Electron Acceptor Groups Research Articles

Highly Efficient Microwave-assisted One-Pot Synthesis of Aromatic Nitriles from Aromatic Aldehydes

A highly efficient and environmentally benign protocol is described for the microwave-assisted one-pot synthesis of aromatic nitriles from aromatic aldehydes by the reaction with hydroxylamine hydrochloride in DMSO, which involves the intermediate formation of aldoximes and subsequent dehydration. The developed synthetic methodology can be readily accomplished with various aldehydes containing both electron-donor and electron-acceptor groups, providing excellent yields of the target products in shorter reaction times (1–2 min) compared to previously reported methodologies.

Diversity of electron acceptor groups in donor–acceptor type electrochromic conjugated polymers

Conjugated polymers have been extensively used for optoelectronic applications such as photovoltaics, light-emitting diodes, thin-film transistors and electrochromics. Over the past decade, a large number of donor-acceptor type conjugated polymers with an alternating array of electron donors and acceptors have been designed and synthesised for organic electrochromics application. The selection of proper electron donors and in particular electron acceptors to construct desired conjugated polymers allows scientists to precisely tailor optical and electronic properties of resulting conjugated polymers. In this review, electrochromic conjugated polymers will be summarised based on a category of widely-used electron acceptors including benzothiadiazole, benzoselenadiazole, benzooxazole, benzotriazole, benzoimidazole, quinoxalines and diketopyrrolopyrroles. This paper would help scientists understand how structurally different electron acceptors to control and modulate the highest occupied molecular orbital and the lowest unoccupied molecular orbital by sophisticatedly synthesizing appropriate electron acceptors, thus creating a broad colour palette, and eventually delivering a variety of desired electrochromic parameters such as switching speed, optical contrast, colouration efficiency as well as long-term stability. This summary account will give an insight into design principle and structure-properties relationship of electrochromic conjugated polymers for interested researchers to find optimal performance electrochromic polymeric materials.

Photophysics and luminescence switching properties of a series of photochromic styrylbenzene-terpyridine conjugate: Experimental and DFT/TD-DFT investigation

Joint experimental and computational investigation have been carried out in this work with regard to photophysical and photo-isomerization behavior of a series of photochromic terpyridine derivatives covalently coupled with styrylbenzene unit. Several electron-donating and electron-accepting groups were incorporated in the compound, tpy-pvp-X (X = H, Me, Cl, NO2, and Ph) to tune their photophysical as well photo-isomerization behaviors. All the compounds underwent trans-to-cis isomerization upon interaction with UV light with substantial changes in their absorption and luminescence spectra. Reversal of cis to trans forms were also achieved upon interacting with visible light. Trans-to-cis isomerization leads quenching of luminescence, while backward cis-to-trans isomerization gives rise to restoration of the original luminescence. Thus, "on-off" and "off-on" emission switching was made possible upon alternate interaction of the compounds with UV and visible light. Interestingly, the photochromic and photo-isomerization behaviors of the compounds are strongly influenced by the presence of acid. Detailed kinetic and thermodynamic aspects of the photo-isomerization process were also addressed in this study.

Synthesis and Spectroscopic Characterisation of Some Novel Butadienyl Asycyanine Colorants having Lepidine Moiety

Twenty-one novel chromophoric chain β-substituted butadienyl asycyanine colorants have been synthesized by catalytic condensation of (i) dimethylaminostyryl phenyl ketone, (ii) 4ʹ-dimethylaminostyryl-4ʹ-nitrophenyl ketone and (iii) 4ʹ-dimethylaminostyryl-4ʹ-methoxyphenyl ketone with seven lepidinium methyliodide salts in ethanolic DMF medium using piperidine as basic catalyst. These colorants were synthesized with the objective to study the effect of electron acceptor and electron donor group substituent at 4ʹ-position in the chain β-phenyl nucleus on visible absorption maxima. The newly prepared colorants were found to exhibit uniform increase in absorption maxima i.e. Red shift (RS), when collated with analogues having no substituent in the β-phenyl nucleus. Again the absorption maxima of the title colorants were found to be higher than the absorption maxima of previously prepared butadienyl colorants having quinoline mioety of same conjugated system.

