Synthesis, spectral characterization, and single crystal X-ray structures of a series of manganese-2,2′-bipyridine complexes derived from substituted aromatic carboxylic acids

Article abstract of DOI:10.1016/j.ica.2010.09.040

Reaction of [Mn(2,2′-bpy)₂(OAc)](ClO₄)(H ₂O) with a series of aromatic carboxylic acids yields new Mn(II)carboxylates [Mn(2,2′-bpy)₂(L)](ClO₄)} ₂ (1-3), [Mn(2,2′-bpy)₂(L)₂

Full text of DOI:10.1016/j.ica.2010.09.040

Inorganica Chimica Acta 365 (2011) 430–438
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, spectral characterization, and single crystal X-ray structures of a series
of manganese-2,20-bipyridine complexes derived from substituted aromatic
carboxylic acids
1
⇑
Nallasamy Palanisami , Ramaswamy Murugavel
Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India
a r t i c l e i n f o
a b s t r a c t
Reaction of [Mn(2,20-bpy)2(OAc)](ClO4)(H2O) with a series of aromatic carboxylic acids yields new
Mn(II)carboxylates [Mn(2,20-bpy)2(L)](ClO4)}2 (1–3), [Mn(2,20-bpy)2(L)2] (4–5) and [Mn(2,20-bpy)2(L)(-
H2O)](ClO4) (6) (L = 2-aminobenzoate (2-aba) (1), 4-hydroxybenzoate (4-hba) (2), thiophene-2-carboxyl-
ate (2-tca) (3), 2-hydroxynapthoate (2-hnapa) (4), 3,5-diisopropylsalicylic acid (dipsa) (5), 2,4,
6-triisopropylbenzoate (tipba) (6)). The new compounds have been characterized with the aid of elemental
analysis, spectroscopy, and single-crystal X-ray diffraction studies. Compounds 1–3, which have been syn-
thesized from less bulky carboxylic acids, are dimeric in the solid-state. Compounds 4–6, which are derived
from more bulkier aromaric carboxylic acids, exist as monomeric complexes. In the case of 6, where very
bulky 2,4,6-triisopropyl benzoic acid is used as the starting material, only one carboxylate ligand binds to
the metal, resulting in a cationic complex. Interestingly in all the six complexes, the C–H hydrogen atoms
of the 2,20-bpy ligands are involved in extensive hydrogen bonding with the carboxylate oxygen atoms of
the adjacent molecules and hence form non-covalent 1-D or 2-D aggregates in the solid state.
Ó 2010 Elsevier B.V. All rights reserved.
Article history:
Received 16 March 2010
Received in revised form 3 August 2010
Accepted 28 September 2010
Available online 8 October 2010
Keywords:
Manganese complexes
Metal carboxylates
Synthesis
Spectroscopy
X-ray structures
1. Introduction
the metal center [23]. This chelator has been widely used as a sub-
stitute for amino acid side groups in mimic chemistry [24]. Chris-
Inorganic–organic hybrid compounds with extended structures
are of current interest for a variety of reasons [1–4]. Among these,
metal carboxylates have been extensively studied because the car-
boxylate group can bind to metal ion in many different coordination
modes, such as monodentate, bidentate and bridging [5–16]. In par-
ticular, manganese carboxylate chemistry has received considerable
attention due to a variety of viewpoints, such as magnetic materials
and bioinorganic chemistry. In the former area, it is now well recog-
nized that polynuclear Mn-carboxylate compounds often possess a
large number of unpaired electrons, thus making them attractive
magnetic materials. Recently, several manganese complexes have
been found to exhibit single-molecule magnetism, where individual
molecules function as magnetizable magnets in the absence of an
external magnetic field and with no long-range ordering from inter-
molecular interactions [17–19]. On the other hand, binuclear Mn(II)
complexes with a carboxylate ligand are of interest due to their pres-
ence in metalloenzymes such as Mn-catalase which is responsible
for disproportionation H2O2 into H2O and O2 [20–22].
tou et al. have studied the Mn-carboxylate-2,20-bpy system and
produced a series of bi- or polynuclear manganese complexes.
Many of these compounds have been found to useful as single
molecular magnets [25–27].
For the above mentioned reasons, we have investigated in the
present work the reactions of a preformed manganese-2,20-bpy
system towards a series of amino and hydroxyl group substituted
aromatic carboxylic acids and other sterically hindered benzoic
acids (the additional functional groups can take part in intra-
and/or intermolecular hydrogen bonding apart from coordinating
to the manganese ion). In order to unravel the role of auxiliary
functionalities on supramolecular structure formation, the studies
were restricted to mono carboxylic acids as ligands, since the pres-
ence of more than one –COOH group on the aromatic system
invariably leads to covalently linked framework structures. The re-
sults of this investigation, describing the synthesis of six new man-
ganese carboxylates, their spectral characterization and X-ray
structure determination, are reported in this contribution.
2,20-Bipyridine is an ancillary ligand that controls the aggrega-
tion behavior of the metal complexes due to its chelation around
2. Experimental section
⇑
Corresponding author. Tel.: +91 022 25767163; fax: +91 022 25767152.
E-mail address: rmv@chem.iitb.ac.in (R. Murugavel).
Present address: School of Advanced Sciences, VIT University, Vellore 632 014,
General: all the starting materials and the products were found
to be stable towards moisture and air, and hence no specific precau-
tion was taken to rigorously exclude air during the manipulation of
1
India.
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.09.040

