Synthesis of Metallophthalocyanines under Solvent-free Conditions using Microwave Irradiation$ Ahmad Shaabani Chemistry Department, Shahid Beheshty University, P.O. Box 1939-4716, Tehran, Iran The phthalocyanine complexes of Cu, Co, Ni, and Fe are easily prepared upon exposure to microwave radiation under solvent-free conditions and reaction times are considerably reduced. Phthalocyanines are of interest not only as model com- pounds for the biologically important porphyrins but also because the intensely colored metal complexes are of commercial importance as dyes and pigments.1 Preparation of metallophthalocyanines from the reaction between metal salts, particularly CuCl, phthalic anhydride and urea is carried out on a large scale industrially, the copper derivatives being an important blue pigment.2 Typically, temperatures around 200 8C and reaction times of hours are needed.3 The reaction is sometimes described as followings: It is not clear what the reducing reagent is in this process.4 Such syntheses because of long reaction times and high temperature are often of low yield and giving mixtures of products from which the pure phthalocyanines may be di�cult to obtain.Microwave (MW) irradiation using commercial domestic ovens has recently been used to accelerate organic reactions, the e�cient heating giving rise to remarkable rate enhance- ments.5,6 Nevertheless, these procedures are seriously limited because of the use of solvents in microwave ovens which gives rise to elevated temperatures and consequently high pressures, thus leading in some cases to dangerous explosions.Here I describe a facile preparation of phthalocyanine complexes of Cu, Co, Ni and Fe in the absence of any solvent (``dry media'' conditions) which reduces consider- ably reaction times in a process that is accelerated by micro- wave irradiation. The experimental procedure involves a simple mixing and grinding of reactants and irradiating the reaction mixture in a microwave oven for about 4 to 7 min in the absence of any solvent.The reaction occurred instantly as the melting of the mixture started after about 3 min. The microwave oven was a domestic (Maximum 900 W) National model NN-6653 with ®ve select power levels (two of which were used for this experiment; high 100% wattage, medium 70% wattage). This extremely rapid, manipulatively simple, and inexpensive protocol avoids the use of excess and toxic solvents.The results for various metallophthalocyanines are summarized in Table 1. In conclusion, I have developed a convenient and rapid procedure for the synthesis of metallophthalocyanines using domestic microwave ovens for a few minutes under solvent-free conditions including ``dry'' media. Investi- gations toward extension of this procedure to other metals are in progress. Experimental Elemental analyses were performed using a Heraeus CHn-O rapid analyser. IR spectra were measured on a Shimadzu IR-470 spectro- meter.All starting solids used were anhydrous. The IR spectra of these compounds were in excellent agreement with those reported.10 The preparation of copper phthalocyanines is representative of the general procedure employed. Phthalic anhydride (26.50 g, 0.18 mol), urea 955.40 g, 0.92 mol), copper chloride (5.00 g, 0.05 mol), and ammonium molybdate (0.75 g, 3.80 mmol) were ground together until homogeneous, placed in a beaker and irra- diated in a microwave oven at high power for 6 min.Upon completion of the reaction the product was ground and washed with 5% caustic soda, water, 2% hydrochloric acid and again with water respectively. The dried phthalocyanine thus obtained weighed 23.3 g, 91% of the theoretical amount based on phthalic anhydride. [Cu(pc)] was subsequently recrystallized two times from con- centrated H2SO4. Usually during recrystallization the solution of phthalocyanine in concentrated H2SO4 was poured into distilled water.11 After complete recrystallization the [Cu(pc)] obtained was puri®ed by Soxhlet extraction using in succession methanol and methylene chloride, yield 86%. After two vacuum sublimations (Found: C, 66.69; H, 2.52; Cu, 11.00; N, 19.18. Calc.for C32H16CuN8: C, 66.74; H, 2.78; Cu, 11.03; N, 19.45%). ~max J. Chem. Research (S), 1998, 672±673$ Table 1 Synthesis of metallophthalocyanines, M(pc), using MW Time/min Yield (%)a Entry Product Found Reported Found Reported T/8C Ref 3a [Cu(pc)] from CuCl 6b 480 91 (86)c 91.8 190±195 7,8 3b [Co(pc)] from CoCl2 5b 480 86 (81) 90 180±190 7,9 3c [Ni(pc)] from NiCl2 4.5b 360 90 (86) 86.5 178 8 3d [Fe(pc)] from FeCl2 7d 660 89 (85) 95 180±190 7,9 aBased on the phthalic anhydride.bAt high power (100% wattage). cAfter Soxhlet extraction. dAt medium power (70% wattage). (KBr)/cm¡1 728 vs, 754 s, 779 m, 874 w, 894 m, 1048 m, 1081 s, 1114 s, 1157 m, 1277 m, 1324 s, 1409 m, 1452 w, 1495 m, 1602 w, 3025 vw.$This is a Short Paper as de®ned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J. Chem. Research (M). 672 J. CHEM. RESEARCH (S), 1998[Co(pc)] (Found: C, 67.30; H, 2.69; Co, 10.08; N, 19.47. Calc. for C32H16CoN8; C, 67.28; H, 2.80; Co, 10.32; N, 19.61%): ~max (KBr)/cm¡1 733 vs, 756 s, 780 m, 870 m, 910 m, 1056 m, 1089 vs, 1118 vs, 1157 m, 1283 s, 1327 s, 1419 m, 1458 w, 1515 s, 1598 w, 3040 vw.[Ni(pc)] (Found: C, 67.23; H, 2.71; N, 19.55; Ni, 10.20. Calc. for C32H16N8Ni; C, 67.30; H, 2.80; N, 19.61; Ni, 10.27%). ~max (KBr)/cm¡1 727 vs, 752 s, 771 m, 861 w, 907 m, 1055 (sh), 1084 s, 1114 s, 1157 m, 1277 m, 1320 s, 1415 m, 1457w, 1517 m, 1596 w, 3025 vw. [Fe(pc)] (Found: C, 67.59; H, 2.78; Fe, 9.76; N, 19.57. Calc. for C32H16FeN8; C, 67.64; H, 2.82; Fe, 9.83; N, 19.71%): ~max (KBr)/cm¡1 734 vs, 756 s, 780 m, 871 w, 904 m, 1076 s, 1117 s, 1156 m, 1279 m, 1327 s, 1411 m, 1456w, 1501 m, 1598 w, 3035 vw.The support of this work by the ministry of Science and Higher Education research council is gratefully acknowledged. Received, 9th December 1998; Accepted, 13th July 1998 Paper E/708858B References 1 A. B. P. Lever, Adv. Inorg. Chem. Radiochem., 1965, 7, 27. 2 F. H. Moser and A. L. Thomas, The Phthalocyanines, CRC Press, Boca Raton, FL, 1983; K. Venkataraman, Synthetic Dyes, Academic Press, 1952, vol. 2, pp. 1118±1142. 3 F. H. Moser and A. L. Thomas, Phthalocyanine Compounds, Reinhold, New York, 1963; Br. Pat., 909 375, 1962; Swiss Pat., 428 046, 1967; Br. Pat., 991 419, 1965. 4 F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 4th ed, Wiley, New York, vol. 134, 1980. 5 E. Gutierrez, A. Loupy, G. Bram and E. Ruiz-Hitzky, Tetrahedron Lett., 1989, 30, 945; D. R. Baghurst and D. M. P. 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