Stable and tunable phosphorescent neutral cyclometalated Au(III) diaryl complexes

Article abstract of DOI:10.1021/ic101437h

A series of novel luminescent cyclometalated Au(III) neutral complexes of the type cis-[(N^{^}C)AuL] [N^{^}C = 2-phenylpyridine (ppy), L = 1,1′-biphenyl (1)] and cis-[(N^{^}C)AuL₂] [N ^{^}C = 2-phenylpyridine (pp

Full text of DOI:10.1021/ic101437h

Inorg. Chem. 2010, 49, 11463–11472 11463
DOI: 10.1021/ic101437h
Stable and Tunable Phosphorescent Neutral Cyclometalated
Au(III) Diaryl Complexes
Jai Anand Garg, Olivier Blacque, Thomas Fox, and Koushik Venkatesan*
Institute of Inorganic Chemistry, University of Zu€rich, Winterthurerstrasse 190, CH-8057, Zu€rich, Switzerland
Received July 19, 2010
A series of novel luminescent cyclometalated Au(III) n∧eutral compl∧exes of the type cis-[(N∧C)AuL] [N∧C =
2-phenylpyridine (ppy), L = 1,10-biphenyl (1)] and cis-[(N C)AuL2] [N C = 2-phenylpyridine (ppy), L = C6H5 (2),
C6F5 (3), C6H4-CF3-p (4), 2-C4H3S (5)]; [N∧C = 2-(2-thienyl)pyridine (thpy), L = C6H5 (6), C6F5 (7)]; [N∧C = 2-(5-
methyl-2-thienyl)pyridine (5 m-thpy), L = C6F5 (8)] were successfully synthesized. The X-ray crystal structures of all
compounds except 3 have been determined. These complexes were found to show long-lived emission in solution at
room temperature. The emission origins of the complexes have been tentatively assigned to be derived from triplet
states predominantly bearing intraligand (IL) character with some perturbation from the metal center. Density
functional theory (DFT) calculations were performed to evaluate the stability associated with the complexes and
TD-DFT calculations to ascertain the nature of the excited state. Variation of the cyclometalated ligands in the
complexes readily leads to the tuning of the nature of the lower energy emissive states.
Introduction
of a cationic diimine Au(III) complex9 and more recently
biscyclometalated complexes of the type [Au(C∧N∧C)L)]
where L = aryl alkynyl11,12 as well as [Au(C∧N∧C)(NHC)]-
[PF6]13 has led to the cognition that strong σ-donating ligands
are key for populating the emissive states and also for
reducing the electrophilicity at the Au(III) metal center. We
hypothesized that cyclometalation, by the way of employing
strong field aromatic stabilized carbanions as ligands, would
sufficiently destabilize the metal centered (MC) transition to
higher energies thereby creating a conducive metal-ligand
environment for effective mixing of singlet-triplet states and
radiative relaxation from the triplet manifold.
Pertinent to our aim of creating Au(III) complexes en-
riched with gold-carbon bonds and evaluating their photo-
physical properties, methods for the syntheses of di- or triaryl
Au(III) complexes were of interest. Vicente and co-workers
have reported extensive investigations, notably devoted toward
development of synthetic methodologies for the creation of
diaryl Au(III) complexes.14-38 Triaryl Au(III) complexes are
relatively less common, nevertheless, not completely unknown;
The search for tunable room-temperature phosphorescent
neutral metal complexes has gained tremendous impetus
following the near-commercialization of cyclometalated Ir(III)
complexes as OLEDs.1-4 Recently, interest in understanding
the basic photoluminescence (PL) properties of previously
under-explored Au(III) complexes has gained attention with
a long-term vision of using them as efficient small molecule
phosphors.5 Although, gold is significantly a “heavy-metal”
with spin-orbit coupling constant ζ = 5100 cm-1 for its 5d
electrons,6,7 thermally accessible, low-lying metal-centered
(d-d) states and the photoreactivity exhibited by these com-
plexes are perhaps much to the disfavor of the metal being
considered for OLED applications.8-10 However, early report
*To whom correspondence should be addressed. E-mail: venkatesan.koushik@
aci.uzh.ch.
(1) Baldo, M. A.; O’Brien, D. F.; You, Y.; Shoustikov, A.; Sibley, S.;
Thompson, M. E.; Forrest, S. R. Nature 1998, 395, 151–154.
(2) Yersin, H. Highly efficient OLEDs with Phosphorescent Materials;
Wiley-VCH: Weinheim, 2008.
(3) Nazeeruddin, M. K.; Gratzel, M. Struct. Bonding (Berlin) 2007, 123,
113–175.
(4) Chou, P.-T.; Chi, Y. Chem.—Eur. J. 2007, 13, 380–395.
(5) Wong, K. M.-C.; Zhu, X. L.; Hung, L.-L.; Zhu, N. Y.; Yam,
V. W.-W.; Kwok, H.-S. Chem. Commun. 2005, 2906–2908.
(6) Griffith, J. S. The Theory of Transition Metals; Cambridge University
Press: Cambridge, 1964.
(7) Gao, L.; Partyka, D. V.; Updegraff, J. B.; Deligonul, N.; Gray, T. G.
Eur. J. Inorg. Chem. 2009, 2711–2719.
(8) Vogler, A.; Kunkely, H. Coord. Chem. Rev. 2001, 211, 223–233.
(9) Yam, V. W.-W.; Choi, S. W.-K.; Lai, T.-F.; Lee, W.-K. J. Chem. Soc.,
Dalton Trans. 1993, 1001–1002.
(10) Chan, C.-W.; Wong, W.-T.; Che, C.-M. Inorg. Chem. 1994, 33, 1266–
1272.
€
(11) Wong, K. M.-C.; Hung, L.-L.; Lam, W. H.; Zhu, N. Y.; Yam,
V. W.-W. J. Am. Chem. Soc. 2007, 129, 4350–4365.
(12) Yam, V. W.-W.; Wong, K. M.-C.; Hung, L.-L.; Zhu, N. Y. Angew.
Chem., Int. Ed. 2005, 44, 3107–3110.
(13) Au, V. K.-M.; Wong, K. M.-C.; Zhu, N. Y.; Yam, V. W.-W. J. Am.
Chem. Soc. 2009, 131, 9076–9085.
ꢀ
(14) Uson, R.; Laguna, A.; Vicente, J. J. Organomet. Chem. 1975, 86, 415–
421.
(15) Uson, R.; Laguna, A.; Vicente, J. J. Organomet. Chem. 1977, 131,
ꢀ
471–475.
ꢀ
(16) Uson, R.; Laguna, A.; Vicente, J.; Garcı
´
a, J.; Bergareche, B.; Brun, P.
Inorg. Chim. Acta 1978, 28, 237–243.
r
2010 American Chemical Society
Published on Web 11/12/2010
pubs.acs.org/IC

11464 Inorganic Chemistry, Vol. 49, No. 24, 2010
Garg et al.
interesting transmetallating procedures using organomercur-
ials have been reported by the same group for obtaining such
complexes.39-43 It is therefore of interest to investigate these
established classes of complexes as potential photoactive
materials.
Scheme 1
Our initial experiments to substitute halides in monocy-
clometalated Au(III) complexes using lithiated aryls were
promising and encouraged us to proceed further in these
lines. However, we noticed that some of these complexes
showed signs of decomposition during reaction and in solid
state after isolation. Complexes with two aryl ligands dis-
posed cis to each other in a square planar environment could
be unstable because of their ability for facile reductive elimi-
nation either forming Au(I) species or metallic gold;10,39,44-46
this could also be understood in light of the fact that Au(III)
complexes tend to have large positive redox potentials. The
instability could also be reminiscent to the phenomenon of
Aryl/PPh3 “transphobia” commonly used in palladium chem-
istry.47,48 We thought that utilization of aryl ligands bearing
fluorinated substituents could render the Au(III) complexes
stable because of the possible increase in the π-back-donation
from the metal. Indeed, in our case, complexes synthesized
with such substituents were found to be more stable.
ꢀ
(17) Uson, R.; Vicente, J.; Cirac, J. A.; Chicote, M. T. J. Organomet.
Results and Discussion
Chem. 1980, 198, 105–112.
(18) Vicente, J.; Chicote, M. T.; Arcas, A.; Artigao, M. Inorg. Chim. Acta
1982, 65, L251–L253.
