Complexes of pendant-armed cyclam derivatives with copper(II) perchlorate: Synthesis and crystal structures

Article abstract of DOI:10.1016/j.poly.2006.06.037

A designed series of cyclam type macrocyclic ligands 1-3 that feature a different degree of saturation and number of functional appendages of the macroring, including preparation of the respective Cu(II) perchlorate complexes 1a-3a, was synthesized. Comparative discussion of the X-ray crystal structures of the free ligands and the corresponding complexes shows that dependent on the structure of the compound, transanular, pendant arm and anion involving conventional and weaker H bond contacts are operating. In the complexes, the coordination environment around the Cu(II) cation is distorted octahedral with the nitrogens of the macroring defining the equatorial sites and either two oxygens, each of a perchlorate anion, or the lateral pyridine nitrogens in apical positions. Thus, only the pyridine containing pendants in 3a proved effective in metal ion coordination while the anisyl groups are engaged in H bonding, respectively. The uncomplexed macrocycle 3 yielded an inclusion compound with chloroform, also indicating a special ability relating to this series of compounds.

Full text of DOI:10.1016/j.poly.2006.06.037

Polyhedron 25 (2006) 3463–3473
www.elsevier.com/locate/poly
Complexes of pendant-armed cyclam derivatives with
copper(II) perchlorate: Synthesis and crystal structures
*
Thomas Scho¨nherr, Wilhelm Seichter, Edwin Weber
Institut fu¨r Organische Chemie, Technische Universita¨t Bergakademie Freiberg, Leipziger Strasse 29, 09596 Freiberg/Sachs., Germany
Received 17 January 2006; accepted 22 June 2006
Available online 14 July 2006
Abstract
A designed series of cyclam type macrocyclic ligands 1–3 that feature a different degree of saturation and number of functional
appendages of the macroring, including preparation of the respective Cu(II) perchlorate complexes 1a–3a, was synthesized. Comparative
discussion of the X-ray crystal structures of the free ligands and the corresponding complexes shows that dependent on the structure of
the compound, transanular, pendant arm and anion involving conventional and weaker H bond contacts are operating. In the com-
plexes, the coordination environment around the Cu(II) cation is distorted octahedral with the nitrogens of the macroring defining
the equatorial sites and either two oxygens, each of a perchlorate anion, or the lateral pyridine nitrogens in apical positions. Thus, only
the pyridine containing pendants in 3a proved effective in metal ion coordination while the anisyl groups are engaged in H bonding,
respectively. The uncomplexed macrocycle 3 yielded an inclusion compound with chloroform, also indicating a special ability relating
to this series of compounds.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Copper; Co-ordination compounds; Macrocyclic ligands; Cyclam derivatives; Crystal structures
1. Introduction
as the tectonic building block, are expected to yield sorp-
tive materials for chemical sensing [12]. Moreover, an
uncomplexed pendant-arm tetraaza macrotricycle was
recently found to form a crystalline inclusion compound
with chloroform [13].
From among the many different oligoaza macrocycles
[14], 1,4,8,11-tetraazacyclotetradecane, commonly known
as cyclam [15], is described as being the most classic exam-
ple and useful representative of this type of compounds
[16]. Currently, cyclam and its pendant-arm derivatives
are extensively investigated in medicine for imaging appli-
cations [17] and as carriers of metal ions in antitumor
[18] and anti-HIV agents [19], as well as in the construction
of multifunctional dendrimers capable of coordinating
metal ions [20].
Macrocycles containing nitrogen donor atoms are an
important class of compounds due to their prominent
behavior of forming highly stable complexes with a variety
of transition metal ions [1,2]. Oligoaza macrocycles were
also found effective receptor molecules for ammonium cat-
ions [1,3], and in its protonated or quaternary form they
are tried and tested in the formation of complexes with
anionic guests [4]. In recent years, growing interest is being
attached to the functionalization of oligoaza macrocyclic
ligands [5–7], producing pendant-arm complexes [8,9] that
show high catalytic potential [10]. Complexes of this type
can stabilize unusual oxidation states of coordinated tran-
sition metal ions, making them a promising tool for the
construction of supramolecular switches [11], while open
framework structures, generated from respective complexes
Considering the promising aspects, we report in this
paper on Cu(II) complexes of a designed series of cyclam
type derivatives 1–3 (Scheme 1) featuring different degree
of saturation of the macroring and different number of
functional appendages involving C-linked 2-anisyl and
*
Corresponding author. Fax: +49 3731 39 3170.
