Synthesis of 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-azacyclotetradecane, a new pentadentate polyamine ligand, and crystal structure of its Co(III) complex

Article abstract of DOI:10.1016/S0020-1693(99)00031-6

The facile synthesis of the hydrochloride salt of the 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-azacyclotetradecane L³ is reported. The Co(III) complex of this new pentadentate ligand crystallizes in the space group P2₁/n, with a=15.5901(3), b=8.9267(2), c=20.6011(4) A, β=100.5960(10)°. X-ray crystal structure analysis has shown the 6-amino group axially coordinated to the metal center, and the cyclam moiety taking a trans I configuration. Water coordinates at the sixth site. The axial Co-N distance is 1.935(3) A, and the cyclam core nitrogen-Co distances are in the range between 1.957(3) and 1.964(3) A, shorter than previously reported data for similar macrocyclic complexes. The crystal structure of the complex [Cu(L²)(NO₃)₂] (L²: 6-nitro-6-(4-nitrobenzyl)-1,4,8,11-tetraazacyclotetradecane), synthetic precursor to the L³ ligand is also reported. It crystallizes in the space group P2₁/n, with a=19.49560(10), b=8.38520(10), c=15.8518(2) A, β=111.03°.

Full text of DOI:10.1016/S0020-1693(99)00031-6

Inorganica Chimica Acta 288 (1999) 40–46
Synthesis of 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-
azacyclotetradecane, a new pentadentate polyamine ligand, and
crystal structure of its Co(III) complex
Giulio A. Amadei, Michael H. Dickman, Rabei A. Wazzeh, Paul Dimmock,
Joseph E. Earley *
Department of Chemistry, Georgetown Uni6ersity, Washington DC 20057-1227, USA
Received 11 August 1998; accepted 8 January 1999
Abstract
The facile synthesis of the hydrochloride salt of the 6-amino-6-(4-aminobenzyl)-1,4,8,11-tetra-azacyclotetradecane L3 is
reported. The Co(III) complex of this new pentadentate ligand crystallizes in the space group P21/n, with a=15.5901(3),
˚
b=8.9267(2), c=20.6011(4) A, i=100.5960(10)°. X-ray crystal structure analysis has shown the 6-amino group axially
coordinated to the metal center, and the cyclam moiety taking a trans I configuration. Water coordinates at the sixth site. The
˚
˚
axial Co–N distance is 1.935(3) A, and the cyclam core nitrogen–Co distances are in the range between 1.957(3) and 1.964(3) A,
shorter than previously reported data for similar macrocyclic complexes. The crystal structure of the complex [Cu(L2)(NO3)2] (L2:
6-nitro-6-(4-nitrobenzyl)-1,4,8,11-tetraazacyclotetradecane), synthetic precursor to the L3 ligand is also reported. It crystallizes in
˚
the space group P21/n, with a=19.49560(10), b=8.38520(10), c=15.8518(2) A, i=111.03°. © 1999 Elsevier Science S.A. All
rights reserved.
Keywords: Crystal structures; Cobalt complexes; Copper complexes; Azamacrocycle complexes; Cyclam complexes
1. Introduction
tetraazamacrocycle with a pendant amine group (L1),
showed that the primary amino group was axially
coordinated to the metal center, with the sixth coordi-
nation position occupied by water. We now report the
facile synthesis and characterization of tetraazamacro-
cycle (L3), along with the crystal structures of the
[Co(L3)(H2O)]3+ complex and of the [Cu(L2)(NO3)2]
complex, synthetic precursor of L3. The principal fea-
tures of this ligand are the presence of two pendants
directly linked to a carbon atom of the main frame of
the tetraazamacrocycle. One pendant is a primary
amino group, able to axially coordinate to the metal
center, the second one is a p-aminobenzyl moiety,
potentially with the ability to link to biomolecules, such
as proteins [8] or antibodies [2,3]. The facile synthetic
route employed for its preparation enhances the intrin-
sic interest of this new cyclam-based ligand.
