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11Порфиразины Porphyrazines
JVJaKporaTapoLii/JurjbJ
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Сообщение Communication
Thianaphthene-Annulated Tetrapyrazinoporphyrazines®
Ekaterina S. Taraymovich,a@ Yulia Yu. Enakieva,b Yulia V. Mitasova,a and Pavel A. Stuzhina@
aIvanovo State University of Chemistry and Technology, Ivanovo, 153000, Russia hFrumkin Institute of Physical Chemistry and Elecrochamistry RAS, Moscow, 119991, Russia @Corresponding authors E-mail: stuzhin@isuct.ru, taraimoviches@bk.ru
Tetrapyrazinoporphyrazine with fused thianaphthene fragments, i.e. tetra(benzo[4',5']thieno[2,,3,:5,6]pyrazino[2,3-b,g,l,q]porphyrazine, [H2TSNpPyzPA], and its tetra-tert-butyl-substituted derivative, [H2TSNpPyzPAtBuJ, having enhanced solubility in organic solvents, have been prepared by cyclotetramerization in a melt of corresponding benzo[4,5]thieno[2,3-b]pyrazine-2,3-dicarbonitriles obtained by condensation of diaminomaleodinitrile with 2,3-thianaphthenquinones [2,3-dihydrobenzo[b]thiophene-2,3-diones] easily available by acylation of thiophenols with oxalylchloride.
Keywords: Porphyrazines, tetrapyrazinoporphyrazines, thianaphthene, benzo[b]thiophene, spectral properties.
Porphyrazines (PA) with annulated aromatic het-erocycles are widely investigated in different areas of practical application and for this reason a steady interest is observed in the synthesis and study of their representatives.™ Among them a family of peripherally substituted tetra(pyrazino)porphyrazines (TPyzPA, see Chart 1) attract an increased attention in recent years. Thus, tetrapyrazinoporphyrazines bearing eight a-pyridyl groups (R = a-Py)[2] exhibit a remarkable electron deficient properties of the macrocy-clic ligand and ability to peripheral coordination of palla-dium.[2d] These species as well as TPyzPA substituted with eight phenyl, 2-thienyl, 2-furyl, alkoxy, dialkylamino and alkylthio groups are actively investigated for their use in photodynamic therapy.[3]
The eight peripheral substituents in these TPyzPA derivatives are only partly involved in conjugation with the macrocyclic chromophore. Annulation of aromatic rings to the pyrazine fragments is another way of structural modification of TPyzPA leading to n-extended macrocyclic systems. Few reports on such n-extended TPyzPA includes
benzohomologues, i.e. octa(2,3-quinoxalino)porphyrazines [MQxPA],[4-7] octa(naphtho)pyrazinoporphyrazines [MTNp-PyzPA],[5,6,8] octa(9,10-phenanthro)-pyrazinoporphyrazines [MTPnPyzPA][9] and species with fused N-heterocycles - tetra(2,3-pyrrolo)-,[10] tetra(2,3-indolo)-,[11] and tetra(2,3-pyrazino)-[12] annulated TPyzPA (Chart 1). We have suc-ceded in preparation of the novel TPyzPA derivatives with fused ^-containing heterocycle and report here the synthesis of the first representative of 2,3-thianaphtheno-annulated species [MTSNpPyzPA], obtained as the free base [H2T-SNpPyzPA] (6a) and its tert-butyl substituted derivative [H2TSNpPyzPAfBu4] (6b).
Easily available commercial chemicals - thiophenol (1), oxalylchloride (2) and diaminomaleodinitrile (4) have been used for the two-step preparation of the dinitrile precursor 5 which can be then used directly for the synthesis of tetra(2,3-thianaphtheno)-annulated TPyzPA derivatives (Scheme 1). Treatment of thiophenol 1 (0.144 mol) with equimolar amount of oxalylchloride 2 (14.6 ml, 0.144 mol) under vigorous stirring leads to acylation of the thiol group and solidification of the
Qrvv
\—N N—/
X N
[MTQxPA] [MT2,3NpPyzPA]
Ô О
[MT1,2NpPyzPAl
[MTPnPyzPAl
R R
[MTPyzPARol
[MTPyzPyzPAl
[MTPyrPyzPA]
[MTIndPyzPAl [MTSNpPyzPA]
Chart 1. Peripherally substituted and annulated tetrapyrazinoporphyrazines (TPyzPA).
® This contribution is dedicated to professor Vasilij Fedorovich Borodkin on the occasion of his 100th Anniversary.
