Neutral Re(I) complexes for anion sensing

Article abstract of DOI:10.1080/10610278.2012.691500

Anion sensing properties toward F, OAc and H2PO4 were studied for new mononuclear and dinuclear Re(I) complexes based on a five-substituted phenanthroline moiety bearing a thiourea hydrogen-bonding receptor. Log(K 1:1) values between 4 and 6 were obtained for the complexes by UV-vis titrations and between 3 and 5 by ¹H NMR titrations. The effect of hydrogen-bonding versus deprotonation of the thiourea receptor upon addition of the anions was also evaluated by UV-vis and NMR titration techniques. In addition, an X-ray structure of the Re(I) precursor complex is reported and the chirality of the mononuclear and dinuclear complexes is discussed.

Full text of DOI:10.1080/10610278.2012.691500

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Neutral Re(I) complexes for anion sensing
André Bessette a , Samik Nag a b , Amlan K. Pal a , Sofia Derossi a & Garry S. Hanan a
a Département de Chimie , Université de Montréal , Pavillon J.-A. Bombardier, 5155 Decelles
Avenue, Montréal , Québec , Canada , H3T-2B1
b Department of Chemical Sciences , Sikkim University , Gangtok , Sikkim , 737102 , India
Published online: 06 Aug 2012.
To cite this article: André Bessette , Samik Nag , Amlan K. Pal , Sofia Derossi & Garry S. Hanan (2012) Neutral Re(I)
complexes for anion sensing, Supramolecular Chemistry, 24:8, 595-603, DOI: 10.1080/10610278.2012.691500
To link to this article: http://dx.doi.org/10.1080/10610278.2012.691500
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Supramolecular Chemistry
Vol. 24, No. 8, August 2012, 595–603
Neutral Re(I) complexes for anion sensing
Andre Bessette , Samik Naga,b, Amlan K. Pala, Sofia Derossia and Garry S. Hanana*
a
´
a
´ ´ ´
Departement de Chimie, Universite de Montreal, Pavillon J.-A. Bombardier, 5155 Decelles Avenue, Montreal, Quebec,
´
Canada H3T-2B1; Department of Chemical Sciences, Sikkim University, Gangtok, Sikkim 737102, India
´
b
(Received 26 March 2012; final version received 26 April 2012)
Anion sensing properties toward F2, OAc2 and H2PO42 were studied for new mononuclear and dinuclear Re(I) complexes
based on a five-substituted phenanthroline moiety bearing a thiourea hydrogen-bonding receptor. Log(K1:1) values between
1
4 and 6 were obtained for the complexes by UV–vis titrations and between 3 and 5 by H NMR titrations. The effect of
hydrogen-bonding versus deprotonation of the thiourea receptor upon addition of the anions was also evaluated by UV–vis
and NMR titration techniques. In addition, an X-ray structure of the Re(I) precursor complex is reported and the chirality of
the mononuclear and dinuclear complexes is discussed.
Keywords: neutral Re(I) complexes; anion binding; thiourea receptors
Introduction
F2. Another report by Lin et al. (26) shows that a dinuclear
neutral Re(I) complex with quinoxaline-bis(sulphona-
mide) functionalisation can be active as a good anion
binder where both sulphonamide groups can orient
themselves to a conducive position to form a cleft around
the incoming anion. A similar approach reported earlier by
Beer’s group to surround the anion by amide functional-
ities attached to a Re(I) core lead to reasonably strong
binding constants (ca. between 35 and 1790 depending on
the anion and the receptor system) (24, 27). Recently, the
group of Lees circumvented this synthetic drawback by
reporting the preparation of thioamide, urea and especially
of readily accessible thiourea Re(I) bridged complexes,
along with their use as luminescent anion receptor (28).
Herein, we report the anion-binding properties of two
neutral Re(I) complexes (3 and 4) also with a thiourea
moiety as the anion receptor group, which can be
synthesised very readily. A comparative anion sensing
study by UV–vis and NMR titrations has been done in
order to better understand the effect of hydrogen-bonding
versus deprotonation of the thiourea receptor upon
addition of monoanionic F2, OAc2 and H2PO42 on the
binding constants obtained.
