Synthesis and Characterisation of Phosphino-Aryloxide Rare Earth Complexes.

A series of homoleptic rare earth (RE) complexes bearing phosphino-aryloxide ligands (, ) has been prepared. The complexes have been characterised using multinuclear NMR and IR spectroscopy, X-ray crystallography and elemental analysis. Structural characterisation highlighted the different RE-P interactions as a result of differing Lewis acidity and ionic size across the series, hinting at the possibility of FLP-type activity.

Heavy Alkaline Earth Cyclic (Alkyl)(Amino)Carbene Complexes Supported by Aryl-Silyl Amides.

A series of 8 trigonal planar, heavy alkaline earth (AE = Ca-Ba) metal complexes containing cyclic (alkyl)(amino)carbene (CAAC) ligands were prepared from AE bis(amide) species. Complexation can be achieved by first generating the free carbene or by direct addition of the free carbene, with the former route giving rise to unexpected mixed-amide AE complexes. The frontier molecular orbitals of the highly equatorial, 3-coordinate AE-CAAC species were also probed computationally, revealing the lowest unoccupied molecular orbital (LUMO) consisting predominantly of the π* system located on the carbene ligand.

Ligand Effects on the Spin Relaxation Dynamics and Coherent Manipulation of Organometallic La(II) Potential Quits.

We present pulsed electron paramagnetic resonance (EPR) studies on three La(II) complexes, [K(2.2.2-cryptand)][La(Cp')] (), [K(2.

B(CF)-Catalyzed Dehydrogenation of Pyrrolidines to Form Pyrroles.

Pyrroles are important -heterocycles found in medicines and materials. The formation of pyrroles from widely accessible pyrrolidines is a potentially attractive strategy but is an underdeveloped approach due to the sensitivity of pyrroles to the oxidative conditions required to achieve such a transformation. Herein, we report a catalytic approach that employs commercially available B(CF) in an operationally simple procedure that allows pyrrolidines to serve as direct synthons for pyrroles.

An immunogenic anti-cancer stem cell bi-nuclear copper(II)-flufenamic acid complex.

An asymmetric bi-nuclear copper(II) complex with both cytotoxic and immunogenic activity towards breast cancer stem cells (CSCs) is reported. The bi-nuclear copper(II) complex comprises of two copper(II) centres bound to flufenamic acid and 3,4,7,8-tetramethyl-1,10-phenanthroline. The bi-nuclear copper(II) complex exhibits sub-micromolar potency towards breast CSCs grown in monolayers and three-dimensional cultures.

Metal-carbon bonding in early lanthanide substituted cyclopentadienyl complexes probed by pulsed EPR spectroscopy.

We examine lanthanide (Ln)-ligand bonding in a family of early Ln complexes [Ln(Cp)] (1-Ln, Ln = La, Ce, Nd, Sm; Cp = CHBu-1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin and relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.

The Anti-Breast Cancer Stem Cell Potency of Copper(I)-Non-Steroidal Anti-Inflammatory Drug Complexes.

Cancer stem cells (CSCs) are thought to be partly responsible for metastasis and cancer relapse. Currently, there are no effective therapeutic options that can remove CSCs at clinically safe doses. Here, we report the synthesis, characterisation, and anti-breast CSC properties of a series of copper(I) complexes, comprising of non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine ligands (-).

A Blueprint for the Stabilization of Sub-Valent Alkaline Earth Complexes.

The study of sub-valent Group 2 chemistry is a relatively new research field, being established in 2007 with the report of the first Mg(I) dimers. These species are stabilized by the formation of a Mg-Mg covalent bond; however, the extension of this chemistry to heavier alkaline earth (AE) metals has been frustrated by significant synthetic challenges, primarily associated with the instability of heavy AE-AE interactions. Here we present a new blueprint for the stabilization of heavy AE(I) complexes, based upon the reduction of AE(II) precursors with planar coordination geometries.

The Bulk Breast Cancer Cell and Breast Cancer Stem Cell Activity of Binuclear Copper(II)-Phenanthroline Complexes.

