Synthesis, crystal structures and theoretical studies of four Schiff bases derived from 4-hydrazinyl-8-(trifluoromethyl) quinoline

Article abstract of DOI:10.1016/j.molstruc.2010.07.010

The molecular structures of three new Schiff base compounds of the form R - hydrazinyl-8-(trifluoromethyl)-quinoline, and the fourth, a structurally related hydrate, have been examined by X-ray crystallography, B3LYP/6-3 G (d) and Hirshfeld surface and fi

Full text of DOI:10.1016/j.molstruc.2010.07.010

Journal of Molecular Structure 980 (2010) 172–181
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, crystal structures and theoretical studies of four Schiff bases derived
from 4-hydrazinyl-8-(trifluoromethyl) quinoline
b
c
c
d
e
Jerry P. Jasinski a, , Ray J. Butcher , Anil N. Mayekar , H.S. Yathirajan , B. Narayana , B.K. Sarojini
*
a Department of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA
b Department of Chemistry, Howard University, 525 College Street NW, Washington, DC 20059, USA
c Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570 006, India
d Department of Studies in Chemistry, Mangalore University, Mangalagangotri 574 199, India
e Department of Chemistry, P.A. College of Engineering, Mangalore 574 153, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The molecular structures of three new Schiff base compounds of the form R – hydrazinyl-8-(trifluoro-
methyl)-quinoline, and the fourth, a structurally related hydrate, have been examined by X-ray crystal-
lography, B3LYP/6-3 G (d) and Hirshfeld surface and fingerprint calculations. Compound (I), C18H14F3N3,
crystallizes in the tetragonal, I 41/a space group (z = 32) while compounds (II) – C18H13BrF3N3; P 21/c, (III)
– C18H14F3N3OꢀH2O; P 21/c, and (IV) – C22H16F3N3; P 21/n, are monoclinic (z = 4). In (I) there are two inde-
pendent molecules in the asymmetric unit. In compounds (I), (II) and (IV) R = ethylidene 1-phenyl, eth-
Received 28 May 2010
Received in revised form 7 July 2010
Accepted 8 July 2010
Available online 16 July 2010
Keywords:
Schiff bases
Crystal structure
Hydrogen bonds
Quinoline
ylidene 3-bromophenyl and ethylidene naphthalen-2-yl while (III) consists of
a 4-[(1E)-1-{2-[8-
(trifluoromethyl)quinolin-4-yl]-hydrazinylidene}ethyl]-phenol hydrate. In all four compounds the tri-
fluoromethyl group lies in the plane of the quinoline ring and the methyl group is in the plane of the
hydrazine moiety. The mean plane of the quinoline ring is planar with hydrazine moiety in (II) and
(IV) and twisted slightly in (I) and (III). In all four compounds weak p-stacking interactions are observed
Hydrazinyl group
Hirshfeld surface
between ring centroids of the various naphthalene(benzene) and quinoline (benzene and pyridine) rings
which contribute to the crystal packing. A comparison of the angles between mean planes of the benzene
and quinoline rings in the crystal and with the DFT theoretical calculation as well as inclusion of strong
and weak intermolecular hydrogen-bond interactions has been included for each molecule. Hirshfeld sur-
face analysis for visually analyzing intermolecular interactions in crystal structures employing 3D molec-
ular surface contours and 2D fingerprint plots have been used to examine molecular shapes.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
substitution of hydrogen by fluorine has been a strategy in design-
ing molecules for biological activity studies [8].
Schiff bases are very interesting compounds because of their
model character and practical applications [1,2] and also these
are very important classes of organic compounds from both prac-
tical and theoretical points of view. Methods of synthesis and
numerous applications in organic chemistry of compounds have
been summarized [3]. Schiff bases have received considerable
attention in the literature, because of their interesting properties,
various applications and properties which are directly related to
the presence of an intramolecular hydrogen bond and the conjuga-
tive interactions in the molecules [4,5]. Some Schiff bases play an
important role in active biological systems [6,7]. Fluorinated or-
ganic compounds have attracted attention due to the ability of
fluorine to act as polar hydrogen or hydroxyl mimic. Therefore,
The synthesis and structure of Schiff bases have attracted much
attention in biology and chemistry [9]. One of the aims of investi-
gating the structural chemistry of Schiff bases is to develop protein
and enzyme mimics [10]. Structural information is useful in inves-
tigating the coordination properties of Schiff bases functioning as
ligands [11]. Some Schiff base derivatives were reported to possess
antimicrobial, anti-inflammatory and central nervous system
activities. Moreover, Schiff bases are also known to have biological
activities such as antimicrobial [12,13], antifungal [14], antitumor
[15–17] and as herbicides.
