Bandrowski's base revisited: Toward a unprecedented class of quinonediimines or new two-way chromophoric molecular switches

Article abstract of DOI:10.1021/jo902437u

Chemical Equation Presented Temperature-controlled reactivity places Bandrowski's base 3 at the crossroads of a new versatile strategy for the preparation of two different categories of chromophores. We describe the access to a new class of quinonediimines (8) with an extended π-conjugation owing to the presence of imine functions. Under slightly different conditions, Bandrowski's base appears to be the precursor of choice in the preparation of a novel pH- and light-dependent binary molecular switch. This molecule (11) is constituted of a benzobis(imidazole) core that can be reversibly protonated and a diarylethene unit which can be reversibly converted into its closed form upon irradiation. Triggered by two independent variables, 11 provides four distinct optical states for molecular number processing.

Full text of DOI:10.1021/jo902437u

pubs.acs.org/joc
Bandrowski’s Base Revisited: Toward a Unprecedented Class of
Quinonediimines or New Two-Way Chromophoric Molecular Switches
Ekaterina A. Shilova, Arnault Heynderickx, and Olivier Siri*
Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), UPR 3118 CNRS, Campus de Luminy,
case 913, F-13288 Marseille Cedex 09, France
siri@univmed.fr
Received November 13, 2009
Temperature-controlled reactivity places Bandrowski’s base 3 at the crossroads of a new versatile
strategy for the preparation of two different categories of chromophores. We describe the access to a
new class of quinonediimines (8) with an extended π-conjugation owing to the presence of imine
functions. Under slightly different conditions, Bandrowski’s base appears to be the precursor of
choice in the preparation of a novel pH- and light-dependent binary molecular switch. This molecule
(11) is constituted of a benzobis(imidazole) core that can be reversibly protonated and a diarylethene
unit which can be reversibly converted into its closed form upon irradiation. Triggered by two
independent variables, 11 provides four distinct optical states for molecular number processing.
Introduction
operations.1 Photochromic compounds such as bisthienyl-
ethenes (BTE) 1, widely investigated,2 are of particular
interest3 since the use of light as an external stimulus for
the interconversion of two states allows rapid and clean
processes.4 Molecules exhibiting a quinoid structure have
attracted the interest of a large scientific community owing
to their remarkable chemical and physical properties.5a
The field of molecular switches has been very attractive for
years owing to the possibility of performing simple logic
(1) For an overview of switchable molecular devices, see: (a) Lehn, J.-M.,
Supramolecular Chemistry, VCH,Weinheim, 1995. (b) Ward, M. Chem. Ind.
1997, 16, 640. (c) Balzani, V.; Gomez-Lopez, M.; Stoddart, J. F. Acc. Chem. Res.
1998, 31, 405. (d) Balzani, V.; , Scandola, F. In Comprehensive Supramolecular
Chemistry; Reinhoudt, D. N., Ed.; Pergamon-Elsevier: Oxford, 1996; Vol. 5.
(e) Feringa, B. L.; Jager, W. F.; de Lange, B. Tetrahedron 1993, 49, 8267. (f) D€urr,
H. Angew. Chem., Int. Ed. 1989, 28, 413.
(4) (a) Irie, M. Jpn. J. Appl. Phys. 1989, 28 (Suppl. 28-3), 215. (b) Uchida,
K.; Nakayama, Y.; Irie, M. Bull. Chem. Soc. Jpn. 1990, 63, 1311.
(c) Nakayama, Y.; Hayashi, M.; Irie, M. Bull. Chem. Soc. Jpn. 1991, 64,
789. (d) Iwata, S.; Ishihara, Y.; Qian, C.-P.; Tanaka, K. J. Org. Chem. 1992,
57, 3726. (e) Saika, T.; Irie, M.; Shimidzu, T. J. Chem. Soc., Chem. Commun.
1994, 2123.
(2) Wang, S.; Li, X.; Luo, Q.; Tian, H. Macromol. Chem. Phys. 2004, 205,
1497.