E-mail address: edwin.weber@chemie.tu-freiberg.de (E. Weber).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.06.037

3464
T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
N
N
Cl HCl
H3CO
NH
N
N
H3CO
NH HN
NH HN
H3CO
NH
N
N
NaBH4
MeOH
KOH, MeOH
OCH3
OCH3
OCH3
HN
HN
N
2
1
3
Cyclohexane,
Ether
K2CO3
O
(
)
Cu ClO
4 2
1a:
2a:
3a:
1
2
3
OCH3
(
)
Cu ClO
4 2
(
)
Cu ClO
2
+
4 2
H2N
NH2
2
Scheme 1. Synthesis of the tetraaza macrocycles and specification of complexes studied.
N-linked 2-picolyl groups. Both, the crystal structures of all
the uncomplexed macrocycles 1–3 and the respective Cu(II)
complexes have been solved and comparatively discussed to
reveal structural consequences on the coordination behav-
ior. Thus, the present study will serve as a useful example
of cyclam-type co-ordination chemistry being supplement
to the known structures of related cyclams and cyclam
complexes that differ in the absence of the methoxy substit-
uents, respectively, anisyl pendants, or show other struc-
tural modifications [21–29].
2.2.1. 7,14-Bis(2-methoxyphenyl)-5,12-dimethyl-1,4,8,11-
tetraazacyclotetradeca-5,12-diene (1)
Prepared from 2-methoxybenzylideneacetone and ethy-
lenediamine with anhydrous potassium carbonate in cyclo-
hexane–diethyl ether (1:2) following the literature
procedure [27]. Recrystallization form chloroform–diethyl
ether yielded 80% yellowish crystals; m.p. 144–145 ꢁC (lit-
erature [32] m.p. 143–145 ꢁC).
2.2.2. 7,14-Bis(2-methoxyphenyl)-5,12-dimethyl-1,4,8,11-
tetraazacyclotetradecane (2)
2. Experimental
Synthesized by treatment of 1 with NaBH4 in dry etha-
nol and workup according to the literature [32] which
yielded 92% colourless crystals; m.p. 197–198 ꢁC (literature
[32] m.p. 198–199 ꢁC).
Caution: Although we did not encounter any problems,
perchlorate salts of metal complexes containing organic
ligands and solvents are potentially explosive and should
be handled only in small quantities and with great caution!
2.2.3. 4,11-Bis(2-pyridylmethyl)-7,14-bis(2-
methoxyphenyl)-5,12-dimethyl-1,4,8,11-
tetraazacyclotetradecane (3)
2.1. General methods and materials
To a stirred solution of 2 (1.0 g, 2.43 mmol) and sodium
hydroxide (0.44 g, 11.0 mmol) in water (20 cm3) was added
dropwise a solution of picolyl chloride hydrochloride in
methylene chloride (20 cm3). The mixture was stirred for
10 h at 25 ꢁC. The organic phase was separated and the
aqueous phase extracted with three 50 cm3 portions of
methylene chloride. The combined organic phases were
evaporated under reduced pressure and the remaining oil
crystallized from ethanol to give a colorless solid with
m.p. 236–238 ꢁC (yield: 82%). Anal. Calc. for C38H50N6-
O2 (FW = 622.85): C, 73.28; H, 8.09; N, 13.49. Found:
C, 73.03; H, 8.19; N, 13.41%. IR (KBr): 3252, 2966,
2934, 2895, 2834, 2817, 1597 (s), 1588 (s), 1491 (s), 1472
(s), 1434 (s), 1364, 1274, 1237, 1135, 1084, 1050, 1029,
Melting points (uncorrected) were taken on a heating
stage microscope (Rapido, Dresden). The IR spectrum (m
in cmꢀ1) was recorded on a Perkin–Elmer 1600 FT-IR
instrument. NMR spectra (d in ppm, J in Hz, Me4Si as
internal standard) were obtained with Bruker Avance
DPX 400 (1H: 400 MHz, 13C: 100.6 MHz). The mass spec-
trum (ESI) was determined on a Hewlett–Packard HP
59987 A instrument.
Reactions were monitored by thin-layer chromatogra-
phy (TLC) carried out on Merck silica gel 60 F254 coated
plates. All reagents were commercial products and were uti-
lized without further purification. The solvents used were
purified or dried by common literature procedures [30].
1
786, 766 (s), 756 (s) cmꢀ1. H NMR (CDCl3): d = 0.96 (s,
2.2. Synthesis of the macrocycles
3H, CH3), 0.98 (s, 3H, CH3), 1.60–1.66 (m, 2H, CH–
CH3), 1.93 (b, 2H, NH), 2.29–2.90 (m, 12H, CH2), 3.81
(s, 6H, OCH3), 3.83 (m, 2H, NCH-Ar), 4.05 (s, 4H, CH2-
Ar), 6.86 (d, J = 8.4, 2H, Ar-H), 6.93 (m, 4H, Ar-H),
7.11 (d, J = 6.8, 2H, Ar-H), 7.20 (m, 2H, Ar-H), 7.59 (t,
2-Methoxybenzylideneacetone was obtained from 2-
methoxybenzaldehyde and acetone according to the litera-
ture [31].

