1,1,4,4-Tetracyanobutadiene-Functionalized Anthracenes: Regioselectivity of Cycloadditions in the Synthesis of Small Near-IR Dyes

Clotilde Philippe, Anh Thy Bui, Sabrinah Batsongo-Boulingui, Ziemowit Pokladek,

Letter

,1,4,4-Tetracyanobutadiene-Functionalized Anthracenes:

Regioselectivity of Cycloadditions in the Synthesis of Small Near-IR

Dyes

Katarzyna Matczyszyn, Olivier Mongin, Lo ï c Lemieg

and Yann Trolez*

re, Fr é d é ric Paul, Trevor A. Hamlin,*

Cite This: Org. Lett. 2021, 23, 2007 −2012

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sı Supporting Information

ABSTRACT: Two small 1,1,4,4-tetracyanobutadiene-functional-

ized chromophores were obtained by careful leverage of the

regioselectivity of the cycloaddition reaction of tetracyanoethylene

with anthracene−ynamide derivatives, inducing either a [2 + 2] or

a [4 + 2] Diels−Alder process. DFT calculations unraveled the

mechanism of the [2 + 2] cycloaddition−retroelectrocyclization

reaction sequence with ynamides and elucidated the diﬀering

mechanisms in the two substrates. The synthesized dyes presented

panchromatic absorption extending into the near-IR and far-red/

near-IR photoluminescence in the solid state up to 1550 nm.

ush−pull chromophores, consisting of electron donor and

tions. As suggested by Armaroli et al., in anilino-TCBDs,

torsional motions following photoexcitation give rise to a low-

energy twisted intramolecular charge transfer (TICT) state

that can deactivate to the ground state through accessible

acceptor groups bridged together by a π-conjugated

backbone, are a class of molecules that play a prominent role

in organic molecular materials. Thanks to their particular

arrangement that facilitates intramolecular charge transfer

conical intersections. As a direct consequence, these

(

ICT) interactions, they feature in scores of applications

molecules are generally nonluminescent and ﬂuorescence

including nonlinear optics (NLO) and organic photovoltaics

that involves a TCBD moiety has seldom been reported.

In an eﬀort to modify the prototypical anilino-TCBD

fragment, our group discovered that ynamides can engage in

the [2 + 2]-CARE reaction with TCNE to form a sulfonamido-

TCBD motif, producing dyes with markedly altered optoelec-

(

OPVs). This persistently intriguing topic has stimulated the

exploration of 1,1,4,4-tetracyanobutadiene (TCBD) derivatives

−12

and their chemistry by several groups in the past decade.

The elegance of their approach stems from the simplicity of its

synthetic route: the TCBD motif can indeed be installed via a

facile, high-yield, catalyst-free [2 + 2] cycloaddition-retro-

electrocyclization (CARE) sequence, using tetracyanoethylene

7−19

tronic properties.

We recently revealed that such

chromophores could exhibit near-infrared (NIR) luminescence

in the solid state, extending to 1350 nm. This surprising

result prompted us to further investigate compounds based on

a similar design, i.e. sulfonamido-TCBD-PAH (polycyclic

aromatic hydrocarbon). Interestingly, others have also

described solid-state ﬂuorescence involving an ICT to TCBD

(

TCNE) and an electron-rich alkyne, thus allowing for

practical synthetic strategies such as postpolymerization

functionalizations. TCBD is now established as a valuable

strong electron acceptor group, with a rapidly expanding family

of dyes including this motif. Beyond its straightforward

incorporation in push−pull chromophores, other advantages

of TCBD were put forward: its twisted conformation was

shown to increase chromophore solubility and reduce

aggregation, thereby improving the poling process eﬃciency

in push−pull chromophores bearing a PAH.

