Self-assembly, structures, and solution dynamics of emissive silver metallacycles and helices

Article abstract of DOI:10.1021/ic060140v

Reactions of 9,10-bis(diphenylphosphino)anthracene (PAnP) and AgX (X = OTf^-, ClO₄^-, PF₆^-, and BF₄^-) led to luminescent Ag-PAnP complexes with rich structural diversity. Helical polymers [Ag(μ-PAnP)(CH₃CN)X] _n (X = OTf^-, ClO₄^-, and PF ₆^-) and discrete binuclear [Ag₂(μ-PAnP) ₂(CH₃CN)₄](PF₆)₂, trinuclear [Ag₃(μ-PAnP)₃?BF₄]-(BF ₄)₂, and tetranuclear [Ag₄(μ-PAnP) ₄?(ClO₄)₂](ClO₄)₂ metallacycles were isolated from different solvents. The tri-and tetranuclear metallacycles exhibited novel puckered-ring and saddlelike structures. Variable-temperature (VT) ³¹P{¹H}-NMR spectroscopy of the complexes was solvent dependent. The dynamics in CD₃CN involve two species, but the exchange processes in CD₂Cl₂ are more complicated. A ring-opening polymerization was proposed for the exchange mechanism in CD₃CN.

Full text of DOI:10.1021/ic060140v

Inorg. Chem. 2006, 45, 4423−4430
Self-Assembly, Structures, and Solution Dynamics of Emissive Silver
Metallacycles and Helices
Ronger Lin and John H. K. Yip*
Department of Chemistry, National UniVersity of Singapore, 3 Science DriVe 3,
Singapore, 11754, Singapore
Received January 24, 2006
Reactions of 9,10-bis(diphenylphosphino)anthracene (PAnP) and AgX (X
luminescent Ag PAnP complexes with rich structural diversity. Helical polymers [Ag(
OTf-, ClO4-, and PF6-) and discrete binuclear [Ag2(
-PAnP)2(CH3CN)4](PF6)2, trinuclear [Ag3(
(BF4)2, and tetranuclear [Ag4( -PAnP)4 (ClO4)2](ClO4)2 metallacycles were isolated from different solvents. The tri-
and tetranuclear metallacycles exhibited novel puckered-ring and saddlelike structures. Variable-temperature (VT)
31P 1H
-NMR spectroscopy of the complexes was solvent dependent. The dynamics in CD3CN involve two species,
)
OTf-, ClO4-, PF6-, and BF4-) led to
-PAnP)(CH3CN)X]n (X
-PAnP)3 BF4]-
−
µ
)
µ
µ
⊃
µ
⊃
{
}
but the exchange processes in CD2Cl2 are more complicated. A ring-opening polymerization was proposed for the
exchange mechanism in CD3CN.
Introduction
Most works on silver-ligand self-assembly invoke N-
heterocyclic ligands.1a,2-6 As an important class of ligands
for late transition metals, phosphines have been recently used
in constructing metallo-supramolecular systems.7-10 A num-
ber of Ag-diphosphine supramolecules have been reported.
Noteworthy is the work of Puddephatt which showed that
Metal directed self-assembly is an effective approach
toward coordination polymers and metallacycles.1 Supramo-
lecular assemblies arising from silver-ligand coordination are
known for their complexity and rich structural diversity.2
Many studies showed that combinations of a AgI ion and
multidentate ligands often give rise to more than one product,
which could be polymer or discrete metallacycles. It is due
to the various coordination geometry possibly adopted by
the AgI ion3 and the labile Ag-ligand bond which results in
equilibrium of different species in solution. The position of
the equilibrium could be influenced by factors such as
temperature, solvent, and anion, making the self-assembly
less predictable and controllable.4,5
(4) Blake, A. J.; Champness, N. R.; Cooke, P. A.; Nicolson, J. E. P.;
Wilson, C. J. Chem. Soc., Dalton Trans. 2000, 3811.
(5) Hannon, M. J.; Painting, C. L.; Plummer, E. A.; Childs, L. J.; Alcock,
M. W. Chem.sEur. J. 2002, 2225.
(6) (a) Chen, C.-L.; Su, C.-Y.; Cai, Y.-P.; Zhang, H.-X.; Xu, A.-W.; Kang,
B.-S.; zur Loye, H.-C. Inorg. Chem. 2003, 42, 3738. (b) Su, C.-Y.;
Cai, Y.-P.; Chen, C.-L.; Smith, M. D.; Kaim, W.; zur Loye, H.-C. J.
Am. Chem. Soc. 2003, 125, 8595. (c) Bray, D. J.; Liao, L. L.; Antonioli,
B.; Gloe, K.; Lindoy, L. F.; McMurtrie, J. C.; Wei, G.; Zhang, X.-Y.
J. Chem. Soc., Dalton Trans. 2005, 2082. (d) Burchell, T. J.; Eisler,
D. J.; Puddephatt, R. J. J. Chem. Soc. Chem. Comm. 2004, 944. (e)
Yue N. L. S.; Jennings, M. C.; Puddephatt, R. J. Inorg. Chem. 2005,
44, 1125. (f) Yue, N. L. S.; Jennings, M. C.; Puddephatt, R. J. J. Chem.
Soc., Chem. Commun. 2005, 4792.
* To whom correspondence should be addressed. E-mail: chmyiphk@
nus.edu.sg. Fax: 65-67791691.
(1) For reviews see (a) Khlobystov, A. N.; Blake, A. J.; Champness, N.
R.; Lemenovskii, D. A.; Majouga, A. G.; Zyk, N. V.; Schro¨der, M.
Coord. Chem. ReV. 2001, 222, 155. (b) Leininger, S.; Olenyuk, B.;
Stang, P. J. Chem. ReV. 2000, 100, 853. (c) Batten, S. R.; Robson, R.
Angew. Chem., Int. Ed. 1998, 37, 1461.
(7) (a) Eisler, D. J.; Puddephatt, R. J. Inorg. Chem. 2003, 42, 8192. (b)
Brandys, M. C.; Puddephatt, R. J. J. Am. Chem. Soc. 2002, 124, 3946.