T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
3465
J = 3.6, 2H, Ar-H),7.71 (d, J = 7.2, 2H, Ar-H), 8.47 (d,
3. Results and discussion
J = 3.6, 2H, Ar-H). 13C NMR (CDCl3): d = 13.8 (CH3),
40.5, 44.6 (CHCH2CH, NCH2CH2N), 54.0, 54.6 (CHCH3,
CHAr), 55.3 (OCH3), 56.1 (NCH2Ar), 110.4, 120.7, 121.6,
123.2, 127.2, 127.4, 132.6, 157.1, 161.4 (Ar). MS (ESI): m/
z = 622 (M+).
3.1. Synthesis
The macrocyclic 1 (Scheme 1) was synthesized via the
cyclocondensation route [36] starting form 2-methoxyben-
zylideneacetone and ethylenediamine [32]. Subjection of 1
to a sodium borohydride reduction yielding the substituted
cyclam 2 [32]. Reaction of 2 with picolyl chloride hydro-
chloride and sodium hydroxide gave the cyclam derivative
3. The complexes 1a, 2a and 3a were prepared from the
respective macrocycles (1–3) with Cu(ClO4)2 Æ 6H2O in
methanolic solution.
2.3. Preparation of the Cu(ClO4)2 complexes
To a stirred solution of the corresponding macrocycle
(0.7 mmol)
in
methanol
(20 cm3)
was
added
Cu(ClO4)2 Æ 6H2O (0.26 g, 0.7 mmol). The precipitate
which had formed during 4 h was collected, washed with
methanol and dried under vacuum.
1 Æ Cu(ClO4)2 (1a): violet crystals (yield: 91%). Anal.
Calc. for C26H36Cl2CuN4O10 (FW = 699.04): C, 44.67; H,
5.19; N, 8.01. Found: C, 44.41; H, 5.21; N 7.94%. MS(ESI):
m/z = 598 ½M ꢀ ClO4ꢀꢁ.
3.2. X-ray structural study
In order to investigate, how complex formation mutu-
ally affects molecular conformations, we performed both
crystal structure determination of the free macrocyclic
ligands and their complexes with Cu(II) perchlorate.
Crystal data and selected experimental details are sum-
marized in Table 1. Perspective views of the structures
including the numbering schemes of relevant atoms are
shown in Figs. 1, 3, 5, 7, 9 and 11. Packing illustrations
are presented in Figs. 2, 4, 6, 8, 10 and 12. Geometric
parameters of the co-ordinative interactions are given in
Table 2.
2 Æ Cu(ClO4)2 (2a): dark-pink crystals (yield: 93%).
Anal. Calc. for C26H40Cl2CuN4O10 (FW = 703.07): C,
44.42; H, 5.37; N, 7.97. Found: C, 44.22; H, 5.78; N
7.91%. MS(ESI): m/z = 601 ½M ꢀ ClO4ꢀꢁ.
3 Æ Cu(ClO4)2 (3a): blue crystals (yield: 95%). Anal.
Calc. for C38H50Cl2CuN6O10 (FW = 885.03): calcd. C,
51.56; H, 5.69; N, 9.49. Found: C, 51.45; H, 5.72; N,
9.38%. MS(ESI): m/z = 783 ½M ꢀ ClO4ꢀꢁ.
2.4. X-ray crystallography
3.2.1. Crystal structure of 1 and 1a [1 Æ Cu(ClO4)2]
In a general procedure, the addition of Cu(ClO4)2 Æ
6H2O to an equimolar solution of the respective ligand
(1–3) in methanol yielded the complexes 1a–3a as
amorphous powders. Further crystallization from selected
solvents produced crystals suitable for X-ray crystallo-
graphic analysis. Crystallographic data of the complexes
and those of the free ligands are summarized in Table 1.
X-ray diffraction studies of 1, 2, 2a, 3 Æ 2CHCl3 and 3a
were carried out on a Bruker-AXS APEX2 diffractometer
The X-ray crystallographic analysis of the macrocyclic
diimine 1 yields the orthorhombic space group P212121.
