Photochromism and light-induced radical behaviours of biindenylidenedione derivatives in solid state

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Journal of Molecular Structure 874 (2008) 28–33 www.elsevier.com/locate/molstruc

Photochromism and light-induced radical behaviours of biindenylidenedione derivatives in solid state Xu Li

a,b

, Jie Han b

a,*

, Meili Pang a, Kaige Cheng a, Zhengjie He a, Jiben Meng

a,*

a Department of Chemistry, Nankai University, Tianjin 300071, China The Chinese People’s Armed Police Forces Academy, Langfang 065000, China

Received 31 December 2006; received in revised form 5 March 2007; accepted 13 March 2007 Available online 21 March 2007

Abstract Reactions of 2,2 0 -biindanylidene-1,1 0 ,3,3 0 -tetraone with arylmagnesium bromide gave 3,3 0 -diaryl-3,3 0 -dihydroxy biindenylidenedione derivatives. These compounds exhibited photochromism in solid state, in which the formation of the isomeric radical species was confirmed by the election spin resonance spectroscopy, and the structures of new compounds 1 and 4 were determined by X-ray crystallography. The relationship between structures and properties was also discussed.  2007 Elsevier B.V. All rights reserved. Keywords: Biindenylidenedione derivatives; Photochromism; Radical; Crystal structure; Synthesis

1. Introduction Photochromism is defined as light-induced reversible transformation of chemical species between two isomers having different absorption spectra. Among a large number of photochromic ones investigated in solution, only quite few kinds of molecules were found to be photochromic in a crystalline state [1,2]. In recent years, photochromic organic crystals have received considerable attention due to their potential applications such as information storage, electronic display, optical switching devices and so on. Typical examples include N-salicylideneanilines, nitrobenzylpyridines, triarylimidazole dimmers, diarylethenes and biindenylidenedione derivatives [3–7]. Among many types of photochromic compounds, the biindenylidenedione derivatives are unusual in that they simultaneously undergo photochromism in the crystalline state as well as the generation of stable organic radicals [8,9]. Moreover, * Corresponding authors. Tel.: +86 022 2350 9933; fax: +86 022 2350 2230. E-mail addresses: [email protected] (J. Han), mengjiben@nankai. edu.cn (J. Meng).

0022-2860/$ - see front matter  2007 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2007.03.028

these pure organic radical crystals show magnetic interaction. Thus, the molecular magnetism could be photocontrolled through a light-induced reversible transformation between two isomeric structures. More recently, we have developed a modified approach to prepare photochromic biindenylidenedione derivatives, and a plausible reaction mechanism was given. The key synthetic step for these compounds is the Grignard reaction of arylmagnesium bromide with 2,2 0 -biindanylidene1,1 0 ,3,3 0 -tetraone. An unusual oxidation procedure is required before adding saturated aqueous NH4Cl to quench the reaction [10,11]. We have also studied the photochromic mechanism and revealed that the generation of the radical derived from the irradiation of this kind of compounds was a single biradical, which displayed reversible temperature-dependent ESR signals [12]. The relationship of 3,3 0 -dialkyl biindenylidenedione compounds has been investigated by our research group [11,13]. In this paper, we report preparation, crystal structures and crystallinestate photochemical properties of a new series of 3,3 0 -diaryl biindenylidenedione derivatives, the synthetic route and the structures of the compounds in this work were shown in Scheme 1.

X. Li et al. / Journal of Molecular Structure 874 (2008) 28–33 O HO

O HO R (1)RMgX (2) O2 (3) H

+

R OH O

OH O F R= 1:

F

Cl 2:

3:

OCH3

6:

SCH3

OCH3 4:

OCH3

7:

C(CH3)3

5:

Scheme 1. Synthesis of biindenylidenedione derivatives.

