Crystal structure of p-formylphenyl, di(p-methylphenyl)amine, and p-bromophenyl, di(o-bromo-p-methylphenyl)amine

Article abstract of DOI:10.1023/A:1012258413674

p-Formylphenyl, di(p-methylphenyl)amine (1), and p-bromophenyl, di(o-bromo-p-methylphenyl)amine (2) were prepared and characterized by X-ray crystallography. Formyl-substituted triphenylamine(1) crystallizes in the monoclinic space group P2₁/c with a = 9.068(1), b = 17.115(2), c = 11.297(2) A, β = 106.73(1)°, V = 1679.0(5) A³ and Z =4. Bromo -substituted compound 2 crystallizes in the monoclinic space group P2₁/n with a = 16.170(4), b = 7.9477(8), c = 16.906(4) A, β = 117.67(2)°, V = 1924.1(7) A³ and Z = 4. The N atoms deviate slightly from the plane of the bonded C atoms and the benzene ring planes are rotated by 25-67° to avoid overlap of the ortho-substituted atoms. The major force of crystal formation comes from the multiple phenyl embraces (MPE).

Full text of DOI:10.1023/A:1012258413674

Journal of Chemical Crystallography, Vol. 30, No. 11, November 2000 (�c 2001)
Crystal structure of p-formylphenyl,
di(p-methylphenyl)amine, and p-bromophenyl,
di(o-bromo-p-methylphenyl)amine
(1)
(1)
(1)
(1)
Minzhao Xue, * Yangang Liu, Deyin Huang, and Bin Gong
Received October 30, 2000
p-Formylphenyl, di(p-methylphenyl)amine (1), and p-bromophenyl, di(o-bromo-p-methyl-
phenyl)amine (2) were prepared and characterized by X-ray crystallography. Formyl-
substituted triphenylamine(1) crystallizes in the monoclinic space group P2
1
/c with
a = 9.068(1), b=17.115(2), c=11.297(2)A, �=106.73(1) , V = 1679.0(5)A and Z= 4. Bromo
substituted compound 2 crystallizes in the monoclinic space group P2
˚
�
˚
3
-
1
/n with a = 16.170(4),
˚
�
˚
3
b= 7.9477(8), c = 16.906(4) A, � = 117.67(2) , V = 1924.1(7) A and Z= 4. The N atoms devi-
ate slightly from the plane of the bonded C atoms and the benzene ring planes are rotated by
�
2
5–67 to avoid overlap of the ortho-substituted atoms. The major force of crystal formation
comes from the multiple phenyl embraces (MPE).
KEY WORDS: Electroluminescence; triphenylamine; multiple phenyl embraces.
Introduction
A prevalent MPE is the sextuple phenyl embrace
(
SPE), which occurs for compounds containing Ph3P
+
Considerable effort has been made in the
last decade in the synthesis of nonlinear optical
NLO) and electroluminescence (EL) chromophores
or Ph P and is a dominant factor in their crys-
tal packing.
4
11,12
SPE have net attractive energies
�
1
(
in the range 60 to 85 kJ mol and P���P sepa-
˚
and their incorporation into a polymer matrix to
develop new organic polymer-based electrooptic
rations in the range 6.4–7.4 A. Another MPE en-
+
+
gaged by Ph P and Ph As groups is the quadruple
4
4
materials.1 Introduction of diarylamino functional-
ities to NLO chromophore molecules has been shown
to enhance the thermal stability dramatically.4
EL devices have been found to possess high per-
formance when triphenylamine containing chro-
mophores were incorporated into the active layer.6
Triphenylamine derivatives are also the compounds
necessary for the preparation of ammonium salt-free
radicals.8
� 3
phenyl embrace (QPE) involving two phenyl groups
on each partner.1
2,13
QPEs frequently occur at rela-
,5
tively longer P���P (or As���As) separations and have
lower attractive energies. Triphenylamine and tri-
p-tolylamine have been presented.1
4,15
In this paper,
,7
we reported the intramolecular electronic interaction
in two Ph N containing compounds and the MPE
3
between Ph N moieties.
