Control of crystal structures of fluorescent two-component supramolecular systems by varying substituents and their positions

Article abstract of DOI:10.1039/c3ce42128g

Although fluorescent, column-like supramolecular network structures were previously obtained by using 2-naphthalenecarboxylic acid and benzylamine or fluorobenzylamine, the use of chlorobenzylamine or bromobenzylamine results in column-like or 2D-layered

Full text of DOI:10.1039/c3ce42128g

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Control of crystal structures of fluorescent
two-component supramolecular systems by
Cite this: CrystEngComm, 2014, 16,
varying substituents and their positions†
1741
Yuki Tanaka,a Hideyuki Tabata,b Nobuo Tajima,c Reiko Kurodab
a
*
and Yoshitane Imai
Received 22nd October 2013,
Accepted 5th December 2013
Although fluorescent, column-like supramolecular network structures were previously obtained by using
2-naphthalenecarboxylic acid and benzylamine or fluorobenzylamine, the use of chlorobenzylamine or
bromobenzylamine results in column-like or 2D-layered network supramolecular structures, indicating
that crystal structures can be controlled by altering the type and position of the substituent on the
benzylamine component.
DOI: 10.1039/c3ce42128g
www.rsc.org/crystengcomm
In this paper, we describe novel fluorescent supramolecu-
lar structures by combining 1 with six different benzylamine
Introduction
In solid-state chemistry, the chemical and physical properties
of organic materials depend on the packing arrangements of
component organic molecules.1 In other words, by changing
the packing arrangements of component molecules, the
chemical and physical properties of solid-state organic mate-
rials can be controlled without utilizing synthetic methods.
Recently, solid-state supramolecular organic fluorophores
with two or more components have attracted attention
because their optical properties can be easily controlled by
simply modifying the component molecules.2 We recently
reported supramolecular organic fluorophores composed of
2-naphthalenecarboxylic acid (1) and benzylamine and of
1 and fluorobenzylamine.3 These supramolecular organic
fluorophores are composed of column-like network structures
built by 1 and benzylamine or fluorobenzylamine.
derivatives (Chart 1). Specifically, we investigate the effects
of substituents and substituent position in benzylamine
derivatives on crystal structures and solid-state optical prop-
erties of two-component supramolecular systems. In this
study, four halogen-containing benzylamine derivatives were
investigated: 2-chlorobenzylamine (2), 3-chlorobenzylamine
(3), 2-bromobenzylamine (4), and 3-bromobenzylamine (5).
In addition, two methyl-substituted benzylamine deriva-
tives were also explored: 2-methylbenzylamine (6) and
3-methylbenzylamine (7). This study elucidates information
concerning the design of novel two-component supramo-
lecular organic fluorophores.
Experimental
In the field of solid-state chemistry, molecules containing
different substituents may lead to unique and specific chemi-
cal and physical properties of the solid-state material due to
changes in the crystal structure. Thus, we expect that by varying
the substituent in the components of 2-naphthalenecarboxylic
acid-based supramolecular organic fluorophores, the structures
and optical properties of the resulting supramolecular com-
plexes can be controlled. However, it is typically difficult to pre-
dict the crystal structures of novel two-component systems.
General
Compounds 2, 4, 5, and the crystallization solvent (methanol,
MeOH) were purchased from Wako Pure Chemical Industry
and used as received. This commercial solvent was used
a Department of Applied Chemistry, Faculty of Science and Engineering,
Kinki University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan.
E-mail: y-imai@apch.kindai.ac.jp
b Research Institute for Science and Technology, Tokyo University of Science,
2641 Yamazaki, Noda-shi, Chiba, 278-8510, Japan
c First-Principles Simulation Group, Computational Materials Science Center,
NIMS, Sengen, Tsukuba, Ibaraki 305-0047, Japan
† CCDC 965542–965547. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3ce42128g
Chart 1
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directly as obtained. Compounds 1, 3, 6, and 7 were pur-
chased from Tokyo Kasei Kogyo Co. and used as received.
c = 28.832(8) Å, β = 104.628(3)°, Z = 8, Dc = 1.260 g cm−3
,
V = 3093.4(14) Å3, μ(Mo Kα) = 0.081 mm−1, 7027 reflections
measured, 3124 unique reflections, final R(F2) = 0.0537 using
1631 reflections with I > 2.0σ(I), R (all data) = 0.1177,
T = 100(2) K. CCDC 965546.
