Azamacrocyclic nickel(II) and copper(II) complexes bearing aryl substituents: Synthesis, properties, and crystal structures

Article abstract of DOI:10.1007/s11172-010-0280-3

A synthetic procedure for preparation of new amphiphilic copper(II) and nickel(II) azamacrocyclic complexes bearing aromatic substituents is developed. The nature of substituents is shown to exert a negligible influence on spectral and electrochemical characteristics of the prepared compounds. The X-ray diffraction analysis of three copper complexes revealed the formation of the dimers of macrocyclic cations associated by noncovalent interactions, nature of which is determined by the structure of the substituent in the macrocyclic ligand.

Full text of DOI:10.1007/s11172-010-0280-3

Russian Chemical Bulletin, International Edition, Vol. 59, No. 8, pp. 1572—1581, August, 2010
1572
Azamacrocyclic nickel(II) and copper(II) complexes bearing aryl
substituents: synthesis, properties, and crystal structures
L. V. Tsymbal,a I. L. Andriichuk,a Ya. D. Lampeka,a and H. Pritzkowb
aL. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of the Ukraine,
31 prosp. Nauki, 03028 Kiev, Ukraine.
Fax: +38 (044) 525 2570. Eꢀmail: lampeka@adamant.net
bUniversität Heidelberg, AnorganischꢀChemisches Institut,
Im Neuenheimer Feld 270, Dꢀ69120 Heidelberg, Germany.
Fax: +49 (6221) 54 6617
A synthetic procedure for preparation of new amphiphilic copper(II) and nickel(II)
azamacrocyclic complexes bearing aromatic substituents is developed. The nature of substituꢀ
ents is shown to exert a negligible influence on spectral and electrochemical characteristics of
the prepared compounds. The Xꢀray diffraction analysis of three copper complexes revealed
the formation of the dimers of macrocyclic cations associated by noncovalent interactions,
nature of which is determined by the structure of the substituent in the macrocyclic ligand.
Key words: nickel(II), copper(II), azamacrocyclic complexes, absorption spectra, redox
properties, Xꢀray diffraction analysis.
Noncovalent interactions (NI) including van der Waals
The present work deals with the synthesis and study of
spectral and electrochemical characteristics of novel
copper(II) and nickel(II) complexes with related pentaꢀ
azamacrocyclic ligands L1—L5 bearing aryl substituents
and analysis of crystal structures of some copper(II) comꢀ
plexes with these ligands aiming at finding the features of
noncovalent interactions in their crystals.
interactions, π—πꢀstacking, CH—π, hydrophobic, ionꢀ
dipole, dipoleꢀdipole, and some other types of weak inꢀ
teractions1—3 play very essential role in chemistry and bioꢀ
chemistry. These attractive forces are invoked to explain
different aspects of physicochemical behavior of various
systems, particularly, functioning of proteins,4 interacꢀ
tions of metals with amino acids5 and DNA,6 mechanisms
of molecular recognition,7,8 to develop chemical sensors,9
and find many other applications.10,11
Experimental
Crystal engineering is yet another rapidly growing field
where NI play an essential role.12,13 In many cases, the
ability of compounds to aggregate with involvement of
just these forces leads to materials with anisotropic crystal
structures (for example, with porous or layered structure)
and possessed valuable applied properties.14 However, the
purposeful construction of such materials is impossible
without disclosing the forces that govern crystal formaꢀ
tion. Hence, it is necessary to accumulate empirical data
of the influence of structural modifications of molecules
on features of their packing in crystals.
Azamacrocyclic complexes of transition metals, parꢀ
ticularly, nickel(II) and copper(II), are currently widely
used as building blocks for construction of new materiꢀ
als.15,16 One of the obvious advantages of such compounds
along with their high thermodynamic stability and kinetic
inertness17 is the possibility of synthetically convenient
chemical modification of macrocyclic framework using
the template synthetic methods.18
The starting hexahydrates of nickel(II) and copper(II) perꢀ
chlorates M(ClO4)2•6H2O (a. p.), N,N´ꢀbis(2ꢀaminoethyl)ꢀ
propaneꢀ1,3ꢀdiamine (2,3,2ꢀtet) (Acros), benzylamine,
4ꢀmethylbenzylamine, 2ꢀ(4ꢀmethylphenyl)ethylamine, tyramine
hydrochloride (all Aldrich), and 4ꢀmethoxybenzylamine (Fluka)
were used without additional purification. The complexes
[I(2,3,2ꢀtet)](ClO4)2 (I = CuII or NiII) were prepared according
to the published methods.19,20
Synthesis of macrocyclic complexes [ML](ClO4)2 (general
procedure). A mixture of [M(2,3,2ꢀtet)](ClO4)2 (M = CuII, NiII)
(2.4 mmol), amine (2.4 mmol), 30% aqueous formaldehyde
(1.0 mL, 13.3 mmol), and triethylamine (0.2 mL) in methanol
(30 mL) was refluxed for 24 h. After cooling and filtration, the
solution was kept in a refrigerator. The redꢀpurple (copper
complexes) or yellow (nickel complexes) precipitates were
filtered off, recrystallized from 1 : 1 acetonitrile—water
([ML1](ClO4)2) and 1 : 1 acetonitrile—ethanol ([ML2](ClO4)2)
mixtures, acetone ([ML3](ClO4)2), or acetonitrile ([ML4](ClO4)2),
and dried in a vacuum desiccator. The complex [CuL5](ClO4)2
was isolated form the reaction mixture by chromatography on
a column loaded with a cation exchanger SPꢀSephadex Cꢀ25
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1535—1543, August, 2010.
