Role of π-interactions in solid state structures of a few 1,8-naphthalimide derivatives

Article abstract of DOI:10.1016/j.molstruc.2006.06.006

Crystal structures of isomeric N-(X-picolyl)-1,8-naphthalimides (X = 2,3,4) are compared with that of N-(benzyl)-1,8-naphthalimide. The comparison on the disposition of aromatic rings from torsion angles determined theoretically and experimentally suggests that the packing patterns in all these four derivatives except in the case of N-(2-picolyl)-1,8-naphthalimide are controlled by π-π and C-H?π interactions. In the case of N-(2-picolyl)-1,8-naphthalimide electronic factor decides the packing pattern. Crystal structures of N-(X-picolinium)-1,8-naphthalimide perchlorates (X = 2, 3, and 4) show that these compounds self-assemble through intermolecular hydrogen bonding involving the pyridinium N⁺-H, C{double bond, long}O and the perchlorate anions. Aromatic π-stacking interactions between the 1,8-naphthalimide units are also observed in the structures of the perchlorate salts. The compounds N-(2-picolinium)-1,8-naphthalimide perchlorate and N-(3-picolinium)-1,8-naphthalimide perchlorate are characterized by hydrogen bonded dimeric motifs that are held by intermolecular N⁺-H?O{double bond, long}C and C-H?π interactions; however, intermolecular interactions in N-(4-picolinium)-1,8-naphthalimide perchlorate result in the formation of hydrogen bonded polymeric structure.

Full text of DOI:10.1016/j.molstruc.2006.06.006

Journal of Molecular Structure 829 (2007) 29–36
www.elsevier.com/locate/molstruc
Role of ꢀ-interactions in solid state structures of a few
1,8-naphthalimide derivatives
Rupam J. Sarma, Chandan Tamuly, Nilotpal Barooah, Jubaraj B. Baruah ¤
Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781 039, India
Received 25 April 2006; received in revised form 3 June 2006; accepted 7 June 2006
Available online 14 July 2006
Abstract
Crystal structures of isomeric N-(X-picolyl)-1,8-naphthalimides (X D 2,3,4) are compared with that of N-(benzyl)-1,8-naphthalimide.
The comparison on the disposition of aromatic rings from torsion angles determined theoretically and experimentally suggests that the
packing patterns in all these four derivatives except in the case of N-(2-picolyl)-1,8-naphthalimide are controlled by ꢀ–ꢀ and C–H,ꢀ
interactions. In the case of N-(2-picolyl)-1,8-naphthalimide electronic factor decides the packing pattern. Crystal structures of N-(X-pico-
linium)-1,8-naphthalimide perchlorates (X D 2, 3, and 4) show that these compounds self-assemble through intermolecular hydrogen
bonding involving the pyridinium N+–H, CBO and the perchlorate anions. Aromatic ꢀ-stacking interactions between the 1,8-naphthali-
mide units are also observed in the structures of the perchlorate salts. The compounds N-(2-picolinium)-1,8-naphthalimide perchlorate
and N-(3-picolinium)-1,8-naphthalimide perchlorate are characterized by hydrogen bonded dimeric motifs that are held by intermolecu-
lar N+–H,OBC and C–H,ꢀ interactions; however, intermolecular interactions in N-(4-picolinium)-1,8-naphthalimide perchlorate
result in the formation of hydrogen bonded polymeric structure.
© 2006 Elsevier B.V. All rights reserved.
Keywords: 1,8-Naphthalimides; Crystal structure; H-bonding; Anion-assisted assembly
1. Introduction
aspects of 1,8-naphthalimide derivatives [13]. Moreover, the
anion-assisted assemblies from 1,8-naphthalimide deriva-
tives should have important implications as demonstrated
in other chromo/Xuorophores [30–34]. To understand weak
interactions among diVerent 1,8-naphthalimide derivatives
in solid-state we have chosen a few N-substituted 1,8-naph-
thalimides derived from diVerent picolyl isomers for struc-
tural studies. It is done with an objective that depending on
the location of the nitrogen in the picolyl unit the packing
pattern will vary and also would make diVerent types of
self-assemblies once protonated with a mineral acid.
Structural understanding of materials used for lumines-
cent probe [1,2], liquid crystalline display [3,4], and on/oV
switching [5,6] is essential. Making such devices by directing
intermolecular interactions in an appropriate material in
solution [7,8] is diYcult than in solid-state[9–13]. From this
point of view the structure and understanding of diVerent
weak interactions in 1,8-naphthalimides are important as
their Xuorescence properties are governed both by substitu-
ent eVects [14–21] as well as by the environment around
Xuorophore [22–29]. It is already demonstrated that the
solid-state Xuorescence properties of organized assemblies
depend on the weak intermolecular interactions [27,28].