While examining the structures of photoactive multi-

component systems that integrate TCBD units, one can

Received: January 13, 2021

Published: February 26, 2021

in NLO materials. Despite a number of studies that have

promisingly demonstrated photoinduced charge separation in

TCBD-appended chromophores, fast nonradiative deactivation

of the excited state in these molecules constitutes a major

drawback to their implementation in optoelectronic applica-

2021 The Authors. Published by

American Chemical Society

007

Org. Lett. 2021, 23, 2007−2012

Organic Letters

Letter

remark that anthracene is a strikingly rare building block, with

only two examples (to the best of our knowledge) bearing a

TCBD motif attached to strong electron-donating groups and

modulation of the equilibrium for addition of TCNE to

anthracene by the solvent was discussed by Brown and

Cookson and the dissociation was found to be favored in

22,23

remote from the anthracene moiety.

A possible explanation

dioxane. Furthermore, Sauer et al. demonstrated the recovery

is the presence of a competing Diels−Alder (DA) reaction

which makes this PAH seemingly incompatible with the [2 +

of the anthracene addend using a diﬀerent anthracene

derivative to trap TCNE. In the light of these studies, we

sought to harness the reversibility of the DA reaction by testing

various methods for the recovery of the anthracene structure

and formation of the TCBD group. When 5a was heated at 80

°C in dioxane in the presence of 1 equiv of TCNE, even

though the retro-DA reaction is expected to be feasible under

these conditions, the ynamide degraded without signiﬁcant

conversion into A-TCBD. At room temperature, the same

reaction led only to cycloadduct 6 in 62% yield. Under UV

irradiation (365 nm) in toluene, compound 5a did not provide

the [4 + 4] photodimerization product and its degradation was

exclusively observed, invalidating the preliminary protection of

the 9,10-positions of the anthracene core by formation of a

dimer as an alternate strategy. We endeavored to construct the

TCBD motif from cycloadduct 6 instead. In the presence of a

second equivalent of TCNE, compound 6 was successfully

converted into bisadduct 7 in 50% isolated yield. Using 5 equiv

of TCNE, 5a could be directly transformed into 7 in a much

higher yield (73%) than through the combined two-step

procedure (40%). Both cycloaddition products 6 and 7 were

moderately stable and decomposed in solution within a few

hours. Diﬀerent conditions for the extrusion of TCNE from

the anthracene core were then assessed. When a 0.01 M

solution of 7 in dioxane was heated at 80 °C, A-TCBD could

be isolated in only 3% yield after 3 h. To inhibit the forward [4

]-CARE sequencea pitfall that was also encountered with

other acenes. Herein we report a synthetic strategy to

overcome this limitation, a complete mechanistic picture by

density functional theory (DFT) calculations, and the optical

properties of the synthesized molecules A-TCBD and DPA-

TCBD (Scheme 1).

Scheme 1. Reaction Pathways for the Synthesis of A-TCBD

and DPA-TCBD

2] cycloaddition, rather than another anthracene derivative

and DA reaction, 1.5 equiv of commercially available 4-

ethynyl-N,N-dimethylaniline 8 were used to scavenge extruded

TCNE, considering the known eﬃciency and irreversibility

of the [2 + 2]-CARE reaction. Thus, when stirred for 3 h at 80

C in the presence of 8, a solution of 7 in dioxane provided

compound A-TCBD in a satisfactory yield of 76%. The newly

synthesized dyes A-TCBD and DPA-TCBD were charac-

terized by H and C NMR spectroscopy, HRMS, and cyclic

voltammetry (Supporting Information ).

Density functional theory (DFT) calculations at COSMO-

DCM)-BLYP-D3(BJ)/TZ2P using ADF (see the Supporting

Information for computational details) were carried out to

pinpoint the origin of disparate regioselectivity of 5a and 5b.

For the calculations, the tosyl group (Ts) of 5a and 5b was

replaced with mesyl group (Ms) and the substrates are

denoted as 5a′ and 5b′. The energy proﬁles associated with the

[2 + 2]-CARE and [4 + 2] DA sequences of 5a′ and 5b′ are

provided in Figure 1 and are in line with others in the

literature. It can be seen that 5a′ preferentially reacts via the

DA sequence, whereas 5b′ reacts via the [2 + 2]-CARE

sequence. The origin of this observed regioselectivity is traced

back to the steric bulk at the 9- and 10-position of the

anthracene: the unsubstituted 5a′ can facilitate the DA

reaction of TCNE at anthracene to aﬀord 6′, whereas the

9,10-diphenylanthracene 5b′ is too sterically demanding for

the DA reaction and the [2 + 2]-CARE pathway becomes

more energetically viable.