3
,9
Molecules carrying triphenyl groups, -XPh3 often
engage in so-called multiple phenyl embraces (MPE),
in which the phenyl rings of two groups are inter-
leaved in such a way that six and/or four edge-to-face
Experimental
Syntheses and identification
ef) phenyl---- phenyl interactions are established.10
(
All reagents were purified by distillation or re-
crystallization. H-NMR measurements with shifts
relative to internal TMS were recorded on a Bruker
AC-500 NMR spectrometer; FT-IR spectra were
1
(
1)
School of Chemistry and Chemical Engineering, Shanghai Jiao
Tong University, Shanghai 200240, P. R. China.
*
To whom correspondence should be addressed.
7
49
1
074-1542/01/1100-0749$18.00/0 �C 2001 Plenum Publishing Corporation

750
Xue, Liu, Huang, and Gong
taken using KBr mulls pressed into pellets, on a
Perkin-Elmer PRA-1000 spectrometer.
Table 1. Crystal Data and Structure Refinement
Molecule
1
2
Formyl-substituted compound 1 was prepared
Formula
C21H19NO
C20H16NBr3
0
by Vilsmerier–Haack formylation of 4,4 -dimethyl-
CCDC no.
CCDC-1003/5970
Yellow, prismatic
301.39
293 K
Monoclinic
P21/c (#14)
CCDC-1003/5971
Yellow, prismatic
510.07
293 K
Monoclinic
P21/n (#14)
triphenylamine: 2.2 g DMF (30 mmol) and 4.6 g
Color/shape
Formula weight
Temperature
Crystal system
Space group
Unit cell
�
POCl3 (30 mmol) were stirred at 0 C under N2
0
atmosphere. A solution of 5.5 g (20 mmol) 4,4 -
dimethyltriphenylamine dissolved in 20 ml 1,2-
dichloroenthane was added. The mixture was kept
�
at 80–90 C for 6 h, then cooled to room temper-
˚
dimensions (A)
a = 9.068(1)
ature, poured into ice-water, and neutralized with
a = 16.170(4)
b= 7.9477(8)
c = 16.906(4)
b= 11.115(2)
c = 11.297(2)
2MNaOH solution. The solid was collected, washed
with water, dried, and purified by recrystallizing from
�
�
�
= 106.73(1)
� = 117.67(2)
0
00
ethanol. The compound obtained, 4,4 -dimethyl-4 -
formyl-triphenylamine (1), was a yellow solid; m.p. :
3
˚
Volume A
1679.0(5)
4
1.192 g/cm
1924.17(7)
4
1.761 g/cm
Z
�
1
3
3
1
6
1
1
05–106 C; H-NMR (500 MHz, CDCl3): 8.50 (1 H),
Density (calculated)
�
1
�
(MoK�), cm
0.73
63.10
.90–7.60 (12 H), 2,30 (6 H); IR (KBr): 2750, 1690,
�
�
�
1
2�max
50
50
590, 1500, 1320, 1290, 1220, 845 cm . Compound
was dissolved in petroleum ether/acetone (vol-
No. of reflections
measured
Total: 3152
Total: 3497
ume, 3/1), and the resulting clear solution was evap-
Unique: 2953
Unique: 3355
orated at room temperature to yield yellow prismatic
(Rint = 0.059)
(Rint = 0.036)
No. of observations
No. variables
Reflection/ para-
meter ratio
Residuals: R/Rw
Goodness of
fit indicator
Max. shift/error
in final cycle
Max. peak in final
diff. map
Min. peak in final
diff. map
(I > 3.00�(I)) 1980 (I > 2.5�(I)) 2094
crystal.
0
210
9.43
218
9.61
Treatment
of
4,4 -dimethyltriphenylamine
�
(
10 mmol) with NBS (35 mmol) in CCl4 at 70 C
for 3 h gave compound 2 a 70% yield. Further
0.051; 0.065
2.29
0.045; 0.054
1.94
purified by recrystallizing from THF/methanol
0
(
volume, 1/1). The pale-yellow product 4,4 -methyl-
0
00
�
0.01
0.00
2
,2 ,4 -tribromo-triphenylamine melts at 138–140 C.
