Asymmetric Boron-Cored Aggregation-Induced Emission Luminogen with Multiple Functions Synthesized through Stepwise Conversion from a Symmetric Ligand

Article abstract of DOI:10.1021/acs.joc.8b01340

Multifunction luminogens have emerged as promising candidates in high-performance sensor and imaging systems. Concise approaches to the synthesis of such molecules are urgently required both for fundamental research and technological applications. In this

Full text of DOI:10.1021/acs.joc.8b01340

Subscriber access provided by Kaohsiung Medical University
Article
Asymmetric Boron-Cored Aggregation-Induced Emission
Luminogen with Multiple Functions Synthesized
through Stepwise Conversion from a Symmetric Ligand
Feng Qiu, Ning Zhang, Ruizhi Tang, Mingan Zhou, Yao
Wang, Weiwei Wei, Shuai Bi, Sheng Han, and Fan Zhang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01340 • Publication Date (Web): 05 Oct 2018
Downloaded from http://pubs.acs.org on October 5, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
Asymmetric BoronꢀCored AggregationꢀInduced Emission
Luminogen with Multiple Functions Synthesized through
Stepwise Conversion from a Symmetric Ligand
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
a,b,‡
c,‡
b
a
b
b
b
Feng Qiu,
Ning Zhang, Ruizhi Tang, Mingan Zhou, Yao Wang, Weiwei Wei, Shuai Bi,
,
a
,b
Sheng Han,* and Fan Zhang*
a.
School of Chemical and Environmental Engineering, Shanghai Institute of Technology,
Shanghai 201418, P. R. China.
b.
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix
Composites, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
c.
Department of Neurosurgery, Shanghai Fengxian District Central Hospital, Shanghai Jiao Tong
University Affiliated Sixth People's Hospital South Campus, Shanghai 201499, P. R. China
Table of Contents Entry
1
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 2 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ABSTRACT
Multiꢀfunction luminogens have emerged as promising candidates in highꢀperformance sensor
and imaging systems. Concise approaches to the synthesis of such molecules are urgently
required both for fundamental research and technological applications. In this study, a new
symmetric ligand of di(2ꢀhydroxyphenyl)phthalazine with multiple binding sites around a
phthalazine unit was readily synthesized, which could be converted efficiently into an
asymmetric luminogen (OBN-DHPP) through the formation of oxygen−boron−nitrogen bonding.
This molecule has a twistable πꢀextended backbone with a tetraꢀcoordinated boron core bearing
two bulky phenyl groups, giving it abundant optical properties including a large Stokes shift,
piezochromism, and aggregationꢀinduced emission enhancement. Importantly, the presence of a
free phenolic hydroxyl group in the backbone of OBN-DHPP enables the incorporation of
various functional moieties into the asymmetric luminogen. As an example, polyethylene glycol
(PEG)ꢀmodified luminogen (OBN-DHPP-PEG ) was synthesized. In the aqueous medium,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4
5
OBN-DHPP-PEG45 could selfꢀassemble into spherical nanoparticles with low cytotoxicity,
excellent emission performance as well as high solubility. The results of flow cytometry and
fluorescence microscopy reveal that these nanoparticles could be internalized successfully by
HeLa cells, demonstrating their potential application in bioimaging.
2
ACS Paragon Plus Environment

Page 3 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
INTRODUCTION
In the past few decades, luminogens containing tetraꢀcoordinated boron centers, such as
BODIPY, have been developed extensively for application in organic electronics, sensors, and
1
–3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
biological imaging, because of their promising optical and electronic properties. When used as
an organic emitters, BODIPY and its analogs often exhibit weak emission due to the
aggregationꢀcaused quenching effect or severe selfꢀabsorption resulting from their small Stokes
4
shifts. For this reason, the formation of boronꢀcored luminogens with aggregationꢀinduced
emission (AIE) moieties is emerging as an efficient strategy for achieving intriguing emission
5
,6
behavior in solid or aggregated states. Chujo et al. demonstrated that the boron diiminate core
with four phenyl substituent groups I (Scheme 1) exhibited crystallizationꢀinduced AIE
characteristics through the suppression of phenyl ring motion around boron diiminate in its solidꢀ
7
state packing structure. Thus, the development of new boronꢀcored AIE luminogens (AIEgens)
still is highly desirable.
Scheme 1. Typical examples of boronꢀcored AIE luminogens
3
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 4 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Recently, considerable research attention has been paid to the construction of AIEgens with
tetraꢀcoordinated boron cores through the incorporation of bulky biphenyl borate moieties into
8
–10
versatile multidentate aromatic ligands.
The alterable fusion of multiple boron moieties in the
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
main backbones of luminogen molecules has a strong effect on the πꢀconjugated system of these
molecules, enabling the tuning of solidꢀstate packing and optoelectronic properties. For example,
Curiel reported ladderꢀtype boronꢀcored complexes II (Scheme 1) that combined the indolo[3,2ꢀ
8
b]carbazole unit with biphenyl borate, and its optical and electrochemical properties could be
tuned effectively by the number of boron complexations. Recently, we synthesized a dualꢀboronꢀ
cored luminogen III (Scheme 1) with a C ꢀsymmetric structure that exhibited a large Stokes
2
v
shift, high AIE activity, and reversible piezochromism, likely due to the condensed donor–
9
acceptor–donor skeleton associated with the two bulky boronꢀcored moieties. Owing to its
unique luminescence behaviors, this dualꢀboronꢀcored luminogen showed the potential
application in biological imaging. However, to meet the requirements of biological imaging,
AIEgens require extra modification and have complex synthetic routes that are strongly
11ꢀ13
dependent on the rational design and synthesis of ligands.
Considering these factors, this
study focused on the synthesis of symmetric heteroatomꢀrich ligands that can be modified with
multiple functional moieties in sequence through the formation of steric hindrance at active sites,
which was a facile approach to obtaining multiꢀfunctionalized boronꢀcored AIEgens. To the best
of our knowledge, the developing of such method for the synthesis of functionalized boronꢀcored
AIEgens is still a challenge.
In this paper, we describe the concise synthesis of a new symmetric ligand, 1,4ꢀdi(2ꢀ
hydroxyphenyl) phthalazine (DHPP), which has multiple binding sites around a phthalazine unit.
Upon complexation with a sterically bulky diphenylboron moiety, a novel asymmetric boronꢀ
4
ACS Paragon Plus Environment