We have previously identiﬁed the lack of reactivity of the

triple bond when the ynamide is grafted to the 9-position of

anthracene, which prompted us to investigate anthracenes

functionalized in a diﬀerent position. Brominated derivatives

a and 1b were therefore selected as starting molecules to

access 2-substituted anthracenes. Sonogashira cross-coupling

with trimethylsilylacetylene and subsequent deprotection gave

the precursor compounds 3a and 3b. The terminal alkynes

were brominated to aﬀord compounds 4a and 4b in 78% and

0% yield, respectively. The latter underwent copper-catalyzed

amidation using Hsung’s conditions, leading to ynamides 5a

in moderate yield (36%) and 5b in very good yield (89%).

Compounds 5a and 5b were then reacted with one equivalent

of TCNE. While 9,10-diphenylanthracene derivative 5b

yielded DPA-TCBD (62%), compound A-TCBD was not

isolated and the DA product 6 was obtained instead (80%

yield).

First, we focus on the reactivity of the unsubstituted

anthracene 5a′. The DA sequence of 5a′ (Figure 1a, go left)

begins with the formation of a reactant complex 5a′-INT1*

that is more stable (from enhanced π−π stacking) than the

corresponding complex 5a′-INT1 of the [2 + 2]-CARE

The [4 + 2] cycloaddition of anthracene with TCNE has

27−29

already been well documented by several groups.

The

008

Org. Lett. 2021, 23, 2007−2012

Organic Letters

Letter

−

Figure 1. (a) Energy proﬁles (ΔE_D_C_Min kcal mol ) for the competing catalyst-free [2 + 2] cycloaddition-retroelectrocyclization (CARE, in black)

and [4 + 2] Diels−Alder (DA) reactions (in blue) of 5a′ and 5b′ with TCNE; (b) key transition state geometries (in Å) and activation strain

analysis (ΔE^⧧

= ΔE^⧧

+ ΔE^⧧

, in kcal mol ). All data computed at COSMO(DCM)-BLYP-D3(BJ)/TZ2P.

−1

DCM

DCM, strain

DCM, int

pathway. From 5a′-INT1*, the DA reaction proceeds through

anthracene that were observed between 335 and 400 nm in

5a and 5b are now indistinct. New features arose in both

TCBD derivatives, causing their absorption spectra to span the

whole visible range. Most remarkably, a very broad and

structureless low-energy absorption band, attributed to an ICT

transition resulting from interactions between the PAH moiety

and TCBD, covers the visible region between 450 and 800 nm,

‡

a concerted asynchronous transition state 5a′-TS1* (ΔE =

−

.4 kcal mol ) to aﬀord the experimentally isolated analog 6′.

The ﬁrst step of the [2 + 2]-CARE sequence involves the

nucleophilic attack of 5a′ at TCNE, which goes via an

‡

unfavorably high energy transition state 5a′-TS1 (ΔE = 2.6

−

kcal mol ) and formation of an unstable zwitterionic

intermediate.

−1

with a maximum located at 527 nm (ε = 3.5 × 10 M cm )

−1

Now, we analyze the reactivity of the 9,10-diphenylan-

thracene derivative 5b′ (Figure 1a, go right). The reactant

complex 5b′-INT1* is a resting state on the energy surface and

cannot proceed further due to an unsurmountable DA barrier

for A-TCBD and at 557 nm (ε = 4.3 × 10 M cm ) for

DPA-TCBD. Comparison with published data on pyrene and

perylene derivatives decorated with a TCBD unit reveals a

pronounced bathochromic eﬀect as well as a slight hyper-

chromic eﬀect associated with the increase in the PAH π-

conjugation and/or resonance stabilization (Table S2 ).

