solvent = MeOH; X = I, solvent = 0.25CH2Cl2·0.5MeOH 4) in moderate to good yields. IR spectroscopy confirms that NCS- acts as a counteranion only and that...
Article
Full-text available
A new sterically bulky Schiff base ligand,N-(8-quinolyl)-5-tert-butylsalicylaldimine (Hqsal-5-tBu) has been prepared and a series of FeIII complexes, [Fe(qsal-5-tBu)2]Y (Y¼Cl 1, ClO4 2, NO3 3, BF4 4) utilising this ligand are reported and fully characterised. UV-vis spectroscopic and electrochemical studies indicate that 1–4 are high spin (HS) in s...
Article
Full-text available
The sonochemical reaction between Zn(NO3)2 and hexamethylenetetramine (HMT) resulted in different products depending on amounts of Zn(II) cations in the aqueous solution. Crystalline phase pure ZnO nanoparticles were obtained by using 0.05 M Zn(NO3)2-HMT. This single phase was formed by low power sonication for 20 min in an ultrasonic bath at ambie...
Article
Full-text available
The reaction of H2salpn (H2salpn = N,N′-bis(salicylidene)-1,3-propanediamine) with Fe(ClO4)3 in a ratio of 1 : 1 and 3 : 2, leads to dark red crystals of the solvatomorphs [(salpn)Fe(μ2-salpn)Fe(salpn)]·0.5MeOH (1) and [(salpn)Fe(μ2-salpn)Fe(salpn)]·MeOH (2), respectively. X-Ray crystallographic studies reveal a slightly distorted octahedral geomet...
Article
A new cobalt(II) coordination polymer containing a flexible dinitrile bridging ligand [Co(ADN)3][FeCl4]2 (1) was synthesized at room temperature from the 1:2:3 reaction of CoCl2, FeCl3, and adiponitrile (ADN) in CH3NO2. The compound was characterized by spectroscopic methods and the structure determined by single crystal X-ray diffraction. The stru...
Article
Full-text available
The first Fe(iii) qsal-X complex exhibiting abrupt complete spin crossover at 228 K with a hysteresis of 8 K, [Fe(qsal-I)2]OTf is reported. Structural studies of the MeOH solvate in the LS and HS state and at the spin transition are described.
Article
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Zinc oxide nanoparticles were synthesized using a commercial ultrasonic homogenizer in a sonochemical reaction between 0.05 M zinc nitrate and hexamethylenetetramine. The solutions in glass vessels of varying shapes i.e. cube, cylinder and sphere were sonicated with a 45 W 20 kHz ultrasonic pulse for 60 min under ambient conditions. The crystalline...
Article
A series of halogen substituted 5-X-N-(8-quinolyl)salicylaldimines (HqsalX, X = F 1, Cl 2, Br 3 and I 4) have been prepared, characterized and the crystal structures of all four are reported. The compounds form stacks, in most cases held together either by π–π or lone pair(N)–π interactions. All compounds exhibit an intramolecular OH⋯N hydrogen bon...
Article
A series of FeIII complexes, [Fe(qsal-5-OMe)2]Y [Y = BF4 (1), PF6 (2), NCS (3), BPh4 (4)], have been prepared and structurally and magnetically characterized. The low-temperature structures of 1 and 3 as solvent adducts were determined by X-ray crystallography with LS FeIII centres found in both cases. π–π and C–H···π interactions between the catio...
Article
A new synthesis of (8-quinolyl)-5-methoxysalicylaldimine (Hqsal-5-OMe) is reported and its crystal structure is presented. Two Fe(III) complexes, [Fe(qsal-5-OMe)(2) ]Cl⋅solvent (solvent=2 MeOH⋅0.5 H(2) O (1) and MeCN⋅H(2) O (2)) have been prepared and their structural, electronic and magnetic properties studied. [Fe(qsal-5-OMe)(2) ] Cl⋅2 MeOH⋅0.5 H...
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In the title polymer, [Cd(C(5)H(3)N(2)O(2))(NO(3))(H(2)O)](n), the Cd(II) atom is seven-coordinate in a distorted capped octa-hedral geometry by two N atoms of two different pyrimidine dicarboxyl-ate (pmc) ligands, three O atoms from three separate pmc ligands, and two O atoms of disordered nitrate anions or water mol-ecules. The Cd(II) atoms are b...
Article
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The synthesis of trans-[Ni(dbm)2(RN=C(Me)NHR)2] (dbm = 1,3-diphenylpropanedionate; R = phenyl, p-tolyl, 3,5-dimethylphenyl, 3,5-dichlorophenyl) has been achieved by reaction of [Ni(dbm)2(H2O)2] with two equivalents of the amidine ligands, RN=C(Me)NHR. X-ray crystallographic studies reveal that trans-[Ni(dbm)2(RN=C(Me)NHR)2] (R = 3,5-dimethylphenyl)...
Article
Full-text available
Cobalt ferrite (CoFe2O4) was synthesized using sol-gel techniques from cobalt nitrate: iron nitrate: polyvinyl alcohol (PVA) gel in a ratio of 1:2:12. Variations in the amount of PVA in water (5 %, 10 % and 15 %) influenced the crystallite size and phases of the ferrite products, which in turn controlled their magnetic properties. X-ray diffraction...