1066ꢀ5285/10/5908ꢀ1572 © 2010 Springer Science+Business Media, Inc.

Arylꢀcontaining azamacrocyclic complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1573
(Na+ꢀform) (eluent, 0.2 M NaClO4). The analytical data and
yields of the prepared compounds are given below.
(3ꢀBenzylꢀ1,3,5,8,12ꢀpentaazacyclotetradecane)copper(II)
diperchlorate, [CuL1](ClO4)2. Yield 0.57 g (46%). Found (%):
C, 34.6; H, 12.4; N, 5.1. C16H29Cl2CuN5O8. Calculated (%):
C, 34.70; H, 12.64; N, 5.28.
[3ꢀ(4ꢀMethylbenzyl)ꢀ1,3,5,8,12ꢀpentaazacyclotetradecane]ꢀ
copper(II) diperchlorate, [CuL2](ClO4)2. Yield 0.37 g (30%).
Found (%): N, 36.0; H, 12.3; N, 5.5. C17H31Cl2CuN5O8. Calꢀ
culated (%): C, 35.95; H, 12.33; N, 5.50.
[3ꢀ(4ꢀMethoxybenzyl)ꢀ1,3,5,8,12ꢀpentaazacyclotetradecane]ꢀ
copper(II) diperchlorate, [CuL3](ClO4)2. Yield 0.30 g (26%).
Found (%): N, 34.8; H, 12.0; N, 5.4. C17H31Cl2CuN5O9.
Calculated (%): C, 34.97; H, 11.99; N, 5.35.
the crystals of [CuL3](ClO4)2 were obtained by diffusion of
hexane vapor into an acetone solution of the compound. The
diffraction experiments were performed using a Bruker AXS
SMART 1000 diffractometer (graphite monochromator,
λ(MoꢀKα) = 0.71073 Å, ωꢀscanning technique). The structures
were solved by the direct method and refined by the fullꢀmatrix
leastꢀsquares method with anisotropic displacement paramꢀ
eters for all nonhydrogen atoms using the program package
SHELXL97.21 The crystallographic data and the main refinement
parameters are given in Table 1. In the crystal structure of
[CuL2](ClO4)2, the substituent in the macrocyclic ligand is
disordered over two positions, the perchlorate anions in the
structure of [CuL4](ClO4)2 are also disordered.
{3ꢀ[2ꢀ(4ꢀMethylphenyl)ethyl]ꢀ1,3,5,8,12ꢀpentaazacycloꢀ
tetradecane}copper(II) diperchlorate, [CuL4](ClO4)2. Yield 0.27 g
(17%). Found (%): N, 37.0; H, 12.1; N, 5.6. C18H33Cl2CuN5O8.
Calculated (%): C, 37.15; H, 12.03; N, 5.72.
{3ꢀ[2ꢀ(4ꢀHydroxyphenyl)ethyl]ꢀ1,3,5,8,12ꢀpentaazacycloꢀ
tetradecane}copper(II) diperchlorate, [CuL5](ClO4)2. Yield 0.21 g
(15%). Found (%): N, 33.8; H, 12.3; N, 5.3. C16H30Cl2CuN5O9.
Calculated (%): C, 33.66; H, 12.27; N, 5.30.
[3ꢀBenzylꢀ1,3,5,8,12ꢀpentaazacyclotetradecane]nickel(II)
diperchlorate, [NiL1](ClO4)2. Yield 0.32 g (42%). Found (%):
N, 35.1; H, 12.8; N, 5.4. C16H29Cl2N5NiO8. Calculated (%):
C, 35.00; H, 12.76; N, 5.32.
[3ꢀ(4ꢀMethylbenzyl)ꢀ1,3,5,8,12ꢀpentaazacyclotetradecane]ꢀ
nickel(II) diperchlorate, [NiL2](ClO4)2. Yield 0.59 g (44%).
Found (%): N, 36.2; H, 12.4; N, 5.6. C17H31Cl2N5NiO8.
Calculated (%): C, 36.26; H, 12.44; N, 5.55.
Results and Discussion
Synthesis of macrocyclic nickel(II) and copper(II)
complexes was carried out using the formerly developed
method,19,20,22 viz., the template condensation of comꢀ
plexes of acyclic tetramine [M(2,3,2ꢀtet)]2+ (M = CuII or
NiII) with formaldehyde and primary aliphatic amines
bearing aryl substituents (Scheme 1). Such oneꢀpot reacꢀ
tions are synthetically convenient and allow obtaining the
desired products in moderate yields even without optimiꢀ
zation of the reaction conditions.
Scheme 1
[3ꢀ(4ꢀMethoxybenzyl)ꢀ1,3,5,8,12ꢀpentaazacyclotetradecane]ꢀ
nickel(II) diperchlorate, [NiL3](ClO4)2. Yield 0.62 g (45%).
Found (%): N, 35.2; H, 12.0; N, 5.5. C17H31Cl2N5NiO9.
