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Synlett 2010(6): 877-880  
DOI: 10.1055/s-0029-1219541
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Towards 2D and 3D Coordination Polymers: Synthesis of Shape-Persistent Star Monomers with 2,2′:6′,2′′-Terpyridin-4′-yl Units at the Periphery

Thomas Bauer, A. Dieter Schlüter, Junji Sakamoto*
Laboratory of Polymer Chemistry, Institute of Polymers, Department of Materials, ETH Zürich, Wolfgang-Pauli-Str. 10, HCI G523, 8093 Zürich, Switzerland
Fax: +41(44)6331395; e-Mail: sakamoto@mat.ethz.ch;
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Publication History

Received 17 December 2009
Publication Date:
23 February 2010 (online)

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Abstract

A set of shape-persistent star-shaped monomers which are multiply equipped with 2,2′:6′,2′′-terpyridin-4′-yl units has been synthesized. The synthetic sequences rest upon the Suzuki-Miyaura cross-coupling reaction which includes a sterically challenging six-fold coupling of a bulky aryl boronate to hexabromobenzene.

Key words

palladium - steric hindrance - chelates - supramolecular chemistry - periodic network

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10

For 2D polymer synthesis using 1 and 2 as monomers, formation of insoluble products with layered structures is expected as a result of their solution polymerization using metal cations such as Zn²+ and Pb²+. The lamellar solid products will be then subjected to delamellation in order to obtain individual 2D polymers eventually. Polymerizations are investigated not only in solution but also on solid substrate and at the air/water interface to ensure exclusive lateral growth. All details are to be reported in subsequent papers.

16

Synthesis of 1a: Compounds 5 (584 mg, 1.34 mmol) and 6a (162 mg, 0.300 mmol) were dissolved in toluene (22 mL) and t-BuOH (6 mL) under nitrogen. Na2CO3 (284 mg, 1.12 mmol) in H2O (19 mL) was added and degassed by freeze-pump-thaw cycle three times. Pd(dppf)Cl2 (37 mg, 0.045 mmol) was then added and followed by freeze-pump-thaw cycle once more. The mixture was heated at 110 ˚C for 4 d. After cooling to r.t., it was extracted with CH2Cl2, and dried over Mg2SO4. After removal of the solvent under reduced pressure, the residue was washed with MeOH and further purified by rGPC with CHCl3 as eluent to give 1a (210 mg, 57%) as a white powder. ¹H NMR (300 MHz, CDCl3): δ = 8.83 (s, 6 H), 8.77 (d, J = 4.7 Hz, 6 H), 8.69 (d, J = 7.9 Hz, 6 H), 8.06 (d, J = 8.4 Hz, 6 H), 7.95 (s, 3 H), 7.87-7.93 (m, 12 H), 7.85 (d, J = 7.2 Hz, 12 H), 7.38 (m, 6 H). ¹³C NMR (75 MHz, CDCl3): δ = 156.3, 156.0, 149.8, 149.2, 142.0, 141.3, 140.4, 139.7, 137.5, 136.9, 127.9, 127.8, 127.61, 127.56, 125.1, 123.8, 121.4, 118.7. HRMS (MALDI-ICR-FT, matrix; 3-hydroxypicolinic acid): m/z [M + H]+ calcd for C87H57N9: 1228.481; found: 1228.480.

17

Synthesis of 2a: Compounds 5 (486 mg, 1.12 mmol) and 7a (150 mg, 0.150 mmol) were dissolved in toluene (11 mL) and t-BuOH (3 mL) under nitrogen. Na2CO3 (237 mg, 2.24 mmol) in H2O (9.5 mL) was added and degassed by freeze-pump-thaw cycle three times. Pd(dppf)Cl2 (22 mg, 0.027 mmol) was added and followed by freeze-pump-thaw cycle once more. The mixture was heated at 110 ˚C for 4 d. After cooling to r.t., it was extracted with CH2Cl2, and dried over Mg2SO4. After removal of the solvent under reduced pressure, the residue was washed with MeOH and further purified by rGPC with CHCl3 as eluent to give 2a (290 mg, 41%) as a white powder. ¹H NMR (700 MHz, CDCl3): δ = 8.69 (s, 12 H), 8.65 (d, J = 4.0 Hz, 12 H), 8.59 (d, J = 7.9 Hz, 12 H), 7.87 (d, J = 8.7 Hz, 12 H), 7.80 (m, 12 H), 7.58 (d,
J = 8.7 Hz, 12 H), 7.22-7.37 (m, 24 H), 7.12 (d, J = 8.1 Hz, 12 H). ¹³C NMR (176 MHz, CDCl3): δ = 156.3, 155.9, 149.6, 149.0, 141.2, 140.3, 139.9, 136.9, 136.7, 136.6, 132.0, 127.4, 127.1, 125.4, 123.5, 121.2, 118.5. HRMS (MALDI-ICR-FT, matrix; 3-hydroxypicolinic acid): m/z [M + H]+ calcd for C168H108N18: 2377.908; found: 2377.912.