(3) (a) Irie, M. Chem. Rev. 2000, 100, 1685. (b) Kim, E.; Choi, K.; Rhee,
S. B. Macromolecules 1998, 31, 5726. (c) Kawai, T.; Koshido, T.; Yoshino, K.
Appl. Phys. Lett. 1995, 67, 795. (d) Lucas, L. N.; Esch, J. V.; Kellogg, R. M.;
Feringa, B. L. Chem. Commun. 2001, 759. (e) Murguly, E.; Norsten, T. B.;
Branda, N. R. Angew. Chem., Int. Ed. 2001, 40, 1752. (f) Mulder, A.; Jukovie,
A.; Lucas, L. N.; Esch, J. V.; Feringa, B. L.; Huskens, J.; Reinhoudt, D. N.
Chem. Commun. 2002, 2734.
(5) (a) Pataï, S.; Rappoport, Z. The Chemistry of the quinonoid compounds;
Wiley and Sons: New York, 1988; Vols. 1 and 2. (b) Siri, O.; Braunstein, P.;
ꢀ
Rohmer, M.-M.; Benard, M.; Welter, R. J. Am. Chem. Soc. 2003, 125, 13793.
(c) Elhabiri, M.; Siri, O.; Sornosa-Tent, A.; Albrecht-Gary, A.-M.; Braunstein, P.
Chem.;Eur. J. 2004, 10, 134.
DOI: 10.1021/jo902437u
r
Published on Web 02/24/2010
J. Org. Chem. 2010, 75, 1855–1861 1855
2010 American Chemical Society

Shilova et al.
SCHEME 1. Reactivity of the Bandrowski’s Base 3
JOCArticle
In particular, quinoid compounds of type 2 appeared more
recently as very attractive acidichromic systems because of
the presence of two localized π-subunits that can be tuned
by reversible protonation to become delocalized.5b,c Thus,
integration of diarylethenes 1 in 2 would give access to a new
class of multistate molecular switches combined in a single
molecule.
The long-known quinonediimine 3, called Bandrowski’s
base,6,7 appeared to be a reagent of choice that might be
easily functionalized owing to the presence of two types of
NH2 groups which can be viewed as aniline-type or cyanine-
type amino functions. As a result, a selectivity of the NH2
reactivity, which prevents protection/deprotection steps,
might be envisaged. Curiously and to the best of our know-
ledge, although prepared more than one century ago,6 the
chemistry of 3 has remained unexplored, and this compound
has been used only in hair colorants and cosmetics for
decades8 or more recently as bioactive species in biology.9
In the course of this study, we observed the unexpected
formation of benzobis(imidazoles) of type 4 which are of
growing interest as precursors of modular fluorescent
probes,10 polymers,11 or Janus bis(carbene)s and transi-
tion-metal complexes.12
or cumulative effects in switching cycles. Compound 11
consists of (a) a benzobis(imidazole) core that can be rever-
sibly protonated and (b) a diarylethene unit which can be
reversibly converted into its closed form upon UV-vis
irradiation. This molecule (11) was obtained from the versa-
tile Bandrowski’s base (3) that is also able to lead under
different temperature conditions to a new class of quinone-
diimines (8).
Results and Discussion
The reactivity of 3 was first investigated by theoretical
calculations for which the geometry optimization was done
using B3LYP/6-31G(d,p).13 The overall charges on the NH2
groups show clearly that the amino functions H2N(1) and
H2N(2) are more electron-rich than those located on H2N(3)
and H2N(4) (Figure 1).
Herein, we report a new class of molecules (11) with
two addressable subunits that can undergo individual and/
(6) (a) Bandrowski, E. Ber. 1894, 27, 480. (b) Blake, A. J.; Hubberstey, P.;
Quinlan, D. J. Acta Crystallogr. C 1996, C52, 1774.
(7) Lauer, W. M.; Sunde, C. J. J. Org. Chem. 1938, 3, 261 and references
cited therein.
