6
Tetrahedron
Compared with the neutral solution, when the solution pH=3, 1.
mixture was evaporated under vacuum and the residue was
chromatographed on a silicagel column and eluted with DCM-
petroleum ether (PE)=1:3, affording 76 mg (0.14 mmol) of
orange solid in 56% yield.1H NMR (400 MHz, Chloroform-d) δ
7.62 (t, J = 7.8 Hz, 1H), 7.43 (d, J = 7.8 Hz, 2H), 4.55 (s, 4H),
4.29 (s, 4H), 4.27 (s, 10H). 13C NMR (101 MHz, Chloroform-d)
δ 143.25 , 136.39 , 127.09 , 83.99 , 77.10 , 75.43 , 72.50 , 70.34 ,
69.86 , 69.71 , 62.24 . HRMS (ESI-TOF) m/z: [M]+ calcd. for
C33H21Fe2N 543.0367; [M + H]+ Found: 544.0446.
the maximum absorption wavelength of UV-Vis had red shift
about 60~80nm; 2. the third-order nonlinear coefficients
increased, the maximum increase was 34×10-12m/W, the
maximum increase of the NLO refractive effects was 1×10-
18m2/W; 3. the first oxidation potentials shifted to the
cathode about 0.03~0.09 V. Electronic spectral, nonlinear optical
and electrochemical studies all shown that the electronic
communication ability between ferrocene and pyridine increased
with the expansion of conjugate structure of the compound, and
that would be enhanced after protonation. Multiresponse to
proton and strong electron delocalization effect of these
compounds made them prospective candidates for chemical
sensors or nonlinear optical (NLO) materials.
4.3.2 2, 6-bis (ferrocenylhexyltriynyl) pyridine (9)
2,6-dibromoethynyl pyridine (86 mg, 0.3 mmol) and
ferrocenylbutadiyne (70 mg ꢅ 0.3 mmol), bis(triphenyl-
phosphine)palladium dichloride (105 mg, 0.15 mmol) and
copper(I) iodide (29 mg, 0.15 mmol) was dissolved in 10 mL of
dry toluene. The solution was deaerated by nitrogen bubbling for
30 minutes. After 30 minutes of nitrogen bubbling, the solution
was stirred for 2h at 30ꢀ, and then 1.5 mL diisopropylamine
was added dropwise to the reaction mixture for 30min under
nitrogen, after which the reaction was terminated after 1.5h. After
the completion of the reaction the solvent was removed in
vacuum and the product was purified by column chromatography
with DCM-PE=1:3 as the eluent, affording 37 mg (0.078 mmol)
of orange solid in 42% yield.1H NMR (400 MHz, Chloroform-d)
δ 7.64 (t, J = 7.8 Hz, 1H), 7.48 (d, J = 7.8 Hz, 2H), 4.56 (t, J = 1.8
Hz, 4H), 4.30 (t, J=1.8Hz, 4H), 4.27 (s, 10H). 13C NMR (101
MHz, Chloroform-d) δ 142.66 , 136.54 , 128.19 , 81.04 , 75.47 ,
72.85 , 70.78 , 70.45 , 70.03 , 68.99 , 63.30 , 61.38 .HRMS (ESI-
TOF) m/z: [M]+ calcd. for C37H21Fe2N 591.0367; [M + H]+ Found:
592.0406.
4. Experimental
4.1. Instruments and reagents
Chemicals were used as received unless otherwise indicated.
All the oxygen or moisture sensitive reactions were carried out
under nitrogen atmosphere. Solvents were freshly dried and
distilled with appropriate drying agents before use. 2,6-
Bis(trimethylsilylethynyl)pyridine
(5)
[37],
2,6-
bis(bromoethynyl) pyridine (7), 2,5-bis(bromoethynyl)pyridine
(13) [38] were prepared following literature methods. All other
materials were purchased from the Energy Chemicals Company.