Calculated (%): C, 35.26; H, 12.09; N, 5.40.
{3ꢀ[2ꢀ(4ꢀMethylphenyl)ethyl]ꢀ1,3,5,8,12ꢀpentaazacycloꢀ
tetradecane}nickel(II) diperchlorate, [NiL4](ClO4)2. Yield 0.21 g
(15%). Found (%): N, 37.2; H, 12.1; N, 5.6. C18H33Cl2N5NiO8.
Calculated (%): C, 37.46; H, 12.14; N, 5.76.
Physicochemical measurements. The electronic absorption
spectra were obtained on a Specord Mꢀ40 spectrophotometer.
The IR spectra in the range of 400—4000 cm–1 were recorded on
a Perkin—Elmer spectrometer (in KBr pellets). The electroꢀ
chemical properties of the compounds were studied by cyclic
voltammetry (CV) in aqueous solutions containing 0.1 M NaClO4
or 0.5 M Na2SO4 (nickel complexes) and in acetonitrile solutions
containing 0.1 M [NEt4]ClO4 as an electrolyte (nickel and
copper complexes). A threeꢀelectrode circuit equipped with
platinum auxiliary and working electrodes and silverꢀchloride
reference electrode (Ag/AgCl) was used for the measurements.
The potential was maintained using a PIꢀ50.1.1 potentiostat
controled with a PRꢀ8 programmer. The voltammograms
were recorded with an Hꢀ307 XY recorder. The potential
sweep rate in the range of 0.5—1.0 V in the aqueous solutions
Compound
n
R
Compound
n
R
[ML1]2+
[ML2]2+
[ML3]2+
0
0
0
H
Me
OMe
[ML4]2+
[ML5]2+
1
1
Me
OH
In addition to elemental analysis, the formation of the
macrocyclic compounds is confirmed by IR spectroscopy.
There are wellꢀdefined differences in the IR spectra of the
starting complexes [M(2,3,2ꢀtet)](ClO4)2 and the conꢀ
densation products. Particularly, the bands of moderate
intensity assigned to vibrations of the secondary amino
groups of the macrocyclic ligands (ν(NH) = 3220—3200
and 3180—3160 cm–1, δ(NH) = 1660—1610 cm–1) are
present in the spectra of the condensation products inꢀ
stead of the intensive bands of stretching and deformation
and 0.5—2.0 V in the acetonitrile solutions was 50 mV s–1
,
the accuracy of measurements of E1/2 values was 5 mV. The
elemental analysis was performed at the Institute of Physical
Chemistry, National Academy of Sciences of the Ukraine using
a Carlo Erba instrument.
Xꢀray diffraction study. Single crystals of the complexes
[CuL2](ClO4)2 and [CuL4](ClO4)2 were obtained by slow
crystallization from a acetonitrile—ethanol (1 : 1, v/v) mixture,

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Tsymbal et al.
Table 1. The Xꢀray diffraction data and refinement parameters for the macrocyclic copper complexes
Parameter
CuL2(ClO4)2
CuL3(ClO4)2
CuL4(ClO4)2
Molecular formula
Molecular weight
C17H31Cl2CuN5O8
567.91
C17H31Cl2CuN5O9
583.91
C18H33Cl2CuN5O8
581.93
Т/К
103(2)
298(2)
103(2)
Crystal system
Space group
Triclinic
P(–)1
Triclinic
P(–)1
Triclinic
P(–)1
а/Å
b/Å
c/Å
α/deg
8.160(3)
8.3789(15)
18.488(3)
96.465(13)
93.409(16)
112.27(3)
1155.1(6)
2
8.2813(4)
8.3130(4)
19.0046(8)
86.300(1)
86.396(1)
67.243(1)
1202.94(10)
2
8.1665(9)
12.3777(14)
12.5582(14)
77.547(2)
84.196(2)
76.662(2)
1204.3(2)
2
β/deg
γ/deg
V/Å3
Z
dcalc/g cm–3
1.627
1.231
1.612
1.187
1.605
1.183
μ/mm–1
F(000)
586
606
606
Crystal dimensions/mm
Total number of reflections
Number of independent reflections (Rint
Number of refinement parameters
GОOF (on F2)
0.35×0.16×0.15
22962
7829 (0.0266)
438
0.29×0.27×0.05
21215
8217 (0.0300)
431
0.18×0.15×0.02
5500
5500 (0.0000)
470
)
1.030
1.003
1.030
R1 (on F for reflections with I > 2σ(I))
0.0305
0.0826
0.0368
0.0873
0.0381
0.0941
0.0632
0.1102
0.0493
0.1204
0.0736
0.1327
wR2 (on F2 for reflections with I > 2σ(I))
R1 (for all reflections)
wR2 (on F2 wR2 for all reflections)
Residual electron density/e•Å–3
,
0.640/–0.360
0.895/–0.722
1.196/–0.742
Δρmax/Δρ
min
vibrations of the primary amino groups of the coordinated
tetramine 2,3,2ꢀtet (ν(NH2) = 3495—3345 cm–1, δ(NH2)
~1640 cm–1). In addition, in the IR spectra of all macroꢀ
cyclic complexes, a set of strong absorption bands appears
in the range of 1450—1560 cm–1, which is assigned to
stretching vibrations ν(C=C) of the aromatic substituents.
