Flexible Porous Coordination Polymers from Divergent Photoluminescent 4-Oxo-1,8-naphthalimide Ligands

Article abstract of DOI:10.1021/acs.inorgchem.6b02137

Two new luminescent ditopic naphthalimide-derived ligands, N-(4-cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphthalimide (L3) and N-(4-carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-naphthalimide (H₂L4), have been prepared, and their coordination chemistry has been explored in the synthesis of three new coordination polymer materials. Complex poly-[Ag(L3)₂]BF₄·4.5H₂O·0.5THF (1) is a 3-fold 2D → 2D parallel interpenetrated coordination polymer in which three interwoven sheets define inter- and intralayer channels containing anions and solvent molecules. Molecules of L3 interact in 1 through dominant head-to-head π-π stacking interactions, in an opposite aggregation mode to that observed in the free ligand in the crystalline phase. Complexes poly-[Cu(L4)(OH₂)]·2DMF·0.5H₂O (2) and poly-[Cd₂(L4)₂(OH₂)₂]·1.5DMF·3H₂O (3) are related noninterpenetrated two-dimensional coordination polymers defined by one-dimensional metal-carboxylate chains, forming layers that interdigitate with adjacent networks through naphthalimide π-π interactions. Both materials undergo structural rearrangements on solvent exchange with acetonitrile; in the case of 3, this transformation can be followed by single-crystal X-ray diffraction, revealing the structure of the acetonitrile solvate poly-[Cd₂(OH₂)₂(L4)₂]·2MeCN (4), which shows a significant compression of the primary channels to accommodate the solvent guest molecules. Both materials display modest CO₂ adsorption after complete evacuation, and the original expanded phases can be regenerated by reimmersion in DMF. The photophysical properties of each ligand and complex were also explored, which revealed variations in emission wavelength, based on solid-state interactions, including a notable shift in the fluorescence emission band of 3 upon structural rearrangement to 4.

Full text of DOI:10.1021/acs.inorgchem.6b02137

Article
pubs.acs.org/IC
Flexible Porous Coordination Polymers from Divergent
Photoluminescent 4‑Oxo-1,8-naphthalimide Ligands
Chris S. Hawes,*,† Kevin Byrne,‡ Wolfgang Schmitt,‡ and Thorfinnur Gunnlaugsson*,†
‡
†School of Chemistry and Trinity Biomedical Sciences Institute (TBSI) and School of Chemistry and Centre for Research on
Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
S
* Supporting Information
ABSTRACT: Two new luminescent ditopic naphthalimide-derived
ligands, N-(4-cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphthali-
mide (L3) and N-(4-carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-
naphthalimide (H2L4), have been prepared, and their coordination
chemistry has been explored in the synthesis of three new coordination
polymer materials. Complex poly-[Ag(L3)2]BF4·4.5H2O·0.5THF (1) is a
3-fold 2D → 2D parallel interpenetrated coordination polymer in which
three interwoven sheets define inter- and intralayer channels containing
anions and solvent molecules. Molecules of L3 interact in 1 through
dominant head-to-head π−π stacking interactions, in an opposite
aggregation mode to that observed in the free ligand in the crystalline phase. Complexes poly-[Cu(L4)(OH2)]·2DMF·
0.5H2O (2) and poly-[Cd2(L4)2(OH2)2]·1.5DMF·3H2O (3) are related noninterpenetrated two-dimensional coordination
polymers defined by one-dimensional metal−carboxylate chains, forming layers that interdigitate with adjacent networks through
naphthalimide π−π interactions. Both materials undergo structural rearrangements on solvent exchange with acetonitrile; in the
case of 3, this transformation can be followed by single-crystal X-ray diffraction, revealing the structure of the acetonitrile solvate
poly-[Cd2(OH2)2(L4)2]·2MeCN (4), which shows a significant compression of the primary channels to accommodate the
solvent guest molecules. Both materials display modest CO2 adsorption after complete evacuation, and the original expanded
phases can be regenerated by reimmersion in DMF. The photophysical properties of each ligand and complex were also explored,
which revealed variations in emission wavelength, based on solid-state interactions, including a notable shift in the fluorescence
emission band of 3 upon structural rearrangement to 4.
imparted by other mechanisms, such as reorientation of the
metal coordination environment, by reorientation of inter-
penetrated networks, or by interlayer rearrangements of two-
dimensional materials.8
INTRODUCTION
■
The study of functional coordination polymer materials has
been a consistent highlight in materials chemistry since the first
reports of rationally designed extended coordination networks
in the early 1990s.1 Since then, enormous progress has been
made in designing and understanding the properties of
coordination polymer materials.2 A particular area of interest
is flexible, structurally responsive materials, in which “breath-
ing” processes can take place upon an external stimulus, often
involving guest exchange.3 Such materials have been widely
explored for gated adsorption processes and can often display
fascinating structural properties.4 A recent example reported by
Kaskel et al. showed the unexpected and rapid desorption of
guest molecules following a pressure-dependent structural
rearrangement upon guest uptake.5 In principle, framework
flexibility can be employed to enhance the adsorption selectivity
for particular analytes, an important consideration for sensing
applications where such behavior is coupled with a signaling
mechanism.6 Framework flexibility can be achieved in several
ways. Ligands containing flexible backbone groups are often
employed, to allow for low-energy structural rearrangements
based on alterations of the bridging geometry between metal
ions, although this approach can lead to materials that undergo
irreversible collapse on evacuation.7 Flexibility can also be
The 1,8-naphthalimide skeleton has been widely employed in
supramolecular chemistry as a photoactive scaffold that can be
readily functionalized with metal binding sites or incorporated
into supramolecular architectures.9 The presence of an
electron-donating group in the 3- or 4-position, typically an
amine group, provides a green-emitting fluorophore with good
photochemical stability and good to excellent quantum yields.10
Such systems have been used to great effect as fluorescent
sensors and probes for ions and biomolecules, as well as in
cellular imaging applications,11 and in the generation of
intriguing supramolecular assemblies.12 Although somewhat
more amenable to larger scale syntheses with a broad scope of
substitution patterns, relatively fewer studies have reported the
properties of 4-oxo-1,8-naphthalimides13 The emission proper-
ties of these compounds are similar to the amino derivatives,
albeit with higher energy of absorption and smaller Stokes
shifts, owing to a decrease in the π-donor capabilities of the
Received: September 4, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
alkoxy or phenolic substituents, as recently demonstrated by
Thilagar and co-workers.14 Although the coordination chem-
istry of many monotopic naphthalimide derivatives has been
well studied,15 few examples are known of naphthalimide
ligands containing divergent coordinating groups for the
synthesis of photoactive coordination polymer materials. This
discrepancy is particularly striking given the wealth of
fascinating extended networks that have been reported
containing the more synthetically facile 1,4,5,8-naphthalenete-
tracarboxylic diimide core.16 Here we report the synthesis of
two divergent 4-oxo-1,8-naphthalimide-derived ligands, their
photophysical properties, and their use in generating novel
luminescent and guest-responsive coordination polymer
materials. To the best of our knowledge, these are the first
examples of coordination polymers derived from ligands
containing the versatile 4-oxo-1,8-naphthalimide core.
organic compounds were confirmed using the standard
methods (see full details in the Experimental Section and the
Supporting Information).
Single crystals of L3 were prepared by recrystallization from
hot ethyl acetate and were analyzed by single-crystal X-ray
diffraction. The diffraction data were solved and the structure
was refined in the triclinic space group P1, providing a model
̅
containing one complete molecule of L3 in the asymmetric unit
with no additional solvent or guest molecules. The two phenyl
rings of L3 adopt the expected non-coplanar orientation with
respect to the central naphthalimide unit by virtue of rotation
about the methylene and oxo spacers, and the resulting anti
orientation of the terminal nitrile groups leads to a separation
between the nitrile nitrogen atoms of 19.085(3) Å. A simple
numerical representation of the conformation of L3 can be
given by the dihedral angle C5−C8−O3−C21, the rotation of
the two ipso carbon atoms of the two outer phenyl rings about
the vector between the two flexible linking atoms, equal to
120.4(2)°. A slight deformation from planarity is evident in the
imide group, leading to a dislocation of 0.31 Å for methylene
carbon atom C8 from the naphthalimide mean plane. The
structure of L3 is shown in Figure 1.
RESULTS AND DISCUSSION
■
Synthesis of L3 and H2L4 and X-ray Crystal Structure
of L3. The synthesis of the ligands L3 and H2L4 is outlined in
Scheme 1. The starting materials L1 and HL2 were each
a
Scheme 1. Synthesis of L1−H2L4
a
Numbering scheme for 1H NMR shown in red. Reagents and
conditions: (i) 4-aminomethylbenzonitrile, HOAc, 120 °C, 6 h; (ii) 4-
aminomethylbenzoic acid, HOAc, 120 °C, 6 h; (iii) 4-cyanophenol,
K2CO3, DMSO (Ar), 110 °C, 3 h; (iv) 4-hydroxybenzoic acid, K2CO3,
DMSO (Ar), 120 °C, 3 h.
Figure 1. (Top) Structure of L3 with partial atom-labeling scheme.
The atoms C5−C8−O3−C21 used to define the torsional behavior of
the ligand in this and the following structures are labeled in blue.
(Bottom) Intermolecular π−π interactions between naphthalimide
groups in the structure of L3, with hydrogen atoms omitted for clarity.
prepared by condensation of the commercially available 4-nitro-
1,8-naphthalic anhydride with the appropriate amine in glacial
acetic acid at 120 °C. In both cases, the final products L3 and
H2L4 were prepared by displacement of the electron-deficient
aromatic nitro group by an appropriate phenolate under basic
conditions in DMSO solution. The reaction of L1 with 4-
cyanophenol in DMSO gave L3 as an off-white powder in an
overall 69% yield (two steps), while the reaction of 4-
hydroxybenzoic acid with HL2 afforded H2L4 in an overall
yield of 71% over two steps. The identity and purity of all
Intermolecular interactions in the structure of L3 are
dominated by parallel offset face-to-face π−π interactions,
which align the naphthalimide groups into head-to-tail stacks
oriented parallel to the crystallographic b axis. The minimum
interatomic distance for these interactions is 3.560(3) Å (C18−
C12), with the mean interplanar distance of 3.35 Å indicative of
a strong π−π interaction. The two unique cyanophenyl groups
B
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
that extend outward from these columns associate into loosely
packed layers in the ab plane with only minor π−π overlap
between nearby groups.
are occupied by an additional two interpenetrating networks,
providing an uncommon 3-fold 2D → 2D parallel inter-
penetrated structure, as demonstrated in Figure 3. The
Structure of Poly-[Ag(L3)2]BF4·4.5H2O·0.5THF, 1. The
soft Lewis-basic nature of the donor sites in L3 prompted the
use of a compatible metal cation to study the coordination
chemistry of the system, and the silver(I) ion was selected
based on its lability and affinity for nitrile donor ligands.17
Crystals of poly-[Ag(L3)2]BF4·4.5H2O·0.5THF (1) were
prepared by combining solutions of L3 and silver tetrafluor-
oborate in THF, giving colorless crystals after standing in the
dark for 48 h. Analysis by single-crystal X-ray diffraction
provided a structure model in the monoclinic space group C2/c.