H-NMR: (500 MHz, CDCl3): 6.75–7.45 (10 H),
,30 (6 H); IR (KBr): 2850, 1590, 1510, 1490, 1330,
1
�
˚ 3
� ˚ 3
0.48 e /A
0.24 e /A
2
1
�
1
070, 810 cm . Single crystals suitable for crystal
�
˚ 3
�
˚ 3
� 0.17 e /A
� 0.58 e /A
analyses were grown from THF solution by slow
evaporation.
Results and discussion
Crystal determination
Thermal ellipsoid plots of the two compounds are
shown in Fig. 1. In compound 1, one of the N-bonded
benzene rings is substituted by formyl at the para
position. This result suggests that the formylation of
Single crystals of the two compounds, each
�
�
having approximate dimensions of 0.20 0.20 0.30,
were mounted on a glass fiber. All measurements
were made on a Rigaku AFC7R diffractometer
with graphite monochromated MoK� radiation and
a 12-kW rotating anode generator. Cell constants
and an orientation matrix for data collection were
obtained from least-squares refinement. Hydrogen
atoms were not refined. The crystal structures were
0
4,4 -dimethyltriphenylamine led to the para-position-
substituted product; electrophilic substitution at the
ortho-position may be sterically inhibited. For com-
pound2, thebromineatomssubstitutednotonlyatthe
para position of one benzene ring but also at the ortho
position of the other two benzene rings. In an early
report, Baker and his co-workers claimed that bromi-
nation of tripenylamine in organic solvent stopped
at the para-substitution stage.18 Our result is in dis-
agreement. The free radical mechanism substitution
can obviously take place at the ortho position when
the para positions were occupied.
16
solved by direct methods and expanded using
Fourier technique.17 A summary of data collec-
tion and structure refinement is given in Table 1;
final atomic positional parameters, selected bond
lengths, and bond angles are given in Tables 2 and 3,
respectively.

Crystal structure of substituted triphenyl amines
751
Table 2. Atomic Parameters and Equivalent Isotropic Thermal Parameters
Compound 1
Compound 2
Atom
x
y
z
B(eq)
Atom
x
y
z
B(eq)
O
N
� 0.5604(3)
0.0549(2)
0.0542(3)
� 0.0602(3)
� 0.0580(3)
0.0574(3)
0.1705(3)
0.1692(3)
0.0616(4)
0.1863(3)
0.2326(3)
0.3604(3)
0.4466(3)
0.4016(3)
0.2732(3)
0.5867(4)
� 0.0752(3)
� 0.1713(3)
� 0.2978(3)
� 0.3367(3)
� 0.2435(3)
� 0.1147(3)
� 0.4709(4)
0.7892(2)
0.6282(1)
0.6277(1)
0.5891(2)
0.5887(2)
0.6239(1)
0.6622(2)
0.6653(2)
0.6204(2)
0.5972(1)
0.6250(1)
0.5932(2)
0.5344(2)
0.5084(2)
0.5391(1)
0.5030(2)
0.6550(1)
0.7106(2)
0.7387(2)
0.7127(2)
0.6568(2)
0.6280(1)
0.7432(2)
0.0535(2)
� 0.0063(2)
� 0.1337(2)
� 0.2209(2)
� 0.3430(2)
� 0.3800(2)
� 0.2912(2)
� 0.1692(2)
� 0.5121(2)
0.0832(2)
0.2042(2)
0.2894(2)
0.2571(2)
0.1359(2)
0.0495(2)
0.3532(3)
0.0240(2)
� 0.0516(2)
� 0.0233(2)
0.0804(2)
0.1540(2)
0.1274(2)
0.1128(3)
7.22(9)
4.01(5)
3.66(5)
4.37(6)
4.85(6)
4.36(6)
4.72(7)
4.47(6)
6.50(8)
3.51(5)
4.03(6)
4.51(6)
4.70(7)
4.80(7)
4.17(6)
8.1(1)
3.55(5)
4.37(6)
