Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic molecule-based organic cathodes
Even though organic molecules with well-designed functional groups can be programmed to have high electron density per unit mass, their poor electrical conductivity and low cycle stability limit their applications in batteries. A team led by Prof Loh Kian Ping report the facile synthesis of π-conjugated quinoxaline-based heteroaromatic molecules (3Q) by condensation of cyclic carbonyl molecules with o-phenylenediamine. 3Q features a number of electron-deficient pyrazine sites, where multiple redox reactions take place, which was probed using in-situ 15N and 13C solid state Nuclear Magnetic Resonance. When hybridized with graphene and coupled with an ether-based electrolyte, an organic cathode based on 3Q molecules displays a discharge capacity of 395 mAh g−1 at 400 mA g−1 (1C) in the voltage range of 1.2–3.9 V and a nearly 70% capacity retention after 10,000 cycles at 8 A g−1. This work is important in demonstrating that heteroaromatic molecules with multiple redox sites are promising in developing high-energy-density, long-cycle-life organic rechargeable batteries.
Cobalt-Catalyzed Asymmetric Hydroboration/Cyclization of 1,6-Enynes and Enantioselective Synthesis of (-)-Magnofargesin
Dr. Ge and his research team in the Department of Chemistry, NUS, have developed the first cobalt-catalyzed enantioselective hydroboration/cyclization of 1,6-enynes to prepare chiral five-membered cyclic organic compounds. In addition, they applied this methodology to synthesize a bioactive natural product (-)-magnofargesin. This work has recently been published in J. Am. Chem. Soc. (DOI: 10.1021/jacs.7b01708).
NUS chemists made C-C coupling based 2D polymer
Professor Kian Ping Loh and PhD student Liu Wei in the Department of Chemistry, National University of Singapore, applied an ingenious strategy based on endogenous polymerization, carried out without catalyst, solvent or initiator, to make 2-D polymer based on C-C coupling reactions.
They discovered that pre-ordering well-designed, flat monomers into a single crystal structure can lead to a 2D crystalline aromatic polymer upon thermal annealing. The achieved polymeric sheets are parallel and can be readily exfoliated into micrometer-sized sheets with nanometer thickness, similar to the case of single-layer graphene. This approach paves the way towards the controlled synthesis of extended crystalline 2D conjugated materials for various applications. Due to its intra-sheet conjugation and ordered open 1D channel, the 2D polymer fabricated by Loh et. al. exhibits unprecedented cycle stability and rate capability when applied as an anode in an ambient temperature sodium cell. The work is published in Nature Chemistry. Link
They discovered that pre-ordering well-designed, flat monomers into a single crystal structure can lead to a 2D crystalline aromatic polymer upon thermal annealing. The achieved polymeric sheets are parallel and can be readily exfoliated into micrometer-sized sheets with nanometer thickness, similar to the case of single-layer graphene. This approach paves the way towards the controlled synthesis of extended crystalline 2D conjugated materials for various applications. Due to its intra-sheet conjugation and ordered open 1D channel, the 2D polymer fabricated by Loh et. al. exhibits unprecedented cycle stability and rate capability when applied as an anode in an ambient temperature sodium cell. The work is published in Nature Chemistry. Link
Toward metallic molecular wires!
Graphene nanoribbons (GNRs) with a width < 10 nm have promising applications in the future nano-electronics. While semi-conducting GNRs can be applied as active components in field effect transistors, the metallic GNRs can be used as conducting wires. So far, the synthesis of GNRs with potential metallic properties is still not successful. In a recent publication in Link, A/P Wu Jishan’s group reported the challenging synthesis and physical characterizations of a series of soluble and stable rylene ribbon molecules with the record length, which can serve as good model compounds of the narrowest armchair graphene nanoribbon. They observed very unusual open-shell diradical character for long rylene molecules, which can be correlated to the potential metallic property of the infinite polyrylene ribbon. This work was selected as a cover in the January issue.
President's Science Award 2016
Congratulations to A/P Liu Xiaogang for receiving the Link for his outstanding research in developing rare-earth-doped nanocrystals that could be used as luminous tags for tracking cancer cells and deciphering various biologically relevant phenomena. Link
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Extended Bis(benzothia)-quinodimethanes and Their Dications: From Singlet Diradicaloids to Isoelectronic Structures of Long Acenes
In a recent article published in Angew. Chem. Int. Ed., 2016, 55, 9316-9320 (hot paper), (Link), Dr. Chi and her co-workers synthesized a series of extended bis(benzothia)-quinodimethanes and their dications as stable species. The neutral compounds mainly have a quinoidal structure in the ground state but show increased diradical character with extension of the central quinodimethane unit. More importantly, the dications exhibit similar electronic absorption spectra, NMR spectra, NICS values, and diatropic ring currents to their aromatic all-carbon acene analogues and thus can be regarded as genuine isoelectronic structures of pentacene, hexacene and heptacene, respectively. This study provides a new way to design and synthesize stable longer acene analogues with similar electronic structures to the traditional all-carbon acenes.
