Synthesis of porphyrin conjugates based on conformationally rigid and flexible resorcin[4]arene frameworks

Article abstract of DOI:10.1016/j.tet.2011.02.024

Porphyrin conjugates were synthesized based on conformationally rigid, bowl shaped cavitand, and flexible unfirm resorcin[4]arenes. The influence of the resorcin[4]arene fragment on the porphyrin fluorescence is investigated.

Full text of DOI:10.1016/j.tet.2011.02.024

Tetrahedron 67 (2011) 2585e2590
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Tetrahedron
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Synthesis of porphyrin conjugates based on conformationally rigid and flexible
resorcin[4]arene frameworks
*
Talal F. Al-Azemi , Mickey Vinodh
Department of Chemistry, Kuwait University, PO Box 5969, Safat 13060, Kuwait
a r t i c l e i n f o
a b s t r a c t
Article history:
Porphyrin conjugates were synthesized based on conformationally rigid, bowl shaped cavitand, and
flexible unfirm resorcin[4]arenes. The influence of the resorcin[4]arene fragment on the porphyrin
fluorescence is investigated.
Received 18 November 2010
Received in revised form 17 January 2011
Accepted 7 February 2011
Ó 2011 Elsevier Ltd. All rights reserved.
Available online 15 February 2011
Keywords:
Porphyrin
Resorcinarene
Hosteguest chemistry
Fluorescence
1. Introduction
functionalized resorcinarene frameworks and to couple them with
suitable porphyrins followed by porphyrin core metalation. The
Well-defined architecture of an artificial receptor is an impor-
tant aspect of molecular recognition and encapsulation. A large
variety of macrocyclic oligomers, such as calixarenes,1 resorcinar-
enes,2 cyclodextrins,3 and crown ethers4 could afford attractive
receptors possessing multipoint recognition ability toward non-
covalently bound guest molecules. Cations, anions, and neutral
guest molecules have been selectively sequestered by these mac-
rocycles of widely varying design, size and shape. Porphyrins on the
other hand, are a suitable class of compound for building artificial
molecular devices because of their photoactive and electronic
properties.5 Combination of Calix and resorcin[4]arene fragments,
which have unique three-dimensional shape and good complexa-
tion ability with porphyrins via covalent bond allows adjustment of
the geometry of the complexing cavity, and thus provides wide
prospects in the design of selective receptors and supersensitive
sensors.6 Though porphyrineresorcin[4]arene conjugates are at-
tractive receptors and possess multipoint recognition ability, they
are not as widely studied as in the case of porphyrinecalixarene
systems.
effect of the resorcin[4]arenes conjugates on fluorescence quen-
ching of the porphyrin moiety by structurally different quinones is
also reported.
2. Results and discussion
The balance between rigidity and flexibility is of particular im-
portance for the binding and dynamic properties of host and guest.
Rigid lock and key type cavitand receptors are expected to offer
efficient recognition but will be too specific about size and shape
of the substrates. When the process of exchange, regulation or
cooperativity is the key parameter, a flexible receptor gains more
significance. In this context, resorcin[4]arenes are a suitable plat-
form for simple covalent modifications of the upper rim to afford
both conformationally rigid, bowl shaped cavitand, and the more
flexible unlocked counterpart.
Functionalized monobromo-methyl-resorcin[4]arenes 2b and
3b were synthesized in three steps (Scheme 1). Compound (1) was
synthesized by acid catalyzed condensation of methyl-resorcinol
and heptaldehyde. The conformationally locked bowl shape resor-
cin[4]arene 2a was synthesized by reacting (1) with BrClCH2, which
introduced methylene bridges between four sets of proximate ox-
ygens of resorcin[4]arenes.7a The synthesis of the unlocked com-
pound 3a was achieved by the reaction of octa-hydroxy (1) with
methyl iodide.
In this work we report efficient synthesis of porphyrin resorcin
[4]arene conjugates in which the resorcin[4]arenes framework is
either a conformationally rigid, bowl shaped cavitand or a flexible
unlocked structure. The strategy we employed was to construct
The functionalization of resorcin[4]arene units was the next
step. Monobromination of one of the benzylic hydrogens of both
* Corresponding author. Tel.: þ965 2498 5540; fax: þ965 2481 6482; e-mail
address: t.alazemi@ku.edu.kw (T.F. Al-Azemi).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.02.024

2586
T.F. Al-Azemi, M. Vinodh / Tetrahedron 67 (2011) 2585e2590
Br
organic solvents. Treatment the porphyrin conjugates with Zn(II)
acetate yielded their metalated derivatives. The porphyrin conju-
gates as well as the Zn(II) derivatives were characterized by NMR,
UVevis, fluorescence, and mass spectroscopic methods.
