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Synthesis and characterization of tetraethynylphthalocyanines
TETRAHEDRON Tetrahedron 54 (1998)4397--4404
Pergamon
Synthesis and Characterization of Tetraethynylphthalocyanines
Eva M. Maya, Peter Haisch, Purificaci6n V/tzquez and Tom/s Torres* Dpto. Qnimica Orgthlica (C-I). Faoultadde Ciencias, UniversidadAut6nomade Madrid, Cantoblanco. 28049-Madrid, Spain. E-mail: tomas.torres~uam.es
Received 31 December 1997; revised 9 February 1998; accepted 12 February 1998
Metallophthalocyaninessubstituted by four ethynyl groups were oblained as a regioisomeric mixture. The compounds, scarcelysolublein organic solvents,were characterizedby MALDI-TOF-MS. © 1998 Elsevier Science Ltd. All rights reserved.
Abstract :
In recent years remarkable progress has been made in the construction of two dimensional (2D) organic polymers in order to obtain materials with high stability and mechanical properties. These materials can be used as electric conductors, electrodes, selective membranes, ¢tc. t A known strategy for the construction of 2D materials involves the synthesis of a monomer, its preorganization as a regular paving in the plane by the Langmuir-Blodgett (LB) technique and the chemical reaction of the monomers on the film with the appropriate coupling reagents. Thus, for example, porphyrins containing four terminal alkynyl groups have been used before to build a polymer by an oxidative coupling reaction between the ¢thynyl peripheral groups.t The use of phthalocyanines 2 instead of porphyrins could be of great interest for the construction of more stable 2D organic polymers3 because of their high thermal stability and their electronic and morphologic characteristics.~4 Few examples of alkynyl substituted Pcs have been described. ~'6 These facts together with our interest in the preparation of phthalocyanines 7 and related compounds s'9 and in the study of their physical properties ~° prompted us to extend our investigations to the synthesis of ¢thynyl functionalized Pc-systemsf~ In the present paper the preparation of tctraethynylphthalocyanines la-¢ is described. These and other related substituted compounds could be used as monomers for the construction of 2D materials.
le M=I-I 2 0040-40201981519.00 © 1998 Elsevier Science Ltd. All rights reserved. PII: S0040-4020(98)00153-7
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RESULTS AND DISCUSSION First of all, the preparation of compound la was attempted by the standard method of cyciotetramerization of 4-ethynylphthalonitfile11 in the presence of zinc chloride in dimethylaminoethanol (DMAE) as solvent at reflux temperature. Under these conditions a complex mixture of compounds with higher molecular weight than la was obtained, as pointed out by LSIMS. Compound la could not be detected even changing the reaction conditions (ethoxyethanol as solvent, lower temperature, etc). Similar results were obtained by using 5-ethynyl-l,3-diiminoisoindoline as starting material. For this reason a protecting group of the ethynyl function was used. Thus, the cyclotetramerizatiun of 4-(2'-trimethylsilylethynyl)phthalonitrile (2) 11 with Ni(OAc)2"4H20 (Scheme 1) in different reaction conditions afforded the corresponding tetrasubstituted Pc 3 together with oligomeric materials (LSIMS) probably originated by partial removal of the protecting groups and subsequent side reactions.12The best results were obtained using DMAE or pentanol as solvent. The compound was purified by flash chromatography on alumina. (CH3)3SiN
Ni(OAc)24H20 c~C (CH3)3Si/
N
DMAE
2
/Si(CH3)3
N
Ni - I~,,N
3
(cH3)3si
N
C~ C\
si(cI-13)3
Scheme I Taking into account these facts, we have employed a different protecting group (dimethyicarbinol) of the ethynyl traction (Scheme 2). Thus, 4-iodophthalonitrile ~1(4) was heated in DMAE as solvent in the presence of the corresponding metal(H) salt to yield phthalocyanines 6a m3and 6b after chromatographic separation. The free base 4c was obtained by cyclotetramerization of 5-iodo-1,3-diiminoisoindoline (5). Tetraiodophthalocyanines 6a and 6b were reacted with an excess of 2-methyibut-3-yn-ol in the presence of bis[triphenylphosphine]palladium(II) dichloride [Pd(PPh3)2CI2] and copper(I) iodide t4 in freshly distilled Et2NH to yield phthalocyanines 7a, b in 86% and 79°/5 yield, respectively. The free base 7c was obtained using tris(dibenzylideneac,etone)dipalladium(0) [Pd2(dba)3] and triphenyiarsine as a catalyst. Is The absence of the copper(I) salt in this particular case is necessary to avoid the introduction of a copper ion into the macrocycle. Thus, when the preparation of 7c was attempted using the copper(I) catalyst-system mentioned above, compound 7d was obtained instead the free base. All these phthalocyanines were purified by flash chromatography on silica gel, followed by trituration with hot acetonitrile or hexane.
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E. M. Maya et al. /Tetrahedron 54 (1998) 4397-4404
]
/•CN
I
DMAE 135 oC MCI2 (For 6a,b)
I
N
M
N
,,
135 °C (For 6¢)
NH s
CN NH
4
I'~
- ' I 6 a M = Zn 6b M -- Ni
6c M = H 2 HC-=CC(CH3)2OH Cul, Et2NK Pd(PPh3hCh (For 7a,b) Piperidm, Pd2(dba)3, Ph3As (For 7c) HO(CH3hCC~
/~CC(CH3)2OH N
"v--{ HO(CH3)2CC ~
7a 7b 7c 7d
M = Zn M=Ni M=H 2 M = Cu
s CC(CH3~hOH
2-ethoxyethanol NaOH la-c Scheme 2
Compounds 7a,b were alternatively obtained in 54% and 50% yield respectively by cyclotetramerization of phthalonitrile 8, previously described by us, e~in the presence of the corresponding metal(H) salt ( Scheme 3 ), Finally, tetraethynylphthalocyanines 16 la-c were obtained from 7a-c in ca. 60 % yield after removing the protecting groups by treatment with NaOH (Scheme 2). The dark green products obtained were washed with MeOH and characterized by IR, MALDI-TOF-MS and UV-visible. Compounds la-¢ are not soluble in common organic solvents.
