Synthesis, photochemical, and electrochemical properties of naphthalene-1,4,5,8-tetracarboxylic acid-bis-(N,N′-bis-(2,2,4(2,4,4)-trimethylhexylpolyimide)) and poly(N,N′-bis-(2,2,4(2,4,4)-trimethyl-6-aminohexyl) 3,4,9,10-perylenetetracarboxdiimide)

Two new soluble polymers (naphthalene containing: TH-NPI, perylene containing: TH-PPI) have been synthesized via incorporation of branched chain substituent unit into their backbones. Because of existence of branched alkyl spacer, the polymers showed good solubility in common solvents such as chloroform without sacrificing their stability and caused a red shifted excimer-like emission. Their monomers (TH-NDI and TH-PDI) have been synthesized for comparison. The compounds are characterized by UV-vis, IR, MS, DSC, TGA, CV, GPC and viscosity measurements. Polymers TH-NPI and TH-PPI with inherent viscosities of 0.50 and 0.30 dL/g were obtained corresponding to their molecular weights 40,000 and 17,000 respectively. Thermogravimetric analysis (TGA) showed that TH-NDI, TH-NPI, TH-PDI and TH-PPI are thermally stable up to 380, 445, 512 and 515 °C respectively. The LUMO energy levels of these compounds are calculated as −3.66, −3.71, −3.62 and −3.61 eV respectively. The red-shifted (TH-NPI: 400-650 nm, TH-PPI: 535-800) excimer-like fluorescence in chloroform is attributed to the formation of ground state complexes probably due to intermolecular and intramolecular π-stackings of the polymers in solution. The fluorescence lifetimes, quantum yields and singlet-state energies are presented.     

N,N′-Diisopropyl- and N,N′-dicyclohexylthiourea cadmium(II) complexes as precursors for the synthesis of CdS nanoparticles

Crystals of the cadmium(II) complexes of N,N-diisopropylthiourea and N,N-dicyclohexylthiourea were obtained and their X-ray single crystal structures determined. These complexes are air-stable, easy to prepare and inexpensive and decompose cleanly to give good quality crystalline CdS. The nanoparticles of CdS thus obtained showed quantum confinement effects in their optical spectra, with close to band-edge emission in luminescence experiments. The broad diffraction patterns observed are typical of nanodimensional particles. The variation of concentration of precursor-to-HDA ratio change the isolated materials from spheres to rod-shaped. TEM images showed agglomerates of needle-like plate of particles.     

Aerobic oxidation of trimethylbenzenes catalyzed by N,N′,N″-trihydroxyisocyanuric acid (THICA) as a key catalyst

The oxidation of trimethylbenzenes was examined with air or O₂ using N,N′,N″-trihydroxyisocyanuric acid (THICA) as a key catalyst. Thus, 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzenes under air (20 atm) in the presence of THICA (5 mol %), Co(OAc)₂ (0.5 mol %), Mn(OAc)₂, and ZrO(OAc)₂ at 150 °C were oxidized to the corresponding benzenetricarboxylic acids in good yields (81-97%). In the aerobic oxidation of 1,2,4-trimethylbenzene by the THICA/Co(II)/Mn(II) system, remarkable acceleration was observed by adding a very small amount of ZrO(OAc)₂ to the reaction system to form 1,2,4-benzenetricarboxylic acid in excellent yield (97%). In contrast, no considerable addition effect was observed in the oxidation of 1,3,5-trimethylbenzene. This aerobic oxidation by the present catalytic system provides an economical and environmentally benign direct method to benzenetricarboxylic acids, which are very important polymer materials.     

Synthesis of N,N′-bis and N,N,N′,N′-tetra-[(3,5-di-substituted-1-pyrazolyl)methyl]para-phenylenediamines: new candidate ligands for metal complex wires

A series of tridentate ligands N,N-bis-[(di-substituted-1-pyrazolyl)methyl]arylamines 2-3a,b and benzylamine 4a,b, tetradentate N,N′-bis-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 7a,b and hexadentate N,N,N′,N′-tetra-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 8a,b has been prepared in good yield by condensation of arylamines, benzylamine or para-phenylenediamine with N-hydroxymethyl disubstituted pyrazoles 1a,b. The synthesis and characterisation of these various polydentate ligands are described.     

