A systematic study of ligand intermolecular interactions in crystals of copper(II) complexes of bidentate guanidino derivatives

Article abstract of DOI:10.1016/j.ica.2005.12.079

The synthesis and X-ray structures of copper(II) complexes of the bidentate ligands, N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)-N′-phenylguanidino, 2-uanidinobenzimidazolo and N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-yl)guanidino, are repo

Full text of DOI:10.1016/j.ica.2005.12.079

Inorganica Chimica Acta 359 (2006) 3565–3580
www.elsevier.com/locate/ica
A systematic study of ligand intermolecular interactions in crystals
of copper(II) complexes of bidentate guanidino derivatives
c
a,
d
Michael M. Bishop a,b, Simon J. Coles , Leonard F. Lindoy *, Andrew Parkin
a
Centre for Heavy Metals Research, School of Chemistry, University of Sydney, NSW 2006, Australia
b
Sydney Grammar School, College Street, Darlinghurst, NSW 2010, Australia
EPSRC National Crystallography Service, School of Chemistry, University of Southampton, Southampton SO171BJ, UK
c
d
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
Received 29 October 2005; received in revised form 15 December 2005; accepted 19 December 2005
Available online 27 March 2006
Dedicated to Professor M. Mingos FRS – An outstanding chemist.
Abstract
The synthesis and X-ray structures of copper(II) complexes of the bidentate ligands, N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-
2-yl)-N0-phenylguanidino, 2-uanidinobenzimidazolo and N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-yl)guanidino, are reported.
These complexes, which possess potential doublet (DA) or triplet (DAD) hydrogen bonding motifs, can form supramolecular structures
based on synthons involving hydrogen bonding or phenyl embraces. The changes in supramolecular structure resulting from small
changes in ligand structure, as well as from the use of different solvents for their crystallisation, are examined. The structures adopted
are compared with others reported previously for complexes of related ligands.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Copper(II); X-ray structure; Supramolecular array
1. Introduction
Recently, as part of these studies, we reported the synthe-
sis and structures of complexes of the related bidentate
ligands, N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-
yl)alkanimidamido (where alk = Me, Et), methyl N-(4-oxo-
5,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)imidocarbamato
and N,N-dimethyl-N0-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-
imidazol-2-yl)guanidino (Scheme 1; Ib–e) [21,22]. These
ligands readily form neutral pseudo-macrocyclic complexes
with self-complementary DA hydrogen bonding motifs and
were shown to be well suited to structural studies of supra-
molecular interactions in crystals of divalent transition metal
complexes (see Scheme 2). Where linking of the potential
doublet hydrogen bonding motifs was not prevented by sol-
vation of the motif or by the steric requirements of substit-
uents on the ligand, the individual complex units were
observed to link together into chains by R22ð8Þ hydrogen
bond patterns. While the complexes within the hydrogen-
bonded chains were often approximately coplanar, twisting
In recent times there has been a growing interest in the
rational design of molecular frameworks containing transi-
tion metal complexes both by the formation of coordina-
tion polymers [1–4] in which metal ions link individual
units throughout the structure or, more recently, by
employing hydrogen bonding and other weak interactions
between the metal-coordinated ligands [5–14].
In earlier papers we have described systems of the latter
type in which a number of transition metal complexes have
been incorporated into supramolecular arrays through the
use of complementary hydrogen bonding motifs to link the
metal-containing units [15–22].
*
Corresponding author. Tel.: +61 2 935 14400; fax: +65 2 9351 3329.
E-mail address: lindoy@chem.usyd.edu.au (L.F. Lindoy).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.079