Page 5 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
cored luminogen (OBN-DHPP) was obtained that could be easily modified at the free phenolic
hydroxyl group in the molecular backbone. For example, the attachment of a poly(ethylene
glycol) (PEG) chain produced the amphiphilic luminogen OBN-DHPP-PEG . The asꢀprepared
4
5
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
luminogens had crowded geometric structures and versatile functionality, including
piezochromism and AIE activity. In particular, PEG modification produced a luminogen with
additional selfꢀassembly behavior and excellent biological imaging properties.
RESULTS AND DISCUSSION
Scheme 2. Synthesis route of asymmetric boronꢀcored AIEgen
The synthetic route for the asymmetric boronꢀcored luminogens OBN-DHPP and OBN-
DHPP-PEG is displayed in Scheme 2. First, commercial 1,2ꢀbenzenedicarbonyl chloride was
45
reacted with 2ꢀmercaptopyridine by using triethylamine as a catalyst to form 1,2ꢀdi(Sꢀ(pyridineꢀ
2
’ꢀyl))benzoylbenzene (1) in a yield of 77%. The key intermediate 1,2ꢀdi(2ꢀ
5
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 6 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
methoxyl)benzoylbenzene (2), a yellow solid, was obtained in a yield of 85% through the
reaction of 1 with the Grignard reagent of 2ꢀmethoxylphenylmagnesium bromide. Subsequently,
di(2ꢀhydroxyl)ꢀbenzoylbenzene (3) was obtained in upon the reduction of 2 with boron
1
4
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
tribromide. Under treatment with hydrazine hydrate, 3 was converted into DHPP. Finally,
OBN-DHPP was obtained through the treatment of DHPP with triphenylboron in toluene (yield:
1
13
9
4%). All compounds were fully characterized using H, C NMR, and highꢀresolution MS. In
1
the H NMR spectrum of DHPP, six wellꢀresolved proton signals in aromatic rings indicated the
material’s C symmetric structure (Figure S1). After DHPP was fused with a biphenylboron
2
v
moiety, the phenol group signals in the spectrum were separated into two peaks, and the peak
corresponding to the fused fragment considerably shifted to the low field compared with that
corresponding to the unfused fragment, because of the electronꢀdeficient nature of the boron
8
center. Notably, the dualꢀboronꢀcored complex, fusing two biphenyl borate moieties with DHPP,
could not be prepared by treatment with an excess amount of triphenylboron (>2.0 eq.),
suggesting that the dense distribution of nitrogen and oxygen atoms in the backbone of DHPP
15
sterically hinders the incorporation of two bulky groups. This unique geometric structure of
DHPP enables different function groups to be conveniently introduced in sequence. Therefore,
the asꢀprepared luminogen (OBN-DHPP) was further modified at the free phenolic hydroxyl
group by coupling a PEG chain through a nucleophilic substitution reaction, forming OBN-
1
6
DHPP-PEG (PEG, Mn = 2000). As shown in Figure S2, a strong C–O–C signal at δ = 3.65
4
5
1
ppm is observed in the H NMR spectrum of OBN-DHPP-PEG , which confirms the
4
5
17
incorporation of PEG onto OBNꢀDHPP.
A single crystal of OBN-DHPP, which was grown by slowly diffusing nꢀhexane into a
chloroform solution containing OBN-DHPP at ambient temperature, was studied by using
6
ACS Paragon Plus Environment

Page 7 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
singleꢀcrystal Xꢀray diffraction (XRD). The top view of the luminogen shows that the middle
phthalazine fragment is fused with one of the phenolic rings through the ligating boron core with
nitrogen and oxygen atoms to form a psuedoꢀsixꢀmembered ring (Figure 1a). Another phenolic
unit linked to the phthalazine ring adopts a twisted conformation, in which the free hydroxyl
group is faced to the boronꢀfused backbone, likely due to the formation of a hydrogen bond with
a distance of 2.06 Å between the free hydroxyl group and the nitrogen atom (N2) in the
phthalazine unit. The dihedral angles defined by the middle phthalazine unit and two benzene
rings are 38.97° (Ph1) and 53.76° (Ph2), respectively (Figure 1b). This difference is caused by
the conformation being locked by the B–O covalent bond. Chelated by nitrogen and oxygen
atoms, a pseudotetrahedron geometry is observed around the boron core bearing two benzene
rings, with the boron atom slightly deviated from the mean plane of the fused backbone. A
dihedral angle of 21.85° is defined between the mean plane of the fused phthalazine backbone
and the plane consisting of boron, nitrogen, and oxygen atoms. This twisted conformation is
resulting from steric congestion upon the fusion of a bulky biphenyl borate moiety with DHPP.
The lengths of B–O and B–N bonds are 1.49 and 1.66 Å, respectively, coinciding with the
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
8,19
covalent and coordination natures of these bonds.
In the packing diagram (Figure 1c-d), the
molecule has a parallel packing motif consisting of staged faceꢀtoꢀface dimers aligned in an
edgeꢀtoꢀedge manner in each stacking column, with distances ranging from 3.34 to 3.52 Å
between neighboring molecules. A weak π−π stacking interaction between two phthalazines with
a shortest distance of approximately 3.6 Å is observed in each dimer, which is probably due to
8,10
steric hindrance of the bulky phenyl substituents on the boron atom.
In each of the parallel
columns, many intermolecular interactions are discovered, such as C–H···O interaction (2.70 Å)
7
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 8 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
9
and C−H···π interactions (2.89 and 3.39 Å). This high congestion in the bulk phase of OBN-
DHPP appears to be favorable for a strong AIE effect.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 1. Crystal structures (a, b) and packing diagrams (c, d) of OBN-DHPP in the topꢀ and
sideꢀview representations, respectively
The optical properties of DHPP and OBN-DHPP in dichloromethane were investigated using
UV−visible (UVꢀvis) and photoluminescence (PL) spectroscopy. The UVꢀvis spectrum of DHPP
contains a set of absorption bands at 253 and 352 nm as well as a shoulder peak at approximately
3
16 nm, which are assigned to the combined transitions of the phthalazine core and two phenol
units. The spectrum of OBN-DHPP, formed through fusion of the B(Ph) moiety, contains
2
absorption bands at 262, 326, and 406 nm, which is considerable bathochromic shift (185185.2
−
1
cm ) with respect to those of DHPP (Figure 2a), confirming the formation of an extended πꢀ
8
ACS Paragon Plus Environment

