the radical pair which slows down the diffusive separation of
the two radicals (in Scheme 2 the cage is represented by a ring).
A solvent ‘cage effect’ is defined simply as the ratio of the rad-
ical pairs which react directly in a geminate reaction to the total
radical pairs generated, and can be calculated by eqn. (1) for the
photochemical reaction of ASO2B.
of 2, 4.0 g of paraformaldehyde and 0.6 ml of 1 KOH in 80
ml of xylene was refluxed under a N2 atmosphere with vigorous
stirring in a 250 ml of flask equipped with a water collector.
After 1 h a white precipitate began to appear. The reaction
mixture was refluxed for 4 h, then was cooled, and filtered. The
precipitate was washed successively with toluene, diethyl ether
and water and was then dried and recrystallized from CHCl3–
CH3OH to afford 9.1 g (51% yield) of 3 as a white powder.
Mp > 300 ЊC. Anal: calcd. for C136H144O16: C, 80.31; H, 7.09.
Found: C, 79.92; H, 7.17%; δH (CDCl3) 9.55 (1 H, OH, s), 7.06
(2 H, ArH, d), 6.84 (2 H, ArH, s), 6.74 (2 H, ArH, d), 3.72
(OCH3, 3 H, s), 4.27, 3.34 (2 H, 2 × d, CH2), 1.48 (3 H, CH3, s)
and 1.43 (3 H, CH3, s); δC(CDCl3) 157.45, 146.67, 144.70, 142.7,
128.63, 127.69, 128.88, 113.35 (ArC), 32.22 (CH2), 55.07
(OCH3), 41.64 (᎐C᎐), 30.82 and 31.28 (CH3); FD-MS: m/z 2032
(M+).
Preparation of p-[1-(4-hydroxyphenyl)-1-methylethyl]calix-
[8]arene 1. A solution (20 ml) of BBr3 (1.5 g) in CH2Cl2 was
added dropwise under N2 to a solution of 1.0 g of 3 in 20 ml
of dry CH2Cl2 cooled in an ice–water bath and the mixture
was stirred at room temp. overnight. The reaction mixture
was poured into 250 ml of water and stirred for 30 min.
Filtration gave a white solid. Recrystallization from ethanol–
H2O yielded 0.75 g (79% yield) of 1 as a slightly brown
powder. Mp > 300 ЊC. Anal: calcd. for C128H128O16: C, 80.00;
H, 6.67. Found: C, 79.71; H, 6.89%; δC[(CD3)2SO] 6.89 (2
H, ArH, d), 6.70 (2 H, ArH, s), 6.58 (2 H, ArH, d), 3.71 (2
H, CH2, s), 1.51 (6 H, CH3, s); δC[(CD3)2SO] 154.84, 148.28,
142.65, 140.76, 127.14, 127.06, 126.23, 114.54 (ArC),
31.06 (CH2), 40.87 (᎐C᎐), 30.76 (CH3); FD-MS: m/z 1920
(M+).
Cage effect % =
(A᎐B Ϫ A᎐A Ϫ B᎐B)/(A᎐B + A᎐A + B᎐B) (1)
Photolysis of ASO2B in acetone results in the products A᎐A,
A᎐B and B᎐B. Analysis of these products according to eqn. (1)
reveals that the cage effect is close to zero. However, photolysis
of ASO2B in acetone in the presence of 1 gives a cage effect of
43%. Obviously, this observation is attributable to the inclusion
of ASO2B in the cavity of 1. Thus, the cavity of 1 plays the role
of supercage to prevent the generated radical pair from dif-
fusive separation.
Conclusions
The base-induced condensation of p-[1-(4-methoxyphenyl)-1-
methylethyl]phenol 2 and paraformaldehyde under various
conditions is shown to yield p-[1-(4-methoxyphenyl)-1-
methylethyl]calix[8]arene 3 as the unique product but no detect-
able amount of the corresponding calix[4]arene and calix-
[6]arene. Demethylation of 3 affords p-[1-(4-hydroxyphenyl)-1-
methylethyl]calix[8]arene 1 in good yield. In the presence of 1,
the ratio of fluorescence intensities of the first to third peaks in
pyrene fluorescence spectrum in all solvents studied were iden-
tical, suggesting formation of inclusion complexes of 1 with
pyrene. Solubilization experiments showed that the association
constants between 1 and aromatic compounds were 10–100
dm3 molϪ1. Photochemical reaction of aryl methyl sulfones in
the presence of 1 exhibited a large cage effect, also providing
evidence for inclusion complex formation.
