Multi-channel receptors and their relation to guest chemosensing and reconfigurable molecular logic gates

Article abstract of DOI:10.1002/ejic.200400844

The synthesis and characterisation of a family of multi-channel receptors containing crown-cation binding sites anchored to a 1-aminophenyl-1,2,2- tricyanoethylene group is reported. The ligands L¹-L⁶bear a 1-aminophenyl-1,2,2-tricyanoethylene scaffolding which is simultaneously a redox-active group (showing reduction processes at moderately modest potentials) and an acceptor moiety in the 1-aminophenyl-1,2,2-tricyanoethylene chromophore. Additionally, dyes L¹-L⁶ also show fluorescence emission. The colour variation of L¹-L⁶ in acetonitrile in the presence of the metal cations Ag⁺, Cd²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Pb²⁺ and Zn²⁺ has been studied. Selective hypsochromic shifts were found for the systems L ⁴-Pb²⁺, L⁵-Hg²⁺ and L ⁶-Hg²⁺ For Hg²⁺ with L⁵ and L ⁶ and Pb²⁺ with L⁴, emission fluorescence enhancements most likely associated with metal coordination to the anilinium nitrogen were observed. The electrochemical behaviour of receptors L ¹-L⁶ was studied in acetonitrile with platinum as working electrode and [Bu₄N][BF₄] as supporting electrolyte. This family of receptors shows a one-electron reversible reduction process at around -0.70 V vs. SCE, attributed to the reduction of the tricyanovinyl group. Additionally, all the receptors also show the oxidation of the anilinium moiety at about 1.2-1.4 V vs. SCE. Significant anodic shifts of both reduction and oxidation waves were found in the presence of certain metal cations. The relationship of these multiple-channel signalling receptors with guest chemosensing and reconfigurable molecular-based logic gates is discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejic.200400844

FULL PAPER
Multi-Channel Receptors and Their Relation to Guest Chemosensing and
Reconfigurable Molecular Logic Gates
Diego Jiménez,[a] Ramón Martínez-Máñez,*[a] Félix Sancenón,*[a] José V. Ros-Lis,[a]
Juan Soto,[a] Ángel Benito,[a] and Eduardo García-Breijo[b]
Keywords: Cations / Chemosensing / Chromophores / Electrochemistry / Molecular logic gates
The synthesis and characterisation of a family of multi-chan-
nel receptors containing crown-cation binding sites anchored
to a 1-aminophenyl-1,2,2-tricyanoethylene group is reported.
were observed. The electrochemical behaviour of receptors
L1–L6 was studied in acetonitrile with platinum as working
electrode and [Bu4N][BF4] as supporting electrolyte. This
The ligands L1–L6 bear a 1-aminophenyl-1,2,2-tricyanoethy- family of receptors shows a one-electron reversible reduction
lene scaffolding which is simultaneously a redox-active
group (showing reduction processes at moderately modest
potentials) and an acceptor moiety in the 1-aminophenyl-
1,2,2-tricyanoethylene chromophore. Additionally, dyes L1–
L6 also show fluorescence emission. The colour variation of
L1–L6 in acetonitrile in the presence of the metal cations Ag+,
Cd2+, Cu2+, Fe3+, Hg2+, Pb2+ and Zn2+ has been studied. Se-
lective hypsochromic shifts were found for the systems L4-
Pb2+, L5-Hg2+ and L6-Hg2+. For Hg2+ with L5 and L6 and Pb2+
with L4, emission fluorescence enhancements most likely as-
sociated with metal coordination to the anilinium nitrogen
process at around –0.70 V vs. SCE, attributed to the reduction
of the tricyanovinyl group. Additionally, all the receptors also
show the oxidation of the anilinium moiety at about 1.2–1.4 V
vs. SCE. Significant anodic shifts of both reduction and oxi-
dation waves were found in the presence of certain metal
cations. The relationship of these multiple-channel signalling
receptors with guest chemosensing and reconfigurable mol-
ecular-based logic gates is discussed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
mentarity with target ions, whereas the signalling unit is
capable of transducing the (usually selective) binding event
into a signal.[3] Following this approach, a number of exam-
ples have been described in recent years on the synthesis
of cation[4] and anion chemosensors.[5] A large number of
coordination sites have been designed that are dependent
on the nature of the guest. Three groups of reporters have
been mainly used as signalling units: fluorescent groups[6]
(the signal is an emission fluorescence change), dyes (the
signal is a colour variation) and redox-active groups[7] (the
signal upon guest coordination is a shift in the redox poten-
tial of the redox-active groups). Advances in this area have
been described as important for the selective and sensitive
development of target molecular probes.
However and despite the development of individual
chromogenic, fluorogenic and electrochemical molecular
sensors, there are few examples of receptors capable of dis-
playing two or more output signals upon guest binding.
Towards the development of multi-signalling receptors, we
have recently reported chemosensors containing both an-
thracene (as fluorescent) and ferrocene (as electroactive)
subunits.[8] Some other recent examples of multi-signalling
include the work of Delavaux-Nicot et al., who have devel-
oped cation chemosensors containing ferrocene and N,N-
diethylbenzene fluorescent groups.[9] A similar approxi-
mation has been used by Beer et al. by synthesising redox-
Introduction
One of the most interesting and expanding fields in
supramolecular chemistry is related to the management of
input/output signals and their relationship with molecular
information. This double “signal-information” concept has,
for instance, been applied to different research fields, such
as those of molecular logic gates[1] and chemosensing.[2] In
the former, chemical species are used as inputs and the out-
put is usually a light signal (emission or colour variation).
In chemosensing protocols, light (emission or colour varia-
tion) or an electrochemical signal can be considered as in-
put events which are related to the presence of certain
chemical species (output information). In many cases these
molecular input/output transducers have in common the
presence of “binding sites” and “signalling” units.
In the development of chemosensors, the binding site is
specifically designed to achieve a high degree of comple-
[a] GDDS, Departamento de Química, Centro de Investigación en
Química Molecular Aplicada, Universidad Politécnica de Va-
lencia,
Camino de Vera s/n, 46071 Valencia, Spain
Fax: +34-963879349
E-mail: rmaez@qim.upv.es
fsanceno@upvnet.upv.es
[b] Grupo de Microelectrónica Híbrida, Departamento de Inge-
niería Electrónica, Universidad Politécnica de Valencia,
Camino de Vera s/n, 46071 Valencia, Spain
Eur. J. Inorg. Chem. 2005, 2393–2403
DOI: 10.1002/ejic.200400844
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2393

R. Martínez-Máñez, F. Sancenón et al.
FULL PAPER
active and photoactive ruthenium(ii) and osmium(ii) bipyri- which 3,6-dioxaoctane-1,8-dithiol (6a) and 3,6-dithiaoc-
dylferrocene and -cobaltocene-containing macrocycles cap- tane-1,8-diol (6b) were deprotonated with potassium car-
able of sensing anionic guests by electrochemical and fluo- bonate and sodium hydride, respectively, followed by treat-
rescence techniques.[10] Also remarkable are the papers pub- ment with the methylsulfonyl ester of N,N-phenyldiethanol-
lished by Shimidzu and Lehn.[11] Chemosensors function- amine (5) to give the sulfur-containing macrocycles 7a and
alised with only one subunit capable of displaying two or 7b. N,N-Dimethylaniline and the synthesised phenyl-con-
more observable events (usually two-channel fluorescence – taining macrocycles were treated with tetracyanoethylene in
colour changes) upon addition of a certain guest are com- warm DMF (60 °C) to give the corresponding receptors L1–
monly observed in the so-called intrinsic sensors, in which L6, which were isolated as dark-reddish solids.
at least one coordination atom from the binding site is also
part of the signalling subunit (usually a dye scaffolding).
For example, Fabbrizzi et al. recently reported the synthesis
of a chemodosimeter for copper(ii), composed of a cyclam
unit functionalised with 7-nitrobenzo[1,2,5]oxadiazol-4-yl-
amine chromophore, which operates through two different
channels − colour change and fluorescence quenching of
the chromophore.[12] A pH sensor operating through both
absorption and emission and based on 1,3-diaryl-5-pyridyl-
4,5-dihydropyrazole has been reported by de Silva.[13] How-
ever, as far we know, chemosensors operating through three
different channels (colour, fluorescence and redox) are very
rare and are not common in the literature.[14] We report
Scheme 1.
