(4-Amino-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl)methyl Radical: A New Constituent of Organic Magnetic Materials

Full text of DOI:10.1021/jo960451v

J . Org. Chem. 1996, 61, 6063-6066
6063
pared and isolated in the solid state, are very similar to
those of PTM, indicating that the absence of the meta-
chlorines does not exert an important effect on the
stability of the molecule.7a
(4-Am in o-2,6-d ich lor op h en yl)-
bis(2,4,6-tr ich lor op h en yl)m eth yl Ra d ica l:
A New Con stitu en t of Or ga n ic Ma gn etic
Ma ter ia ls
Recently, we have prepared the first functionalized
radicals by substitution of one para-chlorine of the
TTM by a functional group.8 In this context, now we
report the synthesis, electrochemical behavior, and elec-
tron spin resonance (EPR) of (4-amino-2,6-dichlorophen-
yl)bis(2,4,6-trichlorophenyl)methyl radical (2), which is
very attractive due to its potential of forming polyamide
and polyimine bonds, constituents of the different FC
units, to prepare polyradicals as magnetic materials. An
X-ray analysis of the molecular and crystalline structure
of 2 is also reported and commented in connection with
its magnetic behavior. In the same way, three simple
examples of condensation of radical 2 to obtain amide
radicals, [4-[(tert-butylcarboxy)amino]-2,6-dichlorophen-
yl]bis(2,4,6-trichlorophenyl)methyl radical (3) and [4-
[(phenylenecarboxy)amino]-2,6-dichlorophenyl]bis(2,4,6-
trichlorophenyl)methyl radical (4), and an imine radi-
cal, [4-(benzylideneamino)-2,6-dichlorophenyl)]bis(2,4,6-
trichlorophenyl)methyl radical (5) are reported to confirm
the stability of the radical character of the molecule with
the reactivity of the amino group.
L. Teruel,1a Ll. Viadel,1a J . Carilla,1a Ll. Fajar´ı,1a
E. Brillas,1b J . San˜e´,1c J . Rius,1c and L. J ulia´*,1a
Departament de Materials Orga`nics Halogenats,
Centre d'Investigacio´ i Desenvolupament (CSIC),
J ordi Girona 18-26, 08034 Barcelona, Spain,
Departament de Quı´mica Fı´sica, Universitat de Barcelona,
Avgda. Diagonal 647, 08028 Barcelona, Spain, and
Institut de Cie`ncia de Materials de Barcelona (CSIC),
Campus de la UAB, 08193 Bellaterra, Spain
Received March 5, 1996
In tr od u ction
One rational approach to design magnetic organic
materials, which has been conceptually proposed by
Dougherty et al.2 and systematically studied by many
authors,3 consists of dividing the high-spin material into
two components: the spin-containing (SC) fragment,
which provides the unpaired electron, and the ferromag-
netic coupling (FC) unit, which connects radical centers
ferromagnetically. In this context, intramolecular ex-
change interactions between two or more radical centers
in π-conjugated systems involving different FC units have
been analyzed. Very recently, the amide bond has shown
to be a good FC unit in some isomeric benzanilides having
a nitrene unit on each benzene ring.4
The chemistry of stable organic free radicals has been
largely stimulated by the fact that these materials can
be used as good SC fragments in the preparation of
persistent ferromagnets.5 Highly chlorinated triphenyl-
methyl radicals of perchlorotriphenylmethyl (PTM) series
are the most stable carbon free radicals described to
date.6,7 On the other hand, the stability and properties
of tris(2,4,6-trichlorophenyl)methyl radical (TTM), pre-
† Dedicated to Professor Fe`lix Serratosa “in memoriam”.
(1) (a) Centre d’Investigacio´ i Desenvolupament. (b) Departament
de Qu´ımica F´ısica. (c) Institut de Cie`ncia de Materials de Barcelona.
(2) Dougherty, D. A. Mol. Cryst. Liq. Cryst. 1989, 176, 25. Novak,
J . A.; J ain, R.; Dougherty, D. A. J . Am. Chem. Soc. 1989, 111, 7618.
