The CO2-Capturing Mechanism of Quaternary Nitrogen-Containing Polymers Revealed Experimentally

A group of scientists from Washington University at St. Louis, USA have disclosed experimentally how CO2 is captured by polymers with quaternary nitrogen cations. Using solid-state nuclear magnetic resonance (NMR), the authors established that CO2 molecules were absorbed as bicarbonate anions (HCO3).

The increasing amount of CO2 has posed a number of concerning environmental issues such as climate change, rising sea level and ocean acidification. Capturing CO2 from the atmosphere is an effective way to lower the CO2 concentration. Recently, a family of polymer absorbents containing quaternary nitrogen functional groups, termed humidity-swing polymers, have been identified as promising absorbents to absorb CO2 directly from air. However, the limited understanding of the chemical mechanism related to their CO2-capturing capability hindered the development of these promising absorbents.

In ChemComm, Yang et al. used solid-state 13C NMR to explore how CO2 molecules were captured and released. Figure 1a presents the NMR spectra of a humidity-swing polymer absorbent itself (top), upon contacting with CO2 (middle) and after releasing CO2 (bottom). The most striking feature is the appearance of an additional sharp peak at a chemical shift of 161 ppm in the middle spectrum, which did not show up in the other two spectra. The authors further studied the shape evolution of the additional peak, with respect to temperature, and concluded that the peak was due to HCO3 anions. Additionally, the authors also identified the presence of hydroxide anions in the absorbent after CO2 was released.

Figure 1. (a) The solid-state 13C NMR spectra of the humidity-swing polymeric absorbent (structure shown in the inset of the middle spectrum) itself (top), upon contacting with CO2 (middle) and after releasing CO2 (bottom). (b) The proposed pathways of how CO2 molecules interact with the quaternary-N anions of the absorbent.

The researchers then proposed the CO2 adsorption-desorption mechanism (illustrated in Figure 1b) based on the experimental results. The storage and release of CO2 depend on the humidity level of the surroundings: When the humidity is low, the polymer absorbs CO2 and forms HCO3 anions; the negative charge of HCO3 is counter-balanced by the neighboring quaternary N cations. When the humidity is increased, HCO3 anions combine with water and decompose to CO2 and hydroxide anions. This proposed pathway does not involve CO32- anions, which differs from the previously-reported mechanisms derived from theoretical simulations.

The published results represent the first set of experimental evidence elucidating how CO2 molecules interact with humidity-swing polymeric absorbents. The acquired mechanistic insight could provide valuable guidelines for the design of CO2 absorbents with ultrahigh absorption capacity.

 

To find out more please read:

Humidity-Swing Mechanism for CO2 Capture from Ambient Air
Hao Yang, Manmilan Singh and Jacob Schaefer
Chem. Commun., 2018, DOI: 10.1039/c8cc02109k

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Amanda Hargrove and Alexander Miller: Winners of the ChemComm Emerging Investigator Lectureship 2018

On behalf of the ChemComm Editorial Board, we are pleased to announce the winners of the 2018 ChemComm Emerging Investigator Lectureship – Amanda Hargrove and Alexander Miller. Our warmest congratulations to Amanda and Alexander!

 

 

Amanda Hargrove

Amanda was awarded her PhD in 2010 at the University of Texas at Austin, where she worked with Professors Eric V. Anslyn and Jonathan L. Sessler on combining recognition motifs for improved sensing and biological activity of oligosaccharides and phosphorylated molecules. During her independent career, she has received the 2014 Ralph E. Powe Junior Faculty Enhancement Award, 2015 Prostrate Cancer Foundation Young Investigator Award, 2017 Cottrell Scholar Awards and 2018 National Science Foundation CAREER Award.

She is currently an Assistant Professor at Duke University and her group works at the interface of chemistry and biology, using organic chemistry tools to study the structure and function of long noncoding RNAs.

 

 

 

 


Alexander Miller

Alexander completed his PhD in 2011 at the California Institute of Technology, where he worked on emissive monocopper amidophosphine complexes and Lewis acid-assisted reductive coupling of carbon monoxide with Professors John E. Bercaw and Jay A. Labinger. He has been awarded several honours during his independent career, including the 2014 University Research Council James Moeser Award for Distinguished Research, 2016 National Science Foundation CAREER Award and 2017 Organometallics Distinguished Author Award.

