Different geometries of novel cobalt(II) compounds with 2-hydroxy-benzophenones and neocuproine: Crystal and molecular structures of [Co(2-hydroxy-benzophenone)2(neoc)], [Co(2-hydroxy-4- methoxybenzophenone)(neoc)Br] and [Co(neoc)Br2

Article abstract of DOI:10.1016/j.poly.2012.06.012

Ten mixed-ligand Co(II) compounds with 2-hydroxy-benzophenones(ketones) and neocuproine(neoc) were synthesized and characterized by physicochemical and spectral (IR, UV-Vis) data. The cyclic voltammetry study in CH₃CN gave all the expected wave

Full text of DOI:10.1016/j.poly.2012.06.012

Polyhedron 52 (2013) 1306–1316
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Different geometries of novel cobalt(II) compounds with
2-hydroxy-benzophenones and neocuproine: Crystal and molecular
structures of [Co(2-hydroxy-benzophenone)2(neoc)],
[Co(2-hydroxy-4-methoxybenzophenone)(neoc)Br] and [Co(neoc)Br2]ꢀCH3OHꢀH2O
a
a
b
Maria Lalia-Kantouri a, , Christos D. Papadopoulos , Antonios G. Hatzidimitriou , Michael P. Sigalas ,
⇑
Miguel Quirós c, Stavroula Skoulika d
a Aristotle University of Thessaloniki, Department of Chemistry, Laboratory of Inorganic Chemistry, Thessaloniki 54 124, Greece
b Aristotle University of Thessaloniki, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54 124, Greece
c University of Granada, Department of Inorganic Chemistry, Faculty of Science, Granada 18071, Spain
d University of Ioannina, Department of Chemistry, Laboratory of Physical Chemistry, Ioannina, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 15 June 2012
Ten mixed-ligand Co(II) compounds with 2-hydroxy-benzophenones(ketones) and neocuproine(neoc)
were synthesized and characterized by physicochemical and spectral (IR, UV–Vis) data. The cyclic vol-
tammetry study in CH3CN gave all the expected waves for the redox processes of the metal Co(II) and
the studied ligands. The X-ray diffraction study of two representative compounds proved the two differ-
ent geometries, octahedral for [Co(2-hydroxy-benzophenone)2(neoc)] (3) and trigonal bipyramidal for
[Co(2-hydroxy-4-methoxybenzophenone)(neoc)Br] (10). Additionally, the precursor compound
[Co(neoc)Br2]ꢀCH3OHꢀH2O (11) was proved by (X-ray) to posses tetrahedral geometry. The molecular
structure and the possible isomers of the trigonal bipyramidal complex 10 were studied by means of den-
sity functional calculations (DFT). The thermal stability was investigated by means of simultaneous TG/
DTG–DTA technique in nitrogen atmosphere up to 1000 °C, where metallic cobalt was found as the solid
residue.
Dedicated to Alfred Werner on the 100th
Anniversary of his Nobel Prize in Chemistry
in 1913.
Keywords:
Cobalt
2-Hydroxy-benzophenones
Neocuproine
DFT study
Thermal study
Crystal structures
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
ever, of cobalt chelates with 2,9-dimethyl-1,10-phenanthroline
(neocuproine, neoc) there is a pronounced reduction in coordina-
Both 1,10-phenanthrolines and 2,20-bipyridines are attractive
building blocks in organic chemistry, strongly chelating for a vari-
ety of metal ions [1]. Metal-ion complexes with functionalized
1,10-phenanthrolines and 2,20-bipyridines have been used as cata-
lyst for the enantioselective hydrolysis of N-protected amino acid
esters [2], in the oxidative cleavage of DNA [3] and in palladium
catalyzed allylic substitution [4]. Specifically, cobalt chelates with
2,20-bipyridine (bipy) or 1,10-phenanthroline (phen) possess vari-
ous geometries forming cationic octahedral complexes, e.g. [Co(bi-
py)3]2+ and [Co(phen)3]2+ [5], which are known to have important
biological properties [6], or neutral octahedral complexes of the
type [Co(bipy)2Br2] and [Co(phen)2Br2], or even cationic square-
pyramidal complexes of the type [Co(bipy)2Br]+. In the case, how-
tion geometry at the metal center, from octahedral in solution,
[Co(neoc)(H2O)4]2+ to tetrahedral in solid state, [Co(neoc)(SiO)2]2+
and [Co(neoc)(SCN)2] [7] or [Co(neoc)Br2] in this work.
Besides, the strong coordinating properties of 2-hydroxy-benz-
ophenones or 2-hydroxy-benzaldehydes (salicylaldehyde, saloH)
and their derivatives with 3d transition metals have stimulated re-
search in these compounds, which find applications in both pure
[8] and applied chemistry fields, especially in extractive metallurgy
as analytical reagents [9,10] and specifically for cobalt compounds
in tyre industry as adhesion promoters [11]. These ligands are
known to coordinate in a bidentate manner with transition metals
in the mono-anionic form, adopting square-planar geometry,
[Zn(salo)2], [Zn-5-Br-salo] [12], [Cu(5-Br-salo)2] [13], [FeII(salo)2]
[14] or octahedral arrangement [VO(3-OCH3-salo)2(H2O)] [15],
[FeIII(2-hydroxy-propiophenone)3] [16].
⇑
Corresponding author. Tel./fax: +30 2310 997844.
For a better understanding of the bonds and properties in these
compounds we have initiated a research project with the metals
cobalt and iron and ligands with N and/or O donor atoms. The
E-mail addresses: lalia@chem.auth.gr (M. Lalia-Kantouri), hatzidim@chem.auth.
gr (A.G. Hatzidimitriou), sigalas@chem.auth.gr (M.P. Sigalas), mquiros@ugr.es
(M. Quirós), vskoul@uoi.gr (S. Skoulika).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.06.012

M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
1307
Scheme 1. Structural formulae of the 2-hydroxy-phenone ligands.
Lewis acidity of [CoII(salo)2] chelates, renders them susceptible to
nucleophilic attack and addition compounds can be obtained, such
as [Co(salo)2( -diimines)] (where -diimines are bipy, phen or
neoc) [17,18]. Recently, from the reaction of the precursor
compound [Co(bipy)2Br2] or [Co(phen)2Br2] with the anion of a
2-hydroxy-phenone ligand(keto), the addition compounds with
octahedral geometry [CoII(keto)2(bipy)]ꢀHketo or [CoII(keto)2
(phen)] have been obtained [19].
2.2. Instrumentation/analytical procedures
a
a
Microanalyses were carried out using a Perkin-Elmer 240 B CHN
microanalyzer and Perkin-Elmer 5100 PC Atomic Absorption Spec-
trophotometer for the metal content. Infrared spectra were re-
corded on a Perkin-Elmer 1600 FT-IR spectrometer in KBr discs
at room temperature and are reported in cmꢁ1. Electronic absorp-
tion spectra in CH3CN solutions were obtained on a Shimatzu 160 A
spectrometer. Molar conductivities were measured in CH3CN solu-
tions, employing a WTW conductivity bridge and a calibrated dip
type cell. Magnetic susceptibility measurements on powdered
samples were performed at 25 °C employing the Faraday method
on a home-build balance calibrated against Hg[Co(SCN)4].
Continuing our research, we present here the results of the
reaction of the precursor compound [Co(neoc)Br2] with the anion
of a 2-hydroxy-benzophenone ligand(keto). This reaction led to
the formation and isolation of two groups of neutral cobalt(II) com-
pounds with two different geometries each one, depending on the
metal-to-ligand stoichiometric ratio. The crystal and molecular
structures of two representative compounds, each one from the
two groups, as well as of the precursor compound were verified
by X-ray diffraction analysis. The thermal stability and decomposi-
tion mode for three of the new compounds were studied in
nitrogen atmosphere by using the simultaneous technique (TG/
DTG–DTA). Results of density functional (DFT) calculations for
compound [Co(opo)(neoc)Br] were used to explore the possibility
for the compound to adopt different conformations.
