The synthesis and characterization of a series of bis-bidentate Schiff base ligands and their coordination complexes with silver(I), copper(I) and zinc(II) d10 metal ions

Article abstract of DOI:10.1039/b301632c

Three bis-bidentate Schiff base ligands 1, 2 and 3 have been prepared and thoroughly characterized, and their complexation behavior with d¹⁰ silver, copper and zinc ions was studied. The coordination assembly of Cu(I) and Ag(I) with ligands 1 a

Full text of DOI:10.1039/b301632c

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The synthesis and characterization of a series of bis-bidentate Schiff
base ligands and their coordination complexes with silver(I), copper(I)
and zinc(II) d10 metal ionsy
Goutam Kumar Patra and Israel Goldberg*
School of Chemistry, Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Ramat Aviv,
Tel Aviv, Israel. E-mail: goldberg@post.tau.ac.il
Received (in London, UK) 12th February 2003, Accepted 28th April 2003
First published as an Advance Article on the web 3rd June 2003
Three bis-bidentate Schiff base ligands 1, 2 and 3 have been prepared and thoroughly characterized, and
their complexation behavior with d10 silver, copper and zinc ions was studied. The coordination assembly of
Cu(I) and Ag(I) with ligands 1 and 2, afforded di-nuclear dimeric complexes [Ag2(1)2](ClO4)2 (1a),
[Cu2(1)2](ClO4)2 (1b), [Ag2(2)2](ClO4)2 (2a) and [Cu2(2)2](ClO4)2 (2b), in which the metal ion auxiliaries adopted
a pseudo-tetrahedral coordination environment. In these compounds the two ligands wrap around the metal
ions in a twisted manner, forming box-like structures. Within these complexes each metal ion binds to two
nitrogen sites of one ligand and two N-sites of the other ligand. The metal assisted self-assembly process is
complemented by supportive p–p overlap interactions between the aromatic fragments of the assembly. In 1a
˚
and 2a the two silver ions lie close to one another at 3.1 A. On the other hand, zinc(II) yields a monomeric
crystalline complex with 2, [Zn(2)(H2O)(CH3CN)](ClO4)2 (2c), interacting with four N-donors of the same
ligand and complementing its octahedral coordination sphere with molecules of water and acetonitrile. The
materials were characterized by UV-VIS, IR, MS, NMR, and X-ray diffraction analysis. Electrochemical
behavior of the copper(I) compounds was also examined.
The chemistry of spontaneously self-assembled architectures
based on coordination compounds is one of the main aspects
of current research in the search after new potentially useful
organic–inorganic hybrid materials.1–4 The methodologies
whereby transition metal ions are used as bridging templates
to hold together organic ligands in pre-defined patterns within
self-assembled oligomeric or polymeric aggregates have been
explored by several groups.5–8 Within this context, it has been
shown that the self assembly of oligopyridyl strands with Cu(I)
and Ag(I) ions give well organized molecular architectures
such as inorganic grids,9 as well as double-10–12 and triple-
stranded13–15 metal helicates. Such complexes are of interest
for their special functional properties like luminescence,14a,16
redox activity,17 molecular switching properties18 and also
potential applications in solar energy conversion schemes.19
Coordination chemistry of copper(I) complexes with polyden-
tate ligands is particularly relevant to the search for model
compounds that can mimic or even ideally duplicate some of
the important physical and chemical properties of Cu(I) con-
taining proteins.20 Self-assembled polymeric Ag(I) complexes
are attracting attention because they are readily available,
and due to the high diversity in the coordination geometries
exhibited by silver(I). It has been shown that Ag(I) can adopt
coordination numbers between two and six, and reveal coordi-
nation geometries from linear through trigonal to tetrahedral,
square planar, trigonal pyramidal and octahedral.21,22
Furthermore, Ag(I) coordination compounds have been used
as drugs and diagnostic agents, which exhibit anti-microbial
and anti-cancer activity.23 Macrocyclic silver(I) complexes
are useful also for 111Ag-based radio-immunotherapy.24 Zinc-
containing compounds are useful model compounds for bio-
chemical research, as zinc(II) plays an important role in several
zinc-containing metal enzymes such as zinc-peptidases,25
human carbonic anhydrase26 and alkalinephosphatase.27
Herein we describe the preparations of several bis-bidentate
Schiff base ligands with two N,N chelating moieties linked
through a spacer. The latter can be either a flexible ethylene
fragment as in 1, a somewhat more spatially constrained –
=
=
N C(Ph)–C(Ph) N– fragment as in 2, or a rigid 1,4-pheny-
lene unit as in 3. Ligands 1–3 are characterized by a C2
symmetry. They were designed to contain multiple imino
donor nitrogen sites arranged in a converging (towards the
center of the molecule) manner, thus promoting the formation
of discrete metal–ligand complexes rather than polymeric
arrangements. We further report on the coordination behavior
of 1 and 2 with Ag(I), Cu(I) and Zn(II) metal ions and a thor-
ough structural characterization of the complexes which form.
y Electronic supplementary information (ESI) available: Views of the
crystal structures of ligands of 1, 2 and 3. See http://www.rsc.org/
suppdata/nj/b3/b301632c/
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DOI: 10.1039/b301632c
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Not surprisingly, the most rigid ligand 3 did not form stable
complexes with these metal ions, as without conformational
flexibility the access to the N-sites in it is somewhat hindered.
tions between the aromatic 2-quinoline rings (or even larger
delocalized fragments) of neighboring molecules has been
observed in the crystals of the free ligands (Figs. 1s, 2s, 3s in
the supplementary materialy). In 2, face-to-face overlap
between the phenyl substituent of one species and the quino-
line substituent of another species provides additional stabiliz-
ing contribution. Similar interactions are also apparent in the
molecular and crystal structures of the metal complexes with
1 and 2 (see below).
Results and discussion
The syntheses of 1–3 and of their complexes with metal ions
proceeded in high yields and the products were characterized
by X-ray crystallography, EI-MS, IR, UV-VIS and NMR
spectroscopy as well as by elemental analysis (see Experimental
for detailed procedures).
Reaction of 1 with AgClO4 in methanol at room tempera-
ture in equimolar proportion yields the yellow dinuclear com-
plex [Ag2(1)2](ClO4)2 (1a). The bright yellow solvated Ag(I)
complex of 2, [Ag2(2)2](ClO4)2ꢁCH2Cl2 (2aꢁCH2Cl2) was syn-
thesized by refluxing the dichloromethane solution of 2 with
AgClO4 in 1:1 molar ratio. The Cu(I) complex of 1 was
prepared by reacting 1 with [Cu(CH3CN)4](ClO4) in anhy-
drous methanol under argon atmosphere in 1:1 ligand-to-metal
ratio, to yield [Cu2(1)2](ClO4)2 (1b). The second Cu(I) complex
The bis(dipyridyl-diimine) ligand 128 was synthesized by
condensing ethylene diamine and 2-quinolinecarboxaldehyde
in 1:2 molar ratio in anhydrous methanol. It contains four
N-sites suitable to coordinate metal ions, and is conformation-
ally flexible about the central saturated C–C bond. In crystals
of the free compound it adopts a fully extended conformation
(Fig. 1a), the torsion angle about the N–CH2–CH2–N bond
being 180.0ꢀ (all molecules are located on crystallographic
inversion). In the presence of suitable metal ions, 1 can adopt
readily a different conformation about this bond (see below) in
order to arrange the nitrogen binding sites in a convergent
manner and optimize the metal–ligand coordination. Ligand
2 was synthesized by refluxing benzildihydrazone and 2-quino-
linecarboxaldehyde in 1:2 molar ratio in anhydrous methanol.
