76g DOI: 10.17344/acsi.2015.1436 Acta Chim. Slov. 2015, 62, 768-774 Scientific paper Liquid/Single Crystal Structure Analysis: Synthesis and Characterization of a Trimethylsilyl Derived Rod Shaped Mesogen Hosapalya Thimmaiah Srinivasa,1, 2 Bandrehalli Siddagangappa Palakshamurthy,3 Devadasan Velmurugan,4 Hirihalli Chickegowda Devarajegowda3 and Suresh HariPrasad*,1 1 Department of Chemistry, Bangalore University, Bengaluru-560001, Karnataka, India 2 Raman Research Institute, Sadashivanagar, Bengaluru-560080, Karnataka, India 3 Department of Physics, Yuvaraja's College (Constituent College), University of Mysore, Mysuru-570005, Karnataka, India 4 CAS in Crystallography and Bio-physics, University of Madras, Guindy Campus, Chennai-600025, Tamilnadu, India * Corresponding author: E-mail: hariprasad@bub.ernet.in Phone: +918022961351; Fax: +918022961331 Received: 17-02-2015 Abstract 4-[4'-Cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate a rod shaped liquid crystal (SmA) is synthesized and characterized. The single-crystals were grown in triclinic crystal system in the space group of PI with unit cell parameters a = 5.9577(2) À, b = 8.0398(3) À, c = 25.8842(9) À, a = 86.096(2)°, ß= 89.912(2)°, у = 2.919(2)°, Z = 2, and V = 1182.16(7). The crystal structure is stabilized by C-H—O intra-molecular interactions. Further, the structure also involves C-H—я interactions and weak n-n stacking interactions [centroid-centroid separation = 3.806 (3) À]. Keywords: Trimethylsilyl benzoates, Single crystal, Liquid crystal, Mesophase, Smectic phase. 1. Introduction Liquid crystal displays (LCDs) have shown a significant capability to spatially manipulate the phase information of an incidental beam of light. This technology is widely applied in a large number of optical applications and hence they have been employed as spatial light modulators (SLMs) in image processing, holography, data storage, programmable adaptive optics, medical optics, and diffractive optics.1 Recently, a new type of reflective LCDs has been developed by employing liquid crystals of silicon (LCoS). These displays have awakened a great amount of interest among researchers due to their specific technical characteristics, which are superior in many aspects to the ones provided by transmissive LCDs.2 For example, as LCoS displays work in reflection, the light impinging such devices perform a double pass through the liquid crystal cell, which leads to a larger phase modula- tion than that of the one related to transmissive LCDs with the same thickness. This greater phase modulation capability allows LCoS displays to become very suitable devices for digital holography applications like laser beam shaping and optical micro-particle manipulation.3 Designing of thermotropic liquid crystals with terminal trimethylsilylacetylene and siloxane units in the core is gaining prominence due to the application of silicon liquid crystals.4 This could be attributed to the presence of terminal acetylene unit, which strongly influences mesophase characteristics by bringing in considerable changes in polarity, polarizability, geometry and birefringence properties of the molecule.5,6 Siloxane units are used for the purpose of building mesogens and have attracted prime attention owing to its applications in the form of alignment studies and optical studies.7'8 From the