O
O
O
O
O
O
O
O
O
O
O
O
(iii)
R
R
R
R
(i)
R
R
R
R
The fluorescence quenching of porphyrin systems by benzoqui-
nones is well known and it is well demonstrated that conjugation of
porphyrin with a molecular trap like a calix[n]arene would enhance
the fluorescence quenching considerably.8 In the present report,
four structurally different quinonesdbenzoquinone (BQ), 1,4-
naphthoquinone (NQ), phenanthrenequinone (PAQ), and dichlor-
odicyanobenzoquinone (DDQ) were used to study the porphyrin
fluorescence quenching. The decay of porphyrin fluorescence was
followed bythe addition of increasing amounts of differentquinones
to the solutions of parent porphyrin P1, 2cP1, and 3cP1 conjugates in
dichloromethane. The variation of fluorescence intensity is plotted
against the concentration of quencher in all the cases.
O
O
O
O
HO
HO
OH
OH
(2a)
(2b)
OH
OH
HO
HO
R
R
R
R
Br
R
MeO
MeO
OMe
MeO
MeO
OMe
OMe
OMe
MeO
MeO
(1)
R = C6H13
MeO
MeO
OMe
R
R
(ii)
R
(iii)
R
R
R
R
OMe
OMe
OMe
(3b)
(3a)
Even though the analysis of the system is complicated by the
possible competition between the quenching by free quinones and
quenching by quinones complexed/trapped in resorcin[4]arene
cavity, the presence of resorcin[4]arenes conjugated to porphyrins
enhances the efficiency of fluorescence quenching. Fig. 1(a) shows
fluorescence intensity as a function of the concentration of phe-
nanthrenequinone [PAQ] for free porphyrin P1, and the conjugates
2cP1 and 3cP1. After addition of 2.5ꢀ10ꢁ5 M of PAQ, the
Scheme 1. Synthesis of monobromo resorcin[4]arene: (i) BrCH2Cl, K2CO3, DMF, 80 ꢂC
(ii) MeI, K2CO3, DMF, 80 ꢂC (iii) 1 equiv NBS, AIBN, benzene.
resorcin[4]arenes (2ae3a) upper rim was carried out for this pur-
pose. A 1:1 M equiv of NBS and resorcin[4]arenes were reacted
together and monobromination was achieved in more than 30%
yield in both cases. The products were easily separated by simple
column chromatography technique followed by vacuum drying, to
give pure functionalized monobromo-methyl-resorcin[4]arenes
(2be3b) frameworks. The NMR and mass spectroscopic data con-
firmed the structure and purity of both systems.
The porphyrin used in this study was an appropriately func-
tionalized meso tetraaryl porphyrin. Since the hydroxyl phenyl
function can easily react with benzylic bromides, one aryl moiety of
the porphyrin was a phenol. The three other aryl functions were
toluyl groups to make the resulting system more soluble in organic
solvents. The porphyrin was synthesized by mixed aldehyde con-
densation inpropionic acid using 1 equivof 3-hydroxybenzaldehyde
with 3 equiv of p-tolualdehyde and 4 equiv of pyrrole followed by
column purification (see Experimental section).
Prophyrin resorcin[4]arene conjugates 2bP1 and 3bP1 were
synthesized by the reaction between hydroxy porphyrin unit P1
and resorcin[4]arenes 2b and 3b (Scheme 2). The compounds were
obtained in reasonably good yield (>75% yields). The resulting
conjugates were easily purified by column chromatography due to
the difference in polarity with the unreacted porphyrins or parent
resorcin[4]arenes, and they were readily soluble in common
Fig. 1. (a) Fluorescence intensity as
a function of the concentration of phenan-
threnequinone [PAQ]; Porphyrin P1 ( ); compound 2cP1 ( ); compound 3cP1 ( ):
;
Scheme 2. Synthesis of prophyrin resorcin[4]arene conjugates based on monobromo
resorcin[4]arenes 2a and 2b.
(b) Fluorescence emission bands at 648 nm measured after addition of 2.5ꢀ10ꢁ5 M of
PAQ to Porphyrin P1, compound 2cP1 and compound 3cP1.

