Unsymmetrical Mono Research Articles

Tuning the Emission Properties of 2,1,3-Benzothiadiazoles via Regioselective Substitution.

The 2,1,3-benzothiadiazole (BTD) unit is a prominent building block commonly used in various research areas such as optoelectronics and bioimaging. Despite its great versatility, the development of strategies to elaborate BTD has been largely neglected, including exploring its reactivity and understanding how regioselective functionalization can be used to tune the fluorescence emission. Previous focus has primarily been on C4- or C4,C7-substitutions. Here, a series of unsymmetrical mono - and disubstituted BTDs was synthesized and characterized for their photophysical properties. The reaction scope includes all six possible substituent patterns on the BTD benzoid ring (C4-, C5-, C4,C5-, C4,C6-, C4,C7- and C5,C6-substitution), which comprise arrangements that previously been synthetically challenging to access. By introducing a methoxy and/or a phenyl group we demonstrate that the emissive behavior of BTD derivatives strongly depends on the position of the substituent (s). We show that regioselective substitution on BTD can engender long-lived fluorescence and circumvent strong fluorescence quenching in polar protic solvents, which is a limitation of many previously described BTD derivatives.

ChemInform Abstract: Glycosylated Metal Phthalocyanines

AbstractReview: preparation of symmetrical and unsymmetrical mono‐; tetra‐; and octa‐glycosylated zinc phthalocyanines; 42 refs.

Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior

A series of unsymmetrical mono(imine)pyrroles (L1–L3) were synthesized by microwave irradiation from 2-acetylpyrrole and a series of dimethylanilines with two methyl groups at different positions on the aniline ring. A simplified synthetic method was initiated to prepare the corresponding nickel complexes NiL2 (1–3) with direct condensation of mono(imine)pyrrole and nickel chloride. The compounds were determined using a suite of techniques (i.e. 1H NMR, 13C NMR, IR, EA, MS). L1–L3 and 3 were further characterized by X-ray crystal diffraction. The structure of 3 showed that the ligand chelated to nickel with 2 : 1 M ratio, in spite of a 1 : 1 rate of charge. Application of 1–3 in ethylene polymerization indicated that mono(imino)pyrrole nickel complexes showed low activities. The polymerization reaction time and temperature, as well as the ligand structure, influenced the catalytic performance to some extent. Experimental data showed higher activity as –CH3 on the aniline ring is closer to the imine group.

Novel chiral ABBB-type unsymmetrical phthalocyanine. Ring-expansion synthesis, spectroscopic, and electrochemical properties

A novel chiral ABBB-type unsymmetrical mono(dinaphtho[1,2-e:1′,2′-g]-1,4-dioxocine)-[2,3-b]phthalocyaninato zinc complex Zn[Pc(AB3)] was synthesized via a subphthalocyanine ring-expansion reaction with the addition of an activated chiral binaphthyl-linked phthalonitrile. The resulting pair of phthalocyanine enantiomers has been fully characterized by a series of spectroscopic methods including electronic absorption, CD, MCD, fluorescence, and IR spectroscopy in addition to electrochemistry. The CD measurement with explicit signals over the entire region provides a direct image to the chirality induction from the optically active binaphthyl group to the phthalocyanine chromophore.

Synthetic, redox and coordination chemistry of bis(pentachlorophenyl)boryl ferrocene, FcB(C6Cl5)2

Two synthetic approaches to bis(pentachlorophenyl)boryl ferrocene have been explored. One mirrors that used in a novel approach to FcB(C6F5)2 from FcBBr2, but is less selective than its perfluorinated counterpart on account of the greater steric bulk of LiC6Cl5 over LiC6F5. This approach does, however, provide a viable route to unsymmetrical mono(pentachlorophenyl) derivatives of the type FcB(C6Cl5)Ar through the intermediacy of the mono-substituted species FcB(C6Cl5)Br. FcB(C6Cl5)2 itself is best synthesized from ferrocenyllithum and ClB(C6Cl5)2 and is a violet–blue species featuring an extremely electron deficient Fe(II) centre (E1/2 = +550 mV with respect to ferrocene/ferrocenium). A combination of structural, spectroscopic and reactivity studies of these and related ferrocenylboranes allow some general comments to be made concerning the relative steric and electronic properties of the C6Cl5 group. Thus, in terms of their relative capabilities as electron-withdrawing groups the substituents examined can be ranked C6Cl5 > C6F5 > Mes, while steric properties are ordered Mes > C6Cl5 > C6F5.