The prepared nickel(II) complexes are well soluble
in polar organic solvents (nitromethane, acetonitrile,
DMSO), moderately soluble in water, and poorly soluble
in ethanol. The similar and even more pronounced beꢀ
havior is also characteristic of the copper(II) complexes.
These features give evidence of considerable hydrophoꢀ
bicity of these compounds, which is explained by the
presence of aromatic substituents in the ligands. This is
confirmed by the fact that complexes [CuL1](ClO4)2,
[CuL2](ClO4)2, and [CuL4](ClO4)2 are virtually insoluble
in water and ethanol, whereas introduction of the oxyꢀ
genꢀcontaining substituents in the aryl fragments increases
hydrophility of the compounds resulting in their better
solubility in these solvents.
The band of electronic d—dꢀtransitions in the nickel(II)
complexes at ~22000 cm–1 is characteristic of the lowꢀ
spin compounds of this ion with a squareꢀplanar chromoꢀ
phore.17 Its energy does not depend on the structure of the
Table 2. The spectral characteristics of the perchlorate salts of
the macrocyclic nickel(II) and copper(II) complexes in different
solvents.
Cation
ν
•10–3/cm–1 (ε/L mol–1 cm–1
)
max
MeNО2
EtOH
Н2О
DMSO MeCN
[NiL1]2+ 22.4 (81) 22.3 (63) 22.4 (59) 22.0 (37) 21.7 (20)
[NiL2]2+ 22.4 (72) 22.1 (62) 22.4 (49) 21.9 (39) 21.6 (20)
[NiL3]2+ 22.5 (81) 22.1 (56) 22.4 (52) 22.1 (39) 21.6 (16)
a
[NiL4]2+ 22.4 (91)
[NiL6]2+ b 22.1 (60)
[CuL1]2+ 20.6 (81)
[CuL2]2+ 20.5 (85)
—
—
—
—
22.4 (54) 22.1 (37) 21.9 (27)
a
a
a
22.3 (50)
—
21.7 (21)
a
—
19.4 (77) 19.5 (85)
19.5 (85) 19.9 (91)
a
—
[CuL3]2+ 20.4 (84) 19.8 (95) 19.8 (114) 19.4 (77) 20.0 (90)
a
a
[CuL4]2+ 20.5 (85)
—
—
19.5 (85) 19.9 (91)
The electronic absorption spectra of the macrocyclic
compounds. The spectral characteristics of the examined
compounds in different solvents are given in Table 2; they
are typical of the complexes of these ions with tetradentate
azamacrocyclic ligands.17
[CuL5]2+ 20.4 (76) 19.4 (80) 19.4 (82) 19.5 (75) 19.7 (87)
a
[CuL6]2+ b 20.4 (78)
—
19.8 (75)
—
19.8 (72)
a The compound is poor soluble in this solvent.
b According to Refs 20 and 23; hereinafter L6 is 3ꢀmethylꢀ
1,3,5,8,12ꢀpentaazacyclotetradecane.

Arylꢀcontaining azamacrocyclic complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1575
aromatic substituent in the macrocycle and is close to the
energy of the complex with the methylꢀsubstituted ligand
[NiL6]2+ (see Table 2).20,23 This fact gives evidence of the
absence of electronic interaction between the substituent
and chromophore and suggests the similar conformation
of the macrocyclic ligands in the examined complexes.
The latter agrees with the Xꢀray diffraction data of the
copper complexes (see below).
Noteworthy is the fact that the molar extinction coefꢀ
ficient (ε) of the absorption band of the nickel complexes
is considerably dependent on the nature of the solvent
(see Table 2), whereas the value of energy is practically
constant. This feature gives evidence of the presence of an
equilibrium between the fourꢀcoordinate lowꢀspin (ls) and
sixꢀcoordinate highꢀspin (hs) forms of the complex in
solutions:17
reflects the increase in the ability of the solvent molecules
to coordinate at the axial positions of the nickel(II) ion:
nitromethane (2.7) < ethanol (20) < water (≥18) < DMSO
(29.8) < acetonitrile (14.1) (Gutman’s donor numbers of
solvents are given in the parantheses). The specific posiꢀ
tion of acetonitrile in this series is typical of nickel(II)
amine complexes.26 A comparison of the obtained conꢀ
stants with the constants for [NiL6]2+ (2.0 and 0.2 in
acetonitrile and aqueous solutions, respectively) allows us
to infer that the substitution of the aryl substituent in the
macrocyclic ligand for the alkyl fragment results in a slight
increase in the values of Keq. Probably, the observed effect
is not caused by the differences in the inductive properties
of the substituents and reflects the changes in the strucꢀ
tures of the solvate spheres of the complexes.
In contrast to the nickel(II) complexes, the axial coorꢀ
dination of the solvent molecules to the copper(II) ion
practically does not influence the intensity of the obꢀ
served absorption band at 20000 cm–1 and appears in the
bathochromic shift of its maximum.17 Taking into account
the value of this shift, the examined solvents could be
arranged in the series according to their coordination abilꢀ
ity with respect to the copper ion(II) in a macrocyclic
environment: MeNO2 < MeCN < H2O < EtOH < DMSO.
This series agrees with the increase in Gutman’s donor
numbers of solvents.
