Solvent dependent tunable energy transfer of d10 metal dicyanide nanoclusters with Eu3+ and Tb3+ rare earth ions

Article abstract of DOI:10.1016/j.cplett.2007.07.071

The luminescence energy and intensity of d¹⁰ copper(I), silver(I) and gold(I) dicyanide nanoclusters exhibit high tunability as energy transfer donors in different organic solvents. For Tb³⁺ acceptor ions, the energy transfer efficiency, which is proportional to the spectral overlap between the donor emission and the acceptor absorption, depends on the solvent tunability of the donor emission energy. For Eu³⁺ acceptor ions, energy transfer can be 'tuned off' or 'tuned on' as the solvent dependent donor emission energy becomes in resonance with a charge transfer state or with the ⁵L₆ Eu³⁺ ion state, respectively.

Full text of DOI:10.1016/j.cplett.2007.07.071

Chemical Physics Letters 445 (2007) 340–344
www.elsevier.com/locate/cplett
10
Solvent dependent tunable energy transfer of d metal dicyanide
3+
3+
nanoclusters with Eu and Tb rare earth ions
Zhonghua Guo, Renante L. Yson, Howard H. Patterson *
Department of Chemistry, University of Maine, Orono, ME 04469-5706, United States
Received 31 May 2007; in final form 24 July 2007
Available online 1 August 2007
Abstract
The luminescence energy and intensity of d copper(I), silver(I) and gold(I) dicyanide nanoclusters exhibit high tunability as energy
1
0
3
+
transfer donors in different organic solvents. For Tb acceptor ions, the energy transfer efficiency, which is proportional to the spectral
overlap between the donor emission and the acceptor absorption, depends on the solvent tunability of the donor emission energy. For
3
+
Eu acceptor ions, energy transfer can be ‘tuned off’ or ‘tuned on’ as the solvent dependent donor emission energy becomes in resonance
5
3+
with a charge transfer state or with the L
6
Eu ion state, respectively.
ꢀ
2007 Elsevier B.V. All rights reserved.
1
. Introduction
Metal–metal bonded excimers and exciplexes are one
exhibit a red shift with increasing concentration or decreas-
ing temperature [9–11]. This tunability of the emission
energy of the pure or mixed dicyanoaurate(I) and dicyan-
oargentate(I) ion systems make them good candidates as
donors in energy transfer studies [12–14]. In a recent Letter,
we reported that the energy transfer efficiency can be tuned
class of luminescent inorganic exciplexes [1–3], and several
metal–metal bonded inorganic exciplexes involving closed
shell d ions have been reported [4]. Recently, our group
has reported aurophilic and argentophilic interactions of
1
0
ꢀ
by varying the concentration of the ½AuðCNÞ ꢁ donor
2
n
ꢀ
ꢀ
3+
3+
½
AuðCNÞ ꢁ and ½AgðCNÞ ꢁ oligomers in both aqueous
using Tb or Eu as acceptor ions in aqueous solution
[15]. The process of energy transfer can usually be inter-
preted by the F o¨ rster mechanism [16] in which the energy
transfer efficiency is proportional to the spectral overlap
between the donor emission and the acceptor absorption.
In this study, we report for the first time tunable energy
2
n
2 n
and methanolic solutions. The luminescence observed
ꢀ
in these compounds are due to *½AuðCNÞ ꢁ and
2
n
ꢀ
*
½AgðCNÞ
2
ꢁ
n
(n P 2) metal–metal bonded excimers and
exciplexes of different cluster size and geometry [5,6].
We first reported that when dicyanoargenate(I) ions are
doped in KCl single crystals several ultraviolet and visible
emission bands are observed and assigned to dimer and tri-
mer nanoclusters [7]. Further, solutions of K[Au(CN) ] and
K[Ag(CN) ] in water or methanol exhibit similar lumines-
1
0
transfer between d metal dicyanide nanocluster donor
3
+
3+
ions and Eu and Tb rare earth acceptor ions in non-
aqueous solvents such as methanol, acetonitrile, and
dioxane.
