'Aggregation-Induced Emission'' of Transition Metal Compounds: Design, Mechanistic Insights, and Applications

In the last decades, compounds with 'Aggregation-Induced Emission' (AIE), which are weakly or non- emissive at all in solution but exhibit a strong luminescence in aggregated states, have emerged as an extraordinary breakthrough in the field of luminescent materials, allowing to circumvent 'Aggre- gation Caused Quenching' (ACQ), which in many cases prevents the development of efficient solid-state materials for optoelectronic applications. Since the discovery of AIE, many AIE-active materials have been developed, most of them composed of organic molecules, and thus fluorescent in nature. Although a wide range of applications such as bioimaging, sensing, multi-stimuli responsive materials, and optoelectronic devices have been proposed for this new class of materials, triplet harvesting phosphorescent materials have much longer lifetimes as compared to their singlet harvesting analogues, and for this particular reason, the development of AIE- active phosphorescent materials seems to be a promising strategy from the applications point of view. In this respect, the synthesis of new AIE-active systems including heavy metals that would facilitate the population of low-lying excited triplet states via spin-orbit coupling (SOC), for which the strength increases as the fourth power of atomic number, i.e. Z4 , is highly desirable. This review covers the design and synthetic strategies used to obtain the AIEgens reported in the literature that contain either d-block metals such as Cu(I), Zn(II), Re(I), Ru(II), Pd(II), Ir(III), Pt(II), Au(I), and Os(IV), describing the mechanisms proposed to explain their AIE. New emerging high-tech applications such as OLEDs, chemical sensors or bioimaging probes proposed for these materials are also discussed in a separate section

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health

Modulating Molecular Aggregation of Luminogens: Bridging the Gap Between Solutions and Solids

In the past two decades, the advancement of aggregation-induced emission (AIE) has greatly advanced our understanding of organic luminescence and facilitated the application of organic luminescent materials. AIEgens emit weakly in solutions but strongly in aggregated states. This significant difference in luminescence between solutions and aggregated states of AIEgens has shown that there is much to explore in the mesoscopic world (the intermediary phase). Accordingly, the research paradigm is shifting towards aggregate science. The path to new aggregate materials relies not only on molecule syntheses but also on the control of molecular aggregation. Molecular aggregation bridges the gap between solutions and solids, which is of great significance for developing aggregate science. In this perspective, we outline three general strategies for managing molecular aggregation to stimulate new ideas and provide guidance on controllable molecular aggregation

Diversity-Oriented Synthesis of Functional Polymers with Multisubstituted Small Heterocycles by Facile Stereoselective Multicomponent Polymerizations

Multicomponent polymerization (MCP) has received world-wide attention as a powerful synthetic strategy toward various polymers with complex structures. However, few studies have been reported to fully utilize the monomer combination diversity of MCPs to facilitate the synthesis of diversified polymers with novel structures and advanced functionalities. Herein, we reported a facile multicomponent polymerization route based on the diversity-oriented synthesis. Using varying combinations of difunctionalizable alkynes, sulfonyl azides and Schiff bases, diverse functional polymers with multisubstituted small heterocycles were successfully produced. High stereoselectivity was observed on specific polymeric products. The obtained azetidine-derivative heterocycles exhibit high stability even after treatment with extra HCl and KOH for 48 h. Additionally, polymers with tetraphenylethylene moieties show strong aggregation-induced emission and can function as promising chemosensors for detecting Pd2+ and Cr2O72-. The facile MCP routes present could bring new inspiration to polymer chemistry, and the fascinating functionalities of the obtained polymers with stable four-membered heterocycles could promote further research on the design, modification, and applications of diversified functional polymer materials

Reverse transcription polymerase chain reaction (RT-PCR) based detection and serotyping of FMD Virus from field samples of Gazipur, Bangladesh, and adaptation of the virus in BHK-21 cell

The study aimed for the detection and serotyping of Foot and Mouth Disease virus (FMDV) circulating in Kapasia Upazila, Gazipur district of Bangladesh during 2013. Twelve samples comprising of tongue epithelium (n=8) and inter digital tissue (n=4) were collected from suspected cattle, and inocula were prepared. The inocula were inoculated into confluent BHK-21 cell line for virus propagation. After 3 subsequent passages; progressive cytopathic effects (CPE) specific for FMDV i.e., rounding and flattening of cells, breaking down of the intercellular bridge and finally cell death (almost 100%) were observed; these were indicative of successful virus propagation in the cells. Viral RNA was extracted, and Reverse Transcription Polymerase Chain Reaction (RT-PCR) was performed using three sets of primers corresponding to the serotype and lsquo;O', and lsquo;Asia-1' and and lsquo;A', respectively. Out of the 12 samples, 10 (83.33%) were found to be positive for FMDV, and all of those were of serotype and lsquo;O'. It is concluded that FMDV serotype and lsquo;O' is circulating among the cattle of Gazipur district, Bangladesh. [J Adv Vet Anim Res 2015; 2(3.000): 291-295

Highly Selective Detection of H⁺ and OH^– with a Single-Emissive Iridium(III) Complex: A Mild Approach to Conversion of Non-AIEE to AIEE Complex

