Encapsulation of ruthenium(II) with macrobicyclic dioxime-functionalized ligands: On the way to new types of DNA-cleaving agents and probes

Article abstract of DOI:10.1039/b107172f

The clathrochelate di- and tri-ribbed-functionalized ruthenium(II) tris-dioximates with alkylamine, thioaryl, thioalkyl, phenoxyl, and crown ether substituents in α-dioximate fragments have been synthesized starting from reactive hexachloride clathrochelate precursors, formed by cross-linking with phenyl-, n-butyl- and fluoro-boronic capping groups. The IR, UV-vis, ¹H, ¹³C NMR and luminescent spectra as well as X-ray data for complexes obtained have been discussed. The redox characteristics (from cyclic voltammograms) for ruthenium(II) clathrochelates have been correlated with the electrochemical parameters of the corresponding iron(II) complexes and σ_para constants for functionalizing substituents.

Full text of DOI:10.1039/b107172f

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Encapsulation of ruthenium(II) with macrobicyclic
dioxime-functionalized ligands: on the way to new
types of DNA-cleaving agents and probes
Yan Z. Voloshin,*a Oleg A. Varzatskii,b Tatyana E. Kron,a Vitaly K. Belsky,a
Valery E. Zavodnik,a Nataly G. Strizhakova,b Victor A. Nadtochenkoc and
Vyacheslav A. Smirnovc
a Karpov Institute of Physical Chemistry, 103064 Moscow, Russia.
E-mail: voloshin@cc.nifhi.ac.ru
b Vernadskii Institute of General and Inorganic Chemistry, 252142 Kiev, Ukraine
c Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow region, Russia
Received 7th August 2001, Accepted 23rd November 2001
First published as an Advance Article on the web 14th February 2002
The clathrochelate di- and tri-ribbed-functionalized ruthenium() tris-dioximates with alkylamine, thioaryl,
thioalkyl, phenoxyl, and crown ether substituents in α-dioximate fragments have been synthesized starting from
reactive hexachloride clathrochelate precursors, formed by cross-linking with phenyl-, n-butyl- and fluoro-boronic
capping groups. The IR, UV-vis, 1H, 13C NMR and luminescent spectra as well as X-ray data for complexes obtained
have been discussed. The redox characteristics (from cyclic voltammograms) for ruthenium() clathrochelates have
been correlated with the electrochemical parameters of the corresponding iron() complexes and σpara constants for
functionalizing substituents.
Introduction
Experimental
A keen recent interest in polyimine ruthenium() complexes
and especially in tris-bipyridinates, phenanthrolinates and
General information
their analogs1–19 has largely been evoked by the ample scope
they offer as selective DNA-cleaving agents and probes in
biochemistry.20–24 Such ruthenium() complexes, as well as their
photophysics, are of particular interest in creating devices
for molecular electronics (e.g., systems of the “light-switch”
type) and in analytical detection of metal ions as well. In the
majority of research performed, the chelating ligands have been
initially functionalized, and this has permitted the obtention of
ruthenium() complexes with improved chemical and physico-
chemical properties. It should be emphasized that through a
highly conjugated aromatic system, both the medium (solvent
and acidity) and functionalizing substituents influence the
energy of the central metal ion d orbitals and ligand π,π*-
orbitals.5,6,13 An electronic effect of aliphatic and aromatic sub-
stituents in the dioximate fragments in the series of previously
synthesized boron-containing ruthenium() clathrochelates is
substantially lower.25 In addition, such substituents exhibit
low reactivity, and their modification involving variations in
physicochemical parameters (and, consequently, in the corre-
sponding characteristics of the clathrochelate itself ) is rather
complicated. We have managed to work out several procedures
for the synthesis of ribbed-functionalized macrobicyclic iron()
complexes (with substituents in the α-dioximate fragments)
starting from the initially obtained reactive chloride clathro-
chelates.26,27 The present study was undertaken first of all
to offer convenient methods for the synthesis of halogenide
clathrochelate ruthenium() precursors with allowance for a
kinetic inertness of ruthenium in different oxidation states, and
second to obtain ribbed-functionalized ruthenium() clathro-
chelates using the previously developed pathways for modifi-
cation of precursors and to determine the geometrical and
physicochemical characteristics of the complexes obtained.
The reagents used, Ru(OH)Cl3, SbCl3, CF3COOH (TFA),
C6H5SH, CH3SH, BF3ؒO(C2H5)2, n-butyl- and phenyl-boronic
acids, organic bases and their salts, and organic solvents were
obtained commercially (Fluka and Reachim). Bis[2-(o-oxy-
phenoxy)]diethyl ether was obtained as described in ref. 28. The
dichloroglyoxime (denoted as H2Cl2Gm) was prepared by
chlorination of glyoxime (H2Gm) as described in ref. 29.
C6H5BCl(OiC4H9) was obtained as described in ref. 30.
The [(CH3)4N]2[Ru(OH)Cl5] salt was obtained from a solu-
tion of Ru(OH)Cl3 in 10% hydrochloric acid with an excess of
(CH3)4NCl. The precipitate was filtered and dried in vacuo. The
sponge lead was prepared by reduction of a 5% Pb(CH3CO2)2
solution in 5% aqueous acetic acid with zinc dust. The zinc dust
was added to the stirring solution in several portions, and the
reaction mixture was left overnight. The sponge metallic lead
obtained was washed with water and then acetone, cooled with
liquid nitrogen and pulverized. The gray powder was washed
with acetone and dried in vacuo.
The analyses for the carbon, hydrogen, and nitrogen content
were carried out with a Carlo Erba model 1106 microanalyzer.
The plasma desorption (PD) mass spectra were recorded in
the positive spectral range on a time-of-flight biochemical mass
spectrometer BC MS SELMI using an accelerating voltage of
20 kV. The ionization was induced by 252Cf spontaneous decay
fragments, and typically 20000 decay acts were registered. The
samples (approximately 1–2 mg) were applied onto a gilded disk
or onto a nitrocellulose layer.
The IR spectra of solid samples (KBr tablets) in the range
400–4000 cmϪ1 were recorded on a Specord M-80 spectro-
photometer. The bands were assigned using the previous
results. The UV-vis spectra of solutions in chloroform in
the range of 230–800 nm were recorded on a Lambda 9
DOI: 10.1039/b107172f
J. Chem. Soc., Dalton Trans., 2002, 1203–1211
This journal is © The Royal Society of Chemistry 2002
1203

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Perkin-Elmer spectrophotometer. The individual Gauss com-
ponents of these spectra were calculated using the SPECTRA
program. The 1H, 13C, and 11B NMR spectra of the solutions in
CDCl3 were recorded on an AC-200 Bruker FT-spectrometer.
Laser photolysis was carried out with the second harmonic
of ruby (347 nm, 18 mJ, 15 ns) operated in the Q-switch mode.
