Halide-modulated bistate and tristate fluorescence switching for Cu(i) and Ag(i) complexes

Article abstract of DOI:10.1039/c4nj01639d

The reaction of a fluorescent trans-chelating ligand L^Ph (where L^Ph = 1,3-bis-(3,5-dimethyl-pyrazol-1-ylmethyl)-2-phenyl-2,3-dihydro-1H-perimidine, QY = 9.7%) with MClO₄ (M = Cu, Ag) can lead to two-coordinate complexes [M(L^Ph)](ClO₄) (M = Cu (1·ClO₄) and Ag (5·ClO₄)). When L^Ph is treated with CuX (X = Cl, Br or I), however, this may lead either to a two-coordinate linear complex [Cu(L^Ph)](CuCl₂) (4·CuCl₂) or to three-coordinate T-shaped complexes [Cu(L^Ph)X] (X = Br (2), I (3)). Moreover, while complex 1·ClO₄ shows a ligand substitution for Cl^- to form 4·CuCl₂, it displays anion coordination for both Br^- and I^- to give 2 and 3, respectively. All of the copper(i) derivatives can readily liberate ligand L^Ph upon reacting with F^-. As such, a cyclic tristate molecular switching system L^Ph 1·ClO₄ 2 or 3 L^Ph can be accomplished. For complex 5·ClO₄, the addition of halides X^- (X = Cl, Br, I) results in the abstraction of the silver ions and release of the ligand L^Ph. A simple L^Ph 5·ClO₄ bistate molecular interconversion may also be constructed. Above all, the complexation of either MClO₄ or CuX with L^Ph can be signalled through different quenching effects, QY = 0.5% for 1·ClO₄, 3.1% for 2, 3.2% for 3, 0.8% for 4·CuCl₂, and 0.3% for 5·ClO₄, to realize facile bistate and tristate fluorescence switching operations.

Full text of DOI:10.1039/c4nj01639d

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ARTICLE TYPE
Halide-modulated bistate and tristate fluorescence switching for Cu(I)
and Ag(I) complexes
Chang-Chuan Chou,* Hsueh-Ju Liu, Lucas Hung-Chieh Chao and Chia-Chi Yang
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
The reaction of a fluorescent transꢀchelating ligand LPh (where LPh = 1,3ꢀbisꢀ(3,5ꢀdimethylꢀpyrazolꢀ1ꢀ
ylmethyl)ꢀ2ꢀphenylꢀ2,3ꢀdihydroꢀ1Hꢀperimidine, QY = 9.7 %) with MClO4 (M = Cu, Ag) can lead to twoꢀ
coordinate complexes [M(LPh)](ClO4) (M = Cu (1·ClO4) and Ag (5·ClO4)). When LPh is treated with CuX
(X = Cl, Br or I), however, this may lead either to twoꢀcoordinate linear complex [Cu(LPh)](CuCl2)
10 (4·CuCl2) or to threeꢀcoordinate Tꢀshaped complexes [Cu(LPh)X] (X = Br (2), I (3)). Moreover, while
complex 1·ClO4 shows a ligand substitution for Cl– to form 4·CuCl2, it displays anion coordination for
both Br– and I– to give 2 and 3, respectively. All of the copper(I) derivatives can readily liberate ligand
LPh upon reacting with F–. As such, a cyclic tristate molecular switching system “LPh ↔ 1·ClO4 ↔ 2 or 3
↔ LPh” can be accomplished. For complex 5·ClO4, the addition of halides X– (X = Cl, Br, I ) results in an
15 abstraction of the silver ions and a release of the ligand LPh. A simple “LPh ↔ 5·ClO4” bistate molecular
interconversion may also be constructed. Above all, the complexation of either MClO4 or CuX with LPh
can be signalled through different quenching effects: QY = 0.5% for 1·ClO4, 3.1% for 2, 3.2% for 3, 0.8%
for 4·CuCl2, and 0.3% for 5·ClO4, to realize facile bistate and tristate fluorescence switching operations.
numbers of copper ions: C. N. = 2, 3 or 4 for Cu(I); and, C. N.= 4,
Introduction
5 or 6 for Cu(II). Recently, an ionꢀtriggered multistate molecular
switching device based on regioselective coordinationꢀcontrolled
30 ion binding was reported in which a fourꢀstate molecular
20 The construction of a molecular or supramolecular system that
has two or more controllable optical states is of great interest for
its potential application in molecular devices such as sensors,
switches or logic gates.1,4 Accordingly, we have begun to develop
a protonꢀcontrolled fluorescent switch for copper(II) complexes2
25 and an Iodideꢀcontrolled fluorescent switch for copper(I)
complexes3 by taking advantage of the flexible coordination
switching
system
involving
copper(I)
and
znic(II)
binding/releasing process was set up.4 This inspired us to further
develop a simple twoꢀstate fluorescence switching system for
Ag(I) and a threeꢀstate fluorescence switching system for Cu(I)
35 based on a fluorescent ligand LPh, shown in Scheme 1. The design
concept of the reversible chemical process and fluorescence
switching are shown in Fig. 1, where the ligand LPh, complex
1ꢁClO4 and complex 2 are referred to as state 1, state 2, and state
3, respectively, and the Cu(I) ion, halide ions X (bromide or
40 iodide) and CuX are referred to as stimulus 1, 2 and 3,
respectively.
