Influence of carboxylate counter anions on the cationic framework of 1,10-phenanthroline cobalt(III) complexes: Syntheses, characterization and single crystal structure determination of [Co(phen)2CO 3]X.nH2O complexes

Article abstract of DOI:10.1016/j.poly.2012.06.092

Cobalt(III) complexes containing carboxylate anions, [Co(phen) ₂CO₃]X·nH₂O, where X = trifluoroacetate (tfa, n = 5; 1), 4-chloro-3-nitrobenzoate (3-cnbz, n = 6; 2), 4-chloro-2-nitrobenzoate (2-cnbz, n = 4; 3), 2,4-dinitrob

Full text of DOI:10.1016/j.poly.2012.06.092

Polyhedron 47 (2012) 173–181
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Influence of carboxylate counter anions on the cationic framework of
1,10-phenanthroline cobalt(III) complexes: Syntheses, characterization
and single crystal structure determination of [Co(phen)2CO3]X.nH2O complexes
a
a
b
b,
Raj Pal Sharma a, , Ajnesh Singh , Paloth Venugopalan , Antonio Rodríguez-Diéguez , Juan M. Salas
⇑
⇑
a Department of Chemistry, Panjab University, Chandigarh 160014, India
b Departamento de Quimica Inorganica, Facultad de Ciencias,Universidad de Granada, 18071 Granada, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Cobalt(III) complexes containing carboxylate anions, [Co(phen)2CO3]XꢀnH2O, where X = trifluoroacetate
(tfa, n = 5; 1), 4-chloro-3-nitrobenzoate (3-cnbz, n = 6; 2), 4-chloro-2-nitrobenzoate (2-cnbz, n = 4; 3),
2,4-dinitrobenzoate (dnbz, n = 1; 4), have been synthesized by the reaction of [Co(phen)2CO3]Clꢀ5H2O
and corresponding sodium salt of carboxylic acid in aqueous medium. These complexes were character-
ized by elemental analysis, solubility product, conductance measurements, thermal studies and spectro-
scopic studies. The crystal structures of 1–4 have been determined by single-crystal X-ray structure
Received 26 April 2012
Accepted 22 June 2012
Available online 22 July 2012
Keywords:
Hydrogen bonding
Cobalt(III) complexes
Carboxylate
determination. The hydrogen bonding (C–Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀO) and
p–p stacking interactions led to the
formation of pillared layer, square cavities type and zig-zag layered arrangements in 2, 3 and 4 respec-
tively, while in complex salt 1, C–Hꢀ ꢀ ꢀF interactions have been observed between the complex cations
and anions.
Framework solids
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
ligands was selected. Cobalt (1,10-phenanthroline) complexes are
well known for their protein and DNA interaction studies, more-
The design and syntheses of metal-organic frameworks stabi-
lized by hydrogen bonds and other weak interactions forms a class
of compounds which is receiving the current interest of chemists in
various fields, i.e. host guest chemistry, crystal engineering, catal-
ysis and adsorption studies [1–5]. The relatively weak interactions,
over, the (1,10-phenanthroline) ligand also provides the possibility
to induce C–Hꢀ ꢀ ꢀ and stacking interactions. In addition, or-
p
p–p
ganic ligands of this type play an important role in studies related
to the evaluation of weak interactions on the formation of different
networks [8]. The choice of counter ions is fulfilled by carboxylate
anions (Scheme 1), as each carboxylate group with its two oxygen
atoms can participate in charge assisted and directional hydrogen
bonding with the cationic moieties. On the other hand, carboxyl-
ates have been widely used in the construction of a number of me-
tal-organic frameworks because of their versatility in the
coordination modes and their ability to form robust and flexible
hydrogen bond networks [9].
including hydrogen bonds,
p–p
stacking, C–Hꢀ ꢀ ꢀ
p, anionꢀ ꢀ ꢀ
p and
electrostatic interactions of smaller magnitude, are major attrac-
tive forces holding together the building blocks that constitute
the solid frameworks [6]. These structures, in response to guest
molecules, can change their conformation by slight modifications,
keeping the overall connectivity pattern intact [7]. These com-
plexes offer a tunable class of compounds where one can design
the desired complex by subtle changes in the counter anions and
the transition metal ions (which can impart other properties like
redox, catalytic, magnetic etc.).
Thus, this paper presents the syntheses, characterization, single
crystal X-ray structure determination and detailed packing analy-
sis of four cobalt(III) complexes, [Co(phen)2CO3](trifluoroace-
tate)ꢀ5H2O (1), [Co(phen)2CO3](4-chloro-3-nitrobenzoate)ꢀ6H2O
(2), [Co(phen)2CO3](4-chloro-2-nitrobenzoate)ꢀ4H2O (3) and [Co
(phen)2CO3](2,4-dinitrobenzoate)ꢀH2O (4).