point of molecular structure, it is observed that the insertion of trimethylsilyl group into the meso-genic core can substantially influence the optical anisotropy and considerably reduce the melting transition temperature due to the tetrahedron geometry of bulky trimethylsilyl group.9,10 In addition, studies have revealed that trimethyl-silyl based mesogens possess a strong hydrophobicity and promote liquidity in general leading to reduction in visco-sity.11 Thus, establishing a relationship between mesogenic structure and the magnitude of the polarizability, anisotropy in trimethylsilyl mesogens is very crucial both for regulating and optimization of optical properties.12-15 Our laboratory is involved in the synthesis, study of reactions and application of organosilyl based com-pounds.16 In continuation of our studies, we were further interested in the synthesis and examination of compounds which possess mesogenic properties as well as single crystal properties. There exist no reports of compounds bearing trimethylsilyl and polar cyano group derived molecules as liquid crystals. Keeping this in mind we hereby report the synthesis, mesomorphic characterization and X-ray single crystal studies of 4-[4'-cyanophenoxy-car-bonyl-phenyl-4-(trimethylsilyl) ethynyl] benzoate. (Rigaku Ultrax-18) operating at 50 kV and 80 mA. Two-dimensional detector Image Plate from Mar Research was used for the collection of scattered radiation. 3. Results and Discussion 3. 1. Synthesis 4-Benzyloxybenzoic acid (1) was condensed with 4-cyanophenol (2) using the simple esterification method to get protected intermediate (3). Hydrogenolysis on 5% Pd-C catalyst offered 4-cyanophenyl-4'-hydroxybenzoate (4) according to reported literature procedure.17 The intermediate 4-[2-(trimethylsilyl)ethynyl]benzoic acid (5) was prepared by Sonogashira coupling reaction with 4-iodo-benzoic acid. The title compound (6) was prepared by the condensation of 4 and 5 using the cross coupling agent MW-dicyclohexylcarbodiimide (DCC) in presence of 4-(N,N-dimethylamino) pyridine (DMAP) catalyst and dichloromethane solvent as shown in Scheme 1. 2. Experimental 2. 1. Materials All chemicals were purchased from Sigma-Aldrich and Merck and used as received. Solvents were distilled and dried prior to the reactions. Single crystals suitable for X-ray diffraction studies were obtained by slow evaporation of hexane at room temperature. 2. 2. Instruments and Experiments All the reactions were monitored by thin layer chro-matography using Merck silica gel pre-coated on aluminium sheets with 1:4 ratio ethyl acetate and petroleum benzene (60-80 oC fraction) as mobile phase. The products were purified by column chromatography on Acme make silica gel 60-120 mesh size. The chemical structures were confirmed by 1H-NMR spectroscopy (Bruker Biospin 500MHz spectrometer), and FTIR spectroscopy (Shimadzu FTIR-8400 spectrometer). The purities of the compounds were established by elemental analysis performed on Carlo-Erba 1106 analyzer. The thermal behavior was investigated by Differential Scanning Calorimetry (DSC) using a Perkin-Elmer, Pyris 1 calibrated using indium and zinc standards. The mesophase characterization of liquid crystal textures were performed by BX50 Olympus Polarized Optical Microscope (POM) equipped with a temperature controlled Mettler FP82HT hot stage and Mettler FP90 central processor. Thermal stability was established by Perkin Elmer TGA4000 analyzer. The heating and cooling profiles were done at the rate of 10 °C min-1. X-ray diffraction studies were performed on non-oriented samples filled using Lindeman capillary, diameter of 1.0 mm using Cu-Ka (0.154 nm) radiation from a rotating anode X-ray generator 3. 