Table Of ContentGeneral introduction 1
General introduction
A Definition and substances
In the context of these tables the term free radical means a chemically stable or transient paramagnetic
atomic or molecular speciesw hich derives its paramagnetism from a single, unpaired valence shell electron.
Following this definition the tables cover
a) Atoms and atomic ions in ground and excited ‘S and 2P states,
b) Diatomic and linear polyatomic molecules in ‘C and 2Zl states,
c) Polyatomic molecules and molecular ions which arise or may be thought to arise from the break of a single
bond of a diamagnetic molecule or molecular ion,
d) Mono-(tri-, penta-, etc.) - negative or - positive ions of neutral organic or inorganic compounds.
Not classified as free radicals are atoms or molecules in ground or excited electronic states with multiplicities
larger than two (e.g. 0, ‘P; 02, 3& N, 4S; molecules in excited triplet states), transition metal ions and their
complexes deriving their paramagnetism exclusively or mainly from d- andf-electrons and charge transfer
complexes. However, a number of polyatomic molecular speciesa re included which do not fulfill the above
definition because their properties closely resemble those of structurally very similar free radicals. These are
e) Polyradicals with electron exchange or dipolar couplings not greatly exceeding the Zeeman or hyperfine
interactions.
f) Selectedt ransition metal complexes deriving their paramagnetism from free radical ligands and electrons of
the center atom.
Within, the individual chapters further deviations from the definition occur and are explained in the appropriate
places.
Only compounds with unambiguously verified or at least very plausible structures are included. Papers
which only state the presence of free radicals in-a sample and do not give detailed structures nor magnetic
properties of the radicals have not been reviewed. Also not reviewed are papers which deal exclusively with other
topics than experimental determinations of magnetic properties of free radicals. Such papers may however be
mentioned in footnotes or as further references at the appropriate entries.
The ordering of the substancesc lassified as free radicals into subclassesi s to be seen in the general table of
contents. The ordering within the subclassesis explained, where not selfexplanatory, in introductory sections to
the individual tables.
The literature was considered for the period of 1975 to 1985 with minor deviations. The literature
published before 1964 and in the period of 1964 to 1975 was covered in: Magnetic Properties of Free Radicals,
Landolt-Bornstein, New Series,G roup II, Vol. 1. Berlin: Springer 1965. Magnetic Properties of Free Radicals,
Landolt-Bornstein, New Series, Group II, Vols. 9a-9d2. Berlin: Springer 1977-80.
Further information on free radicals can also been found in: Radical Reaction Rates in Liquids,
Landolt-Bornstein, New Series, Group II, Vols. 13a-13e. Berlin: Springer 1984-85.
B Magnetic properties
The magnetic properties of most free radicals can conveniently be represented by parameters describing
their interaction with an external magnetic field and the intra-molecular hyperfine interactions, i.e. the
parameters g and a, of the Spin-Hamiltonian
~=~,B,.g.S-C~LNgNIBO.Z~+CS.al.Zn
A 1
whereh , pN1B olg , S, a,, ZLa re the Bohr magneton, the nuclear magneton, the magnetic induction, the g-
gN,,
tensor of the radical, the electron spin operator, the nuclear g-factor of nucleus 1, the hyperfine coupling tensor
of nucleus 1, and the spin operator of nucleus 1, respectively.
g is symmetric and the mean value of its diagonal elements
g= f.i gii
1 1
is called the isotropic g-factor. For many radicals g deviates only slightly from the g-factor of the free electron
g,=2.0023193134(70)
Landolt-B8mstein Fischer
New Series 11/17g
2 General introduction
n,, the hyperfine coupling tensor, describes the dipolar and contact interaction between the electron spin
momentum and the nuclear spin momentum of nucleus I. of the radical. a, is most often also symmetric and
the mean value
is called the isotropic hyperfine coupling constant or splitting parameter. If a radical contains several nuclei
which interact there are several tensors a,. In general their principal axes do not coincide, nor do they with the
principal axes of g.
For polyatomic radicals in the gas phase the above Spin-Hamiltonian does not apply and four magnetic
hyperfine coupling constants n, h, c, dare neededt o describe the interaction between a nuclear and the electron
spin. These are defined and explained in the introduction to the tables on inorganic radicals. Polyradicals and
certain radicals on transition metal complexes have N unpaired electrons located on different molecular
segmentsk . Their Spin-Hamiltonian is
3Y”=p,~BBo.gk.Sk+J5 Sk.S’+S.D.S+ ; ~s’.P:.I:
k I>k=l k=l A
where the nuclear Zeeman terms are omitted and
s= CSk.
k
J is the electron exchange parameter and D the zero-field splitting tensor. D is symmetric and traceless, i.e.