It represents a more spatially hindered molecule (Fig. 1b). Due
to the steric crowding between the two phenyl groups sub-
1
1
[Cu2(2)2](ClO4)2ꢁ2CH2Cl2 (2bꢁ2CH2Cl2) was prepared by the
reaction of 2 with [Cu(CH3CN)4](ClO4) in degassed dichloro-
methane. The red Cu(I) complexes (1b) and (2b) are stable in
air both in the solid state and in solution. The yellow com-
plexes of Ag(I), 1a and 2a, are stable in air in the solid state
only for about 2–4 weeks; on prolonged exposure to air they
turn black. The orange yellow [Zn(2)(H2O)(CH3CN)](ClO4)2
complex 2c was synthesized by refluxing an equimolar mixture
of 2 and hydrated Zn(ClO4)2 in an ethanol-water (5:1 v/v)
mixture and subsequently re-crystallized from acetonitrile-
diethyl ether.
=
=
stituted on the central C14–C15 bond in 2, the N C–C N
and C(Ph)–C–C–C(Ph) torsion angles about this bond are
89.45(3) and 83.92ꢀ, respectively. Thus the resulting structure
consists of two nearly perpendicular, planar and delocalized
fragments. The conformational degrees of freedom upon the
complex formation with this ligand include a limited flexibility
about the central bond and some rotational freedom of the
terminal quinoline rings about the C–C bonds, which connect
them to the central part of the molecules. The configuration
The structure of complex 1a is shown in Fig. 2a. It consists
of a di-nuclear dimer, in which each of the silver ions coordi-
nates to two ligands in a distorted tetrahedral manner. The
binding capacity is enhanced by the chelate effect, as all nitro-
gen sites of the two ligands converge on the silver ions and
form four chelating 5-membered rings. The quinoline rings
turn with their nitrogen sites inward, and the conformation
about the central CH2–CH2 bond is changed from 180ꢀ in
the free ligand to 54.32 and 59.15(8)ꢀ in the 1a complex. The
=
about the C N bonds in 1 and 2 (as well as in all their com-
plexes) is trans, preserving the two sides of the molecule in
an extended form. Ligand 329 was prepared by reacting p-phe-
nylenediamine with 2-quinolinecarboxaldehyde. It has a rigid
planar conformation (Fig. 1c), which allows a limited access
to the inner nitrogen sites. Moreover, this conformation pre-
vents formation of chelates upon complexation with metal
ions. The size and aromatic nature of the quinoline fragment
reveals a high propensity for strong dispersive attractions
between the flat molecular surfaces of these rings in the con-
densed solid phase. This spatial as well as enthalpic element
is well expressed in the crystal packing arrangements of the
free ligands 1–3, as well as in the crystal structures of the var-
ious complexes (see below). For example, p–p stacking interac-
˚
coordination distances are Ag–N1 2.372(2) A, Ag–N12
˚
˚
˚
2.259(2) A, Ag–N15 2.221(2) A and Ag–N26 2.457(2) A,
and the N–Ag–N angles vary from 71.97(8) to 134.90(8)ꢀ
(the lower limit refers to spatially constrained angles which
involve two nitrogens of the same ligand). The two silver ions
˚
also interact with one another at 3.3119(4) A. Noticed is the
parallel alignment at close proximity of the two ‘‘inner’’ qui-
noline groups within 1a, the distance between their mean
˚
planes being 3.33(1) A. The di-nuclear complex 1a is character-
ized by, and is located on, crystallographic twofold symmetry.
In close resemblance, Cu(I) forms a similarly structured
dimeric molecular box 1b, which is sustained by the copper
Fig. 1 Molecular structures in crystals of the free ligands (a) 1 (located on crystallographic inversion), (b) 2 (the dichloromethane solvent is
omitted), and (c) 3 (located on crystallographic inversion; the chloroform solvent is omitted). The thermal displacement parameters are shown
by 50% probability ellipsoids.
New J. Chem., 2003, 27, 1124–1131
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Fig. 2 Molecular structures of the cationic di-nuclear dimeric complexes of (a) 1a, and (b) 1b (only one of the two crystallographically indepen-
dent units is shown). In (a) the left and right sides of the structure are inter-related by a vertical symmetry axis of twofold rotation (e.g., Ag_2 is
1
related to Ag by the symmetry operation ꢂx,y,ꢂzꢂ2).
˚
ions (Fig. 2b). It is characterized also by an approximate two-
fold rotational symmetry (there are two crystallographically
independent dimers in the asymmetric unit of 1b). The respec-
tive coordination parameter ranges are Cu–Nꢀ bonds 1.992–
tion parameters in 2a are within Ag–N ¼ 2.275–2.484(2) A
and N–Ag–N ¼ 70.8–141.3(1)ꢀ, the lower angles involving
two nitrogens of the same ligand (in the quinoline and the
=
nearby C N imino fragment). The respective values in 2b
˚
˚
2.081(8) A and N–Cu–N angles 80.9–133.1(3) . The shorter
are within Cu–N ¼ 2.015–2.096(6) A and N–Cu–N 81.4–
metal-to-N distances pool the two smaller ions outward
towards the surrounding ligands, which results in larger
metal–metal distances within the dimers than in the previous
132.6(3)ꢀ. The dimeric aggregates are further stabilized by four
pairs of overlapping aryl groups (Fig. 3). The average distances
between these two nearly parallel quinoline and phenyl aro-
˚
˚
˚
example [Cuꢁ ꢁ ꢁCu ¼ 3.662 and 3.675(4) A]. In the resulting
matic fragments are 3.45 A in 2a and within 3.3–3.5 A in 2b.
The relatively short metal–metal distance between the silver
˚
ions of 3.3145(5) A in 2a is indicative of intermetalic interac-
tion, as observed earlier in 1a. The smaller copper(I) ions in
2b form shorter coordinative bonds (than the silver ions) to
the N-sites of the surrounding ligands, and they do not interact
with one another as the observed intramolecular Cuꢁ ꢁ ꢁCu
structure of 1b, which optimizes the various interactions, the
average inter-planar distances between the inner quinoline
rings are 3.3 (the dihedral angle between the two planes being
ꢀ
ꢀ
˚
3.7 ) and 3.5 A (dihedral angle between the planes being 11.4 .