Yet, there are only a few reports, which describe structural
2. Experimental section
2.1. General
The X-ray diVraction data were collected on Bruker
3-circle SMART Apex diVractometer with CCD area detec-
tor, using graphite monochromated Mo–Kꢁ; radiation
*
Corresponding author. Tel.: +91 361 2582301; fax: +91 361 2690762.
E-mail address: juba@iitg.ernet.in (J.B. Baruah).
0022-2860/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.06.006

30
R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
Table 1
Crystallographic parameters of compounds I–VII
Compound
I
II
III
IV
V
VI
VII
Formula
Formula
weight
T/K
Wavelengt h/Å 0.71073
Crystal system Monoclinic
Space group P2(1)/c
a/Å
b/Å
c/Å
ꢀ/°
C18H12N2O2
288.30
C18H12N2O2
288.30
C18H12 N2O2
288.30
C19H13NO2
287.30
C18H13ClN2O6
388.75
C18H13ClN2O6
388.75
C18H13ClN2O6
388.75
296(2)
296(2)
296(2)
0.71073
Monoclinic
P2(1)/n
7.383(2)
7.946(3)
23.025(7)
90
94.158(5)
90
1347.2(7)
4
296(2)
296(2)
296(2)
296(2)
0.71073
Orthorhombic
Pbca
11.3218(3)
13.6647(4)
21.4935(4)
90
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
0.71073
Triclinic
P-1
15.803(2)
5.9632(7)
15.487(2)
90
109.416(2)
90
8.264(2)
9.175(2)
9.569(2)
80.740(16)
79.745(16)
71.751(15)
673.8(3)
2
7.3258(2)
9.2327(2)
11.4743(3)
88.881(2)
73.576(2)
68.526(2)
689.67(3)
2
8.1203(4)
14.0898(6)
15.2602(6)
81.598(2)
75.245(2)
81.207(2)
1658.04(3)
4
8.0305(2)
14.2921(4)
15.1776(4)
94.352(2)
104.7270(10)
98.888(2)
1652.38(8)
4
ꢁ/°
90
90
ꢂ/°
V/Å3
Z
1376.5(3)
4
3325.25(5)
8
Density/
mg m¡3
Abs. coeV/
mm¡1
F (000)
1.391
1.421
1.421
1.383
1.557
1.563
1.553
0.093
600
0.095
0.095
0.090
0.272
0.273
0.271
300
600
300
800
800
1600
Abs. correctionNone
None
2.18–25.00
90.9
None
8.98–28.44
93.3
None
1.86–29.59
97.6
None
1.39–28.32
92.8
None
1.45–30.54
94.6
None
1.89–28.25
84.2
ꢃ range/°
4.09–28.31
Completeness 84.9
(%)
Index ranges ¡18 < D h < D 17 ¡9 < D h < D 9
¡9 < D h < D 9
¡10 < D h < D 10 ¡9 < D h < D 10
¡10 < D h < D 11 ¡14 < D h < D 10
(h, k, l)
¡7 < D k < D 7
¡9 < D k < D 10 ¡10 < D k < D 9 ¡12 < D k < D 12 ¡18 < D k < D 18 ¡17 < D k < D 20 ¡5 < D k < D 16
¡11 < D l < D 20 ¡11 < D l < D 11 ¡30 < D l < D 30 ¡12 < D l < D 15 ¡20 < D l < D 20 ¡21 < D l < D 21 ¡26 < D l < D 25
4988 4660 8137 8470 19,471 25,855 11,615
ReXections
collected
ReWnement
method
Data/
Full matrix least- Full matrix least- Full matrix least- Full matrix least-
Full matrix least- Full matrix least- Full matrix least-
squares on F2
2897/0/207
squares on F2
2157/0/207
squares on F2
3175/0/207
squares on F2
3785/0/207
squares on F2
7673/0/503
squares on F2
9582/0/507
squares on F2
3469/0/244
restraints/
parameters
GOF on F2
1.030
0.987
1.029
1.039
1.063
1.048
1.031
Final R indices R1 D 0.0397,
[I > 2ꢄ (I)] wR2 D 0.0983
R indices (all R1 D 0.0577,
R1 D 0.0520,
wR2 D 0.0862
R1 D 0.1261,
wR2 D 0.1466
R1 D 0.0411,
wR2 D 0.1050
R1 D 0.0575,
wR2 D 0.1175
R1 D 0.0456,
wR2 D 0.1243
R1 D 0.0646,
wR2 D 0.1396
R1 D 0.0683,
wR2 D 0.2085
R1 D 0.0845,
wR2 D 0.2276
R1 D 0.0682,
wR2 D 0.2045
R1 D 0.1007,
wR2 D 0.2333
R1 D 0.0411,
wR2 D 0.1096
R1 D 0.0662,
wR2 D 0.1243
data)
wR2 D 0.1123
Largest diV.
