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Synthesis and optical properties of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores
Inorganica Chimica Acta 427 (2015) 259–265
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Synthesis and optical properties of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores Yizhong Shi a,b, Guanglei Li b, Baodong Zhao b, Yu Chen b, Pengjie Chao b, Huiqing Zhang b, Xiaoning Wang c, Tao Wang a,b,⇑ a b c
State Key Laboratory of Chemical Resource Engineering, College of Science, Beijing University of Chemical Technology, Beijing 100029, PR China Department of Organic Chemistry, College of Science, Beijing University of Chemical Technology, Beijing 100029, PR China College of Material Engineering, Beijing Institute of Fashion Technology, Beijing 100029, PR China
a r t i c l e
i n f o
Article history: Received 24 September 2014 Received in revised form 31 December 2014 Accepted 5 January 2015 Available online 12 January 2015 Keywords: Cationic cyclopentadienyl iron complex Diphenylacetylene Synthesis Optical property Conjugated molecular
a b s t r a c t Cationic cyclopentadienyl iron complexes of arenes are applied in photopolymerization and photocatalysis because of their good photophysical and photochemical properties. In this study, a series of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores (Aky-Fc) was obtained via nucleophilic substitution and Suzuki coupling reactions. The linear and nonlinear optical properties of the obtained molecules were tuned by phenylethynyl linkages. The UV–Vis absorption spectra showed that increasing the conjugation by substituting phenylacetylene spacer resulted in a red shift in the absorption bands and much stronger absorption in Aky-Fc than in (g6-cumene) (g5-cyclopentadienyl) iron hexafluorophosphate (I-261). With the single-beam Z-scan technique, the nonlinear absorption of Aky-Fc showed that Aky-Fc (8), (9), and (10) had good nonlinear optical ability, and the two photon absorption (TPA) cross section r was approximately 10 times that of I-261. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Ferrocene-based architectures bearing an unsaturated backbone play an important role in delivering targeted electronic, optical, optoelectronic, catalytic, and medicinal properties [1–7]. Diphenylacetylene is an important unsaturated backbone linkage in p-conjugated systems. The linkage is rigid, has large p-electron delocalization, and it is sterically less demanding [8–10]. These advantageous characteristics are the key elements in the design of organic molecules for optical applications. Some acetylene-connected ferrocene derivatives with charge transfer ability, special redox behavior, electronic properties, and non-linear optical (NLO) properties have been reported [11–17]. Cationic cyclopentadienyl iron complexes of arene (Fc-arene) exhibit some properties similar to ferrocene, such as electrochemical and photochemical activities, and this is an important cationic photoinitiator for epoxy photopolymerization [18–21]. Contrary to ferrocene that oxidize easily. Fc-arene is more stable during reactions and applications. It is susceptible to attack by nucleophiles and is a good electron acceptor. However, few studies have
⇑ Corresponding author at: Beijing University of Chemical Technology, 144#, Beijing 100029, PR China. Tel.: +86 010 64445350. E-mail address: [email protected] (T. Wang). http://dx.doi.org/10.1016/j.ica.2015.01.007 0020-1693/Ó 2015 Elsevier B.V. All rights reserved.
discussed Fc-arene with an unsaturated backbone. A novel Fc-arene with long conjugated structures was designed to further understand the photochemistry of Fc-arene and its derivatives (Fig. 1) [22–29]. Fc-arene bearing a diphenylacetylene unit is believed to possess special properties. To develop novel cationic cyclopentadienyl iron complexes with long conjugated structures as special optical materials, a series of cationic cyclopentadienyl iron complexes bearing diphenylacetylene unit (Aky-Fc) was synthesized via nucleophilic aromatic substitution and Suzuki coupling. The architecture of Fc-arene led to larger p-electron delocalization and correspondingly stronger absorption at the UV–Vis region, as demonstrated by the UV–Vis spectral data of Aky-Fc. The linear and NLO properties of Aky-Fc were further investigated.
2. Experimental 2.1. Reagents and instruments All the chemicals were commercial available and they were used without further purification. (g6-1, 4-Dichlorobenzene) (g5cyclopentadienyl) iron hexafluorophosphate (Cl-Fc-Cl), (g6-chlorobenzene) (g5-cyclopentadienyl) iron hexafluorophosphate (Fc-Cl), and (g6-cumene) (g5-cyclopentadienyl) iron hexafluorophosphate
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(I-261) were prepared through the ligand exchange reaction of ferrocene and arene according to the reference procedure [30]. 4(Phenylethynyl)phenol (1) and 1-bromo-4-phenylethynylbenzene (2) were synthesized and characterized by comparing their 1H NMR and 13C NMR spectra with that of reported ones in reference values [31,32]. The melting point of the compounds were determined using a XT-4 microscopic melting point apparatus. The 1H NMR and 13C NMR spectra were recorded on a Bruker AV400 unity spectrometer operated at 400 MHz using acetone-d6 as deuterated solvent. FT-IR spectra were taken on a Nicolet 5700 instrument (Thermo Electron Corporation, Waltham, MA). Elemental analyses were conducted on a Thermo-FINNI-GAN Flash EA 1112 CHNS/O analyzer. Mass spectrometry was performed with a Nermag R10-10C spectrometer. UV–Vis absorption spectra were recorded on a Hitachi U2500 UV–Vis spectrophotometer (Hitachi High-Technologies Corporation, Tokyo, Japan). An EKSPLA NL303 Q-switched Nd: YAG laser at 532 nm ns laser system was employed to investigate NLO properties of compounds. Fluorescence quantum yields were determined using optically matching solutions of quinine sulfate (/F = 0.54 in 0.1 N H2SO4 [33]) as the standard and the quantum yield was calculated using the Eq. (1):
/s ¼
Ar n2s F s / As n2r F r r
ð1Þ
/s and /r are the radiative quantum yield of the sample and the reference respectively, As and Ar are the absorbance of the sample and the reference respectively, Ns and Nr are the refractive indices of the sample and reference solutions. Cyclic voltammetric measurements were performed on a PCcontrolled LK98BII electrochemical analyzer (LanLike Chemistry & Electron High Technology Co., LTD, Tianjin, China), using 3.33 mM dye solution in Acetonitrile at a scan rate of 100 mV/s using 0.1 M tetrabutyl ammonium hexafluorophosphate as supporting electrolyte. The glassy carbon, standard calomel electrode (SCE) and platinum were used as working, reference and auxiliary electrodes, respectively. For all calculation, GAUSSIAN 09 has been employed. The molecular structures in the ground state were optimized based on density function theory (DFT) at the Becke 3-Lee-Yang-Parr (B3LYP)/Genecp (Fe with Lanl2dz basis set and C, H, N, and O with 6-31G⁄⁄ basis set). 2.2. Synthesis 2.2.1. 4-(Phenylethynyl)benzeneboronic acid (3) 1-Bromo-4-phenylethynylbenzene (2) (2.00 g, 7.78 mmol) was dissolved in freshly distilled THF (30 mL) and cooled to 78 °C under argon. Then n-butyllithium (1.6 M in pentane, 5.3 mL,
Fig. 1. Novel Fc-arenes with long conjugated structures.