An Orial 450 W Xe lamp was used as the monitoring light
source. The fluorescence was monitored with a Spex-2 photon
counting luminescence spectrometer provided with an MX-2
correction unit. The laser photolysis and luminescence
measurements in the liquid media (toluene and acetonitrile)
were carried out under aerobic conditions. The luminescence
spectra were also measured in a frozen toluene glass matrix at
77 K.
a small volume, and precipitated with hexane. The yellow solid
was washed with a small amount of methanol and then hexane
and dried in vacuo. Yield: 0.29 g (22%).
Procedure II. Ru(OH)Cl3 (2.25 g, 10 mmol), freshly distilled
SbCl3 (11.5 g, 50 mmol), H2Cl2Gm (5.2 g, 33 mmol), and
sponge lead (4.0 g, 2 mmol) were dissolved/suspended in dry
nitromethane (50 ml) with stirring under argon. The stirring
reaction mixture was heated to boiling, and a solution of
(nC4H9BO)3 in chloroform was added dropwise [this solution
was obtained by dehydration of a solution/suspension of
n-butylboronic acid (2.6 g, 25 mmol) in chloroform (50 ml) for
6 h under argon in a flask equipped with a Soxhlet extractor
containing 4 Å molecular sieves (15 g)]. The reaction mixture
was refluxed for 3 h (the temperature of the bath was 110 ЊC)
with partial evaporation of solvent (≈50 ml) and left overnight
at room temperature. Then the reaction mixture was evaporated
to a small volume and precipitated with a three-fold volume of
methanol. The solid was filtered, washed with 5% aqueous HCl
solution and then a small amount of methanol, and extracted
with chloroform. The subsequent purification was as described
in Procedure I. Yield: 2.2 g (31%). Anal. calc. for C14H18-
Cyclic voltammograms were recorded in dichloromethane
under an argon atmosphere using a PI-50-1 potentiostat
coupled with a B7-45 teraohmic potentiometer as a current–
voltage convertor. The scan rate was varied from 5 to 10 mV sϪ1
,
which is close to the steady-state conditions for ultramicro-
electrodes.31,32 Tetraethylammonium tetrafluoroborate (0.1 M)
was used as a supporting electrolyte. A platinum microelectrode
(100 µm in diameter, throughly polished and rinsed before
measurements) was chosen as the working electrode and a
platinum wire as the auxiliary electrode. A standard Ag/AgCl
reference electrode was connected to the cell via a salt bridge.
All potentials were referenced to the redox potential of the
ferrocene (Fcϩ/Fc) couple as an internal standard. This poten-
tial is at ϩ0.565 V vs. Ag/AgCl reference electrode under the
present experimental conditions.
N6O6B2Cl6Ru: C, 23.94; H, 2.57; N, 11.97; Cl, 30.35. Found: C,
1
23.94; H, 2.54; N, 11.98; Cl, 30.30%. MS PD: m/z 702 (M)ϩ . H
ؒ
NMR (CDCl3): δ 0.97 (m, 10H, BCH2 ϩ CH3), 1.49 (m, 8H,
CH2CH2). 13C{1H} NMR (CDCl3): δ 14.1 (s, CH3), 16.8 (br s,
BCH ), 25.7 (s, CH ), 25.8 (s, CH ), 129.1 (s, ClC᎐N). IR (cmϪ1
,
᎐
2
2
2
KBr): 908, 936 ν(N–O), 1098 ν(B–O), 1493 ν(C᎐N). UV-vis
᎐
(CHCl3): λmax (10Ϫ3ε/molϪ1 l cmϪ1) 265(6.9), 291(3.0), 354(3.9),
385(5.1), 417(15), 455(4.5) nm.
Ru(Cl2Gm)3(BC6H5)2 (3). Procedure I. This complex was syn-
thesized by a similar method to 2 (Procedure II) except that
(C6H5BO)3, obtained from phenylboronic acid (3.05 g, 2.5
mmol), was used instead of (nC4H9BO)3. The reaction mixture
after heating was left overnight and filtered. The solid was
washed with water, 10% aqueous hydrochloric acid, methanol,
diethyl ether and then a small amount of chloroform. The
desired complex was extracted with benzene or chloroform in
a Soxhlet extractor and precipitated with hexane. The yellow
product was washed with hexane and dried in vacuo. Yield:
1.1 g (15%).
Procedure II. The complex [RuPy4Cl2] (3.0 g, 6.2 mmol),
(C6H5BO)3, obtained as described in Procedure I from phenyl-
boronic acid (1.60 g, 13 mmol), and H2Cl2Gm (2.98 g, 19 mmol)
were dissolved/suspended in TFA (50 ml). The reaction mixture
was refluxed for 10 h, left overnight, and diluted with methanol.
The precipitate obtained was purified as described in Procedure
I. Yield: 0.41 g (9%).
Procedure III. [(CH3)4N]2[Ru(OH)Cl5] (1.68 g, 38 mmol),
H2Cl2Gm (2.56 g, 16 mmol), and sponge lead (1.7 g, 8.0 mmol)
were dissolved/suspended in dry nitromethane (50 ml) with stir-
ring under argon. The reaction mixture was heated to boiling,
and a solution of C6H5BCl(OiC4H9) (2.24 ml, 11.5 mmol) in
chloroform (50 ml) was added dropwise. The reaction mixture
was refluxed for 2 h, and an additional portion of H2Cl2Gm
(1.28 g, 8.0 mmol) was added. The reaction mixture was then
refluxed for 3 h with partial evaporation of solvent (≈30 ml) and
diluted with a two-fold volume of methanol. The precipitate
obtained was purified as described in Procedure I. Yield: 0.45 g
(16%). Anal. calc. for C18H10N6O6B2Cl2Ru: C, 29.12; H, 1.35;
Syntheses
Ru(Cl2Gm)3(BF)2 (1). [(CH3)4N]2[Ru(OH)Cl5] (2.35 g, 5
mmol) and sponge lead (1.5 g) were dissolved/suspended in dry
nitromethane (25 ml) under argon, and H2Cl2Gm (3.14 g, 20
mmol) was added. The reaction mixture was heated to 60 ЊC,
and a mixture of triethylamine (4.2 ml, 30 mmol) and freshly
distilled BF3ؒO(C2H5)2 (18 ml, 150 mmol) was added dropwise
for 30 min. The reaction mixture was heated for 2 h at 60 ЊC,
and an additional portion of sponge lead (1.5 g) was added.
The reaction mixture was refluxed for 1 h with partial evapor-
ation of solvent (≈10 ml), and an additional portion of
H2Cl2Gm (1 g) was added. The reaction mixture was left over-
night at room temperature and then evaporated to a small
volume. The oil-like residue was diluted with a three-fold
volume of methanol and filtered. The filtrate was precipitated
with water, and the yellow solid was reprecipitated with
chloroform–heptane (2 : 1) mixture. The product was washed
with hexane and dried in vacuo. Yield: 1.75 g (54%). Anal. calc.
for C6N6O6B2Cl6F2Ru: C, 11.51; N, 13.42; Cl, 34.04. Found: C,
11.56; N, 13.42; Cl, 34.16 %. MS PD: m/z 626 (M)ϩ
.