peak/hole
0.147 and ¡0.202 0.193 and ¡0.205 0.197 and ¡0.106 0.230 and ¡0.195
0.738 and ¡0.702 0.782 and ¡0.628 0.215 and ¡0.287
(e. Å¡3
)
from a 60W microfocus Bede Microsource® with glass
polycapillary optics. The structures were solved by direct
methods and reWned by Full-matrix least squares against F2
of all data, using SHELXTL software. The crystallographic
data for the compounds I–VII are given in Table 1. To Wnd
out torsion angles in the minimum energy conformers the
MM2 energy minimization for diVerent conformers of I–IV
is done by using chem.3D pro version 7.0.0. From the low-
est energy conformers the torsion angles are determined.
precipitate was collected and washed with THF. Then the
precipitate was recrystallised from a mixture of ethanol and
dichloromethane (2:8). Yield: 96.5%. IR(KBr, cm¡1)
3062(w), 2946(w), 1663(s), 1583(s), 1471(w), 1431(w),
1372(w), 1348(s), 1233(s), 1159(w), 1028(w),) 961(s), 841(s),
777(s), 748(w), 658(w). 1H NMR (CDCl3): 8.58(d,
J D7.2Hz, 2H), 8.48 (d, J D4.4 Hz, 1H), 8.2 (d, J D8 Hz,
2H), 7.7 (t, J D8 Hz 2H), 7.5 (dt, J D2, 8.8Hz, 1H), 7.3 (d,
J D8.4 Hz, 1H), 7.1 (dd, J D5.2, 5.6 Hz, 1H), 5.52 (s, 2H).
2.2. Synthesis of 1,8-napthalimide derivatives
2.2.2. N-(3-Picolyl) 1,8-naphthalimide (II)
To a solution of 1,8-naphthalic anhydride (0.999g,
5mmol) in tetrahydrofuran (25ml) 3-picolylamine (0.54gm,
5mmol) was added dropwise at room temperature.
The solution was stirred for 5h, a white precipitate was
obtained. The solid was washed with THF (5ml). Then the
precipitate was recrystallised from a mixture of ethanol and
2.2.1. N-(2-Picolyl) 1,8-naphthalimide (I)
To a solution of 1,8-naphthalic anhydride (0.999 g,
5mmol) in tetrahydrofuran (25 ml) 2-picolylamine (0.54g,
5mmol) was added dropwise at room temperature. The
solution was stirred for 5h to obtain a white solid. The

R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
31
dichloromethane (3:7 ratio) Yield: 95%. IR (KBr, cm¡1):
3078(w), 2930 (w), 1665(s), 1583(s), 1511(w), 1419(s) 1378(w),
1347(w), 1327(s) 1230(s), 1081(w), 1020(w), 943(w), 840(s),
774(s), 702(w). 1H NMR (CDCl3): 8.8(s 1H), 8.5 (d, JD6.4Hz
2H), 8.4 (d, JD6Hz, 1H), 8.1 (d JD7.6Hz 2H), 7.8 (d,
JD8.4Hz, 1H), 7.7 (t, JD8Hz, 2H), 7.2 (dd, JD5.2, 4.8Hz,
1H), 5.37(s, 2H).
1650(s), 1593(s), 1506(s), 1445(w), 1383(w), 1342(s), 1235(s),
1117(s), 958(w), 840(w), 779(s), 738(w), 615(s).
3. Result and discussions
3.1. Structural aspects of diVerent picolyl 1,8-naphthalimides
A series of 1,8-naphthalimide derivatives I–IV as shown
in Fig. 1 are prepared by condensing corresponding amines
with 1,8-naphthalicanhydride and crystal structures of each
of them are determined.
2.2.3. N-(4-Picolyl) 1,8-naphthalimide (III)
To a solution of 1,8-naphthalic anhydride (0.999 g,
5 mmol) in tetrahydrofuran (25 ml) was added 4-picolyl-
amine (0.54 g, 5 mmol) dropwise at room temperature.
The solution was stirred for 6 h to a white precipitate.
The precipitate was collected and washed with 10 ml of
THF. The solid obtained was recrystallised from a mix-
ture of ethanol and dichloromethane (2:8) Yield: 96%.
Crystal structure of N-(2-picolyl) 1,8-naphthalimide (I)
shows that the molecules in the solid-state are packed in a
manner that does not facilitate aromatic ꢀ-stacking interac-
tions between the 1,8-naphthalimide rings. This results
from an unfavorable geometrical disposition of the 1,8-
naphthalimide groups of the molecules of I (Fig. 2),
although the interplanar distance of 3.42Å does suggest
close approach along the b-axis. In the case of II the 1,8-
napthalimide rings are disposed in opposite manner so that
the carbonyl terminals are apart and the dipolar interac-
tions are possible. In this arrangement the picolyl rings are
arranged such that the molecules occur in pairs which are
held by C–H,ꢀ and ꢀ–ꢀ interactions as depicted in Fig. 2b.