Dougherty, D. A. Pure Appl. Chem. 1990, 62, 519. Dougherty, D. A.;
Kaisaki, D. A. Mol. Cryst. Liq. Cryst. 1990, 183, 71. Kaisaki, D. A.;
Chang, W.; Dougherty, D. A. J . Am. Chem. Soc., 1991, 113, 2764.
(3) Iwamura, H.; Murata, S. Mol. Cryst. Liq. Cryst. 1989, 176, 33.
Murata, S.; Iwamura, H. J . Am. Chem. Soc. 1991, 113, 5547. Doi, T.;
Ichimura, A. S.; Koga, N.; Iwamura, H. J . Am. Chem. Soc. 1993, 115,
8928. Ling, C.; Minato, M.; Lahti, P. M.; Willigen, H. V. J . Am. Chem.
Soc. 1992, 114, 9959.
(4) Ichimura, A. S.; Ochiai, K.; Koga, N.; Iwamura, H. J . Org. Chem.
1994, 59, 1970.
(5) For reviews, see: Miller, J . S.; Epstein, A. J .; Reiff, W. M. Chem.
Rev. 1988, 88, 201. Miller, J . S.; Epstein, A. J .; Reiff, W. M. Acc. Chem.
Res. 1988, 21, 114. Dougherty, D. A. Acc. Chem. Res. 1991, 24, 88.
Iwamura, H.; Koga, N. Acc. Chem. Res. 1993, 26, 346.
To prepare radical 2 we focused our attention on the
reactivity of tris(2,4,6-trichlorophenyl)carbenium hexachlo-
roantimoniate (1),8 a stable dark blue microcrystalline
salt that with an excess of ammonia in CH2Cl2 followed
by treatment with SnCl2 gave mainly radical 2 as a dark
red microcrystalline solid. A secundary reaction product
that arises most probably from the condensation of two
molecules of salt 1 with ammonia, as is suggested by data
from its elemental analysis (see the Experimental Sec-
tion), is now being investigated. Acylation and benzoy-
lation of amino radical 2 with trimethylacetyl chloride
and benzoyl chloride in CHCl3 and in the presence of
triethylamine gave radicals 3 and 4, respectively, and
addition of 2 to benzaldehyde in absolute ethanol yielded
radical 5. These new radicals have been synthesized in
excellent yields. Amino radical 2 is stable in air either
in solution (UV-vis spectroscopy) or in solid form and
shows good solvatochromic properties affecting the less
energetic band in the UV-vis spectrum. This band,
which is due to the radical character of the molecule,
(6) Ballester, M. Acc. Chem. Res. 1985, 18, 380 and references cited
therein. Ballester, M. Adv. Phys. Org. Chem. 1989, 25, 267 and
references cited therein.
(7) (a) Armet, O.; Veciana, J .; Rovira, C.; Riera, J .; Castan˜er, J .;
Molins, E.; Rius, J .; Miravitlles, C.; Olivella, S.; Brichfeus, J . J . Phys.
Chem., 1987, 91, 5608. (b) J ulia´, L.; Riera, J .; Teixido´, R. J . Chem.
Soc., Perkin Trans. 1, 1991, 1101. (c) Veciana, J .; Rovira, C.; Crespo,
M. I.; Armet, O.; Domingo, V. M.; Palacio, F. J . Am. Chem. Soc. 1991,
113, 2552. (d) Carilla, J .; J ulia´, L.; Riera, J .; Brillas, E.; Garrido, J .
A.; Labarta, A.; Alcala´, R. J . Am. Chem. Soc. 1991, 113, 8281. (e)
Veciana, J .; Rovira, C.; Ventosa, N.; Crespo, M. I.; Palacio, F. J . Am.
Chem. Soc. 1993, 115, 57. (f) Domingo, V. M.; Castan˜er, J .; Riera, J .;
Labarta, A. J . Org. Chem. 1994, 59, 2604. (g) Chaler, R.; Carilla, J .;
Brillas, E.; Labarta, A.; Fajar´ı, Ll.; Riera, J .; J ulia´, L. J . Org. Chem.
1994, 59, 4107.
(8) Carilla, J .; Fajar´ı, Ll.; J ulia´, L.; Riera, J .; Viadel, Ll. Tetrahedron
Lett. 1994, 35, 6529.
