Stacked porphyrin arrays from hydrogen-bonded porphyrin-resorcinol 1D chains

Article abstract of DOI:10.1246/bcsj.74.907

The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts 3?(methanol) and 3?1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O-H···O-H) polyresorcinol chains with the porphyri

Full text of DOI:10.1246/bcsj.74.907

c. Jpn.
© 2001 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 74, 907—916 (2001)
907
e Chemical
ciety of Ja-
n
e Chemical
ciety of Ja-
n
Stacked Porphyrin Arrays from Hydrogen-Bonded
Porphyrin–Resorcinol 1D Chains
Stacked Porphyrin Arrays
T. Tanaka et al.
Toshihiro Tanaka, Ken Endo, and Yasuhiro Aoyama*
01
7
6
Institute for Fundamental Research of Organic Chemistry, Kyushu University, CREST, Japan Science and Technology
Corporation (JST), Hakozaki, Higashi-ku, Fukuoka 812-8581
SJA8
09-2673
335
(Received September 27, 2000)
ptember
The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts
3•(methanol) and 3•1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O–H O–H) polyresorci-
nol chains with the porphyrin residues sticking out of the chains. The chains are self-assembled in such a manner as to
give closely stacked interchain porphyrin columns, while the guest molecules are either firmly bound to the hydrogen-
bonding sites (in the case of methanol) or incorporated in the channels running in parallel with the porphyrin stacks (in
the case of acetophenone). The formation of such a stacked porphyrin array is not observed when the guest is changed to
4-heptanone or when the porphyrin is changed to a sterically hindered one 4 or 5 with full substitution at the meso- or the
β-positions. The mode of interchain porphyrin stacking is discussed in light of the crystal structures of adducts 3•(4-hep-
tanone), 4•pyridine, and 5•(2-nonanone).
00
01
Manipulation of stacked aromatic columns1 may be an im-
portant step toward rational design of (photo)electronically po-
tential materials. Aromatic stacking is a frequently encoun-
tered motif arising from π-stacking and/or crystal packing
forces. On the other hand, columnar assemblies of aromatic
building blocks may also be induced through interactions of
peripheral substituents.2 We entered this field with an an-
thracenebisresorcinol derivative 1 as an orthogonal building
block.3 It forms a hydrogen-bonded (O–H O–H) 2D net-
work, thereby inducing a columnar alignment of the orthogo-
nal anthracene residues (Scheme 1). The interplanar distance
can be significantly shortened when a monoresorcinol ana-
logue 2 is used, since it forms 1D chains which come together
via a kind of self-clathration.4 An essential problem, however,
is that single-crystalline materials of hosts 1 and 2 are obtained
as lattice inclusion complexes, where the guest molecules (ke-
tones and esters) hydrogen-bonded to the host (O–H O–
of anthracene, would give a better chance of stacking.9 We re-
port here that a combination of a sterically unhindered porphy-
rin 3 and particular guests leads to closely packed interchain
porphyrin stack columns.
Results and Discussion
Preparation. Three types of porphyrin-monoresorcinol
derivatives were investigated. One, as a Ni(II) complex 3,10 is
a tetraalkylporphyrin having a methyl or ethyl substituent at
the β-positions of remote (with respect to the resorcinol moiety
at a meso-position) pyrrole rings, while those of near ones are
unsubstituted. Another is a tetraarylporphyrin 4, having extra
three phenyl substituents at the remaining meso-positions. The
third is an octaethylporphyrin 5 with exhaustive β-substitution.
The preparative routes to these porphyrins are shown in
Scheme 2. Crystallization of the Ni(II) complex 3 from meth-
anol, 4-heptanone, or acetophenone affords single crystals of
adduct 3•(methanol), 3•(4-heptanone), or 3•1.5(acetophe-
none), where the stoichiometries are based on 1H NMR analy-
sis. X-ray diffraction studies reveal that they all contain hydro-
gen-bonded (O–H O–H) 1D porphyrin arrays, whose pack-
ing modes are guest-dependent. The crystal data are summa-
rized in Table 1.
H
OꢀC) are inserted between the anthracene rings to pre-
vent the latter from forming a continuous stack column
(Scheme 1). The present work is concerned about porphyrin–
monoresorcinol derivatives 3–5 (Scheme 2); the bisresorcinol
analogue5 has been studied before.6–8 The porphyrin is (pho-
to)electronically potential and its size, as compared with that
Adduct 3•(Methanol). In the methanol adduct, the small
alcoholic guest acting as a hydrogen-bond donor as well as an
acceptor bridges the adjacent host–host O–H O–H sites to
form a cyclic array of hydrogen bonds, as schematically shown
in Scheme 3. The 1D chains are thereby rendered coordina-
tively saturated and undergo self-clathration of the porphyrin
residues to give a pseudo 2D sheet composed of closely packed
interchain porphyrin stack columns and methanol-strength-
ened hydrogen-bonded polyresorcinol chains (Scheme 3). The
actual crystal structure of the sheet is shown in Fig. 1 (front
view 1a with a column-to-column distance of lc ꢀ 21.4 Å; side
Scheme 1.