He currently has a position as an Assistant Professor at the University of North Carolina, and his group’s research focusses on the storage of solar energy in chemical fuels, proton-coupled electron transfer reactions, and hydrocarbon transformations.

 

 

 

As part of the Lectureship, Amanda and Alexander will present a lecture at three locations over the coming year, with at least one of these events taking place at an international conference. Details of the lectures will be announce in due course – keep an eye on Twitter for details.

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Read our most cited ChemComm Features from 2016 and 2017

We are showcasing our 20 most cited ChemComm Feature articles from 2016 and from 2017. This collection provides an easy way to access some of the most exciting topics of research across the chemical sciences – from materials and supramolecular chemistry through to physical chemistry and catalysis.

ALL articles are FREE to read and download until 11 June!

We hope you enjoy reading this collection! Some of the highlights are given below:

 

C6CC05568K graphical abstract, Atomic and molecular layer deposition: off the beaten track, van Ommen et al.Atomic and molecular layer deposition: off the beaten track

 

Van Bui, F. Grillo and J. R. van Ommen

Chem. Commun., 2017, 53, 45-71

DOI: 10.1039/C6CC05568K
 

 

 


C6CC08967D Graphical Abstract, Biological and related applications of pillar[n]arenes, Wang et al.

Biological and related applications of pillar[n]arenes

 

CuhaWijay Sathiyajith, Rafik Rajjak Shaikh, Qian Han, Yue Zhang, Kamel Meguellati and Ying-Wei Yang

Chem. Commun., 2017, 53, 677-696

DOI: 10.1039/C6CC08967D

 

 


C5CC08213G Graphical Abstract, Boron clusters in luminescent materials, Mukherjee and ThilagarBoron clusters in luminescent materials

 

Sanjoy Mukherjee and Pakkirisamy Thilagar

Chem. Commun., 2016, 52, 1070-1093

DOI: 10.1039/C5CC08213G

 

 

 


Fluorescent glycoprobes: a sweet addition for improved sensing

C6CC06875H Graphical Abstract, Fluorescent glycoprobes: a sweet addition for improved sensing, Xie et al.

 

Xiao-Peng He, Yi Zang, Tony D. James, Jia Li, Guo-Rong Chen
and Juan Xie

Chem. Commun., 2017, 53, 82-90

DOI: 10.1039/C6CC06875H

 

 

 


C6CC03638D Graphical Abstract, Halogen bonding anion recognition, Brown and Beer

Halogen bonding anion recognition

 

Asha Brown and Paul D. Beer

Chem. Commun., 2016, 52, 8645-8658

DOI: 10.1039/C6CC03638D

 

 

 


C6CC08820A Graphical Abstract, Long range electrostatic forces in ionic liquids, Atkin et al.Long range electrostatic forces in ionic liquids

 

Matthew A. Gebbie, Alexander M. Smith, Howard A. Dobbs, Alpha A. Lee,
Gregory G. Warr, Xavier Banquy, Markus Valtiner, Mark W. Rutland, Jacob N. Israelachvili,
Susan Perkin and Rob Atkin

Chem. Commun., 2017, 53, 1214-1224

DOI: 10.1039/C6CC08820A

 

 


C5CC08216A Graphical Abstract, Pharmaceutical cocrystals: along the path to improved medicines, Zaworotko et al.Pharmaceutical cocrystals: along the path to improved medicines

 

Naga K. Duggirala, Miranda L. Perry, Örn Almarsson and Michael J. Zaworotko

Chem. Commun., 2016, 52, 640-655

DOI: 10.1039/C5CC08216A

 

 

 


C6CC00336B Graphical Abstract, Rational control of nano-scale metal-catalysts for biomass conversion, Yan et al.Rational control of nano-scale metal-catalysts for biomass conversion

 

Yunzhu Wang,  Sudipta De  and  Ning Yan

Chem. Commun., 2016, 52, 6210-6224

DOI: 10.1039/C6CC00336B

 

 

ChemComm is renowned as the fastest publisher of articles providing information on new avenues of research, drawn from all the world’s major areas of chemical research. ChemComm is the ideal place to publish your research.

 

Submit your urgent research to ChemComm today!

 

Stay up to date with ChemComm
Be among the first to hear about the newest articles being published – Sign-up to our journal news alert to receive information about most read articles, themed issues, journal news, as well as calls for papers and invitations.

