Recent Advances in Macrocyclic Fluorescent Probes for Ion Sensing

Small-molecule fluorescent probes play a myriad of important roles in chemical sensing. Many such systems incorporating a receptor component designed to recognise and bind a specific analyte, and a reporter or transducer component which signals the binding event with a change in fluorescence output have been developed. Fluorescent probes use a variety of mechanisms to transmit the binding event to the reporter unit, including photoinduced electron transfer (PET), charge transfer (CT), Förster resonance energy transfer (FRET), excimer formation, and aggregation induced emission (AIE) or aggregation caused quenching (ACQ). These systems respond to a wide array of potential analytes including protons, metal cations, anions, carbohydrates, and other biomolecules. This review surveys important new fluorescence-based probes for these and other analytes that have been reported over the past five years, focusing on the most widely exploited macrocyclic recognition components, those based on cyclam, calixarenes, cyclodextrins and crown ethers; other macrocyclic and non-macrocyclic receptors are also discussed

New Trends in Asymmetric Catalysis

The synthesis of enantiopure organic compounds is a key issue for several applications in pharmacology, food chemistry, agricultural chemistry, perfumery, materials science and other industrial sectors. Nowadays, asymmetric catalysis is undoubtedly the most important tool to achieve this goal. This technology, in fact, enables the production of large amounts of enantiomerically enriched compounds, employing relatively small quantities of chiral enantiopure catalysts, which is exactly what is accomplished by enzymes in nature. Since the pioneering works of Noyori, Knowles and Sharpless, which later earned them the Nobel Prize in Chemistry, asymmetric catalysis has experienced a rapid and relentless development in the last fifty years. The tremendous expansion of enantioselective transformations, the design of novel and more efficient organometallic and organic catalysts, the development of sophisticated bioreactors and cell factories, are just some of the elements responsible for such growth. However, new challenges of asymmetric catalysis are devoted to enhancing the process’s sustainability, by the introduction of recyclable and low-cost catalysts, and the use of renewable starting materials and energy source. This book provides an overview of some of these development directions and comprises a collection of review papers and a research article authored by renowned researchers actively involved in this field. The topics covered by the review papers are photoredox-catalyzed reactions of imines, asymmetric catalytic electrosynthesis, cooperative catalysis of chiral N-heterocyclic carbenes and Lewis acid, and asymmetric ring-opening reactions of epoxides catalyzed by metal–salen complexes. The research article presents a proline-catalyzed aldol reaction in water–methanol solvent mixture