The field of anion recognition has been growing at an
impressive rate since the start of the new millenium (1).
One reason is that anions are ubiquitous throughout
biological systems as they carry genetic information (DNA
is a poly-anion) and the majority of enzyme substrates and
co-factors are anionic (2, 3). Thus, anion binding and
recognition have attracted intense interest (1–10), and
metal complexes have played an important role in anion
receptor chemistry since its earliest examples (11, 12). The
presence of a metal ion can introduce a range of
advantageous physicochemical properties to this class of
receptor (12). Recently, Gale and co-workers (13) have
shown that introduction of a transition metal into a purely
organic system can enhance its anion binding capabilities
dramatically. While both metal–ligand interaction (11,
14–16) and van der Waals interactions (8, 9, 17–19) are
employed to study anion binding phenomena, neutral
metal complexes are challenging candidates for anion
binding as the electrostatic component is not an available
mode of interaction. With a few exceptions of metallocene
complexes (12, 20), neutral metal-based optical anion
sensors are less well known. Neutral anion sensors with
Re(I) as the metal centre are of particular interest, but their
synthesis usually involves multiple steps (21–24).
Recently, neutral alkynylrhenium(I) tricarbonyl diimine
complexes with a triarylboron moiety, which can bind to
F2 with a stability constant in the range of 105 was
reported (25). This high binding constant is due to the
interaction between the highly Lewis acidic and electron-
accepting triarylboron moiety and the electron-rich guest
Results and discussion
Our target ligand for combining both a bidentate binding site
and a scaffold for the thiourea group was a 5-substituted
phenanthroline. The reaction of 1,10-phenanthrolin-5-amine
with Re(CO)5Br in refluxing toluene gave Re(I) complex 1
in 96% yield. Treatment of 1 with thiophosgene in the
presence of Na2CO3 gave isothiocyanate functionalised
*Corresponding author. Email: garry.hanan@umontreal.ca
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.691500
http://www.tandfonline.com

596
A. Bessette et al.
Re(I) complex 2 in nearly quantitative yield. Complex 2
proved to be a good precursor for the synthesis of thiourea
[(ZNH)2CvS] containing rhenium(I) complexes. Reaction
of 2 with 10equiv. of aniline in acetone at ambient
temperature and under inert atmosphere afforded the neutral
Re(I) complex 3 containing thiourea receptor group in
81% yield (Scheme 1). Under similar conditions, reaction of
2 with p-phenylenediamine in a 2:1 ratio afforded the
dinuclear neutral Re(I) complex 4 with two thiourea receptor
units in 60% yield. All of the complexes were characterised
by NMR spectroscopy, high-resolution mass spectrometry
(HR-MS) and elemental analysis.
carbonyl ligands, the rhenium centre and aromatic rings
of the phenanthroline ligand are in a nearly ideal planar
arrangement. The plane containing atoms C16, N3 and S
deviates from the plane formed by N1, N2, Re, C2, C3 by
only 4.5(0.4)8. Bond lengths and angles around the metal
centre are comparable to those in closely related
compounds (see ESI) (29, 30). The CZRe bond lengths
˚
(1.921(4) and 1.919(3) A) trans to phenanthroline are
shorter than the CZRe bond trans to the anionic Br ligand
˚
(1.984(4) A) due to increased backbonding from Re(I)
with the p-donating Br ligand. The CZO bond distances,
as a consequence, show the reverse trend. Whereas the
˚
equatorial CZO bonds are 1.147(4) and 1.149(4) A, the
˚
one trans to the bromide is 1.034(5) A, displaying
considerably less backbonding from the Re(I) centre.
The isothiocyanate precursor 2 was further structurally
characterised by X-ray crystallography (Figure 1).
