Conference Programme

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Overview
Session
T-02: Symp T
Time:
Monday, 19/Jun/2017:
4:00pm - 6:15pm

Session Chair: Hai-Bo Yang, East China Normal University
Location: Nicoll 2

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Presentations
4:00pm - 4:15pm
Oral

How a Small Structural Difference Can Turn Optical Properties of p-Extended Coumarins Upside Down: The Role of Non-Innocent Saturated Rings

Daniel T. GRYKO1, Irena DEPERASINSKA2, Barbara VENTURA3, Yevgen M. PORONIK1

1Institute of Organic Chemistry, Polish Academy of Sciences, Poland; 2Institute of Physics, Polish Academy of Sciences, Poland; 3Istituto ISOF-CNR, Italy

The fluorescence properties of two new families of heterocycles possessing either a seven- or five-membered ring attached at the core molecule are entirely different in solution and in the solid-state. Crystallization has the effect of inhibiting non-radiative excited-state deactivation pathways, operative in solution for the seven-membered ring compounds, thus leading to significant fluorescence efficiency in the solid state, ranging from 0.10 to 0.36. Conversely, the five-membered ring derivatives, which display notable emission properties in solution, are almost non-emissive in the crystals, characterized by a long-range π-stacked arrangement. When embedded in polymeric films, both series show fluorescence features similar to the solution case, with remarkable fluorescence quantum yields ranging from 0.09 to 0.41. According to quantum chemical calculation 3H-chromeno[3,4-c]pyridine-4,5-diones show the specific mechanism of fluorescence quenching. The derivatives bearing the seven-membered ring undergo in solution a significant structural deformation in the excited state, resulting in a large decrease of the energy gap between S1 and S0 and hence to a substantial contribution of the internal conversion in the relaxation process. The fluorescence quenching of the five-membered ring derivatives is in turn related to the intermolecular interaction between adjacent molecules prevailing to a greater extent in the crystal lattice.


4:15pm - 4:30pm
Oral

Aggregation-Induced Emission Active Sensor Molecule for Heavy Metal ions, Anions and Neutral Molecules

Amrita CHATTERJEE

Birla Institute of Technology & Science, Pilani - K.K.Birla Goa Campus, India

Molecular understanding between small molecules and biologically and environmentally important species is the heart of sensing chemistry and motivates the creation of new chemical sensors as useful analytical methods. A powerful set of chemical sensors were also developed to understand the fundamental aspects of intercellular relationships. In recent years, development of the reaction based sensors, technically termed as chemodosimeters received a significant attention as highly important area of research. During the past decade, fluorescent chemosensors have become an important research field and have attracted great attention because of their simplicity, high selectivity and sensitivity. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Keeping in mind, the wide application range, bioaccumulation properties and toxicity to living systems, the trace level estimation of cation and anions in various systems is extremely important. Our research area is mainly focused on the design and synthesis of fluorimetric chemosensor using molecule having aggregation-induced emission property such as tetraphenylethylene (TPE) for the selective recognition of variety of heavy metal ions, anions and neutral molecules. These sensors showed outstanding analytical performance with different biological and environmental sample matrices with high sensitivity, selectivity and good reproducibility. Our future research will continue to focus on the designing of new fluorescent materials with high response characteristics towards particular analyte while maintaining design simplicity and cost effectiveness.


4:30pm - 5:00pm
Invited

Tetraphenylethene-based Functional Metallosupramolecular Structures via Coordination Self-Assembly

Hai-Bo YANG

East China Normal University, China

Tetraphenylethene (TPE)-based functional metallosupramolecular through coordination-driven self-assembly have proven to be novel scaffolds to construct various fluorescent materials with aggregation-induced emission (AIE) properties. For example, Stang group successfully constructed a library of TPE-based discrete organoplatinum(II) metallosupramolecular structures with rich optical properties.[1] Recently, based on our previous research on well-defined functional metallacycles[2], we have expanded our related investigation towards the construction of TPE-based functional materials. For instance, we successfully prepared a new family of tris-TPE metallacycles via coordination-driven self-assembly, which could aggregate into the ordered linear nanostructures upon threading the heparin through the metallacycles driven by multiple electrostatic interaction, thus allowing for the detection of heparin at the clinical dosage level.[3] In addition, with the aim to build novel water-soluble TPE-based functional metallosupramolecular materials, we have developed a facile approach for synthesis of fluorescent supra-amphiphilic star polymers possessing well-defined metallacycles as the core via post-assembly polymerization. The obtained amphiphilic fluorescent star polymers presented high dispersibility in water and good biocompatibility, thus allowing for bioimaging application.

