This year, we have welcomed twenty new members to our Advisory Board. Learn about each member below.
Read the collection of high-impact articles from our new members: https://rsc.li/advisoryboard2020 Free to access until 21st August.
This year, we have welcomed twenty new members to our Advisory Board. Learn about each member below.
Read the collection of high-impact articles from our new members: https://rsc.li/advisoryboard2020 Free to access until 21st August.
Antibiotic resistant bacteria, and the subsequent diseases caused by their infection, are of serious global concern. As more and more bacteria develop antibiotic resistance and jeopardise the current treatments for serious infections, there is a strong imperative to both develop new medicines and to understand these bacterial pathogens. Pseudomonas aeruginosa, Staphylococcus aureus and species from the genus Burkholderia are all such antibiotic resistant bacteria that contribute to various human diseases, and they can pose a serious threat to cystic fibrosis patients through chronic lung infections. These are often polymicrobial infections, meaning that the different bacteria interact by association and can alter the impact of the resulting disease.
P. aeruginosa and Burkholderia generally interact competitively with S. aureus, reducing its viability. This is achieved by the secretion of small molecule respiratory toxins which include 2-alkyl-4(1H)-quinolone N-oxides (AQNOs) by P. aeruginosa or 3-methyl-2-alkyl-4-quinolone N-oxides (MAQNOs) by Burkholderia (see Figure 1). Researchers in Germany and Austria sought to understand the antagonistic interactions of these bacteria and have now reported the synthesis of various representative AQNOs and MAQNOs and investigated their action against S. aureus.

Figure 1: Structures of the quinolone derivatives produced by P. aeruginosa and Burkholderia that act against S. aureus
The researchers approached the synthesis of the AQNOs and MAQNOs by starting with the preparation of the corresponding quinolones, and then converting them to the quinolone N-oxides. They focussed on the C9 nonyl-/nonenyl- derivatives, NQNOs and MNQNOs, as previous studies showed this alkyl chain length proved the most active against S. aureus. Mass spectrometry and fragmentation was primarily used to characterise the synthesised compounds, and the researchers were able to establish a new library of standards to be used for the identification of quinolones and quinolone N-oxides. This therefore allowed the researchers to quantify the specific quinolone derivatives produced by certain strains of P. aeruginosa and Burkholderia using this standard library, as shown in Figure 2.

Figure 2: Quantification of the quinolones (AQs and MAQs) and quinolone N-oxides (AQNOs and MAQNOs) secreted by P. aeruginosa (strains PAO1 and PA14) and Burkholderia thailandesis using calibration against the established standard library
The researchers then investigated the possible activity of these quinolone derivatives against S. aureus. The activity of S. aureus was measured using a chromogenic assay, by varying concentrations of the quinolone derivatives until a minimum inhibitory concentration (MIC) was reached, with complete respiratory inhibition of the bacteria. The C9-quinolones (before N-oxidation) showed no inhibition against S. aureus at the highest concentrations tested, but the corresponding quinolone N-oxides (NQNOs and MNQNOs) showed activity against the bacteria. More specifically, unsaturated derivatives were more active, and the MNQNOs, with 3-methylation of the quinolone core, showed the greatest antibiotic activity against S. aureus. These results suggest that the methylated quinolones produced by species of Burkholderia, as well as unsaturared quinolones produced by P. aeruginosa, have an important role in competitive interactions against S. aureus in polymicrobial infections.
To find out more, please read:
Profiling structural diversity and activity of 2-alkyl-4(1H)-quinolone N-oxides of Pseudomonas and Burkholderia
Dávid Szamosvári, Michaela Prothiwa, Cora Lisbeth Dieterich and Thomas Böttcher
Chem. Commun., 2020, 56, 6328-6331
About the blogger:
Dr. Samantha Apps is a Postdoctoral Research Associate in the Lu Lab at the University of Minnesota, USA, and obtained her PhD in 2019 from Imperial College London, UK. She has spent the last few years, both in her PhD and postdoc, researching synthetic nitrogen fixation and transition metal complexes that can activate and functionalise dinitrogen. Outside of the lab, you’ll likely find her baking at home, where her years of synthetic lab training has sparked a passion in kitchen chemistry too.
We’re celebrating the upcoming 20th anniversary of aggregation-induced emission (AIE), a term which was first coined in 2001. We’ve put together a collection of key AIE articles published in RSC journals. Here are the articles in the collection from ChemComm, including the very first AIE article!
Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole
Ben Zhong Tang et al
Chem. Commun., 2001, 1740–1741