_
+
(ClO4)
AgClO4
N
5
N
N
N
_
N
N
N
N
Ph
N
N
N
N
Ph
X
Ag
( X = Cl, Br, I )
LPh
.
ClO4
The perimidineꢀbased bis(pyrazole) ligand LPh was a semiꢀ
flexible ligand featuring a transꢀchelating mode toward copper(I)
center. Moreover, upon interacting with either the Cu(I) ion or
high fluorescence
( QY = 9.7 % )
low fluorescence
CuX
( QY = 0.3 % )
_
( X = Br, I )
F
_
[Cu(MeCN)4]ClO4
_
2CuCl
F
F
_
_
+
+
(ClO4)
(CuCl2)
N
N
_
_
N
.
N
N
N
( X = Br, I )
AgClO4
X
Cl
N
N
N
Ph
N
N
N
Ph
Cu
N
N
N
Ph
N
Cu
N
Cu
N
X
CuCl2
.
ClO4
4
1
X = I (2), Br (3)
medium fluorescence
( QY = 3.2 %)
low fluorescence
( QY = 0.8 %)
low fluorescence
( QY = 0.5 %)
Fig. 1 Design concept of the molecular operations. State 1 (ligand), high
fluorescence intensity; State 2 (complex 1), low fluorescence intensity;
State 3 (complex 2), medium fluorescence intensity.
Scheme 1 Reversibility of ligand LPh and its copper(I) and silver(I)
derivatives.
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Fig. 2 Molecular structure of 3 with partial labelling showing 50%
probability ellipsoids. Selected bond lengths (Å) and angles (°): Cu1–N1
1.939 (4), Cu1–N6 1.944 (4), Cu1...N3 3.032 (5), Cu1...N4 2.922 (4),
Cu1–Br1 2.544 (1), N1–Cu1–N6 149.2 (2), N6–Cu1–Br1 102.7 (1), N1–
Cu1–Br1 107.8 (1), H17...Br1 .2.875 (1).
Fig. 3 Molecular structure of 4·CuCl2 with partial labelling showing 50%
probability ellipsoids. Selected bond lengths (Å) and angles (°): Cu1–N1
1.872(7), Cu1–N6 1.921 (6), Cu1...N3 2.970 (7), Cu1...N4 2.846 (7),
H17…Cl1 2.697 (3), Cu1…Cu3 3.630 (2), Cu1…Cl1 3.161 (3), Cu3–Cl1
2.110 (4), Cu3–Cl2 2.0770 (4); N1–Cu1–N6 164.3(3), Cl1–Cu3–Cl2
177.5 (2). Cu2–N7 1.878(7), Cu2–N12 1.873 (7), Cu2...N9 2.855 (7),
Cu2...N10 2.883 (8), H52...Cl3 2.500(3), Cu2…Cu4 3.137 (2), Cu2…Cl3
3.910 (3), Cu4–Cl3 2.082 (3), Cu4–Cl4 2.081 (4); N7–Cu2–N12 169.1 (3),
Cl3–Cu4–Cl4 175.7 (2).
CuI, different extents of fluorescence quenching were remarkable
due to the influence of a different degree of N(amine)…Cu(I)
interaction.5 Therefore, the discrimination between 1·ClO4 and 2
can be accomplished through fluorescence emissive spectra. By
iodide addition↔abstraction, a controllable reaction signalled a
structural transformation “1·ClO4 ↔2”.3 As far as we could
ascertain, a conversion of nonemissive twoꢀcoordinate copper(I)
complex to an emissive one by means of additional halide
binding has not been accomplished to date.6 Therefore, we further
10 surveyed other halides and completed simple threeꢀstate
fluorescence switching operations “LPh ↔ 1ꢁClO4 ↔ 2 or 3 ↔
LPh” for copper(I) complexes as well as an ON↔OFF twoꢀstate
fluorescence switching “LPh ↔ 5·ClO4” for a silver(I) complex,
as shown in Scheme 1. The structural characterizations, reactions,
15 and photophysical properties of the presented complexes are
described in the text.
5
structures of cations 1+, 4+ and 5+. The diastereotopic natures of
40 the methylene groups in 4ꢁCuCl2 and 5ꢁClO4 were indeed
exhibited as AB pattern resonances at δ 6.14, 5.94 ppm and 5.96,
5.85 ppm, respectively, which suggested decreased
conformational flexibility for the cation portions of 4ꢁCuCl2 and
5ꢁClO4. Although the fluxional process for 1·ClO4 remained
1
45 inexplicable, the significant difference in H NMR spectra was
very beneficial for differentiating the structural change between
1·ClO4 and either the other related complexes or a free ligand LPh.