All new products were further characterized by high resolution
mass spectrometry (HRMS) on Agilent 1290-6450 Q-Tof LC/MS
under conditions: Gas Temp 325 , Drying Gas 10 l/min,
Nebulizer 45 psig, fragmentor 170 v, Skimmer 65 v, OCT 1 RF
Vpp 750v. Column chromatography (CC) was performed on a
silica gel (300 mesh) column. Thin layer Chromatography (TLC)
was performed using glass plates coated with silica gel GF254.
The pH value of the solution was measured by pH test strips.
UV/Vis spectrums of all compounds were measured on a
Hewlett-Packard 8453 UV/vis spectrophotometer and recorded in
dichloromethane solution. An F-4500 FL Spectrophotometer was
used for fluorescence measurements. Cyclic voltammograms
were recorded on electrochemical analyzer using Glassy carbon
as working electrode and Saturated Calomel Electrode (SCE) as
the reference electrode. The scan rate was 100mVs-1 for Cyclic
4.3.1.2, 5-bis (ferrocenyl butadiynyl) pyridine (14)
2,5-dibromoethynyl pyridine (142 mg, 0.5mmol) and
ferrocenylacetylene (105 mg ꢅ 0.5 mmol), bis(triphenyl-
phosphine)palladium dichloride (10 mg, 0.05 mmol) and
copper(I) iodide (10 mg, 0.05 mmol) was dissolved in 10 mL of
dry toluene and 30 mL of dry diisopropylamine. The solution
was deaerated by nitrogen bubbling for 30 minutes. The solution
was kept at 40ꢀ for 3 hours under nitrogen. The resulting
mixture was evaporated under vacuum and the residue was
chromatographed on a silicagel column and eluted with DCM-
PE=1:3, affording 69 mg (0.127 mmol) of orange solid in 51%
yield.1H NMR (400 MHz, Chloroform-d) δ 8.69 (d, J = 2.1, 1H),
7.72 (dd, J = 8.1, 2.1 Hz, 1H), 7.44 (d, J = 8.1, Hz, 1H), 4.56 (q, J
= 1.8 Hz, 4H), 4.30 (q, J = 1.8 Hz, 4H), 4.27 (d, J = 2.8 Hz, 10H).
13C NMR (101 MHz, Chloroform-d) δ 153.35 , 141.38 , 138.96 ,
127.04 , 119.03 , 85.17 , 85.11 , 80.33 , 77.21 , 75.26 ,77.50,
72.51 , 72.42 , 70.35 , 70.32 , 69.92 , 69.78 , 69.76 , 62.31 , 62.19
, 53.42 . HRMS (ESI-TOF) m/z: [M]+ calcd. for C33H21Fe2N
543.0367; [M + H]+ Found: 544.0432.
Voltammetry.
A
solution
of
tetrabutylammonium
hexafluorophosphate (TBAPF6) in CH2Cl2 (0.1M) was used as
supporting electrolyte.
4.2.NLO Measurement
The nonlinear absorption of compounds 8, 9 and 14 in closed-
aperture mode and nonlinear refraction in closed-aperture mode
were studied by standard picosecond z-scan technique.These
DCM solutions for compounds 8, 9 and 14 were placed in a 1
mm quartz cuvette for NLO measurements. Their nonlinear
optical responses were measured by Q-switched Nd: YAG
532nm laser (GKPPL-1064-1-10, Beijing GK Laser technology
Co., Ltd) , which provided linearly polarized 21 ps pulses with a
repetition rate of 10Hz at 532 nm.
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4.3. Synthesis
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2,6-dibromoethynyl pyridine (142 mg, 0.5mmol) and
ferrocenylacetylene (105 mg ꢅ 0.5 mmol), bis(triphenyl-
phosphine)palladium dichloride (10 mg, 0.05 mmol) and
copper(I) iodide (10 mg, 0.05 mmol) was dissolved in 10 mL of
dry toluene and 30 mL of dry diisopropylamine. The solution
was deaerated by nitrogen bubbling for 30 minutes. The solution
was kept at 40ꢀ for 3 hours under nitrogen. The resulting