Some complexes containing carbon chains end-capped by M(CO)2Tp′ [M = Mo, W; Tp′ = HB(pz)3, HB(dmpz)3] groups

Complexes M(CCCSiMe₃)(CO)₂Tp′ (Tp′ = Tp [HB(pz)₃], M = Mo 2, W 4; Tp′ = Tp^∗ [HB(dmpz)₃], M = Mo 3) are obtained from M(CCCSiMe₃)(O₂CCF₃)(CO)₂(tmeda) (1) and K[Tp′].Reactions of 2 or 4 with AuCl(PPh₃)/K₂CO₃ in MeOH afforded M{CCCAu(PPh₃)}(CO)₂Tp′ (M = Mo 5, W 6) containing C₃ chains linking the Group 6 metal and gold centres.In turn, the gold complexes react with Co₃(μ₃-CBr)(μ-dppm)(CO)₇ to give the C₄-bridged {Tp(OC)₂M}CCCC{Co₃(μ-dppm)(CO)₇} (M = Mo 7, W 8), while Mo(CBr)(CO)₂Tp^∗ and Co₃{μ₃-C(CC)₂Au(PPh₃)}(μ-dppm)(CO)₇ give {Tp^∗(OC)₂Mo}C(CC)₂C{Co₃(μ-dppm)(CO)₇} (9) via a phosphine-gold(I) halide elimination reaction. The C₃ complexes Tp′(OC)₂MCCCRu(dppe)Cp^∗ (Tp′ = Tp, M = Mo 10, W 11; Tp′ = Tp^∗, M = Mo 12) were obtained from 2-4 and RuCl(dppe)Cp^∗ via KF-induced metalla-desilylation reactions. Reactions between Mo(CBr)(CO)₂Tp^∗ and Ru{(CC)_nAu(PPh₃)}(dppe)Cp^∗ (n = 2, 3) afforded {Tp^∗(OC)₂Mo}C(CC)_n{Ru(dppe)Cp^∗} (n = 2 13, 3 14), containing C₅ and C₇ chains, respectively. Single-crystal X-ray structure determinations of 1, 2, 7, 8, 9 and 12 are reported.     

Luminescent rhenium(I)-gold(I) hetero organometallics linked by ethynylphenanthrolines

The first luminescent rhenium(I)-gold(I) hetero organometallics, Re{phenAu(PPh₃)}(CO)₃Cl (3) and Re{(PPh₃)AuphenAu(PPh₃)}(CO)₃Cl (4), have been prepared using the gold(I) complex AuCl(PPh₃) (PPh₃ = triphenylphosphine) and the novel rhenium(I) complexes Re(phenH)(CO)₃Cl (5) (phenH = 3-ethynyl-1,10-phenanthroline) or Re(HphenH)(CO)₃Cl (6) (HphenH = 3,8-bis(ethynyl)-1,10-phenanthroline). All the present rhenium(I) complexes 3-6 were revealed to possess a facial configuration (fac-isomer) with respect to the three carbonyl ligands. The main frameworks for these new gold(I) organometallics were constructed by the Au-C σ-bonding (with the η¹-type coordination) between the ethynylphenanthrolines and the Au(I) phosphine unit. Re(I)-Au(I) heterometallics 3 and 4 have shown single phosphorescence from the ³MLCT excited state and this observation can be interpreted in terms of the efficient intramolecular energy transfer from the Au(I) unit to the Re(I) unit.     

Synthesis, structures and some reactions of Ru(CCCCFc)(PP)Cp (PP = dppm, dppe) and related compounds

The compounds Ru(CCCCFc)(PP)Cp [PP = dppe (1), dppm (2)], have been obtained from reactions between RuCl(PP)Cp and FcCCCCSiMe₃ in the presence of KF (1) or HCCCCFc and K[PF₆] (2), both with added dbu. The dppe complex reacts with Co₂(CO)₆(L₂) [L₂ = (CO)₂, dppm] to give 3, 4 in which the Co₂(CO)₄(L₂) group is attached to the outer CC triple bond. The PPh₃ analogue of 3 (5) has also been characterised. In contrast, tetracyanoethene reacts to give two isomeric complexes 6 and 7, in which the cyano-olefin has added to either CC triple bond. The reaction of RuCl(dppe)Cp with HCCCCFc, carried out in a thf/NEt₃ mixture in the presence of Na[BPh₄], gave [Ru{CCC(NEt₃)CHFc}(dppe)Cp]BPh₄ (8), probably formed by addition of the amine to an (unobserved) intermediate butatrienylidene [Ru(CCCCHFc)(dppe)Cp]⁺. The reaction of I₂ with 8 proceeds via an unusual migration of the alkynyl group to the Cp ring to give [RuI(dppe){η-C₅H₄CCC(NEt₃)CHFc}]I₃ (9). Single-crystal X-ray structural determinations of 1, 2 and 4-9 are reported.     