 

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Ruthenium Currency for a Hydrogen Fuel Economy

A group of researchers at the Chinese Academy of Sciences and Southwest University want us to kick the fossil fuels habit. Their research comes to us from China, a country using roughly one quarter of the world’s yearly energy consumption, and where the finite nature of fossil fuels is a very real threat to energy supply security. Leading in energy use, China also leads the world in electricity production from renewable sources and investment in clean energy projects.

Hydrogen is considered a viable alternative to fossil fuels as it is energy rich, more so than petrol or ethanol at 39 kWh/kg (petrol: 13 kWh/kg, ethanol: 8.2 kWh/kg), and upon combustion emits only water vapour. However, hydrogen is often obtained from fossil fuels, and it will only be a practical option for the world’s future energy needs if it can be produced from a renewable source.

Preparation of the Ru2P/reduced graphene oxide electrocatalyst for the hydrogen evolution reaction

Preparation of the Ru2P/reduced graphene oxide catalyst

To this end, water splitting offers a solution. In a water electrolysis cell, hydrogen is produced at the cathode via the hydrogen evolution reaction (HER, 2H+ + 2e –> H2), and molecular oxygen is produced at the anode (2H2O –> O2 + 4H+ + 4e). It is ideal in theory, but high energy efficiencies are required to make water splitting viable, and this relies on the development of catalytic electrodes to minimize overpotentials required to drive the reaction. Currently, state of the art HER electrocatalysts use platinum, which is expensive and rare. Furthermore, platinum catalysts are most efficient in an acidic electrolyte and proceed 2-3 times slower in alkaline solutions. On the other hand, the best oxygen evolution catalysts perform better in alkaline environments. Using an alkaline electrolyte has overall advantages as it is less corrosive, thus increasing the stability and lifetime of the electrolytic cell.

The authors have developed a HER catalyst, using ruthenium, with overpotentials and current densities superior to Pt/C in both alkaline and acidic conditions.

DFT calculation to probe the hydrogen adsorption energies on the active catalytic surface of the Ru2P on reduced graphene oxide catalyst.

DFT calculation to probe the hydrogen adsorption energies on the active catalytic surface of the Ru2P catalyst. a) and b) front and side views of the calculated Ru2P/reduced graphene oxide surface. c) free energy diagram for the HER with different catalysts.

The electrocatalyst is comprised of small, uniform Ru2P nanoparticles (~2-4 nm) evenly distributed on reduced graphene oxide sheets. The activity of the prepared catalyst (1.0 mg cm-2) for the HER was measured in an acidic medium (0.5 M H2SO4) and the overpotential to achieve a current density of -10 mA cm-2 was -22 mV, superior to Pt/C (-27 mV). In an alkaline environment (1.0 M KOH) catalyst performance was enhanced, with an overpotential of -13 mV (29 mV lower than Pt/C). High Faradaic efficiencies of more than 98% were measured in both acidic and alkaline solutions. Additionally, analysis was undertaken to further understand how the structure and composition of the catalyst influences its activity. Double layer capacitance measurements gave clues about the catalyst surface, while theoretical DFT calculations were used to study H-adsorption energies.

There is no way to avoid the reality that ruthenium is also a rare and costly metal, and for this reason may not hold the key to solving our energy woes. However, of real value are the insights gained from probing the structure function relationship of this highly active catalyst, which may guide the synthesis of rationally-designed catalysts using inexpensive and abundant materials.

To find out more please read:

Ultrasmall Ru2P nanoparticles on graphene: a highly efficient hydrogen evolution reaction electrocatalyst in both acidic and alkaline media

Tingting Liu, Shuo Wang, Qiuju Zhang, Liang Chen, Weihua Hu, Chang Ming Li.
Chem. Commun., 2018, 54, 3343-3346
DOI: 10.1039/c8cc01166d

About the author:

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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3rd Japan-UK Joint Symposium on Coordination Chemistry RSC poster prize winners

The Japan-UK Joint Symposium on Coordination Chemistry is now in its third iteration and highlights the networks and partnerships between the two countries. The meeting, which is supported by Royal Society of Chemistry Dalton Division, Coordination Chemistry interest group, invited 20 excellent coordination chemists from each country to deliver lectures on their recent advances in coordination chemistry, in one of five themes: supramolecular chemistry; materials chemistry; energy and environmental science; organometallic chemistry/catalysis; and bio-coordination chemistry. This year the meeting took place at the University of St Andrews between on 30 April-2 May 2018. The event was attended by a little under a hundred people and 17 posters were presented.