(c) Eisler, D. J.; Puddephatt, R. J. Cryst. Growth Des. 2005, 5, 57.
(8) (a) James, S. J. Macromol. Symp. 2004, 209, 119. (b) James, S. L.;
Xu, X. L.; Law, R. V. Macromol. Symp. 2003, 196, 187. (c) Lozano,
E.; Nieuwenhuyzen, M.; James, S. L. Chem.sEur. J. 2001, 7, 2644.
(d) Miller, P.; Nieuwenhuyzen, M.; Charmant, J. P. H.; James, S. L.
CrystEngComm 2004, 6, 408. (e) James, S. L.; Lozano, E.; Nieuwen-
huyzen, M. J. Chem. Soc., Chem. Commun. 2000, 617.
(9) (a) Lu X.-L.; Leong W. K.; Hor T. S. A.; Goh L. Y. J. Organomet.
Chem. 2004, 689, 1746. (b) Lu, X.-L.; Leong, W. K.; Goh, L. Y.;
Hor, T. S. A. Eur. J. Inorg. Chem. 2004, 2504.
(10) (a) Bessel, C. A.; Aggarwal, P.; Marschilok, A. C.; Takeuchi, K. J.
Chem. ReV. 2001, 101, 1031. (b) Caruso, F.; Camalli, M.; Rimml, H.;
Venanzi, L. M. Inorg. Chem. 1995, 34, 673. (c) Kitagawa, S.; Kondo,
M.; Kawata, S.; Wada, S.; Maekawa, M.; Munataka, M. Inorg. Chem.
1995, 34, 1455. (d) Bachechi, F.; Burini, A.; Galassi, R.; Pietroni, B.
R.; Jesei, D. Eur. J. Inorg. Chem. 2002, 2086.
(2) (a) Dong, Y.-B.; Zhang, H.-Q.; Ma, J.-P.; Huang, R.-Q.; Su, C.-Y.
Cryst. Growth Des. 2005, 5, 1857. (b) Withersby, M. A.; Blake, A.
J.; Champness, N. R.; Hubberstey, P.; Li, W.-S. Schro¨der, M. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2327. (c) Blake, A. J.; Baum, G.;
Champness, N. R.; Chung, S. S.-M.; Cooke, P. A.; Fenske, D.;
Khlobystov, A. N.; Lemenovskii, D. A.; Li, W.-S.; Schro¨der, M. J.
Chem. Soc., Dalton Trans. 2000, 4285. (f) Muthu, S.; Yip, J. H. K.;
Vittal, J. J. J. Chem. Soc., Dalton Trans. 2002, 4561. (g) Muthu, S.;
Yip, J. H. K.; Vittal, J. J. J. Chem. Soc., Dalton Trans. 2001, 3577.
(3) (a) Venkataraman, D.; Du, Y.; Wilson, S. R.; Hirsch, K. A.; Zhang,
P.; Moore, J. S. J. Chem. Edu. 1997, 74, 915. (b) Cotton, F. A.;
Wilkinson, G. AdVanced Inorganic Chemistry, 5th ed.; Wiley: Chich-
ester, 1988.
10.1021/ic060140v CCC: $33.50
Published on Web 05/06/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 11, 2006 4423

Lin and Yip
Scheme 1. Reactions of PAnP and AgX (X ) OTf-, ClO4-, PF6-, and BF4-)
the complexes were carried out at the National University of
Singapore, Singapore.
changing the rigidity of the backbone of the diphosphine
ligand could have drastic effect on the outcome of the self-
assembly.7b The Ag-phosphine supramolecules usually
display complex solution dynamics.8a,b
Synthesis of {[Ag(µ-PAnP)(CH3CN)(OTf)]‚0.5CH3CN}n (1).
A 5 mL CH3CN solution of AgOTf (52 mg, 0.20 mmol) was added
into a 50 mL CH2Cl2 solution of PAnP (110 mg, 0.20 mmol) under
N2. The mixture was stirred for 2 h in the dark. The addition of
Et2O to the concentrated solution precipitated yellow solids.
Yield: 73%. Crystals were obtained from CH3CN/Et2O. Anal. Calcd
for C42H32.5AgF3N1.5O3P2S: C, 58.31%; H, 3.79%. Found: C,
Described in this paper are reactions of 9,10-bis(diphe-
nylphosphino)anthracene (PAnP) (Scheme 1) and various
AgX (AgX, X ) OTf-, PF6 , BF4 , and ClO4 ) and
structures and solution dynamics of the products. PAnP, first
synthesized by our group, has been shown to form stable
gold(I)-metallacycles.11,12 The ligand has two special fea-
tures: First, with the chromophoric anthracenyl ring in its
backbone, the ligand is capable of imparting luminescence
to its metal complexes.11,12 Second, the anthracenyl back-
bone can participate in π-π stacking and C-H‚‚‚π interac-
tions, which could lead to new supramolecular architec-
tures.12,13 Our present study showed that reactions of AgI
ion and the ligand gave rise to discrete metallacycles and
helical polymers which exhibited complicated dynamics in
solution.
-
-
-
1
57.89%; H, 3.49%. 31P{1H}-NMR: see text. H NMR (CD3CN,
300 MHz): δ 7.91-7.87 (m, 4H), 7.52-7.25 (m, 20H), 6.86-
n+
6.82 (m, 4H). ESI-MS (m/z assignment): 654.3, [Ag(PAnP)]n
;
926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+; 1745.4, [Ag-
(PAnP)3]+.
Synthesis of {[Ag(µ-PAnP)(CH3CN)(ClO4)}n (2a) and [Ag4-
(µ-PAnP)4⊃(ClO4)2](ClO4)2‚4CH2Cl2 (2b). The preparation of
complex 2a was similar to that of complex 1. Yield: 77%.
Compound 2a {[Ag(µ-PAnP)(CH3CN)][ClO4]}n was crystallized
from a CH3CN/Et2O solution of the product obtained from the
reaction of AgClO4 and PAnP. Anal. Calcd for C80H62Ag2-
Cl2N2O8P4: C, 60.44%; H, 3.93%. Found: C, 59.52%; H, 3.74%.