2. Experimental 2.1. Materials and apparatus All chemicals were purchased from commercial sources, and solvents were of analytical grade, and were dried by refluxing under N2 over an appropriate drying agent and distilled before use. 1H NMR spectra were recorded at 300 MHz on a Bruker-P300 instrument using TMS as an internal reference. Elemental analysis was performed on a YANACO CHN CORDER MT-3 apparatus. Ultraviolet spectra were recorded on TU-1901 UV–Vis spectrophotometer. ESR measurement was carried out on a Bruker EMX-6/1 EPR spectrometer. X-ray data collection was performed on a Bruker SMART 1000 diffractometer with Mo Ka radiation.

2.2. Synthesis of 3,3 0 -diaryl-3,3 0 -dihydroxy biindenylidenedione derivatives 1–7 2.2.1. 3,3 0 -Di-m-fluorophenyl-3,3 0 -dihydroxy-[2,2 0 -bi-1Hindene]-1,1 0 -dione (1) To a three-necked 250-mL round-bottomed flask containing a stirrer bar, fitted with a pressure-equalizing dropping funnel and a reflux condenser, were added Mg (2.4 g, 0.10 mol), anhydrous THF (15 mL), and a small grain of I2 under N2 atmosphere. To this suspension was added a solution of 1-bromo-3-fluorobenzene (0.10 mol) in anhydrous ether (60 mL) from pressure-equalizing funnel. After addition was complete, the mixture was stirred under reflux for additional 1 h. The pressure-equalizing funnel was then recharged with 2,2 0 -biindanylidene-1,1 0 ,3,3 0 -tetraone (2.88 g, 0.010 mol) suspended in dry benzene (50 mL). The suspension was added portion-wise over a period of 20 min. The dark green reaction mixture was stirred at room temperature under nitrogen atmosphere for 15 h, and then exposed to air for another 5 h. Finally, quenching the reaction with saturated NH4Cl aqueous solution gave immiscible liquid phases. The crude desired compound 1 precipitated as insoluble power between the organic and

29

aqueous phases. Filtration afforded crude product, which was purified by column chromatography on silica gel. Yield: 47.9%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.749–7.125 (m, 16H, 16· –Ar–H), 6.926–6.868 (m, 2H, 2· –OH). IR (KBr) (cm1): 3401, 3335, 3071, 1676, 1595, 1482, 1466, 1441, 1367, 1297, 1270, 1241, 1180, 1136, 1075, 1033, 950, 8460, 784. Anal. Calcd for C30H18F2O4: C, 75.00; H, 3.78; Found: C, 75.17; H, 3.62. The analogues 2–7 were prepared according to the procedure similar to that for 1. The corresponding data were collected in the following: 2.2.2. 3,3 0 -Di-m-chlorophenyl-3,3 0 -dihydroxy-[2,2 0 -bi-1Hindene]-1,1 0 -dione (2) Yield: 39.0%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.73–7.18 (m, 16H, 16· –Ar–H), 6.91 (s, 2H, 2· –OH). IR (KBr) (cm1): 3414, 3079, 1675, 1598, 1572, 1467, 1343, 1296, 1177, 1077, 1036, 930, 795. Anal. Calcd for C30H18Cl2O4: C, 70.19, H, 3.53; Found: C, 70.48; H, 3.21. 2.2.3. 3,3 0 -Di-m-fluoro-p-methoxylpheny-3,3 0 -dihydroxy[2,2 0 -bi-1H-indene]-1,1 0 -dione (3) Yield: 40.7%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.74–7.05 (m, 14H, 14· –Ar–H), 6.92–6.81 (m, 2H, 2· –OH), 3.80 (s, 6H, 2· –O–CH3). IR (KBr) (cm1): 3353, 3013, 2842, 1680, 1599, 1514, 1464, 1293, 1275, 1225, 1119, 1077, 1022, 955, 878, 761. Anal. Calcd for C30H22F2O6: C, 71.11; H, 4.1; Found: C, 70.87; H, 3.92. 2.2.4. 3,3 0 -Di-p-methoxylpheny-3,3 0 -dihydroxy-[2,2 0 -bi-1H-indene]-1,1 0 -dione (4) Yield: 35.8%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.73–6.80 (m, 16H, 16· –Ar–H), 6.97 (s, 2H, 2· –OH), 3.75 (s, 6H, 2· –O–CH3). IR (KBr) (cm1): 3648, 3353, 2934, 2832, 1680, 1601, 1557, 1539, 1507, 1464. Anal. Calcd for C32H24O6: C, 76.18; H, 4.79; Found: C, 76.35; H, 4.51. 2.2.5. 3,3 0 -Di-m-methoxylpheny-3,3 0 -dihydroxy-[2,2 0 -bi-1H-indene]-1,1 0 -dione (5) Yield: 41.6%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.72–6.92 (m, 16H, 16· –Ar–H), 6.73–6.70 (s, 2H, 2· OH), 3.786 (s, 6H, 2· –O–CH3). IR (KBr) (cm1): 3323, 3070, 2958, 2832, 1675, 1600, 1484, 1290, 1247, 1183, 1151, 1077, 1027, 939, 790, 762. Anal. Calcd for C32H24O6: C, 76.18; H, 4.79; Found: C, 76.47; H, 4.48. 2.2.6. 3,3 0 -Di-m-fluoro-p-methylthiopheny-3,3 0 -dihydroxy[2,2 0 -bi-1H-indene]-1,1 0 -dione (6) Yield: 41.6%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.700–7.126 (m, 16H, 16· –Ar–H), 6.925 (s, 2H, 2· –OH), 2.410 (s, 6H, 2· –S–CH3). IR (KBr) (cm1): 3334, 3015, 2918, 1675, 1599, 1489, 1465, 1292, 1233, 1180, 1094, 1084, 911, 803, 765, 728. Anal. Calcd for C32H24S2O4: C, 71.62; H, 4.51; Found: C, 71.33, H 4.27.