Page 9 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
conjugated backbone. The broad featureless absorption bands of OBN-DHPP reveal substantial
conformational isomerization resulting from its rotatable substituents and less rigid backbone.
1
0
This finding is in agreement with those of previous crystallographic analyses. The absorption
peaks at 262 and 326 nm in the UV region are attributed to π−π* transitions of the aromatic
backbone. By contrast, the absorption peak at 406 nm probably originates from intramolecular
charge transfer from the donor of biphenyl borate moieties to the acceptor of phthalazine parts.
The solvatochromic properties of OBN-DHPP in different organic solvents were also
investigated (Figure S4). A moderate hypsochromic shift of the S –S transition is observed with
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
0
1
increasing solvent polarity. This blue shift of the main absorption bands suggests that the dipole
moment of OBN-DHPP is easily polarized in the ground state, with respect to its asymmetric Dꢀ
20
A structure.
DHPP is discovered to exhibit weak fluorescence emission, probably because of lowꢀlying
2
1
n→π* transitions from typical phthalazine units. By contrast, OBN-DHPP, incorporated a
B(Ph) moiety, exhibits green luminescence with an emission maxima (λ ) at 560 nm in CH Cl
2
2
em
2
(Figure 2b). Relative to its absorption spectrum, OBN-DHPP has a broad emission profile with
−
1
a large Stokes shift of 64935.1 cm , which is caused by its lowꢀrigidity backbone. The low
fluorescence quantum yield of OBN-DHPP in CH Cl , determined using an integrating sphere,
2
2
22,23
is probably due to the lowꢀrigidity molecular skeleton and rotatable phenyl substituents.
Moreover, the UVꢀvis absorption and PL spectra of OBN-DHPP-PEG in CH Cl show little
4
5
2
2
differences compared with those of OBN-DHPP, indicative of the weak influence of PEG on the
conjugated backbone of OBN-DHPP. The photophysical properties of OBN-DHPP and OBN-
DHPP-PEG are summarized in Table 1.
4
5
9
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 10 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 2. UV−vis absorption spectra (a) and fluorescence spectra (b) of DHPP and OBN-DHPP
−
5
in CH Cl (2 × 10 M).
2
2
Table 1. Photophysical data of the asꢀprepared compounds
[
a]
[b]
λem
[c]
Φf
[d]
[e]
[f]
λabs
SS
τf
kr
knr
7
sample
log ε
ꢀ1
7
ꢀ1
ꢀ1
[
nm]
[nm]
437
560
[%]
ꢀ
[cm ]
177647.0
64935.1
[ns] [10 s ] [10 s ]
DHPP
352
406
4.13
3.98
ꢀ
OBN-DHPP
3.02
2.91
3.66
1.04
0.86
67.92
26.46
OBN-DHPP-
PEG45
401
398
ꢀ
ꢀ
534
535
3.15
4.98
75188.0
72992.7
OBN-DHPP-
[g]
4.79
1.04
19.84
PEG45
[
a] Longest absorption maximum. [b] Emission maximum upon excitation at the longest
absorption maximum. [c] Absolute quantum yield determined by using with the integrating
sphere. [d] Stokes shift, evaluated from the absorption maxima and emission spectra maxima [e]
Radiative rate constant k = Φ /τ . [f] Nonꢀradiative rate constant k = (1ꢀΦ )/τ . [g] solvent is
r
f
f
nr
f
f
water.
The electronic structure of the asꢀprepared OBN-DHPP was further evaluated by performing
cyclic voltammetry in CH CN. As illustrated in Figure 3a, OBN-DHPP exhibits reversible oneꢀ
3
10
ACS Paragon Plus Environment

Page 11 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
electron reduction with the redox peak at E = −1.33 V, indicative of the electronꢀdeficient nature
1
of boronꢀfused phthalazine. An irreversible oxidation peak is observed at E = 1.56 V, which
2
1
0
likely results from the substituted phenyl groups attached to boron atoms. On the basis of their
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
onset potential values, the LUMO and HOMO energy levels of OBN-DHPP are calculated as
−3.01 and −5.90 eV, respectively. Moreover, calculated from the optical band gap (2.68 eV) and
HOMO energy level, the LUMO energy level of OBN-DHPP is −3.22 eV (Table S1).
To gain insights into the optoelectronic structure of OBN-DHPP, theoretical calculations were
performed using TDꢀDFT (with the RB3LYP/6ꢀ31G (d) level) (Figure 3b). The LUMO energy
level of OBN-DHPP is predominantly localized on the phthalazine backbone, consistent with
the electronꢀdeficient nature of diazanaphthalene. The HOMO energy level is mainly distributed
over the phenyl substituents attached to the boron atom. Such separation of molecular orbitals
between the HOMO and LUMO energy level is caused by steric effect around the boron atom,
2
4
impeding electron delocalization over the entire skeleton, as illustrated in its crystal structure.
In the calculated UVꢀvis spectrum, the absorption band at 467 nm in Figure S5 is governed by
the electron transition from HOMO to LUMO, which represents the absorption band at 406 nm
in experimental result, resulting in a negative solvatochromic effect. Accordingly, the
computational HOMO and LUMO energy levels of OBN-DHPP are −5.84 and −3.24 eV,
25
respectively, which are consistent with those of experimental results.
11
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 12 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ꢀ
3
Figure 3. (a) CV curves for OBN-DHPP in CH CN at the concentration of 1×10 M. (0.1 mol
3
ꢀ1
ꢀ1
L nꢀBu NPF , at a scan rate of 100 mV s ); (b) Calculated molecular orbitals of OBN-DHPP.
4
6
Owing to the rotatable phenyl substituents in boron centers and the weak rigidity of the fused
backbone, the temperatureꢀdependent fluorescence of OBN-DHPP in toluene was evaluated. In
comparison with that at room temperature, the fluorescent intensity of OBN-DHPP at 77 K is
remarkably higher with a blue shift of 34 nm, which can be attributed to reorganization energy at
the low temperature through the restriction of geometric relaxation excitedꢀstate planarization
2
6,27
and the freezing of lowꢀfrequency outꢀofꢀplane vibration (Figure S6).
The fluorescence
properties of OBN-DHPP in the aggregated state were also investigated. A series of emission
spectra of OBN-DHPP in THF/water mixtures with different volumetric ratios of water are
shown in Figure 4a. In pure THF, the fluorescence spectrum shows a flat line parallel to the
abscissa, indicating poor fluorescence. When water is added to the THF solution, the
fluorescence intensity increases rapidly with increasing water content, and is the highest at 70%
(
v/v) water (Figure 4b, Figure S7). This AIE phenomenon is due to considerable restriction of
intramolecular rotational and vibrational motion of the phenyl ring during aggregation. When the
water fraction is higher than 70%, lower fluorescence intensity is obtained, and the emission
12
ACS Paragon Plus Environment