[NiL]2+ + 2 Solv
S = 0
[NiL(Solv)2]2+
S = 3/2
,
(1)
where Solv is a solvent; the complex with S = 0 is squareꢀ
planar, the complex with S = 3/2 is tetragonalꢀbipyraꢀ
midal.
The spectrum of the highꢀspin form of the complex is
characterized22—24 by the presence of the absorption bands
at ~30000, 15000, and <11000 cm–1. Due to the low
intensity of these bands (εhs ≤ 10 L mol–1 cm–1)17 as well as
low equilibrium concentration of the highꢀspin form, the
main visible effect of the equilibrium (1) is a decrease in
the molar extinction coefficient of the absorption band
of the lowꢀspin form at ~22000 cm–1, which becomes
an effective parameter (εeff). The highest ε values are
observed in a noncoordinating solvent, nitromethane (in
this case εeff = εls), and the presence of several additional
lowꢀintensity absorption bands in acetonitrile solutions
comprising maximal amount of highꢀspin form among
the examined solvents agree with this interpretation.
The equilibrium constants (1) can be estimated from
the formula Keq = (εls – εeff)/εeff.* The obtained values Keq
are 2.4—4.1, 0.9—1.5, 0.5—0.7, and 0.2—0.4 for the soluꢀ
tions in acetonitrile, DMSO, water, and ethanol, respecꢀ
tively. This allows us to arrange them in a series that
Redox characteristics of the complexes. The voltamꢀ
mograms in the anodic region in aqueous and acetonitrile
solutions give evidence of the existence of only one redox
process for each compound. On the basis of an approxiꢀ
mate equality of the currents of the cathodic and anodic
peaks and the distance between them, ΔE ≤ 100 mV
(Table 3), this process can be treated as quasireversible.
Table 3. Redox potentials (E1/2) of the pairs MIII/IIL of nickel
and copper complexes in different solventsa
Complex
E1/2/mV
H2O
MeCN,
0.1 М NaClO4 0.5 М Na2SO4 0.1 M [NEt4]ClO4
[NiL1]
[NiL2]
[NiL3]
[NiL4]
[NiL6]b
[CuL1]
[CuL2]
[CuL4]
[CuL3]
[CuL5]
[CuL6]b
820 (75)
830 (85)
820 (85)
850 (90)
775 (80)
—
525 (70)
530 (80)
530 (80)
535 (70)
500 (70)
—
1045 (70)
1035 (100)
1040 (100)
1030 (90)
1960 (60)
1440 (110)
1425 (90)
1460 (160)
1430 (120)
1230 (75)
1455 (90)
* More strict formula for the calculation of equilibrium constant
(1) is Keq = (ε – εeff)/(εeff – ε ), where εhs is the molar absorpꢀ
ls
hs
tion coefficient of the highꢀspin form at the maximum of the
absorption band of the lowꢀspin complex. Since the 100% conꢀ
tent of a highꢀspin form is not observed in any of the solvents,
the estimated value of this parameter can be obtained by decomꢀ
position of the observed spectrum on the Gauss components.
—
—
—
—
—
—
—
—
Earlier,24 we have shown that ε is ~6 L mol–1 cm–1 for suchꢀ
hs
—
—
type complexes. However, slight changes in ε values in this
hs
a
approach considerably influence the value of the denominator
and, thereby, Keq. Thus, this calculation method was not used in
the present work.
E1/2 (mV) vs. Ag/AgCl electrode, the distances between
cathodic and anodic peaks ΔE (mV) are given in parentheses.
b According to Ref. 22.

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Tsymbal et al.
By analogy with earlier published data,19,20,22,23 this proꢀ
cess is a singleꢀelectron redox transformation of the metal
center, i.e., transition in the redoxꢀpair IIII/IIL. On the
whole, the observed values of the redox potentials E1/2
calculated as average values between potentials of the
cathodic and anodic peaks appear in the renges that
are typical of the nickel and copper complexes with
tetradentate azamacrocyclic ligands.
a
C(1)
O(1)
N(3)
N(2)
Cu
The redox potentials of the pair NiIII/IIL appear to
considerably depend on the nature of the solvent and the
electrolyte. Since the azamacrocyclic nickel(III) complexes
exist in solution in the sixꢀcoordinate form,27 this feature
could be explained by the different nature of the axial
ligands. Particularly, the coordination of the sulfate
anions results in considerably higher thermodynamic staꢀ
bilization of nickel(III) than the coordination of neutral
water molecules (in perchlorateꢀcontaining aqueous meꢀ
dia) or acetonitrile.28 On the whole, the changes in the
values E1/2 of the pair NiIII/IIL depending on the nature of
the aryl substituent in the ligand have a nonsystematic
character, however, they are slightly higher than that for
the complex of their methylꢀsubstituted analog L6.
As is known, the azamacrocycles less efficiently stabiꢀ
lize copper(III) as compared with nickel(III)29 and this fact
is confirmed by the results obtained in the present work.
Particularly, on the voltammograms of the copper comꢀ
plexes in aqueous solutions, only anodic peak at potenꢀ
tials > 1 V was observed. The values E1/2 of the pair
CuIII/IIL measured in acetonitrile solutions (see Table 3)
similar to nickel complexes give evidence about insignifiꢀ
cant effect of the nature of the aryl substituent on their
values. The only exception is the complex of the ligand L5
bearing the phenolic substituent. On the basis of literature
data,30 it is most probable that the redox process observed
in this case is the transition phenol/phenoxyl radical.