Two-photon fluorescence imaging of lipid drops polarity toward cancer diagnosis in living cells and tissue

Monitoring the polarity of intracellular lipid droplets (LDs) is of great importance toward cancer diagnosis. Herein, we have rationally designed a novel LDs-targeting and polarity-sensitive fluorescent probe CBMC, which contains carbazole as an electron-donating group and malononitrile as an electron-accepting group forming intramolecular charge transfer mechanism. Due to its excellent solvatochromism, the probe emits stronger fluorescence in normal cells but weaker in cancer cells. By means of CBMC, normal tissues with stronger fluorescence have been obviously pointed out from cancerous tissues. For cancer therapy, the probe CBMC could be an ideal candidate to evaluate tumor, because the tumor area would decrease while the normal tissue area would increase with treatment time. Compared with existing probes with turn-off signal to normal cells, such a new probe with turn on type in normal cells could provide more reliable information with advantages of lower background interference, higher signal to noise ratio, and higher sensitivity. This probe CBMC will be a powerful tool to be potentially applied in tumor diagnosis in the case of treatment.

Nonfullerene Acceptor for Organic Solar Cells with Chlorination on Dithieno[3,2-b:2′,3′-d]pyrrol Fused-Ring

A narrow-band-gap molecular acceptor, IPIC-4Cl, featuring an indacenobis(dithieno[3,2-b:2′,3′-d]pyrrol) (INP) core with 2-butyl-1-octyl side chains and chlorinated (dicyanomethylidene)-indan-1-one (IC) as electron-accepting end group, has been rationally designed as nonfullerene acceptors (NFAs) for organic solar cells (OSCs). The impact of chlorination on the acceptor unit is revealed by a comparison study with two counterpart NFAs bearing a fluorinated or nonhalogenated IC unit. The synergetic photophysical and morphological analyses reveal that PBDB-T:IPIC-4Cl blend possesses efficient exciton dissociation and charge collection integrated with higher crystallinity and optimized phase separation. Consequently, the OSCs constructed by PBDB-T:IPIC-4Cl obtain a champion power conversion efficiency (PCE) of 13.4% with an extremely low energy loss of 0.51 eV. More encouragingly, we achieve a higher photovoltaic performance of 14.3% for ternary solar cells by combining an optimal amount of PC71BM with PBDB-T:...

Strong Ground- and Excited-State Charge Transfer in C3 -Symmetric Truxene-Derived Phenothiazine-Tetracyanobutadine and Expanded Conjugates.

The C3 -symmetric star-shaped phenothiazene-substituted truxene 1 was reacted with the electron acceptors tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The cycloaddition-retroelectrocyclization reaction yields the conjugates 2 and 3. A combination of spectral, electrochemical, and photophysical investigations of 2 and 3 reveals that the functionalization of the triple bond has a pronounced effect on their ground and excited-state interactions. Specifically, the existence of strong ground-state interactions between phenothiazine and the electron-accepting groups results in charge-transfer states, while subsequent ultrafast charge separation yields electron transfer products. This is unprecedented not only in phenothiazine chemistry but also in tetracyanobutadiene- and dicyanoquinodimethane-derived donor-acceptor conjugates. Additionally, by manipulating spectroelectrochemical data, a spectrum of the charge-separated species is construed for the first time, and shown to be highly useful in interpreting the rather complex transient spectra.

Theoretical Study of the Use of Cyano Acid Derivatives as Electron Acceptors in Cyanidin as Compounds of Dye Sensitized Solar Cells (DSSC)