The asymmetric unit of complex 1 contains one molecule of L3
and one silver ion occupying a crystallographic special position.
Charge balance requirements mandate the presence of half of
one tetrafluoroborate anion per asymmetric unit; this anion was
poorly localized, but was modeled over two representative
positions (Supporting Information). The silver ion within the
structure of 1 is coordinated by four nitrile groups from
symmetry-related L3 species and adopts a regular tetrahedral
geometry with all N−Ag−N angles in the range 102.4(2)−
118.21(13)°, as shown in Figure 2. The two unique Ag−N
Figure 3. Interpenetration mode of complex 1 with independent
networks colored separately, showing π−π interactions between three
interpenetrated networks around a single channel (top) and overall
two-dimensional structure of the assembly (bottom).
interwoven networks interact through robust parallel offset
face-to-face π−π interactions with an unusual head-to-head
alignment of adjacent naphthalimide groups enforced by the
directionality of the individual networks. The mean interplanar
distance of these interactions of 3.34 Å and minimum
interatomic distance of 3.282(4) Å (C9−C18) are consistent
with the strong π−π interactions observed in the structure of
the free ligand, albeit with an inverted orientation. Two sets of
one-dimensional channels oriented parallel to the a axis are
present within the extended structure of 1, within which reside
the poorly localized tetrafluoroborate anions, and lattice solvent
molecules. The three interwoven networks encapsulate a series
of narrow, helical intralayer channels, while the offset stacking
of adjacent layers defines slightly larger interlayer channels. The
combined volume of the two channels, containing both anions
and solvent molecules, accounts for approximately 29% of the
unit cell volume, divided approximately 3:2 in favor of the
interlayer channels. Microanalysis on an air-dried sample
suggested a solvation of 4.5 water molecules and 0.5 THF
molecule per [Ag(L3)2]BF4 repeat unit. This assignment is in
agreement with thermogravimetric analysis data (Supporting
Information), which shows the slow loss of 9.4 wt % below 170
°C (calculated 10.0% for 4.5 H2O, 0.5 THF), before the onset
of decomposition at approximately 250 °C. The relatively high
temperature of desolvation is most likely indicative of pore
blocking by the delocalized tetrafluoroborate anions, preventing
free exchange of solvent molecules throughout the narrow
anion/solvent channels. Attempts to perturb these solvent
molecules by soaking in acetonitrile or in 1,4-dioxane led to
destruction of the framework, most likely due to the well-
known coordinative lability of the AgI ion.
Figure 2. (Top) Ligand geometry and coordination environment in
the structure of 1. (Bottom) Extended structure of a single network in
1 viewed perpendicular to the two-dimensional sheet. Hydrogen atoms
and anions are omitted for clarity. Symmetry codes used to generate
equivalent atoms: (i) −x−3/2, y−1/2, + z; (ii) x−3/2, y−1/2, + z;
(iii) −x, +y, 3/2−z.
bond lengths of 2.261(4) and 2.241(3) Å for the oxo- and
methylene-linked benzonitrile groups, respectively, are within
the typically observed values for silver−nitrile interactions from
polynitrile donors in coordination polymers.17 The L3 species
adopts a similar orientation of the nitrile groups to that
observed in the structure of the free ligand, although with the
dihedral angle C5−C8−O3−C21 of 94.7(4)° lessened
compared to L3 itself. As a result, the separation between the
terminal nitrile nitrogen atoms is contracted to 17.506(5) Å,
giving a Ag···Ag distance of 20.7936(16) Å.
The extended structure of 1 comprises a two-dimensional
(4,4) network propagated in the ac plane, with four-connected
silver ions linked by bridging L3 molecules into an undulated
layer. Each individual network of 1 contains large windows
oriented perpendicular to the direction of propagation, which
Structure of Poly-[Cu(L4)(OH2)]·2DMF·0.5H2O, 2. In
order to explore the coordination chemistry of the carboxylic
acid-functionalized ligand H2L4, reactions were carried out with
divalent d-block metal ions copper(II) and cadmium(II), on the
basis of high Lewis acidity of the d9 species and the lack of
interference with ligand fluorescence processes from the d10
species. The reaction of H2L4 with copper nitrate trihydrate in
C
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a 5:95 H2O/DMF solvent mixture at 100 °C for 4 h gave light
green crystals, which were isolated and analyzed by single-
crystal X-ray diffraction. The diffraction data were solved and
molecule adopts a similar conformation to that of L2 in
complex 1, with a dihedral angle C5−C8−O5−C21 of
97.3(4)°, Figure 4.
refined in the triclinic space group P1, with the asymmetric unit
The extended structure of 2 is defined by one-dimensional
columns of carboxylate- and aqua-bridged CuII ions oriented
parallel to the a axis, which are linked in the c direction by L4
ligands. The resulting two-dimensional layer contains one-
dimensional intralayer channels parallel to a and bordered by
the naphthalimide groups of L4, which are oriented
approximately perpendicular to the channel axis. One of the
two unique lattice DMF molecules is localized within these
channels, displaying slight rotational disorder. Unlike the case
of complex 1, in which similar layers undergo parallel 2D → 2D
interpenetration through π−π interactions, adjacent layers in
complex 2 associate in the c direction, without interpenetration
but instead through interdigitation of the naphthalimide groups.
The resulting π−π interactions, with 180° head-to-tail
geometry, are parallel with mean interplanar distances of 3.32
and 3.30 Å and minimum interatomic distances of 3.383(6) Å
(C10−C16) and 3.468(6) Å (C18−C14), respectively, for the
two unique interactions. As well as the intralayer channels,
linkage of adjacent networks through naphthalimide π−π
interactions leaves additional interlayer solvent channels parallel
to the a axis and bordered by the metal−carboxylate chains.
Within these channels, a well-resolved DMF molecule is
observed; this molecule participates in a hydrogen-bonding
interaction with the aqua ligand, at a D···A distance of 2.625(4)
Å and D−H···A angle of 170(6)° for O8−H8D···O9. These
channels are rhombic in shape, with approximate interatomic
dimensions of 9 × 9 Å, compared to the slit-shaped intralayer
channels, in which the DMF molecules occupy bound volumes
of dimensions of ca. 5 × 10 Å, as shown in Figure 5.
̅
containing one molecule of fully deprotonated L4, two unique
CuII ions residing on crystallographic special positions, one
aqua ligand, and two noncoordinating DMF molecules with
slight crystallographic disorder on one site. Both copper ions
adopt Jahn−Teller distorted tetragonal coordination geo-
metries, albeit with varying degrees of axial coordination.
Copper ion Cu1 is coordinated in the equatorial plane by two
carboxylate oxygen atoms and two aqua ligands in a trans
orientation, with Cu−O distances of 1.939(3) Å for carboxylate
and 1.929(3) Å for aqua donors. The axial positions are
occupied by weakly interacting carboxylate oxygen atom O2, at
a Cu−O distance of 2.836(3) Å. Copper ion Cu2 is
coordinated by four carboxylate oxygen atoms in the equatorial
plane, at Cu−O distances of 1.955(3) and 1.941(2) Å for O2
and O6, respectively, while the axial positions are involved in a
weak interaction with the strongly bound aqua ligand of the
adjacent Cu1 site, at a Cu−O separation of 2.499(3) Å. The
metal site environment of 2 is shown in Figure 4. The L4
Figure 4. Ligand geometry (top) and metal coordination and
hydrogen-bonding environment (bottom) in the structure of 2.
Hydrogen bonds are shown as green dashed lines, and long Cu−O
interactions along the Jahn−Teller axes are shown as blue dashes.
Hydrogen atoms not participating in hydrogen bonding and additional
lattice solvent molecules are omitted for clarity. Symmetry codes used
to generate equivalent atoms: (i) +x, +y, z−1.
Figure 5. Extended structure of 2, showing the connectivity of a single
layer (top) and interdigitation of two adjacent layers, with
independent networks colored separately (bottom). Hydrogen atoms
and lattice solvent molecules are omitted for clarity.
molecule within the asymmetric unit interacts with four metal
sites through a bridging carboxylate functionality. The
carboxylate group of the oxo-benzoate arm coordinates in a
μ2-κO:κO′ mode to Cu1 and Cu2, while the other carboxylate
group bridges two metal ions through the same oxygen atom,
coordinating to an equatorial position of the Cu2 coordination
sphere and weakly interacting at the axial position of the Cu1
site. The noncoordinating carboxylate oxygen atom from this
group participates in a hydrogen-bonding interaction with the
aqua ligand, with a donor−acceptor distance of O8···O1
2.560(4) Å and D−H···A angle of 173(7)°. The ligand
Microanalysis suggested the presence of an additional water
molecule per two copper sites, presumably facilitated by the
disordered orientation of the intralayer DMF molecule and
providing a formula for the bulk material of poly-[Cu(L4)-
(OH2)]·2DMF·0.5H2O. Thermogravimetric analysis of 2
revealed a two-step mass loss of 21.2% within the range of
30−250 °C, consistent with the loss of the noncoordinating
solvent molecules (calculated 22%), with the onset of
decomposition above 300 °C.