In the present work, an effort has been made to investigate the
role of weak interactions and the effect of the counter anions on
the topology of the cationic framework. Keeping in mind the nat-
ure of weak interactions and their effect on solid frameworks, a co-
balt(III) complex bearing 1,10-phenanthroline and carbonato
2. Experimental
2.1. Materials and physical measurements
⇑
Corresponding authors. Tel.: +91 0172 2534433; fax: +91 0172 2545074 (R.P.
Sharma), tel.: +34 958248525; fax: +34 958248526 (J.M. Salas).
E-mail addresses: rpsharmapu@yahoo.co.in (R.P. Sharma), jsalas@ugr.es (J.M.
Salas).
All reagents and solvents were commercially available and
were used directly without any further purification. The starting
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.06.092

174
R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
H3); anion, [C7H3NO4Cl]ꢁ, d: 8.30(s, H2), 8.06(d, H5), 7.62(d, H6).
13C NMR/ppm (DMSO-d6) d: 173.5, 163.19, 154.10, 151.64,
147.04, 146.82, 140.84, 139.80, 130.55, 130.30, 130.15, 127.99,
127.79, 126.84. Solubility (H2O, 25 °C): 0.642 g/100 mL. Ksp
:
6.63 ꢂ 10ꢁ5
.
UV–Vis
(kmax/nm
(e
/molꢁ1 L cmꢁ1),
H2O):
510(100.96), 272 (62542), 222 (72628).
2.2.1.2. Synthesis of [Co(phen)2CO3](4-chloro-2-nitrobenzoate)ꢀ4H2O
(3). 0.3 g of [Co(phen)2CO3]Clꢀ5H2O (0.5 mmol) was dissolved in
10 mL of water in a beaker, and in another beaker 0.1 g (0.5 mmol)
of 4-chloro-2-nitrobenzoic acid and 0.020 g (0.5 mmol) sodium
hydroxide were dissolved in 10 mL of water. The two solutions
were mixed. Red coloured crystals appeared after 10 days as a re-
sult of slow evaporation at room temperature. Crystals were col-
lected and dried in air (yield 78%). The complex salt decomposed
at 205 °C. Anal. Calc. (%) for C32H27ClCoN5O11: C, 51.06; H, 3.59;
N, 9.31; Co, 7.85. Found: C, 50.88; H, 3.55; N, 9.22; Co, 7.60%. IR/
cmꢁ1(KBr pellet): 3393(b), 3087(w), 1662(s), 1635(s), 1562(w),
1533(s), 1520(s), 1430(s), 1355(w), 1227(m), 1150(m), 1102(s),
1013(w), 852(s), 850(m), 795(m), 747(m), 720(s), 508(w),
479(m). 1H NMR/ppm (DMSO-d6), cation, [Co(phen)2CO3]+, d:
9.24(m, H9/7), 8.91(d, H2), 8.46(m, H8/6/5), 7.79(m, H3/4); anion,
[C7H3NO4Cl]ꢁ, d: 7.62(m, H3/5/6). 13C NMR/ppm (DMSO-d6) d:
163.17, 154.11, 154.04, 151.67, 151.57, 147.05, 146.82, 140.83,
139.86, 139.72, 131.53, 130.88, 130.31, 130.17, 128.11, 127.86,
Scheme 1. Carboxylate anions used.
material, [Co(phen)2CO3]Clꢀ5H2O, was prepared by the reaction
between CoCl2ꢀ6H2O, 1,10-phenanthroline and sodium bicarbonate
according to the literature procedure [10]. C, H and N were
estimated micro-analytically by an automatic PERKIN ELMER
2400CHN elemental analyzer. Cobalt was determined by a stan-
dard volumetric method of estimation [11]. UV–Vis spectra were
recorded using a HITACHI 330 spectrometer in water as a solvent.
Infrared spectra of the title complex salts were recorded using a
PERKIN ELMER spectrum RX FT-IR system using KBr pellets. 1H
and 13C NMR spectra of title complex salts were run in the solvent
DMSO-d6 at 25 °C, using a BRUKER AC 400 F (400 MHz) spectro-
photometer. The chemical shift values are expressed as d values
(ppm) downfield from tetramethylsilane as an internal standard.
Conductance measurements were performed on a Pico Conductiv-
ity Meter (Model CNO4091201, Lab India) in aqueous medium at
25 °C, using double distilled water.
127.66, 126.81. Solubility (H2O, 25 °C): 3.11 g/100 mL. Ksp
:
1.72 ꢂ 10ꢁ3
.
UV–Vis
(kmax/nm
(e
/molꢁ1 L cmꢁ1),
H2O):
511(96.02), 272(58548), 224 (74388).
