Synthesis of Two Novels-Shaped Dibenzo [ c , l ] Chrysene Derivatives , Crystal Structure , and the Evaluation of their Photophysical Properties

Two s-shaped polyaromatic dibenzo[c,l]chrysene derivatives have been synthesized by a two-step process, via. The Wittig reaction, followed by iodine, promoted photocyclization. These molecules have been characterized by 1H NMR, FAB-MS, and elemental analysis. Further, the molecular structures of 4a and 4b have been confirmed by single crystal X-ray diffraction analysis. The protons located in the cove-regions of molecules 4a and 4b showed downfield shifts of the protons. Molecule 4a crystallized under the monoclinic system with space group C2/c, and the molecule 4b crystallized under the monoclinic system with space group P21/n. Molecules 4a and 4b showed strong absorption maxima wavelengths at 310 nm and 324 nm, respectively. The molar extinctinction coefficients (ε) of the compounds 4a and 4b indicated that molecule 4b has a better ability to absorb UV light than molecule 4a. The emission spectra of the molecules 4a and 4b displayed peaks in the region 429–456 nm. The shape of the UV-Visible and Fluorescence spectra of the molecules 4a and 4b look almost identical. However, molecule 4b exhibited better fluorescence intensity than molecule 4a. This may be due to the difference in the substituents of molecules 4a and 4b.


Introduction
Polyaromatic hydrocarbons or π-conjugated materials are an important class of organic compounds because their important property of conductivity led to tremendous advancements in the field of organic electronics [1].Over the past decade significant research has been done and the search for the new π-conjugated systems has been ongoing because of the important, rapidly growing number of applications in electronic devices such as semiconducting materials [2][3][4][5], organic solar cells [6], sensors [7], organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and flexible displays.π-conjugated materials have been extensively studied for their optoelectronic properties due to the offering of low-cost, large-area, and flexible electronic devices [8][9][10].S-shaped dibenzo[c,l]chrysene derivatives are regarded as a hexacyclic polyaromatic hydrocarbon compound containing two cove-regions, and they have potential applications in biological systems and organic semiconductor materials [11,12].The synthesis of s-shaped benzo[c,l]chrysene derivatives is of great interest, and is challenging because of the steric hindrance in the cove-regions.The synthesis of s-shaped benzo[c,l]chrysene derivatives with substituents like -F, -CF 3 in the cove-region is even more challenging because of the increased steric hindrance.An ideal organic electronic material should have a low HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap, good solid state packing, stability, solubility, and planarity.One of the fundamental principles in designing an air stable semiconducting material is incorporating electron withdrawing groups.It was reported that because of the incorporation of electron withdrawing groups, electron affinity of materials increases and the LUMO energy gap decreases; consequently, the band gap also decreases [13][14][15].It was also reported that the introduction of fluorine atoms in the molecule increases the thermal stability of the molecule, which is important for the effective vapor-phase growth of the corresponding thin films [16].Considering these basic principles, as part of our ongoing research objectives in this article we have investigated the synthesis, crystal structure, and photophysical properties of two fluorinated s-shaped polyaromatic compounds, which are have the dibenzo[c,l]chrysene-like structure.We employed the typical Wittig and iodine-assisted photocyclization strategy for the synthesis of these molecules [17,18].Earlier, we reported the synthesis of various kinds of polyaromatic compounds and evaluated their organic photoelectronic properties [19][20][21][22].We believe that this study may be helpful to the material chemists in designing new materials with a view to achieve desired performance in devices and circuits.