Syntheses and Characterization of Complexes. Our in-
itial aim was to synthesize a planar (π-delocalized) cyclo-
metalated complex using dicarbanionic chelate like 2,20-
biphenyl dianion as an ancillary ligand and evaluate its
PL properties. We hoped that incorporation of biphenyl
ligand would create appropriately placed intermediate
electronic states below the dissociative MC states leading
to interesting photophysical properties. Lithium-halogen
exchange was adopted to be a general synthetic protocol
for generating aryl anions suitable to substitute gold
halides at low temperatures (-78 °C). Creation of com-
plex 1 (Scheme 1) was realized with difficulty overcoming
synthetic impediments to the best of 12% yield following
some optimization experiments. Addition of catalytic
amount of AgOTf significantly aided the formation of
desired product. It needs to be mentioned here that the
desired product could possibly be obtained following a
transmetalation sequence described in literature and was
not investigated by us.17 Much to our encouragement the
complex showed room temperature (RT) phosphores-
cence in fluid medium. In efforts to further improve the
yield, we surmised that complexes bearing aryl carba-
nions as ligands but having less constrained arrangement
around the metal center can be a better alternative and
may exhibit better properties. Also, from a mechanistic
standpoint, ligand substitution in square planar Au(III)
complexes (d8 systems) as in our case is likely to follow an
associative pathway by a stepwise nucleophilic substitu-
tion sequence leading to a five coordinated ionic square
planar or trigonal bipyrimidal intermediate in the transi-
tion state. It is therefore probable that the bidentate
coordination modes in the later transition states would
require greater activation energy than for the monoden-
tate ones. However, on the other hand the products of the
latter case provide greater risk of reductive elimination,
which have been largely circumvented by utilization of
perfluorinated ligands in the study presented here.
ꢀ
(19) Vicente, J.; Chicote, M. T.; Arcas, A.; Artigao, M.; Jimenez, R.
J. Organomet. Chem. 1983, 247, 123–129.
ꢀ
(20) Vicente, J.; Chicote, M. T.; Bermudez, M. D.; Solans, X.; Font-
Altaba, M. J. Chem. Soc., Dalton Trans. 1984, 557–562.
(21) Vicente, J.; Chicote, M. T.; Cayuelas, J. A.; Fernandez-Baeza, J.;
Jones, P. G.; Sheldrick, G. M.; Espinet, P. J. Chem. Soc., Dalton Trans. 1985,
1163–1168.
ꢀ
(22) Vicente, J.; Chicote, M. T.; Bermudez, M. D.; Sanchez-Santano,
M. J.; Jones, P. G.; Fittschen, C.; Sheldrick, G. M. J. Organomet. Chem.
1986, 310, 401–409.
(23) Vicente, J.; Chicote, M. T.; Saura-Llamas, I.; Turpin, J.; Fernandez-
Baeza, J. J. Organomet. Chem. 1987, 333, 129–137.
ꢀ
(24) Vicente, J.; Chicote, M. T.; Bermudez, M. D.; Sanchez-Santano,
M. J.; Jones, P. G. J. Organomet. Chem. 1988, 354, 381–390.
(25) Vicente, J.; Chicote, M. T.; Saura-Llamas, I.; Jones, P. G.; Meyer-
€
€
Base, K.; Erdbrugger, C. F. Organometallics 1988, 7, 997–1006.
ꢀ
(26) Vicente, J.; Bermudez, M. D.; Chicote, M. T.; Sanchez-Santano,
M. J. J. Chem. Soc., Chem. Commun. 1989, 141–142.
ꢀ
(27) Vicente, J.; Bermudez, M. D.; Chicote, M. T.; Sanchez-Santano,
M. J. J. Organomet. Chem. 1989, 371, 129–135.
ꢀ
(28) Vicente, J.; Bermudez, M. D.; Chicote, M. T.; Sanchez-Santano,
M. J. J. Organomet. Chem. 1990, 381, 285–292.
ꢀ
(29) Vicente, J.; Bermudez, M. D.; Chicote, M. T.; Sanchez-Santano,
M. J. J. Chem. Soc., Dalton Trans. 1990, 1945–1950.
ꢀ
(30) Vicente, J.; Bermudez, M. D.; Escribano, J.; Carrillo, M. P.; Jones,
P. G. J. Chem. Soc., Dalton Trans. 1990, 3083–3089.
ꢀ
ꢀ
(31) Vicente, J.; Bermudez, M. D.; Sanchez-Santano, M. J.; Paya, J.
Inorg. Chim. Acta 1990, 174, 53–56.
(32) Vicente, J.; Chicote, M. T.; Saura-Llamas, I. J. Chem. Soc., Dalton
Trans. 1990, 1941–1944.
(33) Vicente, J.; Chicote, M. T.; Lagunas, M. C.; Jones, P. G. J. Chem.
Soc., Dalton Trans. 1991, 2579–2583.
ꢀ
(34) Vicente, J.; Bermudez, M. D.; Carrillo, M. P.; Jones, P. G. J. Chem.
Soc., Dalton Trans. 1992, 1975–1980.
ꢀ
(35) Vicente, J.; Bermudez, M. D.; Carrillo, M. P.; Jones, P. G.
J. Organomet. Chem. 1993, 456, 305–312.
ꢀ
ꢀ
(36) Vicente, J.; Bermudez, M. D.; Carrion, F. J. Inorg. Chim. Acta 1994,
220, 1–3.
ꢀ
ꢀ
(37) Vicente, J.; Bermudez, M. D.; Carrion, F. J.; Jones, P. G.
J. Organomet. Chem. 1996, 508, 53–57.
(38) Vicente, J.; Chicote, M. T. Coord. Chem. Rev. 1999, 195, 1143–1161.
ꢀ
(39) Vicente, J.; Bermudez, M. D.; Escribano, J. Organometallics 1991, 10,
3380–3384.
ꢀ
ꢀ
(40) Vicente, J.; Bermudez, M. D.; Carrion, F. J.; Jones, P. G. Chem. Ber.
1996, 129, 1301–1306.
ꢀ
ꢀ
(41) Vicente, J.; Bermudez, M. D.; Carrion, F. J.; Jones, P. G. Chem. Ber.
1996, 129, 1395–1399.
In this paper, we describe the syntheses, structural char-
acterization, and tunable emission properties of a series of
neutral cycloaurated complexes of the type cis-[(N∧C)AuLn]
(42) Bardaji, M.; Laguna, A. Inorg. Chim. Acta 2001, 318, 38–44.
(43) Bardaji, M.; Laguna, A.; Vicente, J.; Jones, P. G. Inorg. Chem. 2001,
40, 2675–2681.
(44) Komiya, S.; Albright, T. A.; Hoffmann, R.; Kochi, J. K. J. Am.
Chem. Soc. 1976, 98, 7255–7265.
(45) Cinellu, M. A.; Zucca, A.; Stoccoro, S.; Minghetti, G.; Manassero,
M.; Sansoni, M. J. Chem. Soc., Dalton Trans. 1996, 4217–4225.
(46) Kar, A.; Mangu, N.; Kaiser, H. M.; Beller, M.; Tse, M. K. Chem.
Commun. 2008, 386–388.
(47) Vicente, J.; Arcas, A.; Bautista, D.; Jones, P. G. Organometallics
1997, 16, 2127–2138.
(48) Vicente, J.; Abad, J. A.; Frankland, A. D.; de Arellano, M. C. R.
Chem.—Eur. J. 1999, 5, 3066–3075.

Article
Inorganic Chemistry, Vol. 49, No. 24, 2010 11465
Scheme 2
Figure S2). 2 and 3 showed initial weight loss (∼ T10%) in
the interval 100-185 °C and 133-242 °C, respectively;
the onset of total degradation (Td) of 3 was observed at
relatively higher temperature (Td = 250 °C) than 2 (Td =
180 °C).
Structural and Photophysical Characterization. X-ray
single crystal structures were determined for all com-
plexes except 3. The perspective views of 1, 2, 5, and 8 are
shown in Figure 1 (for others see Figures S3-S5 in
Supporting Information). As expected the Au(III) atom
adopts a distorted square planar environment, the average
Au-N bond distance is 2.102 A and the mean Au-Caryl
bond distance of non-cyclometalated ligands (both cis
and trans to nitrogen) was found to be 2.043 A, values
which correspond closely with those reported for similar
[Au(C∧N∧C)] complexes11,12 and the cationic diimine
complexes.9 The N-Au-C bite angles in 1-8 are re-
stricted in the interval of 79.3-80.8° because of the steric
requirements of the cyclometalating N∧C ligands; conse-
quently the respective trans angle to the ancillary carbons
also deviates accordingly. The effect is more pronounced
in 1 where there is an imposing steric congestion of both
the ppy and biphenyl. Further, the molecular packing in the
crystal structures of these complexes showed no Au Au
interactions; the shortest intermolecular Au Au dis-
3 3 3
3 3 3
tance is 4.8022(1) A in 1. It is important to note that the
crystal structures did not reveal the presence of any kind
of solvent coordination to the metal center. Concentration
dependent absorption studies of all the complexes in CH2Cl2
(c ≈ 10-6-10-4 mol dm-3) did not change either the peak
maxima or generate an additional low energy band confirm-
(L = aryl, n = 1, 2) most of which (1, 3, 4, 6-8) exhibits
good stability in common organic solvents and are also
stable in the solid state for months under ambient conditions.
