Three new modes of adenine-copper(II) coordination: Interligand interactions controlling the selective N3-, N7- and bridging μ-N3,N7-metal-bonding of adenine to different N-substituted iminodiacetato-copper(II) chelates

Article abstract of DOI:10.1016/S0020-1693(02)00920-9

The reaction of Cu₂CO₃(OH)₂, various N-substituted-iminodiacetic acids [R-N(CH₂CO₂H)₂)] and adenine (AdeH) in water yields crystalline samples of mixed-ligand copper(II) complexes of formulas [Cu(A)(N7-AdeH)(H₂O)]·H₂O (A=N-methyl- or N-ethyl-iminodiacetato(2-); compounds 1 and 2, respectively), [Cu(B)(N3-AdeH)(H₂O)]·H₂O (B=N-benzyl- or N-(p-methylbenzyl)-iminodiacetato(2-); compounds 3 and 4, respectively) as well as [Cu₄(pheida)₄(μ-N3,N7-AdeH)₂(H ₂O)₄]·2H₂O (pheida=N-phenethyl-iminodiacetato(2-)). Crystal structures of the acid H₂pheida and compounds 1-5 are reported. H₂pheida acid exhibits a typical zwitterionic structure. Copper(II) compounds were also studied by TG analysis (with FT-IR study of the evolved gasses), IR, electronic and ESR spectra and magnetic susceptibility data. The N-alkyl- or N-benzyl-like-iminodiacetato(2-) ligands (A or B) give complexes with Cu(II)/(A or B)/AdeH equimolar ratio, whereas pheida yields an unexpected tetranuclear compound with a 2:2:1 Cu(II)/pheida/AdeH molar ratio. In 1 and 2 AdeH binds to the metal by N7, whereas in 3 and 4 the N3 atom is used. An unexpected bridging μ-N3,N7-AdeH-dicopper(II) binding mode is found in the tetra-nuclear compound 5 (without interligand π,π-stacking interactions). These AdeH-Cu(II) binding modes have not been referred in the literature before. The difference in AdeH-Cu(II) binding modes in compounds 1 or 2 and 3 or 4 is rationalised on the basis of the absence or presence of a flexible N-benzyl-like substituent in the iminodiacetato(2-) ligand skeleton, which prevents or permits the interligand π,π-stacking interactions.

Full text of DOI:10.1016/S0020-1693(02)00920-9

Inorganica Chimica Acta 339 (2002) 160ꢂ170
/
www.elsevier.com/locate/ica
Three new modes of adenine-copper(II) coordination:
interligand interactions controlling the selective N3-, N7- and
bridging m-N3,N7Ã
/
metal-bonding of adenine to different N-
substituted iminodiacetato-copper(II) chelates
E. Bugella-Altamirano a, D. Choquesillo-Lazarte a, J.M. Gonza´lez-Pe´rez a,
M.J. Sa´nchez-Moreno a, R. Mar´ın-Sa´nchez a, J.D. Mart´ın-Ramos b, B. Covelo c,
R. Carballo c, A. Castineiras d, J. Niclo´s-Gutie´rrez a,*
˜
a Department of Inorganic Chemistry, Faculty of Pharmacy, University of Granada, Campus de Cartuja, s/n, E-18071 Granada, Spain
b Department of Mineralogy and Petrology, Faculty of Sciences, University of Granada, E-18071 Granada, Spain
c Department of Inorganic Chemistry, Faculty of Sciences, University of Vigo, E-36200 Vigo, Spain
d Department of Inorganic Chemistry, Faculty of Pharmacy, University of Santiago de Compostela, E-15706 Santiago de Compostela, Spain
Received 6 November 2001; accepted 16 January 2002
Dedicated to Professor Helmut Sigel
Abstract
The reaction of Cu2CO3(OH)2, various N-substituted-iminodiacetic acids [RÃ
yields crystalline samples of mixed-ligand copper(II) complexes of formulas [Cu(A)(N7Ã
ethyl-iminodiacetato(2ꢁ); compounds 1 and 2, respectively), [Cu(B)(N3ÃAdeH)(H2O)]×
zyl)-iminodiacetato(2ꢁ); compounds 3 and 4, respectively) as well as [Cu4(pheida)4(m-N3,N7Ã
phenethyl-iminodiacetato(2ꢁ)). Crystal structures of the acid H2pheida and compounds 1ꢂ5 are reported. H2pheida acid exhibits a
typical zwitterionic structure. Copper(II) compounds were also studied by TG analysis (with FT-IR study of the evolved gasses), IR,
electronic and ESR spectra and magnetic susceptibility data. The N-alkyl- or N-benzyl-like-iminodiacetato(2ꢁ) ligands (A or B)
/
N(CH2CO2H)2)] and adenine (AdeH) in water
AdeH)(H2O)]×H2O (AꢀN-methyl- or N-
H2O (BꢀN-benzyl- or N-(p-methylben-
AdeH)2(H2O)4]×2H2O (pheidaꢀN-
/
/
/
/
/
/
/
/
/
/
/
/
/
/
give complexes with Cu(II)/(A or B)/AdeH equimolar ratio, whereas pheida yields an unexpected tetranuclear compound with a
2:2:1 Cu(II)/pheida/AdeH molar ratio. In 1 and 2 AdeH binds to the metal by N7, whereas in 3 and 4 the N3 atom is used. An
unexpected bridging m-N3,N7Ã
p,p-stacking interactions). These AdeHÃ
AdeHÃCu(II) binding modes in compounds 1 or 2 and 3 or 4 is rationalised on the basis of the absence or presence of a flexible N-
benzyl-like substituent in the iminodiacetato(2ꢁ) ligand skeleton, which prevents or permits the interligand p,p-stacking
/
AdeHÃ
/
dicopper(II) binding mode is found in the tetra-nuclear compound 5 (without interligand
/Cu(II) binding modes have not been referred in the literature before. The difference in
/
/
interactions.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Adenine; N-substituted iminodiacetate; Copper(II); p,p-Stacking; Molecular recognition
1. Introduction
for the past decades because of their chemical and
biological interest. A critical and actualised review
accounts for the multiplicity of the metal ion binding
patterns to nucleobases, mainly concerning the metal
coordination chemistry of nucleic acid and their con-
stituents, has recently appeared [1]. Indeed there is
important research in this field about structural, ther-
modynamics, kinetic and biological aspects, and appro-
The interaction of nucleic acids or their constituents
with metal ions has been a matter of extensive studies
* Corresponding author. Tel.: ꢃ
219
E-mail address: jniclos@ugr.es (J. Niclo´s-Gutie´rrez).