Finally, the photoluminescence (PL) properties of A-TCBD

and DPA-TCBD were examined. As reported with analogous

⧧

−1

via 5b′-TS1* (ΔE = 10.0 kcal mol ) that goes with a highly

destabilizing strain (ΔE^⧧

= 100.3 kcal mol ) due to steric

−1

strain

clash between TCNE and the phenyl groups at the 9- and 10-

positions of the anthracene (Figure 1b). Instead, 5b′-INT1*

reversibly dissociates to the reactants and then can form the

slightly less stable 5b′-INT1, which undergoes the nucleophilic

attack via 5b′-TS1* to generate a metastable zwitterionic

intermediate 5b′-INT2. The facile rotation and subsequent

cyclization via 5b′-TS2 accomplishes the stepwise [2 + 2]

cycloaddition and generates the cycloadduct 5b′-INT3.

Retrocyclization via 5b′-TS3 provides the s-cisDPA-TCBD′

which can then isomerize to complete the CARE sequence and

furnish s-transDPA-TCBD′.

dyes, no emission was detected in dichloromethane, but in

rigid media, both compounds displayed a very comparable and

broad PL band (Figure 2B). In diluted rigid matrices (2-

methyltetrahydrofuran at 77 K and PMMA at room temper-

ature, Table S3), where the intermolecular interactions are

minimized, this band lied between the red and the ﬁrst near-

infrared window (NIR-I, 700−950 nm). Powders of the

products exhibited PL in the NIR-I region with a maximum

centered at 865 and 875 nm for A-TCBD and DPA-TCBD

respectively, and a remarkably long tail extending to 1550 nm

in the second near-infrared window (NIR-II, 1000−1700 nm),

even farther than the upper limit in pyrene and perylene

derivatives (ca. 1350 nm). This PL enhancement in the solid-

The UV−vis absorption spectra of A-TCBD and DPA-

TCBD were recorded in dichloromethane (Figure 2A).

Compared to their ynamide precursors, the clear and

characteristic ﬁnger-like structured absorption bands of

009

Org. Lett. 2021, 23, 2007−2012

Organic Letters

The Supporting Information is available free of charge at

Letter

small dyes. They presented panchromatic absorption in DCM

that extends into the NIR-I region, and solid-state PL signals

lying between the far-red and the NIR-II range. This latter

feature, rare in TCBD-functionalized molecules, thus further

substantiates that new molecular designs comprising this

fragment can oﬀer room for unusual photophysical proper-

ties.

ASSOCIATED CONTENT

sı Supporting Information

■

https://pubs.acs.org/doi/10.1021/acs.orglett.1c00136.

General and synthetic procedures, characterization data,

cyclic voltammograms, complementary UV−vis and

photoluminescence data, excitation spectra, and full

computational details (PDF )

AUTHOR INFORMATION

■

Corresponding Authors

Trevor A. Hamlin − Department of Theoretical Chemistry,

Amsterdam Institute of Molecular and Life Sciences

(

AIMMS), and Amsterdam Center for Multiscale Modeling

ACMM), Vrije Universiteit Amsterdam, 1081 HV

Amsterdam, The Netherlands; orcid.org/0000-0002-

128-1004 ; Email: t.a.hamlin@vu.nl

Yann Trolez − Univ Rennes, Ecole Nationale Supérieure de

Rennes, France; orcid.org/0000-0002-5421-9556;

Email: yann.trolez@ensc-rennes.fr

Figure 2. (A) UV−vis absorption spectra of ynamide precursors 5a

and 5b and compounds A-TCBD and DPA-TCBD in dichloro-

methane. Inset: zoom on the low-energy band of A-TCBD and DPA-

TCBD. (B) Normalized photoluminescence spectra of A-TCBD and

DPA-TCBD in PMMA (λ_e_x_c= 500 and 515 nm, respectively), organic

glass (MeTHF at 77 K, λ_e_x_c= 480 and 520 nm, respectively), and

powders (λ_e_x_c= 585 and 600 nm, respectively). The diﬀerent

detectors used are represented as follows. Continuous line: R928;

ﬁlled symbols: R2658; open symbols: InGaAs.