Theoretical study of the use of cyano acid derivatives as electron acceptor groups in cyanidine as dye compounds of dye sensitized solar cells (DSSC) has been carried out based on energy parameters of HOMO-LUMO, LUMO electron localization, spectra, light absorption efficiency, coupling constants, and sensitizer bond length with TiO2. This study aims to determine the effect of cyanoacetic acid, cyanoacrylic benzothiadizole, cyanovinyl acid and cyanosynamic acid as electron acceptors on the photoelectric characteristics of cyanidine and determine the cyanoic acid derivative which can produce cyanidine photoelectric characteristics better based on energy parameters HOMO-LUMO, LUMO electron localization, spectra, light harvesting efficiency, coupling constant (VRP), and bond length of sensitizer with TiO2. This research begun with molecular optimization using DFT and TDDFT method with basis set of 6.311G *. HOMO-LUMO parameters used the same method with analysis technique using ECCE. The LUMO electron localization parameters use the same method, but the analysis technique used ECCE. Spectra using DFT method, using analytical technique using Chemcraft. Parameters of light absorption efficiency using DFT and TDDFT method with calculation technique using existing equations. Coupling constant parameters using the same method, the calculation technique used the energy equation of dye compounds were calculated in the conditions of HOMO, LUMO and TiO2 energy. Parameter length of the sensitizer bond with TiO2 were calculated used DFT method with avogadro analysis technique. Cyanidin cyanoacetate became the best modification based on HOMO LUMO energy parameter -4.569 and -1.01 eV, respesctively. In the electron localization parameter, the best modification was produced in cyanidine cyanoacetate with an electron-centered pattern on the cyanoacetic group. Spectra parameters produced the best modification, cyanoacetic cyanidine with a wavelength of 378.811 nm with osillator strength of 0.633. The light absorption efficiency parameters resulted in the best modification of cyanidin cyanoacetate with a value of 0.767. For parameter of clutch constant, best modification is cyanidin benzothiadizol sianoakrilik with a value -0.269. The best modification on the parameter length of the sensitizer bond with TiO2 was cyanidine cyanoacetate with a bond length of 1.926 Å.

A DFT/TDDFT investigation on the efficiency of novel dyes with ortho-fluorophenyl units (A1) and incorporating benzotriazole/benzothiadiazole/phthalimide units (A2) as organic photosensitizers with D–A2–π–A1 configuration for solar cell applications

Novel derivatives of OD1 with D–A2–π–A1 configuration have been designed. The calculated geometrical parameters and optoelectronic properties are compared with those of the parent triphenylamine-based dye molecule (OD1) comprising a triphenylamine terminal electron-rich group (D), 3,4-ethylene dioxythiophene π-spacer, fluorophenyl electron-withdrawing group (A1), and cyanoacrylic acid anchor group. The designed derivatives differ from OD1 with D–π–A1 configuration in the incorporation of an electron-acceptor group (A2) between the donor group and π-spacer unit, namely benzotriazole (BTZ), benzothiadiazole (BTDZ), or phthalimide (PHI), denoted as ND2-BTZ, ND3-BTDZ, and ND4-PHI, respectively. The effects of the incorporation of each electron-deficient unit on the geometry, absorption spectra, and electrochemical properties are investigated by using density functional theory (DFT) and time-dependent (TD)DFT methods. Additionally, the preferred dye adsorption process on model Ti(OH)4 is investigated. The results for the binding energy, selected bond distances, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and their distribution, energy gaps, and total density of states (TDOS) plots are discussed and analyzed. The intermolecular interaction between two monomers of each dye and iodine is also investigated, and the complexation energy [corrected for the basis set superposition error (BSSE)] is calculated and analyzed. The results reveal that the introduction of the BTDZ and PHI functional groups is more promising for formation of organic dyes with D–A2–π–A1 configuration.

VIRTUAL SCREENING OF HETEROCYCLIC COMPOUNDS AGAINST ANGIOTENSIN-CONVERTING ENZYME FOR POTENTIAL ANTIHYPERTENSIVE INHIBITORS

Objective: The objective of this study was to investigate the antihypertensive activity of heterocyclic compounds against angiotensin-converting enzyme (ACE) through molecular docking studies.
 Methods: The X-ray crystal three-dimensional (3D) structure of human ACE complexed with lisinopril (PDB ID: 1O86) was retrieved from protein databank. The two-dimensional structures of 10 selected heterocyclic compounds were drawn in ACD-Chemsketch and converted into 3D structures. The 3D structures of compounds were virtually screened in the binding pockets of ACE using FlexX docking program. Further, the chemical entities revealing the molecular electronic structures of the best docked compound (Compound-4) were explored through density functional theory studies.
 Results: The Compound-4 showed the highest docking score of −26.6290 kJ/mol with ACE. The Hbond and non-bonded interactions are favored by phenylalanine, leucine, and arginine. The energy gap of 1.60 eV between highest occupied molecular orbital and lowest unoccupied molecular orbitals explained the presence of strong electron-acceptor group. Furthermore, the molecular electrostatic potential studies clearly envisaged the requirement of electropositive and electronegative groups are crucial for the ACE inhibitor activities.
 Conclusion: The identification of good ACE inhibitors requires the understanding of the current ACE inhibitors. Thus, the docking interactions of Compound-4 and its molecular electronic structure significantly imply its potential as antihypertensive agent. However, further clinical studies are required to ascertain its potential toxic effects.