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
hydrogen bonding of the neutral complexes was not
observed, the complexes formed approximately planar
chains. In these the complex units were linked instead by
phenyl embraces involving offset face-to-face (OFF), edge-
to-face (EF) or aromatic CH-to-p facial (CHp) interactions
in complementary motifs involving two diphenyl moieties
such as OFF(EF)2 and OFF(CHp)2. It is worth noting in
this context that the most advantageous intermolecular
C–C distance is not the sum of the van der Waals radii
˚
˚
(3.4 A) but some 0.3–0.4 A longer. For offset face-to-face
interactions the distance is even greater. In fact, the inter-
molecular potential becomes zero, or slightly destabilising,
at the van der Waals distance [23,24]. Different crystallisa-
tion solvents also gave rise to different supramolecular
structures with molecules of solvent incorporated in differ-
ent ways.
In the study now reported, relative to our previous study
[22] we have changed the potential hydrogen bonding motif
from a doublet to a triplet (DAD) in its corresponding bis-
ligand copper(II) complex by employing the new ligand
N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)-N0-
phenylguanidine (Scheme 1; Ia); in the process we have also
introduced another phenyl group to each ligand.
Scheme 1.
of the chains also occurred in specific cases. Conforma-
tional changes within the ligands necessary to optimise the
hydrogen bonding interactions were also observed. Where
Two experiments involving the complexes of this ligand
were undertaken. In the first, hydrogen-bonded chain for-
mation was prevented by co-crystallisation of the copper
complex with 1,8-naphthalimide, which contains a comple-
mentary ADA triplet motif. Stacking interactions and the
arrangement of the phenyl motifs were then examined.
The second experiment involved exploitation of the fact
that, although the triplet DAD motifs on the complexes
are not self-complementary, there are two self-complemen-
tary doublet hydrogen bonding motifs possible (Scheme 3).
In order to investigate whether interchange between these
modes might occur, the effect of crystallisation of the
respective complexes from different solvents on chain for-
mation was probed. The influence of the additional (third)
phenyl group present in this ligand on the arrangement
adopted in the solid state is also discussed.
The assembly of related complexes of the anionic forms
of 2-guanidinobenzimidazole (II) and N-(4-oxo-3-phenyl-
1,3-diazaspiro[4.4]non-1-en-2-yl)guanidine (III) were also
investigated for comparison with the above.
Scheme 2.
Scheme 3.