Page 13 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
maximum is blueꢀshifted by more than 22 nm. This is probably caused by strong intermolecular
interactions in the aggregate state of OBN-DHPP, as verified by the aforementioned
2
7,28
temperatureꢀdependent fluorescence behavior.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
−4
Figure 4. (a) Fluorescence spectra of OBN-DHPP (10 M) in THF/water mixtures with
different water fractions; (b) The plot of I/I as a function of water fraction; (c) The solid
0
fluorescence spectra of OBN-DHPP; (d) Powder XRD patterns of OBN-DHPP.
Notably, it is found that OBN-DHPP crystallizes in a monoclinic system with high AIE
29
activity confers its mechanoluminescence ability, according to the previous reports. Under
illumination with light at 365 nm, the OBN-DHPP powders emit brilliant green light with an
emission maximum at λem = 503 nm. After grinding, the emission of the powders moves to
yellow light, which could be recovered to green through treatment with CH Cl vapor (Figure 4c,
2
2
13
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 14 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Figure S8). This reversible conversion is attributed to the highly tunable intermolecular
interactions as well as the strong dipole moment associated with the material’s asymmetric DꢀA
3
0
structure in OBN-DHPP. To investigate the influence of molecular packing on luminescence
properties, powder XRD was employed to analyze the aggregation behavior of OBN-DHPP
before and after grinding. OBN-DHPP has an XRD pattern with intense and sharp peaks
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(Figure 4d), indicating its highly crystalline character. Because of weak intermolecular
interactions, OBN-DHPP could be converted into an amorphous state with weak diffraction
peaks through grinding treatment. This alteration of the packing behavior of OBN-DHPP is in
9
agreement with the solid luminescence performance detailed previously.
Figure 5. (a) UVꢀvis absorption and (b) PL spectra of OBN-DHPP-PEG in CH Cl and water.
4
5
2
2
To assess the biological applicability of the boronꢀcored AIEgens obtained in this study, the
water solubility of OBN-DHPP and OBN-DHPP-PEG was examined (Figure S9). In water,
4
5
hydrophobic OBN-DHPP forms numerous large aggregates, making it unsuitable for biological
3
1
application as a fluorescent probe. By contrast, OBN-DHPP-PEG is amphiphilic and can be
4
5
highly dispersible in water. As shown in Figure 5 and Table 1, both the UVꢀvis absorption and
PL spectra of OBN-DHPP-PEG in aqueous solution are similar to those in dichloromethane.
4
5
14
ACS Paragon Plus Environment

Page 15 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
The favorable fluorescence of OBN-DHPP-PEG45 in water is attributed to its unique AIE
properties. To clarify the selfꢀassembly behavior of OBN-DHPP-PEG , the size and
4
5
morphology of OBN-DHPP-PEG45 aggregates in aqueous medium were investigated using
dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS curve
shows a narrow distribution with an average aggregate size of approximately 250 nm (Figure
S9b). The TEM image in Figure 6a indicates the formation of spherical micelles with an average
diameter of 250 ± 50 nm, which is consistent with the DLS data. The selfꢀassembly mechanism
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
32
of OBN-DHPP-PEG45 is further demonstrated in Figure S9c. Overall, these results
demonstrate that OBN-DHPP-PEG is suitable for application in biological imaging.
4
5
Figure 6. (a) TEM photograph of OBN-DHPP-PEG nanoparticles at concentration of 0.5 mg
4
5
mLꢀ1 in water, inset: selfꢀassembly model of OBN-DHPP-PEG45 nanoparticles; (b)
fluorescence images of HeLa cells incubated with OBN-DHPP-PEG for 2h.
45
The in vitro cytotoxicity of OBN-DHPP-PEG45 was evaluated using an MTT assay with
NIH/3T3 normal cells. After 24 h of incubation, cell viability remains above 90% compared with
−1
untreated cells when the concentration of OBN-DHPP-PEG is 1 mg mL , indicating the low
4
5
15
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 16 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
cytotoxicity of OBN-DHPP-PEG nanoparticles containing biocompatible PEG shell (Figure
4
5
S10). According to the high evaluation of AIE properties, biocompatibility and stability, the
−
1
cellular uptake of OBN-DHPP-PEG nanoparticles at 500 ꢁg mL into HeLa cells was
4
5
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
evaluated using flow cytometry. Compared with that of nonꢀpretreated cells, the relative
geometrical mean fluorescence intensity of OBN-DHPP-PEG increases with the prolongation
4
5
of incubation time, suggesting progressive attachment of the nanoparticles to HeLa cells (Figure
3
3
S11). The endocytosis of these nanoparticles was also determined by using a fluorescence
microscope. As shown in Figure 6b, strong green fluorescence is observed mainly in the
cytoplasmic regions of living cells cultured with OBN-DHPP-PEG for 2 h, demonstrating the
4
5
successful internalization of nanoparticles in HeLa cells. The brightness of the fluorescence in
cells is stronger for longer incubation times (Figure S12), which is consistent with the flow
cytometry findings. On the basis of the AIE properties and nanometer size of OBN-DHPP-
PEG in water, biological applications of this AIEgen are currently being investigated.
4
5
CONCLUSIONS
In this study, we synthesized a new symmetric phthalazineꢀbased ligand with dense multiple
binding sites, enabling sequential functionalization through the incorporation of a bulky biphenyl
borate and PEG moiety. Two asymmetric boronꢀcored AIEgens, OBN-DHPP and OBN-DHPP-
PEG , were concisely converted. The asꢀprepared OBN-DHPP exhibits an extended πꢀ
4
5
conjugated DꢀA structure, which is associated with its congested geometric structures. This
unique structure endow the OBN-DHPP with multiple functions, including large Stokes shift,
piezochromism, and AIE property. In the case of OBN-DHPP-PEG , selfꢀassembled
4
5
nanoparticles in water exhibit good fluorescence performance and low cytotoxicity. Through
incubating OBN-DHPP-PEG45 with HeLa cells, the nanoparticles were demonstrated to be
16
ACS Paragon Plus Environment