Boronic Acid: A Bio-Inspired Strategy to Increase the Sensitivity and Selectivity of Fluorescent NADH Probe
Fluorescent probes have been widely used in the molecular recognition events in biological systems; however, it remains challenging to design small-molecule fluorescent probes sensitively and selectively sensing biomolecules with complex structures. Inspired by the enzyme-catalyzed reaction between biomolecule and probe, Prof. Chang and collaborators present a novel combination-reaction two-step sensing strategy to improve sensitivity and selectivity. Based on this strategy, they successfully prepared a boronic acid based fluorescent NADH (reduced nicotinamide adenine dinucleotide) probe and evaluate NADH levels in live cell imaging.
J. Am. Chem. Soc., 2016, 138 (33), pp 10394–10397
Link
J. Am. Chem. Soc., 2016, 138 (33), pp 10394–10397
Link
Development of background-free tame fluorescent probes for intracellular live cell imaging
Fluorescent dyes have been used for bioimaging for long time, but the conventional wisdom says the organic dyes are sticky and leave high background in the biological system. Prof. Chang and collaborators dreamed no-background imaging probes and challenged to figure the physico-chemical properties of such ideal dyes. By testing fluorescent library combined with chemoinformatic analysis, they found three main parameters to achieve the holy grail. The process they called “taming” and the tamed dyes will be of general use for future bioimaging.
Quacquarelli Symonds (QS) World University Rankings 2015
NUS Chemistry has been ranked 7th internationally and 1st in Asia in the latest Quacquarelli Symonds (QS) World University Rankings by Subject. Link.
Dipolar Quinoidal Acene Analogues as Stable Isoelectronic Structures of Pentacene and Nonacene
In a recent article published in Angew. Chem. Int. Ed., 2015, 54, 14412 (Link ), Dr. Chi and her co-workers synthesized quinoidal thia- acene analogues as the respective isoelectronic structures of pentacene and nonacene and an unusual 1,2-sulfur migration was observed during the Friedel-Crafts alkylation reaction. They display a closed-shell quinoidal structure in the ground state with a distinctive dipolar character. In contrast to their acene isoelectronic structures, both compounds are very stable because of existence of more aromatic sextet rings, dipolar character, and kinetic blocking. They exhibit unique packing in single crystals due to balanced dipole-dipole and [C-H•••π]/[C-H•••S] interactions.
Z-Shaped Pentaleno- Acene Dimers with High Stability and Low Band Gap
Dr. Chi’s group reported a new strategy to stabilize reactive acenes by fusion of an anti-aromatic pentalene unit onto the zig-zag edges of two acene units to form a Z-shaped acene dimer, which turned out to be extremely stable and show a small energy gap due to intramolecular donor-acceptor interaction. The stability of pentaleno- tetracene dimer solution is up to 54 days in ambient air and light conditions. X-ray crystallographic analysis revealed their unique geometry and 1D slip-stack columnar structure.
Reference: Angew. Chem. Int. Ed. 2016 (Link
Reference: Angew. Chem. Int. Ed. 2016 (Link
Self-consistent reaction field (SCRF) methods based on multiple expansions
Self-consistent reaction field (SCRF) methods based on multiple expansions are the most popular approaches in incorporation solvation effect in quantum chemical calculations. The Onsager SCRF model was first implemented in the most popular and widely used Gaussian series of programs by Wong, Frisch and Wiberg. The implementation and application of this SCRF method were described in Journal of American Chemistry Society (1991, 113, 4776-4782). The total citations of this landmark paper have reached 1000 recently!
Multiphoton harvesting metal–organic frameworks
Usually multiphoton harvesting property exhibited by the organic molecules in the solution, is quenched in the solid state due to aggregation. However, efficiently luminescent materials in the solid-state form are highly preferable in many photonic applications such as upconversion lasing and light emission due to a higher resistant to photobleaching. By rational choice of ligands with high second hyperpolarizability, MOFs with large nonlinear optical response (up to direct absorption of four photons at 1500 nm) has been reported for the first time by Hong Sheng Quah, Weiqiang Chen, Martin K. Schreyer, Hui Yang, Ming Wah Wong, Wei Ji, and Jagadese J. Vittal in the recent issue of Nature Communications (Vol. 6, Article No. 7954, 2015, doi:10.1038/ncomms8954).