The 2-OH-benzophenones presented in this work have the
molecular formula 2-OH-C6H4C(R)O, where R = CH3, C2H5 or C6H5,
commonly known and abbreviated as 2-OH-acetophenone(Hapo)
(10), 2-OH-propiophenone(Hppo) (20), 2-OH-benzophenone(Hbpo)
(30), respectively, as well as their derivatives 2-OH, 5-CH3-aceto-
phenone(Hmpo) (40) and 2-OH, 4-OCH3-benzophenone(Hopo)
(50), (Scheme 1).
Cyclic voltammetry technique (CV) was used for the electro-
chemical measurements on a
l-AUTOLAB Potentio-Galvanostat
(ECO CHEMIE, Netherlands). A saturated calomel electrode was
used as a reference electrode and a platinum plate one as an auxil-
iary electrode for all measurements. As a working electrode a plat-
inum wire was used. The tests in CH3CN solution were carried out in
the potential region ꢁ1900 to +2200 mV at ambient temperature.
Recrystallized TEA perchlorate 0.1 M was used as the electrolyte
at a scan rate 100 mV/s. All scans were recorded in degassed
solvent, under current of moisture free argon over the solution
surface. The thermal behavior of the title compounds was studied
in nitrogen using the simultaneous TG/DTG–DTA technique, over
the temperature range ambient-to-980 °C, using a Setaram Model
Setsys-1200 thermogravimetric analyzer. The samples, with a mass
of about 12 mg were heated in platinum crucibles, at a heating rate
5 and/or 10 °C/min.
2.2.1. Computational details
2. Experimental
The electronic structure and geometries of the complexes stud-
ied were computed within the density functional theory (DFT)
using gradient corrected functional, at the Becke3LYP computa-
tional level [20,21]. The effective core potential (ECP) approxima-
tion of Hay and Wadt was used [22–24]. For Co atom, the
electrons described by the ECP were those of 1s, 2s and 2p shells.
The basis set used was of valence double-f quality [25]. Full geom-
etry optimizations were carried out without symmetry constraints.
A frequency calculation after each geometry optimization ensured
that the calculated structures are real minima or transition states
2.1. Materials
The ligands, 2-hydroxy-phenones (10–50), the 2,9-dimethyl-
1,10-phenanthroline, neocuproine, abbreviated as neoc), and the
metal salt CoBr2ꢀ6H2O were obtained as reagent grade from Aldrich
and used as received. Solvents for preparation and physical mea-
surements of ‘‘extra pure’’ grade were obtained from Fluka without
further purification.

1308
M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
in the potential energy surface of the molecules and allowed the
calculation of the zero point energy. All the calculations were per-
formed using the GAUSSIAN-03W version 6.0 package [26].
expected positions. All those belonging to the ligands except them
of the methyl group were positioned geometrically, while the rest
were refined using soft restraints on the bond lengths and angles to
regularize their geometry (C–H bonds and angles to 1.00 (Å) and
109 (°), and O–H bonds to 0.90 (Å), angles to 109 (°)). After the
non hydrogen atoms anisotropic refinement, all hydrogen atoms
positions were refined with riding constraints. A summary of the
crystallographic data is listed in Table 1.
2.3. X-ray structural determination
Crystals for compounds [Co(bpo)2(neoc)] (3) (orange-brownish)
and [Co(opo)(neoc)Br] (10) (dark-green) were obtained from the
reaction mixture after slow evaporation. Crystals (green-blue bars)
of the precursor [Co(neoc)Br2]ꢀCH3OHꢀH2O (11), suitable for X-ray,
were prepared by recrystallization from methanol. Crystals of com-
pound 3 were mounted on a Brucker P4 diffractometer employing
Mo Ka radiation. The data collection was accomplished by operat-
ing the diffractometer in the xscan mode using the scintillation
method at ambient temperature. Crystals of compound 10 were
2.4. General procedure for the preparation of the cobalt(II) compounds
2.4.1. Preparation of the compounds [Co(2-OH-benzophenone)2(neoc)]
(1–5)
All complexes have been prepared by the following general pro-
cedure. A solution of 1 mmol 2-hydroxy-benzophenone and CH3O-
Na (1 mmol) in MeOH (30 mL), was added drop-wise to a solution
of [Co(neoc)Br2] (0.5 mmol) in H2O (20 mL) at room temperature,
according to the reaction:
mounted on a Bruker SMART APEX CCD system with Mo K
tion (k = 0.71073 Å). The data collection was accomplished by
operating the diffractometer in the / and scans mode modes
at ambient temperature. Crystals of compound 11 were mounted
on a CAD4 automatic diffractometer employing Mo K radiation.
a radia-
x
½CoðneocÞBr2ꢂ þ 2ketoH þ 2CH3ONa ! ½CoðketoÞ2ðneocÞꢂ
þ 2NaBr þ 2CH3OH
a
The lattice parameters were calculated by least squares refinement
of 25 strong reflections (17° < h < 19°) which were specifically
measured for this purpose. The collection of the reflections was
The solution was stirred for 2 h and then turned darker and an or-
ange-brownish solid was formed. The solid was filtered, washed
with water and dried in vacuo (mean yield 62%). All compounds
were prepared in inert, under argon, conditions and well degassed
solutions have been used.
accomplished by operating the diffractometer in the
mode at ambient temperature.
x/2h scan
All crystals were air and beam stable during the data collection.
The point group’s determination was followed by the position
determination of the non hydrogen atoms using SUPERFLIP program
[27] for 11 and SHELXS-97 [28a] for compounds 3 and 10. Subse-
quent calculations and data refinement were finalized using SHEL-
XL-97 [28b] for 3 and 10 and CRYSTALS version 12.83 [29] for
compound 11. All hydrogen atoms were revealed to be at their
2.4.1.1. Synthesis of [Co(apo)2(neoc)] (1). The compound was pre-
pared according to the general procedure by employing 2-OH-ace-
tophenone(Hapo) (136 mg, 1 mmol) and CH3ONa (54 mg, 1 mmol)
in MeOH (25 mL), to [Co(neoc)Br2] (0.214 g, 0.5 mmol) in H2O
(20 mL) at room temperature, under argon atmosphere. The
Table 1
Crystal data and structure refinements for compounds [Co(bpo)2(neoc)] (3), [Co(opo)(neoc)Br] (10) and [Co(neoc)Br2]ꢀCH3OHꢀH2O (11).