Page 17 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
internalized successfully with favorable visualization in the cytoplasm of cells, indicating their
suitability for cellular imaging and sensing. This work reveals a new and highly efficient method
for concisely synthesizing complex organic luminogens with multiple functions.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
EXPERIMENTAL SECTION
Materials and Methods. Phthaloyl dichloride, boron tribromide, 2ꢀbromoanisole, hydrazine
hydrate, 2ꢀmercaptopyridine, pꢀtoluenesulfonyl chloride, sodium hydrate, potassium carbonate,
sodium chloride, petroleum ether, dichloromethane and all other common solvents were
purchased from Adamasꢀbeta Reagent. Triphenylboron, magnesium and poly(ethylene glycol)
were purchased from Acros. Triethylamine and dichloromethane were distilled from CaH under
2
nitrogen gas. Tetrahydrofuran was refluxed over sodium wires and benzophenone until
anhydride and then distilled to use immediately. All reactions were carried out under a nitrogen
atmosphere and performed using Schlenk techniques.
1
13
H and C nuclear magnetic resonance (NMR) spectra were recorded on a Mercury Plus 400
(400 MHz for proton, 100 MHz for carbon) spectrometer with tetramethylsilane as the internal
reference using CDCl as solvent in all cases. Melting points were taken on a WRSꢀ2A melting
3
point apparatus. Mass spectrometry was measured by an Thermo Scientific Q Exactive Focus
Mass spectrometer. Ultravioletꢀvisible (UVꢀVis) spectra were recorded on a HITACHI Uꢀ4100
Spectrophotometer. Fluorescence spectroscopy (PL) spectra were obtained with a FluoroMaxꢀ4
spectrophotometer. Fluorescent quantum yield (Φ) and Timeꢀresolved fluorescence spectra were
recorded on a PTIꢀQM/TM/IM steadyꢀstate & timeꢀresolved fluorescence spectrofluorometer
(USA/CAN Photon technology international Int.) by using the timeꢀcorrelated singleꢀphoton
counting (TCSPC) technique. Cyclic voltammetry (CV) was performed on a Chenhua 650D
electrochemical analyzer in anhydrous CH CN containing recrystallized tetraꢀnꢀbutylꢀ
3
17
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 18 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ammoniumhexa fluorophosphate (TBAPF , 0.1M) as supporting electrolyte at 298 K. A
6
conventional three electrode cell was used with a platinum working electrode (surface area of 0.3
2
mm ) and a platinum wire as the counter electrode. The Pt working electrode was routinely
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
polished with a polishing alumina suspension and rinsed with acetone before use. The measured
potentials were recorded with respect to Ag/AgCl reference electrode. All electrochemical
measurements were carried out under an atmospheric pressure of nitrogen. Fourier transform
infrared spectroscopy (FTIR) spectra were recorded on a Paragon 1000 instrument by KBr
sample holder method. Transmission electron microscopy (TEM) studies were performed with a
JEOL 2010 instrument at a voltage of 200 kV. Samples were prepared by dropꢀcasting micelle
solutions onto carbonꢀcoated copper grids, and then airꢀdrying at room temperature before
measurement. Dynamic light scattering (DLS) measurements were performed with a Malvern
Zetasizer Nano S apparatus (Malvern Instruments Ltd) equipped with a 4.0 mW HeꢀNe laser
operating at 633 nm. All samples were measured at room temperature and a scattering angle of
o
1
73 .
Synthetic procedures
Synthesis of 1,2-di(S-(pyridine-2’-yl))benzoylbenzene (1). The mixture of 2ꢀmercaptopyridine
(7 g, 63 mmol) and triethylamine (10 mL, 72.14 mmol) was dissolved in THF (80 mL) under the
protection of nitrogen. The mixture was cooled in iceꢀwater bath for 20 min, then, a solution of
phthaloyl dichloride (6 g, 29.55 mmol) in THF solution (20 mL) was quickly added. The reaction
was quenched instantly with 1% HCl (100 mL) and extracted with CH Cl . The combined
2
2
organic fractions were washed with water until neutrality, dried over MgSO and recrystallized
4
1
from Et O. The product was obtained as white solid (8.1 g, 77%). H NMR (400 MHz, CDCl ) δ
2
3
8
.64 (m, J = 7.8 Hz, 2H; PyꢀH), 7.89 (m, 2H; PyꢀH), 7.78 (m, 4H; ArꢀH), 7.66 (m, 2H; PyꢀH),
18
ACS Paragon Plus Environment