2,5-Dimethoxybenzene-1,4-dicarboxaldehyde: An Emissive Organic Crystal and Highly Efficient Fluorescent Waveguide.

To identify the simplest organic structure for an emitter, we focused on 2,5-dimethoxybenzene-1,4-dicarboaldehyde. This symmetric molecule has a very low molecular weight (MW=194), a single benzene unit, and consists of only three elements (H, C and O). It forms highly efficient and pure emitting crystals (λem=499 nm, ΦF =0.42, FWHM=42 nm) due to the rigid structure based on the single benzene framework and four intramolecular hydrogen bonds between electron-donating methoxy and electron-accepting aldehyde groups. This crystal acts as a good optical waveguide with pure green emission (FWHM=34 nm) and very low loss coefficient (0.00120 dB/μm).

New dyes for DSSC containing thienylen-phenylene: a theoretical investigation

Abstract Dye Sensitized Solar Cells (DSSCs) show the most promising future of photovoltaic cells due to their environmental protection, simple synthesis and low cost. The dye sensitized is the key factor for the development of this photovoltaic cells. In this work, a theoretical study on six organic π-conjugated molecules based on thienylen-phenylene, with electron acceptor group 2–cyanoacrylic for all dyes, using together quantum methods, density functional theory (DFT) and its extensible time dependent-density functional theory (TD-DFT) is reported. A different unit based on a series of X moieties (e.g. [1,2,5] Thiadiazolo [3,4-c]pyridine) were introduced as a bridge. However, the electronic structure; The HOMO, LUMO and the key parameters in close connection with the short-circuit current density (JSC), including light-harvesting efficiency (LHE), injection driving force (ΔGinject) were discussed. In addition, the estimated values of open-circuit photovoltage (VOC) for these dyes were presented. The calculated results of these dyes reveal that these dyes can be used as a potential sensitizer for TiO2 nanocrystalline solar cells due to their best electronic and optical properties.

One-Electron-Addition to Pentavalent Phosphorus with the Phosphorus-Chlorine Bond as Acceptor Introducing a Fundamental Distinction in Substitution Mechanism between S<sub>N</sub>2(P) and S<sub>N</sub>2(C)

An electron-addition, under single-crystal conditions, to pentavalent phosphorus compounds as Cl-P (=O, S) Y, Z with the P-Cl bond as electron-accepting group, is selected as an additional model for SN2(P) like reactions. It is demonstrated that the geometric information stored in the tetrahedral configuration (substrate) can be transmitted in the corresponding trigonal bipyramidal (TBP) state for nucleophilic substitution. In this article, we focus on these specific mechanistic aspects of carbon and phosphorus. We consider our study as a contribution to the significance of these (bio)chemical intermediates.

Theoretical Study of Phenothiazine Organic Dyes with Different Spacers for Dye-Sensitised Solar Cells

In this paper, six organic dyes have been studied by density functional theory (DFT). The electron-acceptor group is the cyanoacrylic acid unit for all sensitisers, and the electron-donor unit is a phenothiazine (PTZ) fragment substituted by an ethynyl-pyrene unit; the π-linker was varied, and the influence was investigated. The dye bearing the divinylthiophene linker showed the highest absorption maximum. The theoretical photovoltaic properties revealed that the overall efficiency of the solar cell could be remarkably improved using the designed dyes. The results indicated that all of the studied organic dyes are good candidates as photosensitisers for dye-sensitised solar cells (DSSCs).

Self‐Assembly of Board‐Shaped Diketopyrrolopyrrole and Isoindigo Mesogens into Columnar π‐π Stacks

Diketopyrrolopyrrole and isoindigo are commercially important dyes that have recently found broad application as electron acceptor and light-absorbing groups in organic semiconductors. Their self-assembly into specific supramolecular structures to control optoelectronic properties has been hampered by limited options for substitution and their high propensity for crystallization. Reported here is a molecular design that directs self-assembly into previously elusive columnar mesophases of π-π stacking cores. Although attachment of bis(trisoctyloxyphenyl)-1,3,5-triazine groups to both ends of diketopyrrolopyrrole-thiophene and isoindigo cores generated mesomorphic dyes of similar overall shapes and dimensions, distinct differences in their mesomorphism and optoelectronic properties were observed.