T.F. Al-Azemi, M. Vinodh / Tetrahedron 67 (2011) 2585e2590
2587
fluorescence quenching efficiency was affected considerably by the
structure and the presence of resorcin[4]arene fragments. The free
porphyrin P1 was not affected by the presence of PAQ, where as the
porphyrin resorcin[4]arene conjugates 2cP1 and 3cP1 showed
a decrease in the fluorescence intensities. Compared to the cavitand
porphyrin resorcin[4]arene 2cP1, the more flexible conjugate 3cP1
was more efficient in fluorescence quenching, suggesting its fa-
vorable flexible nature to adapt and to accommodate the aromatic
guest molecules more easily. This effect is depicted in the fluores-
cence emission bands at 648 nm, after addition of 2.5ꢀ10ꢁ5 M of
PAQ in Fig. 1(b).
The fluorescence decay profiles of NQ and BQ showed similar
behavior as that of PAQ, where the quenching of the porphyrin
fluorescence was enhanced due to the presence of resorcinarene
fragments. The structurally unlocked resorcinarene 3cP1 exhibited
more efficiency in fluorescence quenching (see Supplementary
data). Furthermore, the presence of the phenyl group in the qui-
none structure enhanced efficiency of fluorescence quenching at
lower concentration due to the improved accommodation of the
guest molecule in the hydrophobic cavity.
Fig. 3. Fluorescence intensity as
threnequinone [PAQ]; porphyrin P1eZn(II) ( ); compound 2cP1eZn(II) ( ); com-
pound 3cP1eZn(II) ( ).
a
function of the concentration of phenan-
;
As expected the structure of the quinone moiety has an im-
portant role in the enhanced quenching due to the presence of the
resorcin[4]arene unit. When DDQ was used to quench the por-
phyrin fluorescence, the cavitand resorcin[4]arene unit in com-
pound 2cP1 did not exhibit any favorable effect and showed similar
quenching behavior free unconjugated porphyrin P1 (Fig. 2). At the
same time, the structurally flexible resorcinarene fragment in
compound 3cP1 enhanced the porphyrin quenching notably. The
presence of chloro and cyano groups in DDQ makes this quinone
too large to be accommodated within the cavitand of the resorcin
[4]arene framework in compound 2cP1, and hence no improve-
ment of the quenching was possible due to the trapped quinone.
The unlocked structure of the resorcin[4]arene in 3cP1 conjugate,
on the other hand, is sufficiently flexible to associate with these
large sized substituents in DDQ to cause an enhanced effect. Thus,
the quenching of porphyrin fluorescence using various quinones
clearly demonstrates the different behavior of cavitand and flexible
host molecular species toward molecular recognition. Interestingly,
when excess zinc acetate was used to metalate the porphyrin
conjugates, Zn(II) derivatives showed no effect of resorcinarene
fragments in the florescence quenching for both compounds in-
vestigated. The presence of the excess metal prevents the accessi-
bility to resorcinarene cavity (Fig. 3).
The 1H NMR spectrum for compound 3cP1 in the absence of PAQ
contains four signals from the nonequivalent methoxy groups, at
3.36, 3.38, 3.54, and 3.83 ppm. Upon addition of PAQ, the 1H NMR
spectrum shows new signals at 3.46 and 3.47 ppm corresponding
to the methoxy groups. These signals result from noncovalent in-
teractions when PAQ is accommodated inside the resorcinarene
cavity (Fig. 4). This result is in agreement with the data from the
fluorescence quenching studies. For smaller quinones, the in-out
guest exchange is too fast for the NMR time scale to be observed.7b
Fig. 4. 1H NMR spectra of conjugate 3cP1 (600 MHz, CDCl3): (a) before addition of PAQ
and (b) after addition of PAQ.
3. Conclusion
In conclusion, conformationally locked and unlocked porphyrin
resorcin[4]arene conjugates were synthesized. The structures of
these compounds were confirmed by NMR and mass spectroscopic
analyses. The data imply that at low concentration of quinone, the
fluorescence quenching of the porphyrin is considerably enhanced
by the attachment of resorcin[4]arene to the photoactive subunit,
which is supported by 1H NMR experiments. These types of con-
jugates present interesting opportunities for various applications
Fig. 2. Fluorescence intensity as
chlorodicyanobenzoquinone [DDQ]; Porphyrin P1 ( ); compound 2cP1 ( ); com-
pound 3cP1 ( ).
a
function of the concentration of di-
;

2588
T.F. Al-Azemi, M. Vinodh / Tetrahedron 67 (2011) 2585e2590
such as artificial enzyme mimics. Applications and further analyses
of these systems are underway in our laboratories.
showed no peak at 650 nm (650 nm peak is exclusively for free-
base porphyrin). The solvent was then evaporated off and the crude
product was purified by column chromatography (silica gel, 98%
CH2Cl2/2% CH3OH (v/v)). Compound P1 was obtained as brow-
nish red (98 mg, 90% yield). UVevis in CH2Cl2: lmax nm
4. Experimental section
4.1. Material and method
(3
ꢀ10ꢁ5
M
ꢁ1 cmꢁ1): 418 (3.03), 546 (0.118) and 587 (0.009).