Mononuclear copper(II)-phenanthroline complexes have been widely investigated as anticancer agents whereas multinuclear copper(II)-phenanthroline complexes are underexplored. Here the synthesis and characterisation of two new binuclear copper(II)-phenanthroline complexes 1 and 2 is reported, comprising of 2,9-dimethyl-1,10-phenanthroline or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, terminal chloride ligands, and bridging chloride or hydroxide ligands. The binuclear copper(II) complex containing 2,9-dimethyl-1,10-phenanthroline 1 displays nanomolar toxicity towards bulk breast cancer cells and breast cancer stem cells (CSCs) grown in monolayers, >50-fold greater than cisplatin (an anticancer metallodrug) and salinomycin (a gold-standard anti-CSC agent).

Synthesis and characterization of two self-assembled [CuGd] and [CuDy] complexes exhibiting the magnetocaloric effect, slow relaxation of magnetization, and anticancer activity.

Two new paths for coordination driven self-assembly reactions under the binding support of 2-((1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (HL) have been discovered from the reactions of Cu(ClO)·6HO, NEt and GdCl/DyCl·6HO in MeOH/CHCl (2 : 1) medium. A similar synthetic protocol is useful to provide two different types of self-aggregated molecular clusters [CuGd(L)(HL)(μ-Cl)(μ-OH)(OH)]ClO·4HO (1) and [CuDy(L)(HL)(μ-Cl)(μ-OH)(ClO)(HO)](ClO)·2NHEtCl·21HO (2). The adopted reaction procedure established the importance of the HO and Cl ions in the mineral-like growth of the complexes, derived from solvents and metal ion salts.

Structural Investigation of Magnesium Complexes Supported by a Thiopyridyl Scorpionate Ligand.

Herein, we report the synthesis of a series of heteroleptic magnesium complexes stabilized with the scorpionate ligand tris(2-pyridylthio)methanide (Tptm). The compounds of the general formula [Mg(Tptm)(X)] (; X = Cl, Br, I) were obtained via protonolysis reaction between the proligand and selected Grignard reagents. Attempts to isolate the potassium derivative K(Tptm) lead to decomposition of Tptm and formation of the alkene (CHN-S)C=C(CHN-S), and this degradation was also modelled using DFT methods.

Synthesis, characterisation and reactivity of group 2 complexes with a thiopyridyl scorpionate ligand.

Herein we report the reactivity of the proligand tris(2-pyridylthio)methane (HTptm) with various Alkaline Earth (AE) reagents: (1) dialkylmagnesium reagents and (2) AE bis-amides (AE = Mg-Ba). Heteroleptic complexes of general formulae [Mg(Tptm)(R)] (R = Me, Bu; Tptm = {C(S-CHN)}) and [AE(Tptm)(N'')] (AE = Mg-Ba; N'' = {N(SiMe)}) were targeted from the reaction of HTptm with RMg or [AE(N'')]. Reaction of the proligand with dialkylmagnesium reagents led to formation of [{Mg(κ,,-C{Bu}{S-CHN})(μ-S-CHN)}] (1) and [{Mg(κ,,-C{Me}{S-CHN})(μ-OSiMe)}] (2) respectively, as a result of a novel transfer of an alkyl group onto the methanide carbon with concomitant C-S bond cleavage.

A bioinspired redox-modulating copper(II)-macrocyclic complex bearing non-steroidal anti-inflammatory drugs with anti-cancer stem cell activity.

Copper(II) coordination compounds have been investigated for their anticancer properties for decades, however, none have reached advanced human clinical trials. The poor translation of copper(II) complexes from studies to (pre)clinical studies can be attributed to their limited efficacy in animal models, which is largely associated with copper leaching and speciation (in biological fluids). Here we report a biologically stable copper(II) complex based on the active site of Type I Cu electron transport proteins.

Rare Earth Starting Materials and Methodologies for Synthetic Chemistry.

