Chromophore-labelled, luminescent platinum complexes: syntheses, structures, and spectroscopic properties

Ligands based upon 4-carboxamide-2-phenylquinoline derivatives have been synthesised with solubilising octyl hydrocarbon chains and tethered aromatic chromophores to give naphthyl (HL2), anthracenyl (HL3) and pyrenyl (HL4) ligand variants, together with a non-chromophoric analogue (HL1) for comparison. 1H NMR spectroscopic studies of the ligands showed that two non-interchangeable isomers exist for HL2 and HL4 while only one isomer exists for HL1 and HL3. Supporting DFT calculations on HL4 suggest that the two isomers may be closely isoenergetic with a relatively high barrier to exchange of ca. 100 kJ mol−1. These new ligands were cyclometalated with Pt(II) to give complexes [Pt(L1–4)(acac)] (acac = acetylacetonate). The spectroscopically characterised complexes were studied using multinuclear NMR spectroscopy including 195Pt{1H} NMR studies which revealed δPt ca. −2785 ppm for [Pt(L1–4)(acac)]. X-ray crystallographic studies were undertaken on [Pt(L3)(acac)] and [Pt(L4)(acac)], each showing the weakly distorted square planar geometry at Pt(II); the structure of [Pt(L3)(acac)] showed evidence for intermolecular Pt–Pt interactions. The UV-vis. absorption studies show that the spectral profiles for [Pt(L2–4)(acac)] are a composite of the organic chromophore centred bands and a broad 1MLCT (5d → π*) band (ca. 440 nm) associated with the complex. Luminescence studies showed that complexes [Pt(L2–4)(acac)] are dual emissive with fluorescence characteristic of the tethered fluorophore and long-lived phosphorescence attributed to 3MLCT emission. In the case of the pyrenyl derivative, [Pt(L4)(acac)], the close energetic matching of the 3MLCT and 3LCpyr excited states led to an elongation of the 3MLCT emission lifetime (τ = 42 μs) under degassed solvent conditions, suggestive of energy transfer processes between the two states

Noria and its derivatives as hosts for chemically and thermally robust Type II porous liquids

Porous Liquids (PLs) are a new class of material that possess both fluidity and permanent porosity. As such they can act as enhanced, selective solvents and may ultimately find applications which are not possible for porous solids, such as continuous flow separation processes. Type II PLs consist of empty molecular hosts dissolved in size-excluded solvents and to date have mainly been based on hosts that have limited chemical and thermal stability. Here we identify Noria, a rigid cyclic oligomer as a new host for the synthesis of more robust Type II PLs. Although the structure of Noria is well-documented, we find that literature has overlooked the true composition of bulk Noria samples. We find that bulk samples typically consist of Noria (ca. 40%), a Noria isomer, specifically a resorcinarene trimer, “R3” (ca. 30%) and other unidentified oligomers (ca. 30%). Noria has been characterised crystallographically as a diethyl ether solvate and its 1H NMR spectrum fully assigned for the first time. The previously postulated but unreported R3 has also been characterised crystallographically as a dimethyl sulfoxide solvate, which confirms its alternative connectivity to Noria. Noria and R3 have low solubility which precludes their use in Type II PLs, however, the partially ethylated derivative Noria-OEt dissolves in the size-excluded solvent 15-crown-5 to give a new Type II PL. This PL exhibits enhanced uptake of methane (CH4) gas supporting the presence of empty pores in the liquid. Detailed molecular dynamics simulations support the existence of pores in the liquid and show that occupation of the pores by CH4 is favoured. Overall, this work revises the general accepted composition of bulk Noria samples and shows that Noria derivatives are appropriate for the synthesis of more robust Type II PLs

SPICE, A Dataset of Drug-like Molecules and Peptides for Training Machine Learning Potentials

Machine learning potentials are an important tool for molecular simulation, but their development is held back by a shortage of high quality datasets to train them on. We describe the SPICE dataset, a new quantum chemistry dataset for training potentials relevant to simulating drug-like small molecules interacting with proteins. It contains over 1.1 million conformations for a diverse set of small molecules, dimers, dipeptides, and solvated amino acids. It includes 15 elements, charged and uncharged molecules, and a wide range of covalent and non-covalent interactions. It provides both forces and energies calculated at the {\omega}B97M-D3(BJ)/def2-TZVPPD level of theory, along with other useful quantities such as multipole moments and bond orders. We train a set of machine learning potentials on it and demonstrate that they can achieve chemical accuracy across a broad region of chemical space. It can serve as a valuable resource for the creation of transferable, ready to use potential functions for use in molecular simulations.Comment: 19 pages, 6 figure

Synthesis and characterisation of fluorescent aminophosphines and their coordination to gold(i)

Three novel fluorescent aminophosphine ligands have been synthesised that incorporate napthyl (L1), pyrenyl (L2) and anthraquinone (L3) chromophores into their structures. The ligands react with [AuCl(tht)] (tht = tetrahydrothiophene) to give neutral complexes of the form [AuCl(L1–3)]. Solid state, X-ray crystallographic data was obtained for the anthraquinone derivative, [AuCl(L3)], and showed a distorted linear coordination geometry at Au(I). The packing structure also revealed a number of intermolecular π–π interactions that involve the anthraquinone and phenyl units of the aminophosphine ligand. 31P NMR spectroscopic data revealed δP values of +42.2 (L1), +42.1 (L2) and +26.1 (L3) ppm, which shifted downfield upon coordination to Au(I) to +64.6, +64.7, and +55.8 ppm, respectively. Supporting TD-DFT studies were able to reproduce the structure and 31P NMR chemical shifts of [AuCl(L3)] as well as rationalise the HOMO–LUMO compositions. Photophysical studies showed that the appended fluorophore dominates the absorption and emission properties for the ligands and complexes, with the anthraquinone derivatives showing visible emission at ca. 570 nm which was attributed to the intramolecular charge transfer character of the phosphinoaminoanthraquinone fragment