2.2. General synthesis
2.2.1.3. Synthesis of
[Co(phen)2CO3](2,4-dinitrobenzoate).H2O
2.2.1. Synthesis of [Co(phen)2CO3](trifluoroacetate)ꢀ5H2O (1)
(4). [Co(phen)2CO3]Clꢀ5H2O (0.3 g, 0.5 mmol) was dissolved in
10 mL of water in a beaker and to this a 10 mL aqueous solution
of 0.105 g (0.5 mmol) 2,4-dinitrobenzoic acid and 0.020 g
(0.5 mmol) sodium hydroxide, dissolved separately, was added.
When the resultant solution was allowed to evaporate slowly at
room temperature, reddish-pink coloured crystals started appear-
ing after eight hours, which were collected and dried in air (yield
72%). The complex salt decomposed at 208 °C. Anal. Calc. (%) for
[Co(phen)2CO3]Clꢀ5H2O (0.2 g, 0.33 mmol) was dissolved in
5 mL of water and to this 3 mL aqueous solution of 0.045 g
(0.33 mmol) sodium trifluoroacetate was added. When the resul-
tant solution was allowed to evaporate slowly at room tempera-
ture, reddish-pink coloured crystals started appearing after 2 days,
which were collected and dried in air (yield 75%). The complex salt
decomposed at 210 °C. Anal. Calc. (%) for C27H26CoF3N4O10: C,
47.48; H, 3.81; N, 8.21; Co, 8.65. Found: C, 47.01; H, 3.75; N,
8.12; Co, 8.15%. IR/cmꢁ1(KBr pellet, b = broad, s = strong, m = med-
ium, w = weak): 3378(b), 3061(w), 1668(s), 1634(s), 1585(w),
1520(m), 1431(s), 1344(m), 1318(w), 1242(m), 1201(s), 1167(s),
1118(s), 856(s), 821(m), 798(m), 747(m), 718(s), 656(w), 480(m).
1H NMR/ppm (DMSO-d6), cation, [Co(phen)2CO3]+, d: 9.27(d, H9),
9.21(d, H7), 8.92(d, H2), 8.46(m, H8/6/5), 7.80(m, H3/4); 13C
NMR/ppm (DMSO-d6) d: 201.37, 163.16, 154.04, 151.61, 147.04,
141.37, 139.83, 139.75, 130.30, 130.15, 128.0, 126.84. Solubility
(H2O, 25 °C): 2.75 g/100 mL, Ksp: 1.62 ꢂ 10ꢁ3. UV–Vis (kmax/nm
C
32H31CoN6O10: C, 54.20; H, 4.38; N, 11.86; Co, 8.32. Found: C,
53.80; H, 4.25; N, 11.35; Co, 8.16%. IR/cmꢁ1(KBr): 3378(b),
3035(w), 1673(s), 1631(s), 1598(m), 1537(m), 1516(s), 1431(m),
1340(s), 1220(m), 1205(m), 1139(w), 853(s), 816(m), 748(m),
720(s), 653(w), 485(m). 1H NMR/ppm (DMSO-d6), cation, [Co(-
phen)2CO3]+, d: 9.23(m, H9/7), 8.91(d, H2), 8.46(m, H8/5/6),
7.79(m, H3/4); anion, [C7H3N2O6]ꢁ, d: 8.46(m, H3), 8.35(m, H5),
7.79(m, H6). 13C NMR/ppm (DMSO-d6) d: 163.12, 154.08, 151.66,
147.04, 146.81, 140.84, 139.84, 139.69, 130.30, 130.15, 127.89,
127.81, 127.64, 126.82, 126.75. Solubility (H2O, 25 °C): 0.484 g/
(e
/molꢁ1 L cmꢁ1), H2O): 510(80.81), 272(46517), 225(50965), 206
(62349).
100 mL, Ksp
:
4.68 ꢂ 10ꢁ5
. UV–Vis (kmax/nm (e
/molꢁ1 L cmꢁ1),
H2O): 510 (89.75), 272(60510), 225(66802), 203(92211).