/34-958-243 855; fax: ꢃ34-958-246
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 0 9 2 0 - 9

E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
161
priate reviews are made from time to time [2]. In this
broad context certain recent studies are devoted to find
metal complexes that can specifically recognise one
among various nucleobases. We are interested in the
structure of mixed-ligand copper(II) complexes with
[17]. Some of these essays were proposed to students of
Inorganic Aspects of Biological Processes [12,18]. As
Sigel [19] pointed out some years ago, the best way to
prove the formation of a mixed-ligand complex is to
carry out its crystal structure determination, which,
besides, is an excellent source of chemical information.
iminodiacetato(2ꢁ) (IDA) or a closely related com-
/
pound and N-heterocyclic bases. In this sense, we have
considered the use of adenine (AdeH) as an auxiliary
ligand because this N-rich nucleobase has proved to be a
rather versatile metal-binding biomolecule [1]. Surpris-
ingly, only a few copper(II) structures with this non-
substituted nucleobase have been reported, including
Attempts to obtain crystals of a ternary AdeHÃ
/
IDAÃ
/
Cu(II) complex suitable for X-ray diffraction studies
have not been successful yet, but this paper reports the
synthesis, structure and properties of five new ternary
copper(II) complexes with AdeH and N-substituted-
IDA derivatives. IDA-like ligands were chosen concern-
ing whether the N-substituent could or could not be
involved in aromatic p,p-stacking interactions, so im-
portant for molecular recognition phenomena in biolo-
gical systems [20].
anionic adeninato (Adeꢁ) [2ꢂ
/
5], neutral AdeH [6ꢂ
/
8] or
cationic adeninium(1ꢃ
/
) (AdeH2ꢃ) [9ꢂ
/11]. These are
mono-nuclear [2,4,5,8,10,11], binuclear [3,6,7] or tri-
nuclear [9] complexes, which present copper(II) atom in
different coordination polyhedrons (type 4, 4ꢃ
/
1 or 4ꢃ
/
2). In these compounds the nucleobase species (Adeꢁ,
AdeH or AdeH2ꢃ) links the copper(II) atom by the N(9)
donor (as mono-dentate) [2,4,5,8,10,11] or in a bridging
mode m-N(3),N(9) (poly-nuclear) [3,6,7,9]. Such coordi-
nation modes in non-substituted AdeH species can be
understood on the basis that the N(9) donor atom is the
most basic among their five nitrogen atoms [10],
followed by N(1), N(7) and N(3) [1]. In one case [2], it
has been argued that an interligand intra-molecular
hydrogen bond associated with the steric factors around
the metal participates in the base-selectivity. However,
some questions seem to remain unclear. For example,
the reaction of [Cu(H2EDTA)(H2O)] with AdeH affords
2. Experimental
2.1. Ligands and other reagents
Samples of N-methyl- and N-ethyl-iminodiacetic acid
(H2MIDA and H2EIDA, respectively) were supplied by
Mederos and co-workers for previous work [21]. N-
Benzyl-, N-(p-methylbenzyl)- and N-phenethyl-imino-
diacetic acids (H2BzIDA, H2MEBIDA and H2pheida,
respectively) were prepared in our laboratories by
reaction of potassium chloroacetate with the appropri-
ate amine (benzylamine, 4-methylbenzylamine or phe-
nethylamine, respectively, purchased from Aldrich) in
the salt (AdeH2)[Cu(HEDTA)(H2O)]×
/
2H2O [12] but not
a ternary complex (H4EDTAꢀethylenediaminetetraa-
/
alkaline aq. solution (pH ꢀ
/
10ꢂ
/
11) at 70ꢂ90 8C, during
/
cetic acid). The structure of this salt [12] proves that the
ꢃ
approximately 2 h. Then the reaction mixture was
cooled to room temperature (r.t.) and acidified with
AdeH2 ion recognises the counter-anion complex out-
spherically (by means of two inter-ionic hydrogen
bonds) and the resulting ion pair recognises itself by
HCl 6 N (pH ꢀ
/
3.0ꢂ2.5) until the desired white acid
/
precipitated. New additions of HCl 6 N gave successive
fractions of these ligands in their acid forms, which were
collected by filtration, washed with water and re-crystal-
lised in water by reaction with NaHCO3 (until complete
solution) followed by addition of the equivalent amount
of HCl 6 N. Re-crystallised N-(aryl-alkyl)-iminodiacetic
acids were washed with water and C3H6O or EtOH, and
air dried. H2MIDA and H2BzIDA are also commer-
cially available. Crystals of H2pheida were grown by re-
crystallisation in a 30:70 water/ethanol mixture. This
and other similar procedures failed to grow suitable
crystals of H2BzIDA and H2MEBIDA, which produced
extremely long filaments. For H2BzIDA, starting from 1
mol of benzylamine, the yield was 195.5 g, 87.6%. Anal.
Calc. for C11H13NO4: C, 59.19; H, 5.87; N, 6.27. Found:
C, 59.07; H, 5.89; N, 6.22%. FT-IR relevant frequencies
ꢃ
p,p-stacking interaction between both AdeH2 cations
to form di-copper(II) aggregates. Such di-copper(II)
entities act as building blocks of the crystal (with the
corresponding water molecules). In this case, it has been
suggested that the overcrowding of donors from the
penta-dentate chelating HEDTA3ꢁ ligand precludes the
ꢃ
substitution of water by AdeH2 ion around the
copper(II) atom [12]. On the other hand, single metalÃ
/
N3 or ÃN7(AdeH) coordinations are very unusual. The
/
single N3(AdeH) metal coordination only seems sup-
ported by the structures of [Ni(AdeH)(tren)Cl]Cl [13]
and [Pd(thiacyclophane)(AdeH)]BF4 [14]. The mono-
nuclear metalÃ
/
N7 coordination for N9-non-substituted
AdeH is known in AdeH2ꢃ derivatives of Ni(II) [15] and
Zn(II) [16]. In this context and as a part of our present
research project, we are interested in the structure and
properties of mixed-ligand Cu(II) complexes having a
(cmꢁ1): 3064, 3024, 2999 and 2974 for n(CÃ
peaks at 2700ꢂ
2300, including one at 2522 of n(Nꢃ Ã
3420 m (broad), 1729 or 1719, ꢀ1250 and 704 for
n(OÃH), n(CÄO), d(OÃH) and p(OÃH) of ÃCOOH;
1619 and 1385 for nas and ns of Ã
COOꢁ. For H2ME-
/
H) modes;
H);
/
/
N-carboxymethyl-glycinato(2ꢁ
/
) or IDA ligand or a
ꢀ
/
/
IDA-like derivative as a chelating agent and a variety of
N-heterocycles (including AdeH) as an auxiliary ligand
/
/
/
/
/
/

162
E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ170
/
BIDA, starting from 0.5 mol of 4-methylbenzylamine,
the yield was 82.8 g, 69.8%. Anal. Calc. for C12H15NO4:
C, 60.75; H, 6.37; N, 5.90. Found: C, 60.32; H, 6.64; N,
6.01%. FT-IR relevant frequencies (cmꢁ1): 3018, 2966
tion of the products, but usually over 50%. When the
reaction between CuCO3(OH)2 and H2L did not pre-
cipitate, before adding the required amount of AdeH,
the solution should be slowly filtered (without vacuum)
on a Erlenmeyer and left to cool, and after that stirred
until the base was dissolved completely. The resulting
blue solution would be filtered without vacuum on
crystallisation device. This procedure rose considerably
and 2917 for n(CÃ
including one at 2572 of n(Nꢃ Ã
1719, 1250 and 704 for n(OÃH), n(CÄ
p(OÃH) for ÃCOOH; 1619 and 1385 for nas and ns of Ã
COOꢁ. H NMR (300 MHz, D2Oꢃ
NaOD; d, ppm):
2.17 (s, 3H) from CH3Ã, 2.97 (s, 4H) from ÃCH2ÃCOO
moieties, 3.55 (s, 2H) from f-CH2ÃN, and 7.08 (d, 2H,
Jꢀ8.1 H-2,6 arom.), 7.12 (d, 2H, Jꢀ8.1 H-3,5 arom.).
