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N,N,N-Tris[p-(N-oxyl-tert-butylamino)phenyl]amine (N) was obtained as dark violet plates by lithiation of tris(4-bromophenyl)amine, followed by reaction with 2-methyl-2-nitrosopropane and oxidation of the resulting tris(hydroxyamine) with Ag 2 O. An X-ray crystal and molecular structure analysis of the monoclinic single crystal with space group Cc showed that it has neither C 3 symmetry nor zwitterionic quinonoid structure. An EPR spectrum in MTHF solution at room temperature consisted of seven lines (a N ) 4.06 G (3N) at g ) 2.0058). The temperature dependence of the magnetic susceptibility data on N in the range 2-300 K was analyzed in terms of a triangular coupling model for three S ) 1/2 spins to give a set of best-fit parameters which placed a doublet state as the ground state with a quartet state lying 559 K () 1.11 kcal mol -1 ) above it. B3LYP/6-31G*//B3LYP/6-31G computations were performed on both spin states of a model molecule (N′) in which all three N-tert-butyl groups in N were replaced with N-methyl groups. The doublet state was found to be more stable than the quartet state by 0.84 kcal mol -1 . Tris[p-(N-oxyl-tert-butylamino)phenyl]methyl (C) gave a monoclinic single crystal with space group Cc (no. 9) and has been shown to have a benzoquinoneimine N-oxide type diradical structure. Temperature dependence of its magnetic susceptibility showed that C has a triplet ground state with a singlet state lying 410 K above the triplet. Reactions of the corresponding organolithium compounds with BF 3 ‚OEt 2 were not applicable to give tris[4-(N-oxyl-tert-butylamino)phenyl]borane (B) but its 2,2′,2′′,6,6′,6′′-hexamethyl derivative (B′). In the trigonal crystal with space group R 3 h (no. 148), the three benzene rings are tilted by 49.2°with respect to the valence plane of the boron atom. The magnetic susceptibility data on B′ were consistent with a doublet ground state with an energy gap to a quartet state by 9.9 K () 0.0197 kcal mol -1 ). All the results together with ab initio MO studies are consistent with a picture that the ground spin states of title compounds N, C, and B are doublet, triplet, and doublet, respectively. The electronic structures are explained qualitatively by p-(N-oxyl-tert-butylamino)phenyl homologues of (•H 2 C) 3 X in which X ) N, C‚, and B atoms, and two, one, and no π-electrons are contained, respectively.

The photoassisted catalytic degradation of chloroethylene was studied in a tubular photoreactor packed with TiO 2 pellets prepared by a sol-gel method. The experiments were performed in a noncirculating mode. Kinetic data and the reaction products were compared with those for the photodegradation of ethylene, trichloroethylene, and tetrachloroethylene. The theoretical calculations at the MP4/6-31G**//B3LYP/6-31G** level indicated that the addition of OH radicals to chlorinated ethylenes is more exothermic than that of Cl radicals by 14.6-29.5 kcal mol -1 . Examination of Cl mass balance indicated that the concentration of Clcollected from the TiO 2 surface was higher than that from the product gas stream. When the photodegradation of ethylene was performed on the TiO 2 pellets which had been used for that of TCE or which were pretreated with HCl, the formation of chloroacetaldehyde was confirmed by the GC/MS. We proposed that during the photodegradation of the chlorinated ethylenes, the Cl -, as one of the reaction products, accumulated and was oxidized to Cl radical on the TiO 2 surface, which might be due to the oxidation by OH radical. Then, the Cl radical reacted with chlorinated ethylenes, leading to the formation of undesirable chlorinated byproducts.

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The S(N)i mechanism, which was previously proposed for the isomerization of 1-acylaziridines to the oxazolines, was reexamined theoretically by performing molecular orbital (MO) calculations of 1-formylaziridine and its derivatives as model compounds and experimentally by using 1(R)-[alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl]-2(S)-methylaziridine (5). At the MP2/6-31G//RHF/6-31G level, the activation energy was estimated to be 38.9 kcal mol(-1) for the S(N)i mechanism in which N-protonated 1-formylaziridine 8a(NH(+)) isomerizes to the N-protonated oxazoline 9a(NH(+)). Intrinsic reaction coordinate calculations showed that this reaction proceeds with retention of the ring carbon configuration. Methyl substitution in the aziridine ring reduces the activation energy by 10 kcal mol(-1). The ring closure of N-(2-chloroethyl)formamide (10a) to the oxazoline, which is a model reaction of the rate-determining step for the addition-elimination mechanism, was estimated to have an activation energy of 45.4 kcal mol(-1). The results of these MO calculations are consistent with the observation that the isomerization of the acylaziridine 5 to the oxazoline 6 is facilitated in the presence of weak nucleophiles such as with BF(3).OEt(2) while the formation of 6 is very slow in the presence of stronger nucleophiles such as p-toluenesulfonate. Both theoretical and experimental results suggest that the S(N)i mechanism explains well the isomerization of (R,S)-5 to the oxazoline with BF(3).OEt(2) in refluxing benzene.

The effects of axial ligands on the ground-state geometries, electronic structures and the characteristic optical properties of iron phthalocyanine and its derivatives, FePc and FePcL(n) (L = pyridine (Py) and cyanide (CN(-)); n = 1, 2), were investigated using the density functional theory (DFT) method. The geometries of FePc with a triplet spin state and of FePc(Py), FePc(Py)(2), FePc(CN(-)) and FePc(CN(-))(2) with singlet spin states were optimized under D(4h), C(2v), D(2h), C(4v), and D(4h) molecular symmetries, respectively. The highest occupied molecular orbitals (HOMOs) of FePc, FePc(Py), FePc(Py)(2), and FePc(CN(-)) are pi-type orbitals, which have no contribution from the p(z) atomic orbitals of all nitrogen atoms, whereas the HOMO of FePc(CN(-))(2) is the 7e(g) orbital, which has contributions from the d(xz) and the d(yz) orbitals of the Fe atom mixing with the pi-orbitals of the axial CN(-) ligands. The time-dependent (TD) DFT method gives many optically allowed excitations for FePc, FePc(Py), FePc(Py)(2), FePc(CN(-)), and FePc(CN(-))(2) in the UV-VIS region. Our calculated bands corresponded well with the experimental results. In FePc(Py)(2), the metal-ligand charge transfer (MLCT) transitions from the metal d to the axial-ligand pi*-type orbitals contributed to the B band region. In FePc(CN(-))(2), the MLCT transitions from the metal d to the Pc-ring pi*-type orbitals contributed mainly to the first B band region, but those from the metal d to the axial-ligand pi*-type orbitals did not appear in the energy regions of the Q and B bands. Thus, the axial ligands caused a spectral change in FePc through orbital mixing.