8.5 mmol) was added to this solution, and after 30 min, trimethyl borate (1.21 g, 11.67 mmol) was added over 15 min. The reaction was allowed to warm to room temperature over 3 h, and it was quenched by adding 0.5 M HCl (50 mL). The resulting mixture was extracted twice with ethyl acetate, and the combined extracts were washed with water, dried over Na2SO4, and concentrated to dryness. Crystallization of the crude product from toluene gave pure compound 3 as a white powder (1.32 g, 76%). m.p. = 204– 206 °C. 1H NMR (400 MHz, DMSO-d6): 7.42–7.45 (m, 3H), 7.51 and 7.82 (AA0 BB0 system, 4H), 7.55–7.58 (m, 2H), 8.19 (s, 2H). 13C NMR (101 MHz, DMSO-d6): 89.6, 90.1, 122.3, 123.7, 128.8, 128.9, 130.3, 131.4, 134.3 (nine of 10 expected resonances). ESI-MS (m/ z): calcd. for C14H11BO2 222.0852, found 222.0855. 2.2.2. 40 -Phenylethynylbiphenyl-4-ol (4) A 250 mL of round-bottom flask was charged with 4-hydroxyphenylboronic acid (1.10 g, 8.0 mmol), 1-bromo-4-phenylethynylbenzene (2) (1.80 g, 7.0 mmol), K2CO3 (4.40 g, 32.0 mmol), Pd(PPh3)4 (0.025 g, 0.021 mmol), DMF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a water solution of 10% K2CO3 (200 mL), and then the precipitate was filtered under reduced pressure as a gray solid. The obtained residue was purified by column chromatography on silica gel (petroleum ether as eluting agent) to give the corresponding pure cross-coupling product 4 as a white powder (1.42 g, 75%). m.p. = 228–230 °C. 1H NMR (400 MHz, Acetone-d6): 8.56 (s, 1H), 7.67 (d, J = 8.3 Hz, 1H), 7.59 (dd, J = 13.3, 5.2 Hz, 6H), 7.49– 7.37 (m, 3H), 6.97 (d, J = 8.6 Hz, 2H). 13C NMR (101 MHz, Acetoned6): 141.88(1C), 132.81(2C), 132.29(2C), 132.10(1C), 129.48(2C), 129.32(2C), 128.88(2C), 127.17(2C), 124.19(1C), 121.92(1C), 116.65(1C), 116.72(1C), 90.36(1C), 90.13(1C). ESI-MS (m/z): calcd for C20H14O 270.1045, found 270.1048. 2.2.3. (g6-(4-Phenylethynyl)phenoxy benzene) (g5-cyclopentadienyl) iron hexafluorophosphate (5) A 100 mL of round-bottom flask was charged with Fc-Cl (3.8 g, 10.0 mmol), 4-(phenylethynyl)phenol (1) (3.9 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. Reactions were monitored by thin layer chromatography (TLC) using 0.25 mm aluminum-backed silica gel plates. After Fc-Cl was reacted thoroughly, the reaction mixture was transferred into a 15% (v/v) HCl solution, and a granular precipitate was formed. The obtained filtrate was washed by acetone leading to the dissolution of the product. This solution was then concentrated by evaporating acetone and treated with sufficient KPF6 in water to allow for the complete precipitation of 5 as a granular solid. The rough product was purified by column chromatography and further recrystallized from acetone/petrol-ether (1:5). Yield = 68%. m.p. = 238–240 °C. FT-IR m(cm1): 3095.2 (C–H, aromatic), 1594.7, 1528.3, 1457.7 (–C@C–), 828.3 (P–F). 1H NMR (400 MHz, Acetone-d6): 7.74 (d, J = 8.4 Hz, 2H), 7.58 (d, J = 3.6 Hz, 2H), 7.44–7.42 (m, 5H), 6.53 (t, J = 6.2 Hz, 2H), 6.48 (d, J = 6.4 Hz, 2H), 6.35 (t, J = 5.8 Hz, 1H), 5.30 (s, 5H). 13C NMR (101 MHz, Acetone-d6): 153.41(1C), 133.97 (2C), 132.21(1C), 131.57(2C), 129.15(2C), 129.00(1C), 122.20(1C), 121.30(2C), 120.34(1C), 89.96(1C), 88.49(1C), 86.95(2C), 85.21(2C), 77.43(1C), 77.24(5C). ESI-MS (m/z): calcd for C25H19FeO+ [M]+ 391.2705, found 391.2698 (cation+). Anal. Calc. for C25H19F6FeOP (536.2 g mol1): C, 56.00; H, 3.57; O, 2.98. Found: C, 55.79; H, 3.29; O, 2.73%. 2.2.4. (g6-1,4-Bis(4-phenylethynyl)phenoxy benzene) (g5cyclopentadienyl) iron hexafluorophosphate (6) A 100 mL of round-bottom flask was charged with Cl-Fc-Cl (4.1 g, 10.0 mmol), 4-(phenylethynyl)phenol (1) (3.9 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round
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bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products is similar to the synthesis of 5. The fine yellow powder 6 was obtained and weighed 5.68 g. Yield = 78%. m.p. = 220–222 °C. FT-IR m(cm1): 3085.05 (C–H, aromatic), 2216.79 (–C„C–), 1606.00, 1514.79, 1467.48 (–C@C–), 832.00 (P–F). 1H NMR (400 MHz, DMSO-d6): 7.74 (d, J = 8.3 Hz, 1H), 7.58 (d, J = 3.3 Hz, 1H), 7.46 (s, 2H), 7.38 (d, J = 8.2 Hz, 1H), 6.40 (s, 4H), 5.28 (s, 1H). 13C NMR (101 MHz, DMSO-d6): 153.89(2C), 133.78(4C), 131.37(4C), 129.50(2C), 128.96(2C), 128.79(4C), 122.02(2C), 120.62(4C), 119.95(2C), 89.73(2C), 88.29 (2C), 78.13(5C), 75.87(4C). ESI-MS (m/z): calcd for C39H27FeO+2 [M]+ 583.4875, found 583.4864 (cation+). Anal. Calc. for C39H27F6FeO2P (728.4 g mol1): C, 64.30; H, 3.74; O, 4.39. Found: C, 62.05; H, 3.46; O, 4.13%. 2.2.5. (g6-(4-Phenylethynyl)phenyl benzene) (g5-cyclopentadienyl) iron hexafluorophosphate (7) A 100 mL of round-bottom flask was charged with 3 (0.69 g, 3.1 mmol), Fc-Cl (1.00 g, 2.6 mmol), K2CO3 (1.44 g, 10.0 mmol), Pd(PPh3)4 (0.005 g, 0.004 mmol), THF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a saturated water solution of KPF6 (200 mL), and then the precipitate was filtered under reduced pressure as a brown solid. The obtained residue was purified by column chromatography on aluminum oxide (acetone as eluting agent) to give the corresponding pure cross-coupling product 7 as a yellow powder (0.85 g, 1.6 mmol, 63%). m.p. = 223–225 °C. FT-IR m(cm1): 3104.87 (C–H, aromatic), 2218.83 (–C„C–), 1608.05, 1508.28, 1459.38 (–C„C–), 823.7 (P–F). 1H NMR (400 MHz, Acetone-d6): 8.10 (d, J = 8.2 Hz, 2H), 7.76 (d, J = 8.2 Hz, 2H), 7.62–7.59 (m, 0H), 7.47–7.46 (m, 1H), 7.02 (d, J = 6.5 Hz, 2H), 6.73 (t, J = 6.3 Hz, 2H), 6.63 (t, J = 6.1 Hz, 1H), 5.22 (s, 5H). 13C NMR (101 MHz, Acetoned6): 135.28(1C), 132.09(2C), 131.48(2C), 129.14(1C), 128.83(2C), 128.20(2C), 123.88(1C), 121.92(1C), 101.65(1C), 91.30(1C), 88.64(1C), 88.08(2C), 87.32(1C), 86.08(2C), 77.55(5C). ESI-MS (m/ z): calcd for C25H19Fe+ [M]+ 375.2715, found 375.2698 (cation+). Anal. Calc. for C25H19F6FeP (520.2 g mol1): C, 57.72; H, 3.68. Found: C, 57.50; H, 3.43%. 2.2.6. (g6-1,4-Bis(4-phenylethynyl)phenyl benzene) (g5cyclopentadienyl) iron hexafluorophosphate (8) A 100 mL of round-bottom flask was charged with 3 (1.34 g, 6.0 mmol), Cl-Fc-Cl (1.00 g, 2.4 mmol), K2CO3 (1.73 g, 12.0 mmol), Pd(PPh3)4 (0.005 g, 0.004 mmol), THF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a saturated water solution of KPF6 (200 mL), and then the precipitate was filtered under reduced pressure as a brown solid. The obtained residue was purified by column chromatography on aluminum oxide (acetone as eluting agent) to give the corresponding pure cross-coupling product 8 as a yellow powder (1.14 g, 1.63 mmol, 68%). m.p. = 226–228 °C. FT-IR m(cm1): 3118.75 (C–H, aromatic), 2216.66 (–C„C–), 1605.44, 1512.69, 1456.54 (–C„C–), 826.54(P-F). 1H NMR (400 MHz, DMSO-d6): 8.16 (d, J = 8.2 Hz, 1H), 7.79 (d, J = 8.2 Hz, 1H), 7.63–7.62 (m, 4H), 7.50– 7.47 (m, 6H), 7.13 (s, 4H), 4.99 (s, 5H). 13C NMR (101 MHz, DMSOd6): 134.71(1C), 132.12(2C), 131.49(2C), 129.17(1C), 128.85(2C), 128.32(2C), 124.02(1C), 121.91(1C), 100.99(1C), 91.41(1C), 88.66(1C), 85.93(2C), 78.88(2C). ESI-MS (m/z): calcd for C39H27Fe+ [M]+ 551.4895, found 551.4885 (cation+). Anal. Calc. for C39H27F6FeP (696.4 g mol1): C, 67.26; H, 3.91. Found: C, 67.01; H, 3.61%. 2.2.7. (g6-(4-Phenylethynyl)biphenoxy benzene) (g5cyclopentadienyl) iron hexafluorophosphate (9) A 100 mL of round-bottom flask was charged with Fc-Cl (3.8 g, 10.0 mmol), 4 (5.5 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and
DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products is similar to the synthesis of 5. Yield = 64%. m.p. = 222– 225 °C. FT-IR m(cm1): 3125.89 (C–H, aromatic), 1596.91, 1494.32, 1456.69 (–C„C–), 825.83 (P–F). 1H NMR (400 MHz, Acetone-d6): 7.94 (d, J = 8.5 Hz,2H), 7.81 (d, J = 8.2 Hz, 2H), 7.70 (d, J = 8.2 Hz, 2H), 7.63–7.57 (m, 1H), 7.51 (d, J = 8.5 Hz, 2H), 7.47–7.45 (m, 3H), 6.53 (t, J = 6.3 Hz, 2H), 6.48 (d, J = 6.5 Hz, 2H), 6.35 (t, J = 5.8 Hz, 1H), 5.32 (s, 2H). 13C NMR (101 MHz, Acetone-d6): 152.82(1C), 139.04(1C), 137.11(1C), 132.54(1C), 132.07(2C), 131.38(2C), 128.94(2C), 128.78 (2C), 126.92(1C), 126.62(2C), 122.21(1C), 121.53(1C), 121.38(2C), 90.27(1C), 89.11(1C), 86.72(2C), 84.86(2C), 76.96(5C), 76.86(1C). ESI-MS (m/z): calcd for C31H23FeO+ [M]+ 467.3685, found 467.3671 (cation+). Anal. Calc. for C31H23F6FeOP (612.3 g mol1): C, 60.81; H, 3.79; O, 2.61. Found: C, 60.56; H, 3.51; O, 2.32%. 2.2.8. (g6-1,4-Bis((4-phenylethynyl)biphenoxyl)benzene) (g5cyclopentadienyl) iron hexafluorophosphate (10) A 100 mL of round-bottom flask was charged with Cl-Fc-Cl (4.1 g, 10.0 mmol), 4 (5.5 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products are similar to the synthesis of 6. Yield = 78%. m.p. = 223– 224 °C. FT-IR m(cm1): 3113.52 (C–H, aromatic), 2215.56 (–C„C–), 1603.46, 1509.12, 1457.98 (–C@C–), 829.11 (P–F). 1H NMR (400 MHz, DMSO-d6): 7.92 (d, J = 8.5 Hz, 4H), 7.81 (d, J = 8.1 Hz, 4H), 7.69 (d, J = 8.0 Hz, 4H), 7.59 (d, J = 3.2 Hz, 4H), 7.46–7.46 (m, 10H), 6.39 (s, 4H), 5.29 (s, 5H). 13C NMR (101 MHz, DMSO-d6): 153.44(2C), 139.00(2C), 136.94(2C), 132.06(4C), 131.37(4C), 129.98 (2C), 128.92(2C), 128.79(4C), 126.92(4C), 122.19(2C), 121.52(2C), 120.96(4C), 90.26(2C), 89.09(2C), 77.98(5C), 75.32(4C). ESI-MS (m/ z): calcd for C51H35FeO+2 [M]+ 735.6835, found 735.6820 (cation+). Anal. Calc. for C51H35F6FeO2P (880.6 g mol1): C, 69.56; H, 4.01; O, 3.63. Found: C, 69.31; H, 3.73; O, 3.34%. 2.3. Z-scan measurement Open-aperture Z-scan measurements were carried out to determine the nonlinear transmission of laser light through the samples. The Z-scan provides information about the nonlinear absorption coefficient. The samples were prepared as transparent solutions of 5.0 104 M in spectroscopic-grade acetonitrile. The samples were placed in 1 mm cuvettes and then irradiated by planepolarized 5 ns laser pulses at 532 nm from the second harmonic output of a Q-switched Nd:YAG laser. The laser pulse energy was 6 lJ, and the beam focal spot radius (x0) was 16 lm. The laser was run in the single shot mode using a data acquisition program, with an approximate interval of 3–4 s in between each pulse. This low repetition rate prevents sample damage and cumulative thermal effects in the medium. Assuming a GAUSSIAN temporal profile, we expressed the normalized energy transmittance T(z) as [34]:
1 pq0 ðz0 Þ
TðzÞ ¼ pffiffiffiffi
Z
þ1
h i 2 ln 1 þ q0 ðz0 Þet dt
ð2Þ
1 1
where q0 ðz0 Þ ¼ bI0 Leff ð1 þ z2 =z20 Þ , Leff ¼ ½1 ea0 L =a0 ; L is the sample thickness; z0 ¼ kx20 =2 is the Rayleigh length; x0 is the beam waist; k = 2p/k is the wave vector; k is the laser wavelength; z is the sample position; I0 is the on-axis irradiance at the focus (z = 0). The nonlinear absorption coefficient b can be determined by fitting the Z-scan curves with Eq. (1). The nonlinear absorption cross-section can be determined utilizing r = hmb/N, where hm is the excitation energy and N is the number of molecules per cm3.