(8) (a) Corbett, J. F. J. Soc. Cosmetic Chem. 1972, 23, 683. (b) Corbett,
J. F. J. Soc. Dyers and Colourists 1969, 85, 71. (c) Altman, M.; Rieger, M. M.
J. Soc. Cosmetic Chem. 1968, 19, 141.
(9) (a) Coulter, E. V.; Jenkinson, C.; Wu, Y.; Farrell, J.; Foster, B.; Smith,
A.; McGuire, C.; Pease, C.; Basketter, D.; King, C.; Friedmann, P. S.;
Pirmohamed, M.; Park, B. K.; Naisbitt, D. J. J. Invest. Dermatology 2008,
128, 897. (b) Ryan, C. A.; Chaney, J. G.; Kern, P. S.; Patlewicz, G. Y.;
Basketter, D. A.; Betts, C. J.; Dearman, R. J.; Kimber, I.; Gerberick, G. F.
J. Appl. Toxicol. 2008, 28, 518. (c) Basketter, D. A.; Gerberick, F.; Kimber, I.
ꢀ
Contact Dermatitis 2007, 57, 70. (d) Pepin, E.; Goutet, M.; Ban, M. Toxicol.
Lett. 2007, 175, 89. (e) Jiao, K.; Sun, W.; Zhang, S.-S.; Sun, G. Anal. Chem.
Acta 2000, 413, 71. (f) Farrel, J.; Jenkinson, C.; Lavergne, S.; Maggs, J. L.;
Kevin, P. B.; Naisbitt, D. J. Toxicol. Lett. 2009, 185, 153.
(10) Boydston, A. J.; Vu, P. D.; Dykhno, O. L.; Chang, V.; Wyatt, A. R.;
Stockett, A. S.; Ritschodorff, E. T.; Shear, J. B.; Bielawski, C. W. J. Am.
Chem. Soc. 2008, 130, 3143.
(11) Kamplain, J. W.; Bielawski, C. W. Chem. Commun. 2006, 1727.
(12) Khramov, D. M.; Boydston, A. J.; Bielawski, C. W. Angew. Chem.,
Int. Ed. 2006, 45, 6186.
FIGURE 1. Electronic density of the NH2 functions in the
Bandrowski’s base (3).
1
Consequently, the two resonance peaks observed by H
NMR at 4.15 and 5.32 ppm for 3 can be assigned to the
“nonaromatic” (i.e., cyanine-type) and “aromatic” (i.e., ani-
line-type) NH2 groups, respectively (Figure 2). Interestingly,
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SCHEME 2. Synthesis of 9 and 11
molecule 3 does not exist in solution as a degenerated
structure resulting from the presence of two tautomers in
equilibrium in solution, in contrast to N-substituted analo-
gues.5,14
This observation would suggest a selectivity of the NH2
groups which was confirmed experimentally by acylation
of 3. Molecule 37 was smoothly reacted with t-BuC(O)Cl
(2 equiv) in the presence of base to afford 5 (Scheme 1). The
almost-quantitative yield obtained (99%) accounts for a
selectivity of the cyanine-type amines which prevents protec-
1
tion and deprotection steps. The H NMR spectrum of 5
showed a singlet at 5.50 ppm and a broad peak at 9.21 ppm
corresponding to the olefinic and amido NH protons, re-
spectively. The resonance at 6.30 ppm is the diagnostic signal
of the aniline-type NH2 protons which accounts for an
acylation of the cyanine-type amino groups, as expected.
The reactivity of 3 as base was also investigated, and we
observed upon protonation a drastic color change from
yellow to blue. This observation is consistent with the
protonation of the imine functions and the formation of a
dicationic species A which is stabilized by intramolecular
delocalization to afford 6 (Scheme 1).5b,c The charge dis-
tribution in 3 shows a higher electronic density on the imine
nitrogens than on the cyanine-type amino N (-0.643 vs
-0.659, respectively, see Figure S16 in the Supporting
Informations). Thus, the protonation occurs at the imine
FIGURE 2. 1H NMR spectrum of the Bandrowski’s base 3.
