Synthesis, absorption and fluorescence properties of N-triazinyl derivatives of 2-aminoanthracene

N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene was synthesized by substitution of one chlorine atom of 2,4,6-trichloro-1,3,5-triazine with 2-aminoanthracene. A new series of N-triazinyl-2-aminoanthracenes was prepared by nucleophilic substitution of one or both chlorine atoms on N-(4,6-dichloro-1,3,5-triazin-2-yl)-2-aminoanthracene with electron-donating methoxy or phenylamino groups. The UV/Vis absorption, fluorescence and excitation spectra as well as the fluorescence quantum yields of the prepared compounds were measured in 1,4-dioxane, ethyl acetate, dibutyl ether and acetonitrile; nanosecond kinetics of the fluorescence decay was measured in different solvents. The influence of the character of the substituent on triazinyl ring and of the solvent polarity upon the absorption and fluorescence spectra and fluorescence quantum yields are discussed.     

Novel mono- and bis-azo dyes containing the azulen-1-yl moiety: Synthesis, characterization, electronic spectra and basicity

3- and 4-[(Azulen-1-yl)-azo]-azo-benzenes were obtained in good yields using the buffered coupling reaction between several alkyl-substituted azulenes and diazotized phenylazo-phenylamines in dichloroacetic acid. The coupling products were characterized and the recorded electronic spectra are discussed. The isosbestic points obtained by protonation enabled the determination of their pK_a values.     

Syntheses and electrochromic and fluorescence properties of three double dithienylpyrroles derivatives

Three double dithienylpyrroles derivatives have been successfully prepared by performing a Knorr–Paal condensation between 1,4-di(thiophen-2-yl) butane-1,4-dione and various aromatic diamines. Additionally, their corresponding polymer films were synthesized via electropolymerization. Their electrochemical, spectroelectrochemical and electrochromic behaviors were further investigated by thermogravimetric analysis, scanning electron microscopy, cyclic voltammetry, UV–vis absorption and fluorescence emission spectra. Scanning electron microscopy and thermogravimetric analysis demonstrated that the polymer films possessed homogeneous, compact and smooth layer structures and thermal stabilities (up to nearly 180 °C). Cyclic voltammograms and UV–vis absorption spectra studies showed that the polymer films have stable, well-defined, reversible redox processes, low optical band gaps (E_g < 2.2 eV) and multicolor electrochromic behaviors. Additionally, the fluorescence spectra study showed that all of the monomers and polymers exhibited different intensity emission bands at different wavelengths.     

Synthesis and optically acid-sensory properties of novel polyoxadiazole derivatives

New organo-soluble and blue-emissive fluorene-based polyoxadiazoles, PFO_x and PFO_xEH, exhibit colorimetric and fluorescent acid-sensory properties to a strong acid due to the weak basicity of imine-type nitrogen atom(s) in an 1,3,4-oxadiazole ring. To further investigate their protonation with an acid, ¹H NMR spectroscopy and AM1 semiempirical quantum-mechanics are utilized as well as UV-visible absorption and fluorescence spectroscopies. These investigations indicate the protonation does not proceed thermodynamically but kinetically at the initial stage of the complex formation of an acid and an oxadiazole ring in the polymer backbone.     

Poly(9,9-dihexylfluorene) derivatives containing electron-transporting aromatic triazole segments: Synthesis, optical and electrochemical properties