2.2.1.1. Synthesis of [Co(phen)2CO3](4-chloro-3-nitrobenzoate)ꢀ6H2O
2.3. Single crystal structure determination
(2). To
a
10 mL solution of [Co(phen)2CO3]Clꢀ5H2O (0.3 g,
0.5 mmol) in water, a 10 mL solution of 0.1 g (0.5 mmol) 4-
chloro-3-nitrobenzoic acid and 0.020 g (0.5 mmol) sodium hydrox-
ide, dissolved separately, was added. When the solution was al-
lowed to evaporate slowly at room temperature, reddish pink
coloured crystals appeared after 3 days, which were separated
from the mother liquor and dried in air (yield 80%). The complex
salt decomposed at 195 °C. Anal. Calc. (%) for C32H31ClCoN5O13: C,
48.73; H, 3.93; N, 8.88; Co, 7.49. Found: C, 48.50; H, 3.80; N,
8.81; Co, 7.80%. IR/cmꢁ1(KBr pellet): 3377(b), 3058(w), 1665(s),
1634(s), 1596(m), 1580(s), 1520(m), 1430(s), 1360(s), 1220(s),
1152(w), 1039(w), 858(s), 782(m), 746(w), 721(s), 529(w),
481(w). 1H NMR/ppm (DMSO-d6), cation, [Co(phen)2CO3]+, d:
9.24(m, H9/7), 8.91(d, H2), 8.45(m, H8/6/5), 7.83(d, H4), 7.76(t,
Suitable single crystals of 1–4 were mounted on glass fibers and
used for X-ray data collection. Data were collected with a Bruker
AXS APEX CCD area detector equipped with graphite monochro-
mated MoK
a radiation (k = 0.71073 Å) by applying the x-scan
method. The data were processed with APEX2 [12] and corrected
for absorption using SADABS [13]. The structures were solved by
direct methods using SIR97 [14], revealing positions of all non-
hydrogen atoms. These atoms were refined on |F|2 by a full matrix
least-squares procedure using anisotropic displacement parame-
ters [15]. All hydrogen atoms were located in difference Fourier
maps and included as fixed contributions riding on attached atoms
with isotropic thermal displacement parameters 1.2 times those of
the respective atoms. In general, the structures have disorder

R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
175
Table 1
Crystal data and refinement details for complex salts 1–4.
Complex Salt
1
2
3
4
Chemical formula
CCDC
C
27H26N4O10F3Co
C32H31N5O13ClCo
873569
788.00
C32H27N5O11ClCo
873570
751.97
C32H21N6O
873571
708.48
100
873568
682.45
100
M/gmolꢁ1
T (K)
100
100
k (Å)
0.71073
triclinic
0.71073
triclinic
0.71073
triclinic
0.71073
triclinic
Crystal system
Space group
a (Å)
b (Å)
c (Å)
ꢀ
ꢀ
ꢀ
ꢀ
P1
P1
P1
P1
11.428(5)
11.786(5)
11.889(5)
83.772(5)
62.640(5)
78.425(5)
1393.0(1)
2
10.507(5)
12.431(5)
13.501(5)
85.423(5)
80.288(5)
75.600(5)
1682.2(1)
2
11.907(5)
12.789(5)
15.475(5)
109.732(5)
110.525(5)
116.576(5)
1593.1(1)
2
7.426(5)
14.205(5)
14.308(5)
74.071(5)
85.871(5)
77.914(5)
1419.0(1)
2
a
(°)
b (°)
k (°)
V (Aꢁ3
Z
)
q
l
(g cmꢁ3)
1.627
0.703
1.556
0.665
1.568
0.694
1.658
0.681
(mmꢁ1
)
Unique reflections
(Rint
Goodness-of-fit (GOF) on F2
R1 [I > 2 (I)]
wR2 [I > 2 (I)]
13773
0.022
1.043
0.059
16756
0.042
1.041
0.058
15675
0.016
1.064
0.047
13880
0.052
0.934
0.050
)
r
r
0.165
0.143
0.138
0.119
Scheme 2. Schematic representation of the synthetic procedure.
Table 2
Solubility product and molar conductivity at infinite dilution of complex salts 1–4.
S. No
Formula of complex salt
Solubility g/100 ml
Ksp
Ko S cm2 molꢁ1
1
2
3
4
[Co(phen)2CO3](trifluoroacetate)ꢀ5H2O
2.75
1.62 ꢂ 10ꢁ3
6.63 ꢂ 10ꢁ5
1.72 ꢂ 10ꢁ3
4.68 ꢂ 10ꢁ5
70
91
139
80
[Co(phen)2CO3](4-chloro-3-nitrobenzoate)ꢀ6H2O
[Co(phen)2CO3](4-chloro-2-nitrobenzoate)ꢀ4H2O
[Co(phen)2CO3](2,4-dinitrobenzoate)ꢀH2O
0.642
3.112
0.484
Table 3
problems with the solvent molecules. For this reason, in complexes
1–3 some hydrogen atoms have been omitted. Final R(F), wR(F2)
and goodness of fit agreement factors, details of the data collection
and analysis can be found in Table 1.
Selected bond distances (Å) and angles for 1–4 (°).