48 © ISUCT Publishing MaKpoeemenouuKnu /Macroheterocycles 2010 3(1) 48-50
E. S. Taraymovich, P. A. Stuzhin et al.
XX ♦
CI
SH CI^O
r 2
Intens.-x108-2.5-
AICI3/CS2
3
hfelsr CN
/a 6
[H2TSNpPyzPA]
R = H (a), fert-Bu (b)
Scheme 1. Synthesis of thianaphthene annulated TPyzPA.
reaction mixture. After its dissolution in carbon disulfide and cooling till 0-5 °C anhydrous AlCl3 (38.5 g, 0.288 mol) was added cautiously in portions under stirring (30 min) to perform the intramolecular acylation with formation of 2,3-thianaphthenequinone (3). The crude orange product obtained after evaporation of the solvent at 45-50 °C and overnight treatment of the residue with ice was separated by filtration and purified by dissolution in 10% aqueous NaHCO3 solution with following acidification with conc. HCl leading to precipitation of 2,3-thianaphthoquinones [2,3-dihydro-benzo[6]thiophene-2,3-diones] 3 as bright orange products.*
On the second stage quinone 3 (0.03 mol) was condensed with diaminomaleodinitrile 4 (3.3 g, 0.03 mol)
# 3a. Yield 53 %. M.p.= 121-122 °C. Calc. for C8H4SO2 (%): C, 58.54; H, 2.41; S, 19.51; O, 19.51. Found (%): C, 588.03; H, 2.27; S, 19.95; O, 19.81. vmax (KBr)/cm4 1731s (v(C=O)), 1714s (u(C=O)), 1589s, 1573m, 1467s, 1452s, 1359s, 1342s, 1282s, 1241s, 1147s, 1108vs, 1060s, 962s, 842s, 748m.
3b. Yield 63%. M.p.=103 °C. Calc for C12H12SO2 (%): C, 65.43; H, 5.49; S, 14.56; O, 14.53. Found (%): C, 64.581 H,4 .88; S, 13.39; O, 13.48. vmax (KBr)/cm-1 3072m (u(CH)arom), 2964s, 2871m, 1708vs (v(C=O)), 1596s, 1562m, 1477s, 1365m, 1288m, 1257m, 1201m, 1110m, 1004m, 919m, 850m. 1H NMR (CDCl3): 5, ppm 7.84 (1H, m, Ar-H), 7.69 (1H, m, Ar-H), 7.39 (1H, m, Ar-H), 1.33 (9H, s, tert-Bu).
[M+3H]+
11 74
[3M+6HJ+
[2M+5HJ+
2: 46
1000 1500 2000 2500
3500 m/z
Figure 1. MALDI-TOF mass spectrum of [HJSNpPyzPA'BuJ (6b) (matrix - 3,5-dihydroxybenzoic acid).
by heating under reflux in ethanol (30 ml) containing acetic acid (0.8 ml) for 40 min. After evaporation of the solvent and purification by column chromatography on silica (eluent - chloroform) benzo[4,5]thieno[2,3-6]pyrazine-2,3-dicarbonitriles 5 were obtained.§
Dinitriles 5 appeared to be very reactive in cyclotetra-merization and formation of the free base porphyrazine macrocycle occurs spontaneously when they are heated above melting point at 210-220 °C for 10-15 min. Usually cyclotetramerization of dinitriles (e.g. phthalodinitriles) with formation of free base porphyrazines require higher temperatures and/or presence of sterically hindered A-bases[1] (A,A-dimethylaminoethanol, 1,8-diazabicyclo-[5.4.0]undecene) as a basic catalyst. Cyclotetramerization of dinitriles 5 upon melting seems to be a self-catalytic reaction. Due to low solubility of the unsubstituted porphyrazine 6a, its purification is troublesome. The tert-butyl substituted derivative [H2TSNpPyzPAtBu4] (6b) which is well soluble in organic solvents can be easily purified by column chromatography on alumina using chloroform as an eluent.1
The structure of 6b was confirmed by the MALDI-TOF mass-spectrum (Figure 1), which contains the cluster peak at m/z = 1171 (100%) corresponding to molecular ions
§ 5a. Yield 64%. M.p.=214 °C. Calc. for C12H4N4S (%): C, 61.01; H, 1.71; N, 23.71; S, 13.57. Found (%): C, 60.59; H, 1.23; N, 23.09; S, 13.56. vmax (KBr)/cm-1 3076w, 3056w, 3018w, 2239s (v(CN)), 1641m, 1592s, 1513s, 1438s, 1407m, 1332vs, 1311s, 1255m, 1211vs, 1160s, 1103s, 798m, 765s, 736m, 694m, 453m, 426m.
5b. Yield 67%. M.p.=210 °C. Calc. for C16H12N4S (%): C, 65.73; H, 4.14; N, 19.16; S, 10.97. Found (%): C, 64.68; H, 3.84; N, 17.83; S, 10.63. IR (KBr): v, cm-1 3085w, 3033w, 2962s, 2865m, 2239s (v(C=N)), 1606m, 1519m, 1477m, 1465m, 1363m, 1313vs, 1295m, 1268m, 1253m, 1211s, 1160m, 1093m, 977m, 829m, 698m, 464m.1H NMR (CDCl3): 5, ppm 8.59 (1H, m, Ar-H), 7.96 (2H, m, Ar-H), 1.49 (9H, s, tert-Bu).