Formation of complex by crystallization from solvent
Compounds 1 (10 mg, 5.8 × 10−5 mol) and 2 (or 3–7, 5.8 × 10−5 mol)
were dissolved in MeOH (3 mL) and left to stand at room tem-
perature. After one week, a large number of crystals were
obtained in all cases. The total weight of each crystal complex
obtained in one batch was: complex I for the 1–2 system (8 mg);
II for the 1–3 system (9 mg); III for the 1–4 system (7 mg);
IV for the 1–5 system (9 mg); V for the 1–6 system (9 mg); and
VI for the 1–7 system (8 mg).
Crystallographic data for VI (ref. 8). C11H8O2·C8H11N,
M = 293.35, monoclinic, space group P21/c, a = 15.604(4),
b = 6.2630(14), c = 15.601(4) Å, β = 90.680(3)°, Z = 4,
Dc = 1.278 g cm−3, V = 1524.5(6) Å3, μ(Mo Kα) = 0.083 mm−1
,
11 871 reflections measured, 4208 unique reflections, final
R(F2) = 0.0433 using 3501 reflections with I > 2.0σ(I),
R (all data) = 0.0526, T = 100(2) K. CCDC 965547.
Measurement of X-ray powder diffraction (XRPD) spectra
X-ray crystallographic studies of crystals4
X-ray powder diffraction (XRPD) patterns were recorded using
a Rigaku MiniFlex II with graphite-monochromated CuKα
radiation (30 kV, 15 mA). The spectra were measured at room
temperature between 5° and 35° in the 2θ scan mode with a
step size of 0.02° in 2θ and 40° min−1.
X-ray diffraction data for single crystals of I, II, and IV were
collected using BRUKER APEX. X-ray diffraction data for
single crystals of III, V, and VI were collected using RIGAKU
SATURN 70R. The crystal structures were solved using the
direct method5 and refined by full-matrix least-squares using
SHELX97.5 The diagrams were prepared using PLATON.6
Absorption corrections for I, II, and IV were performed using
SADABS.7 Absorption corrections for III, V, and VI were
performed using multi-scan. Nonhydrogen atoms were refined
with anisotropic displacement parameters, and hydrogen
atoms were included in the models in their calculated posi-
tions in the riding model approximation.
Measurement of solid-state fluorescence spectra
Solid-state fluorescence spectra and absolute photoluminescence
quantum yields were measured using an Absolute PL Quantum Yield
Measurement System (C9920-02, HAMAMATSU PHOTONICS K. K.)
under an air atmosphere at room temperature.
Crystallographic data for I. C11H8O2·C7H8ClN, M = 313.77,
monoclinic, space group C2/c, a = 18.671(2), b = 6.0403(6),
Results and discussion
c = 29.098(3) Å, β = 106.031(4)°, Z = 8, Dc = 1.322 g cm−3
,
The formation of fluorescent supramolecular systems was
attempted via crystallization from MeOH. First, chlorine-
containing supramolecular systems 1–2 and 1–3 were investi-
gated. A mixture of 1 and 2 (or 3) was dissolved in MeOH
and left to stand at room temperature. After one week, a large
number of colourless crystals I constructed from only 1 and 2
and colourless crystals II constructed from only 1 and 3
were obtained. Interestingly, although the previously reported
1–2-fluorobenzylamine (or 3-fluorobenzylamine) supramolec-
ular complex formed two types of crystal structures,3 in this
1–2 (or 3) system, only one type of crystal, I (or II), was
formed. As the size of the substituent on the benzylamine
component becomes larger, the difference in the stability of
two polymorphic crystals becomes greater. Therefore, we
hypothesize that when chlorine-containing compounds 2 and
3 were utilized in place of their corresponding fluorine-
containing derivatives, only one type of crystal was formed.
