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

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.

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

References and Notes

<A NAME="RG37709ST-1">1</A> Constable EC. Thompson AMWC. J. Chem. Soc., Dalton Trans.  1992,  3467 

<A NAME="RG37709ST-2">2</A> Barzani V. Juris A. Venturi M. Chem. Rev.  1996,  96:  759 

For recent reviews, see:

<A NAME="RG37709ST-3A">3a</A> Schubert US. Eschbaumer C. Angew. Chem. Int. Ed.  2002,  41:  2892 

<A NAME="RG37709ST-3B">3b</A> Knapp R. Kelch S. Schmelz O. Rehahn M. Macromol. Symp.  2003,  204:  267 

<A NAME="RG37709ST-3C">3c</A> Dobrawa R. Würthner F. J. Polym. Sci., Part A: Polym. Chem.  2005,  43:  4981 

<A NAME="RG37709ST-3D">3d</A> Williams KA. Boydston AJ. Bielawski CW. Chem. Soc. Rev.  2007,  36:  729 

<A NAME="RG37709ST-3E">3e</A> Fox JD. Rowan SJ. Macromolecules  2009,  42:  6823 

<A NAME="RG37709ST-3F">3f</A> Chiper M. Hoogenboom R. Schubert US. Macromol. Rapid. Commun.  2009,  30:  565 

For example, see:

<A NAME="RG37709ST-4A">4a</A> Newkome GR. Cho TJ. Moorefield CN. Baker GR. Cush R. Russo PS. Angew. Chem. Int. Ed.  1999,  38:  3717 

<A NAME="RG37709ST-4B">4b</A> Constable EC. Housecroft CE. Smith CB. Inorg. Chem. Commun.  2003,  6:  1011 

<A NAME="RG37709ST-5">5</A> For example, see: Venturi M. Serron S. Juris A. Campagna S. Balzani V. Top. Curr. Chem.  1998,  197:  192 

<A NAME="RG37709ST-6">6</A> Huheey JE. Keiter EA. Keiter RL. Inorganic Chemistry: Principles of Structures and Reactivity   4th ed.:  HarperCollins; New York: 1993.  p.547 

For example, see:

<A NAME="RG37709ST-7A">7a</A> Diederich F. Rubin Y. Angew. Chem., Int. Ed. Engl.  1992,  31:  1101 

<A NAME="RG37709ST-7B">7b</A> Yaghi OM. O’Keeffe M. Ockwig NW. Chae HK. Eddaoudi M. Kim J. Nature (London)  2003,  423:  705 

<A NAME="RG37709ST-7C">7c</A> Sakamoto J. van Heijst J. Lukin O. Schlüter AD. Angew. Chem. Int. Ed.  2009,  48:  1030 

<A NAME="RG37709ST-8">8</A> For a recent comprehensive review, see: Miyaura N. Metal-Catalyzed Cross-Coupling Reactions of Organoboron Compounds, In Metal-Catalyzed Cross-Coupling Reactions   2nd ed., Vol. 1:  de Meijere A. Diederich F. Wiley-VCH; Weinheim: 2005.  p.41 

<A NAME="RG37709ST-9">9</A> Kissel P. Schlüter AD. Sakamoto J. Chem. Eur. J.  2009,  15:  8955 

<A NAME="RG37709ST-10">10</A>

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 Zn^²+ and Pb^²+. 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.

<A NAME="RG37709ST-11">11</A> Mutai T. Cheon J.-D. Arita S. Araki K. J. Chem. Soc., Perkin Trans. 2  2001,  1045 

<A NAME="RG37709ST-12">12</A> Wang J. Hanan GS. Synlett  2005,  1251 

<A NAME="RG37709ST-13">13</A> Ishiyama T. Murata M. Miyaura N. J. Org. Chem.  1995,  60:  7508 

<A NAME="RG37709ST-14">14</A> Aspley CJ. Williams JAG. New J. Chem.  2001,  25:  1136 

<A NAME="RG37709ST-15">15</A> Rathore R. Burns CL. Guzei IA. J. Org. Chem.  2004,  69:  1524 

<A NAME="RG37709ST-16">16</A>

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.

<A NAME="RG37709ST-17">17</A>

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.

<A NAME="RG37709ST-18">18</A>

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.

<A NAME="RG37709ST-19">19</A> For example, see: Sakamoto J. Schlüter AD. Eur. J. Org. Chem.  2007,  2700 

<A NAME="RG37709ST-20">20</A>

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.

<A NAME="RG37709ST-21">21</A>

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.

<A NAME="RG37709ST-22">22</A> For a six-fold Suzuki-Miyaura cross-coupling of phenyl boronate with hexabromobenzene, see: Mora M. Jiménez-Sanchidrián C. Ruiz JR. Appl. Org. Chem.  2008,  22:  122