Neutral gold(I) metallosupramolecular compounds: Synthesis and characterization, photophysical properties, and density functional theory studies

Article abstract of DOI:10.1021/ic800266m

The reaction of the tris-indole InTREN ligand (L) with different gold phosphine fragments allows the construction of new gold(I) complexes with different geometries depending on the chosen phosphine. A metallodendrimeric structure is obtained when the gold atom is linked to a triphenylphosphine ligand, and neutral gold(I) metallocryptands are constructed when a triphosphine is used. Characterization of the compounds was accomplished by ³¹P{¹H} and ¹H NMR, IR, absorption, and fluorescence spectroscopies, electrospray ionization mass spectrometry (ESI-MS(+)), and elemental analysis, and their geometry was optimized using density functional theory (B3LYP). Time-dependent density functional theory (TD-DFT) calculations have been used to assign the lowest energy absorption bands to LMCT N(p, tertiary amine) → Au transitions. Photophysical characterization of the complexes shows strong luminescence in the solid state. The formation of heterobimetallic species has been detected in solution in the presence of equimolar quantities of metal cations, and their structures have been identified by a combination of spectroscopic methods and mass spectrometry.

Full text of DOI:10.1021/ic800266m

Inorg. Chem. 2008, 47, 4952-4962
Neutral Gold(I) Metallosupramolecular Compounds: Synthesis and
Characterization, Photophysical Properties, and Density Functional
Theory Studies
Laura Rodríguez,*,†,‡ Carlos Lodeiro,† João Carlos Lima,† and Ramon Crehuet§
REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, UniVersidade
NoVa de Lisboa, Quinta da Torre, 2829-516 Monte de Caparica, Portugal, Departament de
Química Inorgànica, UniVersitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain,
and Institut d’InVestigacions Químiques i Ambientals de Barcelona, IIQAB-CSIC, c/ Jordi Girona
18-26, Barcelona 08034, Spain
Received February 11, 2008
The reaction of the tris-indole InTREN ligand (L) with different gold phosphine fragments allows the construction
of new gold(I) complexes with different geometries depending on the chosen phosphine. A metallodendrimeric
structure is obtained when the gold atom is linked to a triphenylphosphine ligand, and neutral gold(I) metallocryptands
are constructed when a triphosphine is used. Characterization of the compounds was accomplished by 31P{1H} and
1H NMR, IR, absorption, and fluorescence spectroscopies, electrospray ionization mass spectrometry (ESI-MS(+)),
and elemental analysis, and their geometry was optimized using density functional theory (B3LYP). Time-dependent
density functional theory (TD-DFT) calculations have been used to assign the lowest energy absorption bands to
LMCT N(p, tertiary amine) f Au transitions. Photophysical characterization of the complexes shows strong
luminescence in the solid state. The formation of heterobimetallic species has been detected in solution in the
presence of equimolar quantities of metal cations, and their structures have been identified by a combination of
spectroscopic methods and mass spectrometry.
Introduction
Although there are numerous examples of metal-mediated
self-assembly bidimensional complexes, especially with
square9,12–22 and rectangular10,23–28 shape, the design of
three-dimensional structures is more scarce, in particular
involving synthetic structures from typically inorganic build-
The construction of metallosupramolecular structures using
transition metal centers and coordination bonds, for the direct
formation of complex structures, has undergone significant
development for more than one decade. It has proved to be
an efficient method to obtain molecular compounds with a
wide range of shapes and sizes, which can be controlled by
the rational choice of the appropriate metals and ligands.1–11
(8) Schalley, C. A.; Lutzen, A.; Albrecht, M. Chem.sEur. J. 2004, 10,
1072–1080.
(9) Wurthner, F.; You, C. C.; Saha-Moller, C. R. Chem. Soc. ReV. 2004,
33, 133–146.
(10) Thanasekaran, P.; Liao, R. T.; Liu, Y. H.; Rajendran, T.; Rajagopal,
S.; Lu, K. L. Coord. Chem. ReV. 2005, 249, 1085–1110.
(11) Ghosh, S.; Batten, S. R.; Turner, D. R.; Mukherjee, P. S. Organome-
tallics 2007, 26, 3252–3255.
* To whom correspondence should be addressed. E-mail: l.raurell@
dq.fct.unl.pt. Phone: +351 212948300 (Ext. 10981). Fax: +351 212948550.
†
Universidade Nova de Lisboa.
Universitat de Barcelona.
Institut d’Investigacions Químiques i Ambientals de Barcelona.
(12) Bera, J. K.; Bacsa, J.; Smucker, B. W.; Dunbar, K. R. Eur. J. Inorg.
Chem. 2004, 368–375.
‡
§
(13) Ferrer, M.; Rodriguez, L.; Rossell, O.; Solans, X. J. Organomet. Chem.
2005, 690, 1612–1619.
(1) Chen, C.-L.; Zhang, J. Y.; Su, C.-Y. Eur. J. Inorg. Chem. 2007, 2997–
3010.
(14) Kraft, S.; Hanuschek, E.; Beckhaus, R.; Haase, D.; Saak, W.
Chem.sEur. J. 2005, 11, 969–978.
(2) Jones, C. J. Chem. Soc. ReV. 1998, 27, 289–299.
(3) Fujita, M. Chem. Soc. ReV. 1998, 27, 417–425.
(4) Swiegers, G. F.; Malefetse, T. J. Chem. ReV. 2000, 100, 3483–3537.
(5) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. ReV. 2000, 100, 853–
907.
(15) Song, L. C.; Jin, G. X.; Wang, H. T.; Zhang, W. X.; Hu, Q. M.
Organometallics 2005, 24, 6464–6471.
(16) Karadas, F.; Schelter, E. J.; Prosvirin, A. V.; Bacsa, J.; Dunbar, K. R.
Chem. Commun. 2005, 1414–1416.
(6) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40, 2022–
2043.
(17) Sautter, A.; Kaletas, B. K.; Schmid, D. G.; Dobrawa, R.; Zimine, M.;
Jung, G.; van Stokkum, I. H. M.; De Cola, L.; Williams, R. M.;
Wurthner, F. J. Am. Chem. Soc. 2005, 127, 6719–6729.
(7) Stang, P. J. Chem.sEur. J. 1998, 4, 19–27.
4952 Inorganic Chemistry, Vol. 47, No. 11, 2008
10.1021/ic800266m CCC: $40.75  2008 American Chemical Society
Published on Web 04/26/2008

Studies on Neutral Au(I) Metallosupramolecular Compounds
ing blocks.29–37 It is interesting to note that the assembly of
three-dimensional compounds using metal coordination pre-
sents additional challenging and interesting applications in
the area of chemical nanosciences, being used as supramo-
lecular containers, reaction vessels, and ion channel models
for biological cells.38
Metallocryptands are an emerging class of inorganic three-
dimensional cage complexes that are well-suited to encap-
sulate a variety of metal ions.39 Unlike their more common
organic analogues, these complexes have the possibility of
binding metal ions either by the formation of metallophilic
interactions or by Lewis base interactions with the electron
donor groups of the ligands. Although the synthesis of
cationic gold(I) metallocryptates has been carried out by
Catalano et al.,39–44 there are no examples in the literature,
to our knowledge, of neutral gold(I) metallocryptands con-
structed directly in a one-step reaction between two tripodal
precursors.