Synthesis and Spectra Analysis
Molecules 4a and 4b have been synthesized in two steps.In the first step, 2,6-bis (triphenylphosphinomethyl)-naphthalene dichloride 1 was condensed with 2,3,4,5-tetrafluoro or 3,5-bis(trifluoromethyl) benzaldehyde (2a, 2b) via.The Wittig reaction generated the precursors 3a and 3b.In the second step, 3a and 3b were subjected to iodine-assisted photocyclization, and yielded the corresponding s-shaped polyaromatic compounds 4a and 4b in moderate yields (Scheme 1).shaped benzo[c,l]chrysene derivatives with substituents like -F, -CF3 in the cove-region is even more challenging because of the increased steric hindrance.An ideal organic electronic material should have a low HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap, good solid state packing, stability, solubility, and planarity.One of the fundamental principles in designing an air stable semiconducting material is incorporating electron withdrawing groups.It was reported that because of the incorporation of electron withdrawing groups, electron affinity of materials increases and the LUMO energy gap decreases; consequently, the band gap also decreases [13][14][15].It was also reported that the introduction of fluorine atoms in the molecule increases the thermal stability of the molecule, which is important for the effective vapor-phase growth of the corresponding thin films [16].Considering these basic principles, as part of our ongoing research objectives in this article we have investigated the synthesis, crystal structure, and photophysical properties of two fluorinated s-shaped polyaromatic compounds, which are have the dibenzo[c,l]chrysene-like structure.We employed the typical Wittig and iodine-assisted photocyclization strategy for the synthesis of these molecules [17,18].Earlier, we reported the synthesis of various kinds of polyaromatic compounds and evaluated their organic photoelectronic properties [19][20][21][22].We believe that this study may be helpful to the material chemists in designing new materials with a view to achieve desired performance in devices and circuits.

