INHIBIT logic operations based on light-driven β-cyclodextrin pseudo[1]rotaxane with room temperature phosphorescence addresses

Article abstract of DOI:10.1039/c3cc49820d

INHIBIT logic gates based on light-driven β-cyclodextrin pseudo[1]rotaxane were conveniently fabricated in aqueous solution utilizing induced circular dichroism (ICD) and photocontrolled reversible room temperature phosphorescence (RTP) as output addresses respectively. The Royal Society of Chemistry 2014.

Full text of DOI:10.1039/c3cc49820d

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INHIBIT logic operations based on light-driven
b-cyclodextrin pseudo[1]rotaxane with room
temperature phosphorescence addresses†‡
Cite this: Chem. Commun., 2014,
50, 3224
Received 29th December 2013,
Accepted 4th February 2014
Jingjing Cao, Xiang Ma,* Mingri Min, Tiantian Cao, Shuaifan Wu and He Tian
DOI: 10.1039/c3cc49820d
www.rsc.org/chemcomm
INHIBIT logic gates based on light-driven b-cyclodextrin pseudo[1]- into the cavity and form inclusion complexes in aqueous
rotaxane were conveniently fabricated in aqueous solution utilizing solution. Moreover, many kinds of chemically modified CDs
induced circular dichroism (ICD) and photocontrolled reversible room have been designed and synthesized to enhance the original
temperature phosphorescence (RTP) as output addresses respectively. binding ability, the molecular selectivity and the spectral
changes upon inclusion complexation with guests.6
The design and construction of molecular systems capable of
Since the establishment of cyclodextrin induced room tem-
information processing potentially used to develop molecular scale perature phosphorescence (CD-RTP) by Cline Love et al. first in
electronics, chemical and biological computers on the molecular 1984,7 it has developed rapidly with its wide applications in
level have attracted considerable attention and may have techno- environmental science, agricultural chemistry, biological and
logical potential. Since the proposal of the first molecular AND medical science.8 Numerous phosphor–CD systems were developed,
gate by de Silva and co-workers about 20 years ago,1 a variety of and the most typical one is the a-bromonaphthalene–b-CD system.9
molecule-based systems capable of realizing Boolean logic gates Phosphor molecules enter the CD cavity, which provides a protective
(AND, OR and NOT gates, etc.) have been realized, with the environment for the emitted triplet state of phosphor from
prospect of creating more sophisticated and complex circuits.2 interaction with oxygen molecules and other dissolved quenchers,
Many of these systems employ stimuli-responsive rotaxanes and and form an inclusion complex. We have reported a photo-
pseudorotaxanes,3 in which the relative positions of the inter- controlled reversible room temperature phosphorescence encoding
locked components can be altered by external stimuli to create b-CD pseudorotaxane based on a ternary system including b-CD,
logic gates with chemical or photonic inputs and recognizable a-bromonaphthalene (a-BrNp) and a photo-responsive azo dye in
output signals such as UV/Vis absorption, fluorescence, electro- aqueous solution.10
chemical signals, circular dichroism, etc.
Herein, a binary system with light-driven pseudo[1]rotaxane
Phosphorescence, especially the room temperature phosphores- based on azobenzene modified b-CD (b-CD-Azo) and a-BrNp was
cence (RTP), is an excellent method expected to obtain the output constructed to investigate the CD-RTP as an efficient tool to address
signals of rotaxanes and pseudorotaxanes to construct more complex the threading and dethreading of pseudorotaxanes (Scheme 1).
devices. RTP possesses some remarkable merits such as fewer
interferences, high selectivity, quick response, easily measurable
and long lifetimes, high signal-to-noise ratios, etc.4 However, only
a few examples of RTP logic gates have been reported up to now.2h
Cyclodextrins (CD) continue to be extensively used in
the construction of various rotaxanes and pseudorotaxanes.5
They can admit a variety of appropriately sized guest molecules
Key Labs for Advanced Materials and Institute of Fine Chemicals,
East China University of Science and Technology, Shanghai 200237, China.
E-mail: maxiang@ecust.edu.cn; Fax: +86 21-64252758; Tel: +86 21-64252758
† This communication is dedicated to Prof. Seiji Shinkai on the occasion of his
70th birthday.
‡ Electronic supplementary information (ESI) available: Experimental details,
1H NMR, UV-Vis, ICD and RTP spectra and other characterization data mentioned
in the text. See DOI: 10.1039/c3cc49820d
Scheme 1 Synthetic routes of pseudo[1]rotaxane b-CD-Azo and its inclusion
phenomenon with a-BrNp in water.
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In this b-CD-Azo–a-BrNp system, light irradiation on b-CD-Azo a negative Cotton peak at about 318 nm (À10.55 cmÀ3 molÀ1 cmÀ1),
can reversibly control its isomerization and the subsequent which, respectively, correspond to the n–p* and p–p* transition
complexation with a-BrNp due to which the association con- bands of the azobenzene group located in b-CD.13 Owing to
stant order is b-CD/trans-azo 4 b-CD–a-BrNp 4 b-CD/cis-azo.10 the trans–cis photoisomerization of the azobenzene unit in the
The ICD responses of b-CD-Azo to the light irradiation with pseudo[1]rotaxane b-CD-Azo and its subsequent dethreading out of
different frequencies correspond to an INHIBIT logic gate. the b-CD cavity, the prolonged irradiation with 360 nm light leads to
While using 360 nm as well as a-BrNp as two inputs and RTP a gradual increase in the intensity of the Cotton peak at 258 nm and
emission as output, compound b-CD-Azo was demonstrated to 436 nm, but a decrease at 320 nm (curve red). And the ICD spectral
be an AND logic gate. Furthermore, its RTP emission output changes can be shifted back by irradiation at 430 nm (blue curve,