908 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Stacked Porphyrin Arrays
Scheme 2.
view 1b with a porphyrin–resorcinol dihedral angle of φ ꢀ
66˚). The adjacent porphyrin rings coming from neighboring
chains are lf ꢀ 3.5 Å face-to-face apart and hence almost in
contact with each other and their centers are l1 ꢀ 3.5 Å lateral-
ly slide-separated. The molecular sheets thus constructed are
layered in a staggered manner with an intersheet distance of ls
ꢀ 7.0 Å, as shown in the top view 1c and side view 1d of three
adjacent sheets.
Adduct 3•(4-Heptanone). In the 4-heptanone adduct, the
ketonic guest serves only as a hydrogen-bond acceptor and is

T. Tanaka et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 909
Table 1.
Crystallographic Data for Adducts 3•(methanol), 3•(4-heptanone), 3•1.5(acetophenone), 4•(pyridine), and
5•(2-nonanone)
3•(methanol)
3•(4-heptanone)
3•1.5(acetophenone)
4•(pyridine)
5•(2-nonanone)
Formula
F.W./g molꢁ1
Crystal size/mm
Crystal color
Crystal system
Space group
a/Å
C33H32N4NiO3
591.34
0.15ꢂ0.10ꢂ0.15
Reddish purple
Monoclinic
Cc
16.525(2)
21.385(1)
9.503(2)
122.439(9)
2834.2(7)
4
C39H42N4NiO3
673.49
0.20ꢂ0.20ꢂ0.20
Reddish purple
Monoclinic
P21/c
C44H40N4NiO3.5
739.52
0.20ꢂ0.20ꢂ0.20
Reddish purple
Monoclinic
Pa
C49H35N5O2
725.85
0.10ꢂ0.10ꢂ0.05 0.20ꢂ0.40ꢂ0.40
C51H68N4O3
785.12
Dark red
Monoclinic
P21/a
14.962(1)
8.685(1)
30.079(1)
100.889(6)
3838.1(6)
4
Reddish purple
Monoclinic
Cc
8.494(3)
50.443(4)
10.835(3)
92.36(2)
4638(1)
4
9.771(2)
12.467(4)
28.796(2)
91.37(1)
3506(1)
4
1.275
1424.00
Mo Kα
9.478(2)
20.209(1)
9.805(2)
109.90(1)
1765.9(5)
2
1.391
776.00
Mo Kα
b/Å
c/Å
β/˚
V/Å3
Z
dcalc/g cmꢁ3
F000
1.386
1240.00
Mo Kα
1.256
1520.00
Cu Kα
1.124
1704.00
Mo Kα
(λ ꢀ 0.71069 Å)
0.069
Radiation
(λ ꢀ 0.71069 Å)
0.726
(λ ꢀ 0.71069 Å)
0.596
(λ ꢀ 0.71069 Å)
0.599
(λ ꢀ 1.54178 Å)
0.616
µ/mmꢁ1
2θmax/˚
Scan mode
T/K
55.0
ω-2θ
295
55.0
ω-2θ
295
55.0
ω-2θ
295
120.1
ω-2θ
295
55.8
ω-2θ
295
No. reflns measured
No. unique reflns
3548
3354
7348
6945
4407
4178
6422
5956
5739
5406
(Rint ꢀ 0.037)
1704
355
0.050, 0.064
1.30
(Rint ꢀ 0.052)
2893
427
0.064, 0.088
1.31
(Rint ꢀ 0.022)
3378
416
0.047, 0.074
1.26
(Rint ꢀ 0.034)
2796
617
0.050, 0.066
1.29
(Rint ꢀ 1.325)
2692
459
0.088, 0.128
1.93
No. reflns used (I > 2σ(I))
No. parameters
b)
Ra), Rw
GOFc)
Final diff four. map
max 0.57,
min ꢁ0.31
max 0.65,
min ꢁ0.37
2
max 0.54,
min ꢁ0.48
max 0.37,
min ꢁ0.17
max 0.62,
min ꢁ0.32
(eꢁÅꢁ3
)
a) R ꢀ Σ||Fo| ꢁ |Fc||/Σ|Fo| b) Rw ꢀ [Σw(|Fo| ꢁ |Fc|)2/ΣwFo ]1/2 c) GOF ꢀ [Σw(|Fo| ꢁ |Fc|]2/(No, refs ꢁ No. params)]1/2
Scheme 4.
Scheme 3.
(Scheme 4 and Fig. 2 where lc ꢀ 17.2 Å, lf ꢀ 3.8 Å, l1 ꢀ 3.6
Å, ls ꢀ 8.2 Å, and φ ꢀ 80˚) follows this general trend.
