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As SO2 removal via traditional aqueous amine scrubbing requires large amounts of energy for absorbent regeneration, phase-change absorption was considered to be a promising alternative, as regenera...

Photophysical properties of 2,6-dicyano-N,N,N ′,N ′-tetramethyl-p-phenylenediamine (DCTMPPD) are reported. Fluorescence quantum yields range from 0.37 to 0.58 and fluorescence lifetimes from 12.2 to 22.9 ns in 28 different solvents. The triplet energy is determined to be 16.8 kK. Steady-state and time-resolved emission anisotropies in glycerol are given. Three correlation times with τ 1 0.8 ns τ 2 = 20 ns and τ 3 > 80 ns are found. The fluorescence solvatochromism is analyzed using empirical one- and multiparameter approaches as well as classical non-empirical continuum models. The excited state dipole moment is estimated to be between 10 and 12 D, depending on the model applied. The ground state p K a is determined to be 2.5, while for the excited state p K a ∗ a range of 0.5–2 can be estimated.

Reaction of 2,4,6-tricyano-s-triazine (TCT) with tetrathiafulvalene (TTF) and N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) leads to 1∶1 charge transfer complexes. The crystal structures of the TTF[TCT], as well as the decomposition product due to hydrolysis of the [TMPD][TCT], i.e. [HTMPD]+[2,4-dicyano-6-oxy-s-triazine]−, are reported and spectroscopically characterized.

Appreciable 14N/15N equilibrium isotope effect has been observed for the electron-transfer process between N,N,N‘,N‘-tetramethyl-p-phenylenediamine (TMPD) and its radical cation perchlorate (TMPD+•...

Two similar anionic dyes, resazurin and resorufin, were used for persistent spectral hole burning (PSHB) experiments at 20 K in polymer matrixes in the presence and absence of N,N,N‘,N‘-tetramethyl...

Using EPR, we have observed the initiating effect of oxygen on generation of active radicals in the donor-acceptor pair benzoin ether - N,N′-tetramethyl-p-phenylenediamine under photostimulation.

The rate constants of the oxidation of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPPD) are measured in water by means of stopped-flow techniques using different inorganic ions, like Fe(CN)63−, MnO4−, Co(NH3)63+, Ru(OH)3+6. The rates do not depend on the different oxidation potentials, but can be correlated well with calculated rate constants from the Marcus cross-relation. The electron self-exchange rates of the inorganic oxidants range over nine orders of magnitude. Measurements were performed at T = 293 K within a pH-range of 7–9.

Tetramethyl-p-phenylenediamine reactant: 54 g. (0.5 mole) of powdered p-phenylenediamine reactant: 320 ml. (3.4 mole) of dimethyl sulfate reactant: 100 ml. of ethanolamine product: Tetramethyl-p-phenylenediamine Keywords: alkylation, N-alkylation; cleavage, dealkylation; dimethyl sulfate, poison; tetramethyl-p-phenylenediamine, skin irritant; distillation, apparatus, for rapid steam distillation

Cytochrome c is the specific and efficient electron transfer mediator between the two last redox complexes of the mitochondrial respiratory chain. Its interaction with both partner proteins, namely cytochrome c1 (of complex III) and the hydrophilic CuA domain (of subunit II of oxidase), is transient, and known to be guided mainly by electrostatic interactions, with a set of acidic residues on the presumed docking site on the CuA domain surface and a complementary region of opposite charges exposed on cytochrome c. Information from recent structure determinations of oxidases from both mitochondria and bacteria, site-directed mutagenesis approaches, kinetic data obtained from the analysis of isolated soluble modules of interacting redox partners, and computational approaches have yielded new insights into the docking and electron transfer mechanisms. Here, we summarize and discuss recent results obtained from bacterial cytochrome c oxidases from both Paracoccus denitrificans, in which the primary electrostatic encounter most closely matches the mitochondrial situation, and the Thermus thermophilus ba3 oxidase in which docking and electron transfer is predominantly based on hydrophobic interactions.

The complex of fullerene C60 withN,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) was synthesized and studied by X-ray analysis.

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Absolute rate constants ( k ) for reduction of substituted methylperoxyl radicals by ascorbate ions and by TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) in aqueous solutions have been determined by pulse radiolysis. The rate constants vary from lo6 to lo9 M-I s-l, increasing as the electron-withdrawing capacity of the substituent on the peroxyl group increases. Linear correlations are observed between log k and the Taft substituent constants u* for a wide variety of substituents, but not all substituents fit the same line. In the case of ascorbate as reductant, the points for peroxyl radicals that contain halogens on the a-carbon lie on a different line ( p * = 0.41) than that for the other substituents ( p * = 1.25). In the case of TMPD there are also two families of peroxyl radicals: those comprising the electron-donating groups Me through t-Bu ( p * = 5.6) and those containing electron-withdrawing substituents ( p * = 0.64).

The Co(II) and triplet exciton ESR spectra of Co(II)-doped [TMPD+]2[Ni(mnt)2] and [TMPD+]2[Pt(mnt)2] were observed at different temperatures. The triplet exciton signals of the solid solutions yielded practically the same ESR parameters as those of the pure Ni(II) and Pt(II) complexes. The Co(II) spectra showed a wellresolved hyperfine structure, each component line of which became broad with increasing temperature. This can be interpreted in terms of exciton transfer from TMPD+ lattices to the metal ions.