The interplanar distance in II between the two 1,8-naph-
thalimide rings is 3.48 Å which suggests strong ꢀ–ꢀ interac-
tion. We also have observed that aromatic ꢀ-stacking
interactions are prominent in N-(4-picolyl) 1,8-naphthali-
mide (III). In this case the 1,8-naphthalimide groups of III
adopt a head-to-tail geometry with an interplanar separa-
tion of 3.50Å. Similar stacking interactions involving the
head-to-tail geometry are also observed in N-(benzyl) 1,8-
naphthalimide wherein the interplanar separation is found
to be 3.56 Å. Thus, the 1,8-naphthalimide rings are aligned
one on top of the other in the crystal lattice of III and IV
unlike in compound I (Fig. 2); the head–tail geometries in
the compounds III and IV are also stabilized by intermolec-
ular C–H,ꢀ interactions, with donor,acceptor distances
(dC,ꢀ) of 3.62 Å and 3.78Å, respectively. However, the
presence of ꢀ-stacking interactions between the 1,8-naph-
thalimide units in these molecules is presumably deter-
mined by the torsion angles as illustrated in Table 2. It may
be pointed out that the head-to-tail orientation of the mole-
cules is preferred in the solid-state because of dipolar inter-
actions between the 1,8-naphthalimide rings; analogous
IR(KBr, cm¡1
) 3073(w), 2960(w), 1660(s), 1588(s),
1506(w), 1373(s), 1347(w), 1230(s), 1178(w), 1071(w),
1
994(w), 938(s), 774(s), 645(s). H NMR (CDCl3, 400 Hz):
8.6 (d, J D 7.6 Hz, 2H), 8.5 (d, J D 5.6 Hz, 2H), 8.2 (d,
J D 8.8 Hz, 2H), 7.7(t, J D 7.6 Hz, 2H), 7.3 (d, J D 5.6 Hz,
2H), 5.3 (s, 2H).
2.2.4. N-(Benzyl) 1,8-naphthalimide (IV)
The compound (IV) was prepared by earlier reported
procedure [26].
2.2.5. N-(2-Picolinium) 1,8-naphthalimide perchlorate (V)
N-(2-Picolyl)-1,8-naphthalimide (288 mg, 1mmol) was
dissolved in mixed solvent of methanol and dichlorometh-
ane (10 ml, 1:1). To this solution perchloric acid (0.085 ml,
60%) was added dropwise and the solution was kept over-
night for crystallisation. Light orange coloured crystals
were formed. Yield 95%. IR(KBr, cm¡1): 3426(w), 3257(w),
3078(w), 1701(s), 1660(s), 1614(w), 1532(w), 1470(w),
1429(w), 1383(s), 1291(s), 1236(s), 1112(s), 1081(s), 938(s),
846(w), 779(s), 625(s).
2.2.6. N-(3-Picolinium) 1,8-naphthalimide perchlorate (VI)
N-(3-Picolyl)-1,8-naphthalimide (288 mg, 1mmol) was
dissolved in a mixed solvent of methanol and dichloro-
methane (1:1, 10 ml). To this solution of perchloric acid
(60%, 0.085 ml) was added dropwise. The solution was kept
overnight for crystallisation. Light orange coloured crystals
were formed. Yield 94%. IR(KBr, cm¡1) 3360(w), 3191(w),
3058(w), 2935(w), 1701(s), 1655(s), 1624(s), 1588(s), 1475(s),
1445(s), 1383(s), 1342(w), 1322(w), 1240(s), 1183(w),
1112(s), 1030(w), 948(w), 774(s), 682(s), 620(s).
N
N
N
2.2.7. N-(4-Picolinium) 1,8-naphthalimide perchlorate
(VII)
O
N
O
O
N
O
O
N
O
O
N
O
N-(4-Picolyl)-1,8-naphthalimide (288 mg, 1mmol) was
dissolved in mixed solvent of methanol and dichlorometh-
ane (10 ml, 1:1), To this solution perchloric acid (60%,
0.085 ml) was added dropwise. The solution on keeping
overnight led to light yellow crystals (370 mg, 95%). IR
(KBr, cm¡1) 3247(w), 3165(w), 3099(w), 2940(w), 1706(s),
I
II
III
IV
Fig. 1. 1,8-Napthalimide derivatives.

