Sulfur-containing terpyridine derivatives: Synthesis, coordination properties, and adsorption on the gold surface

Article abstract of DOI:10.1007/s11172-012-0322-0

Approaches to the synthesis of organic aurophilic ligands, viz., sulfur-containing 2,2′:6′,2'-terpyridine derivatives, were developed. Complexation reactions of the terpyridine ligands having thiophenol, diaryl disulfide, and alkyl aryl sulfide fragments with Co ⁱⁱ, Ni ⁱⁱ, and Rh ⁱⁱⁱ salts were studied. The structures of the coordination compounds obtained were established based on the elemental analysis data, density functional calculations, and electron spectroscopy. The structure of the complex of 4′-(4-methylsulfanyl)-2,2′:6′,2-terpyridine with Ni(BF₄)₂ was also established by X-ray diffraction analysis. A method was proposed for the preparation of gold nanoparticle dimeric aggregates via coordination interactions of the ligands adsorbed on the gold nanoparticle surface with transition metal ions. A degree of nanoparticle aggregation upon their reaction with solutions of complex compounds of aurophilic nitrogen-containing ligands was determined by the concentration of the solution of the complex used.

Full text of DOI:10.1007/s11172-012-0322-0

Russian Chemical Bulletin, International Edition, Vol. 61, No. 12, pp. 2265—2281, December, 2012
2265
Sulfurꢀcontaining terpyridine derivatives: synthesis,
coordination properties, and adsorption on the gold surface
R. B. Romashkina, A. G. Majouga, E. K. Beloglazkina, D. A. Pichugina, M. S. Askerka,
A. A. Moiseeva, R. D. Rakhimov, and N. V. Zyk
Department of Chemistry, M. V. Lomonosov Moscow State University,
Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: bel@org.chem.msu.ru
Approaches to the synthesis of organic aurophilic ligands, viz., sulfurꢀcontaining 2,2´:6´,2ꢀ
terpyridine derivatives, were developed. Complexation reactions of the terpyridine ligands
having thiophenol, diaryl disulfide, and alkyl aryl sulfide fragments with CoII, NiII, and RhIII
salts were studied. The structures of the coordination compounds obtained were established
based on the elemental analysis data, density functional calculations, and electron spectroscopy.
The structure of the complex of 4´ꢀ(4ꢀmethylsulfanyl)ꢀ2,2´:6´,2ꢀterpyridine with Ni(BF4)2
was also established by Xꢀray diffraction analysis. A method was proposed for the preparation of
gold nanoparticle dimeric aggregates via coordination interactions of the ligands adsorbed on
the gold nanoparticle surface with transition metal ions. A degree of nanoparticle aggregation
upon their reaction with solutions of complex compounds of aurophilic nitrogenꢀcontaining
ligands was determined by the concentration of the solution of the complex used.
Key words: sulfurꢀcontaining terpyridines, synthesis, adsorption on the gold surface, transiꢀ
tion metal complexes, density functional calculations, electrochemistry, Xꢀray diffraction,
terpyridineꢀcontaining disulfides.
In the last years, materials based on gold nanoparticles
(NP) have become objects of serious study, since they are
used in optical, nanoelectronic, and photonic devices,
chemical and biological sensors, and catalysts.1—3 The
major problem is that metal NP are unstable in solution
and have tendency to agglomeration. To prepare stable
NP, it is necessary to use stabilizing agents, which, being
adsorbed on the nanoparticle surface, would prevent their
association. Sulfurꢀcontaining organic compounds (thiols,
sulfides, disulfides, etc.) are most often used as gold NP
stabilizers, which undergo chemosorption on the gold surꢀ
face with the formation of an Au—S covalent bond.4
The modification of gold NP with functionalized orꢀ
ganic ligands allows one to impart new useful properties to
the nanoparticles. If terminal donor groups are present in
the ligands, metal complexes can form on the NP surface.
We proposed a new method for the preparation of
dimeric and trimeric NP aggregates via coordination inꢀ
teractions of ligands adsorbed on their surface with transiꢀ
tion metal ions.5 Examples of the preparation of such agꢀ
gregates described in the literature are based on the reacꢀ
tion of complementary parts of DNA molecules,6 electroꢀ
static interactions,7 hydrogen bonding,8 or covalent interꢀ
actions of polythiols with several NP.9 However, in most
cases such interactions proceed with low yields and lead to
the irreversible binding of NP to each other. The advantage
of our method is the controlled preparation of NP ensemꢀ
bles with different degrees of aggregation and reversibility
of their formation, since when a stronger complexing agent
is added to the system, it can bind to the metal ion and the
starting monomeric NP can be regenerated.
The purpose of the present work was to synthesize new
aurophilic terpyridine ligands and study their reactions
with transition metal ions; investigate adsorption of the
ligands and coordination compounds obtained on the surꢀ
face of gold electrodes and gold NP by a combination of
physicochemical and quantum mechanical methods, as
well as to find a possibility of using this type ligands for the
preparation of gold NP dimeric aggregates.
2,2´:6´,2ꢀTerpyridine derivatives (TerPy) containing
three donor nitrogen atoms are widely used as ligands in
coordination chemistry. Such ligands are able to coordiꢀ
nate metal ions of different nature and form complexes of
the composition 2 : 1 or 1 : 1 depending on the metal type
and reaction conditions.10,11 Bisꢀterpyridine complexes
with symmetric structure are commonly formed when
CoII, NiII, CuII, ZnII, FeII, etc. are involved in complexꢀ
ation reactions. In most of such coordination compounds
of the composition [M(TerPy)2X2] (X = Cl–, ClO4
,
–
PF6–, etc.), the metal ion is in the pseudooctahedral enviꢀ
ronment, with six nitrogen atoms of two terpyridine fragꢀ
ments being involved in the complexation.5,10 However,
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2244—2260, December, 2012.
1066ꢀ5285/12/6112ꢀ2265 © 2012 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
Romashkina et al.
usually it is impossible to use these metals for the binding
of two different terpyridine fragments upon a sequential
introduction of the ligands, and the complexes of the comꢀ
position 2 : 1 are formed independently of the initial
ligand : metal salt molar ratio. The involvement of these
metal salts in the complexation reaction with a mixture of
two different ligands gives mixtures of homoꢀ and heteroꢀ
ligand complexes.
were obtained by the Kröhnke condensation from
2ꢀacetylpyridine and aromatic aldehydes containing meꢀ
thylthio or tertꢀbutylthio groups (Scheme 1).
To obtain thiol 3, terpyridine 2 was hydrolyzed with
hydrochloric acid. A mixture of thiol 3 and disulfide 4 was
isolated as the hydrolysis product. To obtain the individuꢀ
al thiol, disulfide 4 was reduced with triphenylphosphine
without isolation from the reaction mixture (Scheme 2).
The terpyridine ligands containing a vinylaryl fragment
were obtained according to Scheme 3. The reaction of
4´ꢀ(4ꢀmethylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (5) with
Nꢀbromosuccinimide led to a mixture of the target monoꢀ
bromide 6 and dibromide 7 (see Scheme 3). Monoꢀ
bromide 6 was isolated from the mixture and involved in
the Arbuzov reaction with triethyl phosphite to obtain
phosphonate 8. The Horner—Wadsworth—Emmons reacꢀ
tion of compound 8 with methylthioꢀ and tertꢀbutylthioꢀ
substituted aromatic aldehydes gave the target terpyridines
9 and 10 (Scheme 4), which contained vinylaryl linkers in
their structures. The spinꢀspin coupling constants of the
vinyl protons in the 1H NMR spectra of compounds 9 and
10 are equal to ~16 Hz, that confirms the Eꢀconfiguration
of the double bond in the compounds obtained.
A strategy for the preparation of bisꢀterpyridine comꢀ
plexes with the unsymmetric structure was developed based
on the stepꢀbyꢀstep introduction of two ligand molecules
into the complexation reaction with metal ions (RhIII
,
RuIII, OsIII, more seldom CoII),11—14 which in the first
step are able to form complexes [M(TerPy)X3] (X = Hal).
The use in the second step of reducing agents, for example
Nꢀethylmorpholine, allows one to obtain the correspondꢀ
ing unsymmetric complexes, in which the metal ion has
oxidation state +2.
In the present work, we describe new bifunctional auroꢀ
philic TerPy derivatives, which are able of both being adꢀ
sorbed on the gold surface and reacting with transition
metal ions to form Aꢀtype complex compounds.
The complex of ligand 1 with cobalt(II) hexafluoroꢀ
phosphate (11) was synthesized according to Scheme 5.
Ligand 1 was refluxed with Co(NO3)2•6H2O in methanol
followed by the addition of a saturated solution of amꢀ
monium hexafluorophosphate.
Structurally related CoII and NiII complexes were obꢀ
tained from ligands 1, 2, 9, 10 and Co(ClO4)2•6H2O or
Ni(BF4)2•6H2O by reflux in methanol (Scheme 6).
The structure of complex 14 was confirmed by Xꢀray
diffraction (the crystallographic data, Xꢀray diffraction
data collection and structure refinement statistics are givꢀ
en in Table 1), as well as by quantum chemical simulaꢀ
tion. According to the crystallographic data (Fig. 1, Table 2),
the metal atom in the structure of complex 14 coordinates
six N atoms of two terpyridine fragments and has a disꢀ
torted octahedral ligand environment, similarly to other
known MII terpyridine complexes.5,10 Optimization of the
XS = SR, SH, S—SR; R = Me, But
The ligands obtained contained aryl and vinylaryl subꢀ
stituents as the linkers.
Results and Discussion
Synthesis of ligands and complexes. 2,2´:6´,2ꢀTerꢀ
pyridine derivatives 1 and 2 containing an aromatic linker
Scheme 1
R = SMe (1), SBut (2)
Yield (%): 42 (1), 45 (2).