This theoretical study reveals a stronger nucleophilic
character (i.e., higher electron density) of the cyanine-type
NH2 groups [i.e., N(1) and N(2)] by comparison with the
aniline-type NH2 functions [i.e., N(3) and N(4)] (Figure 1).
sites to form cyanine subunits
which
are more stable than the [H3N-CdCH-CdN]þ moieties
1
(in case of protonation of the -NH2 groups).5b,c The H
NMR spectrum of 6 shows the presence of a singlet at
5.95 ppm (I = 2H) which is in agreement with a symmetrical
geometry in solution resulting from a double protonation
reaction.
(13) Gaussian 03, Revision B.05: Frisch, M. J.; Trucks, G. W.; Schlegel,
H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.;
Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.;
Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.;
Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda,
R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.;
Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.;
Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz,
P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y. ; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson,
B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian, Inc.,
Pittsburgh, PA, 2003.
The strategy of union of bisthienylethene (BTE) 1 and the
benzoquinonediimine core was first tested by condensation
of thiophene-2-carboxaldehyde 7 with Bandrowski’s base 3
in refluxing EtOH (Scheme 2). The use of the commercially
available molecule 7 was envisaged as a model compound (i.e.,
analogue of BTE) in order to validate this approach for
connecting the two species through conjugation (formation
of the imine function). The expected quinone of type 8 (R2 =
thiophene) was not obtained, and we isolated instead the
unexpected benzobis(imidazoles) 9 as a yellow-brown solid in
(14) Rumpel, H.; Limbach, H. H. J. Am. Chem. Soc. 1989, 111, 5429.
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Shilova et al.
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probably due to the sensitivity of the conjugated imine
functions toward side reactions such as hydrolysis.17
In contrast, the reversible states and the stability could be
studied for 11 upon the combined UV-vis irradiation and/or
pH switching processes in acetone solution at c = 1.64 ꢀ
10-5 mol/L (Figure 4).
The irradiation of 11 (i.e., when BTE is on the open form
11o) at λ1 = 381 nm under air induced a rapid conversion
from yellow to the red form 11c with a bathochromic shift
(λ = 511 nm) which results from a ring-closure of BTE and
an extension of the π-conjugation.
The photostationary equilibrium is attainable in about
1 min, and the compound decomposes slowly but totally
when irradiated continuously at λ1 = 381 nm for 95 min
(see Figure S12 in the Supporting Information). Thus, the
pure closed form 11c could not be isolated but appeared
to be thermally stable for 5 days at 20 °C as expected
FIGURE 3. UV-vis absorption of 8 in acetone at 20 °C.
57% yield. Its 1H NMR spectrum shows aromatic signals in
the range 6.80-7.64 ppm in agreement with the presence of
benzenic protons as expected for 9 in contrast to a quinoid-
type structure of type 8.15 The broad resonance at 5.64 ppm
corresponds to the NH2 protons linked to the phenyl
groups.
In contrast to the preparation of benzobis(imidazolium)
salts from related benzoquinonediimines which requires
para fortho isomerization of the quinonediimine skeleton,15
the formation of 9 can be explained as follows: (1) nucleo-
philic attack of 3 (i.e., p-quinonediimine) leading to B, (2)
prototropic rearrangement to give C, (3) cyclization reaction
and water elimination yielding D, and (4) air oxidation to
afford 9 (Scheme 2).
1
for bisthienylethenes.1 The H NMR spectrum of 11o in
acetone-d6 irradiated during 10 min at 381 nm shows in the
range 5.50-7.50 ppm the signals of 11o and the presence of
two new peaks at 6.40 and 5.82 ppm in agreement with the
proton shielding of the thiophene rings in the closed form
11c (see Figure S13 in the Supporting Information), as
already observed in related dithienylcyclopentenes.18 Ac-
cording to this experiment, only 10% of 11c is obtained,
which accounts for a slow conversion at the NMR scale
(concentration ∼1000 times higher than that for UV-vis
studies). Increasing the irradiation time led to decomposi-
tion reactions as shown previously by UV-vis spectro-
scopy. Irradiation at the wavelength corresponding to the
red absorption band of 11c (λ2 = 511 nm) gave cyclorever-
sion to the open isomer 11o, and the solution turns back to
light yellow (Figure 4). A time of 20 min for irradiation is
necessary to induce a complete cycloinversion. Several cycles
of photocoloration/photodiscoloration at λ1 = 381 and λ2 =
511 nm, respectively, have been achieved, demonstrating a
good reversibility of the system. However, the fatigue resis-
tance of 11 upon twelve switching cycles, which was deter-
mined by the decrease of the absorption at 511 nm, revealed a
loss of efficiency of about 50% (Figure 5).
