Melanie Pilkington

Melanie Pilkington
Brock University · Department of Chemistry

BSc and Ph.D (University of Kent at Canterbury) FRSC

About

115
Publications
22,782
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Introduction
www.mpilkington.net My research group is exploiting Schiff-base and crown ether macrocycles for the self-assembly of magnetic chains, single ion magnets (SIMs) and MRI contrast agents. We are preparing MOFs from flexible bipy ligands and synthesiszing new TTF donors and implementing these into thin films as the electroactive components of OFET devices.
Additional affiliations
October 1997 - March 1999
University of Cambridge
Position
  • PostDoc Position
January 1994 - present
Brock University
Position
  • Professor (Associate)

Publications

Publications (115)
Article
Full-text available
Two mononuclear DyIII crown ether complexes [Dy(15C5)(H2O)4](ClO4)3∙(15C5)∙H2O (1) and [Dy(12C4)(H2O)5](ClO4)3∙H2O (2) have been prepared and characterized. X-ray diffraction studies show that both compounds crystallize as half sandwich type structures with muffin and pseudo-capped square anti-prismatic geometries respectively. Despite the comparab...
Article
Full-text available
A new macrocyclic complex DyCl3(LN5)·4H2O () has been prepared in which the Dy(iii) ion is equatorially bound by an N5-donor macrocycle (LN5). Ac susceptibility data reveal slow relaxation of the magnetisation in zero field below 15 K with a distribution of relaxation rates.
Article
The coordination chemistry of the bis-salicyl-appended Schiff-base ligand L8 with Lewis acidic metal ions affords the mononuclear complex [Sn(L9)Cl4] (1) and two paramagnetic dimers [Cu(L9)(sal)]2(ClO4)2, (2) and [Mn(L9)Cl2(EtOH)]2] (3). The X-ray crystal structures of 1-3 reveal a propensity for L8 to undergo metal catalyzed hydrolysis and cycliza...
Article
The first supramolecular cage formed by three benzo-15-crown-5 macrocycles encapsulating a [Dy(OH2)8]3+ guest cation is reported, with the Dy(III) centre exhibiting local pseudo square antiprismatic D4d symmetry. The anisotropy barrier extracted from ac susceptibility studies, emission spectroscopy and ab initio calculations reveals that the second...
Article
Full-text available
The α-and β-phases of the thiazyl radical p-NCC6F4CNSSN• (1) can be selectively prepared by careful control of the sublimation conditions with the α-phase crystallizing preferentially when the substrate temperature is maintained below -10 °C whereas the β-phase is isolated when maintaining the substrate temperature at/above ambient temperature. DSC...
Article
An N‐propargyl pyrroloimidazolone with syn stereochemistry derived from L‐proline serves as a starting material for the diastereoselective synthesis (>95:5 dr) of propargyl alkynes or allenamides by direct quench of its lithiated intermediate with alkylating agents or aldehydes/ketones, respectively. Use of the epimeric anti pyrroloimidazolone star...
Article
A novel unsymmetrical guanidine‐cyclopropenium proton sponge DAGUN and the related BF2‐chelate DAGBO are reported. Insight into the structural, electronic, bonding and photophysical properties of these two molecules are presented. Joint experimental and theoretical studies reveal the protonated form of DAGUN possesses an intramolecular N‧‧‧H‐N hydr...
Article
Although Spiro-MeOTAD 1 is a superior hole–transporting material (HTM) commonly employed in Perovskite Solar Cells (PSCs), its high cost is one of the major issues holding back commercialization, which has not been resolved to-date. In this article we introduce a new HTM comprising of a cyclic spiro-backbone appended with four diphenylimidazole sub...
Article
The replacement of inorganic semiconductors with molecule-based compounds for applications in current-to-light conversion has led to a significant increase in interdisciplinary collaborations worldwide, affording new improved organic-light emitting diodes (OLEDs) ripe for commercial applications, as well as light-emitting electrochemical cells (LEC...