Theoretical Investigations of Hydrogen Bonding Interactions of (E)-1-(1H-Benzo[d]imidazol-2-yl)-3-Phenylprop-2-en-1-one Momoners and Dimers: NBO, QTAIM and NCI Study

Hydrogen bonding is an essential interaction in nature and plays a crucial role in many formations of materials and biological processes, requiring a deeper understanding of its formation. Benzimidazole is an important structural unit found in a large number of natural and pharmacologically active molecules. In the present work, the electronic structures and properties and relatives stabilities of a series of (E)-1-(1H-benzo[d]imidazol-2-yl)-3-phenylprop-2-en-1-one monomers and dimers have been studied by density functional theory using B3LYP 6-31+G (d, p) calculation level. the strengths of the noncovalent interactions have been analyzed in terms of the QTAIM analysis, NCI analysis and natural bond orbital approaches. It was found that the dimers are formed by double N-H⋯O hydrogen bond. QTAIM analysis proved the presence of intramolecular hydrogen bond in monomers and coexistence of intramolecular and intermolecular hydrogen bond in dimers. Frequency analysis show that intermolecular N-H⋯O interactions are proper hydrogen bond while intramolecular C-H⋯N, C-H⋯O, C-H⋯H-C interactions are improper hydrogen bond. NBO and NCI analyses confirm the existence of hydrogen bonds in the studied monomers and dimers. The presence of weakly electron acceptor group on benzene ring favor the total interaction energy of dimerization.

КІНЕТИЧНІ ДОСЛІДЖЕННЯ МЕТАКРИЛОВИХ МОНОМЕРІВ НА ОСНОВІ 2-СТИРИЛХІНОЛІНУ

Polymethylmethacrylate is widely use material in optics due to its atmosphere resistance, chemical stability, good mechanical properties, transparency and light transmission. Due to these properties, PMMA is often used as a polymeric matrix for creating photosensitive polymers and polymers with nonlinear optical (NLO) properties. Materials with NLO properties can be made by introducing moleculas of chromophores into the polymer chain. There are two fundamentally different ways of doing this. The first is to create composite material where the chromophore is a dispersed phase and is introduced into the system as a "guest". In the second case, the chromophore is introduced into the polymer chain covalently, and can be included in the side and the main chain. Studies of polymers containing NLO chromophore in the side chain have shown a number of advantages: better orientation of the chromophores under the action of an electric field; relaxation processes are much slower; increasing time and thermal stability; increasing the glass transition temperature of the polymer. Based on present knowledge we decided to design new methacrylic polymers with styrylquinoline chromophore in side chain. The polymerization ability of the new monomers for free radical homopolymerization was investigated kinetically by using dilatometric method. It was found that new 2-styrylquinoline containing monomers are able to homopolymerization with high conversions (63–83%). The polymerization was carried out in DMF using 2,2´-azobisisobutyronitrile as initiator at 80°C in argon atmosphere. The products of polymerization were characterized by 1H NMR spectroscopy. It was installed that all new monomers have bigger speed of polymerization (Ksum= 1.36–8.33×103 l/mol×s) then methylmethacrylate (Ksum= 0.5×103 l/mol×s), phenylmethacrylate (Ksum= 1.1×103 l/mol×s) and similar to polymerization of 2-methyl-8-oxyquinoline methacrylate (Ksum= 3.28×103 l/mol×s). It was found that speed of polymerization increases with increasing electron donating power of substitute in paraposition of the aromatic ring. It has been proven that presence of electron acceptor group reduces speed of polymerization.

Tuning of hyperpolarizability, and one- and two-photon absorption of donor-acceptor and donor-acceptor-acceptor-type intramolecular charge transfer-based sensors.

