Mesogenic D-A fluorophores based on cyanovinyl and benzothiadiazole

Article abstract of DOI:10.1039/c8nj02814a

A series of donor-acceptor fluorophores containing the biscyanovinyl dithienebenzothiadiazole central unit with 4-alkoxyphenyl groups at both sides were synthesized. These compounds can display smectic C and hexagonal columnar mesophases in their bulk states, and aggregate into organogels as well as cubic or needle crystals in organic solvents. These cubic or needle crystals exhibit optical waveguide behavior. Additionally, these compounds can exhibit broad absorption up to 625 nm with a narrow band gap of 1.79 eV. The fluorescence emission of these compounds in CHCl₃ can be quenched upon addition of C₇₀. Furthermore, these compounds can detect Cu²⁺ among a series of cations.

Full text of DOI:10.1039/c8nj02814a

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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
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DOI: 10.1039/C8NJ02814A
Mesogenic D-A fluorophores based on cyanovinyl and
benzothiadiazole
Bei Zhang,‡[a] Yulong Xiao,‡[a] Haipeng Fang,[a] Hongfei Gao,[a] Fuke Wang,*[b]
Xiaohong Cheng*[a]
[a] Key Laboratory of Medicinal Chemistry for Natural Resources, Chemistry Department,
Yunnan University
Kunming,
Yunnan 650091,
P. R. China
Fax: (+86) 871 65032905
E-mail: xhcheng@ynu.edu.cn
[b] Department of Sports Medicine, First Affiliated Hospital of Kunming Medical University
E-mail: wfk.04@126.com
‡Both authors contributed equally to this work
Abstract:
A
series
of
donor-acceptor
fluorophores
containing
biscyanovinyl
dithienebenzothiadiazole central unit with 4-alkoxylphenyl groups at both sides were synthesized.
These compounds can display smectic C and hexagonal columnar mesophases in their bulk states,
and aggregate into organogel as well as cubic or needle crystals in organic solvents. These cubic
or needle crystals exhibit optical waveguide behavior. Additionally, these compounds can exhibit
broad absorption up to 625 nm with a narrow band gap of 1.79 eV. The fluorescence emission of
these compounds in CHCl3 can be quenched upon addition of C70. Further these compounds can
detect Cu2+ among a series of cations.
1. Introduction
π-Conjugated polymers and small organic molecules have attracted widespread attention due to
their potential applications in photoelectronic devices. However defects in polymeric backbone
can lead to irreproducible performance and unstable device efficiency. π-Conjugated small organic
molecule can be obtained with high purity and synthesized with controllable molecular weights.
The well defined characteristics of conjugated small molecules can further aggregate into ordered
supramolecular structure, which facilitates the optimal performance of molecular devices.1,2
Cyano group is highly polarisable with a large permanent dipole moment. It has been used to
construct mesogens because it can cause strong dipole-dipole interactions.3 The introduction of
cyano group onto the scaffold of π-conjugated oligomer or polymer can largely lower the LUMO
level of the molecules.4 α-Cyanostilbene derivatives have developed as light-active luminescent
molecules, with aggregation-induced enhanced emission (AIEE) effect for various applications.5
As a strong electron acceptor unit, benzothiadiazole (BTD) have been used to tune the HOMO
and LUMO energy levels of low band gap fluorophores.6,7.BTD-based fluorophores showed great