2
2
cence bands that are assigned to different dimer and trimer
nanoclusters. Thus, as an extension of this work, we report
2. Experiment
1
0
energy transfer from d nanoclusters in different solvents
3
+
3+
to Tb and Eu acceptor ions [6,8].
2.1. Sample preparation
Previous studies indicate that the photoluminescence
emission energies of dicyanoaurate(I) ions are tunable and
ꢀ
2
ꢀ2
The 4.0 · 10
and 1.0 · 10
M
Eu(NO3)3 and
Tb(NO ) stock solutions were prepared by dissolving stoi-
3
3
*
chiometric amounts of Eu(NO ) Æ xH O (x ꢂ 6) (Alfa-
Corresponding author. Fax: +1 207 581 1191.
E-mail address: howardp@maine.edu (H.H. Patterson).
3 3
2
Aesar) and Tb(NO ) Æ 6H O (Alfa-Aesar) in methanol, ace-
3 3 2
0
009-2614/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.cplett.2007.07.071

Z. Guo et al. / Chemical Physics Letters 445 (2007) 340–344
341
Table 1
Enhancement factor (R) of the intensity of Tb acceptor ion emissions at 542 nm ( D
concentration of the d Ag(I), Au(I), and Cu(I) dicyanide clusters in methanol at room temperature
3+
5
7
4
! F
5
) and the excitation peak (kex) of the exciplexes versus the
1
0
ꢀ
ꢀ
ꢀ
Donor ½AgðCNÞ ꢁ
R
k
ex
Donor ½AuðCNÞ ꢁ (M)
R
k
ex
Donor ½CuðCNÞ ꢁ
R
k
ex
(nm)
2
2
2
(
M)
(nm)
(nm)
(M)
ꢀ3
ꢀ3
ꢀ3
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ2
ꢀ3
ꢀ4
2.0 · 10
4.0 · 10
8.0 · 10
1.2 · 10
1.6 · 10
2.0 · 10
2.4 · 10
2.8 · 10
3.2 · 10
0.9
5.6
276
276
282
284
284
284
284
284
284
2.0 · 10
1.0
1.1
1.1
1.2
5.0
7.4
244
244
247
251
260
264
277
286
5.0 · 10
9.9
26.4
111.3
267
276
290
ꢀ3
ꢀ3
ꢀ3
4.0 · 10
1.0 · 10
ꢀ3
113.8
225.1
248.8
254.7
260.4
263.8
264.7
8.0 · 10
2.0 · 10
ꢀ2
1.6 · 10
ꢀ2
2.4 · 10
ꢀ2
3.2 · 10
ꢀ2
4.8 · 10
17.5
116.6
ꢀ2
6.2 · 10
tonitrile and dioxane in separate 10.00 mL volumetric flasks.
K[Au(CN) ], K[Ag(CN) ] and K[Cu(CN) ] solutions were
bonded exciplexes in both water and methanolic solutions
have been reported by our group [5,6]. Similar to aqueous
2
2
2
prepared by directly dissolving a stoichiometric amount of
solution, solutions of K[Au(CN) ] in dioxane at room tem-
2
KAu(CN)2 (P99.9% pure, Alfa-Aesar), K[Ag(CN)2]
perature exhibit strong and tunable emissions with different
excitations as shown in Fig. 1. Three luminescence bands
are observed at 375, 414, and 578 nm when excited at dif-
ferent wavelengths (Fig. 1), and each emission is a mirror
image of its excitation spectrum with a large Stokes shift.
We believe the appearance of the different emission peaks
with different excitations is due to the presence of different
(
P99.9% pure, Alfa-Aesar), and K[Cu(CN) ] (synthesized,
2
see below) solids in methanol, acetonitrile and dioxane.
Then, aliquot(s) of Eu(NO ) or Tb(NO ) solutions were
3
3
3 3
mixed thoroughly with KAu(CN)2, K[Ag(CN)2] or
K[Cu(CN) ] solutions in the same solvent to give the final
2
concentrations listed in Table 1. The mixture was immedi-
ately transferred to standard 1-cm quartz cuvettes for lumi-
nescence measurements at ambient temperatures.
