Diamagnetic characteristics

Ozone, O3, is the triatomic allotrope of oxygen. It is an unstable, blue diamagnetic gas with a characteristic pungent odour indeed, it was first detected by means of its smell, as reflected by its name (Greek o eiv, ozein, to smell) coined by C. F. Schonbein in 1840. Ozone can be detected by its smell in concentrations as low as 0.01 ppm the maximum permissible concentration for continuous exposure is 0.1 ppm but levels as high as 1 ppm are considered non-toxic if breathed for less than 10 min. 

The difficulty of assigning a formal oxidation state is more acutely seen in the case of 5-coordinate NO adducts of the type [Co(NO)(salen)]. These are effectively diamagnetic and so have no unpaired electrons. They may therefore be formulated either as Co -NO or Co -NO+. The infrared absorptions ascribed to the N-O stretch lie in the range 1624-1724 cm which is at the lower end of the range said to be characteristic of NO+. But, as in all such cases which are really concerned with the differing polarities of covalent bonds, such formalism should not be taken literally. 

The electronic absorption spectra of the products of one-electron electrochemical reduction of the iron(III) phenyl porphyrin complexes have characteristics of both iron(II) porphyrin and iron(III) porphyrin radical anion species, and an electronic structure involving both re.sonance forms Fe"(Por)Ph] and tFe "(Por—)Ph has been propo.sed. Chemical reduction of Fe(TPP)R to the iron(II) anion Fe(TPP)R) (R = Et or /7-Pr) was achieved using Li BHEt3 or K(BH(i-Bu)3 as the reductant in benzene/THF solution at room temperature in the dark. The resonances of the -propyl group in the F NMR spectrum of Fe(TPP)(rt-Pr) appear in the upfield positions (—0.5 to —6.0 ppm) expected for a diamagnetic porphyrin complex. This contrasts with the paramagnetic, 5 = 2 spin state observed... 

A characteristic reaction of free radicals is the bimolecular self-reaction which, in many cases, proceeds at the diffusion-controlled limit or close to it, although the reversible coupling of free radicals in solution to yield diamagnetic dimers has been found to be a common feature of several classes of relatively stable organic radicals. Unfortunatly, only the rate constants for self-termination of (CH3)jCSO (6 x 10 M s at 173 K) and (CH3CH2)2NS0 (1.1 X 10 M s at 163K) have been measured up to date by kinetic ESR spectroscopy and consequently not many mechanistic conclusions can be reached. 

The most characteristic feature of nickel dithiolene complexes is the existence of an electron transfer series whose members are interrelated by reversible one-electron steps. Three members I-III of the series, I and III being diamagnetic and II having an S= 1/2 ground state, are preparatively accessible [Ni(S2C2R2)2]2 (I) <- [Ni(S2C2R2)2]1 - (II) <- [Ni(S2C2R2)2] (HI). 

In order to evaluate the individual properties as qubit of each Ln(III) ion within the pertinent [Ln2] complexes, it is necessary to study each ion without the interference of the other. This could be done if it were possible to prepare dinuclear complexes containing the l.n(III) to be studied in the desired position accompanied by a diamagnetic Ln(III) centre (or analogue) at the other site. This was possible thanks to the exceptional structural characteristics of the [Ln2] family. 

Much simpler is the spectrum of other d4 species such as Ticp(cet) (55,55) and Zrcp(cet) (55), having a ground-state diamagnetic configuration (e2)4 in accordance with such configuration, the P.E. spectra have a band at 6.83 (6.94 in the Zr species) eV assigned to the ionization of the e orbitals. The bands at 8.7 and 10.2 eV in Ticp(cet) are characteristic of the cyclopentadienyl e1 and cycloheptatrienyl e1 ionizations, respectively. 

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