UVevis spectra were recorded on a Varian UVevis cary-5
spectrophotometer. Fluorescence (emission) spectra were mea-
sured with Aminco Bowman Series 2 spectrophotometer. FAB mass
analyses were performed using a high resolution GC MS DFS-
Thermo instrument. 1H NMR was done on Bruker Avance II
600 MHz and Burker DPX 400 spectrometers. Flash column chro-
matography was performed using 70e230 mesh ASTM Merck silica
gel-60. DMF was dehydrated by vacuum distillation over Calcium
hydride. Pyrrole was vacuum distilled before each usage. Azobisi-
sobutylonitrile (AIBN) was crystallized form hot ethanol. N-Bro-
mosuccinimide (NBS) was crystallized prior use form boiling water.
All other reagents and solvents were of reagent grade purity and
used without further purification.
4.3.3. Octol-resorcin[4]arene
(1)7a,9. Methyl-resorcinol
(10 g,
0.081 mol) was dissolved in ethanol (62.7 mL, 775 mL/mol) and
37% aqueous HCl (15.1 mL, 185 mL/mol). The solution was cooled in
ice bath and heptaldehyde (11.3 mL, 0.081 mol) was added slowly
over a period of 30 min. The reaction mixture was allowed to warm
to room temperature and refluxed for 12 h. The yellow colored
precipitate was filtered and washed several times with distilled
water until it turns neutral to pH paper. Yield 10.7 g (88%). Mp:
>220 ꢂC (decomposed); 1H NMR (400 MHz, DMSO-d6)
d: 0.84
(t, 12H, J¼6.25 Hz), 1.23 (m, 32H), 1.93 (s, 12H), 2.21 (s, 8H), 4.18
(t, 4H J¼7.75 Hz)), 7.21 (s, 4H), 8.69 (br s, 8H); 13C NMR (100 MHz,
DMSO-d6) d: 10.7, 14.2, 22.9, 28.9, 29.8, 32.1, 35.4, 38.4, 73.0, 113.6,
122.0, 124.6, 154.0.
4.2. Fluorescence decay studydprocedure
4.3.4. Bridged resorcin[4]arene (2a)7a,10. Compound 1 (5 g, 5.5 mmol)
was dissolved in DMF (55 mL) in a sure-sealed tube. Potassium car-
bonate (12 g, 88 mmol) was added and stirred for 0.5 h. Then
bromochloromethane (7.7 mL, 88 mmol) was added at room tem-
perature. The reaction mixture was sealed and immersed in pre-
heated oil bath 80 ꢂC for 24 h. The reaction mixture was poured into
cold ice water and the white solid was collected by section filtration.
Using dichloromethane, 20 mL of a 0.0025 mM solution of
porphyrin (0.0050 mM solution in the case of Zn porphyrins) was
prepared and taken in a vial. 10 mM solution of each quinones was
prepared. Using a micropipette a small amount of Quinone is added
to the porphyrin solution, shaken well and fluorescence at 648 nm
was measured (excitation wave length is 418 nm). More quinone
was added and fluorescence measured again. This was repeated
again until the fluorescence intensity at 648 nm (602 nm in the
case of Zn porphyrins) becomes zero. The result was then expres-
sed as a function of the decay of fluorescence intensity against the
concentration of quinone.
Yield 4.9 g (94%); 1H NMR (400 MHz, CDCl3)
d: 0.92 (t, 12H,
J¼6.80 Hz), 1.37 (m, 32H), 2.00 (s, 12H), 2.22 (q, 8H), 4.28 (d, 4H,
J¼7.2 Hz), 4.78(t, 4H, J¼8.0 Hz), 5.91 (d, 4H, J¼6.8 Hz), 7.00 (s, 4H);13C
NMR (150 MHz, CDCl3) d: 10.3, 14.1, 22.7, 27.9, 29.2, 30.1, 31.8, 37.0,
98.5, 117.6, 123.6, 138.0153.2.