Obviously, under the chosen conditions of crystal growing
spontaneous optical resolution occurs, so that a given crys-
tal consists of molecules of the same absolute configura-
tion, which is R,R or S,S at the chiral centers C(1) and
C(6) (Fig. 1a). The mean planes of the two C-N@C–C ring
fragments are oriented at an angle of nearly 50ꢁ to each
other inducing a boat-like conformation which forces the
two exocyclic methyl groups into a syn-diequatorial
arrangement. The aromatic rings are inclined with an angle
of 40.9ꢁ towards each other. Moreover, as illustrated by the
space filling model (Fig. 1b), partial collapsing of the intra-
molecular cavity leaves only a small ‘hole’ of approxi-
˚
with a CCD area detector (Mo Ka; k = 0.71073 A, graph-
ite monochromator): frames were collected at T = 93 K or
103 K with x and / rotation at 5 or 10 s per frame. The
measured intensities were reduced to F2 and corrected for
absorption with SADABS (SAINT-NT [33]). Structure solution,
refinement and data output were carried out with the
SHELXTL program package [34]. All non-hydrogen atoms
were refined anisotropically. With the exception of the
amino hydrogens in the structures 3a, 2 and 3 all other
hydrogens were included in the models in calculated posi-
tions and were refined as constrained to bonding atoms.
The X-ray diffraction data collection of 1a were collected
on a CAD4 diffractometer in the x–2h scan mode (Cu
˚
mately 2.6 · 2.8 A being defined by the four nitrogen
atoms. The fact, that neither significant conventional
hydrogen bonds [37] nor weak directional contacts like
C–Hꢂ ꢂ ꢂp [38,39] and pꢂ ꢂ ꢂp interactions [40,41] are found
in the crystal structure suggests that the strongly bent
and compact shape of the molecule follows close-packing
requirements. Thus, the crystal packing of 1 (Fig. 2) is
characterized by an intensive nesting of molecules with
the methoxy substituents and the voids of adjacent mole-
cules gearing together.
˚
Ka; k = 1.5418 A, graphite monochromator). The
SHELXS-97 program was applied for structure solution,
while the SHELXL-97 was used for structure refinement
[35]. All data were corrected for Lorentz and polarization
effects.
Crystallization of the complex 1a from acetonitrile/H2O
yields violet crystals of the non-centrosymmetric space
group Pn. Due to the presence of a glide plane, the crystal

Table 1
Crystallographic and structure refinement data of the compounds studied
Compound
1
1a
2
2a
3
3a
Empirical formula
Formula weight
Crystal system
Space group
C
26H36N4O2
C26H36N4O10CuCl2
699.04
monoclinic
Pn
C26H40N4O2
440.62
monoclinic
P21/n
7.5373(2)
14.8712(5)
11.1425(4)
90.0
99.931(2)
90.0
C26H40N4O10CuCl2
703.06
monoclinic
P21/n
17.8549(6)
9.1070(3)
19.5525(8)
90.0
107.507(1)
90.0
C26H36N4O2 Æ 2CHCl3
861.58
triclinic
C38H50N6O10CuCl2
885.28
monoclinic
P21/n
8.9596(2)
12.8072(2)
16.7692(2)
90.0
95.322(1)
90.0
436.60
orthorhombic
P212121
8.0569(3)
13.2765(7)
22.5701(8)
90.0
90.0
90.0
2414.27(18)
4
ꢀ
P1
˚
a (A)
9.455(2)
13.833(2)
11.765(2)
90.0
93.18(3)
90.0
8.6908(2)
9.1665(3)
13.6417(4)
89.295(2)
75.642(1)
87.870(1)
1052.08(5)
1
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
1536.4(5)
2
1230.23(7)
2
3032.06(19)
4
1915.93(8)
2
Z
F(000)
952
1.201
0.077
726
1.511
0.945
480
1.189
0.076
1468
1.540
0.958
452
1.360
0.451
926
1.535
0.777
Dc (Mg mꢀ3
)
l (mmꢀ1
)
Data collection
Temperature (K)
Number of
93(2)
18134
298(2)
3539
103(2)
14433
103(29)
36331
93(2)
61353
93(2)
40344
collected reflections
Within the h-limit (ꢁ)
Index ranges h, k,
Number of
2.4–29.8
2.3–27.0
2.7–28.5
1.4–29.5
2.2–40.5
2.4–31.9
l
ꢀ11/9, ꢀ16/17, ꢀ31/31
0/12, 0/17, ꢀ15/14
ꢀ5/10, ꢀ19/19, ꢀ14/13
ꢀ24/13, ꢀ11/12, ꢀ25/27
ꢀ15/15, ꢀ16/16, ꢀ24/24
ꢀ13/13, ꢀ19/18, ꢀ23/24
6480
3539
3076
8367
13414
6544
unique reflections
Rint
0.0738
0.0000
0.0439
0.0450
0.0263
0.0342
Refinement calculations
full-matrix least-squares
on F2 values
full-matrix least-squares
on F2 values
full-matrix least-squares
on F2 values
full-matrix least-squares
on F2 values
full-matrix least-squares
on F2 values
full-matrix least-squares
on F2 values
2
2
2
2
2
2
Weighting expression wa
½r2ðF 2oÞ þ ð0:0490PÞ
½r2ðF 2oÞ þ ð0:0967PÞ
½r2ðF 2oÞ þ ð0:1000PÞ
½r2ðF 2oÞ þ ð0:1131PÞ
½r2ðF 2oÞ þ ð0:0524PÞ
½r2ðF 2oÞ þ ð0:0000PÞ
þð0:0000PÞꢀ1
ꢁ
þð0:0000PÞꢀ1
ꢁ
þð0:0000PÞꢀ1
ꢁ
þð12:8379PÞꢀ1
ꢁ
þð0:3052PÞꢀ1
ꢁ
þð0:0000PÞꢀ1
ꢁ
Number of
293
401
163
443
252
265
refined parameters
Number of F
4016
2003
2022
5302
10123
5529
values used [I > 2r(I)]
Final R-indices
P
P
R(= jDFj/ jFoj)
0.0598
0.1308
1.014
0.23/ꢀ0.46
0.0617
0.1708
0.984
0.84/ꢀ0.53
0.0530
0.1676
1.031
0.45/ꢀ0.21
0.0785
0.2299
0.992
0.87/ꢀ0.96
0.0408
0.1128
0.984
1.282/ꢀ0.986
0.0419
0.0739
0.956
1.09/ꢀ0.94
wR on F2
S(=Goodness of fit on ꢀF32)
˚
Final Dqmax/Dqmin (e A
)
a
P ¼ ðF 2o þ 2F 2c Þ=3.