We prepared three new poly(9,9-dihexylfluorene) derivatives (P1–P3) containing kinked aromatic triazole (triphenyl-1,2,4-triazole derivative) via Suzuki coupling polymerization. These copolymers were soluble in common organic solvents and showed high decomposition temperatures (T_d = 416–454 °C). The optical and electrochemical properties of P1–P3 were compared with poly(9,9-dihexylfluorene) (PFO) and P4 and P5 in which the linkages of the aromatic triazole were different. After introducing the triazole units, absorption spectra showed blue shift (388 nm → 372 nm) due to reduced conjugation, but PL spectra remained almost unchanged (417–418 nm). The linkages of triazole with fluorene segments in P1–P5 were different: (1) fluorene segments linked with triazole through a kinked angle (P1 and P2), (2) triazole as a branch unit (P3) and as terminal groups (P4), (3) fluorene segments linked with triazole in a linear way (P5). As estimated from semi-empirical MNDO calculation, two twisted conformations (ca. 90° each) exist between triazole core and fluorene groups. These kinked conformation and twisted structure increased the PL efficiency (Φ_PL = 0.60–0.73, Φ_PL = 0.58 for PFO) and partially inhibited annealing-induced excimer formation. From cyclic voltammetric results, P1–P3 exhibited better electron affinity (LUMO: −2.75 to −2.82 eV) than PFO (LUMO: −2.52 eV).     

Synthesis,absorption spectra studies,solvatochromism and halochromism of polymethine cyanine dyes

New polymethine cyanine dyes, including tetramethine and bis‐tetramethine cyanine dyes derived from benzo[2,3‐b;2′,3′‐b′]bis‐pyrazolo[4,5‐b]‐1,4‐(oxa‐, thia‐ and pyra‐)‐zine‐6,12‐dione, were synthesised. Absorption spectra for all the synthesised cyanine dyes were examined in 95% ethanol. The solvatochromism and halochromism for some selected dyes were investigated in pure solvents and in aqueous universal buffer solutions, respectively. Structural confirmations were carried out through elemental and spectroscopic analysis.     

Theoretical studies of the electronic structures and optical properties of stable blue-emitting polymer based on 4H-cyclopenta-[def]-phenanthrene

Geometries, ionization potentials (IPs), electron affinities (EAs) and optical properties of two series of π-conjugated oligomers (2,6-(4,4-bis(2-ethylthexyl)-4H-cyclopenta-[def]-phenanthrene))_nCPPn (2,6-(4,4-bis(2-ethylthexyl)-8,9-dihydro-4H-cyclopenta-[def]-phenanthrene))_nHCPPn (n = 1-4) were studied theoretically. The ground and the excited state geometries were optimized by B3LYP and CIS methods with 6-31G^∗ basis sets, respectively. The absorption and the emission spectra were calculated by TD-B3LYP method. The lowest-lying absorption is assigned to π → π^∗ transition, and the fluorescence can be described as originating from the ¹[ππ^∗] excited state. IPs, EAs, H-L gaps, absorption and emission properties of PCPP (n = ∞) and PHCPP (n = ∞) were obtained by extrapolation method. The fact that the lowest-lying absorption and the emission of PCPP are blue-shifted compared with those of PHCPP, can be interpreted by the smaller effective repeating units of PCPP. The extra absorption band at 289 nm of PCPP is contributed by the π → π^∗ transition involving the extra π-conjugation CC bond.     

A DFT study of electronic structures, energies, and molecular properties of lithium bis[croconato]borate and its derivatives

Theoretical studies on electrolyte salts, lithium bis[croconato(2-)]borate (LBCB) and its derivatives, lithium [croconato(2-) salicylato(2-)]borate (LCSB), and bis[salicylato(2-)]borate (LBSB) are carried out using density functional theory (DFT) method and B3LYP theory level for the first time. Bidentate structures involving two oxygen atoms are preferred. Based on these conformations, a linear correlation was observed between the highest occupied molecular orbital (HOMO) energies and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that strongly electron-withdrawing substituent anions are more resistant against oxidation than their organic counterparts. The correlations were also observed between ionic conductivity and binding energy, solubility and theoretical set of parameters of anion_, thermal stability and the hardness (η)_. Wave function analyses have been performed by natural bond orbital (NBO) method to further investigate the cation-anion interactions.     