1
31P{1H}-NMR: see text. H NMR (CD3CN, 300 MHz): δ 7.91-
Experimental Section
7.88 (m, 4H), 7.52-7.24 (m, 20H), 6.86-6.82 (m, 4H). ESI-MS
General Methods and Physical Measurements. Compound
9,10-bis(diphenylphosphino)anthracene (PAnP) was synthesized
according to the reported method.12 All silver salts were purchased
from Aldrich and used without being purified. The UV-vis
absorption and emission spectra of the complexes were recorded
on a Shimadzu UV-1601 UV-visible spectrophotometer and a
Perkin-Elmer LS-50B fluorescence spectrophotometer, respectively.
Electrospray ionization mass spectra (ESI-MS) were measured on
a Finnigan MAT 731 LCQ spectrometer. Elemental analyses of
(m/z assignment): 654.3, [Ag(PAnP)]nn+; 835.3, [Ag3(PAnP)4]3+
;
926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+. Compound 2b [Ag4-
(µ-PAnP)4⊃(ClO4)2](ClO4)2‚4CH2Cl2 was obtained from the crys-
tallization of CH2Cl2/Et2O solution of the product obtained from
the reaction of AgClO4 and PAnP. Anal. Calcd for C156H120Ag4-
Cl12O16P8: C, 55.84%; H, 3.60%. Found: C, 55.43%; H, 3.51%.
1
31P{1H}-NMR: see text. H NMR (CD2Cl2, 300 MHz): δ 7.91-
7.88 (m, 4H), 7.52-7.25 (m, 20H), 6.85-6.82 (m, 4H). ESI-MS
(m/z assignment): 654.3, [Ag(PAnP)]nn+; 1031.0 [Ag3(PAnP)3-
(ClO4)]2+; 926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+; 1408.6,
(11) Yip, J. H. K.; Prabhavathy, J. Angew. Chem., Int. Ed. 2001, 40, 2159.
(12) Lin, R.; Yip, J. H. K.; Zhang, K.; Koh, L. L.; Wong, K.-Y.; Ho, K. P.
J. Am. Chem. Soc. 2004, 126, 15852.
(13) Zhang, K.; Prabhavathy, J.; Yip, J. H. K.; Koh, L. L.; Tan, G. K.;
Vittal, J. J. J. Am. Chem. Soc. 2003, 125, 8452.
[Ag2(PAnP)2(ClO4)]+ or [Ag4(PAnP)4(ClO4)2]2+
.
Synthesis of {[Ag(µ-PAnP)(CH3CN)(PF6)}n (3a) and [Ag2(µ-
PAnP)2(CH3CN)4](PF6)2‚1.5Et2O‚0.35CH2Cl2 (3b). Similar to the
4424 Inorganic Chemistry, Vol. 45, No. 11, 2006

EmissiWe SilWer Metallacycles and Helices
Table 1. Crystal Data and Structure Refinementsa for Compounds 1, 2a, 2b, 3a, 3b, and 4
1
2a
2b
3a
3b
4
empirical
formula
fw
C42H32.50AgF3N1.50
O3P2S
865.07
C80H62Ag2Cl2
N2O8P4
1589.84
223(2)
orthorhombic
P2(1)2(1)2(1)
9.7009(6)
14.5954(10)
24.0063(16)
90
90
90
3399.0(4)
2
1.553
C
156H120Ag4Cl12
O16P8
C80H62Ag2
F12N2P6
1680.88
223(2)
orthorhombic
P2(1)2(1)2(1)
9.7572(5)
14.8314(8)
24.1685(14)
90
90
90
3497.5(3)
2
1.596
C
90.45H83.90Ag2Cl0.70
F12N4O1.50 P6
C
131H127Ag3
B3F12O5P6
3355.16
223(2)
orthorhombic
Fddd
19.4287(7)
36.4741(12)
42.9932(15)
90
1905.29
293(2)
orthorhombic
Pmn2(1)
18.7319(8)
18.5100(8)
25.8368(11)
90
90
90
8958.3(7)
4
1.413
2551.19
223(2)
monoclinic
Cc
15.7878(14)
39.138(4)
21.1625(17)
90
111.148(2)
90
T (K)
223(2)
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P2(1)/c
14.092(2)
9.7574(15)
29.812(5)
90
101.907(4)
90
4011.0(11)
4
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
30466.9(18)
8
1.463
12195.7(19)
4
1.389
D
calcd (g/cm3)
1.433
0.688
abs coeff (mm-1
)
0.810
0.862
0.777
0.638
0.627
F(000)
1756
1616
13568
1696
3882
5228
total no. of reflns
independent reflns
22 737
23 875
43 028
20 514
51 160
16104 [R(int)
0.0280]
17 538
17538 [R(int)
0.0609]
1181
-18 e h e 18,
-46 e k e 45,
-25 e l e 19
2.94-50.00
7077 [R(int)
0.0667]
477
-16 e h e 16,
-11 e k e 11,
-33 e l e 33
2.96-50.00
)
7791 [R(int)
0.0432]
433
-11 e h e 12,
-18 e k e 18,
-31 e l e 28
3.26-55.00
)
6714 [R(int)
0.0925]
462
-20 e h e 23,
-40 e k e 43,
-51 e l e 51
3.70-50.00
)
6151 [R(int)
0.0433]
461
-11 e h e 11,
-17 e k e 17,
-19 e l e 28
3.22-50.00
)
)
)
no. of params varied
index ranges
1106
-22 e h e 19,
-22 e k e 21,
-30 e l e 30
4.34-50.00
2θ range for data
collection
(deg)
largest difference
2.196 and -0.614
3.699 and -0.409
1.786 and -1.092
1.448 and -0.379
0.822 and -0.308
0.891 and -0.412
peak and hole
(e‚Å-3
)
final R indices
[I > 2σ(I)]b
GOFc on F2
R1 ) 0.0664,
wR2 ) 0.1698
0.954
R1 ) 0.0708,
wR2 ) 0.1853
1.054
R1 ) 0.0843,
wR2 ) 0.2108
1.087
R1 ) 0.0520,
wR2 ) 0.1233
1.148
R1 ) 0.0412,
wR2 ) 0.1158
1.061
R1 ) 0.0660,
wR2 ) 0.1513
0.966
a For all crystal determinations, scan type and wavelength of radiation used are ω and 0.71073 Å, respectively. b R1 ) (||Fo| - |Fc||)/(|Fo|); wR2 )
2
2
4
2
2
[w(Fo - Fc )/w(Fo )]1/2 c GOF ) [(w(Fo - Fc )2/(n - p)]1/2
. .
other reactions of AgX and PAnP, the reaction of AgPF6 and PAnP
led to the formation of a yellow product. Yield: 70%. Compound
3a {[Ag(µ-PAnP)(CH3CN)][PF6]}n was crystallized from a CH3-
CN/Et2O solution. Anal. Calcd for C80H62Ag2F12N2P6: C, 57.16%;
H, 3.72%. Found: C, 56.44%; H, 3.39%. 31P{1H}-NMR: see text.