T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
3467
Table 2
a
b
˚
Structural parameters (distances/A, angles/ꢁ) involving co-ordinative
interactions of complexes 1a, 2a and 3a
C3
Atoms involved
1a
2a
3a
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–N(3)
Cu(1)–N(4)
Cu(1)–O(1)
Cu(1)–O(5)
Cu(2)–N(1A)
Cu(2)–N(2A)
Cu(2)–O(1A)
1.966(12)
1.975(11)
2.032(10)
1.979(11)
2.574(10)
2.976(11)
2.015(4)
2.038(3)
2.036(1)
2.106(1)
2.517(1)
N1
N2
C1
O1
C6
N4
2.562(3)
N3
O2
2.022(3)
2.029(3)
2.363(4)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–N(3)
N(2)–Cu(1)–N(4)
N(1)–Cu(1)–N(4)
N(2)–Cu(1)–N(3)
N(3)–Cu(1)–N(4)
O(1)–Cu(1)–O(5)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(2)
O(1)–Cu(1)–N(3)
O(1)–Cu(1)–N(4)
O(5)–Cu(1)–N(1)
O(5)–Cu(1)–N(2)
O(5)–Cu(1)–N(3)
O(5)–Cu(1)–N(4)
N(1A)–Cu(2)–N(2A)
O(1A)–Cu(2)–N(1A)
O(1A)–Cu(2)–N(2A)
94.7(5)
175.8(6)
177.7(5)
85.7(4)
87.8(5)
91.7(4)
163.6(5)
88.2(5)
90.4(5)
95.2(4)
91.8(5)
71.5(5)
91.0(6)
105.1(4)
86.9(5)
93.2(1)
86.5(1)
91.3(1)
78.5(1)
88.5(1)
101.9(1)
89.8(1)
Fig. 1. (a) Molecular structure with atom labelling of relevant atoms and
displacement ellipsoids at the 40% probability level and (b) space filling
model of 1.
Cu–O bond lengths and the O–Cu–O angle that deviates
significantly from linearity (163.6ꢁ). The Cu–O distances
˚
of 2.574(10) and 2.976(11) A also indicate rather weak
coordination of the anions to the copper center. The Cu–
2
˚
N(sp ) distances [1.975(11), 1.979(11) A] and the Cu–
3
˚
N(sp ) bond lengths [1.966(12), 2.032(10) A] are in the
same order of magnitude. The high degree of conforma-
tional distortion can be attributed to the different binding
behavior of the two perchlorate anions. One of them is
c
b
O2
Cl1
O3
O1
O4
C6
N1
Fig. 2. Packing structure of 1 with carbon-bonded hydrogen atoms
omitted.
Cu1
C1
N3
N1
N4
O7
H1
H3
O10
consists of a racemic mixture of stereoisomers of the con-
figuration R,R and S,S while the meso R,S-stereoisomer
has not been found in the crystalline form. The amino
hydrogens H(10) and H(30) of 1a are located on one side
of the macrocycle. Since they contact to the ether oxygens
of the anisyl residues, their methoxy groups exhibit a syn-
arrangement (Fig. 3). Another interesting structural feature
of 1a can be seen in the highly distorted coordination
sphere of the copper ion, which is reflected by unequal
O9
O6
O5
Cl2
O8
Fig. 3. Molecular structure of 1 Æ Cu(ClO4)2 with atom labelling of
relevant atoms and displacement ellipsoids at the 40% probability level.