3
10
11
Empirical formula
Formula weight (g mol)
C
40H30CoN2O4
C28H23BrCoN2O3
574.32
C15H18Br2Co1N2O2
477.06
661.59
k (Å)
Crystal system
Space group
0.71073
monoclinic
P21/c
0.71073
monoclinic
P21/n
0.71073
monoclinic
P21/n
Unit cell dimensions
a (Å)
b (Å)
c (Å)
11.3689(17)
16.701(2)
17.007(3)
92.090(3)
3226.9(8)
4
9.658(2)
23.556(3)
11.002(1)
100.97(1)
2457.3(6)
4
7.933(5)
13.123(7)
18.211(9)
101.96(2)
1854.7(18)
4
b (°)
V (Å3)
Z
Calculated density
1.362
1.552
1.708
(mg mꢁ3
)
Absorption coefficient
(mmꢁ1
F(000)
0.577
2.358
5.240
)
1372
1164
940
Crystal size (mm)
h range for data collection
(°)
0.49 ꢃ 0.24 ꢃ 0.22
0.13 ꢃ 0.11 ꢃ 0.10
0.19 ꢃ 0.20 ꢃ 0.27
1.71–28.38
2.07–25.00
1.93–25.67
Limiting indices
Reflections observed/
unique
ꢁ13 6 h 6 15,ꢁ21 6 k 6 20,ꢁ21 6 l 6 20 0 6 h 6 11,ꢁ1 6 k 6 28,ꢁ13 6 l 6 12
ꢁ9 6 h 6 9,0 6 k 6 16,0 6 l 6 22
5082/3522 (R(int) = 0.021)
20209/7408 (R(int) = 0.0327)
4760/4301 (R(int) = 0.0265)
Completeness
Refinement method
Weighting scheme
99.0% to h = 25.58
99.4% to hmax
99.9% to hmax
Full-matrix least-squares on F2
Full-matrix least-squares on F2
Full-matrix least-squares on F2
w = 1/[
r
2(Fo2)+(0.07P)2 + 0.7P] where
w = 1/[r r
2(Fo2)+(0.0532P)2 + 5.8035P] where w = 1/[ 2(F2) + (0.07P)2 + 1.03P] where
P = (Fo2 + 2Fc2)/3
7408/426
P = (Fo2 + 2Fc2)/3
4301/316
1.056
P = (max(Fo2,0) + 2Fc2)/3
3486/199
1.010
Data/parameters
Goodness-of-fit on F2
1.037
R1, wR2 [I > 2
R1, wR2 (all data)
r
(I)]
0.0550, 0.1283
0.0733, 0.1380
0.607/ꢁ0.277
0.0454, 0.1151
0.0722, 0.1325
0.509/ꢁ0.512
0.0310, 0.0680
0.0356, 0.0704
0.48/ꢁ0.57
Largest difference in peak/
hole (e Åꢁ3
)

M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
1309
The solution was stirred for 2 h and then turned darker and a dark-
greenish solid was formed. The solid was filtered, washed with
water and dried in vacuum (mean yield 56%). All compounds were
prepared in inert, under argon, conditions and well degassed solu-
tions have been used.
crystalline orange-brownish compound (0.17 g, 61% yield), ana-
lyzed as Anal. Calc. for C30H28N2O5Co1 (MW 537): C, 67.06; H,
4.84; N, 5.21; Co, 10.98. Found: C, 66.85; H, 4.82; N, 5.12; Co,
10.75%. Magnetic value (leff = 4.10 lB), conductivity in freshly pre-
pared CH3CN solutions (9.2 lS/cm). IR spectrum (KBr): selected
peaks in cmꢁ1: 1604 vs 1590 vs 1361 s, 859 m, 731 s, 552 m, 454
m. UV–Vis bands in nm: 345, 400(sh), 660, 995.
2.4.2.1. Synthesis of [Co(apo)(neoc)Br] (6). The compound was pre-
pared according to the general procedure by employing 2-OH-ace-
tophenone(Hapo) (136 mg, 1 mmol) and CH3ONa (54 mg, 1 mmol)
in MeOH (25 mL), to [Co(neoc)Br2] (0.427 g, 1 mmol) in H2O
(20 mL). The dark-green crystalline compound (0.26 g, 52% yield),
analyzed as Anal. Calc. for C22H21Br1N2O3Co1 (MW 482): C, 54.77;
H, 3.94; N, 5.81; Co, 12.24. Found: C, 54.44; H, 3.90; N, 5.68; Co,
2.4.1.2. Synthesis of [Co(ppo)2(neoc)] (2). The compound was pre-
pared according to the general procedure by employing 2-OH-pro-
piophenone(Hppo) (150 mg, 1 mmol) and CH3ONa (54 mg,
1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.214 g, 0.5 mmol)
in H2O (20 mL). The crystalline orange-brownish compound
(0.20 g, 71% yield), analyzed as Anal. Calc. for C32H30N2O4Co1
(MW 565): C, 67.96; H, 5.30; N, 4.95; Co, 10.44. Found: C, 68,04;
12.08%. Magnetic value (leff = 4.20 lB), conductivity in freshly pre-
pared CH3CN solutions (9.3 lS/cm), IR spectrum (KBr): selected
peaks in cmꢁ1: 1601 vs 1581 vs 1363 s, 860 m, 733 s, 565 m,
430 m, 303 m, 215 w. UV–Vis bands in nm: 325, 420(sh), 520, 590.
H, 5.26; N, 4.87; Co, 10.50%. Magnetic value (leff = 4.08 lB), con-
ductivity in CH3CN 7.12 lS/cm. IR spectrum (KBr): selected peaks
in cmꢁ1: 1611 vs 1594 vs 1376 s, 861 m, 732 s, 552 m, 450 m.
UV–Vis bands in nm: 345, 402(sh), 663, 995.
2.4.2.2. Synthesis of [Co(ppo)(neoc)Br] (7). The compound was pre-
pared according to the general procedure by employing 2-OH-pro-
piophenone(Hppo) (150 mg, 1 mmol) and CH3ONa (54 mg,
1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.427 g, 1 mmol) in
H2O (20 mL). The dark-green crystalline compound (0.29 g, 58%
yield), analyzed as Anal. Calc. for C23H21Br1N2O2Co1 (MW 496): C,
55.64; H, 4.23; N, 5.64; Co, 11.89. Found: C, 55,10; H, 4.78; N,
2.4.1.3. Synthesis of [Co(bpo)2(neoc)] (3). The compound was pre-
pared according to the general procedure by employing 2-OH-ben-
zophenone(Hbpo) (198 mg, 1 mmol) and CH3ONa (54 mg, 1 mmol)
in MeOH (25 mL), to [Co(neoc)Br2] (0.214 g, 0.5 mmol) in H2O
(15 mL) The crystalline compound (0.17 g, 51% yield), analyzed as
Anal. Calc. for C40H30N2O4Co1 (MW 661): C, 71.33; H, 4.59; N, 4.33;
Co, 8.92. Found: C, 72.62; H, 4.54; N, 4.23; Co, 8.97%. Magnetic value
5.58; Co, 11.84%. Magnetic value (
leff = 4.22 lB), conductivity in
CH3CN 8.20
l
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1
:
(leff = 4.15 lB), conductivity in CH3CN 6.43 lS/cm. IR spectrum
1609 vs 1588 vs 1372 s, 855 m, 745 s, 560 m, 415 m, 301 m, 215
w. UV–Vis bands in nm: 318, 420(sh), 525, 595.
(KBr): selected peaks in cmꢁ1: 1603 vs 1587 vs 1354 s, 854 m, 759
s, 592 m, 411 m. UV–Vis bands in nm: 345, 400(sh), 670, 990.
2.4.2.3. Synthesis of [Co(bpo)(neoc)Br] (8). The compound was pre-
pared according to the general procedure by employing 2-OH-ben-
zophenone(Hbpo) (198 mg, 1 mmol) and CH3ONa (54 mg, 1 mmol)
in MeOH (25 mL), to [Co(neoc)Br2] (0.427 g, 1 mmol) in H2O
(20 mL). The dark-green crystalline compound (0.27 g, 50% yield),
analyzed as Anal. Calc. for C27H21Br1N2O2Co1 (MW 544): C, 59.56;
H, 3.86; N, 5.14; Co, 10.84. Found: C, 59.61; H, 3.91; N, 5.32; Co,
2.4.1.4. Synthesis of [Co(mpo)2(neoc)] (4). The compound was pre-
pared according to the general procedure by employing 2-OH, 5-
CH3-acetophenone(Hmpo) (150 mg, 1 mmol) and CH3ONa (54 mg,
1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.214 g, 0.5 mmol) in
H2O (15 mL). The crystalline compound (0.19 g, 67% yield), ana-
lyzed as Anal. Calc. for C32H30N2O4Co1 (MW 565): C, 67.96; H,
5.31; N, 4.95; Co, 10.44. Found: C, 68.03; H, 5.40; N, 4.87; Co,
10.80%. Magnetic value (
leff = 4.29 lB), conductivity in CH3CN
10.40%. Magnetic value (
leff = 4.12 lB), conductivity in CH3CN
9.50
l
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1: 1602 vs
5.7
l
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1: 1605 vs
1582 vs 1351 s, 850 m, 731 s, 550 m, 417 m, 305 m, 218 w. UV–
Vis bands in nm: 320, 418(sh), 520, 590.