with oxygen or heat as the third input can express INHIBIT overlapped with the black curve).
logic functions in aqueous solution. To the best of our knowl-
Based on the above results, we designed a logic device that
edge, this is the first light-driven b-CD pseudo[1]rotaxane plat- defined the light irradiation at 360 nm and 430 nm as inputs
form which can conveniently achieve INHIBIT logic operations and the ICD signal of the b-CD-Azo as output. For output, the
with adjustable ICD and RTP as output addresses.
intensity of ICD signals above 30 mdeg at 436 nm is denoted as
The photoisomerization of the pseudo[1]rotaxane b-CD-Azo 1 and the one below as 0 (Fig. 1B). Based on the above
was measured by 1H NMR spectroscopy, 2D 1H ROESY NMR definitions, b-CD-Azo was demonstrated to be an INHIBIT logic
spectroscopy as well as absorption spectroscopy (see details in gate with optical inputs and outputs in aqueous solution.
ESI‡). It suggested that the b-CD-Azo preferentially exhibited
The RTP spectrum of this binary system b-CD-Azo–a-BrNp in
self-inclusive conformation in which the azobenzene moiety is aqueous solution is shown in Fig. 2A (for more detailed data see
deeply self-included in the cavity of the b-CD in the original ESI‡). In the original state, b-CD-Azo in aqueous solution
state rather than forming a polymer.11 Upon irradiation with prefers forming trans-configuration, and then the azobenzene
UV light at 360 nm, b-CD-Azo could be photoisomerized from moiety attached to the b-CD rim can be deeply embedded into
trans to cis until it reaches the photostationary state (the photo- the b-CD cavity to form the intramolecular inclusion complexes
isomerization efficiency is about 60%, see ESI‡) and the cis- in aqueous solution. Most of the a-BrNp molecules were free in
azobenzene unit dethreads from the b-CD cavity. It can be the solution without obvious RTP emission owing to the oxygen
reversibly shifted back after light irradiation at 430 nm. quenching while only a little a-BrNp was included by the b-CD
Compared with the ternary system we reported previously,10 the cavity, which engendered weak RTP signals (green curve in Fig. 2A).
b-CD-Azo–a-BrNp binary system undergoes E/Z photoisomeriza- Upon irradiation by 360 nm light for 60 min, the inducing RTP
tion to reach the photostationary state for a shorter time (2 than emission of b-CD-Azo–a-BrNp in aqueous solution is obviously
15 min, respectively).
enhanced (red curve in Fig. 2A) due to which the azobenzene unit
It is well known that the azobenzene unit can be induced to is photoisomerized to dethread from b-CD and more a-BrNp
generate an ICD signal when it is included into the cavity of CD.12 molecules are included into the b-CD cavity. The RTP lifetime
As seen in Fig. 1A, the ICD spectrum of aqueous b-CD-Azo solution was found to be about 0.58 ms (Fig. S9, ESI‡).9a After the photo-
(curve black) showed positive Cotton peaks at about 258 nm isomerization of the b-CD-Azo–a-BrNp system, the equilibrium
(20.45 cmÀ3 molÀ1 cmÀ1) and 436 nm (17.90 cmÀ3 molÀ1 cmÀ1) and
Fig. 2 (A) RTP emission spectra of b-CD-Azo under different input conditions:
Fig. 1 (A) ICD emission spectra of b-CD-Azo under different light irradiation:13
(a) black, on the initial state; (b) red, after irradiation by 360 nm light for 2 min;
(c) blue, irradiated by light at 430 nm for 2 min. (B) Output (ICD intensity at
436 nm) response to the absence and presence of light irradiation at 360 nm
and 430 nm; (C) corresponding truth tables; and (D) scheme representation for
the INHIBIT logic gates.
(a) black, initial state; (b) red, irradiation by 360 nm light and addition of a-BrNp;
(c) green, a-BrNp; (d) purple, irradiation by 360 nm light, adding a-BrNp and
purging with O2; (e) blue, irradiation by 360 nm light, adding a-BrNp and heated
to 60 1C. (B) Output (RTP intensity at 528 nm) responding to different external
stimuli; (C) corresponding truth tables; and (D) scheme representation for the
INHIBIT logic gates.
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good photoreversibility of the b-CD-Azo pseudo[1]rotaxane, the
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as 0 (Fig. 2B). In addition, the excitation–emission wavelengths
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13 It should be noted that the intensity of the maximum peak of the ICD
spectra was beyond the limit when using 1 cm quartz, so 1 mm quartz
cell was more appropriate to be used at the same concentration during
the RTP measurement ([b-CD-Azo] = 2.0 Â 10À3 mol LÀ1).
In summary, a reversible photocontrolled pseudo[1]rotaxane
based on the azobenzene-modified b-CD was prepared in aqueous
solution, and its photoisomerized movement was characterized by
1
1D and 2D H NMR, circular dichroism and UV-Vis absorption
spectra etc. Their complexation behavior with the typical phos-
phor a-BrNp was addressed with RTP signals. INHIBIT logic gates
based on this system were fabricated with the light irradiation,
temperature change, O2 purging, a-BrNp as the inputs and ICD or
RTP as output, respectively. Significantly, the strategy based on
the RTP intensity as output in this work provides a feasible
approach for the fabrication of other integrated, complicated
and multifunctional molecular logic devices. A possible way to
immobilize the above operation supramolecular system onto
carriers or substrates for further practical applications in
information technology is underway.
This work was financially supported by the National Basic
Research 973 Program (2011CB808400), NSFC/China (21190033 &
21272072), the Shanghai Pujiang Program (13PJD011) and the
Fundamental Research Funds for the Central Universities.
Notes and references
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3226 | Chem. Commun., 2014, 50, 3224--3226
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