Authors

Clotilde Philippe − Univ Rennes, Ecole Nationale Supérieure

de Chimie de Rennes, CNRS, ISCR − UMR6226, F-35000

Rennes, France

Anh Thy Bui − Univ Rennes, Ecole Nationale Supérieure de

Rennes, France; orcid.org/0000-0002-3718-7652

Sabrinah Batsongo-Boulingui − Univ Rennes, Ecole

Nationale Supérieure de Chimie de Rennes, CNRS, ISCR −

UMR6226, F-35000 Rennes, France

Ziemowit Pokladek − Faculty of Chemistry, Wroclaw

University of Science and Technology, 50-370 Wroclaw,

Poland

Katarzyna Matczyszyn − Faculty of Chemistry, Wroclaw

University of Science and Technology, 50-370 Wroclaw,

Poland; orcid.org/0000-0001-8578-8340

Olivier Mongin − Univ Rennes, Ecole Nationale Supérieure de

Chimie de Rennes, CNRS, ISCR − UMR6226, F-35000

Rennes, France

state can be ascribed to the restriction of molecular motions

following light absorption, which helps reduce the nonradiative

losses in these environments.

Besides the successful synthesis of two TCBD-appended

anthracene derivatives A-TCBD and DPA-TCBD, our joined

experimental and theoretical investigations showed that the

regioselectivity of the cycloaddition reaction of TCNE with 5a

and 5b, favoring either a [4 + 2] Diels−Alder process with the

anthracene core in 5a or a [2 + 2]-CARE reaction with the

triple bond in 5b, is dictated by steric eﬀects at the 9,10-

positions. DFT calculations uncovered the mechanism of the

[

2 + 2]-CARE sequence with ynamides for the ﬁrst time,

demonstrating that the reaction proceeds through stepwise [2

2] cyclization to produce a cyclobutene intermediate which

Loïc Lemiegre − Univ Rennes, Ecole Nationale Supérieure de

Rennes, France; orcid.org/0000-0001-6622-171X

Frédéric Paul − Univ Rennes, Ecole Nationale Supérieure de

Complete contact information is available at:

Rennes, France; orcid.org/0000-0002-8256-0129

then opens to give the TCBD moiety. When the DA reaction

was preferential, it could advantageously be used to deactivate

the 9,10-positions prior to the [2 + 2]-CARE, then its

reversibility exploited to unmask the anthracene core thanks to

a scavenger. In addition to insight into the reactivity of some π-

systems with TCNE, we expect the synthetic method

developed to obtain A-TCBD to be applicable to other

acene-TCBD targets. Both A-TCBD and DPA-TCBD

displayed optical properties that were remarkable for such

https://pubs.acs.org/10.1021/acs.orglett.1c00136

Notes

The authors declare no competing ﬁnancial interest.

010

Org. Lett. 2021, 23, 2007−2012

Organic Letters

Diederich, F.; Armaroli, N. Anilino-Substituted Multicyanobuta-1,3-

Letter

phores Containing a 2-Phenyl-Tetracyanobutadienyl Acceptor. J. Am.

Chem. Soc. 1999, 121, 472−473.

ACKNOWLEDGMENTS

■

This study is part of the project ANR JCJC Fluotet 17-CE07-

038-01 from the Agence Nationale pour la Recherche. A.T.B.

and C.P. thank the Région Bretagne for funding postdoctoral

and doctoral grants, respectively. PHC Polonium 37629XG

2017-2018) is aknowledged for funding. The authors would

like to acknowledge Dr. Olivier Maury (Laboratoire de Chimie

at ENS de Lyon) for access to the Horiba Jobin-Yvon

(15) Monti, F.; Venturini, A.; Nenov, A.; Tancini, F.; Finke, A. D.;

Diene Electron Acceptors: TICT Molecules with Accessible Conical

Intersections. J. Phys. Chem. A 2015, 119 (43), 10677−10683.

(16) Perhaps the most notable description of this type of

ﬂuorescence concerns an intramolecular exciplex emission:

Winterfeld, K. A.; Lavarda, G.; Guilleme, J.; Sekita, M.; Guldi, D.