The affinity of gold for the nitrogen atoms, in comparison
with that for phosphorus or sulfur, is low, but a number of
neutral or ionic gold complexes with gold(I)-nitrogen bonds
in the presence of P-donor ligands have been reported.45–48
Furthermore, because of the ability of the indole ligands to
react with gold metal atoms,49 we have explored the reaction
of the new InTREN ligand50 with different gold phosphine
derivatives leading to the formation of one complex with
dendrimeric structure and two new neutral gold(I) metallo-
cryptands with closed-shell geometry.
Experimental Section
General. All manipulations were performed under prepurified
N2 using standard Schlenk techniques. All solvents were distilled
from the appropriate drying agents. The compounds InTREN,50
AuClPPh3,51 Tl(acac),52 Au(acac)PPh3,52 and InTREN50 were
synthesized as described previously. The compounds (AuCl)3(triphos)
and (AuCl)3(tripod) were prepared and isolated as solids from
AuCl(tht)53 solutions by adding the appropriate amount of the
corresponding triphosphine. Zn(OTf)2 (Aldrich, 98%), Cu(OTf)2
(Aldrich, 98%), and Ni(BF4)2 (Strem Chemicals, 99%) were used
as received.
(18) Jude, H.; Disteldorf, H.; Fischer, S.; Wedge, T.; Hawkridge, A. M.;
Arif, A. M.; Hawthorne, M. F.; Muddiman, D. C.; Stang, P. J. J. Am.
Chem. Soc. 2005, 127, 12131–12139.
(19) Cotton, F. A.; Murillo, C. A.; Yu, R. M. Dalton Trans. 2006, 3900–
3905.
Measurements. IR spectra were recorded on an FT-IR 520
Nicolet spectrophotometer. 31P{1H}-NMR (δ (85% H3PO4) ) 0.0
(20) Ferrer, M.; Rodríguez, L.; Rossell, O. J. Organomet. Chem. 2003,
681, 158–166.
(21) Ferrer, M.; Gutiérrez, A.; Mounir, M.; Rossell, O.; Ruiz, E.; Rang,
A.; Engeser, M. Inorg. Chem. 2007, 46, 3395–3406.
(22) Ferrer, M.; Mounir, M.; Rossell, O.; Ruiz, E.; Maestro, M. A. Inorg.
Chem. 2003, 42, 5890–5899.
(23) Mukherjee, P. S.; Min, K. S.; Arif, A. M.; Stang, P. J. Inorg. Chem.
2004, 43, 6345–6350.
(24) Dinolfo, P. H.; Hupp, J. T. J. Am. Chem. Soc. 2004, 126, 16814–
16819.
(25) Han, W. S.; Lee, S. W. Dalton Trans. 2004, 1656–1663.
(26) Lin, R.; Yip, J. H. K.; Zhang, K.; Koh, L. L.; Wong, K. Y.; Ho, K. P.
J. Am. Chem. Soc. 2004, 126, 15852–15869.
(27) Addicott, C.; Oesterling, I.; Yamamoto, T.; Mullen, K.; Stang, P. J.
J. Org. Chem. 2005, 70, 797–801.
(28) Cornpany, A.; Gomez, L.; Valbuena, J. M. L.; Mas-Balleste, R.; Benet-
Buchholz, J.; Llobet, A.; Costas, M. Inorg. Chem. 2006, 45, 2501–
2508.
1
ppm) and H NMR (δ (TMS) ) 0.0 ppm) spectra were obtained
on Bruker DXR 250 and Varian Mercury 400 spectrometers.
Elemental analyses of C, H, and N were carried out at the Serveis
Científico-Tècnics of the Universitat de Barcelona. Electrospray
ionization mass spectrometry (ESI-MS) spectra were recorded on
a LC/MSD-TOF spectrometer at the Universitat de Barcelona and
matrix-assisted laser desorption ionization time-of-flight (MALDI-
TOF) spectra on a Voyager DE-PRO Biospectrometry Workstation
equipped with a nitrogen laser radiating at 337 nm (Applied
Biosystems, Foster City, CA) in the laboratory of mass spectrometry
of the REQUIMTE-UNL. Absorption spectra were recorded on a
Shimadzu UV-2501PC spectrophotometer and fluorescence emis-
sion spectra on a Horiba-Jobin-Yvon SPEX Fluorolog 3.22 spec-
trofluorimeter at 25 °C. Emission spectra in the solid state were
recorded using a Fiberoptic Adaptor model F-3000.
Computational Details. Because of the large size of the system,
the calculations have been carried out on a simplified model of the
molecules. The indole group of the InTREN has been converted
into a pirrole group, and phenyl groups have been substituted with
methyl groups, for compounds 2 and 3. For compound 1, it was
necessary to retain the phenyl rings, as these rings strongly
determine its conformation (vide infra). The use of methyl groups
instead of the simpler hydrogen atoms gives results for geometric
and electronic properties closer to experimental values.54 We have
used the LanL2DZ basis set55,56 for the Au and P atoms and the
(29) Reger, D. L.; Semeniuc, R. F.; Smith, M. D. Inorg. Chem. 2003, 42,
8137–8139.
(30) Ghosh, S.; Mukherjee, P. S. J. Org. Chem. 2006, 71, 8412–8416.
(31) Fujita, M.; Oguro, D.; Miyazawa, M.; Oka, H.; Yamaguchi, K.; Ogura,
K. Nature 1995, 378, 469–471.
(32) Kobayashi, K.; Yamada, Y.; Yamanaka, M.; Sei, Y.; Yamaguchi, K.
J. Am. Chem. Soc. 2004, 126, 13896–13897.
(33) Paul, R. L.; Argent, S. P.; Jeffery, J. C.; Harding, L. P.; Lynam, J. M.;
Ward, M. D. Dalton Trans. 2004, 3453–3458.
(34) Pinalli, R.; Cristini, V.; Sottili, V.; Geremia, S.; Campagnolo, M.;
Caneschi, A.; Dalcanale, E. J. Am. Chem. Soc. 2004, 126, 6516–6517.
(35) Yoshizawa, M.; Nakagawa, N.; Kumazawa, K.; Nagao, M.; Kawano,
M.; Ozeki, T.; Fujita, M. Angew. Chem., Int. Ed. 2005, 44, 1810–
1813.
(36) Liu, Z.-M.; Liu, Y.; Zheng, S.-R.; Yu, Z.-Q.; Pan, M.; Su, C.-Y. Inorg.
