Solvatochromism, acidochromism and aggregation-induced emission of propeller-shaped spiroborates

Article abstract of DOI:10.1039/C8DT03374A

Propeller-shaped pyridyl-enolato-catecholate/-salicyl spiroborates (Sborepy1-6) were synthesized. The complexes Sborepy3-6 show weak emission in fluid solution and aggregation-induced emission enhancement in the aggregation state with large Stokes shifts of 4025-5237 cm^?1. Moreover, intense solid-state emissions with high Φ_f ranging from 25% to 37% were observed for Sborepy3-6 owing to the weak intermolecular interactions in their solid-state. The AIE and intense solid-state emission have been revealed via the X-ray diffraction analysis and theoretical calculations. Furthermore, the solvatochromism in the solution state and the potential application as a fluorescent acidic vapour sensor in the solid state of Sborepy3 and Sborepy6 were also demonstrated.

Full text of DOI:10.1039/C8DT03374A

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ISSN 1477-9226
PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
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Solvatochromism, Acidochromism and Aggregation-Induced
Emission of Propeller-Shaped Spiroborates
Kang Li,a Jichun Cui,a Zeren Yang,a Yanmin Huo,a Wenzeng Duan,*,a Shuwen Gong*,a and Zhipeng
Liu*,b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Propeller-shaped pyridyl-enolato-catecholate/-salicyl spiroborates (Sborepy1-6) were synthesized. The complexes
Sborepy3-6 show weak emission in fluid solution and aggregation-induced emission enhancement in the aggregation state
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with large Stokes shifts of 4025−5237 cm-1. Moreover, intense solid-state emissions with high
Φf ranging from 25% to 37%
were observed for Sborepy3-6 owing to the weak intermolecular interactions in their solid-state. The AIE and intense
solid-state emission have been revealed via the X-ray diffraction analysis and theoretical calculations. Furthermore, the
solvatochromism in solution state and potential application as fluorescent acidic vapour sensor in the solid state of
Sborepy3 and Sborepy6 were also demonstrated.
state is still required.
Introduction
Spiroborates have emerged as an important family of boron
complexes with intramolecular charge-transfer transitions14
The development of highly efficient solid-state fluorescent boron
complexes is of great importance for the applications of
fluorescence sensing and imaging,1-2 luminescent materials,3 and
optoelectronic applications.4 However, due to the notorious
aggregation-caused emission quenching (ACQ), most fluorescent
boron complexes show quenched fluorescence in the solid state in
contrast to their excellent fluorescent properties in solution. With
the famous boron dipyrromethene (BODIPY) as an example, the
small Stokes shift induced by strong self-absorption5 and strong
intermolecular π-π stacking interactions6-7 make BODIPY and its
derivatives rarely emissive in the solid state, which greatly limited
their applications. Aggregation-induced emission (AIE) has been
and thermal and chemical stability.15-16 More importantly,
some spiroborates exhibit improved emission properties in
comparison with their boron-difluoride analogues, allowing
the extended application scope of fluorescent boron
complexes in the field of biological and material science.17-25
For example, replace the fluorine atoms on boron of the
BODIPY core with
a 1,1’-bi(2-naphthol) (BINOL) or 4,4-
diacyloxyl chelate group has been demonstrated by de la Moya
et al.20 and Chiara et al.24 to develop new laser-active dyes. On
the other hand, our previous research have demonstrated that
desymmetrization of BODIPY analogues with propeller-shaped
structure is an efficient way to obtain AIE-active BODIPYs.26-28
In this way, many heterocycle-enolato/enamido-based boron
complexes with propeller-shaped structure have been
developed as new type of AIE-active luminophores, which
provide a convenient method to obtain solid-state emissive
boron complexes.26-30 Considering above, construction of
proved to be an efficient strategy to overcome this obstacle.8
A
variety of AIE-based boron complexes with excellent fluorescence
properties in the solid state have been reported which are
applicable for fluorescence imaging,9 mechanofluorochromic (MFC)
material10-11 and organic light emitting diodes (OLED).12-13 To better
understand the relationship between AIE and molecular
engineering, and expand the scope of application, the development
of new AIE-active boron complexes with novel framework, facile
synthetic procedure, excellent photophysical properties in the solid
propeller-shaped
heterocycle-enolato/enamido-based
spiroborates should be accessible to achieve new AIE-active
luminophores. In the present work, we report the synthesis
and photoproperties of six boron complexes based on
spiroborate-enolate-pyridine (abbreviated as Sborepy1-6,
Scheme 1). Among them, Sborepy3-6 exhibit AIE, large Stokes
shifts and high quantum yields in the aggregation state.
