Inspecting Metal Coordination Induced Perturbation of Molecular Ligand Orbitals at a Sub-molecular Resolution

Transcription

1 Inspecting Metal Coordination Induced Perturbation of Molecular Ligand rbitals at a Sub-molecular Resolution Weihua Wang 1, Yuning Hong 2, Xingqiang Shi 3, C. Minot 3,4, M.A. Van Hove 3, Ben Zhong Tang 2, and ian Lin 1 * 1 Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China 2 Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong, China 3 Department of Physics and Materials Science, City University of Hong Kong, Hong Kong, China 4 Laboratoire de Chimie Théorique, Université Pierre & Marie Curie, Paris 6, CRS, UMR7616, Case 137, 4 place Jussieu, Paris, F Cedex France Supporting Information 1

2 Chemical Synthesis Tetrahydrofuran (THF; Labscan) was purified by distillation from sodium benzophenone ketyl under nitrogen immediately prior to use. 2-Acetylpyridine, sodium hydroxide, ammonium acetate, n-butyllithium, trimethyl borate, and other reagents were all purchased from Aldrich and used as received. The synthesis of 1,2-bis(4-bromophenyl)-1,2-diphenylethene was described in previous publication.(s1) 1 H and 13 C MR spectra were measured on a uker AV 400 spectrometer using tetramethylsilane (TMS; δ = 0) as internal standard. Mass spectra were recorded on a Finnigan TSQ 7000 triple quadrupole spectrometer operating in a MALDI-TF mode. a. Synthesis of 4 -(4-bromophenyl)-2,2 :6,2 -terpyridine (1) (S2). 2-acetylpyridine (5 g, 4.12 mmol) was added to a suspension of crushed ah (1.2 g, 8.25 mmol) in PEG300 (70 ml), and stirred at 0 o C for 10 minutes. 4-omobenzaldehyde (7.64 g, 4.12 mmol) was then added by syringe and the suspension left standing at 0 o C for 2 h. Every 15 minutes the suspension was manually stirred with a spatula as the viscosity became too great for adequate mixing using a magnetic follower. After 2 h, H 4 Ac (20 g, excess) was added and the suspension heated at 100 o C for 2 h. During this time, the color of the mixture changed from red to brown, and was accompanied by formation of a fine brown precipitate of the product. Water (150 ml) was then 2

3 added and the precipitate of 1 was isolated by filtration, washed with water (100 ml) and cold EtH (20 ml). The crude product was purified on a basic aluminium oxide column using hexane/chloroform (1:1 v/v) as eluent. 1 was obtained as white powder in 75% yield (6.05 g). 1 H MR (400 MHz, CDCl 3 ), δ (ppm): (m, 6H), (m, 2H), (d, 2H), (d, 2H), (m, 2H). 13 C MR (100 MHz, CDCl 3 ), δ (ppm): 156.0, 155.9, 149.1, 148.9, 137.3, 136.9, 132.0, 128.8, 123.9, 123.4, 121.3, MS (TF), m/e ((M H) +, calcd ). ah H 4 Ac H aq. EtH EtH 1 b. Synthesis of 4,4'-(1,2-diphenylethene-1,2-diyl)bis(4,1-phenylene)diboronic acid (2). 1,2- bis(4-bromophenyl)-1,2-diphenylethene (0.4 g, 0.82 mmol) was dissolved in 20 ml of THF in a 100 ml flask, and the flask was placed in an acetone dry ice bath at 78 C. A solution of 1.0 ml (2.6 mmol) of n-butyllithium (2.5 M in hexane) was added carefully to the mixture under stirring. After 1h, 0.46 ml (4.0 mmol) of trimethyl borate was added to the solution and allowed to react for 45 min. The mixture was warmed to room temperature and overnight. Then dilute 3

4 HCl was used to quench the reaction. After filtration and drying, the product was purified by silica gel column with ethyl acetate as eluent. The product was obtained as yellow solid in 54% yield. 1 H MR (d-meh, 300MHz) δ (ppm): (m, 10H), (m, 4H), (m, 4H). 13 C MR (d-meh, 75MHz), δ (TMS, ppm): 157.2, 146.2, 141.4, 137.0, 133.9, 132.7, 128.9, 127.4, MS (TF) m/e: ([M 2H] + calcd: 420.1). i) n-buli, THF, -78 o C H B H ii) B(CH 3 ) 3 iii) HCl, H 2 H B H 2 c. Synthesis of 1,2-bis(4 -(4-2,2 :6,2 -terpyridyl)-biphenyl-4-yl)-1,2-tetra-phenylethene (3). 1 (0.5 g, 1.43 mmol), 2 (0.3 g, 0.71 mmol), and tetrakis (triphenylphosphine)palladium(0) (41 mg, mmol) were dissolved in 30 ml of degassed THF. 3 ml of saturated a 2 C 3 aqueous solution was added to the mixture under stirring. After refluxing for 48 h, the reaction mixture was cooled to room temperature and filtered. The solvent was evaporated under vacuum and the organic solution was washed with water for three times. The crude product was purified on a basic aluminium oxide column using hexane/chloroform (1:1 v/v) as solvent. 3 was obtained as yellow powder in 52% yield (0.37 g). 1 H MR (400 MHz, CDCl 3 ), δ (ppm): (m, 8H), (m, 4H), (t, 4H), (d, 2H), (m, 4H), 4

5 (m, 4H), (m, 6H), (m, 4H), (m, 4H), (m, 4H). 13 C MR (100 MHz, CDCl 3 ), δ (ppm): 156.1, 149.1, 143.4, 136.9, 132.0, 128.6, 127.5, 126.2, 123.9, 121.4, 118.6, MS (TF), m/e ([M] +, calcd ). 1 2 Pd(PPh 3 ) 4 /a 2 C 3 THF/H 2 3 References S1. Dong, Y.; Lam, J. W. Y.; Qin, A.; Liu, J.; Li, Z.; Tang, B. Z.; Sun, J.; Kwok, H. S. Appl. Phys. Lett. 2007, 91, S2. Smith, C. B.; Raston, C. L.; Sobolev, A.. Green Chem. 2005, 7,