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2267
Scheme 2
Scheme 3
Scheme 4
i. ButOK, toluene, .
R = SMe (9), SBut (10). Yield (%): 64 (9), 57 (10)
structure of complex 14 by the density functional theoꢀ
ry revealed that the conformations of the nonrigid fragꢀ
ments and the environment of the central atom are similar
to those found for the solid phase. The calculated geometꢀ
ric parameters agree with the results of the Xꢀray diffracꢀ
tion analysis with good accuracy. Thus, an average Ni—N
distance obtained by Xꢀray analysis (2.074 Å) is close to
the calculated distance (2.098 Å).

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Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
Romashkina et al.
Scheme 5
Scheme 6
i. Co(ClO4)2•6H2O, MeOH, ; ii. Ni(BF4)2•6H2O, MeOH, ; iii. Co(ClO4)2•6H2O, MeOH, .
R = SMe (12, 14, 16), SBut (13, 15, 17)
Yield (%): 89 (12), 83 (13), 61 (14), 57 (15), 48 (16), 66 (17).

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2269
Fig. 1. Molecular structure of the [Ni(1)2]2+ cation (in comꢀ
plex 14) according to the Xꢀray diffraction data.
Note. Fig. 1 is available in full color in the onꢀline version of the
journal (http://www.springerlink.com/issn/1573ꢀ9171/current).
Fig. 2. A structural fragment of the Co2+ complex with two
molecules of thiol 3 (compound 19) optimized by the density
functional theory. Hydrogen atoms are not shown.
Note. Fig. 2 is available in full color in the onꢀline version of the
journal (http://www.springerlink.com/issn/1573ꢀ9171/current).
The terpyridine ligands containing thiol and disulfide
groups were involved in the complexation reactions with
cobalt(II) perchlorate. According to the elemental analyꢀ
sis data, a complex of the composition L : M = 1 : 1 was
obtained in the case of disulfide ligand 4, whereas in the
case of thiol 3 it was a complex with the ratio L : M = 2 : 1
(Scheme 7). The optimization of the structure of the comꢀ
plexes with such a ratio by the density functional theory
showed that complexes 18 and 19, like complex 14, have
the octahedral ligand environment. Figure 2 shows a sugꢀ
gested structure for complex 19. The calculated average
Co—N distance was 2.041 Å.
In this case, we failed to obtain crystals suitable for
Xꢀray diffraction studies, since the complexes have an exꢀ
tremely low solubility in organic solvents. In the case of
disulfide complex 18, this fact is possibly explained by its
polymeric structure (see Scheme 7).
Table 1. Crystallographic data, Xꢀray diffraction data collection
and structure refinement ststistics for of compound 14
The mixedꢀligand complexes of terpyridine derivatives
1 and 2 with RhIII ions binding two different terpyridine
ligands were synthesized according to Scheme 8. When
refluxed with RhCl3 in aqueous ethanol, ligands 1 and 2
formed the [Rh(TerPy)Cl3] complexes, which were furꢀ
ther involved in the reaction with 1,4ꢀbis(terpyridinꢀ4´ꢀ
yl)benzene (20).
Adsorption of the ligands and coordination compounds
obtained on the gold surface. The electrochemical studies
of the terpyridine ligands and their complexes were carried
out by cyclic voltammetry (CV) using glassy carbon (GC)
and gold electrodes.
The reduction of alkyl aryl sulfide ligands 1, 2, 9, and
10 on the GC electrode takes place in three steps at the
potentials Epc from –1.79 to –1.92 V corresponding to the
reduction potentials of the terpyridine fragment15 (Table 3,
Fig. 3, a). The oxidation of compounds 1 and 2 occurs in
Parameter
Value
Molecular formula
Molecular weight
Т/K
Crystal size/mm
Crystal shape
Crystal system
Space group
Unit cell parameters
C44H34В2F8N6NiS2
943.22
100(2)
0.42×0.31×0.24
Red prisms
Monoclinic
P21/c
a/Å
b/Å
c/Å
33.8990(16)
15.1523(7)
15.9273(8)
95.4100(10)
8144.6(7)
8
/deg
V/Å3
Z
dcalc/g cm–3
1.538
0.659
3856
Absorption coefficient, /mm–1
F(000)
Scanning range,
0.60—29.00
Table 2. Selected interatomic distances (d) and bond angles ()
for compound 14

min—max/deg
h, k, l ranges
–46  h  43
—20  k  20
–21  l  21
21631
Bond distance d/Å
Bond angle
/deg
Number of measured reflections
Number of unique reflections
Rint
Number of refinement variables
Goodness of fit on F2
R1 (I > 2(I))
wR2 (I > 2(I))
R1 (all data)
wR2 (all data)
Ni(1)—N(1A) 1.998(2)
Ni(1)—N(1) 2.000(2)
Ni(1)—N(2A) 2.108(2)
Ni(1)—N(2) 2.109(2)
Ni(1)—N(3) 2.110(2)
Ni(1)—N(3A) 2.118(2)
S(1)—C(19) 1.759(3)
S(1)—C(22) 1.793(3)
N(1A)—Ni(1)—N(1) 173.48(9)
N(1A)—Ni(1)—N(2A) 77.26(9)
N(1)—Ni(1)—N(2A) 109.23(9)
N(1A)—Ni(1)—N(2) 103.08(9)
13825
0.0393
1139
0.977
0.0525
0.1681
0.1015
0.1364
N(1)—Ni(1)—N(2)
N(2A)—Ni(1)—N(2)
77.84(9)
91.60(9)
N(1A)—Ni(1)—N(3) 101.92(9)
N(2A)—Ni(1)—N(3) 91.67(9)

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Romashkina et al.
Scheme 7
i. Co(ClO4)2•6H2O, MeOH, .
Scheme 8
i. RhCl3, EtOH/H2O, ; ii. 1) EtOH/H2O, 2) NH4PF6, .
R = SMe (21, 23), SBut (22, 24)
Yield (%): 36 (21), 30 (22), 45 (23), 44 (24).

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2271
Table 3. Electrochemical reduction (ERed) and oxidation (EOx) potentials of terpyridine ligands and complexes on GC and Au
electrodes measured by CV relative to Ag|AgCl|KCl(sat.)a
Ox
Red
Ox
Red
Ox
Red
Comꢀ
poum
Elecꢀ
trode
Ep
–Ep
Comꢀ Elecꢀ
pound trode
Ep
–Ep
Comꢀ Elecꢀ
pound trode
Ep
–Ep
V
V
V
1
GC
1.27
1.50
1.92
2.12
2.30 (2.13)
1.39 (ads.)
1.74 (1.65)
9
GC
Au
1.84 (1.72) 12c
2.14
0.74 (0.61)
1.48 (1.36) 13
1.84 (1.68)
Au
1.14
1.54
0.82 (0.54)
1.63 (1.58)
1.80
(ads.)
0.37
(0.22)
1
Au
Pt
1.54
1.70 (1.53)
(ads.)
2
(0.28; 0.26; 0.84) 1.96 (1.86)
1.36 (0.62)
GC
1.13b 1.79
2.07
2.03
13
Au
0.76 (Au—S)
1.64
1.92
0.84 (0.63)
1.19
1.70
10
GC
Au
0.42
(0.24)
0.74 (0.55) (ads.)
1.44 (1.28)
2.71 (2.21)
2
Au
0.93 (Au—S)
1.50 (ads. N)
1.76
1.80
2.04
13d
0.96
1.36 (0.61)
(ads.)
10
0.37 (0.18) 0.77 (0.58)
2.01
(ads.)
1.18
1.19
18
GC 0.31 (0.28)
0.63
4
GC
0.67
1.11
0.95 (S—S)
1.74
1.41 (1.29)
1.54
0.82 (S—S)
1.13
1.99 (1.87)
2.26 (2.18)
2.37
0.82 (Au—S)
1.22 (S—S)
1.59
1.80
2.04
1.61 (1.56)
2.02 (1.86)
0.57
0.78 (Au—S)
1.16
12
GC
Au
1.36
1.54
1.68 (1.52) 18
1.86 (1.63) (ads.)
1.96 (1.84)
Au
4
Au
(ads.)
12
1.36
1.10 (ads.)
1.61
9
GC
0.33
0.65 (0.59)
(ads.)
1.68 (1.52)
1.84
(0.24) 1.44 (1.37)
2.04 (1.86)
2.01
a DMF, 0.1 M Bu4NClO4, 200 mV s–1. The reverse peak potentials are given in parentheses. Ep is the peak potential.
b Only in the second and subsequent potential scans; corresponded to the oxidation of the S—S fragment.
c Adsorbed ligand 1, Au electrode + Co(ClO4)2.
d Adsorbed ligand 2, Au electrode + Co(ClO4)2.
one irreversible step at Epa = 1.27 and 1.13 V, respectively,
apparently, at the sulfide fragment.16,17 For compounds 9
and 10, there is a second peak in the oxidation region
corresponding probably to the oxidation of the C=C bond.
Note that in the reverse potential scan, a reduction peak at
Epc = –0.94 V appears in the CV curve of ligand 2 after
passing the anodic peak potential. A similar peak was found
in the CV curve of disulfide 4; it corresponded to the reꢀ
duction of the S—S fragment. Such a peak was absent in
the CV curve of methyl derivative 1. It is obvious that the
radical cation formed by the oxidation of sulfide 2 decomꢀ
poses to radical ArS•, subsequently giving disulfide 4, and
the stable tertꢀbutyl cation (Scheme 9). In the case of
ligand 1 such a decomposition, which would have led to
a considerably less stable methyl cation, does not take place.
The first step of the reduction of disulfide 4 involves
apparently the S—S bond (Epc = –0.95 V). Further reducꢀ
tion steps take place at the terpyridine fragments.
In the CV curves of cobaltꢀcontaining complexes 12,
13, and 18, in contrast to the CV curve of the free ligands,
two additional peaks corresponding to the transitions
CoII  CoI and CoI  Co0 are present in the cathoꢀ
dic scan (see Table 3, Fig. 3). In the case of complexes 12
and 13, both transitions are reversible. The reduced
forms of the complexes containing CoI and Co0 are
stable in solution. This is confirmed by the absence of
the oxidative desorption of metallic Co from the elecꢀ
trode surface in the CV curves during the reverse potenꢀ
tial scans.
In the CV curves of sulfide complexes 12 and 13,
a reversible peak of the CoIII  CoII transition is also
observed in the oxidation region. The presence of three
reversible redox transitions at low potentials makes comꢀ
plexes 12 and 13 promising for their studies as catalysts for
redox reactions.
Scheme 9
To confirm the adsorption of the compounds under
study on the Au surface, the Au electrode was kept for 20 h
in solution of a ligand or a complex (C = 10–3 mol L–1),
then washed with acetone and dried. The thus treated elecꢀ

