Results and Discussion
Condensation of ms
-arylsubstituted dipyrrolylmethanes 1-3
] with aldehydes RCHO (R = CH3
) gives 5,15-diphenyl-3,7,10,13,17,20-hexamethyl-2,8,12,18-tetrabutylporphyrin (4
), 5,15-diphenyl-3,7,13,17-tetramethyl-2,8,10,12,18,20-hexabutylporphyrin (5
), 5,15-di-(4-methoxyphenyl)- 3,7,13,17-tetramethyl-2,8,10,12,18,20-hexabutylporphyrin (6
) and 5,15-di-(4-nitrophenyl)-3,7,13,17- tetramethyl-2,8,10,12,18,20-hexabutylporphyrin (7
) (cf. Scheme 1
The reactions of 5,5'-dicarboxydipyrrolylmethanes (1
) with appropriate aldehydes was carried out in pyridine at elevated temperatures and pressures. Maximum yields were obtained by the reaction of 1 mole ms
) with 3.6 moles of aldehyde in the presence of 3.6 moles of nitrobenzene. The increased yield observed in the presence of nitrobenzene is probably related to the oxidizing ability of nitro-group. The rather low yields of ms
- tetrasubstituted porphyrins (4
) is probably caused by unfavourable spatial factors affecting the cyclo-condensation process. Similar results were obtained for condensation of 2,5-unsubstituted 3,4-dimethyl-pyrroles with aldehydes [2
]. The porphyrin yield was 5-6% and did not depend on the nature of the al-dehyde.
H-NMR-spectra are in complete accord with the proposed structures 4
. The signals of the ms
-phenyl group protons appear in the range of 7.7-8.0 ppm. The chemical shifts of the β
-alkyl protons are located between 0,8-4,0 ppm. The magnetic field of the porphyrin ring π
-electron current influences the position of signals of the hydrocarbon fragments of the ms
-substituents, a fact reflected in the NMR spectrum by the separate, non-overlapping, signals of the CH2
fragments of the alkyl substitu-ents. Thus, in porphyrins 5
the protons of the CH2
groups of the butyl substituents directly connected to the macroheterocyle appear as a triplet at 4.5 ppm., the adjacent CH2
group gives a pentet at 2.5 ppm., the following CH2
group gives a sextet located at 1.55 ppm. Finally, the terminal CH3
group ap-pears as a triplet at 0.85 ppm. Substitution in the phenyl rings of 5,15-diphenylporphyrins (X = 4-OCH3
in compound 6
) has no significant effects on the position of β
-alkyl and ms
-substituent proton signals. The disappearance of N-H proton bands is unclear. Similar effects have been observed for ms
-Tetrasubstituted octaalkylporphyrins 4
have a deformed porphyrin cycle structure, that causes a red shift and broadening of the absorption in the UV-vis. spectra in a comparison with tetraphenylpor-phyrin and ms
-unsubstituted octaalkylporphyrins [3
]. To confirm the molecular structures the IR spectra of the synthesized porphyrins were investigated. Together with the NMR data they reliably prove the proposed structures 4
in most cases.
1H NMR spectra were recorded on a Bruker AC-500 spectrometer operating at 600 MHz with HMDS as internal standard in CDCl3. UV-vis. spectra were obtained on a Specord M400 spectropho-tometer in CHCl3. IR spectra (KBr disks) were obtained on a Specord M80 spectrophotometer.
A mixture of ms-phenyl-5,5/-dicarboxy-4,4/-dibutyl-3,3/-dimethyl-2,2/-dipyrrolylmethane (1, 0.50 g), anhydrous zinc acetate (0.63 g), nitrobenzene (0.48 mL), pyridine (8 mL) and acetaldehyde (0.20 mL) was heated at 180° C for 2 hours in a sealed ampule. The reaction mixture was cooled, diluted with water (50 mL) and heated at 100° for 30 minutes. The precipitate was isolated by filtration and kept into a solution of sulfuric acid (0.50 mL) in dimethylformamide (50 mL) for 1 hour. The product was extracted with 50 mL of chloroform and washed with water, then ammonia solution and water again. The product was purified by silica gel chromatography (benzene), followed by recrystallization (CHCl3/methanol) to afford the title compound. Yield 32 mg (8%). Rf 0.30 (Silufol, benzene); UV-vis (CHCl3): λmax, nm (lg ε) 629.1(3.48); 547.5(3.62); 540.4(3.68); 507.1(4.01); 421.4(4.89). IR , cm-1: νNH 3325; δNH 974; γNH 710; νCH 3060; δCH 1500. 1H NMR (CDCl3): phenyl protons - [7.97d (4H; o-H); 7.35 t (4H; m-H); 7.70 t (2H; p-H)]; 4.00 s (6H; ms-CH3); 3.92 (t, 8H, CH2CH2CH2CH3); 2,42 s (12H; β-CH3); 2.13 (pentet, 8H, CH2CH2CH2CH3), 1.64 (sextet, 8H, CH2CH2CH2CH3), 1.11 (t, 12H, CH2CH2CH2CH3). Anal. Calcd for C57H84N4: C 83.01, H 10.19, N 6.80. Found: C 82.98, H 10.14, N 6.77.