Similarly, compound 11 was then synthesized in 54% yield
from reaction between 1016 and 3 in refluxing dry EtOH
1
(Scheme 2). The H NMR spectrum of 11 shows the diag-
nostic signals of the bisthienylethene moieties (BTE) such as,
for instance, the presence of the methyl resonances at 1.81
and 1.92 ppm.
Protonation of 11o by addition of HCl in excess in
acetone (c = 6.10-6 M) affords 11o 4Hþ as indicated by
3
a bathochromic effect of Δλ = 13 nm (λmax = 394 nm)
By studying this reaction in more details, we have now
found that the same reaction carried out at room tempera-
ture furnishes 8 which precipitated as an orange solid in 80%
yield. The formation of 8 was monitored by GC/MS until
(Figure 4). This red shift is due to the delocalization of the
π system, induced by protonation, in order to stabilize the
positive charges (color change from yellow to orange). UV
irradiation of 11o 4Hþ at λ01 = 394 nm for 3 min led to the
3
1
formation of the corresponding closed form 11c 4Hþ
which is characterized by an absorption band at 573 nm
the disappearance of Bandrowski’s base 3 (3 days). Its H
3
NMR spectrum reveals a resonance at 5.66 ppm and an
additional peak at 8.46 ppm, compared to 11, in agreement
with the presence of quinoid C-H and iminic protons,
respectively. The UV-vis spectrum of 8 shows an absorp-
tion band with a shoulder at λmax = 363 nm consistent with
π-π* transitions as already observed in related quinonedii-
mines (Figure 3).5
Unfortunatly, molecule 8 decomposes rapidly in solution
preventing further optical studies of the new chromophore
with two addressable subunits. This high instability would be
(green color). This photochromic response for 11c 4Hþ
was also confirmed by protonation of 11c with diluted
3
HCl. The observed bathochromic shifts can be explained
by a cumulative effect (irradiation plus protonation)
which allows an extension of the delocalization of the
positive charges throughout the whole π-system. Depro-
tonation of 11o 4Hþ and 11c 4Hþ with Et3N leads to the
3
3
formation of 11o and 11c, respectively, as expected
(Figure 4). Irradiation of 11c 4Hþ at λ02 = 573 nm for
3
(17) Seillan, C.; Braunstein, P.; Siri, O. Eur. J. Org. Chem. 2008, 3113.
(18) (a) Lucas, L. N.; de Jong, J. J. D.; van Esch, J. H.; Kellogg, R. M.;
Feringa, B. L. Eur. J. Org. Chem. 2003, 155. (b) Irie, M.; Lifka, T.; Kobatake,
S.; Kato, N. J. Am. Chem. Soc. 2000, 122, 4871.
(15) Boydston, A. J.; Khramov, D. M.; Bielawski, C. W. Tetrahedron
Lett. 2006, 47, 5123.
(16) Wigglesworth, T. J.; Branda, N. R. Chem. Mater. 2005, 17, 5473.
1858 J. Org. Chem. Vol. 75, No. 6, 2010

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FIGURE 4. Absorption spectra of 11 (c = 1.64 ꢀ 10-5 mol/L) in acetone at 20 °C upon protonation with HCl (c = 6.10-6 mol/L) and/or
irradiation with UV-vis light.