量子点-聚苯乙烯复合微球的制备及荧光光谱的研究

用无皂乳液聚合制备了交联聚苯乙烯微球,讨论了单体、引发剂浓度,共聚单体等对微球粒径,单分散性的影响,并用FTIR和SEM对上述样品的结构进行了表征。在单体的配方中,加入1%二乙烯基苯作为交联剂,加入1%丙烯酸使小球表面功能化,便于后续与无机量子点和有机材料的结合。以氯仿/正丁醇为混合溶胀剂,将聚合物微球与CdSe量子点或CdSe/ZnS复合,制得含有两种或两种以上的不同量子点的高分子复合荧光微球。通过荧光光谱的测试,出现了两个或两种以上互不干扰的特征峰。为在聚合物微球中注入多种量子点,制得荧光探针,并实施量子点编码进行了初步的前期探索工作。     

Dicyanopyrazine studies. Part VII: Solid state absorption spectra and aggregation behavior of aminovinylpyrazine dyes containing a long chain alkyl group

The solid state absorption maxima of aminovinylpyrazine dyes containing long chain alkyl groups were changed drastically by the differences in their molecular stacking. The spectral shift from solution to the solid state was evaluated by the Δλ values, and the shift was correlated with substituent effects and their three dimensional molecular structures. Related dyes were synthesized by the nucleophilic substitution of 2,3-dichloro-5,6-dicyanopyrazine with various Fisher’s base type enamines having long alkyl chain groups.     

糠醛改性O-季铵化壳聚糖衍生物的合成及其抗菌性能

在制备水溶性较好的O-季铵化壳聚糖基础上,进一步与糠醛反应制备O-季铵化-N-呋喃亚甲基壳聚糖席夫碱及还原产物O-季铵化-N-呋喃亚甲基壳聚糖衍生物,用FTIR、1H NMR、EA（元素分析）、TG（热重分析）对产物进行表征。测定产物的最低抑菌浓度和抑菌率,并与O-季铵化-N-苯亚甲基壳聚糖席夫碱的抑菌效果进行比较。结果表明,产物对革兰氏阳性菌S.aureus的抗菌效果优于革兰氏阴性菌E. coli,在pH值5.5的条件下抗菌效果优于pH 值7.2。并且O-季铵化-N-呋喃亚甲基壳聚糖的抗菌效果>O-季铵化-N-呋喃亚甲基壳聚糖席夫碱>O-季铵化-N-苯亚甲基壳聚糖席夫碱 > O-季铵化-壳聚糖。研究表明,含呋喃杂环的壳聚糖衍生物的抗菌活性明显优于不含杂环的壳聚糖衍生物。     

Fluorescent coumarin derivatives with large stokes shift, dual emission and solid state luminescent properties: An experimental and theoretical study

Coumarin derivatives containing 8-benzothiazole (C-2) and its difluoroboron bound derivative (C-3) were prepared. Both derivatives show dual emission at 322 nm and 513 nm and large Stokes shift (188 nm), compared to the unsubstituted coumarin (C-1), which shows emission at 356 nm with small Stokes shift of 46 nm. C-2 and C-3 show fluorescence in solid state, in contrast the C-1 is non-fluorescent in the solid state. The excited state intramolecular proton transfer (ESIPT) process of C-2 was fully rationalized by DFT/TDDFT calculations with optimization of the ground state (S₀) and excited state (S₁) geometries. TDDFT calculations propose that the large Stokes shift of C-2 and C-3 are due to the re-distribution of the frontier molecular orbitals at excited states. Study of the potential energy curve of C-2 indicated that the dual emission of the C-2 is due to the simultaneous S₁ and S₃ emission, not the rotamer of the enol form.     

Synthesis and photo-induced solution properties of new rigid-rod polyimides

A series of new, substituted pyromellitic dianhydrides were synthesized from 1,2,4,5-tetramethylbenzene. New soluble rigid-rod polyimides were obtained from the dianhydrides and 2,2′-bis(trifluoromethyl)-4,4′-biphenyl (PFMB) in phenolic solvents in the presence of isoquinoline as a catalyst. The polyimides are soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), m-cresol and other solvents, in spite of having no bending in their rigid structures.

UV irradiation changed color of the polyimide solutions and also their viscosity. We observed new absorbance in the 700-nm region and an ESR signal by UV irradiation. The new visible absorbance and the ESR signal are derived from the same origin. They are attributed to the anion radical of the diimide moiety in the polyimide as deduced from the hyper fine structure of the ESR signal. In addition, UV irradiation diminishes the solution viscosity.     