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Usually, r is expressed in Goppert–Mayer (GM) units, where 1 GM = 1 1050 cm4 s molecule1 photon1. The third-order NLO susceptibility v(3) values of Aky-Fcs were obtained as previously described [34].
3. Results and discussion 3.1. Synthesis Nucleophilic substitution (SNAr) reaction is an important property of cationic cyclopentadienyl iron complexes of chloro-substituted arenes because of the good electron-withdrawing nature of the metallic moieties [22,23,25]. With this reaction, Fc-Cl and ClFc-Cl can effectively react with various nucleophilic reagents, such as phenols, aromatic primary amines, and carbazole derivatives. The synthesis of compounds 5–10 is shown in Fig. 2. Aky-Fc 5 and 6 were prepared by the SNAr reaction of Fc-Cl and Cl-Fc-Cl with phenylethynyl phenol 1, respectively, while Aky-Fc 9 and 10 were prepared by the SNAr reaction of Fc-Cl and Cl-Fc-Cl with diphenylethynyl phenol 4. Compounds 1 and 2 were obtained by the palladium-catalyzed Sonogashira alkynylation reaction of phenylacetylene using PdCl2(PPh3)2 as catalyst. Compound 4 was obtained by the Suzuki coupling reaction of Aky-Fc 2 with 4-hydroxyl phenylboronic acid. Synthesized cationic cyclopentadienyl iron complexes were characterized based on physical data and the results of spectral analysis. The infrared (IR) spectra of Aky-Fc showed a weak peak at 2215–2220 cm1, which was assigned to the –C„C–, and a strong peak at approximately 820 cm1, which was assigned to 1 the P–F stretching vibration in PF 6 . Their H NMR spectra are presented in Supporting Information (Figs. S1 and S2). All compounds showed 1H NMR signals for different kinds of protons at their
respective positions. Data of compounds confirmed that the structures were successfully synthesized.
3.2. Electronic spectroscopy The UV–Vis spectra of all target Aky-Fcs and (g6-cumene) (g5cyclopentadienyl) iron hexafluorophosphate (I-261) in 5 105 M CH3CN solution were measured. The data of UV–Vis absorption are listed in Table 1 and the spectra are shown in Fig. S3 (Supporting Information). The Aky-Fc electronic spectra showed strong and broad absorption bands. Absorption below 250 nm was attributed to the p–p⁄ transition of the cyclopentadienyl and diphenylacetylene moieties, while absorption at around 250–350 nm was due to a transition involving electron migration along the entire conjugate system of the ligand. The results demonstrate that increasing conjugation by substituting phenylacetylene spacer resulted in a red shift of the absorption bands and much stronger absorption in Aky-Fc than in I-261. As the degree of p delocalization increased, the maximal absorption peaks of Aky-Fc caused by p–p⁄ transition became bathochromic in the order Aky-Fc 7, 8 > Aky-Fc 9, 10 > Aky-Fc 5, 6. The order is in agreement with that of the conjugated degree of Aky-Fc. For example, in Aky-Fc 5 and 6, diphenylacetylene groups were linked by the C–O bond, while in Aky-Fc 7 and 8, the diphenylacetylene groups were linked with benzene ring complexing with CpFe+ by the C–C bond. The fluorescence emission and excitation spectra of Aky-Fc in the CH3CN solution are shown in Fig. S4 (Supporting Information) and set out in Table 2. All Aky-Fcs showed fluorescence emissions from 350 nm to 500 nm, which were mainly due to the luminescent processes of the conjugated ligands. As the degree of p delocalization in Aky-Fc increased, the maximal emission peaks became bathochromic. Aky-Fc 5 and 6 showed very low
Fig. 2. Preparation of Aky-Fc by SNAr and Suzuki coupling reaction.
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Y. Shi et al. / Inorganica Chimica Acta 427 (2015) 259–265 Table 1 Data of UV–Vis absorption spectra of Aky-Fc in CH3CN solution (5 105 M). Aky-Fc
kmax,1 (nm)
emax,1 104 (M1 cm1)
kmax,2 (nm)
emax,2 104 (M1 cm1)
5 6 7 8 9 10
205 210 206 207 205 213
3.94 5.30 3.78 5.24 4.42 6.10
281 282 308 309 301 301
3.10 7.04 2.98 6.52 4.42 7.86
fluorescence quantum yield relative to the other Aky-Fcs, probably because the rotation of the C–O bond in Aky-Fc 5 and 6 reduced the rigid structure of the arene ligands.
Table 3 Electrochemical data for Aky-Fc 5–10.
3.3. Electrochemistry We also investigated the redox properties of Aky-Fc 5–10 by using cyclic voltammetry in acetonitrile and the results were set out in Table 3. A representative cyclic voltammogram of Aky-Fc 7 was shown in Fig. 3. Cyclic voltammograms of Aky-Fc 5–10 were shown in Fig. S5 (Supporting Information). Each compound shows a irreversible FeIII/II oxidation process and an irreversible waves associated with reductions of the ligand units. We concluded that Aky-Fc 7 and 8 which were prepared by Suzuki coupling reaction had a larger effect to change the Fe(II)/Fe(III) redox potential than those connected by SNAr reaction.
a b
Aky-Fc
Epaa (V)
Epca (V)
Epab (V)
Ferrocene 5 6 7 8 9 10
0.73 0.54 0.51 0.60 0.64 0.53 0.52
0.66 – – – – – –
– 1.08 1.00 1.05 0.94 1.10 1.02
Reversible FeIII/II process (vs. SCE). Irreversible ligand process (vs. SCE).
3.4. Third-order NLO properties The nonlinear absorptions of Aky-Fcs were measured with nanosecond laser excitation at a visible wavelength of 532 nm, where the compounds showed no linear absorption. Fig. 4 shows the obtained open- and closed-aperture Z-scan curves of Aky-Fc 9 at an irradiance of 0.15 GW/cm2. The open- and closed-aperture Z-scan curves of Aky-Fc 5–10 were shown in Figs. S6 and S7 (Supporting Information). The squares represent the experimental data, and the solid curve is the smoothed line. The nonlinear refractive index n2 and the nonlinear absorption coefficient b can be evaluated. The real and imaginary parts of the third-order nonlinear susceptibility v(3) and two-photon absorption cross section r were calculated. Nonlinear optical parameters were shown in Table 4. To compare, the nonlinear absorption of I-261 was also measured at the same conditions. Aky-Fc 6 did not show nonlinear absorption, and Aky-Fc 7 and 5 exhibited weak nonlinear absorption similar to I-261. Aky-Fc 8, 9, and 10 had strong nonlinear absorption. The values of twophoton absorption cross section r follows the order Aky-Fc 8 > Aky-Fc 9 > Aky-Fc 10 > Aky-Fc 7 > Aky-Fc 5. The b value of I-261 was 0.61, and the value of TPA cross section r was 7.63 1046 cm4s/photon. The b values of Aky-Fc 8 and 9 were 8.77 and 14 cm/GW, respectively, and the corresponding values of their TPA cross sections r were 108.8 1046 and 101.0
Fig. 3. Cyclic voltammetry of Aky-Fc 7 and Ferrocene in CH3CN. The arrow indicates the direction of the initial scan.