Compound
1
2
3
4
Co ꢁ OCo
1.890(3)
1.892(2)
1.930(3)
1.889(3)
1.901(3)
1.931(3)
1.891(2)
1.892(2)
1.927(2)
1.880(2)
1.887(2)
1.929(3)
3
Co–Nphen
3. Results and discussion
1.937(3)
1.953(3)
1.953(3)
1.934(3)
1.946(3)
1.953(3)
1.936(2)
1.939(2)
1.952(2)
69.64(10)
91.05(10)
89.01(10)
90.55(9)
92.88(10)
96.75(10)
166.11(9)
165.85(9)
96.94(10)
177.86(9)
94.18(10)
84.22(10)
84.06(10)
94.71(10)
96.84(10)
1.930(3)
1.946(3)
1.951(3)
Though there are sporadic reports in the literature about the
complex cation [Co(phen)2CO3]+ [16], its interactions with differ-
ent carboxylates have not been investigated at all. In these com-
plex salts, understanding the molecular organizational role of
O
ꢁ Co ꢁ O
69.55(11)
90.49(11)
91.37(12)
92.47(12)
90.50(11)
95.91(11)
164.78(12)
168.25(11)
99.21(12)
176.91(12)
84.07(12)
94.74(12)
93.29(12)
83.98(12)
95.55(12)
69.62(11)
91.91(13)
90.17(12)
91.28(12)
91.45(13)
98.05(12)
167.04(12)
168.91(12)
99.96(12)
176.76(13)
94.33(13)
84.68(13)
84.15(13)
92.81(12)
92.59(13)
69.81(11)
89.42(11)
90.62(11)
91.53(11)
88.67(11)
99.83(11)
168.53(11)
169.11(11)
100.11(11)
178.55(11)
84.19(12)
96.72(11)
94.94(11)
83.94(11)
90.55(12)
Co3
Co3
OCo ꢁ Co ꢁ Nphen
3
weak interactions such as C–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀ
p
,
p
–
p
and anionꢀ ꢀ ꢀ
p
amid the strong ionic interactions is significant as it enhances
our perspective towards the role of weak interactions in lattice
stabilization.
3.1. Syntheses
N
phen–Co–Nphen
The complex salts 1–4 were synthesized by the reaction of [Co
(phen)2CO3]Clꢀ5H2O with sodium salts of the respective carboxyl-
ates in aqueous medium in a 1:1 molar ratio (Scheme 2). The newly
synthesized complex salts are soluble in methanol, acetone and

176
R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
Fig. 1. The structural features observed in complex salt 1: (a) Molecular diagram of the complex salt with the atom numbering scheme, (b) Bonding environment around the
anion in the lattice, (c) Packing diagram of the complex salt where the anions are shown in the space filling model and (d) Pictorial representation of the packing arrangement,
anions are shown as red circles. Symmetry codes: (i) x + 1, +y, +z; (ii) ꢁx, y ꢁ 1, ꢁz + 2.
DMSO. The complex salts 1–4 decomposed in the range 195–
Table 4
210 °C. These have been characterized on the basis of elemental
Hydrogen bonding parameters (Å) of complex salt 1.
analyses, spectroscopic studies (IR, UV–Visible, 1H and 13C NMR)
O1W
O1W
O1W
O2W
O2W
O2W
O3C
2.713(4)
2.272(4)
2.721(4)
2.759(4)
2.801(4)
O3W
O3W
O4W
O5W
O4Wii
O4W
2.745(4)
2.614(4)
2.745(4)
2.850(4)
and conductance measurements. The crystal structures of all the
complex salts have been unambiguously established by single
crystal structure determination.
O3Wi
O1D
O3Wii
O1Ciii
O1Wi
3.2. Thermal studies
Symmetry codes: (i) ꢁx + 1, ꢁy, ꢁz + 2, (ii) ꢁx + 2, ꢁy, ꢁz + 1, (iii) x + 1, +y, +z.
The thermal stabilities of complex salts 1–4 were examined
through TGA under nitrogen atmosphere. Complex salts 1–3
showed similar thermal behaviour, where water molecules of crys-
tallization were lost in two steps. The total weight loss (in two
steps) of 12.24%, 13.71% and 9.57% in complexes 1, 2 and 3, respec-
tively, was in agreement with the calculated weight loss of 13.18%,
15.01% and 11.06%. After the loss of lattice water molecules, the
complex salts were stable up to 200 °C. Further heating to
1000 °C led to a continuous weight loss and no clear steps were
observed.
the interactions between the cation and anion. The solubility prod-
uct measurements at 25 °C (see Table 2) show that the affinity of
the cation [Co(phen)2CO3]+ for different carboxylate anions is in
the order tfa < 2-cnbz < dnbz < 3-cnbz. This order may be due to
the increased interactions between the cation and anion. A com-
parison of the solubility products of the complex salts 1–4 is given
in the Table 2.
3.4. Molar conductivity measurements
In the case of complex salt 4, the first step corresponds to a
weight loss of 2.03% (cal. 2.54%), which corresponds to the loss of
one water molecule of crystallization. After the loss of the water
molecule, the complex showed similar thermal behaviour to that
of complexes 1–3. The TG curves of complex salts 1–4 are given
in the supporting information as Figs. S1–S4, respectively.
Molar conductivities of complex salts 1–4 were measured at
25 °C in aqueous medium. The limiting molar conductivity at infi-
nite dilution (Ko) was calculated by plotting the molar conductiv-
ity versus the square root of concentration. The Ko values obtained
for complex salts 1–4 (70, 91, 139 and 80 S cm2 molꢁ1 respectively,
Table 2) are close to the range for 1:1 electrolytes [17]. The lower
values of Ko in the case of complex salts 1 and 4 may be ascribed to
ion pair formation.