M.; Torres, T.; Bottari, G. Subphthalocyanines Axially Substituted

with a Tetracyanobuta-1,3-Diene −Aniline Moiety: Synthesis, Struc-

ture, and Physicochemical Properties. J. Am. Chem. Soc. 2017, 139

(

ﬂuorometers. Dr. Franc o̧ is Riobé (Laboratoire de Chimie at

ENS de Lyon) is also thanked for assistance with the

corresponding measurements and fruitful discussions. T.A.H.

thanks The Netherlands Organization for Scientiﬁc Research

(15), 5520−5529. For other interesting reports, see, for example: Xu,

J.; Liu, X.; Lv, J.; Zhu, M.; Huang, C.; Zhou, W.; Yin, X.; Liu, H.; Li,

Y.; Ye, J. Morphology Transition and Aggregation-Induced Emission

of an Intramolecular Charge-Transfer Compound. Langmuir 2008, 24

(8), 4231−4237. Dar, A. H.; Gowri, V.; Gopal, A.; Muthukrishnan,

A.; Bajaj, A.; Sartaliya, S.; Selim, A.; Ali, Md. E.; Jayamurugan, G.

Designing of Push −Pull Chromophores with Tunable Electronic and

Luminescent Properties Using Urea as the Electron Donor. J. Org.

Chem. 2019, 84 (14), 8941−8947.

(

NWO) for support.

DEDICATION

■

This work is dedicated to the memory of Franc o̧ is Diederich.

REFERENCES

■

(17) Betou, M.; Kerisit, N.; Meledje, E.; Leroux, Y. R.; Katan, C.;

1) Kivala, M.; Diederich, F. Acetylene-Derived Strong Organic

Halet, J.-F.; Guillemin, J.-C.; Trolez, Y. High-Yield Formation of

Substituted Tetracyanobutadienes from Reaction of Ynamides with

Tetracyanoethylene. Chem. - Eur. J. 2014, 20 (31), 9553−9557.

Acceptors for Planar and Nonplanar Push −Pull Chromophores. Acc.

Chem. Res. 2009, 42 (2), 235−248.

E.; Leroux, Y. R.; Toupet, D. L.; Trzop, E.; Roisnel, T.; Trolez, Y.

2) Barlow, S.; Marder, S. R. Nonlinear Optical Properties of

(18) Betou, M.; Durand, R. J.; Sallustrau, D. A.; Gousset, C.; Le Coz,

Organic Materials. In Functional Organic Materials; Muller, T. J. J.,

Bunz, U. H. F., Eds.; Wiley-VCH Verlag: Weinheim, Germany, 2006;

pp 393−437. DOI: 10.1002/9783527610266.ch11 .

Reactivity of Functionalized Ynamides with Tetracyanoethylene:

Scope, Limitations and Optoelectronic Properties of the Adducts.

Chem. - Asian J. 2017, 12 (12), 1338−1346.

(

3) Su, Y.-W.; Lan, S.-C.; Wei, K.-H. Organic Photovoltaics. Mater.

Today 2012, 15 (12), 554−562.

4) Mochida, T.; Yamazaki, S. Mono- and Diferrocenyl Complexes

(19) Bouvier, R.; Durand, R.; Favereau, L.; Srebro-Hooper, M.;

Hernandez, F.; Autschbach, J.; Trolez, Y.; Crassous, J. Helicenes

Dorcet, V.; Roisnel, T.; Vanthuyne, N.; Vesga, Y.; Donnelly, J.;

Grafted with 1,1,4,4-Tetracyanobutadiene Moieties: π -Helical Push-

Pull Systems with Strong Electronic Circular Dichroism and Two-

Photon Absorption. Chem. - Eur. J. 2018, 24 (54), 14484−14494.

with Electron-Accepting Moieties Formed by the Reaction of

Ferrocenylalkynes with Tetracyanoethylene. J. Chem. Soc., Dalton

Trans. 2002, 18 (18), 3559−3564.