Moreover, the solvatochromism and reversible acid/base
vapour stimulated fluorescence of Sborepy3 and Sborepy6
were also demonstrated.
a.Institute of Functional Organic Molecules and Materials, School of Chemistry and
Chemical Engineering, Liaocheng University, No.1 Hunan Road, Liaocheng,
252000, People’s Republic of China. E-mail: duanwenzeng@lcu.edu.cn;
gongshw@lcu.edu.cn.
b.Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials
(IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials
(SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing,
211816, P.R. China. E-mail: iamzpliu@njtech.edu.cn.
†
Electronic Supplementary Informaꢀon (ESI) available: [1H, 13C NMR and
Results and discussion
luminescence spectra of Sborepy1-6. CCDC 1814822, 1814823, 1814824, 1814825,
1587223 and 1814826.]. For ESI and crystallographic data in CIF and other
electronic format See DOI: 10.1039/x0xx00000x
Synthesis of Sborepy1-6
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Sborepy1-6 were obtained via two-steps procedure starting Sborepy4; C1–H1···O4(2.48 Å, 147.0o), C10–H10···O4 (2.61 Å,
from 2-benzylpyridine and ethyl benzoate derivatives (Scheme 140.4o), C19–H19···O2 (2.70 Å, 139.6o) and C4–H4···π (3.48 Å)
1
). Firstly, the corresponding compounds
1-3
were easily interactions in Sborepy5; C2–H2···O4 (2.67 Å, 146.9o) and C24–
synthesized from the reactions of 2-benzylpyridine and ethyl H24···O3 (2.70 Å, 140.2o) interactions in Sborepy6. These weak
benzoate derivatives with yields ranging from 71% to 95%. intermolecular
Then, Sborepy1-6 were obtained in moderate yields (51 62%) conformations of Sborepy1
by reacting of compounds 1-3 with boric acid and catechol or restriction of the intramolecular rotations and blocked
interactions
rigidify
the
molecular
−
-6
in the solid state
,
leading to the
salicylic acid in 1,2-dichloroethane. The structures of nonradiative relaxation, and thus high solid-state emission in
Sborepy1-6 were fully characterized by 1H, 13C NMR, elemental Sborepy1-6 are expected.
analysis, HRMS and single crystal X-ray diffraction.
Figure 1. Molecular structures of Sborepy1-6 (50% probability for thermal
ellipsoids). H atoms are omitted for clarity.
Scheme 1. Synthetic routes for Sborepy1-6
. Reaction conditions: (i) 2-
Photophysical properties of Sborepy1-6
benzylpyridine (1.0 equiv), NaH (3 equiv), THF, reflux; (ii) catechol (1.1 equiv),
boric acid (1.0 equiv), 1,2-dichloroethane, reflux, 6h; (iii) salicylic acid (1.1 equiv),
boric acid (1.0 equiv), 1,2-dichloroethane, reflux, 6h.
The photophysical properties of Sborepy1-6 were measured in
various solvents and in the aggregation state. In tetrahydrofuran
(THF), Sborepy1-6 show their absorption maxima (λabs) ranging
from 371 to 427 nm with absorption coefficient (ε
) of 1.4−7.1×104
X-Ray crystal structure analysis
M-1cm-1 (Fig. 2a and Table 1). Due to the increased electron-
donating ability of R group (from hydrogen to methoxy to N, N-
dimethylamino groups) in D ring, Sborepy2 and Sborepy5, and
Sborepy3 and Sborepy6 exhibit distinct bathochromic shifts of λabs
around 13 and 52 nm in comparison with those of Sborepy1 and
Sborepy4. On the other hand, with the same substituent at D ring,
spiroborates based on catecholate (Sborepy1-3) and salicyl
Single crystals of Sborepy1-6 were obtained by slow evaporation
of their dichloromethane solution at room temperature. The crystal
structures and molecular packing diagrams are shown in Fig. 1 and
S1. As anticipated, Sborepy1-6 adopt a propeller-shaped structure
in the solid state, due to the steric effects of phenyl rings and
catechol or salicylic acid (E ring) around the pyridine ring (A ring)
and N^O−chelate six-membered ring (B ring) in these molecules.