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E. M. Maya et aL / Tetrahedron 54 (1998) 4397-4404
HC-=CC(CH3hOH Cul, Et2NI-I 4
~CN
pd(pph3)2HC~ CH
MCh
[ U . . ,~
DMAE 135 oC
CN
7a,b
3)2 8 Scheme 3
The UV-visible spectra of compounds 7a-c and la-¢ are represented in Figures 1-3. The electronic spectra of 7a and 7¢ in THF are typical of monomeric species (Q-bands at 684, and at 675 and 708 nm, respectively). However, nickel compound 7b is partially aggregated in THF even at 10.7 M concentration, as indicated by the presence of an absorption at 623 ran, attributable to oligomeric species, together with the band corresponding to monomeric species at 679 rim. In strong polar solvents, such as DMSO, this last band has almost disappears and a broad mg,dmum between 600 and 640 rnn dominates the spectrum. The free base 7¢ also undergoes aggregation in DMSO. On the other hand, these aggregation phenomena are particularly notable in compounds la-¢. These derivatives, not soluble in THF, show a broad absorption in DMSO in the 600-750 ran region, corresponding to oligomeric species.
1 o8
(b)
06
~
0.4 0.2 ~ 250
350
450
550
650
750
850
.m
Figure 1: (a) 7a in THF (6.2 10-6M), (b) 7a in DMSO (3.3 10-6M), (c) la in DMSO (6.4 10-6M)
o8
(a)
0.6 0.4 0.2 0
250
.
.
350
.
.
.
150
.
.
550
.
.
650
.
.
750
i
850 ~
L
Fillm¢ 2: (a) 7b in THF (6.9 10-6M); (b) 7b in THF (6.0 10-7M), (c) 7b in DMSO (6.2 IO-6M); (d) lbinDMSO (6.4 10-6 M)
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E. M. Maya et al. / Tetrahedron 54 (1998) 4397--4404
12
0.8 0.6 0.4
0.2 0 250
350
450
SSO
650
750
850 n m
Figm~ 3: (a) 7c in THF (5.9 10-6M), Co)7e in DMSO (3.1 10-6 M); (c) 1¢ in DMSO (5.4 10-6M)
In conclusion, the preceding results show that satisfactory synthesis of compounds la-¢ can be achieved following well known metal-mediated coupling methodologies. Presently, efforts are being made for preparing more soluble derivatives of these parent compounds having four ethynyl functional groups in a well defined special arrangement. This can allow the control of the long range polymerization of these compounds, being therefore potential targets for 2D materials based on phthalocyanines. These results will be reported in due course,
EXPERIMENTAL All phthalocyanines synthetized were obtained as a mixture of 2,9,16,23-; 2,10,16,24, 2,9,17,24- and 2, 9,16,24-regioisomers. $-Ethynyl-l,3-diiminoisoindofine. Through a mixture of 400 mg (2.6 mmol) of 4-ethynylphthalonitrile" and 14 mg (0.26 retool) of NaOCHa in MeOH (10 rnl), NH3 (g) was bubbled during lh at room temperature and then during 8 h at reflux. The solvent was removed under reduced pressure and the brown residue was washed With a saturated solution of NI-LCI. Yield: 404 mg (92%)', rap. 182 °C (Lit.s* 165°C), IH nm.r. 8 (MeOD): 8.0 (s, lI-I, Ar), 7.9 (d, lI-I, Ar), 7.7 (dd, lI-I, At) and 3.7 (s, 1H, C-ffiCI-I),~3C n.m.r. 8 (MeOD): 171.2 (C-l), 169.1 (C-3), 135.4 (C-3, C-8), 126.3 (C-4), 125.2 (C-6), 121.9 (C-7), 120.0 (C-5) and 80.8 (C~C), LSIMS (m-NBA) m/z: 169 [M+]. Tetrakis(7,-trimethyhilyethynyl)phthalecyaninate Nickel(H) (3). A mixture of 4-(2'trimethylsilylethynyl)phthalonitrile(2) H (280 rag, 1.25 mmol) and Ni(OAc)2,4H20 (78 mg, 0.31 mmol) in dimethylaminoethanol(DMAE) (2.5 ml) was heated under argon at reflux temperature during 8h. The reaction mixture was added to MeOH/H2Oand the precipitate washed with n-hexane. The residue was purified by flash column chromatography on alumina using CHCI3 as eluent to give 27 mg (10%) of a blue powder. M.p. > 300 °C.tH n.m.r 8 (CDCI3): 7.2-6.2 (br signal, arom. H) and 0.5-0.3 (br signal, SiCH3);uv-vis (CHCI3) Z,~ (log ~): 683 nm (5.09); v (KBr): 2150 (C-~C);FD-MS m/z : 954 [M*]; MALDI-MS m/z: 955 [M+H+].
