Electromagnetic Modeling of the Propagation Characteristics of Satellite Communications Through Composite Precipitation Layers Science and Technology, 8 (2003) 115-120 © 2003 Sultan Qaboos University Synthesis and Crystal Structure of Overcrowded Non-photochromic Organometallic Fulgide Shar Saad Al-Shihry Department of Chemistry, College of Science, King Faisal University, P.O.Box 1759, Saudi Arabia, Email: sshihry@kfu.edu.sa. نية لمركب فولجايد عضو معدني مزدحم فراغياً غير فوتوكروميتحضير ودراسة األشعة السي شار سعد الشهري عند . فقط، وذلك عن طريق تكاثف شتوبE والمزدحم فراغياً على هيئة المشابه 7تم الحصول على مركب الفولجايد : خالصة وتم . 3ثنائي هيدرونفثالين -أ-8،1تق يحدث تحلق إلى المش ال) nm 366( األشعة فوق البنفسجية باستخدام 7تشعيع المركب . بواسطة تحليل األشعة السينية للبلورات7 فولجايد التثبت من تركيب ABSTRACT: Pure E-isomer overcrowded organometallic fulgide 1 was obtained by using successive Stobbe condensations between ketones and succinate diester. Upon irradiation with UV light at (366 nm) it did not cyclise photochemically to the 1,8a-dihydronaphthalene derivative (1,8a- DHN) 8. The structure of 7 was confirmed by X-ray crystallographic analysis. KEYWORDS: Fulgide, Stobbe Condensation, Organometallic, Crystal Structure. 1. Introduction F ulgides with aryl ring undergo ring-closure photochemically to give highly coloured tricyclic dihydronaphthalene derivatives (Heller 1978). It was found that the preferred isomer was the E-isomer in sterically-hindered fulgide systems (Hart and Heller 1972; McCabe et al. 1993; Liang et al. 2001). McCabe et al. (1993) synthesized the first organometallic fulgide 1, which was obtained as E-isomer 1. Irradiation of 1 underwent E/Z isomerization to Z-isomer 2 rather than ring-closure, despite the introduction of donating groups on the ferrocenyl moiety Scheme 1. O O O Fe O O O Fe1 2 UV Scheme 1: E/Z isomerization of fulgide 1. In the present work diphenylidene was introduced to the system to investigate whether or not photocyclization would occur, according to electrocyclization reaction, in agreement with Woodward-Hofmann rules (Yokoyama 2000). 115 SHAR SAAD AL-SHIHRY 2. Experimental General: Melting points were recorded on a Gallenkamp melting point apparatus and were uncorrected. NMR spectra were obtained in CDCl3 on a Jeol 400 MHz with TMS as internal reference; chemical shifts were expressed in δ (ppm). Irradiation of the prepared fulgide in toluene at 366 nm for 48 hrs was carried out, using UV lamp (UV GL-58, 254/366 nml lamp, 50/60 Hz), while UV–Visible double beam spectrophotometer (Shimadzu UV-1601PC) was used to follow up the irradiation effect. Dimethyl (diphenylmethylene)succinate 4: A mixture of benzophenone (18.2 g, 0.1 moles), dimethyl succinate (17.5 g, 0.12 moles) and potassium t-butoxide (12 g, 0.1 moles) in toluene (200 ml) was stirred for 6 hours. Work-up produced the half ester, which was esterified to give the diester as yellow crystals (17 g, 55% yield) m.p. 78-79ºC. 1H-nmr: 3.46 (2H, s, CH2 proton), 3.45 (3H, s, CH3O), 3.70 (3H, s, CH3O), 7.10-7.40 (10H, m, aromatic proton). Ferrocenylethylidene(diphenylidene)succinic anhydride 7: Stobbe condensation on an equimolar basis of dimethyl (diphenylmethylidene) succinate (10 g, 0.03 moles) and ferrocene (7.5 g, 0.03 moles) in toluene (200 ml) in the presence of potassium t-butoxide, followed by hydrolysis of the half ester gave the diacid, which cyclised with acetyl chloride. The solvent and acetyl chloride were removed and the residue was dissolved in dichloromethane and chromatographed on silica gel to give the fulgide 7 as black crystals from dichloromethane and petroleum ether (4.5 g, 28%). m. p. 234-235ºC 1H-nmr: 2.65 (3H, s, CH3), 4.34 (5H, s, Cp’ and 1H, s, Cp), 4.66 (3H, s, Cp), 3.70 (3H, s, CH3O), 7.13-7.46 (10H, m, aromatic proton).Found: C, 73.07; H, 4.39%. C29H22O3Fe requires: C, 73.42; H, 4.64%. m/z, 474. 