Syntheses, solvatochromism, and antimicrobial activities of new binuclear copper(II) mixed-ligand complexes in a ternary system with β-diketones and diamine ligands

Article abstract of DOI:10.1080/00958972.2011.602402

Ternary complexes of binuclear copper(II) nitrate with bis(β- diketones) [β-diketones = 2-phenyl-1,3-bis-(tetraacetyl-propane), L ₁, or 2-(o-hydroxyphenyl-1,3-bis-(tetraacetyl-propane), L ₂] and diamines [diamines = N,N,N′,N′- tetramethylethylenediamine (tmen), 2,2′-bipyidine (bipy) and 1,10-phenanthroline (phen)] have been synthesized, where [image omitted] groups are counter or coordinated anions. The structures of the complexes and their solvatochromic behavior were investigated by elemental analysis, spectroscopic, magnetic, molar conductance, and thermal analysis. Solvatochromism was observed for only three complexes where they displayed a drastic color change with increasing donor strength of the solvent. This behavior is due to the solute-solvent interaction between the chelate cation and the solvent. Spectroscopic studies of the complexes implicate tetragonal distortions in strongly polar solvents and square planar or square pyramidal geometries in the presence of weakly coordinating molecules. Biological studies of the ligands and their complexes showed a significant inhibition on the growth of selected Gram-positive bacteria and moderate effect against two kinds of Gram-negative bacteria as well as one kind of pathogenic fungi.

Full text of DOI:10.1080/00958972.2011.602402

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Syntheses, solvatochromism, and
antimicrobial activities of new
binuclear copper(II) mixed-ligand
complexes in a ternary system with β-
diketones and diamine ligands
A.A. Abou-Hussein a , Nelly H. Mahmoud a & Wolfgang Linert b
a Faculty of Women for Arts, Science and Education , Ain Shams
University , Heliopolis, Cairo, Egypt
b Institute of Applied Synthetic Chemistry, Vienna University of
Technology , Getreidemarkt, 9/163-AC, 1060 Vienna, Austria
Published online: 26 Jul 2011.
To cite this article: A.A. Abou-Hussein , Nelly H. Mahmoud & Wolfgang Linert (2011) Syntheses,
solvatochromism, and antimicrobial activities of new binuclear copper(II) mixed-ligand complexes
in a ternary system with β-diketones and diamine ligands, Journal of Coordination Chemistry,
64:15, 2592-2605, DOI: 10.1080/00958972.2011.602402
To link to this article: http://dx.doi.org/10.1080/00958972.2011.602402
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Journal of Coordination Chemistry
Vol. 64, No. 15, 10 August 2011, 2592–2605
Syntheses, solvatochromism, and antimicrobial activities
of new binuclear copper(II) mixed-ligand complexes in
a ternary system with b-diketones and diamine ligands
A.A. ABOU-HUSSEINy, NELLY H. MAHMOUDy
and WOLFGANG LINERT*z
yFaculty of Women for Arts, Science and Education,
Ain Shams University, Heliopolis, Cairo, Egypt
zInstitute of Applied Synthetic Chemistry, Vienna University
of Technology, Getreidemarkt, 9/163-AC, 1060 Vienna, Austria
(Received 23 February 2011; in final form 13 June 2011)
Ternary complexes of binuclear copper(II) nitrate with bis(ꢀ-diketones) [ꢀ-diketones ¼
2-phenyl-1,3-bis-(tetraacetyl-propane),
L1,
or
2-(o-hydroxyphenyl-1,3-bis-(tetraacetyl-
propane), L2] and diamines [diamines ¼ N,N,N0,N0-tetramethylethylenediamine (tmen),
2,20-bipyidine (bipy) and 1,10-phenanthroline (phen)] have been synthesized, where NO3ꢀ
groups are counter or coordinated anions. The structures of the complexes and their
solvatochromic behavior were investigated by elemental analysis, spectroscopic, magnetic,
molar conductance, and thermal analysis. Solvatochromism was observed for only three
complexes where they displayed a drastic color change with increasing donor strength of the
solvent. This behavior is due to the solute–solvent interaction between the chelate cation and
the solvent. Spectroscopic studies of the complexes implicate tetragonal distortions in strongly
polar solvents and square planar or square pyramidal geometries in the presence of weakly
coordinating molecules. Biological studies of the ligands and their complexes showed a
significant inhibition on the growth of selected Gram-positive bacteria and moderate effect
against two kinds of Gram-negative bacteria as well as one kind of pathogenic fungi.
Keywords: Mixed-Cu(II) chelates; Ternary complexes; Solvatochromism; Antimicrobial
activities
1. Introduction
Complexes of the Cu(II)-ternary system containing ꢀ-diketones with diamine ligands
are of considerable interest due to their thermochromic properties [1–3]. They can be
used as thermosensitive coloring materials which are chromotropic as a result of
exhibiting color change when exposed to solvent or environmental pollutants [4].
*Corresponding author. Email: wlinert@mail.zserv.tuwien.ac.at
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2011 Taylor & Francis
DOI: 10.1080/00958972.2011.602402