4.3.5. Monobromo bridged resorcin[4]arene (2b). Compound 2a
(2 g, 2.15 mmol) and AIBN (100 mg, 0.6 mmol) dissolved in
degassed benzene (40 mL). N-Bromosuccinimide (0.387 mg,
2.15 mmol) was then added and the reaction mixture refluxed
overnight. After cooling the mixture was filtered and the filtrate
was evaporated to dryness. The solid residue is dissolved in mini-
mum amount of petroleum ethereethyl acetate (1:1 v/v) mixture
and then adsorbed on silica gel and dried. It was then mounted on
the top of a silica gel column and eluted with petroleum ether ethyl
acetate (93:7 v/v). The intended compound was the second last
fraction from the column. The solvent was evaporated off and the
white solid was dried on a vacuum decicator to obtain constant
4.3. Synthesis
4.3.1. meso-5-(3-Hydroxyphenyl)-10,15,20-(4-toluyl)porphyrin
(P1). The porphyrin was synthesized by mixed aldehyde conden-
sation in propionic acid using 1.0 equiv of 3-hydroxybenzaldehyde,
3.0 equiv of 4-tolualdehyde, and 4.0 equiv of pyrrole. Thus to 0.5 L
of hot propionic acid, 3-hydroxybenzaldehyde (4.88 g, 40 mmol)
and 4-tolualdehyde (14.20 mL, 120 mmol) were added and stirred
for 10 min. As the mixture was about to boil, pyrrole (11.08 mL,
160 mmol) was added with vigorous mixing. The reaction was
refluxed for 45 min, allowed to cool to room temperature, and kept
in the refrigerator at 8e10 ꢂC overnight. The precipitate formed was
then collected by filtration and washed with hot water until all
propionic acid was removed. The crude reaction products were
loaded onto a flash silica gel column by dissolving in minimum
quantity of dichloromethane and eluted with a solvent gradient
from 100% CH2Cl2 to 98% CH2Cl2/2% CH3OH (v/v). Compound P1 is
the second band of the column following the tetratoluylporphyrin.
This fraction was collected and did second column purification with
99% CH2Cl2/1% CH3OH (v/v) to remove traces of impurities. Com-
pound P1 was obtained as purple solid (1.57 g, 6% yield). UVevis in
weight. Yield 0.8 g (37%); 1H NMR (600 MHz, CDCl3)
d: 0.90 (m,
12H,), 1.30 (m, 32H), 1.90 (s, 9H), 2.19 (m, 8H), 4.37 (d, 2H, J¼7.2 Hz),
4.42 (d, 2H, J¼7.2 Hz), 4.60 (s, 2H), 4.73 (t, 2H, J¼7.8 Hz), 4.77 (t, 2H,
J¼7.8 Hz), 5.87 (d, 2H, J¼6.6 Hz), 5.95 (d, 2H, J¼7.2 Hz), 6.97 (s, 3H),
7.15 (s, 1H); 13C NMR (150 MHz, CDCl3)
d: 10.2, 10.6, 14.1,14.1, 22.0,
22.7, 24.4, 27.9, 27.9, 29.5, 29.5, 29.7, 30.1, 30.2, 31.9, 31.9, 33.9, 36.9,
37.0, 98.3, 99.1, 117.2, 117.3, 118.4, 121.9, 123.9, 124.0, 123.9, 137.0,
137.8, 138.2, 138.4, 153.3, 153.3, 153.5, 153.6.
4.3.6. Octamethoxy resorcin[4]arene (3a). Compound 1 (5 g, 5.6 mol)
was dissolved in acetone (50 mL) in a sure-sealed tube. Potassium
carbonate (12.1 g, 88 mmol) was added and stirred for 0.5 h.
Then methyl iodide (5.5 mL, 88 mmol) was added at room temper-
ature. After addition, the reaction mixture was sealed and immersed
in preheated oil bath 80 ꢂC for 24 h. The tube was cooled in ice water
and the solid was filtered off. The compound was crystallized
in acetone/methanol mixture. White crystals were obtained. Yield
CH2Cl2: lmax nm (
3
ꢀ10ꢁ5
M
ꢁ1 cmꢁ1): 417 (2.25), 514 (0.086), 548
(0.038), 589 (0.024), and 645 (0.027); 1H NMR (400 MHz, CDCl3)
d
: ꢁ2.80 (s, 2H), 2.70 (s, 9H), 7.20 (m, 1H), 7.54 (m, 7H), 7.63 (t, 1H,
J¼2.4 Hz), 7.76 (m, 1H), 8.09 (d, 6H, J¼8.0 Hz), 8.85 (s, 8H); HRMS
(EI): m/z [M]þ, found 672.2883. C47H36 N4O requires 627.2889.