1
here the synthesis and characterisation of a family of multi-
channel receptors containing different crown cation binding
sites anchored to a 1-aminophenyl-1,2,2-tricyanoethylene
The H NMR spectra of receptors L2–L6 show macro-
group, which is simultaneously a redox-active group (show- cyclic protons in the range of δ = 2.6 to 3.8 ppm, with two
ing reduction processes at moderately modest potentials) clearly defined zones − the methylene protons adjacent to
and an acceptor moiety in the 1-aminophenyl-1,2,2-tricyano- the sulfur atoms at δ = 2.6–2.9 ppm and the methylene pro-
ethylene chromophore. Additionally, the synthesised re- tons adjacent to nitrogen and oxygen atoms in the range δ
ceptors also show fluorescence emission. An advance report = 3.5–3.8 ppm. Two doublets at δ = 6.70 and 8.00 ppm indi-
of the results shown here has recently been published.[14] cate the presence of a 1,4-disubstituted aromatic benzene
These multi-signalling systems are not only of interest in ring. In the 13C NMR spectrum the methylenes adjacent to
sensing protocols but could also be of importance for the the sulfur atoms appear in the range δ = 30–35 ppm,
development of “reconfigurable” molecular-based logic whereas the methylenes adjacent to nitrogen and oxygen
gates.
show signals in the δ = 51–73 ppm range. The aromatic and
cyanide carbons appear in the δ = 113–155 ppm range. The
most significant signals are the three cyanide carbons
centred at δ = 113.7, 114.0 and 114.5 ppm and the signals
at δ = 117.8 and 137.3 ppm attributed to the quaternary
Results and Discussion
Receptors L2–L6 are built of macrocyclic binding sites carbons of the tetrasubstituted double bond.
(of different sizes, also containing different heteroatoms; ni-
Despite their easy synthesis and extensive application in
trogen, oxygen and sulfur) and an (aminophenyl)tricyanovi- different fields, such as optical recording materials or in
nyl signalling reporter (Scheme 1). Ligands L1 and L3 have electrophotography,[18] tricyanovinyl dyes have scarcely
previously been synthesised by Charles[15a] and Beer,[15b] been used for sensing purposes. Phenyltricyanoethylene
respectively. Receptor L1 has an N,N-dimethylamino moiety dyes coupled with a phenylboronic acid have previously
and was selected as a model compound in order to study been used as chromogenic reagents for carbohydrate sens-
the selectivity towards metal cations imposed by the nature ing.[19] Additionally, receptors L1 and L3 have previously
of the binding rings. The Richman–Atkins procedure was been used for electrochemical studies in the presence of
used to synthesise the phenyl-functionalised macrocyclic Na+, K+ and Mg2+ cations.[15b]
subunits.[16] Aza-oxa macrocycles were synthesised in high
The crystal structure of receptor L5 was solved by single-
dilution procedures by deprotonation of N,N-phenyldietha- crystal X-ray procedures. Suitable crystals for X-ray diffrac-
nolamine (3) with sodium hydride followed by reaction with tion were obtained by slow diffusion of diethyl ether into
the methylsulfonyl ester derived from the corresponding dichloromethane solutions of the receptor L5. The com-
¯
polyethylene glycol (2a–2c; see Scheme 2). The macrocycles pound crystallises in the space group P1 with two molecules
used to obtain receptors L3 and L4 were previously synthe- of L5 per asymmetric unit. Figure 1 shows a view of one of
sised in 1978 by Vögtle.[17] The macrocycles used to obtain the two molecules. The aromatic ring, the double bond and
receptors L5 and L6, which contain sulfur atoms in their the three cyanide moieties that form the chromogenic sub-
structures, were synthesised by a modified procedure in unit are planar within the experimental error. This chromo-
2394
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2393–2403

Molecular Logic Gates
FULL PAPER
Scheme 2.
genic subunit is linked to the macrocycle by a nitrogen
atom.
Chromogenic Signaling
The visible spectrum of the chemosensors L1–L6 in ace-
tonitrile solutions (5.0×10–5 m) is characterised by a band
centred at about 520 nm which can tentatively be assigned
to a charge-transfer band from the donor anilinium group
to the acceptor tricyanovinyl moiety.[20] This visible band is
responsible for the red-pink colour shown by the receptors
in acetonitrile solution.
Addition of equimolar quantities of alkali (Li+, Na+,
K+) or alkaline-earth (Ca2+, Ba2+, Mg2+) cations to aceto-
nitrile solutions of receptors L1–L6 produced negligible
changes in this band. The visible behaviour was also studied
in the presence of the metal cations Cd2+, Cu2+, Hg2+, Ni2+
,
Pb2+, Zn2+ and Ag+. The model compound L1, without a
macrocyclic cavity in its structure, shows three different be-
haviours (see Figure 2 and Table 1); namely no changes
with Ag+ and Cd2+, a slight hyperchromic effect (intensity
enhancement of the visible band centred at 516 nm) in the
presence of Zn2+, Pb2+ and Hg2+, and the apparition of a
shoulder at 468 nm in the presence of Fe3+ and Cu2+ (see
Figure 2) attributed to metal coordination with the donor
nitrogen atom of the aniline group.[6] Upon titration of a
Figure 1. Crystal structure of receptor L5. Two molecules of L5
were found in the asymmetric unit but only one is shown. Selected
distances [Å]: C(1)–N(1) 1.118(9), C(3)–N(2) 1.115(9), C(5)–N(3)
1.130(8), C(2)–C(1) 1.434(10), C(2)–C(3) 1.419(11), C(4)–C(2)
1.356(10), C(4)–C(5) 1.497(10), C(4)–C(6) 1.431(19), C(9)–N(4)
1.350(8), S(1)–C(19) 1.772(8), S(1)–C(20) 1.848(9), S(2)–C(14)
1.781(7), S(2)–C(13) 1.794(7).
Eur. J. Inorg. Chem. 2005, 2393–2403
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2395

R. Martínez-Máñez, F. Sancenón et al.
FULL PAPER
solution of receptor L1 with Cu2+ cation, clear isosbestic tions of L2 produced negligible changes in the UV/Vis spec-
points were obtained. The presence of these isosbestic trum, whereas the presence of equimolar quantities of Fe3+
points is indicative of the formation of only one complex, resulted in a remarkable hypochromic change (diminution
with a 1:2 stoichiometry (cation:receptor). Monitoring the of the visible band intensity of 60% for Fe3+). A concomi-
changes at 468 nm upon Cu2+ addition, a logarithm of the tant unremarkable hypsochromic shift of the band centred
stability constant of 4.53 0.03 for the formation of the at 523 nm to 519 nm was also observed for Fe3+. Studies
[Cu(L1)2]2+ complex was obtained.[21] Studies with Fe3+ on the variation of the intensity at 523 nm upon addition
gave no clear isosbestic points, most likely due to the simul- of increasing amounts of this cation suggested the forma-
taneous formation of complexes with different stoichiomet- tion of well-defined 1:1 complexes. A log K value of
ries.
4.69 0.09 was determined for the formation of the [Fe-
(L2)]3+ complex (see Table 2).[21] These results for L2, which
has a relatively small coordination ring, are somehow re-
lated to the characteristics of the Fe3+ metal cation, which
is, of all the metal cations studied, that with the smallest
ionic radius (0.64 Å). The perfect fitting of the Fe3+ cation
within the macrocyclic subunit of L2 probably induces
Fe–N interactions that could be the responsible for the hyp-
sochromic shift observed. The lack of response in the pres-
ence of Cu2+ shown by L2 (when compared to L1) could be
due to the poorer tendency of the Cu2+ cation to fit within
the macrocyclic cavity (Cu2+ ionic radius = 0.69 Å), al-
though steric constraints could make the Cu–N interaction
less effective.
