N,N-Dihydrotetraazaheptacene: A Synthetic Strategy towards Larger Acenes with Ambient Stability

Abstract

We report the synthesis of the first N,N-dihydrotetraazaheptacene, which is solution-processible and stable as a solid under ambient conditions for over three years.

alkynes - heteroacene - condensation

References and Notes

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For long heteroacenes that are interspersed with pyrene or other units, see:

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<A NAME="RB11611ST-14">14</A>

The original sample was prepared in October 2007 for single-crystal X-ray diffraction. The same sample has been continuously exposed to atmospheric conditions; exposure to light has not been continuous, but the sample has been in contact with light for weeks at a time. The original ^¹H NMR is shown in the Supporting Information, as well as the ^¹H NMR taken from the same sample in October 2010 without performing any purification. The October 2010 sample was simply dissolved in CDCl₃ and the spectrum was taken.

<A NAME="RB11611ST-15">15</A>

Into a thick-walled glass bomb (100 mL volume) were added 1,4-bis[(triisopropylsilyl)ethynyl]naphthalene-2,3-diamine (1; 0.400 g, 7.71 × 10^-4 mol, 2 equiv) and 2,5-dihydroxy-benzoquinone (2; 0.054 g, 3.85 × 10^-4 mol, 1 equiv), which were dissolved in AcOH (30 mL). The reaction vessel was sealed and heated to 120 ˚C for 6 d while stirring. The reaction was cooled to r.t. and extracted with CH₂Cl₂ (50 mL). The organic layer was washed with H₂O (2 × 100 mL), dried with Na₂SO₄, and the solvent was removed in vacuo. The crude mixture was purified by column chromatography on silica gel using hexane-CH₂Cl₂ (3:1). Compound 3 was isolated as a dark purple solid (0.080 g, 18.7% yield); mp stable up to 400 ˚C. IR (KBr): 3375, 3055, 2958, 2931, 2719, 2434, 2360, 2133, 1739, 1720, 1596, 1569, 1488, 1461, 1377, 1261, 1226, 1153, 1107 cm^-¹. ^¹H NMR (CDCl₃): δ = 8.60 (dd, J ₁ = 3.3 Hz, J ₂ = 6.7 Hz, 2 H), 7.94 (dd, J ₁ = 3.2 Hz, J ₂ = 6.2 Hz, 2 H), 7.62 (s, 2 H), 7.54 (dd, J ₁ = 3.2 Hz, J ₂ = 6.7 Hz, 2 H), 7.35 (dd, J ₁ = 3.3 Hz, J ₂ = 6.2 Hz, 2 H), 6.82 (s, 2 H), 1.29-1.30 (br m, 42 H), 1.25-1.26 (br m, 42 H). ^¹³C NMR (CDCl₃): δ = 145.7, 141.3, 135.8, 134.1, 130.9, 129.3, 127.3, 127.0, 126.0, 125.1, 119.1, 105.9, 105.7, 105.1, 103.4, 101.7, 99.5, 19.0, 18.9, 11.7, 11.4. HRMS: m/z [M⁺] calcd for C₇₀H₉₆N₄Si₄: 1104.6712; found: 1104.6485.