Synthesis, crystal structures, and electronic spectra of (1,8-naphthyridine)Re(CO)3Cl and [(1,8-naphthyridine)Cu(DPEPhos)]PF6

Two 1,8-naphthyridine (nap) metal complexes (nap)Re^I(CO)₃Cl (1) and [(nap)Cu^I(DPEPhos)]PF₆ (2) were synthesized and characterized by NMR-, emission, and absorption spectroscopy, elemental analysis, mass spectrometry, and X-ray structural analysis. In both complexes, the nap ligand coordinates with both N atoms to the metal centre in a bidentate manner. 1 and 2 exhibit a broad phosphorescence in solid state at T = 300 K, which is completely quenched in solution at r.t. In addition, the gas-phase structures of both complexes were optimized at the B3LYP/6-31G(d,p) level of theory.     

Europium (Eu3+) - doped ZnO nanostructures: Synthesis,characterization, and photocatalytic,chemical sensing and preliminary assessment of magnetic properties

We have successfully synthesized single-phase wurtzite hexagonal ZnO:Eu³⁺ (1, 5 and 10 mol %) nanoparticles via facile co-precipitation method. The samples have been characterized by powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), fourier transform infrared (FTIR) and UV–visible spectroscopy. Change in optical band gap is explained by invoking the existence 4f electronic states of Eu³⁺ in the band gap of ZnO. Photocatalytic performance of these samples for degradation of methyl orange (MO), rhodamine B (Rh B) and picric acid (PA) under UV illumination is found to be 3–3.5 times higher than pure ZnO. However, 5 mol% doping exhibited the highest catalytic efficiency. This sample was also highly sensitive and selective for PA, and the limit of detection was: 1.790 μM, 1.140 μM and 1.751 μM for 1, 5 and 10 mol% Eu³⁺ doped ZnO samples respectively. Finally, all samples behave weak ferromagnetically at room temperature, but a systematic increase in the ferromagnetic-like response is noticed with Eu³⁺ concentration, despite finding no evidence of secondary magnetic phases; EuO and Eu₂O₃ from XRD measurements. Conceivably, the observed ferromagnetic order is attributed to defect induced f⁷– ferromagnetism. Indeed, low concentration of Eu³⁺ dopant is found to be more significant, as reported by different groups.     

Density functional theory study on LDFBDB and its derivatives: Electronic structures, energies, and molecular properties

Theoretical studies on unsymmetrical electrolyte salts, lithium difluoro(1,2-benzene-diolato(2-)-o,o′)borate (LDFBDB), and its derivatives, lithium bis[1,2-benzene-diolato(2-)-O,O′]borate (LBBB) and lithium fluoroborate (LiBF₄) are carried out using density functional theory (DFT) method and B3LYP theory level. Bidentate structures are preferred. Based on these conformations, a linear correlation was observed between adiabatic ionization potential I_p and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that strongly electron-withdrawing substituent anions are more resistant against oxidation. The correlations were also observed between ionic conductivity and binding energy, solubility and theoretical set of parameters of anion. Wave function analyses have been performed by natural bond orbital (NBO) method to further investigate the cation–anion interactions.     

Computational study of the one- and two-photon absorption properties of macrocyclic thiophene derivatives

The geometrical structure, electronic structure, one-photon and two-photon absorption properties of a series of macrocyclic thiophene derivatives C[3T_DA]_n (n = 2-5) have been studied using density functional theory (DFT) and Zerner’s intermediate neglect of differential overlap (ZINDO) methods theoretically. The results showed that the range of λ⁽¹⁾_maxs is 390-470 nm and λ⁽²⁾_maxs is 640-670 nm, while, both λ⁽¹⁾_max and λ⁽²⁾_max gradually enlarge as increasing the number of the C[3T_DA] unit. And C[3T_DA]_n compounds exhibited large TPA cross-section (δ_max), and the factors influencing on the δ_max values were analyzed in detail. Transition dipole moments M_0k and M_kn play important roles on δ_max. Both π-electron number (N_e) and the product of oscillator strengths from ground state to mediate state (?_0k) and from mediate state to final state (?_kn) are in proportion to δ_max. Moreover, δ_max linearly depends on the static second-order nonlinear optical susceptibilities (β₀).     