D
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Structure of Poly-[Cd2(OH2)2(L4)2]·1.5DMF·H2O, 3. The
reaction of H2L4 with cadmium nitrate in a 5:95 H2O/DMF
solvent mixture gave colorless rod crystals after 24 h at 100 °C,
which were analyzed by single-crystal X-ray diffraction, and
from which a structure model was generated in the
orthorhombic space group Pccn. The asymmetric unit of 3
contains one molecule of L4, fully deprotonated, and two
unique cadmium ions. Both cadmium ions adopt six-coordinate,
distorted octahedral coordination geometries, and both occupy
crystallographic special positions. Cadmium ion Cd1 is
coordinated by two equivalent chelating carboxylate groups,
which bridge Cd1 and Cd2 in a μ2-κO,O′:κO coordination
mode, and the remaining two cis-oriented coordination sites are
occupied by carboxylate oxygen atoms from a bridging μ2-
κO:κO′-disposed carboxylate group, as shown in Figure 6.
Figure 7. Extended structure of 3 showing the interdigitation between
two adjacent layers, viewed parallel (top) and perpendicular (bottom)
to the one-dimensional solvent channels, with independent networks
colored separately. Hydrogen atoms and lattice solvent molecules are
omitted for clarity.
Figure 6. Ligand environment (top) and metal coordination
environment (bottom) in the structure of 3 with partial heteroatom
labeling scheme. Hydrogen atoms and lattice solvent molecules are
omitted for clarity. Symmetry codes used to generate equivalent
atoms: (i) x−1/2, 2−y, 3/2−z.
modeled at half-occupancy, which lie nearly flat along the
long axis of the rhombic channels. Reminiscent of the extended
structure of 2, adjacent layers in the structure of 3 associate
through head-to-tail interdigitation of the naphthalimide groups
(Figure 7), forming strong parallel face-to-face π−π interactions
at a mean interplanar distances of 3.37 and 3.38 Å for the two
unique interactions. Microanalysis revealed a formula for the
air-dried sample of 0.75 DMF molecule and 1.5 water
molecules per cadmium ion, although thermogravimetric
analysis of a freshly isolated sample shows a total mass loss
of 16% between 30 and 160 °C with onset at room temperature
(calculated 12.5%), consistent with partial desolvation occur-
ring upon standing in ambient conditions.
Solvent Exchange Studies and Structure of Poly-
[Cd2(OH2)2(L4)2]·2MeCN, 4. The presence of contiguous
solvent-accessible volumes in both 2 and 3 prompted an
investigation into the guest exchange properties of each
compound. Acetonitrile was chosen as the exchange solvent,
as a relatively volatile guest that can readily exchange with
lattice DMF and water molecules, but is unlikely to disrupt the
coordination sites leading to collapse of the structure. In the
case of compound 2, acetonitrile exchange efficiently removed
all lattice solvent molecules, confirmed by thermogravimetric
analysis (TGA), and provided a material that could be readily
desolvated at 100 °C. X-ray powder diffraction showed that
although the exchanged material was crystalline, a transition to
another crystalline phase had taken place (Supporting
Information). Despite our efforts, we were unable to effect
Cadmium ion Cd2 is coordinated by four monodentate
carboxylate oxygen atoms, each of which undergoes the
previously described bridging mode, and two cis-oriented
oxygen atoms from aqua ligands. Each L4 molecule coordinates
to four cadmium ions, and the torsion angle C5−C8−O3−C21
of 90.4(11)° compares closely to that observed in the other
complexes. Each of the seven unique Cd−O distances fall in the
range 2.222(10)−2.362(7) Å, and both ions display moderate
distortion from ideal octahedral geometry (∑ = 153° and 73°
for Cd1 and Cd2, respectively),18 with a smaller value for Cd2
consistent with the entirely monodentate coordination sphere.
The extended structure of 3 is a two-dimensional sheet
consisting of one-dimensional cadmium−carboxylate chains
oriented parallel to the crystallographic b axis, which are linked
in the a direction by the bridging L4 groups. Similarly to the
case of 2, one-dimensional channels remain both within the
sheets and between adjacent layers, as shown in Figure 7. The
intralayer channels are of a comparable size and shape to those
in 2, containing cavities of approximately 5 × 10 Å and
bounded in the b direction by the intruding edges of the
perpendicular-oriented naphthalimide rings. The interlayer
channels are also of comparable dimensions to those observed
in 2, being approximately square with minimum interatomic
distances of ca. 9 × 9 Å. Although the contents of the interlayer
channels could not be crystallographically modeled, the
intralayer channels contain well-resolved DMF molecules
E
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 1. Summary of Crystal and Refinement Parameters for All Compounds
identification code
L3
C27H15N3O3
1
2
3
4
empirical formula
fw
C54H30AgBF4N6O6
1053.52
C33H31CuN3O10
693.15
C57H37Cd2N3O17
C29H18CdN2O8
634.85
100(2)
orthorhombic
Pccn
429.42
1260.69
temp/K
cryst syst
space group
a/Å
100(2)
100(2)
100(2)
100(2)
monoclinic
P21/c
monoclinic
C2/c
triclinic
orthorhombic
P1
Pccn
̅
10.4422(10)
6.8590(7)
29.249(3)
90
4.4466(4)
39.390(3)
31.168(2)
90
6.8306(9)
10.7920(13)
20.523(3)
88.621(3)
88.801(3)
80.851(3)
1492.9(3)
2
37.4447(10)
40.5139(15)
7.2658(3)
18.5724(8)
90
b/Å
7.3470(2)
c/Å
23.1978(6)
α/deg
90
β/deg
95.909(2)
90
90.755(2)
90
90
90
γ/deg
volume/Å3
90
90
2083.8(4)
4
5458.7(8)
4
6381.9(3)
5467.1(4)
8
Z
4
ρcalcg/cm3
μ/mm−1
F(000)
cryst size/mm3
radiation
1.369
1.282
1.542
1.312
1.543
0.091
0.434
0.799
0.73
0.852
888
2128
718
2528
2544
0.37 × 0.11 × 0.05
Mo Kα (λ = 0.71073)
3.922 to 54.972
0.28 × 0.1 × 0.05
Mo Kα (λ = 0.71073)
2.446 to 53
0.08 × 0.05 × 0.05
Mo Kα (λ = 0.71073)
3.824 to 52.17
0.23 × 0.21 × 0.08
Mo Kα (λ = 0.71073)
3.512 to 50.998
0.23 × 0.06 × 0.05
Mo Kα (λ = 0.71073)
4.022 to 52
2θ range for data
collection/deg
index ranges
−13 ≤ h ≤ 10, −8 ≤ k ≤ −5 ≤ h ≤ 5, −46 ≤ k ≤ −8 ≤ h ≤ 8, −13 ≤ k ≤ 9, −45 ≤ h ≤ 29, −8 ≤ k ≤ −46 ≤ h ≤ 49, −8 ≤ k ≤
8, −37 ≤ l ≤ 37 48, −39 ≤ l ≤ 35 −25 ≤ l ≤ 25 5, −28 ≤ l ≤ 28 8, −22 ≤ l ≤ 22
reflns collected
indep reflns
37 208 29 855 21 338 51 379 33 987
4762 [Rint = 0.0989, Rsigma 5684 [Rint = 0.0820, Rsigma 5934 [Rint = 0.0995, Rsigma 5936 [Rint = 0.0813, Rsigma 5366 [Rint = 0.1080, Rsigma
= 0.0633]
= 0.0742]
= 0.1133]
= 0.0440]
= 0.0911]
data/restraints/
params
4762/0/298
5684/135/393
5934/16/462
5936/139/382
5366/70/418
goodness-of-fit on
1.005
1.078
0.982
1.075
1.023
F2
final R indexes [I ≥ R1 = 0.0515, wR2 = 0.1001 R1 = 0.0764, wR2 = 0.2132 R1 = 0.0516, wR2 =
2σ(I)] 0.1037
R1 = 0.1183, wR2 = 0.3186 R1 = 0.0891, wR2 = 0.1929
R1 = 0.1553, wR2 = 0.3496 R1 = 0.1847, wR2 = 0.2357
final R indexes [all R1 = 0.1169, wR2 = 0.1203 R1 = 0.1148, wR2 = 0.2352 R1 = 0.1177, wR2 =
data]
0.1229
largest diff peak/
0.21/−0.28
1.00/−0.69
0.62/−0.63
4.51/−3.14
0.77/−1.30
hole/e Å−3
this transformation on crystals of sufficient quality for single-
crystal X-ray diffraction analysis. The equivalent treatment of
compound 3 with acetonitrile produced similar results;
exchange of the labile lattice DMF molecules from the solvent
channels was observed by TGA, while X-ray powder diffraction
analysis of the exchanged material showed a new crystalline
phase. However, in contrast to 2, this phase was formed with
sufficient retention of crystallinity to allow structure determi-
nation by single-crystal X-ray diffraction, although with
significant disorder in the vicinity of the metal sites.
The X-ray diffraction data for 4 were solved and refined in
the orthorhombic space group Pccn, equivalent to 3. The unit
cell volume of 4 is contracted by ca. 15% from 3, mostly
manifested by a contraction of c from 23.1978(6) Å to
18.5724(8) Å, with a smaller concurrent increase in a from
37.4447(10) Å to 40.5139(15) Å, as summarized in Table 1.
The asymmetric unit of 4 contains one molecule of L4,
coordinating in an equivalent bridging mode to that in 3 to two
unique cadmium sites, although with crystallographic disorder
necessitating the splitting of cadmium ion Cd2 into two
symmetry-related half-occupancy locations on either side of the
previously occupied special position. The torsion angle C5−
C8−O5−C21 of 114.9(10)°, compared to 90.4(11)°, is
indicative of a conformational change in the L4 environment
and an overall flattening of the molecule, which is primarily
manifested by a rotation of the imide-bound carboxyphenyl
group, as shown in Figure 8. Notably, whereas compound 3
contained well-localized lattice DMF molecules within the
intralayer channels, compound 4 contains one acetonitrile
molecule at full occupancy per L4 group. The coordinating
aqua ligands and lattice solvent from the interlayer channels in
4 displayed substantial disorder, related to the disorder present
on the metal sites themselves, and as a result, the
noncoordinating solvent molecules from these channels could
not be crystallographically resolved.
