A Fourfold Benzodehydroannuleno-Fused Porphyrazine

Dedicated to Professor K. Peter C. Vollhardt – eminent chemist and inspirational character

Abstract

Four benzodehydroannulene subunits were implemented on a dibenzoquinoxalinopoprhyrazine core using efficient palladium-mediated alkyne coupling and oxidative acetylene coupling on phenanthrene dione precursors. Despite the significant amount of strain in system, as evidenced by X-ray analysis of an immediate precursor, porphyrazine assembly leads to an extended model for N-doped graphyne with photosensitizing properties.

Key words

acetylene coupling - cycloalkynes - dehydroannulenes - phthalocyanines - singlet oxygen

• References

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• 13 For details, see the Supporting Information.
• 14 Compound 6 A solution of 5 (500 mg, 0.39 mmol) and Cu(OAc)₂ in pyridine (10 mL) was stirred for 2 h at 60 °C. After cooling to r.t. CHCl₃ (50 mL) was added, and the mixture was washed successively with 1 N HCl (50 mL), H₂O (2 × 50 mL), and sat. aq NaCl (50 mL). The organic layer was separated, dried over Na₂SO₄, filtered, and excess solvent was removed under reduced pressure. The residue was purified by column chromatography on silica gel with CHCl₃ to yield a bright yellow solid (450 mg, 0.35 mmol, 90%). ¹H NMR (400 MHz, CDCl₃): δ = 8.51 (s, 2 H, CH_phenan), 7.74 (s, 2 H,, CH_phenan), 7.35 (d, ³ J _HH = 8.2 Hz, 12 H, CH_arom), 7.10 (d, ³ J _HH = 8.2 Hz, 12 H, CH_arom), 7.08 (s, 2 H, CH_arom), 6.42 (s, 2 H, CH_arom), 4.19 (br s, 4 H, OCH₂), 3.91 (s, 6 H, OCH₃), 3.69 (br s, 4 H, OCH₂), 3.39(s, 6 H, OCH₃), 2.32 (s, 18 H, CH₃) ppm. ¹³C NMR (126 MHz, CDCl₃): δ = 149.69, 149.32, 142.56, 136.28, 132.79, 130.93, 130.24, 129.06, 128.99, 128.72, 128.24, 124.42, 118.43, 118.30, 116.33, 113.54, 101.14, 93.10, 92.46, 92.42, 83.76, 82.46, 56.03, 55.72, 55.46, 20.95 ppm. MALDI-MS (DCTB, positive ion mode): m/z = 1279.55 [M + H]⁺.
• 15 Compound 7 A solution of 6 (300 mg, 0.23 mmol) and PTSA·H₂O (134 mg, 0.7 mmol) in glacial AcOH and o-dichlorobenzene was heated at 140 °C for 2 h until the starting material was completely hydrolyzed (TLC control). After cooling to 70 °C diaminomaleonitrile (40 mg, 0.35 mmol) was added, and the solution was stirred for 3 h. The solution was cooled to r.t. and slowly added to MeOH (50 mL). The resulting brownish red precipitate was collected by filtration. The residue was purified by column chromatography on silica gel with PE–EtOAc (2:1) to yield a red solid (243 mg, 0.19 mmol, 82%).¹H NMR (400 MHz, CDCl₃): δ = 9.10 (s, 2 H, CH_phenan),8.50 (s, 2 H, CH_phenan), 7.35 (d, ³ J _HH = 8.2 Hz, 12 H, CH_arom), 7.11 (d, ³ J _HH = 8.2 Hz, 12 H, CH_arom), 6.83 (s, 2 H, CH_arom), 6.21 (s, 2 H, CH_arom), 3.69 (s, 6 H, OCH₃), 3.36 (s, 6 H, OCH₃), 2.36 (s, 18 H, CH₃) ppm. ¹³C NMR (126 MHz, CDCl₃): δ = 149.69, 149.32, 142.56, 136.28, 132.79, 130.93, 130.24, 129.06, 128.99, 128.72, 128.24, 124.42, 118.43, 118.30, 116.33, 113.54, 101.14, 93.10, 92.46, 92.42, 83.76, 82.46, 56.03, 55.72, 55.46, 20.95 ppm. ESI-HRMS: m/z calcd for [C₉₀H₆₂N₄O₄ + Ag]⁺ = 1369.3817; found: 1369.3836 [M + Ag]⁺. UV/vis (CHCl₃): λ_max (ε/10⁵ M^–1 cm^–1) = 312 (1.06), 351 (0.66), 374 (0.48), 409 (0.53) nm.
• 16 Crystallographic data for compound 7 have been deposited with the accession number CCDC 1054333, and can be obtained free of charge from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax [phone]; Email: [e-mail]; web site: www.ccdc.cam.ac.uk/conts/retrieving.html.
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