S0022-3263(96)00451-3 CCC: $12.00 © 1996 American Chemical Society

6064 J . Org. Chem., Vol. 61, No. 17, 1996
Notes
Ta ble 1. EP R P a r a m eter s for Ra d ica ls 2-5
hfc constants (G)
radical
g
∆Hpp (G)
N
1H
a-13
C
arom-13
C
2
3
4
5
2.0030
2.0030
2.0034
2.0032
0.82
0.59
0.59
0.75
1.10
1.10
1.23
1.23
1.25
28.2 12.6, 10.5
28.8 13.1, 10.5
28.8 13.1, 10.6
28.2 12.2: 10.2
0.42
shows a pronounced batochromic shift, losing its hyper-
fine structure, in going from aprotic (cyclohexane, λmax
530 and 567 nm; CHCl3, λmax 535 and 574 nm) to protic
solvents (ethanol, λmax 601 nm), based on the different
solvatation interactions concerning the amino group.
Cyclic voltammograms for the reduction of radicals 2 and
5 in 0.1 M tetrabutylammonium perchlorate (TBAP)
dimethylformamide (DMF) display a reversible, one-
electron O/R couple at E°, -0.76 and -0.28 V vs SSCE
(SCE with NaCl aqueous saturated solution), respec-
tively. The presence of these redox couples is indicative
of the stability of both species, neutral and anionic, in
solution. Since E° value for radical 5 is less negative
than that of 2, the former is more easily reducible than
the latter, which is accounted for by the reduction of the
electron-donating properties of the amino group by the
formation of the aldimine.
X-band EPR spectra of radicals 2-5 were recorded in
deoxygenated CH2Cl2 solution at 173 K, and spectral data
are listed in Table 1. g-values are very closed to that of
the free electron and similar to the TTM radical, indicat-
ing a small spin-orbit coupling. All the coupling con-
stants have been found by computer simulation. The
spectrum of radical 2, displayed in Figure 1, consists of
an overlapped and equally separated nonet of lines
corresponding to the coupling with the six equivalent
aromatic protons and the nitrogen. The small lines in
both sides of the main spectrum correspond to the
coupling of the free electron with the three bridgehead
13C nuclei of the molecule. The spectrum of radical 3 is
identical with that of radical 4. Both spectra have been
simulated without considering the interaction of the free
electron with the nitrogen nucleus of the molecule, whose
value must be too small to be observed.
Radical 2 crystallizes from hexane (monoclinic system,
P21/n space group). A perspective view of the structure
with the atom numbering is displayed in Figure 2.9 All
the distances and angles for the central carbon atom C(1)
with aromatic carbons (2), (8), and (14) are in good
agreement with a sp2 hybridization for the methyl carbon.
C(1), C(2), C(8), and C(14) lie in a plane with rmsd lower
than 0.005 Å. Due to the presence of six chlorine atoms
ortho to C(1), the phenyl rings are twisted around their
bonds to C(1) with torsion angles C(8)-C(1)-C(14)-
C(15), -48.7(9), C(2)-C(1)-C(8)-C(9), -44.4(9), and
C(14)-C(1)-C(2)-C(3), -53.1(9), and the molecule adopts
a propeller-like conformation with an approximate 3-fold
symmetry D3. There are four symmetry-related disor-
dered molecules in the unit cell, and the molecular
packing is compatible with the three different orienta-
tions of the molecule around the ternary axis, thus
leading to a partial disorder. The refined occupation
parameters of the N and Cl atoms are given in Table 2.
F igu r e 1. (a) EPR spectrum of a solution of radical 2 in CH2-
Cl2 at 173 K and amplification showing 13C couplings. (b)
Computer simulation.
Table 2 shows that the molecular orientation with the
nitrogen in position 11 is the most probable (∼52%), the
remaining two being less probable (∼24%). These results
rule out the possibility of any strong hydrogen bonding
between neighboring molecules. The N atoms of the
disordered amine groups were geometrically fixed, d(C-
N) ) 1.40 Å, and the H atoms were not included.