X. Li et al. / Journal of Molecular Structure 874 (2008) 28–33

2.2.7. 3,3 0 -Di-p-tert-butylpheny-3,3 0 -dihydroxy-[2,2 0 -bi-1Hindene]-1,1 0 -dione (7) Yield: 35.9%. 1H NMR (300 MHz, CDCl3): d(ppm) 7.766–7.288 (m, 16H, 16· –Ar–H), 7.06 (s, 2H, 2· –OH), 1.274 (s, 9H, 3· –CH3). IR (KBr) (cm1): 3334, 3070, 2918, 2851, 1680, 1596, 1482, 1465, 1295, 1270, 1241, 1179, 1135, 1074, 1031, 950, 845, 781. Anal. Calcd for C38H36O4: C, 81.99; H, 6.52; Found: C, 82.30; H, 6.75.

0.8

0.7

0.6

Absorbtion

30

0.5

0.4

3. Results and discussion 3.1. Photochromic properties in the solid state

0.3

The photocolor reaction was monitored by UV–Vis spectra in the solid state. All the compounds 1–7 were observed showing photochromism and having absorption band at ultraviolet zone after irradiation. The compounds 1 and 4 were selected to describe the photochromic properties of this class of analogues. When exposed to the sunlight for a few minutes, the yellow powder 1 and 4 turned to brown, respectively. The color change can be seen easily in nake eyes. The measurement of color change was also conducted by UV–Vis spectra in the solid state, which were shown in Figs. 1 and 2. As seen in Figs. 1 and 2, a broad absorption band around 450–700 nm appeared after photoirradiation in the solid state and resulted the photochromism. From Figs. 1 and 2, we may also find that the UV–Vis spectra shape of compounds 1 and 4 are different slightly, this discrepancy may be due to the difference of the aromatic substituents and the different crystal packings, but the different aromatic groups affect the photochromic properties very slightly. The irradiated samples were stable at ambient temperature in air or in the nitrogen atmosphere, however, they could return to the initial isomeric state upon heating above 110 C. This is an important aspect for potential practical use.

0.2 200

300

400

500

600

700

800

λ / nm Fig. 2. UV spectral changes of 4 after (—) before and (ÆÆÆ) after irradiation in the solid.