A conical intersection model to explain aggregation induced emission in diphenyl dibenzofulvene
Quansong Lia and Lluís Blancafort
Chem. Commun., 2013, 49, 5966

Diarylboryl-phenothiazine based multifunctional molecular siblings
Kalluvettukuzhy K. Neena, Pakkirisamy Thilagar* et al.
Chem. Commun., 2017, 53, 3641-3644

Aggregation-induced emission in precursors to porous molecular crystals
Zhenglin Zhang, Ognjen Š. Miljanić* et al.
Chem. Commun., 2017,53, 10022-10025

A cyanine-based fluorescent cassette with aggregation-induced emission for sensitive detection of pH changes in live cells
Mingxi Fang, Haiying Liu* et al.
Chem. Commun., 2018,54, 1133-1136

AIE-active micelles formed by self-assembly of an amphiphilic platinum complex possessing isoxazole moieties
Takehiro Hirao,Takeharu Haino* et al.
Chem. Commun., 2020,56, 1137-1140

A self-delivery DNA nanoprobe for reliable microRNA imaging in live cells by aggregation induced red-shift-emission
Zhe Chen, Leilei Tian* et al.
Chem. Commun., 2020,56, 1501-1504

A light-up probe with aggregation-induced emission characteristics (AIE) for selective imaging, naked-eye detection and photodynamic killing of Gram-positive bacteria
Guangxue Feng, Bin Liu* et al.
Chem. Commun., 2015, 51, 12490-12493

Rational design of substituted maleimide dyes with tunable fluorescence and solvafluorochromism
Yujie Xie, Rachel K. O’Reilly et al.
Chem. Commun., 2018,54, 3339-3342

Understanding metal-metal interactions is of fundamental interest to chemists, especially in the design of new materials or catalysts. Heterometallic metal-metal bonding is particularly fascinating, since the unique properties of each metal can be combined or even manipulated, to enhance structural, electronic or even photochemical effects. Gold and platinum are one such pairing of interest and there have already been several applications of AuPt clusters reported for catalysis. However, well-defined, homogeneous AuPt complexes are comparatively under explored, but there is a huge potential for these heterodinuclear complexes to catalyse useful chemical transformations. Research in Germany by Butschke and co-workers now describes the first example of an AuPt complex with a bound olefin, as a valuable, formal Au+IPt0 precursor for further reactivity and chemical transformations (Figure 1).

Figure 1: The new AuPt heterodinuclear complex with Pt-bound olefins (right), and existing examples in the literature with Pt-bound phosphines (left and centre).
The new cationic AuPt complex described in this report differs from the existing literature by the presence of weakly bound olefin ligands (in this case, norbonene/nbe) coordinated to the platinum. The other existing examples have only strongly σ-donating phosphine ligands coordinated to the Pt centre, which increases the overall stability of the complexes and renders them unreactive for further chemistry. In contrast, the nbe ligands are more weakly bound, and have a much lower dissociation energy, creating a more reactive complex which is therefore a valuable precursor to other formal Au+IPt0 complexes. This increased reactivity is reflected in the preparation and subsequent manipulations of the complex, which had to be conducted at low temperatures to prevent decomposition.
The new AuPt heterodinuclear complex prepared in this report was characterised by a range of spectroscopic and structural techniques. Single-crystal X-ray diffraction confirmed the molecular structure of the complex, as shown in Figure 2. A rearrangement of the three axial nbe ligands was observed in the new AuPt complex compared to the [Pt(nbe)3] platinum precursor; the three olefin ligands are arranged in a spoke-wheel geometry with the bridging methylenes of nbe all pointing in the same direction away from the gold (an ‘up-up-up’ configuration, in comparison to an ‘up-up-down’ arrangement as in the Pt precursor). NMR spectroscopic characterisation also helped to elucidate and confirm the structure. The 195Pt-NMR resonance of the AuPt complex was particularly noteworthy, showing a similar chemical shift to that of the Pt precursor, which indicates little to no electronic change at Pt0 in the new AuPt complex. This was also reflected in the 13C NMR resonances for the olefinic carbons, which again, were similar in the AuPt complex and the Pt precursor.

