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Triboluminescence and high-pressure luminescence are stress-induced phenomena with potential in stress sensing. However, the understanding of the former process and the correlation between the two processes are lacking. In this contribution, we study the influence of the crystal packing and high pressure compression on triboluminescence by using a new family of halogen-containing EuIII diketonate complexes. The size and position of halogens determine the crystal symmetry and packing due to the change in intermolecular interactions. The role of pressure is examined by a diamond anvil cell (DAC), in which the material compression induces phase transition, peak shifting and broadening in the luminescence spectrum of the complex. The experimental results show the triboluminescence of our EuIII complexes occurs at low pressure and is a fracture-induced (mechano stress) process. This work contributes to the understanding of triboluminescence and for the first time explores the possibility of applying lanthanide complexes as stress sensors.

A study of the oxidation of nitrite in aqueous solution and in H2O/CH3CN is conducted by a cationic trans-dioxoruthenium(VI) complex, trans-[[[Ru.sup.VI](L)(O)2].sup.2} (L= 1,12-dimethyl-3,4,9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane). The coordinated macrocyclic ligand L is resistant to oxidative degradation and ligand exchange.

The oxidation of alkanes by various peroxides is efficiently catalyzed by [[[Os.sup.VI](N)[Cl.sub.4]].sup.-]/Lewis acid in C[H.sub.2][Cl.sub.2]/C[H.sub.3]C[O.sub.2]H to give alcohols and ketones. The new mechanism has involved initial O-atom transfer from ROOH to [[[Os.sup.VI](N)[Cl.sub.4]].sup.-]/Lewis acid to generate [[[Os.sup.VIII](N)(O)[Cl.sub.4]].sup.-]/Lewis acid, which has oxidized alkanes via H-atom abstraction.

A study was conducted to examine the kinetics and mechanisms of the oxidation iodide and bromide anion by trans-[[[Ru.sup.VI]([N.sub.2][O.sub.2])[(O).sub.2]].sup.2+] in aqueous solutions. The mechanism was observed to involve initial oxygen atom transfer from trans-[[[Ru.sup.VI]([N.sub.2][O.sub.2])[(O).sub.2]].sup.2+] to bromide to give trans-[[[Ru.sup.IV]([N.sub.2][O.sub.2])(O)(OBr)].sup.+] followed by parallel aquation and oxidation of bromide and both reactions are acid-catalyzed.

The article presents a new approach, which utilizes the N...N coupling of different (salen)ruthenium(VI) nitrides for the general synthesis of the (salen)ruthenium(III) complexes. These ruthenium salen complexes are shown to be widely used as the catalysts in different organic transformations.

The kinetics of the oxidation of trans-[[[Ru.sup.IV](tmc)(O)(solv)].sup.2+] to trans-[[[Ru.sup.VI](tmc)[(O).sub.2]].sup.2+] (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, a tetradentate macrocyclic tertiary amine ligand, solv = [H.sub.2]O or C[H.sub.3]CN) by Mn[O.sub.4.sup.-] is analyzed in aqueous solutions and in acetonitrile. Large deuterium and oxygen isotope effects are seen for reactions in water.

The synthesis and reactivities of a highly electrophillic, cationic ruthenium(VI) nitrido complex containing the cyclohexylene-bridged salen ligand, N,N'-bis(salicylidene) omicron-cyclohexyldiamine dianion is reported. The result indicates that the steric and electronic tunabality of slaen would be utilized to probe the mechanism of the aziridination reaction and reduction of Ru(sub IV) (AZ(-H) to RuIII(AZ).

The synthesis and reactivities of a series of highly electrophilic, cationic ruthenium-(VI) nitrido species containing the cyclohexyl-bridged salen ligand and its derivatives is reported. It is anticipated that the corresponding ruthenium(VI) nitrido complexes would be electrophilic, as high-valent ruthenium oxo complexes are in general much stronger oxidants than that of osmium.

The research shows that the nucleophilic addition to salophen and salen coordinated to a high-valent metal center could be very facile. The reason for the low turnovers of most (salen)-mangnese epoxidation catalysts could be due to attack at the (salen) manganese (V) oxo intermediates by nucleophiles in the reaction mixture, hence suitable modifications of the salen ligand to inhibit attack at the imine carbons could increase the lifetime of the epoxidation catalysts.