Binuclear copper(II)
2593
Scheme 1. Representative structures for the preparation of 2-phenyl-1,3-bis(tetraacetyl)-propane, L1.
Scheme 2. Representative structures for the preparation of 2-(o-hydroxyphenyl)-1,3-bis-(tetraacetyl)-
propane, L2.
These complexes are also of great importance due to their solvatochromic behavior
since they can be used as Lewis acid–base indicators where the color changes can be
ascribed to d–d transitions with a strong Jahn–Teller effect which explains the regular
changes in their electronic spectra according to the strength of interactions with the
solvent molecules at the axial sites [5–12].
Herein we report the syntheses, spectral, thermal, and solvatochromic behavior of six
new mixed-ligand binuclear copper(II) nitrate complexes with bis(ꢀ-diketones)
[ꢀ-diketones ¼ 2-phenyl-1,3-bis-(tetraacetyl-propane), L1, or 2-(o-hydroxyphenyl-1,
3-bis-(tetraacetyl-propane), L2] and diamines [diamines ¼ N,N,N0,N0-tetramethylethyle-
nediamine (tmen), 2,20-bipyidine (bipy) and 1,10-phenanthroline (phen)], while NO3ꢀ
groups are counter or coordinated anions. The two ligands were prepared by the
method reported in [13] (schemes 1 and 2). Scheme 3 shows that the ligands undergo
tautomeric behavior. The structures of the newly synthesized mixed ligand complexes
were proved by elemental analysis, spectroscopic techniques, and thermal gravimetric
analysis. These copper chelates are easily soluble in various organic solvents and show
color changes due to characteristic solvatochromism phenomenon. Scheme 4 is a
representative structure of Cu(II) mixed-chelate complexes. Thermal decomposition
and kinetics studies were carried out and the parameters (DH, DS, and DG) of all the
thermal decomposition stages have been calculated using the Coats–Redfern equations
[14] (Supplementary material). Microbial studies of the ligands and complexes on
the growth of two Gram-positive bacteria strains (Streptococcus pyogenes and
Staphylococcus aureus), two Gram-negative bacteria (Pseudomonas fluorescens and
Pseudomonas phaseolicola), and one selected pathogenic fungi (Aspergillus fumigates)
have been investigated to assess their biological activities.

2594
A.A. Abou-Hussein et al.
Scheme 3. Representation of the tautomeric forms (I–III) of the ꢀ-diketones, where X ¼ H for L1 or X ¼ OH
for L2. Form IV is a general structure.
Geometry
Complex
N–N
X
Y
Z
G
2NO3–
Square planar
Octahedral
1
2
3
4
5
6
tmen
bipy
phen
tmen
bipy
phen
H
H
–
–
2NO3–
2NO3–
2H2O
–
–
Square pyramidal
Square planar
Octahedral
H
–
–
2NO3–
OH
OH
OH
–
2NO3–
2NO3–
2H2O
2H2O
–
–
Octahedral
Scheme 4. Schematic representation of the mixed-chelate Cu(II) complexes.
2. Experimental
2.1. Materials
Copper nitrate trihydrate Cu(NO3)2ꢁ3H2O, N,N,N0,N0-tetramethylethylenediamine
(tmen), bipy, phen, anhydrous sodium carbonate, benzaldehyde, salicylaldehyde,