32 min furnished the corresponding open form 11o 4Hþ.The1H
3
NMR spectrum of 11o 4Hþ in acetone-d6 (protonation of 11oin
3
the NMR tube) shows three singlets and two doublets in the
aromatic range (i.e., at 6.70, 7.75, 7.86, 8.09, and 8.21 ppm,
respectively) in agreement with a symmetrical molecule (see
Figures S14 and S15 in the Supporting Information). These
signals are downfield shielded compared to 11o as expected upon
protonation. The disappearance of the NH2 resonance is con-
sistent with the protonation of the aromatic amines and the
formation of 11o 4Hþ. The protonated forms 11o 4Hþ and
3
3
11c 4Hþ are stable for days at room temperature. However,
3
their fatigue resistance upon protonation, determined by the
decrease of the absorption at 573 nm, shows a loss of efficiency of
18% after five cycles.
Thus, the above interconversion can be described with
binary logic.19 The input signals are UV light (381 nm, I1)
and proton ions (Hþ, I2). Each signal can be either on or off
(19) (a) Jiang, G.; Song, Y.; Guo, X.; Zhang, D.; Zhu, D. Adv. Mater.
2008, 20, 2888. (b) Guo, X.; Zhang, D.; Zhang, G.; Zhu, D. J. Phys. Chem. B
2004, 108, 11942. (c) Zhou, Y.; Wu, H.; Zhang, D.; Zhu, D. J. Phys. Chem. B
2006, 110, 15676.
FIGURE 5. Fatigue resistance of the molecular switch 11 in acetone
at 20 °C.
J. Org. Chem. Vol. 75, No. 6, 2010 1859

Shilova et al.
JOCArticle
is controlled by light and pH. Molecule 11 is constituted of a
benzobis(imidazole)s core that can be reversibly protonated
and a diarylethene unit whichcanbe reversibly convertedinto
its closed form upon irradiation. Triggered by two indepen-
dent variables, 11 provides four distinct optical states that
might be usable for molecular number processing. The addi-
tion of binary numbers which requires the implementation of
a molecular half-adder could be achieved by 11 for which one
or two high inputs lead to a significant displacement of the
absorption band. Such a potential application would need an
improvement of the stability of this binary molecular switch
(11) as well as an effective photochemical quantum yield,
currently under investigation.
Experimental Section
Synthesis of N,N0-[(3Z,6Z)-3,6-Bis[(4-aminophenyl)imino]cyc-
lohexa-1,4-diene-1,4-diyl]bis(2,2-dimethylpropanamide) (5). To a
solution of the Bandrowski’s base 3 (m = 200 mg, 0.63 mmol) in
THF, in the presence of an excess of NEt3, was added trimethyl-
acetyl chloride (m = 150 mg, 1.25 mmol). After the mixture was
stirred for 12 h at room temperature, the solvent was evaporated
under reduced pressure and the residue was taken up in water.
The obtained precipitate is then isolated by filtration and
washed with water affording 5 as a beige solid (m = 305 mg,
99% yield): 1H NMR (DMSO-d6) δ = 1.28 (s, 18H, CH3), 5.50
(s, 2H, olefinic H), 6.30 (br s, 4H, NH2), 6.77 (d, 4H, aromatic
H), 7.66 (d, 4H, aromatic H), 9.21 (br s, 2H, NH); MS (ESI) m/z
= 487 [MþH]þ. Anal. Calcd for C28H34N6O H2O 1/2THF: C,
FIGURE 6. Schematic representation of the 2-input logic half-adder
circuit.
TABLE 1. Truth Table of the 2-Input Logic Half-Adder Circuit
O1 (AND)
(carry digit)
O2 (XOR)
(sum digit)
half-adder
(added number)
I1 (light)
I2 (pH)
2 3
3
0
1
0
1
0
0
1
1
0
0
0
1
0
1
1
0
00
01
01
10
66.64; H, 7.46; N, 15.54. Found: C, 66.32; H, 7.02; N, 15.24.