Chem. 2007, 46, 5814–5816.
(37) Dertz, E. A.; Xu, J. D.; Raymond, K. N. Inorg. Chem. 2006, 45, 5465–
5478.
(45) Nomiya, K.; Noguchi, R.; Ohsawa, K.; Tsuda, K.; Oda, M. J. Inorg.
Biochem. 2000, 78, 363–370.
(38) Cronin, L. Angew. Chem., Int. Ed. 2006, 45, 3576–3578.
(39) Catalano, V. J.; Bennett, B. L.; Malwitz, M. A.; Yson, R. L.; Kar,
H. M.; Muratidis, S.; Horner, S. J. Comments Inorg. Chem. 2003, 24,
39–68.
(46) Nomiya, K.; Noguchi, R.; Oda, M. Inorg. Chim. Acta 2000, 298, 24–
32.
(47) Nomiya, K.; Noguchi, R.; Ohsawa, K.; Tsuda, K. J. Chem. Soc., Dalton
Trans. 1998, 4101–4108.
(40) Catalano, V. J.; Malwitz, M. A.; Noll, B. C. Chem. Commun. 2001,
581–582.
(48) Munakata, M.; Yan, S. G.; Maekawa, M.; Akiyama, M.; Kitagawa,
S. J. Chem. Soc., Dalton Trans. 1997, 4257–4262.
(49) Usón, R.; Oro, L. A.; Cabeza, J. A.; Valderrama, M. J. Organomet.
Chem. 1982, 231, C81–C83.
(41) Catalano, V. J.; Bennett, B. L.; Kar, H. M.; Noll, B. C. J. Am. Chem.
Soc. 1999, 121, 10235–10236.
(42) Catalano, V. J.; Malwitz, M. A. J. Am. Chem. Soc. 2004, 126, 6560–
6561.
(50) Oliveira, E.; Pedras, B.; Santos, H.; Rodríguez, L.; Crehuet, R.; Avilés,
T.; Capelo, J. L.; Lodeiro, C. Manuscript in preparation.
(51) Kowala, C.; Swan, J. M. Aust. J. Chem. 1966, 19, 547.
(52) Vicente, J.; Chicote, M. T. Inorg. Synth. 1998, 32, 172.
(53) Usón, R.; Laguna, A. Organomet. Synth. 1986, 3, 322.
(43) Catalano, V. J.; Malwitz, M. A.; Horner, S. J.; Vasquez, J. Inorg.
Chem. 2003, 42, 2141–2148.
(44) Catalano, V. J.; Bennett, B. L.; Yson, R. L.; Noll, B. C. J. Am. Chem.
Soc. 2000, 122, 10056–10062.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4953

Rodríguez et al.
Scheme 1
3.62 (s, br, 6H, CH2-N-CH), 2.89 (s, br, 6H, CH2-CH2-N-CH),
2.31 (s, 9H, CH3). IR (KBr, cm-1): 3239 w, br (N-H); 3050 w,
2917 w, 2811 w (C-H); 1639 s, 1624 vs, 1617 s, (indole); 1476 m,
1436 s, 1101 s (PPh3). ESI-MS (CH2Cl2, m/z): 1945.2 (M + H+,
calcd: 1945.4), 1487.8 (M - AuPPh3 + 2H+, calcd: 1487.5), 1410.6
(M - AuPPh3 - Ph + 2H+, calcd: 1410.5), 1029.7 (M - 2AuPPh3
+ 3H+, calcd: 1029.5), 973.4 (M + 2H+, calcd: 972.8), 722.4 (M
- 2AuPPh3 - PPh3 - 3CH3 + 3H+, calcd: 722.6), 649.3 (M +
3H+, calcd: 648.8), 570.7 (InTREN + H+, calcd: 570.7). Anal.
Calcd: C, 55.59; H, 4.20; N, 5.04. Found: C, 55.62; H, 4.25; N,
5.09.
Method B. A dichloromethane solution (4 mL) of [Au(acac)-
PPh3] (55 mg, 0.10 mmol) was added dropwise to a dichlo-
romethane solution (6 mL) of InTREN (19 mg, 0.03 mmol). After
4 h of stirring at room temperature, the solution was filtered through
anhydrous magnesium sulfate and concentrated to a final volume
of 2 mL, and then hexane (6 mL) was added. A pale orange solid
was obtained, filtered, washed with diethyl ether and hexane, and
vacuum-dried. During all the manipulations, the solution was
protected from the light in order to avoid decomposition. Yield:
90%. 31P NMR (CH2Cl2, inset acetone-d6 with 1% POMe3): δ 31.4.
1H NMR (CD2Cl2): δ 8.35 (s, 3H, CH2-N-CH), 7.89 (s, 3H,
D95V basis set57 for the remaining atoms. Additional f and d
polarization functions were added to Au (Rf ) 0.2) and P (Rf )
0.34), respectively.58
Ground-state structures were optimized without symmetry con-
straints in the gas phase. The time-dependent density functional
theory (TD-DFT) calculations included the solvent effect via the
polarizable continuum model59 using the gas phase geometries.
Twenty-five singlet excited states were calculated. To check the
influence of the basis set, single point TD-DFT calculations with
solvent for compound 3 were repeated using the LanL2DZdp basis
set, which includes polarization and diffuse functions for all the
atoms.60 All calculations have been performed using the B3LYP
functional and the program Gaussian03.61 Gabedit was used to
generate the graphical three-dimensional representations of the
orbitals.62
Synthesis of (InTREN)(AuPPh3)3 (1). Method A. A methanol
solution (2 mL) of InTREN (10 mg, 0.02 mmol) and potassium
hydroxide (4 mg, 0.07 mmol) was stirred at room temperature for
30 min. Then, a dichloromethane solution (2 mL) of AuClPPh3
(26 mg, 0.05 mmol) was added. After 2 h of stirring, the solvent
was concentrated in vacuum to a final volume of 2 mL, and hexane
(6 mL) was added. A pale orange solid was obtained, filtered,
washed with diethyl ether and hexane, and vacuum-dried. During
all the manipulations, the solution was protected from the light in
order to avoid decomposition. Yield: 92%. 31P NMR (CH2Cl2, inset
acetone-d6 with 1% POMe3): δ 31.4. 1H NMR (CD2Cl2): δ 8.35 (s,
3H, CH2-N-CH), 7.89 (s, 3H, H1,indole, Scheme 1), 7.52–7.41 (m,
48H, Ph + H4,indole), 6.78 (s, 3H, H2,indole), 6.75 (s, br, 3H, H3,indole),
H
1,indole, Scheme 1), 7.52–7.41 (m, 48H, Ph + H4,indole), 6.78 (s,
3H, H2,indole), 6.75 (s, br, 3H, H3,indole), 3.62 (s, br, 6H,
CH2-N-CH), 2.89 (s, br, 6H, CH2-CH2-N-CH), 2.31 (s, 9H,
CH3). IR (KBr, cm-1): 3239 w, br (N-H); 3050 w, 2917 w, 2811 w
(C-H); 1639 s, 1624 vs, 1617 s, (indole); 1476 m, 1436 s, 1101 s
(PPh3). ESI-MS (CH2Cl2, m/z): 1945.2 (M + H+, calcd: 1945.4),
1487.8 (M - AuPPh3 + 2H+, calcd: 1487.5), 1410.6 (M - AuPPh3
- Ph + 2H+, calcd: 1410.5), 1029.7 (M - 2AuPPh3 + 3H+, calcd:
1029.5), 973.4 (M + 2H+, calcd: 972.8), 722.4 (M - 2AuPPh3 -
PPh3 - 3CH3 + 3H+, calcd: 722.6), 649.3 (M + 3H+, calcd: 648.8),
570.7 (InTREN + H+, calcd: 570.7). Anal. Calcd: C, 55.59; H,
4.20; N, 5.04. Found: C, 55.63; H, 4.26; N, 5.07.
