DOI: 10.1002/chem.201405675
Communication
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Logic Gates
Highly Sensitive INHIBIT and XOR Logic Gates Based on ICT and
ACQ Emission Switching of a Porphyrin Derivative**
[a]
[a]
[a]
[a]
[b, c]
Xiao-Ling Xu, Fu-Wen Lin, Wei Xu, Jian Wu,* and Zhi-Kang Xu*
for pathways that weaken the emission is extremely necessary
and crucial.
Abstract: Fluorescence-switch-based logic devices are
very sensitive compared with most of the reported devi-
ces based on UV/Vis absorption systems. Herein, we dem-
onstrate that a simple molecule, 5,10,15,20-tetra-(4-amino-
phenyl)porphyrin (TAPP), shows protonation-induced mul-
tiple emission switches through intramolecular charge
transfer and/or aggregation-caused quenching. Highly
sensitive INHIBIT and XOR logic gates can be achieved by
combining the intermolecular assembly with the intramo-
It is possible to control emission by designing a versatile
molecule with at least one fluorophore–spacer–receptor seg-
[10]
ment, which sustains the emission-switching processes, such
[
11]
as photoinduced electron transfer (PET),
intramolecular
[12]
charge transfer (ICT), twisted intramolecular charge transfer
[13]
[14]
(
TICT), and resonance energy transfer (FRET). A molecule
with two or more switching processes is supposed to be bene-
ficial for increasing the signal diversity. For example, Akkaya
and co-workers reported effective PET and ICT emission switch-
2
+
lecular photoswitching of diprotonated TAPP (TAPPH2 ).
In addition, molecular simulations have been performed
by DFT for a better understanding of the emission-switch-
ing processes.
[15]
ing for a molecular half-subtractor in 2005. Later, they wid-
ened the applications of styryl–boron-dipyrromethene (bodipy)
derivatives in molecular logic and fluorescence sensing by se-
[16]
lective manipulation of ICT and PET processes. Chemosen-
sors, which combine those two or more processes, have at-
[17]
Molecular logic has experienced a boost in popularity since
the introduction of the first AND gate in solution by de Silva
tracted much attention as well.
However, the molecular
complexity increases with the introduction of more intermolec-
ular quenching processes, that is, an increasing number of
spacers and receptors. Extended p systems with strong emis-
sion, except in aggregated states, carry out quenching process
[
1]
et al. in 1993. From then on, most of the common logic oper-
[2]
ations have been derived from switchable molecular systems,
[
3]
[4]
[5]
[6]
[7]
such as OR, XOR, NOR, NAND, and INHIBIT. Among
them, the XOR gate is a digital logic gate with two or more
inputs and one output that performs exclusive disjunction,
whereas the INHIBIT gate produces a certain or fixed output
whatever the inputs might be or even when the input
changes. In fact, the outputs typically rely on photonic pro-
[18]
through aggregation-caused quenching (ACQ). As Xu et al.
reported, molecular flattening can be an efficient quenching
pathway for p–p cooperative interactions between 2D gra-
[19]
phene layers and the large p system of porphyrin molecules.
Accordingly, designing a simple molecule through intermolec-
ular assembly can perhaps produce diversiform signals through
only one intramolecular process. Nonetheless, little attention
has been paid to this type of combinational work.
[
8]
cesses of UV/Vis absorption and emission. Especially, fluores-
cent output has attracted much attention due to its high sensi-
tivity. “On” and “off” fluorescence are referred to as the binary
digitals “1” and “0”, respectively. In general, the fluorescent
sensitivity highly depends on the “on”/“off” ratio, for which the
Porphyrins, which are perfect emissive molecules, quench
fluorescence by forming assemblies through p–p interactions
and hydrophobic effects. Emission is observed when the as-
sembled structures disperse. Therefore, porphyrins are actually
appropriate candidates for combining ACQ with an intramolec-
[
9]
optimal result is absolute quenching. Therefore, the search
[
a] X.-L. Xu, F.-W. Lin, W. Xu, Prof. Dr. J. Wu
Department of Chemistry, Zhejiang University
Hangzhou 310027 (P.R. China)
[20]
ular process. The core N atoms of 5,10,15,20-tetra(4-amino-
phenyl)porphyrin (TAPP, Scheme S1 and Figure S1 in the Sup-
E-mail: jianwu@zju.edu.cn
[8b]
porting Information) can be primarily protonated, and thus
[
b] Prof. Dr. Z.-K. Xu
2+
TAPP changes into TAPPH2 , which is regarded as an ampho-
MOE Key Laboratory of Macromolecular Synthesis and Functionalization
Department of Polymer Science and Engineering
Zhejiang University, Hangzhou 310027 (P.R. China)
E-mail: xuzk@zju.edu.cn
+
[21]
philic molecule for both trapping and releasing H . Herein,
we report the fluorescent switch of INHIBIT and XOR logic
2
+
gates based on TAPPH
by ICT and ACQ processes by using
2
+
À
[
c] Prof. Dr. Z.-K. Xu
Cyrus Tang Center for Sensor Materials and Applications
Zhejiang University
H
and OH as inputs (Scheme 1). Fluorescence quenching re-
sults from the first conjoined use of intramolecular interaction
and intermolecular assembly. In addition, it is also the first
report on a “turn-on” fluorescence approach for TAPP under
strong acidic, aqueous conditions, and hence TAPP may be
used as an emission sensor at low pH values.
Hangzhou 310027 (P.R. China)
[
**] ICT=intramolecular charge transfer; ACQ=aggregation-caused quenching.
Supporting information for this article is available on the WWW under
Chem. Eur. J. 2014, 20, 1 – 5
1
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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