Only one site of the disordered perchlorate ions is displayed. Broken lines
represent hydrogen bond type contacts.

3468
T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
primarily associated to the ligand via intramolecular N–
strained conformation (Fig. 5). With the exception of the
axial amino hydrogens H(20), which for sterical reasons
are not associated, all other strong donors and acceptors
are involved in intramolecular hydrogen bonding. Two of
the N–H bonds are directed towards the ring center, which
opens the possibility of forming asymmetrical bifurcated
hydrogen bonds [37] of the N–Hꢂ ꢂ ꢂN type [N(1)–
˚
Hꢂ ꢂ ꢂO contacts (Oꢂ ꢂ ꢂH 2.243, 2.302 A), while the other
one is involved in intermolecular C–Hꢂ ꢂ ꢂO hydrogen bond-
˚
ing (Oꢂ ꢂ ꢂH 2.495, 2.664 A) [42,43]. The crystal packing of
1a is composed of molecular layers running parallel to
the crystallographic B-plane (Fig. 4). They are held
together by weak C–Hꢂ ꢂ ꢂO hydrogen bond type contacts
0
0
˚
˚
˚
(Oꢂ ꢂ ꢂH 2.49 A) and pꢂ ꢂ ꢂp stacking interactions between
H(1 )ꢂ ꢂ ꢂN(2) 2.32 A, 135.0ꢁ; N(1)–H(1 )ꢂ ꢂ ꢂN(2A) 2.57 A,
110.7ꢁ], thus giving a cyclic four-membered hydrogen bond
motif inside the macroring. As a consequence, van der
Waals type interactions primarily contribute to the stabil-
ization of the columnar packing mode of compound 2
(Fig. 6). Former investigations have shown that reduction
of the unsubstituted diphenyl analogue of the diimine 1
yields the three possible stereo isomeric tetraazacyclote-
tradecanes in ca. 85:15:1 ratio [44,45]. The major product,
the aromatic groups. The interlayer association is accom-
plished by the perchlorate ions that form weak interactions
to arene and methylene hydrogens.
Previous papers have been published on metal com-
plexes formed by the unsubstituted diphenyl analogue of
1 [21,29]. The crystal structure of the Ni(ClO4)2 complex
[29], in which the diimine ligand has the same chirality as
in 1a, shows that the absence of the methoxy groups does
not much effect the molecular conformation. On the other
hand, the Ni(II) cation induces significant changes in coor-
dination behavior compared to the Cu(II) in 1a. Only one
of the perchlorate ions occupies an axial position with both
N–H groups oriented towards the opposite side of the
NiN4 plane, forming N–Hꢂ ꢂ ꢂO hydrogen bonds to oxygen
atoms of different perchlorate ions. Thus, a totally different
molecular assembly within the crystal results.
N1
H1
C1
H2
N2
H1
3.2.2. Crystal structure of 2 and 2a [2 Æ Cu(ClO4)2]
The macrocyclic tetraamine 2 yields colorless crystals of
the monoclinic space group P21/n with two molecules
within the unit cell. The torsion angles along the macroring
are all gauche and anti. Although not all of them adopt
idealized values (ꢀ66.0ꢁ, 175.4ꢁ, ꢀ175.2ꢁ, 69.6ꢁ, 168.3ꢁ,
ꢀ168.8ꢁ, 72.8ꢁ), the macrocycle shows a regular, less
O1
Fig. 5. Perspective view of 2 with numbering of relevant atoms and
displacement ellipsoids at the 40% probability level. Broken lines represent
hydrogen bond type contacts.
b
a
c
Fig. 4. Packing illustration of 1 Æ Cu(ClO4)2. Non-relevant hydrogen atoms are omitted for clarity.

T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
3469
a
c
b
Fig. 6. Packing structure of 2. Non-relevant hydrogen atoms are omitted for clarity.
which has been characterized by X-ray analysis [46] agrees
with the configuration found for 2.
while in the second complex the respective bond is
˚
˚
2.363(4) A. The Cu–N bond lengths [2.015(4)–2.038(3) A]
are within the expected range [7]. The six-membered chelate
rings of the complex molecules adopt a distorted chair-like
conformation with the anisyl and methyl substituents in
equatorial positions, whereas the five-membered chelate
rings are twisted. The aromatic units are arranged nearly
perpendicular (88.4ꢁ, 86.7ꢁ) with respect to the CuN4-
plane. Although the independent molecules have similar
conformations, they deviate in their mode of interactions.