Synthesis of (Triphos)Au3(InTREN) (2). Method A. A metha-
nol solution (4 mL) of InTREN (9 mg, 0.02 mmol) and potassium
hydroxide (4 mg, 0.07 mmol) was stirred at room temperature for
30 min. Then, a dichloromethane solution (3 mL) of (triphos)-
(AuCl)3 (20 mg, 0.02 mmol) was added. A pale orange solid was
obtained after 1 h of stirring. The solid was filtered, washed with
hexane and diethyl ether, and vacuum-dried. During all the
manipulations, the solution was protected from the light in order
to avoid decomposition. Yield: 93%. 31P NMR (CH2Cl2, inset
acetone-d6 with 1% POMe3): δ 17.2. 1H NMR (DMSO-d6): δ 8.31
(s, 3H, CH2-N-CH), 7.99 (s, 3H, H1,indole), 7.78–7.65 (m, 30H,
Ph), 7.62 (s, br, 3H, H4,indole), 7.22 (s, 3H, H2,indole), 6.62 (s, br, 3H,
(54) Bardaji, M.; Calhorda, M. J.; Costa, P. J.; Jones, P. G.; Laguna, A.;
Perez, M. R.; Villacampa, M. D. Inorg. Chem. 2006, 45, 1059–1068.
(55) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270–283.
(56) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284–298.
(57) Dunning, T. H., Jr.; Hay, P. J. In Modern Theoretical Chemistry;
Schaefer, H. F., III, Ed.; Plenum: New York, 1976.
(58) Pyykko, P.; Runeberg, N.; Mendizabal, F. Chem.sEur. J. 1997, 3,
1451–1457.
(59) Tomasi, J.; Mennucci, B.; Cammi, R. Chem. ReV. 2005, 105, 2999–
3093.
H
3,indole), 4.13 (s, br, 6H, CH2-N-CH), 3.50 (s, br, 6H,
(60) Check, C. E.; Faust, T. O.; Bailey, J. M.; Wright, B. J.; Gilbert, T. M.;
Sunderlin, L. S. J. Phys. Chem. A 2001, 105, 8111–8116.
(61) Frisch, M. J. T. G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Montgomery, J. A., Jr.; 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, Revision
C.02; Gaussian, Inc.: Wallingford, CT, 2004.
CH2-CH2-N-CH), 3.12 (s, br, 6H, CH2-P), 2.32 (s, 9H, CH3),
1.60 (s, 3H, CH3-C-). IR (KBr, cm-1): 3253 w, br (N-H);
3047 w, 2921 w, 2844 w, 2811 w (C-H); 1655 s, 1642 s, 1639 s,
1627 s, 1612 s, 1383 s (indole); 1476 m, 1436 s, 1101 s (PPh2).
ESI-MS (CH2Cl2, m/z): 1782.6 (M + H+, calcd: 1782.4), 892.2
(M + 2H+, calcd: 891.7), 595.2 (M + 3H+, calcd: 594.8). Anal.
Calcd: C, 51.89; H, 4.24; N, 5.50. Found: C, 51.93; H, 4.29; N,
5.54.
Method B. A dichloromethane solution (6 mL) of [{Au(acac)}3-
(triphos)] (25 mg, 0.17 mmol; following the same procedure as for
the PPh3 gold derivative52) was added dropwise to a dichlo-
romethane solution (8 mL) of InTREN (9.4 mg, 0.17 mmol). After
4 h of stirring at room temperature, the solution was filtered through
anhydrous magnesium sulfate and concentrated to a final volume
of 2 mL, and then hexane (8 mL) was added. A pale orange solid
was obtained, filtered, washed with diethyl ether and hexane, and
(62) http://gabedit.sourceforge.net/home.htm.
4954 Inorganic Chemistry, Vol. 47, No. 11, 2008

Studies on Neutral Au(I) Metallosupramolecular Compounds
Scheme 2
metal complexes49,63 has been used to explore the reactivity
of the InTREN ligand (L) with different gold(I) phosphine
compounds. Treatment of L with 3 equiv of AuPPh3+ leads
to the obtention of compound 1, with dendrimer-like struc-
ture. The synthesis of 1 has been carried out by two different
methods (Scheme 2). Method A had been employed many
years ago by Usón et al.49 and is based on the treatment of
L with KOH in MeOH for 30 min. The obtained potassium
indole salt gives 1 after addition of a stoichiometric amount
of AuClPPh3. Addition of some CH2Cl2 is required in order
to improve the solubility of the products in the reaction
medium.
vacuum-dried. During all the manipulations, the solution was
protected from the light in order to avoid decomposition. Yield:
90%. 31P NMR (CH2Cl2, inset acetone-d6 with 1% POMe3): δ 17.2.
1H NMR (DMSO-d6): δ 8.31 (s, 3H, CH2-N-CH), 7.99 (s, 3H,
H1,indole), 7.78–7.65 (m, 30H, Ph), 7.62 (s, br, 3H, H4,indole), 7.22 (s,
3H, H2,indole), 6.62 (s, br, 3H, H3,indole), 4.13 (s, br, 6H,
CH2-N-CH), 3.50 (s, br, 6H, CH2-CH2-N-CH), 3.12 (s, br,
6H, CH2-P), 2.32 (s, 9H, CH3), 1.60 (s, 3H, CH3-C-). IR (KBr,
cm-1): 3253 w, br (N-H); 3047 w, 2921 w, 2844 w, 2811 w
(C-H); 1655 s, 1642 s, 1639 s, 1627 s, 1612 s, 1383 s (indole);
1476 m, 1436 s, 1101 s (PPh2). ESI-MS (CH2Cl2, m/z): 1782.6 (M
+ H+, calcd: 1782.4), 892.2 (M + 2H+, calcd: 891.7), 595.2 (M
+ 3H+, calcd: 594.8). Anal. Calcd: C, 51.89; H, 4.24; N, 5.50.