Synthesis and Spectra Analysis
Molecules 4a and 4b have been synthesized in two steps.In the first step, 2,6bis(triphenylphosphinomethyl)-naphthalene dichloride 1 was condensed with 2,3,4,5-tetrafluoro or 3,5-bis(trifluoromethyl) benzaldehyde (2a, 2b) via.The Wittig reaction generated the precursors 3a and 3b.In the second step, 3a and 3b were subjected to iodine-assisted photocyclization, and yielded the corresponding s-shaped polyaromatic compounds 4a and 4b in moderate yields (Scheme 1).Molecules 4a and 4b have been characterized with 1 H NMR, EI-MS, and elemental analysis. 1H NMR spectra for the photo-cyclized products 4a and 4b showed downfield shifts of the protons located in the cove-regions, which consist of four benzene rings.The five carbons in the cove-region were highlighted by using round circles in the molecular structures of 4a and 4b (Figures 1 and 2).The 1 H NMR shift values are 8.40 ppm for 4a, 8.65 ppm for 4b, respectively.The shifts were well explained by the strong ring current effects of the π-systems on the molecules.
Further to confirm the molecular structures of molecules 4a and 4b, good crystals suitable for the measurement of X-ray diffraction analysis were obtained by the slow evaporation of the dichloromethane solution using the slow diffusion method.The crystallographic details are summarized in Table 3.The compound 4a crystallizes with the monoclinic crystal system, space group C2/c.The molecular structure of 4a was depicted in Figure 1.Molecules 4a and 4b have been characterized with 1 H NMR, EI-MS, and elemental analysis. 1H NMR spectra for the photo-cyclized products 4a and 4b showed downfield shifts of the protons located in the cove-regions, which consist of four benzene rings.The five carbons in the cove-region were highlighted by using round circles in the molecular structures of 4a and 4b (Figures 1 and 2).The 1 H NMR shift values are 8.40 ppm for 4a, 8.65 ppm for 4b, respectively.The shifts were well explained by the strong ring current effects of the π-systems on the molecules.
Further to confirm the molecular structures of molecules 4a and 4b, good crystals suitable for the measurement of X-ray diffraction analysis were obtained by the slow evaporation of the dichloromethane solution using the slow diffusion method.The crystallographic details are summarized in Table 3.The compound 4a crystallizes with the monoclinic crystal system, space group C2/c.The molecular structure of 4a was depicted in Figure 1.The asymmetric unit of the title compound C26H8F8, contains one-half of the formula unit.The dihedral angle between the planes of the end phenyl rings was quite large (59.85°).Three phenyl ring planes, A (defined by C1,C2,C3,C4,C9,C10), B (defined by C5,C6,C11,C12,C9,C10), and C (defined by C9,C10,C11,C12,C13,C13 were slightly leaned (Figure 1) and the plane angles between three phenyl rings are 10.56° for A-B, 18.89° for A-C, and 8.39° for B-C, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4a seems to be the planar, but it is a strained one.The steric hindrance due to the cove-region causes a deviation from the planarity of a molecule.The compound 4b also crystallizes with the monoclinic crystal system, space group P21/n.The molecular structure of molecule 4b was depicted in Figure 2. The dihedral angle between the planes of the end phenyl rings was quite large (66.33°).Six phenyl ring planes, A (defined by C1,C2,C3,C4,C17,C18), B (defined by C5,C6,C17,C18,C19,C20), C (defined by C7,C8,C19,C20,C21,C22), D (defined by C15,C16,C21,C22,C23,C24), E (defined by C13,C14,C23,C24,C25,C26), and F (defined by C9,C10,C11,C12,C25,C26) were slightly leaned (Figure 2), and the plane angles between the six phenyl rings are 14.10° for A-B, 25.59° for A-C, 11.54° for B-C, 19.90° for C-D, 31.34° for C-E, 42.52° for C-F, 28.89°, 27.83° for B-E, and 66.33° for A-E, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4b seems to be planar, but it is a strained one.The dihedral angle between the planes of the aromatic rings of molecule 4b is relatively more than molecule 4a, because the bulky -CF3 substituents in the cove-region causes more deviation from planarity.This suggests that molecule 4b is more strained than molecule 4a.
Crystal packing of the molecule 4a was illustrated in Figure 3.In the crystal the molecules are assembled like planar geometry.Intermolecular short contacts of the molecule 4a were listed in Table 1.The ends of the molecules are linked by F In between the layers, The asymmetric unit of the title compound C 26 H 8 F 8 , contains one-half of the formula unit.The dihedral angle between the planes of the end phenyl rings was quite large (59.85 • ).Three phenyl ring planes, A (defined by C1,C2,C3,C4,C9,C10), B (defined by C5,C6,C11,C12,C9,C10), and C (defined by C9,C10,C11,C12,C13,C13 were slightly leaned (Figure 1) and the plane angles between three phenyl rings are 10.56 • for A-B, 18.89 • for A-C, and 8.39 • for B-C, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4a seems to be the planar, but it is a strained one.The steric hindrance due to the cove-region causes a deviation from the planarity of a molecule.The asymmetric unit of the title compound C26H8F8, contains one-half of the formula unit.The dihedral angle between the planes of the end phenyl rings was quite large (59.85°).Three phenyl ring planes, A (defined by C1,C2,C3,C4,C9,C10), B (defined by C5,C6,C11,C12,C9,C10), and C (defined by C9,C10,C11,C12,C13,C13 were slightly leaned (Figure 1) and the plane angles between three phenyl rings are 10.56° for A-B, 18.89° for A-C, and 8.39° for B-C, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4a seems to be the planar, but it is a strained one.The steric hindrance due to the cove-region causes a deviation from the planarity of a molecule.The compound 4b also crystallizes with the monoclinic crystal system, space group P21/n.The molecular structure of molecule 4b was depicted in Figure 2. The dihedral angle between the planes of the end phenyl rings was quite large (66.33°).Six phenyl ring planes, A (defined by C1,C2,C3,C4,C17,C18), B (defined by C5,C6,C17,C18,C19,C20), C (defined by C7,C8,C19,C20,C21,C22), D (defined by C15,C16,C21,C22,C23,C24), E (defined by C13,C14,C23,C24,C25,C26), and F (defined by C9,C10,C11,C12,C25,C26) were slightly leaned (Figure 2), and the plane angles between the six phenyl rings are 14.10° for A-B, 25.59° for A-C, 11.54° for B-C, 19.90° for C-D, 31.34° for C-E, 42.52° for C-F, 28.89°, 27.83° for B-E, and 66.33° for A-E, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4b seems to be planar, but it is a strained one.The dihedral angle between the planes of the aromatic rings of molecule 4b is relatively more than molecule 4a, because the bulky -CF3 substituents in the cove-region causes more deviation from planarity.This suggests that molecule 4b is more strained than molecule 4a.