Proton-coupled electron-transfer reactions of phenols have received considerable attention because of their fundamental interest and their relevance to many biological processes. Here we describe a remarkable four-electron oxidation of phenols by a (salen)ruthenium(VI) complex in the presence of pyridine in CH3OH to afford (salen)ruthenium(II) p-benzoquinone imine complexes. Mechanistic studies indicate that this reaction occurs in two phases. The first phase is proposed to be a two-electron transfer process that involves electrophilic attack by Ru≡N at the phenol aromatic ring, followed by proton shift to generate a Ru(IV) p-hydroxyanilido intermediate. In the second phase the intermediate undergoes intramolecular two-electron transfer, followed by rapid deprotonation to give the Ru(II) p-benzoquinone imine product. [ABSTRACT FROM AUTHOR]

The oxidation of ascorbic acid (H2A) by [RuVI(N)(L)(MeOH)]+ in aqueous acidic solutions has the following stoichiometry: 2[RuVI(N)] + 3H2A → 2[RuIII(NH2-HA)]+ + A. Mechanisms involving HAT/N-rebound at low pH (≤2) and nucleophilic attack at the nitride at high pH (≥5) are proposed. [ABSTRACT FROM AUTHOR]

We report experimental and computational studies of the facile oxidative C-N bond cleavage of anilines by a (salen)ruthenium(VI) nitrido complex. We provide evidence that the initial step involves nucleophilic attack of aniline at the nitrido ligand of the ruthenium complex, which is followed by proton and electron transfer to afford a (salen)ruthenium(II) diazonium intermediate. This intermediate then undergoes unimolecular decomposition to generate benzene and N2. [ABSTRACT FROM AUTHOR]