As in the case of 2, complex 3 showed two sets of doublets (δ
6.13 and 5.92 ppm) for its methylene groups. Obviously, the
50 fluxionality of the complex cation [Cu(LPh)]+ was significantly
susceptible to the third coligand.
Results and Discussion
Synthesis and characterization of the complexes
Copper(I) complexes 3 and 4ꢁCuCl2 were synthesized from the
20 reaction of the LPh ligand with CuCl and CuBr, respectively, in
molar ratios of 1:2 and 1:1 in yields of 87 and 91%. A silver (I)
complex 5ꢁClO4 was prepared from the reaction of the ligand LPh
with AgClO4 in an 90 % yield. The elemental analyses and ESIꢀ
X-Ray crystallography
The crystals were grown from CH2Cl2/Et2O and their structures
were confirmed by Xꢀray diffraction analyses. The structures of
55 complexes 3, 4ꢁCuCl2 and complex cation 5 (5+) are shown in
Figures 1, 2 and 3, respectively. As expected, the coordinated LPh
in 3, 4+ and 5+ behaved as a transꢀchelating ligand with two
coordinated pyrazoles transꢀlocated. On the whole, these
complexes have approximately C2Vꢀsymmetric geometries,
60 analogous to complexes 1·ClO4 or 2.
For complex 3 (Fig. 2), the N(Pz')–Cu–N(Pz') bond angle of
149.2 (2)° severely deviated from linearity because of the
bromide binding, which gave rise to a 10.0 (1)° increment in the
dihedral angle of the coordinated pyrazole rings when compared
65 to 1·ClO4. The Cu(I)–N(heterocycle) threeꢀ and fourꢀcoordination
bond lengths were reported to be 1.89 ~ 1 .92 Å and 1.98 ~ 2.04
Å, respectively.7 The Cu(I)–N(Pz') bond distances of 1.939 (4)
and 1.944 (4) Å that were between the three and four coordinate
copper(I) complexes were comparable to those of the related
1
MS agreed with the proposed formulas. The H and 13C NMR
25 spectra in CD2Cl2 exhibited only one set of ligand resonance
under room temperature, indicating a symmetrical structure for 3
– 5·ClO4, which was in agreement with the solid state structures.
Previous studies showed that the resonances of the methylene
protons of the coordinated LPh ligand can determine the presence,
30 or lack, of a dynamic molecular nature.3 Complex 1·ClO4
displayed only singlet absorption at δ 5.96 ppm for the methylene
protons, and the variableꢀtemperature 1H NMR spectra
demonstrated that 1·ClO4 was indeed stereochemically nonrigid.
As for 2, the AB pattern resonance (δ 5.93, 5.78 ppm) for the two
35 diastereotopic methylene groups indicated that the structure of 2
was stereochemically rigid. It was surprising that both complexes
4ꢁCuCl2 and 5ꢁClO4 were rigid in a CH2Cl2 solution, as shown in
the 1H NMR spectra, despite a similar appearance for the
2
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_
_
F
LPh
+
unnkown yellowꢀoranage ppt
_
Cl
F
F
[Cu(LPh)]+
[Cu(LPh)](CuCl2)
[Cu(LPh)X]
unnkown yellowꢀoranage ppt
unnkown yellowꢀoranage ppt
LPh
LPh
+
+
_
_
X
( X = Br or I )
Ag+
_
( X = Cl, Br or I )
Ag+
X
[Ag(LPh)]+
LPh
Scheme 2 The reaction of Cu(I) and Ag(I) derivatives with halides.
Ag(I)–N(Pz') distances of 2.093 (4) and 2.097 (4) Å were similar
40 to the related twoꢀcoordinate silver(I)ꢀpyrazole complexes (~ 2.1
Å).12 The contacts of Ag(I)⋅⋅⋅N(amine) were 2.877 (4) and 2.965
(4) Å, indicating probable weak N(amine)…Ag(I) interactions. It
was interesting that, unlike 1+, complex cation 5+ was a rigid
molecular in CH2Cl2, suggesting a probable influence arising
Fig. 4 Molecular structure of cation 5+ with partial labelling showing 50%
probability ellipsoids. Selected bond lengths (Å) and angles (°): Ag1–N1
2.097 (4), Ag1–N6 2.093 (4), Ag1...N3 2.965 (4), Ag1...N4 2.877 (4),
Ag1...O4 2.971 (6), O1...H6B 2.453 (5), O4...H17 2.434 (7), O4...H18A
2.567 (7); N1–Ag1–N6 171.65 (13).
45 from counter anion like 4·CuCl2 and/or
a
stronger
complex 2 (1.942 (5) and 1.955 (5) Å), suggesting an electron
neutralization effect of the bromide anion on the copper(I) ion.
