Platinum(II) compounds containing cyclometalated tridentate ligands: Synthesis, luminescence studies, and a selective fluoro for methoxy substitution

Article abstract of DOI:10.1021/om401111t

Two series of potentially tridentate ligands of formula ArCH=N(CH ₂)₂NMe₂ and ArCH=N(CH₂) ₃NMe₂ (Ar = C₆H₅, 2-FC ₆H₄, 4-FC₆H₄

Full text of DOI:10.1021/om401111t

Article
pubs.acs.org/Organometallics
Platinum(II) Compounds Containing Cyclometalated Tridentate
Ligands: Synthesis, Luminescence Studies, and a Selective Fluoro for
Methoxy Substitution
†
†
,†
,†
́
Albert Gandioso, Jennifer Valle-Sistac, Laura Rodrıguez,* Margarita Crespo,*
‡
́
and Merce Font-Bardıa
̀
†
́
́
Departament de Quımica Inorgan
de Raigs-X, Centres Científics i Tecnolog
i Sabarís, 1-3, 08028 Barcelona, Spain
̀
ica, Facultat de Quımica, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain
‡Unitat de Difraccio
́
̀
ics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona,
Sole
́
S
* Supporting Information
ABSTRACT: Two series of potentially tridentate ligands of formula ArCH
N(CH2)2NMe2 and ArCHN(CH2)3NMe2 (Ar = C6H5, 2-FC6H4, 4-FC6H4, 2,3,4-
F3C6H2) were used to prepare [C,N,N′]-cyclometalated platinum compounds
containing either a chloro or a methyl ancillary ligand. The synthesis of the compounds
[PtCl{Me2N(CH2)xNCHR}] (3a−h), via the corresponding compounds
[PtCl2{Me2N(CH2)xNCHAr}] (2), requires drastic conditions and proceeds more
easily for ligands derived from N,N-dimethylpropylenediamine (x = 3). Along the
process, an unexpected selective nucleophilic substitution of a fluoro for a methoxy
substituent took place at the aryl ring for ligands 2,3,4-F3C6H2CHN(CH2)xNMe2.
The syntheses of compounds [PtMe{Me2N(CH2)xNCHR}] (4a−h) using
[Pt2Me4(μ-SMe2)2] as a precursor took place for all ligands under relatively mild conditions. All compounds were fully
characterized, including molecular structure determination for [PtCl{Me2N(CH2)3NCH(4-FC6H3)}] (3b) and [PtCl{Me2N-
(CH2)3NCH(2-OMe,3,4-F2C6H)}] (3g). The absorption and emission spectra were also studied for the [C,N,N′]-
cyclometalated platinum(II) compounds, and all of the compounds were emissive in the solid state and in dichloromethane
solution at room temperature (compounds 3) or at 77 K (compounds 4). The size of the [N,N′]-chelate ring and the number
and position of the substituents in the aryl ring modulate the intensity and the energy of the emission.
explored.4 In this work we report the preparation and
INTRODUCTION
■
luminescence properties of cyclometalated platinum com-
pounds containing tridentate [C,N,N′] imine ligands with
fluoro substituents (compounds 3 and 4 shown in Chart 1).
This study should allow us to compare the behavior of these
compounds in relation with (a) the size of the [N,N′] chelate
ring (five- versus six-membered), (b) the number and position
of the fluoro substituents in the ring, and (c) the nature of the
ancillary ligands (methyl or chloro) coordinated to the
platinum. These effects will also be analyzed in relation to
the choice and success of the preparation procedure.
In the last years significant research effort has focused on the
photophysical properties of luminescent square-planar platinum
complexes. The aim of this research is to provide an
understanding of the factors that govern the luminescence
efficiencies of platinum(II) complexes as well as to apply these
compounds in organic light emitting diodes (OLEDs) and in
other devices.1
Many cyclometalated platinum complexes have proved to be
luminescent in solution at ambient temperature, because [C,N]
ligands increase the energies of metal-centered excited states in
comparison to analogous [N,N] ligands.1 In addition, rigidity
generally favors luminescence over nonradiative decay path-
ways, and therefore tridentate [N,N,C], [N,C,N], and [C,N,C]
ligands generally based on substituted pyridines and poly-
pyridines may offer an advantage over bidentate [C,N] ligands.2
Moreover, systematic studies carried out for several of these
systems indicate that the emission may be tuned by structural
modification of the ligands; in particular, the nature and the
position of the substituents might influence the photophysics of
the platinum complexes.1,3
RESULTS AND DISCUSSION
■
Two series of potentially tridentate ligands of formula ArCH
N(CH2)2NMe2 and ArCHN(CH2)3NMe2 (Ar = C6H5, 2-
FC6H4, 4-FC6H4, 2,3,4-F3C6H2) derived from N,N-dimethyle-
thylenediamine and N,N-dimethylpropylenediamine, respec-
tively, were used in the present work. As stated above, the
ligands were selected in order to compare the results between
those derived from propylene or ethylenediamine, as well as to
analyze the effect of fluorine substituents. In particular, the
In spite of the great number of cycloplatinated compounds
for which the luminescence properties have been studied so far,
those containing aldimine or ketimine ligands have been less
Received: November 14, 2013
Published: January 15, 2014
© 2014 American Chemical Society
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Chart 1
Scheme 1. Synthesis of Compounds 3
position of a single fluoro substituent in an ortho or para
position as well as the increased fluorination will be studied.
Synthesis of Compounds [PtCl{Me2N(CH2)xNCHR}]
(3a−h). The syntheses of compounds [PtCl{Me2N(CH2)3N
CHC6H5}] (3e)5 and [PtCl{Me2N(CH2)2NCHC6H5}]
(3f)6 have been previously reported from the corresponding
ligands, cis-[PtCl2(dmso)2] as metalating agent, methanol as
solvent, and sodium acetate as an external base. However, a
systematic comparison of the reactivities of both series of
ligands containing either an ethylene or a propylene moiety
linking the two nitrogen atoms and different substituents in the
aryl ring has not been carried out so far. With this purpose, in
this work we planned to follow the general synthetic procedure
shown in Scheme 1 for both series of imines.
Initially, several reaction conditions were tested for ligand 1a,
including either one-pot procedures or prior isolation of the
corresponding [N,N′]-chelate complex 2a. As previously
reported for similar systems,5−7 the best results were obtained
when [N,N′] coordination compounds (compounds 2) were
previously isolated and such complexes, when refluxed for
several hours in a donor solvent in the presence of sodium
acetate, further reacted to yield cycloplatinated derivatives via
C−H activation. The best results for the latter step were
obtained when an equivalent amount of sodium acetate was
used and the reaction time in refluxing methanol was 48−72 h,
since the use of larger amounts of added base, prolonged
reaction times, or the use of mixtures of toluene and methanol
as solvents led to partial decomposition with formation of
metallic platinum. Therefore, these optimal reaction conditions
were followed in the synthesis of compounds 3, which requires
previous isolation of the corresponding compounds 2.
The reaction of the imines 1a−g with cis-[PtCl2(dmso)2] in
refluxing methanol gave the corresponding coordination
compounds [PtCl2{Me2N(CH2)xNCHAr}] (2). For ligands
derived from N,N-dimethylpropanediamine a mixture of two
isomers corresponding to the two possible conformations (Z
and E) around the CN bond was obtained. Generally, the Z
isomer was the most abundant, or even the only one which was
isolated and characterized, as for 2b. However, for ligands
derived from N,N-dimethylethylenediamine, the corresponding
coordination compounds were isolated exclusively as the less
sterically crowded E isomer. The different behavior might arise
from the higher flexibility of the six- versus the five-membered
[N,N′]-chelate rings, which minimizes the steric crowding
around the platinum in the Z isomer. As previously reported,5,8
these isomers display striking differences in their spectral
features. In particular, the imine proton of the E isomers is
strongly deshielded (δ ca. 9.30−9.60 ppm) due to the proximity
to platinum and displays lower J(H−Pt) values (48−60 Hz) in
comparison to those for the Z isomers (115−120 Hz). In
addition, for the Z isomer both the methylene and NMe2
protons are nonequivalent. The number of signals observed in
the 19F NMR spectra was in all cases consistent with the
presence of one or two isomers, as well as with the number of
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fluorine substituents in the imine. Formation of the [N,N′]-
chelate compounds [PtCl{Me2N(CH2)xNCHAr}] (2) was
confirmed by ESI(+) mass spectra and elemental analyses.