;: Dii=O
i=l
and consequently the two zero-field splitting parameters
D= ;D,,
completely determine the tensor. Jdetermines the energy separation ofdifferent spin stateso f the N-spin system.
For N=2
and for N=3
Further information on the description of N-electron spin systems are found in the introductions of the
appropriate chapters.
There are many experimental techniques for the determination of the Spin-Hamiltonian parametersg, (I~. J,
D. E. Often applied are Electron Paramagnetic or Spin Resonance (EPR, ESR), Electron Nuclear Double
Resonance (ENDOR) or Triple Resonance, Electron-Electron Double Resonance (ELDOR), Nuclear
Magnetic Resonance (NMR), occasionally utilizing effects of Chemically Induced Dynamic Nuclear
Polarization (CIDNP), Optical Detections of Magnetic Resonance (0DMR)‘or Microwave Optical Double
Resonance (MODR), Laser Magnetic Resonance (LMR), Atomic Beam Spectroscopy, and Muon Spin
Rotation (j&R). The extraction of data from the spectra varies with the methods, the system studied and the
physical state of the sample (gas, liquid, unordered or ordered solid). For these procedures the reader is referred
to the monographs (D). Further, effective magnetic moments p,rr of free radicals are often obtained from static
susceptibilities. In recent years such determinations are rare, but they are mentioned in the tables. A list of
referencesc overing the more abundant literature up to 1964 is found in:
Magnetic Properties of Free Radicals, Landolt-Bornstein, New Series,G roup II, Vol. 1, Berlin: Springer 1965
and Vols. 9a-9d2, Berlin: Springer 1977-80.
General introduction 3
C Arrangements of the tables
For the display of the data these tables on magnetic properties are devided into chapters each dealing with a
specific class of compounds and prepared by authors who are experts in the fields. Each chapter is headed by an
introduction which specifies the coverage, the ordering of substances, details of the arrangement, the special
general literature and special abbreviations, if necessary.T he tables are followed by the referencesb elonging to
the chapter. Grossly, the overall arrangement is equal to that of previous volumes on the same topics. A small
overlap between chapters has been allowed for reasons of comprehensivenessa nd consistency of the chapters.
An index of all substances covered appears at the end of the last subvolume of the series.
Within the individual chapters the data are arranged in columns in a manner, which, as far as possible, holds
for all chapters:
Thefirst column describes the structure of the species.I t contains the gross formula including charge and,
where appropriate, information on the electronic state. Whenever possible a structural formula is also given or a
letter or number referring to a structural formula which is displayed elsewhere.
The secondc olumn briefly describes the method of radical generation and specifies the matrix or solvent in
which the radical was studied.
The third column states the experimental technique applied to obtain the magnetic properties and the
temperature for which the data are valid in Kelvin. 300 normally means an unspecified room temperature.
Thefourth column refers to the g-tensor. If only one value is given it is the isotropic g-factor. If four values
are listed the first three are the principal elements of the diagonal form ofg, the fourth denoted by is: is the mean
value. For axially symmetric g occasionally only the two principal elements and the isotropic g are listed.
Errors are quoted in parentheses after the values in units of the last digit quoted for the value.
In most of the tables thefifth column contains the information on the hyperfine interactions. It states the
nuclei by their chemical symbols, a left upper index specifying the isotope, if necessary.N umbers preceeding the
chemical symbols note the number of equivalent nuclei, i.e. 3H means ihree equivalent ‘H nuclei. Right hand
indices of the symbols or information given in parenthesesf ollowing the chemical symbols point to positions of
the nuclei in the structural formulae. The data are displayed following the symbols. If only one value is given it is
the isotropic part of the coupling tensor. If four values are listed the first three are the principal values of the
diagonalized form of a, the fourth is the isotropic part. Signs are given whereever known, and errors are quoted
in parentheses.I n the tables on polyradicals thefifth column also gives the available information on the exchange
and zero-field parameters 1, D and E. Further, in some tables where liquid-crystal data are reported column five
may give besidest he isotropic coupling constant a the shift Aa causedb y the partial alignment. It is related to the
elements of a by
*
Aa= Gx Oijaji
13J
where Oij are the elements of the tracelesso rdering matrix. In these cases,a ppropriate entries may also occur in
column four. For the extraction of the parameters from the spectra the original literature and the introduction to
the individual chapters should be consulted. Finally, for radicals observed in the gas phase the fifth column lists
the hyperfme coupling constants a, b, c, d. The general unit of column five is milli-Tesla [mT] with the occasional
and well founded exception of MC/S (MHz) for a few cases. The original literature often quotes coupling
:onstants in Gauss and the conversion is
1 mT & 10 Gauss & 28.0247 (g/g,) MC/S .