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Romashkina et al.
a
b
2 A
5 A
0
–1.0
E/V
0
–1.0
–2.0
E/V
2 A
c
d
2 A
0
–1.0
–2.0 E/V
1.0
0
–1.0
–2.0
E/V
Fig. 3. Cyclic voltammograms (DMF, the concentration of solution 5•10–4, 0.1 M Bu4NClO4): a ligand 2, GC electrode (solid line),
and complex 13, Au electrode (dashed line); b ligand 4, Au electrode (the arrows in the figure show the change in the peak intensities
with time; the first curve was recorded in 1 min, the last in 20 min after dipping the electrode in the solution); c complex 18,
Au electrode, solution (solid line), the same complex adsorbed on the Au electrode (dashed line), and complex formed on the surface
of the Au electrode upon keeping the electrode with ligand 2 adsorbed on it in the solution of Co(ClO4)2 (dottedꢀandꢀdashed line);
d complex 12, GC electrode (lower curves) and the same complex, GC electrode, in the presence of excess of BunI (upper curves).
trode was placed in the pure supporting electrolyte to meaꢀ
sure a CV curve.
measured during the first hours of the contact of the Au
electrode with the solution of 2 has a reduction peak of the
terpyridine fragment coordinated to Au at Epc = –1.47 V,
which gradually disappears, being completely replaced
with the peak Epc = –0.82 V approximately after 20 h
(Scheme 10).
For SMeꢀsubstituted terpyridines 1 and 9 no reduction
peak of the Au—S fragment is observed in the CV; thus,
their chemosorption with the formation of the Au—S bond
does not occur.
To validate this suggestion, we calculated the bond
energy of SMeꢀsubstituted terpyridine 9 with the Au20 gold
cluster. This cluster was chosen as a model due to its high
stability;19 the atoms on the cluster faces follow the Au
surface motif. To determine the most probable sorption
centers, a visualization of the molecular orbitals of the
The reduction peaks of sulfide ligands 1, 2, 9, and 10
on the Au electrode were slightly shifted to the anodic
side as compared to the GC electrode. For tertꢀbutylꢀ
containing ligands 2 and 10, an additional reduction peak
of the Au—S bond was observed in the CV curve at
Epc = –0.93 V. This is an evidence of a possibility of its
adsorption on the gold surface with the cleavage of the
C—S bond. However, the initial adsorption process of
ligands 2 and 10 on Au proceeds apparently due to the
coordination of the nitrogen atoms of the terpyridine fragꢀ
ment, similarly to that described in the work,18 and only
after that the "reorientation" occurs with adsorption of the
sulfur atom and the resulting formation of the Au—S bond.
This suggestion is supported by the fact that the CV curve

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2273
Scheme 10
Au20 cluster was carried out. The calculations performed19
showed that the bonding of the gold clusters with the
ligands is effected by means of electron density transfer to
the LUMO of the cluster. The shape of the LUMO of the
Au20 cluster (Fig. 4) shows that the largest deficiency of
electron density is experienced by the apical gold atom
and, consequently, it is a suggested active center.
the thiol with the cluster upon its coordination by the
terpyridine fragment (see Fig. 5, a) is higher than that
involving the thiol fragment (see Fig. 5, b). This is apparꢀ
ently due to the formation of three Au—N donorꢀacceptor
bonds. The calculated bond energies are equal to 146 and
135 kJ mol–1 for the complexes shown in Figs 5a and 5b,
respectively. To sum up, the sorption of the SMeꢀsubstiꢀ
tuted terpyridine on the gold surface with the participaꢀ
tion of the terpyridine fragment, rather than the sulfur
atom, is thermodynamically more favorable.
The optimized structures of the thiol complexes with
the Au20 cluster are shown in Fig. 5. The bond energy of
The adsorption of complex 13 on the gold electrode is
also accompanied by the formation of the Au—S bond
a
2.75
a
2.98
2.71
2.37
2.58
2.75
b
b
2.45
1.80
Fig. 5. Optimized structures of SMeꢀsubstituted terpyridine comꢀ
plexes 9 with the Au20 cluster: coordination by the terpyridine
fragment (a) and the sulfur atom (b). The calculated distances
are given in Angstroms.
Fig. 4. Structure of the Au20 cluster (a) and visualization of its
molecular orbitals (b).

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Romashkina et al.
(the reduction peak at Epc = –0.82 V; see Table 3 and
Fig. 3, b). According to the CV data, the structure of
compound 13 in solution is identical to that on the surface
of the gold electrode. Apparently, the structure of comꢀ
plex 13 adsorbed on the gold surface corresponds to that
shown in Fig. 6.
However, according to the CV data, the keeping the
Au electrode with ligand 2 chemosorbed on it in the solution
of Co(ClO4)2 led to the complex with a different structure,
which is similar to that obtained upon adsorption of comꢀ
plex 18 (Fig. 3, c). A probable structure of this coordinaꢀ
tion compound is presented in Scheme 11.
slow process. During the reverse potential scan, a reoxidaꢀ
tion peak of the thiolate anion at Epa = –0.03 V was obꢀ
served after the reduction peak of the AuI—S bond (Fig. 3, c):
I
Au —S—R + e = Au0 + –S—R (Epc = –0.82 V),
R—S– – e = R—S (Epa = –0.03 V).
The correctness of the peak assignments was supportꢀ
ed by quantum chemical calculation of the change in the
Gibbs energy of the cathodic and anodic reactions (G).
The calculated values of G confirmed the interpretation
of the voltammogram and were equal to –0.827 and
–0.024 eV for the first and the second reactions, resꢀ
pectively.
Scheme 11
No adsorption via the coordination of the Au atom by
the nitrogen atoms of the terpyridine fragment at the iniꢀ
tial moment of the contact of the electrode with the soluꢀ
tion of 4 took place (peaks at Epc from –1.4 to –1.5 V are
absent in the CV curves). However, after 20 h a peak at
Epc = –1.49 V corresponding to the reduction of the
Nꢀadsorbed ligand appeared in the CV curve.
Apparently, cobalt complex 18 based on ligand 4 has
a polymeric structure in the crystalline state, and it is
destroyed upon dissolution. According to the CV data, the
structure of adsorbed complex 18 considerably differs
from the structure of adsorbed complexes 12 and 13 but is
similar to the structure of the complex formed upon keepꢀ
ing of the Au electrode with ligand 2 chemosorbed on it in
the solution of Co(ClO4)2. The results obtained by CV
show that the complex with a similar structure was formed
on the surface by means of the reaction of ligand 4 adꢀ
sorbed on the Au electrode with the solution of Co(ClO4)2.
It can be suggested20 that upon adsorption of complex 18,
a CoII terpyridine complex with the ratio metal : ligand =
= 1 : 1 is formed (Scheme 12). With time, some changes
take place in the CV curve of the adsorbed complex 18:
after 24 h, a strong enough peak at Epc = –1.37 V correꢀ
sponding to the reduction of Nꢀadsorbed ligand appears in
it. Apparently, the free ligand molecules, which are reꢀ
mained in the solution after the dissolution of polymeric
complex 18 and their adsorption on the gold surface,
undergo adsorption on the same surface in the competing
process via binding to it by the terpyridine nitrogen atoms.
The studies of redox processes on the Au electrode for
ligand 4 already in the first reverse scans of the CV curve
also showed the presence of an additional (as compared to
the GC electrode) cathodic peak at Epc = –0.82 V correꢀ
sponding to the reduction of the Au—S bond, which was
formed as a result of chemosorption of compound 4 on the
surface of the electrode. A peak corresponding to the reꢀ
duction of the disulfide bond (Epc = –1.22 V) was also
present in the CV curve during the first several hours after
the gold electrode was immersed in the solution of 4, i.e.
the adsorption of the disulfide ligand on Au is a relatively
Fig. 6. Structure of complex 13 adsorbed on the gold surface.