Molecular structure of the macrocyclic copper comꢀ
plexes. The complexes [CuL2(ClO4)2], [CuL3(ClO4)2], and
[CuL4(ClO4)2] studied by Xꢀray diffraction are characterꢀ
ized by similar molecular structures (see Fig. 1). The
coordination polyhedron of the copper(II) ions in all
compounds is represented by the elongated tetragonal
bipyramid (transꢀN4O2) where four nitrogen atoms of the
macrocyclic ligand form the nearly ideal equatorial plane
(the deviations from the mean plane of N4 do not exceed
0.01 Å for the nitrogen atoms and 0.03 Å for the copper
ions in all three complexes), and two oxygen atoms of the
perchlorate anions occupy the axial positions. The disꢀ
tances Cu—N and angles N—Cu—N in the equatorial
plane (Table 4) have values in the range typical of such
types of macrocyclic complexes,17,31 while the relatively
larger axial distances Cu—O (2.46—2.60 Å) give evidence
of weak coordinative interaction of the metal ion with the
perchlorate anions.
N(1)
N(4)
N(5)
O(6)
Cl(2)
b
O(9)
Cl(2)
O(6)
N(3)
N(2)
N(1)
Cu
N(5)
N(4)
O(1)
C(1)
c
Cl(2)
O(6)
N(2)
N(3)
Cu
N(4)
N(1)
N(5)
O(1)
C(1)
Fig. 1. Molecular structures of macrocyclic copper(II) complexes
[CuL2(ClO4)2] (a), [CuL3(ClO4)2] (b), and [CuL4(ClO4)2] (c).
The thermal ellipsoids are given at 30%ꢀprobability level, hydroꢀ
gens at the nitrogen atoms are outlined as the spheres with arbiꢀ
trary radii, hydrogens at the carbon atoms are not shown.
The coordinated macrocyclic ligands exist in the most
energetically favorable form transꢀIII (R,R,S,S)31 with

Arylꢀcontaining azamacrocyclic complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1577
Table 4. Some characteristics of the coordination polyhedrons of the macrocyclic copper(II) complexes
Parameter
[CuL2(ClO4)2]
[CuL3(ClO4)2]
[CuL4(ClO4)2]
Bond length
d/Å
Сu—N(2)
Сu—N(3)
Сu—N(4)
Сu—N(5)
Сu—O(1)
Сu—O(6)
Cu—N/Cu—Ca
2.018(1)
2.021(1)
2.019(1)
2.025(1)
2.517(1)
2.591(1)
3.306/3.350
2.019(2)
2.017(2)
2.024(2)
2.017(2)
2.580(2)
2.548(2)
3.342/3.348
2.011(3)
2.028(3)
2.018(3)
2.011(3)
2.576(3)
2.459(2)
3.296/3.343
Angle
ω/deg
N—Cu—Nb
86.1(1), 86.6(1)
93.1(1), 94.1(1)
–56.1, 56.2
351.2
86.3(1), 86.2(1)
93.3(1), 94.2(1)
–56.7, 55.4
346.0
85.8(1), 86.3(1)
93.6(1), 94.3(1)
–55.1, 55.1
353.7
N—Cu—Nс
Torsion anglesb
Sum of the angles C—N—C at the N(1) atom
a The distance from the copper ion to the distal atom N/C in sixꢀmembered chelate rings.
b In fiveꢀmembered chelate rings.
c In sixꢀmembered chelate rings. The first digit relates to the chelate ring with noncoordinated nitrogen atom.
the sixꢀmembered chelate rings in the chair conformation
and fiveꢀmembered chelate rings in the gauche conformaꢀ
tion. In each ligand, the sixꢀmembered metallacycles difꢀ
fer in chemical structures, since they contain different
distal atoms (a noncoordinated nitrogen atom or a carbon
atom of the methylene group) and are structurally nonꢀ
equivalent, which is manifested in slight differences in
both angles N—Cu—N and distances between the copper
ions and the respective distal atoms (see Table 4).
As follows form Table 4, the sums of the angles beꢀ
tween the bonds N—C formed by the noncoordinated
nitrogen atom N(1) are considerably larger than the
expected values for the tetrahedral configuration (~330°).
This feature is wellꢀknown for such types of the macroꢀ
cyclic ligands and is explained by the fact that the menꢀ
tioned nitrogen atoms have intermediate hybridization
between sp2 and sp3. Due to certain "flatness" of the fragꢀ
ment under consideration, the assignment of orientation
of the substituents in the respective sixꢀmembered chelate
rings (equatorial or axial) is rather tentative. Nevertheꢀ
less, the orientation of substituents in the complexes
[CuL3(ClO4)2] and [CuL4(ClO4)2] can be considered to
be axial. At the same time, the substituent in the complex
[CuL2(ClO4)2] is disordered, and this compound is the
example of the simultaneous presence in the crystal of
the molecules with axial and equatorial orientations (see
Fig. 1, a).