Aeolianite and barrier dune construction spanning the last two glacial-interglacial cycles from the southern Cape coast, South Africa

The southern Cape region of South Africa has extensive coastal aeolianites and barrier dunes. Whilst previously reported, limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea-level fluctuations that have taken place during the Late Quaternary. Sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial–interglacial cycles. Aeolianite deposition has occurred on the southern Cape coast at ca 67–80, 88–90, 104–128, 160–189 and >200 ka before the present. Using this and other published data coupled with a better understanding of Late Quaternary sea-level fluctuations and palaeocoastline configurations, it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea-level high stands. These marine transgressions and regressions allowed onshore carbonate-rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions. The lack of carbonates in more recent dunes (Oxygen Isotope Stages 1/2 and 4/5) is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and/or changes in the balance between the warm Agulhas and nutrient-rich Benguela ocean current

The TOLIMAN space telescope

The TOLIMAN space telescope is a low-cost, agile mission concept dedicated to astrometric detection of exoplanets in the near-solar environment, and particularly targeting the Alpha Cen system. Although successful discovery technologies are now populating exoplanetary catalogs into the thousands, contemporary astronomy is still poorly equipped to answer the basic question of whether there are any rocky planets orbiting any particular star system. Toliman will make a first study of stars within 10 PC of the sun by deploying an innovative optical and signal encoding architecture that leverages the most promising technology to deliver data on this critical stellar sample: high precision astrometric monitoring. Here we present results from the Foundational Mission Study, jointly funded by the Breakthrough Prize Foundation and the University of Sydney which has translated innovative underlying design principles into error budgets and potential spacecraft systems designs

Organometallic platinum(ii) photosensitisers that demonstrate ligand‐modulated triplet‐triplet annihilation energy upconversion efficiencies

A series of 2‐phenylquinoxaline ligands have been synthesised that introduce either CF3 or OCF3 electron‐withdrawing groups at different positions of the phenyl ring. These ligands were investigated as cyclometalating reagents for platinum(II) to give neutral complexes of the form [Pt(C^N)(acac)] (in which C^N=cyclometalating ligand; acac=acetyl acetonate). X‐ray crystallographic studies on three examples showed that the complexes adopt an approximate square planar geometry. All examples revealed strong Pt−Pt linear contacts of 3.2041(6), 3.2199(3) and 3.2586(2) Å. The highly coloured complexes display efficient visible absorption at 400–500 nm (ϵ ≈5000 M−1 cm−1) and orange red photoluminescent characteristics (λem=603–620 nm; Φem ≤37 %), which were subtly tuned by the ligand. Triplet emitting character was confirmed by microsecond luminescence lifetimes and the photogeneration of singlet oxygen with quantum efficiencies up to 57 %. Each complex was investigated as a photosensitiser for triplet–triplet annihilation energy upconversion using 9,10‐diphenylanthracene as the annihilator species: a range of good upconversion efficiencies (ΦUC 5.9–14.1 %) were observed and shown to be strongly influenced by the ligand structure in each case

A Learning Approach to Monitoring and Evaluation

This article draws on literature from both monitoring and evaluation (M&E) and organisational learning to explore synergies between these two fields in support of organisational performance. Two insights from the organisational learning literature are that organisations learn through ‘double?loop’ learning: reflecting on experience and using this to question critically underlying assumptions; and that power relations within an organisation will influence what and whose learning is valued and shared. This article identifies four incentives that can help link M&E with organisational learning: the incentive to learn why; the incentive to learn from below; the incentive to learn collaboratively; and the incentive to take risks. Two key elements are required to support these incentives: (1) establishing and promoting an ‘evaluative culture’ within an organisation; and (2) having accountability relationships where value is placed on learning ‘why’, as well as on learning from mistakes, which requires trust

Fluorescent functionalised naphthalimides and their Au(i)–NHC complexes for potential use in cellular bioimaging

A series of cationic, dihydroimidazolinium-functionalized 1,8-naphthalimide fluorophores have been isolated as their hexafluorophosphate salts, [HL]PF6. These pro-ligands react with [AuCl(tht)] in the presence of base to form N-heterocyclic carbene (NHC) complexes, [AuCl(L)]. Two X-ray structures represent a pro-ligand and complex pairing: the latter reveals the two-coordinate linear geometry of the NHC–Au(I) species, as well as intermolecular interactions supported by both ligand π–π stacking and a weak aurophilic interaction of 3.3205(6) Å. The luminescence properties of the pro-ligands and complexes are dominated by the ICT character of the substituted fluorophore at ca. 500 nm, which is further modulated via functionalization at the 4-position of the naphthalimide. Cytotoxicity assessments were performed for all [HL]PF6 and [AuCl(L)] species against LOVO, MCF-7, A549 and PC3 cell lines; added lipophilicity seems to correlate with increased cytotoxicity. Confocal fluorescence microscopy was undertaken on a selected [HL]PF6 and [AuCl(L)] species and showed that the intracellular distribution is dependent upon the specific ligand structure. More detailed co-localisation studies show that selected examples present a predominant lysosomal staining pattern. FLIM studies exemplified the applicability of these probes, and secondly suggest that fluorescence lifetime could be used to provide information on the integrity of the complex and thus liberation of gold in a biological environment