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Tetraiodophthalocyaninates Zinc(il) and Nickel(H)13(6a, b). 4-Iodophthalonitrile (4) II (400 rag, 1.6 mmol) was heated at reflux in DMAE (1.5 ml) under argon for 12 h in the presence of the corresponding metal(II) salt (MCI2) (0.4 retool). The solvent was removed under reduced pressure and the blue solid was washed with MeOH, centrifuged, filtered and dried under vacuum with P205. 6a: 280 mg (65%); m.p. > 300 °C. (Found: C, 35.94; H, 1.52; N, 10.69. C32HI2LtNsZnrequires C, 35.54; H, 1.12; N, 10.36%); uv-vis (H2SO4) gm~(Iog ~): 822 (5.24) and 296 nm (4.69)*,MALDI-MS m/z: 1080 [M+FF]. 6b: 279 mg (65%); m.p. > 300 °C. (Found: C, 34.90; H, 1.14; N, 10.72. C32Ht2LtNgNi'H20requires C, 35.17; H, 1.29; N, 10.25%); uv-vis (H2SO4) ~ (log ~): 808 (5.18) and 295 nm (4.90)*,MALDI-MS m/z: 1074 [M+I-F]. S-lodo-l,3-diiminoisoindoline (5). Through a mixture of 4-iodophthalonitrile II (1 g, 3.9 mmol) and NaOCH3 (0.021 g, 0.39 retool) in MeOH (25 ml), NH3 (g) was bubbled during lh at room temperature and then during 8 h at reflux. The solvent was evaporated under reduced pressure and the green solid was washed with an aqueous saturated solution of NH4CI. The solid was dried under vacumm with P205 to yield 783 rag (75%) ofS; m.p. 220 °C. (Found C, 33.28, H, 2.44, N, 14.25. CsI-I6IN3"H20requires C, 33.24; H, 2,79; N 14.54%); ~H n.mr. 8 (dlTFA): 8.8 (s, IH, At), 8.3 (d, IH, Ar) and 8.1 (d, 1H, At); t3C n.mr. 8 (dl-TFA): 165 (C-l, C-2), 136.4 (C-6, C-4), 127.7 and 127.0 (C-8, C-3), 125.5 (C-7) and 105.2 (C-5); FAB-MS m/z: 271 [M+FF]. Tetraiodophthalocyanine (6c). 5-Iodo-l,3-diiminoisoindoline (5) (400 mr, 1.5 mmol) was heated in DMAE (1.5 ml) at reflux under argon for 12 h. The solvent was removed under reduced pressure, and the green sofid was washed with MeOH, collected by centrifugation and dried under vacuum with P205 to give 133 mg (35%) of 6c; m.p. > 300 °C. (Found: C, 37.06', H, 3.18; N, 10.75. C32Hz4 I4Ns'H20 requires C, 37.02; H, 3.30; N, 10.75%); uv-vis (H2SO4) ~ ( l o g ~): 883 (5.17), 822 (5.23), 297 nm (5.17); MALDI-MS m/z: 1018 [M+I-I+]. 4-(3-Hydroxy-3-methyl-l-butynyl)phthalonitrile (8). Bis[triphenylphosphine]-palladium(II) dichloride (55 mr, 0.079 retool) and copper(I) iodide (6.5 mr, 0.039 retool) were added successively to 4-iodophthalonitrile n (4) (2 g, 7.9 retool) and 2-methylbut-3-yn-2-ol (1.23 ml, 9.4 mmol) in a mixture of distilled diethylamine (16 mi) and THF (6 ml). The mixture was stirred under argon at room temperature for 20 h and then evaporated under reduced pressure. The solid was extracted with CH2Ci2, washed with water and passed through a column of silica gel using a mixture of THF/hexane (6:1) to yield 1.27 g (78%) of a brown solid. M.p. 78°C. (Found C, 74.38; H, 5.05; N, 12.98. C13HIoN20requires C, 74.26; H, 4.80*,N, 13.33%); ~H n.m.r. 8 (CDCI3): 7.8 (m, 1H; I-I,~), 7.7 (d, 2H; I-I~), 4.0 (s, 1H; OH) and 1.6 (s, 6H; C(CH3)2); ~3C n.mr. 8 (CDCI3): 136.09 (C-3), 135.78 (C-5), 133.38 (C-6), 115.97 (CN), 115.02 (CN), 114.50 (C-2), 114.28 (C-I), 101.25 (C---C), 78.63 (C-3") and 30.96 (CH3); MS (70 ev, EI) m/z: 210 [M+] and 195 [M+-CH3].
Tetrakis(3-hydroxy-3-methyi-l-butynyl)phthalocyaninates Zinc(H) and Nickei(ED (7a, b). MethodA. Tetraidophthalocyaninate (6a, b) (0.090 retool) was reacted with 2-methylbut-3-yn-2-ol (0.90 mmoi) in the presence ofbis[triphenylphosphlne]palladium(II) dichloride [Pd(PPh3)2CI2](1 ~mol) and copper(I) iodide ~4 (0.5 ttmol) in a mixture of freshly distilled of Et2NH (2 ml) and THF (1 ml). The reaction mixture was stirred at room temperature for 12 h under argon atmosphere. After removing the solvent under reduced pressure, the blue solid was extracted with CH2C12 and chromatographed on silica gel using a mixture of THF:hexane (6:1) as eluent and washed with hot acetonitrile. 7a: 70 rag (86 %); m.p. > 300 °C (Found: C, 66.04; FL 4.74; N, 11.83. Cs2H4oNsO4Zn-2H20requires C, 66.28;
E. M. Maya et al. / Tetrahedron 54 (1998) 4397-4404
4403
H, 4.71; N, 11.89°,4); IH nm.r. 8 (drTFA): 7.5-8.0 (br signals, atom-H), 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3)', uv-vis (THF) ~ (log 8): 684 (5.02) and 358 nm (4.51), v (KBr): 3350 (OH) and 2223 (C-=C), LSIMS m z : 905 [M+W]. 7b: 64 rag (79%); m.p. > 300 °C. (Found: C, 66.46; H, 4.48; N, 12.39. Cs2I-h0NsO4Ni'2H20 requires C, 66.75; H, 4.74; N, 11.98%); ~H nm.r. 8 (drTFA): 7.3-8.2 (br signals, atom-H), 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3); uv-vis (THF) ~ ( l o g 8): 679 (5.04) and 338 nm (4.76); v (KBr): 3372 (OH), 2219 (C---C);LSIMS m/z: 899 [M+I-Y]. M e t h o d B. 400 mg (1.9 retool) of 4-(3-hydroxy-3-methyl-1-butynyl)phthalonitrile (8) was heated under reflux in DMAE (1.5 ml) under argon for 12 h in the presence of the corresponding metal (II) salt (MC12)(0.4 retool). The solvent was removed under reduced pressure and the blue solid was purified following the above procedure. Yield: 51% for 7a and 49°,4 for 7b. TetrakisO-hydroxy-3-methyl-l-butynyl)phthaloeyanine (70 Tetraiodophthalocyanine (6e) (80 rag, 0.076 mmol) was reacted with 2-methylbut-3-yn-2-ol (64 rag, 0.76 retool) in the presence of tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] (24 rag, 0.026 retool) and triphenylarsine (66 rag, 0.078 retool) in freshly distilled piperidine (3 ml)) 5 The reaction mixture was stirred at room tempertaure for 12 h under argon atmosphere. After removing the solvent under reduced pressure, the green solid was extracted with CH2C12 and the extracts were washed with water. The product was purified by chromatography on silica gel using a mixture of TI-~:hexane (2:1) as eluent to give 50 mg (79°4) of 7¢. M.p. > 300 °C. (Found: C, 43.50; H, 4,72; N, 13.05. Cs214_42NsO4.2H20requires C, 43.73, H, 5.05, N, 12.75%); ~H n,m.r. 8 (drTFA): 7,5-8.3 (br signals, arom-H) 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3); uv-vis (THF) ~ (log 8): 708 (5.30), 675 (5.33) and 350 nm (5.17); v (KBr): 3388 (OH), 2200 (C---C);LSIMS m/z: 843 [M+H+]. Tetraethynyiphthalocyanines (la-c). Tetrakis(3-hydroxy-3-methyl-l-butynyl)phthalocyanine (7a-¢) (0.045 retool) was heated with 15 mg (0.36 mmol) of powdered NaOH in 2-¢¢hoxyethanol. The reaction mixture was heated at reflux under argon atmosphere until all the starting phthalocyanine disappeared. The solvent was then removed under reduced pressure and the black solid was washed with MeOH, collected by centrifugation and dried under vacuum with P2Os. la: 15.4 mg (53%); m.p. > 300 °C; (Found: C, 68.02, H, 2.41, N, 15.19. C4oHI6NsZn'2H20requires C, 67.66, H 2.84, N, 15.78%); uv-vis (DMSO) ~ (log 8): 697 (4.46), 359 (4.35) and 291 nm (4.39); v (KBr): 3374 (C--CH); MALDI-MS m/z: 673 [M+I-V]. lb: 16.2 mg (54%); m.p. > 300°C. (Found: C, 68.03, H, 2.22, N, 15.53. C40HI6NsNi'2H20 requires C, 68.36, H
2.58, N, 15.95%); uv-vis (DMSO) ~ (MALDI-TOF) m/z: 667 [M+H+].
