Mendeleev
Communications
Mendeleev Commun., 2012, 22, 278–280
Synthesis and liquid-crystal properties of new amphiphilic long-chain
derivatives of meso-arylporphyrins with terminal polar groups
Kirill A. Formirovsky,*a Natalya A. Bragina,a Andrey F. Mironov,a
Galina A. Anan’eva,b Venera V. Bykovab and Nadezhda V. Usol’tsevab
a M. V. Lomonosov Moscow State University of Fine Chemical Technology, 119571 Moscow, Russian Federation.
b Research Institute of Nanomaterials, Ivanovo State University, 153025 Ivanovo, Russian Federation.
Fax: +7 4932 32 4677; e-mail: nv_usoltseva@mail.ru
DOI: 10.1016/j.mencom.2012.09.018
New amphiphilic alkoxyarylporphyrins with long-chain substituents bearing carboxy, methoxycarbonyl and hydroxy groups, and their
metal complexes, were synthesized. Those of them having mesogenic properties were identified by optical polarisation microscopy,
and their liquid-crystal properties were studied.
Synthesis of analogues of natural tetrapyrrole compounds and
design of new functional structures based on these compounds
by means of self-assembly and self-organization of molecules are
currently a field of intense studies.1,2 The amphiphilic structure
of molecules is the determining factor in the self-assembly of
supramolecular ensembles driven by noncovalent interactions.1,3
Of particular interest in this respect are meso-arylporphyrins
containing both hydrophobic substituents that favour surface
immobilisation of molecules and give them mesogenic properties,4
and polar groups that can be subjected to various chemical trans-
formations and used as sites for binding with various ligands,
including nanoparticles.5 Polar hydroxy and carboxy groups in
which hydrogen bonds act as the driving force are used most
commonly for this purpose.1,3,6 The liquid-crystal state is also
considered as a method for the structural self-organisation of
molecules,1 and porphyrin liquid-crystal ensembles are promising
compounds for optoelectronics and for creating data display and
storage devices.7–9
Previously, we have synthesized amphiphilic cationic 5,10,15,20-
tetra-meso-aryl-substituted porphyrins bearing long-chain sub-
stituents with terminal pyridinium groups.10 These compounds
and their metal complexes possessed thermotropic mesomorphism,
whereas the length of the aliphatic spacer and the metal nature
affected considerably their liquid-crystal properties.
Herein, we studied new structural analogues, namely, amphi-
philic meso-aryl-substituted porphyrins with terminal carboxy,
methoxycarbonyl and hydroxy groups, as well as their metal
complexes (Scheme 1).
Alkaline hydrolysis in a two-phase aqueous–organic system
quantitatively gave amphiphilic porphyrins 3a,b with terminal
carboxy groups. Reduction of terminal methoxycarbonyl groups
in intermediates 2a,b with lithium aluminium hydride afforded
alcohol porphyrins 4a,b.‡ Complexes with zinc, cobalt and copper
5,10,15,20-Tetrakis[4-(5-methoxycarbonylpentyloxy)phenyl]porphyrin
2a: yield 0.14 g (31%). Rf 0.9 (CH2Cl2). UV [lmax/nm (e×10–3)]: 419.5
(365), 515.8 (14.3), 554.8 (6.3), 589.6 (4.89), 649.2 (3). 1H NMR, d: –2.81
(s, 2H, NH), 1.63 [m, 8H, O(CH2)3], 1.78 [m, 8H, O(CH2)4COOMe],
1.95 (m, 8H, OCH2CH2), 2.37 (t, 8H, CH2COOMe, J 7 Hz), 2.47 (t, 8H,
OCH2, J 7 Hz), 3.67 (s, 12H, COOMe), 7.21 (d, 4H, HAr, J 7 Hz), 8.18
(d, 4H, HAr, J 7 Hz), 8.82 (s, 8H, pyrrole). MS, m/z: 1193 [M+ +1].
5,10,15,20-Tetrakis[4-(10-methoxycarbonyldecyloxy)phenyl]porphyrin
2b: yield 0.19 g (34%). Rf 0.9 (CH2Cl2). UV [lmax/nm (e×10–3)]: 421.5
(360), 518.6 (15), 556.2 (6.2), 592 (4.49), 650.4 (3.1). 1H NMR, d: –2.72
(s, 2H, NH), 1.31 [br.m, 40H, (CH2)5], 1.60 [m, 8H, O(CH2)8], 1.93 [m,
8H, (CH2)7COOMe], 2.01 [m, 8H, O(CH2)8], 2.75 (t, 8H, CH2COOMe,
J 7 Hz), 3.91 (s, 12H, COOMe), 4.27 [t, 8H, O(CH2)8, J 7 Hz], 7.46
(d, 8H, HAr, J 2.6 Hz), 8.22 (d, 8H, HAr, J 3.5 Hz), 8.9 (s, 8H, pyrrole).