1H NMR (CD3CN, 300 MHz): δ 7.91-7.88 (m, 4H), 7.52-7.25
(m, 20H), 6.85-6.82 (m, 4H). ESI-MS (m/z, assignment): 654.3,
[Ag(PAnP)]nn+; 926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+.
Compound 3b [Ag2(µ-PAnP)2(CH3CN)4](PF6)2‚1.5Et2O‚0.35CH2-
Cl2 was crystallized from a CH3CN/CH2Cl2/Et2O solution of the
product obtained from the reaction of AgPF6 and PAnP. Anal. Calcd
for C90.45H83.90Ag2Cl10.70F12N4O1.5P6: C, 48.07%; H, 3.74%.
Mo KR radiation (λ ) 0.710 73 Å). The software used were
SMART14a for collecting frames of data, indexing reflection, and
determination of lattice parameters; SAINT14a for integration of
intensity of reflections and scaling; SADABS14b for empirical
absorption correction; and SHELXTL14c for space group determi-
nation, structure solution, and least-squares refinements on [F]2.
The crystals were mounted at the end of glass fibers and used for
the diffraction experiments. Anisotropic thermal parameters were
refined for the rest of the non-hydrogen atoms. The hydrogen atoms
were placed in their ideal positions. A brief summary of crystal
data and experimental details are given in Table 1.
1
Found: C, 48.41%; H, 3.62%. 31P{1H}-NMR: see text. H NMR
Results and Discussion
(CD2Cl2, 300 MHz): δ 7.96-7.93 (m, 4H), 7.62-7.38 (m, 20H),
6.68-6.65 (m, 4H). ESI-MS (m/z, assignment): 654.3, [Ag-
(PAnP)]nn+; 926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+; 1054.3,
-
-
Synthesis Reactions of AgX (X ) OTf-, PF6 , BF4 , and
-
ClO4 ) and PAnP, carried out in CH3CN/CH2Cl2 at room
[Ag2(PAnP)2(PF6)] + or [Ag4(PAnP)4(PF6)2]2+
.
temperature, resulted in clear yellow solutions from which
bright yellow solids were isolated. In the following discus-
sion, the reactions between PAnP and AgOTf, AgClO4,
AgPF6, and AgBF4 are referred to as reactions 1, 2, 3, and
4, respectively. Depending on the solvents used for crystal-
lization, different complexes were isolated. Complexes 1a,
2a, and 3a were crystallized from a CH3CN/ether solution
of the products of reactions 1, 2, and 3, respectively.
Synthesis of [Ag3(µ-PAnP)3⊃BF4](BF4)2‚4Et2O‚CH3OH (4).
The preparation of 4 was similar to that of 1 but with AgBF4 (39
mg, 0.20 mmol) and PAnP (110 mg, 0.20 mmol). Yield: 87%.
Anal. Calcd for C131H127Ag3B3F12O5P6: C, 61.67%; H, 5.02%.
Found: C, 59.73%; H, 4.13%. 31P{1H}-NMR (CD3CN, 121
MHz): δ 2.48 (br). 31P{1H}-NMR: see text. 19F NMR spectrum
1
(CD2Cl2, 282 Hz): δ -84.3(s). H NMR spectrum (CD2Cl2, 300
MHz): δ 7.92-7.89 (m, 4H), 7.52-7.22 (m, 20H), 6.86-6.83 (m,
4H). ESI-MS (m/z, assignment): 654.3, [Ag(PAnP)]nn+; 1025.1,
[Ag3(PAnP)3(BF4)]2+; 926.9, [Ag2(PAnP)3]2+; 1201.0, [Ag(PAnP)2]+;
1561, [Ag2(PAnP)2(BF4)]+ or [Ag4(PAnP)4(BF4)]+.
(14) (a) SMART & SAINT Software Reference Manuals, version 4.0;
Siemens Energy & Automation, Inc., Analytical Instrumentation:
Madison, WI, 1996. (b) Sheldrick, G. M. SADABS: A Software for
Empirical Absorption Correction; University of Gottingen: Gottingen,
Germany, 1996. (c) SHELXTL Reference Manual, version 5.03;
Siemens Energy & Automation, Inc., Analytical Instrumentation:
Madison, WI, 1996.
X-ray Crystallography. The diffraction experiments were
carried out on a Bruker AXS SMART CCD three-circle diffrac-
tometer with a sealed tube at 23 °C using graphite-monochromated
Inorganic Chemistry, Vol. 45, No. 11, 2006 4425

Lin and Yip
Figure 1. ORTEP plots of 1: green, F; red, O; yellow, S. Hydrogen atoms,
Ph rings, and solvent molecules are omitted. Thermal ellipsoids are drawn
with 50% probability.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for Complexes
1, 2a, and 3a
Figure 2. Diagram showing edge-to-face C-H‚‚‚π interactions between
three adjacent anthracenyl rings An1, An2, and An3 in 1. X(1A) and X(1D)
are the centroids of the central rings of An2 and An1, respectively, and
X(1B) and X(1C) are centroids of lateral rings of An3 and An2, respectively.