1594 vs 1359 s, 856 m, 730 s, 551 m, 401. UV–Vis bands in nm:
345, 405(sh), 660, 998.
2.4.2.4. Synthesis of [Co(mpo)(neoc)Br] (9). The compound was pre-
pared according to the general procedure by employing 2-OH, 5-
CH3-acetophenone(Hmpo) (150 mg, 1 mmol) and CH3ONa
(54 mg, 1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.427 g,
1 mmol) in H2O (20 mL). The crystalline compound (0.32 g, 65%
yield), analyzed as Anal. Calc. for C23H21Br1N2O2Co1 (MW 496): C,
55.65; H, 4.23; N, 5.64; Co, 11.89. Found: C, 55.82; H, 4.84; N,
2.4.1.5. Synthesis of [Co(opo)2(neoc)] (5). The compound was pre-
pared according to the general procedure by employing 2-OH, 4-
OCH3-benzophenone(Hopo) (228 mg, 1 mmol) and CH3ONa
(54 mg, 1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.214 g,
0.5 mmol) in H2O (15 mL). The crystalline compound (0.21 g, 58%
yield), analyzed as Anal. Calc. for C42H34N2O6Co1 (MW 721): C,
69.90; H, 4.71; N, 3.88; Co, 8.18. Found: C, 69.54; H, 4.80; N,
5.30; Co, 11.85%. Magnetic value (
leff = 4.19 lB), conductivity in
3.91; Co, 8.20%. Magnetic value (
leff = 4.30 lB), conductivity in
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1
:
CH3CN 8.7
l
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1
:
CH3CN 8.6
l
1603 vs 1590 vs 1360 s, 853 m, 731 s, 560 m, 420, 303 m, 216 w.
UV–Vis bands in nm: 325, 412(sh), 522, 593.
1604 vs 1584 vs 1371 s, 857 m, 730 s, 549 m, 418 m. UV–Vis bands
in nm: 343, 402(sh), 670, 992.
2.4.2.5. Synthesis of [Co(opo)(neoc)Br] (10). The compound was pre-
pared according to the general procedure by employing 2-OH, 4-
OCH3-benzophenone(Hopo) (228 mg, 1 mmol) and CH3ONa
(54 mg, 1 mmol) in MeOH (25 mL), to [Co(neoc)Br2] (0.427 g,
1 mmol) in H2O (20 mL). The crystalline compound (0.31 g, 54%
yield), analyzed as Anal. Calc. for C28H23Br1N2O3Co1 (MW 574): C,
58.53; H, 4.00; N, 4.87; Co, 10.27. Found: C, 58.56; H, 4.05; N,
2.4.2. Preparation of the compounds [Co(2-OH-
benzophenone)(neoc)Br] (6–10)
All complexes have been prepared by the following general pro-
cedure. A solution of 0.5 mmol 2-hydroxy-benzophenone and
CH3ONa (0.5 mmol) in MeOH (20 mL), was added drop-wise to a
solution of [Co(neoc)Br2] (0.5 mmol) in H2O (20 mL) at room tem-
perature, according to the reaction:
4.91; Co, 10.25%. Magnetic value (
leff = 4.17 lB), conductivity in
CH3CN 7.6
l
S/cm. IR spectrum (KBr): selected peaks in cmꢁ1
:
½CoðneocÞBr2ꢂ þ ketoH þ CH3ONa ! ½CoðketoÞðneocÞBrꢂ þ NaBr
þ CH3OH
1606 vs 1584 vs 1368 s, 855 m, 733 s, 550 m, 417 m, 303 m, 217
w. UV–Vis bands in nm: 320, 420(sh), 520, 590.

1310
M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
2.4.3. Synthesis of the precursor compound [Co(neoc)Br2]ꢀCH3OHꢀH2O
(11)
The precursor compound [Co(neoc)Br2] was prepared according
to known procedure [30,18], by reacting CoBr2 with neocuproine in
a metal to ligand ratio 1:2, in CH3CN solution and reflux for 2 h un-
der argon atmosphere. Air stable green-blue crystals, suitable for
X-ray collected after 5 days by recrystallization from methanol.
3. Results and discussion
3.1. Synthesis and characterization
The reaction of the precursor compound [Co(neoc)Br2] with the
anion of a 2-OH-phenone ligand (keto), under proper inert condi-
tions, led to the formation of two groups of cobalt(II) compounds
with two different geometries each one, depending on the metal-
to-ligand stoichiometric ratio. Thus, 1 mmol of a deprotonated
substituted 2-OH-phenone ligand reacted with 0.5 mmol of [Co(n-
eoc)Br2] under argon (1:2 ratio) to give five microcrystalline or-
ange-brown products of the first group. The elemental analyses
and the absence of electrical conductivity in CH3CN solutions indi-
cated neutral adduct compounds, with the general formulae [Co(-
keto)2(neoc)] (1–5). When, however, 1 mmol of a deprotonated
substituted 2-OH-phenone ligand reacted with 1 mmol of [Co(n-
eoc)Br2] under argon (1:1 ratio) the products formed were five
deep-green microcrystalline solids belonging to the second group.
The elemental analyses and the absence of electrical conductivity
in CH3CN solutions indicated neutral mixed-ligand complexes with
the general formulae [Co(keto)(neoc)Br] (6–10).
Fig. 1. Clinographic projection of [Co(bpo)2(neoc)] (3) with displacement ellipsoids
drawn at the 50% probability level. Hydrogen atoms have been omitted.
All new compounds are stable in air, soluble in almost all the or-
ganic solvents, but insoluble in diethylether and water. The exper-
imental magnetic moments at room temperature for the studied
compounds of both groups (mean value
with high-spin Co(II) complexes, in accordance with other analo-
l
eff = ꢄ4.2
lB) corroborate
gous compounds [31,32].
The coordination mode of the ligands in the new cobalt com-
pounds was examined using spectroscopic methods (IR and elec-
tronic excitation (UV–Vis) spectra). The X-ray crystallographic
analysis for two of them (one compound from each group, that is
[Co(bpo)2(neoc)] (3) and [Co(opo)(neoc)Br] (10)) provided evi-
dence regarding the different geometry around cobalt(II) ion and
the configuration of the ligands. Moreover, X-ray study of the pre-
cursor compound [Co(neoc)Br2)]ꢀCH3OHꢀH2O (11), proved this to
possess a tetrahedral geometry with the bromide ions coordinated
to the cobalt atom.
3.2. Description of the structures
Compounds [Co(bpo)2(neoc)] (3) and [Co(opo)(neoc)Br] (10)
crystallize in the Monoclinic crystal system with space groups
P21/c and P21/n, respectively. Figs. 1 and 2 depict the clinographic
projection of the molecules, with displacement ellipsoids drawn at
the 50% probability level, produced with the CAMERON program [33],
while selected distances (Å) and bond angles (°) are given in Tables
2 and 3.
