Imidazolyl-phenyl (IMP) anions: a modular structure for tuning solubility and coordinating ability.

The effect of counteranion upon a cation's solution-phase reactivity depends on a subtle interplay of weak interactions. Although these effects are widely appreciated in synthesis and catalysis, probing and controlling anion-cation interactions remains a significant challenge. Here we report the synthesis, characterisation and reactivity of the IMP anions, a family of anions with a coordinating ability that can be tuned for a given application. The anions are robust, compatible with both strongly basic and acidic media, suitable for isolation of unstable organometallic species, and effective as counteranions for homogeneous catalysis. IMP anions are prepared in two steps: deprotonation of substituted 2-phenylimidazoles with NaH, followed by addition of 2 equiv. B(C6F5)3. The anions prepared feature a range of functionality, including nitro, ester, amide, amine and alcohol groups. Based on the spectroscopic properties of [Pd(IPr)(C(O)C9H6N)] [IMP-R], the coordinating ability of [IMP-R]- ranges between BF4- and BArF4-, depending on the polarity of the R group. Gold complexes of type [L-Au-L'][IMP-R] have been isolated and characterised, resulting in the first X-ray structure of a (η2-diphenylacetylene)Au complex. [(tBuXPhos)Au(MeCN)][IMP-R] catalyses [2 + 2] cyclisation of alkenes and alkynes, as well as the hydroalkoxylation of alkynes. Unlike SbF6- and BArF4-, the [IMP-H]- and [IMP-CF3]- salts are sufficiently soluble to efficiently promote cyclisations in toluene with [(tBuXPhos)Au(MeCN)]+.

Short- and long-term effects of habitat fragmentation differ but are predicted by response to the matrix.

Habitat loss and fragmentation are major threats to biodiversity and ecosystem processes. Our current understanding of the impacts of habitat loss and fragmentation is based largely on studies that focus on either short-term or long-term responses. Short-term responses are often used to predict long-term responses and make management decisions. The lack of studies comparing short- and long-term responses to fragmentation means we do not adequately understand when and how well short-term responses can be extrapolated to predict long-term responses, and when or why they cannot. To address this gap, we used data from one of the world's longest-running fragmentation experiments, The Wog Wog Habitat Fragmentation Experiment. Using data for carabid beetles, we found that responses in the long term (more than 22 yr post-fragmentation ≈22 generations) often contrasted markedly with those in the short term (5 yr post-fragmentation). The total abundance of all carabids, species richness and the occurrence of six species declined in the short term in the fragments but increased over the long term. The occurrence of three species declined initially and continued to decline, whilst another species was positively affected initially but decreased in the long term. Species' responses to the matrix that surrounds the fragments strongly predicted both the direction (increase/decline in occurrence) and magnitude of their responses to fragmentation. Additionally, species' responses to the matrix were somewhat predicted by their preferences for different types of native habitat (open vs. shaded). Our study highlights the degree of the matrix's influence in fragmented landscapes, and how this influence can change over time. We urge caution in using short-term responses to forecast long-term responses in cases where the matrix (1) impacts species' responses to fragmentation (by isolating them, creating new habitat or altering fragment habitat) and (2) is likely to change through time.

Kinetics of 3-chlorotyrosine formation and loss due to hypochlorous acid and chloramines.

The persistent activation of innate immune cells in chronic inflammation is gaining recognition as a contributing factor in a number of human diseases. A distinguishing feature of activated leukocytes at sites of inflammation is their production of reactive species such as hypochlorous acid (HOCl). Investigating the role of reactive molecules such as HOCl in inflammation and human disease requires appropriate biomarkers. The preferred biomarker for HOCl, and by extension its synthesizing enzyme myeloperoxidase, is 3-chlorotyrosine. 3-Chlorotyrosine is a chemically stable product formed when HOCl, or an HOCl-generated chloramine, reacts with the tyrosine side chain and is readily measured by sensitive mass spectrometry methods. However, Whiteman and Spencer ((2008) Biochem. Biophys. Res. Commun., 371, 50 - 53.) noted that 3-chlorotyrosine is degraded by HOCl, calling into question its use as a biomarker. The kinetic rate constants for the reaction of 3-chlorotyrosine with HOCl, histidine chloramine, or lysine chloramine to form 3,5-dichlorotyrosine are reported. The kinetics of tyrosine chlorination in the context of a peptide with a nearby lysine residue was also determined and further supports the role of chloramines in the chlorination of protein-bound tyrosine residues. The likelihood of free and protein-bound 3,5-dichlorotyrosine occurring in vivo, given the reported rate constants, is discussed.