Crystal packing of the molecule 4a was illustrated in Figure 3.In the crystal the molecules are assembled like planar geometry.Intermolecular short contacts of the molecule 4a were listed in Table 1.The ends of the molecules are linked by F•••F, C-H•••F short contacts.In between the layers, The compound 4b also crystallizes with the monoclinic crystal system, space group P2 1 /n.The molecular structure of molecule 4b was depicted in Figure 2. The dihedral angle between the planes of the end phenyl rings was quite large (66.33 • ).Six phenyl ring planes, A (defined by C1,C2,C3,C4,C17,C18), B (defined by C5,C6,C17,C18,C19,C20), C (defined by C7,C8,C19,C20,C21,C22), D (defined by C15,C16,C21,C22,C23,C24), E (defined by C13,C14,C23,C24,C25,C26), and F (defined by C9,C10,C11,C12,C25,C26) were slightly leaned (Figure 2), and the plane angles between the six phenyl rings are 14.10 • for A-B, 25.59 • for A-C, 11.54 • for B-C, 19.90 • for C-D, 31.34 • for C-E, 42.52 • for C-F, 28.89 • , 27.83 • for B-E, and 66.33 • for A-E, respectively.The dihedral angles between the planes of the rings suggest that the shape of the molecule 4b seems to be planar, but it is a strained one.The dihedral angle between the planes of the aromatic rings of molecule 4b is relatively more than molecule 4a, because the bulky -CF 3 substituents in the cove-region causes more deviation from planarity.This suggests that molecule 4b is more strained than molecule 4a.
Crystal packing of the molecule 4a was illustrated in Figure 3.In the crystal the molecules are assembled like planar geometry.Intermolecular short contacts of the molecule 4a were listed in Table 1.Further to investigating the photophysical properties of molecules 4a and 4b, the UV-V is absorption and the Fluorescence emission of the molecules 4a and 4b were measured in a dichloromethane solution (1 × 10 −5 mol/L), and their corresponding spectra were shown in Figures 5  and 6, respectively.The molecules 4a and 4b showed absorption maxima wavelength at 310 nm and 324 nm, respectively.The molar extinctinction coefficients (ε) of the compounds 4a and 4b were calculated as 5.7 × 10 4 (310 nm) and 7.5 × 10 4 (324 nm), L•mol −1 •cm −1 , respectively.These results indicate that molecule 4b has better ability to absorb UV light than molecule 4a.Because of the incorporation of the relatively strong electron withdrawing -CF 3 group in molecule 4b, the band gap between HOMO, LUMO of 4b (3.82 eV) is less than that of molecule 4a (3.98 eV).As a result of this, more molecules of 4b absorb energy than those of molecule 4a.This improves the excitation charge transfer and transport of 4b than 4a.Further to investigating the photophysical properties of molecules 4a and 4b, the UV-V is absorption and the Fluorescence emission of the molecules 4a and 4b were measured in a dichloromethane solution (1 × 10 −5 mol/L), and their corresponding spectra were shown in Figures 5  and 6, respectively.The molecules 4a and 4b showed absorption maxima wavelength at 310 nm and 324 nm, respectively.The molar extinctinction coefficients (ε) of the compounds 4a and 4b were calculated as 5.7 × 10 4 (310 nm) and 7.5 × 10 4 (324 nm), L•mol −1 •cm −1 , respectively.These results indicate that molecule 4b has better ability to absorb UV light than molecule 4a.Because of the incorporation of the relatively strong electron withdrawing -CF3 group in molecule 4b, the band gap between HOMO, LUMO of 4b (3.82 eV) is less than that of molecule 4a (3.98 eV).As a result of this, more molecules of 4b absorb energy than those of molecule 4a.This improves the excitation charge transfer and transport of 4b than 4a.The emission spectra of the molecules 4a and 4b were recorded in dichloromethane solution (1 × 10 −5 mol/L), and their emission spectra is shown in Figure 6.Emission spectra of the complexes were measured by exciting the complexes at their absorption maxima wavelengths 310 nm and 324 nm, respectively.The emission spectra of molecules 4a and 4b displayed peaks in the region 429-456 nm.The strong emissions can be explained by the molecular shapes of the compounds 4a and 4b.In another words, the compounds have no flexible parts; therefore, the excited energy cannot be relaxed through molecular vibrations.The shape of the emission spectrum of both the molecules almost looks identical.However, the molecule 4b displayed relatively higher fluorescence intensity than molecule The emission spectra of the molecules 4a and 4b were recorded in dichloromethane solution (1 × 10 −5 mol/L), and their emission spectra is shown in Figure 6.Emission spectra of the complexes were measured by exciting the complexes at their absorption maxima wavelengths 310 nm and 324 nm, respectively.The emission spectra of molecules 4a and 4b displayed peaks in the region 429-456 nm.The strong emissions can be explained by the molecular shapes of the compounds 4a and 4b.In another words, the compounds have no flexible parts; therefore, the excited energy cannot be relaxed through molecular vibrations.The shape of the emission spectrum of both the molecules almost looks identical.However, the molecule 4b displayed relatively higher fluorescence intensity than molecule 4a.This may be due to the difference in the substituents of molecules 4a and 4b.Also, because of the more strained geometry of molecule 4b, relatively more energy will be used for the charge redistribution in the excited state than for molecule 4a.
HOMO and LUMO energy level calculations of the π systems of the compounds were carried out using density functional theory (DFT) B3LYP 6-31G(d) level on SPARTAN16 Suite program [23].Atomic coordinate data (x, y, z) of the X-ray analysis were used in the calculations.The calculation results were HOMO −5.91eV, LUMO −1.93eV for 4a and HOMO −6.05eV, and LUMO −2.23eV for 4b, respectively (Figure 7).The energy gaps were 3.98eV for 4a and 3.82eV for 4b.
Crystals 2017, 7, 251 6 of 10 4a.This may be due to the difference in the substituents of molecules 4a and 4b.Also, because of the more strained geometry of molecule 4b, relatively more energy will be used for the charge redistribution in the excited state than for molecule 4a.
HOMO and LUMO energy level calculations of the π systems of the compounds were carried out using density functional theory (DFT) B3LYP 6-31G(d) level on SPARTAN16 Suite program [23].Atomic coordinate data (x, y, z) of the X-ray analysis were used in the calculations.The calculation results were HOMO −5.91eV, LUMO −1.93eV for 4a and HOMO −6.05eV, and LUMO −2.23eV for 4b, respectively (Figure 7).The energy gaps were 3.98eV for 4a and 3.82eV for 4b.4a.This may be due to the difference in the substituents of molecules 4a and 4b.Also, because of the more strained geometry of molecule 4b, relatively more energy will be used for the charge redistribution in the excited state than for molecule 4a.
HOMO and LUMO energy level calculations of the π systems of the compounds were carried out using density functional theory (DFT) B3LYP 6-31G(d) level on SPARTAN16 Suite program [23].Atomic coordinate data (x, y, z) of the X-ray analysis were used in the calculations.The calculation results were HOMO −5.91eV, LUMO −1.93eV for 4a and HOMO −6.05eV, and LUMO −2.23eV for 4b, respectively (Figure 7).The energy gaps were 3.98eV for 4a and 3.82eV for 4b.