The dihedral angles between the B and E, C, D rings are 87.12°,
60.46° and 54.44° for Sborepy1, 86.25°, 64.87° and 42.62° for
Sborepy2, 85.02°,58.19° and 42.01° for Sborepy3, 85.84°, 70.06°
and 26.72° for Sborepy4, 84.60°, 68.94° and 33.81° for Sborepy5,
85.93°,61.64° and 43.69° for Sborepy6, respectively.
(Sborepy4-6) display almost the same λabs and ε, indicating that
catecholate and salicyl substitution has neglectable electronic effect
on the ground states of Sborepy1-6.
The fluorescence of Sborepy1-2 is totally quenched in THF
solution and aggregation state owing to the excited-state CT
process from catecholate to boron center, which leads to a
non-emissive CT state.31 In contrary, Sborepy3 emits at 523
nm in THF with low fluorescence quantum yield (Φf = 1%).
This difference should be ascribed to the inhibited CT
process from catecholate to boron center caused by the
strong electron-donating ability of N,N-dimethylamino
In the molecular packing diagrams, intermolecular π−π
interactions are not observed. However, multiple short
hydrogen bonding interactions and C-H···π interactions are
observed in the crystals: C12–H12···O2 (2.47 Å, 172.8o)
interaction in Sborepy1; C10–H10···O1 (2.58 Å, 148.2o), C19–
H19···O2 (2.71 Å, 113.5o), C23–H23···O1 (2.66 Å, 170.9o) and
C16–H16···π (2.62 Å) interactions in Sborepy2; C15–H15···O2
(2.66 Å, 133.8o), C30–H30···O3 (2.48 Å, 157.1o) and C33–
H33B···π (2.78 Å) interactions in Sborepy3; C4–H4···O4 (2.71 Å,
127.8o), C37–H37···O5 (2.60 Å, 172.1o), C27–H27···O4 (2.67 Å,
124.8o) and C28–H28···O4 (2.69 Å,122.2o) interactions in
group in the
D
ring.32 Different from the totally quenched
emission of Sborepy1, weak fluorescence (Φf = 1%) with
emission bands (λem) centered at 450 nm is observed for
Sborepy4, suggesting that salicyl group has less emission
quenching effect than catecholate group (Fig. 2b and Table 1).
2
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Sborepy5 and Sborepy6 display red-shifted λem at 457 (Φf = 2%) Sborepy3-6 display minor changes, indicating that the ground
and 533 nm (Φf = 16%), respectively, in compassion with states of Sborepy1-6 are hardly affected by the solvent polarity. In
Sborepy4, due to the CT enhancement induced by the contrast, the emission spectra of Sborepy3-6 exhibited different
methoxy and N, N-dimethylamino groups.33 Furthermore, the maximum wavelengths in different solvents. With the solvent
Stokes shifts of Sborepy3-6 -6 are
are in the range of 4025–4657 cm-1 polarity changed from hexane to glycol, the λem of Sborepy3
in THF (Table 1), which are larger than those of other red-shifted of 69 nm, 12 nm, 26 nm and 64 nm, respectively,
fluorescent boron complexes such as BODIPY (400–600 cm-1),34 indicating that the fluorescence of Sborepy3 and Sborepy6 is highly
pyridomethene-BF2 complexes (250–400 cm-1),35 and Borepy dependent on the solvent polarity. In the meanwhile, significant
(2200–3340 cm-1 ).27
fluorescence color change from blue to yellow for Sborepy3 and
Sborepy6 are observed under UV irradiation (365 nm) along with
the change of solvent polarity. (Fig. 3a and 3d) Such
solvatochromism should be ascribed to the excited-state CT
enhancement caused by the N,N-dimethylamino group in
In order to elucidate the effects of solvent polarity on the
emission properties, plots of Δ (Stokes shift) versus Δ (solvent
D
ring.37
ν
f
orientation polarizability) according to Lippert-Mataga equation38
were investigated. As shown in Fig. S5, the slopes of the fitting lines
for Sborepy3 and Sborepy6 are 8357.9 and 7043.9, respectively.
From the positive slopes of the Lippert-Mataga plots, the dipole
moments of Sborepy3 and Sborepy6 in excited states are larger
than the corresponding dipole moments in the ground states.
Consequently, the larger dipole moments in the excited states of
Sborepy3 and Sborepy6 can interact with the dipole moments of
polar solvent molecules, which reduce the energies of the excited
states, leading to the pronounced solvatochromic effect of
Figure 2. (a) Absorption spectra of Sborepy1-6 (50
emission spectra of Sborepy3-6 (50 ꢀM) in THF.