In both compounds 3 and 10 the cobalt atom is coordinated to
the 2-OH-benzophenone and neocuproine ligands in a bidendate
mode. The compounds exhibit different coordination geometries
since in the structure of 3 the coordination number is six, while
in the case of 10 the coordination number is five. In the unit cell
of compound 3, [Co(bpo)2(neoc)] four neutral complexes can be
Fig. 2. Clinographic projection of [Co(opo)(neoc)Br] (10) with displacement ellip-
soids drawn at the 50% probability level.
the neocuproine ligands in a parallel arrangement at distances of
3.34 Å. The molecular structure (Fig. 1) reveals a distorted octahe-
dral coordination symmetry around the metal ion with the most
axial vector passing through O(2A), Co and N(1N). If O(2A) and
N(1N) would be considered to occupy the axial positions, then
O(1A), O(1B), N(10N) and O(2B) form the equatorial coordination
found. These four molecules are arranged in a way that,
p
ꢁ
p inter-
actions between the delocalized electronic systems coming from
p
the neocuproine ligands of neighboring molecules, are stacking
them together. These considerably strong interactions are keeping

M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
1311
Table 2
plane. All coordination distances and angles are similar with those
reported in analogous complexes [19,34]. The atoms forming the
equatorial plane present a maximum deviation 0.102(14) Å from
it (for O(2B)), while the Co(II) cation was found to be 0.003(15) Å
lower of the plane (with a deviation smaller than the error). The
neocuproine moiety was found to be practically planar with devi-
ations smaller or equal than the error as well as the phenyl rings of
the 2-OH-benzophenone ligands. The dihedral angle between the
mean equatorial plane and the neocuproine ligand was found to
be 71.98°. The dihedral angles formed between the phenyl rings
of each 2-OH-benzophenone ligand with the equatorial plane were
54.23° and 67.89°.
Selected bond lengths (Å) and angles (°) for 3.
Co–O(1A)
Co–O(1B)
Co–O(2A)
Co–O(2B)
Co–N(1N)
Co–N(10N)
1.9749(17)
2.0278(17)
2.0971(17)
2.1101(17)
2.176(2)
2.179(2)
171.23(7)
O(1A)–Co–O(1B)
O(1A)–Co–O(2A)
O(1B)–Co–O(2A)
O(1A)–Co–O(2B)
O(1B)–Co–O(2B)
O(2A)–Co–O(2B)
O(1A)–Co–N(1N)
O(1B)–Co–N(1N)
O(2A)–Co–N(1N)
O(2B)–Co–N(1N)
O(1A)–Co–N(10N)
O(1B)–Co–N(10N)
O(2A)–Co–N(10N)
O(2B)–Co–N(10N)
N(1N)–Co–N(10N)
85.61(7)
87.86(7)
89.82(7)
83.73(7)
84.52(7)
96.91(7)
89.88(7)
176.47(7)
97.94(7)
97.33(7)
89.61(7)
100.57(7)
171.49(7)
76.69(8)
The crystal structure of 10, [Co(opo)(neoc)Br] contains four
mononuclear neutral Co(II) complex moieties present in the unit
cell. Each mononuclear complex moiety (Fig. 2) is strongly interact-
ing with two neighboring molecules with strong
These are arising from the neocuproine delocalized
p
ꢁ
p
interactions.
p
system to the
same system from a neighboring molecule, with the two systems
being virtually parallel and lying at a distance of 3.29 Å. The same
p
system is also interacting with the phenyl ring of an another
neighboring complex moiety being almost planar to it, with an
angle of 8.11° and in a distance of 3.36 Å, as shown in Fig. 3.
The molecular structure of compound 10 (Fig. 2) consists from a
metal cation bonded to one 2-OH-benzophenone and one neocupr-
oine ligand, both in a chelate bidentate mode. The five-membered
metal coordination sphere is accomplished by one bromine atom.
The bond distances and the bite angles of both the organic ligands
are similar to those found at other analogous cobalt complexes
[35a,35b].
The bond distances and angles of the coordinated atoms
(Table 2) as well as the tau value proposed from Addison et al.
[36], could led us to propose trigonal bipyramidal geometry for
the five-membered coordination sphere around cobalt. Generally
Table 3
Selected bond lengths (Å) and angles (°) for 10.
Co–O(2)
Co–O(1)
1.972(3)
2.068(4)
Co–N(1)
2.109(4)
Co–N(2)
2.141(4)
Br(1)–Co
2.4562(10)
86.08(14)
121.63(16)
104.66(16)
84.86(15)
170.67(15)
78.40(17)
129.81(12)
92.11(11)
107.34(11)
95.38(12)
O(2)–Co–O(1)
O(2)–Co–N(1)
O(1)–Co–N(1)
O(2)–Co–N(2)
O(1)–Co–N(2)
N(1)–Co–N(2)
O(2)–Co–Br(1)
O(1)–Co–Br(1)
N(1)–Co–Br(1)
N(2)–Co–Br(1)
s
= (b ꢁ
midal geometry while values close to one indicate trigonal bypira-
midal geometry. In our case, as and b are the values of the angles
N(2)–Co–O(1) = 170.67 and N(1)–Co–Br(1) = 107.34, respectively,
= 1.0555, value very close to one and the geometry around cobalt
could be virtually considered as trigonal bipyramidal.
a)/60 and values close to zero indicate square-based pyra-
a
s
Fig. 3. Projection along c axis of a part of the structure of compound 10 presenting the two types of intra molecular p–p aromatic interactions.

1312
M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
B3LYP. Fig. 5 shows the optimized structure, whereas selected cal-
culated bond lengths and angles concerning the coordination
sphere are given in Table 5. Mean experimental bond lengths
determined by X-ray structure analysis are also given for compar-
ison. The final optimized structure is a distorted trigonal bipyrami-
dal structure with the nitrogen, the phenolic oxygen and the
bromine atom lying in the basal plane with the axial ligand atoms
being the carbonyl oxygen and the other nitrogen. An overall
agreement has been found between the calculated and experimen-
tal structure in each case with the largest deviation of bond dis-
tances being about 0.1 Å, while this of bond angles being about
8°. The two rings of benzophenone deviate from planarity by 38°
with the experimental value being 59°. This discrepancy is possibly
due to crystal packing effects.
In order to explore the potential energy surface (PES) of complex
10 a series of calculations was carried out on a model representative
complex namely [Co(salo)(neoc)Br] (salo = salicylaldehyde anion).
The starting structures for this full optimization, carried out in
the same level of theory, were all possible trigonal bipyramidal
(TBP) or square pyramidal (SP) geometries. Furthermore, for each
geometry two initial structures were derived by exchanging the
two ligating atoms of the salo ligand, that is the phenolic and the
carbonyl oxygen atoms. The four optimized structures found are
shown in Fig. 5, whereas their relative energy and calculated bond
distances and angles are given in Table 5. No minimum or transition
state has been located with a square pyramidal structure, as all
optimizations led to the TBP structure. The most stable structure
11 located as a minimum is indeed a TBP structure similar to this
experimentally isolated complex 10. The next local minimum 12 lo-
cated only 0.4 kcal/mol higher in energy has also the bromine and a
nitrogen atom in the basal plane of the TBP. The only difference
from the global minimum 10 is that the phenolic oxygen occupies
the axial position instead of the carbonyl oxygen. The rest two
structures that have been located, 13 and 14, have the bromine
atom occupying an axial position of the TBP, the nitrogen atoms
in the basal plane and differ from each other only in positions of
the oxygen atoms. Both are transition states on the PES of the mol-
ecule. Inspection of the normal mode of their single imaginary fre-
quency reveals that 13 and 14, being 3.6 kcal/mol and 1.8 kcal/mol
higher than 11 and 12, interconnect each minimum to its mirror
image structure.
Fig. 4. Clinographic projection of the precursor [Co(neoc)Br2]ꢀCH3OHꢀH2O (11) with
displacement ellipsoids drawn at the 50% probability level. Solvent molecules have
been omitted.