Synthesis Of Functional Group Containing Calix[4]pyrroles

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu çalışmada aşağıda belirtilen başlıklar üzerinde araştırma yapılmıştır. (i) Uzun alkil zincirleri içeren kaliks[4]pirollerin sentezi: Çalışmanın bu kışmına temel teşkil eden ana fikir kalikspirolerin birbirine karışmayan çözücü sistemlerinde çalışıldığında su fazına geçmemesinin sağlanmasıdır. Bu nedenle meso- ya da -pozisyonlarına uzun n-alkil zincirlerinin ester köprüleri ile takıldığı ve -pirolik pozisyonlarının serbest ya da bromlanmış olduğu kaliks[4]pirol bileşikleri hazırlandı ve bunların apolar çözücülerde çözünebilir olduğu gösterildi. Ayrıca sentezlenen bileşiklerin anyon bağlama özellikleri incelenmiştir. (ii) Tetrabanzokaliks[4]pirol: Bu bölümde bisiklo[2.2.2]-oct-2-ene üniteleri içeren ve derin bir kaviteye sahip kaliks[4]pirol bileşiği bir maskelenmiş pirol türevinden çıkılarak sentezlenmiştir. Ayrıca bu kalikspirolün tetrabenzokaliks[4]pirole dönüşrütülme reaksiyonu incelenmiştir. (iii) Pendant kaliks[4]pirol üniteleri içeren polimerlerin sentezi: Araştırmanın bu kısmında metakrilat fonksiyonlandırılmış kaliks[4]pirol bileşiğinin sentezi ve bu bileşiğin homopolimeri ve MMA kopolimeri sentezlenmiştir. Ayrıca kaliks[4]pirol-MMA kopolimerinin organik çözücülerinin TBAF ve TBACl tuzlarını sulu çözeltilerden oktametilkaliks[4]pirol ve PMMA’a göre çok çok daha iyi ekstrakte edebildiği gösterilmiştir. Ayrıca kaliks[4]pirol, benz-15-crown-5 ve MMA monomerlerinin kopolimerleri hazırlanmış ve bu anyon ve katyon reseptörü içeren polimerlerin sulu çözeltilerden KCl ve KF’ü anyon ve katyonu ile birlikte ekstrakte edebildiği gösterilmiştir. (iv) Dendrimerik kaliks[4]piroller: Çalışmanın bu kısmında; dört farklı kalikspirol içeren dednrimerik bileşiğin sentez ve karekterizasyonu çalışılmıştır. Hedef dendrimerik bileşikler basit organik bileşiklerden yola çıkılarak sentezlenmiştir. Dendrimerik yapılar “click” kimyası olarak adlandırılan ve azidlerle alkinler arasında Husigen 1,3-dipolar siklokatılma reaksiyonuna dayanan yöntem temel alınarak sentezlenmiştir. (v) Katı desteklere kaliks[4]pirol bağlanması: Çalışmanın bu kısmında, siloksan fonksiyonlu kaliks[4]pirol bileşiğinin sentezlenmesi ve bu bileşik vasıtası ile çeşitli silika jel yüzeylerinin fonksiyonlandırılması incelenmiştir.In this study, following research topics have been investigated. (i) Synthesis of calix[4]pyrroles with long alkyl chains: As a first step, it was sought to develop long chain n-alkyl ester modified, meso- and -pyrrole functionalized calix[4]pyrroles bearing either hydrogen or bromine atoms in the -pyrrolic positions that would prove soluble in nonpolar organic solvents. Towards this end, the new ester-substituted systems have been prepared and their chloride and acetate anion binding properties have been analyzed by ITC. (ii) Tetrabenzocalix[4]pyrrole: The synthesis of the bicyclo[2.2.2]-oct-2-ene fused calix[4]pyrrole with deep “walls”, was investigated. IT was also studied to convert this precursor to the corresponding calix[4]pyrrole derivative that contains benzo units fused to the -positions of the pyrrole rings. (iii) Polymers with pendant calix[4]pyrrole units: The synthesis and characterization of polymers and copolymers containing calixpyrrole, methyl methacrylate and crown ether units will be detailed. In addition, it will be demonstrated that organic solutions of the copolymers are capable of extracting tetrabutylammonium chloride, tetrabutylammonium fluoride, KCl and KF from aqueous solutions significantly better than octamethylcalix[4]pyrrole and poly(methyl methacrylate). (iv) Dendrimeric calix[4]pyrroles: Synthesis and characterization of four different calixpyrrole based dendrimeric compounds were investigated. The target dendrimeric structures have been prepared starting from simple organic compounds via click chemistry. (v): Calix[4]pyrrole on silica solid supports: Synthesis of siloxane functionalized calix[4]pyrrole and modification of inorganic polymers such as silica gel, fume silica, and nano silica have been investigated.DoktoraPh

A multidisciplinary approach to the development of innovative tools for pharmaceutical and technological applications

