Structure and photochemical isomerization of the dinuclear gold(I) halide bis(diphenylphosphanyl)ethylene complexes: Correlation between quantum yield and aurophilicity

Article abstract of DOI:10.1002/ejic.200700575

The crystal structures for cis-(Ph₂PCH=CHPPh₂)(AuI) ₂ and trans-(Ph₂PCH=CHPPh₂) (AuI)₂ are reported. The structure of cis-(Ph₂PCH=CHPPh₂)(AuI) ₂ reveals a short intramolecular Au-Au distance of 2.9526(5) A, while the structure of trans(Ph₂PCH=CHPPh₂)(AuI) ₂ shows intermolecular Au-Au distances of 3.2292(7) A. Structural data for the iodide complexes are compared to previously reported crystal structural data for cis- and trans-(Ph₂PCH=CHPPh ₂)(AuCl)₂ and dppbz(AuCl)₂. The quantum yields for the photochemical isomerization of cis-(Ph₂PCH=CHPPh ₂)(AuX)₂ with 334-nm light, Φ(cis→trans). are 0.204, 0.269, and 0.363 for X = Cl, Br, and I, respectively. Prior results from ab initio calculations on the model cis- and trans-Au₂X ₂C₂H₂(PH₂)₂ complexes aid in the interpretation of the correlation between the quantum yield for isomerization and the calculated aurophilic attraction potential V(R _e). Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700575

FULL PAPER
DOI: 10.1002/ejic.200700575
Structure and Photochemical Isomerization of the Dinuclear Gold(I) Halide
Bis(diphenylphosphanyl)ethylene Complexes: Correlation Between Quantum
Yield and Aurophilicity
Janet B. Foley,*[a] Stanley E. Gay,[b] Michael J. Vela,[c] Bruce M. Foxman,[c]
Alice E. Bruce,[b] and Mitchell R. M. Bruce*[b]
Keywords: Aurophilicity / Metal–metal interactions / Gold / Photochemistry / Olefin isomerization / Quantum yield
The crystal structures for cis-(Ph2PCH=CHPPh2)(AuI)2 and
trans-(Ph2PCH=CHPPh2)(AuI)2 are reported. The structure of
cis-(Ph2PCH=CHPPh2)(AuI)2 reveals a short intramolecular
Au–Au distance of 2.9526(5) Å, while the structure of trans-
(Ph2PCH=CHPPh2)(AuI)2 shows intermolecular Au–Au dis-
tances of 3.2292(7) Å. Structural data for the iodide com-
plexes are compared to previously reported crystal structural
data for cis- and trans-(Ph2PCH=CHPPh2)(AuCl)2 and
dppbz(AuCl)2. The quantum yields for the photochemical
isomerization of cis-(Ph2PCH=CHPPh2)(AuX)2 with 334-nm
light, Φ(cisǞtrans), are 0.204, 0.269, and 0.363 for X = Cl, Br,
and I, respectively. Prior results from ab initio calculations on
the model cis- and trans-Au2X2C2H2(PH2)2 complexes aid in
the interpretation of the correlation between the quantum
yield for isomerization and the calculated aurophilic attrac-
tion potential V(Re).
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
In the 1980s, the X-ray structures of the cis- and trans
isomers of dppee(AuCl)2 (dppee: Ph2PCH=CHPPh2) were
reported by Jones,[1] and Eggleston, McArdle, and Zuber,[2]
respectively. The crystal structure of cis-dppee(AuCl)2 (1cis)
reveals short intramolecular Au–Au interactions of
3.05(1) Å, whereas trans-dppee(AuCl)2 (1trans) shows only
intermolecular Au–Au interactions of 3.043(1) Å. In the
structure for 1cis reported in 1980, Jones comments that “ra-
diation damage, the exact nature of which is uncertain,
causes the cell constants to increase.” Subsequently, it was
shown by Foley et. al that the series of cis complexes involv-
ing X = Cl, Br, I, and thiolate [Equation (1)] are photo-
chemically reactive in solution, which results in a clean
isomerization to the trans isomers.[3] In addition, the cis
complexes show changes in crystal morphology upon expo-
sure to room light, which suggests the interesting possibility
of solid-state photochemical reactivity,[4] consistent with
Jones’ observations noted above.