The specific magnetic susceptibilities (ø) of the radical
2 were measured in the interval 4-290 K. Least-squares
correlation of the resulting Curie-Weiss plot gave the
Bohr magnetons (µB ) 1.7067), the specific diamagnetic
susceptibility (ødia ) -0.6004 × 10-6 emu),10 and the
Weiss constant (Θ ) -1.3 K). From the µB-value the
radical purity of 2 has been calculated to be 97%. So,
radical 2 behaves as a good paramagnet species in the
range of temperatures studied, except at very low tem-
peratures, where the small and negative value of the
Weiss constant may be associated to the existence of very
weak antiferromagnetic interactions among the radical
centers of neighboring molecules.
The absence of appreciable intermolecular magnetic
phenomena is consistent with a remote separation be-
tween spin centers in the solid. So, an examination of
the molecular structure shows that the unpaired electron
is mainly localized in a pure p-orbital of the methyl
carbon, due to the twisting of the phenyl rings, and the
amino group does not exert any strong influence in the
relative positions of the molecules in the crystalline
lattice, being the intermolecular contacts of the van der
Waals type.
The aim of this work has been to report the synthesis,
properties, and stability of the amino radical 2. Its
(9) The authors have deposited atomic coordinates, bond lengths,
bond angles, torsion angles, anisotropic displacement parameters, and
observed and calculated structure factors for this structure with the
Cambridge Crystallographic Data Centre. The coordinates can be
obtained, on request, from the Director, Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
(10) The value of ødia theoretically estimated by using Pascal’s
systematic11 is -0.569 × 10-6 emu.
(11) Hellwege, K., Hellwege, A., Eds. Landolt-Bo¨rnstein II. Diamag-
netic Susceptibility; Springer-Verlag: Berlin, 1977; Vol. 16, p 1.

Notes
J . Org. Chem., Vol. 61, No. 17, 1996 6065
EAF 16UE operating at 1.5 T. The data were corrected for the
magnetization of the sample holder.
EP R Exp er im en ts. EPR spectra were recorded with a
Varian E-109 spectrometer working in the X band and using a
Varian E-257 temperature controller. The EPR computer
simulation was performed with
a Hewlett-Packard 9835-B
computer, using a modified version of the software package from
the Varian E-935 data acquisition system. Samples of radicals
were prepared in CH2Cl2 (∼10-3 M), placed in quartz EPR tubes,
and degassed by three freeze-pump-thaw cycles before being
inserted into the EPR cavity.
Electr och em ica l Mea su r em en ts. The cyclic voltammetric
(CV) experiments were carried out in a three-electrode cell under
an argon atmosphere. A platinum sphere with an area of 0.093
cm2 was used as the working electrode and a Pt wire as the
counter electrode. The reference electrode was a SSCE (NaCl-
saturated aqueous solution) connected to the cell through a salt
bridge containing a 0.1 M TBAP-DMF solution. The temper-
ature of test solutions and of SCE was kept at 25 °C. In all
experiments, the cell was maintained in the darkness to avoid
the photochemical decomposition of radicals in solution. CV
measurements were performed with standard equipment con-
sisting of a PAR 175 universal programmer, an Amel 551
potentiostat, and a Philips 8043 X-Y recorder. Cyclic voltam-
mograms of all solutions were recorded in the scan rate (v) range
20-200 mV‚s-1. Solutions of substrates had a volume of 25mL
and were prepared with DMF containing 0.1 M TBAP as
supporting electrolyte.
(4-Am in o-2,6-d ich lor op h en yl)bis(2,4,6-tr ich lor op h en yl)-
m eth yl Ra d ica l (2). (a ) Syn th esis. Under an anhydrous
atmosphere, ammonia gas was bubbled through a stirred blue
solution of tris(2,4,6-trichlorophenyl)carbenium hexachloroan-
timoniate (2.12 g, 2.4 mmol) in CH2Cl2 (500 mL) until a rapid
change to a reddish solution was observed. Then, argon was
passed through the solution to eliminate the excess of ammonia.
The resulting mixture was filtered off, and the filtrate was
evaporated to give a reddish residue (1.54 g) that in THF (100
mL) was stirred with anhydrous SnCl2 (0.56 g, 2.95 mmol) under
argon (30 min).