Cyclams (1,4,8,11-tetraazacyclotetradecanes) form
stable N4-complexes [1] of transition metal ions. Syn-
thesis of C- and N-functionalized cyclams has been
extensively explored [2–8]. Kimura and et al. [9] pre-
pared, following a synthetic route that seemed difficult
to reproduce, an octahedral Ni(II) complex of a tetra-
azamacrocycle with a phenol-pendant (L0) showing the
hydroxyl group axially coordinated to the metal center,
with the sixth coordination position occupied by a
perchlorate ion (Fig. 1). More recently [10], crystal
structure analysis of the octahedral Ni(II) complex of a
* Corresponding author. Tel.: +1-202-687 6073; fax: +1-202-687
6209.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00031-6

G.A. Amadei et al. / Inorganica Chimica Acta 288 (1999) 40–46
41
Across. Acetic anhydride (99.5%) and formaldehyde
(40% aqueous solution) were purchased from Fisher
Chemical. 1,3-Dibromopropane (98%) was purchased
from Janssen Chimica and cobalt chloride hexahydrate
(99%) from J.T. Baker Chemical. All solvents (GR) and
potassium hydroxide (85%) were purchased from EM
Science. All chemicals employed were used without
further purification.
All syntheses were carried out by modifications of
published methods. The polyamine 1,9-diamino-3,7-dia-
zanonane starting material was synthesized according
to the method described by Bounsall and Koprich [14].
All the precursors to the L3 hydrochloride ligand were
synthesized according to the method described by
Bayada et al. [8], except for the synthesis of 1-nitro-2-
(4-nitrobenzyl)ethan-2-ol, whose reported preparation
was found difficult to reproduce. The modified proce-
dure described hereafter was employed instead.
Fig. 1. Fully saturated tetraaza macrocyclic ligands.
2.2. Synthesis of 1-nitro-2-(4-nitrobenzyl)ethan-2-ol,
[C8H8N2O5]
2. Experimental
A mixture of p-nitrobenzaldehyde (25.3 g, 0.168
mol), potassium fluoride dihydrate (1.6 g, 0.0170 mol)
and nitromethane (12.65 g, 0.207 mol) was prepared in
iPrOH (270 ml). Stirring the milky suspension overnight
at room temperature (r.t.) yielded a clear orange solu-
tion. Diethyl ether (250 ml) was then added, followed
by several washings with water to remove most of the
iPrOH. The ether layer was then washed several times
with a solution of Na2S2O5 (68 g Na2S2O5 in 400 ml
H2O) to remove any unreacted aldehyde. After washing
with water, drying over MgSO4, and evaporating off
the diethyl ether, the 1-nitro-2-(4-nitrobenzyl)ethan-2-ol
(27.6 g, 78%, m.p.: 79–81°C) was recovered as a golden
solid. IR spectrum (thin film): 3495 cm−1 (OH), 2925,
2868 cm−1 (CH), 1608 cm−1 (aromatic CꢀC), 1555,
2.1. Methods and materials
Electronic spectra were recorded using a Hewlett-
Packard 8451A diode array spectrophotometer. IR
spectra were recorded using a Mattson Instruments
2020 Galaxy Series FT IR. H and 13C NMR spectra
1
were recorded using a Varian FT NMR Mercury-300
NMR spectrometer working at 300.075 and 75.461
MHz, respectively; chemical shifts cited are given versus
TMS (SiMe4). Structural determinations were obtained
using a Siemens SMART CCD diffractometer having
an Mo anode and graphite monochromator. Crystals
were mounted on glass fibers and a sphere of data was
collected using omega scans. Routine Lorentz and po-
larization corrections were applied. A semi-empirical
absorption correction was applied based on multiple
scans of equivalent reflections at different phi and
1
1522, 1350 cm−1 (NO2). H NMR spectrum (CDCl3):
3.11 ppm (t, 1H, CH), 4.56 ppm (d, 2H, J=4 Hz,
CH2), 5.59 ppm (s, 1H, OH), 7.6–8.3 ppm (aromatic
AB system, 4H, dd). 13C NMR spectrum (CDCl3):
aliphatic carbons: 68.3 ppm (CHOH), 80.2 ppm (CH2–
NO2). Aromatic carbons: 122.3, 125.9, 146.2 ppm.