Au(III) complexes, namely, cis-[(N∧C)AuL] [N∧C =
2-phenylpyridine (ppy), L = 1,10-biphenyl (1)]; cis-[(N∧C)-
AuL2] [N∧C = 2-phenylpyridine, L = C6H5 (2), C6F5 (3),
C6H4-CF3-p (4), 2-C4H3S (5)]; [N∧C = 2-(2-thienyl)-
pyridine (thpy), L = C6H5 (6), C6F5 (7)]; [N∧C = 2-(5-
methyl-2-thienyl)pyridine (5 m-thpy), L = C6F5 (8)] were
prepared from their corresponding cycloaurated Au(III)
dichlorides (Scheme 2). Yields for complexes 2-8 were
modest in the range 25-56% owing to the concomitant
biaryl formation via reductive elimination as confirmed
ing the absence of Au Au interactions in solution and also
precludes any excimeric (MMLCT) transitions.
3 3 3
Complexes 1-8 showed emission both in fluid solution
at RT and in rigidified glass media (2-MeTHF) at 77 K.
The spectroscopic data for complexes 1-8 are given in
Table 1, and the absorption and emission profiles of com-
plexes 1-3 and 6-8 are shown in Figure 2, respectively.
Cyclometalated complexes with a ppy core exhibited
intense absorption with lowest energy absorption max-
ima in the range λ = 316-338 nm. The thpy complexes 6
and 7 showed bathochromic shifts (λ ∼ 40 nm) as expected
for compounds, which inherently possess donor-acceptor
(D-A) properties.52 The red shift was more pronounced
for the 5 m-thpy complex 8 with the effect arising from the
methyl substituent.53 In general, the shape and position of
absorption bands in electronic spectra resemble the skeletal
vibrations of their respective ligands with a slight red shift
(5-9 nm). This indicates that the π-conjugation is pre-
served through the metal site by mixing of the contributing
frontier orbitals of the gold atom and the ligand.
1
by H NMR study. To our knowledge this is the first
report of structurally characterized Au(III) monocyclo-
metalated complexes with diaryl ligands. A cycloauration
method described earlier in literature49 was followed for
obtaining dichloride precursor cis-[(N∧C)AuCl2] [N∧C =
2-phenylpyridine (ppy)] for the synthesis of 1-5. Complexes
6 and 7 were obtained from cis-[(N∧C)AuCl2] [N∧C =
2-(2-thienyl)pyridine (thpy)] by following a procedure50
which was also analogously adopted for synthesizing pre-
viously unknown cis-[(N∧C)AuCl2] [N∧C = 2-(5-methyl-
2-thienyl)pyridine (5 m-thpy)], the dihalide precursor for
8. It is important to note that these starting materials do
not exhibit RT phosphorescence.51
The stability of these complexes were found to depend
significantly on the nature of the aryl ligands. Complexes
containing nonperfluorinated groups showed signs of gradual
decomposition in the solid state. The thermal stability of
complexes 2 and 3 in solid state were studied using thermo-
gravimetric analysis (TGA) (See Supporting Information,
Varying ligands ancillary to the cyclometalating (N∧C)
gold center had no marked effect on the absorption wave-
lengths. Increasing solvent polarity from toluene to tetra-
hydrofuran (THF) showed a slight hypsochromic shift
(λ ∼ 6 nm) for complexes 3-5 and for 7-8 indicating the
ground state has more polar character as compared to the
excited state. The emission spectra of the ppy complexes
(49) Constable, E. C.; Leese, T. A. J. Organomet. Chem. 1989, 363, 419–
424.
(50) Fuchita, Y.; Ieda, H.; Wada, S.; Kameda, S.; Mikuriya, M. J. Chem.
Soc., Dalton Trans. 1999, 4431–4435.
(51) Mansour, M. A.; Lachicotte, R. J.; Gysling, H. J.; Eisenberg, R.
Inorg. Chem. 1998, 37, 4625–4632.
(52) Tsuboyama, A.; Iwawaki, H.; Furugori, M.; Mukaide, T.; Kamatani,
J.; Igawa, S.; Moriyama, T.; Miura, S.; Takiguchi, T.; Okada, S.; Hoshino,
M.; Ueno, K. J. Am. Chem. Soc. 2003, 125, 12971–12979.
€
(53) Thomas, S. W., III; Venkatesan, K.; Muller, P.; Swager, T. M. J. Am.
Chem. Soc. 2006, 128, 16641–16648.

11466 Inorganic Chemistry, Vol. 49, No. 24, 2010
Garg et al.
Figure 1. X-ray crystal structures of 1, 2, 5, and 8 with selective atomic numbering scheme. Thermal ellipsoids are drawn at the 30% probability level.
Hydrogen atoms and solvent molecules are omitted for clarity.
Table 1. Photophysical Properties of Complexes 1-8
room temperature solution (CH2Cl2)
absorption λmax[nm]
(εmax/[dm3 mol-1cm-1])
emission λmax[nm]
τ [μs]
ΦP
kr [s-1] ꢀ 103
knr [s-1] ꢀ 105
77 K glassb (2-MeTHF)
a
complex
1
2
3
4
5
6
7
8
308 (5145), 317 (5385)
316 (8480)
324 (7214), 338 (5254, sh)
321 (8623)
319 (7884)
287 (13700), 357 (8070)
286 (12610), 363 (8540)
294 (8810), 380 (5760)
484, 506
1.10
0.33
4.41
1.23
0.53
1.15
1.12
1.21
3.7 ꢀ 10-3
9.5 ꢀ 10-3
1.0 ꢀ 10-3
9.9 ꢀ 10-3
1.9 ꢀ 10-2
2.5 ꢀ 10-3
1.5 ꢀ 10-3
2.0 ꢀ 10-3
3.4
28.7
0.2
8.0
35.8
2.7
1.3
1.6
9.1
30.0
2.3
8.1
18.5
8.6
8.9
8.2
478, 513, 540
453, 485, 512
457, 489, 528
452, 486, 517
453, 489, 515
522, 541, 563
527, 545, 570
548, 593
467 (sh), 490, 519 (sh)
471 (sh), 493, 529 (sh)
470 (sh), 490, 522 (sh)
472 (sh), 492, 526 (sh)
537, 569
544, 577
548, 592
a PL quantum yield determined with quinine sulfate as standard at 298 K. b Vibronic structured emission bands.
1-5 in CH2Cl2 exhibit a low vibronic structured band
with λmax centered around 490 nm and more resolved pro-
gressive vibrational progression spacings of ∼1500 cm-1
at 77 K (2-MeTHF), which is close to stretching modes of
CdC in pyridine systems. Again, the emission wavelengths
did not change with different ancillary ligands like phenyl,
pentafluorophenyl, p-trifluoromethylphenyl, and thienyl.
Emission spectra of the thpy cyclometalates 6-8 depicted
the same trend as for the ppy ones but systematically red-
shifted in line with their respective absorption profiles.
Vibrational spacings of about ∼1400 cm-1 were also observed
here. On the basis of the above observations and considering
the low radiative rate constant54 kr ∼ 103-104 s-1 (see
Table 1), the origin of the emission is assigned to intra-
ligand charge transfer (3ILCT) [π-π*] perturbed by the
metal center. Stokes shifts of the lower lying emission in
the range of 174-220 nm and lifetimes in the sub micro-
second regime together with the observation of a 5 to 10-fold
decrease in PL intensities upon exposure to molecular
dioxygen suggest that the emission occurs from the triplet
state. Isoelectronic biscyclometalated platinum(II) systems
reported possess emission properties with more metal con-
tribution in contrast to these Au(III)diaryl complexes.55,56
(54) Radiative (kr) and non-radiative (knr) decay rates were estimated
from the lifetime data (τ) using the formula kr = ΦP/τ and knr = (1 - ΦP)/τ
assuming radiative rate constants do not show significant temperature
dependence from 77 to 298 K and kisc is considered as unity.