1 6a. Yield 25%. Calc. for C48H18N16S4 (%): C, 60.88; H, 1.92; N, 23.66 ; S, 13.54. Found (%): C, 54.28; H, 1.39; N, 18.46; S, 14.63. Xmax (DMF) (relative intensity)/nm 635 (0.84), 674 (1). °6b. Yield 30%. Calc. for C64H50N16S4 (%): C, 65.62; H, 4.30; N, 19.13; S, 10.95. Found (%): C, 65.90; H, 4.95; N, 18.80; S, 10.17. UV-vis Xmax (CH2Cl2) (lgs)/nm 307 (4.24), 360 (4.41), 418 (4.10), 460sh, 61m3sh, 635 (3.92), 668 (4.41), 691 (4.48). 5H (CDCl3, 298 K) 9.2-9.4 (4H, m, Ar-H), 7.8-8.0 (8H, m, Ar-H), 1.61 (36H, s, tert-Bu), -1.6 (2H, br, NH).
Макрогетер0циmbl /Macroheterocycles 2010 5(1) 48-50
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Thianaphthene-Annulated Tetrapyrazinoporphyrazines 2.5-,
X, nm
Figure 2. UV-vis spectrum of [H2TSNpPyzPA'Bu4] (6b) in CH2Cl2 (1) and its changes after addition of tbaOH (2).
[M+nH]+ (n = 1-3) accompanied by peaks of the dimer [2M+nH]+ at m/z = 2346 (16%, n = 2-5) and trimer at m/z = 3519 [3M+nH]+ (24%, n = 3-6).
The UV-vis spectrum of [H2TSNpPyzPA BuJ (6b) is typical for porphyrazine free bases having the effective D2h symmetry of the п-chromophore (Figure 2, spectrum 1). It contains the intense absorption bands arising from the n-n* transitions of the porphyrazine п-chromophore: the split Q-band in the visible region (668 and 691 nm) and broad Soret band at 360 nm in the UV region. The maxima of the Q- and Soret bands for tetrapyrazinoporphyrazines 6a and 6b with fused thiana-phthene fragments are shifted bathochromically as compared to non-annulated tetrapyrazinoporphyrazines. Thus, for [H2T-PyzPABuJ in CHCl3 solution the Q-bands were observed at 617 and 653 and Soret band at 340 nm.[13] This bathochromic shift is caused mainly by destabilization of HOMOs due to interaction of the thianaphthene fragments with the TPyzPA п-chromophore. However, the observed effect is much less than in the case of formally isoelectronic 2,3-annulation of naphthalene fragments (XQ = 803 nm for [H2T23NpPyzPA] in 1-chloronaphthalene[8b]), and even less than in the case of benzo annulation (XQ = 712 nm for [H2TQxPAiBu4] in CHCl3[7]). It means that the 10n-electron system of thianaphthene is not involved as a whole in conjugation with the macrocyclic TPyzPA п-chromophore. Evidently the S atom exhibits an "insulating" effect and the interaction can be better described as +C effect of phenyl group. Similar situation was observed[11] for the isoelectronic indole annulated TPyzPA, [H2TIndPyzPA'Bu4] (the Soret band at 364 nm and the double Q-band at 688 and 708 nm in CHCl3 for V-amyl substituted species).
The splitting of the Q-band in the UV-vis spectrum of 6b disappears and it is merged in a single band with maximum at 679 nm after addition of tetrabutylammonium hydroxide (tbaOH, Figure 2, spectrum 2). This is due to deprotonation of the internal pyrrolic NH groups with formation of an anionic form with effective D4h symmetry of the n-chromophore. Deprotonation leads also to disappearance of the absorption
in 400-460 nm region which can be very likely assigned to the intramolecular charge transfer transition from thianaphthene fragments to the electron-deficient TPyzPA chromophore.
In conclusion, we have prepared and characterised the first representatives of a new family of S-containing porphyrazine derivatives - tetrapyrazinoporphyrazines with fused thianaphthene fragments, isolated as free bases. They are formed by self-catalytic cyclotetramerization of benzo[4.5]thieno[2.3:5.6]pyrazino-2,3-dicarbonitriles occurring upon their melting. Metal complexes, which are available by template condensation of these dinitriles in the presence of metal salts, are currently investigated.
Acknowledgements. This work was supported by the Federal Target Program "Scientific and Educational Cadres of Innovative Russia for 2009-2013" (State contract №° 2077) and by the Grant of the President of the Russian Federation for the State Support of Young Candidates of Sciences (МК-4752.2009.3).
References
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Received date 12.02.2010 Accepted date 16.03.2010 First published on the web 22.03.2010
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