2.1 X-Ray analysis A dark purple crystal with dimensions 0.483 x 0.260 x 0.188mm3 was placed and optically centered on the Bruker SMART CCD system at –80°C. The initial unit cell was indexed using a least-squares analysis of a random set of reflections collected from three series of 0.3° wide ω scans (25 frames/series) that were well distributed in reciprocal space. Data frames were collected [MoKα] with 0.3° wide ω-scans, 30 seconds/frame, 606 frames per series. Five complete series were collected, including an additional partial, first 160 frames, run of the first series for decay purposes, with a crystal to detector distance of 4.94cm, thus providing a complete sphere of data to 2θmax=55°. A total of 30967 reflections was collected and corrected for Lorentz and polarization effects and absorption using Blessing’s method as incorporated into the program SADABS (Blessing 1995 and Sheldrick 1996) with 5041 unique [R(int)=0.0273]. 3. Results and Discussion Stobbe condensation of benzophenone and dimethyl succinate in the presence of potassium t- butoxide in toluene and subsequent methylation of the condensation product gave dimethyl (diphenylmethylene)succinate 4. A second Stobbe condensation using acetyl ferrocene yielded the half-ester, which was hydrolysed and cyclised using acetyl chloride, to afford solely fulgide 7 as dark purple crystals in 30% yield (Scheme 2). Irradiation of fulgide 7 reveals no changes in wavelengths of absorption bands located at λmax 392 and 544 nm ε 11300, 3940 dm3. ml-1. cm-1 respectively. This may indicate that there is neither E/Z isomerisation, nor electrocyclic ring closure taking place in this specific fulgide, as normally seen in simple fulgides (Yokoyama 2000) (Scheme 3): The structure and stereochemistry of fulgide 7 was confirmed by X-ray crystallographic analysis which is shown in Figure 1. Of particular interest in this fulgide are the following features: • The phenyl rings and the ferrocenyl moiety are rotated from the plane of the anhydride ring. • The angle CT2-Fe-CT1 is 177.46(8) and is less than the expected by 2.54°. 116 SYNTHESIS AND CRYSTAL STRUCTURE • The single bond C11-C12 (1.509 Å) is longer than the single bond C10-C11 (1.457 Å), while the single bonds C17-C18 and C17-C24 have almost the same length 1.489 and 1.484 Å, respectively. Selected bond lengths and angles are given in Table 1. Ph Ph O OMe OMe O O OH OMe O O Ph Ph OMe OMe O O Ph Ph Fe Me O OR1 OR O O Ph Ph Fe Ph Ph 2)iii Fe 7 O O O + i ii 3 4 5 R=H,R 1=Me 6 R=H,R 1=H 1)i iv Scheme 2 : Reagents: i=t-ButOK, toluene, ii=MeOH, H+, iii=KOH, iv=CH3COCl. Ph Fe 7 O O O O Ph O H O Fe Ph Fe O O O X O Ph O O Fe H 8 Scheme 3: Irradiation of 7 shows neither E/Z isomerization, nor ring closure. 117 SHAR SAAD AL-SHIHRY Figure 1. The molecular structure of 7 with the atom-numbering scheme. Hydrogen atoms are drawn as circles of arbitrary small radii for clarity. Table 1 : Selected bond lengths (Å) and bond angles (º) for fulgide 7. _______________________________________________________________________________ Fe(1)-CT2 1.647(2) Fe(1)-CT1 1.661(2) C(10)-C(11) 1.457(2) C(11)-C(13) 1.371(2) C(11)-C(12) 1.509(2) C(13)-C(16) 1.474(2) C(16)-C(17) 1.367(2) CT2-Fe(1)-CT1 177.46(8) C(9)-C(10)-C(11) 128.40(15) C(13)-C(11)-C(10) 123.08(14) C(13)-C(11)-C(12) 120.29(15) C(10)-C(11)-C(12) 116.63(14) C(11)-C(13)-C(16) 131.62(14) C(16)-C(13)-C(14) 105.84(13) C(17)-C(16)-C(13) 130.84(14) C(17)-C(16)-C(15) 121.73(14) C(16)-C(17)-C(24) 121.91(13) C(16)-C(17)-C(18) 122.11(14) Structural determination and Refinement: All crystallographic calculations were performed on a Personal computer (PC) with dual Pentium 450MHz processors and 256MB of extended memory. The SHELXTL (Sheldrick 1994) program package was now implemented, XPREP, to determine the probable space group and set up the initial files. System symmetry and systematic absences 118 SYNTHESIS AND CRYSTAL STRUCTURE indicated the non-standard centrosymmetric space group P21/n (no.14). The structure was determined by direct methods with the successful location of nearly all atoms using the program XS (Sheldrick 1990). The structure was refined with XL (Sheldrick 1993). After the initial refinement difference-Fourier cycle, additional atoms were located and input. After several of these refinement difference-Fourier cycles, all of the atoms were refined isotropically, then anisotropically. Hydrogen atoms were located directly from difference-Fourier maps and input; these atoms were freely refined. Centroids of the Cp rings were calculated. The final structure was refined to convergence [∆/σ ≤ 0.001] with R(F)=3.91%, wR( )=9.52%, GOF=1.060 for all 5041 unique reflections [R(F)=3.30%, wR( )=8.87% for those 4386 data with > 4σ( )]. A final difference-Fourier map was featureless indicating the structure is therefore both correct and complete. 