Synthesis of N,N0-(2,5-Diaminocyclohexa-2,5-diene-1,4-diyli-
dene)bis(4-aminobenzenaminium) Dichloride (6). To a solution of
3 (m = 180 mg, 0.56 mmol) in THF was added dropwise HCl.
The obtained precipitate is then isolated by filtration and
washed with Et2O affording 6 as a deep blue solid (m = 130 mg,
60% yield): 1HNMR(MeOD-d3) δ= 5.95 (s, 2H, olefinic H), 6.65
(d, 4H, aromatic H), 6.82 (d, 4H, aromatic H). Anal. Calcd for
C18H20N6Cl2: C, 55.25; H, 5.15; N, 21.48. Found: C, 55.69; H, 5.52;
N, 21.38. The dication 6 could not be detected by MS (ESI).
Synthesis N1,N10-[(1Z,4Z)-2-[((1E)-[4-[2-(5-Chloro-2-methyl-
3-thienyl)cyclopent-1-en-1-yl]-5-methyl-2-thienyl]methylene)-
amino]-5-[((1Z)-[4-[2-(5-chloro-2-methyl-3-thienyl)cyclopent-1-en-
1-yl]-5-methyl-2-thienyl]methylene)amino]cyclohexa-2,5-diene-1,
4-diylidene]dibenzene-1,4-diamine (8). 4-[2-(5-Chloro-2-methyl-
3-thienyl)cyclopent-1-en-1-yl]-5-methylthiophene-2-carbaldehyde
(10) (155 mg, 0.488 mmol) and Bandrowski’s base 3 (73 mg,
0.286 mmol) were dissolved in EtOH (v = 3 mL) in the presence
of one drop of piperidine. The mixture was stirred at room
temperature for 3 days. The obtained precipitate was isolated by
filtration affording 8 as an orange solid (m = 195 mg, 80%
yield): 1H NMR (CDCl3) δ = 1.87 (s, 6H, CH3), 2.06 (br s, 10H,
CH3, CH2), 2.53-2.57 (m, 8H, CH2), 4.94 (br s, 4H, NH2), 5.66
(s, 2H, olefinic H), 6.60 (s, 2H, aromatic H), 6.89 (d, 4H, CH),
7.11 (s, 2H, aromatic H), 7.23 (d, 4H, aromatic H), 8.46 (s, 2H,
-HCdN-); MS (ESI) 927.2 [M þ H]þ. No 13C NMR data or
satisfactory CHN analyses could be obtained owing to the
unstability of 8.
representing the 1 and 0 of the binary digit system 11.20 The
presence of 11c, 11o 4Hþ, and 11c 4Hþ can be characterized
3
3
by their corresponding typical absorption bands. The ab-
sorption band at 511 nm (due to the open form 11c after UV
light irradiation, I1) can be considered as one of the output
signals (O2) (Figure 6).
Similarly, the absorption band of 11o 4Hþ at 394 nm is a
3
second output signal (O2) observed in acidic medium (Hþ, I2).
Namely, if either I1 = 1 and I2 = 0 or I1 = 0 and I2 = 1,
O2 = 1 in the binary logic convention. Therefore, the
variation of the absorbances upon UV light and protonation
can be interpreted as an XOR gate (Figure 6 and Table 1).
Molecule 11c 4Hþ was formed in solution only under the
3
simultaneous actions of UV light (I1) and Hþ (I2), namely,
only when I1 = 1 and I2 = 1, the output signal O1 is 1.