The tridentate [C,N,N′] cyclometalated compounds 3a−d
were obtained from the equimolar reaction of the coordination
compounds and sodium acetate in refluxing methanol. The
process involves the activation of a C(aryl)−H bond and the
formal release of HCl, which is promoted in the presence of a
base. For compounds 2c,d, the C−H bond activation should be
preceded by an isomerization step from an unreactive E to the
adequate Z conformation. In contrast, compounds 2a,b,
containing the more flexible propylene moiety, were obtained
as a mixture of Z and E conformers (2a) or as the Z conformer
exclusively (2b), thus facilitating the cyclometalation process.
The yields of the cyclometalation reactions were in all cases
moderate; however, slightly higher yields in the range 36−40%
were obtained for propylene derivatives 3a,b after 48 h in
comparison to those for the corresponding ethylene derivatives
3c,d, for which yields in the range 29−32% were obtained after
72 h. These results confirm that the higher flexibility of the
propylene versus the ethylene moieties facilitates the cyclo-
metalation reaction, leading to [C,N,N′]-cycloplatinated
compounds. In all cases, 1H NMR spectra confirmed the
formation of the expected fused [6,5,6]- or [6,5,5]-tricyclic
system. As reported for analogous systems,5,6,8 J(H−Pt) values
for the imine proton (141−144 Hz) are higher than those
observed for compounds 2. The 19F NMR spectra show only
one signal, for which coupling to platinum was only observed
recovered unaltered after 72 h of reflux in methanol in the
presence of an equimolar amount of sodium acetate. Moreover,
the fluoro for methoxy substitution was not observed along the
syntheses of compounds 3a−d, for which only one fluoro
substituent is present. Therefore, it is likely that the combined
effects of coordination of the imine ligand to platinum and the
presence of several fluorine substituents are able to activate the
fluoroaryl group toward nucleophilic aromatic substitution in a
way similar to that for recently reported examples in which
acetylenes are used as electron-withdrawing groups promoting
nucleophilic aromatic substitution.11 The presence of sodium
acetate in the reaction media is also required, since the fluoro
for methoxy substitution process was not observed in the
preparation of compounds 2g,h. It is interesting to point out
that fluorine for alkoxy nucleophilic substitution has been
reported as a strategy leading to blue-emitting cyclometalated
iridium(III) complexes with increased solubility.12
1
In both cases, the H NMR spectra confirmed formation of
the [C,N,N′]-cycloplatinated compounds and the J(H−Pt)
values for the imine proton are similar to those obtained for
compounds 3a−d. Only one resonance corresponding to an
aromatic proton was observed, and a doublet at ca. 4 ppm was
assigned to the methoxy hydrogen atoms which are coupled to
the adjacent fluorine. The 19F NMR spectra show only two
signals, whose multiplicities and coupling constants are in good
agreement with the proposed structures.13 The characterization
of these compounds was completed with ESI(+) mass spectra,
elemental analyses, and the determination of the molecular
structure of 3g.
1
for compound 3a. For 3b, 13C NMR and H−13C-HSQC
spectra were also taken and confirm the cyclometalation
process, since only three resonances corresponding to aromatic
C−H were observed. All compounds were characterized by
ESI(+) mass spectra and elemental analyses, and 3b was also
characterized crystallographically.
Crystal Structures of Compounds 3b,g. Suitable crystals
of compounds 3b,g (Figures 1 and 2, respectively) were grown
With the aim of obtaining the corresponding tridentate
[C,N,N′]-cyclometalated compounds the reactions of the
coordination compounds 2g,h with an equimolar amount of
sodium acetate in refluxing methanol were also carried out.
However, for these ligands the reaction (shown in Scheme 2)
Scheme 2. Synthesis of Compounds 3g,h with Fluoro for
Methoxy Substitution
Figure 1. Molecular structure of compound 3b (molecule a). Selected
bond lengths (Å) and angles (deg) with estimated standard deviations:
Pt(1a)−N(1a), 1.986(9); Pt(1a)−C(1a), 1.998(10); Pt(1a)−N(2a),
2.174(8); Pt(1a)−Cl(1a), 2.297(3); N(2a)−C(10a), 1.483(15);
C(10a)−C(9a), 1.53(2); C(9a)−C(8a), 1.53(2); C(8a)−N(1a),
1.467(15); N(1a)−C(7a), 1.293(15); C(7a)−C(6a), 1.430(18);
C(6a)−C(1a), 1.383(15); N(2a)−Pt(1a)−N(1a), 97.2(4); N(1a)−
Pt(1a)−C(1a), 80.3(4); C(1a)−Pt(1a)−Cl(1a), 93.1(3); N(2a)−
Pt(1a)−Cl(1a), 89.5(3).
was more complex and involved a selective nucleophilic
substitution of the fluorine substituent adjacent to the imine
group for a methoxy group, leading eventually to the
compounds [PtCl{Me2N(CH2)xNCH(2-OMe,3,4-
F2C6H)}] (3g for x = 3 and 3h for x = 2). Selective
platinum-catalyzed activation and subsequent functionalization
of aryl C−F bonds to produce arylmethyl ethers in a process
involving platinum(IV)/platinum(II) species has been re-
ported.9 The involvement of platinum(IV) species is ruled
out in the present case, since previous results indicate that
intramolecular C−F bond activation takes place at electron-rich
platinum substrates such as [Pt2Me4(μ-SMe2)2] but not at cis-
[PtCl2(dmso)2].10 On the other hand, ligands 1g,h were
from dichloromethane−methanol solution. For 3b, the
asymmetric unit contains eight molecules (Figures S1 and S2,
Supporting Information) that are spaced between 5 and 8 Å:
i.e., the distances are too long to be able to establish weak
intermolecular interactions. The crystal structure of 3g is
constituted by two different molecules distributed in anti-
parallel positions (Figure S3, Supporting Information) which
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between the mean planes being 2.3(4)° for 3b and 3.22(15)°
for 3g.
Synthesis of Compounds [PtMe{Me2N(CH2)xNCHR}]
(4a−h). The synthesis of compounds [PtMe{Me2N-
(CH2)xNCHR}] (4a−h) was carried out following the
previously reported procedures for compounds 4c,f,h, which
consist of the reaction of [Pt2Me4(μ-SMe2)2] with the
corresponding imine.14 The mechanism of these reactions has
been thoroughly studied, and it is assumed that prior
coordination of the ligand produces [N,N′]-chelate complexes
that further react to produce cyclometalated compounds with
loss of methane.14 These compounds have been generally
prepared under mild conditions, for instance in acetone at
room temperature, and the bidentate imines used so far are
derived from N,N-dimethylethylenediamines. In this work, as
shown in Scheme 3, the reactions were carried out in refluxing
toluene and were completed within 1 h for both imines derived
from ethylene and propylenediamines. In this case, no further
reaction was observed for the trifluorinated imines 1g,h, which
can be related to the greater electron density of the platinum in
these compounds, as well as to the absence of methanol in the
reaction mixtures. As a whole, this method appear to be a
convenient one-pot procedure that does not require previous
isolation of the corresponding coordination compounds to give
the cyclometalated compounds with good yields. In all cases,
1H NMR spectra confirmed formation of the expected
[C,N,N′] cycloplatinated compounds, in which a methyl ligand
completes the coordination sphere around the platinum. The
methyl ligand, the imine, and the NMe2 are coupled to
platinum, and the J(H−Pt) values for the imine proton (ca. 60
Hz) are lower than those obtained for compounds 3, which is
consistent with the presence of a methyl instead of a chloro
ligand trans to the imine.8a,b The 19F NMR spectra are
consistent with the proposed structures: in particular, the
presence of three signals for 4g,h confirms the presence of the
three fluoro atoms.