(1)
The photochemical conversions depicted in Equation (1)
are rapid and efficient. For example, photolysis of a 2.1 m
solution of cis-(dppee)(AuI)2 in CDCl3 with a 300 W Hg
arc lamp (λՆ320 nm) results in complete conversion of the
cis isomer to the trans isomer within 3 min [as monitored
by 31P(1H) NMR spectroscopy].[3] The quantum yields for
isomerization of 1cis–3cis to the respective trans complexes
were estimated to be greater than 0.1, and control reactions
establish that the isomerization process is not thermally ac-
tivated.
In contrast, the free cis- and trans-dppee ligands do not
undergo photochemical isomerization under similar condi-
tions or when light of higher energy (λՆ220 nm) is used.[3]
In addition, the trans-dppee gold complexes 1trans–3trans do
not photochemically convert into the cis-dppee gold com-
plexes. The photochemical reactivity of 3trans appears to be
limited to a decomposition pathway that is consistent with
release of I2.[4]
[a] Bennington College, Division of Natural Sciences and Mathe-
matics, Bennington College,
Bennington, Vermont 05201, USA
E-mail: jfoley@bennington.edu
[b] University of Maine, Department of Chemistry, University of
Maine,
Orono, Maine 04469, USA
E-mail: mbruce@maine.edu
[c] Brandeis University, Department of Chemistry, Brandeis Uni-
versity,
Waltham, Massachusetts 02454, USA
4946
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Eur. J. Inorg. Chem. 2007, 4946–4951

Correlation Between Quantum Yield and Aurophilicity in Gold(I) Complexes
The cis- and trans-dppee ligands have been used exten- In 3cis, the cis orientation of the rigid phosphane ligand
sively to prepare metal complexes, and examples are re- promotes formation of an intramolecular Au–Au bond of
ported for nearly every transition metal.[5] In addition, there 2.9526(5) Å. The Au–Au distance in 3cis is 0.1 Å shorter
are a few reports of thermal isomerization processes involv- than that found in the related complex 1cis and 0.05 Å
ing dppee. For example, cis-dppee isomerizes to trans-dppee shorter than the intramolecular Au–Au distance in the cis-
[14]
in the presence of GaBr3, GaCl3, and AlBr3 at elevated tem- dppbz(AuCl)2
(Table 3). These distances all fall within
peratures in a catalytic process that is correlated with Lewis the accepted values for aurophilic interactions, which range
acidity.[6] The cis-dppee disulfide and cis-dppee dioxide also from 2.8 Å (strong interaction) to 3.5 Å (weak interac-
thermally isomerize to the trans isomers in refluxing thf in tion).[15] The two P–Au–I arms in 3cis “cross” at the Au
the presence of PCl3.[7] However, photochemical reactivity centers with an I–Au···Au–I torsion angle of 63.61°. The
for dppee is rare, and to date, as far we are aware the photo- structure of 3trans is very similar to that reported for the
[2]
isomerization of dppee has been reported only for the related complex 1trans
.
Both crystallize in the centrosym-
gold(I) complexes 1cis–3cis. These observations suggest a metric space group C2/c with an inversion center at the
pivotal role for gold atoms in photoisomerization. In this midpoint of the ethylene backbone. Only one half of each
report, we present the crystal structures for 3cis and 3trans
,
trans molecule is crystallographically unique. In 3trans, a
details of the quantum yield measurements for the photo- partially disordered dichloromethane molecule is also pres-
isomerization reactions of 1cis–3cis to 1trans–3trans, and the ent. The intermolecular Au–Au interactions in 3trans
correlation between quantum yield and aurophilicity.[8]
[3.2292(7) Å] are 0.19 Å longer than in 1trans.
