Polypyridyl-functionalizated alkynyl gold(i) metallaligands supported by tri- and tetradentate phosphanes

Article abstract of DOI:10.1039/c7dt02732j

A series of alkynyl gold(i) tri and tetratopic metallaligands of the type [Au₃(CC-R)₃(μ₃-triphosphane)] (R = 2,2′-bipyridin-5-yl or C₁₀H₇N₂, 2,2′:6′,2′′-terpyridin-4-yl or C₁₅H₁₀N₃; triphosphane = 1,1,1-tris(diphenylphosphanyl)ethane or triphos, 1,3,5-tris(diphenylphosphanyl)benzene or triphosph) and [Au₄(CC-R)₄(μ₄-tetraphosphane)] (R = C₁₀H₇N₂, C₁₅H₁₀N₃; tetraphosphane = tetrakis(diphenylphosphanylmethyl)methane or tetraphos, 1,2,3,5-tetrakis(diphenylphosphanyl)benzene or tpbz, tetrakis(diphenylphosphaneylmethyl)-1,2-ethylenediamine or dppeda) were obtained in moderate to good yields. All complexes could be prepared by a reaction between the alkynyl gold(i) polymeric species [Au(CC-R)]_n and the appropriate polyphosphane. An alternative strategy that required the previous synthesis of the appropriate acetylacetonate precursors [Au_n(acac)_n(μ_n-polyphosphane)] ("acac method") was assayed, nevertheless only the polyacac derivatives [Au₃(acac)₃(μ₃-triphosphane)] (triphosphane = triphos and triphosph) and [Au₄(acac)₄(μ₄-tetraphos)] could be isolated and characterized. All compounds were characterized by IR, multinuclear NMR spectroscopy and ESI(+) mass spectrometry. The X-ray crystal structure of complexes [Au₄(CC-C₁₀H₇N₂)₄(μ₄-tetraphos)] and [Au₄(CC-C₁₀H₇N₂)₄(μ₄-tpbz)] showed the involvement of all the gold atoms in close intramolecular Au?Au contact as well as intermolecular π stacking interactions between the aromatic rings of the polypyridyl ligands. The photophysical properties of the synthesized compounds were carefully studied and used as a probe of their possible use as multidentate ligands for Cu(i) and Zn(ii). The UV-Vis speciation studies of the complexation reactions were conducted via metal titration and, in most cases the dangling units of the ligand were found to behave in a fairy independent manner. While in the case of Cu(i) multiple equilibria exist in solution a single complex is detected for Zn(ii) under the conditions studied.

Full text of DOI:10.1039/c7dt02732j

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Dalton Trans., 2017, DOI: 10.1039/C7DT02732J.
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Polypyridylꢀfunctionalizated alkynyl gold(I) metallaligands
supported by triꢀ and tetradentate phosphanes
Montserrat Ferrer,a,* Leticia Giménez,a Albert Gutiérrez,a Joao Carlos Lima,b Laura
Rodríguez,a,c Manuel Martínez,a Avelino Martín,d Rakesh Puttreddy e and Kari
Rissanene
a Departament de Química Inorgànica i Orgànica, Secció de Química Inorgànica.
Universitat de Barcelona, c/ Martí i Franquès 1-11 08028 Barcelona, Spain.
b LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, Monte
de Caparica, Portugal.
c Institut de Nanociència i Nanotecnologia (IN2UB). Universitat de Barcelona, 08028
Barcelona, Spain
d.Departamento de Química Inorgánica, Campus Universitario-Edificio de Farmacia,
Universidad de Alcalá, 28871 Alcalá de Henares, Spain
e Department of Chemistry, University of Jyväskylä, POB 35, 40014 Jyväskylä, Finland
Abstract
A series of alkynyl gold(I) tri and tetratopic metallaligands of the type [Au3(C≡Cꢀ
R)3(ꢁ3ꢀtriphosphane)] (R = 2,2’ꢀbipyridinꢀ5ꢀyl or C10H7N2, 2,2’:6’,2’’ꢀterpyridinꢀ4ꢀyl or
C15H10N3; triphosphane = 1,1,1ꢀtris(diphenylphosphanyl)ethane or triphos, 1,3,5ꢀ
tris(diphenylphosphanyl)benzene or triphosph) and [Au4(C≡CꢀR)4(ꢁ4ꢀtetraphosphane)]
(R = C10H7N2, C15H10N3; tetraphosphane = tetrakis(diphenylphosphanylmethyl)methane
or
tetraphos,
1,2,3,5ꢀtetrakis(diphenylphosphanyl)benzene
or
tpbz,
tetrakis(diphenylphosphaneylmethyl)ꢀ1,2ꢀethylenediamine or dppeda) were obtained in
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moderate to good yields. All complexes could be prepared by reaction between the
alkynyl gold(I) polymeric species [Au(C≡CꢀR)]n and the adequate polyphosphane. An
alternative strategy that required the previous synthesis of the appropriate
acetylacetonate precursors [Aun(acac)n(ꢀnꢀpolyphosphane)] (“acac method”) was
assayed, nevertheless only the polyacac derivatives [Au3(acac)3(ꢀ3ꢀtriphosphane)]
(triphosphane = triphos, triphosph) and [Au4(acac)4(ꢀ4ꢀtetraphos)] could be isolated and
characterized.
All compounds were characterized by IR, multinuclear NMR spectroscopy and ESI(+)
mass spectrometry. The Xꢀray crystal structure of complexes [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀ
tetraphos)] and [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtpbz)] showed the involvement of all the gold
atoms in close intramolecular Au···Au contacts as well as intermolecular π stacking
interactions between the aromatic rings of the polypyridyl ligands.
The photophysical properties of the synthesized compounds were carefully studied and
used as a probe of their possible use as multidentate ligands for Cu(I) and Zn(II). The
UVꢀVis speciation studies of the complexation reactions were conducted via metal
titration and, in most of cases the dangling units of the ligand have found to behave in a
fairy independent way. While in the case of Cu(I) multiple equilibria exist in solution a
single complex is detected for Zn(II) under the conditions studied.
Introduction
Gold(I) molecular materials have become an evolving field of research in late decades
due to their promising applications in such fields as sensing,1ꢀ3 nonꢀlinear optics,4ꢀ6
catalysis,7ꢀ10 therapeutics11ꢀ13 and bioimaging.11, 12, 14 This interest in gold(I) complexes
mainly arise from their rich luminescence properties1, 15ꢀ19 as well as their predisposition
to establish aurophilic interactions.20ꢀ24
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In particular, gold(I) alkynyl systems25, 26 are specially attractive due to the preference
for linear twoꢀcoordinate geometry of gold(I), together with the linearity of the alkynyl
unit and its πꢀunsaturated nature. These privileged features have made alkynyl gold(I)
complexes ideal candidates as building blocks to assemble a great variety of
organometallic supramolecular structures that frequently present aurophilic interactions
and significant luminescent properties.22, 27ꢀ37
In addition to the possibility of establishing aurophilic interactions, the functionalization
of the alkynyl moiety with Nꢀ donor groups in gold(I) alkynyl compounds provides an
alternative and/or complementary approach to obtain heterometallic and/or
multicomponent complexes with a wide range of geometries. With this in mind, we
synthesized a series of phosphane gold(I) ethynylpyridine complexes that, in spite of
bearing terminal Nꢀdonor pyridine groups,38, 39 did not allow to build up heterometallic
assemblies. All the attempts to use the named pyridine derivatives in selfꢀassembly
reactions resulted in either complex mixtures in solution or very insoluble materials that
could not be characterized.