13C{1H}
ؒ
NMR (CDCl ): δ 131.3 (s, ClC᎐N). 11B NMR [CDCl3, rel.
᎐
3
= 18 Hz). IR (cmϪ1, KBr):
11B–19
F
to NaB(C6H5)4]: δ 11.1 d (J
906, 947 ν(N–O), 1176, 1242 ν(B–O) ϩ ν(B–F), 1506 ν(C᎐N).
᎐
UV-Vis (CHCl3): λmax (10Ϫ3ε/molϪ1 l cmϪ1) 255(8.6), 278(5.0),
349(5.2), 384(4.8), 417(19), 457(4.0) nm.
Ru(Cl2Gm)3(BnC4H9)2 (2). Procedure I. [(CH3)4N]2[Ru(OH)-
Cl5] (0.84 g, 1.9 mmol), H2Cl2Gm (1.28 g, 8 mmol), n-butyl-
boronic acid (0.41 g, 4 mmol), and sponge lead (1 g) were
dissolved/suspended in TFA (15 ml) under argon. The reaction
mixture was refluxed with stirring for 1 h with partial evapor-
ation of solvent (≈8 ml), and then additional portions of TFA
(10 ml), H2Cl2Gm (0.6 g), n-butylboronic acid (0.2 g) and
sponge lead (0.4 g) were added. The reaction mixture was
refluxed for 40 min with partial evaporation of solvent (≈2 ml)
and precipitated with water. The precipitate was filtered,
washed with water and then a small amount of methanol, and
extracted with chloroform. The chloroform solution was fil-
tered through a Silasorb SPH-300 layer (10 mm), evaporated to
N, 11.33; Cl, 28.72. Found: C, 29.06; H, 1.44; N, 11.23; Cl,
1
28.82%. MS PD: m/z 742 (M)ϩ . H NMR (CDCl3): δ 7.48 (m,
ؒ
6H, Ph), 7.89 (m, 4H, Ph). 13C{1H} NMR (CDCl3): δ 127.8 (s,
Ph), 129.1 (s, Ph), 130.2 (s, ClC᎐N), 131.8 (s, Ph). IR (cmϪ1
,
᎐
KBr): 888, 975 ν(N–O), 1229 ν(B–O), 1501 ν(C᎐N). UV-Vis
᎐
(CHCl3): λmax (10Ϫ3ε/molϪ1 l cmϪ1) 265(15), 350(4.5), 388(5.1),
420(13), 457(4.3) nm.
Preparation of Ru[(CH3S)2Gm]3(BF)2 (4). Methanethiol
(0.12 ml, 2.4 mmol) was dissolved in dry THF (20 ml) and
1204
J. Chem. Soc., Dalton Trans., 2002, 1203–1211

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t
a 0.843 M solution of C5H11ONa (1.9 ml), obtained from
Ru(CwGm)2(Cl2Gm)(BnC4H9)2 (7). Bis[2-(o-oxyphenoxy)]-
metallic sodium with tert-amylalcohol in THF, was added
under argon. The reaction mixture was cooled to Ϫ30 ЊC, and
the complex Ru(Cl2Gm)3(BF)2 (0.12 g, 0.19 mmol) was added
in 10 portions over 12 h. The reaction mixture was stirred for
1 h at Ϫ30 ЊC and left overnight at 0 ЊC. Then K2CO3 (0.5 g)
and CH3I (0.5 ml) were added to the reaction mixture, and it
was stirred for 2 h at room temperature. The reaction mixture
was filtered, and the filtrate was evaporated to dryness. The oil-
like residue was dissolved in warm methanol (≈15 ml) and pre-
cipitated with a small amount of water at 0 ЊC. The solid was
dissolved in chloroform, and chloroform solution was filtered
through the Silasorb SPH-300 layer (20 mm), evaporated to a
small volume, and precipitated with hexane. The precipitate
was washed with hexane and dried in vacuo. Yield: 0.081 g
(61%). Anal. calc. for C12H18N6O6S6B2F2Ru: C, 20.72; H, 2.59;
diethyl ether (1.5 g, 5.1 mmol) was added to a solution of
sodium methoxide, obtained from metallic sodium (0.19 g,
8.2 mmol) with dry methanol (15 ml). The reaction mixture was
refluxed for 30 min and evaporated to dryness, and the solid
residue was left at 90–100 ЊC for 1 h in vacuo. The resulting salt
and interphase carrier [(nC4H9)4N]Br (0.77 g, 5.1 mmol) were
dissolved/suspended in dry THF (50 ml), and a solution of the
complex Ru(Cl2Gm)3(BnC4H9)2 (1.2 g, 1.7 mmol) in THF
(30 ml) was added dropwise to the stirring reaction mixture for
2 h at 50 ЊC. The solution/suspension was stirred for 5 h at
50 ЊC, cooled to room temperature, and filtered. The filtrate was
evaporated to dryness. The solid residue was washed with water
and then methanol, dried in vacuo, and dissolved in chloro-
form. The chloroform solution was filtered through a Silasorb
SPH-300 layer (20 mm), evaporated to dryness and washed with
methanol, a small amount of diethyl ether and then hexane,
and dried in vacuo. Yield: 0.35 g (18%). Anal. calc. for
C46H50N6O16B2Cl2Ru: C, 48.60; H, 4.40; N, 7.40; Cl, 6.25.
N, 12.09; S, 27.68. Found: C, 20.69; H, 2.57; N, 12.12; S,
1
27.58%. MS PD: m/z 695 (M)ϩ . H NMR (CDCl3): δ 2.76
ؒ
(s, 18H, SCH3). 13C{1H} NMR (CDCl3): δ 17.4 (s, SCH3), 147.2
(s, C᎐N). 11B NMR [CDCl3, rel. to NaB(C6H5)4]: δ 10.8 d,
Found: C, 48.65; H, 4.44; N, 7.38; Cl, 6.17%. MS PD: m/z 1136
᎐
1
(J
= 17 Hz). IR (cmϪ1, KBr): 923, 960sh ν(N–O),
(M)ϩ . H NMR (CDCl3): δ Ϫ0.12 (m, 4H, BCH2), 0.33 [m, 4H,
ؒ
11B–19
F
1157,1222 ν(B–O)ϩ ν(B–F), 1479 ν(C᎐N). UV-Vis (CHCl ):
CH2(Bu)], 0.63 (t, 6H, CH3), 0.82 [m, 4H, CH2(Bu)], 3.40 (m,
4H, OCH2), 3.68 (m, 4H, OCH2), 4.03 (m, 8H, OCH2), 6.83 (m,
8H, Ph), 7.09 (m, 8H, Ph). 13C{1H} NMR (CDCl3): δ 14.0 (s,
CH3), 17.1 (br s, BCH2), 25.1 [s, CH2(Bu)], 25.5 [s, CH2(Bu)],
67.0 (s, OCH2), 69.7 (s, OCH2), 111.7 (s, Ph), 119.1 (s, Ph), 120.4
᎐
3
λmax (10Ϫ3ε/molϪ1 l cmϪ1) 259(13), 286(5.2), 391(4.3), 432(15),
479(22), 516(7.9) nm.