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3567
2. Experimental
ammoniacal solution of copper(II) chloride-2-water
(0.085 g, 0.5 mmol). The mixture was heated with stirring
for 15 min after which the purple solid that formed was fil-
tered off, washed with hot methanol (3 · 3 mL) and dried
in air. Yield: 0.275 g, 69%.
2.1. 4-Oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-
ylcyanamide
This was prepared in good yield (66%) from benzil and
dicyandiamide as described previously [25].
2.4. [Bis(N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-
2-yl)-N0-phenylguanidino)copper(II)(1,8-naphthalimide)2]
(5a)
2.2. N-(4-Oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-yl)-
N0-phenylguanidine (Ia)
1,8-Naphthalimide (0.0127 g, 64 mmol) was dissolved in
DMF (2 mL) and 5 (0.0255 g, 32 mmol) was added. Small
crystals formed on standing in near quantitative yield.
Anal. Calc. for C68H50CuN12O6: C, 68.36; H, 4.22; N,
14.07. Found: C, 68.13; H, 4.44; N, 14.10%.
The above product was recrystallised from benzonitrile
to yield crystals, 5b, which were left in the growth solution
until used for X-ray data collection. On isolation, these
crystals lost one equivalent of benzonitrile when dried in
a desiccator over silica gel. Anal. Calc. for C44H36Cu-
N10O2 Æ 0.5C6H5CN: C, 66.96; H, 4.56; N, 17.27. Found:
C, 66.98; H, 4.86; N, 17.30%.
Crystallisation of 5 from DMF gave crystals, 5c, which
were dried in a desiccator over silica gel to yield the di-
DMF solvate. Anal. Calc. for C44H36CuN10O2 Æ 2DMF:
C, 63.44; H, 5.32; N, 17.76. Found: C, 63.25; H, 5.61; N,
17.76%.
When 5 was crystallised from DMSO a corresponding
di-DMSO solvate was obtained after drying in a desiccator
over silica gel. Anal. Calc. for C44H36CuN10O2 Æ 2DMSO:
C, 60.26; H, 5.06; N, 14.65. Found: C, 60.24; H, 5.05; N,
14.75%.
2.2.1. Method A
1-Phenylbiguanide (1.77 g, 10 mmol) was added to a hot
solution of KOH (0.62 g, 10 mmol) in absolute ethanol
(70 mL). To this mixture was slowly added benzil (2.10 g,
10 mmol) and the resulting mixture was then heated under
reflux for 4 h. The volume was reduced on a rotary evapo-
rator to 25 mL and water was added dropwise to the hot
solution. Once the solution became cloudy, the solution
was allowed to cool while triturating. The white solid so
obtained was isolated by filtration, recrystallised from
methanol, then dried in a desiccator over silica gel. Yield
1.74 g, 47%. Anal. Calc. for C22H19N5O: C, 71.52; H,
5.18; N, 18.96. Found: C, 71.34; H, 5.02; N, 18.90%.
2.2.2. Method B
The above product may also be prepared by heating
4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-ylcyanamide
and aniline hydrochloride in n-butanol at the reflux tem-
perature for 8 h, as reported previously for the analogous
reaction employing p-toluidine hydrochloride [26]. Yield
0.18 g, 13%.
2.3. Bis(N-(4-oxo-5,5-diphenyl-4,5-dihydro-1H-imidazol-2-
yl)-N0-phenylguanidino)copper(II) (5)
2.5. [Bis(2-guanidinobenzimidazolo)copper(II)(1,8-
naphthalimide)2] Æ 2dimethylsulfoxide (6)
Ligand Ia (0.369 g, 1 mmol) was dissolved in hot meth-
anol (20 mL). To this solution was added an aqueous
Precursor bis(2-guanidinobenzimidazolo)copper(II) was
prepared in 66% yield by the addition of an ammoniacal
Table 1
Crystallographic Data
5a
5b
5c
6
7
Formula of the refinement model
Model molecular weight
Crystal system
C
68H50CuN12O6
C54.50H43.50CuN11.50O2
955.05
C50H50CuN12O4
946.57
C44H42CuN12O6S2
962.56
C28H34CuN10O3
622.20
triclinic
1194.74
triclinic
orthorhombic
Pbcn (#60)
16.139(2)
19.601(3)
28.809(4)
90.000
90.000
90.000
9114(2)
1.392
monoclinic
P21/c (#14)
28.0687(8)
8.4811(2)
19.7886(4)
90.000
101.0343(7)
90.000
4623.7(2)
1.360
monoclinic
C2/c (#15)
23.2421(15)
7.5572(4)
25.4613(18)
90.000
109.897(4)
90.000
4205.2(5)
1.520
ꢀ
ꢀ
Space group
P1 ð#2Þ
P1 ð#2Þ
˚
a (A)
10.9025(7)
11.9168(8)
12.2807(8)
74.624(4)
75.938(4)
65.560(4)
1384.35(16)
1.433
9.0123(1)
12.2308(2)
13.6773(2)
81.3841(5)
87.6577(6)
81.461(1)
1473.81(4)
1.402
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
DC (g cmꢀ3
)
Z
1
8
4
4
2
Temperature (K)
150(2)
0.464
0.0546, 0.1400
150(2)
0.538
0.0568, 0.1125
120
0.53
0.0477, 0.1181
150(2)
0.685
0.0579, 0.1399
120
0.79
0.0368, 0.0834
l(Mo Ka) (mmꢀ1
)
Residuals R1(F), wR2(F2)