Figure 3: Comparing the new AuPt complex (3) to other systems with fewer bound olefins, in terms of the Au-Pt bond dissociation energy (x-axis) and the overall charge transfer between the Au and Pt (y-axis), according to three different calculations.
The authors then further probed the binding of the gold centre to the platinum, and why there was no apparent significant change in the electronics between the new AuPt complex and the Pt precursor. A comparison to the existing AuPt complexes reported revealed that these are often assigned formally as Au-IPt+II, where there is a dative interaction between the Lewis base (Pt) and the Lewis Acid (Au). In contrast, the new AuPt complex in this report is formally assigned as Au+IPt0, where there is considerably less charge transfer in the metal-metal bonding, as shown by DFT calculations (see Figure 3). This formal Au+IPt0 assignment ultimately results in the coordinated nbe olefin ligands having a low dissociation energy (i.e. they are highly labile and susceptible to ligand substitution), which is further supported by DFT calculations and is reflected in the lack of an identifiable electrospray-ionisation mass spectrometry peak for the [M]+ ion. Therefore, this new AuPt complex is a desirable precursor for the preparation of other formal Au+IPt0 complexes, which will allow for future reactivity studies on these unusual heterodinuclear systems.
To find out more, please read:
A heterodinuclear, formal Au+IPt0 complex with weakly bound alkene ligands
Lukas D. Ernst, Konstantin Koessler, Andreas Peter, Daniel Kratzert, Harald Scherer and Burkhard Butschke
Chem. Commun., 2020, 56, 5350-5353
Electro-oxidizing urea in water has the dual benefit of generating electricity and treating wastewater. In alkaline media, the sluggish kinetics of the urea oxidation reaction, CO(NH2)2 + 6OH– → N2↑ + CO2↑ + 5H2O + 6e–, due to its transfer of six electrons demand efficient catalysts to speed up this process.
A research team led by Xiujuan Sun and Rui Ding, both at Xiangtan University, China, used a co-precipitation method to synthesize urea-oxidation catalysts. These catalysts comprised of graphene-anchored nanoparticles of metallic Ni, Co, and Mo, as well as their alloys and hydro/oxides (NCM/G) (Figure 1). NCM/G with the optimal composition displayed a mass activity of 140.9 mA cm-2 mgcat-1 and an onset potential of 1.32 V vs. RHE (current density = 10 mA/cm2). Their results are published in Chemical Communications (DOI: 10.1039/D0CC02132F).

Figure 1. Representative (a) transmission electron microscopy image and (b-f) elemental mappings of the synthesized catalyst.
The catalysts exhibited different catalytic activities dependent on their chemical compositions, which were tunable by varying the moles of the Ni, Co, and Mo precursors. Cyclic voltammograms of various NCM/G all showed markedly increased current density at potentials beyond 0.3 V vs. Ag/AgCl in urea-containing aqueous solutions (Figure 2a), marking their catalytic activity for urea oxidation. Among all the tested catalysts, NCM/G with Ni:Co:Mo = 80:10:10 achieved the largest current density at 0.6 V vs. Ag/AgCl, indicating its highest catalytic activity. Additionally, chronoamperometry demonstrated that increasing the Mo content was beneficial for maintaining catalyst stability, as the current density of NCM/G with the lowest amount of Mo (the black curve in Figure 2b) decayed the fastest. Combining the results of cyclic voltammetry and chronoamperometry, the authors deduced that the optimal molar ratio of Ni:Co:Mo was 80:10:10.

Figure 2. (a) Cyclic voltammograms (scan rate: 1 mV/s) and (b) chronoamperometry (potential: 0.5 V vs. Ag/AgCl) profiles of NCM/G with different Ni, Co, and Mo contents. Electrolyte: 1.0 M KOH + 0.33 M urea in water. The molar ratios of Ni:Co:Mo of NCM/G 90505, 811, and 71515 are 90:5:5. 80:10:10, and 70:15:15, respectively.
The optimization of the chemical composition demonstrated in this work can rationalize the development of high-performance, metallic electrocatalysts for urea oxidation.
For expanded understanding, please read:
Wei Shi, Xiujuan Sun, Rui Ding, Danfeng Ying, Yongfa Huang, Yuxi Huang, Caini Tan, Ziyang Jia, and Enhui Liu
Chem. Commun., 2020, DOI: 10.1039/D0CC02132F
Tianyu Liu acknowledges Zacary Croft at Virginia Tech, U.S., for his careful proofreading of this post.
About the blogger:
Tianyu Liu obtained his Ph.D. (2017) in Chemistry from the University of California, Santa Cruz, in the United States. He is passionate about the communication of scientific endeavors to both the general public and other scientists with diverse research expertise to introduce cutting-edge research to broad audiences. He is a blog writer for Chem. Comm. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.