The dependence of the line position in the 1H n.m.r. spectra of dilute solutions of the electron acceptor (A) 1, 3, 5-trinitrobenzene on the concentration of excess of the electron donor (D) hexamethylbenzene in various paraffinic solvents has been interpreted in terms of equilibria involving the complex species DA and D2A. The equilibrium quotients have been evaluated on several concentration scales.The same interpretation provides a satisfactory explanation for similar observations involving the interaction of NNN′N′-tetramethyl-p-phenylenediamine with 1, 3, 5-trinitrobenzene. The results are in accord with those obtained from optical measurements.Activity coefficient effects in themselves appear to be too small to provide an alternative explanation of the observed behaviour.

ESR experiments were carried out in the temperature range 80–300 K on the crystalline powders of [TMPD + ] 2 [Cu x Ni 1− x (mnt) 2 ] with various copper concentrations below x = 0.06. At low temperatures, all the solid solutions prepared yielded an ESR spectrum consisting either of a fine structure arising from TMPD + dimers or of a hyperfine structure due to copper. The ESR spectra of the solid solution x = 0.02 exhibited both the fine and hyperfine structures between 150 and 200 K. The spin-Hamiltonian parameters were determined as | D | = 21.6 mT and | E | = 2.7 mT for TMPD + dimers and as g | = 2.082, g ⊥ = 2.022, | A | ( 63 Cu)|=17.0 mT, and | A ⊥ ( 63 Cu)| = 4.2 mT for Cu(II) ions. These values were independent of copper concentration. The interaction energy 2 J within TMPD + dimers was evaluated to be equal to −0.22 eV from the temperature dependence of the signal intensity. The interdimer-interaction energy J ′ and the copper-TMPD + interaction energy J ″ were estimated as | J ′ | ≌ 0.06 | J | and | J ″ | ≌ 0.01| J | on the basis of line broadening of component signals.

Magnetic field effects on the photoionization yield of N,N,N′,N′-tetramethyl- p -phenylenediamine in deaerated 2-propanol have been studied by transient photoconductivity measurements. The photocurrent increases by about 15% in the presence of a magnetic field (720 mT). The results are interpreted in terms of a radical pair model.

The crystal of N,N,N′,N′-tetremethyl- p -phenylenediamine (TMPD) was found to exhibit delayed fluorescence when excited with light having photon energy greater than 3.55 eV. This delayed fluorescence is likely to be associated with the recombination of photo-generated charge carriers in TMPD crystal.

Time-resolved resonance Raman spectra of the lowest state of N,N,N′,N′-tetramethyl- p -phenylenediamine ( 3 TMPD) were observed in solution at room temperature. A new Raman band observed at 1530 cm −1 was assigned to 3 TMPD.

Resonance Raman spectra have been observed for the dimers of p -phenylenediamine cation (PPD + ) and of 2,3,5,6-tetramethyl- p -phenylenediamine cation (TMPD + ). When the exciting light frequency approached the absorption bands characteristic of the dimers, new polarized Raman lines appeared at 161 cm −1 for (PPD + ) 2 and at 117 cm −1 for (TMPD + ) 2 with a striking resonance enhancement. The resonant behaviour as well as the frequency values indicate that they are reasonably assigned to the interradical stretching vibrations of the parallel D 2h dimer molecules.

The ionization threshold IF of N,N,N’,N’‐tetramethyl‐p‐phenylenediamine in ethane, has been measured in the density (ρ) range 0.15–13.30 M/l and over the temperature (T) range 295–413 K, using a multiphoton ionization conductivity technique. The IF was found to be a function of both ρ and T in the ranges studied. At a fixed T (=373 K), IF was found first to decrease with increasing ρ and then to level off at densities of ∼10 M/l. For ρ≥11 M/l and T=295 K, the IF was found to increase with increasing density. At constant density (ρ=5.90 M/l ) IF decreased with increasing T between 323 and 413 K. These results are analyzed and discussed in relation to the effect of ρ and T on the electron conduction band energy V0 and the medium polarization energy P+. The changes in the IF with ρ are attributed to the dependence of V0 and P+ on ρ, while the dependence of IF on T is attributed to the effects of T on V0 rather than on P+.

SCMO calculations in the PPP approximation were carried out on the tetramethyl‐p‐phenylenediamine (TMPD) system. Comparison with experiment was made for TMPD, TMPD+, and TMPD++. In general good agreement for one set of parameters was obtained.

1. Those 2-hydroxy-3-alkyl-1,4-naphthoquinones which are saturated at the β bond in the alkyl group inhibit coupled oxidation of N,N,N′,N′- tetramethyl -p- phenylenediamine (TMPD) in the same range of concentration at which they inhibit succinate oxidation. 2. All quinones examined act as uncouplers in that they stimulate mitochondrial ATPase, while those which are saturated at the β bond inhibit succinate and coupled TMPD oxidation at concentrations below those at which uncoupling effects commence. 3. Inhibition of succinate oxidation and of coupled TMPD oxidation appear to reflect a single interaction with the respiratory chain, and this interaction, probably occurring between cytochromes b and c , should be included in any consideration of phosphorylation sites spanned by the oxidation of TMPD.

The respiratory chain inhibitor, antimycin, stimulates ion transport in rat liver mitochondria when energy is provided by the oxidation of tetramethyl-p-phenylenediamine.

The stability constants of complexes of each of the ten dinitronaphthalenes with N,N,N′,Nt-tetramethyl- p -phenylenediamine in cyclohexane have been measured by a spectroscopic method. The relative stabilities can be satisfactorily explained by assuming that nitro groups in β-positions have higher electronegativities than those in α-positions.