ChemInform Abstract: Solvent‐Controlled Halo‐Selective Selenylation of Aryl Halides Catalyzed by Cu(II) Supported on Al2O3. A General Protocol for the Synthesis of Unsymmetrical Organo Mono‐ and Bis‐selenides.

AbstractMoreover, the catalyst can be reused up to seven times without significant loss in activity.

Synthesis of Unsymmetrical Mono- and Bissquaramides with (3-Amino­propyl)triethoxysilane (APTES) or Dopamine Moieties

A simple and efficient synthesis of unsymmetrical mono- and bissquaramides derivatives and their corresponding methyltrialkyl ammonium salts was achieved in moderate yields from diethyl squarate via sequencial reactions.

Conformational analysis of polymethine dyes derived from the 2-azaazulene

Abstract A systematic investigation of the conformational structure was performed for the series of symmetrical and unsymmetrical mono-, tri-, pentamethine cyanines, and styryl dyes bearing 2-azaazulenium terminal group. The rotation energy barriers of terminal groups were determined via the dynamic variable temperature NMR experiments. The conformational transformation energy was calculated by quantum chemical methods (B3LYP and M05-2X) both for the cases of considering the solvent influence and not tacking it into account. Based on the comparison of theoretical and experimental data, relative electron-donating abilities and geometrical features of the heterocyclic terminal groups in 2-azaazulenium dyes were estimated. The arrangement of certain heterocyclic nuclei in order of basicity by considering the results of the dynamic NMR investigations was proposed. Influence of the conjugated chain length and the solvent nature on the conformational lability of the investigated dye molecules was discussed.

ChemInform Abstract: 1-(Methyldithiocarbonyl)imidazole: A Useful Thiocarbonyl Transfer Reagent for Synthesis of Substituted Thioureas.

1-(Methyldithiocarbonyl)imidazole 1 and its N-methyl quaternary salt 2 have been shown to be efficient methyldithiocarbonyl and thiocarbonyl transfer reagents for the synthesis of dithiocarbamates, symmetrical and unsymmetrical mono-, di- and tri-substituted thioureas in high yields under mild and simple non-hazardous reaction conditions.

Iodine-catalyzed one-pot synthesis of unsymmetrical meso-substituted porphyrins

The wide range use of 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin is well established, but its synthesis requires two steps and is not very practical. This article describes an iodine-catalyzed one-pot synthesis of this unsymmetrical porphyrin that uses commercial reagents and reactants as such, without prior distillation. Unsymmetrical mono functionalized porphyrins with various functional groups have also been obtained to validate this method. The influence of electronic effects of functional groups (donor or acceptor) has also been studied.

Synthesis and characterization of novel flavonoid-substituted phthalocyanines using (±)naringenin

In this study, novel unsymmetrical mono- and di-substituted metal free and metallo phthalocyanines containing peripheral naringeninoxy moieties have been prepared. The naringenin-substituted phthalonitrile was synthesized from 4-nitrophthalonitrile and (±)naringenin in dimethylsulfoxide. Preparation of unsymmetrical mono- and di-substituted phthalocyanines, 2-naringenin-7-O-phthalocyaninatozinc, 2,9-bis-naringenin-7-O-phthalocyaninatozinc, 2,9-bis-naringenin-7-O-phthalocyaninatocobalt and 2,9-bis-naringenin-7-O-phthalocyanine was performed at 120–140 °C using the corresponding phthalonitrile in the presence of N,N-dimethylethanolamine (DMAE), ZnCl 2, CoCl 2 and LiCl, respectively. Synthesized new phthalocyanine compounds have been characterized by elemental analysis and 1H NMR, 13C NMR, FT-IR, MS and UV–vis spectroscopy. These are the first known examples of flavonoid-substituted phthalocyanines.