The common feature of the crystal state of the copper(II)
complexes is the presence of oneꢀdimensional (1D) chains
formed by the hydrogen bonds (HB) between the oxygen
atoms of the coordinated perchlorate anions and the secꢀ
ondary amino groups of the adjacent cations (the disꢀ
tances O...N are 3.26, 3.16, and 2.99 Å for [CuL2(ClO4)2],
[CuL3(ClO4)2], and [CuL4(ClO4)2], respectively). The
spatial arrangement of the chain constituents is similar,
which is confirmed by the closeness of the distances beꢀ
tween the adjacent copper ions (8.379, 8.313, and 8.166 Å
for [CuL2(ClO4)2], [CuL3(ClO4)2], and [CuL4(ClO4)2],
respectively). Two additional HB for [CuL2(ClO4)2] and
[CuL3(ClO4)2] are observed (the distances O...N were
3.077, 3.081 and 3.173, 3.152 Å, respectively), which
connect 1D chains in 2D layers.
Further association of the structural fragments (1D
chains in [CuL4(ClO4)2] or 2D layers in two other comꢀ
plexes) in the threeꢀdimensional crystal structure is
effected by NI. The energy of such interactions (for
example, 7—11 kJ mol–1 (see Ref. 32) for the CH—πꢀ
contacts) is close to the lower limit of the energy of a
classical NI being 12—30 kJ mol–1 (see Ref. 32). In the
case of the studied systems, where the intermolecular NI
are relatively weak (the distances O...N > 3 Å), it could be
supposed that both HB and NI are essential for the crystal
formation.
Indeed, the crystal structures of all three complexes
are characterized by the existence of NI, especially, it
clearly appears in the formation of dimeric aggregates
(Fig. 2).
In the dimer of the complex [CuL2(ClO4)2] (see Fig. 2, a),
the distance between the planes of the parallel aromatic
rings (2.67 Å) is rather short, while they are shifted with
respect to each other (the distance between the centers of
Crystal structures of the compounds. All studied comꢀ
plexes have virtually identical structural and chemical paꢀ
rameters (metal ion, anion, hydrophobic nature of the
substituent) essential for the formation of crystals. Thereꢀ
fore, the examined compounds are convenient subjects to
study the effect of small differences in their molecular
structure on the packing in the crystal state.

1578
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
Tsymbal et al.
a
c
b
Fig. 2. The structures of dimers in crystals [CuL2(ClO4)2] (a), [CuL3(ClO4)2] (b), and [CuL4(ClO4)2] (c) (only hydrogens
involved in noncovalent interactions are shown).
Table 5. The structural characteristics of noncovalent interactions in crystal lattices of the arylꢀsubstituted macrocyclic nickel(II) and
copper(II) complexes
Compounda (packing type)b
d/Å
Reference
c
c
d
CH (aliphatic)...π
CH (aromatic)...π
π...π
[NiL7](ClO4)2 (A)
[NiL7(N3)2] (A)
3.94/3.15
3.96/3.12
000—
3.60/2.84; 3.91/3.24
3.70/3.15
3.66/3.11
000—
3.75/2.86
3.85/2.91
000—
000—
3.92/2.95
3.84/—
2.85/2.43
000—
3.45/2.79
—
—
33
34
35
36
37
38
36
36
39
40
40
41
42
3.68/2.82
(3.71/4.70)e
f
g
[NiL7(in)2] (A)
—
—
—
[NiL7(tp)]n (B)
—
(3.70/4.72)e
(3.69/4.64)e
(2.69/5.35)e,h
—
f
[NiL8](ClO4)2 (A)
[NiL8](BF4)2 (A)
4.12/3.19
4.01/3.12
—
[NiL8(tp)]n (B)
{[NiL8(bdc)]•2DMF}n (A)
{[(NiL8)3(btc)2]•6H2O}n (A)
[Ni(R)ꢀL9)](ClO4)2 (A)
[Ni(S)ꢀL9)](ClO4)2 (A)
[Ni((R)ꢀL9)(NCS)2] (A)
[CuL8(ClO4)2] (A)
[CuL2(ClO4)2] (A)
[CuL3(ClO4)2] (A)
[CuL4(ClO4)2] (B)
—
3.73/2.94e
3.48/2.86
3.48/2.87
3.54/2.69
—
3.75/4.03
—
—
—
3.65/4.16
(2.67/4.35)e
3.44/3.79
—
—
—
—
This work
This work
This work
a Ligand designation: L7 is 3,10ꢀdibenzylꢀ1,3,5,8,10,12ꢀhexaazacyclotetradecane, L8 is 3,10ꢀdiphenethylꢀ1,3,5,8,10,12ꢀhexaazaꢀ
cyclotetradecane, L9 is 3,10ꢀdi((R/S)ꢀαꢀmethylbenzyl)ꢀ1,3,5,8,10,12ꢀhexaazacyclotetradecane, in is isonicotinate, tp is terephthaꢀ
late, bdc is transꢀbutenedicarboxylate, btc is 1,3,5ꢀbenzenetricarboxylate.
b The presence (A) and absence (B) of layered packing with alternation of hydrophobic and hydrophilic layers.
c The distances C...Ct/H...Ct, where Ct is the center of the aromatic ring.
d The distance between the parallel planes of the aromatic rings/distance Ct...Ct.
e The absence of overlapping of πꢀsystems of the aromatic rings.
f The presence of additional CH...πꢀinteractions ("edgeꢀtoꢀface") between the hydrogen atoms of the aromatic substituents and the
aromatic ring of the carboxylate.
g The presence of the π—πꢀinteraction between the carboxylate anions.
h The presence of the additional π—πꢀinteraction between the substituent in the macrocycle and bridging carboxylate.