ꢀM) and (b) normalized
In order to interpret the photophysical behaviours and
investigate the influence of the structural modifications on the
photophysical and electronic properties of Sborepy1-6, the time-
dependent density functional theory (TD-DFT) calculations were
performed in the gas phase with Gaussian 03 program package.36 As
Sborepy3 and Sborepy6
.
Solvatochromism are not observed in the case of Sborepy4-5
,
in Fig. S2 and Table S1
be attributed to the excitation from S0→S2 state arising mainly from
HOMO 1→LUMO transiꢀon, while for Sborepy3-6, the absorption
, the absorption maxima of Sborepy1-2 can
due to their weak CT nature. As shown in Fig. 3, Sborepy4-5 exhibit
weak emission in most solvents, whereas in high-viscosity solvents
(glycol and glycerol), significantly enhanced fluorescence intensities
with higher Φf are observed, which means that the fluorescence
behaviours of Sborepy4-5 are more affected by solvent viscosity,
and thus can be used as AIE molecules.39-40
−
maxima all correspond to the excitation from S0→S1 caused by
HOMO→LUMO transiꢀon for Sborepy4-6 and HOMO-1→LUMO
transition for Sborepy3. For Sborepy1-2 and Sborepy4-6, the
HOMOs (HOMO-1 for Sborepy1-2) are distributed over the whole π-
conjugated system containing A−D rings and the R groups, however,
the HOMO-1 for Sborepy3 is distributed over the B, D, E rings and R
group. While the LUMOs are mainly localized on the
A, B and D
rings. Notably, the excitations from S0→S2 state and S0→S1 state of
Sborepy1-6 are obvious originated from intramolecular charge
transfer (ICT) transitions occurred from B−D rings to
At the same time, the introduction of electron-donating R group to
ring has also enhanced the CT from ring to and rings, which
A and B rings.
D
D
A
B
destabilizes the HOMOs (HOMO-1 for Sborepy1-3) more than it
destabilizes the LUMOs, leading to the red-shifts of Sborepy1-6. The
calculated maximum absorption wavelengths of Sborepy1-6 are
3.80 eV/326 nm, 3.74 eV/331 nm, 3.55 eV/349 nm, 3.77 eV/329 nm,
3.68 eV/337 nm and 3.51 eV/353 nm, respectively. These
calculation results are basically consistent with the experimental
results, indicating that the absorption bands of Sborepy1-6 can be
easily tuned by incorporation of
D ring with different functional
Figure 3. Emission spectra of compounds Sborepy3 (a), Sborepy4 (b), Sborepy5
(c) and Sborepy6 (d) (50
groups and can also be predicted by the theoretical calculations
(Figs. S3 and S4).
ꢀM) in various solvents such as hexane, toluene,
dichloromethane (DCM), tetrahydrofuran (THF), acetonitrile (ACN),
dimethylformamide (DMF), ethanol, ethylene glycol (glycol) and glycerol,
respectively. Inset: photograph of Sborepy3 (a) and Sborepy6 (d) in hexane,
toluene, DCM, THF, ethanol, ACN, DMF, glycol and glycerol with UV irradiation
Solvatochromism
The solvent effects on the absorption and fluorescence spectra of
Sborepy3-6 were also examined in different solvents (Fig. 3, S4 and
S5). As the solvent varies from hexane to glycol, the λabs of
(λ=365
nm).
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Table 1.Photophysical data of Sborepy1-6 in solution and in the solid state.
In solution
In the solid state[f]
Cpd
λ
abs (nm)
λ
em (nm)
λ
em (nm)
λem (nm)
(Φf) Glycerol [b]
[d]
[e]
[d]
SS (cm-1
)
λ
abs (nm)
λ
em (nm)
Φf
SS (cm-1
)
[a]
ε
(mol-1 cm-1
)
(Φf) Solu[a]
(Φf) Aggr [b][c]
--
Sborepy1
Sborepy2
Sborepy3
Sborepy4
Sborepy5
Sborepy6
371 (89000)
384 (95000)
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
423 (131000)
373 (71000)
386 (108000)
427 (142000)
523 (1%)
450 (< 1%)
457 (2%)
533 (16%)
540 (51%)
461 (4%)
479 (6%)
550 (43%)
541 (71%)
452 (30%)
472 (22%)
548 (63%)
4520
4587
4025
4657
426
373
387
433
545
465
475
545
25%
37%
33%
32%
5126
5304
4887
4746
45-46
[a]
[b]
Measured at a concentration of 50
ꢀ
M in THF at 25 oC;
Determined by using 4-methylamino-7-nitro-2,1,3-benzoxadiazole (Φf = 0.38 in acetonitrile) as reference;
[c]Measured at a concentration of 50
ꢀ
M in THF/H2O mixture with fw of 90% at 25 oC;
Frequency units between the longest absorption band and emission band; [e] Absolute
quantum yield determined by calibrated integrating sphere systems; [f] Powder samples were used for the absolute quantum yield determination, absorption and emission spectra
[d]
collection.