The synthesis and crystal structures of related schiff base com-
pounds, viz., bis{4-[(Z)-N0-(4-hydroxybenzylidene) hydrazino]-8-
(trifluoromethyl)-quinolinium} sulfate dihydrate [18], (E)-1-(4-
methylphenyl)ethanone [8-(trifluoromethyl)quinolin-4-yl]hydra-
zone [19], 1-(4-{[8-(trifluoromethyl) quinolin-4-yl]amino}phenyl)-
ethanone [20] and 2-(4-methoxyphenyl)-6-trifluoromethyl-1H-
pyrrolo[3,2-c]quinoline monohydrate [21] have been reported.
* Corresponding author. Tel.: +1 603 358 2563; fax: +1 603 358 2897.
E-mail address: jjasinski@keene.edu (J.P. Jasinski).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.07.010

J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
173
The present investigation is a continuation of our broad pro-
gramme work on the synthesis and structural study of Schiff Base
compounds and its derivatives and to understand the geometrical
features and the underlying intermolecular interactions which
hold the assembly of molecules in the crystalline lattice. In view
of the importance of Schiff Bases, a series of Schiff bases, viz.,
tuted acetophenone (10.2 mmole) in 10 ml of ethanol was
refluxed for 24 h under nitrogen atmosphere and in absence of
light. The reaction mass was then cooled and the solid separated
was collected by filtration (Fig. 1). The characteristic data of the
compounds 4-[(2E)-2-(1-phenylethylidene)hydrazinyl]-8-(trifluo-
romethyl)-quinoline (I), 4-{(2E)-2-[1-(3-bromophenyl) ethyli-
dene]hydrazinyl}8-(trifluoromethyl)-quinoline (II), 4-[(1E)-1-{2-
[8-(trifluoromethyl) quinolin-4-yl]-hydrazinylidene}ethyl]-phenol
C18H14F3N3 (I), C18H13BrF3N3 (II), C18H14F3N3OꢀH2O (III) and
C22H16F3N3 (IV) have been synthesized and their crystal structures
are reported along with the theoretical studies.
hydrate (III) and 4-{(2E)-2-[1-(naphthalen-2-yl)ethylidene] -
hydrazinyl}8-(trifluoro-methyl)quinoline (IV) derived from 4-
hydrazinyl-8-(trifluoromethyl) quinoline are shown below.
I: Recrystallized from methanol. MP: 160–162 °C. 1H NMR
(CDCl3 d ppm, 400 MHz): 2.43 (s, 3H, CH3) 7.39–7.58 (m, 5H,
ArH), 7.85–7.88 (m, 2H, ArH), 8.00 (d, 3H, J = 6.31 Hz, ArH), 8.83
2. Experimental procedures
In the preparation of the four compounds in this study, 4-hydra-
zino-8-(trifluoromethyl) quinoline was prepared in good yield
according to literature procedure [22] and acetophenones were
purchased from Sigma Aldrich. To a solution of 4-hydrazino-8-(tri-
fluoromethyl) quinoline (10 mmole) and unsubstituted/substi-
(bs, 1H, NH). Analysis found:
18H14F3N3 requires: C 65.65, H 4.28, N 12.76%. Yield 82%.
II: Recrystallized from acetonitrile. MP: 194–196 °C. 1H NMR
C 65.58, H 4.25, N 12.71%;
C
(CDCl3 d ppm, 400 MHz): 2.43 (s, 3H, CH3),7.27(d, 1H, J = 6.9 Hz,
NH2
HN
N
Unsbstituted/ Substituted acetophenone
+
O
CF3
CH
3
1)
2)
O
CH
O
3
Ethanol
Reflux
Br
CH
3
3)
4)
HO
O
CH
3
OH
H3C
HN
H3C
HN
H3C
HN
Br
H3C
HN
N
N
N
N
H2O
N
N
N
N
CF3
CF3
CF3
CF3
(I)
(II)
(III)
(IV)
Fig. 1. Reaction scheme for (I)–(IV).

174
J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
ArH), 7.49–7.54 (m, 3H, ArH), 7.78 (d, 1H, ArH), 8.03 (d, 3H,
J = 7.23 Hz, ArH), 8.32 (s, 1H, ArH), 8.83 (bs, 1H, NH). Analysis
found: C 52.88, H 3.18, N 10.23; C18H13BrF3N3 requires: C 52.96,
H 3.21, N 10.29%. Yield 89%.
atoms were located in a difference Fourier map and then refined
using riding model with OAH = 0.82 Å, O1WAH1W1 =
a
0.817(15) Å, O1WAH1W2 = 0.839(15) Å and Uiso(H) = 1.49Ueq(O)
respectively. This worked well for normal C–H bonds since most
of the geometric parameters for these molecules are very similar
to standard values [26]. Details of the data collection and structure
refinement are given in Table 1.