Article
Inorganic Chemistry, Vol. 49, No. 24, 2010 11467
Figure 2. (left) Electronic absorption and normalized emission (I) spectra of 1 (dotted line), 2 (dashed line), 3 (solid line) in degassed CH2Cl2 at 298 K and
(right) electronic absorption and normalized emission (I) spectra of 6 (dotted line), 7 (dashed line), 8 (solid line) in degassed CH2Cl2 at 298 K.
Figure 3. DFT optimized transition states TS-2 (left) and TS-3 (right).
DFT calculations. To gain insight into the properties of
our Au(III) complexes, density functional theory (DFT)
studies were carried out with the Gaussian03 program
package57 using the hybrid functional PBE1PBE58 in con-
junction with the Stuttgart/Dresden effective core poten-
tials (SDD) basis set59 for the Au center augmented with
one f-polarization function (R = 1.050) and the standard
6-31þG(d) basis set60 for the remaining atoms. The relative
stability of the compounds bearing different ancillary aryl
ligands was first investigated. The transition states (TS)
encountered during the intramolecular dimerization of
C6H5 in 2 and C6F5 in 3 were successfully optimized and
characterized (Figure 3). The Caryl Caryl distance of
3 3 3
1.900 for TS-2 and 1.697 A for TS-3 clearly indicates that
the C-C bond formation in 2 occurs in an earlier stage in
comparison with 3. Furthermore, the electronic energies
reveal decomposition barrier heights of 21.9 and 40.7
kcal/mol respectively and therefore confirm that the
decomposition of the Au(III) complexes leading to the
formation of corresponding biphenyl is significantly faster
in 2. This is also consistent with the experimental obser-
vation for these complexes.
(55) Chassot, L.; Muller, E.; von Zelewsky, A. Inorg. Chem. 1984, 23,
4249–4253.
(56) Chassot, L.; von Zelewsky, A. Inorg. Chem. 1987, 26, 2814–2818.
(57) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Rob,
M. A.; Cheeseman, J. R.; Montgomery Jr., J. A.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci,
B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.;
Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.;
Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox,
J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.;
Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.;
Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari,
K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.;
Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.;
Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng,
C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.;
Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03; Gaussian,
Inc.: Wallingford, CT, 2003.
Time-dependent density functional theory (TD-DFT)61-63
combined with the conductive polarizable continuum model
(CPCM)64,65 was used to produce the ten lowest singlet-
singlet and singlet-triplet vertical excitations calculated
(61) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. J. Chem. Phys. 1998,
109, 8218–8224.
(62) Bauernschmitt, R.; Ahlrichs, R. Chem. Phys. Lett. 1996, 256, 454–464.
(63) Casida, M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R. J. Chem.
Phys. 1998, 108, 4439–4449.
(64) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995–2001.
(65) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem.
2003, 24, 669–681.
(58) Adamo, C.; Barone, V. J. Chem. Phys. 1999, 110, 6158–6170.
(59) Dunning, T. H., Jr.; Hay, P. J. Modern Theoretical Chemistry;
Plenum: New York, 1976; Vol. 3.
(60) Ditchfie, R.; Hehre, W. J.; Pople, J. A. J. Chem. Phys. 1971, 54, 724–
728.

11468 Inorganic Chemistry, Vol. 49, No. 24, 2010
Garg et al.
Figure 4. TD-DFT/CPCM calculated LUMOþ2 (left) and HOMO
(right) of the ground state geometry of 1.
Figure 5. TD-DFT/CPCM calculated HOMO (left) and LUMO (right)
of the ground state geometry of 3.
(CH2Cl2) energy difference between the optimized ground
and triplet states. The calculated λmax of 486 nm is in good
agreement with the experimental data of 506 nm. In the
other ppy- containing compounds 2-5, the optimized triplet
states also correspond very well to the lowest vertical
singlet-triplet transitions S0-T1. The main difference in
comparison with 1 is that the orbitals involved in the
π-π* transition are mainly located on the ppy ligand:
H-1fL (83f94%), H fL(98f92%), H-1fL(92f95%),
H-2fL (95f95%) for 2-5, respectively. This indicates
that the excited state exhibits a 3ILCT [πfπ* (ppy)] char-
acter, only slightly perturbed by the metal center (2-6%)
(Figure 5). As a result, it was found that the main geo-
metric changes appear in the ppy group where the bond
distance of the C-C linker is shortened by 0.078-0.079 A
compared to the ground state parameters. The estimated
emission maxima based on the calculated ground and
triplet state energies correlate successfully with the exp-
erimental emission wavelengths (in parentheses) with 466
(490), 472 (493), 468 (490), and 470 (492) nm for 2-5,
respectively.
The same study was adopted for the thpy species 6-8.
For all the three compounds, the lowest vertical triplet
S0-T1 transition corresponds to the H f L excitation. H
and L orbitals are at 96-99% and 92-93% located on the
thpy ligand respectively, indicating a 3ILCT [πfπ*
(thpy)] character of the triplet state. The main variations
in the geometry of the optimized triplet states are no
longer observed on the C-C bridge (only -0.049 to
-0.056 A) but rather in the five-membered thienyl ring
with significant elongations of four over five bond dis-
tances (þ0.011 to þ0.096 A), in agreement with the shape
of the π/π* H and L orbitals. The significant red-shifted
emission of 6-8 in comparison with 1-5 is also well
reproduced by our calculations with 569 (569), 572 (577),
and 604 (592) nm for 6-8, respectively.
at the ground state singlet S0 optimized geometries.
Despite the PBE1PBE64 calculations having systemati-
cally provided underestimated absorption maxima λmax
by 17-20 nm (5-8) or 26-45 nm (1-4), the absorption
properties of 1-8 and the trend observed in the experi-
ments are well reproduced by the calculations (see Sup-
porting Information, Table S5). For 2-8, the lowest
significant singlet transition S0fSn (n = 1 for 3, 6, 7, 8;
n = 2 for 2, 4; n = 3 for 5) is the one showing the largest
coefficient of the calculated excited states. The frontier
molecular orbitals involved in the dominant excitation
are almost exclusively located on the N∧C ligands, ppy for
2-5 or thpy for 6-8 as expected. This can be attributed to
1
a transition with an intraligand charge transfer ILCT
[πfπ*] character. For 1, the picture is different since
three low energy transitions of similar intensity at 311,
288, and 282 nm were calculated. The two lowest-lying
transitions S0fS3 and S0fS6 at 311 and 288 nm are due
to the one-electron excitations from HOMO-2fLUMO
and HOMO-4fLUMO, respectively (hereafter H =
HOMO, L = LUMO). H-2 and H-4 are mainly com-
posed of π orbitals of biphenyl (bip) and ppy, whereas L is
dominantly localized on ppy (86%), consequently the
corresponding band can be attributed to a transition with
an admixture of ligand-to-ligand 1LLCT [π(bip)fπ*(ppy)]
and intraligand 1ILCT [πfπ* (ppy)] characters. The S0fS8
transition at 282 nm with the most relevant contribution
from HfLþ3 accounts for an inverse charge transfer
since H is at 97% on bip and Lþ3 is totally delocalized
over the whole molecule.
The lowest vertical triplet S0-T1 transition of 1 is π-π*
type defined by the configuration HfLþ2 where H is
mainly a π orbital localized at the bip ligand (97%) and
Lþ2 is a π* orbital delocalized at 75% on the bip, 17% on
the ppy ligand, and at 8% on the metal center (Figure 4).
This indicates that the excited state contains both 3LLCT
[π(bip)fπ*(ppy)] and 3ILCT [π(bip)fπ*(bip)] charac-
ters. The DFT optimized triplet state is in agreement with
the lowest-lying π-π* transition since the main varia-
tions of the geometrical parameters relative to the ground
state of 1 correspond well to the electronic transition from
H to Lþ2, especially for the C-C bond bridging the two
rings of the bip, the bond distance of which is hardly
shortened by 0.081 A in the triplet state, a consequence of
the π antibonding character of the C-C bond in H and π
bonding in Lþ2 (which became the lower- and higher-
energy singly occupied molecular orbital of the optimized
triplet state). All bond distances around the metal center
are also slightly shortened in the triplet state. The emission
maximum of 1 was estimated by the solvent-corrected
Conclusion
We have shown for the first time that cyclometalated com-
pounds of the type cis-[(N∧C)AuLn] (L = aryl, n = 2) are
stable with the incorporation of fluorinated functional groups
on the aryl rings. They show phosphorescence emission at RT
in fluid solution and their emission wavelengths can be tuned
by changing the cyclometalating ligand. DFT calculations in
conjunction with experimental work have ascertained the
relative stability of the complexes and the nature of the triplet
excited state. The stability and ease of tunability demon-
strated in this work make these systems amenable for the
development of efficient neutral triplet phosphors for OLED
applications. Several strategies are currently being pursued in

Article
Inorganic Chemistry, Vol. 49, No. 24, 2010 11469
our group for the improvement of quantum yields and to
obtain blue triplet emitters based on these Au(III) complexes.