4.70(6)
4.19(6)
4.20(6)
3.95(6)
5.85(8)
Br(1)
Br(2)
Br(3)
N
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
1.36840(6)
0.93612(5)
0.97627(6)
1.1243(4)
1.2220(5)
1.2775(5)
1.2924(4)
1.2545(4)
1.1977(4)
1.1820(4)
1.0585(5)
1.1360(5)
1.2236(5)
1.2350(5)
1.1576(6)
1.0703(5)
1.1736(5)
1.0214(5)
1.0854(4)
1.1102(5)
1.0731(5)
1.0109(5)
0.9856(5)
0.9659(5)
� 0.4860(1)
0.1921(1)
� 0.0623(1)
0.1128(6)
� 0.0369(8)
� 0.1769(9)
� 0.2984(8)
� 0.2873(8)
� 0.1524(8)
� 0.0251(7)
0.2299(7)
0.1857(8)
0.2144(9)
0.2818(9)
0.3278(8)
0.3025(9)
0.4012(9)
0.1605(8)
0.2165(8)
0.3871(8)
0.494(1)
0.92169(7)
0.89924(6)
0.72200(7)
0.8988(4)
0.8465(5)
0.8511(5)
0.9140(4)
0.9714(4)
0.9649(4)
0.9030(4)
0.9923(4)
0.9800(5)
1.0507(5)
1.1294(5)
1.1414(5)
1.0705(5)
1.2349(5)
0.7375(5)
0.8211(4)
0.8292(4)
0.7561(5)
0.6721(5)
0.6647(5)
0.5884(5)
6.17(3)
5.24(2)
6.42(2)
3.4(1)
3.6(2)
3.7(2)
3.4(2)
3.3(2)
3.4(2)
3.1(2)
3.4(2)
3.4(2)
4.2(2)
4.4(2)
4.6(2)
4.1(2)
4.2(2)
3.7(2)
3.2(2)
3.7(2)
4.3(2)
4.3(2)
4.4(2)
4.7(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
0.432(1)
0.264(1)
0.553(1)
Table 3. Selected Interatomic Distances and Bonds Angles
˚
�
Bond Lengths (A)
Angles ( )
Molecule 1
O ---- C(21)
N ---- C(1)
1.189(4)
1.438(3)
1.377(3)
1.379(3)
1.386(3)
1.373(3)
1.377(4)
1.504(3)
1.383(3)
N ---- C(8)
N ---- C(15)
1.425(3)
1.397(3)
1.402(3)
1.395(3)
1.364(3)
1.389(3)
1.385(3)
1.463(4)
1.377(3)
C(1) ---- N ---- C(8)
118.0(2)
C(1) ---- N ---- C(15)
C(8) ---- N ---- C(15)
N ---- C(1) ---- C(2)
N ---- C(1) ---- C(6)
C(2) ---- C(1) ---- C(6)
N ---- C(15) ---- C(16)
N ---- C(15) ---- C(20)
N ---- C(8) ---- C(9)
119.1(2)
122.8(2)
120.3(2)
120.1(2)
119.6(2)
119.6(2)
122.3(2)
121.6(2)
C(1) ---- C(2)
C(1) ---- C(6)
C(2) ---- C(3)
C(3) ---- C(4)
C(4) ---- C(5)
C(4) ---- C(7)
C(5) ---- C(6)
C(15) ---- C(16)
C(15) ---- C(20)
C(16) ---- C(17)
C(17) ---- C(18)
C(18) ---- C(19)
C(18) ---- C(21)
C(19) ---- C(20)
Molecule 2
Br(1) ---- C(3)
Br(2) ---- C(7)
Br(3) ---- C(14)
C(1) ---- C(2)
C(1) ---- C(6)
C(2) ---- C(3)
C(3) ---- C(4)
C(4) ---- C(5)
C(5) ---- C(6)
C(7) ---- C(8)
1.897(6)
1.894(7)
1.887(7)
1.409(9)
1.383(9)
1.372(9)
1.371(9)
1.383(9)
1.392(9)
1.406(9)
N ---- C(6)
N ---- C(8)
N ---- C(15)
1.419(8)
1.420(8)
1.426(8)
1.373(9)
1.384(9)
1.37(1)
1.41(1)
1.38(1)
1.59(1)
C(6) ---- N ---- C(8)
C(6) ---- N ---- C(15)
C(8) ---- N ---- C(15)
N ---- C(15) ---- C(14)
N ---- C(6) ---- C(1)
N ---- C(15) ---- C(16)
N ---- C(6) ---- C(5)
N ---- C(8) ---- C(7)
N ---- C(8) ---- C(9)
Br(1) ---- C(3) ---- C(2)
Br(1) ---- C(3) ---- C(4)
Br(2) ---- C(7) ---- C(8)
118.5(5)
119.4(5)
117.3(5)
123.9(6)
121.7(6)
119.0(6)
119.0(6)
121.1(6)
121.6(6)
118.8(5)
119.4(5)
119.8(5)
119.4(5)
C(7) ---- C(12)
C(8) ---- C(9)
C(9) ---- C(10)
C(10) ---- C(11)
C(11) ---- C(12)
C(11) ---- C(13)
Br(2) ---- C(7) ---- C(12)

752
Xue, Liu, Huang, and Gong
Fig. 1. Thermal ellipsoid plots of compounds 1 and 2 (30% probability ellipsoids).