The effect of the solvent exchange and framework
contraction in 4 is clear when the extended structure is
considered. The two-dimensional layers in the ab plane are
substantially contracted in thickness along c when compared to
compound 3, with reduction in the size of both the intra- and
interlayer solvent channels. This observation is consistent with
replacement of the comparatively sterically encumbering DMF
molecules in the intralayer channels with the more compact
acetonitrile guests, which can be more effectively encapsulated
by the contracted naphthalimide walls in 4. Although the π−π
stacking interactions between sheets are retained in 4, with
definite head-to-tail arrangement of the naphthalimide groups,
slight variations are present in the mean (naphthyl−naphthyl)
interplanar distances (3.434(7) and 3.384(5) Å, compared to
3.372(7) and 3.384(10) Å for 3) and the distance between
adjacent naphthyl centroids in each interaction (3.572(5) and
4.173(6) Å for 4 and 3.589(6) and 4.308(7) Å for 3).
F
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 9. CO2 adsorption isotherms for compounds 2 and 4,
measured at 273 K after soaking in acetonitrile and activation under
dynamic vacuum at 373 K overnight.
the material after adsorption, though not resembling the
original phase or the acetonitrile-exchanged material, suggesting
a further structural change takes place upon complete
evacuation.
Compound 4 displayed a similar maximum uptake to
compound 2, of 29 cc(STP)/g at 1 bar (5.4 wt %). The
higher density of the cadmium-containing framework, however,
means this value correlates to a marginally higher per-mole
CO2 loading of 0.85 molecule of CO2 per [Cd(L4)(OH2)]
repeat unit, which approaches the loading of (crystallo-
graphically resolved) lattice acetonitrile in 4. Similar to the
case of 2, X-ray powder diffraction of compound 4 after gas
adsorption experiments showed that the material retained some
degree of crystallinity, although with variation in peak positions
consistent with an additional structural rearrangement. In both
cases, however, the solvent-exchanged and evacuated materials
could be reimmersed in DMF to regenerate the original DMF-
solvated phases, as evidenced by X-ray powder diffraction
(Supporting Information).
Figure 8. Comparison of the structures of 3 and 4. (Top) Ligand
conformation in 3 (red) and 4 (blue), overlaid using the rigid
naphthalimide groups as anchor points. (Bottom) To-scale compar-
ison of the unit cells of 3 (top) and 4 (bottom), viewed along the
[010] vector, with a horizontal and c vertical. Hydrogen atoms and
oxo-benzoate ring torsional disorder are omitted for clarity.
Gas Adsorption Studies. Both compounds 2 and 3/4
were examined for their gas uptake properties. In both cases,
the noncoordinating lattice solvents were exchanged by soaking
the materials in acetonitrile for 48 h (in the process, necessarily
converting compound 3 to compound 4), followed by
evacuation at 100 °C overnight under dynamic vacuum. Due
to the very narrow and polar pore environments in both
samples, it was envisaged that CO2 would be the most
appropriate probe gas, where low-temperature N2 uptake is
typically very low for ultramicroporous materials.19 Indeed, no
meaningful 77 K N2 or H2 physisorption could be measured for
compound 3 or 4 in the micropore-filling pressure range, with
any adsorption taking place at or below the instrumental
detection limit. However, both compounds displayed moderate
CO2 adsorption in the pressure range 0−1 bar, albeit with slow
kinetics particularly in the low-pressure region, accompanied by
hysteresis on the desorption branch indicative of a slow
desorption process. The CO2 adsorption isotherms for 2 and 4
are shown in Figure 9.
Compound 2 displayed a maximum uptake of 27 cc(STP)/g
at 1 bar, equivalent to 5 wt %, or ca. 0.66 CO2 molecule per
[Cu(L) (OH2)] unit. This loading is approximately 1/3 of the
observed loading (mol/mol) of DMF guests within the as-
synthesized material, consistent with substantial contraction of
the framework on evacuation. Measuring an X-ray powder
diffraction pattern on the material after the adsorption
experiment showed some degree of crystallinity is retained in
Photophysical Studies. Each compound L1−H2L4 was
examined for its UV−visible absorbance and emission response,
and the results are summarized in Table 2. All four
Table 2. Summary of Solution-State Photophysical
Properties of Compounds L1−H2L4
λem
(nm, λex
= 366
nm)
λabs
ε (L·mol−1
cm−1
·
compound solvent (nm)
)
Φ
L1
CHCl3
DMSO
CHCl3
DMSO
351
354
359
361
10 200 300
11 100 300
14 300 500
15 400 600
HL2
L3
420
440
0.89 0.05
H2L4
∼0.02
naphthalimide compounds displayed broad absorption bands
with λmax in the range 350−360 nm, and no variations in peak
shape or maxima position were observed in the concentration
range of 10−4−10−6 M. The 4-nitro-substituted precursors L1
and HL2 exhibited no meaningful fluorescence upon excitation,
compared to the 4-oxonaphthalimides L3 and H2L4, both of
which possess well-defined emission bands in the blue region
(Figure 10). Upon excitation at 366 nm in CHCl3, compound
L3 displayed an emission band with λmax = 420 nm, with
partially resolved shoulders in both the absorption and
G
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 10. UV−visible absorption (black) and emission (red, λex = 366
nm) spectra of L3 (top) and H2L4 (bottom), recorded in CHCl3 (40
μM) and DMSO (75 μM), respectively.
Figure 11. Solid-state emission spectra (λex = 366 nm) for complex 1
(top) and complexes 3/4 (bottom), compared to their respective free
ligands in solution and in the solid state.
emission bands. In the solid state, this emission was observed at
λmax = 480 nm, with a bathochromic shift following molecular
aggregation in the crystalline state. Compound L3 displayed a
adopts a head-to-tail stacking mode for the naphthalimide
groups in the crystal structure of the free ligand, while a head-
to-head, H-aggregate-type packing mode is adopted in complex
1. Unsurprisingly, complex 2 displayed no measurable photo-
luminescence, presumably due to quenching of the naph-
thalimide excited state by the d9 CuII ions within the
structure.23 Complex 3 exhibits an emission band effectively
superimposable with that of the free ligand in the solid state,
with λmax = 465 nm. Interestingly, complex 4, which differs from
complex 3 only by a slight reorientation of the naphthalimide
stacks and a change in the size, polarity, and volatility of the
encapsulated guest molecules, displays a notably different
emission signature. A bathochromic shift in the emission band
is observed, with λmax = 480 nm, and is accompanied by a peak
broadening, from fwhm = 70 nm for 3 to 90 nm for 4.
relatively high fluorescence quantum yield of 89%
5% in
solution, using quinine sulfate (ΦF = 54.6%, λex = 366 nm) in 2
M H2SO4 as a reference standard.20 The dicarboxylic acid
species H2L4 in DMSO solution displayed an emission
maximum at λmax = 440 nm (λex = 366 nm), undergoing a
less substantial bathochromic shift to 470 nm in the solid state.
The fluorescence quantum yield of H2L4 in DMSO solution
was measured at ca. 2%.
These quantum yield values can be considered a continuation
of the solution-state trend observed for the 4-aryloxo-N-
ethylnaphthalimides reported by Thilagar et al.21 In that study,
the presence of flexible groups or groups capable of strongly
contributing to nonradiative decay attached to the phenolic 4-
position caused a reduction in fluorescence quantum yield from
96% for the most rigid and symmetric phenol derivative to
<10% for the nitro, thioacetyl, and carboxyaldehyde derivatives.
The contributions of carboxylic acid groups to nonradiative
decay pathways are well known22 and most likely lead to the
reduction in fluorescence quantum yield in the case of H2L4.
The fluorescence properties of complexes 1−4 were also
characterized in the solid state, as shown in Figure 11. Complex
1 displayed a broad emission band with λmax = 455 nm, a
notable hypsochromic shift compared to the free ligand in the
solid state. As well as the expected differences in the local
polarity of the fluorophore in the free ligand compared to
complex 1, this variation may be rationalized by the differences
in the naphthalimide aggregation modes between the free
ligand and the complex in the crystalline state. The ligand
DISCUSSION
■
Comparing the structures of L3 and complexes 1−4, the
flexible linkers are seen to exhibit a relatively narrow range of
geometries, where the torsion angle from each aryl group about
the vector between the two sp3 linkers varies in the range 90−
120°. Most likely, the orientation of these freely rotatable
groups is dictated by crystal-packing influences more than any
preferred position for the low-energy bond rotations involved.
More significant in terms of structure direction in the solid state
are the dominant face-to-face π−π interactions between the
naphthalimide groups in each structure. The importance of
such interactions in influencing the extended solid-state
structure of coordination compounds is well established,24
H
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
spectrometer (tof), interfaced to a Waters 2690 HPLC. The
instrument was operated in positive or negative mode as required.
Leucine enkephalin was used as an internal lock mass. Masses were
recorded over the range 100−1000 m/z. Elemental analyses were
carried out at the Microanalytical Laboratory, School of Chemistry and
Chemical Biology, University College Dublin. NMR data were
recorded in commercially available deuterated solvents on an Agilent
and in this case the interactions between the strongly polarized
aromatic surfaces are likely responsible for the resilience of the
three-dimensional structures of 2 and 3/4 to solvent exchange,
evacuation, and resolvation. The low gas loadings and slow
desorption kinetics, implied by the apparent hysteresis on the
desorption branches of both CO2 isotherms, are indicative of a
very narrow pore environment within both samples after
evacuation, which suggests a further contraction of the pores on
evacuation. Given the observed pore contraction in 3 to enclose
the smaller acetonitrile guest molecule in 4, a further
contraction following evacuation of the material is not
unexpected.
The variation in emission behavior in the solid state between
complexes 1, 3, and 4 and their free ligands L3 and H2L4 was
consistent with the expected behavior, based largely on changes
in the solid-state aggregation mode. As the ligand design
provides central fluorophores, which are electronically isolated
from the metal binding groups, little impact on the emission
properties was observed as a direct consequence of metal
coordination, evidenced in the case of H2L4 compared with
complex 3 in the solid state. The variation in emission
properties between complexes 3 and 4 is particularly
interesting, as it provides the basis of a fluorescent signaling
mechanism for a coupled change in both the local polarity of
the fluorophore unit and a structural rearrangement of the host
framework without requiring any chemical change to the
framework atoms themselves.
1
400-MR spectrometer operating at 400 MHz for H NMR and 100
MHz for 13C NMR. Chemical shifts are expressed in parts per million
(ppm/δ) and were referenced relative to the internal solvent signals.