Table 2. Selected bond lengths [Å] and angles [°] for compound
3trans
.
Results and Discussion
Bond lengths [Å]
Structural Characterization of 3cis and 3trans Complexes
Au1–Au1
Au1–P1
P1–C2
3.2292(7)
2.250(2)
1.812(9)
1.309(17)
Au1–I1
P1–C1
P1–C8
2.5435(8)
1.811(9)
1.796(9)
Selected bond lengths and angles for 3cis and 3trans are
presented in Tables 1, 2, and 3, and ORTEP diagrams are
shown in Figure 1. In both 3cis and 3trans, the dppee ligands
bridge two gold atoms and the Au–P (average = 2.25 Å)
and Au–I (average = 2.55 Å) bond lengths are typical for
gold(I).[9–13] The P–Au–I angles are approximately linear.
C1–C1
Bond Angles [°]
Au1–Au1–I1
Au1–Au1–P1
I1–Au1–P1
Au1–P1–C1
Au1–P1–C2
83.51(2)
101.42(6)
174.81(6)
113.3(3)
114.1(3)
C1–P1–C2
Au1–P1–C8
C1–P1–C8
C2–P1–C8
P1–C1–C1
104.1(4)
115.9(3)
103.7(4)
104.4(4)
123.5(9)
Table 1. Selected bond lengths [Å] and angles [°] for compound 3cis.
Bond lengths [Å]
Au1–Au2
Au1–P1
Au2–P2
P1–C11
P2–C2
2.9526(5)
2.256(3)
2.253(2)
1.81(1)
1.831(11)
1.832(9)
Au1–I1
Au2–I2
P1–C1
P1–C31
P2–C21
C1–C2
2.5629(9)
2.5385(9)
1.81(1)
1.82(1)
1.82(1)
Electronic Spectra of dppee Gold Complexes and Quantum
Yield Measurements
The cis- and trans-dppee(AuX)2 complexes (X = Cl, Br,
I) exhibit featureless, broad absorptions above 300 nm. The
bands for each cis complex are slightly redshifted relative
to that of its trans isomer. Quantum yield measurements
were carried out at 334 nm where the molar absorptivities
of the cis complexes range from 0.9–3.0ϫ103 –1 cm–1 and
those of the trans complexes are near zero.[3] The quantum
P2–C41
1.332(14)
Bond Angles [°]
Au2–Au1–I1
Au2–Au1–P1
I1–Au1–P1
Au1–Au2–I2
Au1–Au2–P2
I2–Au2–P2
Au1–P1–C1
Au1–P1–C11
C1–P1–C11
90.24(2)
94.21(6)
174.80(7)
105.40(3)
82.30(6)
170.36(7)
119.1(3)
113.3(3)
103.7(5)
Au1–P1–C31
C1–P1–C31
C11–P1–C31
Au2–P2–C2
Au2–P2–C21
C2–P2–C21
Au2–P2–C41
C2–P2–C41
C21–P2–C41
112.8(4)
98.9(5)
107.6(4)
115.1(3)
116.3(3)
105.0(5)
110.2(3)
102.0(4)
106.9(4)
yields for disappearance, Φdisappearance
,
of the cis-
dppee(AuX)2 complexes measured at 334 nm are:
Φ(1cis,disappearance) = 0.204Ϯ0.062; Φ (2cis,disappearance) =
0.269Ϯ0.092; Φ(3cis,disappearance) = 0.363Ϯ0.055. Because
Table 3. Selected bond lengths and angles for 3cis and 3trans and related phosphane gold(I) complexes.
Complex
Au–P [Å]
Au–X [Å]
P–Au–X [°]
X–Au···Au–X Intramolecular Intermolecular
Ref.