Figure 2. Molecular structure of compound 3g. Selected bond lengths
(Å) and angles (deg) with estimated standard deviations: Pt(1)−N(1),
1.997(4); Pt(1)−C(1), 2.000(3); Pt(1)−N(2), 2.174(3); Pt(1)−
Cl(1), 2.3093(11); N(2)−C(10), 1.498(5); C(10)−C(9), 1.521(6);
C(9)−C(8), 1.514(6); C(8)−N(1), 1.483(5); N(1)−C(7), 1.301(5);
C(7)−C(6), 1.442(6); C(6)−C(1), 1.408(6); N(2)−Pt(1)−N(1),
96.78(13); N(1)−Pt(1)−C(1), 80.76(15); C(1)−Pt(1)−Cl(1),
92.85(13); N(2)−Pt(1)−Cl(1), 89.61(10).
are connected by H bonds between the O atom of the methoxy
units and one hydrogen atom of the central methylene of the
diamine of a second molecule. The 3D packing of the complex
is constituted by different dimers, as shown in the unit cell
(Figure S4, Supporting Information).
The compounds consist of a fused [6,5,6]-tricyclic system
containing an ortho-metalated phenyl group, a five-membered
metallacycle and a six-membered chelate ring with two nitrogen
atoms coordinated to platinum. The square-planar coordination
around the platinum is completed with a chlorine atom. For 3g,
the molecular structure provides conclusive evidence of the
presence of a methoxy group in the position adjacent to the
imine moiety, as deduced from NMR spectra. Bond lengths and
angles are well within the range of values obtained for
analogous compounds.5−8 The Pt−amine distances are greater
than Pt−imine distances in agreement with both the weaker
ligating ability of amines for platinum and the greater trans
influence of the aryl versus the chloro ligand.8c Most bond
angles at platinum are close to the ideal value of 90°, and the
smallest angle corresponds in each case to the metallacycle
(80.3(4)° (3b) and 80.76(15)° (3g)). As previously observed
for related compounds,5 the six-membered chelate ring presents
a strong deviation from planarity and the chelate angles N(1)−
Pt−N(2) (97.2(4)° (3b) and 96.78(13)° (3g)) are in both
cases greater than for analogous compounds with a five-
membered chelate ring. In each case, the metallacycle is nearly
coplanar with the coordination plane, the dihedral angle
Absorption and Emission Spectroscopy. Both absorp-
tion and emission spectra have been recorded in aerated
dichloromethane solutions, and emission spectra were also
recorded in the solid state for cyclometalated platinum
compounds 3 and 4. The resulting data are shown in Table 1
with representative absorption and emission spectra shown in
Figures 3−6.
The absorption spectra of 10−4 M dichloromethane solution
of compounds 3 in solution at 298 K show several bands in the
UV−visible range with moderate ε values. The lowest energy
band in the range 376−400 nm with extinction coefficients
between 2200 and 5100 M−1 cm−1 is attributable to Pt(5d) →
π*(L) metal-to-ligand charge transfer (MLCT) mixed with
intraligand (IL) transitions.15 Compounds 3 emit in the visible
region at 298 K when excited at the wavelength corresponding
in each case to the lowest energy band. The emission spectra of
Scheme 3. Synthesis of Compounds 4
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Table 1. Absorption and Emission Properties of Cyclometalated Platinum Compounds 3 and 4 in CH2Cl2 Solution and in the
a
Solid State
b
complex
absorption λmax/nm (ε/M−1 cm−1
)
emission in solution λmax /nm
emission in solid λmax/nm
ϕ
temp/K
3a
3b
3c
3d
3e
3f
290 (4631), 323 (3517), 388 (3914)
311 (3114), 376 (3022)
588, 639, 707
577, 622, 680
593, 646, 715
575, 626, 690
586, 633, 701
588, 641, 704
590, 642, 698
590, 634, 700
575, 618, 673
557, 604, 664
585, 637, 685
568, 621, 681
566, 615, 665
580, 636, 685
567, 620, 675
578, 633, 684
589, 641, 710
575, 616, 675
595, 644, 712
567, 616, 678
577, 625, 690
580, 638, 702
590, 642, 702
575, 625, 690
586, 630, 680
573, 618, 658
589, 640, 680
569, 619, 678
585, 632, 679
583, 638, 685
587, 630, 680
580, 634, 689
0.0025
298
298
298
298
298
298
298
298
77
0.0038
304 (4917), 330 (4513), 400 (3439)
327 (3870), 381 (2753)
0.0028
0.0048
316 (3663), 383 (2250)
0.0032
329 (4359), 391 (2911)
0.0036
3g
3h
4a
4b
4c
4d
4e
4f
323 (4155), 383 (5074)
0.0028
332 (3250), 391 (3701)
0.0035
325 (2734), 378 (2283), 408 (2324)
319 (2446), 362 (2464), 391 (2298)
337 (3240), 415 (2287)
c
c
c
c
c
c
c
c
77
77
328 (2462), 399 (1853)
77
322 (2053), 401 (1657)
77
332 (2986), 408 (1876)
77
4g
4h
324 (2343), 372 (2145), 403 (2222)
333 (3053), 409 (2359)
77
77
a
b
Emission spectra were recorded upon excitation at the lowest energy absorption band. Quantum yields for emission in solution referred to
c
[Ru(bipy)3]Cl2 in H2O. Not observed.
Figure 3. Absorption spectra of compounds 3 in dichloromethane
solution at 298 K at 10−4 M concentration.
Figure 4. Emission spectra of compounds 3 in dichloromethane
solution at 298 K: λexc 388 (3a), 376 (3b), 400 (3c), 391 (3d), 383
(3e), 391 (3f), 383 (3g), 391 nm (3h); concentration 10−4 M; three
slits. Emission spectra are normalized with respect to the strongest
recorded emission maximum for comparison purposes.
all compounds 3 follow a similar pattern and display three
maxima (one displayed as shoulder) in the range 575−700 nm.
The observation of vibronically structured bands with progres-
sional spacings at ca. 1200 cm−1, typical of ν(CC) and
ν(CN) stretching frequencies in the excited state, demon-
strates the involvement of ligand character in their emission
origin. Solid emission spectra were also recorded upon
excitation of the samples at the corresponding lowest energy
absorption band. In all cases, the same profile (well vibronically
structured band) as recorded in solution is observed (Table 1
and Figures S5 and S6 (Supporting Information)). No
excimeric emission bands that usually present broad emission
bands were recorded in any case. Emission spectra were also
recorded at different concentrations in order to check if
possible aggregate formation was obtained in solution. As can
be seen in Figure S8 (Supporting Information), the emission
profile when going from 1 × 10−4 to 3 × 10−5 M is similar and
the contribution of aggregates on the spectra does not seem to
be very certain. Nevertheless, it cannot be ruled out definitively,
due to the small increase of the longer wavelength emission at
higher concentrations. This is in agreement with the fact that
no π−π stacking interactions are observed in the crystal packing
of the molecules (Figures S1−S4, Supporting Information).
In all cases, the excitation spectra match the absorption
spectra in solution at room temperature. The large red shift
observed for the emission is characteristic of phosphorescence
emission, as expected from a triplet state typical for platinum
complexes due to strong spin−orbit coupling favored by the
well-known heavy-atom effect. This is in agreement with the
high luminescence lifetime values estimated on the order of 1
μs when we record the spectra of the complexes in the presence
and in the absence of oxygen.
Although the differences in emission energies are very small,
it was found that the presence of a fluoro substituent in position
2 produces a small red shift (ca. 5 nm) and a blue shift (10−15
nm) for the substituent in position 4 for both series of
compounds derived from ethylenediamine (3f,c,d) or from
propylenediamine (3e,a,b). The apparently controversial effect
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radiative decay pathways. Attempts to improve the photo-
physical properties by modifying the [N,C,N] ligand, in
particular the size of the chelate rings, have been recently
reported.17
Studies carried out for compounds 4 indicate absorption
spectra similar to those obtained for compounds 3, with the
lowest energy band in the range 391−415 nm. The lower
energy of these bands in comparison to those of compounds 3
(in the range 376−400 nm) can be related to the higher
electron density at the metal center expected for compounds 4.