Aggregation-induced emission
Sborepy3-6 at high values (fw ≥ 90%) can restrict the intramolecular
free rotation of the R substituents and phenyl rings, resulting in the
AIE properties.
To explore the AIE activities of Sborepy3-6, their emission
properties were investigated in the mixed solvent systems of THF-
H2O with varied volumetric fractions of water (fw) (Fig. 4 and S6). In
pure THF solution, Sborepy3
water added to the THF solution, the emission intensities of
Sborepy3 remain almost unchanged until the fw reached 80%. As
-5 show low emission intensities. As
-
5
the fw increased to 90%, the emission intensities are all significantly
enhanced. However, upon addition of 99% water in THF, the
emission intensity of Sborepy3 decreased as the precipitation
occurred. (Fig. S6) It is worth noting that the emission intensity of
Sborepy6 quenched gradually with the increase of fw, but suddenly
increased as the fw exceeds 80%. This phenomenon could be
explained by the combinational effects of ICT, intramolecular
rotation and solvent viscosity:41-42 When at low fw values (< 90%),
Sborepy6 is soluble and has active intramolecular rotation and
strong ICT character. As the fw values increased, the intramolecular
rotation and ICT are enhanced by the increased solvent polarity,
which resulted in the conversion of ICT to the twisted
intramolecular charge transfer (TICT),43 leading to the gradually
decreased emission intensity of Sborepy6 (Fig. 4d). In contrast,
when the fw reaches to 90%, the increment of the fw results in the
transformation of Sborepy6 from the dissolved and well-dispersed
state at low values (fw < 90%) to aggregated particles at high values
Figure 4. Emission spectra of Sborepy3 (a), Sborepy4 (b), Sborepy5 (c) and
Sborepy6 (d) in THF/water mixtures (50 μM) with varied volumetric fractions of
water (fw). Inset: the emission pictures of the solution of Sborepy3-6 with
different fw under UV light (365 nm).
In the solid state, Sborepy3-6 show almost the same absorption
(
fw ≥ 90%). The aggregated state results in the restricted internal
bands in comparison with those in solution (λabs: 426 nm, 373 nm,
387 nm and 433 nm for Sborepy3-6, respectively). However, the
rotation accompanied by the limited ICT effect, which prevent the
non-radiative relaxation channels and thus make the emission
intensity of Sborepy6 increase rapidly.33,44 When fw reaches to 99%,
emission bands of Sborepy3
compared with the corresponding emission bands in solution
(450 532 nm) with green, dodger blue, sky-blue and yellow-green
-6 are slightly red-shifted (465−545 nm)
the emission intensities of Sborepy3-6 are 13–, 38–, 60– and 4–fold
−
higher than those in the pure THF. On the other hand, with the
increase of fw, the emission spectra of Sborepy3 and Sborepy6
show red-shift from 523 to 540 nm and 533 to 550 nm due to the
solvatochromic and TICT effects. Therefore, the aggregation of the
emission in the solid state. (Fig. 5) Particularly, Sborepy3-6 exhibit
larger Stokes shifts in the range of 4746–5304 cm-1 and high Φf of
25%, 37%, 33% and 32%, respectively. Such intense emissions
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are basically consistent with the X-ray crystal structure analysis of Sborepy3-6 show weak emission in fluid solution (
Φf, 1-16%) and
Sborepy3 6. AIEE in the aggregation state with large Stokes shifts
-
Figure 5. (a) The solid-state emission spectra of Sborepy3-6; (b) the photo
pictures of Sborepy3-6 in the drop-cast film and powder state ( λex = 365 nm
using a UV lamp).