Table 4
Selected bond lengths (Å) and angles (°) for 11.
Br(1)–Co(1)
Br(2)–Co(1)
Co(1)–N(1)
2.3981(14)
2.3948(12)
2.047(3)
Co(1)–N(2)
2.028(3)
Br(1)–Co–Br(2)
Br(1)–Co–N(1)
Br(2)–Co–N(1)
Br(1)–Co–N(2)
Br(2)–Co–N(2)
N(1)–Co–N(2)
118.28(4)
113.39(10)
111.02(11)
112.72(11)
110.80(11)
86.23(15)
The trigonal bipyramidal base is formed from N(1), O(2) and
Br(1) atoms while the axial positions are occupied from O(1) and
N(2). The atoms forming the mean 0basal plane belong on it, while
the cobalt atom is placed 0.136(4) ÅA upper this and the O(1) atom
0
0
further upper at 2.165(4) ÅA, while N(2) is placed 1.970(4) ÅA lower.
The neocuproine ligand is practically planar forming an angle of
78.08° with the equatorial plane. The dihedral angle formed be-
tween the phenyl rings of the 2-OH-benzophenone ligand was
63.90°.
3.4. Spectroscopy
Compound [Co(neoc)Br2]ꢀCH3OHꢀH2O (11) crystallizes in the
P21/n space group with four formula units in the unit cell. Fig. 4 de-
picts the clinographic projection of the molecule, while selected
distances (Å) and bond angles (°) are given in Table 4.
The molecular structure of the precursor compound (11) is
quite simple. The central Co(II) metal ion is coordinated to the
two nitrogen atoms of the neocuproine ligand and to two bromine
atoms in a tetrahedral mode. All coordination distances and bond
angles are similar to those found in similar compounds [37]. The
crystal structure of the compound consist from four complex moi-
eties arranged as the previous compounds, but with very light
3.4.1. Infrared spectra (IR)
In the spectra of the free 2-hydroxy-phenone ligands the in-
tense bands stemming from the stretching and bending vibrational
modes of the phenolic OH around 3200 and 1410 cmꢁ1, respec-
tively, disappear from the spectra of all complexes indicating the
ligand deprotonation [38]. Also, the bands originating from the
C–O stretching vibrations at 1245–1285 cmꢁ1, in the complexes
exhibit positive shifts at 1342–1385 cmꢁ1 while their intensity is
enhanced appreciably denoting coordination through the carbonyl
oxygen of the phenone ligand. The band at ꢄ1660 cmꢁ1 attribut-
able to the carbonyl bond v(C@O) of the free ligand, upon coordina-
interactions between neighboring parallel neocuproine ligands at
0
tion, in the complexes is shifted to lower frequencies at
ꢄ1605 cmꢁ1 thus denoting the bidentate mono-anionic character
of the studied hydroxyl-phenone ligands.
distances of 3.87 ÅA. A strong local hydrogen bonding net between
the water molecule, the methanol molecule and the coordinated
bromine anions is present with O(water)–Br mean distances of
The intense bands at 1596 cmꢁ1, attributable to the stretching
vibration of C@N (aromatic bond) are present in all complexes.
The band at 730 15 cmꢁ1, ascribed to the rocking vibrations of
the pyridyl C–H bonds and the band at 860 10 cmꢁ1, attributable
to the deformation vibrations of the pyridyl C–H bonds, disclosed
the occurrence of the nitrogenous base (neocuproine) in the stud-
ied compounds. The medium to low intensity bands at 550–590
and 512, 421 cmꢁ1 are attributed to the coordination bonds (Co–
0
0
3.05 ÅA and O(water)–O(methanol) distance of 2.64(1) ÅA.
3.3. Computational studies using DFT
The molecular structure of complex [Co(opo)(neoc)Br] (10) in
its quadruple ground state was optimized under no symmetry
constrains at the density functional level of theory using the

M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
1313
Fig. 5. The isolated complex [Co(opo)(neoc)Br] (10), the model [Co(salo)(neoc)Br] (11) and its isomers 12, 13 and 14 (hydrogens not shown for clarity).
O and Co–N, respectively). Thus the medium to low intensity
experimental bands located at 420 cmꢁ1 and ꢄ560 cmꢁ1 for all
complexes should be assigned to these Co–N and Co–O vibrations,
respectively.
For the [Co(opo)(neoc)Br] (10) complex, the observed peaks at
217 and 303 cmꢁ1 in the IR spectrum are assigned to Co–Br cova-
lent bond according to the literature [39].
In the visible region the first two bands of low energy for the
complexes 1–5, are clearly located at 990 nm = 20) and
670 nm (
= 80), while the expected third one at ꢄ500 nm is not
shown, possibly masked due to the neighboring position and the
higher of the intra-ligand bands. These bands are assigned as
(
e
e
e
d–d excitations and are indicative of an octahedral high-spin Co(II)
compound.
The three low energy d–d excitations for the trigonal bipyrami-
dal high-spin Co(II) complexes are expected at 580–600 nm, 510–
530 nm and 420–440 nm. The first two bands are clearly located in
the experimental spectra of the complexes 6–10, as it is depicted in
3.4.2. Electronic excitation (UV–Vis) study
Cobalt(II) complexes have electronic spectra which are indica-
tive of their stereochemistry. The experimental absorption spectra
(UV–Vis) of the title compounds in acetonitrile solution presented
four dominant bands in the region 300–1100 nm (representative
spectra are given for compounds 3 and 10 with different geometry
in Fig. 6).
Fig. 6 for the compound 10 (590 nm (e = 75), 520 nm (e = 40)),
while the third one is seen as a shoulder at about 420 nm. The
appearance of the peaks at 520 nm and 590 nm is typical example
of the trigonal bipyramidal geometry around Co(II) [40].

1314
M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
Table 5
Relative energies and selected bond distances (Å) and bond angles (°) calculated for
the isolated complex [Co(opo)(neoc)Br] (10), the model [Co(salo)(neoc)Br] (11) and its
isomers 12, 13 and 14.a
10
11
12
13
14
Co–O1
Co–O2
Co–N1
Co–N2
2.040 (1.956)b
2.017 (2.081)
2.138 (2.084)
2.149 (2.134)
2.539 (2.594)
2.063
2.024
2.136
2.150
2.534
2.127
1.989
2.146
2.154
2.533
2.263
1.941
2.099
2.104
2.528
2.089
2.028
2.119
2.119
2.540
Co–Br
Br–Co–N1
Br–Co–O2
N1–Co–O2
O1–Co–Br
O1–Co–N1
O1–Co–O2
N2–Co–Br
N1–Co–N2
N2–Co–O2
O1–Co–N2
DE (kcal/mol)
102.9 (108.6)
141.7 (133.5)
113.0 (116.9)
96.8 (89.6)
107.8 (102.4)
84.9 (91.5)
90.5 (96.2)
78.3 (80.6)
83.9 (78.2)
168.6 (169.4)
–
104.6
139.9
113.3
95.3
106.9
86.0
91.0
79.0
84.0
169.9
0.0
105.3
100.9
105.1
138.8
112.5
84.8
91.6
78.8
156.2
80.6
0.4
98.1
93.4
100.9
132.2
176.1
80.8
82.4
96.7
81.5
138.0
79.5
2.2
175.5
89.8
90.9
140.6
84.6
93.4
79.5
90.3
139.3
3.6
Fig. 7. Cyclic voltammetry diagram of [Co(bpo)2(neoc)] (3) in CH3CN (0.1 M TEAP,
C = 10ꢁ3 M, scan rate 100 mV/s).
a
Numbering scheme as in Fig. 5.