The resulting green solution was evaporated, and the residue
in ether was washed with a saturated NaHCO3 aqueous solution
and then with water, dried with anhydrous sodium sulfate and
evaporated. The dark residue was flash chromatographed (silica
gel, CCl4:CHCl3, 1:1) to afford (i) tris(2,4,6-trichlorophenyl)-
methyl radical (0.26 g, 9%), identified by IR, (ii) a green solid
compound (0.14 g) (Anal. Calcd for C38H13Cl16N: C, 43.4; H,
1.25; N, 1.3; Cl, 54.0. Found: C, 43.9; H, 1.4; N, 1.3; Cl, 53.9),
and (iii) radical 2 (0.74 g, 58%): mp 250 °C dec (from hexane);
IR (KBr) 3500 (w), 3400 (m), 3100 (w), 3070 (w), 1620 (s), 1590
(s), 1555 (m), 1525 (m), 1420 (m), 1385 (w), 1370 (m), 1305 (m),
1280 (m), 1240 (w), 1180 (m), 1135 (m), 1080 (w), 1060 (w), 920
F igu r e 2. A perspective view of (a) the structure with the
atom numbering of radical 2 and (b) the unit cell, illustrating
the molecular packing.
Ta ble 2. Refin ed Occu p a tion P a r a m eter s of th e N a n d
Cl Atom s
Cl(5)
Cl(11)
Cl(17)
0.746(9)
0.474(9)
0.780(9)
N(5)
N(11)
N(17)
0.254(9)
0.526(9)
0.220(9)
(w), 850 (m), 835 (w), 820 (w), 800 (m), 785 (m), 715 (w) cm-1
;
UV-vis (cychlohexane) λmax (ꢀ) 215 (38 100), 249 (6000 sh), 273
(12 300 sh), 360 (18 600 sh), 375 (27 700), 416 (6770 sh), 528
(2070), 566 (3450). Anal. Calcd for C19H8Cl8N: C, 42.7; H, 1.5;
N, 2.6; Cl, 53.2. Found: C, 42.9; H, 1.5; N, 2.6; Cl, 53.1.
(b) X-r a y An a lysis. Cr ysta l Da ta : molecular formula C19H8-
Cl8N; molecular weight 533.86; monoclinic P21/n, No. 14; cell
dimensions, a ) 8.179(4) Å, b ) 14.064(3) Å, c ) 18.92(1) Å, â )
102.18(3)°, V ) 2127(2) Å3, Z ) 4, F(000) ) 1060, Dc ) 1.667
g/cm3, µ ) 1.066 mm-1, crystal specimen prismatic 0.87 × 0.23
× 0.003 mm. Da ta Collection . The diffractometer was an
Enraf-Nonius CAD4 with graphite-monochromated Mo-KR ra-
diation, λ ) 0.7103 Å. Cell parameters were determined from
refinement of 25 reflections using the CAD4 Express software.12
3851 Reflections were measured with 1.82 e θ e 24.97° and
index ranges -9 e h e 9, 0 e k e 16, 0 e l e 22 in w/1.7 θ scan
mode, 0.7 + 0.49 tan(θ) scanwidth, and maximum final scan time
of 60 s. Three standard reflections were measured every 3600
s to check for the intensity variation, and three more standards
were measured every 50 reflections to check the crystal orienta-
tion. Intensity decay was 0.1% and was corrected. Absortion
correction was made using 8 ψ-scans, Tmax ) 99.64%, and Tmin
) 86.43%. Resolu tion a n d Refin em en t. The structure was
solved using the extended tangent formula13 and refined with
magnetic behavior and its crystal and molecular struc-
ture indicates no appreciable intermolecular interactions.
On the other hand, the preparation of radicals 3-5 has
shown that the condensation reactions of the amino group
with acid chlorides and aldehydes take place without
impairment of the radical character. Further syntheses
of polyradicals are now in progress.
Exp er im en ta l Section
Gen er a l P r oced u r es. Melting points were obtained by
using a Ko¨fler microscope “Reichert” and are uncorrected. The
UV-vis and IR spectra were recorded with Beckman Acta M-VI
and Perkin-Elmer 682 spectrometers, respectively. CH2Cl2 and
CHCl3 were distilled over P2O5 before use. The handling of the
radicals 2-5 was performed in the dark.