Chemical Science, ChemComm, Dalton Transactions and Catalysis Science & Technology supported the meeting with poster prizes for the six most outstanding poster presentations:

Qingshu Zheng from University of Edinburgh was awarded the Chemical Science award for their poster titled: How important are metallophilic interactions?

Ellie Tanaka from University of Edinburgh was awarded the Chemical Science award for their poster titled: Copper iodide complexes for hole transport in solid-state mesoscopic solar cells.

Diego Rota Matir from University of St Andrews was awarded the ChemComm award for their poster titled: Homochiral emissive supramolecular [Ir₈Pd₄]16+ cages.

Hannah Potter from University of St Andrews was awarded the Dalton Transaction award for their poster titled: Design, synthesis and characterisation of Pt(II)-metalloligands used for thermal and photochemical self-assembly.

Cei Provis-Evans from University of Bath was awarded the Catalysis Science & Technology award for their poster titled: Ironing out the competition: iron catalysed alkyne trimerisation at room temperature.

Michael Shipman from University of Glasgow was awarded the Catalysis Science & Technology award for their poster titled: A re-evaluation of Sn(II) phthalocyanine as a catalyst for the electrosynthesis of ammonia.

 

From left to right: Co-organiser Professor Neil Robertson (University of Edinburgh) with winners Hannah Potter, Diego Rota Matir, Cei Provis-Evans, Michael Shipman, Ellie Tanaka, Qingshu Zheng, along with Dr Jeremy Allen (Royal Society of Chemistry).

 

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4th International Conference on Scanning Probe Microscopy on Soft and Polymer Materials

We are proud to reveal that ChemComm will be sponsoring the 4th International Conference on Scanning Probe Microscopy on Soft and Polymeric Materials (SPMonSPM). This symposium will be held on the 20 – 24 August in Leuven (Belgium) and will cover research on SPM applied to soft matter, polymeric materials and biological systems. The conference will include a short course, plenary lectures, a range of talks and dedicated poster sessions on topics across this field.

 

Scanning Probe Microscopy on Soft and Polymeric Materials

 

Registration is currently open and the early bird registration deadline is the 1st May!

 

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Scanning probe frontiers in molecular 2D-architecture world

Scanning probe frontiers in molecular 2D-architecture world

ChemComm is pleased to announce a themed collection in conjunction with the upcoming symposium on Scanning probe frontiers in molecular 2D-architecture world. This collection is being Guest Edited by Professors Xavier Bouju, Frederic Cherioux, Steven De Feyter and Alain Rochefort, co-organisers of the symposium. Both the conference and themed issue will focus on scanning probe microscopy, both experimental and theoretical work, which we hope will encourage and promote the research in this area.

For more details on the conference and the full programme follow this link.

Researchers wishing to contribute to the ChemComm collection should contact the Editorial Office in the first instance.

Hot topics to be covered in the symposium

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Philip Power at 65: an icon of organometallic chemistry

Professor Philip P. Power (University of California, Davis) turned 65 in April 2018 and in honour of this anniversary and his immense influence on the field of organometallic chemistry we’re pleased to introduce a new cross-journal themed collection

Guest edited by Roland C. Fischer, Michael S. Hill, and David J. Liptrot the collection brings together 27 of Professor Power’s key RSC papers with specially commissioned work for Dalton Transactions and Chem. Commun. by over 45 by his coworkers and protégés.

Read the editorial, in which the guest editors give an overview of Professor Power’s career and highlight some of his contributions to the study of low coordinate systems, multiple bonding, small molecule activation, and London dispersion forces, or read on to check out some of the many hot articles inspired by his work.

 

1,3,2-Diazaborole-derived carbene complexes of boron

Dalton Trans., 2018,47, 41-44
10.1039/C7DT04079B

 

1,3,2-Diazaborole-derived carbene complexes of boron were synthesized via 1,2-hydrogen migration.

 

 

A snapshot of inorganic Janovsky complex analogues featuring a nucleophilic boron center

 

Chem. Commun., 2017,53, 12734-12737
10.1039/C7CC07616A

The addition of phenyl lithium (PhLi) to an aromatic 1,3,2,5-diazadiborinine (1) afforded isolable ionic species 2, which can be deemed as an inorganic analogue of a Janovsky complex.