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potentials in light emitting diodes,8 chemosensors,9 solar cells,10 light-harvesting, aDnOdI: 1m0.a10n3yV9ie/wC8ArNtiJcl0e2O8n1l4inAe
others.11
Till now, only a few derivatives consisting of BTD and α-cyanostilbene were reported, the
overall power conversion efficiencies (PCEs) of the photovoltaic devices based on such
derivatives are between 0.1-5.6%.12 So far as we know, there is only one report about the liquid
crystalline properties of BTD α-cyanostilbene derivatives, and only smectic phases were roughly
described.13 It is commonly considered that mesomorphism would be favorable for better
molecular packing, and helpful for good photovoltaic performance.14 Therefore herein we have
designed and synthesized a series of mesogenic D-A fluorophores which contain biscyanovinyl
dithienebenzothiadiazole central unit with 4-alkoxyl phenyl groups at both sides. The main goal of
this study is as follows: Firstly to study the mesomorphism behaviors of these compounds and
establish the relationship between the molecular structure and mesophase properties. Secondly to
study the photophysical properties of these compounds as well as their potentials as functional
molecular devices.
2. Results and discussion
2.1. Synthesis
Together six compounds were synthesized, including five dicatenars I1/n (n = 10-18) and one
hexacatenar I3/16. These target compounds Im/n (the superscript m and the number n stand for the
number and the length of the terminal alkyl chains respectively) were synthesized via
Knoevenagel and Suzuki reactions as key steps (Scheme 1). Firstly, 4-hydroxybenzyl cyanide 4
was
etherified
with
appropriate
halide.
Knoevenagel
reactions
between
5-bromothiophene-2-carbaldehyde 6 and phenylacetonitrile 5m/n gave compounds 7m/n. By
borylation with bis(pinacolato)diborane, 7m/n were changed to compounds 8m/n. Suzuki reaction
between compounds 8m/n and 4,7-dibromobenzothiadiazole 39 gave the final products which were
purified by column chromatography. More details of procedures and corresponding analysis data
were summarized in the Supporting Information (SI).

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DOI: 10.1039/C8NJ02814A
Scheme 1 Synthetic route of compounds Im/n: Reagents and conditions: i) SOCl2, Et3N, CH2Cl2, 40 °C, 7 h; ii) Br2,
HBr, 90 °C, 12 h; iii) DMF, K2CO3, RBr (R = CnH2n+1) or 5-(chloromethyl)-1,2,3-trishexadecyloxy)benzene,15
90 °C, 5 h; iv) EtOH, MeONa, RT, 1 h; v) Toluene, AcOK, Pd(PPh3)2Cl2, PPh3, bis(pinacolato)diboron, 120 °C, 24
h; vi) Toluene, Na2CO3, H2O, EtOH, Pd(PPh3)4, 110 °C, 36 h.
2.2. Mesomorphic properties
The mesomorphic properties of compounds Im/n were investigated by polarized optical
microscopy (POM, Fig. 1a and Fig. S1), differential scanning calorimetry (DSC, Fig. S2) and
X-ray diffraction (XRD, Fig. 1b, Fig. 2a and Fig. S3). The mesomorphic properties of compounds
Im/n were collected in Table 1. More detailed data were listed in Tables S1-S6.
Table 1 Thermotropic LC properties and X-ray data of compounds Im/n.a
Comp.
m
n
T/°C [ΔH/kJ mol−1]
d/nm (T/°C)
a/nm (T/°C)
μ
I1/10
1
10
Cr1 142.1 [1.38] Cr2 164.7 [13.10] Cr3 171.4
[11.10] SmC 258.8 [2.25] Iso
3.90 (200)
/
/
I1/12
I1/14
I1/16
I1/18
I3/16
1
1
1
1
3
12 Cr1 135.2 [18.36] Cr2 143.6 [18.33] Cr3 169.8
[21.32] SmC 263.1 [4.65] Iso
4.19 (260)
4.34 (247)
4.58 (180)
4.74 (200)
/
/
/
14
16
18
16
Cr1 133.4 [5.25] Cr2 147.7 [23.60] Cr3 160.6
[26.40] SmC 253.6 [3.50] Iso
/
/
/
Cr1129.3 [8.88] Cr2 140.7 [4.06] Cr3 156.1
[7.28] SmC 247.9 [1.22] Iso
/
Cr1131.4 [17.50] Cr2 141.9 [11.60] Cr3 150.5
[18.60] SmC 234.3 [3.02] Iso
/
/
Cr 39.3 Colhex 142b Iso
5.44 (110)
3.1
a Transition temperatures (°C) and associated enthalpy values (kJ mol−1), give in brackets were determined by DSC
on the second heating scan, at a rate of 3 K min-1. Cr = crystal; SmC = smectic C phase; Colhex = hexagonal