The preparation of a number of binuclear (salen)osmium phosphinidine and phosphiniminato complexes using various strategies are described. Treatment of [OsVI(N)(L1)(sol)](X) (sol = H2O or MeOH) with PPh3affords an osmium(iv) phosphinidine complex [OsIV{N(H)PPh3}(L1)(OMe)](X) (X = PF61a, ClO41b). If the reaction is carried out in CH2Cl2in the presence of excess pyrazine the osmium(iii) phosphinidine species [OsIII{N(H)PPh3}(L1)(pz)](PF6) 2can be generated. On the other hand, if the reaction is carried out in CH2Cl2in the presence of a small amount of H2O, a μ-oxo osmium(iv) phosphinidine complex is obtained, [(L1){PPh3N(H)}OsIV–O–OsIV{N(H)PPh3}(L1)](PF6)23. Furthermore, if the reaction of [OsVI(N)(L1)(OH2)]PF6with PPh3is done in the presence of 2, the μ-pyrazine species, [(L1){PPh3N(H)}OsIII–pz–OsIII{N(H)PPh3}(L1)](PF6)24can be isolated. Novel binuclear osmium(iv) complexes can be prepared by the use of a diphosphine ligand to attack two OsVIN. Reaction of [OsVI(N)(L1)(OH2)](PF6) with PPh2–CC–PPh2or PPh2–(CH2)3–PPh2in MeOH affords the binuclear complexes [(MeO)(L1)OsIV{N(H)PPh2–R–PPh2N(H)}OsIV(L1)(OMe)](PF6)2(R = CC 5, (CH2)36). Reaction of [OsVI(N)(L2)Cl] with PPh2FcPPh2generates a novel trimetallic complex, [Cl(L2)OsIV{NPPh2–Fc–PPh2N}OsIV(L2)Cl] 7. The structures of 1b, 2, 3, 4, 5and 7have been determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Treatment of [NnBu4][OsVI(N)Cl4] with a stoichiometric amount of H2L (L = N,N′-bis(salicylidene)-o-cyclohexylenediamine dianion) in the presence of PF6−or ClO4−in MeOH affords [OsVI(N)(L)(OH2)](PF6) 1aand [OsVI(N)(L)(CH3OH)](ClO4) 1b, respectively. The structure of 1bhas been determined by X-ray crystallography and the OsN bond distance is 1.627(3) Å. In the presence of a N-donor heterocyclic ligand in CH3CN, 1areacts at room temperature to afford the mixed-valence μ-N2(salen)osmium species [(X)(L)OsIII–NN–OsII(L)(X)](PF6), 2–14(X = py 2; 4-Mepy 3; 4-tBupy 4; pz 5; 3-Mepz 6; 3,5-Me2pz 7; Im 8; 1-MeIm 9; 2-MeIm 10; 4-MeIm 11; 1,2-Me2Im 12; 2-Meozl 13; 4-MeTz 14). These complexes are formed by ligand-induced NN coupling of two [OsVIN]+to give initially [OsIII–N2–OsIII]2+, which is then reduced to give the more stable mixed-valence species [OsIII–N2–OsII]+. Cyclic voltammograms (CVs) of 2–14show two reversible couples, attributed to OsIII,III/OsIII,IIand OsIII,II/OsII,II. The large comproportionation constants (Kcom) of (5.36–82.3) × 1013indicate charge delocalization in these complexes. The structures of 3and 14have been determined by X-ray crystallography, the salen ligands are in uncommon cis-β configuration. Oxidations of 4and 14by [Cp2Fe](PF6) afford the symmetrical species [(X)(L)OsIII–NN–OsIII(L)(X)](PF6)2(X = 4-tBupy 15; 4-MeTz 16). These are the first stable μ-N2diosmium(iii,iii) complexes that have been characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The oxidation of alkanes by various peroxides (tBuOOH, H2O2, PhCH2C(CH3)2OOH) is efficiently catalyzed by [OsVI(N)Cl4]-/Lewis acid (FeCI3 or Sc(OTf)3) in CH2CI2/CH3CO2H to give alcohols and ketones. Oxidations occur rapidly at ambient conditions, and excellent yields and turnover numbers of over 7500 and 1000 can be achieved in the oxidation of cyclohexane with tBUOOH and H2O2, respectively. In particular, this catalytic system can utilize PhCH2C(CH3)2OOH (MPPH) efficiently as the terminal oxidant; good yields of cyclohexanol and cyclohexanone (>70%) and MPPOH (>90%) are obtained in the oxidation of cyclohexane. This suggests that the mechanism does not involve alkoxy radicals derived from homolytic cleavage of MPPH but is consistent with heterolytic cleavage of MPPH to produce a metal-based active intermediate. The following evidence also shows that no free alkyl radicals are produced in the catalytic oxidation of alkanes: (1) The product yields and distributions are only slightly affected by the presence of O2. (2) Addition of BrCCI3 does not affect the yields of cyclohexanol and cyclohexanone in the oxidation of cyclohexane. (3) A complete retention of stereochemistry occurs in the hydroxylation of cis- and trans-1,2-dimethylcyclohexane. The proposed mechanism involves initial O-atom transfer from ROOH to [OsVI(N)Cl4]-/Lewis acid to generate [OsVIII(N)(O)Cl4]-/Lewis acid, which then oxidizes alkanes via H-atom abstraction. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidation of trans-[RuIV(tmc)(O)(soIv)]2+ to trans-[RuVI(tmc)(O)2]2+ (tmc is 1,4,8,-11-tetramethyl-1,4,8,11 -tetraazacyclotetradecane, a tetradentate macrocyclic tertiary amine ligand; solv = H2O or CH3CN) by MnO4- have been studied in aqueous solutions and in acetonitrile. In aqueous solutions the rate law is -d[MnO4]/dt= kH2O[RuIV][MnO4-] = (kx + (Ky)/(Ka)[H+])[RuIV][MnO4-], kx = (1.49 ± 0.09) × 101 M-1s-1 and ky = (5.72 ± 0.29) × 104 M-1 s-1 at 298.0 K and I = 0.1 M. The terms kx and ky are proposed to be the rate constants for the oxidation of RUIV by MnO4 and HMnO4, respectively, and Ka is the acid dissociation constant of HMnO4. At [H+] = I = 0.1 M, ΔH‡ and ΔS‡ are (9.6 ± 0.6) kcal mol-1 and -(18 ± 2) cal mol-1 K-1, respectively. The reaction is much slower in D2O, and the deuterium isotope effects are kx/kxD = 3.5 ± 0.1 and ky/kyD = 5.0 ± 0.3. The reaction is also noticeably slower in H218O, and the oxygen isotope effect is kH216o/kH218o = 1.30 ± 0.07. 18O-labeled studies indicate that the oxygen atom gained by RuIV comes from water and not from KMnO4. These results are consistent with a mechanism that involves initial rate-limiting hydrogen-atom abstraction by MnO4- from coordinated water on RuIV. In acetonitrile the rate law is -d[MnO4-]/dt= kCH3CN[RuIV][MnO4-], kCH3CN = 1.95 ± 0.08 M-1 s-1 at 298.0 K and I = 0.1 M. ΔH‡ and ΔS‡ are (12.0 ± 0.3) kcal mol-1 and -(17 ± 1) cal mol-1 K-1, respectively. 18O- labeled studies show that in this case the oxygen atom gained by RuIV comes from MnO4-1, consistent with an oxygen-atom transfer mechanism. [ABSTRACT FROM AUTHOR]

MnO4−is activated by BF3to undergo intramolecular coupling of two oxo ligands to generate O2. DFT calculations suggest that there should be a spin intercrossing between the singlet and triplet potential energy surfaces on going from the active intermediate [MnO2(OBF3)2]−to the OO coupling transition state. [ABSTRACT FROM AUTHOR]