X-ray crystallography was utilized in order to investigate
the crystal structures of I and II. The crystal structures of I
and II are shown in Fig. 1 and 2, respectively.
V = 3154.0(6) Å3, μ(Mo Kα) = 0.248 mm−1, 8452 reflections
measured, 3107 unique reflections, final R(F2) = 0.0442 using
2667 reflections with I > 2.0σ(I), R (all data) = 0.0511,
T = 93(2) K. CCDC 965542.
Crystallographic data for II. C11H8O2·C7H8ClN, M = 313.77,
orthorhombic, space group Pbca, a = 10.5204(7), b = 8.7184(6),
c = 33.531(2) Å, Z = 8, Dc = 1.355 g cm−3, V = 3075.5(3) Å3,
μ(Mo Kα) = 0.255 mm−1, 17 697 reflections measured,
3610 unique reflections, final R(F2) = 0.0498 using 2827
reflections with I > 2.0σ(I), R (all data) = 0.0647, T = 93(2) K.
CCDC 965543.
Crystallographic data for III (ref. 8). C11H8O2·C7H8BrN,
¯
M = 358.23, triclinic, space group P1, a = 4.6370(18),
b = 11.658(4), c = 15.392(5) Å, α = 67.925(12)°, β = 82.161(15)°,
γ = 85.996(18)°, Z = 2, Dc = 1.558 g cm−3, V = 763.7(5) Å3,
μ(Mo Kα) = 2.698 mm−1, 5471 reflections measured, 3268
unique reflections, final R(F2) = 0.0645 using 2811 reflections
with I > 2.0σ(I), R (all data) = 0.0757, T = 100(2) K. CCDC 965544.
Crystallographic data for IV. C11H8O2·C7H8BrN, M = 358.23,
orthorhombic, space group Pbca, a = 10.6279(9), b = 8.7139(7),
c = 33.989(3) Å, Z = 8, Dc = 1.512 g cm−3, V = 3147.7(4) Å3,
μ(Mo Kα) = 2.618 mm−1, 17 795 reflections measured, 3586
unique reflections, final R(F2) = 0.0524 using 2312 reflections
with I > 2.0σ(I), R (all data) = 0.0913, T = 93(2) K. CCDC 965545.
Crystallographic data for V (ref. 8). C11H8O2·C8H11N, M = 293.35,
monoclinic, space group C2/c, a = 18.404(5), b = 6.0250(15),
X-ray analysis revealed that the stoichiometry of I is 1:2 = 1:1,
and the space group is C2/c. This complex has a column-like
hydrogen- and ionic-bonded network structure along the
b-axis (Fig. 1a and b). This column is formed by the carboxylate
oxygen of the carboxylic acid anion in 1 (Fig. 1, indicated in
blue) and the ammonium hydrogen of the protonated
amine in 2 (Fig. 1, indicated in green). The complex is formed
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structure along the a- and b-axes (Fig. 2a and b). This
2D-layered network structure is formed by the carboxylate
oxygen of the carboxylic acid anion in 1 (Fig. 2, indicated in blue)
and the ammonium hydrogen of the protonated amine in 3
(Fig. 2, indicated in green). The 2D-layered network structure
is maintained by intralayer naphthalene–naphthalene edge-
to-face interactions between the hydrogen atoms of the
naphthalene ring and the naphthalene ring in 1 [3.58 (C⋯π) Å,
indicated by the solid red arrow A in Fig. 2a] and CH–π inter-
actions between the hydrogen atom of the methylamine
group and the benzene ring in 3 [3.59 (C⋯π) Å, indicated by
the solid red arrow B in Fig. 2a].9,10 The self-assembly of this
2D-layered network structure (represented by a red dotted
border in Fig. 2c) with CCl–π (lone pair–π) interactions
between the chlorine atom in 3 and the naphthalene ring in
1 [3.59 (Cl⋯π) Å, indicated by the solid purple arrow C in
Fig. 2c] along the c-axis results in the formation of II
(Fig. 2c).9,10 These results suggest that in two-component
Fig. 1 Crystal structures of complex I. Components 1 and 2 are
indicated in blue and green, respectively. (a) Columnar hydrogen-bonded
and ionic-bonded network parallel to the b-axis. (b) View down the
b-axis. (c) Packing structure observed along the b-axis. Solid red arrows
A, B and C (or D) indicate intercolumnar naphthalene–naphthalene,
naphthalene–benzene, and benzene–naphthalene edge-to-face interac-
tions, respectively. The solid red arrow E indicates a halogen–halogen
interaction. The red dotted circle indicates column-like network structure.