III: Recrystallized from THF. MP: 202–204 °C. 1H NMR (CDCl3
d
ppm, 400 MHz): 2.43 (s, 3H, CH3), 4.98 (s, 1H, AOH), 6.91(d, 2H,
J = 8.9 Hz, ArH), 7.39–7.58 (m, 4H, ArH), 8.00 (d, 3H, J = 6.31 Hz,
ArH), 8.88 (bs, 1H, NH). Analysis found: C 62.53, H 4.03, N
12.13%; C18H14F3N3OꢀH2O requires: C 62.61, H 4.09, N 12.17%. Yield
76%. The elemental analysis data of III does not contain water mol-
ecule, but the crystal structure of III does contain one water mole-
cule. One of the main reason for this is that the samples were
thoroughly dried before using for elemental analysis.
2.2. Density Functional Theory (DFT) calculations
A Density Functional Theory (DFT) geometry optimized molec-
ular orbital calculation (WebMo Pro [27] with the GAUSSIAN-03
program package [28] employing the B3LYP (Becke three parame-
ter Lee–Yang–Parr) exchange correlation functional, which com-
bines the hybrid exchange functional of Becke [29] with the
gradient-correlation functional of Lee, Yang and Parr [30] and the
6-31 G(d) basis set [31] was performed on each of the four title
molecules. Starting geometries were taken from X-ray refinement
data. The geometric results in the free molecule state are, there-
fore, compared to those in the crystalline state. A comparison of se-
lected bond angles and bond distances in the crystal to that from
the DFT calculation is given in Table 2. In addition, a comparison
of the angles between mean planes of the benzene and quinoline
rings in the crystal and with the DFT calculation as well as inclu-
sion of strong and weak intermolecular hydrogen-bond interac-
tions has been included in a discussion of the structural aspects
for each molecule.
IV: Recrystallized from THF. MP: 270–272 °C. 1H NMR (CDCl3
d
ppm, 400 MHz): 2.55 (s, 3H, CH3) 7.49–7.53 (m, 3H, ArH), 7.64 (d,
1H, J = 6.86 Hz, ArH), 7.85–7.90(m, 4H, ArH), 8.01–8.11 (m, 3H,
ArH), 8.21(d, 1H, J = 7.05, ArH), 8.83 (bs, 1H, NH). Analysis found:
C 69.60, H 4.21, N 11.02%; C22H16F3N3 requires: C 69.65, H 4.25,
N 11.08%. Yield 78%.
2.1. X-ray structural analysis
X-ray analysis including data collection, cell refinement and
data reduction were carried out with an Oxford Diffraction Gemini
CCD using the CrysAlisPro software package [23]. Non-H atoms
were refined anisotropically by full-matrix least-squares on F2.
Structure solution and refinement were completed with SHELXS97
[24] and SHELXL97 [24] and molecular graphics were carried out
with SHELXTL [25]. In all four compounds [I, II, III and IV] the H
atoms were placed in their geometrically calculated places and re-
fined using a riding model with NAH = 0.86 Å, CAH = 0.95–0.96 Å,
Uiso(H) = 1.19Ueq(N), Uiso(H) = 1.19–1.50Ueq(C). In III, the water H
2.3. Hirshfeld surface calculations
The Hirshfeld surface of each molecule has been calculated
allowing for a determination of the shape index of each molecule
Table 1
Crystal and experimental data for I–IV.
I
II
III
IV
CCDC deposit No.
Formula
769,166
769,167
C18H13BrF3N3
408.22
Colorless, prism
769,169
769,168
C22H16F3N3
379.38
Colorless, plate
0.53 ꢁ 0.39 ꢁ 0.15
Monoclinic
P 21/n
C
18H14F3N3
C18H14F3N3OꢀH2O
Formula weight
Crystal color, habit
Crystal size (mm)
Crystal system
Space group
Formula weight
Temperature (K)
a (Å)
329.32
363.34
Yellow–orange, chunk
0.55 ꢁ 0.37 ꢁ 0.22
Tetragonal
I 41/a
329.32
295 (2)
29.6389(13)
29.6389(13)
13.9207(9)
90
90
90
Colorless, prism
0.53 ꢁ 0.45 ꢁ 0.38
Monoclinic
P 21/c
363.34
295 (2)
7.8252(3)
21.2505(7)
10.2451(4)
90
103.790(4)
90
1654.55(11)
4
1.459
0.51 ꢁ 0.35 ꢁ 0.31
Monoclinic
P 21/c
408.22
295 (2)
8.4995(3)
14.0844(5)
14.1922(6)
90
98.076(4)
379.38
295 (2)
8.3889(4)
18.4183(8)
12.0344(6)
90
106.931(5)
90
1778.8
4
1.417
784
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
90
Volume (Å3)
Z
12228.8(11)
32
1.431
1662.51(11)
4
1.631
816
Dcalc (Mg mꢂ3
F (0 0 0)
)
5440
752
Reflections, total
35,552
10,991
12,536
15,447
Reflections, Ind [R(int)]
10,325(0.0594)
32.65
0.0707, 0.1551
0.2211, 0.1991
0.883
4909(0.0287)
32.33
0.0441, 0.0819
0.1260, 0.0938
5362(0.0208)
32.55
0.0600, 0.1476
0.1082, 0.1631
1.041
5847(0.0350)
32.44
0.0646, 0.1567
0.1404, 0.1830
0.983
hmax (°) with Mo K
R, Rw [I > 2 (I)]
R, Rw [all data]
Goodness of fit on F2
(e Åꢂ3
a
r
0.890
(D
q
)
)
0.343/ꢂ0.356
0.347/ꢂ0.387
0.259/ꢂ0.213
0.243/ꢂ0.174
max/min
Measurement
Program system
GEMINI (Oxford Diffraction, 2007)
CrysAlisPro
Structure determination
Refinement
SHELXS97
Full-matrix least-squares on F2 (SHELXL97)
CCDC 769,166 (I); 769,167 (II); 769,169 (III); 769,168 (IV) contains supplementary crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or
by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
175
Table 2
Selected crystal and DFT [a] bond lengths (Å), bond angles (°), and torsion angles (°) for (I)–(IV).