The number of rare earth (RE) starting materials used in synthesis is staggering, ranging from simple binary metal-halide salts to borohydrides and "designer reagents" such as alkyl and organoaluminate complexes. This review collates the most important starting materials used in RE synthetic chemistry, including essential information on their preparations and uses in modern synthetic methodologies. The review is divided by starting material category and supporting ligands (, metals as synthetic precursors, halides, borohydrides, nitrogen donors, oxygen donors, triflates, and organometallic reagents), and in each section relevant synthetic methodologies and applications are discussed.

Photoluminescence of Pentavalent Uranyl Amide Complexes.

Pentavalent uranyl species are crucial intermediates in transformations that play a key role for the nuclear industry and have recently been demonstrated to persist in reducing biotic and abiotic aqueous environments. However, due to the inherent instability of pentavalent uranyl, little is known about its electronic structure. Herein, we report the synthesis and characterization of a series of monomeric and dimeric, pentavalent uranyl amide complexes.

Synthesis and characterization of new Pd(ii) and Pt(ii) complexes with 3-substituted 1-(2-pyridyl)imidazo[1,5-a]pyridine ligands.

Several palladium(ii) and platinum(ii) complexes (1-20) of general formula [M(L)(X)(Y)] [M = Pd, X = Y = Cl (1-Cl-4-Cl), X = Y = OAc (1-OAc-4-OAc); M = Pt: X = Y = Cl (5-8); M = Pd, X = Cl, Y = CH (9-12); M = Pt, X = Cl, Y = CH (13-16) or X = Y = CH (17-20); n = 1-4] have been synthesized by reaction of different Pd(ii) and Pt(ii) derivatives with various 3-substituted 1-(2-pyridyl)-imidazo[1,5-a]pyridines; i.e.L = 1-(2-pyridyl)-3-arylimidazo[1,5-a]pyridine (aryl = Phenyl, L; 2-o-Tolyl, L; Mesityl, L) and 1-(2-pyridyl)-3-benzylimidazo[1,5-a]pyridine (L).

Dimerized -Semiquinone Radical Anions Stabilized by a Pair of Rare-Earth Metal Ions.

Here we report stable -quinone-radical-bridged rare-earth complexes involving the ligand tetramethylquinone (QMe). The complexes, {Y[(QMe)Cl(THF)]} () and {Gd[(QMe)Cl(THF)]} (), where THF = tetrahydrofuran, are sufficiently stable that we can measure the single-crystal structures and perform magnetic and electron paramagnetic resonance measurements. These studies show the presence of a semiquinone form and that the magnetic interaction between the radicals in the dimer is strong and antiferromagnetic.

Synthesis and characterisation of light lanthanide bis-phospholyl borohydride complexes.

Organometallic lanthanide (Ln) chemistry is dominated by complexes that contain substituted cyclopentadienyl (CpR) ligands. Closely related phospholyls have received less attention, and although they have proven utility in stabilising low oxidation state Ln complexes the trivalent Ln chemistry of these ligands is limited in comparison. Herein, we synthesise two families of heteroleptic Ln3+ complexes, [Ln(Htp)2(μ-BH4)]2 (Htp = 2,5-di-tert-butylphospholyl; 1-Ln; Ln = La, Ce, Nd, Sm), and [[Ln(Htp)2(μ-BH4)2K(S)]n (2-Ln, Ln = La, Ce, S = 2 DME, n = 2; 3-Ce, Ln = Ce, S = Et2O and THF, n = ∞) via the reactions of parent [Ln(BH4)3(THF)3.

A double-dysprosocenium single-molecule magnet bound together with neutral ligands.

A dinuclear dysprosocenium dication has been synthesised that is bound together by weak interactions between {Dy(Cp*)2}+ fragments and neutral NEt3AlMe3 molecules. The axiality of the Dy3+ crystal fields are perturbed by these equatorial interactions but a relatively large effective barrier to magnetisation reversal of 860(60) cm-1 and magnetic hysteresis up to 12 K are observed.

Probing Relaxation Dynamics in Five-Coordinate Dysprosium Single-Molecule Magnets.