Torsion [°]
Au···Au [Å]
(Յ 3.5 Å)
Au···Au [Å]
(Յ 3.5 Å)
cis-dppee(AuI)2 (3cis
cis-dppee(AuCl)2 (1cis
cis-dppbz(AuCl)2
trans-dppee(AuI)2 (3trans
)
2.256(3), 2.253(2)
2.226(4), 2.239(5)
2.5629(9), 2.5385(9)
2.299(5), 2.289(5)
174.80(7), 170.36(7)
172.5(2), 173.3(2)
63.61
52.49
–63.92
180.00
180.00
2.9526(5)
3.05(1)
2.996(1)
none
none
none
none
3.2292(7)
3.043(1)
this work
[1]
)
[12]
2.2408(15), 2.2360(16) 2.2921(16), 2.2925(16) 173.07(6), 173.21(6)
)
2.250(2)
2.235(2)
2.5435(9)
2.291(2)
174.81(6)
173.5(1)
this work
[2]
trans-dppee(AuCl)2 (1trans
)
none
Eur. J. Inorg. Chem. 2007, 4946–4951
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J. B. Foley, M. R. M. Bruce et al.
FULL PAPER
Figure 1. ORTEP drawings of a) 3cis and b) 3trans at the 50% probability level.
the photochemical isomerization processes are clean and and 22.5 kJmol–1 for X = Cl, Br, and I, respectively. Thus,
appear to be irreversible, the quantum yields are reasonable the aurophilic potential increases as the electronegativity of
estimates of the relative photoefficiencies of the cis to trans X decreases.
isomerizations, e.g. Φ(1cis,disappearance) = Φ(1cis Ǟ1trans).
It is interesting to note that the increase in quantum yield
Photochemical Isomerization of Alkenes – Direct and
Photosensitized
in this series is correlated with an increase in the aurophilic
attraction potential[16] (Figure 2). The quantum yield is also
correlated with a decrease in electronegativity of the halide
ligand X[16] (not shown). Both correlations give linear cor-
relation coefficients above 0.99. The aurophilic attraction
potential is a measure of the energy of interaction between
a dimer and a pair of monomers and has been calculated[16]
as well as estimated experimentally. Experimental values for
the aurophilic attraction potential, V(Re), have been re-
ported in the range 29–42 kJmol–1.[15,17–22] The ligand de-
pendence on aurophilic attraction has been studied on the
interacting, perpendicular X–Au–PH3 monomer by using
19-valence electron quasirelativistic pseudopotentials for
gold.[16] The study estimates that in interacting X–Au–PH3
monomers, the aurophilic potentials, V(Re), are 16.7, 19.3,
The direct and triplet sensitized photochemical isomer-
ization of alkenes and polyenes has been extensively studied
and reviewed. The ground state of the cis olefin is usually
slightly higher in energy than that of the trans isomer, and
photochemical processes have been shown to proceed
through either discrete singlet or triplet pathways. For many
organic dienes, e.g. stilbenes or 1,2-diphenylpropenes, pho-
toisomerization originating from either the cis or trans iso-
mer produces a photostationary state as a result of direct
photolysis or photolysis with the addition of a triplet sensi-
tizer.[23]
While the molar absorptivity of the two isomers at a par-
ticular wavelength affects the direct population of the cis*
and trans* excited states, it is the shape of the excited state
potential surface that is often critical for understanding the
mechanism and photoefficiency of isomerization.[24–29] The
research of Hammond and coworkers in the 1960s laid the
groundwork for an explosion of interest in this field by illus-
trating how suitable photosensitizers could be used to
understand reactivity that ensues after photoexcitation.[28]
To explain the basic photochemical phenomena, we have
included Figure 3, which shows cis and trans olefin ground
states, and an excited state potential surface reached by
photoexcitation. This is a generic diagram similar to many
diagrams used to discuss olefin photoisomerization,[26–28]
and precise details of energy changes of the ground state as
a function of olefin twist angle have been omitted. Exci-
tation, according to the Franck–Condon principle, pro-
duces vertical transitions and initial excited states possess
identical geometries as in the ground state. Three critical
points are important to keep in mind: (a) excitation of
Figure 2. Correlation between aurophilic attraction potential[14]
and quantum yield for isomerization of 1–3cis to 1–3trans
.