Acidochromism
Figure 6. (a) Emission spectra of initial, HCl (g) and NH3 (g) fumed powders
ofSborepy6; (b) Reversible switching of the emission of Sborepy6 by the HCl/NH3
fuming cycle; (c) Fluorescent pictures of HCl (g) and NH3 (g) fumed powders of
Sborepy6. (d) Visible-light pictures of HCl (g) and NH3 (g) fumed powders of
Although Sborepy6 only shows distinct “turn-off” response at
very acidic conditions (pH < 1) in diluted aqueous solutions due to
its low pKa value (2.63)47 (Fig. S6), it can be applied as solid-state
fluorescent sensor for acidic vapours since the N,N-dimethylamino
group in Sborepy6 can be readily protonated/deprotonated. As
shown in Fig. S7, the fluorescence of Sborepy6 is completely
quenched after adding an excess amount of hydrochloric acid to its
THF solution. While the addition of excess ammonia to the acidified
solution results in the recovery of the fluorescence intensity.
However, amount of precipitation are observed after the addition
of hydrochloric acid to the THF solution of Sborepy3, and the
fluorescence quenching cannot be recovered by adding of excess
ammonia, suggesting the decomposition of Sborepy3 may occurred
in acidic condition. We further investigated the application of
Sborepy6 as solid-state fluorescent sensor for acidic vapours. After
exposing of Sborepy6 to HCl vapour for 3 minutes at room
temperature, the fluorescence emission is quenched by about 43%
Sborepy6
.
of 4025-5237 cm-1. Due to the weak intermolecular
interactions in the solid state, Sborepy3-6 showed intense
emission with high Φf ranging from 25 to 37%. The intense
solid-state emission has been well revealed by X-ray diffraction
analysis. Moreover, the theoretical calculations can predict the
absorption spectra of Sborepy1-6, and reveal that the
absorption peaks can be tuned by incorporation of D ring with
different substituent. In particular, the Sborepy3 and
Sborepy6 exhibit solvatochromism, their emissions showed
remarkable bathochromic shifts as the solvent polarity
increase. Furthermore, Sborepy6 can be applied as solid-state
fluorescent sensor for acidic vapours. The excellent AIE
properties, large Stokes shifts, solvatochromism, acidochromic
properties and high solid quantum yields of Sborepy3-6 make
them valuable AIE luminophores and have great applications in
the fields of fluorescence imaging and materials science.
accompanied by a blue-shifted λem from 545 to 485 nm (ꢁλem = 60
nm), and colour changes from yellow-green to blue. (Fig. 6)
Apparently, the blue-shift of λem is due to the diminished CT
interaction caused by the protonated of N,N-dimethylamino group,
and the reason of the quenched emission may be due to the
48-49
changed molecular conformation and packing structure.28,
Experimental
Accordingly, the fluorescence intensity and original colour of
Sborepy6 could be recovered when its protonated powder is
exposed to NH3 vapour for 3 minutes. On the other hand, even
exposing of Sborepy3 to HCl vapour for 30 minutes, only the
fluorescence intensity was slightly decreased (Fig. S9). This
difference implies that Sborepy6 has stronger binding ability to HCl
vapour than Sborepy3. Furthermore, the reversible colours and
red/blue-shifts of Sborepy6 can be repeated by HCl/NH3 vapour
fuming for 10 cycles without obvious intensity decaying. Therefore,
Sborepy6 can be used as a solid-state fluorescent sensor for acidic
vapours.
Spectroscopic measurements
The fluorescence spectra were measured on
spectrofluorimeter (Hitachi, Japan) luminescence
spectrophotometer (the path length of the quartz cell is 1 cm) with
xenon arc lamp as the light source. Absorbance spectra
measurements were performed on T9CS UV–vis
a
F-4600
a
a
spectrophotometer (Persee Instrument Co., Ltd. Beijing, China)
.
X-ray structure determination
X-ray data were collected on Bruker Smart APEX II CCD
diffractometer. The structure was solved by direct methods (SHELX-
97) and refined by the full-matrix least-squares on F
2 (SHELX-97).50
All the non-hydrogen atoms were refined anisotropically and all the
hydrogen atoms were placed by using AFIX instructions.
Conclusions
Sborepy1: C25H18BNO3; Monoclinic, P2(1), a = 9.8468(4) Å, b =
In this article, propeller-shaped pyridyl-enolato-catecholate/-salicyl
10.1242(4) Å, c = 10.1222(3) Å,
α = 90°, β = 103.228(2)°, γ = 90 (9)°,
spiroborates (Sborepy1-6) were synthesized and characterized.