Ru[(C6H5S)2Gm]3(BF)2 (5). This complex was synthesized by
an analogous method to that used for 4 except that thiophenol
(0.21 ml, 1.9 mmol) was used instead of methanethiol and the
realkylation stage was omitted. The reaction mixture was
refluxed for 12 h, filtered, and precipitated with a three-fold
volume of ethanol. The solid was reprecipitated from chloro-
form solution with hexane. Yield: 0.15 g (74%). Anal. calc. for
C42H30N6O6S6B2F2Ru: C, 47.23; H, 2.81; N, 7.87; S, 18.03.
(s, Ph), 123.7 (s, ClC᎐N), 125.5 (s, Ph), 139.8 (s, OC᎐N), 143.6
᎐
᎐
(s, OPh), 148.9 (s, OPh). IR (cmϪ1, KBr): 936, 1004 ν(N–O),
1118 ν(B–O), 1512, 1540sh ν(C᎐N). UV-Vis (CHCl ): λ
᎐
3
max
(10Ϫ3ε/molϪ1 l cmϪ1) 276(10), 307(2.4), 395(12), 433(12) nm.
Ru(CwGm)3(BnC4H9)2 (8). This complex was synthesized by
an analogous method to 7 except that an excess of the disodium
salt of bis[2-(o-oxyphenoxy)]diethyl ether, obtained from
metallic sodium (0.28 g, 12.3 mmol) and bis[2-(o-oxyphenoxy)]-
diethyl ether (2.2 g, 7.7 mmol), was used and the reaction time
was 30 h.
The reaction mixture was filtered, and the filtrate was precipi-
tated with a three-fold volume of hexane. The precipitate was
removed by filtration, and the filtrate was evaporated to dry-
ness. The solid was washed with water and then methanol, and
the product was dissolved in chloroform. The chloroform solu-
tion was filtered through a Silasorb SPH-300 layer (20 mm),
evaporated to dryness, and extracted with a small amount of
diethyl ether. The extract was evaporated to dryness, and the
resulting orange solid was washed with hexane and dried in
vacuo. Yield: 0.32 g (14%). Anal. calc. for C62H66N6O21B2Ru: C,
Found: C, 47.18; H, 2.82; N, 7.80; S, 17.94%. MS PD: m/z 1067
1
(M)ϩ . H NMR (CDCl3): δ 7.07 (m, 12H, Ph), 7.19 (m, 18H,
ؒ
Ph). 13C{1H} NMR (CDCl3): δ 128.5 (s, Ph), 129.3 (s, Ph), 131.2
(s, SPh), 131.5 (s, Ph), 147.5 (s, C᎐N). 11B NMR [CDCl3, rel. to
᎐
11B–19
F
NaB(C6H5)4]: δ 10.8 d, (J
= 14 Hz). IR (cmϪ1, KBr): 904,
926 ν(N–O), 1158–1163, 1227 ν(B–O) ϩ ν(B–F), 1578 ν(C᎐N).
᎐
UV-Vis (CHCl3): λmax (10Ϫ3ε/molϪ1 l cmϪ1) 266(17), 307(5.1),
366(6.9), 428(19), 480(25), 516(9.0) nm.
Ru[(C6H5O)2Gm]3(BnC4H9)2 (6). Phenol (0.66 g) was added to
a solution of potassium methoxide, obtained from metallic
potassium (0.30 g, 7.7 mmol) with dry methanol (10 ml). The
reaction mixture was evaporated to dryness, and the solid
residue was heated at 100 ЊC for 1 h in vacuo. The solution/
suspension of the complex Ru(Cl2Gm)3(BnC4H9)2 (0.8 g, 1.14
mmol) in THF (10 ml) was added to the solution/suspension of
the resulting potassium phenolate in dry THF at Ϫ35 ЊC. The
reaction mixture was stirred for 2 h at this temperature and then
for 5 h at room temperature and filtered. The THF solution was
evaporated to dryness, and the solid residue was washed with
water and a water–methanol mixture (1 : 1) and then dried
in vacuo. The solid was dissolved in chloroform and the solution
was filtered through a Silasorb SPH-300 layer (20 mm). The
filtrate was evaporated to a small volume (≈3 ml), and a three-
fold volume of hexane was added. The resulting solution/
suspension was evaporated to dryness, and the dark-yellow
product was washed with hexane and dried in vacuo. Yield: 0.75
g (63%). Anal. calc. for C50H48N6O12B2Ru: C, 57.32; H, 4.59; N,
55.00; H, 4.88; N, 6.21. Found: C, 55.02; H, 4.81; N, 6.17%. MS
PD: m/z 1353 (M)ϩ
.
1H NMR (CDCl3): δ Ϫ0.12 (m, 4H,
ؒ
BCH2), 0.38 (m, 4H, CH2), 0.67 (t, 6H, CH3), 0.83 (m, 4H,
CH2), 3.68 (m, 12H, OCH2), 4.05 (m, 12H, OCH2), 6.82 (m,
12H, Ph), 7.09 (m, 12H, Ph). 13C{1H} NMR (CDCl3): δ 14.0 (s,
CH3), 25.1 (s, CH2), 25.5 (s, CH2), 67.1 (s, OCH2), 69.7 (s,
OCH2), 111.8 (s, Ph), 119.2 (s, Ph), 120.4 (s, Ph), 125.5 (s, Ph),
139.6 (s, C᎐N), 143.7 (s, OPh), 149.0 (s, OPh). IR (cmϪ1, KBr):
᎐
937, 1006 ν(N–O), 1117 ν(B–O), 1540 ν(C᎐N). UV-Vis (CHCl ):
᎐
3
λmax (10Ϫ3ε/molϪ1 l cmϪ1) 274(15), 304(6.0), 357(5.8), 394(11),
430(20), 458(30) nm.
