N-hydroxyphthalimide (NHPI) combined with stable and recoverable transition metal—aluminium binary hydrotalcite-like compounds (M-Al HTLcs, M = Cu, Ni, Co) as an unprecedented catalytic system was demonstrated for the allylic carbonylation, as the model reaction, of cyclic olefins with tert-butyl hydroperoxide (TBHP), using isophorone (IP) to ketoisophorone (KIP). The results showed NHPI combined with Cu−Al HTLcs to be an efficient catalytic system and the influences of various reaction conditions of the catalytic reaction were optimised. A maximum IP conversion of 68.0% with 81.8% selectivity to KIP was afforded under the optimal reaction conditions. Experiments of repeatability and restorability showed Cu-Al HTLcs to be stable for at least five cycles without noticeable loss of catalytic activity. Expanding substrates could also be efficiently converted to the corresponding ketones under the optimised reaction conditions with appreciable yields. A plausible catalytic reaction mechanism was proposed.

Two cationic iridium complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), using 2,5-diphenyl-1,3,4-oxadiazole (dph-oxd) as the cyclometallating ligand and 2,2′-bipyridine (bpy) or 2-(1H-pyrazol-1-yl)pyridine (pzpy) as the ancillary ligands, have been synthesized, and their photophysical and electrochemical properties have been comprehensively investigated. In solution, both complexes emit efficient blue-green light. For complex 1, the light emission in a neat film is remarkably red-shifted; in solid state, it gives an intriguing piezochromic phenomenon. Compared with archetype [Ir(ppy)2(bpy)]PF6 (ppy is 2-phenylpyridine), complex 1 shows a largely stabilized HOMO (highest occupied molecular orbital) level, induced by the electron-deficient 1,3,4-oxadiazole (oxd) heterocycle of dph-oxd, which results in an enlarged energy gap and blue-shifted emission. Compared with complex 1, complex 2 shows an enhanced LUMO (lowest unoccupied molecular orbital) level, caused by the electron-rich pzpy ancillary ligand, but they exhibit similar emission energy in solution. For both complexes, theoretical calculations reveal that their blue-green emission in solution arises primarily from the 3π–π* states centered on dph-oxd; moreover, complex 1 bears close-lying 3π–π* and 3CT (charge-transfer) states, underlying its remarkably red-shifted emission in the neat film and unique piezochromic behavior in the solid state. Solid state light emitting electrochemical cells (LECs) based on complexes 1 and 2 give efficient yellow and green-blue light, with peak current efficiencies of 18.3 and 5.2 cd A−1, respectively. It is demonstrated that oxd-type cyclometallating ligands are promising as an avenue to stabilize the HOMOs and tune emission properties of cationic iridium complexes to a large extent.

In this study, a novel platelet-like nanocatalyst, Pd/g-C3N4 with easily approachable active sites, was developed. The mesoporous graphitic carbon nitride (g-C3N4) is a layered structure connected by planar amino groups, which can work as stabilizer and active support for noble metal nanoparticles. The palladium nanoparticles with an average particle size of 3.25 nm were evenly dispersed on the surface of g-C3N4 without aggregation. Detailed charaterizations reveal that there is no covalent-bond interaction between g-C3N4 and Pd NPs. The Pd/g-C3N4 catalyst showed excellent catalytic activity in the reduction of nitroarenes by NaBH4, and Suzuki coupling reaction of aryl halides with arylboronic acids under mild conditions. The reduction of 4-nitrophenol has a pseudo-first-order rate constant of 7.29 × 10−3 s−1, and an activity parameter of 1.37 s−1 mM−1, which is higher than those reported in the literature. Furthermore, the Suzuki coupling reactions processed smoothly with 97.0 % isolate yield in less than 30 min in water with PEG600 as the additive. The catalyst could be recycled for five times without significant loss of catalytic activity, which confirmed the good stability of the catalyst.