In some footnotes the unit cm-’ may be used for some interaction energy terms such as J, D and E with
I cm-’ 2 c; 1 .I c/s where cc,i s the vacuum light velocity.
The sixth column lists the reference from which the data are taken. This reference is followed by additional
and secondary references to the same subject. All references belonging to one chapter are collected in a
bibliography at the end of the chapter, the respective pages are referred to at the top of each page.
Throughout the chapters footnotes give additional informations or explanations. A list of general symbols
md abbreviations is given at the end of this volume.
D Monographs
4tkins, P. W., Symons, M. C. R.: The Structure of Inorganic Radicals. Amsterdam: Elsevier 1967.
4yscough, P. B.: Electron Spin Resonance in Chemistry. London: Methuen 1967.
Zarrington, A., McLauchlan, A. D.: Introduction to Magnetic Resonance. Harper International 1967.
Gerson, F.: Hochaufliisende ESR-Spektroskopie.’ Weinheim: Verlag Chemie 1967.
Land&-Biirnstein Fischer
New Series II/17g
4 General symbols and abbreviations
Poole C. P., Jr.: Electron Spin Resonance. New York: Interscience 1967.
Algcr, R. S.: Electron Paramagnetic Resonance. New York: Interscience 1968.
Kaiser, E. T., Kevan, L.: Radical Ions. New York: Interscience 1968.
Schemer, K., Stegmann, H. B.: Elektronenspinresonanz. Berlin, Heidelberg, New York: Springer 1970.
Geschwind, S., (Editor): Electron Paramagnetic Resonance. New York: Plenum Press 1972.
Muus. L. T., Atkins, P. W., (Editors): Electron Spin Relaxation in Liquids. New York: Plenum Press 1972.
Swartz. H. M., Bolton, J. R., Borg, D. C.: Biological Applications of Electron Spin Resonance. New York:
Wiley 1972.
Wertz, J. E., Bolton, J. R.: Electron Spin Resonance. New York: McGraw-Hill 1972.
Atherton. N. M.: Electron Spin Resonance, Theory and Applications. New York: Halsted 1973.
Buchachenko, A. L., Wassermann, A. L.: Stable Radicals. Weinheim: Verlag Chemie 1973.
Kochi. J. K., (Editor): Free Radicals. New York: Wiley 1973.
Norman, R. 0. C., (Editor): Electron Spin Resonance. London: The Chemical Society 1973ff.
Carrington. A.: Microwave Spectroscopy of Free Radicals. London: Academic Press 1974.
Ayscough, P. B., (Editor): Electron Spin Resonance. London: The Chemical Society 1977ff.
Box, H. C.: Radiation Effects, ESR and ENDOR Analysis. New York: Academic Press 1977.
Muus, L. T.. Atkins, P. W., McLauchlan, K. A., Pedersen, J. B., (Editors): Chemically Induced Magnetic
Polarization. Dordrecht: Reidel 1977.
RAnby, B., Rabek, J. F.: ESR Spectroscopy in Polymer Research. Berlin: Springer 1977.
Slichter, C. P.: Principles of Magnetic Resonance. Berlin: Springer 1978.
Harriman, J. E.: Theoretical Foundations of Electron Spin Resonance. New York: Academic Press 1978.
Symons, M. C. R.: Chemical and Biochemical Aspects of Electron Spin Resonance Spectroscopy. New York:
van Nostrand-Reinhold 1978:
Dorio. M. M., Freed, J. H., (Editors): Multiple Electron Resonance Spectroscopy. New York: Plenum
Press 1979.
Kevan. L., Schwartz. R.: Time Domain Electron Spin Resonance. New York: Wiley 1979.