For L3 − the macrocycle in L3 contains one oxygen atom
and one methylene unit more than the macrocycle in L2 −
only Fe3+ is able to induce a hypochromic change in the
visible band at 518 nm similar to that observed for L2 (no
hypsochromic shifts were found). A log K of 4.63 0.15 for
the formation of the [Fe(L3)]3+ complex was obtained from
the intensity changes of the 518 nm band (see Figure 3).
The addition of equimolar quantities of the other metal cat-
ions tested induced negligible changes.
Figure 2. Changes in the UV/Vis spectra of receptor L1 upon ad-
dition of equimolar quantities of metal cations in acetonitrile
(5.0×10–5 m).
Table 1. Absorption λmax [nm]and ε [Lmol–1 cm–1] for receptors L1
to L6 and their variation upon addition of metal cations in acetoni-
trile solutions.
A more selective and remarkable behaviour was found
for chemosensor L4, which contains the largest macrocyclic
cavity of all the receptors studied. A selective colour varia-
tion from red-pink to yellow-orange (hypsochromic shift
from 520 to 475 nm) was observed upon addition of the
heavy metal cation Pb2+ (see Figure 4).[22] This result is in
agreement with the larger radius of Pb2+, which apparently
fits well into the large binding cavity of L4. The correct
combination of ring and cation size would result in a suit-
able coordination to the nitrogen atom of the macrocyclic
subunit, thus inducing the hypsochromic shift of the
charge-transfer band.[6] UV/Vis titration experiments for
the system Pb2+-L4 showed clear isosbestic points indicative
of the formation of 1:1 ligand-to-metal species. The log K
for the formation of the [Pb(L4)]2+ complex, obtained by
nonlinear least-squares treatment of the titration profile, is
6.42 0.03 (see Figure 5).[21] The presence of Fe3+ results in
L1
L2
L3
L4
L5
L6
λmax
ε
517
32500
517
523
47300
523
518
29900
518
518
518
520
33500
520
520
520
520
35200
520
520
520
518
37500
518
518
518
518
504
518
518
Ag+
Cd2+
Cu2+
Fe3+
517
523
ȇ490[a] 523
ȇ490[a] ȇ519[a] ȇ518[a] ȇ513[a] 520
Hg2+ 517
523
523
523
518
518
518
520
475
520
394
520
520
Pb2+
Zn2+
517
517
[a] The downward pointing arrows indicate a significant hypoch-
romic change in the visible band with respect to that of the free
ligand.
On changing from the receptor L1 to those containing
macrocycles, important changes in the selectivity trends
were found. Thus, addition of equimolar quantities of Cd2+
,
Cu2+, Hg2+, Ni2+, Pb2+, Zn2+ or Ag+ to acetonitrile solu-
Table 2. Logarithm of the stability constant for the formation of [M(Ln)]m+ complexes.
L1
L2
L3
L4
L5
L6
Cu2+
Fe3+
Hg2+
Pb2+
4.53 0.03[a]
–
–
–
–
–
–
–
–
–
–
4.69 0.09
4.63 0.15
4.97 0.10
–
6.42 0.03
–
–
–
–
7.57 0.02
–
5.60 0.05
–
[a] 2:1 (receptor:cation) stoichiometry for the complex formed between L1 and Cu2+
.
2396 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2393–2403

Molecular Logic Gates
FULL PAPER
Figure 5. Variation of the intensity at 520 nm for receptor L4 upon
addition of increasing amounts of Pb2+ cation in acetonitrile
(5.0×10–5 m).
Figure 3. Variation of the intensity at 518 nm for receptor L3 upon
addition of increasing amounts of Fe3+ cation in acetonitrile
(5.0×10–5 m).
a hypochromic effect and an unremarkable hypsochromic
shift of less than 10 nm. Monitoring the intensity changes
at 520 nm upon addition of Fe3+ gave moderate log K val-
ues (4.97 0.10). Addition of other metals such as Ag+,
Cu2+, Cd2+, Hg2+, Ni2+ and Zn2+ to acetonitrile solutions
of L4 gave no change in the colour of the solutions.
duced a significant hypsochromic shift of the band centred
at 518 nm to 504 nm associated with a change in colour
from pink to orange. This lesser hypsochromic shift shown
by L6 when compared to L5 can be ascribed to the position
of the sulfur atoms in the macrocyclic subunit. Hypsoch-
romic shifts of a charge-transfer band are observed upon a
suitable interaction (for instance coordination) with the do-
nor group. In receptor L5, the sulfur atoms are placed in
the vicinity of the anilinium nitrogen that is part of the
chromogenic unit. This spatial proximity might favour the
interaction (orbital overlap) of the nitrogen with the Hg2+
cation. In receptor L6, however, the sulfur atoms are sepa-
rated from the anilinium nitrogen by oxygen atoms and the
corresponding methylene subunits. In this case, a preferen-
tial coordination of the highly thiophilic Hg2+ cation with
these sulfur atoms would result in a weaker interaction with
the anilinium nitrogen, with concomitant smaller changes
in the UV/Vis spectra. As in the above cases, the hypsoch-
Figure 4. Changes in the UV/Vis spectra of receptor L4 upon ad-
dition of equimolar amounts of metal cations in acetonitrile
(5.0×10–5 m).
The receptors L5 and L6, which bear oxathiaaza crowns,
were synthesised in an attempt to colourimetrically recog-
nise additional thiophilic cations such as Hg2+ [23]
Thus,
.
red-pink acetonitrile solutions of L5 changed to yellow
upon addition of Hg2+ due to a hypsochromic shift of the
visible band upon cation binding (see Figure 6). Other me-
tal cations (Li+, Na+, K+, Ca2+, Ba2+, Mg2+,Cd2+, Pb2+
,
Ni2+, Cu2+, Zn2+, Ag+ and Fe3+) induced no significant
changes.[24] The behaviour of acetonitrile solutions of recep-
tor L6 in the presence of equimolar quantities of metal cat-
Figure 6. Changes in the UV/Vis spectra of receptor L5 upon ad-
dition of equimolar amounts of metal cations in acetonitrile
ions was very similar to that found for L5: only Hg2+ in- (5.0×10–5 m).
Eur. J. Inorg. Chem. 2005, 2393–2403
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2397

R. Martínez-Máñez, F. Sancenón et al.
FULL PAPER
romic shift of the visible band upon Hg2+ coordination is tors. The emission behaviour of acetonitrile solutions of L2
consistent with a decrease in the donor strength of the do- and L3 (excitation at 518 and 515 nm for L2 and L3, respec-
nor group.[6] UV/Vis titrations showed clear isosbestic tively) upon addition of metal cations was unexciting, with
points, indicating the formation of 1:1 L5-to-Hg2+ com- only minor changes in the emission intensity (centred at
plexes. A log K of 7.57 0.02 was calculated for the forma- 610 nm) upon addition of the Fe3+ cation (see Table 3).
tion of the [Hg(L5)]2+ complex (see Figure 7); 1:1 complexes
were also formed between L6 and Hg2+. In this case, log K
Table 3. Fluorescence emission intensity variation (as % of that of
for the formation of the [Hg(L6)]2+ complex, calculated by
the receptor) obtained for L1–L6 upon addition of metal cations in
acetonitrile solutions.
nonlinear least-squares treatment of the titration profiles,
was 5.60 0.05.
L1[a]
L2[a]
L3[a]
L4[a]
L5[a]
L6[a]
Ag+
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Cd2+
Cu2+
Fe3+
Hg2+
Pb2+
Zn2+
ȇ90[b] Ͻ5
ȇ16[b] Ͻ5
ȇ90[b] ȇ11[b] ȇ18[b] ȇ22[b] Ͻ5
ȇ90[b] Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ȇ90[b] Ȇ20[b]
Ͻ5
Ͻ5
Ͻ5
Ͻ5
Ȇ45[b] Ͻ5
Ȇ10[b] Ͻ5
Ͻ5
Ͻ5
[a] Excitation wavelengths of 517, 518, 515, 467, 450 and 470 nm
for L1, L2, L3, L4, L5 and L6, respectively. [b] The upward and
downward pointing arrows indicate increase and quenching,
respectively, of the emission intensity (690 nm for L1 and 610 nm
for L2–L6).