After the failure of the pyridine appended gold(I) species to act as metallaligands, and
as a rational extension of our studies, we directed our attention to the use of
polypyridylꢀfunctionalized alkynyl ligands such as 5ꢀethynylꢀ2,2’ꢀbipyridine and 4’ꢀ
ethynylꢀ2,2’:6’,2’’ꢀterpyridine to obtain our targeted gold(I) donor compounds. These
polydentate Nꢀ donors should facilitate and stabilize the coordination of a wide range of
dꢀ and fꢀblock metallic units through polypyridyl chelation to the prefabricated gold(I)
akynyl compounds.40 Moreover, the possibility of the incorporation of photoꢀ and/or
redoxꢀactive metal fragments in combination with the known luminescent properties of
alkynyl gold(I) compounds could give rise to interesting properties suitable for potential
applications.
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In fact, some research groups have recently described the synthesis of alkynyl gold(I)
47ꢀ50
complexes with terminal 2,2’ꢀbipyridine41ꢀ46 or 2,2’:6’,2’’ꢀterpyridine units.41,
Interestingly, however, in spite of the stability of these metallaligands, a limited number
of reports on the supramolecular coordination chemistry of these species can be found
in the literature. Some years ago, Chem and col. described the isolation of tetrametallic
Au2Ln2 (Ln= lanthanide) arrays formed by the establishment of aurophilic
interactions.42 Very recently, Vicente and col. reported the obtention of appealing
supramolecular architectures like tripleꢀstranded helicates,51, 52 helical dimers,53 rigidꢀ
rod complexes and coordination oligomers.54
Noteworthy, all the reported alkynyl gold(I) compounds with pendant polypyridyl
moieties mentioned above are supported by mono or diphosphanes as auxiliary ligands,
and consequently are able to act as mono or ditopic metallaligands. However, neither tri
nor tetratopic analogous systems have been described so far. Indeed, although
phosphanes and diphosphanes have been widespread used as ligands in the chemistry of
alkynyl gold(I) compounds,25 the number of derivatives based on tri or tetradentate
phosphanes is rather limited,36, 39, 55ꢀ59 despite their potential in the construction of
multimetallic assemblies. The use of tri or tetratopic building blocks should increase the
complexity of the obtained heterometallic frameworks, allowing the obtention of
architectures with a great diversity of nuclearities and/or topologies and unique
properties.60
Given these considerations, we describe herein the preparation and characterization of a
series of different tri and tetraphosphane alkynyl gold(I) derivatives with appended
bipyridine or terpyridine moieties, suitable for participating in coordination reactions.
The photophysical properties of the synthesised compounds together with a preliminary
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spectrophotometric study of how these properties are modified when they coordinate to
d10 ions like Cu(I) and Zn(II) are also reported.
Results and discussion
Synthesis of poly(diphenylphosphanyl)benzene ligands
The triꢀ and tetraphosphanes with benzene core used in this work (i. e. triphosph and
tpbz) are interesting and versatile ligands in coordination chemistry due to the
possibility of obtaining polynuclear derivatives. However, they have been barely
explored most probably owing to their laborious and no reproducible synthesis. Since
their preparation from PPh3 and Na metal in dry liquid ammonia described by
McFarlane and col., only one report dealing with an improved obtention of tpbz (from
PPh2Cl and Na metal in THF as starting materials) can be found in the literature.61
However, the latter method is time consuming and the reported yield is only moderate.
In this work we have improved significantly the synthesis of both
poly(diphenylphosphanyl)benzene ligands by refluxing 4 hours commercially available
potassium diphenylphosphide in THF and the adequate fluoroarene (Scheme 1). This
method was assayed after the work of James and col.,62 who described it for other
polyphosphanes and resulted in a significant improvement of the reproducibility and the
yield of the desired compounds.
Scheme 1. Synthesis of poly(diphenylphosphanyl)benzene ligands
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Synthesis of alkynyl gold(I) complexes
Except for the case of tpbz and dppeda derivatives, two methods were used to prepare
the targeted polynuclear alkynyl gold(I) compounds. (Schemes 2 and 3) Although the
general method used to synthesize related compounds involves direct reaction between
the polymer [Au(C≡
CꢀR)]n and the free phosphanes (polymer method),41, 42, 50, 55 the
laborious syntheses of 5ꢀethynylꢀ2,2’ꢀbipyridine, 4’ꢀethynylꢀ2,2’:6’,2’’ꢀterpyridine and
the moderate yields of these reactions prompted us to assay an alternative strategy based
on the reaction of the acetylacetonato phosphane complexes with the terminal alkynes
64
(“acac method”).63,
In fact, the acac derivatives [Au3(acac)3(ꢀ3ꢀtripod)] and
[Au3(acac)3(ꢀ3ꢀtriphos)] proved to be useful as intermediates in the obtention of
supramolecular metallocriptands.65
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Scheme 2. Synthesis of tritopic gold(I) metallaligands
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Scheme 3. Synthesis of tetratopic gold(I) metallaligands
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Polymer method. Compounds [Au3(C≡CꢀC10H7N2)3(ꢁ3ꢀtriphosphane)] (triphosphane =
triphos (4), triphosph (5)) and [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtetraphosphane)]
(tetraphosphane = tetraphos (6), tpbz (7), dppeda (8) were obtained in moderate to good
yields by reacting [Au(C CꢀC10H7N2)]n with the adequate triꢀ or tetraphosphane in 3:1
and 4:1 molar ratio, respectively. Analogously, [Au3(C≡CꢀC15H10N3)3(ꢁ3ꢀtriphosphane)]
(triphosphane triphos (9), triphosph (10)) and [Au4(C≡CꢀC15H10N3)4(ꢁ4ꢀ
tetraphosphane)] (tetraphos (11), tpbz (12), dppeda (13)) were obtained by reacting
[Au(C CꢀC15H10N3)]n and the appropriate polyphosphane.
“Acac method”. The acac derivatives [Au3(acac)3( 3ꢀtriphosphane)] (triphosphane =
triphos (1), triphosph (2)) [Au4(acac)4( 4ꢀtetraphos)] (3), were obtained by reacting a
≡
=
≡
ꢀ
ꢀ
10% excess of the required quantity of Tl(acac) with the appropriate
chloro(polyphosphane)gold(I) compound in acetone solution in the dark. The reaction
progress was monitored by 31P NMR spectroscopy and complete consumption of the
starting gold(I) compound was observed after 48h for 1, one week for 2 and 72h for 3.