(I) C18H14F3N3
C4AAN2A
C12AAN3A
C4BAN2B
C12BAN3B
1.372(3)
1.278(3)
1.372(3)
1.271(3)
1.385a
1.294a
N2AAN3A
C8AAC11A
N2BAN3B
C8BAC11B
1.376(2)
1.543(3)
1.372(2)
1.548(3)
1.357a
1.512a
(II) C18H13BrF3N3
C4AN2
C12AN3
1.373(3)
1.281(3)
1.386a
1.294a
N2AN3
C8AC11
1.369(2)
1.503(3)
1.354a
1.512a
(III) C18H14F3N3OꢀH2O
C1AN2
C11AN3
1.367(2)
1.2889(19)
1.480(2)
1.382a
1.296a
1.478a
N2AN3
C5AC10
C16AO1
1.3821(17)
1.492(2)
1.3633(19)
1.362a
1.512a
1.352a
C11AC13
(IV) C22H16F3N3
C1AN2
C11AN3
1.374(2)
1.288(2)
1.385a
1.296a
N2AN3
C5AC10
1.3717(17)
1.498(2)
1.355a
1.512a
(I) C18H14F3N3
C4AAN2AAN3A
N3AAC12AAC13A
C4BAN2BAN3B
N3BAC12BAC13B
118.65(19)
124.2(2)
117.77(18)
124.0(2)
120.27a
122.76a
120.27a
122.76a
N2AAN3AAC12A
C7AAC8AAC11A
N2BAN3BAC12B
C7BAC8BAC11B
118.9(2)
118.84a
119.66a
118.40a
119.66a
120.16(18)
118.35(19)
120.54(19)
(II) C18H13BrF3N3
C4AN2AN3
N3AC12AC13
117.70(18)
124.59(19)
120.33a
122.91a
N2AN3AC12
C7AC8AC11
118.84(18)
120.31(19)
119.02a
119.11a
(III) C18H14F3N3OꢀH2O
C1AN2AN3
N3AC11AC12
119.01(12)
124.64(15)
120.21a
122.48a
N2AN3AC11
C15AC16AO1
117.03(13)
118.28(14)
118.55a
117.88a
(IV) C22H16F3N3
C1AN2AN3
N3AC11AC12
118.93(14)
124.64(15)
120.46a
122.54a
N2AN3AC11
C4AC5AC10
117.94(15)
120.07(13)
118.86a
119.67a
(I) C18H14F3N3
C3AAC4AAN2AAN3A
N2AAN3AAC12AAC13A
C3BAC4BAN2BAN3B
N2BAN3BAC12BAC13B
5.7(3)
0.36a
0.56a
0.36a
0.56a
C4AAN2AAN3AAC12A
C6AAC7AAC8AAC11A
C4BAN2BAN3BAC12B
C6BAC7BAC8BAC11B
177.2(2)
172.71a
179.38a
172.71a
179.38a
ꢂ0.2(4)
ꢂ179.6(2)
167.05(19)
ꢂ178.1(2)
5.3(3)
ꢂ1.2(3)
(II) C18H13BrF3N3
C3AC4AN2AN3
N2AN3AC12AC13
ꢂ0.3(3)
ꢂ1.7(3)
0.40a
0.31a
C4AN2AN3AC12
C6AC7AC8AC11
175.63(17)
ꢂ179.0(2)
173.44a
179.25a
(III) C18H14F3N3OꢀH2O
C2AC1AN2AN3
N2AN3AC11AC12
5.9(2)
ꢂ0.1(2)
1.07a
C1AN2AN3AC11
N1AC4AC5AC10
ꢂ179.55(14)
173.37a
ꢂ0.78a
0.8(2)
ꢂ0.90a
(IV) C22H16F3N3
C2AC1AN2AN3
N2AN3AC11AC12
ꢂ3.3(2)
ꢂ0.9(2)
ꢂ0.59a
C1AN2AN3AC11
N1AC4AC5AC10
ꢂ178.24(14)
ꢂ2.3(2)
174.13a
0.00a
ꢂ1.07a
a
DFT 6-31 G(d) geometry optimization calculations for I–IV [27].