1046 cm4s/photon, which were approximately 10 times those of I-261. The results prove that enlarging the conjugated system can greatly influence nonlinear absorption. The benzene ring complexation with the iron atom and the benzene rings linking –C„C– of Aky-Fc 7 and 8 were via direct C–C bond. The conjugated
Table 2 Fluorescence spectroscopy and fluorescence quantum yields of Aky-Fc.
a b
Aky-Fc
Exmax (nm)a
Emmax (nm)a
Stoke’s Shift (nm)a
Quantum yield (/F)b
5 6 7 8 9 10
314.6 316.0 351.2 276.2 327.8 280.8
403.6 371.4 378.4 351.4 368.4 365.4
89.0 55.4 27.2 75.2 40.6 84.6
0.10 0.15 0.19 0.64 0.66 0.72
In CH3CN solution (5 105 M). In CH3CN solution (106 M).
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Fig. 4. Open- and Closed-aperture Z-scan curves of Aky-Fc 9.
Table 4 Nonlinear optical parameters of Aky-Fc by Z-scan with the comparison of I-261. Sample Aky-Fc Aky-Fc Aky-Fc Aky-Fc Aky-Fc Aky-Fc I-261
6 5 7 8 9 10
c (1018 m2/w)
n2 (1011 esu)
b (cm/GW)
v(3) (1012 esu)
r 1046 cm4 s/photon)
4.85 5.75 9.79 26.26 43.21 6.65 7.95
0.71 1.69 2.88 3.85 6.30 1.95 2.33
– 6.66 0.87 8.77 8.14 6.07 0.61
1.13 1.67 2.62 14.40 15.74 9.15 2.06
– 8.2 10.8 108.8 101.0 75.3 7.63
Fig. 5. Molecular orbital surface and energies of Aky-Fc’s frontier molecular orbitals.
structure pattern highly enhanced the NLO property of these complexes. Closed-aperture Z-scan technique revealed that the Aky-Fc complexes exhibited a nonlinear refractive effect with aperture
transmittance of 20% (S = 0.2). The nonlinear refractive indices of the Aky-Fcs were obtained. The differences in the n2 values among the Aky-Fcs were relatively small. The Z-scan set-up was previously calibrated with standard CS2 to verify measurement validity.
Y. Shi et al. / Inorganica Chimica Acta 427 (2015) 259–265
The resulting nonlinear refractive index of CS2 was 1.36 1011 esu, similar to those in previous reports [35–38]. 3.5. Quantum chemical calculations Quantum chemical calculations were performed at the density functional theory level with the B3lyp/Genecp (6-31G⁄⁄/Lanl2dz) basis set to gain insight into the electronic properties of Aky-Fc. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distribution is illustrated in Fig. 5. The electrons in the HOMO of the cationic cyclopentadienyl iron complexes were spread over the diphenylacetylene moieties of the arene ligand, whereas those in the LUMO of the cationic cyclopentadienyl iron complexes were mainly concentrated on the ferrocenium salt. Charge transfer along the molecules evidently the accompanied the electron transition from HOMO to LUMO. The electron density in the HOMO of Aky-Fc 8 was delocalized over the entire conjugated-p-framework. However, the electron density in the HOMO of Aky-Fc 6 and 9 was mainly trapped at the diphenylacetylene moiety. Additionally, the electron density in the LUMO of Aky-Fc was located at the iron center. Therefore, Aky-Fc 8 showed the largest p-electron delocalization, which may explain the strongest absorption at >400 nm. 4. Conclusions A series of Aky-Fc were synthesized and characterized. Diphenylacetylene groups could be directly linked with the benzene ring of Fc-arene by palladium-catalyzed coupling reactions. The maximal UV absorption of the compounds was more significantly affected by the nature of the Aky-Fc compared with commercial Fc (I-261). NLO properties were further investigated. Aky-Fc 8–10 exhibited large nonlinear absorptions. These compounds can serve as a model system in the investigation of structure–property relationships with respect to the photophysical and photochemical properties of Fc-arene. Further study will be conducted on applications of Aky-Fc in NLO materials. Acknowledgements The authors wish to thank for financial support of National Natural Science Foundation of China (Project Grant No. 21176016) and the Fundamental Research Funds for the Central Universities (YS1406). We also thank Beijing University of Chemical Technology CHEMCLOUDCOMPUTING Platform for providing calculating support. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.ica.2015.01.007.
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References [1] G.S. He, L.S. Tan, Q. Zheng, P.N. Prasad, Chem. Rev. 108 (2008) 1245. [2] M. Pawlicki, H.A. Collins, R.G. Denning, H.L. Anderson, Angew. Chem., Int. Ed. 48 (2009) 3244. [3] J. Chen, R.A. Lalancette, F. Jaekle, Chem. Commun. 49 (2013) 4893. [4] T. Daeneke, A.J. Mozer, T.H. Kwon, N.W. Duffy, A.B. Holmes, U. Bach, L. Spiccia, Energy Environ. Sci. 5 (2012) 7090. [5] H. Zhang, J. Hu, D.H. Qu, Org. Lett. 14 (2012) 2334. [6] J.M. Speck, R. Claus, A. Hildebrandt, T. Rueffer, E. Erasmus, L.V. As, J.C. Swarts, H. Lang, Organometallics 31 (2012) 6373. [7] A. Nagata, H. Sato, Y. Matsui, T. Kaneko, Y. Fujiwara, Vacuum 87 (2013) 182. [8] H.M. Kim, B.H. Jeong, J.Y. Hyon, M.J. An, M.S. Seo, J.H. Hong, K.J. Lee, C.H. Kim, T. Joo, S.C. Hong, B.R. Cho, J. Am. Chem. Soc. 130 (2008) 4246. [9] Y. Morel, A. Irimia, P. Najechalski, Y. Kervella, O. Stephan, P.L. Baldeck, C. Andraud, J. Chem. Phys. 114 (2001) 5391. [10] S. Kawata, Y. Kawata, Chem. Rev. 100 (2000) 1777. [11] K.A. Green, M.P. Cifuentes, M. Samoc, M.G. Humphrey, Coord. Chem. Rev. 255 (2011) 2530. [12] G. Grelaud, M.P. Cifuentes, F. Paul, M.G. Humphrey, J. Organomet. Chem. 751 (2014) 181. [13] P.J. Low, Coord. Chem. Rev. 257 (2013) 1507. [14] P.J. Low, S. Bock, Electrochim. Acta 110 (2013) 681. [15] G.A. Koutsantonis, P.J. Low, C.F.R. Mackenzie, B.W. Skelton, D.S. Yufit, Organometallics 33 (2014) 4911. [16] M.I. Bruce, J. Organomet. Chem. 730 (2013) 3. [17] A. Burgun, B.G. Ellis, T. Roisnel, B.W. Skelton, M.I. Bruce, C. Lapinte, Organometallics 33 (2014) 4209. [18] R.M.G. Roberts, J. Organomet. Chem. 691 (2006) 4926. [19] A.S. Abd-El-Aziz, P.O. Shipman, P.R. Shipley, Macromol. Rapid. Commun. 31 (2010) 459. [20] C. Lambert, W. Gaschler, M. Zabel, R. Matschiner, R. Wortmann, J. Organomet. Chem. 592 (1999) 109. [21] A.S. Abd-El-Aziz, R.M. Okasha, P.O. Shipman, T.H. Afifi, Macromol. Rapid Commun. 25 (2004) 1497. [22] Y. Chen, D.D. Han, T. Wang, X. Li, Ind. Eng. Chem. Res. 52 (2013) 3646. [23] G.L. Li, Y. Chen, J. Han, H. Ye, X. Wang, T. Wang, Dyes Pigm. 94 (2012) 314. [24] G.L. Li, J.Q. Liu, B.D. Zhao, T. Wang, Spectrochim. Acta, Part A 104 (2013) 287. [25] G.L. Li, H. Ye, Y. Chen, B.D. Zhao, T. Wang, Inorg. Chem. Commun. 14 (2011) 1516. [26] G.L. Li, G.C. Zhang, Y. Chen, T. Wang, Res. Chem. Intermed. 37 (2011) 847. [27] T. Wang, J.Q. Liu, J. Han, G. Li, X. Wang, Res. Chem. Intermed. (2014), http:// dxdoi.org/10.1007/s11164-014-1591-z. [28] B.D. Zhao, P.Y. Wan, J.Q. Liu, J.G. Wang, T. Wang, Thermochim. Acta 543 (2012) 232. [29] J. Zhao, S. Jin, Y.W. Weng, Y. Chen, T. Wang, Ind. Eng. Chem. Res. 53 (2014) 1308. [30] I.U. Khand, P.L. Pauson, W.E. Watts, J. Chem. Soc. C: Org. (1968) 2261 [31] D.P. Dickson, C. Toh, M. Lunda, M.V. Yermolina, D.J. Wardrop, C.L. Landrie, J. Org. Chem. 74 (2009) 9535. [32] A.R. Katritzky, A.A.A. Abdel-Fattah, M. Wang, J. Org. Chem. 67 (2002) 7526. [33] K. Rurack, Springer Ser. Fluoresc. 5 (2008) 101. [34] M. Sheik-Bahae, A.A. Said, T.H. Wei, D.J. Hagan, E.W. Van Stryland, IEEE J. Quantum Electron. 26 (1990) 760. [35] L. Zhang, Z. Shi, L. Zhang, Y. Zhou, S.U. Hassan, Mater. Lett. 86 (2012) 62. [36] M. Sheik-bahae, A.A. Said, T.H. Wei, Y.Y. Wu, D.J. Hagan, M.J. Soileau, E.W. Van Stryland, Proc. SPIE. 1148 (1990) 41. [37] W. Zhao, P. Palffy Muhoray, Appl. Phys. Lett. 63 (1993) 1613. [38] H.T. Verber, Opt. Lett. 17 (1992) 1379.