4.3.2. meso-5-(3-Hydroxyphenyl)-10,15,20-(4-toluyl) porphyrinato
zinc(II) (ZnP1). Compound P1 (100 mg) was dissolved in chloro-
form (25 mL) and zinc acetate (100 mg) in methanol (15 mL) was
added. The mixture was refluxed until the UVevis spectrum
4.4 g (80%). Mp¼109 ꢂC; 1H NMR (400 MHz, CDCl3)
d: 0.86
(t, 12H, J¼6.8 Hz), 1.30 (m, 32H), 1.86 (m, 8H), 2.17 (s, 12H), 3.52 (s,
24H), 4.46 (t, 4H, J¼7.2 Hz), 6.55 (s, 4H); 13C NMR (150 MHz, CDCl3)

T.F. Al-Azemi, M. Vinodh / Tetrahedron 67 (2011) 2585e2590
2589
d
: 10.2, 14.1, 22.8, 28.6, 29.6, 31.9, 35.6, 37.5, 59.9, 98.5, 123.4, 124.2,
29.6, 29.7, 29.8, 29.9, 29.9, 29.9, 30.3, 30.4, 31.8, 32.0, 32.1, 32.2, 34.1,
37.2, 61.6, 98.4, 99.9, 113.9, 114.3, 117.3, 117.6, 120.2, 124.3, 127.5,
131.8, 132.2, 132.3, 134.6, 137.4, 137.4,137.5, 137.9, 138.2, 138 9,140.0,
150.1, 150.5, 150.6, 150.6, 153.5, 153.7, 154.3, 156.9.
133.1155.5.
4.3.7. Monobromo octamethoxy resorcin[4]arene (3b). Compound
3a (2 g, 2.01 mmol) and AIBN (100 mg, 0.6 mmol) dissolved in
degassed benzene (40 mL). N-Bromosuccinimide (0.362 mg,
2.01 mmol) was then added and the reaction mixture refluxed
overnight. After cooling the mixture was filtered and the filtrate
was evaporated to dryness. The solid residue in dissolved in mini-
mum amount of petroleum ethereethyl acetate (1:1 v/v) mixture
and then adsorbed on silica gel and dried. It was then mounted on
the top of a silica gel column and eluted with petroleum ether ethyl
acetate (95:5 v/v). The intended compound was the second last
fraction from the column. The solvent was evaporated off and the
white crystalline solid was dried on a vacuum decicator to obtain
4.3.10. Porphyrin resorcin[4]arene conjugate (3cP1). meso-5-(3-
Hydroxyphenyl)-10,15,20-(4-toluyl)porphyrin (P1) (100 mg, 0.149
mmol) and K2CO3 (100 mg, 0.73 mmol) were dissolved in dry DMF
(5 mL) in a sealed tube and stirred for 15 min. Monobrominated
cavitand resorcin[4]arene. (Resorcarene(cavit)eBr) (160 mg,
0.149 mmol) was added to this mixture, the tube sealed and stirred
in an oil bath at 80 ꢂC for one day. The DMF was evaporated off and
the solid residue was washed with water and dried. The crude
produce is adsorbed on silica and mounted on a silica column and
eluted with chloroform. The first band is collected, solvent removed
and dried in a vacuum decicator to get constant weight. Compound
3cP1 was obtained as brownish red solid (203 mg, 82% yield).
constant weight. Yield 0.65 g (30%); 1H NMR (400 MHz, CDCl3)
d:
0.88 (t, 12H, J¼4.8 Hz), 1.29 (m, 32H), 1.87 (m, 8H), 2.12 (s, 6H), 2.22
(s, 3H), 3.44 (s, 6H), 3.45 (s, 6H), 3.58 (s, 6H), 3.87 (s, 6H), 4.49 (q, 4H,
J¼5.2 Hz), 4.70 (s, 2H), 6.42 (s,1H), 6.65 (s,1H), 6.73 (s, 2H); 13C NMR
UVevis in CH2Cl2: lmax nm (
3
ꢀ10ꢁ5
M
ꢁ1 cmꢁ1): 417 (5.22), 514
(0.199), 550 (0.099), 589 (0.059) and 645 (0.053). FAB mass:
(150 MHz, CDCl3)
d
: 10.4, 10.5, 14.2, 22.8, 23.0, 24.8, 26.4, 27.1, 28.7,
[Mꢁ1]þ 1662.8; 1H NMR (400 MHz, CDCl3)
: ꢁ2.76 (s, 2H), 0.84
d
32.1, 36.0, 36.0, 37.6, 37.6, 60.1, 60.1, 60.2, 61.7, 123.7, 123.9, 124.2,
124.4, 125.5,128.7, 132.1,132.9, 133.8,135.1, 155.7,155.9,156.1,156.3.