13C NMR (75 MHz, D2Oꢃ
NaOD; d, ppm): 19.68 from
CH3Ã, 56.45 from ÃCH2ÃN, 57.05 from CH2Ã(COO),
128.43 from C-2,6 arom., 129.69 from C-3,5 arom.,
133.37 from C-1 arom., 137.00 from C-4, 178.92 from Ã
/
H) modes; peaks at 2700ꢂ
H); ꢀ3450 m (broad),
O), d(OÃH) and
/
/
2300,
/
/
/
/
/
/
/
1
/
the yield up to 85ꢂ90%. The use of largest amounts of
/
/
/
/
solvent could avoid such precipitation, but would
increase the time required for crystallisation and, there-
fore, the risk of microbiological contamination. The
formation of filamentous colonies was frequent. When it
happened, we proceeded to add ethanol, cover the
crystallisation device with a plastic film and filtrate the
preparation after several days. However, this undesired
contamination phenomenon did not impede the forma-
tion of many and good crystals, of which we have
photographic evidences available upon request. The re-
crystallisation of the products in water usually required
heat and it did not always give good results. However, a
/
/
/
/
/
/
/
/
/
COO. For H2pheida, starting from 0.5 mol (123.44 g) of
phenethylamine, the yield was 199.9 g, 80.2%. Anal.
Calc. for C12H15NO4: C, 62.64; H, 6.07; N, 5.62. Found:
C, 60.19; H, 6.00; N, 6.90%. FT-IR relevant frequencies
(cmꢁ1): 3030, 2993 and 2969 for n(CÃ
at 2700ꢂ
2300, including one at 2521 for n(Nꢃ Ã
3500 m (broad), 1713, 1195 and 726 for n(OÃH), n(CÄ
O), d(OÃH) and p(OÃH) of ÃCOOH; 1607 and 1383
for nas and ns of Ã
COOꢁ. 1H NMR (300 MHz, d6-
DMSO; d, ppm): 2.69 (m, 2H) and 2.85 (m, 2H) from Ã
/H) modes; peaks
/
/
H); ꢀ
/
re-crystallisation experience with the Cu(II)Ã
/
pheidaÃ
/
/
/
AdeH derivative afforded little amount of crystal which
have enabled the structural results referred below. This
compound was surprisingly a molar ratio Cu/pheida/
AdeH 2/2/1. Indeed the general procedure represents the
use of 100% of AdeH in excess. The compound was also
obtained when a stoichiometric ratio of reactants (Cu/
pheida/AdeH 2/2/1) was employed in the synthesis. The
use of large volume of solvent to preclude some initial
precipitation yields crystalline samples, but not single-
crystals of this compound. Anal. Calc. for [Cu(MIDA)-
/
/
/
/
/
CH2Ã
/
CH2Ã
/
moiety, 3.45 (s, 4H) from NÃ
/
CH2Ã
/
COOꢁ,
and 7.22 (m, 5H) from C6H5-ring. 13C NMR (75 MHz,
d6-DMSO; d, ppm): 33.66, 54.46, 55.66, from CH2
groups, 125.78, 128.13, 128.50 and 139.83, from the
aromatic CÃ
/
H groups, and 172.37 from the COOÃ
/
carboxyl groups). All other chemicals are commercially
available products of reagent grade and were purchased
from Aldrich, and used without further purification.
(AdeH)(H2O)]×
31.62; H, 4.25; N, 22.13. Found: C, 31.70; H, 4.51; N,
22.47%. Anal. Calc. for [Cu(EIDA)(AdeH)(H2O)]×H2O
/H2O (C10H16CuN6O6, compound 1): C,
/
2.2. Synthesis of copper(II) complexes
(C11H18CuN6O6, compound 2): C, 33.55; H, 4.61; N,
21.34. Found: C, 33.50; H, 4.95; N, 21.67%. Anal. Calc.
A general procedure to obtain the studied mixed-
ligand copper(II) complexes can be described as follows:
Cu2CO3(OH)2 (221 mg, 0.5 mmol, Aldrich) and the
appropriate N-substituted iminodiacetic acid (H2L, 1
mmol, Aldrich) reacted in water (150 ml) in a Kitasato
for [Cu(NBzIDA)(AdeH)(H2O)]×
compound 3): C, 42.15; H, 4.42; N, 18.34. Found: C,
42.06; H, 4.63; N, 18.60%. Anal. Calc. for [Cu(ME-
/
H2O (C16H20CuN6O6,
BIDA)(AdeH)(H2O)]×
/
H2O (C17H22CuN6O6, compound
4): C, 43.44; H, 4.72; N, 17.88. Found: C, 43.19; H, 4.72;
flask, by heating (15 min, t B50 8C) and stirring under
/
N, 17.68%. Anal. Calc. for [Cu4(pheida)4(AdeH)2-
reduced pressure (to remove the CO2, by-product). The
resulting slurry or solution was left to cool and AdeH
(135.1 mg, 1 mmol) was added. The reacting mixture
was stirred half an hour and then filtered without
vacuum (to remove a variable amount of the desired
product, as could be confirmed by elemental analysis
and IR spectroscopy, and a very small amount of CuO)
directly on a crystallisation device. By evaporation of
clear blue solutions, abundance of crystals was obtained,
and they were removed by filtration without vacuum on
another crystallisation device. The products were
washed with cool water and air-dried. Yields were
variable, depending on the amount of initial precipita-
(H2O)4]×
/
2H2O (C58H70Cu4N14O22, compound 5): C,
44.27; H, 4.74; N, 12.46. Found: C, 43.93; H, 5.18; N,
12.63%.
2.3. Crystal structure determination
A prismatic crystal of each studied compound was
mounted on a glass fibre and used for data collection.