the shape of the molecule in the crystal which tells one how the
molecule packs in the crystal. Hirshfeld surface analysis [32–34] al-
lows for visually analyzing intermolecular interactions in crystal
structures by employing 3D molecular surface contours and 2D fin-
gerprint plots of intermolecular interactions. The contour shape
occupied by a molecule in a crystal structure surrounds the mole-
cule as a van der Waals (vdW) surface. Distances from points on
the surface to a nucleus (atom) inside (di) and outside (de) the
mean surface are determined by the differing van der Waals radii
of atoms, whereby the contact distances di and de can be normal-
ized (dnorm [35]). Therefore, intermolecular interactions (short,
moderate, long) in a crystal structure resulting from hydrogen
bond donors/acceptors can be visually represented by Hirshfeld
surfaces and contours. As a result distances shorter than vdW radii
sum and longer than vdW radii sum are represented as red through
white to blue fingerprint plots and contour surfaces. Hirshfeld sur-
face plots and fingerprint plots drawn in Crystal Explorer 2.1 [36]
have been produced for each molecule providing a colored two-
dimensional projection of the Hirshfeld surface which is also useful
in comparing the same molecule in different crystalline environ-
Fig. 2. Molecular structure of (IA), drawn with 50% probability displacement
ellipsoids and showing the atom labeling scheme. Figure (IB), similar to (IA), has
been omitted for clarity.
which is found from the electron density, half of which is due to
the atoms comprising the molecule and the other half due to the
electron density of the atoms of the rest of the crystal. It effectively
tells one how much ‘‘space” a molecule takes up in a crystal which
is useful in examining efficiencies of crystal packing and defines

176
J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
ments or crystal structures with more than one unique molecule in
the unit cell.
is 8.3(8)° (A) and 19.4(1)° (B), respectively. The trifluoromethyl
group lies in the plane of the quinoline ring (N1A/C9A/C8A/
C11A = ꢂ3.6(3)°; N1B/C9B/C8B/C11B = ꢂ2.3(3)°). The methyl group
is in the plane of both the hydrazine moiety (N2A/N3A/C12A/
C13A = 0.2(4)°; N2B/N3B/C12B/C13B = ꢂ1.2(3)°) and the benzene
3. Results and discussion
ring
(C13A/C12A/C14A/C15A = ꢂ179.3(2)°;
C13B/C12B/C14B/
3.1. Structural and theoretical study of (I): 4-[(2E)-2-(1-
phenylethylidene)hydrazinyl]-8-(trifluoromethyl)-quinoline
C15B = ꢂ179.9(2)°. The mean plane of the quinoline ring is twisted
slightly with that of the hydrazine moiety (N3A/N2A/C4A/
C10A = ꢂ173.50(17)°); N3B/N2B/C4B/C10B = ꢂ172.60(17)°. In
addition, there is a weak CAHꢀ ꢀ ꢀN interaction between molecule
In (I), C18H14F3N3, the compound crystallizes in the tetragonal
crystal system (I 41/a space group) with two independent molecules
(A and B) in the asymmetric unit (Fig. 2). The dihedral angle be-
tween the mean planes of the planar benzene and quinoline rings
A and B (Fig. 3, Table 3) and weak p-stacking interactions between
ring centroids of the benzene and pyridine rings from A and B (Ta-
ble 4) which link the molecules into chains along the b direction and
contribute to crystal packing. Bond distances and angles are in the
normal range [26]. Hirshfeld shape index and fingerprint plots for
(I) are supportive of the intermolecular observations described
above (Fig. 10). After a DFT calculation the dihedral angle between
the mean planes of the planar benzene and quinoline rings becomes
32.54°, an increase of 24.16° (A) and 13.13° (B), respectively. This in
turn brings about appropriate changes in the bond and torsion an-
gles surrounding the hydrazine moiety (Table 2).
Table 4
Parametersa [Å, °] for
p p interactions in (I) C18H14F3N3, (II) C18H13BrF3N3, (III)
ꢀ ꢀ ꢀ
C
18H14F3N3OꢀH2O and (IV) C22H16F3N3.