Arylꢀcontaining azamacrocyclic complexes
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1579
a
the benzene rings is 4.35 Å) and their aromatic systems
do not overlap. It allows us to rule out π—πꢀstacking as
a driving force of the aggregation of the macrocyclic
cations. The most probable reason of the formation of
the dimer in this compound is the CH—πꢀinteraction
between the methyl substituent in the aromatic ring of
one cation and the aromatic fragment of the other cation.
One hydrogen of the CH3 group is situated practically
above the center (the deviation from the vertical is 5.3°)
of the benzene ring of the adjacent molecule at a distance
of 2.43 Å (the distance C...centroid C6 is 2.85 Å).
Similar type of interactions is typical of a dimer of the
complex [CuL4(ClO4)2] as well (see Fig. 2, b). However,
in this case, the methylene groups of the sixꢀmembered
metallacycle are responsible for the molecular interaction
with the aromatic system (the distances from H and
C atoms to the center of the benzene ring are 2.79
and 3.45 Å, respectively, the deviation of the H atom
from the perpendicular to the center of the ring is 7.4°).
The formation of dimer aggregates due to the interacꢀ
tions between the hydrophobic parts of the molecules
is also observed in the complex [CuL3(ClO4)2] (see
Fig. 2, b). However, on the base of mutual orientation of
the aryl fragments (the distance between their parallel
planes is 3.44 Å, the distance between the centers of the
benzene rings is 3.79 Å), the appreciable overlapping
of the πꢀelectronic systems leading to efficient stackingꢀ
interaction could be expected.
b
The data from X ray diffraction analysis of a number
of nickel(II) and copper(II) complexes with related macroꢀ
cyclic ligands L7—L9 are documented, which allows
performing the comparative analysis of types of NI
observed in the crystals of such compounds (Table 5).
The tabulated data show that the interactions between
the aromatic systems of the substituents and hydrogens of
the methylene groups of the macrocycles are the most
common. Similar "edgeꢀtoꢀface" type interactions of hyꢀ
drogens of the aromatic rings in the compounds containꢀ
ing inorganic anions are less common, thought the presꢀ
ence of aromatic carboxylates in the structure of the comꢀ
pounds results in additional interactions of this type.
As a rule, in crystals of the majority of the considered
complexes, the planes of the aromatic rings of the aryl
substituents are located close to each other and are paralꢀ
lel, but in most cases their centers are considerably shifted,
which makes impossible the overlapping of the πꢀsystems.
Thus, these interactions cannot be characterized as π—πꢀ
stacking. The compounds examined in this work are disꢀ
tinguished from the set of compounds in the shortest conꢀ
tacts responsible for NI (CH—π in [CuL2(ClO4)2] and
[CuL4(ClO4)2]; π—π in [CuL3(ClO4)2], see Table 5).
Yet another type of NI, which plays an essential role
in the formation of the crystals of such compounds, is
hydrophobic interactions between aromatic fragments. In
the case of complexes [CuL2(ClO4)2] and [CuL3(ClO4)2],
c
Fig. 3. The crystal packing of the complexes [CuL2(ClO4)2] (a),
[CuL3(ClO4)2] (b), and [CuL4(ClO4)2] (c). The hydrophobic
substituents are shown as the spheres with the van der Waals radii.

1580
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Tsymbal et al.
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these interactions result in lamellar crystal structures
(Fig. 3), which are formed by the alternating hydrophobic
and hydrophilic layers as a result of "faceꢀtoꢀface" packꢀ
ing of cations. On the whole, such layered structure is
characteristic of a majority of macrocyclic compounds
bearing aryl substituents (Table 5). Similar packing is typiꢀ
cal of the complex [CuL4(ClO4)2]; however, due to other
spatial orientation of the aromatic fragment, it does not
lead to the layered structure.
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In conclusion, in the present work we developed a
method for the synthesis of novel amphiphilic azaꢀ
macrocyclic copper(II) and nickel(II) complexes bearing
different aromatic substituents. It is shown that the nature
of the substituent does not considerably influence specꢀ
tral and electrochemical properties of the compounds
obtained. On the base of the Xꢀray diffraction analysis
of three copper complexes, we established the presence of
similar stack structures in the crystals, where the perchlorꢀ
ate anions serve as the bridges between the macrocyclic
cations due to formation of coordination bonds with the
metal ion and hydrogen bonds with the amino groups of
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negligible effect on the crystal structure, thought it results
in replacement of the CH—πꢀinteraction for π—πꢀstackꢀ
ing as the attractive noncovalent forces. At the same time,
the introduction of additional methylene unit in the bridge
between the aryl and macrocyclic fragments considerably
changes crystal packing. In this case, CH—πꢀinteractions
between the aromatic substituents and methylene groups
of the sixꢀmembered chelate rings of the macrocyclic
ligand are present. The crystal structure of the former two
compounds is layered with alternate hydrophobic and
hydrophilic regions.
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state and can result in appearance of one or other types
of noncovalent intermolecular interactions.
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in revised form March 11, 2010