Sensors 2012, 12, 4421-4430; doi:10.3390/s120404421
2:1 Multiplexing Function in a Simple Molecular System
Sha Xu 1, Yu-Xin Hao 1, Wei Sun 2, Chen-Jie Fang 1,*, Xing Lu 1, Min-Na Li 1, Ming Zhao 1,*,
Shi-Qi Peng 1,* and Chun-Hua Yan 2,*
1 School of Chemical Biology and Pharmaceutical Sciences, Capital Medical University,
Beijing 100069, China; E-Mails: firstname.lastname@example.org (S.X.); email@example.com (Y.-X.H.);
firstname.lastname@example.org (X.L.); email@example.com (M.-N.L.)
2 Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare Earth Materials
Chemistry and Applications & PKU-HKU Joint Lab in Rare Earth Materials and Bioinorganic
Chemistry, Peking University, Beijing 100871, China; E-Mail: firstname.lastname@example.org
* Authors to whom correspondence should be addressed; E-Mails: email@example.com (C.-J.F.);
firstname.lastname@example.org (M.Z.); email@example.com (S.-Q.P.); firstname.lastname@example.org (C.-H.Y.);
Tel.: +86-10-8391-1523 (C.-J.F.); Fax: +86-10-8391-1533 (C.-J.F.).
Received: 31 December 2011; in revised form: 18 February 2012 / Accepted: 12 March 2012 /
Published: 30 March 2012
Abstract: 1-[(Anthracen-9-yl)methylene] thiosemicarbazide shows weak fluorescence due
to a photo-induced electron transfer (PET) process from the thiosemicarbazide moiety to
the excited anthracene. The anthracene emission can be recovered via protonation of the
amine as the protonated aminomethylene as an electron-withdrawing group that suppresses
the PET process. Similarly, chelation between the ligand and the metal ions can also
suppress the PET process and results in a fluorescence enhancement (CHEF). When
solvents are introduced as the third control, a molecular 2:1 multiplexer is constructed to
report selectively the inputs. Therefore, a molecular 2:1 multiplexer is realized in a simple
Keywords: fluorescence; anthracene; molecular 2:1 multiplexer
There is increasing interesting in exploring single molecule species that could be potentially applied
in the construction of binary logic devices and future computers at the molecular scale [1–8]. Since the
Sensors 2012, 12
first molecular AND gate was reported , all common essential logic gates including AND, NOT,
OR, YES, INHIBIT, XOR, NAND and NOR, which are used in conventional silicon circuitry, have
been mimicked at the molecular level with chemical or optical signals [10–21]. With all these logic
gates in hand, the next step is to construct molecular logic networks taking advantage of functional
integration within a single molecule via rational chemical design. This is prior to relying on extensive
physical connection of elementary gates. Recently, molecular-scale arithmetic has also been
reported [21–30]. Those single molecule-based combinatorial circuits are more important because they
are fundamental to a complex information processing system. Tian reported a fluorophore capable of
logic memory . We have systematically explored the combination of logic functions and realized
a safe computing platform with user-identity-directed arithmetic functions to defend information
risk [32,33]. An important function in information technology, e.g. signal multiplexing, has
been realized based on the molecules [34–36]. The construction of molecule-based 1:2 digital
demultiplexer was also reported [37,38]. The signal multiplexing/demultiplexing was demonstrated in
8-methoxyquinoline and enzymes [39,40]. In spite of various logic functions mimicked at molecular
level, however, the combination and integration of advanced functions is still in the infant stage and
reports on this subject are rare [41–45].
In our previous work, up to seven binary logic gates were realized within a single molecule, in
which redox-active tetrathiafulvalene (TTF) was utilized as a switch to control the fluorescence .
Herein, we report a molecular system which is capable of performing multiplexing function in response
to chemical stimuli.
In the present work, the fluorescence of anthracene in the simple molecule 1-[(anthracen-9-yl)
methylene] thiosemicarbazide (L, Figure 1) [47,48] is tuned to realize a molecular 2:1 multiplexer with
anthracene as a signal unit via tuning the PET process. Protonation of amine and chelation with metal
ions can suppress the photo-induced electron transfer (PET) process. Combined with the solvents as
control inputs to switch the fluorescent output, the ligand L can report the binary state of either one of
these inputs or the other.