ꢀ
Complex 2 crystallises in triclinic P1 space group with
˚
The ReZBr bond is 2.6167(7) A whereas the two ReZN
˚
bonds are almost identical at 2.180(3) A. The isothiocya-
an acetone molecule as solvate. Complex 2 presents an
octahedral ligand arrangement with a facial tricarbonyl
moiety. A bidentate diimine ligand and a bromide fill its
octahedral coordination sphere. The two equatorial
nate group is almost linear with a NZCZS angle of
175.19(0.35)8. The molecule is chiral on Re-atom, but the
NH2
NH2
Re(CO)5Br
N
N
Toluene/reflux
96% yield
OC Re Br
N
N
OC CO
1
CSCl2/Na2CO3
Acetone/RT
97% yield
NH
NH
S
NCS
N
H
N
10
2
Acetone/RT
81% yield
N
N
N
OC Re Br
OC CO
2
OC Re Br
OC
CO
3
H2N
NH2
Acetone/RT
60% yield
H
N
H
N
Br
N
N
N
CO
CO
CO
S
Re
OC
OC
Re
Br
S
CO
N
H
N
H
N
4
Scheme 1. Synthesis of the neutral Re(I) complexes: precursors 1 and 2 and thiourea receptors 3 and 4.

Supramolecular Chemistry
597
Figure 1. (Left) Ortep representation of 2 drawn at 50% probability level, showing a view of the molecule from above of the molecule.
(Right) Ball and stick model of two different enantiomeric views of the chiral molecule. H atoms and the solvated acetone molecule have
been omitted for clarity.
effect of this chirality is faded to affect the hydrogen
bonding property of the thiocyanato group due to the long
distance between the chiral Re-centre and the thiocyanate
group.
carbonyl complexes (31, 32). For complex 4, the
irreversible oxidation and reduction are observed at
0.90 V versus SCE and 21.36 V versus SCE, respectively.
The monoanionic ions F2, OAc2 and H2PO42 are well
known to bind to thiourea (31–36) and, therefore, we
studied their binding to the Re(I) thiourea complexes
(Figures 2 and 3; ESI). However, as thiourea receptors are
subject to a deprotonation of relatively acid NH’s when a
strong conjugated anionic base like OAc2 is added (37),
efficiency of the anion sensing properties of our
organometallic systems needed to be establish. In facts,
Yatsimirsky et al. showed that deprotonation is favoured in
highly diluted solutions due to a ratio of H-bonded and
deprotonated forms of thiourea linkage being proportional
to the total receptor concentration. Similar results of acid–
base reaction were also observed by Gale and co-workers
(38) for 3,4-dichloro-2,5-diamidopyrroles. Consequently,
we were curious to establish to which extent apparent
binding constant (Kapp) values resulting from such multi-
equilibrium systems would be affected by varying the
The electrochemical behaviour of complexes 3 and 4
has been examined by cyclic voltammetry at a glassy
carbon electrode in purified N,N0-dimethylformamide
(DMF) under a dry argon atmosphere. At positive
potentials, complex 3 shows an irreversible oxidation at
0.85 V versus saturated calomel electrode (SCE), attribu-
table to the oxidation of the thiourea group, similar to that
reported for the oxidation of a thiourea group of a cationic
Re(I) polypyridyl complexes with thiourea receptors (29).
As the Re(I/II) oxidation couples for similar rhenium
complexes are reported to appear beyond 1.8 V versus
SCE, we did not observe any such couples within the
solvent potential window of DMF. At negative potentials,
the quasi-reversible diimine-based reduction is observed at
21.38 V versus SCE. Similar values were also reported
earlier for reduction of the diimine ligand in Re(I)
Figure 2. (a) UV–vis titrations of receptor 3 (1.5 £ 1025 M) with F2 in DMSO–0.5% water. Inset: Corresponding titration profile at
347 nm. (b) Job plot of receptor 3 with F2 in DMSO–0.5% water at 440 nm, showing 1:1 binding.

598
A. Bessette et al.
Figure 3. (a) (Left) UV–vis titrations of receptor 4 (1.5 £ 1025 M) with F2 in DMSO–0.5% water. Inset: Corresponding titration
profile at 430 nm. (b) (Right) Job plot of receptor 4 with F2 in DMSO–0.5% water at 450 nm, showing 1:2 receptor to anion binding.