Removal of substituents from 3 and preparation of p-H-
calix[8]arene 4. Compound 4 was prepared as described in the
literature:21 a slurry of 5.0 g of 3, 2.2 g of phenol and 6.2 g of
AlCl3 in 80 ml of toluene was stirred at room temp. for 4 h in
an N2 atmosphere. The mixture was poured into 120 ml of 0.2
HCl. The organic phase was separated, and toluene was evap-
orated resulting in the crude product. This product was washed
successively with acetone–HCl, CH3OH, CHCl3, and diethyl
ether to afford 1.8 g (86% yield) of 4 as a slightly grey powder:
δH ([2H5]pyridine) 6.0–6.9 (3 H, ArH, m) and 3.6 (2 H,
ArCH2Ar, s); FD-MS: m/z 848 (M+).
Experimental
Instrumentation
1H NMR spectra were measured with a Varian XL-300 (400
MHz) instrument in CDCl3 or (CD3)2SO using SiMe4 as the
internal standard. Field Desorption (FD) mass spectra were
run on a Finnigan MAT-90 mass spectrometer. UV spectra
were recorded on an Hitachi UV-340 spectrometer. Fluor-
escence spectra were recorded on a Hitachi MPF-4 spectro-
fluorimeter.
Fluorescence measurements
Fluorescence measurements were performed for solutions con-
taining 1.0 × 10Ϫ5 of pyrene and 1.0 × 10Ϫ2 of 1 in various
polar solvents. The samples were purged with nitrogen for at
least 30 min before measurements were taken. The excitation
wavelength for pyrene was 335 nm. The spectra were fully cor-
rected for instrument response. The fluorescence intensity ratio
of the first to third vibrational peaks, I1/I3, was calculated from
the peak heights.
Materials
Preparation of p-[1-(4-methoxyphenyl)-1-methylethyl]phenol
2. To 200 ml of 10% aqueous sodium hydroxide solution
cooled in an ice–water bath was added 45 g (0.2 mol) of bis-
phenol A with vigorous stirring. After bisphenol A had dis-
solved, 25 g (0.2 mol) of dimethyl sulfate was added over a
period of 1 h and the solution was kept at room temp. for 1 h
with vigorous stirring. The resultant precipitate was separated
by filtration with a sintered glass filter and 200 ml of 10% aque-
ous NaOH added again and the mixture filtered to remove the
unreacted material, then the precipitate was heated to 60 ЊC in
another 200 ml of 10% of NaOH. The resultant solution was
filtered while in 60 ЊC. To the filtrate 20% aqueous hydrochloric
acid was added until the solution became acidic. The solution
was extracted with diethyl ether and the organic layer was evap-
orated to give 25.8 g (54% yield) of 2 as a transparent liquid.
δH (CDCl3) 7.15 (4 H, meta to the OH and OCH3 on the phenyl
ring, q), 6.81 (4 H, the ortho site, q), 3.81 (3 H, OCH3, s) and
1.67 (6 H, CH3–C–CH3, s).
Solubilization of polycyclic aromatic compound
Compound 1 was dissolved in 10 ml of ethanol in a stoppered
ampoule resulting in a clear solution, and to this solution excess
of anthracene was added. The sealed ampoule was agitated for
20 min. After 1 d, the suspension was filtered by suction. The
concentration of anthracene solubilized in the filtrate solution
was determined by UV spectroscopy. Assuming the formation
of 1:1 host–guest complex of 1 with anthracene, H + G = HG
where H, G and HG represent the host 1, the guest (anthracene)
and the complex respectively, the association constant (k) can
be calculated from eqn. (2) where [G] is the concentration of
k = [HG]/([H][G])
(2)
Preparation of p-[1-(4-methoxyphenyl)-1-methylethyl]calix-
[8]arene 3. p-[1-(4-Methoxyphenyl)-1-methylethyl]calix[8]-
arene 3 was prepared as follows: a slurry of 17.0 g (0.070 mol)
uncomplexed anthracene and equal to the solubility of anthra-
cene in the absence of 1 (A0), [HG] is the concentration of the
J. Chem. Soc., Perkin Trans. 2, 1997
187