V = 982.32(6) Å3, Z = 2, F(000) = 447,
ρ
= 1.464 mg/m–3, R1 = 0.0327,
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w
R2 = 0.0860, GOF =1.046, residual electron density between 0.129 3 D. Frath, J. Massue, G. Ulrich, R. Ziessel, Angew. Chem. Int. Ed.,
and -0.137 eÅ–3. CCDC: 1814822.
2014, 53, 2290.
Sborepy2: C26H20BNO4; Orthorhombic, Pn21a, a = 14.1106(9) Å, b 4 A. D’Aléo, M. H. Sazzad, D. H. Kim, E. Y. Choi, J. W. Wu, G. Canard,
= 9.7939(6) Å, c = 15.4646(8) Å,
2137.2(2) Å3, Z = 4, F(000) = 880,
α
= 90°,
β
= 90°,
γ
= 90°, V =
R2
F. Fages, J. C. Ribierre, C. Adachi, Chem. Commun., 2017, 53,
ρ
= 1.309 mg/m–3, R1 = 0.0440,
w
7003.
= 0.1085, GOF = 0.951, residual electron density between 0.131 and 5 Q. H. Zhou, M. M. Zhou, Y. X. Wei, X. G. Zhou, S. L. Liu, S. Zhang, B.
-0.177 eÅ–3. CCDC: 1814823.
Zhang, Phys. Chem. Chem. Phys., 2017, 19, 1516.
Sborepy3: C27H23BN2O3; Monoclinic, P21/c, a = 10.3039(3) Å, b = 6 H. Lu, Q. H. Wang, L. Z. Gai, Z. F. Li, Y Deng, X. Q. Xiao, G. Q. Lai
15.2929(4) Å, c = 14.3427(4) Å, = 90°, = 90°, = 90 (9)°, V = and Z. Shen, Chem. Eur. J., 2012, 18, 7852.
2260.02(10)Å3, Z = 4, F(000) = 912, = 1.276 mg/m–3, R1 = 0.0435, 7 Q. L. Zhao, Z. Sun, J. Mater. Chem. C., 2016,
α
β
γ
ρ
4, 10588.
w
R2 = 0.1274, GOF =1.131, residual electron density between 0.195 8 J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam, B.-Z Tang, Chem.
and -0.189 eÅ–3. CCDC: 1814824.
Rev., 2015, 115, 11718.
Sborepy4: C26H18BNO4; Monoclinic, C12/c1, a = 39.352(3) Å, b 9 P. P. Zhang, W. M. Liu, G. L. Niu, H. Y. Xiao, M. Q. Wang, J. C. Ge, J.
=13.0080(6) Å, c = 16.4737(10) Å,
α
= 90°,
β
=95.835(7)°,
γ
= 90 (9)°,
S. Wu, H. Y. Zhang, Y. Q. Li, P. F. Wang, J. Org. Chem., 2017, 82
,
V = 8388.9(9) Å3, Z = 8, F(000) = 3488,
ρ
= 1.328 mg/m–3, R1 = 0.0500,
3456.
w
R2 = 0.1253, GOF = 1.086, residual electron density between 0.145 10 R. Yoshii, K. Suenaga, K. Tanaka, Y. Chujo, Chem. Eur. J., 2015, 21
and -0.189 eÅ–3. CCDC: 1814825.
7231.
Sborepy5: C27H20BNO5; Orthorhombic, Pca2(1), a = 25.1180(18) Å, 11 X. Q. Wang, Q. S. Liu, H. Yan, Z. P. Liu, M. G. Yao, Q. F. Zhang, S.
,
b = 5.8625(4) Å, c = 15.0463(16) Å,
α
= 90°,
β
=90°,
γ
= 90 (9)°, V =
W. Gong, W. J. He, Chem. Commun., 2015, 51, 7497.
2215.6(3) Å3, Z = 1, F(000) = 936, = 1.347 mg/m–3, R1 = 0.0482,
ρ
wR2 12 D. Li, H. Zhang, Y. Wang, Chem. Soc. Rev., 2013, 42, 8416.
= 0.1083, GOF = 1.014, residual electron density between 0.136 and 13 P. Krishnamoorthy, B. Ferreira, C. S. B. Gomes, D. Vila-Viçosa, A.
-0.151 eÅ–3. CCDC: 1587223.
Charas, J. Morgado, M. J. Calhorda, A. L. Maçanita, P. T, Dyes and
Pigments., 2017, 140, 520.
