Comparison of the electronic structure of different perylene‐based dye‐aggregates

Aggregates of functionalized polycyclic aromatic molecules like perylene derivatives differ in important optoelectronic properties such as absorption and emission spectra or exciton diffusion lengths. Although those differences are well known, it is not fully understood if they are caused by variations in the geometrical orientation of the molecules within the aggregates, variations in the electronic structures of the dye aggregates or interplay of both. As this knowledge is of interest for the development of materials with optimized functionalities, we investigate this question by comparing the electronic structures of dimer systems of representative perylene‐based chromophores. The study comprises dimers of perylene, 3,4,9,10‐perylene tetracarboxylic acid bisimide (PBI), 3,4,9,10‐perylene tetracarboxylic acid dianhydride (PTCDA), and diindeno perylene (DIP). Potential energy curves (PECs) and characters of those electronic states are investigated which determine the optoelectronic properties. The computations use the spin‐component‐scaled approximate coupled‐cluster second‐order method (SCS‐CC2), which describes electronic states of predominately neutral excited (NE) and charge transfer (CT) character equally well. Our results show that the characters of the excited states change significantly with the intermolecular orientation and often represent significant mixtures of NE and CT characters. However, PECs and electronic structures of the investigated perylene derivatives are almost independent of the substitution patterns of the perylene core indicating that the observed differences in the optoelectronic properties mainly result from the geometrical structure of the dye aggregate. It also hints at the fact that optical properties can be computed from less‐substituted model compounds if a proper aggregate geometry is chosen. © 2012 Wiley Periodicals, Inc.     

Topochemical Polymerization of 1,3‐Diene Monomers and Features of Polymer Crystals as Organic Intercalation Materials

From the viewpoint of controlled polymer synthesis, topochemical polymerization based on crystal engineering is very useful for controlling not only the primary chain structures but also the higher‐order structures of the crystalline polymers. We found a new type of topochemical polymerization of muconic and sorbic acid derivatives to give stereoregular and high‐molecular weight polymers under photo‐, X‐ray, and γ‐ray irradiation of the monomer crystals. In this article, we describe detailed features and the mechanism of the topochemical polymerization of diethyl‐(Z,Z)‐muconate as well as of various alkylammonium derivatives of muconic and sorbic acids, which are 1,3‐diene mono‐ and dicarboxylic acid derivatives, to control the stereochemical structures of the polymers. The polymerization reactivity of these monomers in the crystalline state and the stereochemical structure of the polymers produced are discussed based on the concept of crystal engineering, which is a useful method to design and control the reactivity, structure, and properties of organic solids. The reactivity of the topochemical polymerization is determined by the monomer crystal structure, i.e. the monomer molecular arrangement in the crystals. Polymer crystals derived from topochemical polymerization have a high potential as new organic crystalline materials for various applications. Organic intercalation using the polymer crystals prepared from alkylammonium muconates and sorbates is also described.     

Selective Synthesis of Fluorine‐Containing Cyclic β‐Amino Acid Scaffolds

Fluorine‐containing organic molecules have generated increasing impact in drug research over the past decade. Their preparation and development of novel synthetic methods towards new types of fluorinated molecules among them of β‐amino acid derivatives has received large interest. Our research group have designed various highly selective and stereocontrolled methods for the construction of fluorine‐containing cyclic β‐amino acid derivatives. The synthetic approaches developed for the synthesis of various pharmacologically interesting cyclic β‐amino acid derivatives as monomers with multiple stereogenic centers might be valuable protocols for the access of other classes of organic compounds.     

Enantioselective Nucleophilic β‐Carbon‐Atom Amination of Enals: Carbene‐Catalyzed Formal [3+2] Reactions

An enantioselective β‐carbon amination for enals is disclosed. The nitrogen atom from a protected hydrazine with suitable electronic properties readily behaves as a nucleophile. Addition of the nitrogen nucleophile to a catalytically generated N‐heterocyclic‐carbene‐bound α,β‐unsaturated acyl azolium intermediate constructs a new carbon–nitrogen bond asymmetrically. The pyrazolidinone products from our catalytic reactions are common scaffolds in bioactive molecules, and can be easily transformed into useful compounds such as β³‐amino‐acid derivatives.     

Synthesis and Structural Characterisation of Derivatives of Tricyclo[5.2.1.02,6]Dec‐8‐Ene‐3,5‐Dione with an Expected Antimicrobial Activity

Anhydrides, imides, N‐ethylimides, N‐hydroxyimides and N‐aminoimides of 1,4,5,6‐tetramethyl‐bicyclo[5.2.1.0^2,6]hept‐5‐ene‐2,3‐dicarboxylic acid, 1,4,5,6,7‐pentamethyl‐bicyclo[5.2.1.0^2,6]hept‐5‐ene‐2,3‐dicarboxylic acid and 7‐ethyl‐1,4,5,6‐tetramethyl‐bicyclo[5.2.1.0^2,6]hept‐5‐ene‐2,3‐dicarboxylic acid were obtained. Antimicrobial activity of the newly obtained derivatives was tested against selected Gram‐positive and Gram‐negative bacteria and fungi of the Candida species. The structures of obtained compounds and their antimicrobial activity were compared. Structure of 1b, 2b and 1e were determined by an X‐ray analysis.     