At this point, the 31P NMR spectra showed one singlet downfield shifted ca. 20 ppm
with respect to the corresponding chloro precursors, accordingly with the complete
substitution of the chloro by the acetylacetonate ligands. In the case of compounds
1
[Au3(acac)3(
ꢀ
3ꢀtriphosphane)] (triphosphane = triphos (1), triphosph (2)), the H NMR
3
spectra display a doublet at ca. 2.5 ppm with J(PꢀH)
≈ 11Hz assigned to the CH of
acac ligand. This fact together with the presence in the IR spectra of two strong broad
vibrations below 1600 cmꢀ1 is consistent with a C2 coordination mode for this ligand,
κ
typically found in gold(I) derivatives.66ꢀ68 After their isolation in solid state and their
characterization by elemental analyses, IR and NMR spectroscopies, compounds 1ꢀ3
were reacted with the terminal alkynes 5ꢀethynylꢀ2,2’ꢀbipyridine and 4’ꢀethynylꢀ
2,2’:6’,2’’ꢀterpyridine in the suitable molar ratio and the expected gold(I) derivatives
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[Au3(C≡CꢀR)3(ꢁ3ꢀtriphosphane)] (triphosphane = triphos (4 and 9), triphosph (5 and
10)) and [Au4(C≡CꢀR)4(ꢁ4ꢀtetraphos)] (6 and 11) were obtained in moderate yield after
long reaction times (from 4h for 4 to 3 days for 11). As a general trend, longer reaction
times and lower yields are observed by increasing the number of phosphorus centres (tri
to tetraphosphanes) and the bulkiness of the polypyridyl ligand (bipyridyl to terpyridyl).
Tpbz compound could not be synthesized by this method due to the impossibility of
preparation of the corresponding tetrachloro species. In the case of dppeda, the reaction
between Tl(acac) and the tetrachoro species did not allow the obtention of the desired
acac derivative. A complex set of signals in the 31P NMR spectra of the reaction
solution was obtained instead of the expected singlet.
Obviously, in this case, the “acac method” did not bring improvement to the more
general method based on the use of polymeric alkynyl gold(I) species although allowed
us to prepare a series of polynuclear acetylacetonato gold(I) derivatives that can have
a widespread use as reactive species in organometallic synthesis.
Characterization of alkynylgold(I) complexes
Complexes 4ꢀ13 were characterized by elemental analyses, IR and (1H, 31P, 13C) NMR
spectroscopies and ESI(+) mass spectrometry. Due to the chemical equivalence of the P
atoms within each compound, 31P{1H} NMR spectra show one sharp singlet, which is
shifted ca. 50 ppm downfield from that corresponding to the free polyphosphanes and
slightly shifted upfield compared to that of the parent acac compounds.
1H NMR and 13C{1H} NMR spectra are indicative of the high symmetry of the
molecules according with single bipyridyl or terpyridyl environment. A complete
assignment of proton and carbon NMR signals of both phosphanes and polypyridyl
alkynyl ligands can be found in the Experimental Section. This assignment was fully
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supported by COSY, gHSQC and gHMBC 2D experiments (for NMR spectra see
Supporting information). Regarding the 13C{1H} NMR spectra, two doublets
corresponding to the carbon atoms of the acetylene unit bonded to Au are observed at ca
140 (Cα) and 102 (Cβ) with coupling constants around 140 and 25 Hz, respectively. In
the particular case of tpbz derivatives (compounds 7 and 12) the resonances of the
acetylenic carbons appear as a multiplets or apparent triplets due to second order effects
that can be attributed to a large 31Pꢀ31P coupling transmitted through the aromatic ring
and/or the existence of intramolecular Au···Au interactions in solution. As it will be
seen later on, this aurophilic interaction has been observed in solid state for the bipy
derivative (7). In addition to satisfactory NMR analysis the structure of the compounds
in solution was supported by mass spectrometry. Generally, the MS ESI(+) spectra of
the obtained compounds display an intense peak that corresponds to that of the double
protonated [M+2H+]2+ species together with the [MꢀC CꢀR]+ signal that arises from the
≡
loss of either bipyridyl or terpyridyl fragments from the corresponding parent
compound. Moreover, in certain cases, additional peaks resulting from polyprotonation
are found. For instance, compound [Au4(C≡CꢀC15H10N3)4(ꢁ4ꢀtpbz)] (12) shows signals
due to monoꢀ [M+H+]+, diꢀ [M+2H+]2+ triꢀ [M+3H+]3+ and tetraprotonated [M+4H+]4+
species.
Crystallographic Studies
The crystal structures of [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtetraphos)] (6) and [Au4(C≡Cꢀ
C10H7N2)4(ꢁ4ꢀtpbz)] (7) were determined by singleꢀcrystal Xꢀray diffraction. The
molecular structure of compound 6 along with the selected bond distances and bond
angles are shown in Figure 1. The unit cell of the compound contains two different
molecules where some differences can be found. Although both molecules display a
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conformation that favours the establishment of aurophilic interactions between pairs of
branches, these are significantly stronger for the molecule on the right (Au(1A)ꢀAu(2A)
2.9445(12) and Au(3A)ꢀAu(4A) 3.0356(10) Å) than for the molecule on the left of the
figure 1 (Au(1)ꢀAu(2) 3.259(3) and Au(3)ꢀAu(4) 3.0310(11) Å). This conformation is
similar to that found for the closely related compound [Au4(C6F4C5H4N)4(ꢁ4ꢀtetraphos)]
where rather long (3.343(1) Å) intramolecular Au···Au interactions were found between
adjacent units.69 On the other hand, this disposition contrasts with that described for the
chloride derivative [Au4Cl4(ꢁ4ꢀtetraphos)], where a pair of gold centres lie far apart
while the other two show a goldꢀgold contact of 3.34 Å.70 Interestingly, only three
compounds bearing gold atoms in the four legs of tetraphos have been structurally
characterized. An inspection of the structure packing reveals the formation of a
supramolecular arrangement (figures S43 and S44 in Supporting Information) as a result
of the establishment of intermolecular
πꢀπ interactions between the bipyridine units
attached to Au(2)ꢀAu(2), Au(3)ꢀAu(3A) or Au(4)ꢀAu(4A) pair of arms. The shortest
πꢀπ
contacts (intercentroid distance = 3.56 Å) are established between the bipyridyl rings of
the Au(2) arms of neighbour molecules. As a result of the presence of these
intermolecular interactions, the Au(2)ꢀC≡CꢀC10H7N2 moiety displays a particularly
small value of the C≡CꢀC10H7N2 angle (C(1C)ꢀC(1B)ꢀC(16) 165(6)°) if it is compared
with those found for the rest of analogous angles (ca.175°). Interestingly, a search on
CSD revealed that among the 157 hits containing C≡CꢀC10H7N2 fragments only five
display values lower than 166° for the mentioned angle,52, 71ꢀ74 in such a way that the
formation of helicates,52 cages71 or stacking interactions74 are favoured.