Ru[(nC4H9NH)2Gm]2(Cl2Gm)(BC6H5)2 (9). The complex
Ru(Cl2Gm)3(BC6H5)2 (0.37 g, 0.5 mmol) was dissolved/
suspended in dry DMF at Ϫ5 ЊC, and a solution of an excess of
n-butylamine (0.9 ml, 9 mmol) in DMF (10 ml) was added
dropwise to the stirring reaction mixture for 2 h at this temper-
ature. The reaction mixture was left overnight at room tem-
perature and precipitated with a two-fold volume of water. The
brown product was filtered, dried in vacuo, and dissolved in
chloroform. The chloroform solution was filtered through a
Silasorb SPH-300 layer (20 mm), diluted with twice the volume
of hexane, and evaporated to dryness. The solid residue was
8.03. Found: C, 57.31; H, 4.57; N, 8.04%. MS PD: m/z 1047
1
(M)ϩ . H NMR (CDCl3): δ 0.50 (m, 4H, BCH2), 0.65 (t, 6H,
ؒ
CH3), 1.03 (m, 8H, CH2CH2), 6.86 (m, 12H, Ph), 7.14 (m, 6H,
Ph), 7.30 (m, 12H, Ph). 13C{1H} NMR (CDCl3): δ 14.0 (s, CH3),
17.2 (br s, BCH2), 25.4 (s, CH2), 25.5 (s, CH2), 116.7 (s, Ph),
124.5 (s, Ph), 129.6 (s, Ph), 142.0 (s, OPh), 155.1 (s, C᎐N).
᎐
᎐
IR (cmϪ1, KBr): 918, 988 ν(N–O), 1090 δ(B–O), 1556 ν(C᎐N).
UV-Vis (CHCl3): λmax (10Ϫ3ε/molϪ1 l cmϪ1) 260(11), 275(5.9),
367(4.5), 417(22), 453(4.3) nm.
J. Chem. Soc., Dalton Trans., 2002, 1203–1211
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Table 1 Crystallographic data and refinement details for Ru(Cl2Gm)3(BnC4H9)2 (2), Ru[(CH3S)2Gm]3(BF)2 (4), and Ru[(C6H5O)2Gm]3(BnC4H9)2 (6)
2
4
6
Empirical formula
FW
Color, habit
C14H18B2Cl6N6O6Ru
701.73
Orange, prism
0.58 × 0.36 × 0.15
C12H18B2F2N6O6RuS6
695.37
Red, prism
C50H48B2N6O12Ru
1047.64
Brown, prism
0.48 × 0.36 × 0.28
Crystal dimensions/mm
0.36 × 0.28 × 0.26
a/Å
b/Å
c/Å
26.238(5)
7.999(2)
13.927(3)
116.76(3)
2610(1)
4
10.518(2)
12.517(2)
19.574(4)
91.83(3)
2504.5(8)
4
17.654(2)
25.336(4)
13.483(1)
120.99(1)
5170(1)
4
β/Њ
V/Å3
Z
Crystal system
Space group
Dcalc/g cmϪ3
µ/mmϪ1
Monoclinic
C2/c
1.786
Monoclinic
P21/n
1.844
Monoclinic
C2/c
1.346
1.258
1.183
0.369
Data/restraints/parameters
Weighting schemea
Rb (%)
1840/0/196
2744/0/389
3757/0/398
2
2
2
1/[σ2(Fo ) ϩ (0.0722P)2 ϩ 2.84P]
1/[σ2(Fo )o ϩ (0.0428P)2 ϩ 1.18P]
1/[σ2(Fo ) ϩ (0.0561P)2 ϩ 3.16P]
0.0275
0.0724
1392
0.0212
0.0558
1392
0.0289
0.0837
2160
Rw c (%)
F(000)
GooFd
1.077
1.063
1.153
1/2
a P = (Fo2 ϩ 2Fc2)/3. b R = (Σ|Fo| Ϫ |Fc|)/Σ|Fo|. c Rw = [(Σ(w|Fo| Ϫ |Fc|)2/Σw|Fo|2]1/2 d GooF = [(Σw|Fo| Ϫ |Fc|)2/(Nobs Ϫ Nparam
. ) .
washed with a small amount of hexane and dried in vacuo.
Yield: 0.085 g (19%). Anal. calc. for C34H50N10O6B2Cl2Ru: C,
with participation of coordinated ligands. In particular, we
have unexpectedly isolated an organic [(CH3)3S]ϩ(CH3SO3)Ϫ
salt34 in the course of the synthesis of a dimethylsulfoxide
Ru(DMSO)4Cl2 solvate by the procedure described earlier.35
Moreover, the Ru3ϩ ion is apt to form stable square-planar
bis-dioximate complexes. Therefore, the attempt to extend the
procedures of the precursor synthesis, developed earlier for
iron(),26 to ruthenium() without any modification met with
failure. The poor donor ability displayed by the H2Cl2Gm
did not permit us to obtain clathrochelate ruthenium()
precursors starting from Ru(DMSO)4Cl2 in the manner pro-
posed by Grzybowski and co-workers for boron-containing
ruthenium() clathrochelates with aromatic, alicyclic, and
acyclic dioximes.25 Therefore, we managed to implement the
synthesis of hexachloride ruthenium() precursors under rigid
conditions [in particular, a mixture of nitromethane and SbCl3,
boiling TFA and BF3ؒO(C2H5)2 were used as reaction media]
with much lower yields compared to iron().
The fact that the approach employed met with success was to
a great extent caused by the low basicity and high protolytic
stability of the H2Cl2Gm. In most cases, the Ru2ϩ ion generated
in situ during the reduction of oxychloride ruthenium com-
pounds in the higher oxidation states with metallic lead in the
presence of electron-accepting SbCl3-type ligands also favored
the elimination of chloride ions from the inner coordination
sphere of ruthenium ions. As a result, we managed to obtain the
Ru(Cl2Gm)3(BF)2 and Ru(Cl2Gm)3(BnC4H9)2 complexes in
reasonable yields. However, the rigid conditions required for the
activation of the Ru2ϩ ions in the reaction with poorly coordin-
ating H2Cl2Gm imposes restrictions on the use of the synthetic
routes worked out in our laboratory. Such methods can be
employed only when capping agents (in particular, BF3,
alkylboronic acids, and their derivatives) are stable to protolytic
dissociation. When arylboronic acids and their derivatives
(especially, phenylboronic acid), which are more apt to proto-
lytic dissociation and transmetallization, were employed as
capping agents, one could observe an abrupt decrease in the
desired product yield induced by the destruction of the capping
agent. Thus, the reaction involved two competitive processes:
the formation of a clathrochelate, which was removed from the
reaction mixture because of its low solubility (this shifted the
equilibrium in the desired direction), and a protolytic dissoci-
ation of the capping agent. Consequently, one should deter-
mine the optimal conditions for a synthetic route (time and
temperature) that make it possible on the one hand to achieve a
maximal formation of the desired complex and, on the other, to
45.96; H, 5.63; N, 15.77. Found: C, 45.87; H, 5.58; N, 15.69%.