32
R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
Fig. 2. Left, crystal structures of (a) N-(2-picolyl)1,8-naphthalimide (I), (b) N-(3-picolyl)1,8-naphthalimide (II), (c) N-(4-picolyl)1,8-naphthalimide (III)
and (d) N-(benzyl)1,8-naphthalimide (IV). Right, the interplanar distances between the 1,8-naphthalimide units in compounds I, II, III and IV are shown
in order to illustrate the geometries which lead to aromatic ꢀ-interactions (thermal ellipsoids drawn to 50% probability).
phenomenon has already been described in the case of
phthalimide derivatives [35,36].
compared to IV. Since the compounds I–III are isomeric
and IV is structurally related to them without having a
nitrogen atom in the substituted part it may be also possi-
ble that the orientation is guided by the electronic eVect too.
We have examined the torsion angle of N–C–C–ꢂ (Fig. 3
where ꢂ is corresponding pyridyl group in case of I–III and
phenyl group in case of IV) in the most stable conformer.
The most stable conformer is determined by MM2 calcula-
tion in the case of all these compounds and that the torsion
angles are determined which are compared with the
experimentally observed torsion angle. In each case two
angles from the orientation of the aromatic ring as deWned
in the case of IV in Fig. 3 are obtained. The torsion angles
In the Fig. 2 it is clearly shown that each of these mole-
cules except I can have C–H,ꢀ and ꢀ–ꢀ interactions. From
the orientation and distance of separation of 1,8-naphthali-
mide rings among the compounds I–IV it is clear that max-
imum ꢀ–ꢀ interactions are observed in the case of
compound II. These results also indicate that the orienta-
tion of the nitrogen atom in the pyridyl ring of picolyl unit
(in compounds such as I–III) is crucial in deciding the
extent of intermolecular ꢀ-stacking interactions. It appar-
ently seems that the presence of ring nitrogen has directing
inXuence on the solid-state assembly of these compounds

R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
33
Table 2
Theoretical and experimental torsion angles N–C–C–ꢂ
3.2. Structure of perchlorate salts of diVerent N-picolinium
1,8-naphthalimides
Compound
Torsion angles N–C–C–ꢂ (°)
Since protonation of the pyridine nitrogen atom con-
verts it into a strong hydrogen bond donor, we anticipate
that corresponding 1,8-naphthalimide picolinium salts of
I–III could be directed to self-assemble in the solid-state
through intermolecular hydrogen bonding interactions and
aromatic ꢀ-interactions. Accordingly, we prepared the per-
chlorate salts, V–VII, in which the pyridinium ions behave
as strong hydrogen bond donors, while the perchlorate
anions as hydrogen bond acceptors. It has already been
pointed out that the N-picolyl 1,8-naphthalimides them-
selves self-assemble predominantly through weak C–H,ꢀ
and aromatic ꢀ-stacking interactions, though in the absence
of strong hydrogen bond donors/acceptors.
Theoretical
Experimental
I
II
III
IV
36.2/142.3
47.0/131.3
45.2/131.0
61.1/119.4
68.6/108.7
54.9/122.9
61.4/115.9
32.9/150.7
88.5/89.8
92.0/86.5
92.0/87.3
92.5/88.1 and 74.2/105.8
95.5/85.8 and 83.2/98.8
43.5/138.2
Va,b
VIa,b
VIIa
¤ꢂ, aromatic ring as deWned in Fig. 3.
a
The torsion angles of protonated compounds excluding the anions are
determined.
b
Two sets of torsion angles are obtained as unit-cell contains two non-
equivalent molecules.
The crystal structure of N-(2-picolinium)-1,8-naphthali-
mide perchlorate (V) shows that the asymmetric unit con-
tains two independent picolinium-1,8-naphthalimide
molecules, and the corresponding perchlorate anions
occupy symmetry independent positions (Fig. 4,left). It is
observed that each of the perchlorate anions is hydrogen
bonded to a 2-picolinium-1,8-naphthalimide unit through
directions, as shown in Fig. 4. The 1,8-naphthalimide units
of the other molecule present in the asymmetric unit are
distinctly oVset from each other, which reduces the possibil-
ity of substantial aromatic ꢀ-interactions.
φ
O
O
N
N
O
O
Fig. 3. The dark lines represent the N–C–C–ꢂ bond for two torsion angles.
The corresponding hydrogen bonding geometry for
this compound (distances in Å and angles in °) is given in
Table 3. It is noteworthy that only one of the two symmetry
theoretically obtained from most stable conformer and
experimentally observed are listed in Table 2. From Table 2
it is clear that except compound I the rest of the com-
pounds in solid-state have torsion angles N–C–C–ꢂ that
are much diVerent from the experimental value. In other
words it is to say that the orientation of the aromatic ring
(pyridine ring) is controlled by the weak interaction rather
than the electronic factors in the case of II–IV. In the case
of I the electronic factor decides the packing and due to the
electronic and steric reason of disposition of the nitrogen
lone pair the ꢀ–ꢀ interactions are not favoured.