The catalytic activity of the heterogeneous catalysts of Mn-mont (where mont represents montmorillonite) coordinated with Schiff-base ligands for epoxidation of cyclohexene by O2 under Mukaiyama conditions was studied. The catalysts were characterized by IR, UV-vis DRS, XRD, SEM and ICP. The heterogeneous catalysts were proved to promote the epoxidation of cyclohexene efficiently, the effects of various reaction conditions on the catalytic reaction were optimized and obtained as high as 100% conversion with 90.0% selectivity of epoxycyclohexane at 40 °C in 5 h with molecular oxygen as oxidant in acetonitrile. Repeated runs indicated that the catalysts were stable for at least 3 cycles. Thus, the heterogeneous catalysts of Mn-mont coordinated with Schiff-base ligands were proved to be environmentally friendly and economical for the epoxidation of cyclohexene.

Four novel pyridine Schiff bases derived from 2,6-pyridinedicarbaldehyde and substituted o-hydroxyl-aromatic amines and their manganese(II) complexes were synthesized and characterized by elemental analyses, ESI-MS analysis, thermal analysis (TGA), H-NMR, IR and UV-vis. The activity of these complexes as catalysts in cyclohexene autoxidation were investigated and the effects of various reaction conditions on the catalytic reaction were optimized to obtain as high as 99.6% conversion with 95.0% selectivity of epoxycyclohexane at 40 °C for 6 h using molecular oxygen as an oxidant in acetonitrile. The result presents excellent catalysts for epoxidation of cyclohexene under mild temperature and atmospheric oxygen (O2) pressure.

A novel aromatic polycarboxylic acid ligand, 2,6-bis(3,5-dicarboxypyrazol-1-ylmethyl) pyridine (L) was designed and synthesized. Its corresponding Tb(III) complex [TbL(H2O)4]Cl·H2O was successfully prepared. The ligand L and the complex [TbL(H2O)4]Cl·H2O were characterized by elemental analysis, IR, 1HNMR, EI–MS and TG–DSC. The investigation of fluorescence property of the complex showed that the Tb(III) ion could be sensitized efficiently by the ligand. In order to explore the potential biologically active value of [TbL(H2O)4]Cl·H2O, the interaction of [TbL(H2O)4]Cl·H2O with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectra, UV–vis absorbance and synchronous fluorescence spectra. The fluorescence quenching mechanism of BSA by [TbL(H2O)4]Cl·H2O was analyzed. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the van der Waals and hydrogen bond interactions were the predominant intermolecular forces in the interaction of [TbL(H2O)4]Cl·H2O with BSA. Furthermore, the effect of [TbL(H2O)4]Cl·H2O on the conformation of BSA was analyzed according to synchronous fluorescence.Highlights► A novel aromatic polycarboxylic acid ligand was designed and synthesized. ► The fluorescence property of the Tb(III) ion could be sensitized efficiently by the ligand. ► The binding affinity between [TbL(H2O)4]Cl·H2O and bovine serum albumin (BSA) is high.

•A new ligand with triphenylamine and carbazole was prepared and characterized.•It is an asymmetric chelating ligand.•Its corresponding Eu complex also be investigated.•The ligand HL has an excellent antenna effect to sensitize the lanthanide ion.•The complex has good quantum efficiency and high thermal stability.A novel β-diketonate ligand with triphenylamine and carbazole moieties named: 1-(4-diphenylamino-phenyl)-3-(9-ethyl-9H-carbazol-3-yl)-propane-1,3-dione (HL), was synthesized by the Claisen condensation reaction and its corresponding europium complex Eu(L)3phen was prepared. The structures of the ligand and complex were characterized by IR spectra, 1H NMR, elemental analysis (EA), UV–Vis spectra and ESI-MS. The photoluminescence (PL) spectra shows that the ligand has an excellent antenna effect to sensitize the Eu3+ and the complex has good quantum efficiency which indicates that the complex is a good candidate as emitter in fabricating organic light-emitting diodes (OLEDs). Thermogravimetric (TG) analysis shows that the complex possesses high thermal stability and good film-forming ability to generate the OLEDs.Graphical abstractA novel ligand and its corresponding Eu3+ complex have been designed and synthesized, and their photophysical properties have also been investigated.