A more significant and selective behaviour was observed
with receptors L4 and L5. The isosbestic points obtained in
the UV/Vis titrations of L4 with Pb2+ (467 nm) and L5 with
Hg2+ (450 nm) were chosen as excitation wavelengths. Upon
excitation unstructured emission bands centred at 610 and
605 nm were observed for L4 and L5, respectively. The re-
sults obtained upon addition of one equivalent of the corre-
sponding metal cations are shown in Table 3. The most re-
markable effect was the selective enhancement of the emis-
sion intensity (90%), coupled with a moderate 10-nm hyp-
sochromic shift of the emission band (from 605 to 595 nm)
Figure 7. Variation of the intensity at 518 nm for receptor L5 upon
addition of increasing amounts of Hg2+ cation in acetonitrile
(5.0×10–5 m).
Fluorogenic Signalling
The 1-aminophenyl-1,2,2-tricyanoethylene chromophore observed upon addition of Hg2+ to solutions of L5 (Fig-
also shows fluorescence emission upon excitation at the vis- ure 8). Other metal cations tested (Ag+, Cd2+, Cu2+, Fe3+
,
ible absorption band. Fluorescence studies were carried out Pb2+ and Zn2+) induced negligible variations (less than 5%)
with acetonitrile solutions (ca. 3.0×10–5m) of the receptors in the fluorescence emission of this receptor. The excitation
by addition of equimolar quantities of the corresponding spectra (λexc = 610 nm) measured upon addition of one
metal cation. L1 shows dual emission features in acetonitrile equivalent of Hg2+ cation to an acetonitrile solution of re-
upon excitation at 517 nm, with a broad, unstructured emis- ceptor L5 show the apparition of a band centred at 380 nm,
sion band centred at 610 nm and another more-intense, red- indicating that the [Hg(L5)]2+ complex is the emissive spe-
shifted band centred at 690 nm. This red-shifted emission cies that induces the apparition of the emission band
can tentatively be ascribed to formation of an excimer by centred at 605 nm. With L4, the addition of equimolar
interaction of an excited state fluorophore with a fluoro- quantities of Pb2+ or Zn2+ induced enhancement in the
phore in the ground state.[25] Addition of Ag+, Pb2+, Zn2+
,
emission intensity (45% with Pb2+ and 10% with Zn2+
)
Ni2+ or Cd2+ resulted in no significant variation in the with a very low hypsochromic shifts in the emission band
emission intensity profiles, whereas the presence of Fe3+
,
(2 nm for Pb2+ and negligible with Zn2+), whereas the pres-
Hg2+ or Cu2+ inhibited the formation of the excimer and ence of Cu2+ or Fe3+ induced moderate quenching and hyp-
caused an almost complete quenching of the red-shifted sochromic shifts (5 and 10 nm for Cu2+ and Fe3+ respec-
band centred at 690 nm.
tively). The fluorescent behaviour of receptor L6 in the pres-
The emission behaviour of receptors functionalised with ence of metal cations is very similar to that found for L5.
macrocyclic subunits (L2–L6) is somewhat different to that Upon excitation at the isosbestic point obtained from UV/
of L1 and, upon excitation, only an emission band centred Vis titrations of L6 with the mercuric cation (470 nm), a
at 600 nm was found; the red-shifted emission found in L1 broad emission band centred at 614 nm developed. Of all
was not observed. This could be related to steric factors the metal cations tested, only Hg2+ induces a 20% enhance-
due to the presence of the bulky macrocyclic moieties, ment of the emission intensity, with a hypsochromic shift
which might prevent excimer formation in the L2–L6 recep- of the emission band to 604 nm.
2398
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2393–2403

Molecular Logic Gates
FULL PAPER
odically out of the solvent redox window). As is well-
known, cation coordination with redox-active molecules re-
sults in significant electrochemical anodic shifts of either
oxidation or reduction processes.[28] A simple explanation
of this effect is related to the idea that it is easier to reduce
and more difficult to oxidize the positively charged [Hg-
(L5)]2+ complex than the corresponding neutral ligand.
Therefore, coordination of Hg2+ to the oxathiaaza ring
would give rise to both an anodic shift in the oxidation
wave of the aniline (the shift is so large that the new wave is
not observed) and an anodic shift of the reduction process
(340 mV). This strong Hg2+–N interaction in L5, suggested
by the electrochemical results, is in agreement with the se-
lective chromogenic results found for this cation (see above).
Table 4. Anodic shifts of the reduction wave (ΔE in mV) obtained
for L4, L5 and L6 in the presence of metal cations in acetonitrile
solutions.
Figure 8. Emission spectra of receptor L5 (λex = 450 nm) upon ad-
dition of equimolar amounts of metal cations in acetonitrile
(3.0×10–5 m).
ΔE(L4)[a]
ΔE(L5)[a]
ΔE(L6)[a]
Ag+
10
170
40
340
370
360
160
17
120
25
240
340
330
140
Ͻ10
80
20
Ͻ10
200
160
20
Cd2+
Cu2+
Fe3+
Hg2+
Pb2+
Zn2+
Table 3 shows that only Hg2+, Pb2+ and Zn2+ display
fluorescence enhancement effects. This is in agreement with
their d10 electronic configuration, for which electron-trans-
fer or energy-transfer processes usually do not occur.[26] For
Hg2+ with L5 and L6, and Pb2+ with L4, the emission fluo-
rescence enhancement is remarkable and is most likely asso-
ciated with a strong metal coordination to the anilinium
nitrogen (this is also supported by the UV/Vis studies, see
above). On the other hand, quenching was observed with
the redox-active metal cations Fe3+ and Cu2+, for which
electron-transfer processes involving the d-orbitals of the
metals and the excited state of the fluorophore can occur.[26]
[a] ΔE(Ln) = E(Ln + Mn+) – E(Ln).
A second sort of electrochemical behaviour was observed
for L5 upon addition of cations such as Pb2+, Zn2+, Fe3+
and Cd2+. In this case, there is also a significant anodic
shift of the reduction wave, but there is no significant shift
of the oxidation peak of L5. A drop of the peak intensity
was found for both the oxidation and reduction waves. This
intensity drop (attributed to the formation of species with
a lower diffusion coefficient), along with the anodic shift of
the reduction wave suggests that there must be some kind
Electrochemical Signalling
The electrochemical behaviour of the tricyanovinyl recep- of interaction between these metal cations and L5. Ad-
tors was studied in acetonitrile with platinum as working ditionally, the absence of changes in the oxidation wave sug-
electrode and [Bu4N][BF4] as supporting electrolyte. This gests that this interaction is not with the anilinium nitrogen.
family of receptors shows a one-electron reversible re- Tentatively, this interaction can be assigned to a weak coor-
duction process at about –0.70 V vs. SCE attributed to the dination of the metal cations with either remote donor
reduction of the tricyanovinyl group.[15b] They also show a atoms from the ring, such as S or O, or due to some interac-
reversible oxidation process at 1.2–1.4 V vs. SCE due to the tion with the electron-rich cyano groups. The absence of
oxidation of the anilinium moiety.[27] This electrochemical significant shifts observed in the oxidation wave is often
interpretation is in agreement with molecular modelling indicative of CE (chemical electrochemical) processes (de-
and orbital calculations performed on L1 at the PM3 level. coordination and oxidation of the free ligand) favoured by
A detailed electrochemical study in the presence of the a weak metal–ligand interaction in these cases. Finally, for
metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Pb2+ and Zn2+ cations such as Ag+, Al3+ and Cu2+ no remarkable changes
was carried out with ligands L4, L5 and L6, which are those were observed in either the oxidation or reduction peaks of
that show a more remarkable optical behaviour (see above). L5.