While the terminal Cu(I)–Br bond distance of 2.544 (1) Å in 3
Ag(I)⋅⋅⋅N(amine) interaction due to the size of Ag(I) (1.16 Å),
which was larger than that of Cu(I) (0.74 Å). Inspection of the
closest ClO4 anion contact to the H6B, H17, H18A and Ag1,
respectively, showed weak interactions indeed, which could lead
50 to a restraint of structural flexibility in solution.
was within the upper limits of the Cu(I)–Br(terminal) lengths of
3ꢀ 8
5
2.5152 (2) Å for tetrahedral anion CuBr4 , it was evidently
longer than that of the 2.365 (3) Å seen in trigonal planar anion
CuBr32ꢀ,9 which showed Tꢀshaped characteristics.10 The distance
of the bromo ligand Br1 to the benzylic hydrogen atom amounted
to 2.875 (1) Å, which was within the sum of the van der Waals
Reactions of 1·ClO4 with n-Bu4NX (X = F, Cl, Br)
We previously confirmed a “2+1” bonding mode for the
formation of Tꢀshaped complex 2.13 Herein, the other halides
binding to the copper(I) and silver(I) derivatives were examined
10 radii for hydrogen and bromine (3.05 Å), suggesting a weak
intramolecular C17–H...Br hydrogen bonding. To the best of our 55 using nꢀBu4NX (X = F, Cl, Br), as shown in scheme 2.
knowledge, complex 3 was the second example of a structurally
characterized, Tꢀshaped copper(I) halide complex with a Nꢀdonor
chelating ligand.
As in the case of 1+ and 2, the interconvertable reaction of 1+ and
3 can be performed and investigated via H NMR spectra. When
complex 1ꢁClO4 reacted stoichiometrically with nꢀBu4NBr,
neutral complex 3 was generated nearly quantitatively. On the
1
15 For complex 4·CuCl2 (Fig. 3), two slightly different
conformations were exhibited in the unit cell. Unfortunately, one 60 other hand, when complex 3 reacted stoichiometrically with
of the two copper centers in the complex cations was disordered
over two positions (93:7 ratio), and the asymmetry in the Cu–N
bonds in another molecule seemed to be due to a crystal packing
20 effect, although the structures unambiguously showed atomic
Ag(ClO4) to eliminate the coordinated bromide, complex 1ꢁClO4
was regenerated. If complex 1ꢁClO4 first reacted with
a
stoichiometric amount of nꢀBu4NBr and then a stoichiometric
amount of Ag(ClO4) was introduced, only the peaks of 1+ and the
1
connectivities within this molecule that were comparable to 65 nꢀbutyl group were observed in the H NMR solution spectrum
cation 1+. The formation of the CuCl2ꢀ counter anion was certain,
which seemed to suggest that the transient species [Cu(LPh)Cl]
was promptly transfomed into [Cu(LPh)]+(Clꢀ) followed by a
25 reaction with CuCl to form a CuCl2ꢀ anion. It was noteworthy that
(S7), which manifested the reversibility between 1+ and 3.
The reaction of 1+ and nꢀBu4NCl was carried out at a molar ratio
of 1:1 in CH2Cl2 solution. Crystal growth from the resultant
solution gave the 1:1 coꢀcrystals of {1ꢁClO4 + 4·CuCl2} (S8).
ꢀ
a
Cu1…Cu3 distance of 3.6300(19)
Å
precluded the 70 Despite the poor quality of the crystals, a CuCl2 anion was
Cu(I)…Cu(I) interaction. However, either a Cu2…Cu4 distance
of 3.1369 (17) Å or a Cu2’…Cu4 distance of 3.2222 (123) Å was
short enough to reveal a probable unsupported Cu(I)…Cu(I)
30 ligand interaction.11 Moreover, the existence of C17–H…Cl1 and
produced, which was indicative of a partial ligand substitution by
Clꢀ. The attempt to synthesize the [Cu(LPh)Cl] adduct by using
CuCl and LPh in a molar ratio of 1:1 proceeded. However, the
isolated product was solely 4·CuCl2, which indicated the
C52–H…Cl3 hydrogen bonds may help to promote cation and 75 instability of [Cu(LPh)Cl]. A strong complexation of Cu (I) by
anion attraction to one another and a restraint of structural
flexibility. Therefore, although the fluxional behavior of cation 1+
was expected for cation 4+, it did not happen.
chloride ions resulted in a favorable CuCl2ꢀ anion.
The reaction of 1ꢁClO4, 2, 3 or 4·CuCl2 with nꢀBu4NF quickly
yielded unknown yellowꢀorange precipitates. The precipitates
were insoluble in water and in most organic solvents such as
35 The structure of complex cation 5+ (Fig. 4) generally is similar to
that of 1+ with the exception of the metal center. The silver(I) ion 80 MeOH, CH3CN, DMSO, DMF, Et2O, EA, or hexane. Also, none
was coordinated by two pyrazole nitrogen atoms of the LPh with a
N(Pz')–Ag–N(Pz') bond angle of 171.65 (13)° toward C17. The
of the absorption peaks for LPh were observed in the IR spectrum.