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Figure 1. Molecular structure of compound [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtetraphos)] (6)
showing the two different class of molecules found in the crystal. Thermal ellipsoids are
draw at 30% probability level. Hydrogen atoms have been omitted for clarity. Selected
bond lengths (Å) and angles (º): Au(1)ꢀAu(2) 3.259(3), Au(3)ꢀAu(4) 3.0310(11),
Au(1A)ꢀAu(2A) 2.9445(12), Au(3A)ꢀAu(4A) 3.0356(10), Au(1)ꢀP(1) 2.260(5), Au(1)ꢀ
C(1) 1.93(3), Au(2)ꢀP(2) 2.220(8), Au(2)ꢀC(1C) 1.910(17), Au(3)ꢀP(3) 2.290(6), Au(3)ꢀ
C(25) 2.00(2), Au(4)ꢀP(4) 2.273(4), Au(4)ꢀC(37) 2.045(18), Au(1A)ꢀP(1A) 2.287(4),
Au(1A)ꢀC(1A) 2.07(6), Au(2A)ꢀP(2A) 2.287(4), Au(2A)ꢀC(13A) 2.006(19), Au(3A)ꢀ
P(3A) 2.269(4), Au(3A)ꢀC(25A) 2.01(2), Au(4A)ꢀP(4A) 2.275(4), Au(4A)ꢀC(37A)
2.006(19); P(1)ꢀAu(1)ꢀC(1) 172.9(10), P(2)ꢀAu(2)ꢀC(1C) 175.3(10), P(3)ꢀAu(3)ꢀC(25)
177.0(8), P(4)ꢀAu(4)ꢀC(37) 173.0(5), P(1A)ꢀAu(1A)ꢀC(1A) 171.9(17), P(2A)ꢀAu(2A)ꢀ
C(13A) 171.7(6), P(3A)ꢀAu(3A)ꢀC(25A) 173.6(7), P(4A)ꢀAu(4A)ꢀC(37A) 173.6(6),
Au(1)ꢀC(1)ꢀC(2) 170(3), Au(2)ꢀC(1C)ꢀC(1B) 162(4), Au(3)ꢀC(25)ꢀC(26) 173(2),
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Au(4)ꢀC(37)ꢀC(38) 172.2(19), Au(1A)ꢀC(1A)ꢀC(2A) 167(7), Au(2A)ꢀC(13A)ꢀC(14A)
175(2), Au(3A)ꢀC(25A)ꢀC(26A) 171(2), Au(4A)ꢀC(37A)ꢀC(38A) 173(2), C(1)ꢀAu(1)ꢀ
Au(2) 94.5(10), C(25)ꢀAu(3)ꢀAu(4) 100.5(6), C(1A)ꢀAu(1A)ꢀAu(2A) 99.5(17),
C(25A)ꢀAu(3A)ꢀAu(4A) 95.9(6), P(2)ꢀAu(2)ꢀAu(1) 83.3(3), P(4)ꢀAu(4)ꢀAu(3)
89.39(13), P(2A)ꢀAu(2A)ꢀAu(1A) 83.60(12), P(4A)ꢀAu(4A)ꢀAu(3A) 85.59(11), C(1C)ꢀ
C(1B)ꢀC(16) 165(6).
The molecular structure of compound [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtpbz)] (7) (Figure 2)
compares well with that of the closely related [Au4(C≡CꢀC6H5)4(ꢁ4ꢀtpbz)] described by
Yam and col.55 Analogously to the latter, the arrangement of every two adjacent Auꢀ
C≡CꢀC10H7N2 moieties displays a crossed geometry, although their relative disposition
with respect to the central benzene core is not the same. In fact, an angle of 0° is formed
by the symmetry related Au(1)ꢀAu(2) and Au(1*)ꢀAu(2*) axes in the phenyl derivative
while an almost perpendicular disposition (71.4°) is found between Au(1)ꢀAu(1A) and
Au(2)ꢀAu(2A) in compound 7. Besides, the distances between adjacent Au units in
compound 7 (Au(1)ꢀAu(1A) 3.077(2) and Au(2)ꢀAu(2A) 3.118(2) Å) are shorter than in
the phenyl derivative that displays a unique contact of 3.1541(4) Å. A comparison
between the structures of compounds 6 and 7 reveals a cisoid disposition of the N atoms
within each bipyridyl unit (torsion angle between pyridine rings: 11.6° and 28.8° for
pyN1ꢀpyN2 and pyN3ꢀpyN4, respectively) that contrasts with the transoid conformation
determined for compound 6 (torsion angle between pyridine rings: 3.47°ꢀ20.79°).
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Figure 2. Molecular structure of compound [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtpbz)] (7).
Thermal ellipsoids are draw at 30% probability level. Hydrogen atoms have been
omitted for clarity. Selected bond lengths (Å) and angles (º): Au(1)ꢀAu(1A) 3.077(2),
Au(2)ꢀAu(2A) 3.118(2), Au(1)ꢀP(1) 2.290(6), Au(1)ꢀC(4) 2.07(2), Au(2)ꢀP(2) 2.294(6),
Au(2)ꢀC(21) 2.03(2), C(4)ꢀC(5) 1.13(3), C(21)ꢀC(22) 1.19(3); P(1)ꢀAu(1)ꢀC(4) 176.9(6),
Au(1)ꢀC(4)ꢀC(5) 174(2), P(2)ꢀAu(2)ꢀC(21) 174.3(7), Au(2)ꢀC(21)ꢀC(22) 175(2), C(4)ꢀ
Au(1)ꢀAu(1A) 102.9(6), P(1)ꢀAu(1)ꢀAu(1A) 80.2(2), C(21)ꢀAu(2)ꢀAu(2A) 107.1(7),
P(2)ꢀAu(2)ꢀAu(2A) 78.0(2).
Photophysical characterization
Absorption and emission spectra of all the complexes were recorded in 10ꢀ6
M
dichloromethane solution at room temperature and the obtained data are summarized in
Table 1.
All complexes display a vibronically resolved absorption profile centered at ca. 320 nm
for bipy (4ꢀ8) and at ca. 290 nm for terpy (9ꢀ13) derivatives (Figures S45 and S46 in
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Supporting Information) that is attributed to the stretching vibrations of the bipyridyl
and terpyridyl moieties in the excited state.
Table 1. Absorption and emission data in 10ꢀ6 M dichloromethane solution and solidꢀ
state emission at room temperature for compounds 4ꢀ13.