(log 8): 682 (4.63) and 292 nm (5.17); v (KB0:3407 (C---CH); MS
1¢: 16.4 mg (60%); m.p.> 300 °C; (Found: C, 73.74, H, 3.21, N, 16.95. C40HIsNs"2H20requires C, 74.29, H 3.43, N, 17.33%); uv-vis (DMSO) ~ (log ~): 689 (4.49), 292 nm (5.07); v (KB0:3419 (C-=CH); MS (MALDI-TOF) m/z: 611 [M+H+]. ACKNOWLEDGEMENTS This work was supported by the Comisi6n Interministerial de Ciencia y Tecnologia CICYT (Spain) and the Comunidad de Madrid grants MAT 96/0654 and 06T/017/96 respectively. A Graduate Research Fellowship of the Comunidad de Madrid to E.M.M. is gratefully acknowledged.
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REFERENCES AND NOTES
1. 2.
3.
4. 5.
6.
7. 8. 9.
10.
11. 12.
13, 14. 15. 16.
a) Lefevre, D.; Porteu, F., Balog, P., Roulliay, G. Z. and Palacin, S., Langmuir. 1993, 9, 150-161. b) Lefevre, D. Ph.D.Thesis, L'Universite Paris XI Orsay, 1995. Phthalocyanines:Properties and Applications; Leznoff, C. C. and Lever, A. B. P. Eds.; VCH Pubfishers: New York, 1989, 1992, 1993, 1996, vols I-IV. 2D polymers based on Pcs have been previously prepared and some of their physical properties studied. See for example: a) WOhrle, D. and Meyer, G., Kontakte, 1985, 3, 38-48. b) Djurado, D., Tadlaqui, S., Harnwi, A. and Cousseins, J. C., Synth. Met. 1991, 41-43, 2595-2600. Hanack, M. and Lang, M., Adv. Mater. 1994, 6, 819-833. See for example: a) Hanack, M. and Naannann, H. DE 40 01 158 (Chem. Abst. 1990, P-208923d). b) Vig,h, S., Lain, H.; Janda, P., Lever, A. B. P. and Leznoff, C. C.; Can. J. Chem. 1991, 69, 1457-1461. c) Terekhov, D. S.; Nolan, K. J. M.; McArthur, C. R. and Leznoff, C. C., J. Org. Chem. 1996, 61, 30343040. d)Isagao, H.; Terekhov, D. S. and Leznoff, C. C., J. Porph. Phthalocy. 1997, 1, 135-140. e)Nolan, K. J. M. and Leznoff, C. C., Synlett. 1997, 593-594. a) A~ H. and Van Lier~ J. E..~ Tetrahedr~n Lett. ~997~ 38~ ~~57-~ ~6~. b) Maya~ E. M..~Vitzqu~z~ P. and Tortes, T., Chem. Commun. 1997, 1175-1176. a) Sastre, A., Tortes, T. and Hanaek, M., Tetrahedron Lett. 1995, 36, 8501-8504. b) Sastre, A., Del Roy, B. and Tortes, T., J. Org. Chem. 1996, 61, 8591-8597. Ftnauindez, F.; Tortes, T.; Hauschel, B. and Hanack, M., Chem. Rev., in press. a) Geyer, M.; Plenzig, F.; Rauschnabel, J., Hanack, M., Del Rey, B.; Sastre, A. and Tortes, T., Synthesis, 1996, 1139-1151. b) Del Rey, B. and Tortes, T., TetrahedronLett. 1997, 38, 5351-5354. c) Cabez6n, B.; Rodriguez-Morgade, S. and Tortes, T., J. Org. Chem. 1995, 60, 1872-1874. a) Sastre, A., Tortes, T.; Diaz-Crarcia, M.A.; AguU6-L6pez, F., Dhermut, C., Brassel~, S., Ledoux, I. and Zyss, J.; J. Am. Chem. Soc. 1996, 118, 2746-2747. b) De la Torte, G., Tortes, T, and AguUb-L6pez, F.; Adv. Mat. 1997, 9, 265-269. c) Duro, J.A.; De la Torte, G., Barber~ J.; Serrano, J.L. and Tortes, T., Chem. Mat. 1996, 8, 1061-1066. Mareuccio, S. M.; Svirskaya, P. I.; Greenberg, S.; Lever, A. B. P. and Leznoff, CC.; Can. J. Chem. 1985, 63, 3057- 3069. Cleavage of TMS-protecting groups in alkynyl derivatives in the presence of metal salts has been described. See for example: Ito, H ; Arimoto, K.; Sensui, H. and Hosomi, A., Tetrahedron Lett. 1997, 38, 3977-3980. a ) Zhang, X. and Xu H J. Chem. Soc. Faraday Trans. 1993, 89, 3347-3351. b) Margaron, P., G-r~goire, M. J., Scasnar, V.; Ali, H. and van Lier, J. E.; Photochem. Photobiol. 1996, 63, 217-223. Nishino, N,, Wagner, R. W. and Lindsey, J. S., J. Org. Chem. 1996, 61, 7534-7544. Wagner, R. W.; Johnson, T. E.; Li, F. and Lindsey, J. S., J. Org. Chem. 19¢Y5,60, 5266-5273. A german patent 5" describes the preparation of tetraethynylphthalocyanine from tetravinylphthalocyanine by successive bromination-dehydrobromination reactions. However, no conclusive data about the structure of this compound were given.