18

Synthesis of 3: Compounds 5 (708 mg, 1.63 mmol) and 8 (172 mg, 0.271 mmol) were dissolved in toluene (22 mL) and t-BuOH (6 mL) under nitrogen. Na2CO3 (173 mg, 1.63 mmol) in H2O (19 mL) was added and degassed by freeze-pump-thaw cycle three times. Pd(dppf)Cl2 (33 mg, 0.040 mmol) was then added and followed by freeze-pump-thaw cycle once more. The mixture was heated at 110 ˚C for 4 d. After cooling to r.t., it was extracted with CH2Cl2, and dried over Mg2SO4. After removal of the solvent under reduced pressure, the residue was washed with MeOH and further purified by rGPC with CHCl3 as eluent to give 3 (180 mg, 33%) as a white powder. ¹H NMR (300 MHz, CDCl3): δ = 8.80 (s, 8 H), 8.74 (d, J = 4.1 Hz, 8 H), 8.68 (d, J = 8.1 Hz, 8 H), 7.99 (d, J = 7.7 Hz, 8 H), 7.87 (m, 8 H), 7.78 (d, J = 8.7 Hz, 8 H), 7.66 (d, J = 8.7 Hz, 8 H), 7.50 (d, J = 8.3 Hz, 8 H), 7.34 (m, 8 H). ¹³C NMR (101 MHz, CDCl3): δ = 156.3, 156.0, 149.8, 149.2, 146.2, 141.2, 138.0, 137.3, 136.8, 131.6, 127.7, 127.5, 126.4, 123.8, 121.4, 118.7, 64.4. HRMS (MALDI-ICR-FT, matrix; 3-hydroxypicolinic acid): m/z [M + H]+ calcd for C109H72N12: 1549.608; found: 1549.603.

20

Synthesis of 1b: Compounds 5 (531 mg, 1.22 mmol) and 6b (85.3 mg, 0.271 mmol) were dissolved in toluene (22 mL) and t-BuOH (6 mL) under nitrogen. Na2CO3 (53 mg, 2.44 mmol) in H2O (19 mL) was added and degassed by freeze-pump-thaw cycle three times. Pd(dppf)Cl2 (36.7 mg, 0.045 mmol) was then added and followed by freeze-pump-thaw cycle once more. The mixture was heated at 110 ˚C for 4 d. After cooling to r.t., it was extracted with CH2Cl2, and dried over Mg2SO4. After removal of the solvent under reduced pressure, the residue was washed with MeOH and further purified by rGPC with CHCl3 as eluent to give 1b (140 mg, 52%) as a white powder. ¹H NMR (300 MHz, CDCl3): δ = 8.84 (s, 6 H), 8.77 (d, J = 3.8 Hz, 6 H), 8.70 (d, J = 7.9 Hz, 6 H), 8.09 (d, J = 8.1 Hz, 6 H), 7.83-8.02 (m, 15 H), 7.37 (m, 6 H). ¹³C NMR (75 MHz, CDCl3): δ = 156.3, 156.1, 149.8, 149.2, 141.9, 141.7, 137.8, 136.9, 127.94, 127.91, 125.5, 123.8, 121.4, 118.8. HRMS (MALDI-ICR-FT, matrix; 3-hydroxypicolinic acid): m/z [M + H]+ calcd for C69H45N9: 1000.387; found: 1000.388.

21

Synthesis of 2b: Compounds 5 (1.06 g, 2.44 mmol) and 7b (150 mg, 0.271 mmol) were dissolved in toluene (22 mL) and t-BuOH (6 mL) under nitrogen. Na2CO3 (474 mg, 4.47 mmol) in H2O (18 mL) was added and degassed by freeze-pump-thaw cycle three times. Pd(dppf)Cl2 (40 mg, 0.049 mmol) was then added and followed by freeze-pump-thaw cycle once more. The mixture was heated at 110 ˚C for 4 d. After cooling to r.t., the mixture was extracted with CH2Cl2, and dried over Mg2SO4. After removal of the solvent under reduced pressure, the residue was washed with MeOH and further purified by rGPC with CHCl3 as eluent to give 2b (140 mg, 30%) as a white powder. ¹H NMR (300 MHz, CDCl3): δ = 8.57 (s, 12 H), 8.56 (d, J = 2.4 Hz, 12 H), 8.50 (d, J = 8.1 Hz, 12 H), 7.74 (m, 12 H), 7.57 (d, J = 8.0 Hz, 12 H), 7.20 (m, 12 H), 7.14 (d, J = 8.6 Hz, 12 H). ¹³C NMR (75 MHz, CDCl3): δ = 156.3, 155.5, 149.6, 148.9, 141.3, 140.3, 136.7, 135.3, 131.9, 126.0, 123.5, 121.2, 118.8. HRMS (MALDI-ICR-FT, matrix; 3-hydroxypicolinic acid): m/z [M + H]+ calcd for C132H84N18: 1921.720; found: 1921.716.