bound as such to each host–host hydrogen-bond (O–H O–
H
OꢀC) with their alkyl chains partially stacked on the por-
Adduct 3•1.5(Acetophenone). The acetophenone adduct
has an unusual stoichiometry of 1:1.5, i.e., 3•1.5(acetophe-
none). It is also atypical in that the included guest molecules
are disordered in crystals. As in the case of the methanol ad-
duct, the porphyrin forms hydrogen-bonded 1D arrays which
come together to give tightly packed porphyrin columns with-
out intervention of the guests (Figs. 3a and 3b where lc ꢀ 20.2
Å, lf ꢀ 3.5 Å, l1 ꢀ 2.2 Å, and φ ꢀ 61˚). The molecular sheets
are layered (ls ꢀ 9.2 Å) in an eclipsed manner (top view 3c, as
opposed to staggered (1c) in case of the methanol adduct) to
phyrin rings. The chains are assembled in such a manner as to
give a stacked dimeric porphyrin unit and a pair of guest mole-
cules inserted in between the units (Scheme 4); there is no con-
tinuous stacked porphyrin column as a consequence. This is
what we call the dimeric lattice pattern for adducts of an-
thracenemonoresorcinol host 2 with relatively small guest mol-
ecules (Scheme 1).4 While larger guests tend to give the mo-
nomeric lattice pattern, all the inclusion compounds of hosts 2
and 1 so far obtained have their guests inserted in between the
parallel-aligned anthracene rings. The present crystal structure

910 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Stacked Porphyrin Arrays
Fig. 1.
Crystal structure of adduct 3•(methanol): front view (a) and side view (b) of a pseudo 2D sheet and top view (c) and side
view (d) of the arrangement of three adjacent sheets; φ is the porphyrin-resorcinol dihedral angle, lf and ll are the vertical face-to-
face and lateral center-to-center distances, respectively, for stacking porphyrin rings in a column, lc is the intercolumn distance,
and ls is the intersheet distance. The porphyrin rings, resorcinol moiety, other peripheral substituents, guest molecules, and hydro-
gen bonds are shown in red, black, yellow, green, and blue, respectively.
give large channels, in which disordered guest molecules (ace-
tophenone) are included.11 Such a packing mode of the sheets
has never been noted before for the adducts of hosts 1 and 2.3,4
As far as NMR-determined host-guest stoichiometries are
concerned, many ketones such as acetone, 2-butanone, 2-pen-
tanone, 3-pentanone, 3-hexanone, 2-heptanone, and 2-
nonanone as guests behave similarly to 4-heptanone, giving
rise to 1:1 adducts with host 3. Propiophenone and isobuty-
rophenone as higher homologues of acetophenone also exhibit
a 1:1 stoichiometry. As for esters, ethyl acetate affords a 1:1
adduct, while methyl benzoate apparently gives a 1:0.5 ad-
duct. Higher-alkyl homologues, i.e., ethyl, isopropyl, isobutyl,
and butyl benzoates, are not included. While many of the ad-
ducts thus obtained unfortunately lack sufficient single crystal-
linity to allow crystal structure determination, a survey of vari-
ous guests suggests that the acetophenone adduct represents an
exceptional case, whose unique crystal structure is a conse-
quence of a delicate balance of a number of energy terms asso-
ciated with porphyrin π-stacking,8 host-guest hydrogen-bond-
ing, and generation of channels and packing of guests therein.
Adducts 4•(Pyridine) and 5•(2-Nonanone). The charac-
teristic crystal structures of the three adducts of porphyrin 3
are commonly based on antiparallel stacking of the porphyrin
rings from neighboring chains. This geometrical arrangement
brings the β-positions and the meso-positions of stacking por-
phyrin rings into close proximity, especially the remote (with
respect to the resorcinol moiety) β’s of one porphyrin and the
near β’s of the other come in contact. Intolerable steric repul-
sion associated therewith could be avoided in case of porphy-
rin 3, which has neither extra meso-phenyl substituent nor near
β-substituent. In order to shed light on this point, the crystal
packing modes of the sterically hindered porphyrins 4 and 5
were also studied.
Single crystals of tetraarylporphyrin 4 were obtained as a
1:1 pyridine adduct 4•(pyridine). Here too, there are hydro-
gen-bonded 1D arrays with pyridine molecules hydrogen-
bonded to them (O–H O–H N) (Scheme 5, a–c). The
chains are assembled not laterally as above but in the front-to-
rear direction (b → d and c → e). The inter-porphyrin voids
along a chain are thereby occupied by the north and south
meso-phenyl groups of the porphyrin residues of the front and
rear chains, respectively, to form a pseudo 2D sheet of a bimo-
lecular thickness, as schematically shown in Scheme 5. There
is no interchain porphyrin stack or overlap. The actual crystal
structure in reference to Scheme 5 is shown in Fig. 4 (lc ꢀ 7.5
Å, lf ꢀ 8.5 Å, and φ ꢀ 64˚).
Octaethylporphyrin derivative 5 forms a 1:1 adduct with 2-
nonanone. The guest molecules are attached to the hydrogen-
bonded chain (O–H O–H OꢀC) with their long alkyl tails
stacked on the porphyrin rings. The chains undergo a front-to-
rear alignment as above (Scheme 5), where the peripheral ethyl
groups at the north and south β-positions act as guests to fill
the inter-porphyrin voids in collaboration with the guest mole-
cules. The crystal structure is shown in Fig. 5 (lc ꢀ 6.6 Å, lf ꢀ
13.8 Å, and φ ꢀ 80˚).
Both crystal structures exhibit a kind of self-clathration by

T. Tanaka et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 911
Fig. 2.
Crystal structure of adduct 3•(4-heptanone): front view (a) and side view (b) of a pseudo 2D sheet and top view (c) and
side view (d) of the arrangement of three adjacent sheets. The angle and distances and different colors have the same meanings as
in Fig. 1.