1. 1. 4-[4'-Cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate (6).18 4-Cyanophenyl-4'-hydroxybenzoate (4) (0.290 g, 1.00 mmol) and 4-[2-(trimethylsilyl) ethynyl]benzoic acid (5) (0.0570 g, 1.1 mmol) were dissolved in 10 ml of dry dichloromethane. Then, DCC (0.226 g, 1.10 mmol) and DMAP (0.013 g, 0.11 mmol) were added and the mixture was stirred for 12 hrs at room temperature. The reaction progress was monitored by TLC. After the completion of Scheme 1. Synthetic scheme for the compound 6. 4.T 40 10 T" Л Ai ЙА a д! t1*1 <1 hi ßi àì s \. i i é i hk T /Si U lini] г Л —■Sé 1 к p 1 \ 1 / Tèi SS é s s г s; ? 1 i P 4000 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 8СЮ 600 400 CN-Est-TMS 1/cm Figure 1. FT-IR spectrum of 4-[4'-cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]- benzoate (6). reaction, the reaction mixture was poured into ice-water. The dicyclohexyl urea precipitate was removed by filtration. The filtrate was separated and concentrated in-vacuo. The residual solid was re-dissolved in dichloromethane. The organic phase was washed with diluted acetic acid and water and the solvent removed under reduced pressure. The compound was purified on silica gel by column chromatography using dichloromethane/hexane as an elu-ent. Recrystallization from hexane gave the target compound 6. Yield: 0.112 g, 34%. 4-[4'-Cyanophenoxy-carbonyl-phenyl-4-(trimethyl-silyl)ethynyl]benzoate (6) IR: 2922, 2854, 2231, 2162, 1743, 1599, 1462, 1259, 1060, 756 cm-1; 1H-NMR: 8.12 (d, 2H, J = 8.6 Hz, Ar-H), 7.95 (d, 2H, J = 8.5 Hz, Ar-H), 7.63-7.44 (dd, 4H, J = 8.4 & 8.6 Hz, Ar-H), 7.22 (m, 4H, Ar-H), 0.30 (s, 9H, -Si(CH3)3); Elemental analysis C26H21NO4Si requires C, 71.05; H, 4.82; N, 3.19; found C, 71.13; H, 4.94; N, 3.10. The FT-IR spectrum of 6 is shown in Figure 1. The peaks observed at 2231 cm-1, 2152 cm-1 and 1743 cm-1 are assigned to the stretching of cyano-, acetylene- and ester functional groups respectively. Table 1. Phase transition temperatures (T/°C) and associated enthalpy values in square brackets (AH/kJ mol-1) of 4-[ 4'-cyanophenoxy-carbonyl-phenyl-4-(trimethyl-silyl)ethynyl]benzoate (6). Compound Heating scan Cooling scan 6 Cr 156.3 [66.4] Iso 161.1 [4.0] SmA 162.1 [4.1] Iso SmA 107.4 [67.9] Cr In order to confirm the chemical composition of the synthesized compound carbon (C), hydrogen (H) and nitrogen (N) analysis was carried out. The experimental and calculated percentages of C, H, and N are given in analysis data. The differences between experimental and calculated percentages of C, H, and N were very close to each other and within the accepted errors. This confirmed the formation of the product 6. 3. 1. 