omega values [11]. Programs used were SMART, SAINT,
SHELXTL [12,13]. Direct methods solutions were suc-
cessful. Hydrogen atoms were refined isotropically in
observed positions. Refinements were full-matrix least-
squares on F2 using all data. The weighting scheme
used throughout was w=1/(|2(Fo2)+(AP)2+(BP)],
where P=(Fo2−2Fc2)/3. Melting points were obtained
using a Lentz 585 SM-LUX-POL microscope equipped
with cross polarizer for crystal clarity enhancement and
a Lentz 350 heating stage connected to a variac and an
Omega HH 21 Microprocessor Thermometer via a JKT
thermocouple. Ethylenediamine (99%), p-nitrobenzal-
dehyde (99%), potassium fluoride dihydrate (98%) and
sodium borohydride (99%) were purchased from
Aldrich. Nitromethane (96%) and the cation resin ex-
changer Dowex 50Wx2-100 were purchased from
2.3. Synthesis of 1-nitro-2-(4-nitrobenzyl)ethyl-
ethanoate [C10H10N2O6]
1-Nitro-2-(4-nitrobenzyl)ethylethanoate was prepared
according to the method developed by Bayada et al. [8].
It was recrystallized from EtOH 95% yielding a golden
solid product (83.0 g, 93%, m.p.: 102–104°C). IR spec-
trum: (thin film): 2925, 2868 cm−1 (CH), 1753 cm−1
(CꢀO), 1608 cm−1 (aromatic CꢀC), 1555, 1522, 1350
1
cm−1 (NO2). H NMR spectrum (CDCl3): 2.23 ppm (s,
3H, CH3–CꢀO), 3.10 ppm (t, 1H, CH), 4.61 ppm (d,
2H, J=4 Hz, CH2), 7.6–8.3 ppm (aromatic AB system,

42
G.A. Amadei et al. / Inorganica Chimica Acta 288 (1999) 40–46
4H, dd). 13C NMR spectrum (CDCl3/DMSO-d6):
aliphatic carbons: 20.7 ppm (CH3 acetate), 70.7 ppm
(CHOH), 77.4 ppm (CH2–NO2), 168.9 ppm (CꢀO).
Aromatic carbons: 124.2, 127.5, 148.2 ppm.
solved in HCl (30 ml, 30 mmol) and excess zinc pow-
der added. The mixture was stirred and warmed at
ca. 60°C until no purple color was detectable (ca.2.5
h). Vacuum filtration was used to remove copper and
unreacted zinc powder. The filtrate was diluted to 200
ml with deionized water and sorbed onto a column
filled with Dowex 50Wx2-100 (H+ form, ca. 40 ml)
cation-exchange resin. Washing with 1 M HCl (ca.
500 ml) removed zinc ions (dithizone test). Washing
with 3 M HCl (ca. 300 ml) removed the macrocycle
(identified by neutralizing an aliquot of the eluate and
adding cupric ions to produce a purple solution). Ro-
tary evaporation of the eluate was performed until
incipient precipitation, to isolate the hygroscopic
macrocyclic amine salt. The compound was vacuum
filtered, washed with ethanol and diethyl ether, then
dried under vacuum (0.42 g, 25%). 1H NMR spec-
trum (D2O): 2.00 ppm (q, 2H, CH2), 3.02 ppm (s,
2H, CH2-benzylic), 3.10–3.50 ppm (unresolved multi-
plet 16H). 13C NMR off-resonance decoupled spec-
trum (D2O): cyclam portion: 21.9 ppm (t, J=123
Hz), 43.0 ppm (t, J=132 Hz), 44.0 ppm (t, J=132
Hz), 44.8 ppm (t, J=132 Hz), 51.6 ppm (s), 57.1
ppm (t, J=130 Hz). Benzylic CH2: 39.4 ppm (t, J=
125 Hz). Microanalysis. Found: C, 35.83; H, 5.29;
Cu, 11.00; N, 19.09; O, 27.67. Calc.: C, 34.84; H,
5.16; Cu, 10.84; N, 19.12; O, 30.03%.