A greenish-blue emissive bis-cyclometalated iridium­(III) complex with octahedral geometry was synthesized in a convenient route where a bulky substituted ligand, <i>N</i>¹<b>-</b>tritylethane-1,2-diamine ligand (trityl-based rotating unit) (<b>L</b>_<b>1</b>), was coordinated to iridium­(III) in nonchelating mode, [Ir­(F₂ppy)₂(L₁)­(Cl)], [F₂ppy = 2-(2′,4′-difluoro)­phenylpyridine; <b>L</b>_<b>1</b> = <i>N</i>¹-tritylethane-1,2-diamine], <b>1</b>. The purpose of introducing a rotor in <b>1</b> was anticipated to initiate aggregation-induced emission (AIE) activity in it. The presence of a secondary amine in <b>L</b>_<b>1</b> has attributed to <b>1</b> the ability to sense acids. The mechanism of this change in <b>1</b> under acidic medium was explored. A bright yellow emissive complex was formed on exposing <b>1</b> to hydroxide ion, which was isolated, characterized, and identified as a new aggregation-induced enhanced emission (AIEE) active complex. The detection limit of hydroxide ion was determined to 126 nM. Ground- and excited-state properties of <b>1</b> were investigated using DFT- and TD-DFT-based calculations, and several important aspects of the experimental facts were validated

Highly Selective Detection of H⁺ and OH^– with a Single-Emissive Iridium(III) Complex: A Mild Approach to Conversion of Non-AIEE to AIEE Complex

A greenish-blue emissive bis-cyclometalated iridium­(III) complex with octahedral geometry was synthesized in a convenient route where a bulky substituted ligand, <i>N</i>¹<b>-</b>tritylethane-1,2-diamine ligand (trityl-based rotating unit) (<b>L</b>_<b>1</b>), was coordinated to iridium­(III) in nonchelating mode, [Ir­(F₂ppy)₂(L₁)­(Cl)], [F₂ppy = 2-(2′,4′-difluoro)­phenylpyridine; <b>L</b>_<b>1</b> = <i>N</i>¹-tritylethane-1,2-diamine], <b>1</b>. The purpose of introducing a rotor in <b>1</b> was anticipated to initiate aggregation-induced emission (AIE) activity in it. The presence of a secondary amine in <b>L</b>_<b>1</b> has attributed to <b>1</b> the ability to sense acids. The mechanism of this change in <b>1</b> under acidic medium was explored. A bright yellow emissive complex was formed on exposing <b>1</b> to hydroxide ion, which was isolated, characterized, and identified as a new aggregation-induced enhanced emission (AIEE) active complex. The detection limit of hydroxide ion was determined to 126 nM. Ground- and excited-state properties of <b>1</b> were investigated using DFT- and TD-DFT-based calculations, and several important aspects of the experimental facts were validated

Room Temperature Phosphorescent Nanofiber Membranes by Bio-fermentation

Stimuli-responsive materials exhibiting exceptional room temperature phosphorescence (RTP) hold promise for emerging technologies. However, constructing such systems in a sustainable, scalable, and processable manner remains challenging. This work reports a bio-inspired strategy to develop RTP nanofiber materials using bacterial cellulose (BC) via bio-fermentation. The green fabrication process, high biocompatibility, non-toxicity, and abundant hydroxyl groups make BC an ideal biopolymer for constructing durable and stimuli-responsive RTP materials. Remarkable RTP performance is observed with long lifetimes of up to 1636.79 ms at room temperature. Moreover, moisture can repeatedly quench and activate phosphorescence in a dynamic and tunable fashion by disrupting cellulose rigidity and permeability. With capabilities for repeatable moisture-sensitive phosphorescence, these materials are highly suitable for applications such as anti-counterfeiting and information encryption. This pioneering bio-derived approach provides a reliable and sustainable blueprint for constructing dynamic, scalable, and processable RTP materials beyond synthetic polymers

Secondary Through-Space Interactions: Achieving Single-Molecule White-Light Emission from Clusteroluminogens with Isolated Phenyl Rings

Clusteroluminogens (CLgens) refer to some non-conjugated molecules that show visible light due to the formation of aggregates and unique electronic properties with through-space interactions (TSI). Although mature and systematic theories of molecular photophysics have been developed to study conventional conjugated chromophores, it is still challenging to endow CLgens with designed photophysical properties by manipulating TSI. Herein, three CLgens with non-conjugated donor-acceptor structures and different halide substituents with secondary TSI are designed and synthesized. These molecules show multiple emissions and even white-light emission in the crystalline state and the intensity ratio of these multiple emission peaks is easily manipulated by changing the halide atom and excitation wavelength. Experimental and theoretical results successfully disclose the electronic nature of these multiple emissions: through-space conjugation for short-wavelength fluorescence, through-space charge transfer based on secondary TSI for long-wavelength fluorescence, and room-temperature phosphorescence. The introduction of secondary TSI to CLgens not only enriches their varieties of photophysical properties but also inspires the establishment of novel aggregate photophysics for clusteroluminescence

Dual emission and multi-stimuli-response in iiridium(III) complexes with aggregation-induced enhanced emission: application for quantitative CO₂ detection

Four new Ir(III) complexes with the general formula [IrHCl(C^N)(PPh3)2] containing different conjugated Schiff base ligands (C^N) have been synthesized and characterized by 1H, 13C, and 31P NMR, HRMS, and IR spectra and one of them by single crystal X-ray diffraction. Their photophysical properties in solution and in the solid state have been analyzed and three main practical results have been obtained: (i) a dual fluorescent and phosphorescent emissive complex in solution, (ii) successful acid/base sensing in the solid state and (iii) quantitative CO2 detection. Quantum chemical calculations have been employed to assign the character of the lowest excited states. A plausible explanation for the observed aggregation induced enhanced emission (AIEE) is given, based on the restriction of intramolecular motions due to the effect of intermolecular C-Hp and C-HCl type interactions upon aggregation