3.3. Solubility product measurements
The solubility of ionic salts in water differs to a greater extent.
On the basis of the solubility, ionic salts are classified as soluble,
slightly soluble, sparingly soluble and insoluble. Measurement of
the solubility product provides an idea about the magnitude of
3.5. Spectroscopic characterization
For low spin Co(III) complexes, two types of transitions, i.e.
1A1g ? 1T1g and 1A1g ? 1T2g, are expected. In [Co(phen)2CO3]+

R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
177
Fig. 2. The structural features observed in complex salt 2: (a) Molecular diagram of the complex salt with the atom numbering scheme, (b) Bonding environment around the
anion in the lattice, (c) Packing diagram of the complex salt showing the pillared-layer arrangement (
ꢁz + 1; (ii) ꢁx + 1, ꢁy + 1, ꢁz + 1.
pꢁp stacking interaction in the pillars). Symmetry codes: (i) ꢁx, ꢁy,
complexes, these transitions are observed around 500 and 350 nm,
as reported in the literature [16h]. For the complex salts 1–4, the
characteristic 1A1g ? 1T1g transitions were observed in the range
512–509 nm. Other transitions due to 1,10-phenanthroline groups
coordinated to cobalt(III) were also observed. Peaks observed
around 272, 224 and 205 nm in all the complex salts were assigned
to those of coordinated 1,10-phenanthroline groups [18]. Detailed
peak assignments are given in the experimental section.
Table 5
Hydrogen bonding parameters (Å) of complex salt 2.
O1W
O1W
O2W
O2W
O52D
O3Ci
2.751(4)
2.742(4)
2.824(4)
2.835(4)
O2W
O3W
O3W
O4Wiii
O52D
2.824(4)
2.786(4)
2.784(4)
O51D
O6Wiii
O51Dii
Symmetry codes: (i) ꢁx, ꢁy + 1, ꢁz + 1, (ii), ꢁx, ꢁy, ꢁz + 1 (iii) ꢁx, ꢁy, ꢁz + 2.
Vibrational spectra of the newly synthesized complex salts have
been recorded in the range 400–4000 cmꢁ1. In the FT IR spectra of
complex salts 1–4, bands in the regions 1662–1673 and 1631–
[PPh3)3Cu(4-np)]2 [24], respectively. Additionally, the peaks due
to m(C–F) in 1 and m(C–Cl) in 2 and 3 were observed at 1167, 782
and 795 cmꢁ1 respectively. The FT IR spectra of complex salts 1–
4 are given in the supporting information as Figures S5–8,
respectively.
1635 cmꢁ1 were assigned to
m
(C@O) and
respectively. The IR bands due to as(COO),
s(NO2) and d(OCO) vibrations were observed in the regions
m
(C@C) vibrations,
m
m
s(COO) as(NO2),
m
m
In complex salts 1–4, 1H and 13C NMR chemical shift values are
in good agreement with the literature values reported for the com-
plex cation [Co(phen)2CO3]+ and the different arylcarboxylates
[25]. Detailed NMR peak assignments for complexes 1–4 are given
in the experimental section.
1598–1562, 1431–1413, 1537–1520, 1360–1340 and 748–
746 cmꢁ1, respectively. Other bands observed in the regions
3393–3377, 3087–3035 and 856–853 cmꢁ1 were assigned to
m
(O–H) of H2O,
assignments have been made in consultation with the literature
values [19]. The carboxylate group has shown as(COO) and
m(@C–H) and d(H–C@), respectively. The spectral
m
m
s(COO) bands at 1562, 1558, 1573, 1585 and 1378, 1397,
3.6. Structure descriptions
1374 cmꢁ1 for dipotassium [20], disodium, disilver terephthalate
[21] and [Co(NH3)6]Clꢀ(C8H4O4) [22], respectively. IR bands at
3.6.1. Coordination geometry and bonding
The coordination around the Co(III) metal center is slightly
distorted octahedral in complex salts 1–4 (as revealed from the
1573, 1322 and 1586, 1337 cmꢁ1 due to
m
s(NO2) and
mas(NO2)
vibrations were reported for [Co(NH)6](4-np)3ꢀ4H2O [23] and

178
R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
Table 6
geometrical parameters in Table 3), which is generated by two
bidentate 1,10-phenanthroline ligands and one chelating carbona-
to ligand. Such a distortion can be explained, considering the spa-
tial juxtaposition of the ligands around the metal atom. The bond
length distribution around the cobalt(III) center is as expected for
Co(III) complexes [16,26]. The aromatic rings of the 1,10-phenan-
throline moieties attached to the cobalt(III) centre are almost pla-
nar in nature for all the complexes. The angles between the least
square planes containing the 1,10-phenanthroline ligands in com-
plex salts 1–4 are 80.14°, 85.09°, 75.43° and 86.36° respectively.