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columnar phase; Iso = isotropic liquid; d = layer spacing determined by XRD; a = lattice parameter determined bVyiew Article Online
DOI: 10.1039/C8NJ02814A
XRD; μ = number of molecules in a slice of a column in the Colhex phases (with assumed height of 0.45 nm). For
2
Colhex phase:
a
, NA = Avogadro constant, M = molecular mass, assuming a density of ρ = 1
  (
) 3h(NA M)
2
g/cm3. b Transition temperature was determined by POM.
2.2.1. Smectic C phase
All compounds were enantiotropic LCs. For the dicatenar compounds I1/n (n = 10-18), upon
elongation of the terminal alkyl chain length, led to decreasing of both the melting and clearing
temperatures (Table 1).
Polarized optical schlieren textures (Fig. 1a and Fig. S1a-d) suggested that all dicatenar
compounds self-assembled into SmC phase.16 The small-angle X-ray scattering (SAXS) patterns
of these smectic phases (Fig. 1b and Fig. S3) showed two reflection peaks in the small angle
region with a ratio of d001/d002 ≈ 2, confirming the smectic organization.3 The layer spacing of
representative compound I1/14 is about d = 4.34 nm at 247 °C (Table S3), which is shorter than
the calculated molecular length (Lmax = 5.82 nm),17 indicating that a monolayer SmC phase. The
tilt angle was calculated to be θ ≈ 42° (based on the relationship cosθ = d/Lmax) from the layer
normal (Fig. 1c). These diameters are also consistent with the sizes of the cores (green) and alkyl
chains (white) in the molecular dynamics (MD) annealed model18 in Fig. 1d.
a)
b)
c)
d)
Fig. 1 SmC phase of compound I1/14: a) texture as seen between crossed polarizer at T = 220 °C cooling from
isotropic state; b) SAXS pattern at T = 247 °C; c) the model of the molecular organization in monolayer of the
SmC phase; d) snapshot after MD annealing.
2.2.2. Hexagonal columnar phase

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The columnar phase of hexacatenar I3/16 which showed spherulitic fan-like textures waVsiew Article Online
DOI: 10.1039/C8NJ02814A
characterized by the POM (Fig. S1e). The SAXS pattern of the columnar phase of I3/16 (Fig. 2a)
showed three small-angle reflection peaks at 4.70 (10), 2.72 (11), and 2.37 (20) nm with the
reciprocal spacing ratio of 1 : 31/2 : 2, indicating a hexagonal columnar (Colhex) arrangement.19
The number of molecules (μ) in a slice of the columns with a height of h = 0.45 nm (maximum of
the diffuse wide angle scattering) was calculated to be about three (Table 1). Thus three molecules
self-assemble into a flat disc (Fig. 2c). In order to magnify the dipolar interactions, the central
BTD dipole should point to the centre of the supramolecular disc. Then the discs further pile up
into columns with 60° alternation along the columnar axis from one disc to the next. The space
surrounding the column can be filled by the interlocking and folding of the alkyl chains.20 The
model of the hexagonal columnar phase was shown in Fig. 2c. It should be noted that the
intermolecular π–π interactions, strong dipole-dipole interactions caused by the cyano, BTD,
thiophene groups, as well as the microsegregation of the rigid aromatic core from the peripheral
alkyl chains would drive the molecular assembly into the columnar structures. The length of the
biscyanovinyl dithienebenzothiadiazole central unit is 3.15 nm, which is corresponding to the
diameter of the regions of medium electron density (green) as shown in Fig. 2b. These diameters
are also in good agreement with the sizes of the cores (green) and alkyl chains (off-white) in the
molecular dynamics (MD) annealed model in Fig. 2d.21,22 The alkyl chains are completely
disordered and partly interdigitated in the continuum of low electron density around these
columns.
b)
a)
d)
c)
Fig. 2 Colhex phase of compound I3/16: a) SAXS diffractogram at T = 110 ºC; b) electron density map area
constructed from the diffraction pattern in (a), and the color code was shown on the right; c) models for the
molecular arrangement in Colhex/p6mm phase; d) snapshots after MD annealing.