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2275
Scheme 12
To sum up, a conclusion can be drawn that all the
ligands studied are able to be chemosorbed on the surface
of the gold electrode with the formation of the AuI—S
bond. The adsorption of the complexes of the sulfide
ligands with CoII follows different mechanisms. Thus, in
the case of methylthioꢀsubstituted ligand 1, the structure
of the complex adsorbed on the surface is similar to its
structure in solution, whereas in the case of tertꢀbutylthioꢀ
substituted ligand 2, the coordination polyhedron changes
and the complex with the metal : terpyridines ligand ratio
of 1 : 1 is formed upon adsorption.
tion of NP dimeric and trimeric ensembles, we used
a method suggested in our earlier study for the induction
of aggregations through the coordination reactions of the
ligands adsorbed on the surface of metallic nanoparticles
with transition metal ions.5 The structure of this dimeric
aggregate is shown in Fig. 7.
There are two possible methods for the preparaꢀ
tion of NP ensembles with such structures: one inꢀ
volves the interaction of NP modified by an organic
ligand with solutions of transition metal salts; the secꢀ
ond involves the adsorption on NP of preliminary obꢀ
tained complexes of organic ligands with the same
metal ions.
Adsorption of coordination compounds of terpyridine
ligands on the surface of gold nanoparticles. For the formaꢀ
Au
S
Linker
M
Linker
S
Au
Fig. 7. Structure of gold NP dimeric aggregate.

2276
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
Romashkina et al.
We used the latter approach since, according to the
electrochemical data and quantum chemical calculations,
the synthesized terpyridine ligands can be adsorbed on the
metal surface not only due to the formation of the S—Au
bond, but also by means of the formation of the N—Au
bond, that can lead to large aggregates by the interaction
of the free ligands with gold NP. We studied the interacꢀ
tion of gold NP stabilized with citrate anions and tannic
acid by the Turkevich method21 with the CoII coordinaꢀ
tion compounds (complexes 11, 13, 17, 19, and 24), which
resulted in obtaining of NP ensembles with different deꢀ
grees of aggregation depending on the complexing ligand
and the concentration of the solution of the complex. The
structure and the size of the aggregates obtained were deꢀ
termined by electronic spectroscopy (from the position of
the plasmon resonance band22 in the electronic spectrum)
and transmission electron microscopy.
Thus, the addition of a solution of complex 11 to
a solution of stabilized gold NP led to a slight shift of the
plasmon resonance band to the longꢀwavelength region in
the electronic absorption spectrum (from 522 nm for the
starting nanoparticles to 524 nm upon the addition of the
complex), that indicated the formation of small aggreꢀ
gates. However, the electron microscopy data showed that
in this case larger aggregates rather than dimers and triꢀ
mers were mainly formed (Fig. 8). In addition, free unagꢀ
gregated NP were observed in the micrographs.
the electronic absorption spectrum (from 516 to 519 nm),
with its position and intensity remaining virtually unꢀ
changed henceforth (Fig. 9). The increase in the concenꢀ
tration of the complex to 10–4—10–3 mol L–1 led to
a gradual broadening and shift of the plasmon resonance
band toward the longꢀwavelength region by 10—40 nm
(see Fig. 9) indicative of the further agglomeration. The
aggregates obtained in this case have proved unstable and
after several hour after the formation, the polyaggregated
NP precipitated from the solution.
According to the electronic spectroscopy data, under
the optimal conditions (at the concentration of the soluꢀ
tion of complex 13 10–5 mol L–1), the dimerization
process occurred within several minutes, and the aggreꢀ
gates formed in the solution remained stable for a long
time (for at least 5 days). These conclusions were conꢀ
firmed by the transmission electron microscopy data. Figꢀ
ure 10 shows the micrographs of the samples obtained for
the gold NP in the course of aggregation caused by soluꢀ
tions of complex 13 of different concentrations.
Similar results were also observed in the studies of the
interaction of gold NP with complex 19 containing a thiol
group. In this case, stable small aggregates were obꢀ
tained when the solution of the complex with the concenꢀ
tration of 10–4 mol L–1 was used. In the electronic abꢀ
sorption spectrum of a solution of NP with this concenꢀ
tration of the aggregateꢀforming compound, a slight shift
of the plasmon resonance bands toward the longꢀwaveꢀ
length region was observed (from 520 to 525 nm). At the
concentration of the complex 10–3 mol L–1, the gold NP
undergo aggregation to form small chain aggregates
(Fig. 11).
For complex 13, we studied the influence of the ratio
of the terpyridine complex to gold nanoparticles on the
aggregation process. The addition of a solution of comꢀ
plex 13 (MeCN : H2O = 1 : 9, concentration 10–5 mol L–1)
to a solution of NP led to the immediate small shift of the
plasmon resonance band to the longꢀwavelength region in
Similar patterns were found in the study of the aggreꢀ
gation of gold NP under the action of compounds 17 and
24. In this case, the maximum yield of dimeric aggregates
D (arb. units)
1.4
4
1.2
1.0
0.8
0.6
0.4
0.2
3
2
1
500 550 600 650 700 750
/nm
200 nm
Fig. 9. Electronic absorption spectra of the starting gold NP
(AuNP) (1) and gold NP treated with solutions of complex 13
(AuNP + 13) with different concentrations: 10–5 (2), 10–4 (3),
10–3 mol L–1 (4).
Fig. 8. Electron micrograph of gold NP modified with comꢀ
plex 11.

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2277
a
b
200 nm
100 nm
c
d
50 nm
100 nm
Fig. 10. Electron micrographs of gold NP samples: a the starting NP; b—d NP treated with solution of complex 13: the concentration
was 10–5 (b, c) and 10–4 mol L–1 (d).
a
b
c
100 nm
100 nm
200 nm
Fig. 11. Electron micrographs of gold NP samples treated with a solution of complex 19: the concentration of the complex was
10–4 (a, b) and 10–3 mol L–1 (c).