Only twinned crystals were available for compounds 4
and 5. Crystal data were collected at 237 (H2pheida) or
291(2) K (Cu derivatives) using a Bruker SMART CCD
1000 diffractometer. Graphite monochromated Mo Ka
radiation (lꢀ
˚
0.71073 A) was used throughout. The
/

E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
163
Table 1
Crystal data and structure refinement for copper(II) compounds 1ꢂ
/
5
Cu(II) compound
1
2
3
4
5
Empirical formula
Formula weight
Temperature (K)
C10H16CuN6O6
379.83
293(2)
C11H18CuN6O6
393.85
293(2)
C16H20CuN6O6
455.92
293(2)
C17H22CuN6O6
469.95
293(2)
C58H70Cu4N14O22
1569.44
293(2)
˚
Wavelength (A)
0.71073
monoclinic
P21/n
0.71073
monoclinic
P21/c
0.71073
orthorhombic
Pbca
0.71073
orthorhombic
Pca21
0.71073
triclinic
¯
P1/
Crystal system
Space group
Unit cell dimensions
/
˚
a (A)
7.546(1)
24.618(3)
7.931(1)
90
14.371(1)
7.861(1)
13.301(1)
90
8.376(1)
13.411(2)
34.106(5)
90
8.361(3)
17.824(7)
13.214(5)
90
10.534(3)
10.534(3)
31.036(9)
90.819(6)
90.819(6)
108.429(4)
3266.3(2)
2
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
101.369(3)
90
90.352(2)
90
90
90
90
90
3
˚
V (A )
Z
1444.4(3)
4
1.747
1502.6(3)
4
1.741
3831.0(9)
8
1969.2(2)
4
Dcalc (Mg mꢁ3
Absorption coefficient
)
1.581
1.188
1.585
1.158
1.596
1.373
1.556
1.499
(mmꢁ1
F(000)
)
780
0.2ꢄ0.07ꢄ0.05
812
0.17ꢄ0.14ꢄ0.07
1880
0.22ꢄ0.21ꢄ0.02
972
0.32ꢄ0.21ꢄ0.15
1616
0.39ꢄ0.22ꢄ0.06
Crystal size (mm)
u Range data collection (8)
Index ranges
1.65ꢂ/28.04
1.42ꢂ/28.08
2.39ꢂ/28.08
2.24ꢂ
/
28.07
0.66ꢂ27.45
/
ꢁ95h 58,
ꢁ325k 532,
ꢁ105l 59
8183/3231
ꢁ155h 518,
ꢁ95k 510,
ꢁ135l 517
8848/3454
ꢁ115h 58,
ꢁ175k 517,
ꢁ455l 534
19 891/4573
[Rintꢀ0.0944]
28.028/98.2%
SADABS
ꢁ105h 510,
ꢁ235k 523,
ꢁ135l 517
9822/3832
ꢁ135h 513,
ꢁ135k 513,
05l 540
14 910/14 910
[Rintꢀ0.0000]
27.458/100%
SADABS
Reflections collected/unique
[Rintꢀ0.0757]
28.028/92.6%
SADABS
[Rintꢀ0.0680]
28.028/94.6%
SADABS
[Rintꢀ0.1896]
28.028/96.8%
empirical
Completeness to u
Absorption correction
Max./min. transmission
Refinement method
1.000/0.785
a
1.000/0.826
a
1.000/0.826
a
0.8454/0.7082
a
0.9222/0.6166
a
FMLS on F2
FMLS on F2
FMLS on F2
FMLS on F2
FMLS on F2
Data/restraints/parameters
Final R indices [I ꢁ2s(I)]
3231/0/272
R1ꢀ0.047,
wR2ꢀ0.064
R1ꢀ0.130,
wR2ꢀ0.078
0.813
3454/0/224
R1ꢀ0.046,
wR2ꢀ0.107
R1ꢀ0.100,
wR2ꢀ0.120
0.903
4573/0/277
R1ꢀ0.051,
wR2ꢀ0.060
R1ꢀ0.170,
wR2ꢀ0.079
0.887
3832/7/277
R1ꢀ0.0817,
wR2ꢀ0.1701
R1ꢀ0.2452,
wR2ꢀ0.2428
0.757
14 910/0/835
R1ꢀ0.082,
wR2ꢀ0.198
R1ꢀ0.084,
wR2ꢀ0.200
1.003
R indices (all data)
Goodness-of-fit on F2
Largest difference peak and
0.613/ꢁ0.411
0.397/ꢁ0.324
0.362/ꢁ0.310
0.570/ꢁ0.756
4.419/ꢁ1.682
ꢁ3
˚
hole (e A
)
Type of crystal
single crystal
single crystal
single crystal
twinned crystals
twinned crystals
a
FMLS, full-matrix least-square.
data were processed with SAINT [22] and corrected for
absorption using SADABS [23]. The structures were
maps. Isotropic displacement parameters for hydrogen
atoms were constrained to be 1.2 (1.5 for methyl
groups). Atomic scattering factors were obtained from
the ‘International Tables for X-ray Crystallography’
[26]. Molecular graphics have been obtained from
SHELXTL [27]. Crystal data for H2pheida (C12H15NO4,
solved by direct methods using the program SHELXS
-
97 [24] and refined by full-matrix least-square techniques
(FMLS below and in Table 1) on F2 using SHELXL-97
[25]. Positional and anisotropic atomic displacement
parameters were refined for all non-hydrogen atoms.
Because of the twinned crystal used, some atoms of the
compound 4 did not present defined maximal on the
anisotropic refinement and were refined isotropically.
For compound 1, hydrogen atoms were located from
difference Fourier maps and refined isotropically. For
FW 237.25, T 293(2) K): orthorhombic system, space
˚
group Pca21, aꢀ
aꢀbꢀgꢀ908, Vꢀ
mꢁ3, mꢀ0.108 mmꢁ1, F(000)ꢀ
0.28ꢄ0.91 mm, u from 2.86 to 28.008, ꢁ
175k 517, ꢁ125l 512, collected/independent re-
flections 6614/2503, completeness to 2uꢀ98.7%, data/
restraints/parameters 2503/1/159, Goodness-of-fit (on
F2)ꢀ
0.993, final R1ꢀ0.043, wR2ꢀ0.103 [I ꢁ2s(I)],
R1ꢀ0.048 and wR2ꢀ0.106 (all data), largest difference
/
8.425(1), bꢀ
/
13.307(1), cꢀ
/
9.851(1) A,
3
˚
/
/
/
/
1104.3(1) A , Zꢀ
504, crystal size 0.26ꢄ
115h 57,
/
4, Dꢀ1.427 Mg
/
/
/
/
/
/
/
/
ꢁ
/
/
/
/
/
/
compounds 2ꢂ/5, hydrogen atoms were placed geome-
/
trically and positional parameters were refined using a
riding model. Water hydrogen atoms in compound 3
were unambiguously located from difference Fourier
/
/
/
/
/
/

164
E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
peak and hole 0.184 and ꢁ
the crystal data, experimental details and refinement
results for copper(II) complexes 1ꢂ5 are listed in Table
/
0.213 e Aꢁ3. A summary of
/
1.
2.4. Physical measurements
Elemental analyses were performed on a Fisonsꢂ
/
Carlo Erba EA 1108 micro-analyser. NMR spectra
were recorded in Bruker AMX300 or ARX400 spectro-
meters. IR spectra were obtained by the KBr disc
technique on a Nicolet FT-IR 20SXB or Jasco FT-IR
410 instrument. TG analysis (pyrolysis) of the studied
compounds (295ꢂ
875 K) in air flow (100 ml minꢁ1) and
/
corresponding IR spectra of evolved gasses were re-
corded using a Shimazu Thermobalance TGA-DTG-
50H coupled with an IR-FT Nicolet Magna 550.