Bay‐Annulated Perylene Tetraesters: A New Class of Discotic Liquid Crystals

Selenium‐annulated perylene tetraesters that stabilize the hexagonal columnar phase have been synthesized and characterized, and their thermal and photophysical behavior has been determined. The mesophase range decreased with an increase in chain length. A comparative account of the structure–property relationships of this series of compounds with respect to parent perylene tetraesters, N‐ and S‐annulated perylene tetraesters, in terms of their thermal, photophysical and electrochemical behavior is provided. The bay‐annulation of perylene tetraesters is a good option to modify the thermal and photophysical properties of perylene derivatives and it can provide a new avenue for the synthesis of several technologically important self‐assembling perylene derivatives.     

Preparation of adamantyl derivatives of 1,4‐; 1,6‐ and 1,7‐dihydroxynaphthalenes and assignment of their NMR data

Adamantylation of dihydroxynaphthalenes with the hydroxyl groups on the same or different rings leads to compounds that are convenient starting materials in target‐oriented organic synthesis. Here, we report the ¹H and ¹³C NMR assignments of eight 1‐adamantyl substituted derivatives of 1,4‐; 1,6‐ and 1,7‐dihydroxynaphthalenes. The data acquired and peculiarities of their molecular structure are useful for extrapolation for prompt characterization of compounds containing adamantane, dihydroxynaphthalenes or naphthoquinone units. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of New Schiff Bases and Polycyclic Fused Thiopyranothiazoles Containing 4,6‐Dichloro‐1,3,5‐Triazine Moiety

New aromatic aldimines, isatine substituted ketimines based on (4,6‐dichloro‐1,3,5‐triazin‐2‐yl)‐hydrazine scaffold and polycyclic fused thiopyranothiazoles formed using hetero‐Diels‐Alder reactions starting from 4‐thioxo‐2‐thiazolidinones and 5‐norbornene‐2,3‐dicarboxylic acid triazino‐derivatives synthetic approach is described. The application of condensation and cyclocondensation reactions of N‐nucleophiles and carbonyl agents for synthesis a number of biologically active triazine derivatives is reported. Screening of anticancer activity in vitro yielded the most active compounds 3a , 8b , and 8f for different cell lines.     

Asymmetric Synthesis of Heterocyclic γ‐Amino‐Acid and Diamine Derivatives by Three‐Component Radical Cascade Reactions

An enantioselective three‐component radical reaction of quinolines or pyridines with enamides and α‐bromo carbonyl compounds by dual photoredox and chiral Brønsted acid catalysis is presented. A range of valuable chiral γ‐amino‐acid derivatives are accessible in high chemo‐, regio‐, and enantioselectivity from simple, readily available starting materials under mild reaction conditions. Using the same strategy, the asymmetric synthesis of 1,2‐diamine derivatives is also reported.     

Synthesis of New Isoxazolo[4,5‐d]pyrimidines as Antitumor Agents

The present paper (publication) concerns the synthesis of new isoxazole[4,5‐d]pyrimidine derivatives. There are only a few publications in the chemical literature that report the derivatives of the [4,5‐d] isomer. Our new compounds, the derivatives of this isomer, were obtained using a new manner that differs from those reported in the aforementioned publications in that we used the tautomers of 3‐arylo‐4‐imino‐5‐carbethoxy isxazole 3 and 4 as the starting compounds instead of using their 4‐amino forms. Their tautomeric form proved chemically stable, and, as a result of ammonolysis, we obtained the compounds 5 and 6 . The cyclization of the amides of 5 and 6 with various aldehydes yielded new derivatives, 10 – 19 , with good yields. As a by‐product, the 4‐amino tautomer form in by degrees and was reacted also with aldehydes, and we isolated Schiff bases 20 – 25 with low yields. Some of these compounds were tested for their antitumor activity at National Cancer Institute, Bethesda, MD, USA.     

One‐pot Three Component Synthesis of ω‐(oxathiolan‐2‐thion‐5‐yl)‐α‐oxazolidin‐2‐ones

We report a practical and one‐pot synthesis of novel series of ω‐(oxathiolan‐2‐thione‐5‐yl)‐α‐ oxazolidin‐2‐ones ( 3a‐h ). The obtained compounds have been designed, synthesized via reaction of oligoethylene glycols diglycidyl ethers, isocyanate and carbon disulfide in the presence of catalytic amount of lithium bromide. A variety of important oxazolidinone derivatives can be obtained from simple starting materials in good yields and the biological activity of these new products will be investigated in complementary study.     