Shulman. R. G., (Editor): Biological Applications of Magnetic Resonance. New York: Academic Press 1979.
Bertini, I., Drago, R.S.: ESR and NMR of Paramagnetic Species in Biological and Related Systems.
Hingham: Kluver Boston 1980.
Gordy, W.: Theory and Applications of Electron Spin Resonance. New York: Wiley 1980.
Carrington, A., Hudson, A., McLauchlan, A. D.: Introduction to Magnetic Resonance, 2nd ed. New York:
Chapman and Hall, 1983.
Weltner, W., Jr.: Magnetic Atoms and Molecules. New York: van Nostrand-Reinhold 1983.
Poole, C. P.: Electron Spin Resonance, 2nd ed. New York: Wiley 1983.
Walker. D. C.: Muon and muonium Chemistry. Cambridge: Cambridge University Press 1983.
Salikhov, K. M., Molin, Yu. N., Sagdeev, R. Z., Buchachenko, A. L.: Spin Polarization and Magnetic Effects
in Radical Reactions. Amsterdam: Elsevier 1984.
Fischer Landoh-BArnswin
New Series II 178
Ref. p. 671 16.0 Semidiones and related species: Introduction 5
16 Semidionesa nd related species
16.0 Introduction
This chapter continues Vol. 11/9dl, chapter 12. Additionally, phosphasemidiones have been included
is well as anion radicals from p-cyclophanedionic systems, from heterocyclic dionic systems with rings
:ontaining more than 6 atoms, and from thioxoketones and dithiones. Adducts of semidiones with organome-
:allic groups are included now; a few older ones can be found in footnotes in Vol. II/9dl.
The anion radicals are devided into four groups :
16.1 Semidiones
16.2 Thiosemidiones and phosphasemidiones
16.3 Semitriones
16.4 Anion radicals from aromatic polycarbonyl compounds
Within the groups, the division is similar as in Vol. 11/9dl, chapter 12. The content of the subgroups
has been slightly changed, if necessary, and a few new subgroups have been added.
The literature has been covered from 1978-1987.
c
Land&-Biimstein
Lehnig
New Series 11/17g
Substance Generation/ Method/ g-Factor a-Value Ref./
Matrix or Solvent T WI bT1 add. Ref.
16.1 Semidiones (R-CO-(=C-C),-COO-R’; n=O, 1, 2, 31
16.1.1 1,2-Semidiones (R-CO-=CO’-R’; n = 0)
16.1.1.1 Anion radicals from a-keto aldehydes (R=H)
.
W-bW- Treatment of polymeric EPR/ 2.00515 H: 0.772 79Rusl
HCO-=CHO’ acrylonitrile peroxide 298
with (CH3)3COK/
DMSO
tram
Reaction of D-xylose, EPR/ 82Gill
D-ribose or L-arabinose
with HO’, flow-mix-
technique (Ti(II1) +
EDTA-H202 system)/
H,O (pHx9)
tram 298 2.0048 H: 0.78
cis 298 2.0050 H: 0.860
[GH.,W- Reaction of cr+rhamnose EPR/ 2.0049 H(CH0): 0.900 82Gill
CH,-CO-=CHO’ with HO’, flow-mix- 298 H(CH,): 0.620
technique (Ti(II1) +
EDTA-H201 system)/
H,O (pHx9)
trans I I I
ubstance Generation/ Method/ g-Factor u-Value Ref./
Matrix or Solvent T &I WI add. Ref.
C13H403]‘- Reaction of a-D-glucose, EPR/ 82Gill
HOCH,-CO-=CHO’ fi-D-glucose, a-D-mannOSe,
D-g&CtOSe, 3-O-methyl-
u-D-glucose, 2-amino-
glucose, B-D-fIWtOSe,
L-sorbose, or sucrose
with HO’, flow-mix-
technique (Ti(II1) +
EDTA--H,O, system)/
H,O (pHx9)
tram 298 2.0050 H(CH0): 0:850
H(CH,): 0.650
cis 298 2.0049 H(CH0): 0.885
H(CH,): 0.650
Z5Hs05]‘- Reaction of D-XylOSe with EPR/ 82Gill
HO’, flow-mix-technique
P PH
HO&C--(i--F--CO-~0 (Ti(II1) + EDTA-H,O,
OH H system)/
H,O (pHx7)
tram 298 2.0050 H(CH0): 0.810
H(CHOH, 8): 0.335
cis 298 2.0049 H(CH0) : 0.875
H(CHOH, /?I): 0.315
:5Hs05]‘- Reaction of L-arabinose EPR/ 2.0050 H(CH0): 0.910 82Gill
or D-ribose with HO’, 298 H(CHOH, B): 0.310
PH PH
HOH&-y-F-CO-“JHO flow-mix-technique
(Ti(II1) + EDTA-H,02
H H
system)/
H,O (pHx7)
tram, cis
Substance Generation/ Method/ g-Factor a-Value Ref./
Matrix or Solvent T WI WI add. Ref.