Electronic (reflectance) spectra (175ꢂ3300 nm) were
/
obtained in a Varian Cary-5E spectrophotometer. ESR
spectra of polycrystalline samples were recorded without
magnetic dilution in a spectrophotometer Bruker ESP
300E (X band) at r.t. Magnetic susceptibilities were
measured in the temperature range 80ꢂ300 K (excepting
/
those of compound 4, measured at r.t.) with a Manics
DM magnetometer. The susceptometer was calibrated
with mercury tetrakis(thiocyanato)cobaltato(II). Cor-
rections for the diamagnetism were estimated from
Pascal’s constants [28a]. Experimental susceptibilities
were also corrected for the metal temperature-indepen-
dent paramagnetism (60ꢄ
10ꢁ6 cm3 molꢁ1) [28b].
/
3. Results and discussion
3.1. Structure of H2pheida acid
Fig. 1. (a) Three hydrogen bonded H2pheida9 zwitterions in a chain
along a-axis. (b) Fragments of two 2D framework in the crystal of
H2pheida acid extending parallel to plane ac.
Tables about this amino-diacid may be obtained from
the corresponding deposited files. Its structure is shown
in Fig. 1, which also gives the numbering schema
adopted for the atoms. H2pheida acid exists as zwitter-
ions stabilised by an intra-molecular hydrogen bond
˚
but a large slipping between rings (b and g ꢀ37.58),
/
(N(1)Ã
/
H(1)Á Á ÁO(1), 2.615(2) A, 108(2)8). These dipolar
suggest that there is a significant s,p-contribution to the
p,p-stacking [20]. In each double chain, the multiplicity
of such interaction is obtained connecting each phe-
nethyl aromatic ring with other two from the anti-
parallel strand. In addition, these double chains supply
ions link to each other (translation) by an inter-
molecular
hydrogen
2.486(2), 1578; symmetry code iiꢀ
bond
(O(4)Ã
/
H(4)Á Á ÁO(1)ii;
/
xꢃ1, y, z) forming
/
chains along a-axis (Fig. 1(a)). Two anti-parallel chains
form a double chain by a multi-p,p-stacking interaction.
The structural parameters for this p,p-stacking (as
depicted in the diagram 1) were obtained with the
program PLATON [29]. Significant results are: cen-
up and down, and to each other sides, N(1)Ã
/
H(1)
H(1)Á Á ÁO(2)i hydro-
/
‘onium’ groups which form N(1)Ã
/
˚
gen bonds (2.833(2) A, 150(2)8, symmetry code iꢀ
/
ꢁ
/
xꢃ
3/2, y, zꢃ1/2). Such links generate a 2D framework
/
troidꢂ
/
centroid distance for stacked rings d(CIÃ
/
CJ)ꢀ
/
˚
4.29 A; dihedral angles between the planes I and J of
with IDA moieties towards the external surfaces
and multi-stacked aromatic phenethyl rings inside it.
2D frameworks are laid out in the crystal parallel
to plane ac and connected by van der Waals contacts
(Fig. 1(b)).
˚
the stacked rings, aꢀ
37.18; d(ÞCJÃCI)ꢀ3.42 A; gꢀ
present an appropriate stacking distance of 3.40(2) A. A
remarkable parallelism between stacked rings (a ꢀ28)
/
2.18; d(Þ
/
CIÃ
/
CJ)ꢀ
/
3.39 A; bꢀ
/
˚
/
/
/
/
37.88. These data re-
˚
/

E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
165
Diagram 1.
Fig. 2. Pair of asymmetric units of [Cu(MIDA)(AdeH)(H2O)]×
/
H2O (1)
showing the intra-molecular interligand hydrogen bond in both
molecules (open dashed lines) and the inter-molecular p,p-stacking
interaction between five- and six-membered rings of AdeH ligands
(black dashed lines).
3.2. Copper(II) coordination in mixed-ligand complexes
Table 2 shows data of metalÃ
/
ligand bond distances in
the studied compounds 1ꢂ5. The numbering schema
/
N7 donor from AdeH in trans to the CuÃ
CuÃpheida chelate, at the basal coordination plane. The
other two metal atoms (Cu2 and Cu2A) also have
roughly 4ꢃ1 coordination. This is built up by one N
/
N bond of the
adopted in each compound is shown in appropriate
figures. Data for Cu(1) and Cu(2) atoms in compound 5
are averaged values from appropriate pairs of very
similar metal atoms. Non-centro-symmetry of the tetra-
nuclear complex unit is due to the space group used for
the solution of the structure (because only few twinned
crystals were obtained). Additional information about
bond distances and angles for these copper(II) com-
pounds could be obtained from appropriate files of
Section 5 or directly from the authors upon request.
/
/
and two O donors from tri-dentate pheida and one N3
donor from AdeH, plus one apical O donor from a
bridging carboxylate group of pheida (O12 or O12A in
Fig. 6). However, these Cu atoms interact very weakly
with an O from water (referred as O20 and O20A in Fig.
˚
6) at approximately 3 A. The coordination around these
Cu(II) atoms could be referred as a very unsymmetrical
Mono-nuclear compounds 1ꢂ
gated square-base pyramidal coordination type 4ꢃ
(see Figs. 2ꢂ5). One N and two O donors from tri-
/4 exhibit a roughly elon-
elongated octahedron, of type 4ꢃ
/
1ꢃ
/
1* (the asterisk
/
1
emphasises the very weak CuÃO interaction). These
/
/
copper(II) coordination polyhedrons are very common
in mixed-ligand complexes which have an equimolar
ratio Cu(II)/IDA or IDA-like/N-heterocyclic (imidazole
(Him) or Him derivative) [17]. In these complexes, the
Him or Him-like binds the copper(II) in trans to the
dentate IDA derivative and the N7 or N3 donor atom
from AdeH (in compounds 1 and 2 or in 3 and 4,
respectively) define the basal coordination plane. An
aqua ligand supplies the apical O donor atom at
˚
approximately 2.30ꢂ2.35(2) A. The tetra-nuclear com-
/
CuÃ/N(IDA or IDA-like) bond, and the chelating IDA
pound 5 exhibits two different Cu(II) coordination
polyhedrons. Two atoms (Cu1 and Cu1A in Fig. 6)
or derivative adopts mer-configuration, as rules in the
structures reported here. The Cu(II) binding to one
have the same type 4ꢃ
for mononuclear complexes 1ꢂ
/
1 of coordination above referred
4, with O(11) and
mono-functional AdeH in compounds 1ꢂ
/
4 or a half of
/
O(10A) water atoms as apical donors (Fig. 6) and the
bridging-bidentate m-AdeH in 5, makes AdeH display a
Table 2
Coordination bond distances in compounds 1ꢂ5 and parameters of the polyhedron distortion
/
1
2
3
4
5(Cu1)
5(Cu2)
CuÃN(amine)
CuÃO(carboxyl)
CuÃO(carboxyl)
CuÃN(AdeH)
CuÃO(water)
t (%)
2.030(3)
1.930(3)
1.945(3)
2.017(3)
2.299(4)
11.93
2.013(3)
1.935(3)
1.962(3)
1.977(3)
2.351(3)
5.93
2.012(3)
1.937(2)
1.943(2)
1.981(3)
2.303(3)
17.35
1.98(2)
1.96(1)
1.99(1)
1.88(1)
2.27(1)
14.67
1.876(4)
1.948(4)
2.002(4)
2.022(4)
2.277(4)
3.27
1.884(5)
2.045(5)
1.991(5)
2.037(5)
2.380(5)
a
0.49
0.73
T
0.86
0.84
0.86
0.86
0.86
a
˚
t is obtained assuming an ‘effective’ coordination type 4ꢃ1, because of the weakness of the ‘additional’ CuÃOw interaction at 3.02(1) A
(averaged).