Highly efficient deep blue organic electroluminescent device based on 1-methyl-9,10-di(1-naphthyl)anthracene

The author have developed 2-methyl-9,10-di(1-naphthyl)anthracene (α,α-MADN) as an effective wide band gap host material for Förster energy transfer to the unsymmetrical mono(styryl)amine deep blue fluorescent dopant (BD-1). This guest/host emitting system, at the optimal doping concentration of 3%, can also increase the probability of carrier recombination near the hole-transport/emitting layer interface for the blue organic light emitting device which produces electroluminescence efficiencies of 3.3cd∕A and 1.3lm∕W and a deep blue CIEx,y color coordinates of (0.15, 0.13) that are 50% better than those of the traditional β,β-isomeric host (MADN) with the same dopant.

Palladium‐Catalyzed Suzuki Couplings of 2,3‐Dibromonorbornadiene: Synthesis of Symmetrical and Unsymmetrical Aryl‐Substituted Norbornadienes

AbstractPalladium‐catalyzed Suzuki coupling reactions between 2,3‐dibromonorbornadiene and arylboronic acids were investigated. These reactions provide an efficient method for the synthesis of symmetrical 2,3‐diarylnorbornadienes which are not accessible using the traditional Diels–Alder cycloaddition reactions. The optimized reaction conditions of the Suzuki coupling reactions were found using [Pd2(dba)3] (0.5 mol%), tBu3P (1.4 mol%) and CsF in THF. High yields of the Suzuki coupling products were obtained when electron‐rich arylboronic acids were used. On the other hand, Suzuki coupling reactions with electronic‐deficient or sterically hindered arylboronic acids gave lower yields of the corresponding 2,3‐di‐arylnorbornadienes. Unsymmetrical mono‐ and diaryl‐substituted norbornadienes were also prepared in good yields using this method. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

New Tetraaza Macrobicyclic Ditopic Receptors for Metal Ions: Synthesis, Redox Response and Kinetics of Phosphate Hydrolysis of Unsymmetrical Macrobicyclic Mono- and Binuclear Nickel(II) Complexes

A new series of macrobicyclic ditopic receptors is derived from the precursor compound 3,4:10,11-dibenzo-1,13[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}di-aza]-5,9-dioxocyclohexadecane. Using this precursor, mono- and binuclear nickel(II) complexes of type [NiL](ClO4) and [Ni2L](ClO4)2 have been synthesized to undertake electrochemical and catalytic studies on the basis of macrocyclic ring size. The receptor is a tricompartmental macrocycle consisting of ether oxygen, tertiary nitrogen and imine nitrogen atoms. The redox studies of these systems show that the nickel(II) complexes undergo quasi-reversible one-electron reduction and oxidation. All the nickel(II) complexes have square planar geometry and are EPR silent. Examination of the kinetics of the hydrolysis of 4-nitrophenyl phosphate shows that the catalytic activities of the complexes increase with the macrocyclic ring size of the complexes. As the macrocyclic ring size of the complexes increases, the spectral, electrochemical and catalytic studies of the complexes show considerable variation due to distortion in the geometry around the nickel(II) centre.

Coordination Behaviour of Novel Macrobicyclic Tricompartmental Ligands: Synthesis, Magnetic, Electrochemical and Kinetic Studies of Unsymmetrical Mono- and Binuclear Copper(II) Complexes

Several mono- and binuclear copper(II) complexes of general formula [CuL](ClO4) and [Cu2L(ClO4)](ClO4) have been synthesized from macrobicyclic ligands having different compartments originating from their corresponding precursor compound (PC: 3,4:9,10-dibenzo-1,12[N,N′-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}diaza]-5,8-dioxacyclohexadecane). Electrochemical studies show that one quasi-reversible reduction wave (E pc=-0.75 to -0.83 V) for the mononuclear complexes and two quasi-reversible one-electron transfer reduction waves (=-0.78 to -0.86 V, =-1.01 to -1.28 V) for the binuclear complexes are obtained in the cathodic region. Room temperature magnetic moment studies indicate the presence of antiferromagnetic coupling in the binuclear complexes (μ eff=1.44–1.56 BM), which is confirmed by the broad ESR spectra with g=2.10–2.11, whereas the mononuclear complexes show hyperfine splitting in the ESR spectra and have magnetic moment values close to the spin-only value (μ eff=1.69–1.72 BM). Variable temperature magnetic susceptibility study of the complex finds that the observed -2J values for the binuclear complexes [Cu2L1(ClO4)](ClO4) and [Cu2L4(ClO4)]-(ClO4) are 216 cm-1 and 236 cm-1, respectively. The observed initial rate constant values for catechol oxidation using the complexes as catalysts range from 6.57×10-3 to 4.93×10-2 min-1 and the values are found to be higher for the binuclear complexes than the corresponding mononuclear complexes. It is proposed that a distortion of the copper ion geometry arises as the macrocyclic ring size increases. This is supported by spectral, electrochemical and catalytic studies.