Link
Link
Singaporean Inorganic Chemistry Symposium 2015
The inaugural Singaporean Inorganic Chemistry Symposium (SICS2015) was held at University Town on the 29th of July, 2015. The symposium featured researchers from over thirteen inorganic based research groups from both the NUS Department of Chemistry and the NTU Division of Chemistry and Biological Chemistry in attendance. A wide range of inorganic research was showcased by eleven speakers, varying from medicinal chemistry to catalysis to fundamental main group chemistry. ‘Best Speaker’ awards were presented to Mr Kennard Gan (NTU), Ms Shi Xiaoyan (NTU) and Mr Kelvin Lim (NUS). The SICS2015 organising committee would like to thank the NUS Department of Chemistry for their support in organising this event. Link.
Energy-Based Molecular Fragmentation Methods
The review covers the state-of-the-art of energy-based molecular fragmentation methods of which both authors have made significant contributions. The defining characteristic of an energy-based molecular fragmentation method is that the molecule (also cluster of molecules, or liquid or solid) is broken up into a set of relatively small molecular fragments in such a way that the electronic energy of the full system is given by a simple linear combination of the energies of these fragment molecules. The successful application of the method enables accurate solution of the Schrodinger equation for molecules the size of proteins. Reported by Associate Professor Ryan P A BETTENS group.
Chem Rev 2015 (in press) Link
Chem Rev 2015 (in press) Link
Nature Nanotechnology
Assoc Professor LIU Xiaogang group reported that producing luminescence materials with tunable emission colors that can be applied for high quality displays is a very difficult task. Especially, it is challenging to develop light-responsive materials that are possible to produce any desired colors in a broad spectrum range on demand through the use of a simple external stimulus. Now they have achieved this goal by exploiting a novel concept, non-steady-state upconversion, based on the design and synthesis of lanthanide-doped core-shell upconversion nanomaterials. The emission color of the core-shell upconversion nanocrystals was turned by adjusting the pulse width and intensity of near-infrared laser excitations. R. Deng, F. Qin, R. Chen, W. Huang, M. Hong, X. Liu, “Temporal full-color tuning through non-steady-state upconversion, ” Nature Nanotechnology, 2015, 10, 237-242. Link
A Tribute to Professor Koh Lip Lin
The department of chemistry deeply mourns for the demise of our colleague Prof Koh Lip Lin on 12 Feb 2015.
Prof Loh Kian Ping (Head, Chemistry Department) received the Certificate of
Accreditation for our BSc curriculum from Royal Society of Chemistry.
Fundamental science won MOE Tier 3!
A research team led by Associate Professor Wu Jishan (co-PIs: Profs. Loh Kian Ping, Link, Link, Chi Chunyan, Link; collaborators: Profs. Christian A. Nijhuis, Link, Link, Link, Neil C. Greenham, Link) was funded 10 million S$ for 5 years for their proposed frontier research on synthetic organic spin chemistry, materials and devices.
Department outing to Gardens by the Bay and Annual Dinner at AquaMarine
on 9 Jan 2015
Congratulations to the winners of Department Best Service Support Staff Awards 2014.
| Admin Support Staff | Ms. Ang Hwee Hiok, Agnes |
| Admin Support Staff | Ms. Linda Janti Oei |
| Service Support Staff | Mr. Gopal Selvarajoo |
| Service Support Staff | Mr. Phua Wei De, Victor |
| Teaching Lab Support Staff | Mr. Lin Hansheng, Gideon |
| Teaching Lab Support Staff | Ms. Ong Bee Hoon, April |
The 8th Singapore International Chemistry Conference (SICC-8)14th - 17th Dec 2014, University Town, NUS
SICC-8, which attracted close to 400 participants, including 180 foreign delegates, was jointly organized by the Department of Chemistry, NUS, and the Singapore National Institute of Chemistry (SNIC). With over 150 oral presentations, including 6 plenary and 16 keynote presentations given by highly-established scientists, and 200 poster presentations, the conference was a huge success with a high level of scientific discourse! Link
Building Bonds in Chemistry @ Kyoto
The inaugural International Collaborative and Cooperative Chemistry Symposium (ICCCS) was initiated and organized by NUS chemistry in 2010. This year, ICCCS-5 shifted to Kyoto. Prof Loh Kian Ping, Prof Lu Yixin, A/P Liu Xiaogang, Assist Prof Ang Wee Han, and Assist Prof Zhao Yu attended the symposium, among 40 professors from 8 universities in the region. Many exciting scientific advances in chemical sciences were presented, and the delegates had thoroughly enjoyed scientific interactions, as well as renewed their friendship during the symposium.