 

Neutral two-dimensional organometallic–organic hybrid polymers based on pentaphosphaferrocene, bipyridyl linkers and CuCl

Dalton Trans., 2018,47, 1014-1017
10.1039/C7DT04286H
 

The reaction of the Pn ligand complex [Cp*Fe(η5-P5)] (1: Cp* = η5-C5Me5) with CuCl in the presence of 4,4′-bipyridine or 1,2-di(4-pyridyl)ethylene leads to the formation of three unprecedented neutral 2D organometallic–organic hybrid networks.

 

 

C–H and H–H activation at a di-titanium centre

 

Chem. Commun., 2017,53, 13117-13120
10.1039/C7CC07726B

An NHC promotes intramolecular C–H activation in bis(pentalene)dititanium; this process is reversed by the addition of hydrogen, forming a dihydride.

 

Divergent reactivity of nucleophilic 1-bora-7a-azaindenide anions

Dalton Trans., 2018,47, 734-741
10.1039/C7DT04350C
 

The reactions of 1-bora-7a-azaindenide anions, prepared in moderate to excellent yields by reduction of the appropriate 1-bora-7a-azaindenyl chlorides with KC8 in THF, with alkyl halides and carbon dioxide were studied.

 

 

Carbodiimides as catalysts for the reduction of a cadmium hydride complex

 

Chem. Commun., 2018,54, 460-462
10.1039/C7CC08393A

A rare terminal cadmium hydride complex has been synthesised. Reduction to the cadmium(I) dimer complex was achieved upon treatment with carbodiimides.

All articles in this collection will be free to access until the 19th of June. 

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In-Situ Electron Paramagnetic Resonance Spectroscopy Revealed the Charge Storage Behavior of Activated Carbon

Recently in Chem. Commun., Wang et al. from University of Manchester and Liverpool John Moores University, U.K. demonstrated that in-situ electron paramagnetic resonance (EPR) spectroscopy was a powerful tool to study the charge storage mechanism of activated carbon.

Activated carbon is a type of microporous carbon used for electrodes of supercapacitors (a family of charge-storage devices similar to batteries). Conventional electrochemical testing techniques (e.g. cyclic voltammetry) are able to evaluate the overall performance of electrode materials but are unable to reveal the charge storage mechanism at the atomic level. Understanding the charge storage mechanism is crucial to guide the design and synthesis of electrode materials with improved performance. During the past decade, the development of numerous in-situ probing techniques has allowed materials researchers to explore the microscopic charge-discharge behaviour of supercapacitor electrodes.

In the published paper, in-situ EPR spectroscopy was used to study the electrochemical properties of activated carbon under different external potentials. EPR is very sensitive to electron spins originating from unpaired electrons that are generated upon charging or discharging electrode materials. This characteristic makes EPR a suitable technique for in-situ studies. To carry out the experiments, the authors designed and constructed a capillary three-electrode testing cell (Figure 1a). This cell was placed in an EPR spectrometer and its activated carbon electrode was connected to an external power source (to apply external potentials to the activated carbon electrode). The authors collected the spectra of the activated carbon electrode at selected applied potentials, an example of which is shown in Figure 1b.

Analysis of the obtained spectra offered important information about how the surface of activated carbon changed at different potentials. Specifically, the authors deconvoluted the signal into two components: the narrow signal and the broad signal corresponding to the blue and red curves in Figure 1b, respectively. The peak intensity of the narrow signal increased drastically when charging the electrode, but remained almost unchanged when altering the testing temperature. This observation suggests that the origin of the narrow peaks was the surface-localized electrons. These localized electrons were likely from the oxidized products (i.e. radicals) of carboxylate and alkoxide groups on the surface of the activated carbon, evolved during the charging process. The broad signal was ascribed to electrons located on aromatic units (e.g. graphene domains) and its intensity was found to be proportional to the number of ions electrically adsorbed on the activated carbon surface.

Figure 1. (a) The structure of the self-built capillary three-electrode cell: CE – counter electrode (Pt wire); RE – reference electrode (Ag/AgCl); WE – working electrode (activated carbon). (b) A typical EPR signal (black) that can be deconvoluted into narrow peaks (blue) and broad peaks (red).

This work highlights EPR spectroscopy as a novel tool for in-situ investigation of the charge-storage mechanism of carbon-based supercapacitor electrodes, and could be potentially extended to study other types of materials. The availability of diverse in-situ techniques is expected to provide more in-depth fundamental understanding that will guide researchers to rationally develop electrodes with optimized performance.