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Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica
Synthesis and optical properties of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores Yizhong Shi a,b, Guanglei Li b, Baodong Zhao b, Yu Chen b, Pengjie Chao b, Huiqing Zhang b, Xiaoning Wang c, Tao Wang a,b,⇑ a b c
State Key Laboratory of Chemical Resource Engineering, College of Science, Beijing University of Chemical Technology, Beijing 100029, PR China Department of Organic Chemistry, College of Science, Beijing University of Chemical Technology, Beijing 100029, PR China College of Material Engineering, Beijing Institute of Fashion Technology, Beijing 100029, PR China
a r t i c l e
i n f o
Article history: Received 24 September 2014 Received in revised form 31 December 2014 Accepted 5 January 2015 Available online 12 January 2015 Keywords: Cationic cyclopentadienyl iron complex Diphenylacetylene Synthesis Optical property Conjugated molecular
a b s t r a c t Cationic cyclopentadienyl iron complexes of arenes are applied in photopolymerization and photocatalysis because of their good photophysical and photochemical properties. In this study, a series of cationic cyclopentadienyl iron complexes with diphenylacetylene chromophores (Aky-Fc) was obtained via nucleophilic substitution and Suzuki coupling reactions. The linear and nonlinear optical properties of the obtained molecules were tuned by phenylethynyl linkages. The UV–Vis absorption spectra showed that increasing the conjugation by substituting phenylacetylene spacer resulted in a red shift in the absorption bands and much stronger absorption in Aky-Fc than in (g6-cumene) (g5-cyclopentadienyl) iron hexafluorophosphate (I-261). With the single-beam Z-scan technique, the nonlinear absorption of Aky-Fc showed that Aky-Fc (8), (9), and (10) had good nonlinear optical ability, and the two photon absorption (TPA) cross section r was approximately 10 times that of I-261. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction Ferrocene-based architectures bearing an unsaturated backbone play an important role in delivering targeted electronic, optical, optoelectronic, catalytic, and medicinal properties [1–7]. Diphenylacetylene is an important unsaturated backbone linkage in p-conjugated systems. The linkage is rigid, has large p-electron delocalization, and it is sterically less demanding [8–10]. These advantageous characteristics are the key elements in the design of organic molecules for optical applications. Some acetylene-connected ferrocene derivatives with charge transfer ability, special redox behavior, electronic properties, and non-linear optical (NLO) properties have been reported [11–17]. Cationic cyclopentadienyl iron complexes of arene (Fc-arene) exhibit some properties similar to ferrocene, such as electrochemical and photochemical activities, and this is an important cationic photoinitiator for epoxy photopolymerization [18–21]. Contrary to ferrocene that oxidize easily. Fc-arene is more stable during reactions and applications. It is susceptible to attack by nucleophiles and is a good electron acceptor. However, few studies have
⇑ Corresponding author at: Beijing University of Chemical Technology, 144#, Beijing 100029, PR China. Tel.: +86 010 64445350. E-mail address: [email protected] (T. Wang). http://dx.doi.org/10.1016/j.ica.2015.01.007 0020-1693/Ó 2015 Elsevier B.V. All rights reserved.
discussed Fc-arene with an unsaturated backbone. A novel Fc-arene with long conjugated structures was designed to further understand the photochemistry of Fc-arene and its derivatives (Fig. 1) [22–29]. Fc-arene bearing a diphenylacetylene unit is believed to possess special properties. To develop novel cationic cyclopentadienyl iron complexes with long conjugated structures as special optical materials, a series of cationic cyclopentadienyl iron complexes bearing diphenylacetylene unit (Aky-Fc) was synthesized via nucleophilic aromatic substitution and Suzuki coupling. The architecture of Fc-arene led to larger p-electron delocalization and correspondingly stronger absorption at the UV–Vis region, as demonstrated by the UV–Vis spectral data of Aky-Fc. The linear and NLO properties of Aky-Fc were further investigated.
2. Experimental 2.1. Reagents and instruments All the chemicals were commercial available and they were used without further purification. (g6-1, 4-Dichlorobenzene) (g5cyclopentadienyl) iron hexafluorophosphate (Cl-Fc-Cl), (g6-chlorobenzene) (g5-cyclopentadienyl) iron hexafluorophosphate (Fc-Cl), and (g6-cumene) (g5-cyclopentadienyl) iron hexafluorophosphate
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(I-261) were prepared through the ligand exchange reaction of ferrocene and arene according to the reference procedure [30]. 4(Phenylethynyl)phenol (1) and 1-bromo-4-phenylethynylbenzene (2) were synthesized and characterized by comparing their 1H NMR and 13C NMR spectra with that of reported ones in reference values [31,32]. The melting point of the compounds were determined using a XT-4 microscopic melting point apparatus. The 1H NMR and 13C NMR spectra were recorded on a Bruker AV400 unity spectrometer operated at 400 MHz using acetone-d6 as deuterated solvent. FT-IR spectra were taken on a Nicolet 5700 instrument (Thermo Electron Corporation, Waltham, MA). Elemental analyses were conducted on a Thermo-FINNI-GAN Flash EA 1112 CHNS/O analyzer. Mass spectrometry was performed with a Nermag R10-10C spectrometer. UV–Vis absorption spectra were recorded on a Hitachi U2500 UV–Vis spectrophotometer (Hitachi High-Technologies Corporation, Tokyo, Japan). An EKSPLA NL303 Q-switched Nd: YAG laser at 532 nm ns laser system was employed to investigate NLO properties of compounds. Fluorescence quantum yields were determined using optically matching solutions of quinine sulfate (/F = 0.54 in 0.1 N H2SO4 [33]) as the standard and the quantum yield was calculated using the Eq. (1):
/s ¼
Ar n2s F s / As n2r F r r
ð1Þ
/s and /r are the radiative quantum yield of the sample and the reference respectively, As and Ar are the absorbance of the sample and the reference respectively, Ns and Nr are the refractive indices of the sample and reference solutions. Cyclic voltammetric measurements were performed on a PCcontrolled LK98BII electrochemical analyzer (LanLike Chemistry & Electron High Technology Co., LTD, Tianjin, China), using 3.33 mM dye solution in Acetonitrile at a scan rate of 100 mV/s using 0.1 M tetrabutyl ammonium hexafluorophosphate as supporting electrolyte. The glassy carbon, standard calomel electrode (SCE) and platinum were used as working, reference and auxiliary electrodes, respectively. For all calculation, GAUSSIAN 09 has been employed. The molecular structures in the ground state were optimized based on density function theory (DFT) at the Becke 3-Lee-Yang-Parr (B3LYP)/Genecp (Fe with Lanl2dz basis set and C, H, N, and O with 6-31G⁄⁄ basis set). 2.2. Synthesis 2.2.1. 4-(Phenylethynyl)benzeneboronic acid (3) 1-Bromo-4-phenylethynylbenzene (2) (2.00 g, 7.78 mmol) was dissolved in freshly distilled THF (30 mL) and cooled to 78 °C under argon. Then n-butyllithium (1.6 M in pentane, 5.3 mL,
Fig. 1. Novel Fc-arenes with long conjugated structures.