Conclusions
In view of applications of the monoresorcinol strategy to the
porphyrin compounds, the present work may be summarized
as follows. (1) All the porphyrin–resorcinol derivatives inves-
tigated here form hydrogen-bonded polyresorcinol chains with
included guest molecules attached thereto. The porphyrin resi-
dues sticking out of the chains form interplanar (inter-porphy-
rin) voids which are filled via assembly of the chains in various
ways. (2) The voids are filled by peripheral substituents as a
kind of guests when the porphyrin (4 or 5) has such substitu-
ents at all the meso-positions or all the β-positions. In this
case, there is no porphyrin stack in the crystals. (3) Sterically
unhindered porphyrin 3, having neither extra meso- nor near β-
substituents, allows the chains to come close enough to give
interchain porphyrin stacks with intervention of the guest mol-
ecules. (4) In the particular two cases of methanol and ace-
Scheme 5.
tophenone as guest, interchain stacking of the porphyrin rings
leads to closely packed columns without interference of the
the peripheral substituents, although rigorous comparison with
unhindered porphyrin 3 is by no means allowed because of the
difference in coordination states (3 as a Ni(II) complex and 4
and 5 as free bases) and that in guest molecules.
guests, the latter being either bound in case of methanol to the
hydrogen-bonded chains or accomodated in case of acetophe-
none in the channels running along the porphyrin stacks. (5)
Thus, the self-assembly of hydrogen-bonded chains is still un-

912 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Stacked Porphyrin Arrays
Fig. 3.
Crystal structure of adduct 3•1.5(acetophenone): front view (a) and side view (b) of a pseudo 2D sheet and top view (c)
and side view (d) of the arrangement of three adjacent sheets. The angle and distances and different colors have the same mean-
ings as in Fig. 1. Disordeed guest molecules incorporated in the channels are not shown.
1.3 mmol) under nitrogen.16 The mixture was stirred for 15 min at
predictably guest-dependent. Choice of shorter bridging units
room temperature, diluted with CH2Cl2 (300 mL), washed succes-
sively with a saturated aqueous NaHCO3 solution and water, and
then dried over Na2SO4. The solvent was removed in vacuo and
unreacted pyrrole was distilled off at room temperature. The re-
sulting brown oil was dissolved in a minimal amount of the eluant
and was purified by flash chromatography with a mixture of cyclo-
hexane, ethyl acetate, and triethylamine (80:20:1) as an eluant to
other than the resorcinol would allow a better chance of por-
phyrin stacking. Inclusion of redox-active guest molecules
such as quinones may also be an interesting extension of this
study. Further work is now under way along this line to shed
light on the dynamics of photo-excited and charge-separated
states of induced porphyrin arrays in crystals.
1
give dipyrromethane 6 (3.17 g, 11.2 mmol, 84% yield): H NMR
Experimental
(CDCl3) δ 3.75 (s, 6 H, OCH3), 5.38 (s, 1 H, meso-H), 5.95 (m, 2
H, pyrrolic-H), 6.19 (dd, 2 H, pyrrolic-H), 6.35 (t, 1 H, J ꢀ 2.2
Hz, dimethoxyphenyl-H), 6.38 (d, 2 H, J ꢀ 2.2 Hz, dimetoxyphe-
nyl-H), 6.66 (dd, 2 H, pyrrolic-H) , 7.92 (bs, 2 H, NH).
General Procedures and Host–Guest Stoichiometries.
Dichloromethane and methanol were distilled from calcium hy-
dride and magnesium, respectively. Analytical TLC was per-
formed on silica gel 60 F254 plates (Merck). Wakogel C-200 was
used for column chromatography. 1H NMR spectra at 400 MHz
were recorded on a Bruker DPX 400 or a JEOL JNM-EX 400
spectrometer. Melting points were measured with a Yanako MP-
500D apparatus. Microanalyses were performed at the microanal-
ysis center of Kyushu University. The host-guest stoichiometries
of all the adducts obtained upon crystallization were determined
by 1H NMR integration after dissolving them in DMSO-d6.
General Preparations. Porphyrins 3, 4, and 5 were ob-
tained according to the general procedures involving [2 ꢃ 2]
dipyrrole–dipyrrole coupling12 (aryl-substituted dipyrromethane-
dicarboxaldehyde13 ꢃ dipyrromethanedicarboxylic acid), [1 ꢃ 1
ꢃ 1 ꢃ 1] pyrrole cyclooligomerization14 (substituted and unsub-
stituted arenecarboxaldehyde ꢃ pyrrole), and [4 ꢃ 0] tetrapyrrole
cyclization15 (arenecarboxyaldehyde ꢃ biladiene), respectively, as
key steps.