1
MS PD: m/z 888 (M)ϩ . H NMR (CDCl3): δ 0.93 (t, 12H,
ؒ
CH3), 1.42 (m, 16H, CH2CH2), 3.29 (m, 8H, NCH2), 5.26 (br s,
4H, NH), 7.46 (m, 6H, Ph), 7.93 (m, 4H, Ph). 13C{1H} NMR
(CDCl3): δ 13.6 (s, CH3), 19.4 (s, CH2), 33.3 (s, CH2), 44.5 (s,
NCH ), 124.6 (s, ClC᎐N), 127.4 (s, Ph), 127.8 (s, Ph), 131.7 (s,
᎐
2
Ph), 148.6 (s, NC᎐N). IR (cmϪ1, KBr): 905, 982 ν(N–O), 1221
᎐
ν(B–O), 1512, 1560 ν(C᎐N). UV-Vis (CHCl ): λmax (10Ϫ3ε/molϪ1
᎐
3
l cmϪ1) 263(9.0), 278(7.8), 436(7.3), 461(12) nm.
X-Ray crystallography
The details of crystal data collection and refinement param-
eters for Ru(Cl2Gm)3(BnC4H9)2 (2), Ru[(CH3S)2Gm]3(BF)2 (4),
and Ru[(C6H5O)2Gm]3(BnC4H9)2 (6) are listed in Table 1. Single
crystals of these complexes were grown from chloroform–
heptane (2), THF–iso-octane (4), and toluene–iso-octane (6).
Data were collected at 293 K on a CAD4 diffractometer using
Mo-Kα (β-filtered) radiation (λ = 0.71073 Å) by θ/2θ scans. The
structures were solved by the heavy-atom method, and refine-
ments were made by full-matrix least squares on F 2 for all data
with anisotropic thermal parameters for non-hydrogen and iso-
tropic parameters for hydrogen atoms. All calculations were
made using the SHELXTL-97 program package.33
CCDC reference numbers 168668–168670.
See http://www.rsc.org/suppdata/dt/b1/b107172f/ for crystal-
lographic data in CIF or other electronic format.
Results and discussion
Synthesis of precursors
Several pathways for the synthesis of ribbed-functionalized tris-
dioximate clathrochelate complexes (i.e., clathrochelates with
functionalizing substituents in α-dioximate fragments) have
been thoroughly analyzed earlier.26 The optimal synthetic route
is based on a preliminary isolation of a reactive halogenide
precursor and its further functionalization via the typical
nucleophilic substitution reactions so well known in organic
chemistry. The synthesis of ruthenium() clathrochelates is
complicated by a kinetic inertness of the starting ruthenium
solvato complexes in the reactions of coordinated ligand substi-
tution, as well as by the ability of ruthenium complexes to
undergo intra- and inter-molecular redox reactions, frequently
1206
J. Chem. Soc., Dalton Trans., 2002, 1203–1211

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Scheme 1
avoid significant decomposition of the capping agent, which
The reaction of Ru(Cl2Gm)3(BC6H5)2 with a 15% excess of
n-butylamine (calculated from tetrasubstituted clathro-
can eventually lead to the decomposition of the already-formed
complex. To avoid such negative phenomena during the syn-
thesis, we believe that it is expedient to add the capping agent in
excess at periodic intervals.
a
chelate) in DMF at 0 ЊC for 2 h resulted solely in trisubstituted
clathrochelate, and the substitution took place in two of the
three dioximate fragments (Scheme 1). In the case of the
Fe(Cl2Gm)3(BC6H5)2 precursor, only tetrasubstituted product
was obtained under analogous conditions. To produce its
ruthenium analog, a two-fold excess of n-butylamine was used,
and the reaction mixture was stirred in the final stage for 10 h at
room temperature. It should also be emphasized that when the
reaction with n-butylamine was carried out in DMF, it afforded
a great variety of clathrochelate framework destruction prod-
ucts and a mixture of square-planar bis-complexes and this
significantly decreased the desired product yield. Therefore, in
this case the reaction was started at a low temperature and
gradually increased up to room temperature (unlike the reac-
tion with iron complexes). When kept in air for a long time,
the Ru[(nC4H9NH)2Gm]2(Cl2Gm)(BC6H5)2 complex underwent
partial destruction, presumably because of redox reactions with
Synthesis of functionalized complexes
The pathways implemented for the modification of synthesized
hexachloride ruthenium() precursors are shown in Scheme 1.
The reactivity of such precursors in the reactions of nucleo-
philic substitution was somewhat lower than that of their
analogs with an encapsulated iron() ion. In particular, the
attempts to prepare a hexathiophenol ruthenium() clathro-
chelate using a C6H5SH/K2CO3 system in 1,4-dioxane proved to
1
be unsuccessful: the H and 13C NMR and PD mass spectra
indicated that a mixture of partial substitution products is
formed [as well as in the case of earlier-studied Fe(Cl2Gm)3-
(BC6H5)2/CH3SH/K2CO3 system].26
J. Chem. Soc., Dalton Trans., 2002, 1203–1211
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the participation of oxygen. A somewhat unexpected result was
obtained when DMF was replaced by chloroform: the inter-
action of Ru(Cl2Gm)3(BC6H5)2 with n-butylamine both at room
temperature and with prolonged stirring at 50–60 ЊC yielded
only one trisubstituted product, 10, as evidenced by the NMR
and mass spectra.
As with iron(), we managed to isolate di- and tri-crown
ether ruthenium() complexes 7 and 8 depending on the molar
ratio of precursor : salt of bis[2-(o-oxyphenoxy)]diethyl ether
and on the reaction time.
Structure and spectra
The composition and purity of the isolated functionalized
1
ruthenium() clathrochelates were first confirmed by H and
13C NMR spectroscopy (the integral intensities of functional-
1
izing and apical substituent protons in the H NMR spectra,
and the number of signals in the 13C NMR spectra was in
accordance with the proposed composition and symmetry of
the molecule). A small (from 1 to 2 ppm) systematic decrease in
the chemical shift of the signals assigned to azomethine frag-
ments in the 13C NMR spectra of ruthenium complexes com-
pared with their iron-containing analogs should be emphasized.
A substantial (from 30 to 40 cmϪ1) systematic short-frequency
shift in the stretching vibrations νC᎐N of such fragments was also
observed in the IR spectra of the ᎐synthesized complexes com-
pared with iron() compounds. The magnitudes of chemical
Fig. 2 Molecular structure of Ru[(CH3S)2Gm]3(BF)2 (4).
11B–19
F
shifts and spin–spin interaction constants (J
≈ 15 Hz)
in the 11B NMR spectra of a fluoroboronic Ru(Cl2Gm)3(BF)2
precursor and its ribbed-functionalized derivatives confirmed
a tetrahedral character of the apical boron atom coordination
polyhedron and the high symmetry of the O3BF moiety.