2278
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
Romashkina et al.
grade) was stirred with anhydrous potassium carbonate (20 g L–1
)
was observed for solutions of complexes with the concenꢀ
tration of 10–5 mol L–1. In the electronic absorption specꢀ
tra, the shift of the plasmon resonance band was 4—5 nm
as compared to the starting NP obtained by the Turkevich
method.
In conclusion, we developed conditions for the prepaꢀ
ration of gold NP ensembles with different degrees of agꢀ
gregation and found that the degree of NP aggregation
was determined by the concentration of the terpyridine
complex solution used for the preparation of the aggloꢀ
merates. The use of a solution of the complex with the
concentration of 10–4—10–5 mol L–1 (depending on the
type of the ligand) was found to be the optimal for the
preparation of predominantly dimeric ensembles. The use
of solutions of lower concentrations did not lead to the
formation of aggregates, whereas excess of the complex
initiated the formation of larger aggregates.
for 4 days at 20 C, decanted, and further purified by consecutive
reflux and distillation in vacuo over calcium hydride and anꢀ
hydrous copper sulfate (10 g L–1). The purified solvent was stored
over 4 Å molecular sieves.
The sample micrographs were obtained on a LEO 912 AB
OMEGA transmission electron microscope (Carl Zeiss, Germaꢀ
ny) operating at an accelerating voltage of 100 kV. Samples were
prepared by the deposition of 1—2 L of the solution on a copper
grid coated with Formvar (d = 3.05 mm), which was then
dried in air.
4´ꢀ(4ꢀDiethoxyphosphorylmethylphenyl)ꢀ2,2´:6´,2ꢀterpyridꢀ
ine (8) was obtained according to the known procedure.25
Quantum chemical calculations were performed using the
Priroda 10 program26 by the density functional theory (DFT)
with the PBE (Perdew, Burke, Ernzerhow) nonempirical funcꢀ
tional27 using the allꢀelectron ꢀbasis set.28 Considerable gold
relativistic effects were allowed for in terms of the relativistic
approach with a modified Dirac—Coulomb—Breit Hamiltonian
in the twoꢀcomponent approximation with renormalization of
the large component of the bispinor.29 Relative molecular enerꢀ
gies were calculated with allowance for the zeroꢀpoint vibrationꢀ
al energy in the harmonic approximation. The bond energies
(Eb) of the substrate molecule R with the Aun gold cluster were
determined using the following formula:
Experimental
The reaction progress and individuality of products were
monitored by thinꢀlayer chromatography on plates precoated
with silica gel (Silufol).
1H NMR spectra were recorded on a Bruker Avance specꢀ
trometer (400 MHz). Deuteriochloroform, dimethyl sulfoxideꢀ
d6, and deuterobenzeneꢀd6 were used as solvents. Chemical shifts
are given relative to hexamethyldisiloxane as an internal stanꢀ
dard. 13C and 31P NMR spectra were recorded on a Bruker
Avance spectrometer (100 MHz). IR spectra were measured
on a URꢀ20 spectrometer in Nujol or on a TermoNicolete
IR200 Fourierꢀtransform infrared spectrometer in KBr pellets.
The UVꢀVis spectra were recorded on a Hitachi Uꢀ2900 spectroꢀ
meter.
Eb = E0(Aun) + E0(R) – E0(AunR),
where E0(Aun), E0(R), and E0(AunR) are the total energies with
allowance for the zeroꢀpoint vibrational energy of the gold clusꢀ
ter, the molecule, and the molecule and cluster complex, reꢀ
spectively.
The changes in the Gibbs energy in the corresponding proꢀ
cess were calculated at 298 K. The temperature correction for
the Gibbs energy was determined by methods of statistical therꢀ
modynamics. The calculations were performed on the SKIF
MSU Chebyshev supercomputer. Visualization of molecular orꢀ
bitals was performed using the Molden software.
Synthesis of 4´ꢀ(4ꢀmethylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterꢀ
pyridine (1) and 4´ꢀ(4ꢀtertꢀbutylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterꢀ
pyridine (2) (general procedure). Potassium hydroxide and 25%
aqueous ammonia were added to a solution of aldehyde and
2ꢀacetylpyridine in EtOH. The solution obtained was stirred at
room temperature for 12 h. The precipitate that formed was filtered
off, washed with methanol, twice recrystallized from a methanꢀ
ol—dichloromethane mixture (1 : 1), and washed with cold diꢀ
ethyl ether.
Laser ionization mass spectra were obtained on a Bruker
Autoflex II (the FWHM resolution 18000) equipped with a nitroꢀ
gen laser (operating at 337 nm wavelength) and a timeꢀofꢀflight
mass analyzer in the reflection mode. The accelerating voltage
was 20 kV. Samples were deposited on a gold substrate. The
spectra were recorded in the positive ion mode. The resulting
spectrum was a sum of 300 spectra obtained at different sites of
the sample.
Xꢀray diffraction study was performed on a CADꢀ4 autoꢀ
matic singleꢀcrystal diffractometer (graphite monochromator,
(MoꢀK) = 0.71073 Å, ꢀscan technique). The structure was
solved by direct methods (SHELXSꢀ97)23 and refined anisotroꢀ
pically by the fullꢀmatrix least squares method on F2 for all the
nonhydrogen atoms (SHELXLꢀ97).24 All the hydrogen atoms
were located in Fourier maps and refined isotropically.
A PIꢀ50ꢀ1.1 potentiostat connected to a PRꢀ8 programmer
was used for electrochemical studies. The working electrodes were
glassꢀcarbon (d = 2 mm), platinum (d = 2.8 mm), and gold
(d = 2 mm) disks, the supporting electrolyte was 0.1 M Bu4NBF4
solution, the reference electrode was Ag/AgCl/KCl (sat.). The
working electrode surfaces were polished with aluminum powꢀ
der with a particle size less than 10  (SigmaꢀAldrich). In the CV
studies, the potential scan rate was 200 mV s–1. All the measureꢀ
ments were carried out under argon. Samples were dissolved in
the preꢀdeoxygenated solvent. Dimethylformamide (reagent
4´ꢀ(4ꢀMethylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (1). The
reaction of 4ꢀmethylthiobenzaldehyde (2 g, 13.2 mmol),
2ꢀacetylpyridine (3.2 g, 2.96 mL, 26.4 mmol), KOH (1.48 g,
26.4 mmol), and 25% aq. NH3 (4.49 g, 4.99 mL, 66 mmol) in
EtOH (40 mL) gave compound 1 (1.95 g, 42%). M.p. 176 C.
1H NMR (400 MHz, CDCl3), : 8.75 (ddd, 2 H, HC(6)Py
,
HC(6)Py, J1 = 1.0 Hz, J2 = 1.8 Hz, J3 = 4.8 Hz); 8.74 (s, 2 H,
HC(3´), HC(5´)Py); 8.68 (dt, 2 H, HC(3)Py, HC(3)Py, J1 = 1.0 Hz,
J2 = 7.9 Hz); 7.89 (dt, 2 H, HC(4)Py, HC(4)Py, J1 = 1.8 Hz,
J2 = 7.9 Hz); 7.87 (d, 2 H, HC(2)C H , HC(6)C H , J = 8.5 Hz);
6
4
6
4
7.39 (d, 2 H, HC(3)C H , HC(5)C H , J = 8.4 Hz); 7.37 (ddd, 2 H,
4
6
HC(5)Py, HC(5)Py, 6J1 = 1.2 Hz, J24 = 4.8 Hz, J3 =7.6 Hz); 2.56
(s, 3 H, CH3—S). Found (%): C, 74.29; H, 4.89; N, 11.78; S, 8.92.
C22H17N3S. Calculated (%): C, 74.37; H, 4.79; N, 11.83; S, 9.01.