MS, m/z: 1473 [M+ +1].
‡
General procedure for the preparation of porphyrins 3a,b. Aqueous
sodium hydroxide (50%, 7 ml) was added to a solution of ester porphyrin
2a,b (90 mg) in THF (10 ml). The reaction mixture was stirred for 16 h
at 60°C, acidified with conc. HCl until the product was completely
transferred to the organic phase, and washed with water. The organic
phase was dried with anhydrous Na2SO4 and concentrated in vacuo. The
product was recrystallised from diethyl ether. Rf 0.2 (CH2Cl2–MeOH, 9:1).
5,10,15,20-Tetrakis[4-(5-carboxypentyloxy)phenyl]porphyrin 3a: yield
1
75 mg (87%). H NMR, d: –2.81 (s, 2H, NH), 1.61 [m, 8H, O(CH2)3],
1.76 [m, 8H, O(CH2)4COOH, J 7 Hz], 1.95 (m, 8H, OCH2CH2, J 7 Hz),
2.39 [t, 8H, O(CH2)4COOMe], 4.16 (t, 8H, OCH2, J 7 Hz), 7.18 (d, 8H,
HAr, J 7 Hz), 8.04 (d, 8H, HAr, J 7 Hz), 8.8 (s, 8H, pyrrole). UV [lmax/nm,
(e×10–3)]: 420 (345), 517 (10.2), 552 (4.80), 592 (3.96), 649 (2.3). MS,
m/z: 987 [M+ +1].
5,10,15,20-Tetrakis[4-(6-hydroxyhexyloxy)phenyl]porphyrin 4a was
obtained by reduction of compound 2a (65 mg, 0.31 mmol) with LiAlH4
(25 mg, 0.66 mmol) in THF. The mixture was stirred for 20 min, then
water (10 ml) was added. The mixture was extracted with CH2Cl2, filtered,
concentrated and crystallised from diethyl ether. Yield, 60 mg (96%).
Rf 0.14 (CH2Cl2–MeOH, 9:1). UV [lmax/nm (e×10–3)]: 418.2 (455.8),
519 (14.4), 556 (7.30), 591 (4.52), 646 (3.79). 1H NMR, d: –2.81 (s, 2H,
NH), 8.68–8.51 (s, 8H, pyrrole), 7.86–7.69 (d, 8H, HAr), 6.98–6.86 (d,
8H, HAr), 3.88 (t, 8H, CH2OH, J 6.4 Hz), 3.41 (t, 8H, OCH2, J 6.6 Hz), 1.69
(m, 8H, CH2CH2OH, J 6.2 Hz), 1.53–1.18 [m, 24H, HOCH2CH2(CH2)3].
MS, m/z: 1078.6 [M+].
Porphyrins 2a,b were synthesized from substituted benz-
aldehydes 1a,b in 35–40% yields using reported techniques.†,11,12
†
For synthesis of compounds 1a,b, see Online Supplementary Materials.
General procedure for the preparation of porphyrins 2a,b. Pyrrole
(100 mg, 1.42 mmol) and 4-(5-methoxycarbonylpentyloxy)benzaldehyde 1a
(0.38 g, 1.5 mmol) were dissolved in dichloromethane (50 ml). The mixture
was bubbled with argon for 5 min under continuous stirring at room tem-
perature, then boron trifluoride etherate (20 ml, 0.15 mmol) and anhydrous
ethanol (20 ml) were added, and the mixture was stirred for 30 min at
room temperature in a stream of argon. DDQ (300 mg, 1.35 mmol) was then
added, and stirring was continued for another 1 h at room temperature.
The reaction mixture was concentrated in vacuo. The oligomeric products
were separated by flash chromatography on G60 silica gel on eluting with
dichloromethane. The target product was finally purified by column chro-
matography on G60 silica gel on eluting with dichloromethane–hexane (6:1).
For characteristics of compounds 3b (yield, 88%) and 4b (yield, 83%),
see Online Supplementary Materials.
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