In molecule 1, the atom H(10) forms an intramolecular
bifurcated hydrogen bond [37] to the oxygens O(2)
Crystallization of complex 2a from acetonitrile/H2O
yields crystals of the monoclinic space group P21/c with
two crystallographically independent halves of molecules
in the asymmetric unit of the cell (Fig. 7), i.e. the copper
atoms are located on crystallographic inversion centers
(1/2,1/2,0 and 1,0,0). In both molecules, the anions are
disordered over two sites. The Cu(II) exhibits an elongated
octahedral coordination environment with the axial posi-
tions being occupied by one oxygen atom of each perchlo-
rate ion. In one of the complexes, the Cu–O distance is
˚
˚
˚
rather long [2.562(3) A] indicating only a weak binding,
(2.245 A) of the perchlorate anion and O(5) (2.225 A) of
O4
O3
molecule 1
Cl1
O1
O2
H2
N2
H1
Cu1
N1
H2
N2A
O4A
N1A
Cu2
Cl2
H1
O5A
O2A
C1A
O1A
O3A
molecule 2
Fig. 7. Molecular structure of 2 Æ Cu(ClO4)2 with numbering of relevant atoms and displacement ellipsoids at the 40% probability level. Only one site of
the disordered perchlorate ions is displayed. Broken lines represent hydrogen bond type contacts.

3470
T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
the anisyl group, while H(20) remains free. In molecule 2,
all amino hydrogens participate in intramolecular hydro-
could be gained from the difference electron density map, is
directed towards the interior of the ring, and its well-
defined N–Hꢂ ꢂ ꢂN geometry suggests the existence of a
gen bonding [H(100)ꢂ ꢂ ꢂO(1A) 2.284 A, H(200)ꢂ ꢂ ꢂO(4A)
˚
0
˚
˚
2.196 A]. The packing of the crystals consists of infinite
weak hydrogen bridge to N(1) [N(2)–H(2 )ꢂ ꢂ ꢂN(1) 2.25 A,
137.7ꢁ]. The packing structure of the solvent complex of
molecular chains extending in direction of the crystallo-
graphic c-axis (Fig. 8). Within these chains, the basal
planes of consecutive molecules are titled to each other
with an angle of 52.5ꢁ thus allowing formation of intermo-
˚
lecular C–Hꢂ ꢂ ꢂO hydrogen bonds (Oꢂ ꢂ ꢂH 2.200, 2.562 A)
between the anions and methyl groups of the ligands.
3.2.3. Crystal structure of 3 Æ 2CHCl3 and 3a
[3 Æ Cu(ClO4)2]
Crystals of compound 3, suitable for diffraction experi-
ments, could only be obtained as 1:2 (host:guest) solvent
ꢀ
complex with chloroform (space group P1). The unit cell
of the crystal contains one complex entity (Fig. 9) with
the solvent molecules associated via C–Hꢂ ꢂ ꢂN hydrogen
bond type interactions [42,43] with the pyridyl nitrogen
N1
˚
[N(3)ꢂ ꢂ ꢂH(1G) 2.37 A]. Also in the present case, intramo-
O1
lecular contacts contribute to the molecular conformation.
The hydrogen atom attached to N(2), the position of which
H2
N2
N3
C1G
Cl2
Cl3
Cl1
a
Fig. 9. Perspective view of the host–guest unit 3 Æ CHCl3 (1:2) with
numbering of relevant atoms and displacement ellipsoids at the 40%
probability level. Hydrogen bond type contacts are displayed as broken
lines.
c
b
Fig. 8. Packing illustration of 2 Æ (ClO4)2.
a
c
Fig. 10. Packing diagram of 3 Æ CHCl3 (1:2). Non-relevant hydrogen atoms are omitted for clarity.

T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
3471
3 is composed of discrete 3 Æ CHCl3 1:2 aggregates stacked
in a columnar array along the crystallographic b-axis
(Fig. 10). Within the stacks, the host molecules are associ-
ated by aromatic edge-to-face (C–Hꢂ ꢂ ꢂp) contacts [38,39]
with the electron deficient pyridyl residues acting as donors
and the electron-rich anisyl groups as hydrogen bond
acceptors. The distance between the para C–H hydrogen
of the pyridine and the ring centroid of the anisyl is
molecule with the copper atom located on the symmetry
center 1/2,1,0. Different from structures 1a and 2a, the per-
chlorate ions of 3a are not involved in complexation
(Fig. 11). Instead, the nitrogen atoms of the two pyridyl-
methyl substituents occupy the apical sites of the octahedral
coordination polyhedron. The axial Cu–N distances are
˚
2.517(1) A, whereas the equatorial Cu–N bonds are
˚
2.036(1) and 2.106(1) A. For steric reasons, the planes of
˚
2.53 A, while the C–Hꢂ ꢂ ꢂcentroid angle is 152.2ꢁ.
the pyridyl residues are inclined at an angle of 54.3ꢁ with
respect to the CuN4 basal plane. Although rich in strong
hydrogen bond acceptors, the anions show only poor asso-
ciation. Obviously, shielding of the amino hydrogens by
the 2-picolyl units prevents effective hydrogen bonding to
the counter ions. The same co-ordination behavior is also
found in reported structures of copper(II) complexes hav-
ing a similar pyridyl-substituted cyclam framework but dif-
fer in the mode of substitution [25–28]. It is also interesting
to compare the structure of 3a with the crystal structure of
the copper(II) complex of the N-acetyl diphenyl substituted
cyclam derivative reported previously [24]. In this struc-
ture, the charged carboxylate oxygens act as apical coordi-
nation sites of the trans-octahedral coordination
environment of Cu(II). In addition, two ethanol molecules
are hydrogen bonded to the two coordinated carboxyl oxy-
gens thus preventing further intermolecular contacts.