Illuminating test measures fat in milk
Prof. Chang Young-Tae’s group reported the first fluorescent milk fat sensor (Chem Comm, 2014, 50, 10398-10410). It exhibits magnificent, yet selective turn-on feature towards fat molecules in complicated milk matrix, through the disaggregation-induced emission mechanism. Further construction of a handy fluorescence milk fat detector provides a convenient rapid tool to measure fat amount quantitatively. This discovery may greatly help enhance the milk quality control process.This work was highlighted in Chemistry World: Link
Reuleaux Triangle Disks: New Shape on the Block (DOI: ja506625y)
A/P Fan Wai Yip and Bernard Ng Choon Hwee reported the preparation of Reuleaux triangle disks from the hydrolysis and precipitation of bismuth nitrate in an ethanol-water system with 2,3-bis(2-pyridyl)pyrazine. Analysis of the intermediates provided insights into the formation of the Reuleaux triangle disk, revealing a unique growth process.
Multicolor Barcoding in a Single Upconversion Crystal
The synthesis of luminescent crystals based on hexagonal-phase sodium yettrium fluoride upconversion microrods is reported by A/P Liu Xiaogang's group. The synthetic procedure involves an epitaxial end-on growth of upconversion nanocrystals comprising different lanthanide activators onto the NaYF4 microrods. This bottom-up method readily affords multicolor-banded crystals in gram quantity by varying the composition of the activators. Importantly, the end-on growth method using one-dimensional microrods as the template enables facile multicolor tuning in a single crystal, which is inaccessible in conventional upconversion nanoparticles. These novel materials offer opportunities as optical barcodes for anti-counterfeiting and multiplexed labeling applications.
Single crystals of a coordination polymer containing an organic polymer ligand!
Prof. JJ Vittal’s group reported an organic polymer comprising cyclobutane rings and a coordination polymer blend together inside this 3D structure obtained in a photochemical dimerization reaction (Angewandte Chemie, 2014). The organic polymer can be depolymerized by the cleavage of cyclobutane rings in an SCSC manner. Read More
You can be made and broken in cycles, Mr. C-C Bond!
The cyclobutane ring can easily be made by solid-state [2+2] cycloaddition reaction. But can this be cleaved? Is it possible to make and break the C-C bond reversible? Can this be achieved in a single-crystal to single-crystal manner? Will this be accompanied by change in properties like photoluminescence? If so the applications for these types of systems are eminent in molecular switching and data storage. For more information see Prof. JJ Vittal’s recent Angewandte Chemie, 2014. Read More
Crystals dance during a reaction! Of course they are excited under UV light!
The self-propulsion of single crystals of three Zn(II) complexes under UV light has been discovered by Prof. JJ Vittal’s group (Angewandte Chemie, 2014). This visually appealing demonstration of the utility of molecular materials for conversion of energy to work. This has been considered as a hot paper by the journal and highlighted as their cover story of the issue. Read More
Distortional isomerism in polyrotaxane coordination polymers!
Of the four supramolecular isomers of coordination polymers synthesized, two have polyrotaxane structures which differ only in the relative positions of the wheel in the neighboring axle. They show different photoreactivity under UV light as well as sensing abilities of a number of organic nitro compounds. Prof. JJ Vittal’s group reported these findings in Angewandte Chemie, 2014. Read More
N
A new benchmark dye for dye-sensitized solar cell! In a recent Article published in JACS (Link), A/P Wu Jishan and his local/international collaborators synthesized a series of N-annulated perylene substituted and fused porphyrin dyes, which showed largely enhanced light harvesting capability in particular in the near infrared region. As a result, one of the dyes exhibited a power conversion efficiency of around 11%, which is comparable and even slightly higher than that of the benchmark dye YD2-o-C8 under same conditions.
Observing High Pressure Chemistry in Graphene Bubbles
The above recent work by the team of Professor Loh Kian Ping has been chosen as a "Hot Paper" by the editors of Angewandte Chemie for its importance in a rapidly evolving field of high current interest. It is also highlighted in Chemistry World published by Royal Society of Chemistry.