2.4. Synthesis of 1-nitro-2-(4-nitrobenzyl)ethane
[C8H8N2O4]
1-Nitro-2-phenylethane was prepared according to
the method developed by Bayada et al. [8]. The crude
compound separated off as a yellow precipitate that
was recrystallized from EtOH/H2O 1/1 mixture (100
mg crude required 2.4 ml of solvent mixture). Pure
1-nitro-2-phenylethane (23.2 g, 49%, m.p.: 78–80°C)
was obtained as a yellow thready solid. 1H NMR
spectrum (CDCl3): 3.44 ppm (t, J=7 Hz, 2H, CH2),
4.69 ppm (t, J=7 Hz, 2H, CH2–NO2), 7.4–8.2 ppm
(aromatic AB system, 4H, dd). 13C NMR spectrum:
aliphatic carbons: 32.8 ppm (Ar–CH2), 75.1 ppm
(CH2–NO2). Aromatic carbons: 129.7 ppm (ipso),
129.4 ppm (o), 123.9 ppm (m), 143.1 ppm (p, C–
NO2).
2.5. Synthesis of [6-nitro-6-(4-nitrobenzyl)-1,4,8,11-
tetraazacyclotetradecane] copper(II) nitrate hydrate,
[Cu(L2)(NO3)2]
1,9-Diamino-3,7-diazanonane [14] (3.2 g, 20.4 mmol)
in MeOH (108 ml) was added to a solution of
Cu(NO3)2 · 2.5H2O (4.75 g, 20.4 mmol) in MeOH (430
ml). An aqueous solution of formaldehyde (40%)
(21.2 g, 283 mmol), 1-nitro-2-(4-nitrobenzyl)ethane
(4.0 g, 20.4 mmol) in MeOH (220 ml) and triethy-
lamine (2.8 g, 47.1 mmol) were then added. The mix-
ture was stirred and refluxed for 2.5 h. By allowing
the solution to stand at r.t. overnight, purple crystals
appeared. Recrystallization from MeOH yielded pure
crystalline solid (6.4 g, 30%). A second crop of crys-
tals were obtained by allowing the mother liquor to
stand at r.t. for 4–7 days (1.2 g, 5.6%). Electronic
spectrum. Solvent: HCl 1.0E–04 M. umax 512 nm
(m=8693 l mol−1cm−1) and 270 nm (m=160009
1400 l mol−1cm−1). IR spectrum (KBr disk): 2925
cm−1, (CH), 1608 cm−1 (aromatic CꢀC), 1552, 1519,
1348 cm−1 (NO2). Microanalysis [C17H30CuN8O11].
Found: C, 35.83; H, 5.29; Cu, 11.00; N, 19.09; O,
27.67. Calc.: C, 34.84; H, 5.16; Cu, 10.84; N, 19.12;
O, 30.03%.
2.7. Synthesis of 6-amino-6-(4-aminobenzyl)-1,4,8,11-
tetraazacyclotetradecane [C17H32N6]
6-Amino-6-(4-aminobenzyl)-1,4,8,11-tetraazacyclote-
tradecane hydrochloride (400 mg, 0.74 mmol) was
dissolved in 20 ml KOH 1 M aqueous solution and
extracted with CHCl3 using a continuous liquid–liq-
uid extractor for 12 h. Evaporation of the solvent
yielded a yellow oil. Toluene (2 ml) was then added,
and the resulting solution was kept overnight in the
1
refrigerator yielding a white solid (180 mg, 56%). H
NMR spectrum (D2O): 1.56 ppm (q, 2H, CH2), 2.50
ppm (t, 4H, CH2–NH), 2.20–2.38 ppm (unresolved
multiplet 12H). 13C NMR off-resonance decoupled
spectrum (CDCl3): cyclam portion: 29.0 ppm (t, J=
123 Hz), 48.5 ppm (t, J=132 Hz), 49.7 ppm (t, J=
132 Hz) 53.7 ppm (s), 58.4 ppm (t, J=130 Hz).
Benzylic CH2: 44.5 ppm (t, J=125 Hz). Aromatic
carbons: 126 ppm (ipso, s), 113 ppm (o, d, J=155
Hz), 130 ppm (m, d, J=155 Hz), 145 ppm (p, C–
NH2, s).