8.5 mmol) was added to this solution, and after 30 min, trimethyl borate (1.21 g, 11.67 mmol) was added over 15 min. The reaction was allowed to warm to room temperature over 3 h, and it was quenched by adding 0.5 M HCl (50 mL). The resulting mixture was extracted twice with ethyl acetate, and the combined extracts were washed with water, dried over Na2SO4, and concentrated to dryness. Crystallization of the crude product from toluene gave pure compound 3 as a white powder (1.32 g, 76%). m.p. = 204– 206 °C. 1H NMR (400 MHz, DMSO-d6): 7.42–7.45 (m, 3H), 7.51 and 7.82 (AA0 BB0 system, 4H), 7.55–7.58 (m, 2H), 8.19 (s, 2H). 13C NMR (101 MHz, DMSO-d6): 89.6, 90.1, 122.3, 123.7, 128.8, 128.9, 130.3, 131.4, 134.3 (nine of 10 expected resonances). ESI-MS (m/ z): calcd. for C14H11BO2 222.0852, found 222.0855. 2.2.2. 40 -Phenylethynylbiphenyl-4-ol (4) A 250 mL of round-bottom flask was charged with 4-hydroxyphenylboronic acid (1.10 g, 8.0 mmol), 1-bromo-4-phenylethynylbenzene (2) (1.80 g, 7.0 mmol), K2CO3 (4.40 g, 32.0 mmol), Pd(PPh3)4 (0.025 g, 0.021 mmol), DMF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a water solution of 10% K2CO3 (200 mL), and then the precipitate was filtered under reduced pressure as a gray solid. The obtained residue was purified by column chromatography on silica gel (petroleum ether as eluting agent) to give the corresponding pure cross-coupling product 4 as a white powder (1.42 g, 75%). m.p. = 228–230 °C. 1H NMR (400 MHz, Acetone-d6): 8.56 (s, 1H), 7.67 (d, J = 8.3 Hz, 1H), 7.59 (dd, J = 13.3, 5.2 Hz, 6H), 7.49– 7.37 (m, 3H), 6.97 (d, J = 8.6 Hz, 2H). 13C NMR (101 MHz, Acetoned6): 141.88(1C), 132.81(2C), 132.29(2C), 132.10(1C), 129.48(2C), 129.32(2C), 128.88(2C), 127.17(2C), 124.19(1C), 121.92(1C), 116.65(1C), 116.72(1C), 90.36(1C), 90.13(1C). ESI-MS (m/z): calcd for C20H14O 270.1045, found 270.1048. 2.2.3. (g6-(4-Phenylethynyl)phenoxy benzene) (g5-cyclopentadienyl) iron hexafluorophosphate (5) A 100 mL of round-bottom flask was charged with Fc-Cl (3.8 g, 10.0 mmol), 4-(phenylethynyl)phenol (1) (3.9 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. Reactions were monitored by thin layer chromatography (TLC) using 0.25 mm aluminum-backed silica gel plates. After Fc-Cl was reacted thoroughly, the reaction mixture was transferred into a 15% (v/v) HCl solution, and a granular precipitate was formed. The obtained filtrate was washed by acetone leading to the dissolution of the product. This solution was then concentrated by evaporating acetone and treated with sufficient KPF6 in water to allow for the complete precipitation of 5 as a granular solid. The rough product was purified by column chromatography and further recrystallized from acetone/petrol-ether (1:5). Yield = 68%. m.p. = 238–240 °C. FT-IR m(cm1): 3095.2 (C–H, aromatic), 1594.7, 1528.3, 1457.7 (–C@C–), 828.3 (P–F). 1H NMR (400 MHz, Acetone-d6): 7.74 (d, J = 8.4 Hz, 2H), 7.58 (d, J = 3.6 Hz, 2H), 7.44–7.42 (m, 5H), 6.53 (t, J = 6.2 Hz, 2H), 6.48 (d, J = 6.4 Hz, 2H), 6.35 (t, J = 5.8 Hz, 1H), 5.30 (s, 5H). 13C NMR (101 MHz, Acetone-d6): 153.41(1C), 133.97 (2C), 132.21(1C), 131.57(2C), 129.15(2C), 129.00(1C), 122.20(1C), 121.30(2C), 120.34(1C), 89.96(1C), 88.49(1C), 86.95(2C), 85.21(2C), 77.43(1C), 77.24(5C). ESI-MS (m/z): calcd for C25H19FeO+ [M]+ 391.2705, found 391.2698 (cation+). Anal. Calc. for C25H19F6FeOP (536.2 g mol1): C, 56.00; H, 3.57; O, 2.98. Found: C, 55.79; H, 3.29; O, 2.73%. 2.2.4. (g6-1,4-Bis(4-phenylethynyl)phenoxy benzene) (g5cyclopentadienyl) iron hexafluorophosphate (6) A 100 mL of round-bottom flask was charged with Cl-Fc-Cl (4.1 g, 10.0 mmol), 4-(phenylethynyl)phenol (1) (3.9 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round
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bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products is similar to the synthesis of 5. The fine yellow powder 6 was obtained and weighed 5.68 g. Yield = 78%. m.p. = 220–222 °C. FT-IR m(cm1): 3085.05 (C–H, aromatic), 2216.79 (–C„C–), 1606.00, 1514.79, 1467.48 (–C@C–), 832.00 (P–F). 1H NMR (400 MHz, DMSO-d6): 7.74 (d, J = 8.3 Hz, 1H), 7.58 (d, J = 3.3 Hz, 1H), 7.46 (s, 2H), 7.38 (d, J = 8.2 Hz, 1H), 6.40 (s, 4H), 5.28 (s, 1H). 13C NMR (101 MHz, DMSO-d6): 153.89(2C), 133.78(4C), 131.37(4C), 129.50(2C), 128.96(2C), 128.79(4C), 122.02(2C), 120.62(4C), 119.95(2C), 89.73(2C), 88.29 (2C), 78.13(5C), 75.87(4C). ESI-MS (m/z): calcd for C39H27FeO+2 [M]+ 583.4875, found 583.4864 (cation+). Anal. Calc. for C39H27F6FeO2P (728.4 g mol1): C, 64.30; H, 3.74; O, 4.39. Found: C, 62.05; H, 3.46; O, 4.13%. 2.2.5. (g6-(4-Phenylethynyl)phenyl benzene) (g5-cyclopentadienyl) iron hexafluorophosphate (7) A 100 mL of round-bottom flask was charged with 3 (0.69 g, 3.1 mmol), Fc-Cl (1.00 g, 2.6 mmol), K2CO3 (1.44 g, 10.0 mmol), Pd(PPh3)4 (0.005 g, 0.004 mmol), THF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a saturated water solution of KPF6 (200 mL), and then the precipitate was filtered under reduced pressure as a brown solid. The obtained residue was purified by column chromatography on aluminum oxide (acetone as eluting agent) to give the corresponding pure cross-coupling product 7 as a yellow powder (0.85 g, 1.6 mmol, 63%). m.p. = 223–225 °C. FT-IR m(cm1): 3104.87 (C–H, aromatic), 2218.83 (–C„C–), 1608.05, 1508.28, 1459.38 (–C„C–), 823.7 (P–F). 1H NMR (400 MHz, Acetone-d6): 8.10 (d, J = 8.2 Hz, 2H), 7.76 (d, J = 8.2 Hz, 2H), 7.62–7.59 (m, 0H), 7.47–7.46 (m, 1H), 7.02 (d, J = 6.5 Hz, 2H), 6.73 (t, J = 6.3 Hz, 2H), 6.63 (t, J = 6.1 Hz, 1H), 5.22 (s, 5H). 13C NMR (101 MHz, Acetoned6): 135.28(1C), 132.09(2C), 131.48(2C), 129.14(1C), 128.83(2C), 128.20(2C), 123.88(1C), 121.92(1C), 101.65(1C), 91.30(1C), 88.64(1C), 88.08(2C), 87.32(1C), 86.08(2C), 77.55(5C). ESI-MS (m/ z): calcd for C25H19Fe+ [M]+ 375.2715, found 375.2698 (cation+). Anal. Calc. for C25H19F6FeP (520.2 g mol1): C, 57.72; H, 3.68. Found: C, 57.50; H, 3.43%. 2.2.6. (g6-1,4-Bis(4-phenylethynyl)phenyl benzene) (g5cyclopentadienyl) iron hexafluorophosphate (8) A 100 mL of round-bottom flask was charged with 3 (1.34 g, 6.0 mmol), Cl-Fc-Cl (1.00 g, 2.4 mmol), K2CO3 (1.73 g, 12.0 mmol), Pd(PPh3)4 (0.005 g, 0.004 mmol), THF (50 mL), and water (10 mL). The mixture was heated to reflux and stirred for 8 h. Then the mixture was poured into a saturated water solution of KPF6 (200 mL), and then the precipitate was filtered under reduced pressure as a brown solid. The obtained residue was purified by column chromatography on aluminum oxide (acetone as eluting agent) to give the corresponding pure cross-coupling product 8 as a yellow powder (1.14 g, 1.63 mmol, 68%). m.p. = 226–228 °C. FT-IR m(cm1): 3118.75 (C–H, aromatic), 2216.66 (–C„C–), 1605.44, 1512.69, 1456.54 (–C„C–), 826.54(P-F). 1H NMR (400 MHz, DMSO-d6): 8.16 (d, J = 8.2 Hz, 1H), 7.79 (d, J = 8.2 Hz, 1H), 7.63–7.62 (m, 4H), 7.50– 7.47 (m, 6H), 7.13 (s, 4H), 4.99 (s, 5H). 13C NMR (101 MHz, DMSOd6): 134.71(1C), 132.12(2C), 131.49(2C), 129.17(1C), 128.85(2C), 128.32(2C), 124.02(1C), 121.91(1C), 100.99(1C), 91.41(1C), 88.66(1C), 85.93(2C), 78.88(2C). ESI-MS (m/z): calcd for C39H27Fe+ [M]+ 551.4895, found 551.4885 (cation+). Anal. Calc. for C39H27F6FeP (696.4 g mol1): C, 67.26; H, 3.91. Found: C, 67.01; H, 3.61%. 2.2.7. (g6-(4-Phenylethynyl)biphenoxy benzene) (g5cyclopentadienyl) iron hexafluorophosphate (9) A 100 mL of round-bottom flask was charged with Fc-Cl (3.8 g, 10.0 mmol), 4 (5.5 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and
DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products is similar to the synthesis of 5. Yield = 64%. m.p. = 222– 225 °C. FT-IR m(cm1): 3125.89 (C–H, aromatic), 1596.91, 1494.32, 1456.69 (–C„C–), 825.83 (P–F). 1H NMR (400 MHz, Acetone-d6): 7.94 (d, J = 8.5 Hz,2H), 7.81 (d, J = 8.2 Hz, 2H), 7.70 (d, J = 8.2 Hz, 2H), 7.63–7.57 (m, 1H), 7.51 (d, J = 8.5 Hz, 2H), 7.47–7.45 (m, 3H), 6.53 (t, J = 6.3 Hz, 2H), 6.48 (d, J = 6.5 Hz, 2H), 6.35 (t, J = 5.8 Hz, 1H), 5.32 (s, 2H). 13C NMR (101 MHz, Acetone-d6): 152.82(1C), 139.04(1C), 137.11(1C), 132.54(1C), 132.07(2C), 131.38(2C), 128.94(2C), 128.78 (2C), 126.92(1C), 126.62(2C), 122.21(1C), 121.53(1C), 121.38(2C), 90.27(1C), 89.11(1C), 86.72(2C), 84.86(2C), 76.96(5C), 76.86(1C). ESI-MS (m/z): calcd for C31H23FeO+ [M]+ 467.3685, found 467.3671 (cation+). Anal. Calc. for C31H23F6FeOP (612.3 g mol1): C, 60.81; H, 3.79; O, 2.61. Found: C, 60.56; H, 3.51; O, 2.32%. 2.2.8. (g6-1,4-Bis((4-phenylethynyl)biphenoxyl)benzene) (g5cyclopentadienyl) iron hexafluorophosphate (10) A 100 mL of round-bottom flask was charged with Cl-Fc-Cl (4.1 g, 10.0 mmol), 4 (5.5 g, 20.2 mmol), K2CO3 (2.7 g, 20.0 mmol), and DMF (30 mL) in a 100 mL round bottom flask under a nitrogen atmosphere, then the mixture was stirred at room temperature. The monitoring method for the reaction and the purification process of the products are similar to the synthesis of 6. Yield = 78%. m.p. = 223– 224 °C. FT-IR m(cm1): 3113.52 (C–H, aromatic), 2215.56 (–C„C–), 1603.46, 1509.12, 1457.98 (–C@C–), 829.11 (P–F). 1H NMR (400 MHz, DMSO-d6): 7.92 (d, J = 8.5 Hz, 4H), 7.81 (d, J = 8.1 Hz, 4H), 7.69 (d, J = 8.0 Hz, 4H), 7.59 (d, J = 3.2 Hz, 4H), 7.46–7.46 (m, 10H), 6.39 (s, 4H), 5.29 (s, 5H). 13C NMR (101 MHz, DMSO-d6): 153.44(2C), 139.00(2C), 136.94(2C), 132.06(4C), 131.37(4C), 129.98 (2C), 128.92(2C), 128.79(4C), 126.92(4C), 122.19(2C), 121.52(2C), 120.96(4C), 90.26(2C), 89.09(2C), 77.98(5C), 75.32(4C). ESI-MS (m/ z): calcd for C51H35FeO+2 [M]+ 735.6835, found 735.6820 (cation+). Anal. Calc. for C51H35F6FeO2P (880.6 g mol1): C, 69.56; H, 4.01; O, 3.63. Found: C, 69.31; H, 3.73; O, 3.34%. 2.3. Z-scan measurement Open-aperture Z-scan measurements were carried out to determine the nonlinear transmission of laser light through the samples. The Z-scan provides information about the nonlinear absorption coefficient. The samples were prepared as transparent solutions of 5.0 104 M in spectroscopic-grade acetonitrile. The samples were placed in 1 mm cuvettes and then irradiated by planepolarized 5 ns laser pulses at 532 nm from the second harmonic output of a Q-switched Nd:YAG laser. The laser pulse energy was 6 lJ, and the beam focal spot radius (x0) was 16 lm. The laser was run in the single shot mode using a data acquisition program, with an approximate interval of 3–4 s in between each pulse. This low repetition rate prevents sample damage and cumulative thermal effects in the medium. Assuming a GAUSSIAN temporal profile, we expressed the normalized energy transmittance T(z) as [34]:
1 pq0 ðz0 Þ
TðzÞ ¼ pffiffiffiffi
Z
þ1
h i 2 ln 1 þ q0 ðz0 Þet dt
ð2Þ
1 1
where q0 ðz0 Þ ¼ bI0 Leff ð1 þ z2 =z20 Þ , Leff ¼ ½1 ea0 L =a0 ; L is the sample thickness; z0 ¼ kx20 =2 is the Rayleigh length; x0 is the beam waist; k = 2p/k is the wave vector; k is the laser wavelength; z is the sample position; I0 is the on-axis irradiance at the focus (z = 0). The nonlinear absorption coefficient b can be determined by fitting the Z-scan curves with Eq. (1). The nonlinear absorption cross-section can be determined utilizing r = hmb/N, where hm is the excitation energy and N is the number of molecules per cm3.