Thermal ellipsoids are drawn with 50% probability.
complex 1
complex 2a
complex 3a
Ag(1)-N(1)
2.389(7)
2.393(7)
2.370(7)
2.4741(13)
2.4875(12)
Ag(1)-P(1)
2.4941(19)
2.4976(19)
2.519(5)
2.4954(15)
2.5035(14)
2.679(14)
Ag(1)-P(2)
of the anions and the silver ions are long, being 2.519(5)
(Ag-O), 2.679(2) (Ag-O), and 2.925(9) Å (Ag-F) for 1,
2a, and 3a, respectively. The three complexes show similar
P-Ag-P angles of ∼150°. The torsional angles between
the Ag-P bonds and the tetrahedral geometry of the metal
ions and the phosphorus centers account for the “helicity”
of the polymers.
Close inspection reveals intriguing edge-to-face C-H‚‚‚
π interactions between adjacent anthracenyl rings in a helix.
As mentioned, part of the anthracenyl rings is embedded in
the interior of the helical chain. As shown in Figure 2, two
lateral ring protons in each anthracenyl ring are pointed to
the central ring of its adjacent anthracenyl unit.
These interactions propagate along the central axis of the
polymer with each anthracenyl ring acting as both hydrogen-
bond donor and acceptor. The distances between the centriod
(X1C) of the lateral ring and the centroid (X1D) of the central
ring is 4.925 Å. Similar edge-to-face C-H‚‚‚π interactions
are also found in 2a and 3a. The two interacting rings are
nearly perpendicular. These structural parameters fall within
the range (4.5 Å < centroid-to-centroid distance < 7 Å) of
aromatic C-H‚‚‚π interactions.13,16,17
Structure of [Ag4(µ-PAnP)4⊃(ClO4)2](ClO4)2‚4CH2Cl2
(2b). A macrocyclic [Ag4(µ-PAnP)4⊃(ClO4)2](ClO4)2‚4CH2-
Cl2 (2b) was crystallized from CH2Cl2/diethyl ether mixture.
The X-ray crystal structure of the cation [Ag4(µ-PAnP)4⊃-
(ClO4)2]2+ reveals an intriguing tetrameric ring composed
of four PAnP ligands and four AgI ions (Figure 3 and Table
3).
Ag(1)-O(1)
Ag(1)-F(6)
2.925(9)
P(1)-Ag(1)-P(2)
C(1)-P(1)-Ag(1)
N(1)-Ag(1)-P(1)
N(1)-Ag(1)-P(2)
150.73(5)
116.40(16)
104.71(16)
96.86(15)
148.71(5)
118.58(18)
103.22(18)
96.68(16)
150.79(5)
116.40(16)
104.71(16)
96.86(15)
Interestingly, the product of reaction 3 gave another complex
3b when the crystallization was carried out in CH2Cl/CH3-
CN/ether. The products of the reactions 2 and 4 afforded
crystals of complexes 2b and 4 in CH2Cl2/ether and CH2-
Cl2/MeOH/ether, respectively.
Structures of Helical Polymers 1, 2a, and 3a. The X-ray
crystal structures of {[Ag(µ-PAnP)(CH3CN)(OTf)]‚0.5CH3-
CN}n (1), {[Ag(µ-PAnP)(CH3CN)(ClO4)]}n (2a), and {[Ag-
(µ-PAnP)(CH3CN)(PF6)]}n (3a) are shown in Figure 1,
Figure S1 (Supporting Information), and Figure S2 (Sup-
porting Information), respectively, and the selected bond
lengths and angles are listed in Table 2.
The three complexes are polymeric, showing similar
helical chains. Each helical chain is composed of PAnP
which is coordinated to two Ag ions. The distances between
adjacent Ag ions are ∼8.2 Å. The two P-Ag vectors in the
[Ag2(µ-PAnP)] unit show small torsional angles of ∼10°.
Part of the anthracenyl ring is “buried” in the interior of the
helix, whereas the other end is exposed to the exterior. The
phenyl rings of PAnP, the coordinated anions, and the
acetonitrile protrude from the central axis of the helix. The
pitches of the helices are 9.76, 9.70, and 9.76 Å for 1, 2a,
and 3a, respectively. While it has been shown that anions
could affect the pitches in some AgI-helices of N-donor
ligands,4,15 they have virtually no effect on the Ag-PAnP
polymers. The AgI ions in the three complexes are coordi-
nated to two P atoms coming from two neighboring PAnP,
the nitrogen atom of CH3CN and the anion, showing a
distorted trigonal pyramidal geometry. In each complex, the
AgI atom is lifted slightly above the triangular plane defined
by the P and N atoms by ∼0.4 Å. The small distortion is
caused by weak bonding interactions between the metal and
the apical anions. The distances between the donor atoms
The four anthracenyl rings are nearly parallel to the central
axis of the metallacycle, whereas the four metal ions are on
the same plane. The complex exhibits a saddlelike structure
with two opposite anthracenyl rings being positioned higher
than the other pair. The torsional angle between two adjacent
Ag-P bonds is 3.96°. In comparison to that of the helical
(16) Burley, S. K.; Petsko, G. A. Science 1985, 229, 23.
(17) (a) Bacon, G. E.; Curry, N. A.; Wilson, S. A. Proc. R. Soc. London,
Ser. A 1964, 279, 98. (b) Kelbe, G.; Diederich, F. Philos. Trans. R.
Soc. London, Ser. A 1993, 345, 37. (c) Oikawa, S.; Tsuda, M.; Kato,
H.; Urabe, T. Acta Crystallogr., Sect. B 1985, 41, 437. (d) Bong, D.
T.; Ghadiri, M. R. Angew. Chem., Int. Ed. 2001, 40, 2163. (e) Dance,
I.; Scudder, M. Chem.sEur. J. 1996, 5, 482.
(15) Hirsch, K. A.; Wilson, S. R.; Moore, J. S. Chem.sEur. J. 1997, 3,
765.