In complex salt 2, the nitro group at the meta position in the 4-
chloro-3-nitrobenzoate anion is out of the plane from the aromatic
ring (C2D–C1D–N11D–O12D torsion angle of ꢁ53.67°) while the
carboxylate group slightly deviates with a torsion angle O52D–
C51D–C5D–C6D of ꢁ5.01°. Probably the presence of the chloro
group at the para position (steric crowding), coupled with overall
lattice constraints along with weak second sphere interactions
(vide intra) to obtain maximum stabilization of the lattice necessi-
tates this out of plane twist of the NO2 group in the anion. In the
case of complex salt 3, the carboxylate and nitro groups are out
of the plane from the benzene ring as C1D–C6D–C61D–O62D is
ꢁ57.69° and C6D–C1D–N11D–O11D is ꢁ22.29°. Similarly, the
adjacent carboxylate and nitro groups are also greatly deviated
from a planar nature (C1D–C6D–C61D–O61D = ꢁ44.47° and C6D–
C1D–N11D–O12D = ꢁ49.73°) in the 2,4-dinitrobenzoate anion in
complex salt 4, while the nitro group at the para position is almost
planar with the aromatic ring (C2D–C3D–N31d–O32D = ꢁ0.52°).
In complex salts 1-4, the average Co–N and Co–O bond lengths,
and the bond angles O(1)–Co–O(2), N(1)–Co–N(2) and N(3)–Co–
N(4) are quite similar to those of reported related complexes
[26]. As expected, the bond lengths and bond angles for the anions
(i.e. carboxylates) are also similar to those ionic complexes of car-
boxylates reported in the literature [27].
Hydrogen bonding parameters (Å) of complex salt 3.
O1W
O1W
O2W
O61D
O61D
O62D
2.823(3)
2.793(3)i
2.816(3)
O2W
O3W
O62Dii
O4Wiii
2.938(3)
2.711(3)
Symmetry codes: (i) ꢁx ꢁ 1, ꢁy, ꢁz, (ii) ꢁx ꢁ 1, ꢁy + 1, ꢁz, (iii) ꢁx, ꢁy + 1, ꢁz + 1.
3.6.2. Packing
3.6.2.1. Complex salt 1. The complex salt 1 crystallizes in the tri-
clinic crystal system with space group P1. The asymmetric unit
ꢀ
of 1 contains one trifluoroacetate anion, one [Co(phen)2CO3]+
cation and five water molecules of crystallization (Fig. 1a). In the
crystal lattice, these components are held together by networks
of hydrogen bonds, like O–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀF (Fig. 1b).
The principal hydrogen bonding parameters are given in Table 4.
The oxygen atoms of the carbonato and carboxylate groups and
the fluorine atom of the trifluoroacetate are involved in hydrogen
bonding interactions with bond lengths ranging from 1.91 to
2.72 Å with water molecules and C–H groups of the 1,10-phenan-
throline ligands. The water molecules of crystallization make an-
ion–anion and cation–cation connections by O–Hꢀ ꢀ ꢀO
interactions. The complex cations form two dimensional sheets
which propagate to both directions by
between the 1,10-phenanthroline rings of the complex cations
with two different centroid-to-centroid separations of 3.672 and
3.722 Å, in the respective directions. These
tions are complemented by C–Hꢀ ꢀ ꢀO interactions between the car-
bonato oxygen atoms and C–H groups of 1,10-phenanthroline
ligands. The trifluoroacetate anions are held in the vacant space be-
tween the 1,10-phenanthroline wings of two complex cations by
C–Hꢀ ꢀ ꢀF interactions, as shown in Fig 1c and d.
p p stacking interactions
ꢁ
pꢁp stacking interac-
Fig. 3. The structural features observed in complex salt 3: (a) Molecular diagram of complex salt 3 with the atom numbering scheme, (b) Packing diagram of the complex salt
showing the anions residing in square cavities formed by complex cations, (c) Bonding environment around the anion in the lattice. Symmetry codes: (i) ꢁx, ꢁy, ꢁz; (ii) x ꢁ 1,
+y, +z ꢁ 1; (iii) ꢁx ꢁ 1, ꢁy + 1, ꢁz; (iv) ꢁx ꢁ 1, ꢁy, ꢁz; (v) x, +y + 1, +z.

