Schiff base macrocycles are emerging as useful scaffolds for binding two or more catalytic metals in close proximity. Such coordination chemistry allows for the evaluation of potentially beneficial ...catalytic cooperative effects. In the field of ring opening polymerization (ROP) of cyclic esters, only a handful of metal systems bound by Schiff base 2 + 2 type macrocycles have been studied. Nevertheless, results to date have, for certain metals, identified some interesting structure activity relationships, whilst for other systems results have revealed particular combinations of metals and macrocycles to be virtually inactive. This perspective review takes a look at two types of recently-reported Schiff base macrocycles that have been employed as pro-ligands in the metal-catalyzed ROP of cyclic esters, specifically ε-caprolactone and rac-lactide.
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•Self-assembly via Qn-mediated tertiary host–guest interactions plus covalent bonding or non-covalent bonding affords a wide variety of structural types.•Oligomers, Bottle brush ...polymers, supramolecular polymers, 2D polymers, Copolymers, Cyclic polymers, Microcapsules, vesicles and hydrogels are all accessible.•Many potential applications ranging from the detection of explosives to photodynamic therapy and the delivery of anti-cancer agents.
In recent years, cucurbitnurils (CBn or Qns) have attracted considerable attention on account of their unique structural and host–guest binding properties. In this review, we provide an overview of their self-assembly into polymeric species via Qn-mediated tertiary host–guest interactions, and where appropriate, focus on potential applications. The first part of the review describes systems in terms of their structural type from the adoption of tertiary complexes through to microcapsules and vesicles, whilst the second part of the review discusses the systems by way of differing applications. Within each section, systems are arranged in terms of Qn size, with n = 5 to 14, and the type of bonding involved, namely the use of either covalent bonding or non-covalent bonding in combination with host–guest interactions.
Pyrene‐based π‐conjugated materials are considered to be an ideal organic electro‐luminescence material for application in semiconductor devices, such as organic light‐emitting diodes (OLEDs), ...organic field‐effect transistors (OFETs) and organic photovoltaics (OPVs), and so forth. However, the great drawback of employing pyrene as an organic luminescence material is the formation of excimer emission, which quenches the efficiency at high concentration or in the solid‐state. Thus, in order to obtain highly efficient optical devices, scientists have devoted much effort to tuning the structure of pyrene derivatives in order to realize exploitable properties by employing two strategies, 1) introducing a variety of moieties at the pyrene core, and 2) exploring effective and convenient synthetic strategies to functionalize the pyrene core. Over the past decades, our group has mainly focused on synthetic methodologies for functionalization of the pyrene core; we have found that formylation/acetylation or bromination of pyrene can selectly lead to functionalization at K‐region by Lewis acid catalysis. Herein, this Minireview highlights the direct synthetic approaches (such as formylation, bromination, oxidation, and de‐tert‐butylation reactions, etc.) to functionalize the pyrene in order to advance research on luminescent materials for organic electronic applications. Further, this article demonstrates that the future direction of pyrene chemistry is asymmetric functionalization of pyrene for organic semiconductor applications and highlights some of the classical asymmetric pyrenes, as well as the latest breakthroughs. In addition, the photophysical properties of pyrene‐based molecules are briefly reviewed. To give a current overview of the development of pyrene chemistry, the review selectively covers some of the latest reports and concepts from the period covering late 2011 to the present day.
Pepping up pyrene: This Minireview highlights direct synthetic approaches to functionalize the pyrene at the active sites (the 1‐, 3‐, 6‐, and 8‐positions), the K‐region (the 4‐, 5‐, 9‐, and 10‐positions), and the nodal plane (the 2‐ and 7‐positions), in order to advance research on luminescent materials for organic electronic applications. Further, this article demonstrates the future direction of pyrene chemistry for organic semiconductor application and highlights some classical asymmetric pyrenes, as well as the latest breakthroughs.
This review describes the recent advances (from 2008 onwards) in the use of Schiff-base metal complexes as catalysts for the ring opening polymerization (ROP) of cyclic esters. The synthesis and ...structure of the metal complexes, as well as all aspects concerning the polymerization process and the characteristics of the polymers formed, will be discussed.
Recent progress in the use of iron-based complex pre-catalysts for ethylene reactivity is reviewed, illustrating the current state-of-the-art and the potential usefulness of such systems for ...delivering solely ethylene oligomerization or polymerization products. The problems associated with the industrial use of late transition metal complex pre-catalysts are generally regarded as catalyst deactivation and the formation of more products of lower molecular weight at elevated temperature. These problems have been addressed for iron-based complex pre-catalysts via the fine tuning of substituents of existing ligands and/or the design of new ligand sets. Results revealed that modified bis(imino)pyridyliron dichlorides were capable of operating at elevated temperatures, and were capable of delivering highly linear polyethylene. Other new models of iron complexes have achieved high activity for ethylene oligomerization and/or polymerization. Particularly successful has been the use of the 2-iminophenanthrolyliron pre-catalyst, which have now been utilized in a 500 tonne pilot plant.
Bis(imino)pyridine, reactive ligands and a gateway to novel families of catalysts are reviewed. The same ligand frame also supports vanadium and chromium.
In this review, we discuss the use of titanium complexes bearing either bridged diphenolate or calixnarene (n = 4, 6, 8) ligation, in the formation of plastics from α-olefins or via the ring opening ...polymerization (ROP) of cyclic esters. The syntheses, molecular structures and catalytic behaviour of these systems are discussed, as well as where possible, the properties of the resultant polymers.
A new fluorescent chemosensor comprised of cucurbit8uril (Q8) and acridine hydrochloride (AC) has been designed and utilized for the recognition of amino acids. The AC was encapsulated by the Q8 ...cavity and formed a 1:2 host-guest inclusion complex both in solution (aqueous) and in the solid-state. Whilst free AC is known to be strongly fluorescent, this strong fluorescence was quenched in the inclusion complex Q 8-AC. This non-fluorescent complex Q8-AC was capable of serving as a fluorescence “off-on” probe, and was able to recognize either L-Phe or L-Trp via the competitive interaction between L-Phe or L-Trp. Moreover, the pH responsive nature of the probe allowed for the detection of basic amino acids, namely L-Arg, L-His, or L-Lys). As a result, a fluorescence method for the detection of five amino acids using a single system has been developed.
A new fluorescent chemosensor comprised of cucurbit 8uril (Q 8) and acridine hydrochloride (AC) has been designed for the recognition of amino acids. As a result of this study, the fluorescence detection of five amino acids in a single system has been accomplished. Display omitted
•A new fluorescent chemosensor comprised of Q8 and acridine has been designed for the recognition of amino acids.•The binding properties of Q8 to acridine was investigated both in solid state and aqueous solution.•A fluorescence method for the detection of five amino acids using a single system has been developed.
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