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2279
4´ꢀ(4ꢀtertꢀButylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (2).
The reaction of 4ꢀ(tertꢀbutylthio)benzaldehyde (0.3 g, 1.5 mmol),
2ꢀacetylpyridine (0.363 g, 0.336 mL, 3.0 mmol), KOH (0.168,
3.0 mmol), and 25% aq. NH3 (0.567 mL) in EtOH (6 mL) gave
ethanol (80 mL) gave compound 5 (4.59 g, 49%), m.p. 174 C.
1H NMR (400 MHz, CDCl3), : 8.76 (s, 2 H, HC(3´)Py
HC(5´)Py); 8.75 (br.s, 2 H, HC(6)Py, HC(6)Py); 8.69 (d, 2 H,
,
HC(3)Py, HC(3)Py, J = 8.0 Hz); 7.89 (dt, 2 H, HC(4)Py
,
,
,
,
1
compound 2 (0.27 g, 45%), m.p. 168 C. H NMR (400 MHz,
HC(4)Py, J1 = 1.6 Hz, J2 = 7.7 Hz); 7.85 (d, 2 H, HC(2)C H
4
CDCl3), : 8.76 (s, 2 H, HC(3´)Py, HC(5´)Py); 8.74 (br.s, 2 H,
HC(6)Py, HC(6)Py); 8.70 (d, 2 H, HC(3)Py, HC(3)Py, J = 8.0 Hz);
7.90 (dt, 2 H, HC(4)Py, HC(4)Py, J1 = 1.6 Hz, J2 = 7.8 Hz);
7.88 (d, 2 H, HC(2)C H , HC(6)C H , J = 8.0 Hz); 7.69 (d, 2 H,
HC(6)C H , J = 8.1 Hz); 7.37 (ddd, 2 H, HC(5)Py, HC(56)Py
J1 = 1.06H4z, J2 = 4.9 Hz, J3 = 6.5 Hz); 7.34 (d, 2 H, HC(3)C H
6
4
HC(5)C H , J = 8.0 Hz), 2.45 (s, 3 H, CH3). Found (%): C, 81.68;
6
4
H, 5.36; N, 12.94. C22H17N3. Calculated (%): C, 81.73; H, 5.30;
N, 13.00.
6
4
6
4
HC(3)C H , HC(5)C H , J = 8.2 Hz); 7.38 (ddd, 2 H, HC(5)Py
,
6
HC(5)P6y,4J1 = 1.0 Hz4, J2 = 4.8 Hz, J3 = 7.3 Hz); 1.35 (s, 9 H,
(CH3)3S). Found (%): C, 75.44; H, 5.85; N, 10.41; S, 7.96.
C25H23N3S. Calculated (%): C, 75.57; H, 5.79; N, 10.58; S, 8.06.
4´ꢀ(4ꢀMercaptophenyl)ꢀ2,2´:6´,2ꢀterpyridine (3) and bis[1ꢀ
(4ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀyl)phenyl)]disulfide (4). A solution
of compound 2 (0.33 g, 0.8 mmol) in 35% aq. HCl (56 mL) was
stirred for 12 h at 90 C under argon. The resulting solution was
cooled to 0 C, neutralized with 6 M NaOH to pH 8, and exꢀ
tracted with ethyl acetate. The solvent was evaporated under
reduced pressure. According to the NMR spectroscopic data,
the solid residue was a mixture of 4´ꢀ(4ꢀmercaptophenyl)ꢀ
2,2´:6´,2ꢀterpyridine (3) and bis{1ꢀ[4ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀ
yl)phenyl]} disulfide (4). On storage in air, the mixture convertꢀ
ed to pure disulfide 4.
Reaction of 4´ꢀ(4ꢀmethylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (5)
with Nꢀbromosuccinimide.30 A suspension of compound 5 (2.5 g,
7.7 mmol), Nꢀbromosuccinimide (1.64 g, 9.2 mmol), and AIBN
(0.097 g, 0.6 mmol) in CCl4 (25 mL) was refluxed for 2 h with
stirring. The hot solution was filtered and the solvent was evapoꢀ
rated under reduced pressure. The resulting solid residue was
a mixture of compounds 6 and 7. To obtain an individual
bromide 6, the mixture was twice recrystallized from an ethaꢀ
nol—acetone mixture (2 : 1).
4´ꢀ(4ꢀBromomethylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (6). The
yield was 1.72 g (56%). M.p. 159 C. 1H NMR (400 MHz,
CDCl3), : 8.75 (br.s, 4 H, HC(3)Py, HC(6)Py, HC(6´)Py
HC(5´)Py); 8.69 (d, 2 H, HC(3)Py, HC(3)Py, J = 8.0 Hz); 7.91
(t, 2 H, HC(4)Py, HC(4)Py, J = 7.7 Hz); 7.89 (d, 2 H, HCC H
,
,
4
6
4´ꢀ(4ꢀMercaptophenyl)ꢀ2,2´:6´,2ꢀterpyridine (3). A suspenꢀ
sion of triphenylphosphine (0.043 g, 0.16 mmol) in methanol
(3 mL) was added to a vigorously stirred mixture of compounds 4
(0.075 g, 0.11 mmol) and 3 (0.15 g, 0.44 mmol) dissolved in
degassed DMF (7 mL) under argon. The reaction mixture was
stirred for 30 min followed by the addition of water (2 mL) and
stirring for another 30 min. The resulting solution was cooled to
0 C and extracted with diethyl ether (3×10 mL). The organic
fractions were washed with cold water (2×5 10 mL) and dried
with anhydrous sodium sulfate. The solvent was evaporated unꢀ
der reduced pressure. The product was isolated by flash chroꢀ
matography in the light petroleum—ethyl acetate system (2 : 1).
The solvents were evaporated under reduced pressure. The yield
of compound 3 was 0.2 g (69%). 1H NMR (400 MHz, CDCl3),
: 8.75 (ddd, 2 H, HC(6)Py, HC(6)Py, J1 = 1.0 Hz, J1 = 1.8 Hz,
J3 = 4.9 Hz); 8.71 (s, 2 H, HC(3´)Py, HC(5´)Py); 8.68 (dt, 2 H,
HC(3)Py, HC(3)Py, J1 = 1.8 Hz, J2 = 7.6 Hz); 7.89 (dt, 2 H,
HC(4)Py, HC(4)Py, J1 = 2.0 Hz, J2 = 8.4 Hz); 7.81 (dt, 2 H,
HC(2)C H , HC(6)C H , J1 = 2.0 Hz, J2 = 8.6 Hz); 7.41 (dd, 2 H,
J = 8.3 Hz); 7.56 (d, 2 H, HCC H , J = 8.1 Hz); 7.38 (ddd, 2 H,
6 4
HC(5)Py, HC(5)Py, J1 = 1.0 Hz, J2 = 4.8 Hz, J2 = 7.2 Hz); 4.59
(s, 2 H, CH2—Br). Found (%): C, 65.55; H, 4.11; N, 10.32.
C22H16BrN3. Calculated (%): C, 65.67; H, 3.98; N, 10.45.
4´ꢀ(4ꢀDibromomethylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (7). The
yield was 0.3 g (8%). M.p. 170 C. 1H NMR (400 MHz, CDCl3),
: 8.76 (br.s, 4 H, HC(6)Py, HC(6)Py, HC(3´)Py, HC(5´)Py);
8.69 (d, 2 H, HC(3)Py, HC(3)Py, J = 8.0 Hz); 7.90 (m, 4 H,
HC(4)Py, HC(4)Py, HCC H ); 7.73 (d, 2 H, HCC H , J = 8.1 Hz);
6
4
6
7.39 (ddd, 2 H, HC(5)Py, HC(5)Py, J1 = 1.1 Hz,4 J2 = 4.8 Hz,
J2 = 7.7 Hz); 6.74 (s, 1 H, CH—Br2).
{4ꢀ[(E)ꢀ(2,2´:6´,2ꢀTerpyridinꢀ4´ꢀyl)phenylvinyl]phenyl}
methyl sulfide (9) and {4ꢀ[(E)ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀyl)ꢀ
phenylvinyl]phenyl} tertꢀbutyl sulfide (10) (general procedure). An
aldehyde was added to a suspension of 4´ꢀ(4ꢀdiethoxyphosphorylꢀ
methylphenyl)ꢀ2,2´:6´,2ꢀterpyridine 8 and ButOK in anhydrous
degassed toluene (50 mL). The reaction mixture was refluxed for
48 h under argon. The resulting solution was washed with brine
(3×20 mL), and the organic fractions were dried with anhydrous
sodium sulfate. The solvent was evaporated under reduced
pressure. The residue was dissolved in the dichloromethꢀ
ane : methanol system (40 : 1) and passed through a columnꢀ
filter with silica gel. The solvent was evaporated under reduced
pressure. The solution obtained was diluted with light petroꢀ
leum—diethyl ether mixture (1 : 1) (5 mL), the precipitate that
formed was filtered off.
{4ꢀ[(E)ꢀ(2,2´:6´,2ꢀTerpyridinꢀ4´ꢀyl)phenylvinyl]phenyl}
methyl sulfide (9). The reaction of compound 8 (0.3 g, 0.6 mmol),
ButOK (0.073 g, 0.6 mmol), and 4ꢀmethylthiobenzaldehyde
(0.099 g, 0.086 mL, 0.6 mmol) gave compound 9 (0.19 g, 64%),
m.p. 262 C. 1H NMR (400 MHz, DMSOꢀd6), : 8.77 (dd, 2 H,
HC(6)Py, HC(6)Py, J1 = 1.6 Hz, J2 = 4.7 Hz); 8.73 (s, 2 H,
HC(3´)Py, HC(5´)Py); 8.66 (d, 2 H, HC(3)Py, HC(3)Py, J = 8.0 Hz);
8.03 (dt, 2 H, HC(4)Py, HC(4)Py, J1 = 1.6 Hz, J2 = 7.7 Hz),
6
6
HC(3)C H4, HC(5)C H4 , J1 = 2.0 Hz, J2 = 8.6 Hz); 7.37 (ddd,
6
4
2 H, HC(5)Py, HC(56)P4 y, J1 = 1.2 Hz, J2 = 4.7 Hz, J3 = 7.4 Hz);
3.59 (s, 1 H, SH). 13C NMR (100 MHz, CDCl3), : 149.1, 136.9,
128.1, 128.0, 123.8, 121.4, 121.3, 128.7. MS (laser ionization),
m/z (I(%)): 342 (100 %) [MH+].
Bis{1ꢀ[4ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀyl)phenyl]} disulfide (4).
The yield was 0.075 g (26%). M.p. 262 C. 1H NMR (400 MHz,
CDCl3), : 8.75 (m, 2 H, HC(6)Py, HC(6)Py); 8.73 (s, 2 H,
HC(3´)Py, HC(5´)Py), 8.69 (d, 2 H, HC(3)Py, HC(3)Py, J= 8.0 Hz);
7.92 (m, 2 H, HC(4)Py, HC(4)Py); 7.90 (d, 2 H, HC(3)C H
,
,
6
4
4
HC(5)C H , J = 7.6 Hz); 7.69 (d, 2 H, HC(2)C H , HC(6)C H
6
J = 8.4 6H4z); 7.36 (dd, 2 H, HC(5)Py, HC(5)P6y,4J1 = 5.5 Hz,
J2 = 7.9 Hz). MS (laser ionization), m/z (I(%)): 681 (100 %) [MH+].
4´ꢀ(4ꢀMethylphenyl)ꢀ2,2´:6´,2ꢀterpyridine (5) was obtained
according to the procedure described for compounds 1 and 2.
The reaction of 4ꢀmethylbenzaldehyde (3.5 g, 29.0 mmol),
2ꢀacetylpyridine (7.02 g, 6.50 mL, 58.0 mmol), KOH (3.25 g,
58.0 mmol), and 25% aq. NH3 (10.96 mL, 9.86 g, 145 mmol) in
7.94 (d, 2 H, HCC H , J = 8.2 Hz); 7.80 (d, 2 H, HCC H ,
6
4
6
4
J = 8.4 Hz); 7.60 (d, 2 H, HCC H , J = 8.4 Hz); 7.52 (dd, 2 H,
6
4
HC(5)Py, HC(5)Py, J1 = 4.9 Hz, J2 = 6.6 Hz); 7.34 (d, 1 H,