Found: C, 51.93; H, 4.29; N, 5.54.
Following the “acac method”,64 we have used the acetyl-
acetonato gold derivative [Au(acac)PPh3] in the reaction with
L (Method B, Scheme 2). In this synthetic procedure, the
deprotonation of the indole nitrogen atom and the formation
of the indole-gold bond are accomplished in only one step.
Although higher reaction times are needed in method B, less
manipulation is required, and the compound is obtained in
similar yield. Characterization of the solid by NMR and IR
spectroscopies and mass spectrometry confirmed the forma-
Synthesis of (Tripod)Au3(InTREN) (3). A similar procedure
was followed for the synthesis of 2, using the previously synthesized
[{Au(acac)}3(tripod)] derivative by the same method as for PPh3.52
Yield: 90%. 31P NMR (CH2Cl2, inset acetone-d6 with 1% POMe3):
1
δ 37.3. H NMR (CD2Cl2-d6): δ 8.34 (s, 3H, CH2-N-CH), 8.17
(s, 3H, H1,indole), 7.83 (d, J(H-H) ) 8.2 Hz), 3H, H4,indole), 7.68 (s,
3H, H2,indole), 7.48–6.82 (m, 30H, Ph), 7.06 (s, 3H, H3,indole), 5.48
(s, 1H, HC-(PPh2)3), 3.67 (s, br, 6H, CH2-N-CH), 2.93 (s, br,
6H, CH2-CH2-N-CH), 2.44 (s, 9H, CH3). IR (KBr, cm-1):
3236 w, br (N-H); 3050 w, 2920 w, 2854 w, 2821 w (C-H);
1652 s, 1642 s, 1635 vs, 1617 s, 1384 vs (indole); 1476 m, 1437 s,
1094 m (PPh2). ESI-MS (CH2Cl2, m/z): 1727.0 (M + H+, calcd:
1727.1), 863.8 (M + 2H+, calcd: 864.0), 576.0 (M + 3H+, calcd:
576.3). Anal. Calcd: C, 50.79; H, 3.91; N, 5.68. Found: C, 50.83;
H, 3.96; N, 5.73.
1
tion of the product. The H NMR spectrum shows that the
protons of the indolyl groups are moved upfield (∼0.2 ppm)
upon the coordination of the gold fragment. 31P NMR led
us to verify the formation of a symmetrical compound and
showed the coordination of all the AuPPh3+ fragments, since
it displays a single resonance at 31.3 ppm, which is shifted
upfield about 7 ppm relative to the corresponding [Au-
(acac)(PPh3)] precursor or 2 ppm from the [AuCl(PPh3)]
Results and Discussion
Syntheses and Characterizations. The well-known ability
of an indole group to act as an N-donor ligand in transition
(63) Pauson, P. L.; Qazi, A. R. J. Organomet. Chem. 1967, 7 (2), 321.
(64) Vicente, J.; Chicote, M. T. Coord. Chem. ReV. 1999, 195, 1143–1161.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4955

Rodríguez et al.
Figure 1. ESI-MS mass spectrum of compound 1.
Scheme 3
derivative. The IR spectrum displays a lower stretching
vibration energy of the indole rings (∆ν¯ ) 15 cm-1) on
coordination. ESI-MS shows the peak of the monoprotonated
species [M + H+] at 1945.2 and those of the corresponding
spectra display a single resonance at 17.2 and 37.3 ppm for
compounds 2 and 3, respectively, that are moved upfield upon
coordination of the [Au3(triphosphine)]3+ fragment. The upfield
shift (∆δ ) 0.3 ppm) of the indole protons and the observed
IR resonances, which are lower than in the case of free L, also
confirm the coordination of the ligand.
ESI-MS shows the peaks corresponding to the mono-, di-,
and triprotonated species (1782.6 [M + H+], 892.2 [M +
2H+], and 595.2 [M + 3H+] for 2 and 1727.0 [M + H+]+,
863.8 [M + 2H+], and 576.0 [M + 3H+] for 3 (Figure 2)).
DFT Geometry Optimization. DFT calculations were
employed in order to optimize the minimum energy geometry
of the complexes, because attempts to grow suitable crystals
for X-ray diffraction were unsuccessful. The phenyl groups
of the phosphine ligands are modeled by methyls for
compounds 2 and 3 (models 2m and 3m) and are retained
in compound 1 (models 1a and 1b). Some relevant distances
and angles are presented in Table 1.
+
loss of AuPPh3 fragments (Figure 1).
Because of the good reactivity of this new tripodal ligand
with the gold triphenylphosphine fragment, we explored the
possibility of constructing new polygold compounds, with a
closed-shell cavity, built with flexible linkers, to generate
pseudorigid metallocryptands that could be tested as the host
in molecular recognition processes. With this goal, the
reaction between L and two flexible gold(I) triphosphine
derivatives was undertaken to obtain the two new metallo-
cryptands 2 and 3 in excellent yields (Scheme 3).
Although 2 could be synthesized following methods A and
B, only method B was successful for the formation of 3, most
probably because of the low solubility of the (AuCl)3(tripod)
derivative. As we have observed for compound 1, 31P NMR
4956 Inorganic Chemistry, Vol. 47, No. 11, 2008

Studies on Neutral Au(I) Metallosupramolecular Compounds
Figure 2. ESI-MS mass spectrum of compound 3.
Å).66The relative geometry obtained may seem unexpected
because the triphosphine ligand has larger interatomic
distances among the P atoms in 2m (4.27 Å) than in 3m
(3.16 Å). The reason for this is that the InTREN ligand is much
more twisted with respect to the triphosphine in the former, as
can be seen from Figure 4 and from the Au-P-P-Au dihedral
angles, which are –56° in 2 and –39° in 3. The twisting of these
two subunits has also the consequence of a less linear N-Au-P
bond in 2m (167°) than in 3m (174°). So, the cavity in 2m is
not larger, as one could expect from the size of the phosphine
ligands. It is also worth pointing out that the lone pairs of the
nitrogen atoms from the tertiary amines are located outside the
cavity and this could influence the reactivity and the geometry
of possible derivatives between the gold complexes and the
metal cations (see below).
From the optimized geometry, one can also see that the
substitution of phenyl with methyl groups does not affect the
geometry of the complex because all phenyl groups would be
pointing outward without any sterical clash. In fact, optimization
with a smaller basis set and including the phenyls did not show
relevant geometrical changes (data not shown).
Photophysical Characterization. Absorption spectra of
compounds 1, 3, and their organic precursor, L, were
recorded in freshly prepared dichloromethane solutions
(Figure 5), and their main features are summarized in Table
2. The absorption spectrum of compound 2 was not
undertaken due to the lack of solubility of this compound.