A summary of the electrochemical responses is shown in
Ligand L6 shows a somehow similar behaviour to L5,
Table 4. For ligand L5, three different cation-induced elec- although in this case, in general, smaller anodic shifts of
trochemical behaviours were observed. The first type of be- the reduction wave are observed. The most remarkable are
haviour was found in the presence of Hg2+, with a remark- the anodic shifts of 200 and 160 mV of the reduction wave
able anodic shift (340 mV) of the reduction wave of L5 observed for L5 in the presence of Hg2+ and Pb2+ cations,
along with a significant drop in the reduction wave inten- respectively.
sity. Additionally, in the presence of this metal cation the
L4 shows a notably large anodic shift of the reduction
oxidation peak of L5 “disappears” (the wave is shifted an- wave of 370 mV with the metal cations Hg2+, Pb2+ and
Eur. J. Inorg. Chem. 2005, 2393–2403
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2399

R. Martínez-Máñez, F. Sancenón et al.
FULL PAPER
Fe3+. Addition of Cd2+ and Zn2+ cations induced a less- upon addition, as inputs, of the metal cations Pb2+ and
important redox shift (170 and 160 mV for Cd2+ and Zn2+ Hg2+. A two-input OR logic gate is observed when the out-
,
respectively). Of all these metal cations, Pb2+ is the only one put is electrochemical, whereas a TRANSFER gate is found
capable of inducing a significant anodic shift of the oxi- for colour variation outputs. Table 5 also shows changes in
dation peak (140 mV), strongly suggesting coordination of L4 upon addition of Pb2+ and Fe3+ input cations. An OR,
the Pb2+ cation with the anilinium nitrogen, in agreement TRANSFER and INHIBIT logic gate is obtained when the
with the chromogenic results. Ag+ and Cu2+ cations gave electrochemical, colour and emission quenching outputs are
unremarkable variations of the electrochemical behaviour selected, respectively. These multi-channel systems can be
of L4.
seen as reconfigurable versatile logic systems. More-com-
plex, three-input reconfigurable molecular logic systems can
also be obtained, as shown in Table 6, where the logic gates
OR, TRANSFER and INHIBIT are found for just one
molecular entity (receptor L4) by selecting the output chan-
Triple Signalling
A very remarkable aspect is that, in their molecular inter- nel.
action with metal cations, the receptors gave a somewhat
Table 5. Two-input logical truth tables associated with electrochem-
different response depending on the transduction channel
studied (electrochemical, chromogenic or fluorogenic). In
order to explain this effect, it has to be taken into account
that the specific response observed in each case strongly
depends on the particularities of each coordination-trans-
duction process. Thus, for instance, chromogenic transduc-
tion (hypsochromic shift) would be expected when there is
a strong enough interaction of a certain metal cation with
the anilinium nitrogen (the donor group involved in the ani-
linotricyanoethylene chromophore). On the other hand, the
electrochemical transduction is related to a coulombic-type
interaction between the reduced form of the redox-active
group (the tricyanovinyl moiety in this case) and the metal
cation. This means that the interaction of a certain metal
cation with “remote” binding sites, such as the oxygen and
sulfur atoms or the cyano groups, might result in an electro-
chemical response, but in a poor optical variation. Also re-
markable is that, in certain cases, the response obtained by
fluorescence is also somehow different to that found chro-
mogenically. Thus, for L4 the coordination of d10 cations
such as Pb2+ induces emission enhancement, whereas re-
dox-active cations such as Fe3+ induce significant quench-
ing, probably by interaction with the photo-excited L4 re-
ceptor through energy or photoelectron transfer processes.
As we have commented above, there is a recent interest
in the development of molecules with intrinsic logic capa-
bilities. This concept has become widespread since it was
realized that the interaction of a receptor molecule with cer-
tain species (input) and the observed response (output) can
follow Boolean logic rules.[29] Since then a number of exam-
ples have been described, most of them using two inputs
(usually the presence of protons and a certain metal cation)
ical, colour and emission quenching measurements using receptor
L4 and different metal cations as input signals.
Input 1 Input 2 ΔE Ͼ 300 mV
Colour
variation
O2
Pb2+
Hg2+
O1
0
1
0
1
0
0
1
1
0
1
1
1
0
1
0
1
Input 1 Input 2 ΔE Ͼ 300 mV
Colour
variation
O2
Emission
quenching
O3
Pb2+
Fe2+
O1
0
1
0
1
0
0
1
1
0
1
1
1
0
1
0
1
0
0
1
0
A related aspect is that multi-channel signalling receptors
that cooperatively control the output observed (usually an such as L4 and L5 can give multiple signalling expressions
optical signal). It is also common to many described mol- (combination of different signals) that can be used for sens-
ecular logic systems to be related to just one Boolean func- ing purposes. This is also depicted in Table 6, where the
tion, whereas it is less common to observe different logical equivalence between the output observed and the sensing
expressions from one unique molecular entity. However the information one can obtain can be seen. Thus a 1/1/0 out-
development of “reconfigurable” molecular logic gates put pattern (ΔE larger than 300 mV/colour variation/emis-
could be of interest.[30] In this context, some of the multi- sion quenching) would only be observed in the presence of
channel signalling chemosensors described above might Pb2+. In the absence of lead (no colour variation), 1/0/0 and
lead to the expression of different logical truth tables by 1/0/1 patterns would be indicative of the presence of Hg2+
selecting different types of output. This is, for instance, ob- and Fe3+, respectively. Some other combinations (not
served in Table 5, which shows the changes in receptor L4 shown in Table 6) are possible; for instance, and despite the
2400
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2393–2403

Molecular Logic Gates
FULL PAPER
Table 6. Three-input logical truth tables associated with electro- cepts of multi-channel signalling and reconfigurable logic
chemical, colour and emission measurements using receptor L4.
gates.
Input 1 Input 2 Input 3 ΔE Ͼ 300 mV
Colour
variation
O2
Emmission
quenching
O3
Pb2+
Hg2+
Fe3+
O1
Experimental Section
0
1
0
1
0
1
0
1
0
0
1
1
0
0
1
1
0
0
0
0
1
1
1
1
0
1
1
1
1
1
1
1
0
1
0
1
0
1
0
1
0
0
0
0
1
0
0
0
General Remarks: All commercially available reagents were used
without further purification. Air/water-sensitive reactions were per-
formed in flame-dried glassware under argon. Acetonitrile was
dried with CaH2 and distilled prior to use.
Physical Measurements: Metal cations (Ag+, Cd2+, Fe3+, Ni2+, Pb2+
as perchlorate salts and Cu2+, Hg2+, Zn2+ as triflate salts) were
used to obtain approximately 1.0×10–3 m acetonitrile solutions.
UV/Vis studies were carried out with a Perkin–Elmer Lambda 35
spectrometer. The concentration of ligands used in the measure-
ments was about 5.0×10–5 m in acetonitrile. UV/Vis spectra were
recorded in the presence of equimolar quantities of the correspond-
ing ligand and metal cation or anion. The fluorescence behaviour
was studied with an FS900CDT Steady State T-Geometry Fluo-
rimeter from Edinburgh Analytical Instruments. All solutions for
photophysical studies were previously degassed. The concentration
of ligands was about 3.0×10–5 m in acetonitrile. Fluorescence emis-
sion spectra were recorded in the presence of equimolar quantities
of ligand and the corresponding metal cation. Electrochemical data
were recorded fors previously degassed dry acetonitrile solution,
with a programmable function generator Tacussel IMT-1, con-
nected to a Tacussel PJT 120–1 potentiostat. The concentration of
ligands and metal ions was about 1.0×10–3 m in acetonitrile (the
low quenching found for copper, a 0/0/1 combination would
be observed with Cu2+; a 0/0/0 pattern, but with variations
of ΔE of about 100 mV. can indicate the presence of Cd2+
or Zn2+ cations. L4 therefore acts as a prototype of molecu-
lar chemosensors capable of sensing several single guests by
multiple signalling combinations. Similar observations can
be made with other receptors and a suitable combination
of input signals.