Cover Page
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Homometallic {NiII4} cubane-like clusters with a rare chiral core have been prepared via the employment of enantiomerically pure 2-(1-hydroxyethyl)pyridine (Hmpm). Comparison with the achiral cubanes derived from the related 2-pyridinemethanol (Hpym) ligand reveals drastic structural changes as a consequence of the transfer of chirality from the li...
Article
The synthesis of a new {Ni8} cluster bearing tetrazolate- and azido-bridging ligands, and supported by chelating α-methyl-2-pyridine-methanol (mpmH) groups, is described herein. The reported compound has a unique trapezoidal prismatic topology, resulting from an unexpected in-situ click reaction between the MeCN reaction solvent and the N3- ions un...
Article
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Homometallic {N iII4 } cubane-like clusters with a rare chiral core have been prepared via the employment of enantiomerically pure 2-(1-hydroxyethyl)pyridine (Hmpm). Comparison with the achiral cubanes derived from the related 2-pyridinemethanol...
Article
Two mixed-valence cobalt complexes, [CoIICoIII2(mpm)6](ClO4)2 (1) and [CoII2CoIII2(μ3-OMe)2(μ-mpm)4(NO3)4] (2), where mpm is the deprotonated form of R or S α-methyl-2-pyridinemethanol, have been structurally and magnetically characterized. Both complexes crystallize in chiral space groups, where 1 is a trinuclear compound with a linear Co(III)–Co(...
Article
The unprecedented synthesis, single-crystal X-ray structure and first catalytic application of a dicarbene-Ag(I) complex [Ag(BAC)2][CO2CF3] (BAC = bis(diisopropyl)aminocyclopropenylidene) is reported. This novel complex provides a versatile catalytic platform for selective aerobic oxidation of benzylic alcohols to aldehyde or ketone products in hig...
Article
The fluorescent 9′-anthracenyl-functionalized dithiadiazolyl radical (3) exhibits four structurally determined crystalline phases, all of which are monomeric in the solid-state. Polymorph 3α (monoclinic P21/c, Z’ = 2) is isolated when the radical is condensed onto a cold substrate (enthalpically favored polymorph) whereas 3β (orthorhombic P212121,...
Article
The pyrimidinyl hydrazone ligand O[dbnd]C{NHN[dbnd]C(Me)(pm)} 2 (pm = 2-pyrimidinyl) (L 3 H 2 ) has two potentially protic H atoms and multiple donor atoms. The reaction of L 3 H 2 with CuCl 2 ·2H 2 O yielded the tetranuclear complex [Cu 4 (L 3 H) 2 Cl 6 (CH 3 OH) 2 ] (1). Structural studies on 1 reveal the molecule is located about a crystallograp...
Article
An integral part of modern organocatalysis is the development and application of thiourea catalysts. Here, as part of our program aimed at developing cyclopropenium catalysts, the synthesis of a thiourea-cyclopropenium organocatalyst with both cationic H-bond donor and electrostatic character is reported. The utility of the aforementioned thiourea...
Article
Full-text available
Reaction of 2,6-dicyanopyridine with 2 equiv. of 2-(propylthio)benzenamine in the presence of lithium bis(trimethylsilyl)amide, followed by ring-closing oxidation with N-chlorosuccinimide affords the novel tridentate ligand, 2,6-bis-(1’,2’,4’-benzothiadiazinyl) pyridine (LH2). Electrochemical studies on the free ligand LH2 reveal a single well-defi...
Article
A versatile synthetic methodology to access the first family of chiral verdazyl N,Nʹ-chelate ligands is described and exemplified by N,Nʹ-dimethyl-, N,Nʹ-di-isopropyl- and N,Nʹ-diphenyl oxoverdazyls bearing two isomers of the pinene-pyridine functional group. Their physical properties were probed by X-band EPR spectroscopy, cyclic voltammetry and D...
Article
The synthesis and coordination chemistry of a new series of open chain diazine base ligands (L3aH2, L3bH2, and L3cH2 ) is reported. The ligands comprise a central disubstituted bipyridine moiety with two bridging alkoxide oxygen donors, together with diazine and pyridine terminal groups strategically located to coordinate three metal centres. React...