′
5,5 -Diformyl-meso-(3,5-dimethoxyphenyl)dipyrromethane
(7). Into a solution of compound 6 (2.53 g, 8.97 mmol) in a mix-
ture of diethyl ether (50 mL) and DMF (3.7 mL, 47 mmol) was
slowly added phosphoryl chloride (2.5 mL, 27 mmol) at ꢁ15 ˚C.17
The mixture was further stirred at room temperature for 30 min,
evaporated, and poured onto ice water (15 mL). Addition of an
aqueous 2 M-NaOH solution (50 mL) caused precipitates, which
were collected by filtration and washed with water and then with
ethanol to give dialdehyde 7 as a pale yellow solid (1.95 g, 5.77
mmol, 64% yield): 1H NMR (CDCl3) δ 3.75 (s, 6 H, OCH3), 5.43
(s, 1 H, meso-H), 6.10 (m, 2 H, pyrrolic-H), 6.38 (t, 1 H, J ꢀ 2.2
Hz, dimethoxyphenyl-H), 6.45 (d, 2 H, J ꢀ 2.2 Hz, dimethox-
yphenyl-H), 6.87 (dd, 2 H, J ꢀ 3.8 and 0.6 Hz, pyrrolic-H), 9.23
(s, 2 H, CHO), 10.28 (bs, 2 H, NH).
5-(3,5-Dimethoxyphenyl)-13,17-diethyl-12,18-dimethylpor-
phyrin (8). Trifluoroacetic acid (0.080 mL, 1.1 mmol) was add-
ed to a solution of 3,3′-diethyl-4,4′-dimethyldipyrromethane-5,5′-
dicarboxylic acid18 (113 mg, 0.355 mmol) and diformyldipyr-
romethane 7 (120 mg, 0.355 mmol) in CH2Cl2 (120 mL) under ni-
α
-(3,5-Dimethoxyphenyl)dipyrromethane (6). To
a solu-
tion of 3,5-dimethoxybenzaldehyde (2.21 g, 13.3 mmol) and pyr-
role (25 mL, 0.36 mol) was added trifluoroacetic acid (0.10 mL,

T. Tanaka et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 913
Fig. 4. Crystal structure of adduct 4•(pyridine) in reference to the schematic representation in Scheme 5: front view (a), side view
(b), and top view (c) of a hydrogen-bonded 1D chain and the front-to-rear arrangement of three neighboring chains to form a pseu-
do 2D sheet (d and e); φ is the porphyrin-resorcinol dihedral angle, lf is the face-to-face distance for adjacent porphyrin rings in a
porphyrin column or ladder along a chain, and lc is the intercolumn or interladder distance in a sheet. Different colors have the
same meanings as in Fig. 1, the peripheral phenyl substituents at the north and south meso-positions and the west meso-position
being shown in yellow and orange, respetively, just for the sake of distinction. A set of porphyrin and guest molecules oriented in
the same direction along a chain are shown in space-filling models to illustrate that the inter-porphyrin voids along a chain are oc-
cupied by the phenyl substituents of the porphyrin building blocks in the neighboring chains.
trogen and the mixture was stirred at room temperature for 9 h. p-
Chloranil (15 mg, 0.061 mmol) was added and the mixture was re-
fluxed under stirring for 1 h, treated with triethylamine (0.80 mL,
5.8 mmol), and evaporated. The residue was chromatographed
with CHCl3 as an eluant. The main porphyrin fraction obtained
was successively washed with aqueous Na2CO3–Na2S2O4, water,
and saturated aqueous NaCl. The organic layer was evaporated
and the residue washed with methanol to give porphyrin 8 as pur-
ple powder (140 mg, 0.264 mmol, 74% yield): mp > 300 ˚C (dec);
TLC Rf ꢀ 0.64 (CHCl3); UV-vis (CH2Cl2) λmax (ε) 403 (132000),
500 (8250), 532 (2100), 569 (3120), 622 nm (571); 1H NMR
(CDCl3) δ ꢁ3.40 (bs, 2 H, NH), 1.90 (t, 6 H, CH2CH3), 3.63 (s, 6
H, CH3), 3.99 (s, 6 H, OCH3), 4.09 (q, 4 H, CH2CH3), 6.92 (t, 1 H,
J ꢀ 2.3 Hz, dimethoxyphenyl-H), 7.45 (d, 2 H, J ꢀ 2.3 Hz,
dimethoxyphenyl-H), 9.12 (d, 2 H, J ꢀ 4.5 Hz, β-H), 9.31 (d, 2 H,
J ꢀ 4.5 Hz, β-H), 10.03 (s, 1 H, meso-H), 10.16 (s, 1 H, meso-H).
Found: C, 76.46; H, 6.48; N, 10.50%. Calcd for C34H34N4O2: C,
76.95; H, 6.45; N, 10.56%.