Table 3
Hydrogen bond geometry (distances in
Å and angles in °) for
compound V
D–H,A
dD–H dH,A dD,A <D–H,A
N1–H,O9 [x, y + 1, z]
N1–H,O1
0.86
0.86
2.15
2.52
2.22
2.36
2.952 155.6
3.071 122.0
2.920 138.4
3.049 136.6
N3–H,O5 [¡x + 2, ¡y + 1, ¡z+ 1] 0.86
N3–H,O3 0.86
Fig. 4. Left, crystal structure of 2-picolinium 1,8-naphthalimide perchlorate (V). Right, the packing diagram which shows that the 1,8-naphthalimide
assembly is held by intermolecular aromatic ꢀ-interactions.

34
R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
Table 4
independent 1,8-naphthalimide units observed in the asym-
metric unit shows distinct aromatic ꢀ-interactions (Fig. 4).
The perpendicular distance between the planes of the 1,8-
naphthalimide units of two such molecules is ca. 3.84Å,
which falls within the regime of ꢀ-stacking interactions in
the solid-state reported elsewhere [37]. However, the dipole
vectors of the two rings are oriented in opposite direction.
Similarly, N-(3-picolinium)-1,8-naphthalimide perchlo-
rate (VI) crystallises in the P-1 space group, wherein the
asymmetric unit contains two symmetry independent mole-
cules. This compound self-assembles through intermolecular
N+–H,O hydrogen bonding interactions as shown in
Fig. 5, in such a way that only one of the picolinium N+–H is
hydrogen bonded to the perchlorate anion that behaves as
acceptor. Intermolecular aromatic ꢀ-stacking interactions
are observed between the 1,8-naphthlimide units of those
molecules that are hydrogen bonded to the perchlorate
anions through the picolinium N+–H. The perpendicular
distance between the planes of the 1,8-naphthalimide units
involved in ꢅ-stacking is 3.73Å, about 0.1Å less than that
found in the case of N-(2-picolinium)-1,8-naphthalimide
perchlorate (V). One of the two symmetry independent 1,8-
naphthalimides in the asymmetric unit is involved in the for-
mation of a hydrogen-bonded dimer with N+–H as the
hydrogen bond donor and OBC as the acceptor (dN2,O1
2.770Å, 166.3°); However the geometry of the molecules
associated into dimers does not facilitate intermolecular
ꢀ-stacking interactions (Fig. 5). The perchlorate anions in
this case are bound to the 1,8-naphthalimide units by weak
C–H,O interactions (dC7,O11 3.397Å, 174.7°). Thus it is
interesting to note that like V, compound VI also assumes a
layered structure in the solid-state, in which the 1,8-naph-
thalimide molecules involved in ꢀ-stacking interactions are
Hydrogen bond geometry (distances in Å and angles in °) for compound
VI
D–H,A
dD–H
dH,A
dD,A
<D–H,A
N4–H,O3 [x ¡ 1, y, z]
N2–H,O1 [¡x, ¡y, ¡z]
0.83
0.86
2.09
1.93
2.899
2.770
160.5
166.3
alternately spaced by hydrogen bonded picolinium 1,8-
naphthalimide dimers. The important hydrogen bond angles
and bond distances of VI are listed in Table 4.
Crystal structure of N-(4-picolinium)-1,8-naphthalimide
perchlorate (VII) shows that the asymmetric unit of this
compound contains one molecule of protonated III and the
perchlorate anion. The perchlorate anion is hydrogen
bonded to the picolinium ion via N+–H,O (dN1,O6
2.904 Å, 144.9°) interactions. Apart from these interactions,
the picolinium N+–H behaves as hydrogen bond donor and
takes part in the formation of bifurcated hydrogen bonds
with O1 of the carbonyl groups of 1,8-naphthalimide units
as acceptors. These intermolecular N+–H,O (dN1,O1
2.969 Å, 125.6°) hydrogen bonds involving the carbonyl
group of the 1,8-naphthalimide units as well as weak
C–H,O interactions lead to the formation of helical
chains that grow along the crystallographic b-axis as shown
in Fig. 6. The packing pattern of VII shows that alternate
hydrogen-bonded chains run in opposite directions and are
stabilized by intermolecular aromatic ꢀ-stacking interac-
tions (Fig. 6, right). The perpendicular distance between the
planes of the 1,8-naphthalimide units is 3.54 Å, which indi-
cates that the molecular chains are strongly associated
though ꢀ-interactions compared to either compounds V or
VI. The hydrogen bond distances and angles for VII are
Fig. 5. Left, crystal structure of 3-picolinium 1,8-naphthalimide perchlorate (VI). Right, the packing diagram shows that the 1,8-naphthalimide units self-
assemble by intermolecular aromatic ꢀ-interactions and hydrogen bonding.