Table 1. Apparent binding constants (Kapp) determine by UV–vis and NMR titrations.
UV–visa
NMRb
Log(K1:1
(^0.1)
)
Log(K2:1
(^0.1)
)
Log(K1:1
(^0.2)
)
Log(K2:1
(^0.2)
)
Log(K3:1
(^0.2)
)
Compound
Anionc
3
F2
4.4
5.8
4.7
3.9
5.4
5.7
NA
NA
NA
10.3
11.2
9.8
3.7
3.9
2.8
3.6
4.8
2.9
NA
8.9
6.2
5.8
9.0
5.5
NA
NA
NA
3.0
6.1
4.0
OAc2
H2PO24
F2
4
OAc2
H2PO24
a Acquisitions at 298 K. In DMSO–0.5% H2O (v/v). Data fitted with the HypSpec software.
b Acquisitions at 298 K. In DMSO-d6–0.5% H2O (v/v). Data fitted with the HypNMR2008 software.
c All anions were added as their TBA salts.
concentration from a 1.5 £ 1025 M of complexes by UV–
vis to a 200-fold concentration of 3 £ 1023 M by NMR
(Table 1).
deprotonation process on bishydrazide derivatives of
isoindoline induced the appearance of a new band between
390 and 2445 nm, a behaviour very similar to what is
observe in our case around 440 nm.
The UV–vis anion-binding studies were performed in
a DMSO–0.5% water medium (Figure 2 and ESI).
Absorption spectra of both complexes show intense intra-
UV–vis titration curves allowed for the determination
of Kapp. Values obtained in log(Kapp) for a 1:1 anion to
complex 3 are 4.4 (F2), 5.8 (OAc2) and 4.7 (H2PO24 ). It is
noteworthy that KðOAc2Þ=KðH2PO24 Þ is ,12.6 and
K(OAc2)/K(F2) is ,25, which demonstrates a preference
for the acetate anion. The K values obtained for 3 are
considerably higher than those previously reported for
neutral Re(I) complexes with cleft-type amide receptors
(22) and of a similar magnitude for positively charged
Re(I) polypyridyl complexes with thiourea receptors (31,
40). Strong binding with neutral receptors is remarkable as
favourable electrostatic interactions are usually one of the
stongest contributors to anion-binding (4–6). The Re(I)
centre is an excellent electron-withdrawing (EWG) group
that acidifies the NH group and the extended p-
conjugation of the phenanthroline stabilises the deproto-
nated form of the receptor by delocalisation of the charge.
ligand (p ! p ) absorption bands in the range of 260–
*
300 nm. The less intense absorption shoulder between 350
and 400 nm is assigned to a spin-allowed metal-to-ligand
charge-transfer (1MLCT) (dp(Re) ! p (phen)) tran-
*
sition. On addition of the F2, OAc2 and H2PO42 ions as
their tetrabutyl ammonium (TBA) salts during titration of
3 and 4, gradual rises in the absorption at ca. 350 and
440 nm were observed.
The use of Job plots by UV–vis allowed a preliminary
fitting of the data to a 1:1 complex:anion model for 3 (ESI)
and to 1:2 for 4 (Figure 3 and ESI). While some of the
results tend to be slightly offset from the ideal fittings,
e.g. 3 with F2 and H2PO24 , it appears that a deprotonation
equilibra exist in the system. Moreover, it has already been
established by Jurczak and co-workers (39) that the

Supramolecular Chemistry
599
This combination of structural elements could be offering
an increased tendancy for deprotonation over H-bonding
behaviour and, therefore, the apparent binding constant
should be driven by basicity of the anion used. Following
this idea, a quick look at the pKa table for acetic acid
(4.76), hydrofluoric acid (3.17) and phosphoric acid (2.12)
gives an insight that acetate anion is the strongest
conjugate base of the three. Between H2PO24 and F2, the
latter should be stronger, but the higher solvation of
unbound F2 in presence of water molecules should hinder
its ability to deprotonate the thiourea group. All together,
this rationalisation seems to support the Kapp obtained
empirically for the mono-receptor complex 3.