Sborepy6: C28H23BN2O5; Monoclinic, P2(1)/c, a = 10.3317(13) Å, b
= 15.4676(14) Å, c = 15.5196(16) Å,
α
= 90°,
β
ρ
= 90.330(10)°,
γ
= 90 14 N. Christinat, E. Croisier, R. Scopelliti, M. Cascella, U.
Röthlisberger, K. Severin, Eur. J. Inorg. Chem., 2007, 5177.
(9)°, V = 2480.1(5)Å3, Z = 38, F(000) = 1000,
= 1.281 mg/m–3, R1 =
0.0854,
wR2 = 0.2909, GOF =1.006, residual electron density 15 B. F. Abrahams, D. J. Price, R. Robson, Angew. Chem. Int. Ed.,
between 0.541 and -0.351 eÅ–3. CCDC: 1814826.
Computational details
2006, 45, 806.
16 R. Nishiyabu, Y. J. Kubo, T. D. James, J. S. Fossey, Chem. Commun.
2011, 47, 1124.
,
The time-dependent density functional theory (TD-DFT) calculations
were performed at the hybrid density functional theory level (CAM- 17 R. Clarke, K. L. Ho, A. A. Alsimaree, O. J. Woodford, P. G.
B3LYP) with the 6-31G(d) basis set, using the Gaussian03 software Waddell, J. Bogaerts, W. Herrebout, J. G. Knight, R. Pal, T. J.
package Penfold, M. J. Hall, Chemphotochem., 2017, , 513.
36 The calculations were carried out in the gas phase, using
the crystal structures of Sborepy1-6 as model structures and THF as 18 Q. Y. Wang, H. Zhou, Organometallics., 2017, 36, 3293.
.
1
the optimized solvent.
19 H. S. Kumbhar, S. S. Deshpanda, G. S. Shankarling, Dyes and
Pigments., 2016, 127, 161.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
20 E. M. Sánchez-Carnerero, F. Moreno, B. L. Maroto, A. R.
Agarrabeitia, M. J. Ortiz, B. G. Vo, G Muller, S. de. la. Moya, J. Am.
Chem. Soc., 2014, 136, 3346.
21 S. W. Zhang, Y. X. Wang, F. D. Meng, C. H. Dai, Y. X. Cheng, C. J.
Zhu, Chem. Commun., 2015, 51, 9014.
22 J. Jiménez, L. Cerdán, F. Moreno, B. L. Maroto, I. García-Moreno,
J. L. Lunkley, G. Muller, S. de. la. Moya, J. Phys. Chem. C., 2017,
121, 5287.
We thank the National Key R&D Program of China
(2017YFA0207201), the Natural Science Foundation of China
(21501085), the Natural Science Foundation of Shandong 23 F. D. Meng, Y. Sheng, F. Li, C. J. Zhu, Y. W. Quan, Y. X. Cheng, RSC
Province (ZR2017MB052, ZR2017MB060), Key University Adv., 2017, , 15851.
Science Research Project of Jiangsu Province (17KJA150004) 24 H. Manzano, I. Esnal, T. Marqués-Matesanz, J. Bañuelos, I. López-
7
and the Liaocheng University Funds for Young Scientists
(31805) for financial support.
Arbeloa, M. J. Ortiz, L. Cerdán, A. Costela, I. García-Moreno, J. L.
Chiara, Adv. Funct. Mater., 2016, 26, 2756.
25 A. Blazquez-Moraleja, L. Cerdán, I. García-Moreno, E. Avellanal-
Zaballa, J. Bañuelos, M. L. Jimeno, I. López-Arbeloa, M. J. Ortiz, A.
Costela, J. L. Chiara, Chem. Eur. J., 2018, 24, 3802.
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Abstract
Propeller-shaped pyridyl-enolato-catecholate/-salicyl spiroborates (Sborepy1-6) were synthesized. The
complexes Sborepy3-6 show weak emission in fluid solution and aggregation-induced emission
enhancement in the aggregation state with large Stokes shifts of 4025-5237 cm-1. Moreover, intense
solid-state emissions with high Φf ranging from 25% to 37% were observed for Sborepy3-6 owing to
the weak intermolecular interactions in their solid-state. The AIE and intense solid-state emission have
been revealed via the X-ray diffraction analysis and theoretical calculations. Furthermore, the
solvatochromism in solution state and potential application as fluorescent acidic vapour sensor in the
solid state of Sborepy3 and Sborepy6 were also demonstrated.