5) Leliege, A.; Blanchard, P.; Rousseau, T.; Roncali, J. Triphenyl-

amine/Tetracyanobutadiene-Based D-A-D π -Conjugated Systems as

(

20) Bui, A. T.; Philippe, C.; Beau, M.; Richy, N.; Cordier, M.;

Molecular Donors for Organic Solar Cells. Org. Lett. 2011, 13 (12),

Roisnel, T.; Lemiegre, L.; Mongin, O.; Paul, F.; Trolez, Y. Synthesis,

Characterization and Unusual near-Infrared Luminescence of 1,1,4,4-

6) Koszelewski, D.; Nowak-Król, A.; Gryko, D. T. Selective

098−3101.

Tetracyanobutadiene Derivatives. Chem. Commun. 2020, 56 (24),

Cycloaddition of Tetracyanoethene (TCNE) and 7,7,8,8-Tetracyano-

p-Quinodimethane (TCNQ) to Afford Meso-Substituted Phenyl-

ethynyl Porphyrins. Chem. - Asian J. 2012, 7 (8), 1887 −1894.

(

571−3574.

21) Simón Marqués, P.; Castan, J. M. A.; Raul, B. A. L.; Londi, G.;

Ramirez, I.; Pshenichnikov, M. S.; Beljonne, D.; Walzer, K.; Blais, M.;

Allain, M.; Cabanetos, C.; Blanchard, P. Triphenylamine/Tetracya-

nobutadiene-based Π -Conjugated Push-Pull Molecules End-capped

with Arene Platforms: Synthesis, Photophysics, and Photovoltaic

Response. Chem. - Eur. J. 2020, 26, chem.202002810.

7) Kato, S.; Noguchi, H.; Jin, S.; Nakamura, Y. Synthesis and

Electronic, Optical, and Electrochemical Properties of a Series of

Tetracyanobutadiene-Substituted Carbazoles. Asian J. Org. Chem.

016, 5 (2), 246−256.

8) Shoji, T.; Ito, S. Azulene-Based Donor −Acceptor Systems:

Synthesis, Optical, and Electrochemical Properties. Chem. - Eur. J.

017, 23 (66), 16696−16709.

9) Wang, Y.; Michinobu, T. Polymeric Chemosensors: A

Conventional Platform with New Click Chemistry. Bull. Chem. Soc.

Jpn. 2017, 90 (12), 1388−1400.

10) Michinobu, T.; Diederich, F. The [2 + 2] Cycloaddition-

(22) Gautam, P.; Misra, R.; Siddiqui, S. A.; Sharma, G. D.

Unsymmetrical Donor −Acceptor −Acceptor −π −Donor Type Benzo-

thiadiazole-Based Small Molecule for a Solution Processed Bulk

Heterojunction Organic Solar Cell. ACS Appl. Mater. Interfaces 2015,

7 (19), 10283−10292.

(23) Rout, Y.; Mobin, S. M.; Misra, R. Tetracyanobutadiene

(TCBD) Functionalized Benzothiadiazole Derivatives: Effect of

Donor Strength on the [2 + 2] Cycloaddition −Retroelectrocycliza-

tion Reaction. New J. Chem. 2019, 43 (31), 12299−12307.

(24) Lehnherr, D.; Adam, M.; Murray, A. H.; McDonald, R.;

Hampel, F.; Tykwinski, R. R. Synthesis, Physical Properties, and

Chemistry of Donor −Acceptor-Substituted Pentacenes. Can. J. Chem.

2017, 95 (3), 303−314.

(25) Back, J. Y.; An, T. K.; Cheon, Y. R.; Cha, H.; Jang, J.; Kim, Y.;

Baek, Y.; Chung, D. S.; Kwon, S.-K.; Park, C. E.; Kim, Y.-H. Alkyl

Chain Length Dependence of the Field-Effect Mobility in Novel

Anthracene Derivatives. ACS Appl. Mater. Interfaces 2015, 7 (1), 351−

358.

Retroelectrocyclization (CA-RE) Click Reaction: Facile Access to

Molecular and Polymeric Push-Pull Chromophores. Angew. Chem.,

Int. Ed. 2018, 57 (14), 3552 −3577.

11) Patil, Y.; Misra, R. Rational Molecular Design towards NIR

Absorption: Efficient Diketopyrrolopyrrole Derivatives for Organic

Solar Cells and Photothermal Therapy. J. Mater. Chem. C 2019, 7

42), 13020−13031.