ꢀ
½AuðCNÞ ꢁ oligomer nanoclusters based on previous
2
n
reports that the luminescence of the Au(I) compound is
related to the formation of Au–Au bonded excimers and
exciplexes, similar to those reported earlier for Ag(I) com-
pounds [5,7,18]. Extended H u¨ ckel calculations on different
dicyanoaurate(I) oligomers showed that the metal–metal
bond in the first excited state is stronger compared to the
ground state [5]. The experimental evidence of the exciplex
assignment includes the very broad and structureless fea-
ture of the luminescence band and the extremely large
Stokes shifts which indicate highly distorted excited states
[5,19]. Further evidence for the presence of different oligo-
K[Cu(CN) ] was synthesized by slight modification of a
2
literature procedure [17]. A solution of KCN (10.0 g,
P99.9% pure, Alfa-Aesar) in 50 mL distilled H O was
2
added slowly to a suspension of CuCN (7 g, P99.9% pure,
Alfa-Aesar) in 50 mL H O. The mixture was heated to
2
6
0 ꢁC while stirring until all the solids dissolved. The result-
ing solution was filtered while hot to remove any suspended
particles, and the filtrate was allowed to evaporate slowly
at room temperature. Crystals of K[Cu(CN) ] were har-
2
vested after 2 days.
mer nanoclusters is the red shift of the emission band from
ꢀ
2
.2. Instrumentation
377 to 410 nm when the concentration of ½AuðCNÞ ꢁ
2
Steady-state photoluminescence spectra at room temper-
ature were recorded with a QuantaMaster-1046 photolumi-
nescence spectrophotometer from Photon Technology
International. The instrument is equipped with two excita-
tion monochromators and a single emission monochroma-
tor with a 75 W xenon lamp. UV–visible absorption
spectra were recorded on a Beckman DU-640 UV/VIS
scanning spectrophotometer with a wavelength range from
3.50E+06
.00E+06
2.50E+06
λ
em= 410 nm
λ
λ
λ
λ
λ
λ
ex= 305 nm
ex= 325 nm
ex= 285 nm
ex= 275 nm
ex= 265 nm
ex= 335 nm
3
2
1
.00E+06
.50E+06
1
3
3
90 to 1100 nm.
1.00E+06
5
0
.00E+05
. Results and discussion
.00E+00
1
.1. Tunability of the luminescence energy of d metal
0
160
260
360
460
560
660
Emission, nm
dicyanide clusters in different solvents
Fig. 1. The emission spectra at various excitation wavelengths of
ꢀ
2
Aurophilic
and
argentophilic
interactions
of
1
.0 · 10 M K[Ag(CN)
2
] in dioxane showing the energy tunability. The
ꢀ
ꢀ
½
AuðCNÞ ꢁ and ½AgðCNÞ ꢁ oligomers with metal–metal
excitation spectrum is shown in the left portion of the figure.
2
n
2
n

342
Z. Guo et al. / Chemical Physics Letters 445 (2007) 340–344
ꢀ
3
ꢀ2
increases from 2.0 · 10
to 1.0 · 10 M in dioxane,
sition bands is directly proportional to the spectral overlap
integral of the dicyanoargentate(I) donor clusters with
Tb acceptor ions absorption within 300–400 nm when
because the oligomerization leads to significant reductions
in HOMO–LUMO band gaps as the oligomer size
increases [6].
3
+
the concentration of the K[Ag(CN) ] donor ion in metha-
2
nol increases.