Compound
4
λabs nm (10ꢀ3 ε, Mꢀ1cmꢀ1)
318 (97.7), 330 (84.3)
λem, nm
392, 500 w, 536 sh (CH2Cl2)
401, 505, 546, 606 (solid)
383, 497 w, 539 sh (CH2Cl2)
429, 474, 511, 557 (solid)
385, 502 w, 530 w (CH2Cl2)
400, 506, 542, 585 (solid)
374, 396, 501, 539 (CH2Cl2)
423, 503d, 604 sh, 599 (solid)
375, 403, 498 w, 537 sh (CH2Cl2)
423, 502, 547, 581 sh (solid)
340 sh, 354, 439 w, 476 w (CH2Cl2)
407, 556w (solid)
316 (145.0), 332 (138.6)
319 (198.1), 333 (198.4)
320 (277.5), 334 (242.3)
318 (229.2), 331 (226.5)
5
6
7
8
277 (172.1), 288 (157.0), 311 sh
(44.5), 332 sh (90.9)
9
276 (200.7), 290 (195.6), 317 sh
(37.6), 331 sh (27.1)
338 sh, 353, 433 w, 473 w (CH2Cl2)
407, 516, 568 (solid)
10
11
12
13
277 (263.4), 294 sh (224.5), 319 sh
(71.1), 333 sh (38.6)
339 sh, 353, 439 w, 476 sh (CH2Cl2)
407, 507, 563 (solid)
266 (371.3), 277 (395.0), 297 sh
366, 480 sh (CH2Cl2)
(265.7), 321 sh (118.0), 334 sh (69.9) 407, 500, 582 (solid)
266 (295.2), 276 (316.0), 291 sh 356, 475 (CH2Cl2)
(247.1), 319 sh (74.2), 332 sh (51.4) 407, 523, 560 (solid)
Taking into account the observed vibrational spacings and previous reports dealing with
Au(I) compounds containing the same aromatic chromophores,41, 42, 50, 52 we assign
these bands to intraligand transitions of [π→π*ꢀ(C≡CꢀC10H7N2)] or [π→π*ꢀ(C≡Cꢀ
C15H10N3)] character. A lower intensity broad band or tail above 350 nm is also
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observed in all complexes and can be assigned to a σ*(Au⋯Au)–π* transitions
according to theoretical calculations.75 The latter transitions have been found in related
complexes recently reported by us.76ꢀ78 The vibronic structured bands are broad and not
completely defined even at low concentrations, which are assigned to excitonic splitting
where Au···Au and π π intramolecular stacking interactions are present between the
arms of the dissolved complexes, as observed in previous studies carried out in our
group.39 The extinction coefficients at the maximum of the absorption band increase
with the number of chromophores present in the molecules. These are higher than those
reported by analogous diphosphane derivatives,29, 41, 50 showing slight deviations of the
monotonic increase due to differences in the intramolecular stacking interactions, where
higher broadening leads to lower extinction coefficient at the maximum of the band.
All complexes are emissive at room temperature in solution and in solid state. Emission
spectra in dichloromethane solutions were recorded upon excitation of the samples at
330 nm (4ꢀ8) and 290 nm (9ꢀ13) (Figure 3) and a dual emission was observed in all
cases with maxima at ca. 400 nm and 530 nm for bipyridyl derivatives and at ca. 350
nm and 475 nm for terpyridyl complexes. The fact that complexes which contain the
same alkynyl moiety present similar emission profiles, and comparing them with
previous studies reported in the literature,40, 41 let us attribute the recorded emissions to
1
3
metal perturbed, alkynyl ligand based, IL [π→π*] (higher energy emission) and IL
[π→π*] (lower energy emission) states. In all cases the presence of the Au heavy atom
is expected to favour intersystem crossing and phosphorescence emission, which can be
enhanced by the proximity of several Au atoms. The higher intensity of the
phosphorescence band for the tetranuclear complex [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtpbz)] (7)
may result from a higher proximity between the arms through favouring Au···Au
interactions, which in the case of the analogous compound [Au4(C≡CꢀC15H10N3)4(ꢁ4ꢀ
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tpbz)] (12) could be hampered by the voluminous terpyridine ligand. As showed above,
the Xꢀray molecular structure of compound 7 shows that all the gold centres of the
compound are involved in rather short intramolecular aurophilic interactions. The
emissions observed in solid state at 298K (λexc= 370 nm for 4ꢀ8 and 350 nm for 9ꢀ13)
are comparable to that obtained in deoxygenated dicloromethane solutions.
Figure 3. Normalized emission spectra of 10ꢀ6 M deoxygenated dichloromethane
solutions of 4ꢀ8 (left) and 9ꢀ13 (right). λexc (4ꢀ8) = 330nm; λexc (9ꢀ13) = 290 nm.
Titration studies
As indicated in the introduction, one of the main aims of this work was to obtain
bipyridyl and terpyridyl functionalized polygold compounds able to coordinate to
cationic metallic species. To exploit the potential of the titled compounds in this regard,
we envisaged the evaluation of the cationꢀbinding ability of the obtained complexes by
solution titrations.
As a starting point, we report here studies of the interaction of the bipyridineꢀcontaining
compounds 4ꢀ7 with cations such Cu+ and Zn2+. Changes in the absorption and emission
bands of the polynuclear alkynyl gold(I) compounds have been monitored in order to
evaluate the cationꢀmetallaligand interaction.
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The addition of increasing amounts of [Cu(CH3CN)4]BF4 to a 10ꢀ6 M dichloromethane
solution of the complexes 4ꢀ7 displays, in all cases, a bathochromic shift of the
maximum of the π → π* absorption band of the bipyridyl moiety from ca. 330 nm (free
complex) to ca. 350 nm (adduct). This behaviour is typical of the coordination of
cations to the N,Nꢀbidentate site of the bipyridine moiety and has been normally
attributed to the transoid to cisoid isomerization of the heteroaromatic core.79ꢀ81 (Figure
4 for compound 5 and figures S47ꢀS49 for compounds 4, 6 and 7 in Supporting
Information).
0.4
0.3
0.2
0.1
0.0
160000
120000
80000
40000
0
100
50
0
3.0
4.5
M)
0
1.4
5.9
[Cu+] (
ꢀ
5
5
5
5
—Cu+
—2Cu+
—3Cu+
300
350
400
450
300
350
Wavelength (nm)
400
450
Wavelength (nm)
Figure 4. Absorption spectra of a 10ꢀ6 M dichloromethane solution of 5 upon addition
of different amounts of [Cu(CH3CN)4]BF4 (left). Spectra of individual species obtained
from Spectit factorial analyses (right). Inset shows calculated speciation of the species
formed upon titration.
The titrations showed the absence of wellꢀdefined isosbestic points, pointing to the
presence of at least two new absorbing species formed during the addition of Cu+
cation. The fitting procedure of the obtained data performed with a nonlinear leastꢀ
squares algorithm implemented in the Specfit software82 allowed the calculation of the
stability constants (β1n) for the studied equilibria (Table 2). In the case of metallaligands
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with three arms the coordination of Cu+ to the different bipyridine units gave rise to the
coexistence of either [4·2Cu+]2+ and [4·3Cu+]3+ or [5·1Cu+]+, [5·2Cu+]2+ and [5·3Cu+]3+
(Figure 4). In the case of tetraphos and tpbz derivatives 6 and 7, the fitting analysis was
consistent with the formation of species with a pair number of coordinated Cu+ i. e.
[6/7·2Cu+]2+ and [6/7·4Cu+]4+ indicating that, in this case, symmetric coordination is
favoured over other stoichiometric possibilities.
Table 2. Calculated stability constants of studied complexes.