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Usually, r is expressed in Goppert–Mayer (GM) units, where 1 GM = 1 1050 cm4 s molecule1 photon1. The third-order NLO susceptibility v(3) values of Aky-Fcs were obtained as previously described [34].
3. Results and discussion 3.1. Synthesis Nucleophilic substitution (SNAr) reaction is an important property of cationic cyclopentadienyl iron complexes of chloro-substituted arenes because of the good electron-withdrawing nature of the metallic moieties [22,23,25]. With this reaction, Fc-Cl and ClFc-Cl can effectively react with various nucleophilic reagents, such as phenols, aromatic primary amines, and carbazole derivatives. The synthesis of compounds 5–10 is shown in Fig. 2. Aky-Fc 5 and 6 were prepared by the SNAr reaction of Fc-Cl and Cl-Fc-Cl with phenylethynyl phenol 1, respectively, while Aky-Fc 9 and 10 were prepared by the SNAr reaction of Fc-Cl and Cl-Fc-Cl with diphenylethynyl phenol 4. Compounds 1 and 2 were obtained by the palladium-catalyzed Sonogashira alkynylation reaction of phenylacetylene using PdCl2(PPh3)2 as catalyst. Compound 4 was obtained by the Suzuki coupling reaction of Aky-Fc 2 with 4-hydroxyl phenylboronic acid. Synthesized cationic cyclopentadienyl iron complexes were characterized based on physical data and the results of spectral analysis. The infrared (IR) spectra of Aky-Fc showed a weak peak at 2215–2220 cm1, which was assigned to the –C„C–, and a strong peak at approximately 820 cm1, which was assigned to 1 the P–F stretching vibration in PF 6 . Their H NMR spectra are presented in Supporting Information (Figs. S1 and S2). All compounds showed 1H NMR signals for different kinds of protons at their
respective positions. Data of compounds confirmed that the structures were successfully synthesized.
3.2. Electronic spectroscopy The UV–Vis spectra of all target Aky-Fcs and (g6-cumene) (g5cyclopentadienyl) iron hexafluorophosphate (I-261) in 5 105 M CH3CN solution were measured. The data of UV–Vis absorption are listed in Table 1 and the spectra are shown in Fig. S3 (Supporting Information). The Aky-Fc electronic spectra showed strong and broad absorption bands. Absorption below 250 nm was attributed to the p–p⁄ transition of the cyclopentadienyl and diphenylacetylene moieties, while absorption at around 250–350 nm was due to a transition involving electron migration along the entire conjugate system of the ligand. The results demonstrate that increasing conjugation by substituting phenylacetylene spacer resulted in a red shift of the absorption bands and much stronger absorption in Aky-Fc than in I-261. As the degree of p delocalization increased, the maximal absorption peaks of Aky-Fc caused by p–p⁄ transition became bathochromic in the order Aky-Fc 7, 8 > Aky-Fc 9, 10 > Aky-Fc 5, 6. The order is in agreement with that of the conjugated degree of Aky-Fc. For example, in Aky-Fc 5 and 6, diphenylacetylene groups were linked by the C–O bond, while in Aky-Fc 7 and 8, the diphenylacetylene groups were linked with benzene ring complexing with CpFe+ by the C–C bond. The fluorescence emission and excitation spectra of Aky-Fc in the CH3CN solution are shown in Fig. S4 (Supporting Information) and set out in Table 2. All Aky-Fcs showed fluorescence emissions from 350 nm to 500 nm, which were mainly due to the luminescent processes of the conjugated ligands. As the degree of p delocalization in Aky-Fc increased, the maximal emission peaks became bathochromic. Aky-Fc 5 and 6 showed very low
Fig. 2. Preparation of Aky-Fc by SNAr and Suzuki coupling reaction.
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Y. Shi et al. / Inorganica Chimica Acta 427 (2015) 259–265 Table 1 Data of UV–Vis absorption spectra of Aky-Fc in CH3CN solution (5 105 M). Aky-Fc
kmax,1 (nm)
emax,1 104 (M1 cm1)
kmax,2 (nm)
emax,2 104 (M1 cm1)
5 6 7 8 9 10
205 210 206 207 205 213
3.94 5.30 3.78 5.24 4.42 6.10
281 282 308 309 301 301
3.10 7.04 2.98 6.52 4.42 7.86
fluorescence quantum yield relative to the other Aky-Fcs, probably because the rotation of the C–O bond in Aky-Fc 5 and 6 reduced the rigid structure of the arene ligands.
Table 3 Electrochemical data for Aky-Fc 5–10.
3.3. Electrochemistry We also investigated the redox properties of Aky-Fc 5–10 by using cyclic voltammetry in acetonitrile and the results were set out in Table 3. A representative cyclic voltammogram of Aky-Fc 7 was shown in Fig. 3. Cyclic voltammograms of Aky-Fc 5–10 were shown in Fig. S5 (Supporting Information). Each compound shows a irreversible FeIII/II oxidation process and an irreversible waves associated with reductions of the ligand units. We concluded that Aky-Fc 7 and 8 which were prepared by Suzuki coupling reaction had a larger effect to change the Fe(II)/Fe(III) redox potential than those connected by SNAr reaction.
a b
Aky-Fc
Epaa (V)
Epca (V)
Epab (V)
Ferrocene 5 6 7 8 9 10
0.73 0.54 0.51 0.60 0.64 0.53 0.52
0.66 – – – – – –
– 1.08 1.00 1.05 0.94 1.10 1.02
Reversible FeIII/II process (vs. SCE). Irreversible ligand process (vs. SCE).
3.4. Third-order NLO properties The nonlinear absorptions of Aky-Fcs were measured with nanosecond laser excitation at a visible wavelength of 532 nm, where the compounds showed no linear absorption. Fig. 4 shows the obtained open- and closed-aperture Z-scan curves of Aky-Fc 9 at an irradiance of 0.15 GW/cm2. The open- and closed-aperture Z-scan curves of Aky-Fc 5–10 were shown in Figs. S6 and S7 (Supporting Information). The squares represent the experimental data, and the solid curve is the smoothed line. The nonlinear refractive index n2 and the nonlinear absorption coefficient b can be evaluated. The real and imaginary parts of the third-order nonlinear susceptibility v(3) and two-photon absorption cross section r were calculated. Nonlinear optical parameters were shown in Table 4. To compare, the nonlinear absorption of I-261 was also measured at the same conditions. Aky-Fc 6 did not show nonlinear absorption, and Aky-Fc 7 and 5 exhibited weak nonlinear absorption similar to I-261. Aky-Fc 8, 9, and 10 had strong nonlinear absorption. The values of twophoton absorption cross section r follows the order Aky-Fc 8 > Aky-Fc 9 > Aky-Fc 10 > Aky-Fc 7 > Aky-Fc 5. The b value of I-261 was 0.61, and the value of TPA cross section r was 7.63 1046 cm4s/photon. The b values of Aky-Fc 8 and 9 were 8.77 and 14 cm/GW, respectively, and the corresponding values of their TPA cross sections r were 108.8 1046 and 101.0
Fig. 3. Cyclic voltammetry of Aky-Fc 7 and Ferrocene in CH3CN. The arrow indicates the direction of the initial scan.