Compounds 4, when excited at the lowest energy absorption
band were nearly nonemissive in solution at room temperature.
This could be due to the presence of a high-energy oscillator
(C−H) in their first coordination sphere, which could provide
an efficient pathway for multiphonon relaxation. On the other
hand, at 77 K deactivation processes are minimized and
emission was observed. The obtained spectra were similar to
those corresponding to compounds 3. In particular, for both
series of ligands derived from either ethylene or propylenedi-
amine, a small red shift is observed when a fluoro substituent is
present in position 2 (4c versus 4f or 4a versus 4e), while the
presence of a fluoro substituent in position 4 produces a small
blue shift (4d versus 4f or 4b versus 4e). The most strongly
emissive compound of this series is 4b, as shown in Figure 6,
where the emission spectra of the complexes are normalized
with respect to 4b.
Figure 5. Absorption spectra of compounds 4 in dichloromethane
solution at 298 K at 10−4 M concentration.
Finally, a comparison of compounds 3 and 4 which only
differ in the ancillary ligand (chloro versus methyl) suggests
that the chloro derivatives are best suited for photophysical
properties, since they are luminescent in solution at room
temperature while methyl analogues only display this behavior
at low temperature. This result supports the fact that the
identity of the remaining ligand in tridentate cycloplatinated
compounds is also crucial in determining whether or not the
compounds are emissive.1b Although C-donor ligands such as
cyanide and acetylide which are able to increase the ligand field
strength have been shown to give good results,1b the methyl
ligand is not such a good choice since, as stated above, it can
provide an efficient pathway for multiphonon relaxation.
Figure 6. Emission spectra of compounds 4 in dichloromethane
solution at 77 K: λexc 405 (4a), 390 (4b), 415 (4c), 400 (4d), 400
(4e), 409 (4f), 402 (4g), 410 nm (4h); concentration 10−4 M; three
slits. Emission spectra are normalized with respect to the strongest
recorded emission maximum for comparison purposes.
CONCLUSIONS
■
The cyclometalated compounds [PtMe{Me2N(CH2)xN
CHR}] (4a−h) with R = C6H4, 2-FC6H3, 4-FC6H3, 2,3,4-
F3C6H were easily obtained from the reaction of [Pt2Me4(μ-
SMe2)2] with the corresponding ligands derived from either
N,N-dimethylpropylene or N,N-dimethylethylenediamine. In
contrast, the synthesis of the corresponding chloro analogues
[PtCl{Me2N(CH2)xNCHR}] (3a−h), carried out from the
corresponding precursors [PtCl2{Me2N(CH2)xNCHAr}]
(2), was found to be more favored for six-membered than for
five-membered [N,N′]-chelates. This result is related to the fact
that for the latter the bidentate ligand adopts the E
conformation and consequently an E−Z isomerization should
precede the cyclometalation step. In addition, for the ligands
2,3,4-F3C6H2CHN(CH2)xNMe2 an unexpected nucleophilic
substitution of a fluoro for a methoxy substituent took place
along the cyclometalation process, leading to the compounds
[PtCl{Me2N(CH2)xNCH(2-OMe,3,4-F2C6H)}] (3g for x =
3 and 3h for x = 2). Further work aimed at analyzing the scope
of this process is currently in progress.
of fluoro substituents can be rationalized by taking into account
the inductive electron-withdrawing and the mesomeric
electron-donating effects of fluorine, which might result in an
decreased or an increased electron density on platinum.3
Compounds 3g,h, which contain a methoxy group at the 2-
position together with fluoro substituents at the 3- and 4-
positions, also display a small red shift in comparison with the
unsubstituted analogues 3e,f. Similar effects in the emission
wavelengths due to the presence of fluoro or methoxy
substituents have been previously reported.3,16
The calculated quantum yields are modest (ca. 10−3) and are
in agreement with the fact that the strongest emission is
recorded for 3d. For each pair of compounds with the same
substituents, the emission is more intense for the compounds
derived from ethylenediamine than for those derived from
propylenediamine (3c > 3a, 3d > 3b, 3f > 3e, and 3h > 3g).
Although the differences are small, this trend is consistent with
the fact that the greater rigidity associated with the five- versus
the six-membered chelates favors luminescence over non-
Cycloplatinated compounds 3a−g are luminescent in the
solid state and in solution at room temperature, and those
containing a [6,5,5]-tricyclic system display higher quantum
566
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Article
CDCl3): δ 8.25 [s, 1H, CHN]; 7.72 [m, 2H, H2,6]; 7.09 [dd, 2H,
yields in comparison to those containing a [6,5,6]-tricyclic
system. Cycloplatinated compounds 4a−g are luminescent in
the solid state and in solution at low temperature. For both
series of cyclometalated platinum compounds, the emission
energies can be tuned by varying the aryl substituents.
4J(H−H) = 2.4, J(F−H) = 8.8, H3, 5]; 3.63 [td, 2H, J(H−H) = 1.2,
3J(H−H) = 7.2, NCH2]; 2.36 [t, 2H, 3J(H−H) = 7.2, CH2NMe2]; 2.24
[s, 6H, NMe2]; 1.87 [qi, 2H, 3J(H−H) = 7.2, CH2CH2CH2]. 19F NMR
(376.5 MHz, CDCl3): δ −109.92 [m, 1F]. CI-MS: 208.9 [M + H]+.
4-FC6H4CHN(CH2)2NMe2 (1d). This compound was prepared as a
pale yellow oil by following the same method from 0.580 g (6.3 mmol)
of 2-dimethylamino-1-ethanamine and 0.880 g (7.1 mmol) of 4-
fluorobenzaldehyde. Yield: 1.119 g (92%). 1H NMR (400 MHz,
CDCl3): δ 8.26 [s, 1H, CHN]; 7.71 [dd, 2H, 4J(F−H) = 5.6, 3J(H−H)
= 8.8, H2,6]; 7.06 [t, 2H, 3J(H−F) = 3J(H−H) = 8.8, H3,5]; 3.71 [t, 2H,
3J(H−H) = 6.8, NCH2]; 2.62 [t, 2H, 3J(H−H) = 6.8, CH2NMe2]; 2.30
[s, 6H, NMe2]. 19F NMR (376,5 MHz, CDCl3): δ −109.79 [m, 1F].
CI-MS: 194.9 [M + H]+.
3
4
EXPERIMENTAL SECTION
■
General Considerations. Microanalyses were performed at the
́
Centres Cientifics i Tecnolog
̀
ics (Universitat de Barcelona).18 Mass
spectra were performed at the Unitat d’Espectrometria de Masses
(Universitat de Barcelona) in a LC/MSD-TOF spectrometer using 1/
1 H2O/CH3CN to introduce the sample (ESI-MS) or in a
ThermoFinnigan TRACE DSQ spectrometer (CI-MS). NMR spectra
were performed at the Unitat de RMN d’Alt Camp de la Universitat de
2,3,4-F3C6H2CHN(CH2)3NMe2 (1g). This compound was prepared
as a yellow oil following the same method from 0.638 g (6.24 mmol)
of 3-dimethylamino-1-propanamine and 1.0 g (6.24 mmol) of 2,3,4-
1
Barcelona using a Mercury-400 (1H, 400 MHz; H−13C HSQC; 13C,
100.6 MHz; 19F, 376.5 MHz) spectrometer and referenced to SiMe4
(1H, 13C) or CFCl3 (19F). δ values are given in ppm and J values in Hz.