2.6. Synthesis of 6-amino-6-(4-aminobenzyl)-1,4,8,11-
tetraazacyclotetradecane hydrochloride, L3-hydrochlor-
ide [C17H32N6 · 6HCl]
2.8. Synthesis of [6-amino-6-(4-ammoniobenzyl)-
1,4,8,11-tetraazacyclotetradecane-aquo]cobalt(III) chlo-
ride hydrate {[Co(L3)(H2O)]Cl3 · 4H2O}
[6-Nitro-6-(4-nitrobenzyl)-1,4,8,11-tetraazacyclotetra-
decane] copper(II) nitrate (2 g, 3.55 mmol) was dis-
A solution of CoCl2 · 6H2O (0.22 g, 0.93 mmol) in
methanol (36 ml) was added to a flask containing a

G.A. Amadei et al. / Inorganica Chimica Acta 288 (1999) 40–46
43
Table 1
J=132 Hz), 52.6 ppm (t, J=132 Hz), 58.3 ppm (s), 68.0
ppm (t, J=130 Hz). Benzylic CH2: 41.0 ppm (t, J=125
Hz). Aromatic carbons: 129 ppm (ipso, s), 123 ppm (o,
d, J=155 Hz), 131 ppm (m, d, J=155 Hz), 136 ppm (p,
C–NH2, s).
Crystal data and structure refinement for [Cu(L2)(NO3)2] complex
Empirical formula
C17H30CuN8O11
Formula weight (g mol−1
Temperature (K)
)
586.03
173(2)
˚
Wavelength (A)
Crystal system
Space group
0.71073
monoclinic
P21/c
3. Results and discussion
Unit cell dimensions
˚
a (A)
19.49560(10)
8.38520(10)
15.8518(2)
111.03
2418.76(4)
4
˚
b (A)
The synthetic strategy used to prepare the ligand
[Cu(L2)(NO3)2] complex was originally introduced by
Lawrence et al. [15]. We used a modification of that
procedure, developed by Bayada et al. [8], because of its
synthetic simplicity and reproducibility. One-pot, Cu(II)-
directed condensation performed between 1,9-diamino-
3,7-diazanonane, formaldehyde, and 1-nitro-2-(4-nitro-
benzyl)ethane gave us the [Cu(L2)(NO3)2] complex in a
35.6% yield. Its characterization was achieved by elemen-
tal analysis, IR, UV–Vis spectrophotometry, and X-ray
diffraction technique (Tables 1 and 2). The Cu–N bond
distances are all in the expected range of 2.011(16)–
˚
c (A)
i (°)
˚
V (A)
Z
Dcalc. (Mg m−3
)
1.609
Absorption coefficient (mm)
F(000)
0.977
1220
0.38×0.30×0.08
Crystal size (mm3)
q Range for data collection (°) 1.12–28.29
Index ranges
−245h525
−105k510
−205l520
24578
5698 [Rint=0.0326]
4766 \2|(I)
94.9%
Semi-empirical from equivalents
0.8307, 0.6448
Full-matrix least-squares on F
5698/0/454
Reflections collected
Independent reflections
Observed reflections
˚
2.024(16) A, as previously reported [16]. The coordina-
tion sphere of the Cu2+ is completed by two axially
bound nitrate ions, and the macrocycle is in its thermo-
dynamically stable trans III configuration (Fig. 2).
Reduction with Zn–HCl at 60° of the [Cu(L2)(NO3)2]
complex thus produced, and ion-exchange separation
from Zn(II) ions, gave the L3-hydrochloride in 25%
yields. Two independent approaches to the synthesis of
the [Co(L3)(H2O)]3+ complex were used. Reaction be-
tween methanolic solutions of L3-hydrochloride and
sodium triscarbonatocobaltato(III) trihydrate [17], re-
ported to be stable when dry [18], gave variable yields.