1-(Methyldithiocarbonyl)imidazole: a Useful Thiocarbonyl Transfer Reagent for Synthesis of Substituted Thioureas

1-(Methyldithiocarbonyl)imidazole 1 and its N-methyl quaternary salt 2 have been shown to be efficient methyldithiocarbonyl and thiocarbonyl transfer reagents for the synthesis of dithiocarbamates, symmetrical and unsymmetrical mono-, di- and tri-substituted thioureas in high yields under mild and simple non-hazardous reaction conditions.

Synthesis of Zn-, Mn-, and Fe-Containing Mono- and Heterometallated Ethanediyl-Bridged Porphyrin Dimers

New ethanediyl-bridged unsymmetrical mono- and heterometallated dimers of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin (H2oep) containing transition-metal ions (Mn and Fe) were synthesized by a facile stepwise metallation/demetallation process under mild conditions. The novel metallation strategy initially involved the predominant insertion of Zn into one of the two porphyrin rings of the free-base dimer, followed by the incorporation of Mn or Fe into the other porphyrin ring under exceptionally mild conditions, giving corresponding heterometallic dimers; the subsequent removal of Zn yielded mono-transition-metal dimers. The emission spectrum of the monozinc dimer predominantly exhibited fluorescence bands of the free-base porphyrin component, indicating a very efficient energy-transfer process. Conversely, emission of the free-base or Zn porphyrin component of transition metal containing dimers was strongly quenched due to photoinduced electron transfer.

ChemInform Abstract: New Chiral Building Blocks from 1,2;5,6‐Di‐O‐isopropylidene‐D‐mannitol: Synthesis of C2‐Symmetrical and Unsymmetrical Mono‐ and Bisepoxides and of a Polyhydroxylated Butenolide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and Properties of Unsymmetrical Mono- and Disubstituted Poly(Diyne Ether)s by Transition Metal Catalysts

Abstract The cyclopolymerization of 2-butynyl-propargyl ether and 3-trimethylsilyl-2-propynyl propargyl ether and its copolymerization with diethyl dipropargyl malonate (DEDPM) were carried out by various transition metal catalysts. MoCl5-based catalyst was found to be very effective and gave high polymer yields. The resulting homopolymers were insoluble in organic solvents, whereas copolymers showed good solubility in organic solvents such as chloroform, tetrahydrofuran, and dimethylsulfoxide. The structure of the products was confirmed by IR, NMR, and UV-visible spectroscopies. From the spectral data it is proposed that mainly cyclized products with conjugated systems are formed. Thermal and morphological properties were also studied.

New chiral building blocks from 1,2;5,6‐di‐O‐isopropylidene‐D‐mannitol: Synthesis of C2‐symmetrical and unsymmetrical mono‐ and bisepoxides and of a polyhydroxylated butenolide

AbstractThe enantiopure epoxides 2–6 were synthesized from 1,2;5,6‐di‐O‐isopropylidene‐D‐mannitol (1). The terminal epoxides 2 and 3 are available from the desoxy mannitol 9 in three steps. The C2‐symmetrical epoxides 4 and 5 were generated via the C‐4‐inverted alcohol 15. The C2‐symmetrical bisepoxide 6 was prepared in a short sequence maintaining the symmetry throughout the entire synthesis. The crystalline butenolide 44 was prepared in five steps from 1 by Wittig olefination and lactonization.