Mild temperature and atmospheric oxygen pressure assisted epoxidation of cyclohexene was achieved with a series of novel montmorillonite-supported Mn(II) complexes of pyridine Schiff-base ligands. The catalysts were characterized by IR, UV–Vis DRS, XRD, SEM and ICP. The heterogeneous catalysts were proved to promote the epoxidation of cyclohexene efficiently, affording the desired product epoxycyclohexane with a yield up to 92 %. The effects of various reaction conditions on the catalytic reaction were optimized. Repeated runs indicated that the catalysts were stable for 3 cycles without noticeable loss of their catalytic activity.

A novel aromatic carboxylic acid ligand (L) was synthesized and its corresponding Eu(III) and Tb(III) complexes, Na3EuLCl3·2H2O (EuL) and Na3TbLCl3·3H2O (TbL), were successfully prepared. L and its corresponding complexes were characterized by means of MS, elemental analysis, IR, 1H NMR and TG. The luminescence spectra of Eu(III) and Tb(III) complexes were investigated and the results showed that L was an efficient sensitizer for Eu(III) and Tb(III) luminescence. The interactions of L, EuL and TbL with bovine serum albumin (BSA) have been investigated through fluorescence spectroscopy under physiological conditions. The Stern–Volmer analysis indicated that the fluorescence quenching of BSA by L, EuL and TbL was resulted from static mechanism, and the binding constants (Ka) were 2.22 × 104, 1.33 × 105 and 4.27 × 105 at 300 K, respectively. The binding sites (n) and the corresponding thermodynamic parameters ΔH, ΔS, and ΔG were calculated at different temperatures. According to the theoretical and experimental results, van der Waals interactions and hydrogen bonds were found to play major roles in the binding reaction. Furthermore, UV–Vis absorption spectroscopy and synchronous fluorescence spectra indicated that the conformation of BSA was changed. The results obtained in the work can help understand the action mode between L and its corresponding Eu(III) and Tb(III) complexes with BSA, and they are also expected to provide important information of designs of new inspired drugs based on Eu and Tb.Graphical abstractHighlights► A novel ligand and its Eu(III) and Tb(III) complexes were synthesized. ► The luminescence properties of Eu(III) and Tb(III) complexes were studied. ► The binding characteristics of L, EuL and TbL with BSA were investigated. ► UV–Vis and synchronous fluorescence indicated the changed conformation of BSA. ► The binding affinity with BSA was determined to be in the order of TbL > EuL > L.

A N-substituted naphthalimide derivative N-[2-(2-hydroxylethylamino)-ethyl]-1,8-naphthalimide (HEAN), which contains potential acceptors for hydrogen bond, was synthesized and fully characterized. The fluorescence and UV/vis behaviors of HEAN in different solvents were investigated, and its Stokes shift value and fluorescence quantum yield (Φf) in each solvent were determined. A remarkable fluorescence enhancement of HEAN in protic–polar solvents but a great quenching effect in apolar, less–polar and aprotic–polar solvents were observed, suggesting the key role of the proticity of solvents. In the protic–polar solvents, the fluorescence intensity and the quantum yield of HEAN increased along with a slight red-shift of the characteristic emission wavelength (λem) with the increase of solvent polarity. Maximum Φf value of 0.453 for HEAN was found in water solvent with a Stokes shift of 4636 cm−1. The inhibition of the photoinduced electron transfer (PET) by the intermolecular hydrogen-bonding interactions between protic solvents and HEAN was proposed to be responsible for its strong fluorescence enhancement. Such solvatofluorochromic property of HEAN may make it as a prospective fluorescent chemosensor to distinguish a protic solvent from aprotic solvents.

A novel bis-pyrazolyl-carboxyl ligand, 2,6-bis(5-methyl-3-carboxypyrazol-1-ylmethyl)pyridine (L), was designed and synthesized and its several lanthanide(III) complexes Eu(III), Tb(III), Sm(III) and Gd(III) were successfully prepared and characterized in detail based on elemental analysis, infrared, mass, proton nuclear magnetic resonance spectroscopy and TG–DTA studies. Analysis of the IR spectra suggested that each of the lanthanide metal ions coordinated to the ligand via the carbonyl oxygen atoms and the nitrogen atom of the pyridine ring and pyrazole rings. The fluorescence spectra exhibits that the Tb(III) complex and the Eu(III) complex display characteristic metal-centered fluorescence in solid state while ligand fluorescence is completely quenched. However, the Tb(III) complex displays more effective fluorescence than the other complexes, which is attributed to especial effectivity in transferring energy from the lowest triplet energy level of the ligand (L) onto the excited state (5D4) of Tb(III).