166
E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ170
/
Fig. 3. (a) Pair of molecules [Cu(EIDA)(AdeH)(H2O)]×H2O (2) showing the intra-molecular interligand hydrogen bond (open dashed lines) and the
/
inter-molecular p,p-stacking interactions between five- and six-membered rings of AdeH ligands (black dashed lines). (b) p,p-Stacking interactions
(black dashed lines) between anti-parallel AdeH ligands of a pair of complex units and other stacking connecting them with AdeH ligands from four
adjacent pairs in the crystal of compound 2 (metal, EIDA and water molecules have been omitted for clarity).
Fig. 4. Three complex units of [Cu(NBzIDA)(AdeH)(H2O)]×
/
H2O (3)
Fig. 5. Three complex units of [Cu(MEBIDA)(AdeH)(H2O)]×H2O (4)
/
in a stacked ‘chain’ showing the intra-molecular interligand hydrogen
bond (open dashed lines) and the inter-molecular p,p-stacking inter-
action (black dashed lines) between six-membered aromatic rings from
NBzIDA and AdeH ligands (non-coordinated water omitted for
clarity).
in a multi-stacked chain, showing the intra-molecular interligand
hydrogen bond (open dashed lines) and the inter-molecular p,p-
stacking interaction (black dashed lines) between six-membered
aromatic ring of MEBIDA and AdeH ligands (non-coordinated water
omitted).

E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
167
and the possibilities of displaying p,p-stacking interac-
tions between ligands. Table 3 and Figs. 2ꢂ5 show intra-
molecular interligand hydrogen bonds in compounds 1ꢂ
4. These data reveal that (N-alkylÃIDA)ÃCu(II) che-
lates form a rather opened hydrogen bond (angles 171
and 1578, in Table 3) between an NÃH bond of the
exocyclic primary amino group from AdeH and one O
carboxylate atom from the N-alkylÃIDA derivative
/
/
/
/
/
/
(Table 3). In contrast, compounds 3 and 4 form a rather
closed hydrogen bond (angles of 115 and 1188, in Table
3) between the N9Ã
/
H heterocyclic group from AdeH
and one O carboxyl atom from the N-(benzyl-like)Ã
/
IDA chelating ligand. In order to discern if such intra-
molecular interligand hydrogen bonds are imposed by
the formation of a CuÃ
/
N7(AdeH) or a CuÃ
/
N3(AdeH)
bond or such coordination modes are selectively pro-
moted by molecular recognition phenomena, we have
proceeded to an analysis of the different possibilities of
displaying p,p-stacking interactions between ligands.
Calculations were carried out using the program PLA-
Fig. 6. Asymmetric unit of [Cu4(pheida)4(AdeH)2(H2O)4]×2H2O (5)
where the m-N3,N7-bridging role of AdeH ligands can be observed.
/
TON [29] estimating short ring interactions which have a
˚
similar role that Him or Him-like in such mixed-ligand
complexes. All these cases are in contrast with the fac-
configuration of IDA or IDA-like in [Cu(IDA)(H2O)2]n
[17] or in mixed-ligand complexes with a 1/1/2 Cu/IDA/
(N-heterocyclic donor) molar ratio (as in [Cu(IDA)(2,2?-
centroidꢂ
/
centroid vector B
/
6 A and b angle B
/
608 (see
diagram 1). Tables 4 and 5 show significant data of
parameters used to describe such p,p-stacking interac-
tion (see diagram 1).
In compound 1 (Fig. 2) there is an anti-parallel p,p-
stacking of AdeH to give pairs of complex units (related
bipy)]×
priate references in [17]) as well as a 1/1/(1ꢃ
like/(N-heterocyclicꢃN-aliphatic) donors ratio (for ex-
ample, [Cu(NBzIDA)(histamine)]×2H2O [30] and related
cases [31]).
/
6H2O and closely related compounds (see appro-
/1) Cu/IDA-
by the symmetry code iꢀ
/
2ꢁ
/
x, ꢁ
/
y, ꢁz). In this way
/
/
the five-membered ring (A5) of each AdeH is stacked to
the five- (A5) and six-membered ring (A6) of the
adjacent AdeH ligand, as it is referred in Table 4 for
the interactions A5/A5 and A5/A6. Note the very low
/
value of a B
/
18 (indicating the AdeHÃ
/
AdeH parallelism)
3.3. Interligand interactions in N-alkyl-, N-benzyl-like or
copper(II) chelates with AdeH as
secondary ligand and molecular recognition significance
and b and g angles of approximately 188 revealing a
moderate slipping of the stacked rings. In this com-
˚
pound the averaged stacking distance is 3.4190.01 A.
N-phenethylÃ
/
IDAÃ
/
/
These interactions indicate that compound 1 recognises
itself by forming pairs of complex units by AdeH/AdeH
p,p-stacking. Then, such pairs and water molecules form
a hydrogen-bonding network to build the crystal.
Compound 2 also displays an anti-parallel p,p-stack-
ing involving the five- and six-membered rings (A5 and
A6, respectively in Table 4) of each AdeH, at a mean
In the compounds studied, the most remarkable
feature is that AdeH binds the copper(II) by N7, N3
or m-N3,N7 when the chelating ligand is a N-alkyl-, N-
benzyl-like or N-phenethylÃ
/IDA. These are three new
and selective modes for the copper(II)Ã/AdeH binding
which could reflect in some way the influence of the N-
substitution in the IDA skeleton on molecular recogni-
tion processes. In attempts to rationalise these finding
we have focused our attention on the hydrogen bonds
˚
distance of 3.42 A, and giving pairs of complex units
(symmetry related by iꢀ
/
1ꢁ
/
x, 2ꢁ
/
y, 1ꢁz) (Fig. 3(a)).