Table 6 shows how reconfigurable logic gates or multi-
channel signalling receptors are both intimately related con-
cepts. This is indicated by using tricyanoethylene receptors,
which are rare electro-optical signalling systems capable of
reporting molecular interaction by a triple-channel trans-
duction. These studies suggest that the development of re-
ceptors containing a number of reporter groups might open
metal ions were perchlorate or triflate salts of Ag+, Cd2+, Cu2+
,
Fe3+, Hg2+, Pb2+ and Zn2+). Electrochemical studies were carried
out in the presence of equimolar quantities of ligand and the corre-
sponding metal cation. The working electrode was platinum con-
nected to a saturated calomel reference electrode separated from
the test solution by a salt bridge containing the solvent and the
supporting electrolyte (0.25 m [Bu4N][BF4]). The auxiliary electrode
was a platinum wire.
The 1H and 13C NMR spectra were recorded with a Varian Gemini
spectrometer. Chemical shifts are reported in ppm downfield from
TMS signal. Spectra recorded in CDCl3 were referenced to residual
CHCl3.
Synthetic Procedures: The syntheses of 2-(2-methylsulfonyloxy-
ethoxy)ethyl methanesulfonate (2a),[31] 2-[(2-methylsulfonyloxy-
new perspectives in the design of a new generation of multi- ethyl)phenylamino]ethyl methanesulfonate (5),[31] 13-phenyl-
1,4,7,10-tetraoxa-13-azacyclopentadecane (4b)[17] and 16-phenyl-
channel signalling molecules capable of being used as either
prototypes of “reconfigurable” molecular logic gates or as
multi-channel guest reporting systems by the use of dif-
1,4,7,10,13-pentaoxa-16-azacycloheptadecane (4c)[17] have been
previously published. Compound 3 is commercially available.
ferent output signals from just one molecular entity.
Synthesis of 10-Phenyl-1,4,7-trioxa-10-azacyclododecane (4a): N,N-
phenyldiethanolamine (3; 10 g, 0.05 mol) was dissolved in dry ace-
tonitrile (400 mL) and then sodium hydride (3.3 g, 0.137 mol) was
slowly added over 60 min with vigorous stirring at room tempera-
ture. The mixture formed was heated to reflux and then, over 4 h,
2-(2-methylsulfonyloxyethoxy)ethyl methanesulfonate (2a; 14.4 g,
0.055 mol) dissolved in dry acetonitrile was added. The crude reac-
tion mixture was refluxed overnight. The mixture was then filtered
and the filtrate concentrated in vacuo to dryness to give an orange
sticky oil that was purified by column chromatography on alumin-
ium oxide with dichloromethane and dichloromethane/ethanol
(50:1 v/v) as eluents to give 10-phenyl-1,4,7-trioxa-10-azacyclodo-
Conclusions
A family of receptors based on functionalised tricyanoe-
thylene moieties has been synthesised and characterised and
their interaction with metal cations monitored by optical
(colour and fluorescence) and electrochemical changes. A
selective chromogenic response was found for the L4-Pb2+
,
L5-Hg2+ and L6-Hg2+ systems in acetonitrile, whereas fluo-
rescence and electrochemical responses were usually less se-
lective. A final discussion suggests that receptors containing
several reporter channels (multi-channel signalling mole-
1
decane (3.8 g, 0.015 mol) as a yellowish oil. Yield: 30%. H NMR
(300 MHz, CDCl3): δ = 3.55 (t, J = 7.5 Hz, 4 H, O-CH2-CH2-N),
3.64 (m, J = 7.5 Hz, 8 H, O-CH2-CH2-O-CH2-CH2-O), 3.83 (t, J
cules) can be used for studying the intimately related con- = 7.5 Hz, 4 H, O-CH2-CH2-N), 6.68 (t, J = 6 Hz, 2 H, C6H5), 6.70
Eur. J. Inorg. Chem. 2005, 2393–2403
www.eurjic.org © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2401

R. Martínez-Máñez, F. Sancenón et al.
FULL PAPER
(d, J = 6 Hz, 1 H, C6H5), 7.18 (t, J = 6 Hz, 2 H, C6H5) ppm. 2 H, C6H4) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ = 53.19
13C{1H} NMR (75 MHz, CDCl3): δ = 52.35 (CH2-N), 69.55 (CH2- (CH2-N), 69.08 (CH2-O), 69.81 (CH2-O), 71.24 (CH2-O), 113.41
O), 69.77 (CH2-O), 71.46 (CH2-O), 112.24 (C6H5), 116.03 (C6H5), (C6H4), 113.76 (CN), 114.03 (CN), 114.48 (CN), 117.79 (C=C),
128.98 (C6H5), 148.44 (C6H5) ppm. MS: m/z = 251 [M+], 220, 176,
132.70 (C6H4), 137.30 (C=C), 154.91 (C6H4) ppm. MS (FAB+):
162, 150, 132, 120, 105, 91 [C6H5N], 77 [C6H5]. C14H21NO3 (251): m/z (%) = 353 (100) [M+ + 1]. HRMS: calcd. for C19H20N4O3
calcd. C 66.91, H 8.42, N 5.57; found C 66.62, H 8.37, N 5.60.
353.1614; found 353.1608.
Synthesis of 10-Phenyl-1,4-dioxa-7,13-dithia-10-azacyclopentade-
cane (7a): 3,6-Dioxaoctane-1,8-dithiol (6a; 3.6 g, 0.022 mol) and
anhydrous potassium carbonate (12.2 g, 0.088 mol) were dissolved
in dry acetonitrile (400 mL) and heated to reflux. Then, 2-[(2-meth-
ylsulfonyloxyethyl)phenylamino]ethyl methanesulfonate (5; 7.4 g,
0.022 mol) was added over 4 h. The crude reaction mixture was
refluxed overnight. The resultant mixture was then filtered and the
filtrate concentrated in vacuo to dryness to give a yellow sticky oil
that was purified by column chromatography on silica with dichlo-
romethane as eluent to give 10-phenyl-1,4-dioxa-7,13-dithia-10-az-
acyclopentadecane (2.9 g, 0.009 mol) as a white solid. Yield: 40%.
1H NMR (300 MHz, CDCl3): δ = 2.73 (t, J = 7 Hz, 4 H, O-CH2-
CH2-S), 2.88 (t, J = 7 Hz, 4 H, N-CH2-CH2-S), 3.62 (s, 4 H, O-
CH2-CH2-O), 3.64 (t, J = 7 Hz, 4 H, O-CH2-CH2-S), 3.79 (t, J =
7 Hz, 4 H, N-CH2-CH2-S), 6.63 (m, 3 H, C6H5), 7.20 (d, J = 6 Hz,
2 H, C6H5) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ = 29.29
(CH2-S), 30.95 (CH2-S), 51.63 (CH2-N), 70.56 (CH2-O), 74.11
(CH2-O), 111.57 (C6H5), 115.98 (C6H5), 129.29 (C6H5), 146.46
(C6H5) ppm. MS: m/z = 327 [M+], 204, 192, 179, 164, 149, 132, 119,
105, 91 [C6H5N], 77 [C6H5]. C16H25NO2S2 (327): calcd. C 58.68, H
7.69, N 4.28; found C 58.60, H 7.61, N 4.23.
Receptor L4: Flash chromatography (dichloromethane/acetonitrile,
8:2 v/v) on silica gel gave a dark reddish oil. Yield: 68%. 1H NMR
(300 MHz, CDCl3): δ = 3.53–3.64 (m, 16 H, O-CH2-CH2-O), 3.73
(t, J = 4.7 Hz, 4 H, O-CH2-CH2-N), 3.80 (t, J = 4.7 Hz, 4 H, O-
CH2-CH2-N), 6.80 (d, J = 9.4 Hz, 2 H, C6H4), 8.00 (d, J = 9.4 Hz,
2 H, C6H4) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ = 51.80
(CH2-N), 68.40 (CH2-O), 70.61 (CH2-O), 70.72 (CH2-O), 70.76
(CH2-O), 70.92 (CH2-O), 112.74 (C6H4), 113.84 (CN), 114.08
(CN), 114.47 (CN), 117.54 (C=C), 132.92 (C6H4), 137.10 (C=C),
154.31 (C6H4) ppm. MS (FAB+): m/z (%) = 440 (100) [M+ + 1].
HRMS: calcd. for C23H28N4O5 440.2060; found 440.2057.