Binuclear copper(II)
2595
acetylacetone, and piperidine were of analytical reagent grade and obtained from either
Merck or Aldrich and used without purification. Acetonitrile, methanol, ethanol,
acetone, methylene chloride, DMF, and DMSO used for spectral studies were of
spectro-grade and used without purification.
2.2. Synthesis of 2-phenyl-1,3-bis-(tetraacetyl)-propane, L1
Acetylacetone (50.00 g, 0.50 mol) and benzaldehyde (26.60 g, 0.25 mol) were dissolved
in 50 g of 70% ethanol. Following the addition of 20 drops of piperidine, the mixture
was allowed to stand, solidifying after 1 week. The product (35.40 g) was filtered,
washed with 50% ethanol, and recrystallized from benzene.
2.3. Synthesis of 2-(o-hydroxyphenyl)-1,3-bis-(tetraacetyl)-propane, L2
Acetylacetone (50.00 g, 0.50 mmol) and salicylaldehyde (30.50 g, 0.25 mmol) were
dissolved in 50.00 g of 70% ethanol. About 20 drops of piperidine were added and the
mixture was solidified after 2 days of standing. The product (43.80 g) was filtered,
washed with 50% ethanol, and recrystallized from a mixture of water and 95% ethanol.
2.4. Syntheses of Cu(II) mixed-ligand complexes
These complexes were prepared by adding a mixture of 5.00 mmol of ꢀ-diketone
in 20 mL absolute ethanol and 10.00 mmol of anhydrous Na2CO3 to an ethanolic
solution of 10.00 mmol of Cu(NO3)2ꢁ3H2O. The mixture was stirred for 30 min resulting
in a green solution, which was then filtered. A solution of 10.00 mmol of diamine
represented by tmen, bipy, or phen in 10.00 mL absolute ethanol was added dropwise to
the filtrate under continuous stirring for an additional 30 min. Complexes were filtered
off, left to stand overnight, and then recrystallized from CH2Cl2 where violet
crystals were obtained for [Cu2(L1)(tmen)2](NO3)2 (1) and [Cu2(L2)(tmen)2](NO3)2 (4),
bluish-violet crystals for [Cu2(L1)(phen)2(NO3)2] (3) and green crystals for
[Cu2(L1)(bipy)2(NO3)2(H2O)2] (2), [Cu2(L2)(bipy)2(NO3)2(H2O)2] (5), and [Cu2(L2)
(phen)2(NO3)2(H2O)2] (6). The following detailed preparation routes are given as
examples and the other complexes were obtained similarly.
2.4.1. Synthesis of 1. A mixture of (0.72 g, 5.00 mmol) of 2-phenyl-1,3-bis-(tetra-
acetyl)-propane, (L1) in 20.00 mL absolute ethanol and (1.060 g, 10.00 mmol) of
anhydrous Na2CO3 was added to an ethanolic solution of Cu(NO3)2ꢁ3H2O (1.2079 g,
10.00 mmol). The mixture was stirred for 30 min to give a green solution, which was
filtered. Then a solution of (0.7546 mL, 10.00 mmol) of tmen in 10.00 mL absolute
ethanol was added dropwise to the filtrate under continuous stirring for an additional
30 min. After filtration the complexes were left to stand overnight and then
recrystallized from CH2Cl2 yielding violet crystals. The yield was 1.024 g (77.50%).
2.4.2. Synthesis of 5. A mixture of (0.76 g, 5.00 mmol) of 2-(o-hydroxyphenyl)-1,3-bis-
(tetraacetyl)-propane (L1) in 20.00 mL absolute ethanol and (1.060 g, 10.00 mmol) of