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DOI: 10.1039/C8NJ02814A
2.3. Gelation properties
The gelation abilities of compounds Im/n for different organic solvents were evaluated at the
critical gelation concentration (CGC) of 4.0 mg mL-1 (Table 2). The relationship of the gel
stability and Tgel (the temperature at which the gel is broken) indicated that the gel stability
increased with increasing the gelator concentration (Fig. S5). The representative dicatenar
compound I1/16 cannot form gel, while compound I3/16 can form gel in ethyl acetate: petroleum
ether = 1 : 1. Blackred gel was formed in ethyl acetate : petroleum ether = 1 : 1 by cooling the
heated solution of compound I3/16 to room temperature (Fig. 3a and Fig. S6). The morphology of
the xerogel formed by I3/16 was investigated by scanning electron microscopy (SEM). Fig. 3b
showed the formation of three-dimensional fibrous networks. The length of the fibers is more than
20 μm with a diameter of 0.27-1.35 μm. It should be mentioned that there is no gelating functional
groups such as amide, cholesterol, triazol and acetylene etc. in the structure of compound I3/16,
therefore the gelation property of compound I3/16 in solution should be mainly promoted by
donor-acceptor interaction, π-π interactions and van der Waals forces.
Table 2 Gelation properties of compounds I1/16 and I3/16.a
Solvent
Chloroform
Ethyl acetate
THF
I1/16
I3/16
Solvent
1,4-Dioxane
I1/16
I3/16
P
P
P
S
P
P
P
S
P
P
P
P
P
IS
S
Hexane
IS
S
Toluene
Ethanol
P
Dichloromethane
Ethyl acetate : petroleum ether =1:1
S
Acetone
P
G
Petroleum ether
S
aS = solution, P = precipitation, G = gelation, IS = insoluble gelator.
b)
a)
Fig. 3 a) Photos of gel prepared with compound I3/16 in ethyl acetate : petroleum ether = 1 : 1 at 20 °C; b) SEM
image of xerogel formed by compound I3/16.
2.4. Absorption and emission properties
The UV-vis absorption and emission spectra of two representative compounds I1/16 and I3/16 in

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New Journal of Chemistry
DCM are shown in Fig. 4. Compounds I1/16 and I3/16 exhibited dual-band absorptioDnOsI:i1n0.1t0h3Ve9ie/wC8ArNtiJcl0e2O8n1l4inAe
ranges of 330-440 nm and 440-625 nm, corresponding to the π-π* transition and internal charge
transfer (ICT) transition between the donor and acceptor units respectively.14d,23 The emission
bands are in the ranges of 632 nm to 653 nm, therefore the Stokes shifts are 111-136 nm. The
absorption and emission spectra of I1/16 and I3/16 have similar shape, indicating that the
electronic properties of both compounds are dictated by the similar extended chromophore. The
absorption edge of I1/16 is red shifted slightly compared to that of I3/16, which indicates that the
terminal alkoxy substituent in I1/16 is a better donor than the benzyloxy moiety in I3/16.
Fig. 4 Normalized UV-vis absorption and emission spectra of compounds I1/16 and I3/16 (10-6 M) at 20 °C in
DCM.
The solvatochromic behaviors of compounds Im/n were investigated in organic solvents with
different polarity from toluene to THF (shown in Fig. S7) and the photophysical data were listed
in Table S7. As shown in Fig. S7g, the solvent polarity has less impact on the absorption spectra of
I1/16, which exhibits two prominent bands at λ = 330-440 nm and λ = 440-625 nm. The
fluorescence spectra (Fig. S7h) however, showed evidently solvatochromism (red-shifted from
632 nm in toluene to 653 nm in THF) as the polarity of solvents increased. Therefore Im/n have
large Stokes shifts (111-136 nm). The wavelength range of compounds Im/n are close to near
infrared and wider than those of the literatures reported biscyanovinyl dithienebenzothiadiazole
analogues.24,25,26 The ICT effect should cause the solvatochromism in fluorescence. Becasue ICT
compounds usually have large dipole moments in the excited state, therefore the dipole-dipole
interactions between polar solvent and ICT compounds would reduce the energy of the excited
state.27
The energy band gaps of compounds I1/16 and I3/16 can be estimated from the UV spectra of
the thin film to be about 1.79 eV (Fig. S8).28 Using Gaussian 09 software, by density functional
theory (DFT) based on B3LYP with a polarized 6-31G(d) basis,29 the ground-state geometries and
electronic structures of I1/16 and I3/16 were calculated. The electron distributions of the HOMO
and LUMO of I1/16 and I3/16, in which the alkoxy chains are replaced by methoxy groups, are
shown in Fig. S9. The calculation results show that the central dithienebenzothiadiazole moiety
with its two adjacent cyanovinyl 4-alkoxylphenyl units, represents a large conjugated planar
conformation. While the structure of I3/16 appears a slightly non-planar from the methylene
connected on the terminal alkoxylphenyl moieties. In these two compounds, electron density of
the HOMO localized on the rigid π-conjugated dithienebenzothiadiazole and cyanovinyl
4-alkoxylphenyl units. In the LUMO orbital however the electrons are localized on the central of