A new family of five-coordinate lanthanide single-molecule magnets (Ln SMMs) [Dy(Mes*O) (THF) X] (Mes*=2,4,6-tri-tert-butylphenyl; X=Cl, 1; Br, 2; I, 3) is reported with energy barriers to magnetic reversal >1200 K. The five-coordinate Dy ions have distorted square pyramidal geometries, with halide anions on the apex, and two Mes*O ligands mutually trans- to each other, and the two THF molecules forming the second trans- pair. These geometrical features lead to a large magnetic anisotropy in these complexes along the trans-Mes*O direction.

Studies of hysteresis and quantum tunnelling of the magnetisation in dysprosium(iii) single molecule magnets.

We report magnetic hysteresis studies of three Dy(iii) single-molecule magnets (SMMs). The three compounds are [Dy(BuO)Cl(THF)][BPh] (1), [K(18-crown-6-ether)(THF)][Dy(BIPM)] (2, BIPM = C{PPhNSiMe}), and [Dy(Cp)][B(CF)] (3), chosen as they have large energy barriers to magnetisation reversal of 665, 565, and 1223 cm, respectively. There are zero-field steps in the hysteresis loops of all three compounds, that remain in magnetically dilute samples and in samples that are isotopically enriched with Dy, which has no nuclear spin.

Light Lanthanide Metallocenium Cations Exhibiting Weak Equatorial Anion Interactions.

As the dysprosocenium complex [Dy(Cp ) ][B(C F ) ] (Cp =C H tBu -1,2,4, 1-Dy) exhibits magnetic hysteresis at 60 K, similar lanthanide (Ln) complexes have been targeted to provide insights into this remarkable property. We recently reported homologous [Ln(Cp ) ][B(C F ) ] (1-Ln) for all the heavier Ln from Gd-Lu; herein, we extend this motif to the early Ln. We find, for the largest Ln cations, that contact ion pairs [Ln(Cp ) {(C F -κ -F)B(C F ) }] (1-Ln; La-Nd) are isolated from reactions of parent [Ln(Cp ) (Cl)] (2-Ln) with [H(SiEt ) ][B(C F ) ], where the anion binds weakly to the equatorial sites of [Ln(Cp ) ] through a single fluorine atom in the solid state.

New Variations on the Theme of Gold(III) CNN Cyclometalated Complexes as Anticancer Agents: Synthesis and Biological Characterization.

A series of novel (CNN) cyclometalated Au complexes of general formula [Au(bipy-H)X][PF] (bipy-H = CNN cyclometalated 6-(1,1-dimethylbenzyl)-2,2'-bipyridine) were prepared with a range of anionic ligands X in the fourth coordination position, featuring C (alkynyl)-, N-, O-, or S-donor atoms. The X ligands are varied in nature and include three coumarins, 4-ethynylaniline, saccharine, and thio-β-d-glucose tetraacetate, the tripeptide glutathione (GSH), and a coumarin-substituted amide derived from 4-ethynylaniline. The gold(I) complex [Au(CArNHCOQ)(PPh)] (HCArNHCOQ = N-(4-ethynylphenyl)-2-oxo-2 H-chromene-3-carboxamide) was also prepared for comparison.

Field- and temperature-dependent quantum tunnelling of the magnetisation in a large barrier single-molecule magnet.

Understanding quantum tunnelling of the magnetisation (QTM) in single-molecule magnets (SMMs) is crucial for improving performance and achieving molecule-based information storage above liquid nitrogen temperatures. Here, through a field- and temperature-dependent study of the magnetisation dynamics of [Dy(BuO)Cl(THF)][BPh]·2THF, we elucidate the different relaxation processes: field-independent Orbach and Raman mechanisms dominate at high temperatures, a single-phonon direct process dominates at low temperatures and fields >1 kOe, and a field- and temperature-dependent QTM process operates near zero field. Accounting for the exponential temperature dependence of the phonon collision rate in the QTM process, we model the magnetisation dynamics over 11 orders of magnitude and find a QTM tunnelling gap on the order of 10 to 10 cm.