Chemistry of tricarbonylrhenium(I) chelates of azopyrimidines, azoimidazoles and anion radicals thereof

The azopyrimidine and azoimidazole ligands (general abbreviations, RL) used in the present work are 2-(p-R-C₆H₄NN)C₄H₃N₂, RL_pm (R=H, Cl) and 2-(p-R-C₆H₄NN)-1-(Me)C₃H₂N₂, RL_im (R=Me, Cl), respectively. The reaction of Re(CO)₅Cl with a slight excess of RL in boiling benzene has furnished blue-violet complexes of type Re(CO)₃Cl(RL) which have been spectrally characterized. In Re(CO)₃Cl(HL_pm) and Re(CO)₃Cl(ClL_im) the Re-N^h, Re-N^a distances are 2.173(6), 2.136(6) Å and 2.150(5), 2.166(5) Å, respectively (N^h and N^a are heterocyclic and azo N atoms, respectively). Their N-N lengths (1.271(8), 1.281(7) Å) implicate relatively weak Re-azo(π^*) back-bonding. In the lattice of Re(CO)₃Cl(HL_pm), pair-wise C-H?O hydrogen bonding between symmetry related molecules is present (C?O; 3.264(9) Å, H?O; 2.460(10) Å; C-H?O; 130.6(5)°). The lattice of Re(CO)₃Cl(ClL_im) also consists of centrosymmetric dimers held by aromatic π-π stacking between parallely placed pendant aryl rings (centroid?centroid distance, 3.781(9) Å). Extended Hückel calculations reveal that the LUMO of Re(CO)₃Cl(RL) is ∼60% azo in character. One-electron quasireversible electrochemical reduction occurs near −0.1 and −0.4 V vs. SCE in the cases of Re(CO)₃Cl(RL_pm) and Re(CO)₃Cl(RL_im), respectively. The redox orbital is believed to be to the above noted LUMO. Electrogenerated Re(CO)₃Cl(RL⁻) underwent spontaneous solvolytic chloride displacement in MeCN furnishing Re(CO)₃(MeCN)(RL⁻) which has been isolated. The latter in turn reacted with imidazole and triphenyl phosphine furnishing Re(CO)₃(C₃H₄N₂)(RL⁻) and Re(CO)₃(PPh₃)(RL⁻), respectively. The pattern of carbonyl stretching frequencies of these radical anion complexes is similar to that of Re(CO)₃Cl(RL) but for shifts to lower frequencies by 10-40 cm⁻¹. All the three radical anion systems are one-electron paramagnets (1.7-1.8 μ_B). The unpaired electron is primarily localized in a predominantly azo-π^* orbital. A small metal contribution (^{185, 187}Re, I=5/2) is present and both Re(CO)₃(MeCN)(RL⁻) and Re(CO)₃(C₃H₄N₂)(RL⁻) display six-line EPR spectra (A∼28 G). The line shapes and intensities are characteristic of the presence of g-strain. In the case of Re(CO)₃(PPh₃)(RL⁻) seven nearly equispaced lines are observed due to virtually equal coupling with metal and ³¹P (I=1/2) nuclei. The g values of the radical species span the range 2.0033-2.0066.     

Synthesis and crystal structures of cyclodiazastannoxides fused cyclopentadienyl M-Sn (M = Mo, W) bonded organometallic heterocycle