4426 Inorganic Chemistry, Vol. 45, No. 11, 2006

EmissiWe SilWer Metallacycles and Helices
Figure 3. ORTEP plots of 2b showing (a) the cation and two included ClO4- ions (Ph rings, solvent molecules, H atoms, and two anions are omitted) and
(b) top view of the cation of 2b (H atoms and two anions are omitted). Thermal ellipsoids are drawn with 50% probability.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Complexes
2b, 3b, and 4
2b
Ag(1)-P(1)
Ag(2)-P(2)
Ag(1)-O(1)
Ag(2)-O(2)
2.4224(18)
2.4416(19)
3.014(18)
2.783(9)
P(1A)-Ag(1)-P(1)
P(2B)-Ag(2)-P(2)
168.20(9)
149.97(9)
3b
Ag(1)-N(1)
Ag(1)-N(2)
Ag(1)-P(1)
Ag(1)-P(2)
Ag(2)-N(3)
Ag(2)-N(4)
Ag(2)-P(3)
Ag(2)-P(4)
2.404(5)
2.432(5)
2.478(11)
2.4869(10)
2.413(6)
2.388(5)
2.4757(11)
2.4828(11)
P(1)-Ag(1)-P(2)
N(1)-Ag(1)-P(1)
N(2)-Ag(1)-P(1)
N(1)-Ag(1)-N(2)
P(3)-Ag(2)-P(4)
N(3)-Ag(2)-P(3)
N(4)-Ag(2)-P(3)
N(3)-Ag(2)-N(4)
144.29(3)
96.28(11)
104.88(13)
89.63(19)
142.79(4)
100.02(14)
109.39(15)
87.6(2)
Figure 4. ORTEP plot of 3b. Thermal ellipsoids are drawn with
50% probability. Solvent molecules and hydrogen atoms are omitted for
clarity.
4
Ag(1)-P(1)
Ag(1)-P(2)
Ag(3)-F(9A)
2.401(2)
2.410(2)
2.796(9)
P(1)-Ag(1)-P(2)
P(2)-Ag(2)-P(3)
P(6)-Ag(3)-P(5)
C(1)-P(1)-Ag(1)
167.04(10)
165.10(10)
156.83(9)
109.2(3)
PAnP)(CH3CN)2]2(PF6)2‚1.5Et2O‚0.35CH2Cl2 (3b) were iso-
lated from a Et2O/CH3CN/CH2Cl2 mixture. X-ray analysis
showed two independent molecules in the crystals whose
structures are very similar, and accordingly, only one of them
is discussed here. The cation of 3b is a metallacycle
composed of two PAnP linked by two Ag ions (Figure 4
and Table 3).
polymers, the Ag-Ag distance in 2b is significantly shorter
(6.903 Å). Intriguingly, two of the four ClO4 ions are
-
encapsulated in the ring. The complex shows a D2 symmetry
with two C2-axes, two pairs of opposite Ag ions Ag(1)-
Ag(1A) and Ag(2)-Ag(2A), while the third C2-axis passes
through center of the ring. The encapsulated anions are close
to the center of the ring with the two Cl atoms being
The complex displays C2h symmetry with the C2-axis
passing through the two Ag ions. The two anthracenyl rings
are parallel and partially overlapped. The shortest distance
between the rings is 4.33 Å. The two Ag ions are widely
separated by 8.041 Å, and both [Ag2(µ-PAnP)] units are in
syn conformation. Apart from the P atoms of PAnP, each
Ag ion is bonded to two CH3CN molecules, showing a
-
separated by 4.673 Å. While the ClO4 ion has a Td
symmetry, the two ions form a dimeric unit of D2 symmetry.
That the metallacyle and the included anions share the same
symmetry suggests that the formation of the ring is templated
by the anions. As such, the complex represents a rare
example where the formation of a metallacycle of low
symmetry (D2) is templated by a combination of two anions
of high symmetry (Td). The two pairs of perchlorate oxygen
atoms, O(2) and O(2B) and O(2A) and O(2AB), are weakly
coordinated (Ag-O ) 2.786 Å) to Ag(2) and Ag(2A),
respectively (Figure 3b). As a result of the interactions, the
two silver ions exhibit a distorted tetrahedral geometry with
the P-Ag-P units (P(2)-Ag(2)-P(2B) ) 149.97(9)°). On
the other hand, the coordination of the other two silver ions
Ag(1) and Ag(1A) is almost linear.
-
distorted tetrahedral geometry. Notably, the PF6 ions do
not coordinate to the metal ions. The Ag-P (2.4757(1)-
2.4869(1) Å) and Ag-N bond (2.388(5)-2.432(5) Å)
distances are similar to the corresponding parameters found
in the polymeric complexes.
Structure of [Ag3(µ-PAnP)3⊃BF4] (BF4)2‚4Et2O‚CH3OH
(4). Crystals of [Ag3(µ-PAnP)3⊃BF4](BF4)2‚4Et2O‚CH3OH
(4) were obtained from a CH2Cl2/diethyl ether mixture. X-ray
analysis shows that the cation of [Ag3(µ-PAnP)3⊃BF4](BF4)2‚
4Et2O‚CH3OH is a trinculear ring composed of three bridging
PAnP ligands and three Ag ions (Figure 5 and Table 3).
Structure of [Ag2(µ-PAnP)2(CH3CN)4](PF6)2‚1.5Et2O‚
0.35CH2Cl2 (3b). Crystals of the binuclear complex [Ag(µ-
Inorganic Chemistry, Vol. 45, No. 11, 2006 4427

Lin and Yip
Figure 5. ORTEP plots of the cation of 4 showing (a) the top view and (b) side view of the molecule. Thermal ellipsoids are drawn with 50% probability.
Solvent molecules, H atoms, phenyl rings, and anions (for the side view) are omitted for clarity.
Table 4. 31P{1H}-NMR Data of Complex 1, 2a, 2b, 3a, 3b, and 4
CD3CN
P, J
CD2Cl2
P, J
107Ag-31
109Ag-31
107Ag-31
109Ag-31
P/Hz)
δ (J
P/Hz)
δ (J
complexes
300 Ka
238 K
300 K
193 K
complex 1
3.26
3.20
3.23
3.20
4.52 (458, 515)
1.43 (438, 500)
4.53 (454, 523)
1.24 (431, 504)
4.55 (454, 526)
1.19 (435, 504)
4.50 (453, 522)
complex 2a
complex 3a
complex 2b
3.72 (515, 599)
7.01 (443, 523), 3.39 (530, 610), 2.45 (477, 557),
0.89 (504, 584), 0.25 (522, 603)
1.35 (431, 496)
4.50 (453, 520)
1.23 (434, 501)
4.42 (454, 519)
1.19 (435, 500)
complex 3b
complex 4
3.23
2.48
5.13 (526, 607)
4.02 (522, 603)
four double doublet signals in δ -3.72 to 9.51
two broad signals at δ 3.0 and 0.3
a All signals are broad and show no JAg-P coupling.