Page 19 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
13
7
.31 (m, 2H; PyꢀH). C NMR (100 MHz, CDCl ) δ 190.3, 151.4, 150.4, 137.4, 136.7, 132.0,
3
o
+
1
31.5, 128.8, 123.8. mp = 78ꢀ85.7 C. HRMS (ESI, m/z) calcd for C H N O S [M + H]
28 13 2 2 2
353.0413; Found 353.0399.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Synthesis of 1,2-di(2-methoxyl)benzoylbenzene (2). A solution of 2ꢀbromoanisole (465 mg, 2.5
mmol) in THF (10 mL) was slowly added to a mixture of iodine activated magnesium (70 mg,
o
2
.92 mmol) in THF (5 mL) to form the Grignard reagent in 5 h at 60 C. Afterwards, the cold
reagent was slowly added to a flask containing compound 1 (352 mg, 1.0 mmol) in absolute THF
o
(
50 mL) at 0 C and stirred overnight. The suspension became brown gradually. Then, the
reaction was quenched with 10% HCl (100 mL). After adding dichloromethane, the organic
phase was washed with NaOH aqueous solution and water, and the dichloromethane was
removed under reduced pressure, the solid was collected and purified by silicaꢀgel column
chromatography (dichloromethane: petroleum ether = 1:1, v/v) to give compound 2 as a yellow
1
solid powder (294 mg) in yield of 85%. H NMR (400 MHz, CDCl ) δ 7.50 (t, J = 3.4 Hz, 4H),
3
1
3
7.37 (dd, J = 3.2 Hz, 5.8 Hz, 4H), 6.88 (dd, J = 3.2 Hz, 5.8 Hz, 4H), 3.63 (s, 6H). C NMR (100
MHz, CDCl ) δ 196.0, 158.8, 141.2, 135.0, 133.5, 131.5, 130.4, 129.3, 127.9, 120.4, 112.0, 55.8.
3
o
+
mp = 125.4ꢀ136.8 C. HRMS (ESI, m/z) calcd for C H O [M + H] 347.1278; Found
2
2
19
4
347.1267.
Synthesis of di(2-hydroxyl)benzoylbenzene (3). Under the protection of nitrogen, compound 2
o
(
0.38 g, 1.1 mmol) was well dissolved in dichloromethane (10 mL) at 0 C, the mixture of boron
tribromide (0.84 mL, 9 mmol) and dichloromethane (10 mL) was added dropwise under stirring.
The reaction temperature was heated to room temperature for overnight. Then, the reaction was
quenched with water, the obtained organic phase was collected and concentrated under reduced
pressure. The solid was purified by silicaꢀgel column chromatography with dichloromethane: to
19
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 20 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
give compound 3 as a white solid powder (0.3 g) in yield of 75%. H NMR (400 MHz, CDCl ) δ
3
1
1.63 (s, 2H, OH), 7.64 (m, 4H; ArꢀH), 7.49 (t, J = 7.6 Hz, 4H; ArꢀH), 7.02 (d, J = 8.8 Hz, 2H;
1
3
ArꢀH), 6.84 (dd, J = 1.2 Hz, 2H; ArꢀH). C NMR (100 MHz, CDCl ) δ 201.5, 163.2, 138.9,
3
o
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
37.0, 133.4, 130.4, 129.8, 119.1, 118.6. mp = 156.6ꢀ171.7 C. HRMS (ESI, m/z) calcd for
+
C H O [M + H] 319.0965; Found 319.0955.
20
15
4
Synthesis of 1,4-di(2-hydroxyphenyl) phthalazine (DHPP). A suspension of compound 3 (1.4
g, 4.7 mmol) and hydrazine hydrate (0.24 mL, 5 mmol) in ethanol (30 mL) was stirred for 48 h at
o
7
5 C. After reaction, the ethanol was removed by filtration, and the precipitate was washed with
1
ethanol three time, the product was obtained as pale yellow solid (1.35 g) in yield of 80.3%. H
NMR (400 MHz, CDCl ) δ 11.39 (s, 2H, OH), 8.48 (dd, J = 3.6 Hz, 3.2 Hz, 2H; ArꢀH), 7.98 (dd,
3
J = 3.2 Hz, 3.2 Hz, 2H; ArꢀH), 7.76 (d, J = 8.0 Hz, 2H; ArꢀH), 7.48 (t, J = 8.4 Hz, 2H; ArꢀH),
13
7
.26 (d, J = 8.0 Hz, 2H; ArꢀH), 7.10 (t, J = 8.0 Hz, 2H; ArꢀH). C NMR (100 MHz, CDCl ) δ
3
o
2
01.5, 163.2, 138.9, 137.0, 133.4, 130.4, 129.8, 119.1, 118.6. mp > 230.5 C. HRMS (ESI, m/z)
+
calcd for C H N O [M + H] 315.1128; Found 315.1117.
2
0
15
2
2
Synthesis of diphenylboron-fused di(2-hydroxyphenyl) phthalazine (OBN-DHPP). A
mixture of DHPP (314 mg, 1 mmol) and triphenylboron (484 mg, 2 mmol) was dissolved in
dried toluene (50 mL). The mixture solution was heated to reflux at 110 °C for 24 hour under
nitrogen. After cooling to room temperature, toluene was removed under reduced pressure, the
solid was collected and washed with petroleum ether for four times to give OBN-DHPP (455 mg)
1
as a yellow solid powder in yield of 94%. H NMR (400 MHz, CDCl ) δ 8.72 (d, J = 9.6 Hz; 1H,
3
ArꢀH), 8.42 (d, J = 9.6 Hz; 1H, ArꢀH), 8.35 (s, 1H; OH), 8.11 (d, J = 9.6 Hz; 2H, ArꢀH), 7.76 (d,
J = 9.6 Hz, 1H; ArꢀH), 7.66 (d, J = 8.0 Hz, 1H; ArꢀH), 7.58 (t, J = 8.0 Hz, 1H; ArꢀH), 7.50ꢀ7.42
1
3
(
m, 6H; ArꢀH), 7.28ꢀ7.23 (m, 6H; ArꢀH), 7.18ꢀ6.97 (m, 3H; ArꢀH). C NMR (100 MHz, CDCl )
3
20
ACS Paragon Plus Environment

