Y. Tokutome, T. Okuno / Journal of Molecular Structure 1047 (2013) 136–142
139
Fig. 2. Crystal packing of polymorph I.
(100 MHz, CDCl3): 56.5; 81.8; 121.4; 124.7; 129.4; 143.2. IR (KBr):
2186, 2165 cmꢁ1. Anal. Calc. for C28H20N2: C, 87.47; H, 5.24; N,
7.29. Found: C, 87.17; H, 5.48; N, 7.38. Mp: 124 °C(decom.).
is 60.2(2)°. The dihedral angles of the planes with two phenyl
groups (the C1AC6 plane and the C7AC12 plane for the N1/C1/
C7/C13 plane, the C17AC22 plane and the C23AC28 plane for the
N2/C16/C17/C23 plane) are 19.8(2)°, 52.3(2)°, 31.9(2)°, 44.8(3)°,
respectively. Two possible conformations of two benzene rings, a
propeller type [11–13,18–20] and a perpendicular type [11], are
known in N-ethynyldiphenylamine derivatives.
The bond lengths of N1AC13 and N2AC16 are 1.339(6) Å and
1.342(6) Å, respectively, which are consistent with the reported
lengths [11–13,18–20]. The distances of C13AC14, C14AC15 and
C15AC16 are 1.193(6) Å, 1.376(6) Å and 1.206(6) Å, showing a
clear bond alternation. The diacetylene moiety curves slightly,
where the angles of N1AC13AC14, C13AC14AC15, C14AC15AC16
and C15AC16AN2 are 177.8(6)°, 178.8(6)°, 178.8(7)° and
175.4(6)°, respectively.
2.3. Computational methods
DFT calculations of 2 were performed using the Spartan 04 soft-
ware [17] (Wavefunction, Inc.) with B3LYP 6-31G (d) level. The
geometrical optimization was carried out without symmetry con-
straints, where the initial structures for calculations were set at
those obtained by crystallographical analyses. The angular
dependence of the energies was calculated with the twist angle
of C1AN1ꢂ ꢂ ꢂN2AC3 as a parameter because the planes around N1
and N2 were planar exactly.
The structures around the nitrogens in IB (the N3/C29/C35/C41
plane; r.m.s. deviation = 0.0082 Å and the N4/C44/C45/C51 plane;
r.m.s. deviation = 0.0173 Å) are almost planar and the twist angle
between the planes is also 60.2(2)°. The dihedral angles of the
planes with two phenyl groups (the C29AC34 plane and the
C35AC40 plane for the N3/C29/C35/C41 plane, the C45AC50 plane
and the C51AC56 plane for the N4/C44/C45/C51 plane) are
22.5(2)°, 57.2(2)°, 29.0(3)° and 45.4(2)°, respectively.
3. Results and discussion
3.1. Preparation of 2
Preparation of 2 is shown in Scheme 1. Reaction of N-phenyl-
N-(1,2,2-trichlorovinyl)aniline with n-BuLi afforded N-ethynyl-
N-phenylaniline (1), and a following Hay coupling reaction of 1
gave 2 in 63% yield [11,16].
The bond lengths of N3AC41 and N4AC44 are 1.333(7) Å and
1.363(7) Å, respectively, which are consistent with the reported
lengths [12–14,19–21]. The distances of C41AC42, C42AC43 and
C43AC44 are 1.218(8) Å, 1.372(8) Å and 1.182(8) Å, showing a
clear bond alternation. The diacetylene moiety curves slightly,
where the angles of N3AC41AC42, C41AC42AC43, C42AC43AC44
and C43AC44AN4 are 175.7(5)°, 179.2(6)°, 177.1(6)° and
177.0(6)°, respectively.
Fig. 2 shows the crystal packing of polymorph I viewed from the
b axis. The molecules (IA and IB) stack along the b axis with the
intervals of 5.46 Å. Inclination angles between diacetylenic units
and the b axis are 72.8(1)° for IA and 74.0(1)° for IB. These stacking
parameters do not satisfy the Baughman’s condition for solid-state
polymerization of diacetylenes [21–23]. The molecules (IA and IB)
also make arrays along the a axis independently to give a layered
3.2. Crystal polymorph of 2
The compound 2 was found to have two crystal polymorphs
(I and II) depending on a condition of recrystallization. The single
crystals of polymorph I suitable for X-ray crystallography were ob-
tained by slow evaporation of an ethanol solution at room temper-
ature. While those of polymorph II were given by slow
concentration of a dichloromethane solution in a refrigerator. Crys-
tal data and details of refinement for polymorphs I and II are sum-
marized in Table 1. Selected bond distances and angles of them are
listed in Table 2. In both polymorphs, there are two independent
molecules (A and B) in the unit cell.
Fig. 1 shows the crystal structure of polymorph I. The two inde-
pendent molecules (IA and IB) have a similar structure. The struc-
tures around the nitrogens in IA (the N1/C1/C7/C13 plane; r.m.s.
deviation = 0.0063 Å and the N2/C16/C17/C23 plane; r.m.s. devia-
tion = 0.0269 Å) are planar and the twist angle between the planes
structure parallel to the ac plane. There are some weak CAHꢂ ꢂ ꢂ
p
interactions within the layer as shown in Fig. 2.