R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
35
Fig. 6. Left, hydrogen-bonded chains obtained from 4-picolinium 1,8-naphthalimide perchlorate (VII). Right, The perchlorate anions are held by the pyri-
dinium 1,8-naphthalimide chains through N+–H,O hydrogen bonds, while weak aromatic ꢀ-interactions are observed between the naphthalimide units
of two anti-parallel chains as depicted by arrows.
Table 5
3.3. Conclusions
Hydrogen bond geometry (distances in Å and angles in °) for compound
VII
In conclusion the crystal structures of isomeric N-picolyl
D–H,A
dD–H dH,A dD,A <D–H,A
derivatives of 1,8-naphthalimide are determined and the
packing patterns of each of the structures are compared.
The torsion angles deciding the orientation of aromatic
rings of the four structurally related 1,8-naphthalimide
derivatives are theoretically determined and compared with
the torsion angle from the crystallography determined
structures. It is found that in deciding the packing pattern
ꢀ-interactions and C–H,ꢀ predominate over electronic
eVect in the packing pattern of the compounds II–IV
whereas in the case of I the electronic eVect predominates.
Perchlorate anion assists in the formation of assemblies of
1,8-naphthalimide attached to picolinium group and the
structure of the assemblies is stabilised by weak C–H,O
and ꢀ–ꢀ interactions and while forming such assemblies the
position of nitrogen in the picolyl group has an important
role.
N1–H,O1 [x + 1/2, y, ¡z + 3/2]
0.86 2.34
2.926 125.6
2.904 144.9
N1–H,O6 [¡x + 3/2, ¡y + 1, z + 1/2] 0.86 2.14
given Table 5. It may be pointed out that the perchlorate
anions occupy the concave region created by the hydrogen
bonded chains of N-(4-picolinium)-1,8-naphthalimide part
(Fig. 6).
In this regard study on the structure of N-bis (4-picolyl)
pyromelliticdiimide [38,39] and the perchlorate salt of the
same was recently reported, which in contrast, did not
exhibit features of a hydrogen bonded self-assembly pro-
cess. Presumably the self-assembly of the compounds such
as VII originates from the directing inXuence of the dipolar
and the hydrogen bonding interactions of N-(4-picolin-
ium)-1,8-naphthalimide perchlorate and the ability of the
1,8-naphthalimide units to participate in the formation of
aromatic ꢀ-stacks. To probe this we have examined the tor-
sion angles of N–C–C–ꢂ of lowest energy protonated form
of I–III without the anion and found that there is signiW-
cant diVerence in the theoretical value with the experimen-
tally observed value (Table 2). In the case of V and VI we
have considered both the non-equivalent molecules in the
unit cell and found signiWcant deviation from the theoreti-
cal torsion angles. Although these results we have observed
electronic eVect to be predominant in controlling the pack-
ing of I, in the anion assisted assembly of protonated I there
is a deWnitive contribution from the weak inter-molecular
interactions. Apparently the eVects of crystal packing on
the aromatic ꢅ-interactions between the 1,8-naphthalimide
units in compounds V and VI are similar.
Acknowledgement
The authors thank Department of Science and Technol-
ogy, New Delhi, for Wnancial assistance.
Appendix A. Supplementary data
Crystallographic data for the structures reported in this
paper have CCDC Nos. 281888, 281889, 281891–281894,
and 281939. They can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB21EZ,
UK.
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.
molstruc.2006.06.006.

36
R.J. Sarma et al. / Journal of Molecular Structure 829 (2007) 29–36
[18] T.C. Barros, P.B. Filho, V.G. Toscano, M.J. Politi, J. Photochem. Pho-
References
tobiol. A. 89 (1995) 141.
[19] X. Qian, Y. Xiao, Tetrahedron Lett. 43 (2002) 2991.
[20] A.P. de Silva, G.D. McClean, T.S. Moody, Encyclopedia of Supramo-
lecular Chemistry, Mercel Dekker Inc., New York, 2004, p. 572.
[21] F. Dobrawa, F. Wurtner, Chem. Commun. (2002) 1878.
[22] S.C. Lo, T.D. Anthpoulos, E.B. Namdas, P.L. Burn, I.D.W. Samuel,
Adv. Mater. 17 (2005) 1945.
[23] M. Pope, C.E. Swenberg, Electronic Processes in Organic Crystals,
Clarendon, Oxford, 1982.
[24] J.S. Wilson, A.S. Dhoot, A.J.A.B. Seeley, M.S. Khan, A. Kohler, R.H.
Friend, Nature 413 (2001) 828.
[1] J. Gawronski, K. Gawronska, P. Skowronek, A. Holmen, J. Org.
Chem. 64 (1999) 234–241.
[2] D. Kolosov, V. Adamovich, P. Djurovich, M.E. Thompson, C.
Adachi, J. Am. Chem. Soc. 124 (2002) 9945.