by the assembly of a column-like structure (represented by a
red dotted circle in Fig. 1c). Each column interacts via inter-
columnar naphthalene–naphthalene edge-to-face interactions
between the hydrogen atoms of the naphthalene ring and the
naphthalene ring in 1 [3.42 (C⋯π) Å, indicated by the solid
red arrow A in Fig. 1c], naphthalene–benzene edge-to-face
interactions between the hydrogen atoms of the naphthalene
ring in 1 and the benzene ring in 2 [3.76 (C⋯π) Å, indicated
by the solid red arrow B in Fig. 1c], two benzene–naphthalene
edge-to-face interactions between the hydrogen atom of the
benzene ring in 2 and the naphthalene ring in 1 [3.45 and
3.59 Å, indicated by the solid red arrows C and D in Fig. 1c],
and a halogen–halogen interaction between the chlorine
atoms of the benzene rings in 2 [3.42 (Cl⋯Cl) Å, indicated by
the solid red arrow E in Fig. 1c].9,10
Fig. 2 Crystal structures of complex II. Components 1 and 3 are
indicated in blue and green, respectively. (a) Extracted 2D-layered net-
work structure observed along the a-axis. (b) View down the c-axis.
(c) Packing structure comprising the 2D-layered network structure
observed along the b-axis. Solid red arrows A and B show intralayer
naphthalene–naphthalene edge-to-face and CH–π interactions, respec-
tively. The solid purple arrow C indicates an interlayer CCl–π interaction.
The red dotted border indicates the 2D-layered network structure.
The crystal structure of II is shown in Fig. 2. Although the
stoichiometry of II is also 1 : 3 = 1 : 1, the space group is Pbca.
Interestingly, also in contrast to I, this crystal has a supramo-
lecular 2D-layered hydrogen- and ionic-bonded network
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supramolecular complexes containing 2-naphthalenecarboxylic
acid and benzylamine derivatives, the substituent and its posi-
tion on the benzylamine derivatives can dramatically alter the
complexation behaviour and resulting crystal structures.
Next, preparation of supramolecular complexes containing
bromobenzylamines 4 and 5 was attempted. Using the proce-
dure described previously, a supramolecular complex was
prepared via the complexation of 1 and 4 or 5. In 1–4- and
1–5-systems, one type of complex, III, composed of 1 and 4,
and IV, composed of 1 and 5, was obtained, respectively.
X-ray crystallography was utilized to analyze complexes III
and IV. The crystal structure of III is shown in Fig. 3. The
a-axis (Fig. 3a and b). In addition, this column-like structure
is maintained by one intracolumnar CH–π interaction
between the hydrogen atom of the methylamine group and
the benzene ring in 4 [3.37 (C⋯π) Å, indicated by the solid
red arrow A in Fig. 3a].9,10 The self-assembly of this column-
like structure (represented by a red dotted circle in Fig. 3c),
without any major intercolumnar interactions, results in the
formation of III (Fig. 3c).9,10
Comparison of I and III reveals the effect of substitution
with chlorine vs. bromine. Although the organization of
the column-like structures of I and III is similar, the
orientation of their two component molecules is different
(Fig. 1b and 3b). In addition, their packing styles are quite dis-
parate (Fig. 1c and 3c). In I, the two neighbouring face-to-face
naphthalene rings are independent when observed along
the b-axis (Fig. 1c). On the other hand, the neighbouring
face-to-face naphthalene rings in III are continuous when
¯
stoichiometry of III is 1 : 4 = 1 : 1, and the space group is P1.