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dithienbenzothiadiazole unit. It indicates that during the molecule excited from HOMO tDoOLI:U10M.10O39/C8NJ02814A
energy levels, charge transfers from the alkoxylphenyl units to the central
a
dithienebenzothiadiazole moiety might be occurred. Such photophysical properties indicated that
these molecules could be applied in fabrication of high performance solution processable
photoelectrical molecular devices such as OPV and OLEDs.
It was found that the fluorescence emission of I1/16 could be significantly quenched as the
concentration of C70 increased (Fig. 5 and Fig. S10). This phenomenon indicated the presence of
photoinduced charge separation process between I1/16 and C70.30 To further study the quenching
constant (KSV) of C70 to I1/16, the dependence of fluorescence intensity on the concentration of
C70 at low quencher concentrations was analyzed. It agreed with the Sterne-Volmer equation.
F0/F = 1 + KSV·C
Here, F0 and F represent the fluorescence intensity in the absence and present of C70, respectively,
and C is the concentration of C70. The KSV value of I1/16 is 1.7×104 M-1.
The charge separation led to photoinduced electron transfer. Therefore there could exist
31
electron transfer between BTD fluorophore and C70,
this indicated that the BTD
fluorophore–fullerene blend was favorable component for fabrication the highly efficient
photovoltaic (PV) cells.
a)
b)
Fig. 5 a) Emission spectra (left) of I1/16 (1.0×10-5 M) in CHCl3 with increasing concentration of C70 (1.0×10-5 M):
0.0 (0), 1.0 (1), 2.0 (2), 4.0 (3), 8.0 (4), 10.0 (5); b) Sterne-Volmer quenching plots for I1/16.
2.5. Optical waveguide behavior
The compounds I1/n (n = 10, 12, 14, 16, 18) can form needle crystals in DCM/MeOH and cubic
crystals in THF/petroleum ether (Fig. 6 and Fig. S11). For compound I1/18, the needle aggregates
are about 1.7-6.7 μm in width and 128-267 μm in length (Fig. S11i), whereas the cubic aggregates
are about 3.7-10 μm in width (Fig. S11j). These aggregates were investigated by the fluorescent
microscope. Irradiated with a light beam at different λ, these aggregates exhibited very bright red
luminescence at both sides but relatively weaker emission from the body. It suggested that these
compounds exhibited optical waveguide behavior.32 It showed that these solvated crystals could
be used as light-emitting and propagation materials in miniaturized optoelectronic devices.