1
.2. Energy transfer between d metal dicyanide clusters and
0
3
Tb ions in selected solvents
Fig. 3 shows the solvent dependence of the emission of
3
+
ꢀ
3+
½CuðCNÞ ꢁ donor ions with Tb acceptor ions. The strong
2
and broad structureless bands between 220–400 nm in the
excitation spectrum and their mirror images in the emission
3
+
When the concentration of the Tb acceptor ions is
1
0
10
kept constant, and the concentrations of d metal dicya-
spectrum are assigned to exciplexes of d metal dicyanide
ꢀ
ꢀ
3+
nide donor ions such as ½CuðCNÞ ꢁ, ½AgðCNÞ ꢁ,
nanoclusters with Tb ions. The lowest energy excitation
2
2
ꢀ
3+
7
5
½
AuðCNÞ ꢁ in methanol and acetonitrile are increased,
band of Tb ions observed at 376 nm ( F ! G ) is due
2
6
6
3+
the intensities of the four distinctive sharp f–f transition
to direct excitation of Tb ions [23,24]. Because the exci-
plex donor emission spectra at about 407 nm (Fig. 3a and
b) lies below 376 nm, small overlap occurs with the accep-
3
+
bands of Tb ions observed at ꢃ 488, 542, 585, 620 nm
5
7
[
20] (corresponding to D ! F (J = 6, 5, 4, 3) transi-
4
J
3
+
tions, respectively) dramatically increase with increasing
tor excitation spectra of the Tb ions, and no energy
transfer from the d metal dicyanide to Tb
1
0
10
3+
concentration of the d metal dicyanide donor ions, as
shown in Fig. 2. It is well established [21] that the energy
transfer rate, PD–A, between donor D and acceptor A can
ions is
observed. Therefore, the strong exciplex emission, as a mir-
ror image of its exciplex excitation, stay the same without
decrease while the f–f emissions of Tb ions stay the same
without increase as shown in Fig. 3a,b. However, when the
exciplex emission energy levels lie above 376 nm, good
3
+
be expressed by:
Z
e
D
a
A
P
D–A ¼ F ðRÞ f ð ꢀv Þf ð ꢀv Þd ꢀv
3
+
overlap with the excitation bands of Tb acceptor ions
occurs and results in good energy transfer. This is evi-
denced by a sharp decrease of exciplex emission and large
increase of the intensity of the f–f emission bands of
F(R) summarizes the essential mechanism of energy
transfer, as well as the distance between the donor D and
acceptor A. The integral is the spectral overlap of the
donor emission with the acceptor absorption profile which
describes the resonance condition [22]. The luminescence
energies of the exciplexes are found to be tunable because
3
+
Tb ions (Fig. 3c). This is the reason why we did not
observe the exciplex emission band in Fig. 3c.
The energy transfer efficiency was monitored with the
intensity enhancement factor (R), which is defined as the
ratio of the luminescence of the f–f transition bands of
1
0
an increase in the size of d metal dicyanide nanoclusters
occurs with an increase in the concentration of the donor
3
+
3
+
10
ions. Since the energies of the f–f transitions of Tb accep-
tor ions are not sensitive to the environment and can be
considered as fixed, the spectral overlap integral, that is
the energy transfer rate, mainly depends on the tunability
of the donor emission. Fig. 2 (inset) shows that the inte-
Tb ions with and without the presence of d metal dicy-
anide(I) donor ions. The R values given in Table 1 reveal
that the higher the concentration of the donor, the better
the energy transfer and, thus, the larger the R values.
Fig. 4 shows the R values of the f–f transition bands of
5
7
3
+
grated emission intensity of D ! F (J = 6, 5, 4, 3) tran-
4
J
the Tb
ions at ꢃ488, 542, 585 and 620 nm from
J
5
7
D ! F (J = 6, 5, 4, 3) transitions, respectively, increase
4
with increasing concentration of K[Ag(CN) ] in acetoni-
2
4
4
3
3
2
2
1
1
5
0
.50E+06
.00E+06
.50E+06
.00E+06
.50E+06
.00E+06
.50E+06
.00E+06
.00E+05
.00E+00
λem= 543 nm
λex= 285 nm
R = 0.9311
λem = 407 nm
3
6 mM [Ag]
0 mM [Ag]
2 mM [Ag]
mM [Ag]
λex = 301 nm
a
2
1
8
4
0
λem = 406 nm
mM [Ag]
mM [Ag]
λex = 305 nm
b
λem = 543 nm
c
×4
λex = 285 nm
λem = 543 nm
2
00
300
400
500
600
700
800
×
100
d
λex = 285 nm
Wavelength, nm
2
00
300
400
500
600
700
ꢀ3
Fig. 2. Excitation (left) and emission (right) spectra of 4.0 · 10
Tb(NO
methanol. Inset: Integrated emission intensity of
) transitions versus the spectral overlap integral of the dicyanoargen-
tate(I) donor clusters with Tb acceptor ions absorption in the 300–
00 nm range.