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
Table 2
Hydrogen bond Summary
˚
˚
˚
Donor
Hydrogen
Acceptor
D–H (A)
H–A (A)
D–A (A)
DHA angle (ꢁ)
5a
N(2)
N(4)
N(6)
N(5)
H(2)
H(4)
H(6A)
H(5)
O(3)
O(2)
N(3)
O(1)a
0.88
0.88
0.88
0.88
1.95
2.07
2.14
1.93
2.797(3)
2.942(3)
3.022(3)
2.720(3)
161.9
168.3
177.2
148.7
5b
N(7)
N(2)
N(5)
N(10)
N(4)
H(7)
H(2)
H(5)
H(10)
H(4)
N(3)b
N(8)c
O(2)
O(1)
N(11)
0.88
0.88
0.88
0.88
0.88
2.21
2.11
2.10
2.10
2.50
3.019(6)
2.942(6)
2.842(5)
2.837(5)
3.166(6)
153.7
157.0
142.0
141.0
132.9
5c
N(2)
N(10)
N(4)
N(9)
N(7)
N(5)
H(2N)
H(10N)
H(4N)
H(9N)
H(7N)
H(5N)
O(3)
O(1)
N(8)d
N(3)e
O(4)
O(2)
0.888(17)
0.856(17)
0.898(17)
0.899(17)
0.896(17)
0.870(17)
1.868(18)
1.98(2)
2.129(18)
2.081(18)
1.885(18)
2.00(2)
2.750(3)
2.749(3)
3.007(3)
2.964(3)
2.779(3)
2.780(3)
172(3)
149(2)
166(2)
167(3)
175(3)
148(3)
6
N(6)
N(4)
N(2)
N(2)
H(6N)
H(4N)
H(2NA)
H(2NB)
N(3)
O(1)
O(2)
O(3)
0.86(3)
0.82(4)
0.88(4)
0.88(4)
2.08(4)
2.04(4)
2.01(4)
2.05(4)
2.940(4)
2.857(3)
2.883(4)
2.929(4)
177(3)
169(4)
176(3)
170(4)
7
N(2)
N(2)
O(3)
N(6)
N(7)
N(2)
O(3)
H(2N)
O(3)
O(3)
0.888(17)
0.883(15)
0.840(17)
0.868(16)
0.878(16)
0.885(16)
0.840(17)
1.868(18)
2.142(17)
2.13(2)
2.128(16)
2.104(18)
2.317(18)
2.26(3)
2.750(3)
2.933(2)
2.878(2)
2.977(2)
2.906(2)
3.167(2)
2.904(2)
172(3)
148.7(19)
148(3)
165(2)
151(2)
161(2)
134(3)
H(2NA)
H(3OA)
H(6N)
H(7NA)
H(2NB)
H(3OB)
N(3)
O(2)f
O(3)g
N(8)h
N(8)i
Symmetry operators: a1 ꢀ x, 1 ꢀ y, 1 ꢀ z; bꢀx + 3/2, y + 1/2, z; cꢀx + 3/2, y ꢀ 1/2, z; dx, ꢀy + 1/2, z + 1/2; ex, ꢀy + 1/2, z ꢀ 1/2; fx ꢀ 1, y, z; gx, y + 1, z;
i
h1 ꢀ x, 1 ꢀ y, 1 ꢀ z; x, y ꢀ 1, z.
solution of copper(II) chloride to a methanol solution of
2-guanidinobenzimidazole, as previously described for the
corresponding nickel(II) complex [15]. Crystals of 6 suit-
able for X-ray crystallography were obtained by dissolving
a mixture of 1,8-naphthalimide (0.04 g, 0.2 mmol) and the
above complex (0.04 g, 0.1 mmol) in hot dimethylsulfoxide
(6 mL) and allowing the solution to stand. Clusters of
brown crystals of product formed in near quantitative
Table 3
Selected metal environmental geometry details for compounds 5a–c, 6 and 7
Cu(1)–N(1)
Cu(1)–N(5)
Cu(1)–N(6)
Cu(1)–N(10)
˚
Coordination bond (Cu–N) lengths in A
5aa
5b
5c
6a
7
2.011(2)
1.983(4)
2.0320(18)
1.930(3)
1.9177(16)
1.946(2)
1.920(4)
1.9252(19)
1.941(2)
1.9576(15)
1.998(4)
2.0276(19)
1.919(4)
1.9215(19)
1.9177(16)
1.9597(15)
N(1)–Cu–N(5)
N(1)–Cu–N(6)
N(1)–Cu–N(10)
N(5)–Cu–N(6)
N(5)–Cu–N(10)
N(6)–Cu–N(10)
Coordination bond angles in ꢁ
5aa
5b
5c
6a
7
85.94(9)
87.23(17)
87.30(8)
88.56(11)
89.93(7)
180
94.06(9)
92.92(17)
92.44(8)
97.20(11)
101.35(7)
180
171.96(17)
178.66(8)
151.39(18)
145.03(7)
94.24(16)
93.22(8)
168.89(18)
178.02(9)
156.61(15)
143.03(7)
87.16(17)
87.09(8)
101.61(7)
89.09(6)