CgIꢀ ꢀ ꢀCgJ
Cgꢀ ꢀ ꢀCg
a
b
c
CgIperp
CgJperp
I
Cg1ꢀ ꢀ ꢀCg7(i) 3.8979(14) 8.70(11) 52.21 47.83 3.5052(9)
ꢂ3.7290(10)
Cg3ꢀ ꢀ ꢀCg5(ii) 3.7517(13) 4.40(11) 16.79 15.05 3.6231(10) ꢂ3.5917(8)
Cg3ꢀ ꢀ ꢀCg6(ii) 3.8564(14) 3.10(11) 19.83 20.12 3.6211(10) ꢂ3.6278(9)
II
Cg2ꢀ ꢀ ꢀCg3(iii) 3.6389(8) 3.37(11) 24.41 21.65 3.6389(8)
3.5651(10)
III
Cg2ꢀ ꢀ ꢀCg2(iv) 3.6599(9)
0
10.75 10.75 ꢂ3.5956(7) ꢂ3.5956(7)
IV
Cg1ꢀ ꢀ ꢀCg3(v) 3.9536(10) 2.05(8) 28.52 27.21 ꢂ3.5162(7) 3.4739(7)
Cg2ꢀ ꢀ ꢀCg2(vi) 3.6185(9)
0
19.33 19.33 ꢂ3.4144(7) ꢂ3.4144(7)
Cg2ꢀ ꢀ ꢀCg3(vii) 3.6316(10) 2.46(8) 17.12 15.37 ꢂ3.5018(7) ꢂ3.4707(7)
(I) Ring 1 centroid defined by N1AAC2AAC3AAC4AAC10AAC9A; Ring 3 centroid
defined by C14A to C19A; Ring centroid defined by N1BAC2BAC3BAC4BA
5
C10BAC9B; Ring 6 centroid defined by C5B to C10B; Ring 7 centroid defined by
C14B to C19B. Symmetry codes: (i) x, y, z; (ii) ꢂ1/2 + x, y, ꢂ1/2ꢂz.
(II) Ring 2 centroid defined by C5 to C10; Ring 3 centroid defined by C14 to C19;
Symmetry codes: (iii) 2 ꢂ x, ꢂy, ꢂz.
(III) Ring 2 centroid defined by C4 to C9. Symmetry code: (iv) 1 ꢂ x, 1 ꢂ y, ꢂz.
(IV) Ring 1 centroid defined by N1AC3AC2AC1AC9AC4; Ring 2 centroid defined by
C4 to C9; Ring 3 centroid defined by C13AC14AC15AC20AC21AC22; Symmetry
Fig. 3. Packing diagram of (I), viewed down the a axis. Dashed lines indicate weak
CAHꢀ ꢀ ꢀN intermolecular hydrogen-bond interactions. Molecules
A and B are
depicted.
codes: (v) ꢂ1 + x, y, z; (vi) ꢂx, 1 ꢂ y, 1 ꢂ z; (vii) 1 + x, y, z.
a
a
= dihedral angle between planes I and J. b = angle between CgIꢀ ꢀ ꢀCgJ and
CgIperp. c = angle between CgIꢀ ꢀ ꢀCgJ and CgJperp. Cgꢀ ꢀ ꢀCg = distance between ring
centroids. CgIperp = perpendicular distance of CgI on ring J. CgJperp = perpendicular
distance of CgJ on ring I.
Table 3
Hydrogen bonds and weak hydrogen bond intermolecular interactions for (I)
18H14F3N3, (II) C18H13BrF3N3, (III) C18H14F3N3OꢀH2O and (IV) C22H16F3N3 [Å, °].
C
DAHꢀ ꢀ ꢀA
I
C5AAH5AAꢀ ꢀ ꢀN1B #1
II
d(DAH)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
3.355(3)
3.411(3)
<(DHA)
0.93
2.45
165
C17AH17Aꢀ ꢀ ꢀF1 #2
0.93
2.50
168
III
O1AH1Aꢀ ꢀ ꢀO1W
O1WAH1W1ꢀ ꢀ ꢀN1 #3
O1WAH1W2ꢀ ꢀ ꢀN3 #4
0.82
0.817(15)
0.839(15)
1.86
2.052(17)
2.265(17)
2.6773(18)
2.8537(19)
3.001(2)
171.8
167(2)
147(2)
IV
C6AH6Aꢀ ꢀ ꢀF1A #4
0.93
0.93
2.53
2.51
3.270(5)
3.237(5)
136.2
134.9
C21AH21Aꢀ ꢀ ꢀF3A #5
Symmetry transformations used to generate equivalent atoms: (I) #1 5/4 ꢂ x, ꢂ1/
4 + y, ꢂ3/4 ꢂ z; (II) #2 ꢂ1 + x, 1 + y, z; (III) #3 ꢂx, ꢂy + 1, ꢂz + 1 #4 x ꢂ 1, y, z; (IV)
#4 ꢂx ꢂ 1, ꢂy + 1, ꢂz + 1 #5 ꢂx + 1, ꢂy + 1, ꢂz + 2.
Fig. 4. Molecular structure of (II), drawn with 50% probability displacement
ellipsoids and showing the atom labeling scheme.

J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
177
Fig. 7. Packing diagram of (III), viewed down the b axis. Dashed lines indicate
OAHꢀ ꢀ ꢀO and OAHꢀ ꢀ ꢀN intermolecular hydrogen-bond interactions linking mole-
cules into chains in (1 0 1).
Fig. 5. Packing diagram of (II), viewed down the a axis.