The research activity carried out during the Ph.D. in Chemical and Pharmaceutical Sciences has regarded the design, synthesis, and characterization of innovative tools relevant to both pharmaceutical and technological fields. Great interest has been dedicated to the investigation of the “affinity polymerization” mechanism of novel polymeric materials founded on repetitive monomeric units based on the 3-phenylbenzofulvene scaffold that spontaneously polymerize by simple removal of the solvent. In this context, the attention has been focused on the synthesis of novel benzofulvene-based derivatives bearing complexed and non-complexed pyridine rings in different positions of the benzofulvene scaffold, to evaluate the effects generated by the insertion of a bulky substituent in the aggregation/polymerization behavior. The experience acquired with this study has been then capitalized on the design, synthesis, and characterization of a novel visible-light-sensitive biomimetic molecular switch inspired by the benzofulvene scaffold and the Green Fluorescent Protein (GFP) chromophore. The chemical-structural manipulation of the benzofulvene structure has made possible the development of a novel set of biomimetic photoswitches inspired by the supramolecular properties of the 3-phenylbenzofulvene scaffold and the molecular features of the GFP chromophore. In the framework of material chemistry, the well-known click-chemistry reaction of hyaluronic acid (HA) derivatives bearing propargylated ferulic groups has been exploited to obtain biomimetic and biocompatible materials useful in different biopharmaceutical fields. In particular, low molecular weight HA has been anchored on the hydrophobic surface of low-generation poly(propylene imine) (PPI) dendrimers by the click-chemistry reaction between their azido-functionalized surfaces and low molecular weight HA derivatives bearing propargylated ferulic groups. The resulting materials have been proposed as biocompatible drug delivery systems (DDSs) of Doxorubicin. Another application of HA has concerned the hyaluronan-based graft copolymers showing low and medium molecular weight values that have been exploited in cross-linking by the click-chemistry reaction. Interestingly, the interaction of resulting HA materials with water led to the formation of hydrogels, and the tunable rheological behavior of these materials led to their applicability in different biomedical fields. Lastly, the knowledge in medicinal chemistry has guided the design and synthesis of innovative bioactive compounds such as novel Cyclooxygenase‑2 (COX-2) inhibitors containing Nitric Oxide (NO) donor moiety (CINODs) endowed with vasorelaxant properties. The outcomes of these studies would provide fertile ground for future projects that will hopefully contribute to accelerate the research in several fields. Indeed, the increased knowledge on the behavior of these innovative tools, by means of a multidisciplinary approach, is the key for boosting the development of novel materials for pharmaceutical and technological applications

Towards the synthesis of multinuclear, branched and cyclic metallocene-containing complexes

Branched and cyclic multinuclear metallocene systems are of great interest due to their remarkable chemical and physical properties, which often differ greatly to their mononuclear, or linear, analogues. In particular, the presence of multiple redox centres, either directly covalently bound or linked by conjugated organic motifs, offers the prospect of studying a plethora of electronic features, such as electron transfer, electronic communication between redox centres and multi-valence states. Due to its easily accessible analogues, ease of handling, and redox properties, ferrocene-containing systems are by far the most studied. Investigation of such multinuclear species has been hindered by synthetic issues arising from the flexibility of the metallocene, resulting in complex synthetic procedures and low yields. Described herein is the optimisation of the preparation of valuable bi- and tri-ferrocenyl synthons, Fc2I2 and Fc3I2, respectively, via the traditional route of halogenation of the lithiated intermediate. Ultimately, an improved methodology in which dilithioferrocene was reacted directly with diiodoferrocene (FcI2) gave notably improved yields of the multinuclear systems. To achieve covalently bonded metallocenes, Suzuki-Miyaura and Ullmann-like couplings were explored. Although mono-ferrocenyl boronic acids could be prepared, the bi-ferrocenyl derivatives could not and attempts to couple these to iodoferrocenes were unsuccessful. Such reactions resulted mainly in hydrodehalogenation products and degradation, however, in some cases, intramolecular cyclisation of Fc2I2 was observed under Suzuki-Miyaura conditions. Replacing the NMP medium used in the CuTc-mediated Ullmann-like coupling of iodoferrocenes with acetonitrile revealed a change in reactivity. This allowed a competing oxygen arylation reaction, in which the thiophene carboxylate moiety is transferred from the copper centre to the Cp rings of ferrocene, to take place in tandem. The combination of both the C-C and C-O bond forming reactions allowed for the isolation of a series of ferrocene-based thiophene carboxylate derivatives. The same reactivity pathway gave the ruthenocene analogues in both NMP (N-methyl pyrrolidone) and acetonitrile solvents. The mono- and bis-metallocenyl thiophene carboxylate adducts were transformed into the corresponding metallocenol by means of a base-mediated ester hydrolysis reaction. Overall, this revealed a modified reaction pathway towards oxygen substituted metallocenes, the higher order analogues of which are novel. A number of related synthetic pathways were explored for the preparation of branched and cyclic ethynylarene-containing materials, which heavily featured subsequent Sonogashira couplings and alkyne protection/deprotection strategies. Essentially, the nature of the organic functionalities introduced to both the bridging and terminal positions was found to dictate the efficacy of a given methodology. A series of novel, branched ferrocene systems, containing diethynylpyridine, diethynylbipyridine and diethynylthiophene bridging moieties, were prepared with a variety of terminal ligands by utilising symmetric and asymmetric protecting group strategies. It was found that materials containing the bipyridyl motif, in either the bridging or terminal positions, presented the most complications with regards to preparation and isolation. Attempts to synthesise analogous cyclic systems via both Sonogashira couplings and Ullmann-like couplings were also made with limited success, owing to the formation of side products and degradation of starting materials under the chosen conditions. This resulted in the isolation of a novel diethynylpyridine-bridged tris-ferrocenyl macrocycle as well as evidence of the analogous thiophenyl species. Evidence was also found for the formation of hydrodehalogenation products from the starting material utilised in the attempted Ullmann-like cyclisation reactions.Open Acces