Abbreviations used: s, singlet; d, doublet; t, triplet; q, quadruplet; qi,
quintuplet; m, multiplet; br, broad. UV−visible spectra of CH2Cl2
solutions of compounds 1, 3, and 4 were recorded at 298 K with a
Cary 100 scan 388 Varian UV spectrometer, and the emission and
excitation spectra of aerated solutions of compounds 3a−h and 4a−h
were obtained on a Horiba Jobin-Yvon SPEX Nanolog-TM
spectrofluorimeter at 298 K or at 77 K. Deoxygenated solutions of
the compounds have been also used for the estimation of
luminescence lifetimes. This experiments have been done bubbling
N2(g) previously saturated with dichloromethane in order to minimize
the concentration of the sample. Total luminescence quantum yields
were measured at 298 K relative to [Ru(bipy)3]Cl2 in water (ϕ =
0.042) as a standard reference.19 The corresponding absorption of the
complexes used for these measurements is lower than 0.1.
1
trifluorobenzaldehyde. Yield: 0.838 g (55%). H NMR (400 MHz,
CDCl3): δ 8.49 [s, 1H, CHN]; 7.71 [dd, 1H, 3J(H−H) = 8.0, 4J(H−F)
3
= 4.0, H6]; 7.01 [m, 1H, H5]; 3.67 [t, 2H, J(H−H) = 6.8, NCH2];
2.34 [t, 2H, 3J(H−H) = 7.2, CH2NMe2]; 2.24 [s, 6H, NMe2]; 1.86 [qi,
3
2H, J (H−H) = 7.2, CH2CH2CH2]. 19F NMR (376,5 MHz, CDCl3):
δ −131.08 [m, F2]; - 143.07 [dtd, 3J(F−F) = 18.8, 4J(F−F) = 3J(H−F)
4
3
4
= 7.5, J(F−H) = 3.8, F4]; −160.90 [tdd, J(F−F) = 18.8, J(F−H) =
7.5, J(F−H) = 2.2, F3]. CI-MS: 244.7 [M + H]+.
5
[PtCl2{Me2N(CH2)3NCH(2-FC6H4)}] (2a). A mixture formed by
0.303 g (0.72 mmol) of cis-[PtCl2(dmso)2] and 0.153 g (0.73 mmol)
of imine 1a was treated with dry methanol and heated at 65 °C for 4 h
with continuous stirring. The mixture was filtered; the solvent was
evaporated to half volume, allowing crystallization at room temper-
ature. Yield (white solid; mixture of E and Z isomers): 0.223 g (65%).
3
1H NMR (400 MHz, CDCl3): Z isomer δ 10.96 [t, 1H, J(H−H) =
3
8.0, H6]; 8.89 [s, 1H, J(Pt−H) = 118.4, CHN]; 7.68 [m, 1H, H4];
Numbering scheme for NMR data:
7.46 [t, 1H, 3J(H−H) = 8.0, H5]; {5.00 [m, 1H]; 4.21 [m, 1H],
CH2N}; 3.20 [m, 1H, CH2NMe2]; {2.99 [s, 3H]; 2.86 [s, 3H], NMe2};
1
{2.41 [m, 1H]; 1.97 [m, 1H], CH2CH2CH2}. H NMR (400 MHz,
3
CDCl3): E isomer δ 9.35 [s, 1H, J(Pt−H) = 60.0, CHN]; 7.56 [m,
3
3
1H, H4]; 7.37 [t, 1H, J(H−H) = 7.2, H5]; 4.02 [t, 2H, J(H−H) =
6.8, CH2N]; 3.01 [s, 6H, NMe2]; 2.72 [m, 2H, CH2NMe2]; 2.21 [m,
2H, CH2CH2CH2]. 19F NMR (376.5 MHz, CDCl3): δ −110.7 [m, Z
isomer]; − 115.75 [m, E isomer]. ESI (+)-MS: 492.07 [M + NH4]+ ;
439.07 [M − Cl]+; 497.03 [M + Na]+. Anal. Found (calcd for
C12H17Cl2FN2Pt): C, 29.7 (30.39); H, 3.5 (3.62); N, 5.7 (5.92).
[PtCl2{Me2N(CH2)3NCH(4-FC6H4)}] (2b). This compound was
prepared by following the same procedure from 0.302 g (0.72 mmol)
of cis-[PtCl2(dmso)2] and 0.153 g (0.73 mmol) of imine 1b. Yield (off-
white solid; Z isomer): 0.165 g (49%). 1H NMR (400 MHz, CDCl3):
3
δ 9.34 [m, 2H, H2,6]; 8.47 [s, 1H, J(Pt−H) = 115.6, CHN]; 7.27 [t,
3
3
2H, J(H−F) = J(H−F) = 8.0, H3,5]; {4.93 [m, 1H]; 4.13 [m, 1H],
CH2N}; {3.20 [m, 1H]; 2.72 [m, 1H], CH2NMe2}; {2.97 [s, 3H]; 2.84
[s, 3H], NMe2}; {2.50 [m, 1H]; 1.97 [m, 1H], CH2CH2CH2}. 19F
NMR (376.5 MHz, CDCl3): δ −101.64 [m]. ESI (+)-MS: 492.08 [M
+ NH4]+ ; 971.01 [2 M + Na]+. Anal. Found (calcd for
C12H17Cl2FN2Pt): C, 31.1 (30.39); H, 3.6 (3.62); N, 5.5 (5.92).
[PtCl2{Me2N(CH2)2NCH(2-FC6H4)}] (2c). This compound was
prepared by following the same procedure from 0.301 g (0.71
mmol) of cis-[PtCl2(dmso)2] and 0.160 g (0.82 mmol) of imine 1c.
Preparation of the Complexes. The compounds cis-
[PtCl2(dmso)2]20 and [Pt2Me4(μ-SMe2)2],21 ligands 1c,f,h13 and
1e,5 and compounds 2e and 3e,5 2f and 3f,6 and 4c,f,h14 were
prepared as reported elsewhere.
2-FC6H4CHN(CH2)3NMe2 (1a). This compound was obtained
from the reaction of 0.500 g (4.9 mmol) of 3-dimethylamino-1-
propanamine with 0.610 g (4.9 mmol) of 2-fluorobenzaldehyde in 20
mL of toluene. The reaction mixture was stirred at room temperature
for 2 h, sodium sulfate was added and filtered off, and the solvent was
1
1
Yield (yellow solid; E isomer): 0.149 g (45%). H NMR (400 MHz,
removed under vacuum to give a yellow oil. Yield: 0.969 g (95%). H
3
CDCl3): δ 9.60 [s, 1H, J(Pt−H) = 57.6, CHN]; 7.60 [m, 1H, H4];
NMR (400 MHz, CDCl3): δ 8.25 [s, 1H, CHN]; 7.96 [dd, 1H, 3J(H−
7.44 [d, 1H, 3J(H−H) = 7.6, H6]; 7.30 [td, 1H, 4J(H−H) = 1.2, 3J(H−
3
3
H) = 2.0, J(H−H) = 7.6, H6]; 7.38 [m, 1H, H5]; 7.17 [t, 1H, J(H−
H) = 7.6, H5]; 7.19 [t, 1H, 3J(F−H) = 9.2, H3]; 3.82 [t, 2H, 3J(H−H)
H) = 7.6, H4]; 7.07 [ddd, 1H, 4J(H−H) = 1.2, J(H−H) = 8.4, J(F−
H) = 10.4, H3]; 3.68 [td, 2H, 4J(H−H) = 1.6, 3J(H−H) = 7.2, NCH2];
2.37 [t, 2H, 3J(H−H) = 7.2, CH2NMe2]; 2.26 [s, 6H, NMe2]; 1.89 [qi,
2H, 3J(H−H) = 7.0, CH2CH2CH2]. 19F NMR (376,5 MHz, CDCl3): δ
−122.09 [m, 1F]. CI-MS: 208.9 [M + H]+ .
3
3
3
= 6.0, CH2N]; 3.12 [s, 6H, J(Pt−H) = 33.2, NMe2]; 2.67 [t, 2H,
3J(H−H) = 6.0, CH2NMe2]. 19F NMR (376.5 MHz, CDCl3): δ
−108.32 [m]. ESI (+)-MS: 478.06 [M + NH4]+ ; 483.01 [M + Na]+ .