5-(3,5-Dihydroxyphenyl)-13,17-diethyl-12,18-dimethylpor-
phyrin (9). Into a CH2Cl2 solution (250 mL) of the dimethoxy
derivative 8 (827 mg, 1.56 mmol) was added dropwise a CH2Cl2
solution (20 mL) of BBr3 (4.5 g, 18 mmol) at 0 ˚C in the period of
30 min.19 The mixture was stirred for 9 h at room temperature,
poured onto a saturated aqueous NaHCO3 solution, and extracted
with ethyl acteate. The extracts were combined, washed with sat-
urated aqueous NaCl, dried on Na2SO4, and evaporated. The resi-
due was chromatographed. The crude porphyrin product eluted
with ethyl acetate was recrystallized from hexane/ethyl acetate
and dried at 180 ˚C in vacuo to give the dihydroxy derivative 9
(462 mg, 0.92 mmol, 58% yield) as purple powder: mp > 250 ˚C
(dec); TLC Rf ꢀ 0.51 (9:1 CHCl3/methanol); UV-vis (ethyl ace-
tate) λmax (ε) 401 (128000), 498 (7240), 528 (1750), 570 (2640),
624 nm (536); 1H NMR (DMSO-d6) δ ꢁ3.8 (bs, 2 H, NH), 1.82 (t,
6 H, CH2CH3), 3.60 (s, 6 H, CH3), 4.09 (q, 4 H, CH2CH3), 6.69 (t,
1 H, J ꢀ 2.1 Hz, dihydroxyphenyl-H), 7.90 (d, 2 H, J ꢀ 2.1 Hz,
dihydroxyphenyl-H), 9.08 (d, 2 H, J ꢀ 4.5 Hz, β-H), 9.54 (d, 2 H,
J ꢀ 4.5 Hz, β-H), 9.75 (bs, 2 H, OH), 10.12 (s, 1 H, meso-H),
10.42 (s, 2 H, meso-H). Found: C, 76.10; H, 5.78; N, 10.98%.
Calcd for C32H30N4O2: C, 76.47; H, 6.01; N, 11.15%.
5-(3,5-Dihydroxyphenyl)-13,17-diethyl-12,18-dimethylpor-
phyrinatonickel(II) (3) and its Adducts.
A mixture of free
base porphyrin 9 (462 mg, 0.92 mmol) and [Ni(CH3COO)2]-
(4H2O) (332 mg, 1.33 mmol) in DMF (100 mL) was stirred at 120
˚C for 2 h, allowed to cool to room temperature, poured onto ice
water (100 mL), and extracted with ethyl acetate (100 mL).20 The
extract was washed with water and evaporated. The crude product
was purified by means of column chromatography (9:1 CHCl3/
methanol) and recrystallization from hexane/ethyl acetate; the sol-
vent was removed at 150 ˚C in vacuo to give the nickel complex 3
(392 mg, 0.70 mmol, 76% yield) as reddish purple powder: mp >
250 ˚C (dec); TLC Rf ꢀ 0.43 (9:1 CHCl3/methanol); UV-vis (eth-
yl acetate) λmax (ε) 393 (198000), 513 (117000), 546 (17600); 1H
NMR (CDCl3) δ 1.96 (t, 6 H, CH2CH3) , 3.63 (s, 6 H, CH3) , 4.01
(q, 4 H, CH2CH3), 5.24 (s, 2 H, OH), 6.83 (t, 1 H, J ꢀ 2.1 Hz, di-

914 Bull. Chem. Soc. Jpn., 74, No. 5 (2001)
Stacked Porphyrin Arrays
Fig. 5. Crystal structure of adduct 5•(2-nonanone) in reference to Scheme 5, where porphyrin 4 and guest pyridine should read as
5 and 2-nonanone, respectively, and the two yellow and one orange circles for the three phenyl substitunets at the meso-positions
should stand for the eight ethyl substituents at the β-positions. Otherwise, the definitions are the same as in Fig. 4.
hydroxyphenyl-H), 7.22 (d, 2 H, J ꢀ 2.1 Hz, dihydroxyphenyl-H),
9.15 (d, 2 H, J ꢀ 4.6 Hz, β-H), 9.29 (d, 2 H, J ꢀ 4.6 Hz, β-H),
9.92 (s, 1 H, meso-H), 9.99 (s, 2 H, meso-H). Found: C, 68.62; H,
5.17; N, 9.95%. Calcd for C32H28N4NiO2: C, 68.72; H, 5.05; N,
10.02%.
Slow diffusion of gaseous hexane into a solution of porphyrin 3
in an appropriate guest liquid afforded the corresponding adduct.
The methanol adduct 3•(methanol). Found: C, 67.42; H, 5.56; N,
9.78%. Calcd for C33H32N4NiO3: C, 67.03; H, 5.45; N, 9.47%.
The 4-heptanone adduct 3•(4-heptanone). Found: C, 69.56; H,
6.25; N, 8.29%. Calcd for C39H42N4NiO3: C, 69.55; H, 6.29; N,
8.32%. The acetophenone adduct 3•1.5(acetophenone). Found:
C, 71.06; H, 5.68; N, 7.48%. Calcd for C44H40N4NiO3.5: C, 71.46;
H, 5.45; N, 7.58%.
5-(3,5-Dimethoxyphenyl)-10,15,20-triphenylporphyrin (10).
A solution of 3,5-dimethoxybenzaldehyde (830 mg, 5.0 mmol),
benzaldehyde (1.62 g, 15 mmol), and pyrrole (1.34 g, 20 mmol) in
CH2Cl2 (2 L) containing diethyl ether–boron trifluoride (1/1) (0.83
mL, 6.7 mmol) was stirred at room temperature for 1.5 h under ni-
trogen. p-Chloranil (3.94 g, 16.0 mmol) was added and the mix-
ture was stirred under reflux for 1 h and evaporated. The residue
was purified by means of chromatography (1:1 CH2Cl2/hexane).