Similar to I, complex III also has a column-like hydrogen-
and ionic-bonded network structure composed of 1 (Fig. 3,
indicated in blue) and 4 (Fig. 3, indicated in green) along the
Fig. 4 Crystal structures of complex IV. Components 1 and 5 are
indicated in blue and green, respectively. (a) Extracted 2D-layered
network structure observed along the a-axis. (b) View down the c-axis.
(c) Packing structure comprising the 2D-layered network structure
observed along the b-axis. Solid red arrows A and B show intralayer
naphthalene–naphthalene edge-to-face and CH–π interactions. The
solid purple arrow C indicates an interlayer CBr–π interaction. The red
dotted border indicates the 2D-layered network structure.
Fig. 3 Crystal structures of complex III. Components 1 and 4 are
indicated in blue and green, respectively. (a) Columnar hydrogen-
bonded and ionic-bonded network parallel to the a-axis. (b) View
down the a-axis. (c) Packing structure observed along the a-axis. The
solid red arrow A indicates an intracolumnar CH–π interaction. The red
dotted circle indicates column-like network structure.
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observed along the a-axis (Fig. 3c). Furthermore, the previously
reported supramolecular complexes of 1–2-fluorobenzylamine
resulted in two types of complexes: a chiral complex and a
complex with a 2 : 1 stoichiometry (1 : 2-fluorobenzylamine).3
This is in stark contrast to I and III, indicating that
in 2-naphthalenecarboxylic acid-containing supramolecular
complexes, the type of the substituent present on other com-
ponents has a drastic effect on the complexation behaviour
and crystal structures of the resulting complexes.
The crystal structure of IV is shown in Fig. 4. The
previously reported 1–3-fluorobenzylamine supramolecular
system also has two types of complexes. One of the com-
plexes is chiral and the stoichiometry of the other complex is
1 : 3-fluorobenzylamine = 2 : 1. The crystal structure of IV is
quite different from that of the 1–3-fluorobenzylamine com-
plex, but it is identical to that of II. The stoichiometry of
IV is 1 : 5 = 1 : 1 and the space group is Pbca. Compound IV
also has a supramolecular 2D-layered hydrogen- and ionic-
bonded network structure composed of 1 (Fig. 4, indicated in
blue) and 5 (Fig. 4, indicated in green) maintained by intra-
columnar naphthalene–naphthalene edge-to-face interactions
between the hydrogen atoms of the naphthalene ring and the
naphthalene ring in 1 [3.57 (C⋯π) Å, indicated by the solid
red arrow A in Fig. 4a] and CH–π interactions between the
hydrogen atom of the methylamine group and the benzene
ring in 5 [3.57 (C⋯π) Å, indicated by the solid red arrow B
in Fig. 4a] (Fig. 4a and b).9,10 The self-assembly of this
2D-layered network structure (Fig. 4c, represented by a dotted
red border) with CBr–π (lone pair–π) interactions between the
bromine atom in 5 and the naphthalene ring in 1 [3.68 (Br⋯π) Å,
indicated by the solid purple arrow C in Fig. 4c] along the
c-axis results in the formation of IV (Fig. 4c).9,10
In order to investigate the bulk-formation behaviour of
this supramolecular system, the X-ray powder diffraction
(XRPD) patterns of bulk crystals obtained from solution
were recorded in systems 1–2, 1–3, 1–4, and 1–5 and com-
pared to simulated XRPD patterns calculated from the
crystal structure data (Fig. 5).
As a result, in all systems, the XRPD patterns of bulk crys-
tals were the same as the simulated XRPD patterns calculated
from the crystal structure data. This shows that one type of
complex is obtained in systems 1–2, 1–3, 1–4, and 1–5.