/
Table 3
Intra-molecular interligand hydrogen bonds in compounds [Cu(A or B)(AdeH)(H2O)]×H2O
Compound
DÃHÁ Á ÁA
d(DÃH)
d(HÁ Á ÁA)
d(DÁ Á ÁA)
Ç(DHA)
1
2
3
4
N(5) aÃH(5B)Á Á ÁO(21)
N(5) aÃH(5B)Á Á ÁO(11)
N(2) bÃH(2)Á Á ÁO(21)
N(9)ÃH(9)Á Á ÁO(2)
0.72(4)
0.86
2.06(4)
2.06
2.78(1)
2.88(1)
2.91(1)
2.96(1)
171(5)
157
0.71(3)
0.86
2.54(4)
2.46(1)
115(4)
118
a
Exocyclic N6 atom in AdeH conventional notation.
Heterocyclic N9 atom in AdeH conventional notation.
b

168
E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ170
/
Table 4
Parameters for inter-molecular interligand p,p-stacking interactions between five- (A5) and six-membered (A6) rings of anti-parallel AdeH in
compounds [Cu(A)(AdeH)(H2O)]×H2O of N-alkyl-iminodiacetato ligands (A) with N-methyl- (1) or N-ethyl- (2) groups
1 (pairs)
1 (pairs)
2 (pairs)
2 (between pairs)
Ring I/ring J
˚
A5/A5
A5/A6
3.59/0.4
A5/A6
3.52/2.2
A5/A6
3.74/9.1
0
d(CIÃCJ) (A)/a
3.60/0.02
3.41/18.5
3.41/18.5
anti-parallel
0
˚
d(ÞCIÃCJ) (A)/b
d(ÞCIÃCJ) (A)/g
Stacking
3.42/41.9
3.42/41.4
anti-parallel
3.46/9.1
3.48/11.2
anti-parallel
3.11/24.8
3.40/33.8
ꢀanti-parallel
0
˚
group in N-(benzyl-like)Ã
/
IDA for molecular recogni-
Table 5
tion in 4 is not significant. Curiously, the electron-
donating effect of the p-methyl group does not represent
a shortening of the stacking distance. Finally, there are
Parameters for the B/AdeH inter-molecular interligand p,p-stacking
interactions in compounds [Cu(B)(AdeH)(H2O)]×H2O of N-(benzyl-
like)Ãiminodiacetato ligand (B) between the aromatic benzyl ring (I or
B6 ring) and the six-membered ring (A6 or J ring) of AdeH
not aromatic ringꢂring stacking interactions in the
/
crystal of compound 5 (Fig. 5).
Compound 3
Compound 4
Ring I/ring J
˚
B6/A6
B6/A6
3.4. Properties of copper(II) compounds
0
d(CIÃCJ) (A)/a
3.53/6.24
3.42/15.8
3.41/14.4
3.65/3.41
3.46/15.3
3.53/18.6
0
˚
d(ÞCIÃCJ) (A)/b
d(ÞCIÃCJ) (A)/g
0
˚
A summary of some physical properties of the studied
Cu(II) compounds is shown in Table 6. TG/DTG
analyses of compound 1ꢂ5 are rather similar and
/
present three or four steps. The first step is only due
to the dehydration process (non-coordinated and apical
coordinated water) but starting from an ‘actual formula’
with less water than calculated contents. That is due to
This p,p-stacking is something different from that
referred for compound 1. Each pair of stacked molecules
of 2 connects with four adjacent pairs by additional p,p-
stacking interactions at an averaged distance of approxi-
˚
mately 3.3 A (Fig. 3(b)). That represents four slightly
the effect of air-dried flow during 20ꢂ30 min before each
/
experiment. The other steps are due to the pyrolysis of
organic ligand with production of various gasses. In all
cases there is a production of ammonia (more or less
evident, but easily identified by two peaks at 934.7 and
970.3 cmꢁ1 in the FT-IR spectra), and NO and/or N2O
(at higher temperatures). Curiously the pyrolysis of
MIDA or EIDA derivatives produces trimethylamine.
tilted (aꢀ9.18) and clearly slipped (bꢀ24.88 and gꢀ
/
/
/
33.88) A5/A6-stacking interactions. Consequently, pairs
of complex units recognise themselves by additional p,p-
stacking links, which co-operate with hydrogen bonds to
build the crystal. We can see how a small modification in
the N-alkylÃ/IDA substituent modifies the molecular
recognition in the crystals building of compounds 1 and
2.
At the end, all complexes give a residue of CuO at 425ꢂ
/
475 8C (with calculated and experimental values in
agreement within approximately 1%). The IR spectra
show peaks and bands due to modes of water and/or
The aromaticity in the N-benzyl-like groups from
NBzIDA or MEBIDA ligands in compound 3 and 4,
respectively, opens new possibilities of p,p-stacking
interactions. Indeed, the crystal of compound 3 contains
complex units connected in the chain along b-axis by a
p,p-stacking interaction between the six-membered rings
of the N-benzyl group (B6) and the adjacent AdeH (A6)
(see Fig. 4 and Table 5). This stacked rings are laid out
aqua, AdeH and the N-substitutedÃ
Table 6).
Electronic spectra show an unsymmetrical dꢂ
with nmax usually in the range of 14ꢂ15 kK in agreement
with the elongated pyramidal chromophore CuN2O2ꢃ
O. Powder ESR spectra at room temperature is of axial
type for compounds 1, 2 and 5 (g ꢀ2.23ꢂ2.25ꢁgÞ ꢀ
2.05) and quasi-isotropic or near isotropic gavꢀ2.10 for
3 and 4. These spectra are in accordance with a dx ꢁy
/
IDA ligands (see
/
d band
/
/
roughly parallel (aꢀ
/
6.248) and moderately slipped (b
/
/
/
/
Š
˚
and g ꢀ158), at an averaged distance of 3.4 A. No other
/
/
p,p-stacking interactions could be considered in this
compound. This means that compound 3 recognises
itself by a multi-stacking interaction between NBzIDA
and AdeH ligands. Chains are connected by hydrogen
bonds in the crystal. A very similar p,p-stacking system
and crystal building is observed in compound 4 (see Fig.