Ligand/cation
log(β11
10±1
)
log(β12
)
log(β13
)
log(β14)
4/Cu+
5/Cu+
6/Cu+
7/Cu+
4/Zn2+
15±1
19±1
20±1
15±1
20±1
28±1
35±1
28±1
15±1
Emission titrations gave very interesting profiles. As it can be seen in Figure 5 for
compound 5 and in Figures S47ꢀS49 in Supporting Information for the rest of
compounds, the addition of copper(I) salt to a dichloromethane solutions of compounds
4ꢀ7 induced a decrease on both fluorescence and phosphorescence bands of the hosts.
8.0x105
4.0x105
0.0
400
500
600
Wavelength (nm)
Figure 5. Emission spectra of a 10ꢀ6 M dichloromethane solution of 5 upon addition of
different amounts of [Cu(CH3CN)4]BF4 .
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Similar behaviour has been reported for Cu+ titrations on organic fluorophores that
contain appended 5ꢀethynylꢀ2,2’ꢀbipyridyl fragments.83 In contrast, the emission spectra
recorded for the 1:1 complex (after adding 1 equivalent of [Cu(CH3CN)4]BF4 in
deoxygenated samples display an increase of both fluorescence and phosphorescence
emission bands (Figure S50 in Supporting Information), which could be related with the
presence of an equilibrium between singlet and triplet states as observed in systems that
present activated delayed fluorescence.
Additionally, the possibility of interaction with other cations able to coordinate to
bipyridyl units, such as Zn2+ was envisaged. Preliminary experiments carried out with 4
as a representative compound of these series showed changes in absorption and
emission spectra that present noteworthy differences from those obtained with Cu+.
(Figure S51 in Supporting Information). On the one hand, a progressive decrease of the
host absorption bands with a concomitant development of a longer wavelength
transition was observed. The observation of a wellꢀdefined isosbestic point at 338 nm is
indicative of a neat interconversion between the uncomplexed and complexed states,
which contrasts with the equilibrium among various species found in the case of Cu+
addition. Fitting of the titration data82 gave a single stability constant value (Table 2)
that corresponds to the formation of [4·3Zn2+]6+ as unique species. On the other hand,
the emission titration results in a redꢀshifted and clearly enhancement (15ꢀfold) of the
fluorescence band of compound 4, which is in agreement with a bindingꢀinduced
conformational restriction of the bipyridine moiety by Zn2+chelation.84
Conclusions
An improved method for obtaining polyphosphanyl benzene phosphanes has been
developed.
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Trinuclear and tetranuclear phosphane alkynyl gold(I) systems with appended bipyridyl
or terpyridyl moieties has been obtained using two different methods. While the
reaction between the gold(I) polymeric species [Au(C≡CꢀR)]n and the adequate
polyphosphane (polymer method) afforded the desired compounds in good yield in all
the cases, the “acac method” implied long reactions times and only allowed the
synthesis of a limited number of complexes due to the impossibility of isolating the
adequate polyacetylacetonate precursor. In spite of this, the new isolated poly ”acac”
species [Au3(acac)3(ꢀ3ꢀtriphosphane)] (triphosphane = triphos, triphosph)
and
[Au4(acac)4(ꢀ4ꢀtetraphos)] are reactive species that can be widely used as a precursors
in organometallic synthesis.
All the prepared compounds are luminescent at room temperature in solution and in
solid state and exhibit dual emissions that have been assigned to gold perturbed, alkynyl
ligand based, 1IL [π→π*] and 3IL [π→π*] states.
Dissimilar behaviour has been found on studying the absorption and emission properties
of the synthesized bipyridyl metallaligands upon complexation with closedꢀshell cations
like Cu+ and Zn2+. Absorption titrations showed a clean process for Zn2+ while complex
equilibria that involve the simultaneous formation of various absorbing species are
detected for Cu+. In emission titrations, a quenching or an enhancement of the
fluorescence in the resulting supramolecular aggregates are observed on adding Cu+ or
Zn2+, respectively.
Finally, we have demonstrated that the species reported here have a great potential as
chelating or bridging polytopic metallaligands with interesting photophysical properties.
For this reason, further studies of the reactivity of the complexes reported here against a
wide range of metallic cations as well as of the properties exhibited by the resulting
species are currently in progress.
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Experimental Section
General Methods.
All manipulations were performed under prepurified nitrogen atmosphere using
Schlenckꢀtube techniques. Solvents were dried by standard methods and distilled under
nitrogen immediately prior to use, or alternatively from a Solvent Purification System
(Innovative Technologies).
Literature methods were used to prepare [AuCl(tht)],85 Tl(acac),86 [Au(C≡Cꢀ
C10H7N2)]n,41
5ꢀtrimethylsilylethynylꢀ2,2’ꢀbipyridine,87
4’ꢀethynylꢀ2,2’:6’,2”ꢀ
87, 88
terpyridine,
tetrakis(diphenylphosphanylmethyl)methane (tetraphos),70 N, N, N’,
90
N’-tetra(diphenylphosphanylmethyl)ꢀ1,2ꢀethylenediamine (dppeda),89,
[(AuCl)3(ꢀ3ꢀ
triphos)],91 [(AuCl)3(ꢀ3ꢀtriphosph)],92 [(AuCl)4(ꢀ4ꢀtetraphos)],70 and [(AuCl)4(ꢀ4ꢀ
dppeda)].93 All other reagents were obtained from commercial suppliers and used as
received.
1
Infrared spectra were recorded on a FTꢀIR 520 Nicolet Spectrophotometer. H NMR
(δ(TMS) = 0.0 ppm), 31P{1H} NMR (δ(85% H3PO4) = 0.0 ppm), 13C{1H} NMR
(δ(TMS) = 0.0 ppm), spectra were obtained at 250, 300, 400 or 500 MHz with Varian
and Bruker spectrometers at 25 ºC unless otherwise stated. Elemental analyses of C, H,
and N were carried out at the Centres Científics i Tecnològics (Universitat de
Barcelona). ESIꢀMS mass spectra were recorded on a LC/MSD TOF Argilent
Technologies 61969A spectrometer in H2O:CH3CN (1:1) solutions. Absorption spectra
were recorded on a Varian Cary 100 Bio spectrophotometer. Emission and excitation
spectra were recorded on a HoribaꢀJobinꢀYvon SPEX Nanolog spectrofluorimeter.
Solutions were prepared with spectroscopic grade solvents. Titrations were carried out
by addition of aliquots of 10ꢀ4 M solutions of the cations prepared in dichloromethane to
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the host solution (10ꢀ6 M in dichloromethane). Absorption and emission spectra were
measured after each addition.
XꢀRay Structure Determination
Crystal data for complexes 6 and 7 are presented in the Supporting Information (Table
S1).