Next, in order to further evaluate the effect of halogen-
containing substituents on complexation behaviour, two
methylbenzylamine derivatives, 6 and 7, were investigated
and compared to their halogen-containing benzylamine coun-
terparts, 2–5. Using the aforementioned procedure, a supra-
molecular complex was formed. In both 1–6- and 1–7-systems,
one type of complex for each system was obtained and is
denoted as V and VI, respectively. The crystal structures of
complexes V and VI are shown in Fig. 6 and 7.
The stoichiometries of complexes V and VI are identical:
1 : 6 (or 7) = 1 : 1. However, the space groups for the two com-
plexes are different: C2/c for V and P21/c for VI. Interestingly,
both V and VI have a columnar hydrogen- and ionic-bonded
network structure along the b-axis (Fig. 6a, b and 7a, b),
although VI uses a meta-substituted benzylamine derivative.
Specifically, the column-like network structure in VI is a
21-helical columnar network. In V and VI, although these
column-like structures are primarily formed by the carboxylate
Fig. 5 X-ray powder diffraction (XRPD) patterns of complexes I–IV. (a) Simulated XRPD patterns of I–IV from crystal structure data and (b) XRPD
patterns of complexes obtained by crystallization from solution.
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6 [3.73 (C⋯π) Å, indicated by the solid red arrow B in Fig. 6c];
and (3) benzene–naphthalene edge-to-face interactions between
the hydrogen atom of the benzene ring in 6 and the naphthalene
ring in 1 [3.42 Å, indicated by the solid red arrow C in
Fig. 6c].9,10 On the other hand, in VI, each column interacts via
intercolumnar naphthalene–naphthalene edge-to-face interac-
tions between the naphthalene rings in 1 [3.40 (C⋯π) Å, indi-
cated by the solid purple arrow C in Fig. 7c] and CH–π
interactions between the hydrogen atom of the methylene
group and the benzene ring in 7 [3.43 (C⋯…π) Å, indicated by
the solid purple arrow D, Fig. 7c], and the hydrogen atom of
the methylamine group and the benzene ring in 7.9,10 Although
the packing style of V is different from that of III, it is similar
Fig. 6 Crystal structures of complex V. Components 1 and 6 are
indicated in blue and green, respectively. (a) Columnar hydrogen-
bonded and ionic-bonded network parallel to the b-axis. (b) View
down the b-axis. (c) Packing structure observed along the b-axis. Solid
red arrows A, B and C indicate intercolumnar naphthalene–naphthalene,
naphthalene–benzene and benzene–naphthalene edge-to-face inter-
actions, respectively. The red dotted circle indicates column-like
network structure.
oxygen of the carboxylic acid anion in 1 (Fig. 6 and 7, indi-
cated in blue) and the ammonium hydrogen of the proton-
ated amine in 6 (or 7) (Fig. 6 and 7, indicated in green), the
21-helical column structure in VI is also maintained by
the intracolumnar naphthalene–benzene edge-to-face inter-
actions between the hydrogen atom of the naphthalene ring
in 1 and the benzene ring in 7 [3.61 (C⋯π) Å, indicated by
the solid red arrow A in Fig. 7b] and CH–π interactions
between the methyl group in 7 and the naphthalene ring in
1 [3.74 (C⋯π) Å, indicated by the solid red arrow B in Fig. 7b].9,10
Both complexes are formed by the assembly of these col-
umns. In V, each column interacts via three intercolumnar
interactions: (1) naphthalene–naphthalene edge-to-face interac-
tions between the naphthalene rings in 1 [3.37 (C⋯π) Å, indi-
cated by the solid red arrow A in Fig. 6c]; (2) naphthalene–
benzene edge-to-face interactions between the hydrogen
atoms of the naphthalene ring in 1 and the benzene ring in
Fig. 7 Crystal structures of complex VI. Components 1 and 7 are
indicated in blue and green, respectively. (a) Columnar hydrogen-
bonded and ionic-bonded network parallel to the b-axis. (b) View
down the b-axis. (c) Packing structure observed along the b-axis. Solid
red arrows
A and B indicate intracolumnar naphthalene–benzene
edge-to-face and CH–π interactions, respectively. Solid purple arrows
C and D indicate intercolumnar naphthalene–naphthalene edge-to-face
and CH–π interactions, respectively. The red dotted circle indicates
column-like network structure.