Density functional theory study on lithium bis[1,2-benzenediolato(2-)-O,O′] borate and its derivatives: electronic structures, energies, and molecular properties

Theoretical studies on electrolyte salts, lithium bis[1,2-benzenediolato(2-)-O,O′] borate (LBBB) and its derivatives, lithium bis[3-fluoro-1,2-benzenediolato(2-)-O,O′]borate (1FLBBB), and lithium bis[tetrafluoro-1,2-benzenediolato(2-)-O,O′] borate(4FLBBB) are carried out using density functional theory (DFT) method and B3LYP theory level for the first time. Bidentate structures involving two oxygen atoms are preferred. The GIAO–DFT results for all molecules suggest that the corresponding RB3LYP/6-31++G(2df,2p) geometries can be deemed reasonably good representations of the geometries of relatively free molecules in solution. Based on these conformations, a linear correlation was observed between the highest occupied molecular orbital (HOMO) energies and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that inorganic fluorine-containing anions are more resistant against oxidation than their organic counterparts. The correlations were also observed between ionic conductivity and binding energy, solubility and anion polarizability_, thermal stability and the energy difference between E_LUMO and E_HOMO. Wave function analyses have been performed by natural bond orbital (NBO) method to further investigate the cation–anion interactions.     

Density functional theory study on LBDOB and its derivatives: Electronic structures, energies, and molecular properties

Theoretical studies on unsymmetrical electrolyte salts, lithium [1,2-benzenediolato(2-)-O,O′ oxalato]borate (LBDOB), and its derivatives, lithium bis[1,2-benzenediolato(2-)-O,O′]borate (LBBB), and lithium bis(oxalate)borate (LBOB) are carried out using density functional theory (DFT) method and B3LYP theory level. Bidentate structures involving two oxygen atoms are preferred. Based on these conformations, a linear correlation was observed between the highest occupied molecular orbital (HOMO) energies and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that strongly electron-withdrawing substituent anions are more resistant against oxidation. The correlations were also observed between ionic conductivity and binding energy solubility and theoretical set of parameters of anion, thermal stability and the hardness (η). Wave function analyses have been performed by natural bond orbital (NBO) method to further investigate the cation-anion interactions.     

Synthesis,fluorescence emission spectra and chiroptical properties of copolymers of N-vinylcarbazole and optically active fumarates

Optically active (?)menthylethylfumarate (2) and (?)dimenthylfumarate (3) have been synthesised and free radically copolymerized with N-vinylcarbazole (1). Copolymers of (1) and (2) exhibit a strong tendency to alternation in agreement with earlier conclusions from studies of copolymerization of (1) with diethylfumarate. Surprisingly the much more hindered, but symmetrical fumarate, (3) yields copolymers which always have carbazole monomer contents in excess of the 1:1 alternating ratio. Chiroptical measurements indicate significant induced optical activity in the carbazole chromophores of all the copolymers obtained but, in accord with the predominance of alternating structures, there is no real evidence for any sequence-determined maximum in induced circular dichroism. Fluorescence emission spectra of all copolymer samples exhibit significant asymmetric broadening on the long wavelength (low energy) side of the normal carbazole monomeric emission. This broadening is exhibited even by poly (1-co-2) samples for which the monomer compositions strongly indicate alternating sequences and must, therefore, represent interaction between carbazole segments. Accordingly, and in contrast to widely held assumptions, it is concluded that excimer-like emission may be exhibited by alternating copolymers of N-vinylcarbazole. Further evidence for electronic interactions between non-nearest neighbour carbazole units is provided by u.v. absorption and ¹H-n.m.r. spectra of appropriate copolymers.