 

To find out more please read:

In-Situ Electrochemical Electron Paramagnetic Resonance Spectroscopy as A Tool to Probe Electric Double Layer Capacitance

Bin Wang, Alistair J. Fielding and Robert A. W. Dryfe

Chem. Commun. 2018, DOI: 10.1039/c8cc00450a

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is an online blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Synthesis of Maleimide Dyes with Colourful Fluorescent Emissions

A group of researchers based at universities spanning the UK, China and Spain have synthesised a diverse library of fluorescent maleimide dyes with the aim of developing a structure-function relationship, relating substituent effects to the optical properties of such molecules. This work is not only important to build upon fundamental understanding of the fluorescence mechanism, but to develop knowledge that may be used to guide the synthesis of organic fluorophores which demand particular optical properties.

Organic fluorescent molecules are used as tools in many areas such as forensics, genetic analysis, DNA sequencing and biotechnology. Maleimides are commonly used as fluorescent labels for proteins, as they can couple with the thiol groups of cysteine residues. They are suited to this purpose as they are stable, easily functionalised, give strong emissions and do not perturb the protein structure to a large extent.

Molecules fluoresce upon absorption of UV or visible light, elevating an electron from a ground state orbital to a higher-energy orbital and resulting in a singlet excited state. Relaxation to the ground state occurs rapidly (~ 10 ns) with concomitant emission of a photon – this is what we observe as ‘fluorescence’. The emitted photon almost always has a longer wavelength than the absorbed light, a phenomenon known as the ‘Stokes shift’.

 

Structures of selected aminohalomaleimides and alkoxyhalomaleimides

Structures of selected amino-halo-maleimides and alkoxy-halo-maleimides synthesised for the study

With three dihalomaleimide precursers in hand (Cl, Br and I) the researchers assembled a library of amino-halo-maleimides, amino-alkoxy-maleimides, and amino-thio-maleimides. They varied the R groups bound to the N, O and S heteroatoms to include aliphatic, phenyl and benzyl examples.

The optical properties of the amino-halo-maleimides in diethyl ether were examined and the emission wavelengths were measured to be 461-487 nm, giving green-blue fluorescence. The fluorescence quantum yields, a measure of the quantity of emitted photons compared to absorbed photons and an indication of emission brightness, decreased with the electronegativity of the halide (Cl: 37%, Br: 30%, I: 8%). Like many fluorescent molecules in solution the compounds exhibited solvafluorochromism: when the polarity of the solvent alters the optical properties. In protic solvents (methanol and water) the fluorescence quantum yields decreased to below 1% and the emission wavelengths increased by 73-109 nm. On the other hand, in non-polar solvents (cyclohexane) the fluorescence quantum yield increased, up to 56% for the chloro analogue.

a) The UV and emission spectra of fluorescent maleimides bearing amino (2a-c) and alkoxy (3a, 3b) substituents. b) The quantum yields of selected amino and alkoxymaleimides. c) The solvafluorochromism effect for three aminomaleimides (2a-c) in increasingly non-polar solvents.

a) The UV and emission spectra of fluorescent maleimides bearing amino (2a-c) and alkoxy (3a, 3b) substituents. b) The quantum yields of selected amino and alkoxymaleimides. c) The solvafluorochromism effect for three maleimides (2a-c) in various solvents.

Compared to their amino-substituted counterparts, alkoxy-halo-maleimides have lower quantum yields (reduction of 20-25%), indicating the increased electron-donating capacity of the amine substituent is important for fluorescence intensity. Furthermore, the slight decrease in the emission wavelengths of alkoxy-halo-maleimides (458-465 nm) gives them blue fluorescent emissions. Amino-thio-maleimides, with greater electron-donating capacity than both the amino and alkoxy analogues, have increased emission wavelengths (526-564 nm), thus yellow fluorescent emissions.

This study is a worthwhile read for anyone who uses fluorescent molecules in their work, those wishing to understand a little more about the practical principles of fluorescence and all those curious minds who like to form their own hypotheses.

To find out more please read:

Rational design of substituted maleimide dyes with tunable fluorescence and solvafluorochromism

Yujie Xie, Jonathan T. Husband, Miquel Torrent-Sucarrat, Huan Yang, Weisheng Liu, Rachel K. O’Reilly.
Chem. Commun., 2018, 54, 3339 – 3342
DOI: 10.1039/C8CC00772A

About the author:

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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