Anal. Found (calcd) for C11H15Cl2FN2Pt): C 28.4 (28.71); H 2.9
(3.29); N 6.3 (6.10).
4-FC6H4CHN(CH2)3NMe2 (1b). This compound was prepared as a
yellow oil by following the same method from 0.510 g (5.0 mmol) of
3-dimethylamino-1-propanamine and 0.620 g (5.0 mmol) of 4-
fluorobenzaldehyde. Yield: 0.912 g (88%). 1H NMR (400 MHz,
[PtCl2{Me2N(CH2)2NCH(4-FC6H4)}] (2d). This compound was
prepared by following the same procedure from 0.302 g (0.71 mmol)
of cis-[PtCl2(dmso)2] and 0.150 g (0.82 mmol) of imine 1d. Yield
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Organometallics
Article
(yellow solid; E isomer): 0.131 g (43%). 1H NMR (400 MHz,
CDCl3): δ 9.47 [s, 1H, 3J(Pt−H) = 54.4, CHN]; 7.58 [dd, 2H, 4J(F−
3J(H−Pt) = 36.0, 2H, NCH2]; 2.85 [m, 8H, NMe2 + CH2NMe2]; 2.02
[qi, 2H, 3J(H−H) = 5.3, CH2CH2CH2]. 19F NMR (376.5 MHz,
CDCl3): δ −104.07 [m, 1F]. 13C NMR (100.6 MHz, CDCl3): δ 27.23
[3J(C−Pt) = 31.0, CH2CH2CH2]; 50.19 [NMe2]; 57.50 [2J(C−Pt) =
3
3
3
H) = 5.6, J(H−H) = 8.0, H2,6]; 7.19 [t, 2H, J(H−F) = J(H−H) =
3
8.4, H3,5]; 4.04 [t, 2H, J(H−H) = 6.0, CH2N]; 3.13 [s, 6H, NMe2];
2.69 [t, 2H, 3J(H−H) = 6.0, H7]. 19F-NMR (376,5 MHz, CDCl3): δ −
104.40 [m]. ESI (+)-MS: 478.06 [M + NH4]+ ; 483.02 [M + Na]+.
Anal. Found18 (calcd for C11H15Cl2FN2Pt): C, 28.5 (28.71); H, 3.1
(3.29); N, 6.1 (6.10).
2
38.0, NCH2]; 64.12 [CH2NMe2]; 110.37 [d, J(C−F) = 24.1, C3];
2
3
121.17 [d, J(C−F) = 20.1, C5]; 129.01 [d, J(C−F) = 10.1, C2];
141.00 [d, 4J(C−F) = 2.0, C1]; 146.00 [d, 3J(C−F) = 7.0, C6]; 163.54
[d, 1J(C−F) = 257.5, C4]; 175.13 [2J(C−Pt) = 96.6, CHN]. ESI
(+)-MS: 439.07 [M + H]+ ; 456.10 [M + NH4]+ . Anal. Found18
(calcd for C12H16ClFN2Pt): C, 32.0 (32.92); H, 3.7 (3.68); N, 6.3
(6.40).
[PtCl2{Me2N(CH2)3NCH(2,3,4-F3C6H)}] (2g). This compound was
prepared by following the same procedure from 0.319 g (0.71 mmol)
of cis-[PtCl2(dmso)2] and 0.173 g (0.71 mmol) of imine 1g. Yield (off-
1
white solid; mixture of E and Z isomers): 0.265 g (73%). H NMR
[PtCl{Me2N(CH2)2NCH(2-FC6H3)}] (3c). This compound was
prepared by following method 2 from 0.150 g of 2c and an equimolar
amount of sodium acetate and increasing the reaction time to 72 h.
(400 MHz, CDCl3): Z isomer δ 10.75 [m, 1H]; 9.04 [s, 1H, 3J(Pt−H)
= 120.0, CHN]; 7.29 [m, 1H]; {5.00 [m, 1H]; 4.26 [ddd, 1H, J(H−
H) = 11.2, 6.8, 2.0], CH2N}; {2.97 [s, 3H]; 2.86 [s, 3H], NMe2}; 2.73
1
Yield (orange solid): 44 mg (32%). H NMR (400 MHz, CDCl3): δ
1
4
3
[m, 2H,CH2NMe2]; {2.48 [m, 1H]; 2.01 [m, 1H], CH2CH2CH2}. H
8.62 [t, 1H, J(H−H) = 1.2, J(Pt−H) = 144.4, CHN]; 7.29 [m, 1H,
3
H3]; 7.23 [t, J(H−H) = 7.8, 1H, H4]; 6.47 [d, 1H, J(H−H) = 8.1,
3
3
NMR (400 MHz, CDCl3): E isomer δ 9.33 [s, 1H, J(Pt−H) = 56.0,
CHN]; 7.18−7.14 [m, 2H]; 4.03 [t, 2H, 3J(H−H) = 6.8, CH2N]; 3.00
[s, 6H, NMe2]; 2.73 [m, 2H, CH2NMe2]; 2.24 [m, 2H, CH2CH2CH2].
19F NMR (376,5 MHz, CDCl3): Z isomer δ −122.53 [m, 1F, F2]; −
H5]; 4.03 [td, 2H, J(H−H) = 6.0, J(H−H) = 1.2, J(H−Pt) = 34.4,
NCH2]; 3.10 [t, 2H, 3J(H−H) = 6.0, CH2NMe2]; 2.89 [s, 3J(H−Pt) =
14.8, 6H, NMe2]. 19F NMR (376.5 MHz, CDCl3): δ −108.14 [m, 1F].
ESI (+)-MS: 423.06 [M + H]+. Anal. Found18 (calcd for
C11H14ClFN2Pt): C, 31.9 (31.20); H, 4.0 (3.33); N, 6.1 (6.62).
[PtCl{Me2N(CH2)2NCH(4-FC6H3)}] (3d). This compound was
prepared by following method 2 from 0.150 g of 2d and the
equimolar amount of sodium acetate and increasing the reaction time
3
4
3
3
4
3
135.92 [dddd, 1F, J(F−F) = 22.6, J(F−F) = 15.2, J(F−H) = 7.6,
3J(F−H) = 3.8, F4]; − 158.97 [tdd, 1F, J(F−F) = 22.5, J(F−H) =
3
4
7.6, J(F−H) = 3.8, F3]. 19F NMR (376,5 MHz, CDCl3): E isomer: δ
5
3
−125.98 [m, 1F]; − 130.76 [m, 1F]; − 157.03 [tdd, 1F, J(F−F) =
18.8, J(F−H) = 7.6, J(F−H) = 3.8, F3]. ESI (+)-MS: 528.06 [M +
NH4]+; 475.05 [M − Cl]. Anal. Found (calcd) for C12H15Cl2F3N2Pt:
C, 28.0 (28.29); H, 3.0 (2.97); N, 5.7 (5.50).
4
5
1
to 72 h. Yield (orange solid): 40 mg (29%). H NMR (400 MHz,
CDCl3): δ 8.26 [s, 1H, 3J(Pt−H) = 141.2, CHN]; 7.41 [dd, 1H, 3J(F−
H) = 9.5, 4J(H−H) = 2.8, 3J(H−Pt) = 50.8, H5]; 7.24 [dd, 1H, 3J(H−
[PtCl2{Me2N(CH2)2NCH(2,3,4-F3C6H)}] (2h). This compound was
prepared by following the same procedure from 0.300 g (0.71 mmol)
of cis-[PtCl2(dmso)2] and 0.163 g (0.71 mmol) of imine 1h. Yield
(yellow solid; E isomer): 0.250 g (71%). 1H NMR (400 MHz,
H) = 8.0, J(H−F) = 5.6, H2]; 6.69 [td, 1H, J(F−H) = J(H−H) =
8.8, 4J(H−H) = 2.8, H3]; 4.06 [t, 2H, 3J(H−H) = 6.0, NCH2]; 3.11 [t,
2H, 3J(H−H) = 6.0, CH2NMe2]; 2.90 [s, 6H, NMe2]. 19F NMR (376.5
MHz, CDCl3): δ −102.92 [m, 1F]. ESI (+)-MS: 442.08 [M + NH4]+.