2F 2F oF oF The function minimized during the full-matrix least-squares refinement was Σw( F - F ) where w=1/[σ 2 o 2 c 2( ) +(0.0517*P)2oF 2 +1.0474*P] and P=(max( ,0)+2* )/3. An empirical correction for extinction was attempted but found to be negative and therefore not applied. 2 oF 2 cF Crystal data for fulgide 7 Empirical formula: C29 H22 Fe O3 Formula weight 474.32 Temperature 193(2) K Wavelength 0.71073 Å Crystal system Monoclinic Space group P2(1)/n Unit cell dimensions a = 9.6446(10) Å α= 90°. b = 12.0427(12) Å β= 90.183(2)°. c = 19.1244(19) Å γ = 90°. Volume 2221.2(4) Å Z 4 Density (calculated) 1.418 Mg/m3 Absorption coefficient 0.709 mm-1 F(000) 984 Crystal size 0.13 x 0.210 x 0.424 mm3 Theta range for data collection 2.00 to 27.50°. Index ranges -12<=h<=12, -15<=k<=15, -24<=l<=24 Reflections collected 30967 Independent reflections 5041 [R(int) = 0.0273] Completeness to theta = 27.50° 99.0 % Absorption correction SADABS Max. and min. transmission 1.000000 and 0.895124 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 5041 / 6 / 392 Goodness-of-fit on F2 1.060 Final R indices [I>2sigma(I)] R1 = 0.0330, wR2 = 0.0887 [4386 Data] R indices (all data) R1 = 0.0391, wR2 = 0.0952 Largest diff. peak and hole 0.351 and -0.248 e. 4. Acknowledgements The author would like to thank Dr. J. Fitteger, X-Ray Crystallographic Facility, Chemistry and Biochemistry College Park, University of Maryland, USA, for carrying out the x-ray performance. 119 SHAR SAAD AL-SHIHRY References BLESSING, R.H. 1995. An empirical correction for absorption anisotropy. Acta Crystallographica. A51: 33-38. HART, R.J. and HELLER, H.G. 1972. Overcrowded Molecules. Part VII. Thermal and Photochemical Reactions of Photochromic (E)- and (Z)- Benzylidene(diphenylmethylene)succinic Anhydrides and Imides. Journal of the Chemical Society, Perkin Transactions, 1: 1321-1324. HELLER, H.G. 1978. The development of photochromic compounds for use in optical information stores. Chemistry and Industry, 18 March. 193-196. LIANG, Y., DVORNIKOV, A.S. and RENTZEPIS, P.M. 2001. Photochemistry of photochromic 2-indolylfulgides with substituents at the 1’-position of the indolylmethylene moiety. Journal of Photochemistry and Photobiology A: Chemistry, 146( 1): 83-93 (11). McCABE, R.W., PARRY, D.E. and SABERI, S.P. 1993. Organometallic Fulgides. Part 1. Synthesis and Photochemistry of Ferrocenyl Fulgides [Ferrocenylethylidene (isopropylidene)succinic Anhydrides]. Journal of the Chemical Society, Perkin Transactions, 1: 1023-1029. SHELDRICK, G.M., 1996. SADABS ‘Siemens Area Detector Absorption Correction’ University of Götِtingen: Göِttingen, Germany. SHELDRICK, G.M., 1994. SHELXTL/PC. Version 5.03. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA. SHELDRICK, G.M., 1993. Shelxl93 Program for the Refinement of Crystal Structures. University of Götِtingen, Germany. SHELDRICK, G.M., 1990. Phase annealing in SHELX-90: direct methods for larger structures. Acta Crystallographica. A46: 467-473. YOKOYAMA, Y., 2000. Fulgides for memories and switches. Chem. Rev. 100(5): 1717-1739. Received 29 April 2003 Accepted 24 June 2003 120 Shar Saad Al-Shihry Department of Chemistry, College of Science, King Faisal University, P.O.Box 1759, Saudi Arabia, Email: sshihry@kfu.edu.sa. 2. Experimental Dimethyl (diphenylmethylene)succinate 4: A mixture of benzophenone (18.2 g, 0.1 moles), dimethyl succinate (17.5 g, 0.12 moles) and potassium t-butoxide (12 g, 0.1 moles) in toluene (200 ml) was stirred for 6 hours. Work-up produced the half es 2.1 X-Ray analysis Stobbe condensation of benzophenone and dimethyl succinate in the presence of potassium t-butoxide in toluene and subsequent methylation of the condensation product gave dimethyl (diphenylmethylene)succinate 4. A second Stobbe condensation using acetyl Scheme 2 : Reagents: i=t-ButOK, toluene, ii=MeOH, H+, iii=KOH, iv=CH3COCl.