Completeness to q=28.29°
Absorption correction
Max./min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F
Final R indices [I\2|(I)]
R indices (all data)
1.104
R1=0.0352, wR2=0.0705
R1=0.0487, wR2=0.0784
0.275, −0.430
Largest difference peak, hole
−3
˚
(e A
)
slurry of L3-hydrochloride (0.5 g, 0.93 mmol) in
methanol (10 ml). Triethylamine (0.94 g, 9.3 mmol) was
then added, and the mixture refluxed and aerated for 2
h. Concentrated HCl (ca. 2 ml) was added, the solution
filtered, diluted to 500 ml and sorbed onto a column of
Dowex 50Wx2-100 (H+ form, ca. 40 ml) cation exchange
resin. Washing with 1 M HCl removed unreacted Co2+
(thiocyanate/EtOH test). The brown–red band of the
product was eluted using 3 M HCl. Evaporation of most
of the solvent to a 10 ml final volume, followed by
standing in refrigerator for several weeks, yielded crim-
son crystals (0.12 g, 22%). Electronic spectrum. Solvent:
HCl 1.0E–04 M. umax 488 nm (m=75 l mol−1cm−1) and
364 nm (m=120 l mol−1cm−1). IR spectrum (KBr disk):
2925 cm−1, (CH), 1611 cm−1 (aromatic CꢀC), 1560,
1521, 1346 cm−1 (NO2). Microanalysis [C17H43Cl4-
CoN6O5]. Found: C, 33.92; H, 7.10; Co, 9.65; N, 14.00;
O, 13.01. Calc.: C, 33.35; H, 7.08; Co, 9.62; N, 13.73; O,
Table 2
2
a
˚
Selected bond lengths (A) and angles (°) for [Cu(L )(NO3)2] complex
˚
Bond lengths (A)
Cu–N(2)
Cu–N(4)
Cu–N(3)
Cu–N(1)
Cu–O(5)
Cu–O(8)
N(1)–C(2)
N(1)–C(3)
N(3)–C(8)
N(3)–C(7)
2.0112(16)
2.0121(16)
2.0138(16)
2.0244(16)
2.4846(15)
2.5253(16)
1.476(2)
1.490(2)
1.484(3)
1.485(3)
Bond angles (°)
N(2)–Cu–N(4)
N(2)–Cu–N(3)
N(4)–Cu–N(3)
N(2)–Cu–N(1)
N(4)–Cu–N(1)
N(3)–Cu–N(1)
N(2)–Cu–O(5)
177.81(7)
91.95(7)
85.92(7)
86.08(6)
96.02(6)
176.35(7)
93.23(6)
1
13.07%. H NMR spectrum (D2O): 1.56 ppm (q, 2H,
CH2), 2.50 ppm (t, 4H, CH2–NH), 2.20–2.38 ppm
(unresolved multiplet 12H). 13C NMR off-resonance
decoupled spectrum (D2O): cyclam portion: 28.2 ppm (t,
J=123 Hz), 50.5 ppm (t, J=132 Hz), 52.0 ppm (t,
a Symmetry transformations used to generate equivalent atoms:
c1 x, −y+1/2, z−1/2.

44
G.A. Amadei et al. / Inorganica Chimica Acta 288 (1999) 40–46
Co–N bond lengths show significant differences in
various Co(III)–cyclam derivatives. For cis- and trans-
cyclam Co(III) complexes the Co–N distances range
˚
from 1.986(7) to 2.016(6) A [20]. In centrosymmetric
[Co(L4)]3+, the equatorial Co–N bond lengths were
˚
short, 1.936(2) and 1.937(2) A compared with the axial
˚
Co–N bond length of 1.9469(2) A. In contrast, the
[Co(L3)(H2O)]3+ structure has a short axial Co–N bond
˚
length of 1.936(2) A, while the equatorial Co–N bond
˚
lengths range from 1.957(3) to 1.964(3) A. Aside from
obvious difference in coordination between the two (H2O
versus NH2 in the sixth position), the reason for this
difference in axial and equatorial bond lengths is not
clear. However, the present structure is consistent with
that of [Co(L4)]3+ in having shorter Co–N bond lengths
than tetradentate cyclams.