R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
179
3.6.2.2. Complex salt 2. The complex salt 2 crystallizes in the tri-
clinic crystal system with space group P1. The asymmetric unit
placed in between the square cavities formed by the 1,10-phenan-
throline moieties. The packing diagram of the complex salt is
shown in Fig. 3b. The complex cation cavities are stabilized by C–
Hꢀ ꢀ ꢀO interactions between neighbouring complex cations and
ꢀ
of 2 contains one 4-chloro-3-nitrobenzoate anion, one [Co(phen)2-
CO3]+ cation and six water molecules of crystallization (Fig. 2a). In
this case, the constituent units are arranged in a Pillared layer like
structure where complex cations form the layers and anions are ar-
ranged like pillars, as shown in Fig. 2b. In the layers, the complex
p p stacking interactions between the phenanthroline moieties
ꢁ
of the complex cations (the centroid to centroid distances between
the phenanthroline moieties are 3.563 and 3.625 Å, which is indic-
cations are connected by
Both the 1,10-phenanthroline moieties coordinated to the cobal-
t(III) center (Co1) are involved in stacking with centroid-cen-
troid distances of 3.554 and 3.59 Å. The stacking interactions
are also instrumental in the formation of the pillars. Cation-anion
and anion-anion units are stacked with centroid-centroid dis-
tances of 3.846 and 3.838 Å respectively. The water molecules of
crystallization reside in the empty space between the pillars and
interact with anionic and cationic units through O–Hꢀ ꢀ ꢀO hydrogen
bonds. The oxygen atoms of the carboxylate (O51D, O52D) and ni-
tro groups (O11D, O12D) of anionic moieties are also involved in
C–Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀO interactions (Fig. 2c), thereby stabilizing
the crystal lattice. The hydrogen bonding parameters are given in
Table 5.
p
ꢁ
p
stacking and C–Hꢀ ꢀ ꢀO interactions.
ative of a significant
p p stacking interaction). The water mole-
ꢁ
cules of crystallization link the different constituent units in the
crystal lattice. The anionic moieties are held in the square cavity
by C–Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀO interactions. These anionic moieties are
p p
ꢁ
pꢁp
involved in
p p stacking interactions with one of the phen moie-
ꢁ
p
ꢁ
p
ties (the centroid to centroid distance is 3.743 Å and the dihedral
angle between the planes of the aromatic rings is 16.90o). In this
case, the anionic moieties are not involved in a
pꢁp stacking inter-
action with each other due to the steric hindrance produced by the
nitro group present in the ortho position. All the hydrogen bond
acceptor groups in the anionic moiety are involved in non-covalent
interactions, as shown in Fig. 3c. Additionally, one oxygen atom of
the nitro group is involved in Oꢀ ꢀ ꢀ
p (3.05 Å) interactions with the
aromatic ring of the complex cation, and the chloro atom present
in the para position is involved in a weak C–Hꢀ ꢀ ꢀCl (2.701 Å) inter-
action, with a closest Clꢀ ꢀ ꢀCl distance of 3.37 Å.
3.6.2.3. Complex salt 3. Complex salt 3 crystallizes in the triclinic
ꢀ
crystal system with space group P1 and consists of one complex
cation, one 4-chloro -2-nitrobenzoate anion and four water mole-
cules of crystallization. The molecular diagram of the complex salt,
along with the atom numbering scheme employed, is shown in
Fig. 3a. The hydrogen bonding parameters are given in Table 6. In
this complex salt, the packing arrangement of the constituent units
is quite different from complex salt 2. The anionic moieties are
3.6.2.4. Complex salt 4. The complex salt 4 crystallizes in the tri-
ꢀ
clinic crystal system ðP1Þ. The asymmetric unit of 4 consists of
one 2,4-dinitrobenzoate anion, one [Co(phen)2CO3]+ cation and
one water molecule of crystallization (Fig. 4a). In the crystal lattice,
these components are held together by a network of O–Hꢀ ꢀ ꢀO and
C–Hꢀ ꢀ ꢀO hydrogen bonds and
pꢁp stacking interactions. The main
Fig. 4. The structural features observed in complex salt 4: (a) Molecular diagram of the complex salt with the atom numbering scheme, (b) Bonding environment around the
anion in the lattice, (c) Packing diagram of the complex salt showing the zig-zag layer arrangement and on the right only cations are shown in the space filling model for
clarity. Symmetry codes: (i) ꢁx + 1, ꢁy + 1, ꢁz + 2; (ii) x ꢁ 1, +y + 1, +z; (iii) ꢁx, ꢁy + 1, ꢁz + 1; (iv) ꢁx, ꢁy, ꢁz + 2.

180
R.P. Sharma et al. / Polyhedron 47 (2012) 173–181
hydrogen bond distances are 2.944(4) and 2.720(4) Å for
O1Wꢀ ꢀ ꢀO2C and O1Wꢀ ꢀ ꢀO61D, respectively. In this case, the oxygen
atoms of the carboxylate and nitro groups of the 2,4-dinitrobenzo-
ate anions strongly interact with C–H groups of the cations result-
ing in a zig-zag layered arrangement of the complex cations
(Fig. 4c). The anions and water molecule of crystallization reside
in the voids created by the two layers. The anions are held in the
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2012.06.092.
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