Pergamon
Synthesis and Characterization of Tetraethynylphthalocyanines
Eva M. Maya, Peter Haisch, Purificaci6n V/tzquez and Tom/s Torres* Dpto. Qnimica Orgthlica (C-I). Faoultadde Ciencias, UniversidadAut6nomade Madrid, Cantoblanco. 28049-Madrid, Spain. E-mail: tomas.torres~uam.es
Received 31 December 1997; revised 9 February 1998; accepted 12 February 1998
Metallophthalocyaninessubstituted by four ethynyl groups were oblained as a regioisomeric mixture. The compounds, scarcelysolublein organic solvents,were characterizedby MALDI-TOF-MS. © 1998 Elsevier Science Ltd. All rights reserved.
Abstract :
In recent years remarkable progress has been made in the construction of two dimensional (2D) organic polymers in order to obtain materials with high stability and mechanical properties. These materials can be used as electric conductors, electrodes, selective membranes, ¢tc. t A known strategy for the construction of 2D materials involves the synthesis of a monomer, its preorganization as a regular paving in the plane by the Langmuir-Blodgett (LB) technique and the chemical reaction of the monomers on the film with the appropriate coupling reagents. Thus, for example, porphyrins containing four terminal alkynyl groups have been used before to build a polymer by an oxidative coupling reaction between the ¢thynyl peripheral groups.t The use of phthalocyanines 2 instead of porphyrins could be of great interest for the construction of more stable 2D organic polymers3 because of their high thermal stability and their electronic and morphologic characteristics.~4 Few examples of alkynyl substituted Pcs have been described. ~'6 These facts together with our interest in the preparation of phthalocyanines 7 and related compounds s'9 and in the study of their physical properties ~° prompted us to extend our investigations to the synthesis of ¢thynyl functionalized Pc-systemsf~ In the present paper the preparation of tctraethynylphthalocyanines la-¢ is described. These and other related substituted compounds could be used as monomers for the construction of 2D materials.
le M=I-I 2 0040-40201981519.00 © 1998 Elsevier Science Ltd. All rights reserved. PII: S0040-4020(98)00153-7
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RESULTS AND DISCUSSION First of all, the preparation of compound la was attempted by the standard method of cyciotetramerization of 4-ethynylphthalonitfile11 in the presence of zinc chloride in dimethylaminoethanol (DMAE) as solvent at reflux temperature. Under these conditions a complex mixture of compounds with higher molecular weight than la was obtained, as pointed out by LSIMS. Compound la could not be detected even changing the reaction conditions (ethoxyethanol as solvent, lower temperature, etc). Similar results were obtained by using 5-ethynyl-l,3-diiminoisoindoline as starting material. For this reason a protecting group of the ethynyl function was used. Thus, the cyclotetramerizatiun of 4-(2'-trimethylsilylethynyl)phthalonitrile (2) 11 with Ni(OAc)2"4H20 (Scheme 1) in different reaction conditions afforded the corresponding tetrasubstituted Pc 3 together with oligomeric materials (LSIMS) probably originated by partial removal of the protecting groups and subsequent side reactions.12The best results were obtained using DMAE or pentanol as solvent. The compound was purified by flash chromatography on alumina. (CH3)3SiN
Ni(OAc)24H20 c~C (CH3)3Si/
N
DMAE
2
/Si(CH3)3
N
Ni - I~,,N
3
(cH3)3si
N
C~ C\
si(cI-13)3
Scheme I Taking into account these facts, we have employed a different protecting group (dimethyicarbinol) of the ethynyl traction (Scheme 2). Thus, 4-iodophthalonitrile ~1(4) was heated in DMAE as solvent in the presence of the corresponding metal(H) salt to yield phthalocyanines 6a m3and 6b after chromatographic separation. The free base 4c was obtained by cyclotetramerization of 5-iodo-1,3-diiminoisoindoline (5). Tetraiodophthalocyanines 6a and 6b were reacted with an excess of 2-methyibut-3-yn-ol in the presence of bis[triphenylphosphine]palladium(II) dichloride [Pd(PPh3)2CI2] and copper(I) iodide t4 in freshly distilled Et2NH to yield phthalocyanines 7a, b in 86% and 79°/5 yield, respectively. The free base 7c was obtained using tris(dibenzylideneac,etone)dipalladium(0) [Pd2(dba)3] and triphenyiarsine as a catalyst. Is The absence of the copper(I) salt in this particular case is necessary to avoid the introduction of a copper ion into the macrocycle. Thus, when the preparation of 7c was attempted using the copper(I) catalyst-system mentioned above, compound 7d was obtained instead the free base. All these phthalocyanines were purified by flash chromatography on silica gel, followed by trituration with hot acetonitrile or hexane.
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E. M. Maya et al. /Tetrahedron 54 (1998) 4397-4404
]
/•CN
I
DMAE 135 oC MCI2 (For 6a,b)
I
N
M
N
,,
135 °C (For 6¢)
NH s
CN NH
4
I'~
- ' I 6 a M = Zn 6b M -- Ni
6c M = H 2 HC-=CC(CH3)2OH Cul, Et2NK Pd(PPh3hCh (For 7a,b) Piperidm, Pd2(dba)3, Ph3As (For 7c) HO(CH3hCC~
/~CC(CH3)2OH N
"v--{ HO(CH3)2CC ~
7a 7b 7c 7d
M = Zn M=Ni M=H 2 M = Cu
s CC(CH3~hOH
2-ethoxyethanol NaOH la-c Scheme 2
Compounds 7a,b were alternatively obtained in 54% and 50% yield respectively by cyclotetramerization of phthalonitrile 8, previously described by us, e~in the presence of the corresponding metal(H) salt ( Scheme 3 ), Finally, tetraethynylphthalocyanines 16 la-c were obtained from 7a-c in ca. 60 % yield after removing the protecting groups by treatment with NaOH (Scheme 2). The dark green products obtained were washed with MeOH and characterized by IR, MALDI-TOF-MS and UV-visible. Compounds la-¢ are not soluble in common organic solvents.