Fig. 2. View of the [Cu(L2)(NO3)2] complex showing the labeling
scheme. Displacement ellipsoids are shown at the 50% probability
level.
Table 3
Assignment of the 13C NMR spectra of L3, L3 hydrochloride and
Co(III)L3 complexa
4. Supplementary material.
C atom c
L3
L3 hydrochloride
Co(III)–L3
Atomic coordinates, equivalent isotropic displace-
ment parameters and a full set of bond lengths and
angles are available upon request from the authors.
2
3
5
6
13
14
48.5
48.5
49.7
53.7
29.0
58.4
44.0
44.8
43.0
51.6
21.9
57.1
52.0
52.6
50.5
58.3
28.2
68.0
Table 4
Crystal data and structure refinement for [Co(L3)(H2O)]3+ complex
a Solvent: D2O. Chemical Shifts (ppm) relative to TMS (SiMe4).
Empirical formula
C17H43Cl4CoN6O5
612.30
173(2)
0.71073
monoclinic
P21/n
Formula weight (g mol−1
Temperature (K)
)
Air oxidation of Co(II) ions in the presence of L3-hy-
drochloride and triethylamine, in refluxing methanol [19]
gave more reproducible results, with higher overall yields
(22%). No evidence of ligand oxidation was observed,
although the reaction conditions were basic.
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
˚
a (A)
15.5901(3)
8.9267(2)
20.6011(4)
100.5960(10)
2818.13(10)
4
1.443
1.025
1288
0.40×0.32×0.08
˚
b (A)
The cyclam portion of the macrocyclic ligand, both in
its free form and as Co(III) complex, possesses a |6
element of symmetry, therefore it should only show six
different 13C NMR absorptions. Broadening of the peaks
due to conformational inequivalence would be expected.
We observed six peaks for the ligand hydrochloride
(absorptions due to C2 and C3 were well resolved) and
five peaks for the free ligand (absorptions due to C2 and
C3 were collapsed into a single broad intense peak)
(Table 3). The [Co(L3)(H2O)]3+ complex 13C NMR
spectrum showed six peaks, indicating that the complex
is in its trans conformation (higher degree of symmetry).
Crystal structure analysis shows a five-coordinate ligand
with the 6-amino group of the ligand axially coordinated
(Tables 4 and 5). The sixth coordination position of
cobalt(III) ion is filled by a water molecule (Figs. 3 and
4).
˚
c (A)
i (°)
˚
V (A)
Z
Dcalc. (Mg m−3
)
Absorption coefficient (mm)
F(000)
Crystal size (mm3)
q Range for data collection (°) 1.51–28.24
Index ranges
−205h520
−115k511
−275l527
30073
6778 [Rint=0.0398]
5373 \2|(I)
97.4%
Semi-empirical from equivalents
0.9280, 0.7386
Full-matrix least-squares on F
6778/11/354
Reflections collected
Independent reflections
Observed reflections
Completeness to q=28.24°
Absorption correction
Max./min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F
Final R indices [I\2|(I)]
R indices (all data)