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Correlation Between Quantum Yield and Aurophilicity in Gold(I) Complexes
either isomer populates a common potential surface, (b) the the dppee ligand [see Equation (1)]. Thus, the ground state,
energy of the excited state is a function of the degree of excited state, and mixing of X, Au, and C=C orbitals all
olefin twist, and (c) deactivation pathways (e.g. thermal re- play important roles in the observed photoisomerization re-
laxation, luminescence) as well as the lifetime of the excited action.
state dictate how far the excited state travels along the ex-
Ab initio MP2 calculations on the model complexes cis-
cited state potential surface. The excited state perpendicular and trans-Au2X2C2H2(PH2)2 were previously reported and
geometry, p*, with a twist angle of 90° may be thought of the excited states were investigated by the CIS (configura-
ideally as the state from which it is equally possible to con- tion interaction with single excitations only) and CAS-
vert to either isomer (see Figure 3). In the diagram in Fig- LMP2 procedures.[30] The results show that in the cis com-
ure 3, the excited states trans* or p* occur at local minima pounds the degree of aurophilic interaction increases with
while cis* is found at a transient position. However, the an increase in the softness of the ligand. Thus, 3cis would
actual shape of the process under consideration varies and be expected to have a greater aurophilic interaction than
has a significant effect on the ensuing chemistry.
1cis. The aurophilic interactions stabilize the ground state of
the cis complexes relative to that of the trans complexes. In
addition, the aurophilic interactions stabilize the first ex-
cited state, which leads to a red shift and an increased tran-
sition moment for the cis complexes, in contrast to that ob-
served for the trans complexes. While the overall effect
lowers the energy needed for promotion into the first ex-
cited state of the 1cis–3cis complexes (i.e. the red shift), it
does not explain the increase in photoefficiency, since quan-
tum yield measures the ratio of the number of cis molecules
that isomerize relative to those that absorb light, regardless
of what the energy gap is at 334 nm.
The stabilization of the first excited state was found to
be critically dependent on the intramolecular Au–Au dis-
tance. The CIS calculations produce results that suggest
that the HOMO–LUMO transitions (as well as the first
few singlet excitations) are primarily halide to gold
[Au(5d6s6p)] charge transfer transitions. However, there
Figure 3. Relative energy of ground and excited states as a function
of the angle of twist around the C–C olefin bond.
We may also consider photolysis of a system that con- were significant admixtures from a variety of other orbitals.
tains a photosensitizer. In this case, photolysis produces an For both the cis and trans complexes, phosphorus p orbital
excited state sensitizer that must either become covalently character is found in the LUMO orbitals. In addition, for
attached or is pre-complexed to the olefin in order for pho- the cis complexes, the HOMO has some gold character, and
toisomerization to occur. Examples of sensitizers in both in the LUMO, there is significant ethylene π* character.
categories exist. In order for the sensitizer to influence the Population of an orbital with ethylene π* character in the
olefin, energy transfer must occur. If the excited state life- cis complexes would be predicted to weaken the carbon–
times are short compared to processes involving rotation carbon double bond. The shorter Au–Au bond length in
about the carbon–carbon double bond or if rotation is hin- 3cis than in 1cis may indicate a higher degree of aurophilic
dered, the excited state will undoubtedly relax with little or interaction. Although the ab initio calculations do not eas-
no photoisomerization. However, if the lifetime is suffi- ily permit quantification of orbital mixing, it seems reason-
ciently long for either a system involving a sensitizer or for able to suggest that the aurophilic interaction in the cis
direct photolysis of an olefin, then the shape of the excited complexes facilitates mixing of ethylene π* character in the
state potential surface and the energy available to the ex- excited states. Thus, it may be inferred that 3cis would have
cited state complexes will dictate the process that occurs.
a greater degree of ethylene π* character in the excited state
than 1cis.