Article
The first {Mn31} cluster (1) has been prepared from carboxylate ions and the chelating/bridging ligand α-methyl-2-pyridine-methanol. Compound 1 possesses a unique nano-sized structural topology with one of the largest energy barriers reported to-date for high-nuclearity 3d-metal clusters. Single-crystal magnetic hysteresis studies reveal the presen...
Article
Two complexes comprising 9-coordinate capped square antiprismatic [Ln(NO3)3(OH2)2(MeOH)] units [Ln(III) = Dy 6; Tb 7] are reported in which the metal complexes are hydrogen-bonded to 15C5 (15-crown-5) macrocycles to form supramolecular chains, {[Ln(NO3)3(OH2)2(MeOH)]·(15C5)}n. Alternating current magnetic susceptibility measurements supported by ab...
Article
The introduction of the Schiff base ligand N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2) in 4f-metal chemistry has afforded a new dinuclear complex, [Dy2(NO3)4(sacbH)2(H2O)2(MeCN)2] (1), with the metal ions adopting a rare spherical tricapped trigonal prismatic coordination geometry. The deprotonated phenoxido O atoms of the organic chelate...
Article
The synthesis and coordination chemistry of a new open-chain diazine ligand (L4H2) containing bipyridine, oxime and hydrazone functionalities is reported. Reaction of L4H2 with CuCl2·2H2O affords the mononuclear complex [Cu(L4H2)Cl2] (1) in which the ligand acts as a neutral tridentate N,N',N'' donor, whereas treatment with a large excess of CuCl2·...
Article
A major challenge in designing artificial photosynthetic systems is to find a suitable mimic of the highly oxidizing photoactive species P680 in photosystem II. Highpotential phosphorus(V) porphyrins have many attractive properties for such a mimic but have not been widely studied. Here, we report the synthesis and photophysical characterization of...
Article
Full-text available
The first supramolecular cage formed by three benzo-15-crown-5 macrocycles encapsulating a [Dy(OH2)¬8]3+ guest cation is reported, with the Dy(III) centre exhibiting local pseudo square antiprismatic D4d symmetry. The anisotropy barrier extracted from ac susceptibility studies, emission spectroscopy and ab initio calculations reveals that the secon...
Article
Three macrocyclic complexes DyCl3(N5)×4H2O (4), DyCl3(N3O2)×6H2O (5) and DyCl3(db-N3O3)×6H2O (6) (where db = dibenzo) have been prepared in which the DyIII ion is equatorially bound by the Schiff-base macrocycles conferring a pseudo- D5h geometry on complexes 4 and 5 that is supported by TGA, molar conductance measurements, as well as Raman and far...
Article
A new tetrathiafulvalene (TTF) donor covalently appended with a 1,5-diisopropylverdazyl radical through a cross-conjugated pyridyl linker (3) has been prepared and characterised. Reaction of 3 with tetracyanoquinonedimethane (TCNQ) afforded the 2:1 charge-transfer complex (3)2 ⋅TCNQ (4), in which the IR and structural data are consistent with 0.25...
Article
Full-text available
The preparation and characterization of a novel chiral macrocycle S,S-[FeII(PhCH2OCH2)2(N3O2)(CN)2] (4) is presented. Magnetic susceptibility studies reveal that this complex undergoes a gradual spin crossover in the solid state with no thermal hysteresis. Variable temperature X-ray diffraction studies on single crystals of 4 reveal that at 150 K t...
Article
Full-text available
a The distance dependence of sequential electron transfer has been studied in six, vertical, linear supramo-lecular triads, (TTF-Ph n-py → AlPor-Ph m-C 60 , n = 0, 1 and m = 1, 2, 3), constructed using tetrathiafulva-lene (TTF), aluminum(III) porphyrin (AlPor) and fullerene (C 60) entities. The C 60 and TTF units are bound to the Al center on oppos...