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3569
yield. Anal. Calc. for C40H30CuN12O4 Æ 2DMSO: C, 54.90;
H, 4.40; N, 17.47. Found: C, 54.86; H, 4.14; N, 17.16%.
was isolated and air dried. Yield 0.25 g, 18%. IR 3540,
3420, 3390 cmꢀ1; m(C@O) 1720 cmꢀ1
.
2.6. N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-
yl)guanidine (III)
2.7. Bis(N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-
yl)guanidino)copper(II)-1-water (7)
Phenylbiguanide (0.885 g, 5 mmol) was suspended in
absolute ethanol (20 mL) and cyclohexanedione (0.566 g,
5 mmol) was added. The yellow suspension was stirred
for 20 min at room temperature and then heated under
reflux for 20 min. The volume of the solution was reduced
15 mL on a rotary evaporator. The residue was transferred
to a small flask and crystallisation was induced by scratch-
ing the sides of the flask; the flask was sealed and allowed
to stand until crystallisation was complete. The product
Ligand III (0.135 g, 0.5 mmol) was dissolved in warm
ethanol (10 mL). To this solution was added an ammonia-
cal solution of copper(II) chloride-2-water (0.043 g,
0.25 mmol) and the mixture was allowed to stand. The
dark green solid that formed was isolated, washed with
Et2O (1 · 2 mL) and air dried. Yield 0.09 g, 29%. The prod-
uct was crystallised from DMF to yield crystals that proved
suitable for X-ray diffraction. The material was dried in a
desiccator over silica gel before microanalysis. Anal. Calc.
Fig. 1. An ORTEP [36] depiction of 5a with thermal ellipsoids drawn at the 20% level.

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
for C28H32CuN10O2 Æ H2O: C, 54.05; H, 5.51; N, 22.52.
Found: C, 54.13; H, 5.52; N, 22.45%.
equipped with an Oxford Cryosystems low temperature
device [27], and using graphite monochromated Mo Ka
sealed tube radiation. Data for these three structures were
integrated using SAINT [28], and an absorption correction
was applied based on the method of Blessing [29] using
the program SADABS [30]. Data for 5c and 7 were collected
at 120 K on a Nonius Kappa CCD diffractometer equipped
with an Oxford Cryosystems low temperature device [27],
and using graphite monochromated MoKa radiation gen-
erated using a rotating anode. Data for these two struc-
tures were integrated using the program DENZO [31], and
an absorption correction was applied based on the method
The product was also recrystallised from DMSO to yield
further crystals that, after drying in a desiccator over silica
gel, analysed as the corresponding sesquihydrate. Anal.
Calc. for C28H32CuN10O2 Æ 1.5H2O: C, 53.28; H, 5.59; N,
22.20%. Found: C, 53.13; H, 5.61; N, 21.80%.
2.8. X-ray structure determinations
Crystallographic data for 5a, 5b and 6 were collected at
150 K on a Bruker SMART 1000 CCD diffractometer
Fig. 2. An ORTEP [36] depiction of 5b with thermal ellipsoids at the 20% level.

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3571
Fig. 3. An ORTEP [36] depiction of 5c with thermal ellipsoids drawn at the 20% level.
of Blessing [29], and using the program SORTAV [29]. All five
3. Results and discussion
structures were solved by direct methods; 5a, 5c and 7 were
solved using SIR92 [32], 5b and 6 were solved using SIR97
[33]. All structures were extended and refined against F2
using full matrix least squares using the WINGX [34] and
SHELXTL [35] suites of programs. All non-hydrogen atoms
were refined anisotropically, and hydrogen atoms were
refined as riding and rotating groups, with the exception
of those hydrogen atoms involved in hydrogen bonding,
which were freely refined with isotropic displacement
parameters. Deviations from this refinement strategy are
given below for individual structures. Final refinement data
for all five structures are given in Table 1, and details of
hydrogen bond geometry and metal environment geometry
are given in Tables 2 and 3, respectively. ORTEP [36] plots
are shown in Figs. 1–5.
3.1. Ligand synthesis and structure
Ligand Ia was obtained using two procedures (Scheme
4a) based on related literature syntheses [21,22]. Ligand
III, N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-yl)-
guanidine, was prepared from phenylbiguanide and cycloh-
exanedione (which undergoes a rearrangement similar to
the benzilic acid rearrangement in base) [37] (Scheme 4b).
Interestingly, we obtained this product rather than the iso-
meric N-(4-oxo-1,3-diazaspiro[4.4]non-2-en-2-yl)-N0-phe-
nylguanidine (IV) previously reported as the most likely
structure [38,39]; the physical data presented to support
the assignment of the structure of IV (microanalysis,
molecular weight by mass spectrometry and spectral data,
including an 8-proton multiplet corresponding to the cyclo-
pentanylidene ring and the carbonyl IR absorption) [39] is
also consistent with structure III. The carbonyl stretch in
III occurs at 1720 cmꢀ1, which is higher than the
1688 cmꢀ1 observed for the free ligand Ie and suggests that
5a: Hydrogen atoms involved in hydrogen bonding were
observed in the Fourier difference map, then placed geo-
metrically and refined as riding groups.
5b: Hydrogen atoms involved in hydrogen bonding were
placed geometrically and refined as riding groups.