Ma gn etic Mea su r em en ts. The routine magnetic suscepti-
bilities of radicals 3-5 were measured with a Varian 4-in.
magnet with constant-force caps operating at 8 KOe and a Cahn
RG electrobalance. Measurements for radical 2 were collected
in the range 4-290 K with a Manics DSM8 magnetometer
equipped with a Helium continous flow cryostat and a DRUSCH
(12) CAD4-Express Operating Software, V. 5.1, Enraf-Nonius, Delft
Instruments X-Ray Diffraction, Deft, The Netherlands, 1992.

6066 J . Org. Chem., Vol. 61, No. 17, 1996
Notes
3735 unique reflections with 266 parameters and 1 restraint.
The N atoms of the disordered amine groups were geometrically
fixed (d(C-N) ) 1.40 Å) but the H atoms were not included.
Final R factors (I > 2σ(I)): R ) 6.97%, ωR2 ) 16.59%, Goof )
(0.076 g, 0.75 mmol) in CHCl3 (3 mL) under argon. The resulting
solution was stirred at 0 °C for a further 1 h and then at rt for
48 h. Evaporation of the solvent gave a residue that was worked
up as before and flash chromatographed (silica gel, CHCl3) to
give (i) starting radical 2 (0.025 g, 10%), identified by IR, and
(ii) radical 4 (0.215 g, 72%): mp 263-5 °C (from hexane-CHCl3);
IR (KBr) 3420 (w), 3240 (w), 3130 (w), 3060 (w), 1670 (m), 1650
(s), 1570 (s), 1555 (s), 1525 (m), 1500 (m), 1485 (m), 1375 (s),
1295 (s), 1250 (w), 1230 (w), 1190 (w), 1180 (m), 1135 (m), 1080
(w), 1020 (w), 950 (w), 920 (w), 895 (w), 850 (s), 820 (m), 800 (s),
790 (s), 715 (w), 700 (s), 685 (m), 6155 (w) cm-1; UV-vis
(cyclohexane) λmax (ꢀ) 213 (58 600), 251 (16 400), 278 (11 600 sh),
373 (30 400), 391 (23 700), 405 (17 000 sh), 515 (1360), 557
(1470). Anal. Calcd for C26H12Cl8NO: C, 48.9; H, 1.9; N, 2.2.
Found: C, 48.8; H, 1.8; N, 2.2. Magnetic susceptibility ødia
(Pascal) - 0.568 × 10-6 emu, Θ -7.8 K, µB ∼1.73 (∼100% pure).
1.102, where R ) ∑||Fo| - |Fc||/∑|Fo|, ωR2 ) [∑ω(Fo - Fc2)2/∑ω-
2
(Fo2)2]1/2, ω ) 1/[∑δ(Fo2)2 + (0.554P)2 + 0.92P], P ) [max(Fo2,0)
+ 2Fc2]/3, Goof ) [(∑ω(Fo - Fc2))/(n - p)]1/2 (n, number of
2
reflections, and p, number of parameters). Final shifts/esd were
less than 0.001 in the last cycle, and the maximum and
minimum residual electron density in the final Fourier difference
were 0.44 and -0.45 e Å-3, respectively. A SHELXL-93 pro-
gram14 was used for refinement, and plots were made with
PLUTON programs.15
[4-[(ter t-Bu t ylca r b oxy)a m in o]-2,6-d ich lor op h en yl]b is-
(2,4,6- tr ich lop h en yl)m eth yl Ra d ica l (3). A solution of tert-
butyl chloride (0.090 g, 0.63 mmol) in CHCl3 (1 mL) was added
dropwise to a stirred and cold (0 °C) solution of radical 2 (0.229
g, 0.43 mmol) and triethylamine (0.076 g, 0.75 mmol) in CHCl3
(3 mL) under argon. The resulting mixture was stirred at 0 °C
for a further 1 h and then at rt for 22 h. Evaporation of the
solvent gave a residue that was placed in CHCl3, washed with
diluted aqueous hydrochloric acid and water, and dried with
anhydrous sodium sulfate, and flash chromatographed (silica gel,
CHCl3) to afford radical 3 (0.225 g, 85%) mp 268-70 °C (from
hexane-CHCl3); IR (KBr) 3330 (m), 3120 (w), 3080 (w), 2950
(w), 2870 (w), 1670 (s), 1560 (s), 1550 (s), 1520 (m), 1470 (m),
1390 (w), 1365 (s), 1290 (m), 1250 (w), 1215 (m), 1185 (w), 1175
(m), 1160 (m), 1135 (m), 1070 (m), 1050 (w), 1020 (w), 915 (m),
875 (m), 865 (m), 850 (m), 815 (m), 810 (s), 800 (s), 785 (s), 715
(m) cm-1; UV-vis (cyclohexane) λmax (ꢀ) 215 (54 600), 248 (16 800
sh), 276 (5900 sh), 373 (24 700), 510 (1170), 554 (1430). Anal.