Article
Full-text available
Three new unsymmetrical hydroxyl-functionalized donors H1–H3 closely related to hydroxymethyl-BEDT-TTF have been synthesised and characterised. Cyclic voltammetry studies showed that the compounds exhibit reversible two one-electron redox processes typical for BEDT-TTF derivatives. X-ray diffraction studies of H1 and H2 reveal π-stacking interactio...
Article
Two classes of complexes of 15-membered Schiff base macrocycles with a pentadentate (N3X2) cavity (where X = O, N, S) prepared via a metal templated condensation reaction between suitably functionalized 2,6-diacetylpyridine and polyamines are surveyed. The structures and properties of transition metal and lanthanide complexes are presented. Particu...
Article
Full-text available
The Schiff-base condensation of the R,R-(+)-diamine (2a) with 2,6-diacetyl pyridine in the presence of FeII affords the macrocyclic complex [Fe(dpN3O2)(CN)2] (4a) (dp = diphenyl) with ligand centred chirality comprising of a 1:1 mixture of LS 6- and HS 7-coordinate FeII centres. Variable temperature magnetic susceptibility and Mössbauer studies rev...
Article
Full-text available
Cu2+-promoted aerial oxidation of a series of benzothiadiazines (1) under ambient conditions affords the first structurally characterised examples of thiadiazine Soxides (2) The isolation of the homoleptic CuII 10 3-(2ʹ- pyridyl)benzothiadiazide-S-oxide complex provides insight into the reaction mechanism.
Article
Full-text available
The use of a previously unexplored Schiff-base ligand in Ni(II) carboxylate chemistry has afforded a Ni26 cluster with a record nuclearity that crystallizes with a unique ‘rabbit-face’-like topology, and a Ni18 compound that adopts an unusual ‘molecular chain’ structure.
Article
Full-text available
A new ligand, 3,3′-di(pyrazinamoyl)-2,2′-bipyridine, L3H2 has been prepared and comprises of distinct binding domains capable of facilitating the formation of coordination polymers. Reaction of L3H2 with [Cu2(OAc)4(H2O)2] in the presence of Et3N·HCl affords the complex {[Cu6(L3)2(Cl)2(OAc)6]·2H2O·2MeOH}n (1) in which the [L3]2- anion binds two uniq...
Article
Full-text available
The use of a previously unexplored Schiff-base ligand in Ni(II) carboxylate chemistry has afforded a Ni26 cluster with a record nuclearity that crystallizes with a unique ‘rabbit-face’-like topology, and a Ni18 compound that adopts an unusual ‘molecular chain’ structure.
Article
Full-text available
Three new unsymmetrical thiophene-functionalized bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF) donors (1- 3) have been synthesized, characterised and examined as semiconducting materials for organic field-effect transistor (OFET) devices. The X-ray crystal structures of (1) and (2) reveal both neutral donors pack as dimers with lateral S⋅⋅⋅S co...
Article
Full-text available
Reaction of the novel ligand 3-(2′-pyridyl)-benzo-1,2,4-thiadiazine (L) with the transition metal chloride salts MCl2•xH2O (MII = Mn, Fe, Co, Cu and Zn) in a 2:1 mole ratio afforded the mononuclear octahedral (high spin) complexes L2MCl2 (1a – 1e respectively) in which L binds in a chelate fashion via N(2) and the pyridyl N atoms. In the case of Cu...
Article
Full-text available
A new Schiff base complex [Ni(H2L1)(NO3)](NO3) (1) (H2L1 = 3-[N,N′-bis-2-(5-bromo-3-(morpholinomethyl) salicylideneamino) ethyl amine]) was synthesized from reaction of the ditopic ligand H2L1 with Ni(NO3)2 in anhydrous MeOH. Complex 1 is stable in the solid state, but prone to hydrolysis. Recrystallization of 1 from wet MeOH led to the isolation o...
Article
The syntheses, structures, and magnetic properties of three new coordination complexes, tetranuclear [Zn2L3(OAc)-(OMe)]2·3MeOH·H2O (3), trinuclear [Ni3(L3)3]·6H2O (4), and a 1-D chain {[Cu2L3(OAc)2]2·H2O}n (6), of a polydentate, doubly deprotonated, 3,3′-disubstituted bipyridine ligand [L3]2‑ are reported. The X-ray crystal structures demonstrate t...