2596
A.A. Abou-Hussein et al.
anhydrous Na2CO3 was added to an ethanolic solution of Cu(NO3)2ꢁ3H2O (1.2079 g,
10.00 mmol). The mixture was stirred for 30 min resulting in a green solution, which was
filtered. Then a solution of (0.99 g, 10.00 mmol) of phen in 10.00 mL absolute ethanol
was added dropwise to the filtrate under continuous stirring for an additional 30 min.
The solution was filtered off, left to stand overnight, and then recrystallized from
CH2Cl2. Green crystals were formed. The yield was 0.8738 g (63.9%).
2.5. Physical measurements
Carbon, hydrogen, and nitrogen analyses were carried out on a Perkin-Elmer 2400
Series II Analyzer. Copper was determined by EDTA solution using muroxide as an
indicator. FT-IR spectra (4000–200 cmꢀ1) of the compounds were recorded using an
FT-IR (Shimadzu) spectrophotometer Model 4000. UV-VIS spectra of the compounds
were obtained on a JASCO model V-550 UV-VIS spectrophotometer. Mass spectra
were obtained on a Shimadzu-GC–MS–QL mass spectrometer model 1000EX using a
direct inlet system. TGA curves were obtained using a NETZSCH-Gerateban Beste
ll-Nr 348472c. The magnetic susceptibilities were measured using a Johnson Matthey
Alfa balance. Diamagnetic corrections were calculated from Pascal’s constants [15] to
obtain the molar paramagnetic susceptibility. Conductance measurements were made
at 25ꢂC with a Corning conductivity meter Model NY 14831 model 441(USA).
2.6. Biological studies
The in vitro biological screening of the synthesized ligands and complexes were
carried out against phytopathogenic bacteria and fungi at the Faculty of Agriculture,
Department of Plant Pathology, Al-Azhar University.
In vitro antibacterial activity studies were carried out using the standardized disc-agar
diffusion method [16] to investigate the inhibitory effect of the synthesized compounds
against Gram-positive bacteria, Sta. aureus (ATCC25923) and Str. pyogenes
(ATCC19615), and Gram-negative bacteria, P. fluorescens (S 97) and P. phaseolicola
(GSPB 2828), as well as the fungi A. fumigatus.
The antibiotic chloramphencol was used as standard reference for Gram-negative
bacteria, cephalothin was used as standard reference for Gram-positive bacteria, and
cycloheximide as antifungal standard reference [17]. An inhibition zone diameter
indicates that the tested compounds are active against bacteria and fungi.
3. Results and discussion
The ternary metal complexes were prepared in the molar ratio 1 : 2 : 2 from bis-
ꢀ-diketone, bidentate nitrogen bases (tmen, bipy and phen), and copper ions in absolute
ethanol. The new bis-ꢀ-diketone possesses two mono basic bidentate dioxide units
on both sides, so the resulting Cu(II) complexes have two positive charges balanced
by nitrates.
The new Cu(II) complexes were identified by ultraviolet, infrared, electronic, mass
spectra, and thermal gravimetric analysis. Solvatochromic properties were studied to

Binuclear copper(II)
2597
investigate the effect of ligands on the chromotropic behavior. The Cu(II) complexes
exhibit square planar, square pyramidal, or octahedral geometrical arrangements. Table
1 lists the physical and analytical data of the complexes.
3.1. Infrared spectra
All the complexes show two weak intensity bands at 2916–2922 and 2827–2884 cmꢀ1
corresponding to asymmetric and symmetric stretching vibrations of the aromatic C–H
groups [18]. The broad band at 3423–3442 cmꢀ1 for 2, 5, and 6 is assigned to ꢁ(OH) of
water, in accord with thermal studies and supported by elemental analyses [19].
One feature in the infrared spectra of the complexes is the coordination behavior of
nitrate. NOꢀ3 is coordinated unidentate for 2, 3, 5, and 6 with three non-degenerate
modes of vibration for C2v symmetry (ꢁs, v0s and ꢁas), where ꢁs(NO3ꢀ) is 1360–1380 cmꢀ1
,
v0s(NOꢀ3 ) 1232–1270 cmꢀ1, and ꢁas(NO3ꢀ) 1018–1027 cmꢀ1. The ꢁs(NOꢀ3 ) of unidentate
NOꢀ3 is markedly shifted to lower frequency compared to that of free nitrate
(1384 cmꢀ1), providing a measure of the covalent bond strength. The frequencies of the
two nitrates in 1 and 4 are at 1384 cmꢀ1 [19, 20]. The molar conductivities of the
complexes in DMF, shown in table 2, reveal that the measured values of 2, 3, 5, and 6
are higher than expected due to uncoordinated nitrates, perhaps DMF replaced NOꢀ3 in
the complexes, resulting in 1 : 1 or 1 : 2 electrolytes [21]. The conductivity data reveal
that NOꢀ3 is only a counter ion for 1 and 4 (Table 2).
Infrared spectra of the ꢀ-diketones in the complexes exhibit two stretching
frequencies at 1637–1697 and 1522–1582 cmꢀ1, assigned to ꢁas(COO) and a single
band at 1457–1484 cmꢀ1 for ꢁs(COO). Generally, the free ꢀ-diketone showed a strong
broad band at 1739 cmꢀ1 [22]. This shift may be due to the chelation of oxygen of the
ꢀ-diketone. These observations are consistent with the presence of a new medium band
at 432–519 cmꢀ1 assigned to ꢁ(Cu–O) [23]. Characteristic bands of tmen, bipy, and
phen [19, 24] are shifted to lower frequencies on complexation. A new medium band
at 520–591 cmꢀ1 appears due to ꢁ(Cu–N) [25].
3.2. Electronic spectra of the complexes in various solvents
The absorption spectra of complexes were measured in different organic solvents with
different donor numbers (DNs) (table 3). The spectra of Cu(II) mixed-chelate
complexes are studied in CH2Cl2 (Supplementary material). The spectra of the ligands
1
1
show four absorptions corresponding to 1La ! A1 and 1Lb ! A1 of the aromatic ring
of phen and bipy, ꢂ ! ꢂ* transition of the phenyl rings of phen and bipy and n ! ꢂ*
from carbonyl of ꢀ-diketones. The transition at 367–479 nm is assigned to
intermolecular charge transfer [26].
The green Cu(II) complexes (1 and 4) have a broad band at 586 and 566 nm, assigned
2
2
to B1g 2A1g of a square planar geometry. The band due to B1g 2Eg may be
obscured by the high-intensity absorption of the ligand. The magnetic moments for 1
and 4 are 1.92 and 1.87 B.M., respectively, in accord with the previous spectral data.
Electronic spectra of 2, 5, and 6 show one unsymmetrical band, 681, 665, and 703 nm,
respectively, assigned to T2g(G) 2Eg transition in a distorted octahedral geometry.
2
The measured value of the magnetic moments for 2, 5, and 6 lie in the range 1.81–178
2
2
B.M., while for 3 absorption spectra show ꢃmax at 609 nm, attributed to B1 ! Eg,