N,N,N′,N′-Tetrakis(2-hydroxyethyl)ethylenediamine palladium(II) complex as efficient catalyst for the Suzuki/Miyaura reaction in water

A new water soluble palladium(II) complex (2) derived from N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (edteH₄) (1) was synthesized in high yield and characterized by ¹H, ¹³C, HMQC and COSY NMR spectroscopy. X-ray diffraction studies on a single crystal of 2 confirmed the cis square planar geometry; the edteH₄ ligand (1) is κ² (N,N)-coordinated with four pendant CH₂CH₂OH groups. This new complex [PdCl₂(edteH₄)] (2) and the previously synthesized triethanolamine complex [Pd(OCH₂CH₂N(CH₂CH₂OH)₂)₂] (3) were tested as catalysts for the Suzuki/Miyaura cross-coupling reaction of various aryl bromides with phenylboronic acid in water. Electronically activated aryl bromides, such as 4-bromoacetophenone and 4-bromobenzaldehyde undergo the cross-coupling with extremely high turnover numbers (TON) of up to 1,00,000 without organic solvent.     

Catalytic photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine and carbon dioxide

Photocarboxylation of 1,1-diphenylethylene with N,N,N′,N′-tetramethylbenzidine (TMB) in MeCN under bubbling of CO₂ proceeded with high catalytic efficiency, giving 3,3-diphenylacrylic acid (DPA) and 3-hydroxy-3,3-diphenylpropionic acid (20). The turnover number (TON=(DPA+20)/TMB) reached 17. Similarly, 1-phenyl-1-cyclohexene yielded cis-2-acetamido-2-phenylcyclohexanecarboxylic acid with TON 5.9. As compared with related N,N-dimethylaniline derivatives, TMB is more resistant to photodecomposition, has the much larger absorbance in the S₀→S₁ transition, and has the lower quenching efficiency by CO₂. Probably these factors are partly responsible for the high TON observed for TMB.     

Mild and regioselective iodination of aromatic compounds with N,N′-diiodo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide)

N,N′-Diiodo-N,N′-1,2-ethanediylbis(p-tolouenesulphonamide) [NIBTS] and catalytic trifluoroacetic acid can be used for the regioselective iodination of aromatic compounds in acetonitrile under mild conditions in excellent yields.     

Synthesis,spectral characterization of the zinc(II) mixed-ligand complexes of N(4)-allyl thiosemicarbazones and N,N,N′,N′-tetramethylethylenediamine,and crystal structure of the novel [ZnL2(tmen)] compound

Mixed-ligand zinc complexes with N,N,N′,N′-tetramethylethylenediamine (tmen) and R-salicylaldehyde N(4)-allyl thiosemicarbazones (R: 3-OCH₃ (L₁), 5-Br(L₂)), [ZnL_1,2(tmen)], were synthesized and the complexes were characterized by elemental analysis, atomic absorption spectrometer, magnetic susceptibility, molar conductivity, electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectra and IR, UV–Vis, ¹H NMR and ¹⁵N spectroscopies. Crystal of [ZnL₂(tmen)] have a slightly distorted square pyramid involving O, N, S atoms of thiosemicarbazone and one N atom of tmen in basal plane and the other N atom of tmen in apex of the pyramid. The non-coordinated allyl group is disordered.     

Poly(N-bromobenzene-1,3-disulfonamide) and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide as novel catalytic reagents for silylation of alcohols, phenols, and thiols using hexamethyldisilazane

Poly(N-bromobenzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] are effective catalysts for the silylation of alcohols, phenols, and thiols in the presence of hexamethyldisilazane with, or without solvent, and also under microwave irradiation.     

Liquid crystal behaviour of ionic allylpalladium complexes containing 2-pyrazolylpyridine as bidentate N,N′-ligand