Infrared spectra were recorded on a PerkinElmer Spectrum 100 FTIR
spectrometer with universal ATR sampling accessory, in the range
4000−650 cm−1. X-ray powder diffraction patterns were collected
using a Bruker D2 Phaser instrument with Cu Kα radiation (λ =
1.5418 Å). Samples were ground and mounted on silicon sample
holders, and data were collected in the 2θ range 5−55° at room
temperature while rotating φ at a speed of 1 rpm. Sample background
due to fluorescence was subtracted, and the patterns were compared
with those simulated from the single-crystal data collected at 100 K.
UV−visible absorption spectra were measured using spectroscopic
grade solvents (Sigma-Aldrich) in the range 250−800 nm (CHCl3) or
270−800 nm (DMSO) on a Varian Cary 50 Bio spectrophotometer.
Fluorescence spectra were measured on a Varian Cary Eclipse
fluorimeter. Quantum yields were calculated by comparison with
quinine sulfate in 2 M H2SO4 with excitation at 366 nm using an
excitation slit width of 2.5 nm for all samples, and emission was
integrated across the range 380−600 nm. Solid-state emission spectra
were measured at room temperature with powdered samples pressed
into films between quartz plates. Gas adsorption isotherms were
measured using a Quantachrome Autosorb IQ gas sorption analyzer.
Chemically pure (CP) grade He, N2, H2, and CO2 gases from BOC
gases were used for the measurements.
CONCLUSIONS
■
X-ray Crystallography. Structural and refinement parameters are
presented in Table 1. All diffraction data were collected using a Bruker
APEX-II Duo dual-source instrument using graphite-monochromated
Mo Kα (λ = 0.710 73 Å) radiation. Data sets were collected using ω
and φ scans with the samples immersed in oil and maintained at a
constant temperature of 100 K using a Cobra cryostream. The data
were reduced and processed using the Bruker APEX suite of
programs.25 Multiscan absorption corrections were applied using
SADABS.26 The diffraction data were solved using SHELXT and
refined by full-matrix least-squares procedures using SHELXL-2015
We have prepared three new coordination polymers, 1, 2, and
3, from the novel luminescent naphthalimide-derived linkers L3
and H2L4. In each case, substantial π−π interactions dominate
the extended structures, leading to dense 3-fold interpenetra-
tion in the silver coordination network poly-[Ag(L3)2]BF4·
4.5H2O·0.5THF (1) and a robust and flexible interlayer
interaction in the related two-dimensional networks poly-
[Cu(L4) (OH2 )]·2DMF·0.5H2 O (2) and poly-
[Cd2(L4)2(OH2)2]·1.5DMF·3H2O (3). Both compounds 2
and 3 undergo structural rearrangements on solvent exchange;
in the case of 3, this transition can be monitored with single-
crystal X-ray diffraction, using which we elucidated the
structure of the acetonitrile solvate poly-[Cd2(L4)2(OH2)2]·
2MeCN (4). Moreover, CO2 adsorption experiments showed
that both activated materials retained modest guest uptake
capacity on complete evacuation, and both materials could be
reverted to their original phases by reimmersion in DMF after
evacuation. Furthermore, the photophysical properties of the
complexes and their parent ligands have been studied, which
relate the aggregation mode of the fluorophores in the
crystalline state to the photoluminescent properties of the
resulting materials. This relationship can be exploited as a
means of signaling a structural transformation, as in the case of
the transition from 3 to 4 on solvent exchange. These results
highlight the usefulness of electronically isolated organic
fluorophores in flexible coordination polymer assemblies as
reporting elements for chemical sensor devices, and this area of
research is currently being pursued in our laboratory.
within the OLEX-2 GUI.27−29 The functions minimized were ∑w(Fo
2
− Fc2), with w = [σ2(Fo ) + aP2 + bP]−1, where P = [max(Fo)2 + 2F2 ]/
2
c
3. All non-hydrogen atoms were refined with anisotropic displacement
parameters. All carbon-bound hydrogen atoms were placed in
calculated positions and refined with a riding model, with isotropic
displacement parameters equal to either 1.2 or 1.5 times the isotropic
equivalent of their carrier atoms. Where appropriate, the positions of
hydrogen atoms involved in hydrogen-bonding interactions were
refined to provide the best fit for the residual Fourier peaks and
assigned a Uiso value equal to 1.5 times that of the nearest associated
atom, with the appreciation that the exact positions of these atoms
cannot be meaningfully inferred from X-ray diffraction data. The data
sets for 1, 3, and 4 contained regions of diffuse electron density
consistent with totally delocalized lattice solvent molecules, alongside
regions of ordered or partially ordered solvents; the scattering
contribution from only the diffuse electron density regions to the
measured structure factors was accounted for with the SQUEEZE
routine to allow for more representative refinement statistics for the
framework atoms,30 and the solvent channel contents were ascertained
using TGA and elemental analysis. The reported crystallographic
formulas, densities, and F000 values are based on the crystallo-
graphically localized atoms only. Particular refinement strategies for
each structure, including the specific use of restraints, are provided in
the refine_special_details sections of the combined crystallographic
information file. CCDC 1497724−1497728.
EXPERIMENTAL SECTION
■
Materials and Methods. All reagents, solvents, and starting
materials were purchased from Sigma-Aldrich, Merck, or Fisher
Scientific, were of reagent grade or better, and were used as received.
Mass spectra were acquired using a Micromass time-of-flight mass
Synthesis. N-(4-Cyanophenylmethylene)-4-nitro-1,8-naphthali-
mide, L1. 4-Nitro-1,8-naphthalic anhydride (300 mg, 1.2 mmol) and
4-aminomethylbenzonitrile (200 mg, 1.5 mmol) were combined in 5
I
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
mL of glacial acetic acid. The mixture was heated at 120 °C for 6 h and
cooled to room temperature. A 5 mL amount of water was added to
the solution, causing the precipitation of an orange powder, which was
collected by filtration. The solids were washed with water and
methanol and dried in air. Yield: 330 mg (77%). Mp: 243−245 °C.
Anal. Found: C, 66.96; H, 2.95; N, 11.65. Calcd for C20H11N3O4:
temperature. A 20 mL amount of water was added, to give a dark green
solution, which was acidified with dilute acetic acid, causing
precipitation of a tan solid. The solid was filtered, washed with 3
mL of DMSO, 100 mL of water, 100 mL of methanol, and 50 mL of
diethyl ether, and dried in air. Yield: 237 mg (96%). Mp: >300 °C.
Anal. Found: C, 67.51; H, 3.50; N, 2.90. Calcd for C27H17NO7·
1
1
67.23; H, 3.10; N, 11.76. H NMR δH (400 MHz, CDCl3): 5.42 (s,
0.66H2O: C, 67.64; H, 3.86; N, 2.92. H NMR δH (400 MHz, d6-
2H, H3), 7.64 (second-order multiplet, 4H, H1 + H2), 8.02 (dd, 1H, 3J1
= 8.7 Hz, 3J2 = 7.4 Hz, H5), 8.42 (d, 1H, 3J = 7.9 Hz, H7), 8.72 (d, 1H,
DMSO): 5.31 (s, 2H, H3), 7.22 (d, 1H, 3J = 8.2 Hz, H8), 7.34 (d, 2H,
3
3
3J = 8.9 Hz, H9), 7.46 (d, 2H, J = 8.3 Hz, H2), 7.88 (d, 2H, J = 8.3
3
3
3J = 7.9 Hz, H8), 8.77 (d, 1H, J = 7.4 Hz, H4), 8.86 (d, 1H, J = 8.8
Hz, H6). 13C NMR δC (100 MHz, CDCl3): 43.55, 111.75, 118.57,
122.61, 123.73, 123.88, 126.50, 129.13, 129.67, 129.79, 130.01, 130.28,
132.40, 132.89, 141.65, 149.87, 162.46, 163.26. MS: m/z (APCI)
357.0749 [M]−, calcd for C20H11N3O4 357.0755. IR νmax (ATR,
cm−1): 3073m, 2231s, 1700s, 1660s, 1622m, 1583m sh, 1521s sh,
1461w, 1431m, 1410m, 1378m, 1336s sh, 1309m, 1228s, 1170m,
1024w, 969m, 932w, 862w, 817m sh, 787s, 761s, 713w, 663m, 631m.
UV λmax (CHCl3): 351 nm (10 200 300 L·mol−1·cm−1).
Hz, H1), 7.93 (dd, 1H, 3J1 = 8.3 Hz, 3J2 = 7.5 Hz, H5), 8.07 (d, 2H, 3J =
8.8 Hz, H10), 8.48 (d, 1H, J = 8.2 Hz, H7), 8.60 (d, 1H, J = 7.4 Hz,
3
3
H4), 8.64 (d, 1H, J = 8.5 Hz, H6). 13C NMR δC (100 MHz, d6-
3
DMSO): 42.82, 113.26, 117.11, 119.65, 122.16, 123.79, 127.36,
127.51, 128.45, 129.22, 129.46, 129.71, 131.89, 131.96, 132.92, 142.30,
157.85, 158.71, 162.87, 163.52, 166.61, 167.10. MS m/z (HR-ESMS):
−
466.0916 ([M − H]−, calcd for C27H16NO7 466.0927); 232.5413
2−
([M − 2H]2−, calcd for C27H15NO7 232.5430). IR νmax (ATR,
cm−1): 2992w br, 2657w, 2546w, 1680s sh, 1651s, 1579s sh, 1504m,
1468w, 1424m, 1384s, 1346m, 1317w, 1292m, 1234s sh, 1213m,
1168m, 1126m, 1100m, 1017w, 939w, 874m, 780s, 754s, 704m. UV
λmax (DMSO): 361 nm (15400 600 L·mol−1·cm−1).
N-(4-Carboxyphenylmethylene)-4-nitro-1,8-naphthalimide, HL2.
4-Nitro-1,8-naphthalic anhydride (400 mg, 1.6 mmol) was slurried in 7
mL of glacial acetic acid. To this mixture was added 4-amino-
methylbenzoic acid (300 mg, 2.0 mmol), and the mixture was heated
at 120 °C for 6 h. The mixture was cooled to room temperature and
filtered, and the resulting tan solid was washed with water, methanol,
and diethyl ether and dried in air. Yield: 458 mg (74%). Mp: >300 °C.
