Structure property studies revealed a new
indoylfuranone based bifunctional chemosensor
for Cu
2+
and Al
3+
†
Lokesh Kumar Kumawat,‡
a
Manoj Kumar,‡
b
Priyanka Bhatt,
c
Anjali Jha,
c
Vinod Kumar Gupta
a
and Anuj Sharma
*
b
The present report highlights the role of comprehensive structure property relationships (SPRs) in the
discovery of a new and more effective molecular system for sensing purposes. From an extensive survey
of different classes of amino substituted annulated furanones, it was realized that with some exceptions,
these functionalized furanones could sense Cu
2+
ions in the semi-aqueous phase irrespective of the
nature of substituents; furthermore the same scaffolds could also detect Al
3+
, if the aldehydic position is
specifically filled by a 3-indoyl group. As a result, amino substituted annulated furanones with 3-indoyl
groups could detect both metal ions, response time of which mainly depends on the overall molecular
framework. After replacing different furanone frameworks, a dual metal ion sensor (for Cu
2+
and Al
3+
)
with short response time and high selectivity and association constant was identified. The proposed
bifunctional sensor displayed a distinct but observable response (turn off colorimetric for Cu
2+
and turn
on fluorescence for Al
3+
) to both metal ions with potential applications in the area of real sample analysis
and membrane sensing.
Introduction
From the beginning, analytical chemistry has been in a state of
continuous and rapid change from the level of theory to prac-
tise. The direction of these developments is denitely guided by
the criteria set for the future purposes. While automation,
miniaturisation and hyphenated techniques seem to be the
main themes of these changes, roles of other factors such as
portability, easy monitoring ability, fast response time, real
sample applicability, higher sensitivity and selectivity, etc.
cannot be ruled out.
1–9
It is these qualications which make
sensor based techniques highly suitable for further exploration.
A recent surge in the sensor related literature highlights this
fact and indeed this is an active area of research.
10–23
A sensor is a system which has the ability to selectively
recognize an analyte and provides an output in the form of
a distinguishable and measureable change in any signal (elec-
trochemical/uorescence/optic, etc.).
4
From a chemist's perspective,
design and synthesis of novel receptor molecules or chemical
sensors is a research goal of signicant interest.
Despite the fact that the domain of chemical sensors is very
vast and in recent years a large number of molecular probes
have been put forth for different analytical purposes, still the
approaches for designing new sensors are rather limited. Two
very common approaches are based on the concept of Pearson's
hard-so acid base (HSAB) theory
24–26
and the shape/size
compatibility between the receptor and analyte.
27–33
HSAB
theory (or Irving–Williams stability series)
24–26
assumes that so
acids form stronger bonds with so bases, whereas hard acids
prefer hard bases. By changing the nature of donor atoms (such
as replacement of oxygen by sulphur) sensing properties of
a receptor can be modulated.
27–33
Similarly, in many cases,
analyte species occupy a cavity of the receptor molecule. For this
to happen there must be a size match between the receptor
and analyte. These kinds of interactions are very common in
macrocyclic receptors such as crown ethers, inclusion
compounds, etc.
Once the sensing properties of a particular scaffold class
(such as rhodanine,
34–43
coumarin,
44–51
Schiff base,
52–60
etc.) are
established, its random structural modications (including
simple derivatization) sometimes lead to a new molecular
system with different performance indices. Although this hit
and trial exercise is a very common theme of many of the
current research endeavours, it lacks in providing comprehen-
sive insight into the problem. In this connection, authors
believe that, instead of studying the sensing characteristics of
a
Department of Applied Chemistry, University of Johannesburg, Johannesburg,
South-Africa
b
Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667,
India. E-mail: anujsharma.mcl@gmail.com; anujsfcy@iitr.ac.in; Fax: +91 13 3227
3560; Tel: +91 13 3228 475
c
Department of Chemistry, GITAM Institute of Science, GITAM University,
Visakhapatnam, Andhra Pradesh 530045, India
† Electronic supplementary information (ESI) available: Spectral data, spectra and
gures. See DOI: 10.1039/c6ay01786j
‡ Contributed equally as co-rst authors (LKK and MK).
Cite this: Anal. Methods, 2016, 8, 7369
Received 23rd June 2016
Accepted 5th September 2016
DOI: 10.1039/c6ay01786j
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