The packing structure of 3a is characterized by two-
dimensional layers of complex cations which are stacked
along the crystallographic c-axis (Fig. 12). The arrange-
ment is stabilized by perchlorate ions, which fill the intersti-
tial spaces between the layers and bridge the cations by
The Cu(II) complex 3a yields blue crystals of the mono-
clinic space group P21/n when crystallized from methanol.
The asymmetric unit of the cell contains one half of the
H1
C5
Cu1
N1
O1
N2
C1
N3
O4
O2
O5
Cl1
˚
weak C–Hꢂ ꢂ ꢂO contacts (Oꢂ ꢂ ꢂH 2.34–2.58 A) [42,43]. Aro-
O3
matic pꢂ ꢂ ꢂp interactions [40,41] are formed within the lay-
ers. The interacting aryl groups are displaced relative to
Fig. 11. Molecular structure of 3 Æ Cu(ClO4)2 with numbering of relevant
atoms and displacement ellipsoids at the 40% probability level. Broken
lines represent hydrogen bond type interactions.
˚
each other, showing centroid–centroid distances of 4.50 A
˚
for the phenyl rings and 4.30 A for coordinated pyridyl
c
b
a
Fig. 12. Packing illustration of 3 Æ Cu(ClO4)2 with aromatic p–p interactions depicted as broken double lines. All hydrogen atoms are omitted for clarity.

3472
T. Scho¨nherr et al. / Polyhedron 25 (2006) 3463–3473
fragments. Other types of non-covalent cation–cation
interactions are not observed in the crystal.
ture of the respective complex 1a has also an enantiomor-
phous configuration attributed to the R,R or S,S
configuration at the chiral C atoms. Obviously, the reduced
number of strong hydrogen bond donors, which is only
half of those found in the complexes 2a and 3a and which
determine the degree of cation–anion interactions, results
in a less symmetric boat-like geometry of the complexed
macrocycle.
Thus, only the pyridine containing pendants in 3a
proved effective in coordination of the metal ion while
the uncomplexed macrocycle 3 yielded an inclusion com-
pound with chloroform, also indicating a special ability
relating to this series of compounds.
4. Conclusion
A comparative structural study involving a designed ser-
ies of cyclam type derivatives 1–3 that feature a different
degree of saturation, and thus flexibility of the macroring,
different number of functional appendages, and thus power
of coordination, including their respective complexes with
Cu(II) perchlorate has been reported.
X-ray crystal structures of the uncomplexed macrocycles
1–3 reveal that steric shielding caused by the ring substitu-
ents prevents the amino hydrogens from forming effective
non-covalent bonding between molecules. Instead, these
donors are either free or are used for intramolecular hydro-
gen bonding. The unsaturated diimine macrocycle 1 crystal-
lizes in a non-centrosymmetric crystal structure. According
to the given space group, a selected crystal contains mole-
cules of the same absolute configuration and therefore is
optically active. The strongly distorted geometry with a
nearly complete collapsing of the macrocyclic cavity means
that no intramolecular hydrogen bonds are present. In the
case of 2, two of the amino hydrogens are directed to the
interior of the macrocycle giving a four-membered system
of bifurcated hydrogen bonds, which is also found in crystal
structures of related cyclam derivatives [22,23]. Intramolec-
ular hydrogen bonding of the N-substituted macrocyclic
ring is also found in the 1:2 inclusion compound of 3 with
chloroform. However, only two bent N–Hꢂ ꢂ ꢂN hydrogen
bonds are present giving the molecule a pseudo-tricyclic
structure.
5. Supplementary data
Full details of the crystal structure analyses of 1, 2, 3, 1a,
2a and 3a have been deposited with the Cambridge Crystal-
lographic Data Centre (CCDC Nos. 288907–288909 and
288904–288906, respectively). Copies may be obtained free
of charge on application to the Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK [fax (int. code): +44 1223
336 033, e-mail: deposit@ccdc.cam.ac.uk].
Acknowledgements
We gratefully acknowledge financial support by the
firms of Hoechst and Clariant, as well as the Fonds der
Chemischen Industrie.
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