The electronic absorption spectrum of the InTREN precur-
Table 1. Relevant Calculated Distances (Å) and Angles (deg) for
Models of Complexes 1–3
distance/angle
1a
2m
3m
Au· · ·Au
16.325
13.905
2.306
2.033
19.101
179
3.672
4.842
2.314
2.041
4.270
167
4.137
5.535
2.305
2.024
3.156
174
N(imidazole)· · ·N(imidazole)
Au-P
Au-N
P-P
P-Au-N
Compound 1 is computationally challenging because of
its flexibility. An added difficulty is that its conformation is
strongly influenced by the phenyl groups of the triphenyl-
phosphines. Therefore, we have modeled 1 with the explicit
inclusion of these groups. The DFT method used is too time
demanding to afford an extensive conformational search.
However, we have optimized two different conformations,
an extended (with the CH2-CH2 group of the InTREN ligand
in the trans position) and a compact conformation (with the
CH2-CH2 group of the InTREN ligand in the cis position)
that we have called 1a and 1b, respectively (Figure 3).
The flexibility and the large size of the molecule allowed
us to locate structures converged only within the gradient
threshold.65 In vacuum, 1b is 3 kcal/mol more stable than
1a, but solvation effects reverse this situation dramatically,
and 1a is predicted to be 13 kcal/mol more stable than 1b.
This large difference allows us to be confident to say that
1a will be the predominant conformer in solution.
The metallocryptands models 2m and 3m were also
optimized by DFT (Figure 4).
Complexes 2m and 3m form a cavity where the distance
between the gold atoms is 3.67 and 4.14 Å, respectively.
These distances are longer than the ones found in aurophilic
interactions, typically considered for Au · · · Au distances
shorter than the sum of two van der Waals radii (3–3.5
(65) Gaussian03 also uses an estimated displacement to consider full
convergence. But, because of the large size of this molecule and the
use of a nonexact Hessian, this convergence criterium was difficult to
meet even when the energy did not lower for several steps.
(66) Schmidbaur, H. Chem. Soc. ReV. 1995, 24, 391.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4957

Rodríguez et al.
Figure 3. Minimized energy molecular structure of the model compound of 1 in its opened (1a) and closed (1b) possible conformations. Hydrogen atoms
have been omitted for clarity.
Figure 4. Minimized energy molecular structure of models 2m and 3m. Hydrogen atoms have been omitted for clarity.
Table 2. Electronic Absorption and Emission Data in 1 × 10-5
M
Freshly Prepared Dichloromethane Solution, and Emission Maxima for
the Powders at Room Temperature
emission
absorption
max/nm
(10-3ε/M-1 ·cm-1
(λexc ) 360 nm)
λ
λ
max/nm max/nm
λ
compound
)
(CH2Cl2)
(solid)
1
260 (46.4), 265 (43.8), 275 (37.0),
305 (34.0), 316 (33.9)
440, 520
564
2
3
562
597
260 (47.3), 285 sh (33.2), 315 (19.6), 415, 515 sh
350 (15.4), 390 (5.1)
L
262 (56.6), 286 (46.1),
300 sh (35.1)
Figure 5. Absorption spectra in 1 × 10-5 M freshly prepared dichlo-
romethane solution of compounds 1, 3, and free InTREN ligand (L).
by 3, as discussed for other luminescent gold com-
pounds,54,71–84 could be related with the presence of Au-Au
interactions. However, in all three cases, the calculated
Au-Au distances in the DFT optimized geometries are
greater than those typically considered for the establishment
of aurophilic interactions (Table 1).70
TD-DFT Calculations. DFT calculations have been
carried out in order to know the geometry of the frontier
orbitals of the gold complexes. Model compounds 1m, 2m,
and 3m where phenyl groups were substituted by methyls
have been used for these calculations. The occupied orbitals
are mostly localized in the central tertiary amine, and the
lowest unoccupied molecular orbitals (LUMOs) have a large
sor shows the characteristic shape of the indole group
attributed to the two close low-lying ππ* excited states 1La
50,67–69
1
and Lb of this chromophore.
Absorption spectra of
the gold derivatives 1 and 3 present their lowest energy band
at longer wavelength with respect to the case of the organic
ligand (∼310 and 350 nm, respectively), and that band could
be assigned as a ligand-to-metal charge transfer (LMCT)
transition based on TD-DFT calculations (see below).
The emission of compounds 1 and 3 in dichloromethane
solution is very weak (data not shown).
Excitation of the powders at 360 nm gives no lumines-
cence for L and emission bands at 564, 562, and 597 nm for
the gold complexes 1–3 (Figure 6). The red shift displayed
4958 Inorganic Chemistry, Vol. 47, No. 11, 2008

Studies on Neutral Au(I) Metallosupramolecular Compounds
Table 3. Calculated TD-DFT Low-Energy Singlet Excitation Energies,
Wavelengths, and Oscillator Strengths (OS) and Experimental Data for
Model 1m
transition
E/nm E/eV
λmax/nm
OS
H f L (58%), H f L+2 (24%)
306 4.06
316
0.182
0.003
0.319
0.001
0.200
H-1 f L+3 (33%), H f L+3 (17%) 298 4.17
H-1 f L (59%), H-1 f L+2 (15%) 289 4.29
H f L+3 (87%), H-2 f L+3 (13%) 283 4.38
305
275
H f L (58%), H-1 f L (27%),
H-1 f L+2 (16%)
H-2 f L+2 (31%), H-1 f L (37%), 273 4.53
H-2 f L (13%), H f L (12%)
H f L+2 (39%), H f L (38%),
H-1 f L+2 (16%)
276 4.49
0.056
269 4.60
265
0.0852
Figure 6. Normalized solid emission spectra of compounds 1–3 upon
excitation of the samples at λ ) 360 nm.
Table 4. Calculated TD-DFT Low-Energy Singlet Excitation Energies,
Wavelengths, and Oscillator Strengths (OS) for Model 3m
transition
E/nm E/eV
λ
max/nm OS
contribution of the gold and the phosphine moieties and are
Au-P antibonding. In the case of compound 1, there is also
a contribution of the indole group in these orbitals.
H f L (99%)
432 2.86
386 3.21
372 3.33
335 3.69
0.000
H-1 f L (33%), H-2 f L (66%)
H f L+1 (50%), H f L+2 (50%)
H-1 f L (20%), H f L+3 (34%),
H-2 f L (13%), H-2 f L+2 (23%)
H-2f L (32%)
390
350
0.001
0.001
0.054
TD-DFT studies were performed in order to interpret the
optical properties of these compounds. The most relevant
calculated electronic transitions of the models are presented
in Table 3 (compound 1m), Table S1 in the Supporting
Information (compound 2m), and Table 4 (compound 3m).
The low energy excitations obtained by this method are
in the range 288–305 nm (1m), 333–395 nm (2m), and
335–386 nm (3m) including dichloromethane effects and are
in good agreement with the recorded experimental data.