The metallacycle shows a puckered conformation similar
to the chair conformation of cyclohexane (Figure 5b). Similar
structure was observed in the gold ring [Au3(µ-PAnP)3)⊃ClO4]-
(ClO4)2.11 Unlike the other Ag-PAnP complexes, the Ag-P
bonds show a large dihedral angle of 102°. The three
anthracenyl rings are nearly parallel to the central axis of
the ring, and the distance between P1 and P4 is 9.897 Å.
rocyclic 2b are shown in parts a and b of Figure 6,
respectively (see Figures S3-S6 for the spectra of 2a, 3a,
3b, and 4). The spectroscopic data are summarized in Table
4.
107/109Ag-31
P
All spectra show a broad signal at ∼δ 3 with no J
1
coupling. Unlike the broad 31P NMR signals, the H NMR
spectra are well resolved. This indicates that the dynamics
involve dissociation and formation of the Ag-P bond, the
rate of which should be comparable to the NMR time scale.8e
The temperature dependence of all of the spectra is similar:
lowering the temperature to 278 K leads to the appearance
of two broad peaks which are resolved at 238 K into two
double doublets at δ 4.42-4.55 (low field) and δ 1.19-
1.43 (high field). Both sets of signals display JAg-P coupling.
Notably, the signals of all the spectra show similar chemical
shifts and coupling constants (Table 4). For 1, 2a,b, and 3a,b,
the low-field signals (δ 4.50-4.55) are weaker than the high-
field signals (δ 1.19-1.43), but the low-field signal (δ 4.42)
in the spectrum of 4 is more intense than the high-field one
(δ 1.19).
-
One of the BF4 ions is included in the middle of the ring
-
and is disordered over two positions. Another BF4 ion is
weakly bonded to one of the Ag ions, showing a long Ag-F
distance of 2.79 Å.8c Because of the bonding interactions,
the silver ion displays a distorted trigonal planar geometry,
showing a P-Ag-P angle (P(5)-Ag(3)-P(6) ) 156.83-
(9)°) significantly smaller than the other two Ag ions in the
complex (167.04(10)° and 165.10(10)°). Analogous to the
diatopic axial and equatorial H atoms of cyclohexane, the
silver ring has six axial phenyl rings lying up and down along
the central axis of the ring and six equatorial phenyl rings
alternating about a plane at right angles to the central axis.
VT 31P{1H}-NMR in CD3CN. The existence of an
equilibrium of different Ag-PAnP complexes in solution
was first suggested by the fact that different products were
isolated by changing the crystallization solvents and was
further verified by a VT 31P{1H}-NMR study. Despite their
different structures, room-temperature spectra of the poly-
meric and macrocyclic complexes measured in CD3CN are
surprisingly similar. The spectra of polymeric 1 and mac-
Variable-Temperature 31P{1H} NMR in CD2Cl2. Be-
cause of the insolubility of the polymeric 1, 2a, and 3a in
CD2Cl2, only the VT 31P NMR spectra of 2b, 3b, and 4 in
that solvent were studied. The room-temperature 31P NMR
spectra of the three complexes (Figure 7 for 2b and Figures
S7 and S8 for 3b and 4, respectively) are drastically different
from the corresponding ones recorded in CD3CN.
4428 Inorganic Chemistry, Vol. 45, No. 11, 2006

EmissiWe SilWer Metallacycles and Helices
Figure 6. VT 31P{1H}-NMR spectra of (a) 1 and (b) 2b measured in CD3CN.
between δ -3.72 and 9.51 at 193 K (Figure S7). The sharp
double doublet of 4 becomes two broad peaks at δ 3.0 and
0.3 as the temperature is lowered from 300 to 233 K (Figure
S8). Four broad signals are observed when the sample is
cooled to 193 K.
Proposed Dynamics. The VT NMR study shows that the
solution dynamics of the complexes are solvent-dependent
with the exchange in CD3CN being “simpler” than the ones
in CD2Cl2. Despite their different structures, the ESI-MS of
1, 2a,b, 3a,b, and 4 (Figures S9, S10, S12, and S14) are
n+
similar, showing peaks ascribable to [Ag(PAnP)]n (m/z
654.3), [Ag2(PAnP)3]2+ (m/z 926.9), [Ag(PAnP)2]+ (m/z
1201.0), and [Ag(PAnP)3]+(m/z 1745.4). The molecular ions
could arise from fragmentation of the helical polymer and/
or oligomers (cyclic or linear). Although no peak assignable
to the metallacycles 2b, 3b, and 4 are found, the existence
of the complexes could not be ruled out as the rings could
have low ionizability or poor stability under the conditions
of ESI-MS measurements.
Figure 7. VT 31P{1H}-NMR spectra of 2b recorded in CD2Cl2.
Unlike the spectra measured in CD3CN, the room-
temperature spectra of 2b, 3b, and 4 in CD2Cl2 all exhibit a
sharp double doublet with JAg-P couplings. While the
chemical shifts of the signals are different, being δ 3.72,
5.13, and 4.02 for 2b, 3b, and 4, respectively, their JAg-P
Interestingly, all the 31P NMR spectra recorded in CD3-
CN show similar signals and temperature-dependent behav-
ior; regardless of their different structures (discrete metal-
lacycles or polymers), all the spectra recorded in CD3CN
display a broad peak at room temperature which is resolved
into two double doublets at low temperature. As the dynamics
involve dissociation of the Ag-P bond, it is unlikely that
the two signals are due to different conformations of a
complex. Rather, the results are more consistent with an
exchange involving two different species. Furthermore, as
all of the complexes show similar signals at low temperature,
it is likely that the complexes convert to the same two species
when they are dissolved in acetonitrile. In other words, the
two species must be attainable from all of the silver
complexes, and they should be more stable than other
possible structures in acetonitrile. It is therefore possible that
one of them is the helical polymer [Ag(µ-PAnP)(CH3CN)X]n
(X ) OTf, ClO4, BF4, or PF6) as the helices were universally
obtained from acetonitrile solutions of the products of all
the reactions. The other complex could be the dimeric
[Ag2(µ-PAnP)2(CH3CN)2]2+, the cation of 3b. The reason is
that of all the silver metallacycles isolated, the dimer is the
only one that does not have an encapsulated anion. It suggests
that the formation of the dimer is independent of the anion.