PBE1PBE58 in conjunction with the Stuttgart/Dresden effective
core potentials (SDD) basis set59 for the Au center augmented
with one f-polarization function (exponent R = 1.050) and the
standard 6-31þG(d) basis set60 for the remaining atoms. Several
exchange-correlation functionals (B3LYP,67-69 MPW1K,70,71
BB1K,67,72,73 PBE1PBE,58 G96LYP,68,72 TPSS74,75 and TPSS-
LYP1W75) were tested on the geometry structures of 1 and 2; the
hybrid PBE1PBE provided the best match with the geometrical
X-ray data and was selected for our study (see Supporting
Information). Full geometry optimizations without symmetry
constraints were carried out in the gas phase for both the singlet
ground states (S0) and the lowest triplet excited states (T1). The
optimized geometries were confirmed to be potential energy
minima by vibrational frequency calculations at the same level
of theory, as no imaginary frequencies were found. The first 10
singlet-singlet and singlet-triplet transition energies were computed
at the optimized S0 geometries, by using the time-dependent
DFT (TDDFT) methodology.61-63 Solvent effects were taken
into account using the conductive polarizable continuum model
(CPCM)64,65 with dichloromethane as solvent for single-point
calculations on all optimized gas-phase geometries.
Experimental Section
Materials and General Methods. Commercially available
reagents were purchased from Aldrich and were used as such
without further purification. Diethylether used in reactions was
dried by distillation under N2 atmosphere using sodium benzo-
phenone ketyl radical prior to use. Sodium tetrachloroaurate
(III) dihydrate was purchased from Strem chemicals. Gold(III)
dichloride precursor complex [(N∧C)AuCl2][N∧C = 2-phenyl-
pyridine (ppy)] (A) was prepared according to a known procedure49
and [(N∧C)AuCl2][N∧C = 2-(2-thienyl)pyridine (thpy)] (B) was
synthesized based on a different cycloauration procedure.50
A
procedure analogous to the latter was adopted for preparing
precursor complex [N∧C = 2-(5-methyl-2-thienyl)pyridine
(5 m-thpy)][AuCl2] (C), which is described below. All manipula-
tions requiring an inert atmosphere were carried out using
standard Schlenk techniques under dinitrogen. 1H, 13C{1H},
and 19F NMR spectra were recorded on Bruker AV2-400
(400 MHz) or AV-500 (500 MHz) spectrometers. Chemical
shifts (δ) are reported in parts per million (ppm) referenced to
tetramethylsilane (δ 0.00 ppm) using the residual proton solvent
peaks as internal standards (1H NMR experiments) or the
characteristic resonances of the solvent nuclei (13C NMR experi-
ments). 19F NMR was referenced to CFCl3 (δ0.00 ppm). Coupling
constants (J) are quoted in hertz (Hz), and the following abbre-
viations are used to describe the signal multiplicities: s (singlet);
d (doublet); t (triplet); q (quartet); m (multiplet); dd (doublet of
doublet); td (triplet of doublet); dm (doublet of multiplet).
Proton and carbon assignments have been made using routine
one and two-dimensional NMR spectroscopies where appropriate.
Infrared (IR) spectra were recorded on a Perkin-Elmer 1600
Fourier Transform spectrophotometer using KBr pellet with
frequencies (νmax) quoted in wavenumbers (cm-1). Elemental
microanalysis was carried out with Leco CHNS-932 analyzer.
Mass spectra were run on a Finnigan-MAT-8400 mass spectro-
meter. TLC analysis was performed on precoated Merck Silica
Gel 60F254 slides and visualized by luminescence quenching
either at (short wavelength) 254 nm or (long wavelength) 365 nm.
Chromatographic purification of products was performed on a
short column (length 15.0 cm: diameter 1.5 cm) using silica gel
60, 230-400 mesh using a forced flow of eluent. UV-vis measure-
ments were carried out on a Perkin-Elmer Lambda 19 UV/vis
spectrophotometer. Emission spectra were acquired on Perkin-
Elmer spectrophotometer using 450 W xenon lamp excitation by
exciting at the longest-wavelength absorption maxima. All samples
for emission spectra were degassed by at least three freeze-
pump-thaw cycles in an anaerobic cuvette and were pressurized
with N2 following each cycle. 77 K emission spectra were
acquired in frozen 2-methyltetrahydrofuran (2-MeTHF) glass.
Luminescence quantum yields of (φ) were determined at 298 K
(estimated uncertainty (15%) using standard methods;66 wave-
length-integrated intensities (I) of the corrected emission spectra
were compared to iso-absorptive spectra of quinine sulfate standard
(φr = 0.54 in 1N H2SO4 air-equilibrated solution) and were
corrected for solvent refractive index. Phosphorescence lifetime
measurements were performed on an Edinburgh FLS920 spec-
trophotometer, using nF900 with 30000 Hz frequency, with
15 nm excitation and 15 nm emission slit widths. Thermogravi-
metric analysis (TGA) was done using a NETZSCH STA 449C
instrument. The thermal stability of the samples under a nitro-
gen atmosphere was determined by measuring their weight loss
while heating at a rate of 1 °C min-1 from 25 to 600 °C.
X-ray Diffraction Analyses. Relevant details about the struc-
ture refinements are given in Supporting Information, Tables S1
and S2, and selected geometrical parameters are included in the
captions of the corresponding figures (Supporting Information,
Figures S3, S4, and S5). Intensity data were collected at 183(2) K
an Oxford Xcalibur diffractometer (4-circle kappa platform,
Ruby CCD detector, and a single wavelength Enhance X-ray
source with Mo KR radiation, λ = 0.71073 A)76 The selected
suitable single crystals were mounted using polybutene oil on the
top of a glass fiber fixed on a goniometer head and immediately
transferred to the diffractometer. Pre-experiment, data collec-
tion, data reduction, and analytical absorption corrections77
were performed with the Oxford program suite CrysAlisPro.78
The crystal structures were solved with SHELXS-9779 using
direct methods. The structure refinements were performed by
full-matrix least-squares on F2 with SHELXL-97.79 All programs
used during the crystal structure determination process are
included in the WINGX software.80 The program PLATON81
was used to check the result of the X-ray analyses. CCDC-778147-
778153 contain the supplementary crystallographic data (excluding
structure factors) for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Center
via www.ccdc.cam.ac.uk/data_request/cif.
[N∧C = 2-(5-Methyl-2-thienyl)pyridine][AuCl3]. 2-(5-methyl-
2-thienyl)pyridine (0.150 g, 0.856 mmol) in acetonitrile (3.5 mL)
was added to Na[AuCl4] 2H2O (0.313 g, 0.787 mmol) in H2O
3
(3.5 mL), and the resulting mixture was stirred at room tem-
perature for 12 h. The orange solids that precipitated out were
(67) Becke, A. D. Phys. Rev. A 1988, 38, 3098–3100.
(68) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785–789.
(69) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J.
J. Phys. Chem. 1994, 98, 11623–11627.
(70) Lynch, B. J.; Fast, P. L.; Harris, M.; Truhlar, D. G. J. Phys. Chem. A
2000, 104, 4811–4815.
(71) Lynch, B. J.; Zhao, Y.; Truhlar, D. G. J. Phys. Chem. A 2003, 107,
1384–1388.
(72) Gill, P. M. W. Mol. Phys. 1996, 89, 433–445.
(73) Zhao, Y.; Lynch, B. J.; Truhlar, D. G. J. Phys. Chem. A 2004, 108,
2715–2719.
(74) Tao, J. M.; Perdew, J. P.; Staroverov, V. N.; Scuseria, G. E. Phys.
Rev. Lett. 2003, 91, 146401.
(75) Dahlke, E. E.; Truhlar, D. G. J. Phys. Chem. B 2005, 109, 15677–
15683.
(76) Xcalibur CCD System; Oxford Diffraction Ltd: Abingdon, Oxfordshire,
England, 2007.
(77) Clark, R. C.; Reid, J. S. Acta Crystallogr., Sect. A 1995, 51, 887–897.