Anal. Found: C, 63.66; H, 3.05; N, 7.29. Calcd for C20H12N2O6: C,
Poly-[Ag(L3)2]BF4·4.5H2O·0.5THF, 1. Compound L3 (20 mg, 47
μmol) was suspended in 1 mL of THF with the aid of brief sonication.
To this mixture was added a solution of silver tetrafluoroborate (8 mg,
41 μmol) in 2 mL of THF, and the mixture was capped and sealed in
foil and allowed to stand for 2 days. After this period, colorless crystals
of the product were isolated by filtration, washed with THF, and dried
in air. Yield: 13 mg (47%). Mp: 169−172 °C (dec). Anal. Found: C,
57.42; H, 3.09; N, 6.73. Calcd for [Ag(L3)2]BF4·0.5THF·4.5H2O,
C56H43N6O11BF4Ag: C, 57.45; H, 3.70; N, 7.18. IR νmax (ATR, cm−1):
3420w br, 3071w, 2954w, 2872w, 2248s, 1696s, 1650s sh, 1624w,
1578s sh, 1498s, 1466m, 1402m, 1382s, 1350s, 1303m sh, 1232s sh,
1180m, 1132w, 1109w, 1053s sh, 987m, 942m, 883m, 846m, 813m,
780s, 757m, 665m. Phase purity was confirmed by X-ray powder
diffraction (Supporting Information).
Poly-[Cu(L4) (OH2)]·2DMF·0.5H2O, 2. Compound H2L4 (20 mg,
42 μmol) and copper nitrate trihydrate (24 mg, 99 μmol) were
combined in 2 mL of a mixture of 5% H2O in DMF. The mixture was
briefly sonicated, capped, and heated to 100 °C. After 4 h, the mixture
was sonicated for 5 s to separate the product from a small quantity of
copper oxide particles, and the green solids were decanted and isolated
by filtration. The solids were washed with several portions of DMF
and dried in air. Yield: 13 mg (44%). Mp: >300 °C. Anal. Found: C,
56.39; H, 4.26; N, 5.66. Calcd for [Cu(L4)(OH2)]·2DMF·0.5H2O:
C33H32N3O10.5Cu: C, 56.45; H, 4.59; N, 5.98. IR νmax (ATR, cm−1):
2870w, 2802m br, 1698m, 1654s sh, 1591s sh, 1545m, 1502m, 1467w,
1436w, 1380s, 1347s, 1233m sh, 1209m, 1184m, 1164w, 1134w,
1092w sh, 1019m, 991m, 948m, 884m, 787s, 767s, 711m sh. Phase
purity was confirmed by X-ray powder diffraction (Supporting
Information).
Poly-[Cd2(L4)2(OH2)2]·1.5DMF·3H2O, 3. Compound H2L4 (10 mg;
21 μmol) and cadmium nitrate tetrahydrate (12 mg; 39 μmol) were
added to 1 mL of a 5% H2O in DMF mixture and sealed in a screw-cap
vial. The mixture was briefly sonicated before being heated to 100 °C
and left to dwell at this temperature for 24 h. After this period, the
mixture was filtered hot, and the pale yellow crystals were washed with
DMF and dried in air. Yield: 6 mg (43%). Mp: >300 °C. Anal. Found:
C, 53.36; H, 3.13; N, 3.74. Calcd for [Cd2(L4)2(OH2)2]·1.5DMF·
3H2O, C58.5H46.5N3.5O18.5Cd2: C, 53.26; H, 3.55; N, 3.72. IR νmax
(ATR, cm−1): 3300 w br, 1700m, 1654s sh, 1593s sh, 1518m, 1507m
sh, 1398m, 1379s, 1345m, 1256m, 1234s, 1209m, 1173m, 1131m,
1107m, 1078m, 1016w, 997m, 960w, 946m, 887m, 804w, 791w, 778m,
754m, 710m, 672m. Phase purity was confirmed by X-ray powder
diffraction (Supporting Information).
1
63.83; H, 3.21; N, 7.44. H NMR δH (400 MHz, d6-DMSO): 5.30 (s,
2H, H3), 7.48 (d, 2H, 3J = 8.3 Hz, H2), 7.86 (d, 2H, 3J = 8.3 Hz, H1),
8.08 (dd, 1H, 3J1 = 8.7 Hz, 3J2 = 7.5 Hz, H5), 8.53 (d, 1H, 3J = 7.8 Hz,
3
H7), 8.60−8.64 (m, 2H, H4 + H8), 8.7 (d, 1H, J = 8.7 Hz, H6). 13C
NMR δC (100 MHz, d6-DMSO): 43.17, 122.66, 122.79, 124.23,
126.52, 127.47, 128.56, 129.02, 129.40, 129.61, 129.92, 130.13, 131.97,
141.87, 149.34, 162.33, 163.10, 167.03. MS m/z (HR-ESMS): found
375.0617 [M − H]−, calcd for C20H11N2O6 375.0617. IR νmax (ATR,
cm−1): 3078w, 2968w, 2819w, 2653w, 2541w br, 1687s, 1665s, 1611m
sh, 1581m sh, 1523s, 1430m, 1380w, 1338s, 1317m, 1296s, 1230s,
1182m, 1099m, 1020w, 965m, 932m, 864m sh, 825m, 784s, 759s,
704m. UV λmax (DMSO): 354 nm (11100 300 L·mol−1·cm−1).
N-(4-Cyanophenylmethylene)-4-(4-cyanophenoxy)-1,8-naphtha-
limide, L3. N-(4-Cyanophenylmethylene)-4-nitro-1,8-naphthalimide
(L1) (200 mg, 0.56 mmol), 4-cyanophenol (133 mg, 1.1 mmol),
and potassium carbonate (240 mg, 1.7 mmol) were combined in 5 mL
of anhydrous DMSO. The mixture was heated at 110 °C under argon
for 3 h. The mixture was cooled to room temperature, and 20 mL of
water was added, causing precipitation of an orange solid. The solids
were collected by filtration, washed with 100 mL of water, 50 mL of
methanol, and 50 mL of diethyl ether, and dried in air. Yield: 216 mg
(90%). Single crystals were prepared by recrystallization from ethyl
acetate. Mp: 247−248 °C. Anal. Found: C, 75.31; H, 3.44; N, 9.72.
1
Calcd for C27H15N3O3: C, 75.52; H, 3.52; N, 9.79. H NMR δH (400
MHz, d6-DMSO): 5.33 (s, 2H, H3), 7.32 (d, 1H, 3J = 8.3 Hz, H8), 7.42
(d, 2H, 3J = 8.6 Hz, H9), 7.55 (d, 2H, 3J = 8.3 Hz, H2), 7.78 (d, 2H, 3J
3
3
= 8.4 Hz, H1), 7.94 (dd, 1H, J1 = 8.5 Hz, J2 = 7.3 Hz, H5), 7.99 (d,
2H, J = 8.5 Hz, H10), 8.49 (d, 1H, J = 8.2 Hz, H7), 8.57−8.62 (m,
2H, overlapping, H4 + H6). 13C NMR δC (100 MHz, d6-DMSO):
42.85, 107.42, 109.83, 114.26, 117.77, 118.41, 118.76, 120.35, 122.25,
123.93, 127.68, 128.18, 128.37, 129.31, 131.92, 132.35, 132.78, 135.07,
143.08, 157.00, 159.21, 162.88, 163.52. MS m/z (APCI): 327.0771
([M − C6H4CN]−), calcd for C20H11N2O3 327.0770. IR νmax (ATR,
cm−1): 3070w br, 2227s, 1692s, 1655s, 1581s, 1495s, 1465m, 1404w,
1381m, 1340s sh, 1305w, 1234s sh, 1170m, 1109w, 1071w, 1023w,
984m, 943m, 834m, 781s, 758m, 662m. UV λmax (CHCl3): 359 nm
(14300 500 L·mol−1·cm−1). Phase purity was confirmed by X-ray
powder diffraction (Supporting Information).
3
3
N-(4-Carboxyphenylmethylene)-4-(4-carboxyphenoxy)-1,8-naph-
thalimide, H2L4. N-(4-Carboxyphenylmethylene)-4-nitro-1,8-naph-
thalimide (HL2) (200 mg, 0.53 mmol), 4-hydroxybenzoic acid (147
mg, 1.1 mmol), and potassium carbonate (440 mg, 3 mmol) were
combined in 5 mL of anhydrous DMSO. The mixture was heated at
120 °C under an argon atmosphere for 3 h and cooled to room
Conversion of Poly-[Cd2(L4)2(OH2)2]·1.5DMF·3H2O, 3, to Poly-
[Cd2(L4)2(OH2)2]·2MeCN, 4. A sample of solid 3 (20 mg) was
suspended in 20 mL of acetonitrile with vigorous mixing. The mixture
was allowed to stand for 48 h, with the solvent decanted and replaced
with fresh acetonitrile, with mixing, every 12 h. The exchanged
material was recovered by filtration in quantitative yield. The lattice
J
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
solvent is lost almost immediately on standing in air, and so the
solvation of the bulk material is estimated based on the crystallo-
graphically located solvent molecules only. Mp: >300 °C. IR νmax
(ATR, cm−1): 3257 w br, 2359m, 2342m sh, 1702m sh, 1655s sh,
1592m, 1579m, 1559m, 1518m, 1500s, 1399s, 1383s, 1346s, 1259s,
1235s, 1209m, 1173m, 1132w, 1105w, 1069w, 1017m, 995m, 945m,
861m, 804m, 779s, 755m, 669m. Phase purity was confirmed by X-ray
powder diffraction (Supporting Information).
Wang, Z.; Cohen, S. M. Modulating Metal−Organic Frameworks To
Breathe: A Postsynthetic Covalent Modification Approach. J. Am.
Chem. Soc. 2009, 131, 16675−16677. Chang, Z.; Yang, D.-H.; Xu, J.;
Hu, T.-L.; Bu, X.-H. Flexible Metal−Organic Frameworks: Recent
Advances and Potential Applications. Adv. Mater. 2015, 27, 5432−
5441.
(4) Llewellyn, P. L.; Horcajada, P.; Maurin, G.; Devic, T.; Rosenbach,
N.; Bourrelly, S.; Serre, C.; Vincent, D.; Loera-Serna, L.; Filinchuk, Y.;
́
Ferey, G. Complex Adsorption of Short Linear Alkanes in the Flexible
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b02137.