increments of 0.2 equiv. were used until 2 equiv. of anion
was reached, followed by 1 equiv. additions until the final
6 equiv. was reached. For complex 4, which bears two
thiourea receptor groups, the same starting concentration
of complex was used, but initial increments of 0.25 equiv.
were used until 6 equiv. of anion was reached, followed by
2 equiv. additions until the final 10 equiv. was reached
(Figure 5 and ESI). Interestingly, both complexes exhibit
broadening then quick disappearance of the two NHs
signals (around 10.25 ppm) upon addition of the various
anions, which has been noted previously during deproto-
nation (39). Based on stabilisation arguments, the NH
proton next to the phenanthroline moiety is the more likely
to be deprotonated.
Complex 4 also shows high apparent stability
constants for the three anions. Having two identical
receptor sites, 4 is expected to furnish two Kapp values, K1:1
and K2:1, respectively, where the latest should be lower due
For determination of Kapp, the three peaks showing
biggest variation in ppm were used in order to diminish the
potential error on the binding constant obtained. A priori,
one might think that the protons providing higher
variations in shift upon addition of anions should be the
nearest to the thiourea receptor. However, peaks presenting
this behaviour are the ones allowing the stabilisation of an
electronic charge by delocalisation. In this respect,
positions 3-, 7- and 9- on the phenanthroline moiety are
the more sensible to receive this charge. Therefore, they
should exhibit the largest shift during the titration. In
to disfavourable electrostatic arguments. The log(Kapp
)
values obtained for 4 are 3.9 and 10.3 (F2), 5.4 and 11.2
(OAc2); 5.7 and 9.8 (H2PO24 ). Those values are greater
than the ones found for other bis-thiourea receptors (37),
although the contribution of deprotonation must also be
considered. Interestingly enough, the results obtained
clearly exhibit a K2:1 between ca. 4 and 6 orders of
magnitude higher than the K1:1, which at first look might
seem counterintuitive. However, a precedent in literature is
known from Jurczak and co-workers (39) where the
interaction of H2PO42 with a mono-receptor led to a K2:1 of
three orders of magnitude higher than K1:1 (i.e.
log(K2:1) ¼ 7.2 vs log(K1:1) ¼ 4.3). While no formal
explanation for the presence of a second binding constant
was reported there, it seems plausible that the presence of
two hydrogens on hydrophosphate anions can play a role,
that is, multiple H-bonding with the receptor’s heteroa-
toms of their hydrazide linkages might add their effect to
the classical NH bond interaction. In our case, as
observation of the second binding constants for F2,
OAc2 or H2PO24 all displayed a higher value than the first
one in a system where no multiple H-bonding of the anion
with receptors was possible, it seems that the presence of
deprotonated receptors do interfer with a good fitting of
data. To further prove that idea and evaluate its impact,
NMR titrations were also performed (41).
1
complex 3, the H NMR shifts of positions 7- and 9-,
appearing at 8.94 and 9.41 ppm, respectively, were studied.
The H para (7.18 ppm) to the thiourea in the phenyl group
also exhibited a large shift by NMR. For complex 4, the
peak at position 3- on the phenanthroline (8.08 ppm)
replaced the para- one of the phenyl for Kapp
determination due to a bigger shift observed in that case.
Positions 7- and 9- presented similar NMR displacements
as in complex 3.