Rational Design of Metal-organic Electronic Devices: a Computational Perspective

Organic and organometallic electronic materials continue to attract considerable attention among researchers due to their cost effectiveness, high flexibility, low temperature processing conditions and the continuous emergence of new semiconducting materials with tailored electronic properties. In addition, organic semiconductors can be used in a variety of important technological devices such as solar cells, field-effect transistors (FETs), flash memory, radio frequency identification (RFID) tags, light emitting diodes (LEDs), etc. However, organic materials have thus far not achieved the reliability and carrier mobility obtainable with inorganic silicon-based devices. Hence, there is a need for finding alternative electronic materials other than organic semiconductors to overcome the problems of inferior stability and performance. In this dissertation, I research the development of new transition metal based electronic materials which due to the presence of metal-metal, metal-?, and ?-? interactions may give rise to superior electronic and chemical properties versus their organic counterparts. Specifically, I performed computational modeling studies on platinum based charge transfer complexes and d10 cyclo-[M(?-L)]3 trimers (M = Ag, Au and L = monoanionic bidentate bridging (C/N~C/N) ligand). The research done is aimed to guide experimental chemists to make rational choices of metals, ligands, substituents in synthesizing novel organometallic electronic materials. Furthermore, the calculations presented here propose novel ways to tune the geometric, electronic, spectroscopic, and conduction properties in semiconducting materials. In addition to novel material development, electronic device performance can be improved by making a judicious choice of device components. I have studied the interfaces of a p-type metal-organic semiconductor viz cyclo-[Au(µ-Pz)]3 trimer with metal electrodes at atomic and surface levels. This work was aimed to guide the device engineers to choose the appropriate metal electrodes considering the chemical interactions at the interface. Additionally, the calculations performed on the interfaces provided valuable insight into binding energies, charge redistribution, change in the energy levels, dipole formation, etc., which are important parameters to consider while fabricating an electronic device. The research described in this dissertation highlights the application of unique computational modeling methods at different levels of theory to guide the experimental chemists and device engineers toward a rational design of transition metal based electronic devices with low cost and high performance

Exclusive Feature Papers in Colorants

“Exclusive Feature Papers in Colorants” is a collection of important high-quality papers (original research articles or comprehensive review papers) published in open access. This Special Issue aims to discuss new knowledge or new cutting-edge developments in the colorants research field through selected works, in the hope of making a great contribution to the community. We intend for this issue to be the best forum for disseminating excellent research findings as well as sharing innovative ideas in the field