(78) CrysAlisPro, Versions 1.171.32.34d-55; Oxford Diffraction Ltd: Abingdon,
Oxfordshire, England.
Computational Details. All calculations were performed with
the Gaussian 03 program package57 using the hybrid functional
(79) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.
(80) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(81) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
(66) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, 991–1024.

11470 Inorganic Chemistry, Vol. 49, No. 24, 2010
Garg et al.
filtered off, and the precipitate was successively washed with
water and diethylether to give the title product. Yield = 0.278 g,
68%. Positive EI-MS: m/z: 476 [M]þ; IR (KBr): ν(Au-Cl) 363
cm-1; 1H NMR (500 MHz, CD3CN, 298 K) δ 2.63 (s, 3H), 7.06
(d, J = 4.0 Hz, 1H), 7.72 (t, J = 5.5 Hz, 1H), 7.76 (d, J = 4.0 Hz,
1H), 7.79 (d, J = 6.5 Hz, 1H), 8.22 (t, J = 5.5 Hz, 1H), 8.93 (d,
J = 6.0 Hz, 1H); 13C NMR (125 MHz, CD3CN, 298 K) δ 15.2,
127.2, 128.0, 130.4, 132.6, 136.2, 143.4, 147.6, 150.9, 153.4;
elemental analysis (%) calcd for C10H9AuCl3NS: C, 25.10; H,
1.90; N, 2.93. Found: C, 25.00; H, 1.88; N, 2.99.
and then the mixture was allowed to warm to RT and stirred
further for 1 h. (Note: At this stage the reaction mixture turns
dark (violet coloration), more in the case of non-fluorinated
analogues indicating partial decomposition of the product to
metallic gold). TLC examination (EtOAc/Hexane = 1/5) of the
reaction mixture at this stage usually showed two major spots,
the first (Rf ∼ 0.7) corresponding to the homocoupled diaryl and
the second being the desired organometallic product (Rf ∼ 0.4)
which also gets faintly illuminated in UV lamp longwave (365
nm). The reaction was quenched by addition of water (5 mL)
followed by extraction with ethyl acetate/dichloromethane.
After separation, the organic layer was dried over MgSO4 and
concentrated in vacuo to obtain the crude product. Purification
on a short silica gel column (eluent: EtOAc and hexane mixture)
was adopted to obtain analytically pure products. Some deri-
vatives were prepared with modifications in the general proce-
dure and are described individually.
cis-[(N∧C)AuL2][N∧C = 2-phenylpyridine, L = C6H5] (2).
Phenyllithium (0.61 mL, 0.746 mmol, 1.8 M soln. in di-n-
butylether) was syringed into a Schlenk flask containing cooled
(-78 °C) suspension of A (150.0 mg, 0.35 mmol) in diethylether
(5.0 mL) under N2 atmosphere. The cold bath was removed
15 min after addition, and the reaction mixture was allowed to
warm up to RT and stirred for 12 h. The reaction was then
quenched by adding H2O (8.0 mL) and extracted with dichlor-
omethane (2 ꢀ 10 mL). The combined dichloromethane layers
were dried over MgSO4, filtered, and concentrated in vacuo to
yield the crude product. Further purification by flash column
chromatography using silica gel (eluent: Hexane/EtOAc = 3/1)
afforded 2 as off-white solid. Single crystals suitable for X-ray
diffraction analysis were obtained from slow evaporation by
layering of pentane over concentrated solution of the complex in
dichloromethane at 0-5 °C. Yield = 100.0 mg, 55.0%. IR
(KBr): νmax 3413, 2924, 2853, 1638, 1618, 1605, 1571, 1478,
1422, 1163, 1062, 1019, 751, 734, 695, 631, 471 cm-1; 1H NMR
(500 MHz, CDCl3, 298 K): δ 7.03-7.09 (m, 3H), 7.15 (t, J = 8.0
Hz, 2H), 7.19 (t, J = 7.0 Hz, 1H), 7.22-7.31 (m, 4H), 7.45 (d,
J = 8.0 Hz, 2H), 7.49 (d, J = 7.0 Hz, 2H), 7.80 (d, J = 7.5 Hz,
1H), 7.92-7.98 (m, 2H), 8.18 (d, J = 5 Hz, 1H); 13C{1H}NMR
(125 MHz, CDCl3, 298 K): δ 119.9, 123.1, 124.1, 124.6, 126.2,
127.1, 127.2, 128.7, 131.1, 132.4, 135.2, 135.9, 140.1, 142.0,
145.8, 149.2, 166.7, 166.9, 169.6; elemental analysis (%) calcd
for C23H18AuN; C, 54.66; H, 3.59; N, 2.77; Found: C, 54.52; H,
3.42; N, 2.80.
[N∧C = 2-(5-Methyl-2-thienyl)pyridine][AuCl2] (C). Silver(I)
tetrafluoroborate (0.084 g, 0.431 mmol) was added to [N∧C =
2-(5-methyl-2-thienyl)pyridine][AuCl3] (0.200 g, 0.418 mmol) in
dichloromethane (60 mL), and the resulting mixture was re-
fluxed for 4 h. After filtration under hot condition, the filtrate
was evaporated to dryness, and the residue was washed with a
minimum amount of acetonitrile (3.0 mL) to remove silver salts,
giving the title complex C as a green solid. Yield = 0.073 g, 40%.
Positive EI-MS: m/z: 405 [M - Cl]þ; IR (KBr): ν (Au-Cl) 304,
1
354 cm-1; H NMR (500 MHz, DMSO-d6, 298 K): δ 2.60 (s,
3H), 7.07 (s, 1H), 7.56 (td, J = 6.0, 1.5 Hz, 1H), 7.86 (d, J =
7.5 Hz, 1H), 8.25 (td, J = 6.0, 1.5 Hz, 1H), 9.25 (d, J = 5.5 Hz,
1H); 13C NMR (125 MHz, DMSO-d6, 298 K): δ 15.6, 120.3,
122.4, 126.0, 137.0, 144.0, 144.2, 147.8, 150.3, 158.3; elemental
analysis (%) calcd for C10H8AuCl2NS; C, 27.17; H, 1.82; N, 3.17
Found: C, 27.32; H, ∧1.94; N, 3.19.
cis-[(N∧C)AuL][N C = 2-phenylpyridine, L = 2,20-biphenyl]
(1). To 2,20-Dibromobiphenyl (88.0 mg, 0.28 mmol) in dry
diethylether (5.0 mL), n-BuLi (0.35 mL, 0.55 mmol, 1.6 M in
hexanes) was added slowly via syringe at -78 °C and then stirred
for 1 h at RT. The dilithiated solution was then transferred into a
flask containing diethylether suspension of A (100.0 mg, 0.23
mmol) and AgOTf (4.6 mg, 0.018 mmol) maintained at -78 °C.
The cold bath was removed immediately after addition, and the
mixture was allowed to stir for 10 h. It was then quenched by
addition of water (5.0 mL) and extracted with dichloromethane
(2 ꢀ 15 mL). The separated organic layers were combined and
dried over MgSO4. Filtration followed by concentration of the
solvent in vacuo gave the crude product as a light brown solid. It
was washed with pentane (5.0 mL), and the residue was purified
by flash column chromatography using silica gel (eluent: Hexane/
EtOAc = 3/2) to afford 1 as an off-white solid. Single crystals
suitable for X-ray diffraction analysis were obtained from slow
evaporation by layering of pentane over concentrated solution
of the complex in dichloromethane at 0-5 °C. Yield = 15.0 mg,
12%. IR: (KBr) νmax 3414, 2924, 2853, 1638, 1618, 1605, 1581,
1482, 1429, 1160, 1104, 1013, 736, 734, 726, 615, 479 cm-1; 1H
NMR (500 MHz, CD2Cl2, 298 K): δ 7.11 (td, J = 6.0, 1.0 Hz,
1H), 7.18-7.25 (m, 3H), 7.36 (td, J = 6.5, 1.0 Hz, 1H), 7.50-
7.57 (m, 4H), 7.62 (d, J = 6.5 Hz, 1H), 7.92 (d, J = 8.5 Hz, 1H),
7.95 (d, J = 8.5 Hz, 1H), 8.08 (d, J = 6.5 Hz, 2H), 8.19 (d, J =
7.0 Hz, 1H), 9.2 (d, J = 5.5 Hz, 1H); 13C{1H} NMR (125 MHz,
CD2Cl2, 298 K): δ 121.1, 121.3, 121.7, 123.8, 125.0, 126.5, 126.9,
127.0, 127.1, 127.5, 131.1, 132.0, 134.0, 135.7, 140.7, 147.3,
148.5, 149.4, 154.0, 155.8, 167.3, 171.4, 174.1; elemental analysis
(%) calcd for C23H16AuN; C, 54.88; H, 3.20; N, 2.78; Found: C,
54.60; H, 3.12; N, 2.68 (Note: 1H NMR and IR analyses of late
eluting fractions from the column (eluent:ethyl acetate) suggest
the presence of about 10% of monocoordinated biphenyl Au(III)
chloride complex, characterization details of which are not pres-
ented here).
cis-[(N∧C)AuL2][N∧C = 2-phenylpyridine, L = C6F5] (3).