Reference: C H Y X Lim, M Nesladek and K P Loh, Angew. Chem., Int. Ed., 2013, DOI: 10.1002/ange.201308682
Reference: C H Y X Lim, M Nesladek and K P Loh, Angew. Chem., Int. Ed., 2013, DOI: 10.1002/ange.201308682
Dibenzoheptazethrene Isomers with Different Biradical Characters: An Exercise of Clar’s Aromatic Sextet Rule in Singlet Biradicaloids
Extension of the Clar’s Aromatic Sextet Rule to the singlet biradicaloids!
In a recent Article published in JACS (Link), A/P Wu Jishan and his local/international collaborators demonstrated that Clar’s Aromatic Sextet Rule can be further extended from the closed-shell polycyclic aromatic hydrocarbons to the open-shell polycyclic hydrocarbon systems, and provides an important guideline for the design of singlet biradicaloids with tailored biradical character and tunable optical, electronic and magnetic properties.
In a recent Article published in JACS (Link), A/P Wu Jishan and his local/international collaborators demonstrated that Clar’s Aromatic Sextet Rule can be further extended from the closed-shell polycyclic aromatic hydrocarbons to the open-shell polycyclic hydrocarbon systems, and provides an important guideline for the design of singlet biradicaloids with tailored biradical character and tunable optical, electronic and magnetic properties.
Order–disorder Transition in a Two-dimensional Boron–Carbon–Nitride Alloy
A team lead by Professor Loh Kian Ping reported the mixing and demixing of 2-D boron–nitrogen and carbon phases and found that energetics for such processes are modified by the metal substrate. The brick-and-mortar patchwork observed of stoichiometrically percolated hexagonal boron–carbon–nitride domains surrounded by a network of segregated graphene nanoribbons can be described within the Blume–Emery–Griffiths model applied to a honeycomb lattice.The isostructural boron nitride and graphene assumes remarkable fluidity and can be exchanged entirely into one another by a catalytically assistant substitution. Visualizing the dynamics of phase separation at the atomic level provides the premise for enabling structural control in a 2-D network for broad nanotechnology applications
Read more: Link
Read more: Link
Hot News
Congratulations to Dr Ge Shaozhong for being awarded the 2015 NUS Young Investigatorship.
Congratulations to Prof Loh Kian Ping for winning the Provost's Chair (Tenable for 3 years from July 2015). Prof Loh was awarded the 2014 President’s Science Award for his outstanding research on graphene chemistry. His research effort on advanced carbon materials is internationally acclaimed and has contributed to Singapore’s and NUS’ position as world leader in this research area.
Congratulations to Asst Prof Chng Shu Sin and Dr Adrian Michael Lee for winning the Annual Teaching Excellence Award 2013/2014.
Congratulations to Assistant Prof Goki EDA for winning the University Young Researcher Award !! Read more.
The Department has just established a research collaboration with its counterpart at the King Fahd University of Petroleum & Minerals (KFUPM), Dhahran, Saudi Arabia. Under the collaboration, six projects involving faculty members from both departments will receive funding of S$1.1 million over three years. From our department, Professors Lu Yixin, Richard Wong and Lee Hian Kee, and Associate Professors Chuah Gaik Khuan, Han Vinh Hyunh and Stephan Jaenicke will be involved in the collaboration with their colleagues from KFUPM on environmental analytical chemistry, catalysis, nanostructured materials and computational electrochemistry.
Professor WONG Ming Wah, Richard has joined the editorial board of Australian Journal of Chemistry as Associate Editor for 3 years.
Congratulate Mr Fung Fun Man for being the 1st Singaporean and 3rd Asian to be elected into the IChO (International Chemistry Olympiad) Steering Committee.
Congratulate Associate Professor Wu Jishan for being appointed as the Dean's Chair from 1st July 2014.
Congratulations to our graduate student Raghavender Medishetty for winning the Best Poster Presenter Award at the '6th-HOPE meeting with Nobel Laureates' March 11-15, 2014 in Tokyo, Japan.
Professor JJ Vittal has been invited to give a talk at the Gordon Research Conference on Crystal Engineering, June 1-6, 2014 at Waterville Valley, NH, USA. He was a discussion leader at the last GRC meeting in 2012 on the same topic.
Professor Lee Hian Kee has been placed in the technical trade journal The Analytical Scientist's (print circulation: 21,000; digital circulation: 58,000) "Power List: 100 Most Influential People in the Analytical Sciences"
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