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Fig. 4. An ORTEP [36] depiction of 6 with thermal ellipsoids drawn at the 20% level.
the carbonyl stretch in III is less affected by conjugation
than that of Ie.
ing hydrogen-bonded chains through the presence of
bound solvent molecules or due to the steric nature of
the ligand, chains in which the units are linked by phenyl
embraces tend to form instead. The formation of the
three-component unit in 5a effectively prevents the forma-
tion of hydrogen-bonded chains and OFF(CHp)2 embraces
occur that link individual units (Figs. 6 and 7). The
arrangement differs from that observed in other potentially
similar crystalline products (namely 2b, 3d, 4a and 4b)
[21,22].
It is noted that a diphenyl group can form an
OFF(CHp)2 embrace in two ways, which are perpendicular
to one another. In the earlier instances (2b, 3d, 4a and 4b)
the embraces resulted in chains, represented diagramati-
cally in Scheme 5a, in which two of the Cu–N bonds are
aligned with the chain axis and adjacent Cu atoms are sep-
3.2. Crystal packing: phenyl embraces and p stacking in 5a
and 6
The species 5a incorporates three-component units;
namely, a pseudo-macrocyclic metal complex together with
two molecules of 1,8-naphthalimide, with the latter hydro-
gen bonded to the copper(II)-bound ligands via comple-
mentary triplet motifs (Table 2). The centro-symmetric
copper complex is square-planar (Table 3) with the copper
˚
arated by 16 A. In contrast, in 5a the embrace adopts the
orientation shown in Scheme 5b with the result that the
˚
adjacent Cu atoms are 14.3 A apart. In addition to this
embrace there is another OFF(CHp)2 embrace present
involving one of the phenyl groups on the imidazole ring
and the phenyl group attached to N(4) on the other ligand
in the pseudo-macrocyclic structure (Fig. 7). These
embraces link the chains into sheets that lie quasi-perpen-
dicular to the b-axis.
˚
lying just 0.098 A out of the plane defined by the rest of the
metallaring N(1)–C(3)–N(3)–C(4)–N(5). The phenyl group
on N(4) is syn, which is necessary for the formation of the
hydrogen bonds mentioned above.
In earlier papers we have shown that when metal-con-
taining motifs such as that in 5a are prevented from form-
The naphthalimide molecules in the above structure are
involved in staggered stacking interactions with the ligands

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3573
Fig. 5. An ORTEP [36] depiction of 7 with thermal ellipsoids at the 20% level.
Scheme 4.

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
Fig. 6. A PLATON [37] depiction of the offset face to face phenyl embraces, labelled (I), linking adjacent complexes in 5a; other broken lines indicate
hydrogen bonds. The 1,8-naphthalimide moieties have been omitted for clarity.
Fig. 7. A PLATON [37] depiction of the view of 5a along the b-axis showing the two types of phenyl embrace present. The three complexes running from top
left to bottom right are linked by embraces of type (I) as shown in Fig. 6. The second type of embrace is labelled (II). The 1,8-naphthalimide moieties are
omitted for clarity; the hydrogen bonds are also not shown so that all the broken lines represent phenyl–phenyl interactions.
Scheme 5.

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3575
Fig. 8. A PLATON [37] depiction of the stacking of 1,8-naphthalimide moieties with the ligands in (a) 5a and (b) 6. The bonds in the molecules in the upper
layer of the stack are shaded.
in such a way that each of the three naphthalimide rings
has a ligand nitrogen atom aligned with its centroid
(Fig. 8a). The naphthalimide C(27) and C(28) make an
edge-to-face contact with a phenyl ring. The stacks do
not run through the crystal but involve just two ligands
and two naphthalimides (between which the stacking is
graphite-like).
the steric ‘clash’ between the hydrogen atoms on C(7)
and N(1) on opposite ligands. This results in a tetrahedral
distortion from square planar geometry (Table 3) that in
turn prevents formation of the stacking motif that occurs
in 5a; instead, that shown in Fig. 8b is observed.
3.3. Solvation by benzonitrile (5b)
The assembly 6 was prepared to provide another exam-
ple of stacking of 1,8-naphthalimide with 2-guanidinobenz-
imidazole, a planar ligand somewhat similar, especially in
the arrangement of heteroatoms, to the ligand in 5a; 6 dif-
fers only in detail from the nickel analogue described ear-
lier [16]. The metal complex cannot be planar because of
When 5 was crystallised from benzonitrile, a weak
hydrogen bond acceptor, crystals of 5b were obtained. In
these crystals the coordination geometry of the complex
shows a tetrahedral distortion from square planar but the
hydrogen bonds that close the pseudo-macrocycle remain