The second porphyrin fraction out of four was washed successive-
ly with aqueous Na2CO3–Na2S2O4, aqueous NaHCO3, water, and
saturated aqueous NaCl. The organic layer was evaporated and
the residue washed with methanol to give the dimethoxy porphy-
rin derivative 10 (373 mg, 0.55 mmol, 11% yield): mp > 300 ˚C;
TLC Rf ꢀ 0.44 (1:1 CH2Cl2/hexane): UV-vis (CH2Cl2) λmax (ε)
418 (464000), 514 (18700), 549 (6760), 590 (5300), 645 nm
(3490); 1H NMR (CDCl3) δ ꢁ2.78 (s, 2 H, NH), 3.96 (s, 6 H,
OCH3) , 6.90 (t, 1 H, J ꢀ 2.4 Hz, dimethoxyphenyl-H) , 7.77 (d, 2
H, J ꢀ 2.4 Hz, dimethoxyphenyl-H), 7.65–7.85 (m, 9 H, phenyl-
H), 8.10–8.30 (m, 6 H, phenyl-H), 8.83 (s, 6 H, β-H), 8.95 (s, 2 H,
β-H). Found: C, 81.80; H, 5.13; N, 8.28%. Calcd for
C46H39N4O2: C, 81.88; H, 5.08; N, 8.30%.
5-(3,5-Dihydroxyphenyl)-10,15,20-triphenylporphyrin (4)
and its Adduct. Into a solution of the dimethoxy derivative 10
(1.65 g, 2.44 mmol) in CH2Cl2 (400 mL) was added BBr3 (10 g,
40 mmol) at 0 ˚C over a period of 30 min.19 The mixture was
stirred for 17 h at room temperature, poured onto saturated aque-
ous NaHCO3 (500 mL), and extracted with ethyl acetate (2 ꢂ 300
mL). The extracts were combined, washed with saturated aqueous
NaCl (300 mL), dried over Na2SO4, and evaporated. The usual
workup procedure involving chromatography (CHCl3/ethyl ace-
tate), recrystallization from hexane/ethyl acteate, and solvent re-
moval at 150 ˚C in vacuo gave the dihydroxy derivative 4 (1.38 g,
2.13 mmol, 87% yield) as violet powder: mp > 300 ˚C; TLC Rf ꢀ
0.55 (9:1 CHCl3/methanol); UV-vis (ethyl acetate) λmax (ε) 415
(550000), 512 (21200), 547 (8190), 589 (5920), 645 nm (3840);
1H NMR (DMSO-d6) δ ꢁ2.96 (s, 2 H, NH), 6.67 (t, 1 H, J ꢀ 2.0
Hz, dihydroxyphenyl-H), 7.05 (d, 2 H, J ꢀ 2.0 Hz, dihydroxyphe-
nyl-H), 7.75–7.90 (m, 9 H, phenyl-H), 8.15–8.30 (m, 6 H, phenyl-

T. Tanaka et al.
Bull. Chem. Soc. Jpn., 74, No. 5 (2001) 915
H), 8.81 (s, 6 H, β-H), 8.98 (s, 2 H, β-H), 9.70 (s, 2 H, OH).
Found: C, 81.59; H, 4.70; N, 8.55%. Calcd for C44H30N4O2: C,
81.71; H, 4.68; N, 8.66%.
Slow diffusion of gaseous hexane into a pyridine solution of
porphyrin 4 afforded adduct 4•(pyridine). Found: C, 80.84; H,
5.01; N, 9.71%. Calcd for C49H35N5O2: C, 81.08; H, 4.86; N,
9.65%.
N, 7.13%. Calcd for C51H68N4O3: C, 78.02; H, 8.73; N, 7.14%.
X-Ray Crystal Structure Determinations. A selected sin-
gle crystal was mounted on a glass fiber. Diffraction data were
collected on a Rigaku AFC7R four-circle automated diffractome-
ter with graphite-monochromated Mo Kα or Cu Kα radiation.
The unit cell parameters used for refinement were determined by
least-squares calculations on the setting angles of 25 reflections in
the range of 2θ ꢀ 28.0–29.9, 28.0–29.6, 29.7–30.0, 45.1–56.4,
and 29.7-30.4˚ for adducts 3•(methanol), 3•(4-heptanone),
3•1.5(acetophenone), 4•(pyridine), and 5•(2-nonanone), respec-
tively. Reflection data were corrected for both Lorentz and polar-
ization effects, while no absorption correction was applied. The
structures were solved by the direct methods with the programs
SIR92 and the Fourier techniques DIRDIF94. Some nonhydrogen
atoms were refined anisotropically, while the rest were refined iso-
tropically. Some hydrogen atoms were located by differential
Fourier calculations and their positions refined isotropically. The
remaining hydrogen atoms were located on the calculated posi-
tions and were treated as riding atoms with a distance of 0.95 Å
and Uiso(H) ꢀ 1.2Ueq of attached atom. Refinements were carried
out by a full-matrix least squares method based on F. The weight-
2,3,7,8,12,13,17,18-Octaethylbiladiene-ac Dihydrobromide
(11). A mixture of 3,3′,4,4′-tetraethyldipyrromethane-5,5′-dicar-
boxylic acid21 (1.80 g, 5.20 mmol) and 3,4-diethylpyrrole-2-
carboxyaldehyde22,23 (1.42 g, 9.38 mmol) in methanol (90 mL)
was warmed to give a solution.24 Hydrobromic acid (47% in wa-
ter, 7 mL) was added and the solution was allowed to cool to room
temperature and then kept at 0 ˚C for 1 h. The crystalline product
which separated was collected, washed with methanol containing
a small amount of hydrobromic acid and then with ether, and dried
to give biladiene dihydrobromide 11 (2.32 g, 3.37 mmol, 72%
1
yield) as brown powder: H NMR (DMSO-d6) δ 1.00–1.35 (a set
of t, 24 H, CH3), 2.49–2.85 (a set of q, 16 H, CH2), 5.63 (s, 2 H,
CH2), 6.75 (s, 2 H, CꢀCH), 7.25 (s, 2 H, ꢃ NꢀH), 10.3 and 10.75
(both s, both 2 H, ꢃ NH and NH).