M
Wavelength, nm
3
)
3
upon addition of increasing amounts of K[Ag(CN)
2
] in
5
7
ꢀ
D
4
! F
J
(J = 6, 5, 4,
Fig. 3. Excitation and emission spectra of (a) 0.5 mM ½CuðCNÞ ꢁ þ 1 mM
2
3
+
ꢀ
3+
3
Tb in dioxane; (b) 2 mM ½CuðCNÞ ꢁ þ 4 mM Tb in acetonitrile; (c)
2
3+
ꢀ
3+
3+
2 mM ½CuðCNÞ ꢁ þ 4 mM Tb in methanol; and (d) 4 mM Tb in
2
4
methanol.

Z. Guo et al. / Chemical Physics Letters 445 (2007) 340–344
343
ꢀ
3+
low-lying CT transition from ½AuðCNÞ ] to Eu ions.
8
7
6
5
4
3
2
1
00.0
00.0
00.0
00.0
00.0
00.0
00.0
00.0
R
2
λ
λ
λ
λ
em= 488 nm
em= 542 nm
em= 585 nm
em= 620 nm
2
ꢀ1
ꢀ1
Extinction coefficients in the order of 10 L mol cm
are quite normal for absorptions into a CT state of lantha-
nide ions because of the small overlap between the donor
and the acceptor 4f orbitals [33,34]. We observe broad
near-UV absorption bands around 402 nm with extinction
ꢀ1
ꢀ1
ꢀ3
coefficients of 163 and 160.5 L mol cm for 2 · 10
M
ꢀ
3
K[Ag(CN) ] and 1 · 10 M Eu(NO ) in acetonitrile and
2
3 3
methanol, respectively. Since most of the emission intensity
0
.0
1
0
0
10
20
30
40
of the exciplexes of d metal dicyanide nanocluster donors
are located between 350–400 nm which is higher than the
−
[
2
Ag(CN) ], mM
3
+
CT state of Eu ion, and the CT state is higher than the
ꢀ
3
3+
Fig. 4. Enhancement of the emission bands of 4.0 · 10 M Tb ions
with increasing concentrations of K[Ag(CN)
temperature.
5
3+
D (J = 3, 2, 1, 0) excited states of the Eu acceptor ions,
J
2
] in acetonitrile at room
the exciplex energy will transfer via a CT state with a non-
radiative pathway instead of the D states, leaving non-
sensitized or even weakened f–f emissions of the Eu
acceptor ions. Thus, energy transfer can be ‘tuned off’ as
the donor emission energy blue-shifts above the CT state
5
J
3
+
1
0
trile solutions. That is, the energy transfer rate from d sil-
ver dicyanide donor ions to the Tb
3
+
acceptor ions
1
0
increases with increasing concentration of d metal dicya-
nide donor ions due to improved overlap of the acceptor’s
excitation spectra with increasing donor’s emission as the
donor’s concentration increases. The result in acetonitrile
solvent is similar to that in methanol as shown in Fig. 2.
3+
of the Eu ion.