The experimental broad band at ∼310 nm of compound
1 is expected to have contributions from the two transitions
with the higher oscillator strength value (calculated value:
306 nm; experimental value: 316 nm) and is assigned to a
mixed transition from the highest occupied molecular orbital
327 3.79
0.033
0.003
H-2 f L+3 (61%), H-1 f L+3 (34%) 309 4.01
315
(HOMO) to the LUMO (58%) and LUMO+2 (24%). The
second observed band (calculated value: 289 nm; experi-
mental value: 305 nm) is a mixed transition from the
HOMO-1 to the LUMO (59%) and L+2 (15%) orbitals.
The involved orbitals in these transitions are represented in
Figure 7.
The electronic density of the HOMO-1 orbital is mainly
centered at the indole group while the central tertiary amine
concentrates the electronic density of the HOMO orbital. The
unoccupied orbitals are Au-P antibonding orbitals with a
slight contribution of the indole groups. Assuming that DFT
underestimates the Au contribution in the virtual orbitals,85
the lower energy electronic transition could be mainly
attributed to a LMCT N(p, tertiary amine) f Au mixed with
an indole f Au transition.
The LMCT N(p, tertiary amine) f Au transition has also
been calculated to be responsible for the lowest-energy transi-
tions for compounds 2 and 3. These complexes present a closed-
conformation structure by the substitution of the triphenylphos-
phine ligands of 1 by a triphosphine. Although the absorption
spectrum of 2 has not been recorded, the predicted electronic
transition and the involved orbitals have also been calculated
(see the Supporting Information). The calculated transitions with
higher oscillator strength are also in good agreement with the
experimental results for compound 3m. Thus, the experimental
band at ∼350 nm is calculated at 335 nm. The absorption is
assigned to a mixed transition from the HOMO-2, HOMO-1,
and HOMO orbitals to the LUMO, LUMO+2, and LUMO+3.
The three-dimensional representation of these orbitals is pre-
sented in Figure 8.
(67) Serrano-Andrés, L.; Roos, B. O. J. Am. Chem. Soc. 1996, 118, 185–
195.
(68) Borin, A. C.; Serrano-Andrés, L. Chem. Phys. 2000, 262, 253–265.
(69) Sinha, S.; De, R.; Ganguly, T. Spectrochim. Acta, Part A 1998, 54,
145–157.
(70) Schmidbaur, H. Gold Bull. (London, U. K.) 2000, 33, 3–10.
(71) Bardaji, M.; de la Cruz, M. T.; Jones, P. G.; Laguna, A.; Martinez, J.;
Villacampa, M. D. Inorg. Chim. Acta 2005, 358, 1365–1372.
(72) Stott, T. L.; Wolf, M. O.; Patrick, B. O. Inorg. Chem. 2005, 44, 620–
627.
(73) Yam, V. W. W.; Cheung, K. L.; Yip, S. K.; Cheung, K. K. J.
Organomet. Chem. 2003, 681, 196–209.
(74) Ovejero, P.; Mayoral, M. J.; Cano, M.; Lagunas, M. C. J. Organomet.
Chem. 2007, 692, 1690–1697.
(75) Lee, Y. A.; Eisenberg, R. J. Am. Chem. Soc. 2003, 125, 7778–7779.
(76) Mohamed, A. A.; López-de-Luzuriaga, J. M.; Fackler, J. P. J. Cluster
Sci. 2003, 14, 61–70.
(77) Zheng, S. L.; Nygren, C. L.; Messerschmidt, M.; Coppens, P. Chem.
Commun. 2006, 3711–3713.
(78) van Zyl, W. E.; López-de-Luzuriaga, J. M.; Fackler, J. P. J. Mol. Struct.
2000, 516, 99–106.
(79) van Zyl, W. E.; López-de-Luzuriaga, J. M.; Mohamed, A. A.; Staples,
R. J.; Fackler, J. P. Inorg. Chem. 2002, 41, 4579–4589.
(80) Pintado-Alba, A.; de la Riva, H.; Nieuwhuyzen, M.; Bautista, D.;
Raithby, P. R.; Sparkes, H. A.; Teat, S. J.; López-de-Luzuriaga, J. M.;
Lagunas, M. C. Dalton Trans. 2004, 3459–3467.
(81) Fernandez, E. J.; Gimeno, M. C.; Laguna, A.; López-de-Luzuriaga,
J. M.; Monge, M.; Pyykko, P.; Sundholm, D. J. Am. Chem. Soc. 2000,
122, 7287–7293.
(82) Li, C. K.; Lu, X. X.; Wong, K. M. C.; Chan, C. L.; Zhu, N. Y.; Yam,
V. W. W. Inorg. Chem. 2004, 43, 7421–7430.
The large Stokes shift between absorption and emission
suggests triplet contribution to the emission.
(83) Onaka, S.; Yaguchi, M.; Yamauchi, R.; Ozeki, T.; Ito, M.; Sunahara,
T.; Sugiura, Y.; Shiotsuka, M.; Horibe, M.; Okazaki, K.; Iida, A.;
Chiba, H.; Inoue, K.; Imai, H.; Sako, K. J. Organomet. Chem. 2005,
690, 57–68.
(84) Ferrer, M.; Gutierrez, A.; Rodriguez, L.; Rossell, O.; Lima, J. C.; Font-
Bardía, M.; Solans, X. Submitted for publication.
(85) Costa, P. J.; Calhorda, M. J. Inorg. Chim. Acta 2006, 359, 3617–
3624.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4959

Rodríguez et al.
Figure 7. Isodensity representation of the orbitals of the model 1m of complex 1 involved in the lowest energy transitions.
Figure 8. Isodensity representation of the orbitals of the model 3m of complex 3 involved in the lowest energy transitions.
Molecular Recognition Studies of Metal Cations in
Solution. Molecular recognition of metal cations constitutes
a potential application for these compounds.86–88 With this
goal in mind, titrations of 1 and 3 with Zn2+, Ni2+, and Cu2+
salts were undertaken in dichloromethane solution, and
changes in their electronic spectra were recorded.
The addition of different amounts of the corresponding
triflate or tetrafluoroborate salts to a 1 × 10-5 M solution
of the dendrimeric compound 1 conduces to a decrease
of the lowest energy absorption band at ∼310 nm and
the formation of a new band at longer wavelengths (∼350
nm, see Figure 9).
The representation of the variation maxima as a function
of the number of Zn2+ equivalents added to the solution leads
us to conclude the formation of a 1:1 complex between the
gold derivative and the metal atom (Figure 9, inset). The
affinity of these metals to coordinate with amines suggests
that the metal atom could coordinate to the secondary amines
of the InTREN ligand. This fact is supported by the results
obtained with the free InTREN ligand. The Zn2+ derivative
of this precursor was isolated and characterized, and the
recorded IR spectrum clearly indicates the coordination by
(86) Liang, Z.; Liu, Z. L.; Gao, Y. H. Tetrahedron Lett. 2007, 48, 3587–
3590.