2598
A.A. Abou-Hussein et al.

Binuclear copper(II)
2599

2600
A.A. Abou-Hussein et al.
Table 3. Electronic absorption bands ꢃmax (nm) for the Cu(II) complexes in various organic solvents.
Complex
CH2Cl2
MeCN
Me2CO
EtOH
DMF
DMSO
1
2
3
4
5
6
[Cu2(L1)(tmen)2](NO3)2
586
681
609
566
665
703
592
682
619
578
696
704
626
686
629
589
698
710
637
684
645
604
696
708
664
689
660
647
700
705
684
704
681
669
699
709
[Cu2(L1)(bipy)2(NO3)2(H2O)2]
[Cu2(L1)(phen)2(NO3)2]
[Cu2(L2)(tmen)2](NO3)2
[Cu2(L2)(bipy)2(NO3)2(H2O)2]
[Cu(L2)(phen)2(NO3)2(H2O)2]
Figure 1. Electronic absorption spectra of 1 in different solvents.
corresponding to square-pyramidal structure. The values of the magnetic moment
(1.63 B.M.) confirm the result [27].
The donor number proposed by Gutmann expresses a measure of coordinating
ability of solvent to metal ion [28]. The spectra of the complexes show only one broad
band, shifted to lower wavelength as the donor number of solvent increases [29]. This
shift depends on the diamine ligands which affect the magnitude of in-plane ligand field
strength, the strength of the axial bonds between copper(II) ion and solvent, and finally
the counter ion to neutralize the charge of the Cu(II) mixed chelate complexes.
Thus, while a solvent of lower donor number (basicity) has less effect in the band
maxima, others induce a larger red shift. The positions of the d–d absorption bands
of the complexes were 566–710 nm. Solvatochromism appeared in 1, 3, and 4 with
a color change from violet or bluish-violet through blue to green according to the DN
of the solvent (figure 1). Negative solvatochromism was observed for 2, 5, and 6,
suggesting that short-range interactions between the dipole moment of the solute and
the solvent can induce structural changes in accord with alignment of the transition
moment for ground and excited states of a certain transition [30].
The solvatochromic behavior of 1, 3, and 4 are studied by applying the linear
solvation free energy relationship ꢁmax/103 ¼ ꢁꢂ þ a (DN), where ꢁmax is the measured
d–d absorption frequency, ꢁꢂ is the extrapolated frequency and a is the slope,