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E. M. Maya et aL / Tetrahedron 54 (1998) 4397-4404
HC-=CC(CH3hOH Cul, Et2NI-I 4
~CN
pd(pph3)2HC~ CH
MCh
[ U . . ,~
DMAE 135 oC
CN
7a,b
3)2 8 Scheme 3
The UV-visible spectra of compounds 7a-c and la-¢ are represented in Figures 1-3. The electronic spectra of 7a and 7¢ in THF are typical of monomeric species (Q-bands at 684, and at 675 and 708 nm, respectively). However, nickel compound 7b is partially aggregated in THF even at 10.7 M concentration, as indicated by the presence of an absorption at 623 ran, attributable to oligomeric species, together with the band corresponding to monomeric species at 679 rim. In strong polar solvents, such as DMSO, this last band has almost disappears and a broad mg,dmum between 600 and 640 rnn dominates the spectrum. The free base 7¢ also undergoes aggregation in DMSO. On the other hand, these aggregation phenomena are particularly notable in compounds la-¢. These derivatives, not soluble in THF, show a broad absorption in DMSO in the 600-750 ran region, corresponding to oligomeric species.
1 o8
(b)
06
~
0.4 0.2 ~ 250
350
450
550
650
750
850
.m
Figure 1: (a) 7a in THF (6.2 10-6M), (b) 7a in DMSO (3.3 10-6M), (c) la in DMSO (6.4 10-6M)
o8
(a)
0.6 0.4 0.2 0
250
.
.
350
.
.
.
150
.
.
550
.
.
650
.
.
750
i
850 ~
L
Fillm¢ 2: (a) 7b in THF (6.9 10-6M); (b) 7b in THF (6.0 10-7M), (c) 7b in DMSO (6.2 IO-6M); (d) lbinDMSO (6.4 10-6 M)
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E. M. Maya et al. / Tetrahedron 54 (1998) 4397--4404
12
0.8 0.6 0.4
0.2 0 250
350
450
SSO
650
750
850 n m
Figm~ 3: (a) 7c in THF (5.9 10-6M), Co)7e in DMSO (3.1 10-6 M); (c) 1¢ in DMSO (5.4 10-6M)
In conclusion, the preceding results show that satisfactory synthesis of compounds la-¢ can be achieved following well known metal-mediated coupling methodologies. Presently, efforts are being made for preparing more soluble derivatives of these parent compounds having four ethynyl functional groups in a well defined special arrangement. This can allow the control of the long range polymerization of these compounds, being therefore potential targets for 2D materials based on phthalocyanines. These results will be reported in due course,
EXPERIMENTAL All phthalocyanines synthetized were obtained as a mixture of 2,9,16,23-; 2,10,16,24, 2,9,17,24- and 2, 9,16,24-regioisomers. $-Ethynyl-l,3-diiminoisoindofine. Through a mixture of 400 mg (2.6 mmol) of 4-ethynylphthalonitrile" and 14 mg (0.26 retool) of NaOCHa in MeOH (10 rnl), NH3 (g) was bubbled during lh at room temperature and then during 8 h at reflux. The solvent was removed under reduced pressure and the brown residue was washed With a saturated solution of NI-LCI. Yield: 404 mg (92%)', rap. 182 °C (Lit.s* 165°C), IH nm.r. 8 (MeOD): 8.0 (s, lI-I, Ar), 7.9 (d, lI-I, Ar), 7.7 (dd, lI-I, At) and 3.7 (s, 1H, C-ffiCI-I),~3C n.m.r. 8 (MeOD): 171.2 (C-l), 169.1 (C-3), 135.4 (C-3, C-8), 126.3 (C-4), 125.2 (C-6), 121.9 (C-7), 120.0 (C-5) and 80.8 (C~C), LSIMS (m-NBA) m/z: 169 [M+]. Tetrakis(7,-trimethyhilyethynyl)phthalecyaninate Nickel(H) (3). A mixture of 4-(2'trimethylsilylethynyl)phthalonitrile(2) H (280 rag, 1.25 mmol) and Ni(OAc)2,4H20 (78 mg, 0.31 mmol) in dimethylaminoethanol(DMAE) (2.5 ml) was heated under argon at reflux temperature during 8h. The reaction mixture was added to MeOH/H2Oand the precipitate washed with n-hexane. The residue was purified by flash column chromatography on alumina using CHCI3 as eluent to give 27 mg (10%) of a blue powder. M.p. > 300 °C.tH n.m.r 8 (CDCI3): 7.2-6.2 (br signal, arom. H) and 0.5-0.3 (br signal, SiCH3);uv-vis (CHCI3) Z,~ (log ~): 683 nm (5.09); v (KBr): 2150 (C-~C);FD-MS m/z : 954 [M*]; MALDI-MS m/z: 955 [M+H+].
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Tetraiodophthalocyaninates Zinc(il) and Nickel(H)13(6a, b). 4-Iodophthalonitrile (4) II (400 rag, 1.6 mmol) was heated at reflux in DMAE (1.5 ml) under argon for 12 h in the presence of the corresponding metal(II) salt (MCI2) (0.4 retool). The solvent was removed under reduced pressure and the blue solid was washed with MeOH, centrifuged, filtered and dried under vacuum with P205. 6a: 280 mg (65%); m.p. > 300 °C. (Found: C, 35.94; H, 1.52; N, 10.69. C32HI2LtNsZnrequires C, 35.54; H, 1.12; N, 10.36%); uv-vis (H2SO4) gm~(Iog ~): 822 (5.24) and 296 nm (4.69)*,MALDI-MS m/z: 1080 [M+FF]. 6b: 279 mg (65%); m.p. > 300 °C. (Found: C, 34.90; H, 1.14; N, 10.72. C32Ht2LtNgNi'H20requires C, 35.17; H, 1.29; N, 10.25%); uv-vis (H2SO4) ~ (log ~): 808 (5.18) and 295 nm (4.90)*,MALDI-MS m/z: 1074 [M+I-F]. S-lodo-l,3-diiminoisoindoline (5). Through a mixture of 4-iodophthalonitrile II (1 g, 3.9 mmol) and NaOCH3 (0.021 g, 0.39 retool) in MeOH (25 ml), NH3 (g) was bubbled during lh at room temperature and then during 8 h at reflux. The solvent was evaporated under reduced pressure and the green solid was washed with an aqueous saturated solution of NH4CI. The solid was dried under vacumm with P205 to yield 783 rag (75%) ofS; m.p. 220 °C. (Found C, 33.28, H, 2.44, N, 14.25. CsI-I6IN3"H20requires C, 33.24; H, 2,79; N 14.54%); ~H n.mr. 8 (dlTFA): 8.8 (s, IH, At), 8.3 (d, IH, Ar) and 8.1 (d, 1H, At); t3C n.mr. 8 (dl-TFA): 165 (C-l, C-2), 136.4 (C-6, C-4), 127.7 and 127.0 (C-8, C-3), 125.5 (C-7) and 105.2 (C-5); FAB-MS m/z: 271 [M+FF]. Tetraiodophthalocyanine (6c). 