Thus, the precipitates were tentatively assigned as copper(I)
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30000
25000
20000
15000
10000
5000
0
80
60
40
20
0
260
280
300
320
340
360
380
400
350
400
450
500
550
wavelength (nm)
wavelength (nm)
Fig. 6 UVꢀvis spectra of ligand LPh (solid line) and complexes 1·ClO4
(dotted line), 2 (dashꢀdotꢀdot line), 3 (long dash line) and 4·CuCl2
(medium dash line) in CH2Cl2.
Fig. 5 Fluorescence spectra of ligand LPh (solid line) and complexes
1·ClO4 (dotted line), 2 (dashꢀdotꢀdot line), 3 (long dash line), 4·CuCl2
(medium dash line) and 5·ClO4 (dashꢀdot line) in CH2Cl2 excited at 340nm
at room temperature.
25 took place when Br− was introduced to 1+ (S9), indicating that 1+
changed from a bromideꢀunbound twoꢀcoordinated species to a
bromideꢀbound threeꢀcoordinated species 3, as in the case of 2.
By monitoring the change in fluorescent spectra, the
interconversion of 1+ and 3 was reversible in the presence (ON)
30 and absence (OFF) of Br−, giving an ON↔OFF emission switch.
The fluorescence quenching was considered to be a result of both
the fluxional behavior15 and the electronic factor from 1·ClO4,
whereas the electronic factor was predominately taken into
account for the rigid complexes. The rigidity and quantum yield
35 are compared in Table 1. It was evident that the influence of
fluxionality on the quenching effect for 1·ClO4 was small when
1·ClO4 was compared with 4·CuCl2 for their high similarity in a
cationic structure. A similar situation was found for complex 2
when it was compared with a related Tꢀshaped nonrigid complex
40 [Cu(LH)I] (QY = 0.034).16 Thus, the major reason for quenching
was ascribed mostly to the extent of the electronic perturbation of
the perimidine fluorophore upon complexation of Cu(I), Ag(I) or
CuX by LPh, as observed by the UVꢀvis spectra.
halocuprates. These species are known to have various molecular
assemblies and diverse polymeric extended systems.14 This made
the analysis of these species very difficult. Nonetheless,
inspection of the colorless filtrate from the reactions for 1ꢁClO4, 2
and 3 by NMR showed only a free ligand LPh and (nꢀBu4N)(ClO4)
salt. For the reaction of 4·CuCl2, the filtrate color turned green.
However, it continued to display a strong emission comparable to
that of LPh. Evidently, LPh were released. Upon further removal of
the green species via the addition of hexane, most of the LPh was
10 recovered. Therefore, by using only the halides, an
interconvertable tristate switching system “LPh ↔ 1·ClO4 ↔ 2 or
3 ↔ LPh” was constructed, as shown in scheme 1.
On the other hand, treatment of 5ꢁClO4 with nꢀBu4NX (X= Cl, Br,
I) gave readily the AgX precipitates and the released ligand LPh.
15 Then, the LPh can react with the additional Ag(I) again to reform
5ꢁClO4, showing a simple “LPh ↔ 5·ClO4” bistate switching
system.
5
Photophysical properties
The absorption spectra of the ligand LPh and its copper(I) and
45 silver(I) derivatives are shown in Figures 6 and S10. The
prominent absorption peaks for the ligand and its copper(I)
derivatives were indeed different and were characterized by a
blueꢀshift spectra that is known to be relative to the presence of a
free ligand,3 indicating that the vibronic π–π* transtions of the
50 perimidine nucleus in these complexes were really affected. The
absorption envelope in the range of π–π* transition of the
perimidine nucleus between 1·ClO4 and 4·CuCl2 was similar due
to the structural similarity in the cationic portion whereas the
difference in the range of 260ꢀ300 nm appeared to suggest the
The fluorescent emission profiles originating from the ligandꢀ
20 centered π–π* transitions of the perimidine moiety are compared
in Figure 5. The fluorescent properties of complexes 3 (λmax
=
394 nm, Φf = 0.032), 4·CuCl2 (λmax = 388 nm, Φf = 0.008), and
5·ClO4 (λmax = 385 nm, Φf = 0.003) in CH2Cl2 were examined
when excited at λ = 340 nm. Besides, fluorescence enhancement
Table 1 Comparison of rigidity and quantum yield.
Compound
Quantum Yield
Rigidity
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
ꢀ
Free ligand LPh
Complex 1·ClO4
Complex 2
Complex 3
Complex 4·CuCl2
Complex 5·ClO4
0.097
0.005
0.031
0.032
0.008
0.003
Rigid
Nonrigid
Rigid
Rigid
Rigid
55 influence of the attraction of the CuCl2 anion. As in the case of
complex 2, complex 3 had a broad shoulder at ~ 273 nm, which
can be assigned to the Cu(I) to pyrazole MLCT transition
(dσ*→π*).17 The absorption envelope of the π–π* transition of
the perimidine nucleus of 3 changed back to that of a free ligand
60 to a large extent because the perturbation of the π–π* transition
was lessened by the bromide coordination, which was consistent
Rrigid
4
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with the emission spectra. For complex 5·ClO4, the absorption
All manipulations were carried out using standard Schlenk lines
envelope of the π–π* transition of the perimidine nucleus was 30 or gloveꢀbox techniques under an atmosphere of dinitrogen.
similar to that of 1·ClO4, showing a blue shift of the absorption
spectrum despite its lower extinction coefficient (S10). A
strikingly quenching effect for 5·ClO4 was therefore displayed in
spite that the involvement of a heavy atom effect could also be
instrumental in fluorescence quenching.