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
Fig. 9. A PLATON [37] depiction of the hydrogen-bonded chains in 5b. Notice the twisting of the complexes that form the chain and that it is the imidazole
N–H that is utilised in chain formation, not the amino N–H.
Fig. 10. A PLATON [37] depiction of the hydrogen-bonded chains in 5c; the DMF molecules have been omitted for clarity. Notice the extreme twisting of
each complex with respect to its neighbours. Also note that it is the amino N–H that is utilised in chain formation; the imidazole N–H is hydrogen bonded
to a DMF solvent molecule.
˚
intact (Tables 2 and 3). The copper ion lies 0.38 and 0.34 A,
respectively, out of the planes defined by the ligand atoms
N(1)–C(3)–N(3)–C(4)–N(5) and N(6)–C(25)–N(8)–C(26)–
N(10).
phenyl groups. N(11) is involved in a long hydrogen bond
with N(4). The centroid of the benzene ring lies over N(5)
with the average C–N distance 3.63 A.
˚
An examination of 2-guanidinobenzimidazole com-
plexes in earlier work [15,16,19] shows that in these the
imidazole nitrogen is used in preference to the guanidine
nitrogen as the donor in the R22ð8Þ patterns that lead to
chain formation. The hydrogen bonds involving the imid-
azole nitrogen are also consistently shorter than those
involving the guanidino nitrogen in complementary triplet
motifs and, if one hydrogen bond is broken so reducing the
triplet to a doublet, it is the bond involving the guanidino
nitrogen.
The complexes are linked into chains, quasi-parallel
with the b-axis, by R22ð8Þ hydrogen bonding patterns in
which the imidazole nitrogen atoms N(2) and N(7) act as
donors (Scheme 3a). Of the other possible donors, only
N(4) is involved in a long and not very linear interaction
with a benzonitrile nitrogen N(11) (Table 2). The R22ð8Þ pat-
terns, and hence the chains, are far from planar (Fig. 9)
with the plane defined by N(6)–C(25)–N(7)–N(8) making
an angle of 42.5ꢁ with the plane defined by N(1)–C(3)–
N(2)–N(3). The chains are stacked on top of one another
in the a direction, with the copper ions offset.
3.4. Solvation by N,N-dimethylformamide (5c)
There are two distinctly different benzonitrile sites. The
molecule containing N(11) is associated with the hydrogen-
bonded chains and the other, containing N(12), is located
on a special site and lies in a pocket surrounded by ligand
Crystallisation of 5 from DMF gives crystals of 5c,
which once again contains an almost square planar copper
complex, with hydrogen bonds again forming a pseudo-

