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Organic aerosol is a highly complex mixture of ∼104to 105unique compounds all possessing their own set of physico-chemical properties such as saturation vapour pressure and hygroscopicity. Most of these properties have not been experimentally measured and so must be estimated, resulting in large uncertainties in their predicted gas-particle partitioning and subsequent effect on human health and the climate. Dicarboxylic acids (DCAs) have been used extensively to represent oxidised organic aerosol due to their ubiquity in the atmosphere and commercial availability. Pure component saturation vapour pressures have been obtained by different techniques to enable accurate treatment of their partitioning in atmospheric models. However, an understanding of the synergistic interactions between molecules in multi-component droplets containing DCAs under atmospherically relevant conditions remains limited, relying on group contribution models to estimate physicochemical properties such as activity coefficients in complex organic multicomponent matrices. In this work, a method for extracting activity coefficients of organic species in binary organic component droplets has been developed for investigating the effect of matrix character (such as functionality and molecular weight) on component volatility. Droplets containing a compound of interest and a low-volatility organic liquid are suspended in an electro-dynamic balance for hours to days and the evaporation rate is estimated as the droplet evolves in composition. Comparison with a liquid-like evaporation model allows for the extraction of experimental activity coefficients for a range of mole fractions. Activity coefficients extracted from simple binary organic systems have been compared to and have shown good agreement with an activity coefficient estimator, Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC). The activity coefficients of a range of DCAs dissolved in a mixed-component organic droplet have also been measured and compared to AIOMFAC. The changes in DCA activity coefficient with evolving composition from experiments mostly show reasonable agreement with AIOMFAC for all systems investigated. This showcases the ability of AIOMFAC to predict activities for multi-organic systems containing no water.

In this paper we demonstrate that the effect of aromatic CF substitution in ligands does not always abide by conventional wisdom for ligand design to enhance sensitisation for visible lanthanide emission, in contrast with NIR emission for which the same effect coupled with shell formation leads to unprecedented long luminescence lifetimes. We have chosen an imidodiphosphinate ligand, N‐{P,P‐di(pentafluorophinoyl)}‐P,P‐dipentafluorophenylphosphinimidic acid (HF20tpip), to form ideal fluorinated shells about all visible‐ and NIR‐emitting lanthanides. The shell, formed by three ligands, comprises twelve fully fluorinated aryl sensitiser groups, yet no‐high energy XH vibrations that quench lanthanide emission. The synthesis, full characterisation including X‐ray and NMR analysis as well as the photophysical properties of the emissive complexes [Ln(F20tpip)3], in which Ln=Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y, Gd, are reported. The photophysical results contrast previous studies, in which fluorination of alkyl chains tends to lead to more emissive lanthanide complexes for both visible and NIR emission. Analysis of the fluorescence properties of the HF20tpip and [Gd(F20tpip)3] reveals that there is a low‐lying state at around 715 nm that is responsible for partially quenching of the signal of the visible emitting lanthanides and we attribute it to a π–σ* state. However, all visible emitting lanthanides have long lifetimes and unexpectedly the [Dy(F20tpip)3] complex shows a lifetime of 0.3 ms, indicating that the elimination of high‐energy vibrations from the ligand framework is particularly favourable for Dy. The NIR emitting lanthanides show strong emission signals in powder and solution with unprecedented lifetimes. The luminescence lifetimes of [Nd(F20tpip)3], [Er(F20tpip)3] and [Yb(F20tpip)3] in deuteurated acetonitrile are 44, 741 and 1111 μs. The highest value observed for the [Yb(F20tpip)3] complex is more than half the value of the Yb ion radiative lifetime.

The potentially pentadentate ligand 2,6-bisN-2′-pyridylmethylcarbamylpyridine H2L1, readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid H2dipic and 2-aminomethylpyridine ampy, shows limited tendency to form 1 1 M L complexes with labile metal ions, although CuL1 and NiL1 were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Coiii was characterized by a crystal structure as the neutral 1 2 complex CoL1HL1 with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Feiii is known to form a symmetrical 1 2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Coiii complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cuii complex Cu2L12 forms, as well as a trinuclear Niii complex Ni3L12OAc2MeOH)2. Moreover, in the presence of added H2dipic, the tetranuclear complex Cu4L12dipic2OH22 is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand π-stacking inter-ring distances of 3.2–3.8 Å of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione acac, each of the two pairs of adjacent monodentate ligands in Ni3L12OAc2OH22 have been shown to be available for substitution without destroying the helical structure, to form Ni3L12acac2, also characterized by a crystal structure.