(87) Ipe, B. I.; Yoosaf, K.; Thomas, K. G. J. Am. Chem. Soc. 2006, 128,
1907–1913.
(88) Tamayo, A.; Pedras, B.; Lodeiro, C.; Escriche, L.; Casabo, J.; Capelo,
J. L.; Covelo, B.; Kivekas, R.; Sillanpaa, R. Inorg. Chem. 2007, 46,
7818–7826.
4960 Inorganic Chemistry, Vol. 47, No. 11, 2008

Studies on Neutral Au(I) Metallosupramolecular Compounds
Figure 9. Absorption spectra of compound 1 in the presence of 1–3 equiv
of Zn2+ in dichloromethane solution ([1] ) 1 × 10-5 M, [Zn2+] ) 1 ×
10-4 M).
Figure 12. ChemDraw representation of the new supramolecular compound
with sandwich structure obtained by the titration of the metallocryptand 3
with Zn(OTf)2.
formation of a new blue-shifted band while a valley appears
at 300 nm. The recorded changes in absorption as a function
of metal ion concentration reach a plateau at 0.5 equiv of
metal ion that indicates the formation of a 1:2 complex
(Figure 11, inset).
These results are clearly different from those obtained for
the dendrimeric derivative. The recorded blue-shifted band
suggests that in this case the charge transfer process is less
favored; that is, it suggests complexation involving the
tertiary amine. On the other hand, the formation of a complex
with 1:2 stoichiometry, Zn2+/3, also points to the formation
of a compound with a different structure. The HOMO
electronic density of the metallocryptand is mainly located
in the tertiary amine with the lone pairs of the InTREN ligand
pointing outside the cavity and a single coordinative bond
that will not stabilize the formation of the new complex with
the Zn2+. This is probably one of the reasons why complex-
ation with Zn2+ leads to the formation of a complex with
2:1 stoichiometry. A possible structure is exemplified in
Figure 12.
Figure 10. ChemDraw representation of the new supramolecular compound
obtained by the titration of the dendrimer 1 with Zn(OTf)2.
High resolution ESI-MS and MALDI-TOF-MS have been
very useful to verify the formation of these new heterome-
tallic complexes. The recorded mass spectrum for a 1:1
3/Zn2+ dichloromethane solution confirms the formation of
the 3 · Zn2+ · 3 species with sandwich structure with peaks at
m/z ) 1194.9, 1178.6, and 887.3 that correspond to the
[3 · Zn(H2O)4 · 3 + H+]3+, the [3 · Zn(H2O) · 3 + H+]3+, and
the [3 · Zn(H2O)2 · 3 + 2H+]4+ fragments.
Figure 11. Absorption spectra of compound 3 in the presence of 1–3 equiv
of Zn2+ in dichloromethane solution ([3] ) 1 × 10-5 M; [Zn2+] ) 1 ×
10-4 M).
the secondary amines.50 Moreover, X-ray crystal structures
of other similar tripodal compounds show the coordination
with metal atoms by the secondary amines.89 These reported
results strongly suggest that the same coordination occurs
with the gold derivative 1 (Figure 10). On the other hand,
the coordination with the Zn2+ increases the electron deficient
character of the environment in the direction of the charge
transfer, which is in agreement with the observed red shift
of the band for the LMCT transition.
The mass spectrum recorded for a 1:1 1 · Zn2+ dichlo-
romethane solution shows peaks at m/z ) 1022.2 and 1013.9
indicative of the presence of the [1 · Zn(H2O)2]2+ and the
[1 · Zn(H2O)]2+ species. These results are in agreement with
spectroscopic data, since absorption variations recorded at
the maxima reach a plateau with 1 equiv of Zn2+ in the case
of compound 1 and with 0.5 equiv in the case of 3.
Similar results were obtained in the titrations of 1 and 3
with Ni2+ and Cu2+ salts.
Similar experiments carried out with a 1 × 10-5
M
dichloromethane solution of the metallocryptand 3 show the
opposite effect (Figure 11). In this case, the addition of
different quantities of the metal solution leads to the
Conclusions
Self-assembly reactions between the tris-indole InTREN
ligand (L) and the gold(I) phosphine fragments lead to the
construction of new gold(I) complexes by two different
(89) Nakamura, H.; Fujii, M.; Sunatsuki, Y.; Kojima, M.; Matsumoto, N.
Eur. J. Inorg. Chem. 2008, 1258–1267.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4961

Rodríguez et al.
methods. A metallodendrimer-like complex (1) has been
synthesized when the AuPPh3 fragment is used, and two
2006 for financial support and to the Ministerio de Educación
y Ciencia (Spain) for the Project CTQ2006-02362/BQU,
Acción Integrada Hispano-Portuguesa HP2006-0101, and
CRUP (Portugal) Acção Integrada Luso-Espanhola E-68/07.
L.R. acknowledges the postdoctoral grant given by the
Fundação para a Ciência e Tecnologia (Portugal, SFRH/BPD/
26882/2006). R.C. thanks the Spanish Ramón y Cajal
program for financial support. This research has been partly
performed using the CESCA resources. The authors also
would like to thank Dr. Montserrat Ferrer and Dr. Oriol
Rossell from the Inorganic Departament of the Universitat
de Barcelona for fruitful discussions.
+
neutral gold(I) metallocryptands with empty cavities (2 and
3) have been constructed when the chosen gold fragments
are [Au3(triphosphine)]3+ derivatives with different lengths.
Density functional theory (B3LYP) has been used to
optimize the minimum energy geometry of the complexes.
TD-DFT has been a very useful tool to attribute the
absorption bands to LMCT N(p, tertiary amine) f Au
transitions. Emission in the solid state seems to originate
3
from the LMCT state.
Spectroscopic titrations with metals of 1 and 3 dichlo-
romethane solutions conduce to the formation of new
heterometallic compounds with different structures in both
cases. While the dendrimeric species mainly gives the 1:1
complex with coordination of the secondary amines, com-
pound 3 leads to the formation of a new 3 · M2+ · 3 hetero-
metallic sandwich type structure with 2:1 stoichiometry. The
evidence is supported by spectroscopy, mass spectrometry,
and DFT calculations.
Supporting Information Available: ESI-MS mass spectrum of
compound 2 (Figure S1), table with calculated TD-DFT low-energy
singlet excitation energies, wavelengths, and oscillator strengths
for model 2m (Table S1), and isodensity representation of the
orbitals of model 2m involved in the lowest energy transitions of
compound 2 (Figure S2). This material is available free of charge
via the Internet at http://pubs.acs.org.
Acknowledgment. We are indebted to FEDER/Fundação
para a Ciência e Tecnologia (Portugal) PTDC/QUI/66250/
IC800266M
4962 Inorganic Chemistry, Vol. 47, No. 11, 2008