The relatively high quantum yield for photoisomerization
of 1cis–3cis suggests that the HOMO–LUMO transition di-
rectly populates an orbital with sufficient ethylene π* char-
The Photochemical Process and Quantum Efficiency
To consider why the quantum yield for photoisomeriza- acter to weaken the C=C bond and permit rotation. Our
tion of 1cis–3cis is correlated with the aurophilic potential, results can be compared to the ReX(CO)3L2 complexes {see
it is useful to consider the overall photoisomerization as [Equation (2)]; X = Cl, Br; L = trans-4-styrylpyridine}
occurring in distinct steps involving absorption of a photon whose IL transitions involve a spin-allowed π–π* transition,
by a ground state molecule, the creation of an excited state which directly weakens the C=C bond, permitting rotation
complex, rotation about the C=C bond, and relaxation to and high quantum yields (Φ = 0.49–0.64). In this case, the
various isomers. The gold complexes may be thought of as quantum yields are very similar to that of the free ligand.[31]
an assembly involving a chromophore (X–Au) that is coval- In contrast, the quantum yield for photoisomerzation of
ently attached to the olefin through phosphorus atoms in cis-styrylferrocene [Equation (3)] is ca. 0.001. The inef-
Eur. J. Inorg. Chem. 2007, 4946–4951
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4949

J. B. Foley, M. R. M. Bruce et al.
FULL PAPER
the solutions were protected from light while transferring them to
a dark room for quantum yield experiments. No attempts were
made to exclude oxygen from the solutions. Previous studies con-
firmed that the presence of oxygen does not affect the photochemi-
cal isomerization reaction.[4] Solutions were irradiated at room tem-
perature in 1-cm quartz cells and were stirred during irradiation.
Absolute quantum yield measurements for the cis to trans isomer-
ization were made by monitoring the decrease in absorbance for
the cis complexes at 334 nm (X = I, Br, Cl). Absorbances were
measured by using a Beckman DU spectrophotometer. Quantum
yield measurements were replicated 4–6 times for each complex.
ficiency of this isomerization is attributed to rapid deactiva-
tion of the triplet cis excited state by the heavy atom ef-
fect.[26,32]
Crystal Structure Determination: Details of the X-ray experiments
and crystal data for 3cis and 3trans are summarized in Table 4. Crys-
tals of 3cis and 3trans were grown from CH2Cl2/Et2O. Crystals of
(2)
(3)
3trans turned opaque when exposed to the atmosphere owing to loss
of solvent, and no longer diffract X-rays. In order to prevent loss
of solvent, crystals of 3trans were coated with a thin film of epoxy.
Crystals of 3cis did not require any special treatment.
Table 4. Crystallographic data for compounds 3cis and 3trans
·
2CH2Cl2.
3cis
3trans·2CH2Cl2
We are continuing to explore the correlation between
quantum yield and aurophilic potential as a function of the
ligands attached to gold. Preliminary results indicate that
substitution of thiolate ligands for halides increases the
photoefficiency, while substitution of arsenic for phospho-
rus in dppee decreases the photoefficiency.