Anal. Found (calcd for C11H14ClFN2Pt): C, 30.7 (31.20); H, 3.4
(3.33); N, 6.7 (6.62).
4
3
3
3
CDCl3): δ 9.59 [s, 1H, J(Pt−H) = 48.0, CHN]; 7.34 [m, 1H]; 7.16
3
[m, 1H]; 3.87 [t, 2H, J(H−H) = 6.0, CH2N]; 3.13 [s, 6H, NMe2];
3
2.71 [t, 2H, J(H−H) = 6.0, H7]. 19F NMR (376,5 MHz, CDCl3): δ
3
4
3
[PtCl{Me2N(CH2)3NCH(2-OMe,3,4-F2C6H)}] (3g). This compound
was prepared following method 2 from 0.150 g of 2g and an equimolar
amount of sodium acetate and increasing the reaction time to 72 h.
−125.34 [dddd, 1F, J(F−F) = 18.8, J(F−F) = 15.0, J(F−H) = 7.5,
4J(F−H) = 3.8, F4]; − 128.91 [m, 1F, F2]; − 156.80 [tdd, 1F, 3J(F−F)
= 18.8, 4J(F−H) = 7.5, 5J(F−H) = 3.8, F3]. ESI (+)-MS: 514.04 [M +
NH4]+. Anal. Found (calcd for C11H13Cl2F3N2Pt): C, 26.0 (26.66); H,
3.2 (2.65); N, 5.3 (5.66).
1
Yield (orange solid): 40 mg (28%). H NMR (400 MHz, CDCl3): δ
8.59 [s, 1H, 3J(Pt−H) = 144.0, CHN]; 7.48 [dd, 1H, 3J(F−H) = 11.5,
5
4J(H−F) = 7.5, H5]; 4.01 [d, 3H, J(H−F) = 4.0, OMe]; 3.86 [t, 2H,
[PtCl{Me2N(CH2)3NCH(2-FC6H3)}] (3a). This compound was
obtained using method 1: a mixture of 0.250 g (0.59 mmol) of cis-
[PtCl2(dmso)2], 0.128 g (0.61 mmol) of imine 1a, and 0.050 g (0.61
mmol) of sodium acetate in 20 mL of dry methanol was refluxed for
48 h. Upon evaporation of the solvent to 10 mL, small amounts of
compound 2a and metallic platinum were filtered off, and the solution
was kept at 5 °C until crystallization was completed. The solid was
recrystallized in CH2Cl2/ MeOH to produce orange crystals. Yield: 22
mg (9%). Alternatively, compound 3a was prepared using method 2: a
mixture of 0.150 g (0.316 mmol) of compound 2a and 0.026 g (0.316
mmol) of sodium acetate in 20 mL of dry methanol was heated under
reflux for 48 h, and the solvent was evaporated to produce an oily
residue that was extracted with 5 mL of CH2Cl2. Methanol was added,
and the solution was kept at 5 °C until crystallization was completed.
Yield (orange solid): 60 mg (43.3%). 1H NMR (400 MHz, CDCl3): δ
3J(H−H) = 4.0, NCH2]; 2.83 [m, 8H, NMe2 + CH2NMe2]; 2.01 [m,
2H, CH2CH2CH2]. 19F NMR (376.5 MHz, CDCl3): δ −127.20 [dd,
3
3
4
1F, J(F−F) = 18.8, J(H−F) = 11.3, J(H−Pt) = 45.2, F4]; − 163.15
[ddq, 1F, J(F−F) = 18.8, J(H−F) = 7.5, J(H−F) = 3.8, F3]. HR-
ESI(+)-MS: m/z 486.0705, calcd for C13H18F2ClN2OPt [M + H]+
486.0718; 450.0937, calcd for C13H17F2N2OPt [M − Cl]+ 450.0951.
Anal. Found (calcd for C13H17F2ClN2OPt): C, 31.7 (32.16); H, 3.5
(3.53); N, 5.6 (5.77).
3
4
5
[PtCl{Me2N(CH2)2NCH(2-OMe,3,4-F2C6H)}] (3h). This compound
was prepared by following method 2 from 0.150 g of 2h and an
equimolar amount of sodium acetate and increasing the reaction time
1
to 72 h. Yield (orange solid): 42 mg (29%). H NMR (400 MHz,
CDCl3): δ 8.56 [s, 1H, 3J(Pt−H) = 140.0, CHN]; 7.17 [dd, 1H, 3J(F−
4
H) = 11.5, J(H−F) = 7.5, H5]; 4.06 [t, 2H, 3J(H−H) = 6.0, NCH2];
5
3
4
3
4.02 [d, 3H, J(H−F) = 3.2, OMe]; 3.01 [t, 2H, J(H−H) = 6.0,
8.67 [t, 1H, J(H−H) = 1.6, J(Pt−H) = 142.4, CHN]; 7.80 [d, 1H,
CH2NMe2]; 2.89 [s, 6H, J(Pt−H) = 15.2, NMe2]. 19F NMR (376.5
3
3J(H−H) = 8.0, J(H−Pt) = 40.0, H5]; 7.20 [m, 1H, H4]; 6.64 [ddd,
3
3
3
1H, J(H−H) = 0.8, J(H−H) = 8.0, J(F−H) = 10.0, H3]; 3.92 [m,
2H, NCH2]; 2.86 [m, 2H, CH2NMe2]; 2.85 [s, 6H, NMe2]; 2.04 [qi,
2H, 3J(H−H) = 5.2, CH2CH2CH2]. 19F NMR (376.5 MHz, CDCl3): δ
4
3
3
MHz, CDCl3): δ −126.14 [dd, 1F, J(F−F) = 18.8, J(H−F) = 12.0,
F4]; − 163.00 [ddq, 1F, J(F−F) = 18.8, J(H−F) = 7.5, J(H−F) =
3.8, F3]. ESI (+)-MS: 472.05 [M + H]+. Anal. Found (calcd for
C12H15F2ClN2OPt): C, 30.4 (30.57); H, 3.4 (3.21); N, 5.8 (5.94).
[PtMe{Me2N(CH2)3NCH(2-FC6H3)}] (4a). This compound was
obtained using the following procedure: 0.100 g (0.17 mmol) of
[Pt2Me4(μ-SMe2)2] and 0.072 g (0.34 mmol) of imine 1a were
dissolved in 20 mL of toluene, and the obtained solution was refluxed
for 1 h. The solvent was removed, and the residue was treated with
3
4
5
3
4
4
− 115.00 [dd, J(F−H) = 9.8, J(F−H) = 6.0, J(Pt−F) = 56.5]. ESI
(+)-MS: 438.08 [M + H]+ ; 461.06 [M + Na]+. Anal. Found18 (calcd
for C12H16ClFN2Pt): C, 33.1 (32.92); H, 3.7 (3.68); N, 6.1 (6.40).