Experimental values in parentheses.
b
Fig. 8. Cyclic voltammetry diagram of [Co(opo)(neoc)Br] (10), in CH3CN (0.1 M
TEAP, C = 10ꢁ3 M, scan rate 100 mV/s).
equivalent. In the case of compounds 6–10 both are one electron
transformations as expected. Wave V around 1860 mV and at high-
er voltage values can be attributed to the oxidation of the nitrogen
atoms of the nitrogenous base.
Fig. 6. Electronic absorption spectra (UV–Vis) of the complexes 1: [Co(bpo)2(neoc)]
(3) and 2: [Co(opo)(neoc)Br] (10) in C = 10ꢁ4 M CH3CN.
3.6. Thermal studies
Finally, the excitations at 310–320 nm and 280–295 nm arising
The thermal behavior for three of the title compounds, (3-
belonging to the octahedral addition compounds) and (9 and 10-
belonging to the trigonal bipyramidal complexes), was studied in
nitrogen atmosphere, over the temperature range ambient to
980 °C by using the simultaneous TG/DTG–DTA technique. The
studied compounds are unstable upon heating, decomposing in
successive stages.
from intra-ligand
and neoc ligands, are seen in the spectra of the complex 10 at 320
= 11000) and 283 ( = 13000) not shown here), respectively.
pꢁp transitions within the 2-OH-benzophenone
(e
e
3.5. Cyclic voltammetry (CV)
All the studied compounds exhibit similar behavior during the
cyclic voltammetry experiments. The typical CV diagrams of com-
pounds 3 and 10 are representatively depicted in Figs. 7 and 8,
while the experimental data for the studied compounds are pre-
sented in Table 6. The CVs in the region ꢁ1950 to 2100 mV for
all compounds revealed five redox waves.
Waves I and II exhibited at around ꢁ830 and 550 mV represent
the single electron redox potentials of the assigned couples Co(I)–
Co(II) and Co(II)–Co(III), respectively. Both are reversible and, as
compared with the waves observed from equimolar amount of fer-
rocene under the same experimental conditions, are due to one
electron transformations [17,18 and references therein].
Wave III around 1510 mV and wave IV around ꢁ1820 mV are
assigned to the oxidation and the reduction, respectively, of the
phenolic oxygen from the deprotonated 2-OH-phenone ligands in
the complexes. In the case of compounds 1–5, both are two elec-
trons wave transformations and this suggests that the deproto-
nated 2-OH-phenone ligands in the octahedral complexes are
The first sudden mass loss for compound 3, [Co(bpo)2(neoc)]
(Fig. 9) coincides with the mass loss of a benzophenon moiety
(PhCO) derived from a bpo ligand, (DTGmax at 305 °C, experimen-
tal mass loss 15.3% and theoretical 15.88%). The second sudden
mass loss until 550 °C with DTGmax at 368 °C, coincides well with
the further mass loss of one bpo ligand (29.7% f. and 29.8% c.). The
DTA curve shows one sharp endothermic peak at 254 °C, which is
attributed to simultaneous melting and decomposition of the com-
pound, while the next two small endothermic peaks to further
decomposition. Upon increasing the temperature, the unstable
intermediates undergo further decomposition with gradually mass
loss in a wide temperature range (550–980 °C), which is attributed
to the remaining organic fragments of the ketone ligand and frag-
ments of the neocuproine. The amount of the solid residue at
980 °C, is much higher than the calculated for the metallic cobalt
8.92% or for the cobalt oxide CoO 11.34%. This suggests that the
residue consists from a carbonaceous mixture, resulted from the
uncompleted pyrolysis of the compound [34,41].

M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
1315
Table 6
Redox waves of the studied compounds in CH3CN (0.1 M TEAP, C = 10ꢁ3 M, scan speed 100 mV/s).
Comp.
Wave I
Wave II
Wave III
Wave IV
Wave V
Epa
Epc
E1/2
Epa
Epc
E1/2
Epa
Epc
Epa
1
2
3
4
5
6
7
8
9
ꢁ0.87
ꢁ0.85
ꢁ0.87
ꢁ0.85
ꢁ0.86
ꢁ0.86
ꢁ0.85
ꢁ0.86
ꢁ0.85
ꢁ0.86
ꢁ0.83
ꢁ0.80
ꢁ0.83
ꢁ0.81
ꢁ0.81
ꢁ0.84
ꢁ0.82
ꢁ0.82
ꢁ0.82
ꢁ0.82
ꢁ0.85
ꢁ0.82
ꢁ0.85
ꢁ0.83
ꢁ0.84
ꢁ0.85
ꢁ0.83
ꢁ0.84
ꢁ0.84
ꢁ0.84
0.58
0.56
0.56
0.56
0.56
0.57
0.57
0.55
0.56
0.57
0.53
0.52
0.51
0.53
0.52
0.54
0.53
0.52
0.54
0.53
0.56
0.54
0.53
0.55
0.54
0.56
0.55
0.53
0.55
0.55
1.53
1.53
1.51
1.50
1.53
1.51
1.52
1.54
1.50
1.51
ꢁ1.83
ꢁ1.84
ꢁ1.81
ꢁ1.82
ꢁ1.84
ꢁ1.82
ꢁ1.82
ꢁ1.84
ꢁ1.80
ꢁ1.82
1.92
1.93
1.95
1.95
1.89
1.88
1.87
1.89
1.89
1.89
10
tatively, for compound 9 (Fig. 10) the sudden mass loss 12.5%
found of the first stage (115–215 °C, DTG peak at 188 °C, DTA broad
endothermic centered at 384 °C) could be attributed to the elimi-
nation of a bromide (calculated 14.70%). The decomposition con-
tinues again with sudden mass loss of 30.0% found until 500 °C
and successively gradual mass loss until 680 °C (36.0% found for
the temperature range 215–680 °C), which coincides with the
elimination of one bpo molecule (calculated 36.21%). The existence
of a double sharp endothermic peak on the DTA curve at 252 and
274 °C, at the beginning of the second decomposition stage, de-
notes a possible transformation that could take place after the
elimination of the bromide atom.
In order to verify the solid residues, as they deduced and esti-
mated from the TG and DTG curves, powder XRD studies were
used. It was found that the solid material, at 980 °C consists mainly
from cubic metallic cobalt.
4. Conclusions
Five octahedral [Co(2-hydroxy-benzophenone)2(neoc)] and five
trigonal bipyramidal [Co(2-hydroxy-benzophenone)(neoc)Br] (ke-
tone = anion of 2-hydroxy-benzophenones) compounds were syn-
thesized and characterized.
The theoretical DFT investigation with GAUSSIAN-03 showed that
the most stable structure located as a minimum is indeed a TBP
structure similar to this described by the crystal structure for com-
plex [Co(2-hydroxy-4-methoxybenzophenone)(neoc)Br].
X-ray study of the compounds 3, 10 and 11 verified the exis-
tence of mononuclear Co(II) compounds with different geometries
around the metal ion.
Fig. 9. Thermoanalytical curves (TG, DTG, DTA) for the compound 3, [Co(bpo)2(-
neoc)] with heating rate 5 °C minꢁ1 in N2 atmosphere.
In the trigonal bipyramidal complexes 9, [Co(bpo)(neoc)Br] and
10, [Co(opo)(neoc)Br], the thermal decomposition starts with the
elimination of the coordinated bromide without melting of the
compounds, as it is evident from the DTA curves and continues
with the elimination of the organic parts of the ligands. Represen-
The cyclic voltammetry study in CH3CN gave all the expected
waves for the redox processes of the metal Co(II) and the studied
ligands.
The compounds are stable at ambient temperature, but unsta-
ble upon heating decomposing in several stages, giving at 980 °C
in nitrogen atmosphere a solid product consisting of carbonaceous
metallic cobalt.