Receptor L5: Flash chromatography (dichloromethane) on silica gel
gave a dark reddish solid. Yield: 58%. 1H NMR (300 MHz,
CDCl3): δ = 2.75 (t, J = 4.8 Hz, 4 H, O-CH2-CH2-S), 2.89 (t, J =
7.9 Hz, 4 H, N-CH2-CH2-S), 3.62 (s, 4 H, O-CH2-CH2-O), 3.76–
3.83 (m, 8 H, O-CH2-CH2-S and N-CH2-CH2-S), 6.70 (d, J =
9.4 Hz, 2 H, C6H4), 8.04 (d, J = 9.4 Hz, 2 H, C6H4) ppm. 13C{1H}
NMR (75 MHz, CDCl3): δ = 29.65 (CH2-S), 31.88 (CH2-S), 52.40
(CH2-N), 70.64 (CH2-O), 74.30 (CH2-O), 112.54 (C6H4), 113.58
(CN), 113.84 (CN), 114.36 (CN), 117.76 (C=C), 133.14 (C6H4),
Synthesis of 4-Phenyl-1,7-dioxa-10,13-dithia-4-azacyclopentadecane 137.51 (C=C), 153.03 (C6H4) ppm. MS (FAB+): m/z (%) = 429
(7b): 3,6-Dithiaoctane-1,8-diol (6b; 3.6 g, 0.022 mol) was dissolved
in dry acetonitrile (400 mL) and then sodium hydride (1.6 g, 0.066
mol) was slowly added over 1 h with vigorous stirring at room tem-
perature. The mixture formed was heated to reflux and then, over
4 h methanesulfonic acid 2-[(2-methylsulfonyloxy-ethyl)phen-
ylamino]ethyl methanesulfonate (5; 7.4 g, 0.022 mol) dissolved in
dry acetonitrile was added. The crude reaction mixture was re-
fluxed overnight, filtered, and the filtrate concentrated in vacuo to
dryness to give a yellow sticky oil that was purified by column
chromatography on silica with dichloromethane as eluent to give 4-
phenyl-1,7-dioxa-10,13-dithia-4-azacyclopentadecane (1.8 g, 0.0055
(100) [M+ + 1]. HRMS: calcd. for C21H24N4O2S2 429.1419; found
429.1426.
Receptor L6: Flash chromatography (dichloromethane) on silica gel
gave a dark reddish solid. Yield: 61%. 1H NMR (300 MHz,
CDCl3): δ = 2.72 (t, J = 5.7 Hz, 4 H, O-CH2-CH2-S), 2.81 (s, 4 H,
N-CH2-CH2-S), 3.70 (t, J = 5.7 Hz, 4 H, O-CH2-CH2-O), 3.77 (t,
J = 4.7 Hz, 4 H, O-CH2-CH2-S), 3.85 (t, J = 4.7 Hz, 4 H, N-CH2-
CH2-S), 6.78 (d, J = 9.4 Hz, 2 H, C6H4), 8.03 (d, J = 9.4 Hz, 2 H,
C6H4) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ = 31.93 (CH2-
S), 32.96 (CH2-S), 51.73 (CH2-N), 69.23 (CH2-O), 72.16 (CH2-O),
112.65 (C6H4), 113.50 (CN), 113.78 (CN), 114.35 (CN), 117.80
(C=C), 132.93 (C6H4), 137.52 (C=C), 154.26 (C6H4) ppm. MS
(FAB+): m/z (%) = 429 (100) [M+ + 1]. HRMS: calcd. for
C21H24N4O2S2 429.1419; found 429.1413.
1
mol) as a yellowish oil. Yield: 25%. H NMR (300 MHz, CDCl3):
δ = 2.72 (t, J = 7 Hz, 4 H, O-CH2-CH2-S), 2.88 (s, 4 H, S-CH2-
CH2-S), 3.60–3.82 (m, 12 H, N-CH2-CH2-O), 6.63 (m, 3 H, C6H5),
7.20 (d, J = 6 Hz, 2 H, C6H5) ppm. 13C{1H} NMR (75 MHz,
CDCl3): δ = 31.50 (CH2-S), 32.72 (CH2-S), 51.06 (CH2-N), 69.73
(CH2-O), 72.02 (CH2-O), 112.02 (C6H5), 116.33 (C6H5), 129.18
(C6H5), 148.02 (C6H5) ppm. MS: m/z = 327 [M+], 204, 192, 179,
164, 149, 132, 119, 105, 91 [C6H5N], 77 [C6H5]. C16H25NO2S2
(327): calcd. C 58.68, H 7.69, N 4.28; found C 58.55, H 7.73, N
4.31.
Structure Determination of L5: C21H24N4O2S2, M = 428.56, triclinic
¯
space group P1, a = 9.654(4), b = 13.643(6), c = 17.196(5) Å, α =
96.68(3)°, β = 102.98(3)°, γ = 97.72(3)°, Z = 4, V = 2161.7(14) Å3,
Dcalcd. = 1.317 gcm–3, λ(Mo-Kα) = 0.71073 Å, T = 293(2) K, μ(Mo-
Kα) = 0.271 mm–1. Measurements were carried out with a Siemens
P4 diffractometer with graphite-monochromated Mo-Kα radiation
on a crystal of dimensions 0.17×0.17×0.15 mm3. A total of 5963
General Procedure for the Synthesis of Tricyanovinyl Dyes: N,N-
Dimethylaniline or the corresponding phenyl macrocycle
(1.0 mmol) and tetracyanoethylene (192 mg, 1.5 mmol) were dis-
solved in dry DMF (12 mL) and heated at 60 °C for 90 min. The
crude reaction mixture was concentrated in vacuo to dryness and
purified by column chromatography as indicated below. Receptors
L1 and L3 were previously synthesised by Beer et al. in 1990. CAU-
TION: Synthesis of L2 to L6 occurs with elimination of HCN.
reflections was collected of which 5558 were independent (Rint
=
0.0468). Lorentz, polarisation and absorption (ψ-scan, max. and
min. transmission 0.295 and 0.210) corrections were applied. The
structure was solved by direct methods (SHELXTL) and refined
by full-matrix least-squares analysis on F2 (SHELXTL).[32] The re-
finement converged at R1 = 0.090 [F Ͼ 4σ(F)] and wR2 = 0.2494
(all data). Largest peak and hole in the final difference map +0.58
and –0.37 eÅ3.
Receptor L2: Flash chromatography (dichloromethane/acetonitrile,
9:1 v/v) on silica gel gave a dark reddish solid. Yield: 65%. 1H
CCDC-252155 contains the supplementary crystallographic data
NMR (300 MHz, CDCl3): δ = 3.58 (m, 8 H, O-CH2-CH2-O), 3.73 for this paper. These data can be obtained free of charge from The
(t, J = 4.9 Hz, 4 H, O-CH2-CH2-N), 3.92 (t, J = 4.9 Hz, 4 H, O- Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
CH2-CH2-N), 6.86 (d, J = 9.4 Hz, 2 H, C6H4), 8.01 (d, J = 9.4 Hz,
data_request/cif.
2402
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 2393–2403

Molecular Logic Gates
FULL PAPER
[16] K. E. Krakowiak, J. S. Bradshaw, D. J. Zamecka-Krakowiak,
Chem. Rev. 1989, 89, 929.
Acknowledgments
[17] J. P. Dix, F. Vögtle, Angew. Chem. Int. Ed. Engl. 1978, 17, 857.
[18] a) S. Maeda, Jpn. Kokai Tokkyo Koho, 1998, JP 10244752; b)
L. Vanmaele, W. Janssens, Eur. Pat. Appl., 1994, EP 594238.
[19] C. J. Wood, P. Patel, T. D. James, Org. Lett. 2002, 4, 477.
[20] J. Aihara, K. Araya, Y. Matsunaga, Bull. Chem. Soc. Jpn. 1981,
54, 615.
[21] J. Bourson, J. Pouget, B. Valeur, J. Phys. Chem. 1993, 97, 4552.
[22] a) A. Mason, A. Sheridan, J. O. Sutherland, A. Vincent, J.