Fitting of the data for complex 3 led to Kapp values in
the same order of magnitude as to what was obtained by
UV–vis titration (log(K1:1) ¼ 3.7 ^ 0.2 by NMR vs
4.4 ^ 0.1 for UV–vis) for F2 (Table 1). However,
necessity for a K2:1 appeared to better fit data in the cases
of stronger conjugate bases H2PO24 and OAc2. Values of
log(K2:1) were higher than the one of one anion binding to
one receptor for both OAc2 (log(K1:1) ¼ 3.9 ^ 0.2;
log(K2:1) ¼ 8.9 ^ 0.2) and H2PO24 (log(K1:1) ¼ 2.8 ^
0.2; log(K2:1) ¼ 6.2 ^ 0.2). Data for complex 4 (Table 1)
are even more peculiar as they force to consider for a good
fitting an association of three anions to one complex
bearing two receptors (K3:1). While we have no formal
explanation for this unusual behaviour from a supramo-
lecular point of view, it might only be artefacts arising
from the interference of deprotonation equilibra compared
to H-bonding at the concentrations required for NMR
experiments. Another point to take in consideration is the
appearance in the baseline of NMR spectrums of what
seems to be a new species upon addition of anions;
potentially due to a decomposition phenomena leading
NMR titration experiments were conducted in a 99.5%
DMSO-d6/0.5% H2O solvent mixture to match with the
conditions used in UV–vis tritration. As mentioned
previously, a 200-fold higher concentration of complexes 3
and 4 was used, i.e. 3 £ 1023 M, in order to evaluate the
impact of concentration on the Kapp observed at a suitable
concentration for NMR. To keep the overall concentration
of complex 3 constant throughout the titration, microlitre-
scale additions of a solution containing ,30-fold higher
concentration of the anion as its TBA salt (1 £ 1021 M)
over the complex were done to 0.7 ml of starting solution
containing the complex alone (Figure 4 and ESI). Initial

600
A. Bessette et al.
Figure 4. NMR titration of receptor 3 (3 £ 1023 M) from 0 to 6 equiv. of OAc2 added by increments in 99.5% DMSO-d6/0.5% water.
Only aromatic region is shown for clarity.
back to the 5-amino-1,10-diaminophenanthroline deriva-
tive in basic conditions. Overall, the titrations by NMR of
complexes 3 and 4 allowed a better understanding of the
possible deprotonation equilibra in competition with
H-bonding, as this technique offers access to structural
characterisation of anion interactions with the receptor at
higher concentration compared to UV–vis.
terephtalate could potentially form a dimeric structure in
the case of 3 and or even a molecular triangle by
combining three complexes 4 with three bridging dianions.
In order to quickly test if such assemblies were easily
accessible, HR-MS studies by direct infusion of 2.8E–
03 M solutions of both the complex and the dianion were
done under the mildest ESI conditions possible. While
self-assembled structures are not always stable in the HR-
MS due to the weak nature of H-bonding, many examples
were still observed and reported in the literature.
Unfortunately, complex 3 exhibited mainly the deproto-
nated specie [3 2 H]2 at 678.9536 m/z along with a 1:1
assembly with the dianion still bearing one of the two TBA
cations [3 þ terephtalate þ TBA]2 at 1086.2502 m/z. For
complex 4, only the doubly deprotonated specie
[4 2 2H]22 at 639.9224 m/z and the TBA-stabilised one
[4 þ TBA 2 2H]2 at 1522.1217 m/z were observed.
Therefore, no indication of dimer or molecular triangle is
reportable. However, the presence of deprotonated
complexes in the HR-MS for both cases further support
the hypothesis of a thiourea deprotonation phenomena.
In conclusion, we have demonstrated in this work a very
simple and high-yielding synthetic protocol for mono and
polynuclear Re(I) complexes based on a five-substituted
Of note, titration attempts were also made using
fluorescence emission quenching method; however, no
useful results were obtained in order to determine Kapp
.
In fact, the appearance of a second emission peak
overlapping with the one under evaluation render the
tracking of emission maxima impossible. This second
peak might be the result of emission from the deprotonated
receptor R2. In any case, this behaviour is an additional
point which suggests that a competitive system exists in
which both H-bonding and deprotonation equilibria are at
play. Decomposition phenomena may also be implied, as
the NMR titration experiments showed, a situation that
further can affect apparent binding constants.