Figure 1. The molecular structure of the ligand L.
2. Experimental Section
The UV-vis absorption spectra were recorded on a Shimadzu 2500 UV-VIS spectrophotometer. The
fluorescence spectra were recorded on a Shimadzu RF-5301 spectrofluorophotometer using 5 nm input
and 5 nm output width. 1H- and 13C-NMR (TMS) are recorded on a Bruker Avance II 500MHz
spectrometer. The mass spectra were measured on a Waters Quattro micro TM API mass spectrometer.
Elemental analyses were performed on a Vario EI Elementar system.
Sensors 2012, 12
41. Strack, G.; Ornatska, M.; Pita, M.; Katz, E. Biocomputing security system: Concatenated
enzyme-based logic gates operating as a biomolecular keypad lock. J. Am. Chem. Soc. 2008, 130,
42. Frezza, B.M.; Cockroft, S.L.; Ghadiri, M.R. Modular multi-level circuits from immobilized
DNA-basde logic gates. J. Am. Chem. Soc. 2007, 129, 14875–14879.
43. López, M.V.; Vázquez, M.E.; Gómez-Reino, C.; Pedridoa, R.; Bermejo, M.R. A
metallo-supramolecular approach to a half-subtractor. New J. Chem. 2008, 32, 1473–1477.
44. Pischel, U.; Heller, B. Molecular logic devices (half-subtractor, comparator, complementary output
circuit) by controlling photoinduced charge transfer processes. New J. Chem. 2008, 32, 395–400.
45. Zhang, L.; Whitfield, W.A.; Zhu, L. Unimolecular binary half-adders with orthogonal chemical
inputs. Chem. Commun. 2008, 16, 1880–1882.
46. Fang, C.J.; Zhu, Z.; Sun, W.; Xu, C.H.; Yan, C.H. New TTF derivatives: Several molecular logic
gates based on their switchable fluorescent emissions. New J. Chem. 2007, 4, 580–586.
47. Lu, M.; Ma, X.; Fan, Y.-J.; Fang, C.-J.; Fu, X.-F.; Zhao, M.; Peng, S.-Q.; Yan, C.-H. Selective
“turn-on” fluorescent chemosensors for Cu2+ based on anthracene. Inorg. Chem. Commun. 2011,
48. Fu, X.-F.; Yue, Y.-F.; Guo, R. Li, L.-L. Sun, W.; Fang, C.-J.; Xu, C.-H.; Yan, C.-H. An enhanced
fluorescence in a tunable face-to-face π–π stacking assembly directed by the H-bonding. Cryst.
Eng. Comm. 2009, 11, 2268–2271.
49. Rehm, D.; Weller, A. Rehm and Weller equation. Isr. J. Chem. 1970, 8, 259–276.
50. Grabowski, Z.R.; Dobkowski, J. Twisted intramolecular charge transfer (TICT) excited states:
Energy and molecular structure. Pure Appl. Chem. 1983, 55, 245–252.
51. Beer, P.D.; Szemes, F.; Balzani, V.; Salà, C.M.; Drew, M.G.B.; Dent, S.W.; Maestri, M. Anion
selective recognition and sensing by novel macrocyclic transition metal receptor systems. 1H NMR,
electrochemical, and photophysical investigations. J. Am. Chem. Soc. 1997, 119, 11864–11875.
52. De Silva, A.P.; Gunaratne, H.Q.N.; Gunnlaugsson, T.; Huxley, A.J.M.; McCoy, C.P.;
Rademacher, J.T.; Rice, T.E. Signaling recognition events with fluorescent sensors and switches.
Chem. Rev. 1997, 97, 1515–1566.
53. Rohatgi, K.K.; Singh, B.P. Solvent effect on anthracene monosulfonates in the first excited state.
J. Phys. Chem. 1971, 75, 595–598.
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