A novel ligand, N2,N6-bis[2-(3-methylpyridyl)]pyridine-2,6-dicarboxamide (L2) and the corresponding Eu(III) and Tb(III) hydrochlorate complexes have been synthesized and characterized in detail based on elemental analysis, IR and NMR. The crystal and molecular structure of the complexes was determined by X-ray crystallography. The Eu(III) and Tb(III) ions were found to coordinate to the amido nitrogen atoms and pyridine nitrogen atoms. The luminescence properties of lanthanide complexes in solid state, in different solutions and in different pH value were investigated. The result shows that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, and the ligand (L2) is an excellent sensitizer to Tb(III) ion.

Novel transition metal complexes of bis(diarylsubstitutedthiophosphoryl)imines ligand derived from O,O-di(p-methoxylphenyl)thiophosphoryl chloride and O,O-di-(p-methoxylphenyl)thiophosphoryl amine with Cu(II), Co(II), Ni(II), Fe(II) and Mn(II) were synthesized. The formation mechanism of complexes and their stereochemistry structures were investigated according to elemental analysis, infrared spectra and 31P-nuclear magnetic resonance spectra. The extractions of the ligand for different divalent metal ions, such as Zn(II), Cd(II), Cu(II), Ni(II), Fe(II), Sn(II), Mn(II), Pd(II), Hg(II) and Fe(III), were investigated in sulphate solution, respectively. The results show the metal atom is coordinated by 4 sulfur atoms in a square-planar fashion, and the titled compound has not only powerful ability to coordinate with cadmium from aqueous solution with a high extractive rate about 61.20% and a relatively weak complexation for other divalent metals with the extractive rate from 2.46% to 36.66%, but also a good selectivity to Fe(III).

Two novel ligands named 4-styrylpyridine-2,6-dicarboxylic acid (4-SPDA) and 4-(4-(2-(2, 6-dicarboxypyridin-4-yl)-vinyl)styryl)pyridine-2,6-dicarboxylic acid(DSPDA) and their complexes with Tb(III) were synthesized and characterized by infrared spectrometry, 1H nuclear magnetic resonance, elemental analysis and gas chromatograph-mass spectrometry. The ligand synthetic route was optimized. The fluorescence properties of the complex in solid state, in different kind of solvents and in solutions with different pH values were investigated in detail. The results show that the yields of DSPDA and 4-SPDA reach over 78% by Wittig-Horner reaction and other eight pyridine-2, 6-dicarboxylic acid derivatives with different substituents on pyridine ring, and their complexes with Tb(III) are also obtained. The fluorescence intensities of the complexes with electron-donating groups are more intense than those of the complexes with electron-withdrawing groups on pyridine ring; fluorescence intensities of the complexes are the strongest in neutral solution (pH=7), and the less the dipole moment of solvent molecule is, the stronger the fluorescence intensity is. It is found that the two ligands (4-APDA and DSPDA) are the good sensitizers for Tb(III) ion.

A practical catalytic method to oxidize α-ionone with molecular oxygen using N-hydroxyphthalimide(NHPI) combined with acetylacetone cobatt(II) (Co(acac)2) was developed, and the probable catalytic mechanism was proposed. The influences of the reaction conditions on conversion of α-ionone and the selectivity of the major product (5-keto-α-ionone) were investigated, and the technical parameters for 5-keto-α-ionone were optimized. The results show that the primary product is 5-keto-α-ionone, and by-products include epoxy-α-ionone, as well as rearrangement products 4-keto-β-ionone and epoxy-β-ionone, which are characterized by infrared spectra, proton nuclear magnetic resonance spectra, mass spectra and elemental analysis. The selectivity of 5-keto-α-ionone and the conversion of α-ionone are 55.0% and 97.0%, respectively, when 30%(molar fraction) NHPI, 1.0%(molar fraction) Co(acac)2 and no solvent are employed under O2 pressure of 1.0 MPa and the reaction temperature of 65 °C for 11 h. The procedure shows good reproducibility in the parallel experiments.