The crystal and molecular structures of three clathrochelates
obtained (one precursor and two functionalized complexes)
were determinated by X-ray analysis (Figs. 1–3). As expected,
the Ru–N distances (approximately 1.98–1.99 Å, Table 2) are
longer than the Fe–N ones (approximately 1.90–1.91 Å), but
Fig. 3 Molecular structure of Ru[(C6H5O)2Gm]3(BnC4H9)2 (6).
the increase (0.07–0.08 Å) is not significant. A similar variation
in the metal–nitrogen distance has also been observed in the
series of cyclohexanedion-1,2-dioximate clathrochelates.36
Judging from the magnitude of the physical ionic radius of a
low-spin Ru2ϩ ion in an octahedral environment,37 one might
have expected a more significant increase in the Ru–N distance.
However, such an increase is impeded by strong π-back-
bonding effects in the ruthenium() complexes.36 The increase
in the metal–nitrogen distance in ruthenium complexes led to
a decrease in the magnitude of the distortion angle φ of
the coordination polyhedron with a geometry intermediate
between a trigonal prism (TP, φ = 0Њ) and a trigonal antiprism
(TAP, φ = 60Њ).
Thus, the variation in geometry of coordination polyhedra in
passing from iron complexes to their ruthenium analogs may be
described as a rotary-translational expansion that gives rise to a
considerable (0.06–0.09 Å) increase in the distance, h, between
the bases of TPs and, consequently, to an increase in the size of
a macrobicyclic ligand cavity. In the series of both iron and
ruthenium compounds, the maximal distance between the
coordination polyhedron bases and minimal distortion angle
Fig. 1 Molecular structure of Ru(Cl2Gm)3(BnC4H9)2 (2).
1208
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φ (and, consequently, a maximal cavity size) were observed for
hexachloride precursors. Their functionalized derivatives have
greater distortion angles φ and smaller h values (Table 2).
The UV-vis spectra of the ruthenium() complexes obtained
exhibited bands of high intensity in the visible region, charac-
teristic of clathrochelates. A short wavelength shift of such
asymmetric Ru d
L π* charge transfer bands (CTBs)
proved to be 15–35 nm compared with the position of CTBs
in analogous iron complexes. The CTBs in C3-symmetric
ruthenium complexes were decomposed into three Gaussian
components: two of less intensity at the edges and one of higher
intensity in the center. The CTBs in the UV-vis spectra of the
synthesized sulfur-containing complexes were substantially (by
approximately 60 nm) shifted compared with their hexachloride
precursors. At the same time, the oxygen-containing substitu-
ents in dioximate fragments had practically no effect on the
position of the CTB. In passing from iron() to ruthenium()
complexes, the position of bands of high intensity in the UV
region, stipulated by the π–π* transitions in dioximate frag-
ments, changed negligibly as well.
All complexes synthesized in the toluene and acetonitrile
solutions exhibited extremely low luminescence quantum
yields, at least 500 times lower relative to [Ru(bpy)3]2ϩ in
acetonitrile solution. Also transient signals were not observed
during laser photolysis under these conditions. At the same
time, luminescence was observed in a frozen toluene matrix at
77 K. The clathrochelates obtained have wide luminescence
bands in the range of 500 to 700 nm. Summarized data on
luminescence maxima and relative quantum yields of lumin-
escence are presented in Table 3.
Electrochemistry
The cyclic voltammograms of the ruthenium complexes syn-
thesized exhibit reversible or quasi-reversible anodic processes
assigned to the Ru(/) couples.25 The oxidation half-wave
potentials as well as Tomesˇ criteria values, which were deter-
mined as a wave slope (∆E = E3/4 Ϫ E1/4) to characterize the
reversibility of a corresponding electrochemical redox process
(the ∆E value is equal to 56 mV for a one-electron revers-
ible reaction at 25 ЊC), are listed in Table 3. The cyclic voltam-
metry data give some information concerning the stability of
electrochemically generated ruthenium() clathrochelates.
The existence of a reverse wave on backscanning the potential
might provide evidence on the relative stability of these
complexes on the cyclic voltammetry time scale. Among the
ruthenium() clathrochelates studied, for Ru[(CH2)4Gm]3-
(BnC4H9)2, Ru(CwGm)2(Cl2Gm)(BnC4H9)2, Ru(CwGm)3(BnC4-
H9)2, Ru[(CH3S)2Gm]3(BF)2 and Ru[(nC4H9NH)2Gm]2(Cl2G-
m)(BC6H5)2 complexes the reverse waves were only observed,
both direct and reverse waves being well reproduced at repeated
cycling. For the rest of compounds there were no reverse waves
due to the reduction processes. Moreover, the oxidation process
was accompanied by formation of insoluble products followed
by passivation of the working electrode.
The data obtained make it possible to analyze the effects of
apical and ribbed substitutes on the half-wave potential E1/2
values. Earlier it was found26 for analogous iron() clathro-
chelates, that both the inductive and mesomeric changes,
characteristics of substituents in dioximate fragments with a
conjugated π-bond system, have more significant effects on the
oxidation potential values than the properties of the apical sub-
stituents. These conclusions are also true for ruthenium()
clathrochelates. As seen from Table 3, there is a relation
between E1/2 values and the Hammett σpara constants, whereas
no agreement has been found for Taft σI inductive constants.