This reaction was performed according to the general proce-
dure. To iodopentafluorobenzene (153.2 mg, 0.521 mmol) in
diethylether (5.0 mL), n-BuLi (0.33 mL, 0.541 mmol, 1.6 M soln.
in hexanes) was added. The lithiated product was transferred to
a flask containing A (100.0 mg, 0.237 mmol) in diethylether. The
crude product thus obtained after workup was purified by flash
column chromatography using silica gel (eluent: Hexane/EtOAc =
5/1) to obtain an off-white solid. The solid was further recrys-
tallized from a mixture of ether and pentane to obtain 3 as a
white solid. Yield = 66 mg, 40%. IR (KBr): νmax 3414, 2923,
2853, 1738, 1637, 1610, 1509, 1462, 1477, 1365, 1309, 1263, 1073,
967, 906, 885, 812, 785, 757, 732, 629, 466 cm-1; 1H NMR (500
MHz, CDCl3, 298 K): δ 6.83 (d, J = 7.5 Hz, 1H), 7.29 (td, J =
6.5, 1.5 Hz, 1H), 7.37 (t, J = 7.0 Hz, 2H), 7.78 (d, J = 7.5 Hz,
1H), 8.04 (d, J = 8.0 Hz, 1H), 8.12 (td, J = 8.0, 1.5 Hz, 1H), 8.25
(d, J = 8.0 Hz, 1H); 13C{1H} NMR (125 MHz, CDCl3, 298 K): δ
1
120.8, 124.3, 125.2, 127.8, 132.3, 133.8, 137.5 (dm, JC-F
General Procedure for the Synthesis of Cyclometalated Au
(III) Complexes (2-8). n-BuLi (0.52 mmol, 1.6 M in hexanes)
was added via syringe to a cooled (-78 °C) solution of the aryl
halide (0.50 mmol) in dry diethylether under nitrogen atmo-
sphere and stirred for 20 min at that temperature. It was then
transferred via cannula into a flask containing an diethylether
suspension of cycloaurated Au(III)dichloride (0.22 mmol) pre-
cooled at -78 °C. This temperature was maintained for 20 min
=
=
251.0 Hz), 138.1 (dm, 1JC-F = 251.0 Hz), 139.5 (dm, 1JC-F
1
251.0 Hz), 141.8, 144.1 (dm, JC-F = 232.0 Hz), 145.1, 146.5
(dm, 1JC-F = 232.0 Hz), 149.3, 158.0, 165.8, 166.7, (note: reso-
nances for 2C submerged in baseline); 19F NMR (470 MHz,
CDCl3, 298 K): δ -122.2 (m, 2F, o-C6F5), -122.3 (m, 2F,
o-C6F5), -157.8 (t, J = 20.2 Hz, 1F, p-C6F5), -158.7 (t, J = 20.2
Hz, 1F, p-C6F5), -161.5 (t, J = 19.2 Hz, 2F, m-C6F5), -162.5

Article
Inorganic Chemistry, Vol. 49, No. 24, 2010 11471
(t, J = 19.7 Hz, 2F, m-C6F5); elemental analysis (%) calcd. for:
C23H8AuF10N CH3C(O)OC2H5: C, 41.93; H, 2.09; N, 1.81;
Found: C, 41.86; H, 2.00; N, 1.97.
evaporation by layering of pentane over concentrated solu-
tion of the complex in dichloromethane at 0-5 °C. Yield =
3
1
30.0 mg, 25%. H NMR (500 MHz, CD2Cl2, 298 K): δ 6.71
cis-[(N∧C)AuL2][N∧C = 2-phenylpyridine, L = C6H4-CF3-p]
(4). This reaction was performed according to the general proce-
dure. To 1-bromo-4-(trifluoromethyl)benzene (117.2 mg, 0.521
mmol) in diethylether (5.0 mL), n-BuLi (0.33 mL, 0.541 mmol,
1.6 M soln. in hexanes) was added. The lithiated product was
then transferred to a flask containing A (100.0 mg, 0.237 mmol)
in diethylether. The crude product thus obtained after workup
was purified by flash column chromatography using silica gel
(eluent: Hexane/EtOAc = 5/1) to obtain 4 as off-white solid.
Single crystals suitable for X-ray diffraction analysis were obtained
from slow evaporation by layering of pentane over concentrated
solution of the complex in dichloromethane at 0-5 °C. Yield =
51.0 mg, 33%. IR (KBr): νmax 3413, 3064, 1637, 1607, 1482,
1439, 1390, 1327, 1157, 1120, 1087, 1078, 1066, 1050, 1013, 906,
820, 755, 733, 679, 666, 648, 599, 478 cm-1; 1H NMR (500 MHz,
CD2Cl2, 298 K): δ 6.89 (dd, J = 8.5, 1.5 Hz, 1H), 7.23-7.30 (m,
3H), 7.41 (d, J = 8.5 Hz, 2H), 7.48 (d, J = 8 Hz, 2H), 7.60 (d,
J = 9.0 Hz, 2H), 7.66 (d, J = 8.5 Hz, 2H), 7.82 (dd, J = 8.5, 1.5
Hz, 1H), 7.99-8.03 (m, 2H), 8.05 (d, J = 8.0 Hz, 1H); 13C{1H}
NMR (125 MHz, CD2Cl2, 298 K): δ 120.7, 121.9, 123.9, 124.0,
124.8, 125.2, 125.3 (q, 2JC-F = 3.8 Hz), 125.6 (q, 2JC-F = 3.9
(d, J = 4.5 Hz, 1H), 7.06 -7.12 (m, 3H), 7.16 (t, J = 7.5 Hz,
2H), 7.26 (t, J = 7.5 Hz, 2H), 7.43-7.46 (m, 3H), 7.50 (d, J =
7.5 Hz, 2H), 7.64 (d, J = 7.5 Hz, 1H) 7.90 (td, J = 8.0, 1.5 Hz,
1H), 7.97 (d, J = 5.5 Hz, 1H); 13C{1H} NMR (125 MHz,
CD2Cl2, 298 K): δ 119.0, 121.4, 124.5, 125.0, 128.5, 128.7,
129.0, 133.1, 134.1, 135.0, 136.3, 140.9, 147.0, 148.8, 161.0,
164.1, 178.9; elemental analysis (%) calculated for C21H16
-
AuNS: C, 49.32; H, 3.15; N, 2.74; Found: C, 49.17; H, 3.00; N,
2.80.
cis-[(N∧C)AuL2] [N∧C = 2-(2-thienyl)pyridine, L = C6F5] (7).
This reaction was performed according to the general proce-
dure. To iodopentafluorobenzene (151.0 mg, 0.514 mmol) in
diethylether (5.0 mL), n-BuLi (0.33 mL, 0.537 mmol, 1.6 M soln.
in hexanes) was added, and this was transferred to a flask
containing B (100.0 mg, 0.233 mmol) in diethylether. The crude
product thus obtained was purified by flash column chromato-
graphy using silica gel (eluent: Hexane/EtOAc = 5/1) to obtain
7 as light yellow solid. Single crystals suitable for X-ray diffrac-
tion analysis were obtained from slow evaporation by layering
of pentane over a concentrated solution of the complex in diethyl-
ether at 0-5 °C. Yield = 61 mg, 38%. IR (KBr): νmax 3414,
2923, 2853, 1738, 1637, 1610, 1509, 1477, 1462, 1365, 1309, 1263,
1163, 1073, 967, 906, 885, 812, 785, 757, 732, 629, 466 cm-1; 1H
NMR (500 MHz, CDCl3, 298 K): δ 6.55 (d, J = 4.5 Hz, 1H),
7.24 (td, J = 4.5, 1.5 Hz, 1H), 7.47 (d, J = 5 Hz, 1H), 7.67 (d,
J = 8 Hz, 1H), 8.02 (td, J = 6.5, 1.5 Hz, 1H), 8.07 (d, J = 5.5 Hz,
1H); 13C{H} NMR (125 MHz, CDCl3, 298 K): δ 119.7, 122.5,
1
1
Hz), 126.5 (q, JC-F = 32.0 Hz), 127.2 (q, JC-F = 31.6 Hz),
131.5, 133.0, 135.7, 135.8, 141.3, 146.2, 147.0, 149.5, 167.0,
167.1, 172.4; 19F NMR (376 MHz, CDCl3, 298 K): δ -62.19
(s, 3H), -62.22 (s, 3H); elemental analysis (%) calcd for: C25-
H16AuF6N: C, 46.82; H, 2.51; N, 2.18 Found: C, 46.70; H, 2.65;
N, 2.18.
cis-[(N∧C)AuL2][N∧C = 2-phenylpyridine, L = C4H3S] (5).