References:

[1] (a) Yan, X.; Cook, T. R.; Wang, P.; Huang, F.; Stang, P. J. Nat. Chem. 2015, 7, 342.

[2] (a) Li, Z.-Y.; Zhang, Y.-Y.; Zhang, C.-W.; Chen, L.-J.; Wang, C.; Tan, H.; Yu, Y.; Li, X.; Yang, H.-B. J. Am. Chem. Soc. 2014, 136, 8577. (b) Jiang, B.; Zhang, J.; Ma, J.-Q.; Zheng, W.; Chen, L.-J.; Sun, B.; Li, C.; Hu. B.-W.; Tan, H.; Li, X.; Yang, H.-B. J. Am. Chem. Soc. 2016, 138, 738. (c) Zheng, W.; Chen, L.-J.; Yang, G.; Sun, B.; Wang, X.; Jiang, B.; Yin, G.-Q.; Zhang, L.; Li, X.; Liu, M.; Chen, G.; Yang, H.-B. J. Am. Chem. Soc. 2016, 138, 4927.

[3] Chen, L.-J.; Ren, Y. Y.; Wu, N. W.; Sun, B.; Ma, J. Q.; Zhang, L.; Tan, H.; Liu, M.; Li, X.; Yang, H.-B. J. Am. Chem. Soc. 2015, 137, 11725


5:00pm - 5:30pm
Invited

Non-helical π-conjugated Polymer Meets Helical σ-conjugated Polymers: Heteroaggregation-enhanced Far-red CPL Materials with Glum = ±0.02 at 700 nm

Michiya FUJIKI, Shosei YOSHIMOTO

Nara Institute of Science and Technology, Japan

Recently, highly emissive chiroptical materials in red, far-red (FR) and infrared (IR) region are a growing interest for curiosity and several potent applications. However, such the chiroptical emitters are rare because the corresponding building blocks are very limited and/or are needed a tedious multiple-step synthesis. Based on our recent finding [1], herein we demonstrated an aggregation-induced enhanced circularly polarized luminescent (AIEnh-CPL) systems by aggregating non-helical poly{(dioctylfluorene)-alt-[bis(thiophenyl)benzothiazole]} (PF8DBT) with help of helical polysilane pair, poly(n-hexyl-(S)-2-methylbutylsilane(PSi-S)and poly(n-hexyl-(R)-2-methylbutylsilane)(PSi-R), in chloroform-methanol cosolvent. An aging at ambient temperature after production of the heteroaggregate (PF8DBT-PSi-S and PF8DBT-PSi-R) was a crucial to enhance CPL amplitude. The glum value of the heteroaggregate became a maximum over 24 hrs. The corresponding circular dichroism (CD) extremum (λext) concurrently redshifted with the aging time. Temporal CPL characteristics of the heteroaggregate under optimized conditions reached glum ≈ –0.02 (with PSi-S) and ≈ +0.02 (with PSi-R) at 700 nm for several days after production of the heteroaggregate. We assumed that these behaviors arise from significant structural transition from highly disorder structures (high-entropy) to an ordered structure (low-entropy) with a prolonged time, leading to a highly delocalized p-electron system. Actually, DFT/TD-DFT calculations (B3/LYP, 6-31G(d,p) basis set) for model oligomers of PF8DBT had multiple rotational isomers that have energetically almost identical local minima. Noticeably, the glum at 700 nm of PF8DBT- PSi-S heteroaggregate was maintained even after photoscissoring of PSi-S at 313 nm.

Reference:

[1] N. A. A. Rahim and M. Fujiki, Polym. Chem., 7, 4618 (2016).