109Ag-P
constants are rather similar (J
) 599-603 Hz and
107Ag-P
J
) 515-522 Hz).
The temperature-dependent behaviors of the spectra of the
CD2Cl2 are more complicated than the ones in CD3CN. In
addition to the intense double doublet (Figure 7, signal A)
107
109
at δ 3.72 (J Ag-P ) 515 Hz, J Ag-P ) 599 Hz), the room-
temperature spectrum of 2b shows some weak and broad
signals which resolve at 273 K into two double doublets
107Ag-P
(Figure 7, signals B and C) at δ 7.28 (J
) 496 Hz,
109Ag-P
107Ag-P
109Ag-P
J
) 572 Hz) and 5.65 (J
) 465 Hz, J
)
595 Hz), respectively. However, the appearance of the signals
B and C does not affect the intensity of signal A, suggesting
that the signals could come from small amounts of unknown
Ag-PAnP complexes crystallized along with 2b. At 193 K,
the broad signal derived from signal A is resolved into three
107
109
double doublets at δ 3.39 (J Ag-P ) 530 Hz, J Ag-P ) 610
107
109
Hz), 0.89 (J
) 504 Hz, J
) 584 Hz), and 0.25
Ag-P
Ag-P
107
109
(J Ag-P ) 522 Hz, J Ag-P ) 603 Hz). Similarly, the double
doublet in the room-temperature spectrum of 3b is broadened
as temperature decreases, and several doublets are found
Inorganic Chemistry, Vol. 45, No. 11, 2006 4429

Lin and Yip
Scheme 2
Furthermore, the dimer and the helix could be stabilized by
the coordination of CH3CN.
A reversible ring-opening polymerization of the binuclear
complex is proposed to be the exchange mechanism. Ring-
opening polymerization was invoked to explain generation
of polymeric structures from gold(I)-phosphine,7b,18 silver-
(I)-phosphine, and silver metallacycles.8 In the first step of
the proposed mechanism (Scheme 2), a Ag-P bond in
[Ag2(µ-PAnP)2(CH3CN)2]2+ dissociates to form an interme-
diate I, which has a Ag ion and a free phosphorus atom at
its head and tail positions.
The bond cleavage could be facilitated by coordination
of the anion or solvent. Head-to-tail polymerization of the
intermediate I leads to the helix. The free energy of the
intermediate I could be significantly higher in energy than
that of the binuclear complex and the helix as only the signals
of the two species are observed at 238 K.
Exchange processes in CD2Cl2 solutions of 2b, 3b, and 4
are complicated. The solutions of the three complexes show
different temperature-dependent behaviors, and more than
two species are involved in the exchange. The ESI-MS of
the complexes recorded in CH2Cl2 are similar to the ones in
CH3CN. All three complexes show a sharp double doublet
signal at room temperature, suggesting that either the Ag-P
dissociation and formation are faster than the NMR time scale
or the two processes occur concomitantly. It is reasonable
because dichloromethane, being a very weak ligand, is unable
to stabilize intermediates arising from Ag-P cleavage.
Luminescence. All of the silver complexes display intense
solid-state emission. The fluorescence spectra are shown in
Figure 8.
Figure 8. Room-temperature solid-state emission spectra of 1-4.
Concluding Remarks. In this work we have demonstrated
the rich structural diversity of Ag-PAnP compounds arising
from the equilibrium of different complexes in solutions. The
structures obtained are dependent on the solvent used for
crystallization and the anion. Helical polymers are obtained
from CH3CN, whereas discrete metallacycles of different
nuclearity are crystallized from CH2Cl2 or mixtures of CH2-
Cl2 and CH3CN. VT NMR spectroscopy shows that the
solution dynamics and distribution of the silver complexes
are influenced by the solvent. The mechanism of the
exchange in CD3CN is believed to be a ring-opening
polymerization of the dinuclear metallacycle. On the other
hand, the dynamic processes in CD2Cl2 are far more
complicated, involving more than two exchanging species.
Acknowledgment. The authors thank National University
of Singapore for financial support and Ms. Tan Geok Kheng
and Professor Koh Lip Lin for assistance with the X-ray
crystal structure determination.
All emissions show two vibronic peaks at 488 and 530
nm. It is believed that the luminescence arises from a ππ*
excited-state localized in the anthracenyl ring of the ligand
PAnP. It is supported by the fact that emissions of similar
energy were observed in spectra of other PAnP-containing
complexes such as [Au3(µ-PAnP)3⊃ClO4](ClO4)211 and [Au4-
(µ-PAnP)2(4,4′-bipyridine)2](OTf)4.12
Supporting Information Available: Crytallographic data in
CIF format, synthetic procedures and characterizations of the
complexes, crystal structures of 2a and 3a, and ESI-MS and VT
31P{1H}-NMR spectra of 2a, 3a, 3b, and 4 in CD3CN and 3b and
4 in CD2Cl2. This material is available free of charge via the Internet
at http://pubs.acs.org.
(18) (a) Burchell, T. J.; Eisler, D. J.; Jennings, M. C.; Puddephatt, R. J. J.
Chem. Soc., Chem. Commun. 2003, 2228. (b) Puddephatt, R. J.
Macromol. Symp. 2003, 196, 137. (c) Qin, Z. Q.; Jennings, M. C.;
Puddephatt, R. J. Chem.sEur. J. 2002, 8, 735.
IC060140V
4430 Inorganic Chemistry, Vol. 45, No. 11, 2006