Materials and Instrumentation
All reagents and solvents were obtained from commercial sources and used without further purification.The 1 H NMR spectra were recorded on a Bruker AVANCE400S spectrometer (Bruker, Yokohama, Japan) in CDCl 3 with tetramethylsilane (Me 4 Si) as an internal reference.The positive fast atom bombardment (FAB) mass spectrum (MS) of the complex were obtained on a Nippon Densi JEOL JMS-SX102A spectrometer (JEOL, Tokyo, Japan) using NBA (nitrobenzylalcohol) as the matrix and DCM (dichloromethane) as the solvent.The instrument was operated in positive ion mode over an m/z range of 100-2000.Elemental analysis data were recorded on a Yanako MT-4 analyzer.A JASCO V-550 spectrophotometer (Yanako group, Kyoto, Japan) was used for obtaining UV-Vis spectra in dichloromethane with a 250-900 nm range.The HITACHI F-2500 spectrophotometer (Hitachi High-Technologies Corporation, Tokyo, Japan) was used for fluorescence spectra measurements in dichloromethane with a 250-900 nm range.CCDC no.1551483 and 1551484 contain the supplementary crystallographic data for the complexes 4a and 4b, respectively.
3.2.2.Typical Procedure for the Photo Cyclization of the Compounds 4a and 4b 4,9-Bis{2'-(2,3,4,5-tetrafluoro or 3,5-bis(trifluoromethyl) phenyl)ethenyl}-naphthalene (1.0 mmol) 3 was dissolved in 200 mL of benzene in a round-bottom flask.To this iodine (10 mmol) was added, the mixture was stirred and irradiated UV light using high-pressure Hg lamp for 14 h, quenched with 1.0 mol/L Na 2 S 2 O 3 solution, allowed to warm to room temperature, and extracted twice with ethyl acetate.The organic layers were washed once with 50 mL water, twice with 50 mL of brine solution, dried over MgSO 4 , and then the solvent was removed under reduced pressure.The title compound was obtained using silica gel (Wako gel C-300) column chromatography (100 mg, 21% yield for 4a, 130 mg, 22% for 4b) with CH 2 Cl 2 as an eluent.