2. Mesomorphic Studies Thermal behavior of compound 6 was evaluated in conjunction with polarizing optical microscope (POM), Figure 2. DSC scan of 4-[4'-cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]-benzoate. differential scanning calorimeter (DSC) and the transition temperatures gathered from calorimeter measurements of first heating and cooling scanned at rate of 5 °C/min. The results of our observations are tabulated in Table 1. The title compound exhibit enantiotropic Smectic A phase is confirmed by DSC and POM studies. The DSC scan of compound 6 is shown in Figure 2. The compound 6 melts at temperature 156.3 °C with enthalpy AH (66.4) from crystal to Smectic phase and it went isotropic state at 162.1 °C (AH 4.1), and the same sample cooled from isotropic state the Smectic phase reappears at 161.1 °C (AH 4.0) then it crystallizes at 107.4°C (AH 67.9) from liquid crystal state. The POM studies were carried out by sandwiching the sample between untreated glass plate and cover slip. The sample was heated to its isotropic state, and then the sample upon cooling showed characteristic fan shaped texture for typical Smectic phase. The POM pictures are shown in Figure 3(a) taken at early growing state of Smectic phase and Figure 3(b) is taken at complete grown liquid crystal state. 3. 1. 3. X-ray Studies at Liquid Crystalline State We have studied the X-ray diffraction at 140 °C. The X-ray intensity versus 28 pattern is shown in Figu- Figure 3. Polarized Optical Micrographs of 4-[4'-Cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate 6. ilutioil Figure 4. X-ray scan at liquid crystal state for 4-[4'-cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate. re 4. The X-ray diffraction pattern has a sharp peak in the small-angle region with d-spacing of about 36.97 À, and an additional broad peak in the wide-angle region with d-spacing of about 4.75 À, reflecting the liquid-like arrangement of the molecules within each layer. Length of the molecule was also estimated from energy-minimized structure using ChemDraw software. The average length of the molecule was L = 36.89 À, which suggests that L was parallel to the Smectic layer and that normal and flexible chains were randomly oriented in the plane of the Smectic in its stretched conformation. 3. 1. 4. Single Crystal X-ray Diffraction Method Single crystals of size 0.1 x 0.2 x 0.3 mm were selected under a polarizing microscope and affixed to Hampton research cryoloop using paratone oil for data collection. The X-ray diffraction data sets were collected Table 3. Bond lengths (À), of the title compound. Atom-Atom Bond length Atom- Atom Bond length C25-Si1 1.834(3) C12 C13 1.380(3) C26-Si1 1.808(4) C12 O3 1.397(2) C1-N1 1.133(3) C12 O3 1.397(2) C1-C2 1.443(3) C13 C14 1.370(3) C2-C3 1.379(3) C15 O4 1.188(3) C2-C7 1.382(3) C15 O3 1.362(2) C3-C4 1.378(3) C15 C16 1.480(3) C4-C5 1.373(3) C16 C17 1.376(3) C5-C6 1.375(3) C16 C21 1.389(3) C5-O1 1.399(2) C17 C18 1.376(3) C6-C7 1.373(3) C18 C19 1.386(3) C8-O1 1.358(2) C19 C20 1.389(3) C8-C9 1.485(3) C19 C22 1.444(3) C9-C14 1.389(3) C20 C21 1.374(3) C8-O2 1.189(2) C22 C23 1.190(3) C9-C10 1.389(3) C23 Si1 1.831(2) C10-C11 1.378(3) C24 Si1 1.857(3) C11-C12 1.374(3) CIS Figure 5. The ORTEP diagram of the molecule with 50% probability displacement thermal ellipsoids. Figure 6. The packing diagrams depicting the C---H intermolecular interactions. on a Bruker SMART CCD diffractometer using Mo Ka radiation. The crystal-to-detector distance was fixed at 40 mm. The scan width per frame was Дю = 0.5°. The cell refinement and data reduction were carried out using the SAINT19. The crystal structures were solved by direct methods using