From Ligand to Phosphor: Rapid, Machine-Assisted Synthesis of Substituted Iridium(III) Pyrazolate Complexes with Tuneable Luminescence

A first generation machine-assisted approach towards the preparation of hybrid ligand/metal materials has been explored. A comparison of synthetic approaches demonstrates that incorporation of both flow chemistry and microwave heating, can be successfully applied to the rapid synthesis of a range of new phenyl-1H-pyrazoles (ppz) substituted with electron withdrawing groups (-F, -CF3, -OCF3, -SF5), and these, in turn, can be translated in to heteroleptic complexes, [Ir(ppz)2(bipy)]BF4 (bipy = 2,2’-bipyridine). Microwave-assisted syntheses for the IrIII complexes allows isolation of spectroscopically pure species in less than 1 hour of reaction time from IrCl3. All new complexes have been explored photophysically (including nanosecond time-resolved transient absorption spectroscopy), electrochemically and by TD-DFT studies which show that the complexes possess ligand-dependent, and thus, tuneable green-yellow luminescence (500-560 nm), with quantum yields in the range 5-15 %

Exploiting satellite measurements to explore uncertainties in UK bottom-up NOx emission estimates

Nitrogen oxides (NOx, NO + NO2) are potent air pollutants which directly impact on human health and which aid the formation of other hazardous pollutants such as ozone (O3) and particulate matter. In this study, we use satellite tropospheric column nitrogen dioxide (TCNO2) data to evaluate the spatiotemporal variability and magnitude of the United Kingdom (UK) bottom-up National Atmospheric Emissions Inventory (NAEI) NOx emissions. Although emissions and TCNO2 represent different quantities, for UK city sources we find a spatial correlation of ∼0.5 between the NAEI NOx emissions and TCNO2 from the high-spatial-resolution TROPOspheric Monitoring Instrument (TROPOMI), suggesting a good spatial distribution of emission sources in the inventory. Between 2005 and 2015, the NAEI total UK NOx emissions and long-term TCNO2 record from the Ozone Monitoring Instrument (OMI), averaged over England, show annually decreasing trends of 4.4 % and 2.2 %, respectively. Top-down NOx emissions were derived in this study by applying a simple mass balance approach to TROPOMI-observed downwind NO2 plumes from city sources. Overall, these top-down estimates were consistent with the NAEI, but for larger cities such as London and Birmingham the inventory is significantly (>25 %) less than the top-down emissions

Lanthanide complexes for luminescence imaging applications

In this article, imaging applications of luminescent complexes and recent advances in the design and photophysical behaviour of near-IR responsive complexes are reviewed. Various properties of the luminescent lanthanide complexes are also discussed in detail. © Taylor and Francis, Inc

Visible-light sensitisation of near-infrared luminescence from Yb(III), Nd(III) and Er(III) complexes of 3,6-bis(2-pyridyl)tetrazine

Reaction of the potentially bis-bidentate bridging ligand 3,6-bis(2-pyridyl)tetrazine (BPTZ) with various lanthanide complexes [Ln(tta)3(H2O)2] [Htta = thenoyl(trifluoro) acetone; Ln = La, Nd, Gd, Er, Yb] in aqueous ethanol afforded the mononuclear complexes [Ln(tta)3(BPTZ)] (Ln = La, Nd) or the dinuclear complexes [{Ln(tta)3}2(μ-BPTZ)] (Ln = Gd, Er, Yb) in which one or two, respectively, lanthanide tris-diketonate {Ln(tta)3} units are bound to the N,N-bidentate compartments of BPTZ. Crystal structures of the dinuclear complexes [{Yb(tta)3}2(μ-BPTZ)] ·CH2Cl2 and [{Gd(tta)3} 2(μ-BPTZ)]·2CH2Cl2 show that the metal centres have an approximately square-antiprismatic eight-coordinate geometry; there are close contacts above and below the plane of the BPTZ bridging ligand between peripheral trifluoromethyl groups from a tta ligand associated with each metal centre. It is not apparent why the larger lanthanides La and Nd only give a mononuclear complex whereas the smaller lanthanides Gd, Er and Yb give the dinuclear complex in each case. UV/Vis spectroscopic titrations of a solution of BPTZ in CH2Cl2 with increasing amounts of [Ln(tta)3(H2O)2] (Ln = La and Yb) show very similar behaviour, with stepwise binding constants K1 and K2 for association of the two {Ln(tta)3} units of ca. 106 M-1 and 105 M-1; allowing for the expected statistical factor of 4 there is an additional reduction in the value of K2 compared to K1 which may be associated with a steric interaction between the two {Ln(tta)3} units when the dinuclear complex forms. Steady-state and time-resolved luminescence studies on the complexes with Yb, Nd and Er, both in the solid state and CH 2Cl2 solution, show that near-IR luminescence on the microsecond timescale can be sensitised by irradiation either at 337 nm into the tta-based transition, or at 520 nm into the low-energy BPTZ-centred transition. © The Royal Society of Chemistry 2003

Synthesis, structures and properties of a new series of platinum - diimine - dithiolate complexes

The new square-planar platinum–diimine–dithiolate compounds [Pt(mesBIAN)SS] have been synthesised {mesBIAN = bis(mesityl)biazanaphthenequinone; SS = 1,2-dithiooxalate (dto) 1, maleonitriledithiolate (mnt) 2, 1,2-benzenedithiolate (bdt) 3, 3,4-toluenedithiolate (tdt) 4 and 1,3-dithia-2-thione-4,5-dithiolate (dmit) 5}, and the X-ray crystal structures of 3 and 5 determined. Cyclic voltammetry reveals that all the compounds form stable anions, and ESR spectroscopy of these anions shows that the SOMO is based upon the mesBIAN ligand; compounds 2–5 also show a reversible oxidation wave in their CV. Computational studies reveal that charge-transfer processes from orbitals that are combinations of metal and dithiolate ligand to a mesBIAN π*-based LUMO are responsible for the low energy absorptions seen in the UV/visible spectra of these compounds, and that the reverse process is responsible for the observed room-temperature solution luminescence of [Pt(mesBIAN)Cl2] and 1, 2 and 5. Compounds 3 and 4, containing aromatic thiolates, were not found to luminesce under the same conditions. Resonance Raman experiments have shown the origin of band-broadening of the lowest-energy absorption band in the absorption spectra of 2–5 to be due to vibronic structure within one electronic transition

Sensitised near infrared emission from lanthanides via anion-templated assembly of d-f heteronuclear [2]pseudorotaxanes

The first example of assembling novel heteronuclear lanthanide-transition metal pseudorotaxanes where interpenetration of the lanthanide stoppered thread into the transition metal sensitiser containing macrocycle is signalled via sensitised near-infrared (NIR) lanthanide luminescence is described. © the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006