From a supramolecular point of view, complexes 3 and
4 should be a priori integrable into higher order self-
assembled structures when combine with suitable H-
bonding linkers. Based on that concept, the dianionic

Supramolecular Chemistry
601
Figure 5. NMR titration of receptor 4 (3 £ 1023 M) from 0 to 12 equiv. of OAc2 added by increments in 99.5% DMSO-d6/0.5% water.
Only aromatic region is shown for clarity.
1
phenanthroline moiety with thiourea linkages. An X-ray
molecular structure of the precursor 2 also confirmed that
these systems are inherently chiral. To the best of our
knowledge, complexes 3 and 4 in our present work
represent the first example of neutral Re(I) complexes with
thiourea receptor groups that can be used as anion binding
agents. Moreover, we have studied the tendency of thiourea
receptors toward deprotonation in presence of F2, OAc2
and H2PO24 to conclude such an equilibrium might be
present in our systems as Re(I) centre can be considered as
an EWG, which greatly enhances the NH proton’s acidity.
In addition, delocalisation into the extended p-conjugation
on the phenanthroline moiety may also stabilise the
negative charge generated by deprotonation. Future work
will be focus towards the incorporation of such high-energy
absorbing Re(I) polynuclear complexes by the developed
synthetic protocol into artificial molecular antenna for
light-harvesting applications.
400 MHz for H NMR and at 100 MHz for 13C NMR.
Chemical shifts are reported in part per million (ppm)
relative to residual solvent protons and the carbon
resonance of the solvent (1.93 and 33.5 ppm, respectively,
for DMSO-d6). Absorption spectra for UV–vis titration
and the Job plot method were measured in DMSO–0.5%
water at r.t. on a Cary 500i UV–vis–NIR spectropho-
tometer. Experimental uncertainties are as follows:
absorption maxima, ^2 nm; molar absorption coefficient,
10%. Solvents were removed under reduced pressure using
a rotary evaporator unless otherwise stated.
Re(CO)3Br(5-NH2-phen) (1)
To a suspension of Re(CO)5Br (406 mg, 1 mmol) in
toluene (30 ml) was added the 1,10-phenanthroline-5-
amine (200 mg, 1 mmol). The mixture was then stirred and
refluxed for 1 h, during which time an orange compound
precipitated. After cooling to ambient temperature, the
orange precipitate was isolated by filtration and was
washed with n-hexane and air dried. Yield ¼ 525 mg
(96%). 1H NMR (DMSO-d6, 400 MHz); 9.40 (dd,
J d ¼ 5.0 Hz, J d ¼ 1.0 Hz, 1H, H), 9.11 (dd,
Experimental section
Experimental NMR spectra were recorded in DMSO-d6 at
room temperature (r.t.) on a Bruker AV400 spectrometer at

602
A. Bessette et al.
J d ¼ 9.0 Hz, J d ¼ 1.0 Hz, 1H), 8.95 (dd, J d ¼ 5.0 Hz,
J d ¼ 1.0 Hz, 1H), 8.47 (dd, J d ¼ 8.0 Hz, J d ¼ 1.0 Hz,
1H), 8.05 (dd, J d ¼ 8.0 Hz, J d ¼ 5.0 Hz, 1H), 7.78 (dd,
J d ¼ 8.0 Hz, J d ¼ 5.0 Hz, 1H), 7.07 (s, 1H, H7), 6.90 (s,
2H, ZNH2). Elemental analysis: calcd for C15H9BrN3O3-
Re: C ¼ 33.04%, H ¼ 1.66%, N ¼ 7.71%; found:
C ¼ 33.95%, H ¼ 1.62%, N ¼ 7.60%.