The ligand L3 consists of a 14-membered cyclam
macrocycle with both primary amine and p-aminobenzyl
pendents linked to the 6-position of the cyclam ring. As
reported previously [19] for [Co(L4)]3+, the 6-amino
group coordinates in the axial position. Interestingly, the
1.070
R1=0.0490, wR2=0.1195
R1=0.0694, wR2=0.1362
0.841, −0.702
Largest difference peak, hole
−3
˚
(e A
)

G.A. Amadei et al. / Inorganica Chimica Acta 288 (1999) 40–46
45
Table 5 (continued)
Table 5
Selected bond lengths (A) and angles (°) for [Co(L3)(H2O)]3+
˚
complexa
N(5)–C(1)–C(11)
C(2)–C(1)–C(11)
C(10)–C(1)–C(11)
N(1)–C(2)–C(1)
N(1)–C(3)–C(4)
N(2)–C(4)–C(3)
N(2)–C(5)–C(6)
N(3)–C(7)–C(6)
N(3)–C(8)–C(9)
N(4)–C(9)–C(8)
N(4)–C(10)–C(1)
C(16)–C(15)–N(6)
C(14)–C(15)–N(6)
111.7(2)
111.2(2)
112.2(2)
109.1(2)
107.9(3)
107.3(3)
112.0(3)
111.5(3)
107.1(3)
108.0(2)
108.9(2)
118.7(3)
119.9(3)
˚
Bond lengths (A)
Co–N(5)
Co–O(1W)
Co–N(1)
Co–N(2)
Co–N(3)
Co–N(4)
1.936(2)
1.952(2)
1.957(3)
1.957(3)
1.962(3)
1.964(3)
Bond angles (°)
N(5)–Co–O(1W)
N(5)–Co–N(1)
O(1W)–Co–N(1)
N(5)–Co–N(2)
O(1W)–Co–N(2)
N(1)–Co–N(2)
N(5)–Co–N(3)
O(1W)–Co–N(3)
N(1)–Co–N(3)
N(2)–Co–N(3)
N(5)–Co–N(4)
O(1W)–Co–N(4)
N(1)–Co–N(4)
N(2)–Co–N(4)
N(3)–Co–N(4)
C(3)–N(1)–C(2)
C(3)–N(1)–Co
C(2)–N(1)–Co
C(3)–N(1)–H(1N)
C(2)–N(1)–H(1N)
Co–N(1)–H(1N)
C(5)–N(2)–C(4)
C(5)–N(2)–Co
174.40(10)
85.43(11)
90.34(11)
94.38(11)
89.09(11)
87.51(12)
94.21(11)
89.76(11)
176.13(11)
96.36(11)
85.10(10)
91.15(11)
88.77(11)
176.27(12)
87.36(11)
114.7(3)
108.6(2)
108.09(19)
112(3)
106(3)
107(3)
112.2(3)
118.8(2)
107.7(2)
108(2)
106(2)
103(2)
112.1(3)
118.2(2)
108.20(18)
106(2)
108(2)
103(2)
115.4(3)
108.01(18)
107.99(18)
111(2)
108(2)
106(2)
100.93(16)
112(2)
113(2)
109(2)
112(2)
110(3)
102(3)
114(3)
111(4)
102(4)
123(5)
a Symmetry transformations used to generate equivalent atoms:
c1 x, −y+1/2, z−1/2.
Fig. 3. View of the [Co(L3)(H2O)]3+ complex showing the labeling
scheme. Displacement ellipsoids are shown at the 50% probability
level.
C(4)–N(2)–Co
C(5)–N(2)–H(2N)
C(4)–N(2)–H(2N)
Co–N(2)–H(2N)
C(7)–N(3)–C(8)
C(7)–N(3)–Co
C(8)–N(3)–Co
C(7)–N(3)–H(3N)
C(8)–N(3)–H(3N)
Co–N(3)–H(3N)
C(9)–N(4)–C(10)
C(9)–N(4)–Co
C(10)–N(4)–Co
C(9)–N(4)–H(4N)
C(10)–N(4)–H(4N)
Co–N(4)–H(4N)
C(1)–N(5)–Co
C(1)–N(5)–H(5Na)
Co–N(5)–H(5Na)
C(1)–N(5)–H(5NB)
Co–N(5)–H(5NB)
H(5Na)–N(5)–H(5NB)
C(15)–N(6)–H(6Na)
C(15)–N(6)–H(6NB)
H(6Na)–N(6)–H(6NB)
C(15)–N(6)–H(6NC)
H(6Na)–N(6)–H(6NC)
H(6NB)–N(6)–H(6NC)
N(5)–C(1)–C(2)
N(5)–C(1)–C(10)
C(2)–C(1)–C(10)
Fig. 4. View of the [Co(L3)(H2O)]3+ complex showing the 6-amino
group axial coordination. Displacement ellipsoids are shown at the
50% probability level.
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