Acetonitrile and dichloromethane were distilled from calcium
hydride before use. Diethyl ether was dried by distillation from
sodium benzophenone prior to use. nꢀBu4NF (1.0M in THF) and
nꢀBu4NX (X = Cl, Br, I) were obtained from commercial sources
35 and used as received without further purification. The starting
materials CuX (X = Cl, Br, I) and AgClO4 are purchased and
used as received. The ligand LPh, complex 1·ClO4 and 2 were
prepared according to literature procedures.3 Warning:
Perchlorate compounds are potentially explosive! Extreme care
40 must be taken when working with perchlorate complexes, and
only small quantities should be handled.
5
Conclusions
This study marks the first implementation of a controllable
10 interconversion among free ligands and linear twoꢀcoordinate, as
well as Tꢀshaped threeꢀcoordinate, copper(I) complexes. This
accomplishment could result in a facile tristate fluorescent
switching system when halides are used only as the modulators
for copper(I) complexes. Also, a simple ON↔OFF bistate
15 fluorescence switching between a free ligand and a twoꢀ
coordinate silver(I) complex can be easily achieved by the
addition/abstraction of the silver(I) ion. The examination of other
metal centres using the presented and modified ligand systems for
the development of intriguing functional molecules or catalysts18
20 is now in progress.
Physical measurements
Infrared spectra were recorded on a Bruker AlphaꢀT FTIR
spectrometer as Nujol mulls. Variableꢀtemperature 1HꢀNMR
45 spectra were obtained on Bruker Avance 400.13 or 500.13 MHz
NMR spectrometer. Data were recorded in CD2Cl2 at room
temperature. 13C NMR spectra were recorded on Bruker Avance
125.77 or 150.04 MHz spectrometer. Mass spectra were acquired
on a Finnigan TSQ 700 spectrometer. Elemental analyses were
50 performed on a HERAEUS CHNꢀOꢀSꢀRapid elemental analyzer
by Instruments Center, National Chung Hsin University, and a
HERAEUS VarioELꢀ Ⅲ Analyzer by Advanced Instrument
Center, National Taiwan University. Fluorescence emission
Acknowledgements
This work was supported by the Ministry of Science and
Technology of the Republic of China (NSC 100ꢀ2113ꢀMꢀ255ꢀ
001ꢀMY3) and Chang Gung Memorial Hospital (BMRP981). We
25 also thank Mr. TingꢀShen Kuo (NTNU) for assistance with Xꢀray
crystallography.
spectra were recorded at ambient on
a Hitachi Fꢀ7000
55 fluorescence spectrophotometer. Ultravioletꢀ Visible spectra
were recorded on a JASCO Vꢀ650 Ultraviolet/Visible Absorption
Spectrometer. Fluorescence quantum yields (Φf) were determined
using degassed dichloromethane solution at room temperature.
The complex and the reference dye, coumarine 151 (QY = 0.49 in
60 dichloromethane), were excited at same wavelength, maintaining
Experimental Section
General information and materials
Table 2 Selected Xꢀray crystallographic data for complexes 3⋅CH2Cl2 – 5⋅ClO4
3⋅CH2Cl2
4⋅CuCl2⋅CH2Cl2
5⋅ClO4
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
Empirical formula
M
C30H32BrCl2CuN6
690.97
C30H32Cl4Cu2N6
745.50
C29H30AgClN6O4
669.91
T/K
200(2)
200(2)
200(2)
λ/Å
0.71073
Monoclinic
P21/c
13.3142(3)
15.6092(3)
14.3394(4)
90
98.7790(10)
90
2945.16(12)
4
1.558
0.71073
Monoclinic
P21/c
25.9994(17)
15.1102(10)
17.1561(11)
90
107.436(3)
90
6430.2(7)
8
1.540
0.71073
Triclinic
Pī
Crystal system
Space group
a /Å
10.2448(9)
12.5810(11)
13.3336(11)
71.022(2)
86.393(2)
66.479(2)
1485.7(2)
2
b /Å
c /Å
α
β
γ
/°
/°
/°
V /Å3
Z
Dcalcd /g cmꢀ1
1.498
0.813
ꢀ
/mmꢀ1
2.311
1.686
θ range for data collection/°
No. reflns. collected
2.34 – 25.04
19154
1.58 – 25.03
44655
2.23 – 25.02
14245
No. indep. reflns. [ I > 2σ(I) ]
No. param.
R1
5197 (Rint = 0.0916)
361
0.0610
11342 (Rint = 0.0725)
756
0.0920
5171 (Rint = 0.0424)
370
0.0474
wR2
0.1627
1.086
0.2418
1.020
0.1193
1.031
GOF on F2
CCDC No.