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3577
Fig. 11. A PLATON [37] depiction of view along the c-axis showing the edge to face interactions (broken lines) between phenyl groups in 5c; DMF molecules
have been omitted for clarity, as have the hydrogen bonds.
macrocycle (Tables 2 and 3). The copper ion lies 0.12 and
0.17 A, respectively, out of the planes defined by the ligand
3.5. Bis(N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]non-1-en-2-
yl)guanidino)copper(II)-1-water
˚
atoms N(1)–C(3)–N(3)–C(4)–N(5) and N(6)–C(25)–N(8)–
C(26)–N(10).
The new ligand, N-(4-oxo-3-phenyl-1,3-diazaspiro[4.4]-
non-1-en-2-yl)guanidine, III, forms a green uncharged bis
complex with copper(II) in ammoniacal solution. An
X-ray diffraction study of the crystals, 7, obtained by crys-
tallisation of the initial product from DMF is shown in
Fig. 5. Individual complex units have a distorted tetrahe-
dral geometry and are linked into extended arrays by
hydrogen bonding (Tables 2 and 3). Whereas in 5 there is
a carbonyl group on the ligand that leads to the formation
of pseudo-macrocycles, in III there is a five-membered
hydrocarbon ring leading to steric hindrance such that a
square planar, or approximately square planar, coordina-
tion geometry is no longer possible. The two crystallo-
graphically distinct metallarings in each complex are
approximately planar with the copper ion lying 0.08 and
The complexes are linked into chains, quasi-parallel
with the c-axis, by R22ð8Þ hydrogen bonding patterns in
which the imidazole nitrogen atoms are not involved but
instead the guanidino nitrogen atoms N(4) and N(9) act
as donors (Scheme 3b). The imidazole donors N(2) and
N(7) are hydrogen bonded to DMF molecules, with the
DMF methyl groups oriented away from the copper ion.
The R22ð8Þ patterns, and hence the chains, are far from pla-
nar (Fig. 10) with the plane defined by N(10)–C(26)–N(9)–
N(8) making an angle of 54.9ꢁ with the plane defined by
N(5)–C(4)–N(4)–N(3).
The complexes are also linked into chains quasi-parallel
to b by centrosymmetric pairs of EF interactions between
the imidazole phenyl rings (Fig. 11); this leads to the for-
mation of sheets of complexes, with DMF methyl to phenyl
p-facial interactions within these sheets.
˚
0.06 A from the planes defined by the ligand atoms in each
metallaring; these planes make an angle of 55.5ꢁ with one
another. There is no DMF, coordinated or hydrogen
bonded to a ligand donor, in the crystal.
The N-phenyl groups on the ligands prevent the forma-
tion of a R22ð8Þ hydrogen bond pattern between complexes.
What is observed instead is that a water molecule, which
Because the chains lie directly above one another, there
are channels, occupied by the DMF molecules, running
through the crystal. The channels are somewhat constricted
by the lack of co-planarity between complexes within the
chains.

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M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
Fig. 12. A PLATON [37] depiction of the view along the c-axis of 7 showing the formation of sheets by hydrogen bonding. The complexes are linked directly
into chains quasi parallel to a by N–Hꢁ ꢁ ꢁO hydrogen bonds. These chains are cross-linked indirectly by hydrogen bonding with water molecules; these
linkages run quasi-parallel to b.
Fig. 13. A PLATON [37] depiction of the view along the b-axis of 7 showing the hydrogen bonding, quasi-parallel to c, between a pair of sheets.
has two donor and two acceptor sites, links the potentially
complementary DA motifs by forming two R22ð6Þ patterns
with one atom, O(3), in common. Thus, hydrogen-bonded
chains, quasi-parallel to b, are formed, though the com-
plexes are not directly linked. The plane defined by N(6)–
C(15)–N(7)–N(8) makes an angle of 63.6ꢁ with that defined
by N(1)–C(1)–N(2)–N(3). The water oxygen, O(3), lies
close to the faces of the two N-phenyl groups.
The carbonyl groups that act as hydrogen bond accep-
tors in coordinated (deprotonated) Ia to form pseudo-
macrocycles cannot do so in these complexes. In this latter
case they are oriented so that they have the potential to
link neighbouring complexes. In fact, only one of the car-
bonyl oxygens, O(2), does this, accepting a proton from a
coordinated imino nitrogen, N(6), forming chains quasi-
parallel to a. The guanidino nitrogen, N(7), is aligned with

M.M. Bishop et al. / Inorganica Chimica Acta 359 (2006) 3565–3580
3579
the centroid of a phenyl ring (which has a water posi-
Acknowledgements
tioned over the other face) in the neighbouring complex
in the chain. Overall, the presence of the two hydrogen-
bonded chains corresponds to the formation of sheets
(Fig. 12).
Interestingly, the other carbonyl oxygen, O(1), is not
involved in hydrogen bond formation, which would lead
to a three-dimensional hydrogen-bonded array. Instead,
the sheets are paired, linked by N(2)–Hꢁ ꢁ ꢁN(8)p hydrogen
bonds as shown in Fig. 13.
We thank the Australian Research Council for support
and the EPSRC National Crystallography Service, South-
ampton, for the collection of X-ray diffraction data on
two of the compounds. We thank Dr. D. Hibbs for exper-
imental assistance.
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