SHELXS9720 and refined in the spherical-atom approximation (based on F2) by using SHELXL201421. The ORTEP diagrams (Figure 5) and packing diagram (Figure 6) is generated using ortep3v222 and Mercury.23 The experimental and all crystallographic data, including structure refinement details are reported in Table 2 (Supplementary Information). A few bond lengths, bond angles, torsion angles, and Hydrogen-bond are reported in Table 3, 4, 5 and 6 respectively. The dihedral angle between the aromatic rings A B, A C, and B C are 50.47(1)°, 10.51(2)o and 50.02(1)o respectively. In the extended structure the molecular packing is stabilized by C10-H10-01, C17-H17-O3 and C14-H14-Cg2, C24-H24—Cg2 interactions. Further a weak n-n stacking interaction is also observed [cen-troid-centroid separation = 3.806 (3) À]. According to theory the C-C single bond length is 1.54 À. In the case of Si-C and Si = C bonds distances are 1.89 À and 1.72 À respectively. The experimentally determined data indicates that the Si-C bond length is between 1.808 to 1.857 À, which is good agreement with the theoretical values. Table 4. Bond angles (?) of the title compound. Atom-Atom Atom-Atom -Atom Angle -Atom Angle N1-C1-C2 177.4(3) C3-C2-C7 120.35(19) C7-C2-C1 120.7(2) C4-C3-C2 120.13(19) C5-C4-C3 118.5(2) C13-C12-O3 121.50(18) C14-C13-C12 118.82(19) C13-C14-C9 121.0(2) O4-C15-O3 123.34(19) O4-C15-C16 125.3(2) O3-C15-C16 111.36(19) C17-C16-C21 119.44(19) C17-C16-C15 123.10(19) C21-C16-C15 117.46(19) C16-C17-C18 120.3(2) C17-C18-C19 120.7(2) C4-C5-C6 122.12(18) C1-C5-O1 116.21(18) C6-C5-O1 121.61(18) C7-C6-C5 118.91(19) C6-C7-C2 119.8(2) O2-C8-O1 123.52(18) O2-C8-C9 125.08(19) O1-C8-C9 111.39(17) C14-C9-C10 119.17(18) C14-C9-C8 117.02(18) C10-C9-C8 123.79(18) C11-C10-C9 120.08(18) C12-C11-C10 119.52(19) C11-C12-C13 121.37(19) C11-C12-O3 116.96(18) C13-C12-O3 121.50(18) C11-C12-O3 116.96(18) C18-C19-C20 118.76(19) C18-C19-C22 119.3(2) C20-C19-C22 121.9(2) C21-C20-C19 120.53(19) C20-C21-C16 120.2(2) C23-C22-C19 178.0(3) C22-C23-Si1 177.2(2) C8-O1-C5 117.50(15) C15-O3-C12 119.49(17) C26-Si1-C23 107.57(15) C26-Si1-C25 113.8(3) C23-Si1-C25 109.52(14) C26-Si1-C24 109.5(3) C23-Si1-C24 108.74(15) C25-Si1-C24 107.60(17) Table 5. Selected torsion angles (°) of the title compound. Atom-Atom-Atom-Atom Angle N1-C1-C2-C3 -61(6) N1-C1-C2-C7 117(5) C7-C2-C3-C4 -2.8(3) C1-C2-C3-C4 175.19(19) C2-C3-C4-C5 0.4(3) C3-C4-C5-C6 2.5(3) C3-C4-C5-O1 179.83(17) C4-C5-C6-C7 -3.0(3) O1-C5-C6-C7 179.85(17) C5-C6-C7-C2 0.5(3) C3-C2-C7-C6 2.4(3) C1-C2-C7-C6 -175.63(19) O2-C8-C9-C14 7.1(3) O1-C8-C9-C14 -173.63(17) O2-C8-C9-C10 -171.5(2) O1-C8-C9-C10 7.7(3) C14-C9-C10-C11 0.4(3) C8-C9-C10-C11 179.06(18) O3-C15-C16-C21 175.68(17) C21-C16-C17-C18 -1.2(3) C15-C16-C17-C18 178.42(19) C16-C17-C18-C19 0.4(3) C17-C18-C19-C20 0.2(3) C17-C18-C19-C22 178.4(2) C18-C19-C20-C21 -0.2(3) C22-C19-C20-C21 -178.28(19) C19-C20-C21-C16 -0.6(3) C17-C16-C21-C20 1.3(3) C15-C16-C21-C20 -178.36(18) C18-C19-C22-C23 18(8) C20-C19-C22-C23 -164(8) C19-C22-C23-CSi1 -65(11) O2-C8-O1-C5 8.3(3) C9-C8-O1-C5 -170.98(16) C4-C5-O1-C8 120(2) Table 6. Hydrogen-bond geometry of the molecule in (À, o), Cg2 -is the centroid for the ring C16/C17/C18/ C19 /C20 /C21 D-H—A D-H H-A D-A D-H-A C10-H10-01 0.93 2.46 2.760(2) 98.9 C17-H17-O3 0.93 2.42 2.732(3) 99.7 C14-H14-Cg2 0.93 2.80 3.414(2) 124 C24-H24C-Cg2 0.93 2.99 3.797(4) 143 4. Conclusions The synthesis and analysis of 4-[4'-cyanophenoxy-carbonyl-phenyl-4-(trimethylsilyl)ethynyl]benzoate is reported. The three phenyl ring core exhibited enantiotropic Smectic A phase. The single crystal X-ray diffraction studies shows that the title compound crystallizes in triclinic system. The crystal structure is stabilized by C-H—O in-tra-molecular and C-H - n interactions and also by ж—ж interactions [centroid-centroid separation = 3.806 (3) À]. 