An exceptional case in which energy transfer does occur
with 26- and 67-fold enhancement of the bands at 616 nm
5
5
5
5
(
D ! F ) and 589 nm ( D ! F ), respectively, for
0
2
0
1
3+ ꢀ3
Eu acceptor ion is observed for 2 · 10 M K[Ag(CN) ]
2
ꢀ3
and 1 · 10 M Eu(NO ) in methanol (Fig. 5a). Since
3
3
1
.3. Energy transfer between d metal dicyanide donor
0
3
clusters and Eu acceptor ions in different solvents
there is no near-UV absorption band observed as men-
tioned previously, we conclude that no CT process to
3
+
3
+
Eu ion occurs in this system. The probable reason is that
the exciplex emission of the dicyanoargentate(I) donor with
the Eu ions is tuned in resonance with the Eu ion L
Fig. 5 shows the f–f transition emissions at 615
5
5
5
5
3+
(
D ! F ) and 589 nm ( D ! F ) of the Eu acceptor
3+
3+
5
0
2
0
1
6
1
0
ions in the presence of d metal dicyanide donor ions in
7
5
(
394 nm, F ! L ) excited state [11,35] through which the
0
6
3
+
methanol. The un-sensitized f–f emission bands of Eu
emission energy relaxes vibrationally to the lowest sub-level
acceptor ions at 589 and 615 nm (Fig. 5b and c) may indi-
cate a non-radiative deexcitation process via a charge-
transfer (CT) state which competes with and overcomes
the radiative pathway. Quenching of excited-state energy
5
of the excited state D (579 nm) and then radiatively
decays to the ground F manifold. The quantum yield of
the D emission of Eu ions is about 5.5 ± 0.5% upon
excitation to the L level compared to 31 ± 2% upon exci-
0
7
J
3+
5
0
5
6
3
+
3+
by a CT state has been observed previously in Eu /Ce
5
tation to the D state in methanolic solution. Thus, the
0
systems [25–28], in europium cryptates [29–33], as well as
in the crystal [EuAu] complex for which the most intense
excitation band observed around 410 nm is assigned to a
energy transfer can be ‘tuned on’ as the donor emission
5
energy becomes in resonance with the L state acceptor
6
3+
Eu ion.
4. Conclusions
1
0
The luminescence energy and intensity of d metal cop-
a
per(I), silver(I) and gold(I) dicyanide nanoclusters as
energy transfer donors exhibit high tunability by varying
concentration, excitation wavelength and solvents, such
as in methanol, acetonitrile and dioxane. Efficiency of
energy transfer depends on the tunability of the emission
×
×
10
20
b
c
1
0
energy of d metal dicyanide nanocluster donor ions with
3
+
the Tb acceptor ions in different solvents. For example,
ꢀ
3+
d
energy transfer of ½CuðCNÞ ꢁ clusters with Tb acceptor
2
2
00
300
400
500
600
700
ions in acetonitrile solution exhibits no energy transfer
while in methanol solvent energy transfer is clearly
observed. For the Eu acceptor ions, energy transfer can
be ‘tuned off’ or ‘tuned on’ as the solvent dependent donor
emission energy become in resonance with the charge
Wavelength, nm
3
+
Fig. 5. Excitation (kem = 591 nm) and emission (kex = 285 nm) spectra in
methanol of (a) 2.0 · 10 M Eu(NO
ꢀ
3
ꢀ2
3
)
3
2
+ 2.0 · 10 M K[Ag(CN) ]; (b)
K[Au(CN)
ꢀ
3
ꢀ2
ꢀ3
M
2
.0 · 10
M
Eu(NO
3
)
3
+ 2.0 · 10
M
2
ꢀ3
]; (c) 2 · 10
ꢀ
3
3+
Eu(NO
3
)
3
+ 1.0 · 10 M K[Cu(CN)
2
]; and (d) 2 · 10 M Eu(NO
3
)
3
.
transfer state for Eu ion complexes resulting in non-radi-

344
Z. Guo et al. / Chemical Physics Letters 445 (2007) 340–344
5
3+
ative decay or with the L state of the Eu ion resulting in
radiative decay.
[13] J.C.F. Colis, R. Staples, C. Tripp, D. Labrecque, H. Patterson, J.
Phys. Chem. B 109 (2005) 102.
6
[14] J.C.F. Colis, C. Larochelle, R. Staples, R. Herbst-Irmer, H. Patter-
son, Dalton Trans. (2005) 675.
Acknowledgements
[15] Z. Guo, R.L. Yson, H.H. Patterson, Chem. Phys. Lett. 433 (2007)
3
73.
This work was supported by the National Science Foun-
dation (CHE-0315877). We thank Mr. David LaBrecque
and Mr. David Welch for assistance.
[16] P. Leonard Joseph, T. Gunnlaugsson, J. Fluores. 15 (2005) 585.
[
[
17] E. Staritzky, D.I. Walker, Anal. Chem. 28 (1956) 419.
18] M.A. Omary, T.R. Webb, Z. Assefa, G.E. Shankle, H.H. Patterson,
Inorg. Chem. 37 (1998) 1380.