Metal-Organic-Framework MIL-53(Fe). J. Am. Chem. Soc. 2009, 131,
13002−13008. Fletcher, A. J.; Thomas, K. M.; Rosseinsky, M. J.
Flexibility in metal-organic framework materials: Impact on sorption
properties. J. Solid State Chem. 2005, 178, 2491−2510. Hawes, C. S.;
Hamilton, S. E.; Hicks, J.; Knowles, G. P.; Chaffee, A. L.; Turner, D.
R.; Batten, S. R. Coordination Chemistry and Structural Dynamics of a
Long and Flexible Piperazine-Derived Ligand. Inorg. Chem. 2016, 55,
6692−6702. Haraguchi, T.; Otsubo, K.; Sakata, O.; Fujiwara, A.;
Kitagawa, H. Remarkable Lattice Shrinkage in Highly Oriented
Crystalline Three-Dimensional Metal−Organic Framework Thin
Films. Inorg. Chem. 2015, 54, 11593−11595.
■
S
Additional X-ray crystallography figures, thermogravi-
metric analysis data, X-ray powder diffraction patterns,
NMR spectra for all compounds, and additional
photophysical characterization data (PDF)
Crystallographic data (CIF)
(5) Krause, S.; Bon, V.; Senkovska, I.; Stoeck, U.; Wallacher, D.;
Tobbens, D. M.; Zander, S.; Pillai, R. S.; Maurin, G.; Coudert, F.-X.;
̈
AUTHOR INFORMATION
Kaskel, S. A pressure-amplifying framework material with negative gas
adsorption transitions. Nature 2016, 532, 348−352.
■
Corresponding Authors
*E-mail (C. S. Hawes): hawescs@tcd.ie.
*E-mail (T. Gunnlaugsson): gunnlaut@tcd.ie.
(6) Manna, B.; Chaudhari, A. K.; Joarder, B.; Karmakar, A.; Ghosh, S.
K. Dynamic structural behavior and anion-responsive tunable
luminescence of a flexible cationic metal-organic framework. Angew.
Chem., Int. Ed. 2013, 52, 998−1002.
Author Contributions
́ ́
(7) Deria, P.; Gomez-Gualdron, D. A.; Bury, W.; Schaef, H. T.;
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Wang, T. C.; Thallapally, P. K.; Sarjeant, A. A.; Snurr, R. Q.; Hupp, J.
T.; Farha, O. K. Ultraporous, Water Stable, and Breathing Zirconium-
Based Metal−Organic Frameworks with ftw Topology. J. Am. Chem.
Soc. 2015, 137, 13183−13190. Haigis, V.; Coudert, F.-X.; Vuilleumier,
R.; Boutin, A.; Fuchs, A. H. Hydrothermal Breakdown of Flexible
Metal−Organic Frameworks: A Study by First-Principles Molecular
Dynamics. J. Phys. Chem. Lett. 2015, 6, 4365−4370. Hawes, C. S.;
Chilton, N. F.; Moubaraki, B.; Knowles, G. P.; Chaffee, A. L.; Murray,
K. S.; Batten, S. R.; Turner, D. R. Coordination polymers from a highly
flexible alkyldiamine-derived ligand: structure, magnetism and gas
adsorption studies. Dalton Trans. 2015, 44, 17494−17507.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors gratefully acknowledge the Irish Research Council
(IRC) (Postdoctoral Fellowship GOIPD/2015/446 to C.S.H.),
Science Foundation Ireland (SFI) for SFI PI Awards (10/IN.1/
B2999 and 13/IA/1865 to T.G., 13/IA/1896 to W.S.), TCD
Dean of Research Pathfinder Award (T.G. and C.S.H.), the
European Research Council (ERC; CoG 2014-647719 to
W.S.), and TCD School of Chemistry for financial support.
(8) Kitagawa, S.; Uemura, K. Dynamic porous properties of
coordination polymers inspired by hydrogen bonds. Chem. Soc. Rev.
2005, 34, 109−119. Maji, T. K.; Matsuda, R.; Kitagawa, S. A flexible
interpenetrating coordination framework with a bimodal porous
functionality. Nat. Mater. 2007, 6, 142−148. Haldar, R.; Inukai, M.;
Horike, S.; Uemura, K.; Kitagawa, S.; Maji, T. K. 113Cd Nuclear
Magnetic Resonance as a Probe of Structural Dynamics in a Flexible
Porous Framework Showing Selective O2/N2 and CO2/N2
Adsorption. Inorg. Chem. 2016, 55, 4166−4172.
(9) Duke, R. M.; Veale, E. B.; Pfeffer, F. M.; Kruger, P. E.;
Gunnlaugsson, T. Colorimetric and fluorescent anion sensors: an
overview of recent developments in the use of 1,8-naphthalimide-
based chemosensors. Chem. Soc. Rev. 2010, 39, 3936−3953. Shelton,
A. H.; Sazanovich, I. V.; Weinstein, J. A.; Ward, M. D. Controllable
three-component luminescence from a 1,8-naphthalimide/Eu(III)
complex: white light emission from a single molecule. Chem. Commun.
2012, 48, 2749−2751. Izawa, H.; Nishino, S.; Sumita, M.; Akamatsu,
M.; Morihashi, K.; Ifuku, S.; Morimoto, M.; Saimoto, H. A novel 1,8-
naphthalimide derivative with an open space for an anion: unique
fluorescence behaviour depending on the binding anion’s electrophilic
properties. Chem. Commun. 2015, 51, 8596−8599.
REFERENCES
■
(1) Hoskins, B. F.; Robson, R. Design and construction of a new class
of scaffolding-like materials comprising infinite polymeric frameworks
of 3D-linked molecular rods. A reappraisal of the zinc cyanide and
cadmium cyanide structures and the synthesis and structure of the
diamond-related frameworks [N(CH3)4][CuIZnII(CN)4] and CuI-
[4,4′,4″,4‴-tetracyanotetraphenylmethane]BF4.xC6H5NO2. J. Am.
Chem. Soc. 1990, 112, 1546−1554. Batten, S. R.; Hoskins, B. F.;
Robson, R. 2,4,6-Tri(4-pyridyl)-1,3,5-triazine as a 3-Connecting
Building Block for Infinite Nets. Angew. Chem., Int. Ed. Engl. 1995,
34, 820−822.
(2) Cui, Y.; Li, B.; He, H.; Zhou, W.; Chen, B.; Qian, G. Metal−
Organic Frameworks as Platforms for Functional Materials. Acc. Chem.
Res. 2016, 49, 483−493. Furukawa, H.; Cordova, K. E.; O’Keeffe, M.;
Yaghi, O. M. The Chemistry and Applications of Metal-Organic
Frameworks. Science 2013, 341, 123044. Farruseng, D. Metal-Organic
Frameworks: Applications from Catalysis to Gas Storage; John Wiley &
Sons: Weinheim, 2011. Batten, S. R.; Neville, S. M.; Turner, D. R.
Coordination Polymers: Design, Analysis and Application; Royal Society
of Chemistry: Cambridge, 2009.
(3) Clearfield, A. Flexible MOFs under stress: pressure and
temperature. Dalton Trans. 2016, 45, 4100−4112. Schneemann, A.;
Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A. Flexible
metal-organic frameworks. Chem. Soc. Rev. 2014, 43, 6062−6096.
(10) Stewart, W. W. Lucifer dyeshighly fluorescent dyes for
biological tracing. Nature 1981, 292, 17−21. de Silva, A. P.; Gunaratne,
H. Q. N.; Habib-Jiwan, J.-L.; McCoy, C. P.; Rice, T. E.; Soumillion, J.-
P. New Fluorescent Model Compounds for the Study of Photo-
induced Electron Transfer: The Influence of a Molecular Electric Field
in the Excited State. Angew. Chem., Int. Ed. Engl. 1995, 34, 1728−1731.
Veale, E. B.; Frimannsson, D. O.; Lawler, M.; Gunnlaugsson, T. 4-
Amino-1,8-naphthalimide-Based Troger’s Bases As High Affinity DNA
̈
K
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Targeting Fluorescent Supramolecular Scaffolds. Org. Lett. 2009, 11,
4040−4043. Banerjee, S.; Kitchen, J. A.; Gunnlaugsson, T.; Kelly, J. M.
The effect of the 4-amino functionality on the photophysical and DNA
binding properties of alkyl-pyridinium derived 1,8-naphthalimides.
Org. Biomol. Chem. 2013, 11, 5642−5655.
(16) Han, L.; Qin, L.; Xu, L.; Zhou, Y.; Sun, J.; Zou, X. A novel
photochromic calcium-based metal−organic framework derived from a
naphthalene diimide chromophore. Chem. Commun. 2013, 49, 406−
408. Leong, C. F.; Faust, T. B.; Turner, P.; Usov, P. M.; Kepert, C. J.;
Babarao, R.; Thornton, A. W.; D’Alessandro, D. M. Enhancing
selective CO2 adsorption via chemical reduction of a redox-active
metal−organic framework. Dalton Trans. 2013, 42, 9831−9839. Wade,
(11) Banerjee, S.; Veale, E. B.; Phelan, C. M.; Murphy, S. A.; Tocci,
G. M.; Gillespie, L. J.; Frimannsson, D. O.; Kelly, J. M.; Gunnlaugsson,
T. Recent advances in the development of 1,8-naphthalimide based
DNA targeting binders, anticancer and fluorescent cellular imaging
agents. Chem. Soc. Rev. 2013, 42, 1601−1618. Xu, Z.; Baek, K.-H.;
Kim, H. N.; Cui, J.; Qian, X.; Spring, D. R.; Shin, I.; Yoon, J. Zn2+-
Triggered Amide Tautomerization Produces a Highly Zn2+-Selective,
Cell-Permeable, and Ratiometric Fluorescent Sensor. J. Am. Chem. Soc.
2010, 132, 601−610. Lee, M. H.; Han, J. H.; Kwon, P.-S.; Bhuniya, S.;
Kim, J. Y.; Sessler, J. L.; Kang, C.; Kim, J. S. Hepatocyte-Targeting
Single Galactose-Appended Naphthalimide: A Tool for Intracellular
Thiol Imaging in Vivo. J. Am. Chem. Soc. 2012, 134, 1316−1322. Dai,
Z.-R.; Ge, G.-B.; Feng, L.; Ning, J.; Hu, L.-H.; Jin, Q.; Wang, D.-D.; Lv,
X.; Dou, T.-Y.; Cui, J.-N.; Yang, L. A Highly Selective Ratiometric
Two-Photon Fluorescent Probe for Human Cytochrome P450 1A. J.