Binuclear copper(II)
2601
representing the sensitivity of the complex toward the solvent (table 4). Linearity of ꢁmax
versus DN confirms the solvatochromic behavior of 1, 3, and 4. The slope values (a) are
in the order ([Cu2(L1)(phen)2(NO3)2] 5 [Cu2(L1)(tmen)2](NO3)2 5 [Cu2(L2)(tmen)2]
(NO3)2) (figure 2) [12, 28].
3.3. Mass spectra
The mass spectra of 3 and 5 show molecular ion peaks (table 2) coinciding with the
formula weight of the complexes (Supplementary material).
3.4. Thermal gravimetric analysis
TGA–DrTGA curves of 2 and 4 were chosen as examples (Supplementary material).
The stages of decomposition, temperature ranges as well as the found and calculated
weight loss percentages are given in table 4.
Table 4. Relation between the absorption spectra of the Cu(II) complexes 1, 3, and 4 and the donor number
of the solvent.
(ꢃmax, nm)b, (ꢁmax/103, cmꢀ1 c
)
Solvent
DNa
[Cu2(L1)(tmen)2](NO3)2 (1)
[Cu2(L1)(phen)2(NO3)2] (3)
[Cu2(L2)(tmen)2](NO3)2 (4)
CH2Cl2
MeCN
Me2CO
EtOH
DMF
DMSO
00.00
14.10
17.00
19.10
26.60
29.80
586(17.06)
592(16.89)
626(15.97)
637(15.69)
664(15.06)
684(14.61)
609(16.42)
619(16.15)
629(15.89)
645(15.50)
660(15.15)
681(14.68)
566(17.66)
578(17.30)
589(16.97)
604(16.55)
647(15.45)
669(14.94)
aDonor number of the solvent.
bMaximum absorption in nm.
cReferring to the wavenumber of the d–d transition bands of the complexes.
Figure 2. Solvation free energy relationship between the DN of the solvent and the maximum absorption
max/1000.
ꢁ

2602
A.A. Abou-Hussein et al.
Thermal decomposition of 2 involves three steps, starting at 105ꢂC and finishing at
670ꢂC. The first decomposition involves the removal of two H2O at 105–170ꢂC,
accompanied by a weight loss of 4.502%. The second stage occurs at 170–422ꢂC,
corresponding to the loss of nitrate of NO2 and (L2), accompanied by the weight loss
of 43%. The third stage involves the removal of two bipy’s from 424ꢂC to 670ꢂC,
accompanied by 35% weight loss.
Thermal decomposition of 4 also involves three steps. The first involves loss of
uncoordinated nitrate as two molecules of NO2 at 127–250ꢂC, accompanied by a weight
loss of 21%. The second stage of decomposition occurs from 252 to 410ꢂC,
corresponding to the loss of two tmen molecules (30%). The third stage involves the
removal of L2 at 415–570ꢂC, accompanied by a weight loss of 39%.
4. Biological activities
The results of biological studies of the ligands and complexes are shown in figure 3,
compared with standard antibiotics, chloramphencol for Gram-negative, and cepha-
lothin for Gram-positive bacteria. Cycloheximide was used as standard antifungal
reference. The complexes show higher antimicrobial activity than the ligands in all the
tested strains (table 5), where it showed no inhibitory activity against Gram-negative
strains. Coordination reduces the polarity of the metal [31, 32].
The in vitro antibacterial and antifungal activities (table 6) demonstrate that
complexes with L2 have higher antimicrobial activity than L1 and its complexes;
L1 showed moderate biological activity while L2 has no inhibitory effect against the
tested strains. Complexes 5 and 6 displayed significant inhibition against the growth
Figure 3. Biological screening data of the ligands and Cu(II) complexes against Gram-positive bacteria,
Gram-negative bacteria, and fungi.