Fig. 4 demonstrates the E1/2 Ϫ σpara correlation plot for fluoro-
boronic ruthenium clathrochelates, and this correlation is com-
pared with that obtained earlier for iron() complexes26 (the
correlation coefficient is 0.84 for ruthenium and 0.86 for iron
J. Chem. Soc., Dalton Trans., 2002, 1203–1211
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Table 3 Redox and emission characteristics for hexachloride clathrochelate ruthenium() precursors, resultant functionalized complexes and
analogous iron() clathrochelates
em
∆E/
λmax /
a
a
b
Compound
σI
σpara
E1/2/mV
mV
nm
φem
Ru(Cl2Gm)3(BC6H5)226
Fe(Cl2Gm)3(BC6H5)2
Ru(Cl2Gm)3(BnC4H9)226
Fe(Cl2Gm)3(BnC4H9)2
Ru(Cl2Gm)3(BF)226
0.47 [0.10]
0.227 [Ϫ0.01]
0.227 [Ϫ0.19]
0.227 [0.062]
1360
1360
1330
1320
1340
1415
1120
895
830
670
840
800
60
80
60
90
80
60
60
80
65
60
85
100
90
60
60
570
550
590
0.0010
0.031
0.040
0.035
0.033
0.0031
0.12
0.47 [Ϫ0.08]
0.47 [0.52]
Fe(Cl2Gm)3(BF)2
Ru[(C6H5S)2Gm]3(BF)2
Fe[(C6H5S)2Gm]3(BC6H5)2
Ru[(CH3S)2Gm]3(BF)2
[0.52]
0.27
0.15 [0.062]
[Ϫ0.01]
0.00 [0.062]
[Ϫ0.01]
620, 700
610
26
[0.10]
0.19 [0.52]
[0.10]
0.38 [Ϫ0.08]
26
Fe[(CH3S)2Gm]3(BC6H5)2
Ru[(C6H5O)2Gm]3(BnC4H9)226
Fe[(C6H5O)2Gm]3(BnC4H9)2
Ru(CwGm)3(BnC4H9)226
Ϫ0.32 [Ϫ0.19]
500
0.38 [Ϫ0.08]
Ϫ0.32 [Ϫ0.19]
690
460
780
580
Fe(CwGm)3(BnC4H9)2
Ru(CwGm)2(Cl2Gm)(BnC4H9)2
0.38(OPh)
0.47(Cl)
[Ϫ0.08]
0.47(Cl)
0.10(nBuNH)
[Ϫ0.10]
Ϫ0.32(OPh)
0.227(Cl)
[Ϫ0.19]
500, 600
0.049
0.41
0.22
Ϫ0.14
Ϫ0.14
·
·
·
·
Fe(CwGm)2(Cl2Gm)(BnC4H9)2
670
560
65
95
26
Ru[(nC4H9NH)2Gm]2(Cl2Gm)(BC6H5)2
0.227(Cl)
550
0.010
Ϫ0.63(nBuNH)
[Ϫ0.01]
Fe[(nC4H9NH)2Gm]2(Cl2Gm)(BC6H5)2
Ru[(CH2)4Gm]3(BF)240
200
850
745
645
570
940
785
1250
1100
170
70
80
60
70
70
60
65
70
26
Ϫ0.05 [0.52]
Ϫ0.15 [0.062]
Fe[(CH2)4Gm]3(BF)2
Ru[(CH2)4Gm]3(BnC4H9)241
Ϫ0.05 [Ϫ0.08]
Ϫ0.15 [Ϫ0.19]
Fe[(CH2)4Gm]3(BnC4H9)2
40
Fe[(C6H5)2Gm]3(BF)2
0.10 [0.52]
Ϫ0.05 [0.52]
0.00 [0.52]
0.10(Ph)
0.47(Cl)
[0.52]
0.10(Ph)
0.38(OPh)
[0.52]
0.10(Ph)
0.10(nBuNH)
[0.52]
0.10(Ph)
0.19(CH3S)
[0.52]
Ϫ0.01 [0.062]
Ϫ0.17 [0.062]
0.00 [0.062]
Ϫ0.01(Ph)
0.227(Cl)
40
Fe[(CH3)2Gm]4(BF)2
26
FeGm3(BF)2
27
Fe[(C6H5)2Gm]2(Cl2Gm)(BF)2
0.223
0.193
0.10
0.069
·
·
·
·
·
·
·
·
[0.062]
27
Fe[(C6H5)2Gm]2(CwGm)(BF)2
Ϫ0.01(Ph)
Ϫ0.32(OPh)
[0.062]
Ϫ0.01(Ph)
Ϫ0.63(nBuNH)
[0.062]
Ϫ0.01(Ph)
Ϫ0.00(CH3S)
[0.062]
800
400
880
90
75
70
Ϫ0.113
Ϫ0.217
Ϫ0.007
Fe[(C6H5)2Gm]2[(nC4H9NH)2Gm](BF)2
27
27
Fe[(C6H5)2Gm]3[(CH3S)2Gm](BF)2
0.13
a Taft (σI) and Hammet (σpara) constants for substituents in α-dioximate fragments [capping groups]. σΣ = n/(m ϩ n)σ1 ϩ m/(m ϩ n)σ2, σn
σn/2.5.38,39 b Quantum yield of luminescence in the frozen toluene glass matrix relative to [Ru(bpy)3]2ϩ acetonitrile solution.
=
1
ϩ
than in iron complexes (the correlation plot slopes are 1.35 and
2.02, respectively). At the same time, an attempt to obtain
a similar plot for n-butylboronic clathrochelates turned out
to be less successful. In our opinion, this might be the result
of other effects, in particular structural changes of coordin-
ation polyhedra, rather than electromeric properties of the
substituents.
The peculiarity of the electrochemical behavior of ruthen-
ium clathrochelates, which distinguishes them from analogous
iron() complexes, is their lower sensitivity to the replace-
ment of substituents in the capping groups. Moreover, if the
dioximate fragments contain electron-accepting substituents,
the ruthenium complexes oxidation potential becomes practic-
ally independent of apical substituent features as seen from
the E1/2 values for the hexachloride precursors). At the same
time, for the macrobicyclic ruthenium() tris-dioximates the
replacement of fluoroboronic capping groups onto n-butyl-
boronic ones resulted in a cathodic shift of the E1/2 value by
approximately 200 mV (Table 3).
Fig. 4 Correlation of E1/2 for Ru3ϩ/Ru2ϩ (1, ᭹) and Fe3ϩ/Fe2ϩ (2, ꢀ)
couples of the fluoroboronic clathrochelates with Hammett σpara values.
Conclusion
clathrochelates). It should be noted that this correlation is
rather qualitative because of the quasi-reversible nature of
the oxidation processes for these clathrochelates. However,
they enable us to conclude that ruthenium complexes are less
sensitive to the change of substituent in dioximate fragments
Ribbed-functionalized clathrochelate ruthenium() tris-
dioximates were obtained by the nucleophilic substitution of
reactive chlorine atoms in the initially obtained hexachloride
precursors using procedures proposed earlier for their iron()
analogs.
1210
J. Chem. Soc., Dalton Trans., 2002, 1203–1211

View Article Online
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However, the synthesis of clathrochelate ruthenium() pre-
cursors was successfully performed under substantially more
rigid conditions than in the case of iron(). The luminescent
characteristics (in particular, quantum yield) of the obtained
ruthenium complexes lose to those of ruthenium() tris-
phenanthrolinates and tris-bipyridinates. At the same time,
ruthenium() clathrochelates have highly intense absorption
bands in the visible region and their maxima depend on the
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The directed apical and ribbed functionalization of ruthen-
ium() tris-dioximate clathrochelates allows high selectivity in
the binding of DNA fragments. The possibility of effective
functionalization of both free and DNA-bound complexes is
the significant advantage of reactive tris-dioximates compared
with most of their phenanthroline and bipyridine analogs. We
assume that variation of both apical and ribbed substituents (in
particular, increasing the clathrochelate framework rigidity and
increasing the number of aromatic substituents) as well as
interaction of complexes with DNA will allow improvement of
the luminescent parameters of ruthenium() clathrochelates.
We also plan to investigate thoroughly the photophysics of
both synthesized macrobicyclic ruthenium() complexes and
products of their interaction with nucleic acids.
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Acknowledgements
Support of the Russian Fund of Basic Research (Grants
N99-03-32498 and 00-03-32578) is gratefully acknowledged. We
acknowledge Prof. J.-P. Sauvage, who directed our attention to
the investigation of clathrochelate ruthenium() compounds.
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