Am. Chem. Soc. 2015, 137, 14488−14495.
̆
C. R.; Li, M.; Dinca, M. Facile Deposition of Multicolored
Electrochromic Metal−Organic Framework Thin Films. Angew.
Chem., Int. Ed. 2013, 52, 13377−13381. McCormick, L. J.; Turner,
D. R. Inclined 1D→2D polycatenation of chiral chains with large π-
surfaces. CrystEngComm 2013, 15, 8234−8236.
(17) Genuis, E. D.; Kelly, J. A.; Patel, M.; McDonald, R.; Ferguson,
M. J.; Greidanus-Strom, G. Coordination Polymers from the Self-
Assembly of Silver(I) Salts and Two Nonlinear Aliphatic Dinitrile
Ligands, cis-1,3-Cyclopentanedicarbonitrile and cis-1,3-Bis-
(cyanomethyl)cyclopentane: Synthesis, Structures, and Photolumines-
cent Properties. Inorg. Chem. 2008, 47, 6184−6194. Min, K.-S.; Suh,
M. P. Silver(I)−Polynitrile Network Solids for Anion Exchange:
Anion-Induced Transformation of Supramolecular Structure in the
Crystalline State. J. Am. Chem. Soc. 2000, 122, 6834−6840. Beeching,
L. J.; Hawes, C. S.; Turner, D. R.; Batten, S. R. The influence of anion,
ligand geometry and stoichiometry on the structure and dimension-
ality of a series of AgI-bis(cyanobenzyl)piperazine coordination
polymers. CrystEngComm 2014, 16, 6459−6468.
(12) Ogi, S.; Stepanenko, V.; Thein, J.; Wurthner, F. Impact of Alkyl
̈
Spacer Length on Aggregation Pathways in Kinetically Controlled
Supramolecular Polymerization. J. Am. Chem. Soc. 2016, 138, 670−
678. Reger, D. L.; Leitner, A.; Smith, M. D. Homochiral, Helical
Coordination Complexes of Lanthanides(III) and Mixed-Metal
Lanthanides(III): Impact of the 1,8-Naphthalimide Supramolecular
Tecton on Structure, Magnetic Properties, and Luminescence. Cryst.
Growth Des. 2015, 15, 5637−5644. Veale, E. B.; Gunnlaugsson, T.
Synthesis, Photophysical, and DNA Binding Studies of Fluorescent
(18) Drew, M. G. B.; Harding, C. J.; McKee, V.; Morgan, G. G.;
Nelson, J. Geometric control of manganese redox state. J. Chem. Soc.,
Chem. Commun. 1995, 1035−1038.
(19) Chen, K.-J.; Madden, D. G.; Pham, T.; Forrest, K. A.; Kumar, A.;
Yang, Q.-Y.; Xue, W.; Space, B.; Perry, J. J. P., IV; Zhang, J.-P.; Chen,
X.-M.; Zaworotko, M. J. Tuning Pore Size in Square-Lattice
Coordination Networks for Size-Selective Sieving of CO2. Angew.
Chem., Int. Ed. 2016, 55, 10268−10272. Pillai, R. S.; Benoit, V.; Orsi,
A.; Llewellyn, P. L.; Wright, P. A.; Maurin, G. Highly Selective CO2
Capture by Small Pore Scandium-Based Metal−Organic Frameworks.
J. Phys. Chem. C 2015, 119, 23592−23598. Scott, H. S.; Ogiwara, N.;
Chen, K.-J.; Madden, D. G.; Pham, T.; Forrest, K.; Space, B.; Horike,
S.; Perry, J. J. P., IV; Kitagawa, S.; Zaworotko, M. J. Crystal engineering
of a family of hybrid ultramicroporous materials based upon
interpenetration and dichromate linkers. Chem. Sci. 2016, 7, 5470−
5476. Ziaee, A.; Chovan, D.; Lusi, M.; Perry, J. J. P., IV; Zaworotko, M.
J.; Tofail, S. A. M. Theoretical Optimization of Pore Size and
Chemistry in SIFSIX-3-M Hybrid Ultramicroporous Materials. Cryst.
Growth Des. 2016, 16, 3890−3897. McCormick, L. J.; Duyker, S. G.;
Thornton, A. W.; Hawes, C. S.; Hill, M. R.; Peterson, V. K.; Batten, S.
R.; Turner, D. R. Ultramicroporous MOF with High Concentration of
Vacant CuII Sites. Chem. Mater. 2014, 26, 4640−4646.
Troger’s Base Derived 4-Amino-1,8-naphthalimide Supramolecular
̈
Clefts. J. Org. Chem. 2010, 75, 5513−5525. Ryan, G. J.; Elmes, R. B. P.;
Erby, M.; Poynton, F. E.; Williams, D. C.; Quinn, S. J.; Gunnlaugsson,
T. Unexpected DNA binding properties with correlated downstream
biological applications in mono vs. bis-1,8-naphthalimide Ru(II)-
polypyridyl conjugates. Dalton Trans. 2015, 44, 16332−16344.
Banerjee, S.; Bright, S. A.; Smith, J. A.; Burgeat, J.; Martinez-Calvo,
M.; Williams, D. C.; Kelly, J. M.; Gunnlaugsson, T. A Supramolecular
Approach to Enantioselective DNA Recognition using Enantiomeri-
cally Resolved Cationic 4-Amino-1,8-Naphthalimide based Troger’s
̈
Bases. J. Org. Chem. 2014, 79, 9272−9283.
(13) Mukherjee, S.; Thilagar, P. Insights into the AIEE of 1,8-
Naphthalimides (NPIs): Inverse Effects of Intermolecular Interactions
in Solution and Aggregates. Chem. - Eur. J. 2014, 20, 8012−8023.
(14) Mukherjee, S.; Thilagar, P. Molecular flexibility tuned emission
in “V” shaped naphthalimides: Hg(II) detection and aggregation-
induced emission enhancement (AIEE). Chem. Commun. 2013, 49,
(20) Brouwer, A. M. Standards for photoluminescence quantum yield
measurements in solution (IUPAC Technical Report). Pure Appl.
Chem. 2011, 83, 2213−2228.
(21) Mukherjee, S.; Thilagar, P. Fine-tuning solid-state luminescence
in NPIs (1,8-naphthalimides): impact of the molecular environment
and cumulative interactions. Phys. Chem. Chem. Phys. 2014, 16,
20866−20877.
(22) Feitelson, J. On the Mechanism of Fluorescence Quenching.
Tyrosine and Similar Compounds. J. Phys. Chem. 1964, 68, 391−397.
Ricci, R. W.; Nesta, J. M. Inter- and intramolecular quenching of
indole fluorescence by carbonyl compounds. J. Phys. Chem. 1976, 80,
974−980.
(23) Veale, E. B.; Kitchen, J. A.; Gunnlaugsson, T. Fluorescent tren-
based 4-amino-1,8-naphthalimide sensor for Cu(II) based on the use
of the (fluorophore-spacer-receptor) Photoinduced Electron Transfer
(PET) principle. Supramol. Chem. 2013, 25, 101−108.
́
7292−7294. Biczok, L.; Valat, P.; Wintgens, V. Effect of molecular
structure and hydrogen bonding on the fluorescence of hydroxy-
substituted naphthalimides. Phys. Chem. Chem. Phys. 1999, 1, 4759−
4766. Magalhaes, J. L.; Pereira, R. V.; Triboni, E. R.; Filho, P. B.;
̃
Gehlen, M. H.; Nart, F. C. Solvent effect on the photophysical
properties of 4-phenoxy-N-methyl-1,8-naphthalimide. J. Photochem.
Photobiol., A 2006, 183, 165−170.
(15) Kitchen, J. A.; Martinho, P. N.; Morgan, G. G.; Gunnlaugsson,
T. Synthesis, crystal structure and EPR spectroscopic analysis of novel
copper complexes formed from N-pyridyl-4-nitro-1,8-naphthalimide
ligands. Dalton Trans. 2014, 43, 6468−6479. Reger, D. L.; Leitner, A.
P.; Smith, M. D. Supramolecular Metal−Organic Frameworks of s- and
f-Block Metals: Impact of 1,8-Naphthalimide Functional Group. Cryst.
Growth Des. 2016, 16, 527−536. Reger, D. L.; Semeniuc, R. F.; Elgin, J.
D.; Rassolov, V.; Smith, M. D. 1,8-Naphthalimide Synthon in Silver
Coordination Chemistry: Control of Supramolecular Arrangement.
Cryst. Growth Des. 2006, 6, 2758−2768. Reger, D. L.; Debreczeni, A.;
Smith, M. D. Zinc Paddlewheel Dimers Containing a Strong π···π
Stacking Supramolecular Synthon: Designed Single-Crystal to Single-
Crystal Phase Changes and Gas/Solid Guest Exchange. Inorg. Chem.
2011, 50, 11754−11764.
(24) Janiak, C. A critical account on π−π stacking in metal complexes
with aromatic nitrogen-containing ligands. J. Chem. Soc., Dalton Trans.
2000, 3885−3896. Klosterman, J. K.; Yamauchi, Y.; Fujita, M.
Engineering discrete stacks of aromatic molecules. Chem. Soc. Rev.
2009, 38, 1714−1725.
(25) Bruker APEX-3; Bruker-AXS Inc.: Madison, WI, 2016.
L
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(26) SADABS; Bruker-AXS Inc.: Madison, WI, 2016.
(27) Sheldrick, G. M. SHELXT − Integrated space-group and crystal-
structure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015,
71, 3−8.
(28) Sheldrick, G. M. Crystal structure refinement with SHELXL.
Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 3−8.
(29) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. OLEX2: a complete structure solution, refinement and
analysis program. J. Appl. Crystallogr. 2009, 42, 339−341.
(30) Spek, A. L. PLATON SQUEEZE: a tool for the calculation of
the disordered solvent contribution to the calculated structure factors.
Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71, 9−18.
M
DOI: 10.1021/acs.inorgchem.6b02137
Inorg. Chem. XXXX, XXX, XXX−XXX