The following substances were similarly prepared:
Yield 37,7 mg (9.5%). Rf 0.39 (Silufol, benzene); UV-vis (CHCl3): λmax, nm (lg ε) 629.9 (3.50); 548.1 (3.67); 540.9 (3.70); 507.7 (4.08); 422.1 (4.90). IR, cm-1: νNH 3322; δNH 971; γNH 712; νCH 3067; δCH 1505. 1H NMR (CDCl3): phenyl protons: 7.92d (4H; o-H); 7.37 t (4H; m-H); 7.68 t (2H; p-H)]; 4.50 t (4H; ms-CH2CH2CH2CH3); 4.07 s (6H; ms-CH3); 3.90 (t, 8H, CH2CH2CH2CH3); 2.50 pentet (4H; ms-CH2CH2CH2CH3); 2.42 s (12H; β-CH3); 2.10 (pentet, 8H, CH2CH2CH2CH3); 1.62 (sextet, 8H, CH2CH2CH2CH3); 1.55 sextet (4H; ms-CH2CH2CH2CH3); 1.08 (t, 12H, CH2CH2CH2CH3); 0.85 t (6H; ms-CH2CH2CH2CH3). Anal. Calcd for C63H96N4: C 83.26, H 10.57, N 6.17. Found: C 83.21, H 10.52, N 6.12.
Yield 39 mg (10%). Rf 0.47 (Silufol, benzene); UV-vis (CHCl3): λmax, nm (lg ε) 626.8 (3.43); 548.9 (3.61); 542.3 (3.78); 508.7 (4.11); 425.1(4.99). IR, cm-1: νNH 3326; δNH 978; γNH 717; νCH 3072; δCH 1510. 1H NMR (CDCl3): phenyl protons: 7,90 d (4H; o-H); 7,33 t (4H; m-H); 4,52 t (4H; ms- CH2CH2CH2CH3); 4,11 s (6H; ms-CH3); 4.00c(6H; CH3O); 3.90 (t, 8H, CH2CH2CH2CH3); 2.55 pentet (4H; ms-CH2CH2CH2CH3); 2.40 s (12H; β-CH3); 2.16 (pentet, 8H, CH2CH2CH2CH3); 1.69 (sextet, 8H, CH2CH2CH2CH3); 1.53 sextet (4H; ms-CH2CH2CH2CH3); 1.12 (t, 12H, CH2CH2CH2CH3); 0.80 t (6H; ms-CH2CH2CH2CH3). Anal. Calcd for C65H100N4O2: C 80.58, H 10.33, N 5.78. Found: C 80.52, H 10.30, N 5.72.
Yield 40 mg (10%). Rf 0.17 (Silufol, benzene); UV-vis (CHCl3): λmax, nm (lg ε) 631.1(3.53); 549.2(3.71); 541.2 (3.71); 508.7(4.11); 424.7(4.94). IR (KBr), cm-1: νNH 3328; δNH 976; γNH 723; νCH 3070; δCH 1511. 1H NMR (CDCl3): phenyl protons: 7.92d (4H; o-H); 7,37 t (4H; m-H)]; 4.50 t (4H; ms-CH2CH2CH2CH3); 4.07 s (6H; ms-CH3); 3.90 (t, 8H, CH2CH2CH2CH3); 2.50 pentet (4H; ms- CH2CH2CH2CH3); 2.42 s (12H; β-CH3); 2.10 (pentet, 8H, CH2CH2CH2CH3); 1.62 (sextet, 8H, CH2CH2CH2CH3); 1.55 sextet (4H; ms-CH2CH2CH2CH3); 1.08 (t, 12H, CH2CH2CH2CH3); 0.85 t (6H; ms-CH2CH2CH2CH3). Anal. Calcd for C63H94N6O4: C 75.75, H 9.42, N 8.42. Found: C 75.72, H 9.38, N 8.37.