Article
Full-text available
4-([2,2′-Bi(1,3-dithiolylidene)]-4-yl)benzonitrile undergoes a [2 + 2] photocycloaddition reaction upon irradiation with polychromatic light, an unusual single-crystal-to-single-crystal transformation for a TTF derivative. In contrast, the closely related pyridylnitrile derivative adopts a different packing motif and is stable to light under the sa...
Article
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A unique octanuclear copper(ii) cluster with a saddle-shaped structural topology has been prepared from a large, flexible polydentate ligand comprising a 4,4'-bipyridine linker bearing four pendant pyrazolate heterocycles.
Article
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The reactivity of a Schiff-base bis-imine ligand 3 is probed by X-ray diffraction studies. Its susceptibility to hydrolysis, oxidation and nucleophilic addition reactions is demonstrated by the isolation of the methanol adduct 4 and two diazapene heterocycles 5 and 6. This reactivity is also reflected in the molecular structures of two coordination...
Article
Full-text available
The first application of 1-methyl-1H-pyrrole-2-carbaldehyde oxime as a ligand for the coordination of paramagnetic transition metal ions has afforded a new {Mn(III)25} barrel-like cluster linked via Na(+) cations into a 1D polymeric topology that exhibits single-molecule magnetic behaviour.
Article
Full-text available
The targeted replacement of acetate groups in the optically inactive [Mn(III)3O(O2CMe)3(mpko)3](ClO4) single-molecule magnet with their naphthalene, anthracene, and pyrene fluorescent analogues has led to three new emissive SMMs with enhanced photoluminescence properties and potential applications in the field of molecular electronics.
Article
The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are r...
Article
Full-text available
The triptycene skeleton has been used to measure (1,5) interactions between aldehyde groups, placed at both sp3 centres, and hydroxy or methoxy groups, placed at the respective ortho position on a benzene ring; HO•••CHO interactions of 2.621-2.624 Å and MeO•••CHO interactions of 2.528-2.584 Å were observed with the O•••C vector making angles of 105...
Article
Full-text available
The triptycene skeleton has been used to measure (1,5) interactions between aldehyde groups, placed at both sp3 centres, and hydroxy or methoxy groups, placed at the respective ortho position on a benzene ring; HOCHO interactions of 2.621-2.624 A and MeOCHO interactions of 2.528-2.584 A were observed with the OC vector making angles of 105.3-133.7[...
Article
Six new enantiopure chiral organosulfur donors, with structures related to BEDT-TTF, have been synthesised for use in the preparation of organic metals, starting either by double nucleophilic substitutions on the bis-mesylate of 2R,4R-pentane-2,4-diol or by a cycloaddition with subsequent elimination of acetic acid on the enol acetate of (+)-nopino...
Article
The chiral hydroxymethyl-substituted derivative of bis(ethylenedithio)tetrathiafulvalene, has been synthesized from D-mannitol via the cyclic sulfate ester of (2R)-3-(2-methoxyethoxymethoxy)propane-1,2-diol. The latter substance slowly decomposes at 45°C and should be used when freshly prepared. In contrast, the cyclic sulfate ester of (2R)-3-benzo...
Article
The spin-spin interactions in a complex consisting of a metalloporphyrin with a verdazyl radical attached at one of the beta positions of the porphyrin ring are investigated. The X-ray crystal structure of the copper porphyrin complex shows that the plane of the verdazyl moiety is oriented such that it is nearly perpendicular to the plane of the po...
Article
A series of PdCl2, PtCl2, and Ir(COD)BArF complexes bearing a rare class of racemic bidentate 2-phosphino-1-dimethylaminoferrocene ligands were prepared and characterized by NMR spectroscopy and X-ray crystallography. The new complexes displayed a structural trend relating a decrease in heteroatom-metal bond length with an increase in ligand bite a...