[3] W. Pisula, M. Kastler, D. Wasserfallen, J.W.F. Robertson, F. Nolde,
K. Kohl, K. Mullen, Angew. Chem. Int. Ed. 45 (2006) 819.
[4] M. Sone, T. Wada, B.R. Harkness, J. Watanabe, H. Takahashi, H.W.
Huang, T. Yamashita, K. Horie, Macromolecules 31 (1998) 8865.
[5] K. Rurack, U. Resch-Genger, J.L. Bricks, M. Spieles, Chem. Commun.
(2000) 2103.
[6] M.E. Vazquez, J.B. Blanco, B. Imperiali, J. Am. Chem. Soc. 127 (2005)
1300.
[7] E.V. Garcia-Baez, F.J. Martinez-Martinez, H. HoepX, I.I. Padilla-
Martinez, Cryst. Growth Des. 3 (2003) 35.
[8] J.A. Marsden, J.J. Miller, L.D. ShirtcliV, M.M. Haley, J. Am. Chem.
Soc. 127 (2005) 2464.
[9] I. Vaya, M.C. Jimenez, M.A. Miranda, Tetrahedron: Asymmetry 16
(2005) 2167.
[10] A. Islam, C.C. Cheng, S.H. Chi, S.J. Lee, P.G. Hela, I.C. Chen, C.H.
Cheng, J. Phys. Chem. B 109 (2005) 5509.
[11] G. Yu, S.W. Yin, Y.Q. Liu, J.S. Chen, X.J. Xu, X.B. Sun, D.G. Ma,
X.W. Zhan, Q. Peng, Z.G. Shuai, B.Z. Tang, D.B. Zhu, W.H. Fang, Y.
Luo, J. Am. Chem. Soc. 127 (2005) 6335.
[12] G.Q. Zhang, G.Q. Yang, L.Y. Yang, Q.Q. Chen, J.S. Ma, Eur. J. Inorg.
Chem. (2005) 1919.
[13] D.L. Reger, J.D. Elgin, R.F. Semeniuc, P.J. Pellechia, M.D. Smith,
Chem. Commun. (2005) 4068.
[14] S.K. Lee, Y. Zu, A. Herrmann, Y. Greets, K. Mullen, A.J. Bard, J. Am.
Chem. Soc. 121 (1999) 3513.
[15] A. Samanta, B. Ramachandram, G. Saroja, J. Photochem. Photobiol.
A 101 (1996) 29.
[16] B. Ramachandram, N.B. Sankaran, R. Karmakar, S. Saha, A.
Samanta, Tetrahedron 56 (2000) 7041.
[17] M. Lichhelli, A.O. Biroli, A. Poggi, D. Sacchi, C. Sangermani, M.
Zema, J.C.S. Dalton Trans. (2003) 4537.
[25] R. Dobwara, F. Wurthner, Chem. Commun. (2002) 1878.
[26] C. Tamuly, N. Barooah, A. Batsanov, R. Kataky, J.B. Baruah, Inorg.
Chem. Commun. 8 (2005) 689.
[27] B.-Q. Ma, L.F.V. Ferreieira, P. Coppens, Org. Lett. 6 (2004) 1087.
[28] S.-L. Zheng, P. Coppens, Cryst. Eng. Comm. 7 (2005) 289.
[29] S.-L. Zheng, P. Coppens, Cryst. Growth Des. 5 (2005) 2050.
[30] A. Bianchi, K. Bowman-James, E. Gracia-Espana (Eds.), Supramolec-
ular Chemistry of Anions, Wiley, New York, 1997.
[31] G.R. Desiraju (Ed.), Crystal Design: Structure and Function in Per-
spectives in Supramolecular Chemistry, vol. 7, John Wiley, Chiches-
ter, 2003.
[32] P.D. Gale, Coord. Chem. Rev. 213 (2001) 9.
[33] D. VanderVelde, D. Powell, K. Bowman-James, J. Am. Chem. Soc.
126 (2004) 12272.
[34] T. Gunnlaugsson, P.E. Kruger, P. Jensen, F.M. PfeVer, G.M. Hussey,
Tetrahedron Lett. 44 (2003) 8909.
[35] K. Kishikawa, S. Tsubokura, S. Kohmoto, M. Yamamoto, K. Yamgu-
chi, J. Org. Chem. 64 (1999) 7568.
[36] N. Barooah, R.J. Sarma, J.B. Baruah, Cryst. Growth Des. 3 (2003) 639.
[37] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond, IUCr Mono-
graphs on Crystallography 9, Oxford University Press, Oxford, 1999.
[38] X-Q. Lu, L. Zhang, C-L. Chen, C.-Y. Su, B.-S. Kang, Inorg. Chim.
Acta. 358 (2005) 1771.
[39] X-Q. Lu, L. Zhang, C.-L. Chen, C.-Y. Su, B.-S. Kang, S.W. Ng, Acta.
Crystal. Sec. E. 59 (2003) 1891.