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Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
Romashkina et al.
HC=C, J = 15.6 Hz); 7.31 (d, 1 H, HC=C, J = 15.6 Hz); 7.28
Bis[4´ꢀ(4ꢀtertꢀbutylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
nickel(II) ditetrafluoroborate (15). The reaction of ligand 2 (0.025 g,
0.06 mmol) and Ni(BF4)2•6H2O (0.011 g, 0.03 mmol) in methꢀ
anol (15 mL) gave complex 15 (0.017 g, 57%) as a beige powder,
m.p. >400 C. Calculated (%): C, 58.42; H, 4.48; N, 8.18.
C50H46B2F8N6S2Ni. Found (%): C, 58.61; H, 4.59; N, 8.13.
Bis({4ꢀ[(E)ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀyl)phenylvinyl]phenyl}
methyl sulfide)cobalt(II) diperchlorate (16). The reaction of ligand
9 (0.025 g, 0.06 mmol) and Co(ClO4)2•6H2O (0.01 g, 0.03 mmol)
in methanol (20 mL) gave complex 16 (0.026 g, 83%) as a claretꢀ
colored powder, m.p. >400 C. Calculated (%): C, 61.43; H, 3.92;
N, 7.17; S, 5.46. C60H46Cl2N6O8S2Co. Found (%): C, 61.23; H,
3.90; N, 7.18; S, 5.20.
(d, 2 H, HCC H , J = 8.2 Hz); 2.47 (s, 3 H, CH3—S). 13C NMR
4
(100 MHz, C6DCl3), : 156.3, 155.9, 149.1, 138.2, 136.9, 134.1,
128.9, 127.6, 127.0, 126.7, 123.9, 121.4, 118.5, 15.78. MS (ESI),
m/z (I (%)): 458 (100) [MH+]. Found (%): C, 78.82; H, 5.06;
N, 9.08. C30H23N3S. Calculated (%): C, 78.78; H, 5.03; N, 9.19.
{4ꢀ[(E)ꢀ(2,2´:6´,2ꢀTerpyridinꢀ4´ꢀyl)phenylvinyl]phenyl}
tertꢀbutyl sulfide (10). The reaction of compound 6 (0.3 g, 0.6
mmol), ButOK (0.073 g, 0.6 mmol), and 4ꢀ(tertꢀbutylthio)ꢀ
benzaldehyde (0.126 g, 0.6 mmol) gave compound 10 (0.18 g,
57%). M.p. 182 C. 1H NMR (400 MHz, C6D6), : 9.33 (s, 2 H,
HC(3´)Py, HC(5´)Py); 8.89 (d, 2 H, HC(3)Py, HC(3)Py, J = 7.9 Hz);
8.72 (ddd, 2 H, HC(6)Py, HC(6)Py, J1 = 1.0 Hz, J2 = 1.7 Hz,
J3 = 4.7 Hz); 7.77 (d, 2 H, HCC H , J = 8.3 Hz); 7.67 (d, 2 H,
Bis({4ꢀ[(E)ꢀ(2,2´:6´,2ꢀterpyridinꢀ4´ꢀyl)phenylvinyl]phenyl}
tertꢀbutyl sulfide)cobalt(II) diperchlorate (17). The reaction of
ligand 10 (0.025 g, 0.05 mmol) and Co(ClO4)2•6H2O (0.009 g,
0.025 mmol) in methanol (20 mL) gave complex 17 (0.025 g,
80%) as a claretꢀcolored powder. M.p. >400 C. Calculated (%):
C, 63.06; H, 4.62; N, 6.69. C66H58Cl2N6O8S2Co. Found (%):
C, 62.80; H, 4.76; N, 6.68.
({1ꢀ[4ꢀ(2,2´:6´,2ꢀTerpyridinꢀ4´ꢀyl)phenyl]} disulfide)cobalt(II)
diperchlorate (18). The reaction of ligand 4 (0.020 g, 0.03 mmol)
and Co(ClO4)2•6H2O (0.011 g, 0.03 mmol) in methanol (10 mL)
gave complex 18 (0.023 g, 82%) as a claretꢀcolored powder.
M.p. >400 C. Calculated (%): C, 53.73; H, 2.98; N, 8.95.
C42H28Cl2N6O8S2Co. Found (%): C, 53.56; H, 3.20; N, 8.94.
Bis[4´ꢀ(4ꢀmercaptophenyl)ꢀ2,2´:6´,2ꢀterpyridine]cobalt(II)
diperchlorate (19). The reaction of ligand 3 (0.025 g, 0.07 mmol)
and Co(ClO4)2•6H2O (0.013 g, 0.04 mmol) in methanol (15 mL)
gave complex 19 (0.020 g, 58%) as a claretꢀcolored powder, m.p.
>400 C. Calculated (%): C, 53.62; H, 3.19; N, 8.94; S, 6.81.
C42H30Cl2N6O8S2Co. Found (%): C, 53.43; H, 3.32; N, 8.71;
S, 6.55.
Preparation of compounds 21 and 22 (general procedure).
A suspension of a ligand and RhCl3 in ethanol—water mixture (2 : 1)
was refluxed for 48 h. The precipitate that formed was filtered
off, washed with methanol and diethyl ether, and dried in air.
{4´ꢀ[4ꢀ(Methylsulfanyl)phenyl]ꢀ2,2´:6´,2ꢀterpyridine}rhodꢀ
ium(III) trichloride (21). The reaction of ligand 1 (0.30 g,
0.84 mmol) and RhCl3 (0.18 g, 0.84 mmol) gave complex 21
(0.17 g, 36%) as a dark green powder. M.p. >400 C. Calculatꢀ
ed (%): C, 46.77; H, 3.01; N, 7.44; S, 5.67. C22H17Cl3N3SRh.
Found (%); C, 46.23; H, 3.53; N, 7.58; S, 5.12.
[4´ꢀ(4ꢀtertꢀButylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
rhodium(III) trichloride (22). The reaction of ligand 2 (0.05 g,
0.13 mmol) and RhCl3 (0.026 g, 0.13 mmol) gave complex 22
(0.024 g, 30%) as a dark brown powder, m.p. >400 C. Calculatꢀ
ed (%): C, 49.46; H, 3.79; N, 6.92; S, 5.28. C25H23Cl3N3SRh.
Found (%); C, 48.99; H, 3.61; N, 6.50; S, 5.03.
4
HCC H , J = 8.2 Hz); 7.45 (dt, 2 H, 6HC(4)Py, HC(4)Py, J1 = 1.8 Hz,
4
J2 = 67.8 Hz); 7.37 (d, 2 H, HCC H , J = 8.4 Hz); 7.28 (d, 2 H,
4
HCC H , J = 8.3 Hz); 7.02 (d, 1 6H, HC=C, J = 15.0 Hz); 6.99
6
4
(d, 1 H, HC=C, J = 15.1 Hz); 6.88 (ddd, 2 H, HC(5)Py, HC(5)Py
,
J1 = 1.0 Hz, J2 = 4.7 Hz, J3 = 7.4 Hz); 1.35 (s, 9 H, (CH3)3S).
13C NMR (100 MHz, CDCl3), : 156.2, 155.9, 149.1, 137.8,
136.9, 132.2, 128.9, 127.6, 127.1, 126.6, 123.8, 121.4, 118.5,
46.3, 31.0. MS (ESI), m/z I (%): 500 (100) [MH+]. Found (%):
C, 79.33; H, 5.83; N, 8.44. C33H29N3S. Calculated (%): C, 79.36;
H, 5.81; N, 8.42.
Bis[4´ꢀ(4ꢀmethylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
cobalt(II) dihexafluorophosphate (11). A solution of ligand 1 (0.05 g,
0.14 mmol) and Co(NO3)2•6H2O (0.02 g, 0.07 mmol) in methꢀ
anol (40 mL) was refluxed with stirring for 12 h. The resulting
solution was cooled and treated with a saturated solution of amꢀ
monium hexafluorophosphate in methanol. A dark red precipiꢀ
tate was filtered off and dissolved in minimum acetonitrile. Comꢀ
plex 11 was crystallized from the solution by a slow diffusion of
diethyl ether into the solution of the complex in acetoniꢀ
trile, m.p. >400 C. Found (%): C, 49.75; H, 3.18; N, 7.88.
C44H34F12N6P2S2Co. Calculated (%): C, 49.86; H, 3.21; N, 7.93.
Complexes with Co(ClO4)2 and Ni(BF4)2 (general procedure).
A solution of the ligand and metal salt in methanol was refluxed
with stirring for 12 h. The precipitate that formed was filtered
off, washed with methanol and diethyl ether, and dried under
reduced pressure.
Bis[4´ꢀ(4ꢀmethylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
cobalt(II) diperchlorate (12). The reaction of ligand 1 (0.05 g,
0.14 mmol) and Co(ClO4)2•6H2O (0.026 g, 0.07 mmol) in methꢀ
anol (40 mL) gave complex 12 (0.060 g, 89%) as a finely crystalꢀ
line claretꢀcolored powder. M.p. >400 C. Calculated (%):
C, 54.54; H, 3.51; N, 8.68. C44H34Cl2N6O8S2Co. Found (%):
C, 54.42; H, 3.67; N, 8.60.
Bis[4´ꢀ(4ꢀtertꢀbutylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
cobalt(II) diperchlorate (13). The reaction of ligand 2 (0.05 g,
0.13 mmol) and Co(ClO4)2•6H2O (0.023 g, 0.06 mmol) in methꢀ
anol (40 mL) gave complex 13 (0.052 g, 83%) as a finely crystalꢀ
line claretꢀcolored powder, m.p. >400 C. Calculated (%):
C, 57.03; H, 4.37; N, 7.98. C50H46Cl2N6O8S2Co. Found (%):
C, 56.97; H, 4.50; N, 8.01.
Bis[4´ꢀ(4ꢀmethylsulfanylphenyl)ꢀ2,2´:6´,2ꢀterpyridine]ꢀ
nickel(II) ditetrafluoroborate (14). The reaction of ligand 1 (0.05 g,
0.14 mmol) and Ni(BF4)2•6H2O (0.024 g, 0.07 mmol) in methꢀ
anol (40 mL) gave complex 14 (0.40 g, 61%) as brown crystals
suitable for Xꢀray diffraction analysis. M.p. >400 C. Calculꢀ
ated (%): C, 55.99; H, 3.60; N, 8.91. C44H34B2F8N6S2Ni.
Found (%): C, 55.90; H, 3.67; N, 8.70.
Preparation of compounds 23 and 24 (general procedure).
A suspension of complexes 21 or 22 and 1,4ꢀbis(terpyridinꢀ4´ꢀ
yl)benzene (20) in an ethanol—water mixture (1 : 1) was reꢀ
fluxed with stirring for 18 h. The resulting mixture was filtered,
a solution of ammonium hexafluorophosphate in water (1 mL)
was added to the filtrate. The precipitate that formed was filtered
off, washed with water, methanol, and diethyl ether, and dried
under reduced pressure.
Bis{4´ꢀ[4ꢀ(methylsulfanyl)phenyl]ꢀ2,2´:6´,2ꢀterpyridine}[1,4ꢀ
bis(terpyridinꢀ4´ꢀyl)benzene]dirhodium(III) hexakishexachloroꢀ
phosphate (23). The reaction of complex 21 (0.05 g, 0.09 mmol) with
1,4ꢀbis(terpyridinꢀ4´ꢀyl)benzene (0.024 g, 0.04 mmol) in an ethꢀ