3.2. Structural and theoretical study of (II): 4-{(2E)-2-[1-(3-
bromophenyl)ethylidene] hydrazinyl}8-(trifluoromethyl)-quinoline
Bond distances and angles are in the normal range [26]. Hirshfeld
shape index and fingerprint plots for (II) are also supportive of
the intermolecular observations described above (Fig. 11). The
dihedral angle between the mean planes of the planar benzene
and quinoline rings becomes 30.30°, an increase of 27.08° from
that observed in the crystal, after a DFT calculation. This in turn
also brings about appropriate changes in the bond and torsion an-
gles surrounding the hydrazine moiety (Table 2).
In (II), C18H13BrF3N3 the molecule crystallizes in the monoclinic
system (P 21/c space group; z = 4) (Figs. 4 and 5). The dihedral angle
between the mean planes of the planar benzene and quinoline
rings is 3.2(2)°. The trifluoro methyl group lies within the mean
plane of the quinoline ring (N1/C9/C8/C11 = ꢂ1.2(3)°). The methyl
group is in the plane of the hydrazine moiety (N2/N3/C12/
C13 = ꢂ1.7(3)° and slightly twisted from the mean plane of the
benzene ring (C13/C12/C14/C15 = 5.8(3)°). The hydrazine moiety
is in the same plane as the quinoline ring (N3/N2/C4/
C10 = ꢂ179.19(17)°). In addition, there is a weak CAHꢀ ꢀ ꢀF intermo-
3.3. Structural and theoretical study of (III): 4-[(1E)-1-{2-[8-
(trifluoromethyl)quinolin-4-yl]-hydrazinylidene}ethyl]-phenol
hydrate
lecular interaction (Fig. 3, Table 3) as well as weak
p-stacking
interactions between ring centroids of the benzene and quinoline
(benzene) rings (Table 4) which contributes to the crystal packing.
In (III), C18H14F3N3OꢀH2O, the molecule crystallizes in the
monoclinic system (P 21/c space group; z = 4) (Fig. 6). The dihedral
Fig. 6. Molecular structure of (III), drawn with 50% probability displacement ellipsoids and showing the atom labeling scheme. Dashed line indicates OAHꢀ ꢀ ꢀO hydrogen bond
within the asymmetric unit.

178
J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
angle between the mean planes of the planar benzene and quino-
line rings is 9.1(2)°. The trifluoro methyl group lies within the
mean plane of the quinoline ring (N1/C4/C5/C1 = 0.8(2)°). The
methyl group is in the plane of the hydrazine moiety (N2/N3/
C11/C12 = ꢂ0.1(2)° and slightly twisted from the mean plane of
the benzene ring (C14/C13/C11/C12 = ꢂ7.8(2)°). The hydrazine
moiety is slightly twisted from the mean plane of the quinoline
ring (N3/N2/C1/C9 = ꢂ173.83(13)°). OAHꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀN hydro-
gen bonds between a crystallized water molecule and the hydroxyl
group on the benzene ring (Table 3) links the molecules into chains
along the b direction (Fig. 7) in 101). In addition, weak intermolec-
ular
p-stacking interactions between ring centroids of the quino-
line (benzene) rings (Table 4) contribute to the crystal packing.
Bond distances and angles are in the normal range [26]. Hirshfeld
shape index and fingerprint plots for (II) are also supportive of
the intermolecular observations described above (Fig. 12). After a
DFT calculation, the dihedral angle between the mean planes of
the planar benzene and quinoline rings becomes 28.73° an increase
of 17.63°. This in turn also brings about appropriate changes in the
bond and torsion angles surrounding the hydrazine moiety
(Table 2).
3.4. Structural and theoretical study of (IV): 4-{(2E)-2-[1-
(naphthalen-2-yl)ethylidene]-hydrazinyl}8-(trifluoro-
methyl)quinoline
In (IV), C22H16F3N3, the molecule crystallizes in the monoclinic
system (P 21/n space group; z = 4) (Fig. 8). The dihedral angle be-
tween the mean planes of the naphthalene and quinoline rings is
2.6(2)°. The trifluoro methyl group lies within the mean plane of
the quinoline ring (N1/C4/C5/C10 = ꢂ2.3(2)°). The methyl group
is in the plane of the hydrazine moiety (N2/N3/C121C12 =
ꢂ0.9(2)° and in the plane of the naphthalene ring (C14/C13/C11/
C12 = ꢂ1.1(2)°). The hydrazine moiety is in the same plane as the
quinoline ring (N3/N2/C1/C9 = 178.03(13)°). The molecules pack
in layers along the a axis in (101) (Fig. 9). Weak C–Hꢀ ꢀ ꢀF intermo-
Fig. 9. Packing diagram of (IV), viewed down the b axis. Dashed lines indicate weak
CAHꢀ ꢀ ꢀF intermolecular hydrogen-bonding interactions.