3.2. Light-induced radical behaviours in the solid state The ESR measurement was carried out in air at room temperature. Measurement conditions are as follows: center field, 3505.00 G; sweep width, 100.00 G; modulation, 100.00 kHz; amplitude, 0.2 G. All the unirradiated yellow compounds 1–7 did not show ESR signals at room temperature, and all the corresponding irradiated brown compounds showed distinct ESR signals. The selected ESR spectrum of the irradated compounds 1 (g = 2.0035) and 4 (g = 2.0030) were shown in Figs. 3 and 4, respectively. As seen in Figs. 3 and 4 apparently, the ESR signal shapes of compounds 1 and 4 are very similar, which meant that the different Ar substituents affect the light-induced radical behaviours of the class of analogues 1–7 slightly. The radical species were also stable at room temperature, for its ESR signal could also be observed even after three months in solid state. While 1 and 4 were dissolved in dichloromethane, the ESR signals disappeared.

0.8 0.7

Absorbtion

0.6 0.5 0.4 0.3 0.2 0.1 0.0 200

300

400

500

600

700

800

λ / nm Fig. 1. UV spectral changes of 1 (—) before and (ÆÆÆ) after irradiation in the solid.

3400

3450

3500

3550

3600

Magnetic Field / G Fig. 3. ESR spectrum of 1 in the solid state.

3650

X. Li et al. / Journal of Molecular Structure 874 (2008) 28–33

3460

3480

3500

3520

3540

3560

3580

Magnetic Field / G Fig. 4. ESR spectrum of 1 in the solid state.

3.3. Relationship between crystal structure and properties Single crystals of 1 and 4 suitable for X-ray crystallographic analysis were obtained by slow evaporation from the dichloromethane and acetone (1:1) at room temperature respectively. The X-ray diffraction data were collected ˚ ) on a Bruker using Mo Ka radiation (k = 0.71073 A SMART 1000 diffractometer and the scan mode at room

temperature. Structure solution and refinement were carried out using the programs SHELXS97 [14] and SHELXL97 [15]. The crystallographic data obtained and experimental details employed were summarized in Table 1. The molecular structures of 1 and 4 are depicted in Figs. 5 and 6, respectively. The compounds 1 and 4 are analogues, they have the similar backbones. One one hand, there are two justly symmetrical indandione moieties linked by a double bond in the compounds, and the two loops of indanione are almost perfectly parallel, which makes the double bond have little distortion. On the other hand, the two aryl groups locate at different sides of the double bond with trans-configuration referring to the indanione planes. As for the compounds 1, The O1/C7–C15 and O1A/ C7A–C15A indenone ring systems linked by a double bond ˚ ). The O1/C7–C15 and O1A/C7A– C15–C15A (1.345(3) A C15A indenone ring systems are essentially planar with ˚ , respectively, and the two deviation from plane 0.0155 A loops of indanione are perfectly parallel, with perpendicu˚ . The C1–C6 and C1A– lar interplanar distance 0.2704 A C6A phenyl rings are twisted away from the attached indenone rings by 97.3, respectively. The dihedral angle between the C1–C6 and C1A–C6A planes is 0.0. The perpendicular interplanar distance between the two phenyl ˚ . The crystal structure is stabilized by rings is 3.1483 A

Table 1 Crystal data and structure refinement for compounds 1 and 4 Compound

1

4

Empirical formula Formula weight Temperature (K) 0 ) Wavelength (A Crystal system Space group Unit cell dimensions

C30H18F2O4 480.44 293(2) 0.71073 Triclinic P1 0 0 0 ; b = 8.1830(18) A ; c = 10.528(2) A ; a = 7.2313(16) A a = 72.060(4); b = 89.694(4); c = 80.385(4) 583.6(2) 1 1.367

C32H24O6 504.51 294(2) 0.71073 Triclinic P1 0 0 0 ; b = 8.778(2) A ; c = 11.894(3) A ; a = 6.4035(15) A a = 91.998(4); b = 102.691(4); c = 104.670(4) 628.0(3) 2 1.334