1046 cm4s/photon, which were approximately 10 times those of I-261. The results prove that enlarging the conjugated system can greatly influence nonlinear absorption. The benzene ring complexation with the iron atom and the benzene rings linking –C„C– of Aky-Fc 7 and 8 were via direct C–C bond. The conjugated
Table 2 Fluorescence spectroscopy and fluorescence quantum yields of Aky-Fc.
a b
Aky-Fc
Exmax (nm)a
Emmax (nm)a
Stoke’s Shift (nm)a
Quantum yield (/F)b
5 6 7 8 9 10
314.6 316.0 351.2 276.2 327.8 280.8
403.6 371.4 378.4 351.4 368.4 365.4
89.0 55.4 27.2 75.2 40.6 84.6
0.10 0.15 0.19 0.64 0.66 0.72
In CH3CN solution (5 105 M). In CH3CN solution (106 M).
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Fig. 4. Open- and Closed-aperture Z-scan curves of Aky-Fc 9.
Table 4 Nonlinear optical parameters of Aky-Fc by Z-scan with the comparison of I-261. Sample Aky-Fc Aky-Fc Aky-Fc Aky-Fc Aky-Fc Aky-Fc I-261
6 5 7 8 9 10
c (1018 m2/w)
n2 (1011 esu)
b (cm/GW)
v(3) (1012 esu)
r 1046 cm4 s/photon)
4.85 5.75 9.79 26.26 43.21 6.65 7.95
0.71 1.69 2.88 3.85 6.30 1.95 2.33
– 6.66 0.87 8.77 8.14 6.07 0.61
1.13 1.67 2.62 14.40 15.74 9.15 2.06
– 8.2 10.8 108.8 101.0 75.3 7.63
Fig. 5. Molecular orbital surface and energies of Aky-Fc’s frontier molecular orbitals.
structure pattern highly enhanced the NLO property of these complexes. Closed-aperture Z-scan technique revealed that the Aky-Fc complexes exhibited a nonlinear refractive effect with aperture
transmittance of 20% (S = 0.2). The nonlinear refractive indices of the Aky-Fcs were obtained. The differences in the n2 values among the Aky-Fcs were relatively small. The Z-scan set-up was previously calibrated with standard CS2 to verify measurement validity.
Y. Shi et al. / Inorganica Chimica Acta 427 (2015) 259–265
The resulting nonlinear refractive index of CS2 was 1.36 1011 esu, similar to those in previous reports [35–38]. 3.5. Quantum chemical calculations Quantum chemical calculations were performed at the density functional theory level with the B3lyp/Genecp (6-31G⁄⁄/Lanl2dz) basis set to gain insight into the electronic properties of Aky-Fc. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distribution is illustrated in Fig. 5. The electrons in the HOMO of the cationic cyclopentadienyl iron complexes were spread over the diphenylacetylene moieties of the arene ligand, whereas those in the LUMO of the cationic cyclopentadienyl iron complexes were mainly concentrated on the ferrocenium salt. Charge transfer along the molecules evidently the accompanied the electron transition from HOMO to LUMO. The electron density in the HOMO of Aky-Fc 8 was delocalized over the entire conjugated-p-framework. However, the electron density in the HOMO of Aky-Fc 6 and 9 was mainly trapped at the diphenylacetylene moiety. Additionally, the electron density in the LUMO of Aky-Fc was located at the iron center. Therefore, Aky-Fc 8 showed the largest p-electron delocalization, which may explain the strongest absorption at >400 nm. 4. Conclusions A series of Aky-Fc were synthesized and characterized. Diphenylacetylene groups could be directly linked with the benzene ring of Fc-arene by palladium-catalyzed coupling reactions. The maximal UV absorption of the compounds was more significantly affected by the nature of the Aky-Fc compared with commercial Fc (I-261). NLO properties were further investigated. Aky-Fc 8–10 exhibited large nonlinear absorptions. These compounds can serve as a model system in the investigation of structure–property relationships with respect to the photophysical and photochemical properties of Fc-arene. Further study will be conducted on applications of Aky-Fc in NLO materials. Acknowledgements The authors wish to thank for financial support of National Natural Science Foundation of China (Project Grant No. 21176016) and the Fundamental Research Funds for the Central Universities (YS1406). We also thank Beijing University of Chemical Technology CHEMCLOUDCOMPUTING Platform for providing calculating support. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.ica.2015.01.007.
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References [1] G.S. He, L.S. Tan, Q. Zheng, P.N. Prasad, Chem. Rev. 108 (2008) 1245. [2] M. Pawlicki, H.A. Collins, R.G. Denning, H.L. Anderson, Angew. Chem., Int. Ed. 48 (2009) 3244. [3] J. Chen, R.A. Lalancette, F. Jaekle, Chem. Commun. 49 (2013) 4893. [4] T. Daeneke, A.J. Mozer, T.H. Kwon, N.W. Duffy, A.B. Holmes, U. Bach, L. Spiccia, Energy Environ. Sci. 5 (2012) 7090. [5] H. Zhang, J. Hu, D.H. Qu, Org. Lett. 14 (2012) 2334. [6] J.M. Speck, R. Claus, A. Hildebrandt, T. Rueffer, E. Erasmus, L.V. As, J.C. Swarts, H. Lang, Organometallics 31 (2012) 6373. [7] A. Nagata, H. Sato, Y. Matsui, T. Kaneko, Y. Fujiwara, Vacuum 87 (2013) 182. [8] H.M. Kim, B.H. Jeong, J.Y. Hyon, M.J. An, M.S. Seo, J.H. Hong, K.J. Lee, C.H. Kim, T. Joo, S.C. Hong, B.R. Cho, J. Am. Chem. Soc. 130 (2008) 4246. [9] Y. Morel, A. Irimia, P. Najechalski, Y. Kervella, O. Stephan, P.L. Baldeck, C. Andraud, J. Chem. Phys. 114 (2001) 5391. [10] S. Kawata, Y. Kawata, Chem. Rev. 100 (2000) 1777. [11] K.A. Green, M.P. Cifuentes, M. Samoc, M.G. Humphrey, Coord. Chem. Rev. 255 (2011) 2530. [12] G. Grelaud, M.P. Cifuentes, F. Paul, M.G. Humphrey, J. Organomet. Chem. 751 (2014) 181. [13] P.J. Low, Coord. Chem. Rev. 257 (2013) 1507. [14] P.J. Low, S. Bock, Electrochim. Acta 110 (2013) 681. [15] G.A. Koutsantonis, P.J. Low, C.F.R. Mackenzie, B.W. Skelton, D.S. Yufit, Organometallics 33 (2014) 4911. [16] M.I. Bruce, J. Organomet. Chem. 730 (2013) 3. [17] A. Burgun, B.G. Ellis, T. Roisnel, B.W. Skelton, M.I. Bruce, C. Lapinte, Organometallics 33 (2014) 4209. [18] R.M.G. Roberts, J. Organomet. Chem. 691 (2006) 4926. [19] A.S. Abd-El-Aziz, P.O. Shipman, P.R. Shipley, Macromol. Rapid. Commun. 31 (2010) 459. [20] C. Lambert, W. Gaschler, M. Zabel, R. Matschiner, R. Wortmann, J. Organomet. Chem. 592 (1999) 109. [21] A.S. Abd-El-Aziz, R.M. Okasha, P.O. Shipman, T.H. Afifi, Macromol. Rapid Commun. 25 (2004) 1497. [22] Y. Chen, D.D. Han, T. Wang, X. Li, Ind. Eng. Chem. Res. 52 (2013) 3646. [23] G.L. Li, Y. Chen, J. Han, H. Ye, X. Wang, T. Wang, Dyes Pigm. 94 (2012) 314. [24] G.L. Li, J.Q. Liu, B.D. Zhao, T. Wang, Spectrochim. Acta, Part A 104 (2013) 287. [25] G.L. Li, H. Ye, Y. Chen, B.D. Zhao, T. Wang, Inorg. Chem. Commun. 14 (2011) 1516. [26] G.L. Li, G.C. Zhang, Y. Chen, T. Wang, Res. Chem. Intermed. 37 (2011) 847. [27] T. Wang, J.Q. Liu, J. Han, G. Li, X. Wang, Res. Chem. Intermed. (2014), http:// dxdoi.org/10.1007/s11164-014-1591-z. [28] B.D. Zhao, P.Y. Wan, J.Q. Liu, J.G. Wang, T. Wang, Thermochim. Acta 543 (2012) 232. [29] J. Zhao, S. Jin, Y.W. Weng, Y. Chen, T. Wang, Ind. Eng. Chem. Res. 53 (2014) 1308. [30] I.U. Khand, P.L. Pauson, W.E. Watts, J. Chem. Soc. C: Org. (1968) 2261 [31] D.P. Dickson, C. Toh, M. Lunda, M.V. Yermolina, D.J. Wardrop, C.L. Landrie, J. Org. Chem. 74 (2009) 9535. [32] A.R. Katritzky, A.A.A. Abdel-Fattah, M. Wang, J. Org. Chem. 67 (2002) 7526. [33] K. Rurack, Springer Ser. Fluoresc. 5 (2008) 101. [34] M. Sheik-Bahae, A.A. Said, T.H. Wei, D.J. Hagan, E.W. Van Stryland, IEEE J. Quantum Electron. 26 (1990) 760. [35] L. Zhang, Z. Shi, L. Zhang, Y. Zhou, S.U. Hassan, Mater. Lett. 86 (2012) 62. [36] M. Sheik-bahae, A.A. Said, T.H. Wei, Y.Y. Wu, D.J. Hagan, M.J. Soileau, E.W. Van Stryland, Proc. SPIE. 1148 (1990) 41. [37] W. Zhao, P. Palffy Muhoray, Appl. Phys. Lett. 63 (1993) 1613. [38] H.T. Verber, Opt. Lett. 17 (1992) 1379.