This reaction was performed according to the general proce-
dure. To 2-bromothiophene (0.83 mL, 0.52 mmol) in diethy-
lether (5.0 mL), n-BuLi (0.33 mL, 0.541 mmol, 1.6 M soln. in
hexanes) was added, and this mixture was transferred to flask
containing A (100.0 mg, 0.237 mmol) in diethylether. The crude
product thus obtained after workup was purified by column
chromatography on silica gel (eluent: Hexane/EtOAc = 5/1) to
obtain 5 as off-white solid. Single crystals suitable for X-ray
diffraction analysis were obtained from slow evaporation by
layering of pentane over concentrated solution of the complex in
dichloromethane at 0-5 °C. Yield = 68 mg, 55%. IR (KBr):
130.2, 132.0, 137.5 (dm, 1JC-F = 251.0 Hz), 138.0 (dm, 1JC-F
=
1
251.0 Hz), 139.5 (dm, JC-F = 251.0 Hz), 142.4, 145.6 (dm,
1JC-F = 250.0 Hz), 146.0, 146.5 (dm, 1JC-F = 250.0 Hz), 149.0,
161.1, 162.4, (note: resonances for 3C submerged in baseline);
19F NMR (376 MHz, CDCl3, 298 K): δ -120.5 (m, 2F,
3
o-C6F5), -120.6 (m, 2F, o-C6F5), -156.0 (t, JF-F =18.8 Hz,
1F, p-C6F5), -156.9 (t, 3JF-F = 18.6 Hz, 1F, p-C6F5), -160.1 (t,
3JF-F =18.8 Hz, 2F, m-C6F5), -161.2 (t, 3JF-F = 19.1 Hz, 2F,
m-C6F5); elemental analysis (%) calcd for C21H6AuF10NS: C,
36.49; H, 0.87; N, 2.03; Found: C, 36.77; H, 0.89; N, 1.97.
cis-[N∧C = 2-(5-methyl-2-thienyl)pyridine, L = C6F5] (8).
This reaction was performed according to the general proce-
dure. To iodopentafluorobenzene (146.3 mg, 0.497 mmol) in
diethylether (5.0 mL), n-BuLi (0.33 mL, 0.537 mmol, 1.6 M soln.
in hexanes) was added, and this mixture was transferred to a
flask containing C (100.0 mg, 0.226 mmol) in diethylether. The
crude product thus obtained after workup was purified by flash
column chromatography using silica gel (eluent Hexane/EtOAc =
5:1) to obtain 8 as yellow-green solid. Yield = 90 mg, 56%.
Alternatively, direct recrystallization of the crude product using
ether and pentane mixture also afforded analytically pure
compound. Single crystals suitable for X-ray diffraction anal-
ysis were obtained from slow evaporation by layering of pentane
over concentrated solution of the complex in diethylether at 0-5 °C.
IR (KBr): νmax 3413, 2925, 2027, 1637, 1615, 1508, 1463, 1477,
1366, 1264, 1250, 1160, 1072, 967, 880, 842, 812, 789, 765, 620,
473 cm-1; 1H NMR (500 MHz, CD2Cl2, 298 K): δ 2.49 (d, J =
1.0 Hz, 3H), 6.19 (d, J = 1.0 Hz, 1H), 7.13 (td, J = 6.0, 1.5 Hz,
1H), 7.52 (dd, J = 6.0, 1.5 Hz, 1H), 7.95 (td, J = 6.0, 1.5 Hz,
1H), 7.97 (dd, J = 6.0,1.5 Hz, 1H); 13C{1H}NMR (125.MHz,
νmax 3413, 1638, 1617, 1481, 1437, 1402, 1259, 1202, 1064, 1028,
834, 806, 751, 690, 626, 471 cm-1; 1H NMR (500 MHz, CDCl3,
298 K): δ 6.98 (d, J = 5.0 Hz, 1H), 7.04 (d, J = 5.0 Hz, 1H),
7.12-7.14 (m, 1H), 7.16-7.18 (m, 1H), 7.24-7.28 (m, 2H),
7.29-7.32 (m, 2H), 7.47 (d, J = 5.0 Hz, 1H), 7.61 (d, J = 5.0 Hz,
1H), 7.75-7.77 (m, 1H), 7.95-8.00 (m, 2H), 8.35 (d, J = 5.0 Hz,
1H); 13C{H} NMR (125 MHz, CDCl3, 298 K): δ 119.9, 123.4,
124.3, 125.0, 125.6, 127.9, 129.4, 131.5, 132.3, 135.3, 140.8,
145.5, 149.4, 151.7, 158.7, 160.3, 163.2, 164.7, 166.8; elemental
analysis (%) calcd for C19H14AuNS2: C, 44.10; H, 2.73; N, 2.71;
Found: C, 43.90; H, 2.87; N, 2.63.
cis-[(N∧C)AuL2] [N∧C = 2-(2-thienyl)pyridine, L = C6H5]
(6). Phenyllithium (0.64 mL, 0.780 mmol, 1.8 M soln. in di-n-
butyl ether) was slowly syringed into a Schlenk flask containing
cooled (-78 °C) suspension of B (100.0 mg, 0.233 mmol) in
diethylether (5.0 mL) under N2 atmosphere. The cold bath was
removed after 15 min, and the reaction mixture was allowed to
warm up to RT and stirred further for 1 h. H2O (8.0 mL) was
added to quench the reaction mixture and was then extracted
with ethyl acetate (20.0 mL). The organic layer was dried over
MgSO4, filtered, and concentrated in vacuo to obtain the crude
product. It was washed with pentane (2 ꢀ 2.0 mL), and the
residue was then extracted by adding toluene (2 ꢀ 5.0 mL). The
toluene layer was concentrated, and further recrystallization of
the residue with diethylether and pentane mixture (2:1) and
storing at -30 °C afforded 6 as a light green solid. Single crystals
suitable for X-ray diffraction analysis were obtained from slow
CD2Cl2, 298 K): δ 15.4, 119.6, 122.2, 130.6, 137.5 (dm, 1JC-F
=
=
251.6 Hz), 138.0 (dm, 1JC-F = 251.0 Hz), 140.0 (dm, 1JC-F
1
251.0 Hz), 143.0, 143.8, 145.0 (dm, JC-F = 251.0 Hz), 147.0,
147.1 (dm, 1JC-F = 251.0 Hz), 148.0 (dm, 1JC-F = 251.0 Hz),
149.0, 161.4, 163.0, (note: resonances for 2C submerged in
baseline); 19F NMR (376 MHz, CDCl3, 298 K): δ -120.5 (m,
2F, o-C6F5), -120.6 (m, 2F, o-C6F5), -156.2 (t, 3JF-F = 18.8 Hz,
1F, p-C6F5), -157.1 (t, 3JF-F = 21.5 Hz, 1F, p-C6F5), -160.20
(t, 3JF-F = 18.8 Hz, 2F, m-C6F5), -161.21 (t, 3JF-F = 22.5 Hz,

11472 Inorganic Chemistry, Vol. 49, No. 24, 2010
Garg et al.
2F, m-C6F5); elemental analysis (%) calcd for C22H8AuF10NS:
C, 37.46; H, 1.14; N, 1.99; Found: C, 37.63; H, 1.27; N, 2.06.
Supporting Information Available: X-ray crystallographic
data for complexes 1-2 and 4-8 in CIF format, absorbance
and emission spectra of 4 and 5 (Figure S1), thermogravimetric
analysis of 2 and 3 (Figure S2); ORTEP plots of 4, 6, and 7
(Figures S3-S5); crystallographic details of all X-ray structures
(Tables S1 and S2); and computational details. This material is
available free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. We thank S. V. Rocha and Dr. N. Finney
for help with excited-state lifetime measurements. K.V. is grate-
€
ful to the University of Zurich and Prof. H. Berke for generous
support.