Otherwise, O1 is equal to 0. Therefore, the presence of the
absorption band at 573 nm upon the two inputs (I1 and I2)
can be viewed as an “AND” logic gate (Table 1).19
Concluding Remarks
In summary, we determined the reactive sites of Ban-
drowski’s base 3 as a reagent in organic synthesis. The
temperature-controlled reactivity places 3 at the crossroads
of a new versatile strategy for the preparation of two
different categories of chromophores: (1) a new class of
quinonediimines of type 8 with conjugated imine functions
and (2) a unexpected novel binary molecular switch (11) that
Synthesis of 1,5-Diphenylamine 2,6-Bis(2-thienyl)benzo[1,2-
d:4,5-d0]diimidazole (9). Compound 7 (m = 21.0 mg, 0.17 mmol)
and Bandrowski’s base 3 (m = 24.9 mg, 0.08 mmol) were
dissolved in EtOH, and the mixture was heated to reflux under
argon. After being stirred for 20 h, the mixture was then cooled
to room temperature and the obtained precipitate was isolated
by filtration and washed with ethanol to give 9 as a brown solid
(m = 21.6 mg, 57% yield): 1H NMR (DMSO-d6) δ = 5.64 (s,
3
4H, NH2), 6.80 (d, JHH = 8.5 Hz, 4H, aromatic H), 6.91 (m,
2H, aromatic H), 7.01-7.04 (m, 2H, aromatic H), 7.12-7.17 (m,
(20) de Silva, A. P.; McClenaghan, N. D. Chem.;Eur. J. 2004, 10, 574.
1860 J. Org. Chem. Vol. 75, No. 6, 2010

Shilova et al.
JOCArticle
6H, aromatic H), 7.62-7.64 (m, 2H, aromatic H); 13C NMR
(DMSO-d6) δ = 97.7, 114.6, 123.3, 127.6, 127.7, 128.8 (aromatic
C), 129.0 (C-S), 132.7, 136.4, 139.9 (C-N), 148.0, 150.0
(CdN); HRMS (ESI) calcd for C28H20N6S2 [M þ H]þ 505.1264,
found 505.1259.
(CH3), 22.08, 37.63 (CH2), 97.47 114.46, 123.24, 123.57,
127.19, 128.51, 128.58, 128.73, 133.08, 133.81, 134.28,
134.80, 135.73, 136.26, 137.39, 139.91 (aromatic C), 147.67,
149.84 (CdN), only two peaks could be observed for the CH2
groups owing to a signal overlap; 13C DEPT 135 NMR
(DMSO-d6) δ = 13.76, 13.84 (CH3), 22.07, 37.63 (CH2),
97.47, 114.46, 127.19, 128.58, 128.72 (aromatic CH); HRMS
(ESI) calcd for C50H42N6S4Cl2 [M þ H]þ 925.1804, found
925.1810.
Synthesis of 1,5-Diphenylamine 2,6-Bis(2-[4-[2-(5-chloro-2-
methyl-3-thienyl)cyclopent-1-en-1-yl]-5-methylthienyl)benzo[1,2-
d:4,5-d0]diimidazole (11). 4-[2-(5-Chloro-2-methyl-3-thienyl)-
cyclopent-1-en-1-yl]-5-methylthiophene-2-carbaldehyde (10)
(140.0 mg, 0.43 mmol) and Bandrowski’s base 3 (62.75 mg,
0.197 mmol) were dissolved in EtOH in the presence of one
drop of piperidine. The mixture was stirred under reflux
during 20 h under argon. The solvent was then removed under
reduced pressure, and the residue was purified by column
chromatography (eluent cyclohexane/EtOAc (6/4)) affording
11 as an orange solid (m = 102 mg, 54% yield): 1H NMR
(DMSO-d6) δ = 1.81 (s, 6H, CH3), 1.92 (br s, 10H, CH3,
CH2), 2.58-2.75 (m, 8H, CH2), 5.65 (br s, 4H, NH2), 6.66
(s, 2H, CH), 6.76-6.84 (m, 6H, CH), 7.05-7.11 (m, 6H,
aromatic H); 13C APT NMR (DMSO-d6) δ = 13.75, 13.83
Acknowledgment. This work was supported by the Centre
ꢁ
National de la Recherche Scientifique, the Ministere de la
Recherche et de l’Enseignement Superieur. We also thank
ꢀ
Prof. V. Khodorkovsky for theoretical studies and fruitful
discussions.
Supporting Information Available: NMR data of the new
compounds and atomic coordinates of 3. This material is
available free of charge via the Internet at http://pubs.acs.org.
J. Org. Chem. Vol. 75, No. 6, 2010 1861