0.101

0.092

248 0.26 · 0.22 · 0.12 mm 2.04–25.00

264 0.38 · 0.32 · 0.24 mm 1.76–25.01

7 6 h 6 8; 9 6 k 6 9; 10 6 l 6 12 3062 2039 [R(int) = 0.0174] Full-matrix least-squares on F2 2039/1/166

6 6 h 6 7; 10 6 k 6 10; 14 6 l 6 10 3222 2211 [R(int) = 0.0155] Full-matrix least-squares on F2 2211/0/174

R1 = 0.0421, wR2 = 0.1037

R1 = 0.0458, wR2 = 0.1145

R1 = 0.0568, wR2 = 0.1154 0.173 and 0.235

R1 = 0.0649, wR2 = 0.1288 0.138 and 0.178

˚ 3) Volume (A Z Calculated density (Mg/m3) Absorption coefficient (mm1) F(0 0 0) Crystal size h, range for data collection Limiting indices Reflections collected Unique reflections Refinement method Data/restraints/ parameters Final R indices [I > 2d(I)] R indices (all data) Largest diff. peak and ˚ 3) hole (e A

31

32

X. Li et al. / Journal of Molecular Structure 874 (2008) 28–33

The p-conjugation extends throughout the whole molecule, which results the UV–Vis absorption spectra of the irradiated samples change greatly and display photochromism, consequently. At the same time, the

Fig. 5. Molecular structure of 1.

Fig. 7. Stacking structure of 1.

Fig. 6. Molecular structure of 4.

˚ ], O2–H2...O1A O2–H2...O1A [H2...O1A 2.057(15) A 136(2), symmetry code (i) x + 1, y + 1, z + 1, intramolecular hydrogen bonds, O2–H2...O1 [H2...O1 ˚ ] O2–H2...O1 145(2), x  1, y, z, intermolecu2.343(17) A lar hydrogen bonds. As we know, the UV absorption is dependent on the substituent effects and the p-conjugation length in the molecule. Both of the factors are beneficial to form the extended conjugation in the molecules and could be crucial to its photochromic and photoinduced properties.

Fig. 8. Stacking structure of 4.

X. Li et al. / Journal of Molecular Structure 874 (2008) 28–33

irradiation of the compounds may result in the reorganization of electron distribution to generate radicals and the light-induced radical behaviours. Further analysis of the X-ray single crystallographic data analysis showed that both intramolecular and intermolecular H-bonding existed in the compounds 1 and 4. The former may be seen from Figs. 5 and 6, and the latter may be seen in the stacking structures (Figs. 7 and 8) of compounds 1 and 4, respectively. Both kinds of H-bonding are important to stabilize the photochromic and light-induced radical’s state. In summary, the photochromic properties and the light-induced radical behaviours could be explained reasonably by the molecular structure and the H-bonding interactions existed in the compounds, which are consistent with the results reported before by us. The work in this paper not only provide a solid evidence to the photochromic mechanism proposed by our research group [12], but also prepared many candidates of this kind of novel materials to explore their potential applications in hightechnical fields. 4. Conclusions A series of 3,3 0 -diaryl-3,3 0 -dihydroxy biindenylidenedione derivatives were prepared by Grinard addition reaction following by a special oxidation procedure. This family of new compounds simultaneously undergo photochromism in crystalline state as well as generation of radicals. The structure of the compounds has been discussed and found that the title compounds 1–7 had similar molecular structure with two aryl groups locating on different sides of the two parallel indanione planes, which is responsible for the photochromic and photoinduced properties of this kind of materials.

33

Acknowledgement This work was financially supported by Grants from the National Natural Science Foundation of China (No. 20490210, 20372039). Appendix A. Supplementary data The crystallographic data for this paper can be obtained from the Cambridge Crystallographic Data Center (CCDC: 258917, 611525). Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc.2007.03.028. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]

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