5. Supplementary Data CCDC 1057495 contains the supplementary crystal-lographic data for compound 6. 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Sheldrick, Acta Cryst, 2008, A64, 112-122. http://dx.doi.org/10.1107/S0108767307043930 21. G. M. Sheldrick, Acta Cryst. 2015, C71, 3-8. 22. L. J. Farrugia, J. Appl. Cryst. 2012, 45, 849-854. http://dx.doi.org/10.1107/S0021889812029111 23. C. F. Macrae, I. J. Bruno, J. A. Chisholm, P. R. Edgington, P. McCabe, E. Pidcock, L. Rodriguez-Monge, R. Taylor, J. Van de Streek, P. A. Wood, J. Appl. Cryst, 2008, 41, 466-470. http://dx.doi.org/10.1107/S0021889807067908 Povzetek Sintetizirali smo tekoče kristale (SmA) spojine 4-[4'-cianofenoksi-karbonil-fenil-4-(trimetilsilil)etinil]benzoata in jih karakterizirali z rentgensko strukturno analizo. Spojina kristalizira v triklinskem kristalnem sistemu, prostorski skupini PI; podatki osnovne celice: a = 5.9577(2) À, b = 8.0398(3) À, c = 25.8842(9) À, a = 86.096(2)°, ß = 89.912(2)°, у =2.919(2)°, Z = 2, and V = 1182.16(7). Kristalno strukturo stabilizirajo intra molekularne interakcije C-H—O. Prisotne so tudi šibke C-H—я interakcije in tudi n-n interakcije [centroid-centroid razdalja = 3.806 (3) À]. Scheme 1. Synthetic scheme for the compound 6. Figure 1. FTIR spectrum of the compound 6. Table 1. Phase transition temperatures (T/°C) and associated enthalpy values in square brackets (AH/kJ mol 1) of 6. Compound Heating scan Cooling scan 6 Cr 156.3 [66.4] SmA 162.1[4.1] Iso Iso 161.1 [4.0] SmA 107.4 [67.9] Cr |Compd 6| Heating Cooling \ Mesophase Isotropic Crystal 60 120 180 Temperature in C 0 Figure 2. DSC Scan of 4-[4'-cyanophenoxy-carbonyl-phenyl 4-(trimethylsilyl)ethynyl]benzoate. Figure 3. Polarized Optical Micrographs of compound 6. 40000 -py 20000 - 0 - iCompd б| 36.97A 4.75A —i— 10 20 —I— 30 2 theta Figure 4. X-ray scan at liquid crystal state for 4-[4'-cyanophenoxy-carbonyl-phenyl 4-(trimethylsilyl)ethynyl]benzoate. Table 2. Crystal data, data collection and refinement parameters for the structure of 6. Empirical formula Formula weight Temperature Wavelength Crystal system, space group a(Ä), b(Ä), c(Ä) a (Ä) ß (Ä) y(ä) Volume, Z Calculated density Absorption coefficient F(000), F'(000) Crystal size Theta range for data collection Limiting indices Reflection collected/unique Completeness to theta Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I>2o(I)] R indices (all data) Largest diff. peak and hole Measurement Program system Structure determination C26H21NO4Si 439.53 296 K 0.71073 Ä Triclinic, PI 5.9577(2), 8.0398(3), 25.8842(9) 86.096(2), 89.912(2), 72.919(2) V=1182.16(7), 2 1.235mg/m3 0.131 mm-1 460.0, 460.37 0.10x 0.20 X 0.30 mm 1.6-25.0° -7< h <7, -9 < k <9, -30< l <30 4161/2996 [Rint =0.0474] 1.0 Full-matrix least-square on F2 4161/0/292 1.123 R1 = 0.0474,wR2 = 0.1476 R1 = 0.0691,wR2 = 0.1476 0.42 and -0.39 eÄ-3 Bruker SMART APEX II