2
5-(3,5-Dimethoxyphenyl)-2,3,7,8,12,13,17,18-octaethylpor-
phyrin (12). A suspension of salt 11 (2.32 g, 3.37 mmol) in
methanol (450 mL) containing 3,5-dimethoxybenzaldehyde (3.42
g, 20.6 mmol) and a 30% HBr solution in acetic acid (3 mL) was
heated under reflux for 48 h. The mixture was cooled and treated
with an excess amount of Na2CO3. The precipitates which sepa-
rated were collected, washed with water and methanol, dried, and
recrystallized from CH2Cl2/methanol to give the dimethoxy por-
phyrin derivative 12 (985 mg, 1.47 mmol, 44% yield) as purple
prisms: mp 257–258 ˚C, TLC Rf ꢀ 0.81 (CH2Cl2): UV-vis (ethyl
acetate) λmax (ε) 401 (195000), 501 (16100), 532 (7470), 572
(6390), 626 nm (3190); 1H NMR (CDCl3) δ ꢁ3.17 (s, 1 H, NH),
ꢁ3.04 (s, 1 H, NH), 1.29 (t, 6 H, CH3), 1.86–1.94 (a set of t, 18 H,
CH3), 2.93 (q, 4 H, CH2), 3.94 (s, 6 H, OCH3), 4.02–4.13 (a set of
q, 12 H, CH2), 6.93 (t, 1 H, J ꢀ 2.0 Hz, dimethoxyphenyl-H), 7.41
(d, 2 H, J ꢀ 2.0 Hz, dimethoxyphenyl-H), 9.93 (s, 1 H, meso-H),
10.18 (s, 2 H, meso-H). Found: C, 78.52; H, 8.06; N, 8.23%. Cal-
cd for C44H54N4O2: C, 78.77; H, 8.11; N, 8.35%.
ing scheme was w ꢀ 1/[σc2(Fo) ꢃ 0.00090Fo ] for 3•(methanol),
2
w ꢀ 1/[σc2(Fo) ꢃ 0.0025Fo ] for 3•(4-heptanone) and 3•1.5(ace-
2
tophenone), w ꢀ 1/[σc2(Fo ꢃ 0.0012Fo ] for 4•(pyridine), and w
2
ꢀ 1/[σc2(Fo) ꢃ 0.0030Fo ] for 5•(2-nonanone). Atomic scattering
factors and anomalous dispersion terms were taken from Interna-
tional Tables for X-Ray Crystallography.25 Calculations were per-
formed on an INDY workstation with the teXsan crystallographic
software package from Molecular Structure Corporation. The
crystal structures were visualized with the Cerius 2 set of comput-
er programs of Molecular Simulations Incorporated.
Crystallographic data have been deposited at the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK and copies can be ob-
tained on request, free of charge, by quoting the publication cita-
tion and the depositon numbers 157852–157856. The detail of
structures have been deposited as Document No. 74029 at Office
of the Editor of Bull. Chem. Soc. Jpn.
This work was supported by CREST (Core Research for
Evolutional Science and Technology) from Japan Science and
Technolopgy Corp. and also by a grant-in-aid for COE Re-
search (no. 08CE2005) from the Ministry of Education, Sci-
ence, Sports and Culture.
5-(3,5-Dihydroxyphenyl)-2,3,7,8,12,13,17,18-octaethylpor-
phyrin (5) and its Adduct. Into a CH2Cl2 solution (250 mL) of
the dimethoxy derivative 12 (985 mg, 1.47 mmol) was added
dropwise a CH2Cl2 solution (20 mL) of BBr3 (2.5 g, 10 mmol) at 0
˚C over a period of 30 min.19 The mixture was stirred for 12 h at
room temperature, poured onto saturated aqueous NaHCO3, and
extracted with ethyl acetate. The extract was washed with water
and saturated aqueous NaCl, dried over Na2SO4, and evaporated.
Workup with chromatography (CHCl3/ethyl acetate), recrystalli-
zation from hexane/ethyl acetate, and solvent removal at 180 ˚C in
vacuo gave the dihydroxy derivative 5 (809 mg, 1.26 mmol, 86%
yield) as purple powder: mp > 250 ˚C (dec); TLC Rf 0.56 (9:1
CHCl3/methanol); UV-vis (ethyl acetate) λmax (ε) 402 (187000),
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