Chemical formula
Formula mass
Space group
a [Å]
b [Å]
c [Å]
C26H22Au2I2P2
1044.15
P1 21/n 1
12.6165(15)
14.505(1)
15.2955(9)
103.457(7)
2722.3(4)
4
C28H26Au2Cl4I2P2
1214.02
C 1 2/c 1
11.7391(14)
20.3363(16)
15.634(3)
108.255(17)
3544.6(9)
4
β [°]
V [Å3]
Z
T [°C]
Summary
21
21
λ [Å]
0.71073
2.547
13.164
0.0476
0.0548
0.71073
2.267
10.419
0.0380
0.0379
The crystal structure of the cis-(AuI)2dppee shows a
shorter gold–gold distance than the analogous chloride and
bromide complexes. This is consistent with the assertion,
made by Pyykkö and others, that soft ligands should in-
crease the gold–gold interaction. We have demonstrated
that the quantum yield for the photoisomerization of cis-
(AuX)2dppee to the trans-(AuX)2dppee [X = Cl(Φ = 0.204);
Br(Φ = 0.269); I(Φ = 0.363)] increases as the aurophilic at-
traction potential increases. We suggest that the increase in
quantum yield is indicative of increased ethylene π* charac-
ter in the first excited state of the iodide complex (3cis) rela-
tive to that in the chloride complex (1cis). This experimental
approach allows a quantitative comparison of the effect of
different ligands on the strength of gold–gold interactions.
ρcalcd. [g cm–1]
µ [cm–1]
R[a]
[b]
Rw
[a] R = ∑||Fo| – |Fc||/∑|Fo|. [b] Rw = [∑w(|Fo| – |Fc|)2/∑w|Fo|2]1/2
.
Data on 3cis and 3trans were collected with an Enraf–Nonius CAD4-
Turbo diffractometer at Brandeis University by using the Enraf–
Nonius EXPRESS program with Mo-Kα radiation (λ = 0.71073 Å).
The structures were solved by direct methods by using SHELXS-
86 and refined with the Oxford CRYSTALS package. Drawings
were made (50% probability ellipsoids) with the Oxford CAM-
ERON program. All non-hydrogen atoms were located from suc-
cessive difference-Fourier syntheses for both structures. Final re-
finement of positional and anisotropic displacement parameters for
all non-hydrogen atoms in compound 3cis led to R = 0.0476 and
Rw = 0.0548 by using 4602 data for which IϾ1.96σ(I). For com-
pound 3trans, final refinement of positional and isotropic displace-
ment parameters for all non-hydrogen atoms [anisotropic displace-
ment parameters for Au, P, I, C(1), C(2), and C(8), a total of 77
parameters] led to R = 0.0380 and Rw = 0.0379 by using 2272 data
for which IϾ1.96σ(I). Attempts to refine all non-hydrogen atoms
by using anisotropic displacement parameters led to unsatisfactory
values. Hence the non-ipso carbon atoms in each of the phenyl
rings were refined by using isotropic displacement parameters. The
hydrogen atoms were placed in calculated positions (dC–H = 0.95 Å)
in both structures.
Experimental Section
General Procedures: Methylene chloride (spectral grade) was ob-
tained from Aldrich and used as received. Complexes 1cis–3cis and
3trans were synthesized and purified as previously reported.[3,4] The
following abbreviations are used: dppee = 1,2-bis(diphenylphos-
phanyl)ethylene; dppbz = 1,2-bis(diphenylphosphanyl)benzene.
Quantum Yield Measurements: A 200-W Oriel mercury arc lamp
was used for quantum yield measurements. The wavelengths for the
experiments were isolated by using a model 77250 Oriel mono-
chrometer with 6-mm gratings. Ferrioxalate actinometry was used
for determining lamp flux for quantum yield calculations.[33] The
flux for the 200-W lamp had an average value of 6.12ϫ1015 pho-
tons/Ls. Gold(I) complexes were dissolved in dichloromethane, and
For the solvent molecule present in 3trans, only atom Cl(1) was re-
fined by using an anisotropic displacement parameter, while the
other atoms in the solvent molecule were refined by using isotropic
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Correlation Between Quantum Yield and Aurophilicity in Gold(I) Complexes
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Supplementary Crystallographic Data: CCDC-646580 and -646581
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Received: June 1, 2007
Published Online: September 14, 2007
Eur. J. Inorg. Chem. 2007, 4946–4951
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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