5 and Table 5), with a stacking distance of approxi-
/
2
2
Cu(II) ground state and grossly misaligned tetragonal
axes in the crystal of magnetically diluted compounds
[28]. A plot of x data versus T (K) (Tꢀ
linear (1/xꢀ(1/C)Tꢁ
(u/C) with a statistical factor r2ꢁ
0.998) according to a CurieꢂWeiss behaviour, xꢀC/
(Tꢁu) [32,33]. Curie constant is Cꢀ0.37ꢂ0.43 K emu
molꢁ1 and Weiss constant uꢀ
19.8ꢂ41.1. Estimated
values of meff for Cu(II) atom are 1.73ꢂ1.85 BM, in
/
80ꢂ/300 K) is
/
/
/
/
/
/
/
/
˚
mately 3.5 A and the chains extending along c-axis of
/
/
the crystal. Comparing with 3, the influence of p-methyl
/

E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ
/170
169
Table 6
Summary of thermal, spectral and magnetic properties of Cu(II) compounds 1ꢂ
/5
1
2
3
4
5
TG
Steps
4
3
4
4
3
Dt (8C)
1st step loss
2nd step loss
Residue
90ꢂ
/
425
95ꢂ
/
440
65ꢂ
/
480
100ꢂ
/475
65ꢂ470
/
H2O
N(CH3)3ꢃX
CuO
H2O
N(CH3)3ꢃX
CuO
H2O
a
X
CuO
H2O
a
X
CuO
H2O
a
X
CuO
a
a
IR spectrum (cmꢁ1
H2O
)
nas
d
3456
1630
3465
1635
3450
1617
3430
1650
3440
1630
AdeH
nas(NH2)
n(NÃH)
Carboxylate
nas
3383
3191
3381
3214
3317
3117
3250
3114
3336
3200
1592
1382
1591
1385
1602
1385
1596
1385
1610
1389
ns
Electronic spectrum
nmax (cmꢁ1
)
14.225
12.885
14.300
13.775
14.990
13.330
15.015
13.475
14.000
13.035
nbaricenter (cmꢁ1
)
ESR
Type
axial
2.23
2.05
axial
2-24
2.05
quasi-iso
2.08
quasi-iso
2.2
axial
2.25
2.05
g
Š
gÞ
gaverage
Magnetic properties (80ꢂ300 K)
Behaviour type
m (MB)
/
b
b
b
b
b
CÃW
CÃW
CÃW
CÃW
CÃW
1.81
0.41
19.8
1.85
0.43
30.0
1.83
0.42
41.1
1.73
0.37
27.3
1.77
0.39
26.2
C (Curie constant)
u (Weiss constant)
a
Other gasses: H2O, CO2, CO and NH3 (plus NO and /or N2O in various cases).
b
CurieꢂWeiss type.
/
accordance with the structures reported here and metalÃ
/
HÁ Á ÁO(carboxyl) and a CuÃ
/
N3(AdeH) coordination
˚
5.5(1) A. In the studied compounds,
metal separation ]
/
bond. The resulting complexes (3 and 4) recognise
themselves through a multi-p,p-stacking interaction of
alternating six-membered aromatic rings from N-(ben-
˚
Cu distance (5.23(1) A) corresponds to
the shortest CuÃ
/
metal atoms of compound 5 connected by the bridging
carboxylato group of pheida ligand (Fig. 6).
zyl-like)Ã
complex chain. A surprising m-N3,N7-bridging mode is
observed for Cu(II)ÃAdeH coordination in the structure
/IDA and AdeH ligands, giving a ‘stacked’
/
of the tetra-nuclear compound 5 where no p,p-stacking
interaction is operative. Perhaps an excess of conforma-
tional free-down in the phenethyl arm of pheida ligand
and other unclear reasons govern the tetra-nuclear
formula.
4. Concluding remarks
In the complexes studied here, the copper(II) atom
exhibits a typical metal ion coordination and a typical
mer-chelating configuration in the CuÃ
late moiety. Copper(II) complexes with N-alkylÃ
ligands and AdeH recognise each other selectively by an
interligand hydrogen bond N(6,
exocyclic)Ã
N7(AdeH) coordination
/
(IDA-like) che-
/IDA
/
5. Supplementary material
HÁ Á ÁO(carboxyl) and a CuÃ
/
bond. The resulting mixed-ligand complexes (1 and 2)
recognise themselves by a p,p-stacking interaction
between anti-parallel AdeH ligands, forming pairs of
complex units. On the other hand, copper(II) com-
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC Nos. 172940 for H2pheida acid,
172944 for [Cu(MIDA)(AdeH)(H2O)]×
1), 172941 for [Cu(EIDA)(AdeH)(H2O)]×
pound 2), 172942 for [Cu(NBzIDA)(AdeH)(H2O)]×
H2O (compound 3), 172945 for [Cu(MEBIDA)(AdeH)-
/H2O (compound
pounds with N-(benzyl-like)Ã
recognise one another selectively by means of an
interligand hydrogen bond N(9, heterocyclic)Ã
/
IDA ligands and AdeH
/
H2O (com-
/
/

170
E. Bugella-Altamirano et al. / Inorganica Chimica Acta 339 (2002) 160ꢂ170
/
[15] Md. Abdus Salam, K. Aoki, Inorg. Chim. Acta 311 (2000) 15
(and references therein).
(H2O)]×
/
H2O (compound 4) and 172943 for [Cu4-
2H2O (compound 5). Copies
(pheida)4(AdeH)2(H2O)4]×
/
[16] (a) M.R. Taylor, Acta Crystallogr., B 29 (1973) 884;
(b) P.T. Muthiah, S.K. Mazumdar, S. Chaudhuri, J. Inorg.
Biochem. 19 (1983) 237;
of this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge, CB2
(c) M.R. Taylor, J.A. Westphalen, Acta Crystallogr., A 37 (1981)
C63.
[17] M.J. Roma´n-Alpiste, J.D. Mart´ın-Ramos, A. Castineiras-Cam-
˜
1EZ, UK (fax: ꢃ44-1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
/
pos, E. Bugella-Altamirano, A.G. Sicilia-Zafra, J.M. Gonza´lez-
Pe´rez, J. Niclo´s-Gutie´rrez, Polyhedron 18 (1999) 3341.
[18] Inorganic Aspects of Biological Processes is an specific optional
subject offered by J.N.-G. to students in the Faculty of Pharmacy
(University of Granada) which consists of theoretical (30 h) and
experimental (30 h) essentials of Inorganic Chemistry regarding
bioinorganic applications. An introduction to Bioinorganic Chem-
istry is also offered in different faculties of the University as an
optional subject, with theoretical (40 h) and practical (20 h)
sessions.
Acknowledgements
The authors are very honoured to devote this
contribution in Inorganica Chimica Acta to Professor
Dr. Helmut Sigel. He has encouraged many significant
contributions in metal complexes on the exciting field of
Bio-inorganic Chemistry. We are grateful to the DGE-
SIC/DGI (MECD/MCYT, Spain) for financial support
(Research Projects PB98-0605-C03-02 and -03). EBA,
MJSM and DChL are gratefully indebted to the
MECD, MCT and MAE (AECI) Ministers, respec-
tively, for their Doctoral research grants. BC also
thanks the Xunta de Galicia for a Doctoral research
grant. RMS thanks the Inorganic Chemistry Depart-
ment (University of Granada) for the opportunity of
taking part in this research during a course on Inorganic
Aspects of Biological Processes [18].
[19] H. Sigel, Met. Ions Biol. Syst. 2 (1973) 64.
[20] (a) Ch. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885 (and
references therein);
(b) K. Barton, in: I. Bertini, H.B. Gray, S.J. Lippard, J.S.
Valentine (Eds.), Bioinorganic Chemistry, University Science
Books, Mill Valley, CA, 1994, p. 455.
[21] A. Castineiras Campos, A.G. Sicilia Zafra, J.M. Gonza´lez Pe´rez,
˜
J. Niclo´s Gutie´rrez, E. Chinea, A. Mederos, Inorg. Chim. Acta
241 (1996) 39.
[22] SMART and SAINT, Area Detector Control and Integration Soft-
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1997.
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Correction of Area Detector Data, University of Gottingen,
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