The present work aims to study the effect of solvent as well as arrangement of donor-acceptor groups on linear and non-linear optical (NLO) response properties of two experimentally studied intramolecular charge-transfer (ICT)-based fluorescent sensors. One of them (molecule 1) is a donor-acceptor (D-A) system with hemicyanine and dimethylanilino as electron withdrawing and donating groups, respectively, while the other one (molecule 3) is molecule 1 fused with a boron-dipyrromethene (BODIPY) moiety. BODIPY acts as the electron acceptor group of molecule 2 that as well consists of dimethylanilino as the electron donor. Density functional theory (DFT) as well as time-dependent DFT has been employed to optimize the geometry of the molecules, followed by computation of dipole moment (μ), static first hyperpolarizability (βtotal), and one- and two-photon absorption (TPA) strengths. The results reveal that dipole moment as well as total static first hyperpolarizability (βtotal) of the studied molecules is dominated by the respective components in the direction of charge transfer. The ratio of vector component of first hyperpolarizability (βvec) to βtotal also supports the unidirectional charge transfer in the studied systems. In molecule 3, which is a donor-acceptor-acceptor (D-A-A)-type system, the BODIPY moiety is found to play a major role in controlling the NLO response over the other acceptor group. Solvents are also found to play an important role in controlling the linear as well as NLO response of the studied systems. A significant increase in the first hyperpolarizability as well as TPA cross-section of the studied molecules is predicted due to an increase in the dielectric constant of the medium. The results presented are expected to provide a clue in tuning the NLO response of many ICT-based chromophores, especially those with D-A-A arrangements.

1,2,5-Triphenylpyrrole Derivatives with Dual Intense Photoluminescence in Both Solution and the Solid State: Solvatochromism and Polymorphic Luminescence Properties.

Five organic luminophores, 1,2,5-triphenylpyrrole (TPP) derivatives 3 a-e bearing electron-withdrawing or electron-donating groups, have been synthesized by Pd-catalyzed Suzuki coupling of 1-phenyl-2,5-di(4'-bromophenyl)pyrrole and para-substituted phenylboronic acid derivatives. They possess good thermal stabilities with high decomposition temperatures above 310 °C. Investigation of the photophysical properties of the luminogens 3 a-e indicated that they exhibited dual intense photoluminescence in both solution and the solid state due to their twisted conformations, and their fluorescence quantum yields (ΦF ) were determined as 68.7-94.9 % in THF solution and 19.1-52.0 % in solid powder form. Compounds 3 a-c bearing electron-accepting groups exhibited remarkable solvatochromism with large Stokes shifts, attributable to their D-π-A structure and intramolecular charge-transfer effect. In particular, 3 a, bearing aldehyde groups, displayed an obvious red-shift of the emission band from 445 to 564 nm with increasing solvent polarity. However, no obvious solvatochromic behavior was observed for compounds 3 d,e bearing electron-donating groups. The luminophore 3 a exhibited polymorphic luminescence properties and crystallization-induced emission enhancement.

Synthesis and Antioxidant Activities of Ferrocenyl-containing Curcumin Analogues

Background: Metal organic compounds have attracted considerable attention since the advent of Salvarsan, a metal organic compound for the treatment of syphilis. Ferrocene as an effective phenyl bioisostere is becoming a viable platform for drug design by virtue of its redox properties, high lipophilicity and three-dimensional metallocene unit, which may lead to some changes in selectivity toward biological targets compared with phenyl or alkyl groups. Therefore, ferrocene seems to an appropriate candidate for improving the antioxidant activity of drugs. Methods: We synthesized four ferrocenyl-containing curcumin analogues by introducing ferrocenyl groups into the active methylene groups to obtain higher antioxidant activity than the parent ferrocene- substituted curcumin analogues, and their antioxidant activities were evaluated in 2, 2′- azobis (2-amidinopropane hydrochloride) (AAPH) and Cu2+/glutathione(GSH) -induced oxidation of DNA, and in trapping 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), 2, 2′-azinobis(3-ethylbenzothiazoline- 6-sulfonate) cationic radicals (ABTS+•) and galvinoxyl radicals. Results: These ferrocenyl-containing curcumin analogues can protect DNA against Cu2+/GSHinduced oxidation, and scavenge 5.7, 6.9, 5.5 and 5.3 radicals in protecting DNA against AAPHinduced oxidation. Compounds (3)~(5) can trap more DPPH, ABTS+• and galvinoxyl radicals than compound (6). The substituents and iron atoms play an antioxidant role in ferrocenyl-containing curcumin analogues. Conclusion: The introduction of ferrocenyl group results in a higher antioxidant activity than the traditional hydroxyl-involved curcumin analogues. The ferrocenyl group is a powerful antioxidative group that could be used to modify natural antioxidants. The electron-accepting group attaching to the phenyl-group could further increase the antioxidant activity. Ferrocene-containing curcumin analogues show higher activities in quenching radicals and protecting DNA against radical-induced oxidation. Therefore, the introduction of ferrocenyl group into the natural antioxidant may contribute to increase the antioxidant activity.