(m, 12H), 1.27 (m, 32H), 1.86 (m, 8H), 2.09 (s, 6H), 2.17 (s, 3H), 2.72
(s, 9H), 3.39 (s, 6H), 3.42 (s, 6H), 3.58 (s, 6H), 3.87 (s, 6H), 4.46 (t, 2H,
J¼7.2 Hz), 4.52 (t, 2H, J¼7.2 Hz), 5.27 (s, 2H), 6.38 (s, 1H), 6.65
(s, 1H), 6.74 (s, 2H), 7.45 (m, 1H), 7.57 (d, 6H, J¼7.6 Hz), 7.69 (t, 1H,
J¼8.0 Hz), 7.89 (m, 2H), 8.12 (d, 6H, J¼7.6 Hz), 8.91 (m, 8H); 13C NMR
4.3.8. Porphyrin resorcin[4]arene conjugate (2cP1). meso-5-(3-
Hydroxyphenyl)-10,15,20-(4-toluyl)porphyrin (P1) (100 mg, 0.149
mmol) and K2CO3 (100 mg, 0.73 mmol) were dissolved in dry DMF
(5 mL) in a sealed tube and stirred for 15 min. Monobrominated
cavitand resorcin[4]arene, 2b,(150.3 mg, 0.149 mmol) was added to
this mixture, the tube sealed and stirred in an oil bath at 80d ꢂC for
one day. The DMF was evaporated off and the solid residue was
washed with water and dried. The crude produce is adsorbed on
silica and mounted on a silica column and eluted with chloroform.
The first band is collected, solvent removed and dried in a vacuum
decicator to get constant weight. Compound 2cP1 was obtained as
brownish red solid (183 mg, 77% yield). UVevis in CH2Cl2: lmax nm
(150 MHz, CDCl3) d: 9.1, 9.3, 13.0, 20.5, 21.8, 27.5, 30.9, 34.7, 34.7,
36.4, 36.4, 58.8, 58.9, 58.9, 60.7, 61.8, 113.0, 118.5, 122.1, 126.4, 126.9,
133.5, 136.3, 138.3, 142.7, 154.2, 154.8, 154.9, 155.6, 156.4.
4.3.11. Porphyrin Resorcin[4]arene conjugate (3cP1eZn(II)).
Compound 3cP1 (30 mg) was dissolved in chloroform (10 mL) and
zinc acetate (30 mg) in methanol(5 mL) was added. The mixturewas
refluxed until the UVevis spectrum showed no peak at 650 nm. The
solvent was then evaporated off and the crude product was purified
by column chromatography (silica gel, CH2Cl2. Compound 3cP1eZn
(II) was obtained as brownish red solid (28 mg, 92% yield). UVevis in
(
3
ꢀ10ꢁ5 Mꢁ1 cmꢁ1): 417 (3.64), 514 (0.134), 549 (0.057), 590 (0.032)
and 644 (0.032). FAB mass: [Mꢁ1]þ 1599.1; 1H NMR (400 MHz,
CH2Cl2: lmax nm (
3
ꢀ10ꢁ5 Mꢁ1 cmꢁ1): 419 (3.22), 550 (0.137) and 595
CDCl3)
d: ꢁ2.79 (s, 2H), 0.89 (t, 12H, J¼6.8 Hz), 1.34 (m, 32H), 1.87
(0.034); 1H NMR (400 MHz, CDCl3), 0.82 (m,12H),1.26 (m, 32H),1.86
(m, 8H), 2.07 (s, 6H), 2.16 (s, 3H), 2.73 (s, 9H), 3.38 (s, 6H), 3.40 (s, 6H),
3.58 (s, 6H), 3.87 (s, 6H), 4.46 (t, 2H, J¼7.2 Hz), 4.50 (t, 2H, J¼7.2 Hz),
5.27 (s, 2H), 6.36 (s, 1H), 6.61 (m, 1H), 6.75 (s, 2H), 7.45 (m, 1H), 7.57
(d, 6H, J¼7.2 Hz), 7.69 (t, 1H, J¼8.0 Hz), 7.89 (m, 2H), 8.12 (d, 6H,
(s, 6H), 1.92 (s, 3H), 2.21 (m, 8H), 2.71 (s, 9H), 4.32 (d, 2H, J¼7.2 Hz),