Data for [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtetraphos)] (6) was collected at 120.0 K on a dual
source Rigaku Oxford SuperNova diffractometer equipped with an Atlas detector using
mirrorꢀmonochromated CuꢀKα radiation (λ = 1.54184 Å). The data collection and
reduction were done using the program CrysAlisPro94 and the intensities were corrected
for absorption using the Gaussian faceꢀindex absorption correction method.94 The
95, 96
structure was solved with direct methods (SHELXS)
and refined by fullꢀmatrix
least squares on F2 using the OLEX2,97 which utilizes the SHELXL module.95, 96 No
attempt was made to locate the hydrogens for disordered organic molecules in the unit
cell. Constraints (EADP) and restraints (ISOR) commands are used where appropriate
to suppress the alerts for large displacement parameter in checkcif. For a few aromatic
rings and CꢀC bond distances, constraints (AFIX) and restraints (DFIX) commands
were to suppress Hirshfeld differences for nonꢀhydrogen atoms in A and Bꢀalerts. Two
of the Auꢀatoms are severely disordered, and attempts to resolve high electron residual
density create additional A and Bꢀalerts. Finally, continuous four Fourier cycles of
refinement were performed till the convergence is achieved. The final refinement
convergence was achieved at R1 = 0.1094 and wR2 = 0.2561 for intensities I>2(I) with
largest peak/hole in the final difference map as 8.516/ꢀ3.240 e/Å3.
The intensity data sets for [Au4(C≡CꢀC10H7N2)4(ꢁ4ꢀtpbz)] (7) were collected at 200 K
on a BrukerꢀNonius KappaCCD diffractometer equipped with an Oxford Cryostream
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700 unit. The structure was solved, by using the WINGX package,98 by direct methods
(SHELXSꢀ2013)95, 96, 99 and refined by leastꢀsquares against F2 (SHELXLꢀ2014).95, 96, 99
All the hydrogen atoms were positioned geometrically and refined by using a riding
model. Crystals of compound 7 diffracted very weakly, and only data collections up to θ
= 23° could be performed. Crystals of compound 7 crystallized with a huge number of
solvent molecules, but it was not possible to get sensible chemical models for them. The
Squeeze procedure of the PLATON100 package was employed to remove the
contribution of that electronic density to the structure factors, obtaining a solvent
accessible volume equivalent to 21% of the unit cell volume. EADP constrains were
applied to bipyridine and phenyl ring atoms to suppress the alerts for large displacement
parameter in checkcif. The final refinement convergence was achieved at R1 = 0.092
and wR2 = 0.223 for intensities I>2(I) with largest peak/hole in the final difference map
as 3.139/ꢀ1.577 e/Å3.
These data can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Synthesis and Characterization
Preparation of 5ꢀethynylꢀ2,2’ꢀbipyridine
The compound was prepared by a modified procedure of the deprotection of the
trimethylsilylethynyl group described by Ziessel in ref. 87.
To a solution of 500 mg of 5ꢀtrimethylsilylethynylꢀ2,2’ꢀbipyridine (obtained by a
copperꢀcatalyzed Sonogashira coupling)87 in 50 ml of MeOH, KF (140 mg, 2.41 mmol)
was added and the mixture was stirred overnight at room temperature. The resulting
suspension was evaporated to dryness under vacuum and the residue was
chromatographed on silica and eluted with CH2Cl2/MeOH (100:2) to yield a darkish
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solid that contains copper as impurity. The solid was dissolved in 100 mL of chloroform
acidified with a few drops of HCl(aq) and the mixture stirred for 3 hours at RT. After this
time the red suspension was filtered through celite and extracted (3x100 mL) with
15.5% NH3(aq) saturated with EDTA. The organic layer was separated, washed with
brine and dried over MgSO4. The resulting solution was evaporated to dryness and the
crude product purified by vacuum sublimation at 70°C to yield a white crystalline solid,
which gave analytical data identical to those previously reported.87 Yield: (303 mg,
85%).
Preparation of 1,3,5ꢀtris(diphenylphospanyl)benzene (triphosph) and 1,2,4,5ꢀ
tetrakis(diphenylphosphanyl)benzene (tpbz)
The
syntheses
of
1,3,5ꢀtris(diphenylphospanyl)benzene
and
1,2,4,5ꢀ
tetrakis(diphenylphosphanyl)benzene were based on that described for
1,2(diphenylphosphanyl)benzene.62 From 0.75 mL of the starting fluorinated
compounds (7.2 mmol of 1,3,5ꢀtrifluorobenzene and 6.7 mmol of 1,2,4,5ꢀ
tretrafluorobenzene), 2.19 g (48%) and 3.06 g (56%) of the above indicated triꢀ and
tetraphosphanes were obtained, respectively. Analytical data was identical to those
previously reported.101
Preparation of [Au(C≡CꢀC15H10N3)]n
The synthesis of [Au(C≡CꢀC15H10N3)]n was based on that described by [Au(C≡Cꢀ
C10H7N2)]n.41 [AuCl(tht)] (125 mg, 0.39 mmol) and recently distilled NEt3 (0.16 mL,
1.17 mmol) were added to a solution of 4’ꢀethynylꢀ2,2’:6’,2”ꢀterpyridine (100 mg, 0.39
mmol) in 10 ml of CH2Cl2. The mixture was protected from light and stirred for 2 h.
The obtained yellowish suspension was concentrated to dryness under vacuum giving a
yellow solid that was washed subsequently with MeOH and Et2O and dried under
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vacuum. Yield (124 mg, 70%). Anal. Found: C, 45.70; H, 2.33; N, 9.35; Calc. for
C17H10AuN3: C, 45.05; H, 2.22; N, 9.27 %. IR νmax/cmꢀ1 2119 (C≡C).
Preparation of [Au3(acac)3(ꢀ3ꢀtriphos)] (1)
To an acetone solution of [(AuCl)3(ꢁ3ꢀtriphos)] (200 mg, 0.16 mmol), solid Tl(acac)
(160 mg, 0.53 mmol) was added. The resulting mixture was protected from light and
stirred for 48 h. The obtained suspension was concentrated to dryness and the residue
was extracted with dichloromethane (3 x 5 mL). The combined extracts were
concentrated under vaccum (5 mL) and nꢀhexane was added to precipitate a white solid.
1
Yield (172 mg, 71%). IR νmax/cmꢀ1 1648, 1622 (acac); 1504, 1436, 1096 (triphos). Hꢀ
NMR (300 MHz, CDCl3, 298 K) 7.80ꢀ7.35 (30H, br s, PPh2), 3.09 (6H, d, 2J(H-P) 10.8,
3
CH2ꢀP), 2.33 (3H, d, J(H-P) 11.4, COꢀCHꢀCO), 1.94 (18H, s, CH3ꢀCO), 1.01 (3H, s,
CH3ꢀC). 31P{1H}ꢀNMR (121.4 MHz, CDCl3, 298 K) 24.9 (s, PPh2).