1024054
1024055
1024056
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Journal Name, [year], [vol], 00–00 | 5

New Journal of Chemistry
Page 6 of 7
View Article Online
DOI: 10.1039/C4NJ01639D
nearly equal absorbance, and the emission spectra were recorded.
Fluorescence quantum yields were taken as the average of three
separate determinations and were reproducible to within 10%.
7.42 (s, 1H, CH), 7.27~7.15 (m, 9H, CH of naphthalene and
phenyl), 6.44 (d, 2H, CH of phenyl), 6.05 (s, 2H, CH of pyrazole),
2
2
6.13 (d, 2H, JHH = 13.5 Hz, CH2), 5.94 (d, 2H, JHH = 13.5 Hz,
60 CH2), 2.57 (s, 6H, CH3), 2.43 (s, 6H, CH3) ppm. 13C NMR
(CD2Cl2, 125.77 MHz): δ 151.82, 143.05, 140.49, 137.42, 135.47,
129.38, 128.95, 127.50, 126.84, 120.45, 117.06, 107.93, 106.25,
78.04, 63.64, 15.75, 12.17 ppm. Positive ESIꢀMS: 525.3 ([Mꢀ
CuCl2]+, 100%). UVꢀVis (CH2Cl2) λmax, nm (ε, Mꢀ1cmꢀ1): 332
65 (16613), 346 (17117). Anal. Calcd for C29H30Cl2Cu2N6 (4⋅CuCl2):
C, 52.73; H, 4.58; N, 12.72. Found: C, 52.96; H, 4.51; N, 12.88.
X-Ray crystallography
5
Crystal data collection and processing parameters are given in
Table 2. Diffraction data were carried out on a Bruker Kappa (3)
and Bruker APEX II (4·CuCl2ꢁCH2Cl2 and 5ꢁClO4) CCD
diffractometers with graphite monochromated MoꢀKα radiation
(λ = 0.7107 Å). The structures 3ꢁCH2Cl2, 4·CuCl2ꢁCH2Cl2 and
10 5ꢁClO4 were solved by direct methods and refined by fullꢀmatrix
leastꢀsquares procedures using the SHELXLꢀ97 program.19 The
higher but acceptable R values for 4·CuCl2ꢁCH2Cl2 (9.2%) was
due to the slightly poor quality of the crystals. In the lattice, part
Synthesis of complex 5·ClO4
A 8 ml CH2Cl2 solution of AgClO4 (103 mg, 0.50 mmol) and LPh
(240 mg, 0.52 mmol) was stirred at 0 °C for 1 hr in the dark.
of the copper atoms in the cationic 4+ was disordered over two 70 Then the solution was filtered. Addition of 10ml hexane results in
15 positions (93:7 ratio). Complex 5ꢁClO4 was squeeze half CH2Cl2
using the SQUEEZE option of PLATON. All of the nonꢀ
hydrogen atoms were refined with anisotropic temperature factors.
All hydrogen atoms were located geometrically and refined in the
the precipitate of white solid, which was separated by filtration
and washed by 10ml hexane for two times. The resulting white
solid was dried under vacuum to yield 301 mg (90 %) of 5·ClO4.
Single crystals of 5·ClO4 were obtained from CH2Cl2/Et2O in the
riding mode. Additional crystallographic data as CIF files are 75 dark. IR (KBr): ν
CO4ꢀ 1096 cmꢀ1. 1H NMR (CD2Cl2, 500.13 MHz):
20 available as Supporting Information.
δ 7.28~7.19 (m, 9H, CH of naphthalene and phenyl), 6.95 (s, 1H,
CH), 6.36 (dd, 2H, CH of phenyl), 6.10 (s, 2H, CH of pyrazole),
Synthesis of complex 3
2
2
5.95 (d, 2H, JHH = 13.5 Hz, CH2), 5.85 (d, 2H, JHH = 13.4 Hz,
CH2), 2.59 (s, 6H, CH3), 2.29 (s, 6H, CH3) ppm. 13C NMR
80 (CD2Cl2, 150.04 MHz): δ 151.06, 143.43, 139.68, 137.62, 135.48,
129.49, 1298.19, 127.67, 126.80, 120.21, 116.21, 107.49, 105.23,
78.01, 63.26, 15.76, 12.01 ppm. Positive ESIꢀMS: 569.0 ([Mꢀ
ClO4]+, 100%). UVꢀVis (CH2Cl2) λmax, nm (ε, Mꢀ1cmꢀ1): 322
Method 1: The reaction of CuBr (72 mg, 0.50 mmol) and LPh
(232 mg, 0.50 mmol) was carried out following a procedure
similar to that of described for the synthesis of complex 2 in a
25 87% yield (263 mg). Single crystals of 3⋅CH2Cl2 were grown
1
from CH2Cl2/Et2O. H NMR (CD2Cl2, 500.13 MHz): δ 7.54 (s,
1H, CH), 7.29~7.13 (m, 9H, CH of naphthalene and phenyl), 6.65
(d, 2H, CH of phenyl), 6.13 (d, 2H, 2JHH = 13.8 Hz, CH2), 5.97 (s,
2H, CH of pyrazole), 5.92 (d, 2H, JHH = 13.7 Hz, CH2), 2.54 (s,
(10681), 327 (11017), 342 (11660).
