Supporting Information. for. Angew. Chem. Int. Ed. Z Wiley-VCH 2002

Transcription

1 Supporting Information for Angew. Chem. Int. Ed. Z19663 Wiley-VCH Weinheim, Germany

2 Selective Measurements of a itroxide-itroxide Distance of 5 nm and a itroxide-copper distance of 2.5 nm in a Terpyridine-based Copper(II) Complex by Pulse EPR Evelyn arr, Adelheid Godt, Gunnar Jeschke* Max Planck Institute for Polymer Research, Postfach 3148, D Mainz, Germany Terpyridyl ligand 2. To a degassed solution of 1-ethynyl- 2,5-dihexyl-4-{2-[4-(tetrahydropyran-2-yloxy)phenyl]ethynyl}benzene [1] (326 mg, 0.69 mmol) and 4'-trifluoromethylsulfonyloxy-2,2':6',2''-terpyridine [2] (244 mg, 0.64 mmol) in dry THF (25 ml) and dry diisopropylamine (10 ml) were added CuI (42 mg, 0.22 mmol) and PdCl 2 (PPh 3 ) 2 (42 mg, 0.06 mmol) at room temperature. [3] The reaction mixture was stirred for 3 h at room temperature. After removal of the solvent in vacuo the residual brown solid was dissolved in THF (30 ml) and Et 2 O (100 ml). The organic phase was washed with water. Removal of the solvent gave an orange colored solid (600 mg). To remove the protecting group, this solid was dissolved in THF (50 ml) and conc. HCl (a few drops) was added. After 1 h the yellow precipitate was isolated by filtration, washed with Et 2 O and dissolved in THF and 1

3 saturated aqueous KOH. The aqueous phase was extracted with Et 2 O. The combined organic phases were dried (MgSO 4 ). The solvent was removed in vacuo. Flash chromatography [petroleum ether (bp C) /Et 2 O 2:1 1:4] gave 2.2,5-dihexyl-1-[2-(4-hydroxyphenyl)ethynyl]-4-[2- (2,2':6',6''-terpyridin-4'-yl)ethynyl]benzene (3) (302 mg, 71 %) as a pale yellow solid. To a solution of 3 (302 mg, 0.49 mmol), 1-oxyl-2,2,5,5- tetramethylpyrroline-3-carboxylic acid (139 mg, 0.76 mmol) and dimethylaminopyridine (92 mg, 0.75 mmol) in CH 2 Cl 2 (10 ml) was added '-(3-dimethylaminopropyl)--ethylcarbodiimide hydrochloride (229 mg, 1.48 mg) dissolved in CH 2 Cl 2 (10 ml). The reaction mixture was stirred for 2 days at room temperature. The slowly formed precipitate was separated by filtation and washed with diethyl ether. The filtrate was washed with water, dried (MgSO 4 ) and the solvent was removed in vacuo. Flash chromatography [petroleum ether (bp o C) /CH 2 Cl 2 1:1 1:2, then petroleum ether /diethyl ether 2:1 1:2] gave the spinlabeled terpyridyl ligand 2 (98 mg, 26 %) as a pale yellow solid. The low yield maybe due to the documented [1] lability of spin labeled compounds when they are adsorbed onto silica gel to get a freely flowing powder that is applied to the column. [1] 1 H MR(300 MHz, CD 2 Cl 2, rt): δ = 8.73 (d, J 2

