Crystal Structures of Ethyl 4-( 4-Florophenyl )-6-phenyl-2-substituted-3-pyridinecarboxylates

Three substituted pyridinecarboxylates were synthesized; (I) ethyl 2-bromo-4-4(fluorophenyl)-6-phenyl-3-pyridinecarboxylate, C 20 H 15 BrFNO 2 , (II) ethyl 4-(4-fluorophenyl)-2-(4-morpholinyl)-6-phenyl-3-pyridinecarboxylate, C 24 H 23 FN 2 O 3 , and (III) ethyl 4-(4-fluorophenyl)-6-phenyl-2-(1-piperidinyl)-3-pyridinecarboxylate, C 25 H 25 FN 2 O 2 . It was found that compound (I) belongs to the orthorhombic system with space group P212121, compound (II) to the monoclinic system with space group P21/c, and compound (III) to the monoclinic system with space group C2/c.The morpholine ring in (II) and piperidine ring in (III) have the shape of the distorted chair configuration.


X-Ray Single Crystal Diffraction.
The crystals were examined under the microscope to check for imperfections and, then, mounted onto thin glass fibers glued with epoxy glue.The selected crystals were mounted on an Enraf-Nonius 590 Kappa CCD single crystal diffractometer at National Research Center of Egypt [11].X-ray diffraction data were collected at room temperature with graphite monochromated Mo-K ( = 0.71073 Å) radiation [12].Refinement and data reduction were carried using Denzo and Scalepack programs [13].The crystal structures were solved by direct method using SIR92 program [14] which revealed the positions of all nonhydrogen atoms and refined by the full matrix least squares refinement based on F 2 using maXus package [15].The anisotropic displacement parameters of all nonhydrogen The molecular structure of (I) showing 50% probability displacement ellipsoids and the atom-numbering scheme.
atoms were refined; then, the hydrogen atoms were introduced as a riding model with C-H = 0.96 Å and refined isotropically.The molecular graphics were prepared using ORTEP [16] program.

Results and Discussion
In Compound (I) belongs to the orthorhombic system with space group P212121 and (II) to monoclinic system with space group P21/c.Compound (III) belongs to monoclinic system with space group C2/c.The crystal and experimental data of compounds (I), (II), and (III) are given in Tables 1, 2, and 3, respectively.The morpholine ring in (II) and piperidine ring in (III) take the shape of the distorted chair configuration.In ring (A), the lengths of the bond N1-C2 are 1.325(4), 1.327(3), and 1.3323 (11) Å for (I), (II), and (III), respectively, suggesting shortened partial double bond.The bond distance C2-C3 in (I) is shorter than the same bond distance in the other compounds, which may be due to the Br effect at C2.The average values of bond lengths of ring (A) agree well with the average values reported for the same ring in other compounds [17].The average values of bond lengths of ring (B) and ring (C) agree with each other and with the average values of other workers [18].The longest bond length in ring (D) is C28-C29 = 1.471(4)Å in (II) and C28-C27 = 1.531(2)Å in (III).The shortest bond length in the same ring is C26-O27 = 1.404(4)Å in (II) and N24-C29 = 1.4577 (12) Å in (III), with mean values 1.448(4) Å in (II) and 1.4899 (16) Å in (III).These values reflect the shortened character of the single bonds of the chair configuration of the morpholine and piperidine rings, which is consistent with the reported values in [19,20].The values of the valency angles N1-C2-C3 in ring (A) are 128.1(2),122.4(2), and 122.20 (10) ∘ in the investigated compounds, respectively.These variations may be due to the substitution effect at C2.The decrease in the bond angle less than 120 ∘ for the angles C2-N1-C6 (116.3(2),118.9(2) and 119.21(8) ∘ in (I), (II), and (III), resp.) may be attributed to the nonprotonated ring system.Some selected geometric parameters are given in Table 4.

Conclusions
The molecular and crystal structures of three pyridinecarboxylate derivatives have been determined by X-ray single crystal diffraction.Two compounds were found to belong to the monoclinic system and the third was found to belong to the orthorhombic one.The obtained results showed a very good agreement with other reported results for similar compounds.

Figure 3 :Figure 4 :
Figure 3: The molecular structure of (II) showing 50% probability displacement ellipsoids and the atom-numbering scheme.

Figure 5 :Figure 6 :Figure 7 :
Figure 5: The packing diagram of (I) with hydrogen bonds shown as dashed lines.

Table 1 :
Crystal and experimental data of compound (I).

Table 2 :
Crystal and experimental data of compound (II).