The C---- N bond lengths (Table 3) of compound 1
˚
are 1.438(3) and 1.425(3) A for p-methyl-substituted
˚
benzene rings and 1.396(3) A for the formyl-
substituted benzene ring, respectively. The decrease
of the C---- N bond length related to the formyl-
substituted benzene ring may be due to the electron-
withdrawing power of p-formyl group. CNC bond
�
�
�
angles are 118.0 (2), 119.1 (2), and 122.8 (2). The
C---- N bond length of compund 2 is 1.419(8) A for
˚
the p-bromo-substituted benzene. The others are
˚ ˚
1
.420(8) Aand 1.426(8) A, and the CNC bond angles
�
�
are 118.5 (5) (C6---- N ---- C8), 119.4 (5) (C6---- N ---- C15)
�
and 117.3 (5) (C8---- N ---- C15). The CNC bond angles
�
of the two compounds are close to 120 , which cor-
2
responding to the sp hybridization of the N-bonding
orbits. The N atom deviates slightly from the plane
�
of the bonded C atoms by about 15 . The benzene
rings in each molecule are planar and their geome-
try is unexceptional. The value of the dihedral an-
gles (deposited) showed that the dihedral angles be-
tween phenyl-ring planes and the plane of N-bonded
�
C atoms vary from 25 to 55 for compound 1 and
�
from 43 to 67 for compound 2. The dihedral angles
of compound 2 (in which two bromide atoms substi-
tuted at the ortho position of two benzene rings) are
larger than those of compound 1 (in which the ortho
positions are unoccupied). Hence, it can be inferred
from the previous discussion that the N atom and
adjacent C atoms are coplanar, whereas the three
phenyl rings rotated some angles to avoid overlap of
the ortho-substituted atoms. Substitutions at the para
Fig. 2. Quadruple phenyl embrace (QPE) and sextuple phenyl
embrace (SPE) in the crystal structure of compound 1 (a) and
compound 2 (b). The connecting lines identify the intermolecular
interactions by their N���N distance marked (A).
˚

Crystal structure of substituted triphenyl amines
753
and ortho positions of benzene rings do not greatly
influence the geometry of the central fragment. In-
troduction of substitutions to the ortho positions re-
sult in the large rotation angels of benzene rings. The
molecule geometry of triphenylamines shows that the
lone electron pair of the N atom occupies the p or-
bit, which favors the realization of the intramolec-
ular p-� interaction. The interaction may be inter-
rupted to some extent when the ortho positions are
substituted.
patterns of their occurrence and formation of net-
works in molecular crystals.
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1
2
3
4
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˚
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˚
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9
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8. Baker, III, T.N.; Doherty, Jr., W.P.; Kelley, W.S.; Newmeyer
W.; Rogers, Jr., J.E.; Spalding, R.E.; Walter, R.I. J. Org. Chem.
1965, 30, 3714.
action are established. The geometry (Fig. 2(b)) and
˚
the N���N separation of 6.62 A are similar to those
of SPE. This interaction could be defined as a SPE
dimer. Each dimer is in contact with two neighbor-
˚
ing molecules at N���N separation 8.84 A. This inter-
action is a weak QPE. The geometry and the calcu-
lated energies of MPE motifs for the ---- Ph3N group
1
will be presented in a separate paper, as well as the