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Table 1 Crystal form and solid-state fluorescence spectral data of
complexes I–VIa
Acknowledgements
λem nm−1
ΦF
a
This study was supported by a Grant-in-Aid for Scientific
Research (no. 24550165) from the Ministry of Education,
Culture, Sports, Science and Development Program from JST
and the KDDI Foundation.
Complex
Crystal colour
Crystal shape
I
II
III
IV
V
Yellow
Block
Plate
Needle
Plate
Block
Block
348
352
ND
ND
350
350
0.12
0.09
Weak
Weak
0.28
Colourless
Colourless
Colourless
Colourless
Colourless
VI
0.10
Notes and references
a
Excitation wavelengths are 329, 339, 332, and 333 nm for
complexes I, II, V, and VI, respectively.
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to the packing style of I. On the other hand, the packing style
of VI is different from that of both I and III. These results sug-
gest that in 2-naphthalenecarboxylic acid-based supramolecu-
lar complexes, control of crystal structures may be influenced
not only by the size of the substituent on the benzylamine
derivative, but also by the halogen–π or CH–π interactions of
the substituent on the benzylamine derivative.
To investigate the solid-state optical properties of the
obtained supramolecular complexes I–VI, solid-state fluores-
cence spectra of these complexes were measured. The crys-
tal form and solid-state fluorescence spectral data of I–VI
are presented in Table 1. Although one important issue
involving solid-state organic fluorophores is fluorescence
quenching in the crystalline state, chlorine-containing com-
plexes I and II and methyl-containing complexes V and VI
exhibit fluorescence in the solid state. Bromine-containing
complexes III and IV did not exhibit fluorescence. This is
due to the heavy atom effect of bromine within the crystals.
The solid-state fluorescence maxima (λem) in complexes I,
II, V, and VI were not dramatically different. However, the
absolute value of the photoluminescence quantum yield
(ΦF) increases in ortho-substituted complexes as compared
to meta-substituted complexes. This might be explained
by the lesser degree of interactions with neighbouring
naphthalene units in the ortho-substituted complexes.
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Conclusions
Two-component fluorescent supramolecular organic com-
plexes were successfully created using 1 and chloro-, bromo-,
or methyl-substituted benzylamine derivatives. Supramolecu-
lar complexes utilizing ortho-substituted, halogen-containing
benzylamine derivatives are composed of column-like network
structures. In contrast, supramolecular complexes employing
meta-substituted, halogen-containing benzylamine derivatives
are composed of 2D-layered network structures. These two
types of crystal structures can be controlled by altering the
substituent type and its position on the benzylamine compo-
nent. In addition, 2-naphthalenecarboxylic acid-based supra-
molecular complexes show solid-state fluorescence when
complexed with chlorobenzylamine or methylbenzylamine.
These supramolecular systems are a substantial advancement
in the development of novel solid-state organic fluorophores.
This journal is © The Royal Society of Chemistry 2014
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6 A. L. Spek, PLATON, A Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, Netherlands, 2010.
7 G. M. Sheldrick, SADABS, Program for Empirical Absorption
Correction of Area Detector Data, University of Gottingen,
Germany, 1996.
4 Crystallographic table of complexes I–VI is shown in
Table ESI-1.†
8 Sufficient diffraction intensities could not be obtained
because the crystal size was too small.
5 G. M. Sheldrick, SHELXL97 Acta Crystallogr., Sect. A: Found.
Crystallogr., 2008, 64, 112–122.
9 It was determined using PLATON geometry calculation.
10 The details of interactions are shown in Table ESI-2–7.†
1748 | CrystEngComm, 2014, 16, 1741–1748
This journal is © The Royal Society of Chemistry 2014