Sulfurꢀcontaining terpyridines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 12, December, 2012
2281
anol—water mixture (18 mL) and NH4PF6 (0.043 g, 0.27 mmol)
gave complex 23 (0.046 g, 45%) as a yellow powder. M.p. >400 C.
EAS (10–6 M solution in CH3CN), /nm (/L cm–1 mol–1): 248
(4.3•104); 290 (9.8•104); 345 (6.5•104); 362 (7.0•104). Calculatꢀ
ed (%): C, 41.27; H, 2.49; N, 7.22; S, 2.75. C80H58F36N12P6S2Rh2.
Found (%): C, 41.45; H, 2.87; N, 6.89; S, 3.24.
Bis{4´ꢀ[4ꢀ(tertꢀbutylsulfanyl)phenyl]ꢀ2,2´:6´,2ꢀterpyridꢀ
ine}[1,4ꢀbis(terpyridinꢀ4´ꢀyl)benzene]dirhodium(III) hexakishꢀ
exachlorophosphate (24). The reaction of complex 22 (0.025 g,
0.04 mmol) with 1,4ꢀbis(terpyridinꢀ4´ꢀyl)benzene (0.011 g,
0.02 mmol) in an ethanol—water mixture (9 mL) and NH4PF6
(0.02 g, 0.12 mmol) gave complex 24 (0.05 g, 44%) as a brown
powder. M.p. >400 C. EAS (10–6 M solution in CH3CN), /nm
(/L cm–1 mol–1): 247 (4.3•104); 291 (9.7•104); 344 (6.6•104);
361 (7.0•104). Calculated (%): C, 42.82; H, 2.90; N, 6.97; S, 2.65.
C86H70F36N12P6S2Rh2. Found (%): C, 42.17; H, 2.99; N, 6.86;
S, 2.02.
3. G. Schmid, M. Baumle, M. Greekens, I. Heim, C. Oseꢀ
mann, T. Sawitowski, Chem. Soc. Rev., 1999, 28, 179.
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5. R. B. Romashkina, E. K. Beloglazkina, A. N. Khlobystov,
A. G. Majouga, D. A. Pichugina, V. I. Terenin, N. V. Zyk,
N. S. Zefirov, Mendeleev Commun., 2011, 21, 129.
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liams, A. P. Alivisatos, J. Phys. Chem. B., 2002, 106, 11758.
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12, 576.
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20, 10317.
9. R. Sardar, T. B. Heap, J. S. ShumakerꢀParry, J. Am. Chem.
Soc., 2007, 129, 5356.
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1990, 1405.
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ky, I. Sasaki, G. Dupic, J.ꢀC. Daran, G. G. A. Balavoine,
J. Chem. Soc., Dalton Trans., 1999, 667.
Synthesis of modified gold NP
12. J. Paul, S. Spey, H. Adams, J. A. Thomas, Inorg. Chim. Acta,
2004, 357, 2827.
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W. Cargill Thompson, Inorg. Chem., 1995, 34, 2759.
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J. Am. Chem. Soc., 1991, 113, 8521.
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Zyk, Russ. J. Gen. Chem. (Engl. Transl.), 2010, 80 [Zh. Obshch.
Khim., 2010, 80, 201].
16. E. K. Beloglazkina, A. G. Majouga, I. V. Yudin, R. D. Rahiꢀ
mov, B. N. Tarasevich, N. V. Zyk, J. Sulfur. Chem., 2007,
28, 201.
17. E. K. Beloglazkina, A. G. Majouga, A. A. Moiseeva, M. G.
Tsepkov, N. V. Zyk, Russ. Chem. Bull. (Int. Ed.), 2007, 351
[Izv. Akad. Nauk, Ser. Khim., 2007, 339].
Nanoparticles stabilized with sodium citrate and tannic acid
(Turkevich method).
A solution of compound 1, 1%
aq. HAuCl4•3H2O (1 mL), and distilled water (80 mL) was
heated to 60 C. The resulting hot solution was diluted with vigꢀ
orous stirring with a solution of 1% aq. sodium citrate (4 mL),
1% aq. tannic acid (0.08 mL), and distilled water (15 mL) preꢀ
liminary heated to 60 C. The solution obtained was refluxed
for 2 h (until the solution acquired red color). Then the solution
was cooled to room temperature with stirring. The resulting soꢀ
lution of gold NP was stored at about 4 C. Further the NP
stabilized with sodium citrate and tannic acid were involved
in the reaction with appropriate sulfurꢀcontaining ligands and
complexes.
18. L. S. Pinheiro, M. L. A. Temperini, Surface Science, 2000,
464, 176.
19. J. Li, X. Li, H.ꢀJ. Zhai, Science, 2003, 299, 864.
20. M. Maskus, H. D. Abruna, Langmuir, 1996, 12, 4455.
21. J. Turkevich, P. C. Stevenson, J. Hillier, Discuss. Faraday
Soc., 1951, 11, 55.
22. S. P. Gubin, N. A. Kataeva, G. Yu. Yurkov, Nanochastitsy
blagorodnykh metallov i materialy na ikh osnove [Nanopartiꢀ
cles of Noble Metals and Materials on Their Basis] N. S. Kurꢀ
nakov Institute of General and Inorganic Chemistry of Russian
Academy of Sciences, Moscow, 2006, 155 pp. (in Russian).
23. M. Sheldrick, Acta. crystallogr. Sect. A, 1990, 46, 467.
24. G. M. Sheldrick, SHELXLꢀ97. Program for the Refinement of
Crystal Structures, University of Gottingen, Gottingen, Gerꢀ
many, 1997.
Nanoparticles modified with {4ꢀ[(E)ꢀ(2,2´:6´,2ꢀterpyridinꢀ
4´ꢀyl)phenylvinyl]phenyl} tertꢀbutyl sulfide (2). The reaction of
HAuCl4•3H2O (0.2 g, 0.56 mmol) in distilled water (20 mL),
tetraoctylammonium bromide (0.342 g, 0.63 mmol) in toluene
(15 mL), 2 (0.056 g, 0.11 mmol) in toluene (2 mL), and sodium
borohydride (0.234 g, 6.2 mmol) in distilled water (14 mL) gave
modified gold NP (0.16 g).
Reaction of gold nanoparticles stabilized with sodium citrate
and tannic acid with terpyridine cobalt(II) complexes (general proꢀ
cedure). A solution of a complex (11, 13, 17, 19, and 24) in
acetonitrile (100 L) (complexes 11, 13, 17, and 24) or dimethylꢀ
formamide (complex 19) at the concentration of 10–2, 10–3, or
10–4 mol L–1 was mixed with distilled water (900 L). A solution
of gold NP (1.25 mL) stabilized by Turkevich method was dilutꢀ
ed twofold with distilled water. A solution of the complex (100 L)
was added to the obtained solution of gold NP (2.5 mL). The
resulting samples were studied by UVꢀVis and transmission elecꢀ
tron microscopy.
25. A. Winter, D. A. M. Egbe, U. S. Schubert, Org. Lett., 2007,
9, 2345.
26. D. N. Laikov, PRIRODA, Electronic Structure Code, Version 10,
2010.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 10ꢀ03ꢀ00707a).
27. J. P. Perdew, K. Burke, M. Ernzerhoff, Phys. Rev. Lett.,
1996, 77, 3865.
28. D. N. Laikov, Chem. Phys. Lett., 2005, 416, 116.
29. K. G. Dyall, J. Chem. Phys., 1994, 100, 2118.
30. H. L. Smith, R. L. Usala, E. W. McQueen, J. I. Goldsmith,
Langmuir, 2010, 26, 3342.
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Received June 28, 2011;
in revised form November 14, 2012