Two types of Pd-complexes containing the new N,N′-ligands 2-[3-(4-alkyloxyphenyl)pyrazol-1-yl]pyridine (pz^Rpy; R = C₆H₄OC_nH_2n+1, n = 6 (hp), 10 (dp), 12 (ddp), 14 (tdp), 16 (hdp), 18 (odp)) (1-6), namely c-[Pd(Cl)₂(pz^Rpy)] (7-10) and c-[Pd(η³-C₃H₅)(pz^Rpy)]BF₄ (11-16), have been synthesised and characterised by different spectroscopic techniques. Those members of the second type containing the largest chains (R = ddp 13, tdp 14, hdp 15, odp 16) have been found to have liquid crystal properties showing smectic A mesophases. By contrast, neither the free ligands pz^Rpy nor their related c-[Pd(Cl)₂(pz^Rpy)] complexes exhibited mesomorphism. The new synthesised metallomesogens are mononuclear complexes with an unsymmetrical molecular shape as deduced from the X-ray structures of c-[Pd(η³-C₃H₅)(pz^Rpy)]BF₄ (R = hp, 11; dp, 12). Both compounds, which are isostructural, show a distorted square-planar environment on the palladium centres defined by the allyl and the bidentate pz^Rpy ligands. The crystal structure reveals that both the counteranion and the pz^Rpy ligand function as a source of hydrogen-bonding and intermolecular π?π contacts resulting in a ²D supramolecular assembly.     

Synthesis and properties of N,N,N′,N′-tetrasubstituted 1,3-bis(5-aminothien-2-yl)azulenes and their application as a hole-injecting material in organic light-emitting devices

Two title compounds, N,N,N′,N′-tetraphenyl-1,3-bis(5-aminothien-2-yl)azulene (3a) and 1,3-bis{5-(9-carbazolyl)thien-2-yl}azulene (3b), were synthesized from 1,3-di(2-thienyl)azulene (4) by a two-step sequence involving bromination and subsequent Pd-catalyzed amination. These compounds were characterized by spectroscopic analyses and the structure of 3a was determined by X-ray crystallographic analysis. Their HOMO energy levels were estimated using their electrochemical oxidation potentials, and these compounds were used as a hole-injecting material in organic light-emitting devices. The device with 3a showed greater durability than that with copper phthalocyanine.     

Synthesis and characterizations of N,N,N′,N′-tetrakis (diphenylphosphino)ethylendiamine derivatives: Use of palladium(II) complex as pre-catalyst in Suzuki coupling and Heck reactions

Oxidation of N,N,N′,N′-tetrakis(diphenylphosphino)ethylendiamine (1) with elemental sulfur and selenium gives the corresponding sulfide and selenide, respectively, [(Ph₂P(E))₂NCH₂CH₂N(P(E)Ph₂)₂] (E: S 1a, Se 1b). Complexes of 1 [(M₂Cl₄){(Ph₂P)₂NCH₂CH₂N(PPh₂)₂}] (M: Ni(II) 1c, Pd(II) 1d, Pt(II) 1e) were prepared by the reaction of 1 with NiCl₂ or [MCl₂(COD)] (M = Pd, Pt). The new compounds were characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of Pd(II) complex 1d was tested in the Suzuki coupling reaction and Heck reaction. The palladium complex 1d catalyses the Heck reaction between styrene and aryl bromides as well as Suzuki coupling reaction between phenylboronic acid and arylbromides affording stilbenes and biphenyls in high yield, respectively.     

Electrochemical and electrochromic properties of novel aromatic poly(amine-amide)s derived from N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine

A series of novel triphenylamine-containing aromatic poly(amine-amide)s were prepared from the dicarboxylic acid, N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine, and various diamines by direct phosphorylation polycondensation. All the poly(amine-amide)s were amorphous, soluble in a variety of organic solvents, and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (195-280 °C). These polymers exhibited strong UV-Vis absorption bands at 330-346 nm and their photoluminescence showed maximum bands around 516-535 nm in NMP solution. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-amide)s prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidative redox couples at potential 0.73-0.78 V and 1.12-1.18 V, respectively vs Ag/AgCl in acetonitrile solution. All the poly(amine-amide)s exhibited excellent reversibility of electrochromic characteristics by continuous ten cyclic scans between 0.0 and 1.40 V, with a color change from original pale yellowish neutral form to the green and then to blue oxidized forms.     