4 = 3.7 Hz, 2H; tpy: H-6, H-6 ), 8.66 (d, J = 7.6 Hz, 2H; tpy: H-3, H-3 ), 8.60 (s, 2H; tpy: H-3, H-5 ), 7.91 (pseudo t, J = 7.2 Hz, 2H; tpy: H-4, H-4 ), 7.63 (broad s, 2H; H meta to OR), 7.50 (s, 1H; C 6 H 2 ), 7.45 (s, 1H; C 6 H 2 ), 7.40 (m, 2H; H-5, H-5 ), (broad s, 2H; ortho to OR), 2.91 (m, 4H; ArCH 2 ), 1.76 (broad s, 4H; CH 2 ), (m, 12H; CH 2 ), 0.90 (m, 6H; CH 3 ); 13 C MR(75 MHz, CD 2 Cl 2, rt): [4] δ = 155.6, (quat.c of tpy), (CH of tpy), (C Ar -O), and (C Ar -), (CH of tpy), (quat.c of tpy), 132.8, 132.5, and (CH of C 6 H 4 and C 6 H 2 ), (CH of tpy), (C Ar -C C), and (CH of tpy and CH ortho to OR), and (C Ar -C C), (CH of tpy), 93.1, 92.3, 91.9, 88.4 (C C), 33.9, 31.6, 30.6, 30.4, 29.1, and 22.5 (CH 2 ), 13.7 (CH 3 ); elemental analysis calcd(%) for C 52 H 55 4 O 3 ( ): C 79.66, H 7.07, 7.15; found C 79.15, H 7.16, 6.96; FD- MS: m/z (%) = (25, [M+CH 3 ] + ), (100, M + ), 768.1(20, [M CH 3 ] + ), (15, [M 2CH 3 ] + ), (5, [M- (spin-label)] + ). Copper complex 1. A solution of CuCl 2 (0.34 mg, 2.6 µmol) in EtOH (1.3 ml) was added to a pale yellow solution of ligand 2 (4.0 mg, 5.1 µmol) in CH 2 Cl 2 (1.3 ml). The resulting green solution with a concentration of 1 mmol/l of copper complex 1 was used for the EPR measurements. It 3

5 formed a stable glass when being shock-frozen by immersion in liquid nitrogen. Scheme: a OTf H OTHP a) OR b) c) R = THP R = H O HO 3 O O O O 2 a Key: a) Pd(PPh 3 ) 2 Cl 2, CuI, THF, i Pr 2 H, room temp., 3h; b) conc. HCl, THF; c) Me 2 H(CH 2 ) 3 =C=EtCl, DMAP, CH 2 Cl 2, room temp., 20h. 4

6 Details of EPR measurements: Generally, the pump frequency is selected to coincide with the center frequency of the 3 mm split-ring resonator (9.335 GHz), except for the frequency difference of 1465 MHz, where pump and observer frequency have negative and positive offsets of approximately 730 MHz from the center frequency, respectively. At the center frequency, a π pulse length of 32 ns corresponds to 14 db attenuation of the 1.3 kw microwave power of our travelling wave tube amplifier. Accordingly, pump pulse lengths down to 8 ns are feasible. The modulation depth enhancement achievable by such shorter pulses as well as suppression of proton modulations will be discussed elsewhere. For an observer frequency offset of 200 MHz from the center frequency of the resonator, a π pulse length of 32 ns can still be achieved. For frequency offsets of 730 MHz of the pump and observer frequencies, actual flip angles are somewhat smaller than the nominal flip angles in the pulse sequence. This causes a significant loss in sensitivity, which is partially responsible for the longer measurement time and lower signal-to-noise ratio of the data shown in Figure 3b. However, it does not change the signal modulation apart from a decrease in modulation depth. 5

7 The measurement temperature of 15 K was selected for the reasons that at significantly lower temperatures the longitudinal relaxation time increased faster than the square of the Boltzmann population difference and at significantly higher temperatures the transverse relaxation time of the copper center decreased. At the temperature of 15 K, observation in the copper spectrum (positions B, C in Figure 2) could be performed with a repetition rate of 1000 Hz and observation in the nitroxide spectrum (positions A, D) with a repetition rate of 100 Hz without causing significant saturation. References: [1] A. Godt, C. Franzen, S. Veit, V. Enkelmann, M. Pannier, G. Jeschke, J. Org. Chem. 2000, 65, [2] K. T. Potts, D. Konwar, J. Org. Chem. 1991,56, [3] In analogy to: V. Grosshenny, R. Ziessel, J. Organomet. Chem. 1993, 453, C19-C22. [4] The assignment is in agreement with the result of a DEPT experiment. 6