Chem. Soc., Chem. Commun. 1994, 2627; b) N. J. van der Veen,
R. J. M. Egberink, J. F. J. Engbersen, F. J. C. M. Van Veggel,
D. N. Reinhoudt, Chem. Commun. 1999, 681.
[23] a) F. Sancenón, R. Martínez-Máñez, J. Soto, Angew. Chem. Int.
Ed. 2002, 41, 1416; b) A. B. Descalzo, R. Martínez-Máñez, R.
Radeglia, K. Rurack, J. Am. Chem. Soc. 2003, 125, 3418.
[24] a) M. J. Choi, M. Y. Kim, S. K. Chong, Chem. Commun. 2001,
1664; b) O. Brümmer, J. J. La Clair, K. D. Janda, Org. Lett.
1999, 1, 415; c) F. Sancenón, R. Martínez-Máñez, J. Soto,
Chem. Commun. 2001, 2262.
[25] a) Principles of Fluorescence Spectroscopy (Ed.: J. R. Lakow-
icz), Plenum Publishers Corporation, New York, 1999; b) B.
Valeur, Top. Fluoresc. Spectrosc. 1994, 4, 21.
We wish to thank the Ministerio de Ciencia
y Tecnología
(MAT2003-08568-C03 and REN2002-04237-C02-01) and the Ge-
neralitat Valenciana (GRUPOS03/035) for support. F.S. wishes to
thank the Ministerio de Ciencia y Tecnología for the award of a
Ramón y Cajal contract.
[1] a) F. M. Raymo, S. Giordani, Molecular Logic Gates, Encyclo-
pedia of Nanoscience and Nanotechnology 2004, vol. 5, p. 677;
b) A. P. de Silva, B. McCaughan, B. O. T. McKinney, M.
Querol, Dalton Trans. 2003, 1902.
[2] J. P. Desvergne, A. W. Czarnik Chemosensors for Ion and Mole-
cule Recognition, NATO Asi Series, Series C, Kluwer Academic
Publisher, London, 1997.
[3] a) L. Fabbrizzi, A. Poggi, Chem. Soc. Rev. 1995, 197; b) R. A.
Bissell, A. P. de Silva, H. Q. N. Gunaratne, P. L. M. Lynch,
G. E. M. Maguire, K. R. A. S. Sandanayake, Chem. Soc. Rev.
1992, 187.
[4] A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M.
Huxley, C. P. McCoy, J. T. Rademacher, T. E. Rice, Chem. Rev.
1997, 97, 1515.
[26] L. Fabbrizzi, M. Licchelli, P. Pallavicini, L. Parodi, A. Taglietti
Transition Metals in Supramolecular Chemistry, John Wiley &
Sons Ltd, New York, 1999, p. 93.
[5]
[6]
[7]
a) R. Martínez-Máñez, F. Sancenón, Chem. Rev. 2003, 103,
4419; b) P. D. Beer, P. A. Gale, Angew. Chem. Int. Ed. 2001, 40,
486.
a) B. Valeur, I. Leray, Coord. Chem. Rev. 2000, 205, 3; b) A. W.
Czarnik, Acc. Chem. Res. 1994, 27, 302; c) K. Rurack, U.
Resch-Genger, Chem. Soc. Rev. 2002, 31, 116.
a) P. D. Beer, Chem. Commun. 1996, 689; b) R. Martínez-
Máñez, J. Soto, J. M. Lloris, T. Pardo, Trends Inorg. Chem.
1998, 5, 183; c) P. D. Beer, Coord. Chem. Rev. 2000, 205, 131.
[27] We have found (unpublished results) oxidation values for prod-
ucts 4a, 4b, 4c, 7a and 7b of +0.8–0.9 V in acetonitrile. How-
ever, in the electrochemical studies carried out with L1–L6 there
was no oxidation peak in this anodic region − the first anodic
peak was found at +1.2–1.4 V and attributed to the oxidation
of the anilinium moiety. The different nature of the ligands and
the existence of CE (chemical electrochemical) mechanisms
(the anilinium oxidation peak is not reversible) might account
for this difference between the oxidation peaks of the anilinum
crowns 4a, 4b, 4c, 7a, 7b and those of L1–L6.
[8] F. Sancenón, A. Benito, F. J. Hernández, J. M. Lloris, R. Mart-
ínez-Máñez, T. Pardo, J. Soto, Eur. J. Inorg. Chem. 2002, 866.
[9] a) J. Maynadie, B. Delavaux-Nicot, S. Fery-Forgues, D. Lava-
bre, R. Mathieu, Inorg. Chem. 2002, 41, 5002; b) B. Delavaux-
Nicot, S. Fery-Forgues, Eur. J. Inorg. Chem. 1999, 1821.
[10] a) P. D. Beer, A. R. Graydon, L. R. Sutton, Polyhedron 1996,
15, 2457; b) P. D. Beer, F. J. Szemes, J. Chem. Soc., Chem. Com-
mun. 1995, 2245; c) P. D. Beer, A. R. G. Graydon, A. O. M.
Johnson, D. K. Smith, Inorg. Chem. 1997, 36, 2112.
[11] a) T. Saika, T. Iyoda, K. Honda, T. Shimidzu, J. Chem. Soc.,
Perkin Trans. 2 1993, 1181; b) T. Iyoda, T. Saika, K. Honda,
T. Shimidzu, Tetrahedron Lett. 1989, 30, 5429; c) T. Shimidzu,
T. Iyoda, K. Honda, Pure Appl. Chem. 1988, 60, 1025; d) F. P.
Funeriu, J. M. Lehn, K. M. Fromm, D. Fenske, Chem. Eur. J.
2000, 6, 2103; e) J. M. Lehn, Chem. Eur. J. 2000, 6, 2097.
[12] M. Boiocchi, L. Fabbrizzi, M. Licchelli, D. Sacchi, M.
Vázquez, C. Zampa, Chem. Commun. 2003, 1812.
[28] J. M. Lloris, R. Martínez-Máñez, M. E. Padilla-Tosta, T.
Pardo, J. Soto, P. D. Beer, J. Cadman, D. K. Smith, J. Chem.
Soc., Dalton Trans. 1999, 23, 2359.
[29] A. P. de Silva, N. D. McClenaghan, Chem. Eur. J. 2004, 10, 574.
[30] a) G. J. Brown, A. P. de Silva, S. Pagliari, Chem. Commun.
2002, 2461; b) F. Pina, M. J. Melo, M. Maestri, R. Ballardini,
V. Balzani, J. Am. Chem. Soc. 1997, 119, 5556; c) F. M. Raymo,
S. Giordani, A. J. P. White, D. J. Williams, J. Org. Chem. 2003,
68, 4158; d) A. Saghatelian, N. H. Voelcker, K. M. Guckian,
V. S.-Y. Lin, M. R. Ghadiri, J. Am. Chem. Soc. 2003, 125, 346;
e) S. Ami, M. Hliwa, C. Joachim, Chem. Phys. Lett. 2003, 367,
662; f) K. Rurack, A. Kovalchuck, J. L. Bricks, J. L. Slominskii,
J. Am. Chem. Soc. 2001, 123, 6205; g) S. Alves, F. Pina, M. T.
Albelda, E. García-España, C. Soriano, S. V. Luis, Eur. J. Inorg.
Chem. 2001, 405; h) A. P. de Silva, N. D. McClenaghan, Chem.
Eur. J. 2002, 8, 4935.
[13] A. P. de Silva, H. Q. N. Gunaratne, M. Lynch, J. Chem. Soc.,
Perkin Trans. 2 1995, 685.
[14] D. Jiménez, R. Martínez-Máñez, F. Sancenón, J. Soto, Tetrahe-
dron Lett. 2004, 45, 1257.
[15] a) R. G. Charles, Org. Synth. 1959, 39, 61; b) P. D. Beer, H.
Sikanyika, Polyhedron 1990, 9, 1747.
[31] P. E. Stott, J. S. Bradshaw, W. W. Parish, Heterocycles 1981, 15,
179.
[32] SHELXTL, version 5.03, Siemens Analytical X-ray Instru-
ments, Madison, WI, 1994.
Received: October 07, 2004
Eur. J. Inorg. Chem. 2005, 2393–2403
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2403