12) Shoji, T.; Okujima, T.; Ito, S. Development of Heterocycle-

Substituted and Fused Azulenes in the Last Decade (2010 −2020). Int.

J. Mol. Sci. 2020, 21 (19), 7087.

13) Li, Y.; Ashizawa, M.; Uchida, S.; Michinobu, T. Colorimetric

Sensing of Cations and Anions by Clicked Polystyrenes Bearing Side

(

Chain Donor −Acceptor Chromophores. Polym. Chem. 2012, 3 (8),

(26) Zhang, Y.; Hsung, R. P.; Tracey, M. R.; Kurtz, K. C. M.; Vera,

E. L. Copper Sulfate-Pentahydrate-1,10-Phenanthroline Catalyzed

Amidations of Alkynyl Bromides. Synthesis of Heteroaromatic Amine

Substituted Ynamides. Org. Lett. 2004, 6 (7), 1151−1154.

996−2005.

(14) Wu, X.; Wu, J.; Liu, Y.; Jen, A. K.-Y. Highly Efficient, Thermally

and Chemically Stable Second Order Nonlinear Optical Chromo-

011

Org. Lett. 2021, 23, 2007−2012

Organic Letters

(27) Middleton, W. J.; Heckert, R. E.; Little, E. L.; Krespan, C. G.

Letter

Cyanocarbon Chemistry. III. 1 Addition Reactions of Tetracyano-

ethylene. J. Am. Chem. Soc. 1958, 80 (11), 2783 −2788.

(28) Masci, B.; Pasquale, S.; Thuéry, P. Supramolecular Control of a

Fast and Reversible Diels −Alder Reaction. Org. Lett. 2008, 10 (21),

29) Ronson, T. K.; Pilgrim, B. S.; Nitschke, J. R. Pathway _I -_I

835−4838.

Dependent Post-Assembly Modification of an Anthracene-Edged M

L ₆ Tetrahedron. J. Am. Chem. Soc. 2016 , 138 (33), 10417 −10420.

30) Brown, P.; Cookson, R. C. Kinetics of Addition of

Tetracyanoethylene to Anthracene and Bicyclo[2,2,1]Heptadiene.

Tetrahedron 1965, 21 (8), 1977−1991.

31) Sauer, J.; Schröder, B.; Wiemer, R. Eine Studie der Diels-Alder-

Reaktion, VI. Kinetischer Nachweis des Moleku

der Athylentetracarbonsau

(

ls C6O6 (Dianhydrid

re). Chem. Ber. 1967, 100 (1), 306−314.

32) Michinobu, T.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.;

Frank, B.; Moonen, N. N. P.; Gross, M.; Diederich, F. Donor-

Substituted 1,1,4,4-Tetracyanobutadienes (TCBDs): New Chromo-

phores with Efficient Intramolecular Charge-Transfer Interactions by

Atom-Economic Synthesis. Chem. - Eur. J. 2006, 12 (7), 1889−1905.

(33) Salamatova, E.; Kozlov, O. V.; Luponosov, Y. N.; Solodukhin,

A. N.; Toropynina, V. Y.; Ponomarenko, S. A.; Pshenichnikov, M. S.

Visualization of Molecular Excitons Di ﬀ usion. In Proc. SPIE

Nanoscience + Engineering Conference; Bakulin, A. A., Lovrincic, R.,

Banerji, N., Eds.; San Diego, 2016; p 99230K. DOI: 10.1117/

(

2.2237620 .

34) Philippe, C.; Bui, A. T.; Batsongo-Boulingui, S.; Pokladek, Z.;

Matczyszyn, K.; Mongin, O.; Lemiegre, L.; Paul, F.; Hamlin, T.;

Trolez, Y. 1,1,4,4-Tetracyanobutadiene-Functionalized Anthracenes:

Regioselectivity of Cycloadditions in the Synthesis of Small Near-IR

Dyes. ChemRxiv 2020, DOI: 10.26434/chemrxiv.13491135.v1.

012