The condensation reaction of CH₃COC₅H₄M(CO)₃SnCl₃ (M = Mo or W) with PyCONHNH₂ (Py = 2,3,4-pyridyl or 2-pyridylmethyl) in mild conditions yields cyclodiazastannoxides fused cyclopentadienyl M-Sn bonded organometallic heterocycle {μ-[C₅H₄(CH₃)CN-NC(O)PyH]M(CO)₃SnCl₃}. The similar reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with ArCONHNH₂ (Ar = 2-furanyl) gives complexes μ-[C₅H₄(CH₃)CN-NC(O)Ar]M(CO)₃SnCl₂(H₂O), in which the water molecule can be replaced by other N-donor ligands, such as pyridine or 4,4-bipyridine. Arene-bridged organometallic heterocyclic complexes μ-{[C₅H₄(CH₃)CN-NC(O)]₂C₆H₄}{M(CO)₃SnCl₂(Solvent)}₂ have also been prepared by the reaction of CH₃COC₅H₄M(CO)₃SnCl₃ with terephthaloyl hydrazine. In these new organometallic heterocyclic complexes, it seems that the tin atom prefers to be six-coordinate through absorbing the chloridion or solvent molecules.     

Spin density distribution in mononuclear Rh(0) complexes: A combined experimental and DFT study

The paramagnetic complex [Rh(trop₂dach)]2 was obtained by reduction of the almost planar 16-electron cationic precursor complex, [Rh(trop₂dach)]⁺1 and characterized by EPR spectroscopy [g₁₁ = 2.069, g₂₂ = 2.014, g₃₃ = 1.964, g_iso = 2.016; A(Rh) = (<40, 29, 30)]. The unobservable small nitrogen hyperfine coupling and DFT calculations show that most of the spin density is localized on the hydrocarbon ligand framework and only about 35% on the metal center. DFT calculations on various 17 electron rhodium complexes with carbonyl, olefine, or phosphane ligands like [Rh(CO)₄], [Rh(cod)₂], and [Rh(dppe)₂] reveal that in none of these the spin density at the metal center exceeds 45%. That is all formally Rh(0) complexes reported to date are better described as highly delocalized radicals and an assignment of the formal metal oxidation state is not meaningful.     

Synthesis and characterization of (CHCH)n-bridged (n = 1, 2, 3) heterobimetallic and trimetallic ferrocene-ruthenium complexes

A series of heterobinuclear ferrocene-ruthenium complexes Fc(CHCH)_nRuCl(CO)(PMe₃)₃ (n = 1, 3; n = 2, 12), Fc(CHCH)RuCl(CO)(Py)(PPh₃)₂ (4), and trimetallic Fc(CHCH)RuCl(CO)(PPh₃)₂(Py-E-(CHCH)Fc) (6) have been prepared. The length of the molecular rods is extended by successive insertion of CHCH spacers in the bridging ligands or the ancillary ligands. The respective products have been fully characterized and the structures of 3 and 12 have been established by X-ray crystallography. Electrochemical studies have revealed that ethenyl heterobimetallic complexes display two successive one-electron processes, and that intermetallic electronic communication between the two endgroups is attenuated with the increase of the length of the conjugated bridge. The electrochemical behavior of the trimetallic complex reveals strong electronic communication between ruthenium and ferrocene transmitted through the ethenyl bridge, however, it also reveals a very weak interaction between ruthenium and ferrocene transmitted through the (E)-CHCH-Py bridge.     

Solvent and phosphine dependency in the reaction of cis-RuCl2(P-P)2 (P-P = dppm or dppe) with terminal alkynes

Reaction of cis-[RuCl₂(dppm)₂] (dppm = 1,2-bis(diphenylphosphino)methane) with PhCCH and NaPF₆ utilising methanol as solvent results in the formation of the η³-butenynyl complex [Ru(η³-PhCCCCHPh)(dppm)₂][PF₆] in good yield. Similar reactions with Bu^tCCH and PrⁿCCH resulted in the corresponding alkyl-substituted complexes and all three of these compounds have been characterised by NMR spectroscopy and X-ray crystallography. The mechanism of this reaction has been probed by employing labelling experiments with both PhCCD and PhC¹³CH allowing the identity of possible intermediates in the reaction to be determined. Furthermore, [Ru(η³-PhCCCCHPh)(dppm)₂][PF₆] has been shown to be an effective regio- and stereo-selective catalyst for the dimerisation of PhCCH to Z-PhCCCHCHPh in the absence of solvent. In contrast, no evidence for the formation of alkyne coupling was obtained from the reaction of cis-[RuCl₂(dppe)₂] (dppe = 1,2-bis(diphenylphosphino)ethane) with PhCCH and NaPF₆.     