Binuclear copper(II)
2603
Table 5. Thermal decomposition stages of Cu(II) complexes.
Decomposition
product
lost (Formula wt.)
DrTGA
peak (ꢂC)
Temperature
range (ꢂC)
Wt. (%)
Found (Calcd)
Complexes
1
2
[Cu2(L1)(tmen)2](NO3)2
256.26
350.17
75.00–310.12
315.00–490.00
2(tmen) þ 2NO2 (324)
42.023 (42.115)
37.461 (37.354)
(L1) (288)
[Cu2(L1)(bipy)2(NO3)2(H2O)2]
[Cu2(L1)(phen)2(NO3)2]
142.00
372.37
526.35
115.00–169.84
170.22–422.74
424.04–670.12
2H2O (36)
NO2 þ (L1) (380)
4.502 (4.068)
43.124 (42.712)
35.293 (35.254)
2(2,20-bipyridine) (312)
3
4
5
252.09
411.89
140.00–277.17
280.00–550.24
2NO2 (92)
2(1,10-phenanthroline) þ
10.371 (10.256)
72.901 (72.241)
(L1) (648)
[Cu2(L2)(tmen)2](NO3)2
248.00
385.00
557.00
127.12–250.00
252.00–410.00
415–570.20
2NO2 (92)
2(tmen) (232)
(L2) (304)
11.788 (11.719)
30.012 (29.554)
38.799 (38.726)
[Cu2(L2)(bipy)2(NO3)2(H2O)2]
130.11
255.08
398.97
87.00–147.48
150.00–296.77
300.14–580.89
2H2O (36)
2NO2 (92)
4.305 (3.996)
10.609 (10.211)
68.564 (68.369)
2(2,20-bipyridine) þ (L2)
(616)
6
[Cu2(L2)(phen)2(NO3)2(H2O)2]
129.78
264.00
371.16
473.08
402.78
537.00
644.16
746.08
2H2O (36)
2NO2 (92)
(L2) (304)
2(1,10-phenanthroline)
(360)
3.998 (3.794)
10.025 (9.695)
32.488 (32.033)
38.024 (37.935)
Table 6. Antimicrobial activity of L1, L2 and their Cu(II) complexes.
Mean of zone diametera, mm (mg mLꢀ1
)
Gram-positive bacteriab Gram-negative bacteriab
Fungib
Complexes
Sta. aureus
Str. pyogenes
P. phaseolicola
P. fluorescens
A. fumigatus
(c)
L1
L2
1
2
3
4
5
6
3 ꢃ 0.4
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
9ꢃ0.1
ꢀ
ꢀ
ꢀ
8 ꢃ 0.1
11 ꢃ 0.2
23 ꢃ 0.1
5 ꢃ 0.2
29 ꢃ 0.2
31 ꢃ 0.2
42
ꢀ
ꢀ
ꢀ
8 ꢃ 0.1
18 ꢃ 0.4
ꢀ
ꢀ
ꢀ
22 ꢃ 0.3
20 ꢃ 0.4
ꢀ
7 ꢃ 0.3
ꢀ
ꢀ
4 ꢃ 0.3
5 ꢃ 0.2
2 ꢃ 0.2
38
23 ꢃ 0.3
26 ꢃ 0.5
38
6 ꢃ 0.1
7 ꢃ 0.3
36
28 ꢃ 0.8
25 ꢃ 0.2
40
Antibioticd
ꢀ represents no inhibitory effect.
(b)
(a)
Calculated from three average values.
Chloramphencol in the case of Gram-positive bacteria, cephalothin in the case of Gram-negative bacteria and
cycloheximide in the case of fungi.
Control.
(d)
of Gram-positive, Gram-negative, and fungi. In contrast, 1 and 4 did not show
inhibition activity on the growth of Str. pyogenes, P. phaseolicola, and A. funigatus.
Complexes 2 and 3 showed antimicrobial activity towards Gram-positive bacteria
superior to that of the Gram-negative bacteria [33, 34].

2604
A.A. Abou-Hussein et al.
5. Conclusions
Binuclear copper(II) bis(ꢀ-diketone) complexes derived from L1 and L2 have been
characterized by different spectroscopic techniques as well as thermal studies.
Solvatochromism is observed in 1, 3, and 4, where the d–d absorptions in weak
donor solvents suggest square-planar or distorted square pyramidal geometries,
confirming the possibility of using these complexes as Lewis acid–base color indicators.
An octahedral structure is identified for 2, 5, and 6, where the electronic transition
occurred in strong donor solvents. Ligands and their complexes exhibit antimicrobial
activity compared with standard antibiotics.
Acknowledgments
Authors thanks the ‘‘Austrian Science Foundation’’ (Project 19335-N17) for financial
support.
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