Page 21 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
δ 162.8, 157.1, 156.2, 150.8, 135.3, 134.9, 133.9, 133.3, 132.7, 131.5, 130.6, 128.2, 128.0, 127.3,
o
1
27.2, 126.8, 126.5, 121.8, 119.6, 119.5, 119.4, 117.1, 116.7. mp > 161.7 C. HRMS (ESI, m/z)
ꢀ
calcd for C H BN O [M ꢀ H] 477.1769; Found 477.1778.
3
2
22
2
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
16
Synthesis of OBN-DHPP-PEG . A mixture of OBN-DHPP (100 mg, 0.21 mmol), PEGꢀOTs
4
5
(680 mg, 0.32 mmol) and excess potassium carbonate was dissolved in dried acetonitrile (80 mL)
with the protection of nitrogen. The mixture solution was heated to reflux for 24 hour under
nitrogen. After cooling to room temperature, water and dichloromethane were added into
solution, the organic phase was washed with deionized water several times to remove unreacted
PEG, and dried under a vacuum. The final product was obtained as pale yellow solid in yield of
1
8
2%. H NMR (400 MHz, CDCl ) δ 8.64 (d, J = 9.6 Hz; 1H, ArꢀH), 8.42 (d, J = 9.0 Hz, 1H, Arꢀ
3
H), 8.08 (br, 1H, ArꢀH), 7.98ꢀ7.72 (m, 6H, ArꢀH), 7.57ꢀ7.30 (m, 6H, ArꢀH), 7.21ꢀ7.05 (m, 6H,
ArꢀH), 6.96 (t, J = 8.0 Hz, 1H; ArꢀH), 6.96 (t, J = 8.0 Hz, 1H; ArꢀH), 6.87 (d, J = 9.0 Hz, 1H,
ArꢀH); 3.81ꢀ3.46 (m, 88H, OCH CH ) 3.37 (s, 3H, OCH ).
2
2
3
ASSOCIATED CONTENT
Supporting Information
1
13
Biological experimental information, H/ C NMR spectra, HRMS Spectra, FTIR Spectra, UVꢀ
vis spectra, fluorescence spectra, and Singleꢀcrystal Xꢀray diffraction data for OBN-DHPP
(CIF). These materials are available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: fanꢀzhang@sjtu.edu.cn; hansheng654321@sina.com.
Author Contributions
21
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 22 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
‡
These authors contributed equally to this work.
Notes
The authors declare no competing financial interest.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ACKNOWLEDGMENT
This work was financially supported by the National Natural Science Foundation of China
(51403126, 21574080, 61306018 and 21504057), Shanghai Committee of Science and
Technology (15JC1490500, 16JC1400703, and 17ZR1441700), Open Project Program of the
State Key Laboratory of Photocatalysis on Energy and Environment (SKLPEEꢀKF201702,
Fuzhou University), State Key Laboratory of Supramolecular Structure and Materials
(sklssm201732, Jinlin University) and Scientific Research Foundation of Shanghai Institute of
Technology (YJ2015ꢀ31). We also thank Jingjing Guo and Anjun Qin (South China University
of Technology) for the measurement of temperatureꢀdepended fluorescence spectroscopy.
REFERENCES
1
. Anthony, J. E. Functionalized Acenes and Heteroacenes for Organic Electronics. Chem. Rev.
006, 106, 5028ꢀ5048.
2
2. Narita, A.; Wang, X.ꢀY.; Feng, X.; Müllen, K. New advances in nanographene chemistry.
Chem. Soc. Rev. 2015, 44, 6616ꢀ6643.
3
. Tanaka, K.; Chujo, Y. Recent progress of optical functional nanomaterials based on
organoboron complexes with βꢀdiketonate, ketoiminate and diiminate. NPG Asia Mater.
2
015, 7, e223.
4
. Thomas III, S. W.; Joly, G. D.; Swager, T. M. Chemical Sensors Based on Amplifying
Fluorescent Conjugated Polymers. Chem. Rev. 2007, 107, 1339ꢀ1386.
22
ACS Paragon Plus Environment

Page 23 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
5
. Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Aggregationꢀinduced emission: phenomenon,
mechanism and applications. Chem. Comm. 2009, 4332ꢀ4353.
6. Liu, J.; Chen, C.; Ji, S.; Liu, Q.; Ding, D.; Zhao, D.; Liu, B. Long wavelength excitable nearꢀ
infrared fluorescent nanoparticles with aggregationꢀinduced emission characteristics for
imageꢀguided tumor resection. Chem. Sci. 2017, 8, 2782ꢀ2789.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
7
. Yoshii, R.; Hirose, A.; Tanaka, K.; Chujo, Y. Boron Diiminate with AggregationꢀInduced
Emission and CrystallizationꢀInduced EmissionꢀEnhancement Characteristics. Chem.–Eur. J.
2
014, 20, 8320ꢀ8324.
8
. Curiel, D.; MásꢀMontoya, M.; Usea, L.; Espinosa, A.; Orenes, R. A.; Molina, P.
IndolocarbazoleꢀBased Ligands for LadderꢀType FourꢀCoordinate Boron Complexes. Org.
Lett. 2012, 14, 3360ꢀ3363.
9
. Fu, Y.; Qiu, F.; Zhang, F.; Mai, Y.; Wang, Y.; Fu, S.; Tang, R.; Zhuang, X.; Feng, X. A dualꢀ
boronꢀcored luminogen capable of sensing and imaging. Chem. Comm. 2015, 51, 5298ꢀ5301.
0. Qiu, F.; Zhang, F.; Tang, R.; Fu, Y.; Wang, X.; Han, S.; Zhuang, X.; Feng, X. Triple Boronꢀ
Cored Chromophores Bearing Discotic 5,11,17ꢀTriazatrinaphthyleneꢀBased Ligands. Org.
Lett. 2016, 18, 1398ꢀ1401.
1
1
1. Chen, B.; Feng, G.; He, B.; Goh, C.; Xu, S.; Ramos‐Ortiz, G.; Aparicio‐Ixta, L.; Zhou, J.;
Ng, L.; Zhao, Z. Silole‐Based Red Fluorescent Organic Dots for Bright TwoꢀPhoton
Fluorescence In vitro Cell and In vivo Blood Vessel Imaging. Small 2016, 12, 782ꢀ792.
2. Liu, Y.; Yu, Y.; Lam, J. W. Y.; Hong, Y.; Faisal, M.; Yuan, W. Z.; Tang, B. Z. Simple
Biosensor with High Selectivity and Sensitivity: ThiolꢀSpecific Biomolecular Probing and
Intracellular Imaging by AIE Fluorogen on a TLC Plate through a Thiol–Ene Click
Mechanism. Chem –Euro. J. 2010, 16, 8433ꢀ8438
1
23
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 24 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
1
3. Leung, C. W. T.; Hong, Y.; Chen, S.; Zhao, E.; Lam, J. W. Y.; Tang, B. Z. A Photostable
AIE Luminogen for Specific Mitochondrial Imaging and Tracking. J. Am. Chem. Soc. 2013,
135, 62ꢀ65.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
4. Lee W. Y.; Moon B. G.; Park C.ꢀH.; Bang S.ꢀH.; Lee J. H. Synthetic Studies on the
Derivatives of Dibenzoylbenzenes. Bull. Korean Chem. Soc. 1988, 9, 325ꢀ328.
5. Tamgho, I.ꢀS.; Hasheminasab, A.; Engle, J. T.; Nemykin, V. N.; Ziegler, C. J. A New Highly
Fluorescent and Symmetric Pyrrole–BF2 Chromophore: BOPHY. J. Am. Chem. Soc. 2014,
1
1
36, 5623ꢀ5626.
1
6. Qiu, F.; Wang, D.; Zhu, Q.; Zhu, L.; Tong, G.; Lu, Y.; Yan, D.; Zhu, X. RealꢀTime
Monitoring of Anticancer Drug Release with Highly Fluorescent StarꢀConjugated Copolymer
as a Drug Carrier. Biomacromolecules, 2014, 15, 1355ꢀ1364.
1
7. Qiu, F.; Tu, C.; Chen, Y.; Shi, Y.; Song, L.; Wang, R.; Zhu, X.; Zhu, B.; Yan, D.; Han, T.
Control of the Optical Properties of a Star Copolymer with a Hyperbranched Conjugated
Polymer Core and Poly(ethylene glycol) Arms by Self‐Assembly. Chem –Euro. J. 2010, 16,
1
2710ꢀ12717.
1
8. Balijapalli, Iyer, U. S. K. Synthesis and Optical Properties of a Series of GreenꢀLightꢀ
Emitting 2ꢀ(4ꢀPhenylquinolinꢀ2ꢀyl)phenolꢀBF Complexes (Boroquinols). Eur. J. Org. Chem.
2
2
015, 2015, 5089ꢀ5098.
19. Zhou, Y.; Xiao, Y.; Chi, S.; Qian, X. Isomeric Boron−Fluorine Complexes with
Donor−Acceptor Architecture:ꢂ Strong Solid/Liquid Fluorescence and Large Stokes Shift.
Org. Lett. 2008, 10, 633ꢀ636.
20. Araneda, J. F.; Piers, W. E.; Heyne, B.; Parvez, M.; McDonald, R. High Stokes Shift
AnilidoꢀPyridine Boron Difluoride Dyes. Angew. Chem. Int. Ed. 2011, 50, 12214ꢀ12217.
24
ACS Paragon Plus Environment