Syntheses, characterization and sensitized lanthanide luminescence of heteronuclear Pt-Ln (Ln = Eu, Nd, Yb) complexes with 2,2′-bipyridyl ethynyl ligands

Reaction of [Pt()Cl]⁺ ( = 4,4′,4′′-tri-tert-butyl-2,2′:6′,2′′-terpyridine) with 5-ethynyl-2,2′-bipyridine (HCCbpy) or 5,5′-bis(trimethylsilylethynyl)-2,2′-bipyridine (Me₃SiCCbpyCCSiMe₃) in the presence of cuprous iodide gives [Pt(^tBu₃tpy)(CCbpy)]⁺ (1) or [{Pt()}₂(CCbpyCC)]²⁺ (2) through Pt-acetylide σ-coordination, respectively. Incorporating 1 or 2 with Ln(hfac)₃(H₂O)₂ through 2,2′-bipyridyl chelating the Ln^III (Ln = Nd, Eu, and Yb) centers induces formation of a series of [Pt()(CCbpy){Ln(hfac)₃}]⁺ (PtLn) or [{Pt()}₂(CCbpyCC){Ln(hfac)₃}]²⁺ (Pt₂Ln) complexes, respectively. The structures of binuclear platinum(II) complex 2(PF₆)₂ and heterobinuclear PtNd complex 3(CF₃COO) were determined by single crystal X-ray diffraction. Both 1 and 2 exhibit typical low-energy absorption bands in near UV-Vis region, ascribed to dπ(Pt) → π^∗() MLCT and π(CCbpy/CCbpyCC) → π^∗() LLCT transitions. Upon formation of the PtLn or PtLn₂ complexes, the low-energy absorption bands are obviously blue-shifted (15-20 nm) compared with those in the Pt^II precursor 1 or 2. With excitation at 350 nm < λ < 550 nm which is the absorption region of MLCT and LLCT transitions, sensitized luminescence that is characteristic of the corresponding lanthanide(III) ions occurs in both PtLn and Pt₂Ln complexes. In contrast, Pt-based luminescence from the MLCT and LLCT states are mostly quenched in these Pt-Ln heteronuclear complexes, revealing that quite effective Pt → Ln energy transfer is operating from the Pt()(acetylide) chromophore to the lanthanide(III) centers.     

Reactivity of TpRu(L)(NCMe)R (L = CO, PMe3; R = Me, Ph) systems with isonitriles: Experimental and computational studies toward the intra- and intermolecular hydroarylation of isonitriles

The Ru(II) phenyl complex TpRu(PMe₃)(NCMe)Ph {Tp = hydridotris(pyrazolyl)borate} reacts with isonitriles to form complexes of the type TpRu(PMe₃)(CNR)Ph (R = ^tBu, CH₂Ph, CH₂CH₂Ph). Neither thermal nor photolytic reactions of these systems with excess isonitrile and benzene resulted in the production of corresponding imines. DFT studies that probed the energetics of the desired catalytic transformations revealed that (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph {Tab = tris(azo)borate} is the most stable species in a proposed catalytic cycle. Exclusive of calculated transition states, the highest points on the calculated free energy surface are 34 kcal/mol, for (Tab)Ru(PH₃)(o,η²-C,C-CNCH₂CH₂Ph)Ph {relative to the starting material (Tab)Ru(PH₃)(CNCH₂CH₂Ph)Ph}, and 27 kcal/mol for the C-H activation product (Tab)Ru(PH₃)(o-C₆H₄CH₂CH₂NC) and benzene. The substantial increases in free energy result primarily from the loss of the stable ruthenium-η¹-isonitrile interaction.     

Argon matrix effect on the geometry and infrared spectrum of H2CMH2 (M = Ti, Zr, Hf): A theoretical study