W-MM*2- Reaction of o-glucuronic EPR/ 82Gill
acid with HO’,
-o,,;i+~co-,, flow-mix-technique
(Ti(II1) + EDTA-H202
OH OH H
system)/
Hz0 (pHz7)
tram 298 2.0050 H(CH0): 0.840
H(CHOH, 8): 0.450
Cis 298 2.0049 H(CH0): 0.900
H(CHOH, 8): 0.485
LJWJ2- Reaction of a-D-galacturonic EPR/ 2.0049 H(CH0): 0.890 82Gill
acid with HO’, 298 H(CHOH, 8): 0.155
P YHYH
-o,C-~-~-~-CO-=cHO flow-mix-technique
(Ti(II1) + EDTA-H20,
OHH H
system)/
Hz0 (pHx7)
Kd-WJ- Treatment of 3-methylpent- EPR/ H(1) : 0.291 73Elsl
3-en-2-one with Na/ - H(3, CH,): 0.262
H,C-&I +so-&IO
NH3 H(4, H): 0.478
a3 H(4, CH,): 0.510
LHmW- Reaction of a+rhamnose with EPR/ 82Gill
HO’, flow-mix-technique
P P PH (Ti(III)+ EDTA-H20,
H&- - - -CO--O
system)/
w H OH H
Hz0 (pHx7)
tram 298 2.0050 H(CH0): 0.815
H(CHOH, 8): 0.370
cis 298 2.0049 H(CH0): 0.890
H(CHOH, /!I): 0.355
LHmW- Reaction of L-sorbose with EPR/ 2.0050 H(CH0): 0.835 82Gill
HO’, flow-mix-technique 298 H(CHOH, /3): 0.310
r PHP
(Ti(III)+ EDTA-H202
HOH,C-(f-F-F-CO-440
system)/
OH H OH
Hz0 (pHx7), tram
NL R
ew Series II/17g andolGB6mstein ef. p. 671
1
6
.1
Le S
h e
n m
ig id
io
n
e
s
1 9
Substance Generation/ / h+et&od/ ) g-Factor 1 ;-my
Matrix or Solvent
16.1.1.2 Anion radicals from dionic systems (R, R’IH)
16.1.1.2.1 Anion radicals from noncyclic diketones
16.1.1.2.1.1 Anion radicals from 2Jdiketones (R--Cl&, R’=alkyl)
W-WJ- Treatment of acetyl EPR/ 83Alb
CH3-CO-==CO’-CHJ trimethylsilane with
W-UCOKI
DMSO 298
tram H(CH,): 0.584
cis H(CH,): 0.719
Treatment of the EPR/ 82Rus2/
bis(trimethylsiloxy)alkene 80Rusl
with (CH&COK/
DMSO with [2.2.2]-cryptand 298
tram 2.00506 H: 0.566
cis 2.00510 H: 0.676
DMSO with 18-crown-6
2.00488 H: 0.697
DGO with LiI
2.00476 H: 0.770
DE0 with NaI
2.00484 H: 0.740
DE0 with KI
trans 2.00487 H: 0.623
CiS 2.00490 H: 0.726
DMF with Cs 183 2.00495 3H(CH,): 0.66l)
3H(CH,): 0.55 ‘)
UV-irr. of biacetyl with EPR/ 8OBar2 3,
(continued) (n-C4H&Snt or UV-irr.
of DTBP with
I) The spectrum was a mixture of fruns free ions and (n-C,H,),Sn-O-
lruns ion pairs. CHW-M--CW-b)=O/
2, (n-C,H,)$n adduct (“‘Sn: 0.85 mT at 323 K). Toluene 223
, ‘) The (CH,),Sn and the trineophyl stannyl adducts cis 2.0040 H(CH,): 0.85’)
were studied, loo. Pan.9 2.0045 H(CH,): 0.75