Synthesis, structural and spectroscopic properties of a new Schiff base ligand N,N′-bis(trifluoromethylbenzylidene)ethylenediamine

The Schiff base compound, N,N′-bis(trifluoromethylbenzylidene)ethylenediamine (C₁₈H₁₄F₆N₂) (1), CF₃C₆H₄CHNCH₂CH₂NCHC₆H₄CF₃ has been synthesized by adding a solution of ethylenediammine (en), 0.1 mmol in chloroform to 4-(trifluoromethyl)-benzaldehyde, CF₃C₆H₄CHO (0.2 mmol) and the product was crystallized in ethanol with the mp, 109.2 °C and 75% yield. The crystal structure was investigated by a single-crystal X-ray diffraction study at 150 K. The compound crystallizes in monoclinic space group, P2₁/c with a = 9.295(3), b = 5.976(5), c = 15.204(9) Å and α = 90°, β = 96.56(5)° and γ = 90°. The crystal structure is stabilized by intermolecular CH · · · F hydrogen bonds. The asymmetric unit contains only one-half of the molecule related to the center of symmetry coinciding with C(1)-C(1′) and as a whole, the title molecule is in the staggered conformation. The phenyl rings and the CN imine bonds are co-planar. The infrared spectrum showed a sharp peak at 1640 cm⁻¹ which is typical of the conjugated CN stretching and strong peaks at 800-1400 cm⁻¹ regions are due to the C-C and C-H stretching modes. Electronic absorption spectra exhibits strong absorption in the UV region (240 nm wavelength) which have been ascribed to , and electronic transitions. The ¹H NMR spectra showed three distinct peaks at 2.5, 7.8 and 8.5 ppm which are assigned based on the splitting of resonance signals and are clearly confirmed by the X-ray molecular structure. The aromatic protons appear at about 7.8 ppm and the imine protons at 8.5 ppm. The sharp singlet at about 3.95 ppm is assigned to the CH₂-CH₂ protons. Mass spectra of the titled compound showed the molecular ion peak at m/e 372 (M⁺), and fragments at m/e 353 (M-F), 342 (M-2F), 200 (M-CF₃C₆H₄CHN), 186 (M-CF₃C₆H₄CHNCH₂).     

Lateral lithiation of N,N′-diaryl ureas

Aromatic ureas bearing N-(2-alkylaryl) groups may be laterally lithiated by treatment with sec-butyllithium. Quenching with a range of electrophiles yields functionalised aryl ureas in excellent yield. Lateral lithiation is favoured when the urea nitrogen adjacent to the aromatic ring in question is alkylated, and when competitive lithiations of such a ring are possible, lateral lithiation is more favourable than the alternative ortholithiation.     

Synthesis of N,N,N′,N′-tetrasubstituted 1,3-bis(4-aminophenyl)azulenes and their application to a hole-injecting material in organic electroluminescent devices

After a preliminary search of the reaction conditions for the Suzuki-Miyaura cross-coupling of haloazulenes with arylboronic acids, the title compounds were synthesized either by the direct coupling reaction between 1,3-dihaloazulene and the corresponding N,N-disubstituted 4-aminophenylboronic acids or by a two-step sequence involving the cross-coupling with 4-bromophenylboronic acid and subsequent Pd-catalyzed amination. Application of the title diamines to a hole-injecting material in organic electroluminescent devices was carried out to provide their prominent characteristics as a novel durable, non-cyanine and non-polyamine substance without color fade. The diamine derivatives, extended by an ethynyl unit between the azulenyl core and the 4-aminophenyl moiety, were also synthesized and found, unfortunately, unsuitable for vacuum deposition in preparing a multilayer composite.     

Chiral N,N′-dioxide-Yb(III) complexes catalyzed enantioselective hydrophosphonylation of aldehydes

Chiral N,N′-dioxide-Ytterbium(III) complexes promoted the asymmetric addition of diethyl phosphate to aldehydes, giving the corresponding products with good yields and enantioselectivities. The addition of pyridine favored both reactivity and enantioselectivity. A possible catalytic cycle was proposed to explain the mechanism of the asymmetric hydrophosphonylation of aldehydes.     

Lithium and sodium N,N′-di(2,6-dialkylphenyl)formamidinate complexes

A study has been undertaken of the lithium and sodium metallation of N,N′-di(aryl)formamidines with alkyl groups at the 2- and 6-aryl position. ¹H NMR and X-ray diffraction data indicate an increase in steric bulk from 2,6-dimethylphenyl to 2,6-diethylphenyl to 2,6-diisopropylphenyl incites incremental changes in amidinate binding and nuclearity. In selected instances, this invokes the first lithium and sodium amidinate/guanidinate complexes to exhibit metal-arene contacts.