Within the framework of polarizable continuum model with integral equation formalism (IEF-PCM), an argon matrix effect on the geometry and infrared frequencies of the agostic H₂CMH₂ (M = Ti, Zr, Hf) methylidene complexes was investigated at B3LYP level of theory with the 6-311++G(3df,3pd) basis set for C, H, and Ti atoms and Stuttgart/Dresden ECPs MWB28 and MWB60 for the Zr and Hf atoms. At the B3LYP/IEF-PCM level of theory, H₂CTiH₂ was optimized to an energy minimum having a pyramidal structure. The calculated dipole moment of this structure is 3.06 D. The B3LYP/IEF-PCM simulations gave the three complexes’ agostic angle ∠HCM (°), distance r(H?M) (Å), and CM bond length r(CM) (Å) as follows: ∠HCTi = 87.4, r(H?Ti) = 2.079, r(CTi) = 1.803; ∠HCZr = 89.3, r(H?Zr) = 2.243, r(CZr) = 1.956; ∠HCHf = 94.7, r(H?Hf) = 2.343, r(CHf) = 1.972. As a comparison, the B3LYP simulations gave the values as follows: ∠HCTi = 91.5, r(H?Ti) = 2.150, r(CTi) = 1.811; ∠HCZr = 92.9, r(H?Zr) = 2.299, r(CZr) = 1.955; ∠HCHf = 95.6, r(H?Hf) = 2.352, r(CHf) = 1.967. As far as the MH₂ symmetric and asymmetric stretching and CH₂ wagging frequencies are concerned, the IEF-PCM calculated values are in better agreement with the experimental argon matrix ones than those calculated based on a gas phase model.     

Theoretical studies on the imine germylenoid HNGeNaF and its insertion reaction with R-H (R = F, OH, NH2, CH3)

The geometries and isomerization of the imine germylenoid HNGeNaF as well as its insertion reactions with R-H (R = F, OH, NH₂, CH₃) have been systematically investigated at the B3LYP/6-311+G^∗ level of theory. The potential barriers of the four insertion reactions are 117.2, 172.6, 219.7, and 322.3 kJ/mol, respectively. Here, all the mechanisms of the four reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted germylene (HNGeHR) and NaF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the four reactions are 185.0, 208.1, 224.4, and 266.9 kJ/mol, respectively, which are linearly correlated with the calculated barrier heights. Compared with the insertion reaction of HNGe: and R-H, the introduction of NaF makes the insertion reaction occur easily though it is more difficult to proceed than that of insertion reaction between H₂GeNaF and R-H. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the four insertion reactions should be as follows: H-F > H-OH > H-NH₂ > H-CH₃.     

Oxidation of polyethylene under irradiation at low temperature and low dose rate. Part II. Low temperature thermal oxidation

This paper deals with the kinetic modelling of unstabilised polyethylene thermal oxidation, particular attention being paid to the domain of low temperatures, typically below 80 °C. Experimental data show that the temperature dependence of the induction time t_i and the steady state rate of oxygen absorption r_S display a discontinuity at 80 °C. A model based on the hypothesis that this discontinuity concerns only the PO₂ bimolecular combination processes and is essentially explained by the competition between terminating and non-terminating PO₂ + PO₂ reactions, was proposed. With pertinent values of the Arrhenius parameters of the elementary reactions under consideration, the model fits well the experimental data (in the 40-200 °C temperature range) and is consistent with previously analysed results of radiochemical ageing. According to this model, 35-40% of the bimolecular PO₂ combinations would not be terminating at 45 °C and this proportion would increase with the temperature. Concerning terminations, the relative fraction of coupling processes, leading to peroxide bridges, would decrease relatively to the disproportionation processes when the temperature increases.     

NHC-Pd(II)-Im (NHC = N-heterocyclic carbene; Im = 1-methylimidazole) complexes as efficient catalysts for Suzuki-Miyaura coupling reactions of aryl chlorides

A new type of well-defined N-heterocyclic carbene (NHC)-palladium chloride-imidazole complexes derived from IPrHCl or IMesHCl, PdCl₂ and 1-methylimidazole exhibits high catalytic activity in the room-temperature Suzuki-Miyaura coupling reactions of aryl or heteroaryl chlorides. Moreover, the large-scale (20.0 mmol) couplings in the presence of 0.01 mol% catalyst loading can also give the corresponding coupling products in high yields.     

Tertiary phosphine abstraction from a platinum(II) coordination complex with SeCN: Crystal and molecular structures of SePTA and [SePTA-Me]I · CH3OH

Reacting [PtCl(PTA)₃]Cl(PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1^3,7]decane) with KSeCN in aqueous or MeOH medium results in the abstraction of the PTA ligands to yield SePTA. The reaction also proceeds quantitatively by direct reaction of PTA and KSeCN in water or methanol. The methylated PTA ligand, [PTA-Me]I (1-methyl-1-azonia-3,5-diaza-7-phosphatricyclo[3.3.1.1^3,7]decane iodide), reacts accordingly with KSeCN, albeit significantly slower. The crystal structure of SePTA, 1, and [SePTA-Me]I · CH₃OH, 2, revealed PSe bond distances of 2.0991(19) and 2.100(2) Å, respectively. The first order phosphorous selenium coupling constants, ¹J_P-Se (D₂O), of 722 and 788 Hz for SePTA and [SePTA-Me]I, respectively, indicates the latter is significantly less electron rich.     