[4-(Be n zylid e n e a m in o)-2,6-d ich lor op h e n yl]b is(2,4,6-
tr ich lor op h en yl)m eth yl Ra d ica l (5). Benzaldehyde (0.1 mL,
0.98 mmol) was added dropwise to a solution of radical 2 (0.50
g, 0.94 mmol) in ethanol (30 mL), and the resulting solution was
refluxed under argon for 32 h. Evaporation of the solvent gave
a residue that was digested in n-pentane to afford radical 5 (0.55
g, 94%): mp 222-5 °C; IR (KBr) 3050 (w), 2940 (w), 2870 (w),
1620 (m), 1550 (s), 1520 (s), 1510 (s), 1445 (m), 1380 (m), 1360
(s), 1305 (w), 1280 (w), 1230 (w), 1185 (m), 1175 (s), 1160 (m),
1125 (m), 1070 (w), 1050 (w), 1015 (w), 965 (w), 945 (m), 915
(w), 900 (w), 875 (m), 850 (s), 840 (m), 815 (m), 795 (s), 785 (s),
745 (m), 715 (w) cm-1; UV-vis (cychlohexane) λmax (ꢀ) 213
(68 800), 251 (22 100), 293 (10 600 sh), 373 (28 900), 408 (18 500),
444 (9600 sh), 524 (940 sh). Anal. Calcd for C26H12Cl8N: C,
50.2; H, 1.9; N, 2.2; Cl, 45.6. Found: C, 50.4; H, 2.1; N, 2.2; Cl,
45.4. Magnetic susceptibility ødia (Curie-Weiss) -0.5425 × 10-6
emu, Θ -1.3 K, µB ∼1.74 (∼100% pure).
Calcd for
C24H16Cl8NO: C, 46.6; H, 2.6; N, 2.3; Cl, 45.9.
Found: C, 46.3; H, 2.5; N, 2.2; Cl, 46.0. Magnetic susceptibility
ødia (Pascal) -0.566 × 10-6 emu, Θ -2.3 K, µB ∼1.73 (∼100%
pure).
Ack n ow led gm en t. Support of this research by
DGICYT of MEC (Spain) through project PB92-0031
and by the “Generalitat de Catalunya” (Grant: GRQ93-
8036) is gratefully acknowledged. J .S. thanks the
“Generalitat de Catalunya” for a doctoral scholarship.
The authors express their gratitude to the EPR service
of Centre d'Investigacio´ i Desenvolupament (CSIC) in
Barcelona.
[4-[(P h en ylen eca r boxy)a m in o]-2,6-d ich lor op h en yl]bis-
(2,4,6- tr ich lor op h en yl)m eth yl Ra d ica l (4). Benzoyl chloride
(0.07 mL, 0.60 mmol) was added dropwise to a stirred and cold
(0 °C) solution of radical 2 (0.25 g, 0.47 mmol) and triethylamine
(13) Rius, J . Acta Crystallogr., 1993, A49, 406.
(14) Sheldrick, J . SHELXL93, Program for Crystal Structure De-
termination; Institut fur Anorg. Chemie: Goettingen, Germany, 1993.
(15) Spek, A. L. PLUTON, Program for Display and Analysis of
Cristal and Molecular Structures; Utrecht University: Utrecht, The
Netherlands, 1993.
J O960451V