Page 25 of 26
The Journal of Organic Chemistry
1
2
3
4
5
6
7
8
9
2
2
1. Tang, R.; Zhang, F.; Fu, Y.; Xu, Q.; Wang, X.; Zhuang, X.; Wu, D.; Giannakopoulos, A.;
Beljonne, D.; Feng, X. Efficient Approach to ElectronꢀDeficient 1,2,7,8ꢀTetraazaperylene
Derivatives. Org. Lett. 2014, 16, 4726ꢀ4729.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2. Sun, L.; Zhang, F.; Wang, X.; Qiu, F.; Xue, M.; Tregnago, G.; Cacialli, F.; Osella, S.;
Beljonne, D.; Feng, X. Geometric and Electronic Structures of Boron (III)‐Cored Dyes
Tailored by Incorporation of Heteroatoms into Ligands. Chem.–Asian J. 2015, 10, 709ꢀ714.
3. Glotzbach, C.; Godeke, N.; Frohlich, R.; Daniliuc, C.ꢀG.; Saito, S.; Yamaguchi, S.;
Wurthwein, E.ꢀU. Fluorescent benzeneꢀcentered monoꢀ, bisꢀ and trisꢀtriazapentadieneꢀboron
complexes. Dalton Trans. 2015, 44, 9659ꢀ9671.
2
2
4. Xu, S.; Liu, T.; Mu, Y.; Wang, Y. F.; Chi, Z.; Lo, C. C.; Liu, S.; Zhang, Y.; Lien, A.; Xu, J.
An Organic Molecule with Asymmetric Structure Exhibiting Aggregation ‐ Induced
Emission, Delayed Fluorescence, and Mechanoluminescence. Angew. Chem. Int. Ed. 2015,
5
4, 874ꢀ878.
2
5. Dou, C.; Ding, Z.; Zhang, Z.; Xie, Z.; Liu, J.; Wang, L. Developing Conjugated Polymers
with High Electron Affinity by Replacing a C=C Unit with a B←N Unit Angew. Chem. Int.
Ed. 2015, 54, 3648ꢀ3652.
26. Zeng, Q.; Li, Z.; Dong, Y.; Di, C. a.; Qin, A.; Hong, Y.; Ji, L.; Zhu, Z.; Jim, C. K. W.; Yu, G.;
Li, Q.; Li, Z.; Liu, Y.; Qin, J.; Tang, B. Z. Fluorescence enhancements of benzeneꢀcored
luminophors by restricted intramolecular rotations: AIE and AIEE effects. Chem. Comm.
2007, 70ꢀ72.
2
7. Wu, Q.; Zhang, T.; Peng, Q.; Wang, D.; Shuai, Z. Aggregation induced blueꢀshifted emission
ꢀ
the molecular picture from a QM/MM study. Phys. Chem. Chem. Phys. 2014, 16, 5545ꢀ
5
552.
25
ACS Paragon Plus Environment

The Journal of Organic Chemistry
Page 26 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
8. Chen, M.; Chen, R.; Shi, Y.; Wang, J.; Cheng, Y.; Li, Y.; Gao, X.; Yan, Y.; Sun, J. Z.; Qin,
A.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. MalonitrileꢀFunctionalized
Tetraphenylpyrazine: AggregationꢀInduced Emission, Ratiometric Detection of Hydrogen
Sulfide, and Mechanochromism. Adv. Funct. Mater. 2018, 28, 1704689.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
3
3
3
3
9. Wang, C.; Xu, B.; Li, M.; Chi, Z.; Xie, Y.; Li, Q.; Li, Z. A stable tetraphenylethene
derivative: aggregationꢀinduced emission, different crystalline polymorphs, and totally
different mechanoluminescence properties. Mater. Horiz. 2016, 3, 220ꢀ225.
0. Gong, Y.; Zhang, Y.; Yuan, W. Z.; Sun, J. Z.; Zhang, Y. D–A Solid Emitter with Crowded
and Remarkably Twisted Conformations Exhibiting Multifunctionality and Multicolor
Mechanochromism. J. Phys. Chem. C 2014, 118, 10998ꢀ11005.
1. Qiu, F.; Tu, C.; Wang, R.; Zhu, L.; Chen, Y.; Tong, G.; Zhu, B.; He, L.; Yan, D.; Zhu, X.
Emission enhancement of conjugated polymers through selfꢀassembly of unimolecular
micelles to multiꢀmicelle aggregates. Chem. Comm. 2011, 47, 9678ꢀ9680.
2. Huang, P.; Wang, D.; Su, Y.; Huang, W.; Zhou, Y.; Cui, D.; Zhu, X.; Yan, D. Combination
of Small Molecule Prodrug and Nanodrug Delivery: Amphiphilic Drug–Drug Conjugate for
Cancer Therapy. J. Am. Chem. Soc. 2014, 136, 11748ꢀ11756.
3. Qiu, F.; Zhu, Q.; Tong, G.; Zhu, L.; Wang, D.; Yan, D.; Zhu, X. Highly fluorescent coreꢀ
shell hybrid nanoparticles templated by a unimolecular star conjugated polymer for a
biological tool. Chem. Comm. 2012, 48, 11954ꢀ11956.
26
ACS Paragon Plus Environment