5-Iodo-l,3-diiminoisoindoline (5) (400 mr, 1.5 mmol) was heated in DMAE (1.5 ml) at reflux under argon for 12 h. The solvent was removed under reduced pressure, and the green sofid was washed with MeOH, collected by centrifugation and dried under vacuum with P205 to give 133 mg (35%) of 6c; m.p. > 300 °C. (Found: C, 37.06', H, 3.18; N, 10.75. C32Hz4 I4Ns'H20 requires C, 37.02; H, 3.30; N, 10.75%); uv-vis (H2SO4) ~ ( l o g ~): 883 (5.17), 822 (5.23), 297 nm (5.17); MALDI-MS m/z: 1018 [M+I-I+]. 4-(3-Hydroxy-3-methyl-l-butynyl)phthalonitrile (8). Bis[triphenylphosphine]-palladium(II) dichloride (55 mr, 0.079 retool) and copper(I) iodide (6.5 mr, 0.039 retool) were added successively to 4-iodophthalonitrile n (4) (2 g, 7.9 retool) and 2-methylbut-3-yn-2-ol (1.23 ml, 9.4 mmol) in a mixture of distilled diethylamine (16 mi) and THF (6 ml). The mixture was stirred under argon at room temperature for 20 h and then evaporated under reduced pressure. The solid was extracted with CH2Ci2, washed with water and passed through a column of silica gel using a mixture of THF/hexane (6:1) to yield 1.27 g (78%) of a brown solid. M.p. 78°C. (Found C, 74.38; H, 5.05; N, 12.98. C13HIoN20requires C, 74.26; H, 4.80*,N, 13.33%); ~H n.m.r. 8 (CDCI3): 7.8 (m, 1H; I-I,~), 7.7 (d, 2H; I-I~), 4.0 (s, 1H; OH) and 1.6 (s, 6H; C(CH3)2); ~3C n.mr. 8 (CDCI3): 136.09 (C-3), 135.78 (C-5), 133.38 (C-6), 115.97 (CN), 115.02 (CN), 114.50 (C-2), 114.28 (C-I), 101.25 (C---C), 78.63 (C-3") and 30.96 (CH3); MS (70 ev, EI) m/z: 210 [M+] and 195 [M+-CH3].
Tetrakis(3-hydroxy-3-methyi-l-butynyl)phthalocyaninates Zinc(H) and Nickei(ED (7a, b). MethodA. Tetraidophthalocyaninate (6a, b) (0.090 retool) was reacted with 2-methylbut-3-yn-2-ol (0.90 mmoi) in the presence ofbis[triphenylphosphlne]palladium(II) dichloride [Pd(PPh3)2CI2](1 ~mol) and copper(I) iodide ~4 (0.5 ttmol) in a mixture of freshly distilled of Et2NH (2 ml) and THF (1 ml). The reaction mixture was stirred at room temperature for 12 h under argon atmosphere. After removing the solvent under reduced pressure, the blue solid was extracted with CH2C12 and chromatographed on silica gel using a mixture of THF:hexane (6:1) as eluent and washed with hot acetonitrile. 7a: 70 rag (86 %); m.p. > 300 °C (Found: C, 66.04; FL 4.74; N, 11.83. Cs2H4oNsO4Zn-2H20requires C, 66.28;
E. M. Maya et al. / Tetrahedron 54 (1998) 4397-4404
4403
H, 4.71; N, 11.89°,4); IH nm.r. 8 (drTFA): 7.5-8.0 (br signals, atom-H), 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3)', uv-vis (THF) ~ (log 8): 684 (5.02) and 358 nm (4.51), v (KBr): 3350 (OH) and 2223 (C-=C), LSIMS m z : 905 [M+W]. 7b: 64 rag (79%); m.p. > 300 °C. (Found: C, 66.46; H, 4.48; N, 12.39. Cs2I-h0NsO4Ni'2H20 requires C, 66.75; H, 4.74; N, 11.98%); ~H nm.r. 8 (drTFA): 7.3-8.2 (br signals, atom-H), 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3); uv-vis (THF) ~ ( l o g 8): 679 (5.04) and 338 nm (4.76); v (KBr): 3372 (OH), 2219 (C---C);LSIMS m/z: 899 [M+I-Y]. M e t h o d B. 400 mg (1.9 retool) of 4-(3-hydroxy-3-methyl-1-butynyl)phthalonitrile (8) was heated under reflux in DMAE (1.5 ml) under argon for 12 h in the presence of the corresponding metal (II) salt (MC12)(0.4 retool). The solvent was removed under reduced pressure and the blue solid was purified following the above procedure. Yield: 51% for 7a and 49°,4 for 7b. TetrakisO-hydroxy-3-methyl-l-butynyl)phthaloeyanine (70 Tetraiodophthalocyanine (6e) (80 rag, 0.076 mmol) was reacted with 2-methylbut-3-yn-2-ol (64 rag, 0.76 retool) in the presence of tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] (24 rag, 0.026 retool) and triphenylarsine (66 rag, 0.078 retool) in freshly distilled piperidine (3 ml)) 5 The reaction mixture was stirred at room tempertaure for 12 h under argon atmosphere. After removing the solvent under reduced pressure, the green solid was extracted with CH2C12 and the extracts were washed with water. The product was purified by chromatography on silica gel using a mixture of TI-~:hexane (2:1) as eluent to give 50 mg (79°4) of 7¢. M.p. > 300 °C. (Found: C, 43.50; H, 4,72; N, 13.05. Cs214_42NsO4.2H20requires C, 43.73, H, 5.05, N, 12.75%); ~H n,m.r. 8 (drTFA): 7,5-8.3 (br signals, arom-H) 4.0 (s, 4H; OH) and 1.6 (br signals, 24H; CH3); uv-vis (THF) ~ (log 8): 708 (5.30), 675 (5.33) and 350 nm (5.17); v (KBr): 3388 (OH), 2200 (C---C);LSIMS m/z: 843 [M+H+]. Tetraethynyiphthalocyanines (la-c). Tetrakis(3-hydroxy-3-methyl-l-butynyl)phthalocyanine (7a-¢) (0.045 retool) was heated with 15 mg (0.36 mmol) of powdered NaOH in 2-¢¢hoxyethanol. The reaction mixture was heated at reflux under argon atmosphere until all the starting phthalocyanine disappeared. The solvent was then removed under reduced pressure and the black solid was washed with MeOH, collected by centrifugation and dried under vacuum with P2Os. la: 15.4 mg (53%); m.p. > 300 °C; (Found: C, 68.02, H, 2.41, N, 15.19. C4oHI6NsZn'2H20requires C, 67.66, H 2.84, N, 15.78%); uv-vis (DMSO) ~ (log 8): 697 (4.46), 359 (4.35) and 291 nm (4.39); v (KBr): 3374 (C--CH); MALDI-MS m/z: 673 [M+I-V]. lb: 16.2 mg (54%); m.p. > 300°C. (Found: C, 68.03, H, 2.22, N, 15.53. C40HI6NsNi'2H20 requires C, 68.36, H
2.58, N, 15.95%); uv-vis (DMSO) ~ (MALDI-TOF) m/z: 667 [M+H+].