diffractometer SAINT Direct method (SHELX97, SHELXS97) i. Figure 6. The packing diagrams depicting the C--H intermolecular interactions. Figure 7. Molecular packing of compound 6, the dotted lines indicates intermolecular C-H O interactions and n-n stacking. Table 3. Selected bond lengths (A), of the title compound. Atom-Atom Bond length C25- —Si1 1.834(3) C26- —Si1 1.808(4) C1— -N1 1.133(3) C1— C2 1.443(3) C2— C3 1.379(3) C2- -C7 1.382(3 C3— C4 1.378(3) C4— C5 1.373(3) C5— C6 1.375(3) C5— O1 1.399(2) C6— C7 1.373(3) C8— O1 1.358(2) C8— C9 1.485(3) C9— C14 1.389(3) C8— O2 1.189(2) C9— C10 1.389(3) C10— C11 1.378(3) C11— C12 1.374(3) Atom-Atom Bond length C12— C13 1.380(3) C12— O3 1.397(2) C12— O3 1.397(2) C13— C14 1.370(3) C15— O4 1.188(3) C15— O3 1.362(2) C15— C16 1.480(3) C16— C17 1.376(3) C16— C21 1.389(3) C17— C18 1.376(3) C18— C19 1.386(3) C19— C20 1.389(3) C19— C22 1.444(3) C20— C21 1.374(3) C22— C23 1.190(3) C23— Si1 1.831(2) C24— Si1 1.857(3) Table 4. Selected bond angles (◦) of the title compound. Atom—Atom—Atom Angle Atom—Atom—Atom Angle N1— -C1—C2 177.4(3) C3— C2—C7 120.35(19) C7— -C2—C1 120.7(2) C4— C3—C2 120.13(19) C5— C4—C3 118.5(2) C13— —C12—O3 121.50(18) C14— -C13—C12 118.82(19) C13— —C14—C9 121.0(2) O4— -C15—O3 123.34(19) O4— -C15—C16 125.3(2) O3— -C15—C16 111.36(19) C17— -C16—C21 119.44(19) C17— -C16—C15 123.10(19) C21— -C16—C15 117.46(19) C16— —C17—C18 120.3(2) C17— —C18—C19 120.7(2) C4— C5—C6 122.12(18) C1— C5—O1 116.21(18) C6— C5—O1 121.61(18) C7— C6—C5 118.91(19) C6— C7—C2 119.8(2) O2— C8—O1 123.52(18) O2— -C8—C9 125.08(19) O1 — C8—C9 111.39(17) C14— —C9—C10 119.17(18) C14— C9—C8 117.02(18) C10— —C9—C8 123.79(18) C11— -C10—C9 120.08(18) C12— -C11—C10 119.52(19) C11— —C12—C13 121.37(19) C11— —C12—O3 116.96(18) C13— —C12—O3 121.50(18) C11— —C12—O3 116.96(18) C18— —C19—C20 118.76(19) C18— —C19—C22 119.3(2) C20— —C19—C22 121.9(2) C21— —C20—C19 120.53(19) C20— —C21—C16 120.2(2) C23— —C22—C19 178.0(3) C22— —C23—Si1 177.2(2) C8— O1 —C5 117.50(15) C15— -O3—C12 119.49(17) C26— —Si1—C23 107.57(15) C26— —Si1—C25 113.8(3) C23— —Si1—C25 109.52(14) C26— —Si1—C24 109.5(3) C23— —Si1—C24 108.74(15) C25— —Si1—C24 107.60(17) Table 5. Selected torsion angles (◦) of the title compound. Atom—Atom—Atom—Atom Angle N1 —C1 —C2—C3 -61(6) N1 —C1 —C2—C7 117(5) C7—C2—C3—C4 -2.8(3) C1—C2—C3—C4 175.19(19) C2—C3—C4—C5 0.4(3) C3—C4—C5—C6 2.5(3) C3—C4—C5—O1 179.83(17) C4—C5—C6—C7 -3.0(3) O1—C5—C6—C7 179.85(17) C5—C6—C7—C2 0.5(3) C3—C2—C7—C6 2.4(3) C1—C2—C7—C6 -175.63(19) O2—C8—C9—C14 7.1(3) O1—C8—C9—C14 -173.63(17) O2—C8—C9—C10 -171.5(2) O1—C8—C9—C10 7.7(3) C14—C9—C10—C11 0.4(3) C8—C9—C10—C11 179.06(18) O3—C15—C16—C21 175.68(17) C21—C16—C17—C18 -1.2(3) C15—C16—C17—C18 178.42(19) C16—C17—C18—C19 0.4(3) C17—C18—C19—C20 0.2(3) C17—C18—C19—C22 C18—C19—C20—C21 C22—C19—C20—C21 C19—C20—C21 —C16 C17—C16—C21 —C20 C15—C16—C21 —C20 C18—C19—C22—C23 C20—C19—C22—C23 C19—C22—C23—CSi1 O2—C8—O1 —C5 C9—C8—O1 —C5 C4—C5—O1—C8 178.4(2) -0.2(3) -178.28(19) -0.6(3) 13(3) -178.36(18) 18(8) -164(8) -65(11) 8.3(3) -170.98(16) 120(2) Table 6. Hydrogen-bond geometry of the molecule in (A, o), Cg2 - is the centroid for the ring C16/C17/C18/ C19 /C20 /C21 D—H. . .A_D—H H. . . A D. . . A D—H. . . A C10—H10. . .O1 0.93 2.46 2.760(2) 98.9 C17—H17. . .O3 0.93 2.42 2.732(3) 99.7 C14—H14. . .Cg2 0.93 2.80 3.414(2) 124 C24—H24C. . .Cg2 0.93 2.99 3.797(4) 143