=
=
The N C–C N torsion angles about the central boꢀnd in
=
the ligands are N C13–C14 N of 72.1 and 74.2(10) and
=
ꢀ
˚
=
=
N C39–C40 N of 69.3(7) and 71.1(10) . The wider torsions
in 1b than in 1a are associated also with slightly different orien-
tations of the outer quinoline rings with respect to the core of
the dimeric entity in the two structures.
distance in 2b is only 4.423(2) A.
The zinc(II) auxiliary was anticipated to exhibit a different
coordination behavior than silver(I) and copper(I). First, it
was introduced into the reaction with 2 in the form of an octa-
hedral complex [Zn(H2O)6], a structural property which was
carried on into the product. Then, formation of a di-nuclear
complex with bivalent cations would be associated with unfa-
vorable electrostatic repulsion. Correspondingly, complex 2c
was found to be a monomeric mono-nuclear, rather than
di-nuclear, entity (Fig. 4). To allow a simultaneous coordination
of the two inner and the two outer N-sites of the ligand to a
single metal ion, the N C–C N torsion about the central
C14–C15 bond is decreased from nearly 90ꢀ (in 2, 2a and 2b)
to only 66.18(2)ꢀ in the present case. The multi-dentate ligand
replaces four of the water molecules in the octahedral coordi-
nation sphere of the zinc ion in the starting reagent. Another
water is replaced by acetonitrile from the crystallization
Ligand 2 also forms di-nuclear dimeric complexes of C2
symmetry (crystallographic in 2a and approximate in 2b) with
the monovalent silver and copper ions. The latter adopt a
pseudo-tetrahedral coordination environment tessellating two
ligands together in the form of a square supramolecular box
(Fig. 3). The geometry of this interlocked entity is affected
mostly by the ‘‘scissors’’ shape of the ligand species, which
in turn is dictated by the framework torsion about the central
=
=
=
=
carbon–carbon bond. The corresponding N CH–CH N
angles are 93.21(2)ꢀ in 2a and 99.79(4) and 104.66(4)ꢀ in 2b.
In both structures, the metal ions are connected to two of
the imino nitrogens of one ligand and two N-sites of another
ligand within the dimeric entity. The corresponding coordina-
Fig. 3 Molecular structures of the cationic di-nuclear dimeric complexes of (a) 2a, and (b) 2b. In (a) the molecule exhibits a crystallographic C2
symmetry (e.g., Ag_2 is related to Ag by symmetry operation ꢂx,y,12-z). Note the apparent p–p overlap interaction between the quinoline and
phenyl aromatic fragments of these two structures.
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that such interactions affect in many cases the intra-molecular
structure of the discrete complexes. Fig. 5 demonstrates that
they are also well expressed in the intermolecular organization
in these materials, by illustrating three representative crystal
structures of complexes 1a, 2a and 2c.
The structural characterizations of the new materials
reported in this study are complemented by spectroscopic
and electrochemical data:
FT IR spectroscopy
The FT IR spectrum of the ligands 1, 2 and 3 show character-
istic bands at 1557 and 1642 cmꢂ1 (for 1); 1562 and 1614 cmꢂ1
(for 2) and 1559 and 1627 cmꢂ1 (for 3), which we assign to the
=
pyridine ring and imine C N stretching frequencies respec-
=
tively. The C N stretching frequency of the ligand 2 appears
Fig. 4 Molecular structure of the mono-nuclear complex cation of
2c, with H2O and CH3CN co-ligands, showing an approximate octa-
hedral coordination around the metal ion.
at lower energy because it has an extensive conjugative system.
In the IR spectrum of (1a), (1b), (2a), (2b) and (2c) these bands
are shifted to higher energies, which agrees with coordination
of the metal to the nitrogen donor atoms. The typical strong
bandꢂs due to the stretching vibrations of the non-coordinated
ClO4 ions30 in (1a), (1b), (2a), (2b) and (2c) appear at the
expected regions; 1098 and 621 cmꢂ1 (for 1a), 1098 and 629
cmꢂ1 (for 1b), 1090 and 624 cmꢂ1 (for 2a), 1088 and 630
cmꢂ1 (for 2b) and 1098 and 625 cmꢂ1 (for 2c).
solvent, to formulate the [Zn(2)(H2O)(CH3CN)]2+ entity. The
coordination distances in this species are Zn–N(ligand) ¼
˚
˚
2.105–2.181(3) A, Zn–(OH2) ¼ 2.051(3) A and Zn–N(aceto-
˚
nitrile) ¼ 2.378 (5) A. The corresponding bond angles between
the cis-related ligands are within 77.8–114.4(1)ꢀ, and those
between the trans-related moieties are within 157.8–164.0(1)ꢀ.
As commonly observed in crystal structures of organic com-
pounds containing aromatic fragments, optimization of p–p
stacking interactions is an important factor in determining
the intermolecular organization. This should be expected also
in the present study, due to the presence of the sizeable quino-
line moieties in all compounds. We have shown above already
UV-VIS spectroscopy
The absorption spectra of 1 (in methanol); 2 (in dichloro-
methane) and
3 (in dichlorometane) show intra-ligand
charge transfer bands at 290 (e, 10 260 Mꢂ1cmꢂ1), 242 nm
(e, 42 710 Mꢂ1cmꢂ1); 320 (e, 34 660 Mꢂ1cmꢂ1), 274 nm (e,
Fig. 5 Crystal structures of (a) 1a, (b) 2a, and (c) 2c, showing the inter-molecular p–p stacking interactions between the quinoline rings of
adjacent species. The mean interplanar distances between the overlapping rings are in the range of 3.3–3.5 A. The counter ions and solvent
species are omitted for clarity. The metal ions are denoted by spheres in pink color.
˚
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28 100 Mꢂ1cmꢂ1); 374 (e, 33 214 Mꢂ1cmꢂ1) and 294 (e, 22 660
ꢂ1cmꢂ1), respectively. These charge transfer bands appear at
M
320, 252 nm (for 1a); 316, 250 nm (for 1b); 356, 276 nm (for
2a); 350, 290 nm (for 2b) and 322, 256 nm (for 2c). The
Cu(I) complexes (1b) and (2b) display additional broad
unstructured band at 532 and 530 nm respectively, which is
supposed to be MLCT in origin, and these bands are respon-
sible for the red color of the complexes. All data also demon-
strate the coordination of the metal ions to the ligands.
FAB mass spectroscopy
The solution behavior of the coordination complexes is ana-
lyzed by fast atom bombardment mass spectrometry (FAB-
MS). The FAB-MS spectra of the complexes 1a, 1b, 2a and
2b in 3-nitrobenzyl as a matrix and dimethylformamide as sol-
vent indicate the di-nuclear species with the highest masses
being assigned to [M2:2 ꢂ ClO4]+. For the complex 2c the high-
est mass observed at m/z ¼ 740.2 is assigned to [M1:1 ꢂ ClO4]+
(see Experimental section).
Fig. 6 Cyclic voltammogram of [Cu2(2)2](ClO4)2 (2b) (approximately
10ꢂ3 M in dichloromethane, 0.2 M Bu4NClO4) at a glassy carbon elec-
trode. Scan rate n ¼ 50 mV sꢂ1
.
Conclusion
NMR spectroscopy
Coordination motifs in a series of hybrid organic–inorganic
complexes of the Ag(I), Cu(I) and Zn(II) d10 ions have been
presented employing the inexpensive, easy to prepare bis-
bidentate flexible Schiff base ligand 1 and the somewhat more
rigid ligand 2. X-ray single crystal diffraction studies revealed
that the silver(I) and copper(I) complexes are di-nuclear, have
C2 symmetry, and adopt molecular box like structures. While
the coordination bonds and chelating rings provide the major
cohesive force, p–p stacking interactions play also an impor-
tant role in the metal assisted self-assembling process of these
complexes. The bivalent zinc ion afforded as expected a mono-
nuclear complex. UV-VIS and FAB-MS data are consistent
with the formulation of these species in the solution. The d10
metal-ion auxiliaries preserved in this study their commonly
observed coordination geometries, i.e., tetrahedral in the case
of silver(I) and copper(I) and octahedral in the case of the
zinc(II) ion.
The complexation reactions in this study were designed to
yield discrete molecular hybrid organic–inorganic entities,
being based on ligands (e.g., 1 and 2) with multiple binding
sites that are arranged in a converging manner. A slight varia-
tion of the ligand design, by substituting the 2-quinolyl(N1)
peripheral group with the 2-quinolyl(N4) function, places the
quinolyl N-sites on the outer surface of the molecular frame-
work (Fig. 7). We have shown that in such case, the divergent
disposition of the N-donor sites would promote, with the aid
of silver(I) ion auxiliaries, a facile construction of polymeric
materials.32
The 1H and 13C NMR spectra of 1, 2 and 3 in CDCl3 consist of
sharp and well-resolved signals for each of the organic group-
1
ing present. The H NMR of 1a and 1b are also made up of
sharp signals indicative of the single species and the symmetri-
cal nature of the molecule in the solution. In 13C NMR, the
=
C N carbon atom of 1, 2 and 3 appear at 163.91, 160.56
and 160.61 ppm respectively.
Cyclic voltammetry
Preliminary data on the electrochemical properties of the
di-nuclearcopper(I)complexes[Cu2(1)2](ClO4)2 (1b)and[Cu2(2)2]-
(ClO4)2 (2b) were obtained by cyclic voltammetry in dichloro-
methane at glassy carbon electrode under dry nitrogen
atmosphere. Both of the complexes show more or less similar
I
II
type of quasi-reversible voltammograms with single Cu –Cu
1
couple, occurring at E ¼ 1.28 and 1.35 V (vs Ag/AgCl in 1
2
M KCl, scan rate 50 mV sꢂ1) for [Cu2(1)2](ClO4)2 (1b) and
[Cu2(2)2](ClO4)2 (2b), respectively (Fig. 6). The DEp values of
[Cu2(1)2](ClO4)2 (1b) and [Cu2(2)2](ClO4)2 (2b) are 235 and
220 mV, respectively. At higher scan rates the voltammograms
become irreversible. The electrode processes can be described
by the eqn. (1).
4þ
2þ
½CuII2L2ꢃ þ 2e Ð ½CuI L2ꢃ
ð1Þ
2
I
II
The high potential of the Cu –Cu couple in [Cu2(1)2]ClO4 (1b)
and [Cu2(2)2](ClO4)2 (2b) indicates that 1 and 2 are capable of
stabilizing Cu(I) much more than Cu(II). A more thorough
investigation of these features, their dependence on the experi-
mental conditions, and nature of the generated products, is
however still required. Incidentally, it has not been possible
so far to isolate any Cu(II) complexes of 1 and 2. In this context
it should be mentioned that the highest CuII/I potential
hitherto known for any copper complex is 1.55 V vs SCE.31
Experimental
Caution! Perchlorate salts are potentially explosive and should
only be handled in small quantities.
Fig. 7 Ligand design for promoting, in complexation reactions with metal ions, the construction of either discrete (as is this study) or polymeric
(as described in ref. 32) hybrid materials, shown in (a) and (b), respectively.
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General
nm (e/dm3 molꢂ1 cmꢂ1)(CH2Cl2): 320 (34 660), 274 (28 100).
Crystals suitable for X-ray diffraction were obtained by
direct diffusion of n-hexane into the dichloromethane
solution. It crystallizes with one molecule of dichloromethane
solvent.
Ligand 3. 0.81 g (7.5 mmol) of 1,4-phenylenediamine was
dissolved in 75 ml anhydrous methanol. To this solution,
2.36 g (15 mmol) of solid 2-quinolinecarboxaldehyde was
added and dissolved with stirring. The resulting reaction mix-
ture was refluxed for 4 h maintaining dry conditions. Then, it
was cooled to room temperature. Yellowish crystalline solid
separated out. It was filtered out, washed with 5 ml of metha-
nol and dried in air. Yield, 1.72 g (78%), mp 163–164 ꢀC. Anal.
found (calc. for C26H18N4): C, 80.71 (80.80); H, 4.69 (4.70); N,
16.39 (14.50)%. EI-MS: 386.2 (M+, 98%), 229.1 (M+ ꢂ C10H6-
NO, 15%). FTIR/cmꢂ1 (KBr): 545 m, 620 s, 673 m, 744 vs,
770 m, split, 821 m, 844 vs, 903 m, 956 m, 1108 s, 1202 vs,
The complex [Cu(CH3CN)4]ClO4 was synthesized by
a
reported procedure.33 All other reagents were procured com-
mercially and used without further purification. Copper was
estimated gravimetrically as CuSCN. Microanalyses were per-
formed by Perkin-Elmer 2400II elemental analyzer and CE
instruments. The melting points were determined by an elec-
trothermal IA9000 series digital melting point apparatus and
are uncorrected. IR spectra (KBr disc) were recorded on a
Nicolet Magna-IR spectrophotometer (Series II), UV-VIS
1
spectra on a Shimadzu UV-160A spectrophotometer, H and
13C NMR spectra by a Bruker DPX200 spectrometer and EI
and FAB mass spectra on a VG Autospec M-250 instrument.
Cyclic voltammetry was performed at room temperature at a
planar glassy carbon milli electrode (polished with alumina
before measurement) using m-Autolab II with GPES software,
version 4.8.5 (EcoChemie, The Netherlands) in purified and
anhydrous dichloromethane under dry nitrogen atmosphere
in conventional three electrode configurations. Under the
experimental conditions employed here, the ferrocene–ferro-
cenium couple appears at 0.42 V vs. Ag/AgCl in 1 M KCl with
1225 m, 1304 m, 1358 s, 1427 vs, 1455 m, 1500 vs, 1559 s,
=
1
1597 s, 1627 vs (C N), 3460 wb. H NMR (200 MHz, CDCl3 ,
TMS): d 8.87 (s, 2 H), 8.41–8.22 (m, 8 H), 7.91–7.65 (m, 4 H),
7.79 (d, J ¼ 4 Hz, 4 H). 13C NMR (200 MHz, CDCl3 , TMS):
d 160.61, 154.58 (quaternary), 147.69 (quaternary), 136.62,
129.71, 129.39, 128.74 (quaternary), 127.67, 127.39, 122.35,
121.19 (quaternary), 118.62. UV-VIS lmax/nm (e/dm3 molꢂ1
cmꢂ1)(CH2Cl2): 374 (33 214), 294 (22 660). Crystallization
from direct diffusion of n-hexane into chloroform solution of
3 yielded single crystals of the chloroform solvate of 3.
Complex [Ag2(1)2](ClO4)2 (1a). 0.338 g (1 mmol) of 1 was
dissolved in 25 ml of methanol. To this solution 0.208 g (1
mmol) of solid AgClO4 was added and dissolved with stirring.
Continuous stirring at room temperature for about 3 h yielded
a yellow solid. It was filtered off, washed with 5 ml of methanol
and dried in vacuo over fused CaCl2 . Yield, 0.350 g (64%).
Anal. found (calc. for C22H18N4ꢁAgClO4): C, 48.48 (48.40);
H, 3.37 (3.32); N, 10.36 (10.27)%). FAB-MS: m/z 990.5
[(M ꢂ ClO4)+ 12.0%]; 890.02 [(M ꢂ ClO4 ꢂ HClO4)+, 8.9%].
FTIR/cmꢂ1 (KBr): 481 m, 531 w, 621 vs, 756 s, 775 m, 819
s, 1098 vs, split (ClO4), 1294 m, 1330 s, 1373 m, 1426 s, 1470
an DEp of 110 mV at a scan rate of 50 mV sꢂ1
.
Syntheses
Ligand 1. 2.36 g (15 mmol) of 2-quinolinecarboxaldehyde was
dissolved in 100 ml of anhydrous methanol. To this yellowish
solution 0.5 ml (7.5 mmol) of freshly distilled ethylene diamine
was added dropwise with stirring. Then, the reaction mixture
was allowed to reflux for 6 h, maintaining dry conditions.
The solvent was evaporated under reduced pressure to obtain
a yellow semi-solid, which on re-crystallization from diethyl
ether gave yellow solid suitable for X-ray analysis. Yield,
1.75 g (69%); mp 128–130 ꢀC. Anal. found (calc. for C22H18-
N4): C, 77.65 (78.07); H, 5.37 (5.36); N, 16.65 (16.56)%.
EI-MS: 338.1 (M+, 84%); 181.1 (M+ ꢂ C10H6NO, 25%); 169.1
(M+/2, 98%). FTIR/cmꢂ1 (KBr): 492 m, 619 m, 748 vs, 840 vs,
868 s, 893 s, 941 m, 971 s, 1015 w, 1030 s, 1108 s, 1142 m,
=
m, 1500 s, 1564 s, 1592 m, 1650 vs (C N), 2928 w, 3055 m,
1
1206 m, 1280 s, 1321 w, 1382 m, 1432 s, 1461 s, 1500 vs, 1557 s,
=
3461 vb. H NMR (200 MHz, (CD3)2SO, TMS): d 9.02 (s, 2
1
1592 vs, 1642 vs (C N), 2890 m, 3050 m, 3451 vb. H NMR
H), 8.37 (d, J ¼ 4 Hz, 2 H), 7.99 (d, J ¼ 4 Hz, 2 H), 7.66–
7.44 (m, 6 H), 7.37 (d, J ¼ 4 Hz, 2 H), 4.44 (s, methylene,
4 H). VIS lmax/nm (e/dm3 molꢂ1 cmꢂ1)(CH3OH): 320 (9 875),
252 (36 980). Single crystals suitable for X-ray analysis were
grown as acetonitrile solvate by direct diffusion of diethyl ether
into an acetonitrile solution of the complex.
Complex [Cu2(1)2](ClO4)2 (1b). Solid [Cu(CH3CN)4]ClO4
(0.165 g, 0.5 mmol) was added to 30 ml anhydrous degassed
methanol solution of 0.17 g (0.5 mmol) of 1 under argon
atmosphere and stirred for 1 h maintaining dry conditions.
A deep-red compound precipitated out. Then, the solvent
was evaporated down to ꢄ10 ml by purging argon to get
more crop. It was filtered off, washed with few drops of
methanol and dried in vacuo over fused CaCl2 . Yield, 0.175
g (70%). Anal. found (calc. for C22H18N4ꢁCuClO4): C,
52.59 (52.68); H, 3.68 (3.62); N, 11.19 (11.17); Cu, 12.75
(12.68%). FAB-MS: m/z 903.1 [(M ꢂ ClO4)+, 6.1 %]; 802.2
[(M ꢂ ClO4– ꢂ HClO4)+, 4.2%]. FTIR/cmꢂ1 (KBr): 477 m,
589 m, 629 vs, 751 vs, 786 s, 825 vs, 868 vs, 927 s, 996 w,
1098 vs (ClO4), split, 1225 s, 1260 m, 1295 s, 1323 vs, 1374
(200 MHz, CDCl3 , TMS): d 8.63 (s, 2 H), 8.17 (s, 4 H), 8.11
(d, J ¼ 4 Hz, 2 H), 7.83–7.69 (m, 4 H), 7.57 (t, J ¼ 4 Hz, 2 H),
4.18 (s, methylene, 4 H). 13C NMR (200 MHz, CDCl3 , TMS):
d 163.91, 154.52 (quaternary), 147.65 (quaternary), 136.50,
129.70, 129.50, 128.71 (quaternary), 127.63, 127.34, 118.40,
61.43. UV-VIS lmax/nm (e/dm3 molꢂ1 cmꢂ1)(CH3OH): 290
(10 260), 242 (42 710)
Ligand 2. 1.79 g (7.5 mmol) of benzil dihydrazone synthe-
sized by a reported procedure,34 was dissolved in 150 ml of
anhydrous methanol. 2.36 g (15 mmol) of solid 2-quinolinecar-
boxaldehyde was dissolved with stirring in this colorless solu-
tion. The resulting reaction mixture was refluxed for 3 h in a
dry atmosphere. After 1 h of reflux, yellow solid began to pre-
cipitate out. Then the reaction mixture was cooled to room
temperature, kept in air overnight. The yellowish precipitated
solid was filtered off, washed with few drops of methanol
and dried in air. Yield, 2.40 g (62%); mp 158 ꢀC. Anal. found
(calc. for C34H24N6): C, 79.10 (79.04); H, 4.62 (4.69); N,
16.36 (16.27)%. EI-MS: m/z 516.2 (M+, 10%); 258.1 (M+/2,
18%). FTIR/cmꢂ1 (KBr): 475 m, 571 w, 590 w, 621 s, 648
m, 678 s, 755 vs, 771 vs, 824 vs, 888 s, split, 961 s, 1015 m,
1133 w, 1162 m, 1182 s, 1201 s, 1322 m, 1373 w, 1422 m,
=
m, 1432 s, 1456 m, 1505 vs, 1588 vs, 1648 vs(C N), 2914
w, 3428 vb. 1H NMR (200 MHz, (CD3)2SO, TMS): d 8.78
(s, 2 H), 8.62 (d, J ¼ 4 Hz, 2 H), 8.08 (d, J ¼ 4 Hz, 2 H),
7.68–7.47 (m, 6 H), 7.18 (d, J ¼ 4 Hz, 2 H), 4.42 (s, methy-
lene, 4 H). UV-VIS lmax/nm (e/dm3 molꢂ1 cmꢂ1)(CH3OH):
532 (5 450, per copper), 316 (14 750), 250 (45 260). Single
crystals were grown by direct diffusion of diethyl ether into
a moderately concentrated methanol solution of the complex.
They were found to contain molecules of the methanol and
diethyl ether solvent.
=
1447 s, 1505 vs, 1541 s, 1562 s, 1589 s, 1614 vs (C N), 3056
m, 3441 vb. H NMR (200 MHz, CDCl3 , TMS): d 8.70 (s, 2
H), 8.06 (s, 4 H), 8.03–7.97 (m, 6 H), 7.80–7.76 (m, 2 H),
7.57–7.42 (m, 10 H). 13C NMR (200 MHz, CDCl3 , TMS): d
165.65 (quaternary), 160.56, 153.48 (quaternary), 147.83 (qua-
ternary), 136.22, 133.70 (quaternary), 131.16, 129.59, 129.53,
1
128.78, 128.60, 127.90, 127.55, 127.45, 118.99. UV-VIS lmax
/
New J. Chem., 2003, 27, 1124–1131
1129

View Article Online
Complex [Ag2(2)2](ClO4)2 (2a). 0.258 g (0.5 mmol) of 2 was
dissolved in 25 ml of dichloromethane. To this yellow solution
0.105 g (0.5 mmol) of solid AgClO4 was added, and the reac-
tion mixture was refluxed for 2 h with stirring and then filtered
out. The filtrate was taken in a stoppered tube and n-hexane
was layered on it. Bright yellow crystals suitable for X-ray ana-
lysis deposited after two days. These were taken out by decan-
tation of the remaining solvent and dried in vacuo under fused
CaCl2 .Yield, 0.275 g (72%). The complex crystallized with one
mol of dichloromethane. Anal. found (calc. for 2C34H24N6ꢁ
2AgClO4ꢁCH2Cl2): C, 54.32 (54.04); H, 3.68 (3.29); N,
11.99 (10.97%). FAB-MS: m/z 1347.6 [(M2:2 ꢂ ClO4)+, 2.3%];
1248.2 [(M2:2 ꢂ 2ClO4)+, 6.7%]. FTIR/cmꢂ1 (KBr): 478 m,
580 m, 624 vs, 692 s, 756 vs, split, 824 s, 932 m, 981 w, 1090 vs
(ClO4), 1142 s, 1181 m, 1230 w, 1256 m, 1358 s, 1460 s, 1505
results. The crystal structures were solved by direct
(SHELXS-86, SIR-92)35,36 and Patterson methods (DIRDIF-
96),37 and refined by full-matrix least-squares on F2
(SHELXL-97).38 Intensity data of the metal complexes were
routinely corrected for absorption effects. All non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were
located in idealized positions, and were refined using a riding
model with fixed thermal parameters [Uij ¼ 1.2 Uij (eq.) for
the atom to which they are bonded]. The crystal and experi-
mental data for all the compounds are:
¯
1: C22H18N4 , Mr ¼ 338.40, triclinic, space group P1, a ¼
˚
6.7590(2), b ¼ 7.4030(2), c ¼ 17.3190(5) A, a ¼ 78,267(1),
3
ꢀ
˚
b ¼ 87.281(1), g ¼ 85.421(2) , V ¼ 845.34(4) A , Z ¼ 2, rcalcd.
¼
1.399 gꢁcmꢂ3
,
F(000) ¼ 356, m(MoKa) ¼ 0.081 mmꢂ1
,
2ymax ¼ 56.5ꢀ, 3868 unique reflections, 235 refined parameters,
=
vs, 1565 s, 1624 vs (C N), 3061 m, 3456 vb. VIS lmax/nm
final R1 ¼ 0.057 for 2333 reflections with Fo > 4s(Fo), R1 ¼
(e/dm3 molꢂ1 cmꢂ1)(CH2Cl2): 356 (36 500), 276 (29 680).
Complex [Cu2(2)2](ClO4)2 (2b). 0.258 g (0.5 mmol) of 2 was
dissolved in 30 ml of anhydrous degassed dichloromethane to
which 0.165 g (0.5 mmol) of freshly prepared [Cu(CH3CN)4]-
ClO4 was added under argon atmosphere, to yield a deep red
solution. The reaction mixture was stirred for 2 h at room tem-
perature, filtered, and then 15 ml of n-hexane was added drop-
wise to the filtrate. The resulting cloudy solution was kept in
the refrigerator for 8 h, after which a red microcrystalline solid
was isolated. The solution was filtered out and stored in vacuo
over fused CaCl2 . Yield, 0.210 g (60%). Anal. found (calc. for
0.103, wR2 ¼ 0.167 and GoF ¼ 1.039 for all 3868 data, |Dr|max ¼
˚
0.34 e.Aꢂ3. The molecules are located on centers of crystallo-
graphic inversion, and the asymmetric unit consists of two
half-molecules.
2ꢁCH2Cl2 : C34H24N6ꢁCH2Cl2 , Mr ¼ 601.52, triclinic, space
¯
group P1, a ¼ 9.7370(1), b ¼ 11.4350(2), c ¼ 14.9620(3)
A, a ¼ 91.454(1), b ¼ 102.707(1), g ¼ 112.455(1)ꢀ, V ¼
˚
3
1490.79(4) A , Z ¼ 2, rcalcd. ¼ 1.340 gꢁcmꢂ3, F(000) ¼ 624,
˚
m(MoKa) ¼ 0.254 mmꢂ1, 2ymax ¼ 56.5ꢀ, 6977 unique reflec-
tions, 388 refined parameters, final R1 ¼ 0.050 for 4463 reflec-
tions with Fo > 4s(Fo), R1 ¼ 0.099, wR2 ¼ 0.143 and
ꢂ3
1
˚
2C34H24N6ꢁ2CuClO4ꢁ2CH2Cl2): C, 58.61 (58.67); H, 3.68
GoF ¼ 1.015 for all 6977 data, |Dr|max ¼ 0.60 e.A
.
(3.53); N, 11.87 (11.99); Cu, 9.15 (9.07)%. FAB-MS: m/z
1259.0 [(M2:2 ꢂ ClO4)+, 2.8%]; 1159.8 [(M2:2 ꢂ 2ClO4)+,
4.5%]. FTIR/cmꢂ1 (KBr): 482 m, 565 w, 590 m, 630 vs, 683
s, 756 vs, 824 s, 863 m, 933 m, 986 w, 1088 vs (ClO4) 1142 s,
1177 m, 1225 m, 1305 s, 1358 m, 1383 m, 1465 w, 1500 vs,
=
3ꢁ2CHCl3 : C26H18N4ꢁ2CHCl3 , Mr ¼ 625.18, triclinic, space
˚
¯
group P1, a ¼ 6.2340(1), b ¼ 9.3440(2), c ¼ 12.6120(3) A,
a ¼ 70.957(1), b ¼ 77.614(1), g ¼ 84.160(2)ꢀ, V ¼ 677.89(2)
A , Z ¼ 1, rcalcd. ¼ 1.531 gꢁcmꢂ3, F(000) ¼ 318, m(MoKa) ¼
3
˚
0.661 mmꢂ1, 2ymax ¼ 56.3ꢀ, 3162 unique reflections, 172
refined parameters, final R1 ¼ 0.031 for 2712 reflections with
Fo > 4s(Fo), R1 ¼ 0.040, wR2 ¼ 0.078 and GoF ¼ 1.032 for
1520 m, 1564 s, 1622 vs (C N), 3055 m, 3432 wb. VIS lmax
/
nm (e/dm3 molꢂ1 cmꢂ1)(CH2Cl2): 530 (5155, per copper),
350 (31 150), 290 (25 380). Single crystals suitable for X-ray
analysis were grown by direct diffusion of n-hexane into
dichloromethane solution of the complex. The complex crys-
tallized in a solvated form with one molecule of CH2Cl2 and
one molecule of n-hexane.
all 3162 data, |Dr|max ¼ 0.33 eꢁAꢂ3. The ligand molecules are
˚
located on centers of crystallographic inversion.
1aꢁ2MeCN: 2(C22H18N4ꢁAgClO4)ꢁ2CH3CN, Mr ¼ 1173.56,
monoclinic, space group C2/c, a ¼ 18.1870(3), b ¼
ꢀ
˚
13.8900(2), c ¼ 20.1180(4) A, b ¼ 107.450(1) , V ¼ 4848.3(1)
3
A , Z ¼ 4, rcalcd. ¼ 1.608 gꢁcmꢂ3, F(000) ¼ 2368, m(MoKa) ¼
˚
Complex [Zn(2)(H2O)(CH3CN)](ClO4)2 (2c). To a 30 ml
ethanol–water (5:1 v/v) mixture 0.130 g (0.25 mmol) of 2
and 0.095 g (0.25 mmol) of Zn(ClO4)2ꢁ6H2O were added and
dissolved with stirring. The yellowish reaction mixture was
refluxed for 8 h, then cooled to room temperature, and the
solvent was removed under reduced pressure to yield a pale
yellow solid. It was washed with 5 ml of methanol and dried
in air and re-crystallized from acetonitrile–diethyl ether. Yield,
0.110 g (52%). Anal. found [calc. for C34H24N6ꢁZn(ClO4)2ꢁ
CH3CNꢁH2O]: C, 51.59 (51.45); H, 3.38 (3.48); N, 11.56
(11.67%). FAB-MS: m/z 740.2 [(M1:1 ꢂ ClO4)+, 2.1%]; 640.5
[(M1:1 ꢂ 2ClO4)+, 6.1%]. FTIR/cmꢂ1 (KBr): 492 m, 516 w,
625 vs, 692 s, 771 vs, 834 s, 922 m, 1098 vs (ClO4), 1216 m,
1290 s, 1333 s, 1373 s, 1436 s, split, 1510 vs, 1570 s, 1628 vs
0.98 mmꢂ1
,
2ymax ¼ 55.8ꢀ, 5748 unique reflections, 317
refined parameters, final R1 ¼ 0.036 for 4409 reflections with
Fo > 4s(Fo), R1 ¼ 0.057, wR2 ¼ꢂ03.093 and GoF ¼ 1.066 for
˚
all 5748 data, |Dr|max ¼ 0.99 eꢁA
.
1
1bꢁMeOHꢁ2Et2O: 2[2(C22H18N4ꢁCuClO4)]ꢁ2CH3OHꢁ(C2H5)2O,
Mr ¼ 2143.78, monoclinic, space group P21/c, a ¼
ꢀ
˚
11.9300(2), b ¼ 36.5370(5), c ¼ 21.2510(4) A, b ¼ 97.714(5) ,
V ¼ 9179.2(3) A , Z ¼ 4, rcalcd. ¼ 1.551 gꢁcmꢂ3, F(000) ¼
3
˚
4408, m(MoKa) ¼ 1.11 mmꢂ1, 2ymax ¼ 51.4ꢀ, 15 583 unique
reflections, 1196 refined parameters, final R1 ¼ 0.088 for
8876 reflections with Fo > 4s(Fo), R1 ¼ 0.157, wR2 ¼ 0.269
ꢂ3
˚
and GoF ¼ 1.011 for all 15 583 data, |Dr|max ¼ 1.76 eꢁA
.
The asymmetric unit contains two independent species of the
di-nuclear complex. The analyzed crystals were characterized
by high mosaicity and were diffracting poorly. The diethyl
ether and the perchlorate anions were found severely disor-
dered in the crystal lattice even at 110 K, and their structural
parameters could not be precisely determined.
(C N), 2221 vs, 3065 m, 3465 vb. VIS lmax/nm (e/dm3 molꢂ1
=
cmꢂ1)(CH3CN): 322 (15 870), 256 (12 190). Single crystals sui-
table for X-ray analysis were grown by direct diffusion of
diethyl ether into an acetonitrile solution of the complex.
The complex crystallized with additional 2 mols of acetonitrile
and one mol of diethyl ether.
2aꢁ2CH2Cl2 : 2(C34H24N6ꢁAgClO4)ꢁ2CH2Cl2 , Mr ¼ 1617.68,
monoclinic, space group C2/c, a ¼ 27.9900(3), b ¼ 12.7400(2),
3
ꢀ
˚
˚
c ¼ 22.6650(3) A, b ¼ 125.802(1) , V ¼ 6557.0(1) A , Z ¼ 4,
Crystallography
rcalcd. ¼ 1.639 gꢁcmꢂ3, F(000) ¼ 3264, m(MoKa) ¼ 0.91 mmꢂ1
,
The diffraction measurements were carried out on a Nonius
KappaCCD diffractometer, using graphite monochromated
2ymax ¼ 55.8ꢀ, 7695 unique reflections, 442 refined parameters,
final R1 ¼ 0.041 for 5654 reflections with Fo > 4s(Fo),
R1 ¼ 0.071, wR2 ¼ 0.103 and GoF ¼ 1.020 for all 7695 data,
˚
MoKa radiation (l ¼ 0.7107 A). The crystalline samples of
ꢂ3
.
˚
the analyzed compounds were covered with a thin layer of light
oil and freeze-cooled to ca. 110 K in order to minimize solvent
escape (when included in the crystal), structural disorder and
thermal motion effects, and increase the precision of the
|Dr|max ¼ 0.72 eꢁA
2bꢁCH2Cl2ꢁC6H14 : 2(C34H24N6ꢁCuClO4)ꢁCH2Cl2ꢁC6H14 , Mr ¼
1530.26, monoclinic, space group P21/c, a ¼ 12.8350(2), b ¼
ꢀ
˚
41.4820(7), c ¼ 13.3050(3) A, b ¼ 110.628(1) , V ¼ 6629.7(3)
1130
New J. Chem., 2003, 27, 1124–1131

View Article Online
3
A , Z ¼ 4, rcalcd. ¼ 1.533 gꢁcmꢂ3, F(000) ¼ 3152, m(MoKa) ¼
˚
Chowdhury, P. B. Iveson, M. G. B. Drew, D. A. Tocher and D.
Datta, New. J. Chem., 2003, 27, 193–196; (c) S. Chowdhury,
M. G. B. Drew and D. Datta, New. J. Chem., 2003, 27 831; (d )
R. Ziessel, A. Harriman, J. Suffert, M.-T. Youinou, A. De. Cian
and J. Fischer, Angew. Chem., Int. Ed., 1997, 36, 2509–2511.
12 K. T. Potts, M. Keshavarzk, F. S. Tham, K. A. G. Raiford, C.
Arana and H. D. Abruna, Inorg. Chem., 1993, 32, 5477–5484.
13 (a) J. Hamblin, A. Jackson, N. W. Alcock and M. J. Hannon,
J. Chem. Soc., Dalton Trans., 2002, 1635–1641; (b) A. Lavalette,
J. Hamblin, A. Marsh, D. M. Haddleton and M. J. Hannon,
Chem. Commun., 2002, 3040–3041.
14 (a) G. K. Patra, I. Goldberg, S. K. Chowdhury, B. C. Maiti, A.
Sarkar, P. R. Bangal, S. Chakravorti, N. Chattopadhyay, D. A.
Tocher, M. G. B. Drew, G. Mostafa, S. Chowdhury and D.
Datta, New. J. Chem., 2001, 25, 1371–1373; (b) C. Piguet, G.
Bernardinelli, B. Bocquet, O. Schaad and A. F. Willams, Inorg.
Chem., 1994, 33, 4112–4121.
15 R. F. Carina, G. Bernardinelli and A. F. Williams, Angew. Chem.,
Int. Ed., 1993, 32, 1463–1465.
16 (a) S.-S. Sun and A. J. Lees, Inorg. Chem., 1999, 38, 4181–4182;
(b) R. V. Slone, K. D. Benkstein, S. Belanger, J. T. Hupp, I. A.
Guzei and A. L. Rheingold, Coord. Chem. Rev., 1998, 171, 221–
243
17 C. J. Matthews, Z. Q. Xu, S. K. Mandal, L. K. Thompson, K.
Biradha, K. Poirier and M. J. Zaworotko, Chem. Commun.,
1999, 347–348 and references therein.
0.87 mmꢂ1
,
2ymax ¼ 50.9ꢀ, 11 469 unique reflections, 928
refined parameters, final R1 ¼ 0.078 for 6679 reflections with
Fo > 4s(Fo), R1 ¼ 0.147, wR2 ¼ 0.215 and GoF ¼ 0.967 for
all 11469 data, |Dr|max ¼ 0.79 eꢁAꢂ3. The analyzed crystals
˚
were characterized by high mosaicity and were diffracting
poorly. The dichloromethane and the n-hexane solvent were
found severely disordered in the crystal lattice even at 110 K,
and could not be modeled precisely. One of the perchlorates
is partly disordered as well.
2cꢁ112MeCNꢁEt2O: C34H24N6ꢁZn(ClO4)2ꢁ212CH3CNꢁ(C2H5)2Oꢁ
H2O, Mr ¼ 975.63, monoclinic, space group P21/c, a ¼
˚
18.8160(3),
b ¼ 12.6210(2),
c ¼ 20.3570(4)
A,
b ¼
107.689(1) , V ¼ 4605.8(1) A , Z ¼ 4, rcalcd. ¼ 1.407 gꢁcmꢂ3
,
3
ꢀ
˚
F(000) ¼ 2020, m(MoKa) ¼ 0.72 mmꢂ1
,
2ymax ¼ 55.8ꢀ,
10 472 unique reflections, 671 refined parameters, final R1 ¼
0.068 for 7343 reflections with Fo > 4s(Fo), R1 ¼ 0.102, wR2 ¼
0.202 and GoF ¼ 1.024 for all 10 472 data, |Dr|max ¼ 1.02
eꢁAꢂ3. The acetonitrile and diethyl ether solvent species as well
˚
as the perchlorate anions were found partly disordered in the
crystal lattice. One of the acetonitriles and the water molecule
are coordinated to the zinc ion as well.
The apparent disorder of the solvent and the perchlorate
anions in the above structures had only a limited effect on
the structural determinations of the metal–ligand entities and
their coordination motifs.
CCDC reference numbers 204782–204789. See http://
www.rsc.org/suppdata/nj/b3/b301632c/ for crystallographic
data in .cif or other electronic format.
18 Y. Jekins, A. E. Friedman, N. J. Turro and J. K. Barton, Bio-
chemistry, 1992, 31, 10 809–10 816.
19 M. Graetzel, Coord. Chem. Rev., 1991, 111, 167–174.
20 T. N. Sorrell and M. R. Malachowski, Inorg. Chem., 1983, 22,
1883–1887.
21 H. Oshio and T. Ito, Coord. Chem. Rev., 2000, 198, 329–346.
22 A. N. Khlobystov, A. J. Blake, N. R. Champness, D. A.
Lemenovskii, A. G. Majouga, N. V. Zyk and M. Schro¨der, Coord.
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23 S. J. Berners-Price and P. J. Sadler, Coord. Chem. Res., 1996, 151,
1–40.
24 A. S. Craig, R. Kataky, R. C. Matthews, D. Parker, G. Ferguson,
A. Lough, H. Adams, N. Bailey and H. Schneider, J. Chem. Soc.,
Perkin. Trans. 2, 1990, 1523.
Acknowledgements
This research was partially supported by the Israel Science
Foundation.
25 D. C. Ress, M. Lewis and W. N. Lipscomb, J. Mol. Biol., 1983,
168, 367.
26 D. N. Silverman and S. Lindskog, Acc. Chem. Res., 1988, 21,
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