4.42 (d, 2H, J¼7.2 Hz), 4.73 (t, 2H, J¼8.0 Hz), 4.81 (t, 2H, J¼8.0 Hz),
5.21 (s, 2H), 5.76 (d, 2H, J¼6.8 Hz), 5.97 (d, 2H, J¼6.8 Hz), 6.93
(s, 1H), 6.97 (s, 2H), 7.24 (s, 1H), 7.33 (m, 1H), 7.56 (m, 6H), 7.68
(t, 1H, J¼8.0 Hz), 7.77 (t, 1H, J¼2.0 Hz), 7.91 (d, 1H, J¼7.6 Hz), 8.09
J¼7.6 Hz), 9.01 (m, 8H); 13C NMR (150 MHz, CDCl3)
d: 10.2, 10.3,14.1,
(d, 6H, J¼6.8 Hz), 8.86 (s, 8H); 13C NMR (150 MHz, CDCl3)
d: 10.4,
21.5, 22.8, 22.8, 28.5, 28.6, 28.9, 29.2, 29.6, 29.6, 29.7, 29.7, 35.7, 35.7,
37.4, 37.5, 59.9, 59.9, 60.0, 62.8, 113.9, 114.1, 115.9, 120.6, 121.2, 121.3,
121.8, 123.1, 123.4, 123.5, 123.6, 124.1, 127.3, 127.4, 127.5, 128.8, 131.8,
131.9,131.9,132.0,133.3,134.4,137.1,139.3,139.9,144.3,150.0,150.3,
150.3, 150.4, 155.2, 155.8, 155.9, 156.6, 157.3.
10.5, 14.1, 14.1, 14.1, 21.5, 22.7, 22.7, 27.9, 28.9, 29.0, 29.2, 29.4, 29.5,
29.6, 29.7, 29.7, 30.1, 30.3, 31.8, 31.9, 31.9, 33.8, 37.0, 37.1, 72.1, 98.6,
100.0, 100.3, 110.4, 114.1, 117.1, 122.0, 123.3, 124.1, 124.5, 127.6, 127.7,
127.8, 128.4, 132.9, 132.9, 134.5, 136.3, 137.6, 137.9, 137.9, 138.3,
138.5, 138.6, 139.3, 139.6, 142.7, 153.2, 153.4, 153.7, 153.9, 160.3.
Acknowledgements
4.3.9. Porphyrin
resorcin[4]arene
conjugate
(2cP1eZn(II)).
Compound 2cP1 (30 mg) was dissolved in chloroform (10 mL) and
zinc acetate (30 mg) in methanol (5 mL) was added. The mixture
was refluxed until the UVevis spectrum showed no peak at
650 nm. The solvent was then evaporated off and the crude product
was purified by column chromatography (silica gel, CH2Cl2. Com-
pound 2cP1eZn(II) was obtained as brownish red solid (27 mg,
Thefinancialsupportof theUniversityofKuwaitreceived through
research grant (SC09/09) and the facilities of GRF-Science (project
numbers GS01/01 and GS01/03) are gratefully acknowledged.
Supplementary data
90% yield). UVevis in CH2Cl2: lmax nm (
3
ꢀ10ꢁ5
M
ꢁ1 cmꢁ1): 418
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2011.02.024. These data in-
clude MOL files and InChIKeys of the most important compounds
described in this article.
(4.64), 546 (0.179) and 586 (0.039); 1H NMR (400 MHz, CDCl3)
d:
0.92 (t, 12H, J¼6.8 Hz), 1.36 (m, 32H), 1.91 (s, 6H), 1.96 (s, 3H), 2.26
(m, 8H), 2.75 (s, 9H), 4.35 (d, 2H, J¼7.2 Hz), 4.43 (d, 2H, J¼7.2 Hz),
4.74 (t, 2H, J¼8.0 Hz), 4.82 (t, 2H, J¼8.0 Hz), 5.22 (s, 2H), 5.79 (d, 2H,
J¼6.8 Hz), 5.98 (d, 2H, J¼7.2 Hz), 6.96 (s, 1H), 6.99 (s, 2H), 7.26
(s, 1H), 7.34 (m, 1H), 7.59 (m, 6H), 7.71 (t, 1H, J¼8.0 Hz), 7.82 (s, 1H),
7.95 (d, 1H, J¼7.6 Hz), 8.13 (m, 6H), 9.01 (s, 8H); 13C NMR (150 MHz,
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