5:30pm - 5:45pm
Oral

Water Soluble Cationic Tetraphenylethene: An Aggregation Induced Emission (AIE) Active Auto-fluorescent Probe for the Selective Detection of E. coli

Vikas KUMAR, Amrita CHATTERJEE, Mainak BANERJEE

Birla Institute of Technology & Science, Pilani - K.K.Birla Goa Campus, India

Fluorescent probes, in particular emission based fluorescent “light-up” probes are important tool in the field of bio-medical applications. Tetraphenylethylene (TPE) is the most useful scaffold in making several luminescent materials because of its inherent aggregation induced emission (AIE) property. Water solubility and biocompatibility are two important factors for the use of AIE compounds in bio-technological applications [1]. These TPE based probes could become more water soluble and bio-compatible by incorporating glycol units in the chain and cationic pyridinium unit at the terminal respectively so that they would be more suitable for biotechnological applications. This unique feature provides an opportunity to design light-up probes for cellular and vascular imaging.

Bacterial identification play important roles in clinical aspects and the food industry, which helps identify origins of infections and food contamination due to different harmful bacteria, as well as provide information for selection of antibiotic against these antibacterial reagents. Different from conventional techniques such as plating and culturing, gene sequence identification etc., which requires either long time to test or sophisticated equipment, fluorescence based method has been widely accepted as a rapid and sensitive bacterial detection approach [2].

The present work describes synthesis of three water soluble TPE derived cationic amphiphiles with variable glycol spacer. Their inherent AIE property was utilized to explore their potential biotechnological applications. In preliminary study, TPE amphiphile with hexaethylene glycol spacer showed good bacterial detection efficiency on Gram-negativeE. coli (Fig. 1c,d) bacteria in 25 μM concentration.


5:45pm - 6:00pm
Oral

Non-Conventional Luminogen with Aggregation-Induced Emission Characteristic

Haoke ZHANG

Hong Kong University of Science and Technology, Hong Kong S.A.R. (China)

In this work a non-conjugated compound, namely s-TPE-TM has been designed and synthesized (Figure 1). Different from tetraphenylethylene (TPE), a conventional and typical luminogen with aggregation-induced emission (AIE) feature, the four phenyl rings are connected to a single C-C bond in s-TPE-TM. From its crystal structure, the only weak intermolecular interaction was observed due to the strong steric hindrance exists between molecules. According to traditional photophysical theories, s-TPE-TM should only show emission from the trimethylphenyl moiety at ~307 nm both in solution and aggregate state. While this holds true in the solution state, s-TPE-TM shows an additional redder emission peak at around 380 nm when aggregated (Figure 1). The emission was further red-shift to 425 nm in its powder form. What is the origin of the longer emission? As no strong intermolecular interactions, such as π-π stacking and C-H···π interaction, are detected in its crystals, the longer emission thus should be stemmed from the intramolecular interaction of a single molecule. Results from the molecular simulation show that electronic communication occurs among the phenyl rings. In other words, they interact in a through-space fashion. It is noteworthy that the emission peak at ~307 nm becomes weaker when the molecules are aggregated and have an aggregation-caused quenching (ACQ) effect, that at around 380 nm is AIE-active.

Thus, the present study brings us new ideas to design and synthesize luminogens with unique photophysical properties and help us to deeply understand the mechanism of molecular conjugation and photoluminescence.


6:00pm - 6:15pm
Oral

In vivo Fluorescence Imaging of Cancer Cell Progression in Xenografted Zebrafish

Purnima MANGHNANI, Gengwei LIN

National University of Singapore, Singapore

We present a robust red AIE fluorophore (t-BPITBT-TPE) with strong aggregate-state photoluminescence and biocompatibility. Micelles with t-BPITBT-TPE as core and DSPE-mPEG as polymeric encapsulation exhibit photoluminescence peak at 660 nm with a high relative fluorescence quantum yield of 32% in aqueous media. The biocompatibility, toxicity, circulation and bio-distribution of various surface functionalized nanoparticles (NPs) are assessed using the zebrafish model through whole embryo soaking and intravenous delivery. Based on the uptake profile, HeLa and MCF-7 cells are tagged with t-BPITBT-TPE in DSPE-PEG-NH2-TAT polymer NPs. Furthermore, they are xenografted into zebrafish yolkscac to observe the cell line aggressiveness. The NPs successfully track the cancer cell proliferation and metastasis, validating these new NPs as efficient cell trackers.



 
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