(log 8): 682 (4.63) and 292 nm (5.17); v (KB0:3407 (C---CH); MS
1¢: 16.4 mg (60%); m.p.> 300 °C; (Found: C, 73.74, H, 3.21, N, 16.95. C40HIsNs"2H20requires C, 74.29, H 3.43, N, 17.33%); uv-vis (DMSO) ~ (log ~): 689 (4.49), 292 nm (5.07); v (KB0:3419 (C-=CH); MS (MALDI-TOF) m/z: 611 [M+H+]. ACKNOWLEDGEMENTS This work was supported by the Comisi6n Interministerial de Ciencia y Tecnologia CICYT (Spain) and the Comunidad de Madrid grants MAT 96/0654 and 06T/017/96 respectively. A Graduate Research Fellowship of the Comunidad de Madrid to E.M.M. is gratefully acknowledged.
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REFERENCES AND NOTES
1. 2.
3.
4. 5.
6.
7. 8. 9.
10.
11. 12.
13, 14. 15. 16.
a) Lefevre, D.; Porteu, F., Balog, P., Roulliay, G. Z. and Palacin, S., Langmuir. 1993, 9, 150-161. b) Lefevre, D. Ph.D.Thesis, L'Universite Paris XI Orsay, 1995. Phthalocyanines:Properties and Applications; Leznoff, C. C. and Lever, A. B. P. Eds.; VCH Pubfishers: New York, 1989, 1992, 1993, 1996, vols I-IV. 2D polymers based on Pcs have been previously prepared and some of their physical properties studied. See for example: a) WOhrle, D. and Meyer, G., Kontakte, 1985, 3, 38-48. b) Djurado, D., Tadlaqui, S., Harnwi, A. and Cousseins, J. C., Synth. Met. 1991, 41-43, 2595-2600. Hanack, M. and Lang, M., Adv. Mater. 1994, 6, 819-833. See for example: a) Hanack, M. and Naannann, H. DE 40 01 158 (Chem. Abst. 1990, P-208923d). b) Vig,h, S., Lain, H.; Janda, P., Lever, A. B. P. and Leznoff, C. C.; Can. J. Chem. 1991, 69, 1457-1461. c) Terekhov, D. S.; Nolan, K. J. M.; McArthur, C. R. and Leznoff, C. C., J. Org. Chem. 1996, 61, 30343040. d)Isagao, H.; Terekhov, D. S. and Leznoff, C. C., J. Porph. Phthalocy. 1997, 1, 135-140. e)Nolan, K. J. M. and Leznoff, C. C., Synlett. 1997, 593-594. a) A~ H. and Van Lier~ J. E..~ Tetrahedr~n Lett. ~997~ 38~ ~~57-~ ~6~. b) Maya~ E. M..~Vitzqu~z~ P. and Tortes, T., Chem. Commun. 1997, 1175-1176. a) Sastre, A., Tortes, T. and Hanaek, M., Tetrahedron Lett. 1995, 36, 8501-8504. b) Sastre, A., Del Roy, B. and Tortes, T., J. Org. Chem. 1996, 61, 8591-8597. Ftnauindez, F.; Tortes, T.; Hauschel, B. and Hanack, M., Chem. Rev., in press. a) Geyer, M.; Plenzig, F.; Rauschnabel, J., Hanack, M., Del Rey, B.; Sastre, A. and Tortes, T., Synthesis, 1996, 1139-1151. b) Del Rey, B. and Tortes, T., TetrahedronLett. 1997, 38, 5351-5354. c) Cabez6n, B.; Rodriguez-Morgade, S. and Tortes, T., J. Org. Chem. 1995, 60, 1872-1874. a) Sastre, A., Tortes, T.; Diaz-Crarcia, M.A.; AguU6-L6pez, F., Dhermut, C., Brassel~, S., Ledoux, I. and Zyss, J.; J. Am. Chem. Soc. 1996, 118, 2746-2747. b) De la Torte, G., Tortes, T, and AguUb-L6pez, F.; Adv. Mat. 1997, 9, 265-269. c) Duro, J.A.; De la Torte, G., Barber~ J.; Serrano, J.L. and Tortes, T., Chem. Mat. 1996, 8, 1061-1066. Mareuccio, S. M.; Svirskaya, P. I.; Greenberg, S.; Lever, A. B. P. and Leznoff, CC.; Can. J. Chem. 1985, 63, 3057- 3069. Cleavage of TMS-protecting groups in alkynyl derivatives in the presence of metal salts has been described. See for example: Ito, H ; Arimoto, K.; Sensui, H. and Hosomi, A., Tetrahedron Lett. 1997, 38, 3977-3980. a ) Zhang, X. and Xu H J. Chem. Soc. Faraday Trans. 1993, 89, 3347-3351. b) Margaron, P., G-r~goire, M. J., Scasnar, V.; Ali, H. and van Lier, J. E.; Photochem. Photobiol. 1996, 63, 217-223. Nishino, N,, Wagner, R. W. and Lindsey, J. S., J. Org. Chem. 1996, 61, 7534-7544. Wagner, R. W.; Johnson, T. E.; Li, F. and Lindsey, J. S., J. Org. Chem. 19¢Y5,60, 5266-5273. A german patent 5" describes the preparation of tetraethynylphthalocyanine from tetravinylphthalocyanine by successive bromination-dehydrobromination reactions. However, no conclusive data about the structure of this compound were given.