[19] M.A. Omary, H.H. Patterson, Inorg. Chem. 37 (1998) 1060.
References
[20] G.H. Dieke, H.M. Crosswhite, Appl. Opt. 2 (1963) 675.
[21] T. Forster, Fluoreszenz Organischer Verbindungen, Vandenhoeck
[
[
[
[
[
[
1] N. Srisook, J. Rizzolo, G.E. Shankle, H.H. Patterson, Inorg. Chim.
Acta 300–302 (2000) 314.
2] C.N. Pettijohn, E.B. Jochnowitz, B. Chuong, J.K. Nagle, A. Vogler,
Coord. Chem. Rev. 171 (1998) 85.
3] S.A. Clodfelter, T.M. Doede, B.A. Brennan, J.K. Nagle, D.P. Bender,
W.A. Turner, P.M. LaPunzina, J. Am. Chem. Soc. 116 (1994) 11379.
4] K.S.K. Shin, J.D. Barrie, B. Dunn, J.I. Zink, J. Am. Chem. Soc. 112
und Ruprecht, Germany, 1951.
[22] H. Yersin, D. Truembach, J. Strasser, H.H. Patterson, Z. Assefa,
Inorg. Chem. 37 (1998) 3209.
[23] D.F. Parra, A. Mucciolo, H.F. Brito, J. Appl. Polym. Sci. 94 (2004)
865.
[24] A. Kudo, E. Kaneko, Chem. Commun. (1997) 349.
[25] W.D. Horrocks, W.E. Collier, J. Am. Chem. Soc. 103 (1981) 2856.
[26] W.D. Horrocks, D.R. Sudnick, Acc. Chem. Res. 14 (1981) 384.
[27] R.C. Holz, C.A. Chang, W.D. Horrocks, Inorg. Chem. 30 (1991)
3270.
[28] P.J. Breen, E.K. Hild, W.D. Horrocks, Biochemistry 24 (1985) 4991.
[29] M. Ciampolini, P. Dapporto, N. Nardi, J. Chem. Soc., Chem.
Commun. (1978) 788.
[30] N. Sabbatini, L. Decola, L.M. Vallarino, G. Blasse, J. Phys. Chem. 91
(1987) 4681.
[31] N. Sabbatini, S. Perathoner, G. Lattanzi, S. Dellonte, V. Balzani, J.
Phys. Chem. 91 (1987) 6136.
(1990) 5701.
5] M.A. Rawashdeh-Omary, M.A. Omary, H.H. Patterson, J.P. Fackler
Jr., J. Am. Chem. Soc. 123 (2001) 11237.
6] M.A. Rawashdeh-Omary, M.A. Omary, H.H. Patterson, J. Am.
Chem. Soc. 122 (2000) 10371.
[
[
7] M.A. Omary, H.H. Patterson, J. Am. Chem. Soc. 120 (1998) 7696.
8] M.A. Rawashdeh-Omary, M.A. Omary, J.P. Fackler Jr., R. Galassi,
B.R. Pietroni, A. Burini, J. Am. Chem. Soc. 123 (2001) 9689.
9] N. Nagasundaram, G. Roper, J. Biscoe, J.W. Chai, H.H. Patterson,
N. Blom, A. Ludi, Inorg. Chem. 25 (1986) 2947.
[
[
[
[
10] M.A. Rawashdeh-Omary, C.L. Larochelle, H.H. Patterson, Inorg.
Chem. 39 (2000) 4527.
11] Z. Assefa, G. Shankle, H.H. Patterson, R. Reynolds, Inorg. Chem. 33
[32] L. Prodi, M. Maestri, R. Ziessel, V. Balzani, Inorg. Chem. 30 (1991)
3798.
[33] G. Blasse, M. Buys, N. Sabbatini, Chem. Phys. Lett. 124 (1986) 538.
[34] C.K. Jorgensen, Mol. Phys. 5 (1962) 271.
[35] Y. Haas, G. Stein, J. Phys. Chem. 75 (1971) 3668.
(1994) 2187.
12] J.C.F. Colis et al., J. Phys. Chem. B 109 (2005) 4317.