A simple and effective route for the synthesis of mibolerone was described starting from the estr-5(10)-en-3,17-dione in four steps with the overall yield of 47.0%. Thus, two methods for key intermediate methylnorandrost were investigated: one(method A) starting from estr-4-en-3,17-dione underwent 3-keto group protected with ethyl orthoformate to give 3-ethoxy-3,5-dien-estr-17-one, the other(method B) from estr-5(10)-en-3,17-dione and protected 3-keto group to give 3,3-dimethoxy-estr-5(10)-7-one in a mild acidic condition. Then, two intermediates were subsequently reacted with methyllithium followed by a mild hydrolytic procedure and gave methylnorandrost with total yield 25.0% and 86.0%, respectively. In the preparation of 6-dehydrogenation product of methylnorandrost, two procedures(method C and method D) were investigated: one was the protected 17α-methyl-17β-hydroxy Δ3,5-enol ethers estrendiene brominated and the resulting 6-bromo-19-methylnortestosterone was then immediately dehydrohaloenated to give 6-dehydro-19-methylnortestosterone, the total yield only reaches 36.0%; the other was directly dehydrogenated with chloranil and the yield reaches 75.6% under the optimum conditions: in refluxing tetrahydrofuran, the molar ratio of methylnorandrost to chloranil is 0.66 and reaction time of 5 h. The titled compound and intermediates were characterized by 1H and 13C NMR, IRMS and elemental analysis.

A novel ligand, N2,N6-bis[2-(3-methylpyridyl)]pyridine-2,6-dicarboxamide (L2) and the corresponding Eu(III) and Tb(III) hydrochlorate complexes have been synthesized and characterized in detail based on elemental analysis, IR and NMR. The crystal and molecular structure of the complexes was determined by X-ray crystallography. The Eu(III) and Tb(III) ions were found to coordinate to the amido nitrogen atoms and pyridine nitrogen atoms. The luminescence properties of lanthanide complexes in solid state, in different solutions and in different pH value were investigated. The result shows that Tb(III) complexes exhibit more efficient luminescence than Eu(III) complexes, and the ligand (L2) is an excellent sensitizer to Tb(III) ion.

Two cationic iridium complexes, namely [Ir(dph-oxd)2(bpy)]PF6 (1) and [Ir(dph-oxd)2(pzpy)]PF6 (2), using 2,5-diphenyl-1,3,4-oxadiazole (dph-oxd) as the cyclometallating ligand and 2,2′-bipyridine (bpy) or 2-(1H-pyrazol-1-yl)pyridine (pzpy) as the ancillary ligands, have been synthesized, and their photophysical and electrochemical properties have been comprehensively investigated. In solution, both complexes emit efficient blue-green light. For complex 1, the light emission in a neat film is remarkably red-shifted; in solid state, it gives an intriguing piezochromic phenomenon. Compared with archetype [Ir(ppy)2(bpy)]PF6 (ppy is 2-phenylpyridine), complex 1 shows a largely stabilized HOMO (highest occupied molecular orbital) level, induced by the electron-deficient 1,3,4-oxadiazole (oxd) heterocycle of dph-oxd, which results in an enlarged energy gap and blue-shifted emission. Compared with complex 1, complex 2 shows an enhanced LUMO (lowest unoccupied molecular orbital) level, caused by the electron-rich pzpy ancillary ligand, but they exhibit similar emission energy in solution. For both complexes, theoretical calculations reveal that their blue-green emission in solution arises primarily from the 3π–π* states centered on dph-oxd; moreover, complex 1 bears close-lying 3π–π* and 3CT (charge-transfer) states, underlying its remarkably red-shifted emission in the neat film and unique piezochromic behavior in the solid state. Solid state light emitting electrochemical cells (LECs) based on complexes 1 and 2 give efficient yellow and green-blue light, with peak current efficiencies of 18.3 and 5.2 cd A−1, respectively. It is demonstrated that oxd-type cyclometallating ligands are promising as an avenue to stabilize the HOMOs and tune emission properties of cationic iridium complexes to a large extent.