3.3.Data Collection, Refinement, and Structural Determination
Single crystals of compounds 4a and 4b were obtained from a solution of dichloromethane at room temperature using the slow diffusion method.The crystallographic data of these complexes were summarized in Table 3. APEX2 software was used for the preliminary determination of the unit cell [24].The determination of the integrated intensities and unit cell refinement were performed using SAINT program [25].The structures were solved with SHELXL-2014/7, and subsequent structure refinements were performed with SHELXL-2014/7 [26].

Conclusions
In conclusion, we have reported the synthesis of two s-shaped fluorinated polyaromatic organic materials.These molecules were characterized by 1 H NMR, EI-MS, and elemental analysis.The protons located in the cove-regions of molecules 4a and 4b showed downfield shifts of the protons.The molecular structures of molecules 4a and 4b were determined by X-ray diffraction analysis.Molecules 4a and 4b have different crystal packing.Furthermore, molecules 4a and 4b showed strong absorption maxima at wavelengths 310 nm and 324 nm, respectively.The molar extinctinction coefficients (ε) indicated that molecule 4b (7.5 × 10 4 L•mol −1 •cm −1 ) has a better ability to absorb UV light than molecule 4a (5.7 × 10 4 L•mol −1 •cm −1 ).The emission spectra of molecules 4a and 4b displayed peaks in the region 428-456 nm.However, molecule 4b exhibited better fluorescence intensity than molecule 4a.This may be due to the difference in the substituents of molecules 4a and 4b.

Scheme 1 .
Scheme 1. Schematic representation of synthesis of title compounds.

Scheme 1 .
Scheme 1. Schematic representation of synthesis of title compounds.

Figure 1 .
Figure 1.The molecular structure of 4a; thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 2 .
Figure 2. The molecular structure of 4b; the thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 1 .
Figure 1.The molecular structure of 4a; thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 1 .
Figure 1.The molecular structure of 4a; thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 2 .
Figure 2. The molecular structure of 4b; the thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 2 .
Figure 2. The molecular structure of 4b; the thermal ellipsoids were drawn on 50% probability level.Pale green ellipsoid represents F atoms.
The ends of the molecules are linked by F•••F, C-H•••F short contacts.In between the layers, molecules are stacked by C-H•••F, C•••C and F•••F short contacts, forming a flat, layer-like structure.In the packing diagram, molecular layers almost look like they are assembled parallel to each other.Crystal packing of the molecule 4b was illustrated in Figure 4. Intermolecular short contacts of the molecule 4b were listed in Table 2.The molecular packing of the molecule 4b is not a planar one.Molecule 4b has a herring bone-like crystal packing system.In the crystal packing diagram, C-H•••F, C•••F, and F•••F short contacts together generated three dimensional molecular networks.Crystals 2017, 7, 251 4 of 10 molecules are stacked by C-H•••F, C•••C and F•••F short contacts, forming a flat, layer-like structure.In the packing diagram, molecular layers almost look like they are assembled parallel to each other.Crystal packing of the molecule 4b was illustrated in Figure 4. Intermolecular short contacts of the molecule 4b were listed in Table 2.The molecular packing of the molecule 4b is not a planar one.Molecule 4b has a herring bone-like crystal packing system.In the crystal packing diagram, C-H•••F, C•••F, and F•••F short contacts together generated three dimensional molecular networks.

Figure 3 .
Figure 3. Molecular packing of the compound 4a and thermal ellipsoids are drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 4 .
Figure 4. Molecular packing of the compound 4b along with a-axis, slightly bent towards front (thermal ellipsoids are drawn on 50% probability level).Pale green ellipsoid represents F atoms.

Figure 3 .
Figure 3. Molecular packing of the compound 4a and thermal ellipsoids are drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 3 .
Figure 3. Molecular packing of the compound 4a and thermal ellipsoids are drawn on 50% probability level.Pale green ellipsoid represents F atoms.

Figure 4 .
Figure 4. Molecular packing of the compound 4b along with a-axis, slightly bent towards front (thermal ellipsoids are drawn on 50% probability level).Pale green ellipsoid represents F atoms.Figure 4. Molecular packing of the compound 4b along with a-axis, slightly bent towards front (thermal ellipsoids are drawn on 50% probability level).Pale green ellipsoid represents F atoms.

Figure 4 .
Figure 4. Molecular packing of the compound 4b along with a-axis, slightly bent towards front (thermal ellipsoids are drawn on 50% probability level).Pale green ellipsoid represents F atoms.Figure 4. Molecular packing of the compound 4b along with a-axis, slightly bent towards front (thermal ellipsoids are drawn on 50% probability level).Pale green ellipsoid represents F atoms.