Preparation of [Au3(acac)3(ꢀ3ꢀtriphosph)] (2)
To an acetone solution of [(AuCl)3(ꢁ3ꢀtriphos)] (226 mg, 0.17 mmol), solid Tl(acac)
(170 mg, 0.56 mmol) was added. The obtained mixture was protected from light and
stirred for 1 week. The resulting suspension was filtered and the solid was extracted
with acetone (3 x 5 mL). The combined extracts together with the filtrate were
concentrated to dryness. The remaining solid was dissolved in the minimum amount of
dichloromethane and nꢀhexane was added to precipitate a beige solid. Yield (130 mg,
50%). Anal. Found: C, 44.99; H, 3.52; Calc. for C57H54Au3O6P3: C, 45.07; H, 3.58%. IR
ν
max/cmꢀ1 1647, 1631 (acac); 1504, 1439, 1096 (triphosph). 1HꢀNMR (300 MHz, CDCl3,
3
298 K) 7.58ꢀ7.34 (33H, m, PPh2 + PꢀC6H3-P), 2.61 (3H, d, J(H-P) 11.1, COꢀCHꢀCO),
2.12 (18H, s, CH3ꢀCO). 31P{1H}ꢀNMR (121.4 MHz, CDCl3, 298 K) 42.6 (s, PPh2).
Preparation of [Au4(acac)4(ꢀ4ꢀtetraphos)] (3)
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Dalton Transactions
Page 28 of 44
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DOI: 10.1039/C7DT02732J
Compound 3 was synthesized following an analogous procedure to that described for
compound 2. From (300 mg, 0.17 mmol) of [(AuCl)4(ꢁ3ꢀtetraphos)] and (230 mg, 0.76
mmol) Tl(acac) and a reaction time of 72 h compound 3 was obtained as a white solid.
Yield (187 mg, 55%). Anal. Found: C, 43.41; H, 3.80; Calc. for C73H76Au4O8P4: C,
1
43.99; H, 3.84%. IR νmax/cmꢀ1 1652, 1622 (acac); 1504, 1435, 1096 (tetraphos). Hꢀ
NMR (300 MHz, CDCl3, 298 K) 7.70ꢀ6.80 (br m, PPh2 + CHCl3), 3.11 (12H, br s, COꢀ
CHꢀCO + CꢀCH2ꢀP), 2.03 (24H, br s, CH3ꢀCO).31P{1H}ꢀNMR (121.4 MHz, CDCl3, 298
K) 22.8 (s, PPh2).
Preparation of [Au3(C≡CꢀC10H7N2)3(ꢁ3ꢀtriphos)] (4)
Polymer method: To a suspension of [Au(C≡CꢀC10H7N2)]n (50 mg, 0.13 mmol) in
CH2Cl2 (15 mL), the stoichiometric amount of solid triphos (28 mg, 0.04 mmol) was
added and the mixture was stirred for 2 h. The resulting pale yellow solution was
concentrated (5 mL) and nꢀhexane was added to precipitate a white solid, which was
filtered off washed with nꢀhexane (3x5mL) and dried in vacuo. Yield (53 mg, 75%).
Acac method: To a solution of [Au3(acac)3(ꢀ3ꢀtriphos)] (1) (75 mg, 0.05 mmol) in
CH2Cl2 (15 mL), the stoichiometric amount of 5ꢀethynylꢀ2,2’ꢀbipyridine (27 mg, 0.15
mmol) was added. The solution was stirred for 4h and concentrated to 5mL in vacuo.
Subsequent addition of nꢀhexane caused the precipitation of a white microcrystalline
solid, which was filtered off washed with nꢀhexane (3x5 mL) and dried in vacuo. Yield
(44 mg, 50%).
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Page 29 of 44
Dalton Transactions
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DOI: 10.1039/C7DT02732J
Anal. Found: C, 52.89; H, 3.42; N, 4.81; Calc. for C77H60Au3N6P3: C, 52.75; H, 3.45; N,
1
4.79%. IR νmax/cmꢀ1 2116 (C≡C); 1429, 1097 (triphos). HꢀNMR (400 MHz, CDCl3,
298 K) 8.72 (3H, m, 6ꢀH), 8.67 (3H, ddd, J(H-H) 4.8, 1.8, 0.8, 6’ꢀH), 8.38 (3H, dt, J(H-
H) 8.0, 1.0, 3’ꢀH), 8.31 (dd, J(H-H) 8.2, 0.7, 3ꢀH), 7.96ꢀ7.89 (12H, m, PPh2), 7.82 (3H,
dd, J(H-H) 8.4, 2.4, 4ꢀH), 7.81 (3H, td, J(H-H) = 7.5, 1.8, 4’ꢀH), 7.46ꢀ7.43 (18H, br m,
PPh2), 7.29 (3H, ddd, J(H-H) 7.5, 4.8, 1.2, 5’ꢀH), 3.46 (6H, d, 2J(H-P) 10.9, CH2), 0.89
(3H, s, CH3). 31P{1H}ꢀNMR (121.4 MHz, CDCl3, 298 K) 25.4 (s, PPh2). 13C{1H}ꢀNMR
(100.6 MHz, CDCl3, 298 K) 156.0, 153.6 (C2+C2’), 152.5 (C6), 149.4 (s, C6’), 139.9 (s,
2
2
C4), 138.4 (d, J(C-P) 140, PꢀAuꢀC≡C), 137.0 (C4’), 134.1 (d, J(C-P) 14, CorthoPh),
1
3
132.1 (CparaPh), 131.0 (d, J(C-P) 56, CipsoPh), 129.6 (d, J(C-P) 12, CmetaPh), 123.7
3
(C5’), 122.3 (C5), 121.3 (C3’), 120.3 (C3), 101.4 (d, J(C-P) 26, PꢀAuꢀC≡C), 42.8 (d,
1J(C-P) 31, CH2), 39.0 (Cqꢀtriphos), 30.7 (CH3). MS ESI(+) m/z 1573.2 (100%, [Mꢀ
C12H7N2]+, calc. 1573.2), 697.1 (6%, [Mꢀ2(C12H7N2)]2+, calc. 697.1) 877.2 (85%,
[M+2H+]2+, calc. 877.2), 585.1 (8%, [M+3H+]3+, calc. 585.1).
Preparation of [Au3(C≡CꢀC10H7N2)3(ꢁ3ꢀtriphosph)] (5)
Compound 5 was successfully synthesized following analogous procedures to those
described for compound 4.
Polymer method. From (50 mg, 0.13 mmol) of [Au(C≡CꢀC10H7N2)]n and (28 mg, 0.04
mmol) of triphosph. Yield (50 mg, 71%).
Acac method. From (76 mg, 0.05 mmol) of [Au3(acac)3(ꢀ3ꢀtriphosph)] (2) and (27 mg,
0.15 mmol) of 5ꢀethynylꢀ2,2’ꢀbipyridine and a reaction time of 6 h. Yield (45 mg, 51%).
Anal. Found: C, 53.23; H, 3.03; N, 4.80; Calc. for C78H54Au3N6P3: C, 53.26; H, 3.09; N,
1
4.78%. IR νmax/cmꢀ1 2110 (C≡C); 1434, 1097 (triphos). HꢀNMR (400 MHz, CDCl3,
298 K) 8.79 (3H, dd, J(H-H) 2.1, 0.9, 6ꢀH), 8.67 (3H, ddd, J(H-H) 4.9, 1.8, 0.9, 6’ꢀH),
8.36 (3H, dt, J(H-H) 8.0, 1.1, 3’ꢀH), 8.32 (3H, dd, J(H-H) 8.3, 0.9, 3ꢀH), 7.88 (3H, dd,
29