[PtCl{Me2N(CH2)3NCH(4-FC6H3)}] (3b). This compound was
prepared by following method 2 from 0.150 g of 2b and an equimolar
1
amount of sodium acetate. Yield (orange solid): 50 mg (36.0%). H
1
NMR (400 MHz, CDCl3): δ 8.32 [t, 1H, 4J(H−H) = 1.6, 3J(Pt−H) =
141.6, CHN]; 7.72 [dd, 1H, 3J(H−Pt) = 40.0, 3J(F−H) = 10.0, 4J(H−
H) = 2.4, H5]; 7.24 [dd, 1H, 3J(H−H) = 8.0, 4J(H−F) = 4.0, H2]; 6.70
diethyl ether to give a red solid. Yield: 115 mg (79%). H NMR (400
3
MHz, CDCl3): δ 8.91 [s, 1H, J(Pt−H) = 60.4, CHN]; 7.44 [d, 1H,
3J(Pt−H) = 64.0, J(H−H) = 8.0, H5]; 7.17 [td, 1H, J(H−H) = 8.0,
3
3
[td, 1H, J(F−H) = J(H−H) = 8.5, J(H−H) = 2.4, H3]; 3.86 [m,
4J(H−F) = 6.4, H4]; 6.61 [ddd, 1H, 3J(F−H) = 10.4, J(H−H) = 8.0,
3
3
4
3
568
dx.doi.org/10.1021/om401111t | Organometallics 2014, 33, 561−570

Organometallics
Article
4J(H−H) = 0.8, H3]; 3.89 [m, 2H, NCH2]; 2.91 [m, 2H, CH2NMe2];
integration of the data using a monoclinic unit cell yielded a total of
14556 reflections to a maximum θ angle of 30.54° (0.70 Å resolution),
3778 of which were independent and 3142 were greater than 2σ(F2).
The structures were solved and refined using the Bruker SHELXTL
software package.22 Further information is given in Table S1
(Supporting Information).
3
3
2.73 [s, 6H, J(Pt−H) = 24.0, NMe2]; 2.03 [qi, 2H, J(H−H) = 5.6,
CH2CH2CH2]; 1.02 [s, 3H, 2J(Pt−H) = 80.0, Me-Pt]. 19F NMR
(376.5 MHz, CDCl3): δ −117.53 [dd, 1F, 3J(F−H) = 11.3, 4J(F−H) =
7.5, 4J(Pt−F) = 56.5]. ESI (+)-MS: 443.12 [M − H + CH3CN]+. Anal.
Found (calcd for C13H19FN2Pt): C, 37.8 (37.41); H, 4.8 (4.59); N, 6.3
(6.71).
[PtMe{Me2N(CH2)3NCH(4-FC6H3)}] (4b). This compound was
obtained by using the same procedure from 0.100 g (0.17 mmol) of
[Pt2Me4(μ-SMe2)2] and 0.078 g (0.35 mmol) of imine 1b. Yield (red
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF files for 3b,g. Asymmetric unit of 3b constituted by eight
unequivalent molecules (Figure S1), unit cell of 3b (Figure S2),
antiparallel disposition of the 3D structure of 3g (Figure S3),
unit cell of 3g (Figure S4), normalized emission spectra of 3c in
solution (solid line) and in the solid state (dashed line) (Figure
S5), normalized emission spectra of 4c in solution (solid line)
and in the solid state (dashed line) (Figure S6), excitation
spectra of compounds 3 collected at the corresponding
emission maxima at room temperature (Figure S7), emission
spectra of a dichloromethane solution of compound 3c at three
different concentrations (λexc = 400 nm, three slits; Figure S8),
1H and 19F NMR spectra of compounds 2d, 3a−c, and 4d
(Figures S9−S13), and crystallographic and refinement data for
compounds 3b,g (Table S1). This material is available free of
charge via the Internet at http://pubs.acs.org.
1
solid): 105 mg (72%). H NMR (400 MHz, d6-acetone): δ 8.66 [s,
1H, 3J(Pt−H) = 62.8, CHN]; 7.32 [m, 1H, H2]; 7.21 [dd, 1H, 3J(H−
4
3
F) = 11.2, J(H−H) = 2.5, J(Pt−H) = 35.6, H5]; 6.60 [ddd, 1H,
3J(F−H) = 9.1, J(H−H) = 8.0, J(H−H) = 2.0, H3]; 3.85 [t, 2H,
J(H−H) = 5.0, NCH2]; 2.87 [m, 2H, CH2NMe2]; 2.66 [s, 6H, 3J(Pt−
H) = 23.3, NMe2]; 1.99 [m, 2H, CH2CH2CH2]; 0.81 [s, 3H, 2J(Pt−H)
= 81.7, Me-Pt]. 19F-NMR (376.5 MHz, CDCl3): δ −107.58 [ddd, 1F,
3J(F−H) = 11.3, 3J(F−H) = 7.5, 4J(F−H) = 3.7, 4J(F−Pt) = 71.5]. ESI
(+)-MS: 443.12 [M − H + CH3CN]+. Anal. Found (calcd for
C13H19FN2Pt·2H2O): C, 34.5 (34.44); H, 4.8 (5.11); N, 6.0 (6.17).
[PtMe{Me2N(CH2)2NCH(4-FC6H3)}] (4d). This compound was
obtained by using the same procedure from 0.100 g (0.17 mmol) of
[Pt2Me4(μ-SMe2)2] and 0.068 g (0.35 mmol) of imine 1d. Yield (red
3
4
1
solid): 109 mg (77%). H NMR (400 MHz, d6-acetone): δ 8.71 [s,
3
3
4
1H, J(Pt−H) = 61.0, CHN]; 7.30 [dd, J(H−H) = 8.0, J(H−F) =
6.0, 4J(H−Pt) = 27.0, 1H, H2]; 7.10 [dd, 1H, 3J(H−F) = 10.4, 4J(H−
H) = 2.6, 3J(Pt−H) = 85.0, H5]; 6.57 [ddd, 1H, 3J(F−H) = 9.2, 3J(H−
H) = 8.0, J(H−H) = 2.6, H3]; 4.11 [t, 2H, J(H−H) = 6.0, NCH2];
3.18 [t, 2H, 3J(H−H) = 6.0, CH2NMe2]; 2.77 [s, 6H, 3J(Pt−H) = 21.0,
NMe2]; 0.77 [s, 3H, 2J(Pt−H) = 79.0, Me-Pt]. 19F NMR (376.5 MHz,
4
3
AUTHOR INFORMATION
Corresponding Author
*M.C.: tel, +34934039132; fax, +34934907725; e-mail,
margarita.crespo@qi.ub.es. L.R.: tel, +34934039130; fax,
+34934907725; e-mail, laura.rodriguez@qi.ub.es.
■
CDCl3): δ −106.64 [td, 1F, 3J(F−H) = 9.5, J(F−H) = 5.9, J(F−Pt)
= 88.0]. ESI (+)-MS: 429.10 [M - H + CH3CN]+; 401.09 [M - Me +
CH3CN]+. Anal. Found18 (calcd for C12H17FN2Pt): C, 34.5 (35.72);
H, 4.2 (4.25); N, 6.7 (6.95).
4
4
Notes
[PtMe{Me2N(CH2)3NCHC6H4}] (4e). This compound was ob-
tained by using the same procedure from 0.100 g (0.17 mmol) of
[Pt2Me4(μ-SMe2)2] and 0.065 g (0.35 mmol) of imine 1e. Yield (red
solid): 95 mg (69%). 1H NMR (400 MHz, d6-acetone): δ 8.49 [s, 1H,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by the Ministerio de Ciencia y
■
3
3
3J(Pt−H) = 60.0, CHN]; 7.61 [d, J(H−H) = 7.6, J(H−Pt) = 64.0,
́
1H, H5]; 7.20 [m, 1H]; 7.07 [t, 1H, 3J(H−H) = 8.2, H4]; 6.88 [t, 1H,
Tecnologıa (project CTQ2009-11501) and by the Ministerio
3
3J(H−H) = 7.4, H3]; 3.78 [t, 2H, J(H−H) = 4.8, NCH2]; 2.84 [m,
́
de Economıa y Competitividad (project CTQ2012-31335).
3
2H, CH2NMe2]; 2.66 [s, 6H, J(Pt−H) = 22.4, NMe2]; 1.95 [qi, 2H,
3J(H−H) = 5.5, CH2CH2CH2]; 0.93 [s, 3H, 2J(Pt−H) = 81.0, Me-Pt].
ESI (+)-MS: 425.13 [M − H + CH3CN]+; 383.10 [M − Me]+. Anal.
Found (calcd for C13H20N2Pt·H2O): C, 37.1 (37.41); H, 5.0 (5.31);
N, 6.1 (6.71).
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1
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4
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for absorption effects using the multiscan method. For 3g, the
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