85 C29H30N6AgClO4 (5⋅ClO4): C, 51.99; H, 4.51; N, 12.55. Found: C,
52.32; H, 4.53; N, 12.78.
Anal. Calcd for
2
30 6H, CH3), 2.35 (s, 6H, CH3) ppm. 13C NMR (CD2Cl2, 125.77
MHz): δ149.63, 141.91, 141.34, 138.49, 135.38, 129.10, 128.48,
127.33, 126.98, 120.21, 117.91, 107.50, 107.15, 76.38, 63.80,
15.23, 12.24 ppm. Positive ESIꢀMS: 525.3 ([MꢀBr]+, 100%).
UVꢀVis (CH2Cl2) λmax, nm (ε, Mꢀ1cmꢀ1): 339 (17487), 348
35 (18140). Anal. Calcd for C29H30BrCuN6 (3): C,57.47; H, 4.99; N,
13.87. Found: C, 56.95.10; H, 4.96; N, 13.97. Method 2: To a
stirred solution of complex 1·ClO4 (31 mg, 0.05mmol) in 10
CH2Cl2 was added a solution of nꢀBu4NBr (16 mg, 0.05mmol) in
5ml CH2Cl2. After reaction for 20 min at room temperature, the
40 resulting solution was dried under vacuum. The solid was
General procedure for the reactions of copper(I) derivatives,
1·ClO4, 2, 3 or 4 ·ClO4, with n-Bu4NF
To a stirred solution of complex 1ꢁClO4 (40 mg, 0.064 mmol) in
90 10ml CH2Cl2 was added a solution of nꢀBu4NF in THF (0.064 ml,
0.064 mmol). The orangeꢀyellow precipitates were formed in 5
minutes at room temperature under N2. The solution was filtered
and the resulting solution was dried under vacuum. The solid was
analyzed by 1H NMR in CD2Cl2 to firm the liberation of LPh.
95 Reactions of 5·ClO4 with n-Bu4NX (X = Cl, Br, I)
1
To a stirred solution of complex 5ꢁClO4 (40 mg, 0.064 mmol) in 5
ml CH2Cl2 was added a solution of nꢀBu4NX (X = Cl, Br, I) in 5
ml CH2Cl2. The white (AgCl) or yellow (AgBr, AgI) precipitates
were formed immediately. The solution was filtered and the
100 resulting solution was dried under vacuum. The solid was
analyzed by 1H NMR in CD2Cl2 to firm the liberation of LPh.
analyzed by H NMR in CD2Cl2 and the yield of 3 is nearly
quantitative. 1H NMR (CD2Cl2, 400.13 MHz): δ 7.34 (s, 1H, CH),
7.32~7.15 (m, 9H, CH of naphthalene and phenyl), 6.73 (d, 2H,
2
CH of phenyl), 6.08 (d, 2H, JHH = 13.8 Hz, CH2), 5.99 (s, 2H,
2
45 CH of pyrazole), 5.95 (d, 2H, JHH = 13.8 Hz, CH2), 3.23~3.19
(m, 8H, CH2 of nꢀbutyl), 2.55 (s, 6H, CH3), 2.37 (s, 6H, CH3),
1.70~1.64 (m, 8H, CH2 of nꢀbutyl), 1.50~1.44 (m, 8H, CH2 of nꢀ
butyl), 1.06 (t, 12H, CH3 of nꢀbutyl) ppm.
Notes and references
Center for General Education, Chang Gung University of Science and
Technology, TaoꢀYuan, 333, Taiwan, R.O.C. Eꢀmail: Fax: +886ꢀ3ꢀ
Synthesis of complex 4·CuCl2
50 A 10ml CH2Cl2 solution of CuCl (100 mg, 1.00 mmol) and LPh 105 2118866; Tel: +886ꢀ3ꢀ2118999 ext. 5583; Eꢀmail:
(235mg, 0.51 mmol) was stirred at room temperature for 0.5 hr
under N2. After the addition of 10 ml Et2O, the white precipitates
formed was filtered off and washed by 5 ml Et2O for two times.
The resulting white solid was dried under vacuum to yield 301
55 mg (91 %) of 4·CuCl2. Single crystals of 4⋅CuCl2⋅CH2Cl2 were
grown from CH2Cl2/Et2O. 1H NMR (CD2Cl2, 500.13 MHz): δ
ccchou@mail.cgust.edu.tw
† Electronic Supplementary Information (ESI) available: 1H&13C NMR
spectra, absorption and emission spectra, crystal structures CCDC
1024054–1024056. See DOI: 10.1039/b000000x/
110
1
J. M. Lehn, Supramolecular Chemistry: Concepts and Perspectives,
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DOI: 10.1039/C4NJ01639D
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