lecular interactions and
p–p-stacking interactions between ring
centroids of the benzene and quinoline (benzene) rings (Tables 3
and 4) contribute to the crystal packing. Bond distances and angles
are in the normal range [26]. Hirshfeld shape index and fingerprint
plots for (II) are also supportive of the intermolecular observations
described above (Fig. 13). After a DFT calculation, the dihedral an-
gle between the mean planes of the naphthalene and quinoline
rings becomes 25.32°, an increase of 22.70°. This in turn brings
about appropriate changes in the bond and torsion angles sur-
rounding the hydrazine moiety (Table 2). The mean plane of the
quinoline ring is in the same planar with the hydrazine moiety in
(II), N3/N2/C4//C10 = 179.19(17)°, and (IV), N3/N2/C1//C9 =
178.03(13)°, and twisted slightly in (I), N3A/N2A/C4A/C10A =
ꢂ173.50(17)°, and (III), N3B/N2B/C4B/C10B = ꢂ173.50(17)°.
4. Summary and conclusions
The results of this structural and theoretical study with visual
corroboration suggest that the outcome of crystallization plays a
role in the balance between intermolecular bonding patterns and
crystal packing interactions. Theoretical calculations of the free
atom molecule compared to the crystal structure provides direct
evidence of the role that both strong and weak intermolecular
hydrogen-bond interactions and p-stacking interactions may have
on molecular structure in the solid state and in the stabilization of
crystal packing, and particularly, with this series of Schiff base
compounds.
Fig. 8. Molecular structure of (IV), drawn with 50% probability displacement ellipsoids and showing the atom labeling scheme.

J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
179
Fig. 10. Hirshfeld surface and fingerprint plots for (I), C18H14F3N3. On the shape index diagram, hydrogen bonds (red concave regions around acceptor atoms and blue convex
regions around donor atoms; CAHꢀ ꢀ ꢀN) and three
p – stacking interactions (Cgꢀ ꢀ ꢀCg: Table 3; red and blue complementary region triangles on rings that overlay each other)
are observed. The presence of a weak red zone in the fingerprint plot indicates a weak CAHꢀ ꢀ ꢀN intermolecular interaction (Table 3). Nꢀ ꢀ ꢀH fingerprint spike is at di, de ꢃ 1.1,
1.1 Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 11. Hirshfeld surface and fingerprint plots for (II), C18H13BrF3N3. On the shape index diagram hydrogen bonds (red concave regions around acceptor atoms and blue
convex regions around donor atoms; CAHꢀ ꢀ ꢀF) and one
p – stacking interaction (Cgꢀ ꢀ ꢀCg: Table 3; red and blue complementary region triangles on rings that overlay each
other) is observed. The presence of a weak red zone in the fingerprint plot indicates a weak CAHꢀ ꢀ ꢀF intermolecular interaction. Hꢀ ꢀ ꢀF fingerprint spike is at di, de ꢃ 1.2, 1.2 Å.
(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

180
J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
Fig. 12. Hirshfeld surface and fingerprint plots for (III), C18H14F3N3OꢀH2O. On the shape index diagram hydrogen bonds (red concave regions around acceptor atoms and blue
convex regions around donor atoms; OAHꢀ ꢀ ꢀO and OAHꢀ ꢀ ꢀN) and one
p – stacking interaction (Cgꢀ ꢀ ꢀCg: Table 3; red and blue complementary region triangles on rings that
overlay each other) is observed. The presence of a strong red zone in the fingerprint plot indicates strong OAHꢀ ꢀ ꢀO and OAHꢀ ꢀ ꢀN interactions. Oꢀ ꢀ ꢀH and Oꢀ ꢀ ꢀN fingerprint
spikes are at di, de ꢃ 0.7, 1.0 Å; ꢃ1.0, 1.0 Å; 1.1, 0.7 Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 13. Hirshfeld surface and Hirshfeld fingerprint diagrams for (IV), C22H16F3N3. On the shape index diagram hydrogen bonds (red concave regions around acceptor atoms
and blue convex regions around donor atoms; CAHꢀ ꢀ ꢀF) and three
p – stacking interactions (Cgꢀ ꢀ ꢀCg: Table 3; red and blue complementary region triangles on rings that
overlay each other) are observed. The presence of a moderate red zone in the fingerprint plot indicates a moderate CAHꢀ ꢀ ꢀF intermolecular interaction. Hꢀ ꢀ ꢀF fingerprint spike
is at di, de ꢃ 1.0, 1.0 Å. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

J.P. Jasinski et al. / Journal of Molecular Structure 980 (2010) 172–181
181
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Acknowledgements
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[19] G. Dutkiewicz, A.N. Mayekar, H.S. Yathirajan, B. Narayana, M. Kubicki, Acta
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ANM thanks the University of Mysore for use of their research
facilities. HSY thanks UOM for sabbatical leave. RJB acknowledges
the NSF MRI program (Grant No. CHE-0619278) for funds to pur-
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