Vibrational spectra and structural parameters of some XNCO and XOCN (X = H, F, Cl, Br) molecules

Ab initio calculations with full electron correlation by the perturbation method to second order and hybrid density functional theory calculations by the B3LYP method utilizing the 6-31G(d), 6-311+G(d, p), and 6-311+G(2d, 2p) basis sets have been carried out for the XNCO and XOCN (X = H, F, Cl, Br) molecules. From these calculations, force constants, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios, and structural parameters have been determined and compared to the experimental quantities when available. By combining previously reported rotational constants for HNCO, ClNCO and BrNCO with the ab initio MP2/6-311+G(d, p) predicted structural values, adjusted r₀ parameters have been obtained. The r₀ values for BrNCO are: r(BrN) = 1.857(5); r(NC) = 1.228(5); r(CO) = 1.161(5) Å; BrNC = 117.5(5) and NCO = 172.3(5)°. For ClNCO the determined r₀ parameters are in excellent agreement with the previously determine r_s values, whereas those for HNCO the HNC angle is larger with a value of 126.3(5)° compared to the previous reported value of 123.9(17)°. However, considering the relatively large uncertainty in the value given initially the two results are in near agreement. Structural parameters are also estimated for FNCO and XOCN (X = H, F, Cl, Br). The centrifugal distortion constants have been calculated and are compared to the experimentally (XNCO: X = H, Cl, Br) determined values. Predicted values for the barriers of linearity are given for both the XNCO (X = H, F, Cl, Br) molecules and the results were compared to the corresponding isothiocyanate molecules. The predicted frequencies for the fundamentals of the XNCO molecules compare favorably to the experimental values but some of the predicted intensities differ significantly from those in the observed spectra. The two OCN bends for HOCN have been assigned and the frequencies for the two corresponding fundamentals of DOCN are predicted.     

Molecular complexes of octafluoronaphthalene with catenated chalcogen-nitrogen compounds C6H5-X-NSN-SiMe3 (X = S, Se)

Mismatched molecular 1:1 complexes of C₁₀F₈ with catenated chalcogen-nitrogen compounds C₆H₅-X-NSN-SiMe₃ (X = S, Se) were prepared and characterized by X-ray crystallography. The complexes provide examples of structurally non-rigid polyheteroatom molecules involved in non-covalent arene-polyfluoroarene π-stacking interactions. In going from homocrystals to the co-crystals, the molecular Z, E configuration of the catenated compounds changes from noticeably non-planar to perfectly planar, i.e. C₁₀F₈ acts as “molecular iron”. On the other hand, C₁₀H₈ does not produce complexes with C₆F₅-X-NSN-SiMe₃ (X = S, Se).     

Evaluation of chemiluminescence reagents for selective detection of reactive oxygen species

In order to evaluate the chemiluminescence (CL) reagents for selective detection of reactive oxygen species (ROS), we comprehensively measured the CL responses of 20 CL reagents (three luminol derivatives, two imidazopyrazinone derivatives, eight lophine derivatives, six acridinium ester derivatives and lucigenin) against six types of ROS (superoxide anion: O₂⁻, hydroxyl radical: OH, hydrogen peroxide: H₂O₂, hypochlorite anion: ClO⁻, singlet oxygen: ¹O₂, and nitric oxide: NO). As a result of the screening, it was found that nine CL reagents selectively detected O₂⁻ while one CL reagent selectively detected OH. However, no CL reagent had selectivity on the detection of H₂O₂, ClO⁻, ¹O₂ and NO. Our screening results could help to select the most suitable CL reagent for selective determination of different ROS.As an application study, 4-methoxyphenyl-10-methylacridinium-9-carboxylate (MMAC), one of the acridinium ester derivatives, showed high selectivity on the detection of O₂⁻, and thus was applied to the assay of superoxide dismutase (SOD) activity. The dynamic range and detection limit of the developed CL assay were 0.1-10 and 0.06 U mL⁻¹, respectively. Significant correlation (r = 0.997) was observed between the results by the CL assay using MMAC and the spectrophotometric assay using 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt.