Synthesis, characterization, molecular structure and supramolecular architectures of some copper(II) complexes derived from salicylaldehyde semicarbazone

Article abstract of DOI:10.1016/j.ica.2015.04.019

A series of new copper(II) complexes, [Cu(HSalsc)Cl]·1/2H₂O (1), [{Cu(HSalsc)}₂(NO₃)₂][{Cu(HSalsc)}₂(NO₃)·H₂O]NO₃ (2), [{Cu(Salsc)}₂]H₂O (3), [Cu

Full text of DOI:10.1016/j.ica.2015.04.019

Accepted Manuscript
Synthesis, Characterization, Molecular Structure and Supramolecular Architec-
tures of some Copper(II) Complexes Derived from Salicylaldehyde Semicar-
bazone
Nahed M.H. Salem, Amal R. Rashad, Laila El Sayed, Sabine Foro, Wolfgang
Haase, Magdi F. Iskander
PII:
S0020-1693(15)00207-8
http://dx.doi.org/10.1016/j.ica.2015.04.019
ICA 16512
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
17 February 2015
8 April 2015
10 April 2015
Please cite this article as: N.M.H. Salem, A.R. Rashad, L. El Sayed, S. Foro, W. Haase, M.F. Iskander, Synthesis,
Characterization, Molecular Structure and Supramolecular Architectures of some Copper(II) Complexes Derived
from Salicylaldehyde Semicarbazone, Inorganica Chimica Acta (2015), doi: http://dx.doi.org/10.1016/j.ica.
2
015.04.019
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1
Synthesis, Characterization, Molecular Structure and Supramolecular
Architectures of some Copper(II) Complexes Derived from
Salicylaldehyde Semicarbazone.
a
a
a
b
Nahed M. H. Salem , Amal R. Rashad , Laila El Sayed , Sabine Foro , Wolfgang
c
a*
Haase , Magdi F. Iskander
a) Chemistry Department, Faculty of Science, Alexandria University, P.O. box 426,
Ibrahimia, Alexandria 21321, Egypt.
b) Clemens-Schöpf-Institut für Organische Chemie und Biochemie, Technische Universität
Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany.
c) Eduard-Zintl-Institute of Inorganic and Physical Chemistry, Darmstadt University of
Technology, Petersenstrasse 20, 64287 Darmstadt, Germany.
*
Corresponding author. Tel.: +20 3 3911794
E-mail address: m.iskander@link.net (M. F. Iskander)

2
Abstract: A series of new copper(II) complexes,
[Cu(HSalsc)Cl].1/2H
(2) , [{Cu(Salsc)} ]H
[{Cu(HSalsc)HIm} ](NO (5)
Cu(HSalsc)(HIm)]OAc (6) derived from salicylaldehyde semicarbazone (H
2
O (1),
[
[
[
{Cu(HSalsc)}
2
(NO
3
)
2
][{Cu(HSalsc)}
2
(NO
3
)
.
H
2
O]NO
3
2
2
O (3),
Cu(HSalsc)(HIm)]Cl.1/2H
2
O
(4),
2
3
)
2
and
2
Salsc) have
been prepared and characterized by elemental analysis, infrared and ultraviolet – visible
absorption spectra as well as electrospray mass spectra (ESI – MS). The crystal and
molecular structure of 1, 2, 5 and 6 have been determined by X-ray single crystal
diffraction. The supramoleuclar architectures in 1, 2, 5 and 6 have been also discussed.
Keywords: Salicylaldehyde semicarbazone Cu(II) complexes, Synthesis, Characterization,
X-ray crystal structures, Supramoleclar architectures.

3
1
. Introduction
Self-assembly of organic molecular building blocks through intermolecular non-
covalent bond interactions (hydrogen bonds, π–π stacking, ….) leads to the formation of
1
2
3
D, D and D supramolecular frameworks [1 – 6]. Transition and non-transition metal
complexes with multidentate organic ligands are also used as molecular building blocks for
the construction of metal-containing supramolecular architectures via non-covalent ligand
-
ligand interactions associated with the outermost functional groups which are
synthetically grafted onto the backbones of coordinated ligands and can operate as donors,
acceptors, or combinations therein [7 - 10].
Semicarbazones are a class of compounds obtained from the condensation of
semicarbazide with suitable aldehyde or ketone. In metal complexes, the semicarbazone
ligand may exist in neutral ketoamine form (I – i) or deprotonated monoanionic enolimine
tautomer (I – ii) [11, 12]. The neutral semicarbazone ligand (I – i) possesses both proton
donor (terminal aminic NH
2
and hydrazinic NH protons) and proton acceptor (ketoamide
also acts as proton donor site, while both
oxygen) sites. In (I – ii) the terminal aminic NH
2
deprotonated hydrazinic and enolimine oxygen act as proton acceptor sites. Metal
complexes containing coordinating semicarbazone moiety (I – i or I – ii) are self
complementary and several modes of supramolecular self-assemblies have been reported
[
13 – 28]. In absence of non-semicarbazone proton acceptors, the terminal aminic NH
proton can be involved in (NH···O) hydrogen bond formation with the ketoamide oxygen
2
2
(
II – i) [13 – 15] or deprotonated enolimine oxygen (II – ii) [16 - 17] forming R (8)
2
2
cyclic hydrogen bond motif. Cyclic R (8) ring can be also generated through the
formation of pair of NH···N hydrogen bonds between the terminal amine NH proton and

4
deprotonated hydrazinic nitrogen (II-iii) [17 – 19]. In addition to these semicarbazone-
semicarbazone interactions (II, i – iii), several supramolecular assemblies are formed
through interactions between the proton donor sites of the coordinated semicarbazone
ligand and the complementary acceptor sites of the free or coordinated anion(s) present in
the metal complex [14, 15, 20 – 29]. In these assemblies, the orientation of both aminic
NH and hydrazinic NH protons of the coordinated semicarbazone ligand favour the
formation of a variety of stable hydrogen bond patterns with the oxygen atom(s) of formate
[
20], acetate [21 – 23], nitrate [14, 21, 24], perchlorate [15, 24 – 27] and sulphate [15, 28]
anions. Hydrogen bonds with chloride anion have been also reported [21, 24, 29].
The coordination chemistry of salicyladehyde semicarbazones as well as their metal
complexes have been the subject of extensive investigation partially because of their wide
spectrum of biological activities [30 – 35] and the diversity in their binding and
stereochemistry [15, 16, 20, 23, 24, 31 – 40]. Salicylaldehyde semicarbazone (H
exist in neutral, monoanionic and dianionic forms depending on the pH of the medium
41]. In metal complexes, salicylaldehyde semicarbazone usually acts as monoanionic
2
Salsc) can
[
ONO tridentate ligand and coordinates to the central metal ion via deprotonated phenoxy
oxygen, imine nitrogen and ketoamide oxygen forming 5- and 6-membered chelate rings. It
can also function as dianionic tridentate ligand through the deprotonation of both phenoxy
and enolimide oxygens [41].
In the present work, some new copper(II) complexes, [Cu(HSalsc)Cl].1/2H
{Cu(HSalsc)} (NO ] [{Cu(HSalsc)} (NO O] NO (2), [{Cu(Salsc)} ]H O (3)
Cu(HSalsc)(HIm)]Cl.1/2H (4) [{Cu(HSalsc)(HIm} ](NO (5)
2
O (1),
[
[
2
3
)
2
2
3
)
.
H
2
3
2
2
[
2
O
2
3
)
2
and
Cu(HSalsc)(HIm)]OAc (6) , have been prepared and characterized by elemental analysis,
infrared and ultraviolet – visible absorption spectra as well as electrospray mass spectra

5
(
ESI – MS). The X-ray crystal structures of 1, 2, 5 and 6 have been determined, aiming to
identify the different types of intermolecular interactions involved in self-assembly of the
molecular units present in the crystal lattice. The role played by i) the Cu(II) coordination
preferences, ii) the nature and position of the proton acceptor and proton donor sites of the
coordinated ligand(s) and iii) the nature of the counter anions, on the architecture of the
supramolecular assemblies of these building blocks has been also discussed.
2
. Experimental
2
.1 Materials used
Salicylaldehyde and semicarbazide hydrochloride were purchased from Aldrich and
used as received. Salicylaldehyde semicarbazone was prepared as previously described
39] from the reaction of salicylaldehyde and semicarbazide hydrochloride in presence of
[
sodium acetate. Imidazole was commercially available from Sigma and used without
further purification. Copper(II) chloride dihydrate, copper(II) acetate monohydrate and
copper(II) nitrate trihydrate were commercial products of highest chemical grade.
2
2
.2 Preparation of copper(II) complexes
.2.1 Preparation of [Cu(HSalsc)Cl].1/2H
2
O ( 1)
A stirred suspension of H
2
Salsc (0.54 gm, 3.0 mmol) in absolute ethanol (25 ml)
.2H O (0.60 gm, 3.5 mmol) in the same solvent (30
was treated with a solution of CuCl
2
2
ml). The resulting mixture was heated under reflux for 1 hr. The green crystalline complex
which separated on cooling to ambient temperature was filtered off, washed with ethanol
then dried in vacuo. Yield: 58 %. Anal. Calc. for C
8
H
8
N
3
O
2
ClCu.1/2H
2
O: C, 33.58; H,
.17; N, 14.68. Found: C, 33.45; H, 3.25; N, 14.65 %. IR (KBr) (cm ): 3547 υasym (H O);
O); 3395s, υasym(NH ); 3320s, υsym (NH ); 3200s, hydrazinic υ(N–H); 1657s,
-1
3
3
2
450 υsym(H
2
2
2

6
amide I [υ(C=O)]; 1635 sh, δ(NH
2
); 1602m, υ(C=N); 1538s, amide II [δ(N–H) + υ(C–
N)]. UV–Vis. (DMF, λmax / nm (log ε)): 317 (4.19); 380 (4.07); 395 sh; 714 (2.08).
(+)
+
ESI MS (DMF/CH
3
OH) m/z Calcd. (RA): 241.0 (241.7162) (100), [Cu(HSalsc)] ; 264.0
+
+
(
263.6979) (12.0), [Cu(Salsc) + Na] ; 314.0 (314.8106) (44.78), [{Cu(HSalsc)(DMF)}] ;
+
+
4
80.9 (482.4245) (3.7), [{Cu(Salsc)}
2
+ H] ; 722.8 (723.1325) (8.2), [{Cu(Salsc)}
3
+ H] .
-
(
–) ESI MS (DMF/CH
3
OH) m/z Calcd. (RA): 240.0 (239.7003) (70.15), [Cu(Salsc) – H] ;
-
2
71.7 (271.7423) (35.82), [{Cu(Salsc)}OCH
3
]
;
276.0 (276.1612) (76.12),
-
-
[
[
(
{Cu(Salsc)}Cl] ; 312.6 (313.7) (100), [{Cu(HSalsc)}Cl
2
] ; 512.4 (512.4505) (17.91),
-
-
{Cu(Salsc)}
2
(OCH
3
)] ; 516.8 (516.8694) (17.16), [{Cu(Salsc)}
2
Cl] ; 551.3 (551.3145)
-
2 2
55.22), [{Cu(HSalsc)} Cl – H] .
2
.2.2 Preparation of [{Cu(HSalsc)}
This complex was prepared using the same procedure described for (1) using
Cu(NO .3H O instead of CuCl .2H O. The isolated green crystals were filtered, washed
with ethanol and then dried in vacuo . Yield: 60 %. Anal. Calc. for C Cu: C,
2 3 2 2 3 . 2 3
(NO ) ] [{Cu(HSalsc)} (NO ) H O] NO (2) :
3
)
2
2
2
2
8 10 4 6
H N O
-
1
2
9.87; H, 3.13; N, 17.41. Found: C, 29.85; H, 3.22; N, 17.05 %. IR (KBr) (cm ): 3547
O); 3478 m, υsym(H O); 3400s, υasy(NH ); 3320s, υsym (NH ); 3200, hydrazinic
); 1605 s, υ(C=N) ; 1535 m, amide II
δ(N–H) + υ(C–N)]; 1430s, 1303m, 1015 m, vibration modes of unidentate NO3; 1385vs,
υasym (H
2
2
2
2
υ(N–H); 1655s, amide I [υ(C=O)]; 1625 sh, δ(NH
2
[
1
3
2
044m, 820m, vibration modes of ionic NO
3
. UV–Vis. (DMF, λmax / nm (log ε)): 302(sh),
OH) m/z Calcd. (RA):
3 2
19.1 (220.9220) (100), [Cu(HSalsc)(NO ) DMF + 3H] ; 237.1 (238.9372) (8.27)
16 (4.09); 380 (4.15); 395 sh; 688 (2.18). (+) ESI MS (DMF/CH
3
+
+
+
+
[
(
Cu(HSalsc)(NO
3
)
2
(H
2
O)
2
3
(DMF) + 3H] ; 245.1 (245.0080) (12.03) [Cu(HSalsc)(NO )
+
+
++
2 2 2
DMF) + K + H] ; 250.0 (250.7237) (63.91) [{Cu(HSalsc)} H O] ; 326.4 (326.7109)

7
+
+
(
9.77) [Cu(HSalsc)(NO
3
) + Na] ; 331.9 (332.8257) (6.02) [{Cu(HSalsc)} H
2
O.DMF] ;
+
3
75.0 (377.8234) (5.26) [Cu(HSalsc)(NO
3
)(DMF) + H] . (–) ESI MS (DMF/CH
3
OH) m/z
-
Calcd. (RA): 289.9 (289.7574) (100), [Cu(Salsc)(H
2
O) + CH
3
O] ; 302.7 (302.7130) (2.98),
-
--
[
(
{Cu(Salsc)NO
3
] ; 305.8 (307.7538) (48.51), [{Cu(Salsc)}
2
(NO
3
)(DMF) – H] ; 376.8
1
-
375.8076) (32.84) [{Cu(Salsc)NO
3
(DMF)] .
2
.2.3 Preparation of [{Cu(Salsc)}
A solution of Cu(OAc) .H O ( 0.80 gm, 4.0 mmol) in methanol (30 ml) was added drop -
wise to a stirred suspension of H Salsc (0.54 gm, 3.0 mmol) in methanol (30 ml). The
2 2
].H O (3)
2
2
2
reaction mixture was treated with triethylamine (1.0 ml) then heated under reflux for 3
hours. The isolated complex (3) was filtered, washed with hot methanol then dried in
vacuo. Yield: 75 %. Anal. Calc. for C16
C, 38.54; H, 3.23; N, 16.31 %. IR (KBr) (cm ): 3467s, υsym (H
270m, υsym(NH ); 1640 sh, δ(NH ); 1625s (υ(C=N–N=C); 1545s, amide II [δ(N – H) +
υ(C–N)]. UV–Vis. (saturated solution in DMF, λmax / nm (log ε)): 305, 317; 382. (+) ESI
H
16
N
6
O
5
Cu
2
: C, 38.48; H, 3.23; N, 16.83. Found:
-1
2
O); 3400s υasym(NH );
2
3
2
2
MS
(DMF/CH
3
OH)
m/z
Calcd.
Na
(RA):
236.1
(237.4894)
(73.68),
+
+
[
[
{Cu(Salsc)}(DMF)
2
(MeOH)
2
+
+
H]
; 296.3 (296.7480) (12.03),
+
+
{Cu(Salsc)}
2
(MeOH) + Na + H] ; 326.4 (327.7820) (61.65), [{Cu(Salsc)}(MeOH) +
2
+
+
Na] ; 346.0 (346.8528) (25.56), [{Cu(Salsc)}(DMF)(MeOH) + H] . (–) ESI MS
-
(
(
(
(
[
DMF/CH
3
OH) m/z Calcd. (RA): 238.9 (239.7004) (80.0), [{Cu(Salsc)} – H] ; 265.0
--
264.7289) (41.82), [{Cu(Salsc)}
2
+ CH
3
2
O + OH] ; 281.0 (280.7499), [{Cu(Salsc)} +
-
-
--
MeOH)(MeO)(OH)] ; 307.0 (308.2895) (94.55), [{Cu(Salsc)}
2
(DMF)(CH
3
O)
2
] ; 545.8
-
544.4768) (100), [{Cu(Salsc)}
2
(MeOH)
+
CH
3
O] ; 785.0 (785.2007) (33.5)
-
{Cu(Salsc)}
3
(MeOH)(MeO)] .

8
2
.3.4 Preparation of [Cu(HSalsc)(HIm)]Cl .1/2H
A solution of CuCl .2H O (0.55 gm, 3.2 mmol) in absolute ethanol (30 ml) was added
dropwise to a stirred suspension of H Salsc (0.54 gm, 3.0 mmol) in absolute ethanol (30
2
O (4)
2
2
2
ml). Solid imidazole (0.545 gm, 8.0 mmol) was then added and the reaction mixture was
heated under reflux for 1 hr. The resulted green solution was filtered, and the filtrate was
concentrated to half its volume. On cooling, the green crystalline complex which separated
out, was collected by filtration then dried in vacuo. Yield: 62 %. Anal. Calc. for
C
11
H
12
N
5
O
2
ClCu.0.5H
2
O: C, 37.30; H, 3.70; N, 19.77. Found: C, 37.82; H, 3.52; N,
-
1
1
9.77%. IR (KBr) (cm ): 3395 s, υasym(NH
2
); 3335m, υsym(NH
2
); 3208s, hydrazinic υ(N–
); 1600m, υ(C=
N); 1535, amide II [δ(N–H)+υ(C–N)]. UV–Vis. (DMF, λmax / nm (log ε)): 304 (4.09), 318
H); 3165s, imidazole υ(N–H) ; 1672vs, amide I [υ(C=O)]; 1630s, δ(NH
2
(
(
(
4.19); 380 (4.12); 395 sh; 648 (2.15). (+) ESI MS (DMF/CH
3
OH) m/z Calcd. (RA): 240.9
+
+
241.7161) (100), [Cu(HSalsc)] ; 309.0 (309.7947) (22.5), [Cu(HSalsc)HIm] ; 314.0
+
+
314.8105) (17.78), [{Cu(HSalsc)}(DMF)] ; 480.9 (482.4243) (2.96), [{Cu(Salsc)}
2
+ H] ;
+
7
21.8 (723.1325) (2.24), [{Cu(Salsc)}
3
+ H] . (–) ESI MS (DMF/CH
3
OH) m/z Calcd.
-
-
(
(
(
[
RA): 235.9 (235.4873) (83.58), [{Cu(Salsc)}(Im)(DMF)
2
+ OH] ; 274.8 (274.2432)
--
-
100), [{Cu(Salsc)}
2
(Im) – H] ; 306.9 (307.7783) (65.67), [{Cu(Salsc)}(Im) ] ; 371.7
-
371.8624) (18.66), [{Cu(HSalsc)}(HIm) + (CH
3
O)
2
] ; 512.8 (512.4505) (20.89),
-
2 3
{Cu(Salsc)} + OCH ] .
2
.2.5 Preparation of [{Cu(HSalsc)HIm}
Complex 5 was prepared using the same procedure described for 4, using Cu(NO
instead of CuCl .2H O. Yield: 64 %. Anal. Calc. for C11 Cu: C, 35.54; H, 3.25; N,
2 3 2
](NO ) (5):
3 2 2
) .3H O
2
2
12 6 5
H N O

9
-
1
2
2.60. Found: C, 35.92; H, 3.35; N, 22.03 %. IR (KBr) (cm ): 3414m, υasym(NH
2
); 3327m,
υ
sym(NH
2
); 3210 m, hydrazinic υ(N–H); 3148m, imidazole υ(N–H) ; 1653s, amide I
); 1602s, υ(C=N); 1540m, amide II [δ(N–H) + υ(C–N)]; 1415s,
385vs, 825m vibration modes of ionic NO . UV–Vis. (DMF, λmax / nm (log ε)): 304
4.09), 318 (4.09); 380 (4.19); 648(2.18). (+) ESI MS (DMF/CH OH) m/z Calcd. (RA):
[
υ(C=O)]; 1635s, δ(NH
2
1
3
(
3
+
2
40.9
(241.7161)
(100),
[{Cu(HSalsc)}] ;
314.0
(314.8105)
(36.30),
+
+
[
(
{Cu(HSalsc)(DMF)}] ; 480.9 (482.4243) (3.7), [{Cu(Salsc)}
2
+ H] . (–) ESI MS
DMF/CH
3
OH) m/z Calcd. (RA): 235.9 (235.4873) (100), [{Cu(Salsc)}(Im)(DMF) +
2
--
-
OH] ; 301.9 (302.7132) (79.70), [{Cu(Salsc)}(NO
3
)] ; 306.9 (307.7783) (60.90),
-
-
[
(
{Cu(Salsc)}(Im)] ; 543.8 (543.4214) (22.56), [{Cu(Salsc)}
2
(NO
3
)] ; 789.1 (789.1946)
-
3
10.53), [{Cu(Salsc)} (Im) – H] .
2
.2.6 Preparation of [Cu(HSalsc)(HIm)]OAc (6):
Complex 6 was prepared as described for 4, using Cu(OAc)
Yield: 58 %. Anal. Calc. for C13 Cu: C, 42.33; H, 4.10; N, 18.99. Found: C, 42.29;
H, 4.07; N, 18.82 %. IR (KBr) (cm ): 3380, υasym(NH
hydrazinic υ(N–H); 3114s imidazole υ(N–H); 1672vs, amide I [υ(C=O)]; 1635, δ(NH
2
2 2 2
.H O instead of CuCl .2H O.
15 5 4
H N O
-1
2
); 3323s, υsym(NH ); 3180s,
2
2
);
-
-
1
.
605s, υ(C=N); 1530, amide II [δ(N–H) + υ(C–N)]; 1580vs, υasymCOO ; 1420vs, υsymCOO
UV–Vis. (DMF, λmax / nm (log ε): 304(4.17), 317(4.19); 380(4.19); 580(2.14). ESI (+)
+
MS (DMF/CH
3
OH) m/z Calcd. (RA): 240.9 (241.7162) (100), [{Cu(Salsc)} + H] ; 309.0
+
(
309.7947) (74.81), [{Cu(Salsc)}(HIm) + H] ; 481.0 (482.4243) (48.15), [{Cu(Salsc)}
2
+
+
H] . ESI (–) MS (DMF/CH
3
OH) m/z Calcd. (RA): 306.9 (307.7789), (100),
–
–
[
{Cu(Salsc)}(HIm) – H] ; 547.9 (548.4865) (71.43), [{Cu(Salsc)}
2
(Im)] ; 620.9

1
0
–
(
2 4
621.5809) (42.11), [{Cu(Salsc)} (Im)(DMF)] ; 961.5 (961.8249) (35.82), [{Cu(Salsc)}
–
–
H] .
2
.3 Physical measurements
The infrared spectra were recorded on a Perkin–Elmer 1430 Data system and/or a
Perkin–Elmer (FT-IR) Paragon 1000 PC spectrophotometer. Solid samples were examined
as KBr discs. The ultraviolet and visible absorption spectra were recorded on V-530 UV–
Vis. recording spectrophotometer, Jasco, using 10 mm quartz cells and/or a double beam
ratio recording Lambada 4B Perkin–Elmer spectrophotometers. ESI mass spectra were
-1
recorded on Esquire-LC from Bruker Daltonic Nebulizer 10 psi (dry gas 8 L min , dry
temperature 250°C). Theoretical isotopic distribution patterns for ionic species were
generated using ISOFORM program.
X-ray diffraction data were collected on CrysAlis CCD, Oxford Diffraction limited,
version 1.70.14 (2002), using graphite monochromated Mo Ka radiation (k = 0.71013Å).
The structures were solved by direct method with SHELXS-97 [42]; refinement was done
by full-matrix least squares on F2 using the SHELXL-97 [42]. Drawings of the molecules
were produced with ORTEP 3 [43] or PLATON [44]. Data collection and structure
refinement for 1, 2, 5 and 6 complexes are given in Table 1.
3
. Results and discussion
3
.1 Synthesis
The dark blue [Cu(HSalsc)Cl] H
from the reaction of salicylaldehyde semicarbazone (H
methanol at room temperature, using (1:1) molar ratio. However, in boiling absolute
2
O.1/2 CH
3
OH complex was previously prepared [16]
2
Salsc) with CuCl .2H O in
2
2

1
1
ethanol the reaction proceeded with the formation of the new chloro complex
Cu(HSalsc)Cl].1/2H O (1). Salicylaldehyde semicarbazone can also react with one
equivalent Cu(NO .3H in boiling ethanol, giving the nitrato complex
{Cu(HSalsc)} (NO ][{Cu(HSalsc)} (NO O]NO (2). The reaction with
Cu(OAc) .H O, however, afforded the binuclear [{Cu(Salsc)} ].H O complex (3). In
presence of imidazole, the reaction of H Salsc with CuCl .2H O, Cu(NO .3H O or
Cu(OAc) .H O in methanol gives [Cu(HSalsc)HIm]Cl.1/2H O (4), [{Cu(HSalsc)HIm}
NO (5) and [Cu(HSalsc)HIm]OAc (6) respectively. The presence of the anion, Cl,
NO or OAc in the final reaction product, suggests that the salicylaldehyde semicarbazone
residue in these complexes reacts in the ketoamide form. Attempts to prepare
Cu(Salsc)HIm] complex, from the reaction of the dinuclear [{Cu(Salsc)} ] with excess
] complex was recovered
[
2
3
)
2
2
O
[
2
3
)
2
2
3
)
.
H
2
3
2
2
2
2
2
2
2
3
)
2
2
2
2
2
2
]
(
)
3 2
3
[
2
imidazole, were unsuccessful and the starting [{Cu(Salsc)}
2
unchanged.
3
.2 Infrared Spectra
The IR spectra of both 1 and 2 complexes show a series of absorption bands at ca.
225, 1655, 1605, and 1535, respectively due to hydrazinic υ(N–H), amide I [υ(C=O)],
3
imine υ(C=N) and amide II [δ NH + υ(C–N)]. The presence of these characteristic
absorptions together with the observed shift to lower frequencies for both amide I
[
υ(C=O)] band and imine υ(C=N) as compared to the metal free ligand indicate that the
salicylaldehyde semicarbazone is coordinated to the central Cu(II) via deprotonated
phenolic oxygen, imine nitrogen and ketoamide oxygen. The IR spectrum of 2 also shows
-1
absorptions at 1430s, 1303m and 1015m cm respectively due to υasym(NO
2 2
), υsym(NO )
and υ(NO) vibration modes of coordinated unidentate NO [45, 46]. The spectrum also
3

1
2
shows absorptions at 1385vs, 1044m, 820m, due to the vibration modes of ionic NO
3
[45].
The spectrum of the neutral dinuclear [Cu(Salsc)] .H O (3) lack absorptions which can be
2
2
attributed to phenolic υ(O–H), hydrazinic υ(N–H), amide I [υ(C=O)] and amide II [δ NH +
υ(C–N)]. The spectrum, however, shows strong absorption at 1638 due to υ(–C=N–N=C–
O). The observed spectral pattern suggests the deprotonation of both phenolic oxygen and
enolimide oxygen and the salicylaldehyde semicarbazone ligand in this complex acts as
dianionic ONO tridentate ligand.
The IR spectra recorded for 4, 5, 6 complexes show a series of bands at 3200-
-1
3
205, 3130-3160, 1650-1670, 1615-1625 and 1520-1545 cm respectively due hydrazinic
υ(N–H), imidazole υ(N–H), amide I [υ(C=O)], imine υ(C=N) and amide II [δ NH + υ(C–
N)]. The observed spectral pattern is in agreement with the ketoamide coordination mode.
Salicylaldehyde semicarbazone in the imidazole complexes acts as monoanionic tridentate
ligand and is coordinated to the central Cu(II) ion via the deprotonated phenolic oxygen,
imine nitrogen and ketoamide oxygen. The IR spectra of the nitrate complex show the
three absorption bands at ca. 1415, 1385 and 825 characteristic of ionic nitrate anion [45].
-1
Furthermore, the IR spectrum of 6 shows two absorption bands at ca. 1420 and 1580 cm
which are not present in the spectra of the corresponding chloride complex. Thus these two
absorptions can be safely assigned, respectively, to sym(COO) and asym(COO) stretching
-1
vibration modes of the acetate anion with ∆υ = 160 cm . The recorded ∆υ value is within
the range reported for ionic acetate rather than coordinated acetate [47].
3
.3 Electronic Spectra
The solution electronic absorption spectra of both 1 and 2 in DMF display
absorptions at 315-318 and 380 nm which can be attributed to the different L – L*

1
3
-1
transitions of the mononegative ONO tridentate semicarbazone (HSalsc) ligand. The
spectra are also characterized by an intense absorption at ca 395 nm which can be
attributed to LMCT transition from the phenoxy oxygen to the central Cu(II). The d – d
(
ligand field) spectra of both 1 and 2 appear as broad unsymmetrical band centered at ca.
00 nm, with a shoulder at higher wavelengths (ca 750 nm). The observed spectral patterns
7
suggest tetragonally distorted octahedral copper(II) [48, 49] most probably due to the
presence of octahedral solvated species formed in DMF.
The solution electronic absorption spectra of 4, 5 and 6 in DMF also show intense
absorption bands at 315 - 318 and 380 nm due to the different L – L* transitions in
addition to an intense absorption at ca 395 nm due to LMCT transition. The d – d spectra
of both 4 and 6 are quite similar and display a broad unsymmetrical absorption band
centered at 650 nm, suggesting a distorted square pyramidal environment around the
copper(II) center [48, 49]. This is in agreement with the dimeric structure of the nitrate
complex (6) in which each Cu(II) is in a square pyramidal environment (c.f. section 3.5.2).
A similar structure can be adopted for the chloride complex 4. The d – d transitions of the
acetate complex [Cu(HSalsc)(HIm)]OAc (6), however, appear at much lower wavelengths
ca. 580 nm as compared to the corresponding chloride and nitrate complexes. This may
suggest four-coordinate square planar geometry and the acetate anion acts as counter ion
[
48, 49].
3
.4 Electrospray ionization mass spectra (ESI MS)
Both positive and negative mode ESI mass spectra of 1, 2, 3, 4, 5 and 6 complexes
have been recorded using DMF/MeOH (1:1 by volume) as solvent. A careful study of ESI
mass spectra of these complexes can assist for better understanding the behavior of these

1
4
complexes in solution, since the generated ions in the gas phase closely reflect those in
solution [50]. The positive ESI mass spectra of [Cu(HSalsc)Cl].1/2H
2
O (1) display peaks
+
at m/z = 240.0 and 314 respectively due to mononuclear [Cu(HSalsc)] and
+
[
Cu(HSalsc)(DMF)] species. The spectrum also shows peaks, of much lower relative
abundance at m/z = 481 corresponding to the phenoxy bridged dimeric species
+
[
{Cu(Salsc)}
2
+ H] . The negative ESI mass spectrum, on the other hand, shows peaks at
-
m/z = 276 and 312.6 respectively due to monochloro [Cu(Salsc)Cl] and dichloro
-
-
[
(
Cu(HSalsc)Cl
2
] species. Monochloro and dichloro bridged binuclear [{Cu(Salsc)}
2
Cl]
-
m/z = 516.8) and [{Cu(HSalsc)}
2
Cl
2
– H] (m/z = 551.3) anions have been also detected.
The presence of methanol, as solvent, resulted in the formation of the mononuclear
-
monomethoxy anion [Cu(Salsc)(OCH
3
)] (m/z = 271.7) as well as monomethoxy bridged
-
dimer [{Cu(Salsc)}
2
(OCH
positive
(NO
3
)] (m/z = 512.4).
The
ESI-mass
spectrum
of
2 3 2
[{Cu(HSalsc)} (NO ) ]-
[
{Cu(HSalsc)}
2
3
)
.
H
2
O] NO
3
(2), displays peaks at m/z = 332.0 and 250.0 respectively
+
due to the
{Cu(HSalsc)}
formation of mononuclear [Cu(HSalsc)(H
2
O)(DMF)] and binuclear
++
[
2
(H
2
O)]
monoaqua cations, where the water molecule is directly
coordinated to the central Cu(II). Peaks corresponding to other cationic species having
+
+
coordinated NO
Cu(HSalsc)(NO )(DMF)
and [Cu(HSalsc)(NO
3
,
[Cu(HSalsc)(NO
3
)
2
(DMF)
+
3H]
(m/z
=
219.1),
++
+
[
3
2
+K+H] (m/z 245.0), [Cu(HSalsc)(NO
3
) + Na] (m/z = 326.4)
+
3
)(DMF) + H] (m/z = 375.0) have been also observed. The spectrum
++
also shows peaks at m/z = 237.1 due to [Cu(HSalsc)(NO
3 2 2 2
) (H O) (DMF) + 3H] cation
which indicates that both nitrate and H O are coordinated to Cu(II). The negative ESI
2
spectra, also show peaks which can be attributed to i) anions having coordinated water
-
molecule, [Cu(Salsc)(H
2
O) + CH
3
O] (m/z = 289.7), ii) anions having coordinated NO
3
,

1
5
-
--
[
[
Cu(Salsc)NO
3
] (m/z = 302.7), [{Cu(Salsc)}
2
(NO
3
)(DMF) – H] (m/z = 307.7) and
--
{Cu(Salsc)}(NO
3
)(DMF)] (m/z = 376.8), indicating the coordination of both NO
3
and
DMF to the central Cu(II).
The positive ESI mass spectra of 4, 5 and 6 in DMF/MeOH mixture, are more or
less similar and display peaks at m/z = 240.9, 314, 480.9, 721.8 respectively due to
+
+
+
+
[
Cu(HSalsc)] , [Cu(HSalsc)(DMF)] , [{Cu(Salsc)}
2
+ H] , [{Cu(Salsc)} + H] positive
3
ions. Their negative ESI-mass spectra, show peaks at m/z = 235.9, 274.8 and 306.9 due to
--
--
-
[
Cu(Salsc)(Im)(DMF)
2
+ OH] , [{Cu(Salsc)} Im – H] and [Cu(Salsc)Im] respectively.
2
The presence of MeOH as cosolvent assists the formation of negative ions having the
methoxy ion as evident from the negative ESI mass spectrum of
[
[
2
Cu(HSalsc)(HIm)Cl].1/2H O which displays peaks at m/z = 371.7, 512.8 due to
-
-
3 2 3
Cu(HSalsc)HIm + 2CH O] and [{Cu(Salsc)} + CH O] respectively.
3
3
.5 X-ray molecular and supramolecular structures
.5.1 X-ray molecular structure and self-assembly of [Cu(HSalsc)Cl].1/2H
The structure of 1, Figure 1, consists of two molecular units, namely Cu1- and
2
O (1):
Cu2-molecular units which are both crystallographically and chemically independent, in
addition to one lattice water molecule. Selected bond distances and angles for Cu1- and
Cu2-molecular units are listed in Table 2. In the Cu1-molecular unit, each Cl1 ion acts as a
bridging atom and coordinates to the Cu1 atom of the neighboring Cu1-molecular unit,
leading to a polymeric chain [Cu(HSalsc)Cl]
n
extending along c-axis as shown in Figure 2.
Each Cu1 atom in this polymeric chain is five-coordinate and is bound in the equatorial

1
6
plane to the phenoxy O2 oxygen, imine N1 nitrogen and ketoamide O1 oxygen of the
-
mononegative ONO tridentate semicarbazone (HSalsc) anion. The fourth coordination
site is occupied by Cl1 while the fifth apical site is occupied by the Cl1 of the adjacent
Cu1-molecular unit. The Cu1 polyhedron in each molecular unit can best be described as
(
4+1) slightly distorted square pyramid with tetragonality parameter [51] τ = [(β – α)] / 60
0.006 (almost perfect square pyramidal) where β and α angles are N1–Cu1–Cl1 = 168.39
=
and O1–Cu1–O2 = 168.06 respectively). It is of interest to note that in the Cu1-molecular
chain, the equatorial Cl1 atom of one Cu1-molecular unit is the apical Cl1 atom of the next
neighboring unit. The Cu1–Cl1–Cu1 and Cl1–Cu–Cl1 angles are respectively 113.8 and
o
9
1.09 .
Both H51 and H52 protons of each lattice water molecule are respectively involved
in hydrogen bond formation with the phenoxy O2 oxygen of Cu1-molecular unit and the
2
2
apical Cl1 of the adjacent Cu1-molecular unit, giving rise to a chain of R (8) hydrogen
bonded eight- membered rings [52, 53] sharing a common (Cu1–Cl1) edge and
propagating along the c-axis (Cu1-chain) as shown in Figure 2. The Cu1-chain is further
stabilized by π⋅⋅⋅π interactions between the five-membered chelate rings (N1, N2, C1, O1,
Cu1) with centroid – centroid separation (C
interactions between O5H51 water protons and the π system of the 6-membered chelate
rings (Cu1, N1, C2, C3, C8, O2) (O5H51⋅⋅⋅C 2 = 3.042 Ǻ). The parameters of the
g g
1⋅⋅⋅C 1) equals to 4.003 Ǻ [54,55], and OH⋅⋅⋅π
g
intermolecular non-covalent bond interactions in Cu1 - chain are listed in Table S1.
In the Cu2 - molecular unit, the central Cu2 is in a distorted square planar
1
-
environment and is coordinated to the ONO tridentate HSalsc anion via the phenoxy O4
oxygen, imine N4 nitrogen and ketoamide O3 oxygen. The fourth coordination site is
occupied by the chloride Cl2. Deviation from idealized square planar arrangement in Cu2-

1
7
molecular unit is evident from the deviation of cis angles (O3 – Cu2 –N4, O3 – Cu2 – Cl2,
o
O4 – Cu2 – N4 and O4 – Cu2 – Cl2) from 90 and trans angles (O3 – Cu2 – O4 and N4 –
o
Cu2 – Cl2) from 180 (Table 2). Similar to other semi- [13 - 15] and thiosemicarbazone
metal(II) complexes [56], each Cu2-molecular unit is connected to another adjacent Cu2-
molecular unit, of inverted symmetry, through pair of reciprocal hydrogen bonds between
2
2
aminic NH61 proton and ketoamide O3 oxygen, forming a R (8) [52, 53] hydrogen-
bonded dimer. In this dimeric structure, the two Cu2 - molecular units are also linked
together by two reciprocal hydrogen bonds (N6H61⋅⋅⋅Cl2) between the chloride ion Cl1 of
2
1
one unit and the aminic NH61 proton of the other adjacent unit, thus forming two R (4)
rings between the Cu2- molecular units. The two reciprocal (N6H61⋅⋅⋅Cl2) hydrogen bonds
2
2
lead to the formation of an R (12) ring [52, 53] and the extended tricyclic hydrogen bond
pattern has two (H61⋅⋅⋅O3) edges in common.
In the crystal lattice, the dimeric Cu2-molecular units are arranged parallel to each
other and are stacked together via π-π interactions between the salicylidene aromatic ring
(
C11 – C16) π-system of one Cu2-molecular unit and the delocalized 5-membered chelate
ring (O3, C9, N5, N4, Cu2) of the adjacent Cu2-unit with centroid – centroid separation
Cg3 – Cg4) of 3.465 Å [54, 55]. These π-π interactions, Table S1, lead to the formation
of two-dimensional network of stacked Cu2-dimers extended along the bc plane. Each Cu2
(
-
molecular unit is connected, from one side, to one of the adjacent lattice water molecules
1
2
of the Cu1-chain via chelated R (6) hydrogen bond (N5H⋅⋅⋅O5) and (N6H62⋅⋅⋅O5). From
the other side, this Cu2-unit is directly connected to Cu1-molecular units of another Cu1-
chain by (N2H2⋅⋅⋅Cl2) and (N3H32⋅⋅⋅O4) hydrogen bonds, thus generating an 8-membered
2
2
ring R (8) [52, 53] between Cu2- and Cu1-molecular units. The Cl2 atoms of Cu2-

1
8
molecular units are also participating in the formation of (N3H31⋅⋅⋅Cl2) hydrogen bonds
with the aminic N3H31 protons of adjacent Cu1-molecular units of the same Cu1-chain
1
2
which generate with (N2H2⋅⋅⋅Cl) another cyclic R (12) hydrogen bond pattern [52, 53].
The linkage between the dimeric Cu2- molecular units and the Cu1-chains gives rise to a
1
three-dimensional network through which D rectangular channels are propagating along
b-axis.
3
.5.2 X-ray structure and self - assembly of
{Cu(HSalsc)} (NO ] [{Cu(HSalsc)}
The X-ray structure of 2, Figure 3, consists of a distorted unsymmetrical
[
2
3
)
2
2 3 . 2 3
(NO ) H O] NO (2):
1
+
monopositive dimeric unit, [{Cu(HSalsc)}
2
(NO
3
) H
2
O] , a symmetrical neutral dimeric
-
unit [{Cu(HSalsc)(NO
3
)}
2
] and nitrate anion (NO
3
) as counter ion. Selected bond
distances and bond angles for the symmetric cationic and neutral symmetric dimeric
molecular units are given in Table 3 In the unsymmetrical dimeric unit, [{Cu(HSalsc)}
2
1
+
(
NO
3
) H O] , both Cu1 and Cu2 are in a distorted square pyramidal environment. This is
2
evident from the values of the tetragonality parameters [51], τ = [(β – α)] / 60 [51],
o
calculated for Cu1 (τCu1 = 0.03, α = O1–Cu1–O3 = 167.78 and β = N1–Cu1–O2 = 169.5 )
o
and Cu2 (τCu2 = 0.10, α = O2–Cu2–O4 = 160.33 and β = N3–Cu2–O1 = 166.40 ). The
basal plane of Cu1 is defined by the deprotonated phenolic oxygen O1, imine nitrogen N1
and ketoamide oxygen O3 of the mononegative semicarbazone ligand, while the fourth
coordination site is occupied by the bridging phenoxy oxygen O2. The apical site is
occupied by the nitrate O5 oxygen. Meanwhile the phenoxy O2 oxygen, imine N3
nitrogen, ketoamide O4 oxygen and phenoxy oxygen O1 form the basal plane of the Cu2
polyhedron, and the water O6 oxygen occupies the apical position. The nitrate anion and

1
9
the water molecule which are respectively coordinated to Cu1 and Cu2 are in cis positions
with respect to each other. The Cu1 atom deviates from the basal plane (O1, O2, O3, N1,
Cu1) by 0.128 Ǻ towards the apical nitrate O5 oxygen, while Cu2 deviates from the basal
plane (O1, O2, O4, N3, Cu2) by 0.203 Ǻ towards the apical water O6 oxygen.
1
-
Coordination of the mononegative ONO tridentate semicarbazone ligand (HSalsc) to the
copper(II) (Cu1 or Cu2) resulted in the formation of five- and six-membered bicyclic
chelate rings. The five- and six-membered chelate rings involving Cu1 are strictly coplanar
o
(
dihedral angle = 0.0 ) while those bound to Cu2 are not coplanar but makes an angle of
o
1
1.38 with each other. Moreover, the mean coordination planes of Cu1 and Cu2 are not
o
.
coplanar and the torsion angle between them is 25.7
The phenoxy oxygen atoms O
1
and
O2 together with Cu1and Cu2 atoms form a distorted four-membered ring with torsion
o
angle of 7.0 and the Cu1⋅⋅⋅Cu2 distance is 2.954 Ǻ.
The neutral symmetrical unit [{Cu(HSalsc)NO
3
2
} ] is a centrosymmetric dimer in
which each copper(II) atom (Cu3) is coordinated in the equatorial (basal) plane to the
-
1
mononegative N-salicylidene semicarbazone anion (HSalsc) through the deprotonated
phenolic O9 oxygen, imine N8 nitrogen and ketoamide O10 oxygen, the fourth
coordination site of the basal plane is occupied by the symmetry related phenoxy oxygen
of the other monomeric residue, while the nitrate oxygen O11 is positioned in the apical
site. The coordination polyhedron around each Cu3 atom is best described as (4+1)
distorted square pyramidal. This is in agreement with the value of the tetragonality
parameter τ = [(β – α)] / 60 = 0.064 [51] where the angles α (O9–Cu3 – N8) and β (O9–
o
o
Cu3 – O10) are equal to 169.63 and 173.46 respectively. In this symmetrical dimer, the
two coordinated nitrates are in trans positions with respect to each other and are almost
perpendicular to the Cu3 coordination plane. Both of the coordinated semicarbazone

2
0
ligands are almost planar and their planes are parallel to each other. Here again, the two
'
phenoxy oxygens O9, O9 together with the two Cu3 atoms form a planar four-membered
ring with Cu3⋅⋅⋅Cu3 = 2.942 Ǻ.
In the crystal lattice, the uncoordinated nitrate anion acts as a bridge connecting
2
1
two adjacent unsymmetrical units through a chelated R (4) hydrogen bond [52, 57]
between the coordinated water H6A proton and both O14 (O6H6A⋅⋅⋅O14) and O15
(
O6H6A⋅⋅⋅O15) oxygen atoms of the nitrate anion, while the third O16 nitrate oxygen is
involved in hydrogen bond formation with the aminic NH5A proton (N5H5A⋅⋅⋅O) of the
2
2
neighboring unsymmetrical unit, giving rise to C (5) infinite chain extending along b-axis.
2
1
The formed chain is linked to another adjacent chain through chelated R (4) hydrogen
bonds, (N4H4···O14) and (N4H4···O16), in addition to another 6-membered cyclic
1
2
R (6) hydrogen bonds [52, 53], (N4H····O14) and (N7H7B···O14), thus giving rise to a
double chain structure, Figure 4, propagating along b-axis. The double chain structure is
further stabilized by offset face to face π–π interactions between the π-system of the
salicylidene rings (C9 – C14) of one chain and the delocalized π-system of the six-
membered chelate rings (C14, C15, N3, Cu2, O2, C9) of the other chain (Cg1···Cg2 =
3
.656 Å) [56]. The structural parameters of the different non-covalent interactions in the
double chain structure are listed in Table S2. The double chains are interconnected by a
pair of reciprocal (CH11···O7) hydrogen bonds [58] between the salicylidene ring CH11
protons of one double chain and the coordinated nitrate O7 oxygen atoms of the adjacent
double chain, forming a two-dimensional layer of double chains extended parallel to the
ab-plane. The layers are further assembled together through π–π interactions between the
salicylidene rings (C1 – C6) of one layer and the delocalized π- system of the six-

2
1
membered chelate rings (Cu1, O1, C1, C6, C7, N1) of the adjacent layer (Cg3···Cg4 =
.409 Ǻ) leading to a three - dimensional network in which rectangular channels (ca 5 x 10
Ǻ) are running along c-axis.
The symmetrical molecular units are also connected together by a pair of reciprocal
3
CH⋅⋅⋅π interactions [59] between the salicylidene ring (C17 – C22) CH19 proton and the
neighboring salicylidene ring (C17 – C22) π-system (CH19⋅⋅⋅Cg = 3.725 Ǻ), forming a
linear stepped chain running along b-axis. The chains are further connected to each others
by nitrate anion bridges through (CH23⋅⋅⋅O14) and (NH9⋅⋅⋅O15) hydrogen bonds, leading
2
to a stepped D sheet of symmetrical molecular units extending parallel to the bc-plane. In
4
4
this sheet, the pairs of (CH23⋅⋅⋅O14) and (NH9⋅⋅⋅O15) form a R (16) 16-membered ring
which extends between the adjacent chains.
The three-dimensional network of the unsymmetrical molecular units,
+
[
{Cu(HSalsc)}
2
(NO
3
) H
2
O] , is interpenetrated [59] by the stepped two-dimensional
sheets of symmetrical molecular units, [{Cu(HSalsc)(NO
3
2
)} ], where the sheets of
symmetrical units lie in between the layers of the double chains of the unsymmetrical
molecular units as shown in Figure 5. The symmetrical molecular units occupy the voids
between the unsymmetrical molecular units and are connected together by a series of
hydrogen bonds. The structural parameters of these hydrogen bonds are included in Table
S2.
3
.5.3 X-ray molecular structure and self-assembly of
{Cu(HSalsc)(HIm} ](NO (5):
The X-ray crystal structure of 5, Figure 6, consists of di-µ-phenoxy bridged
dicationic centrosymmetric dimer and nitrate counter anions. In this dication, each Cu(II) is
[
2
3 2
)

2
2
coordinated , in the equatorial plane, to the semicarbazone ligand through the deprotonated
phenolic O2 oxygen, imine N1 nitrogen and ketoamide O1 oxygen. The fourth
coordination site is occupied by the imidazole N3 nitrogen. The phenoxy O2 oxygen acts
as a bridge between the two Cu(II) centers (Cu1⋅⋅⋅⋅Cu1 = 3226 (4) Å) and is situated in the
fifth coordination site. Selected bond distances and bond angles for the di-µ-phenoxy
bridged dicationic centrosymmetric dimer are given in Table 4. The coordination
polyhedron around each Cu1 is better described as a (4 +1) distorted square pyramid. This
is in agreement with the value of the tetragonality parameter [51] τ = [(β – α) / 60 =
o
o
0
.027, where α and β are N1–Cu1–N3 (170.61 ) and O1–Cu1–O2 (172.24 ) angles,
respectively. In this dimer, the two imidazole rings are in trans positions with respect to
each other and are almost perpendicular to the Cu
the imidazole (C9, C10, N4, C11, N3) and Cu
2
O
2
plane. The dihedral angle between
o
2
O
2
plane equals to 85.29 .
In the crystal structure of 5, each nitrate ion is linked to the dimeric unit through a
2
1
chelated R (4) hydrogen bond, (N4H4⋅⋅⋅O3) and (N4H4⋅⋅⋅O), between the imidazole
N4H4 proton and both O3 and O5 oxygen atoms of the nitrate, while the adjacent dimeric
2
2
unit is linked to the nitrate anion through chelated R (6) hydrogen bond, (N5H51⋅⋅⋅O4)
and (N2H2⋅⋅⋅O5), giving rise to a linear one-dimensional chain running parallel to a-axis
(
a-chain) as shown in Figure 7a. The nitrate anion is also linked to a dimeric unit through
2
1
a chelated R (4) hydrogen bond, (N5H52⋅⋅⋅O3), and N5H52⋅⋅⋅O4), between the nitrate
O3 and O4 oxygen atoms and the aminic N5H52 proton of the dimeric unit, while the
2
1
nitrate O4 and O5 oxygen atoms form another chelated R (4) hydrogen bond with the
hydrazinic N2H2 proton of the adjacent dimeric unit. The nitrate O4 and O5 oxygen atoms
2
2
also form a six-membered R (6) hydrogen bond respectively with aminic N5H51and

2
3
hydrazinic N2H2 protons, (N5H51⋅⋅⋅O4) and (N2H2⋅⋅⋅O5), of this dimeric unit. These
intermolecular interactions lead to the formation of one-dimensional wavy chain
propagating parallel to c-axis (c-chain) as shown in Figure 7b. Combination of a- and c-
chains leads to a two-dimensional wavy sheet of dimeric units extending parallel to ac-
plane. The non-covalent bond interactions in the formed sheet together with their structural
parameters are given in Table S3. The formed sheets are further interconnected to each
other through reciprocal π–π interactions between the imidazole π-systems of one sheet
and the delocalized π-system of the 5-membered chelate rings (C1, N2, N1, Cu1, O1) of
the neighboring sheet, thus generating a three-dimensional layered structure.
5
.4 X-ray molecular structure and self-assembly of [Cu(HSalsc)(HIm] OAc (6)
The X-ray crystal structure of 6, Figure 8, consists of the [Cu(HSalsc)(HIm)]
1
+
cation and acetate counter ion. Selected bond distances and bond angles for 6 are listed in
1
+
Table 5. In [Cu(HSalsc)(HIm)] , the Cu(II) is four-coordinate and has a distorted square
-1
planar geometry. The mononegative salicylaldehyde semicarbazone (HSalsc) is
coordinated to the Cu(II) through the deprotonated phenoxy oxygen O2, imine nitrogen
N1and ketoamide O1 oxygen. The fourth coordination site is occupied by the imidazole N3
-
1
nitrogen. Coordination of the planar ONO tridentate (HSalsc) to the Cu1 gives rise to 5-
and 6-membered bicyclic chelate rings which are almost coplanar with the salicylidene
o
ring (dihedral angle = 2.36 ). The imidazole plane (N3, C9, N4, C10, C11) makes an angle
o
of 5.52 with the Cu1 coordination plane (N1, O1, Cu1, O2, N3).
The acetate anion acts as a mediator for hydrogen bonds between the adjacent
cationic units. Both hydrazinic N2H and aminic NH52 protons of each cationic unit form
2
2
R (6) hydrogen bonded 6-membered ring with O4 oxygen of the acetate anion, while the

2
4
2
1
hydrazinic N2H proton is involved in R (4) hydrogen bond formation with both O3 and
O4 oxygen atoms of the acetate anion The (NH2⋅⋅⋅⋅O4) hydrogen bond is a common edge
2
2
between the R (4) and R (6) hydrogen bonded rings. The two hydrogen bond motifs
1
2
2
(
NH2⋅⋅⋅O3) and (NH52⋅⋅⋅O4) form 8-membered R (8) cyclic hydrogen bond. Meanwhile,
2
the O3 acetate oxygen is participating in hydrogen bond formation (NH4⋅⋅⋅O3) with the
imidazole N4H proton, giving rise to a zigzag chain propagating along c-axis. In this chain,
the mean coordination planes of Cu1 of the cationic units are almost perpendicular to each
o
others with dihedral angle of 71.77 . The formed chain is linked to another adjacent chain
via (NH51⋅⋅⋅O4) hydrogen bonds between the aminic NH51 protons and acetate O4
oxygen, leading to a double chain structure as shown in Figure 9. The structural
parameters of the intermolecular non-covalent bond interactions within the double chain
are given in Table S4. The double chains are further interconnected to each other by a pair
of reciprocal (NH51⋅⋅⋅O4) hydrogen bonds between the other semicarbazone NH51 proton
and acetate O4 oxygen, as well as CH⋅⋅⋅π interactions between the CH10 protons of the
imidazole rings of one double chain and the π-system of the salicylidene (C3 – C8) rings of
another double chain, giving rise to a two-dimensional layer of interwoven double chains
extending along the bc-plane.
Conclusion
A series of new Cu(II) complexes 1, 2, 3, 4, 5 and 6 derived from salicylaldehyde
semicarbazone have been prepared and characterized. X-ray crystal and molecular
structures of 1, 2, 5 and 6 clearly showed that the semicarbazone ligand contains both
proton acceptor and proton donor sites capable of forming a variety of supramolecular
architectures through self-assembly process. In the absence of other competing proton

2
5
2
2
acceptor sites, square planar Cu(II) molecular units favour the formation of R (8)
hydrogen bonded dimer through ligand-ligand interactions between the semicarbazone
aminic NH proton and ketoamide oxygen. Semicarbazone hydrazinic and /or aminic NH
protons can form NH···O hydrogen bonds with oxygen atoms of nitrate and acetate
counter ions present in the crystal lattice (ligand – counter ion interactions) giving rise to
infinite double chain structures. In mixed ligand Cu(II) complexes, 5 and 6, the imidazole
NH proton also contributes in double chain formation through NH···O hydrogen bond
with nitrate or acetate oxygen atoms (imidazole – counter ion interactions). Semicarbazone
five- and six-membered delocalized chelate rings can be also involved in chelate ring –
chelate ring or aromatic (salicylidene) ring – chelate ring π – π interactions. These π – π
interactions participate either in the stabilization of the double chain structures or increase
the dimensionality of the formed supramolecular assemblies.
Acknowledgments
Thanks are due to DFG (1.8131e-2/09) for supporting this bilateral project.
Supplementary data
CCDC 1025580, 1025581, 1025582 and 1025583 contain the supplementary
crystallographic data for 1, 2, 5 and 6 respectively. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
3
36-033; or e-mail: deposit@ccdc.cam.ac.uk. Structural parameters of hydrogen bond and
other non-covalent bond interactions of 1, 2, 5 and 6 are respectively listed in Tables S1,
S2, S3 and S4 as supplementary materials.
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