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Fig. 6 Photoluminescence microscopy images of the crystalline aggregates at 540-560 nm of I1/12 produced in
THF/petroleum ether mixed solution.
2.6. Chemosensor behavior
The selective binding abilities of compounds Im/n towards different metal ions (all anions are
-
ClO4 ), including Ag+, Cd2+, Co2+, Cu2+, Hg2+, K+, Li+, Mg2+, Ni+, Pb2+, Zn2+, Cr3+, Fe3+ and Al3+,
were examined. The concentration of all metal ions is 10-3 mol L-1. All compounds Im/n can
recognize Cu2+. The result of the representative compound I1/10 was shown in Fig. 7. The
fluorescence spectra of I1/10 by the addition of 20 equiv. of selected cations in CH3CN : DCM =
2 : 1 solution were investigated. No obvious change of the fluorescence intensity of the compound
I1/10 by addition of most metal ions. Only upon the increasing addition of Cu2+ (Fig. 7a and Fig.
S12a), obvious fluorescence quenching was observed. The selective response of I1/10 to Cu2+ can
be detected by naked eye as shown in Fig. 7b.The selective response of I1/10 to Cu2+ was
examined by fluorescence titration with addition of Cu2+ (from 0 to 25 equiv.) in solution of
CH3CN : DCM = 2 : 1. It was clearly shown that the fluorescence reached its quenching plateau
by addition of about 16 equiv. of Cu2+ (Fig. S12b, c).33 The calculated detection limit of I1/10
towards Cu2+ was 4.83×10-7 M based on 3σ/k34 (Fig. S13), which is much lower than those of the
reported α-cyanostilbene-based chemosensors.35 Therefore, compound I1/10 could be used as
Cu2+ chemosensor with high selectivity and low detection limit in the solution of CH3CN : DCM =
2 : 1. The binding stoichiometry was determined by Job’s plot method, indicating that compound
I1/10 and Cu2+ could form a 1 : 1 complex (Fig. S14). The FTIR spectrum of I1/10 (Fig. S15a)
indicated that the characteristic peak at 2310 cm-1 was assigned to the C≡N stretching vibration.36
After interacting with Cu2+, the peak of C≡N stretching vibration showed obvious blue shift to
2248 cm-1. It indicated that the N atom of C≡N of compound I1/10 was the binding site. This
indicated that the coordination of Cu2+ with C≡N induced fluorescence quenching of Im/n
solutions. Therefore the chelation enhanced quenching (CEQ) sensing mechanism37 was the main
reason for inducing fluorescence quenching of Im/n solutions. In the FTIR spectra of I1/10+other
metal ions, the characteristic peaks at 2310 cm-1 showed little change (Fig. S15b) indicating no
binding interaction between Im/n and other metal ions. It should be noted that even though BTD
α-cyanostilbene derivatives could display excellent fluorescence property,12a,12b,13,38,39 however
their application as fluorescent probe are few. Therefore, this should be the first time that the
chemosensor behaviors of such compounds have been studied. The aggregation-induced emission
(AIE) of biscyanovinyl dithienebenzothiadiazole has not been observed, probably ascribed to the

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DOI: 10.1039/C8NJ02814A
strong fluorescence properties of BTD.
a)
b)
Fig. 7 The fluorescence response of I1/10 (10-6 M, CH3CN : DCM = 2 : 1) upon addition of different metal ions
(20 equiv.) at pH = 7.0 (a and b) (λex = 510 nm); F0 = the fluorescence emission maximum of a blank sample; F =
the fluorescence emission maximum of samples with addition of different metal ions; b) Fluorescence changes of
I1/10 (10-6 M) on addition of different metal ions (20 equiv.).
3. Conclusions
In conclusion, D-A fluorophores based on cyanovinyl and BTD have been successfully
synthesized. The liquid crystalline properties of these fluorophores were well investigated by
POM, DSC and XRD. They can self-assemble into SmC and Colhex/p6mm phases. Suggested
phase structures are based on XRD patterns, electron density reconstruction and simulations. The
molecular packing models for these phase structures are well established. Additionally the
compound I3/16 can also self-assemble into organogel in solvents. These fluorophores exhibit
broad and strong absorption band at the range of 330-625 nm with a red emissive color and large
Stokes shifts. The fluorescence emission of the compound I1/16 in CHCl3 was significantly
quenched upon addition of C70, indicating the presence of electron transfer between BTD
compounds and C70. In organic solvents, these red emissive molecules can form solvated crystals,
which exhibit optical waveguide behaviors. Finally these compounds can act as chemosensors for
detection of Cu2+. Thus, these multifunctional materials can be potentially applied in diverse areas
such as liquid crystals, chemosensors, red emission waveguides etc.
Acknowledgment
We thank National Natural Science Foundation of China (Nos. 21664015 and 21602195) and the
Yunnan Science Foundation (No. 201701UH00095) for financial supports. We thank beamline
BL16B1 at Shanghai Synchrotron Radiation Facility (SSRF), China. The calculations were
performed with the support of the Yunnan University Supercomputer Center.
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DOI: 10.1039/C8NJ02814A
Graphical abstracts
Mesogenic D-A fluorophores based on cyanovinyl and benzothiadiazole
Bei Zhang,‡[a] Yulong Xiao,‡[a] Haipeng Fang,[a] Hongfei Gao,[a] Fuke Wang,*[b]
Xiaohong Cheng*[a]
[a] Key Laboratory of Medicinal Chemistry for Natural Resources, Chemistry Department,
Yunnan University
Kunming,
Yunnan 650091,
P. R. China
Fax: (+86) 871 65032905
E-mail: xhcheng@ynu.edu.cn
[b] Department of Sports Medicine, First Affiliated Hospital of Kunming Medical University
E-mail: wfk.04@126.com
‡Both authors contributed equally to this work