was added p-phenylenediamine (11 mg, 0.1 mmol) under a
N2 atmosphere. The resulting mixture was stirred for 24 h
under N2, by which time a brownish orange precipitate
formed, which was filtered, washed with n-hexane and air
dried. Yield ¼ 61 mg (60%). 1H NMR (DMSO-d6,
400 MHz); 10.35 (s, 1H, Phen-NH-CS-NH-Ph), 10.25 (s,
1H, Phen-NH-CS-NH-Ph), 9.47 (d, J d ¼ 5.0 Hz, 1H), 9.41
(d, J d ¼ 5.0 Hz, 1H), 8.94 (d, J d ¼ 8.0 Hz, 1H), 8.87 (d,
J d ¼ 8.0 Hz, 1H), 8.34 (s, 1H, H7), 8.13 (dd, J d ¼ 8.0 Hz,
J d ¼ 5.0 Hz, 1H), 8.08 (dd, J d ¼ 8.0 Hz, J d ¼ 5.0 Hz,
1H), 7.54 (s, 4H, Ph). Elemental analysis: calcd for
Re(CO)3Br(5-NCS-phen) (2)
To a suspension of Re(CO)3Br(5-NH2-phen) (240 mg,
0.45 mmol) in acetone (90 ml) was added the Na2CO3
(180 mg, 1.7 mmol). To the mixture was added CSCl2
(0.16 ml) and stirring was continued at ambient tempera-
ture for 6 h under N2 atmosphere. The reaction mixture
was then filtered and the filtrate was evaporated under
reduced pressure. The resulting brownish yellow solid was
dissolved in minimum volume of dichloromethane and
was filtered again. Evaporation of the solvent under
reduced pressure yielded the product 2 as a brownish
yellow powder. Yield ¼ 250 mg (97%). 1H NMR (DMSO-
d6, 300 MHz); 9.55 (dd, J d ¼ 5.0 Hz, J d ¼ 1.0 Hz, 1H, H),
9.45 (dd, J d ¼ 5.0 Hz, J d ¼ 1.0 Hz, 1H), 8.98 (dd,
J d ¼ 8.0 Hz, J d ¼ 1.0 Hz, 1H), 8.89 (dd, J d ¼ 8.0 Hz,
J d ¼ 1.0 Hz, 1H), 8.60 (s, 1H, H7), 8.21 (dd, J d ¼ 8.0 Hz,
J d ¼ 5.0 Hz, 1H), 8.11 (dd, J d ¼ 8.0 Hz, J d ¼ 5.0 Hz,
1H). Elemental analysis: calcd for C16H7BrN3O3-
ReS(CH3)2CO: C ¼ 35.35%, H ¼ 2.03%, N ¼ 6.51,
S ¼ 4.97%; found: C ¼ 35.05%, H ¼ 1.83%, N ¼ 6.28,
S ¼ 5.07%.
C36H22Br2N8O6Re2S2:
N ¼ 8.73, S ¼ 5.00%; found: C ¼ 36.06%, H ¼ 1.75%,
N ¼ 8.60, S ¼ 4.57%.
C ¼ 35.57%,
H ¼ 1.73%,
Supporting Information Available
UV–vis and NMR titrations, corresponding titration
profile and Job plots of compounds 3 and 4; table
containing bond lengths of structurally similar compounds
and CIF file for 2 (available online). The CCDC deposit
number for the X-ray crystal structure of 2 is 796139.
Acknowledgements
GSH thanks the Natural Sciences and Engineering Research
Council of Canada (NSERC), the Centre for Self-Assembled
´
Chemical Structures and the Universite de Montreal (UdeM) for
financial support. AB thanks the NSERC, the Fonds Quebecois
´
´ ´
de la Recherche sur la Nature et les Technologies and Saint-Jean
Photochimie, Inc. for a BMP-Innovation scholarship and UdeM
´
for a fellowship. AB thanks Anne-Catherine Bedard for useful
scientific discussions. SN thanks the Canadian Bureau for
International Education for a fellowship.
Re(CO)3Br(5-(NHZCSZNHZPh)-phen) (3)
Re(CO)3Br(5-NCS-phen) (60 mg, 0.1 mmol) was dissolved
in acetone (15 ml) with stirring. To this was added aniline
(20 ml, 0.1 mmol) under a N2 atmosphere. The resulting
mixture was stirred for 20 h under N2, by which time a pale
yellow precipitate formed, which was filtered, washed with
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