Synthesis of New Heterocyclic Mono‐ and Bisorganophosphorus Acids and Their Derivatives with 1,2‐Phenylene Fragments

The interaction of esters of phosphorous acid containing POSiMe₃ and PH fragments with anhydrides of phthalic and 2‐sulfobenzoic acids is proposed as convenient methods for the synthesis of new heterocyclic mono‐ and bisorganophosphorus acids and their derivatives with 1,2‐phenylene fragments, carboxyl and sulfonyl groups. Also some properties of the obtained compounds are presented.     

Perylene-3,4,9,10-tetracarboxylic acid diimides: synthesis, physical properties, and use in organic electronics

Perylene-3,4,9,10-tetracarboxylic acid diimides (perylene diimides, PDIs) have been used as industrial pigments for many years. More recently, new applications for PDI derivatives have emerged in areas including organic photovoltaic devices and field-effect transistors. This Perspective discusses the synthesis and physical properties of PDI derivatives and their applications in organic electronics.     

Synthesis and Antioxidant Properties of New Substituted 8‐Methyl‐6‐phenyl‐5,6‐dihydro‐4H‐1,3,2‐benzodioxaphosphocine‐2‐oxide Derivatives

A new route for the synthesis of substituted 8‐methyl‐6‐phenyl‐5,6‐dihydro‐4H‐1,3,2‐benzodioxaphosphocine‐2‐oxide derivatives has been developed by using cinnamic acid and p‐cresol via condensation, reduction, and followed by phosphorylation steps. The title compounds were characterized by IR, ¹H, ¹³C, ³¹P, and mass spectral studies and elemental analysis. The title compounds have been investigated for their antioxidant activity with respect to their IC₅₀ values using 2,2‐diphenyl‐1‐picrylhydrazyl, NO radical scavenging activities, and reducing power assay. The results obtained from the aforementioned methods revealed that 2‐phenylamino derivatives have shown greater free radical scavenging activity when compared with those of the phenoxy derivatives and is attributed to the presence of secondary amino group, which is able to produce free radicals easily.     

“One‐pot” synthesis of aromatic poly(1,3,4‐oxadiazole)s in novel solvents—ionic liquids

The new convenient method for the synthesis of high molecular weight aromatic poly(1,3,4‐oxadiazole)s (PODs) has been proposed. These polymers were prepared by “one‐pot” procedure from dicarboxylic acid and hydrazine's salt (sulfate, phosphate) or dicarboxylic acid dihydrazides. The mixture of ionic liquid and triphenyl phosphite was used both as a solvent and condensing agent. The polycyclization occurred at a sufficiently low temperature of 210 °C for 2–5 h and resulted in obtaining film‐forming PODs having inherent viscosities up to 0.9 dL/g and good thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 380–394, 2006     

Synthesis of tetronic acid derivatives from novel active esters of α‐hydroxyacids

Active esters, produced by condensation of O‐acetyl protected α‐hydroxyacids with N‐hydroxysuccin‐imide, react with anions of active methylene compounds to afford β,β‐tricarbonyl derivatives which upon deprotection undergo cyclization to 3‐alkoxycarbonyl and 3‐acyl tetronic acids. Incorporation of (S)‐2‐ace‐toxyphenylacetic acid in this reaction sequence enables the synthesis of optically active 5‐phenyltetronic acid derivatives.     

Synthesis of β‐Substituted γ‐Aminobutyric Acid Derivatives through Enantioselective Photoredox Catalysis

β‐Substituted chiral γ‐aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β‐substituted γ‐aminobutyric acid derivatives through visible‐light‐induced photocatalyst‐free asymmetric radical conjugate additions is reported. Various β‐substituted γ‐aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42–89 %) and with excellent enantioselectivity (90–97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)‐pregabalin, (R)‐baclofen, (R)‐rolipram, and (S)‐nebracetam.     

Catalytic Asymmetric 1,2‐Addition of α‐Isothiocyanato Phosphonates: Synthesis of Chiral β‐Hydroxy‐ or β‐Amino‐Substituted α‐Amino Phosphonic Acid Derivatives

α‐Amino phosphonic acid derivatives are considered to be the most important structural analogues of α‐amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2‐addition reactions of α‐isothiocyanato phosphonate were developed. Through these processes, derivatives of β‐hydroxy‐α‐amino phosphonic acid and α,β‐diamino phosphonic acid, as well as highly functionalized phosphonate‐substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α‐phosphonic acid derivatives.     

A novel synthetic route for the synthesis of 4,6‐diaryl‐2‐methyl‐1,3‐benzoxazoles

A new synthetic route was developed for the synthesis of 4,6‐diaryl‐2‐methyl‐l,3‐benzoxazoles and their hydrogenated derivatives. The target compounds were obtained via the Neber rearrangement from 3,5‐diaryl‐2‐cyclohexen‐l‐ones. The formation of the isomers in the dihydro derivatives was explained by the [1,5] sigmatropic shift of hydrogen under thermal condition. DDQ was employed for the dehydrogenation of the dihydro benzoxazoles.