Appendix A. Supplementary data
CCDC 707802, 709172, and 803882 contain the supplementary
crystallographic data for 3, 10, and 11, 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 Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk.
References
Fig. 10. Thermoanalytical curves (TG, DTG, DTA) for the compound 9, [Co(bpo)(-
neoc)Br] with heating rate 5 °C minꢁ1 in N2 atmosphere.
[1] (a) F. Barigelletti, B. Ventura, J.-P. Collin, R. Kayhanian, P. Gavina, J.-P. Sauvage,
Eur. J. Inorg. Chem. (2000) 113;

1316
M. Lalia-Kantouri et al. / Polyhedron 52 (2013) 1306–1316
(b) M.S. Lüth, L.E. Kapinos, B. Song, B. Lippert, H. Sigel, J. Chem. Soc., Dalton
Trans. (1999) 357.
[2] G.J. Weijnen, A. Koudijs, J.F. Engbersen, J. Org. Chem. 57 (1992) 7258.
[3] D.S. Siegman, Biochemistry 29 (1990) 9097.
[4] E. Peña-Cabrera, P.-O. Norrby, M. Sjögren, A. Vitagliano, V. De Felice, J. Oslob, S.
Ishii, D. O’Neill, B. Åkermark, P. Helquist, J. Am. Chem. Soc. 118 (1996) 4299.
[5] D.J. Szalda, C. Creutz, D. Mahajan, N. Sutin, Inorg. Chem. 22 (1983) 2372.
[6] J. Reedijk, in: G. Wilkinson, R.D. Gillard, J.A. Mc-Cleverty (Eds.),
Comprehensive Coordination Chemistry, vol. 2, Pergamon Press, Oxford, UK,
1987, pp. 73–98.
[7] C.M. Taylor, S.P. Watton, P.A. Bryngelson, M.J. Maroney, Inorg. Chem. 42 (2003)
312.
[8] R.N. Prasad, A. Agrawal, J. Ind. Chem. Soc. 83 (2006) 75.
[9] S.T. Hussain, H. Ahmad, M.A. Atta, M. Afzal, M. Saleem, J. Trace Microprobe
Tech. 16 (1998) 139.
[25] T.H. Dunning Jr., P.J. Hay, in: H.F. Schaefer (Ed.), Modern Theoretical Chemistry,
vol. 3, third ed., Plenum Press, New York, 1977, pp. 1–28. Chapter 1.
[26] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
V.G. Zakrzewski, J.A. Montgomery, R.E. Stratmann, J.C. Burant, S. Dapprich, J.M.
Millam, A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M.
Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G.A.
Petersson, P.Y. Ayala, Q. Cui, K. Morokuma, P. Salvador, J.J. Dannenberg, D.K.
Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J. Cioslowski, J.V. Ortiz,
A.G. Baboul, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaroni, R.
Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A.
Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong,
J.L. Andres, C. Gonzalez, M. Head-Gordon, E.S. Replogle, J.A. Pople, Gaussian 03,
Gaussian, Inc., Pittsburgh, PA, 2003.
[27] L. Palatinus, G. Chapuis, J. Appl. Crystallogr. 40 (2003) 786.
[28] (a) G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112;
(b) G.M. Sheldrick, SHELX-97, Program for Crystal Structures Refinement,
University of Gottingen, Gottingen, Germany, 1997.
[10] K. Fujinaga, Y. Sakaguchi, T. Tsuruhara, Y. Seike, M. Okumura, Solvent Extr. Res.
Dev. 8 (2001) 144.
[11] P. Sajith, M.T. Ummer, N. Mandal, S.K. Mandot, S.L. Agrawal, S. Bandyopadhyay,
R. Mukhopadhyay, B. D’Cruz, A.S. Deuri, P. Kuriakose, J. Adhes. Sci. Technol. 19
(2005) 1475.
[29] P.W. Betteridge, J.R. Carruthers, R.I. Cooper, K. Prout, D.J. Watkin, J. Appl.
Crystallogr. 36 (2003) 1487. Program CRYSTALS, Ver. 12.83 and 12.86.
[30] Th. Kramer, J. Strahle, Z. Naturforsch. B 41 (1986) 692.
[12] (a) Z.-Y. Xiong, Li-J. Liu, Z.-Y. Xiong, L.-J. Liu, Acta Crystallogr., Sect. E 61 (2005)
m863;
[31] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, John Wiley, NY,
1988. p. 730.
(b) Q. Chen, Acta Crystallogr., Sect. E 62 (2006) m56.
[13] Y.-X. Sun, G.-Z. Gao, Acta Crystallogr., Sect. E 61 (2005) m354.
[14] Y.-M. Yang, P.-C. Lu, T.-T. Zhu, C.-H. Liu, Acta Crystallogr., Sect. E 63 (2007)
m1613.
[32] K.N. Patel, N.H. Patel, K.M. Patel, M.N. Patel, Synth. React. Inorg. Met.-Org.
Chem. 30 (2000) 921.
[33] D.J. Walker, C.K. Prout, F.J. Bearch, CAMERON Program, Chemical Crystallographic
Laboratory, Oxford University, UK, 1996.
[15] J.C. Pessoa, I. Cavaco, I. Correia, I. Tomaz, T. Duarte, P.M. Matias, J. Inorg.
Biochem. 80 (2000) 35.
[16] M. Lalia-Kantouri, T. Dimitriadis, C.D. Papadopoulos, M. Gdaniec, A. Czapik,
A.G. Hatzidimitriou, Z. Anorg. Allg. Chem. 635 (2009) 2185.
[17] C.D. Papadopoulos, A.G. Hatzidimitriou, G.P. Voutsas, M. Lalia-Kantouri,
Polyhedron 26 (2007) 1077.
[34] M. Lalia-Kantouri, M. Gdaniec, A. Czapik, K. Chrissafis, W. Ferenc, J. Sarzynski,
Ch.D. Papadopoulos, J. Therm. Anal. Calorim. (2012), http://dx.doi.org/10.1007/
s10973-011-1692-5.
[35] (a) A.K. Patra, M. Ray, R. Mukherjee, J. Chem. Soc., Dalton Trans. (1999) 2461;
(b) C.E. Searls, S.T. Kleespies, M.L. Eppright, S.C. Schwartz, G.P. Yap, R.C.
Scarrow, Inorg. Chem. 49 (2010) 11261.
[18] C.D. Papadopoulos, M. Lalia-Kantouri, J. Jaud, A.G. Hatzidimitriou, Inorg. Chim.
Acta 360 (2007) 3581.
[36] A.W. Addison, T.R. Nagaswara, J. Reedijk, J. Van Rijn, G.C. Verschoor, J. Chem.
Soc., Dalton Trans. (1984) 1349.
[19] C.D. Papadopoulos, A.G. Hatzidimitriou, M. Quiros, M.P. Sigalas, M. Lalia-
Kantouri, Polyhedron 30 (2011) 486.
[37] V.M. Leovac, Z.D. Tomic, K.M. Szecsenyi, L.S. Jovanovic, M.D. Joksovic, J. Serb.
Chem. Soc. 72 (2007) 1281.
[20] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[38] R.M. Silverstein, G.C. Bassler, G. Morvill, Spectrometric Identification of
Organic Compounds, sixth ed., Wiley, New York, 1998. p. 87.
[39] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, fifth ed., Wiley-Interscience, New York, 1997.
[40] A.B. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier, 1984. p. 480.
[41] W. Ferenc, B. Cristvao, J. Sarzynski, J. Therm. Anal. 101 (2010) 761.
[21] K.Y. Lee, W. Yang, R.G. Parr, Phys. Rev. B37 (1988) 785.
[22] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270.
[23] W.R. Wadt, P.J. Hay, J. Chem. Phys. 82 (1985) 284.
[24] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299.