N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
431
the compounds. Elemental analyses were performed on a Carlo
309 (993). Fluorescence: (kex = 309 nm, MeOH): 417 nm.
0.0192.
U =
Erba (Italy) Model 1106 Elemental Analyzer at IIT-Bombay. Infrared
spectra were recorded on a Perkin Elmer Spectrum One spectrom-
eter One as KBr diluted disks. UV–Vis spectra were obtained on a
Shimadzu UV-260 spectrophotometer. Magnetic susceptibility
was measured on a PAR vibrating sample magnetometer. Commer-
cial grade solvents were purified by employing conventional
procedures and were distilled prior to their use [28]. Commercially
available starting materials Mn(OAc)2ꢀ4H2O (E. Merck), 4-hydroxy-
benzoic acid (s.d. fine), 2-hydroxynapthoic acid (SISCO), 2-amino-
benzoic acid (s.d. fine), 3,5-diisopropylsalicylic acid (Aldrich),
2,4,6-triisopropylbenzoic acid and thiophene-2-carboxylic acid
(Aldrich) were used as received. [Mn(O2CCH3)(2,2,-bpy)2]ClO4ꢀH2O
was synthesized as described previously in the literature [29].
Synthesis: compounds 1–6 were prepared using a similar syn-
thetic procedure. Only the details of the preparation of complex
1 is described here: [Mn(OAc)(H2O)(2,2,-bpy)2](ClO4) (544 mg,
1 mmol) was dissolved in methanol (40 mL). To this, a clear solu-
tion of 2-aminobenzoic acid (137 mg in 10 mL of methanol,
1 mmol) was added. The resulting solution was stirred for 2 h
and filtered. The filtrate was kept at room temperature for crystal-
lization. X-ray quality crystals of 1 were formed from this solution
after one week.
Single-crystal X-ray diffraction: single crystals of 4–5 for X-ray
structure analysis were obtained from methanol-dichloromethane
mixture, 1–3 and 6 were from methonal at room temperature. A
suitable crystal of each compound was used for the diffraction
studies on a STOE AED2 diffractometer. The structure solution
was achieved by direct methods as implemented in SHELXS-97 and
the final refinement of the structures was carried using full least-
squares methods on F2 using SHELXL-97 [30]. The positions of hydro-
gen atoms attached to oxygen or nitrogen atoms were identified
from the successive difference Fourier maps and were included
in further calculations and refinement. The CꢁH hydrogen atoms
were placed on calculated positions and refined using a riding
model. Other details pertaining to data collection, structure solu-
tion, and refinement are given in Table 1.
3. Result and discussion
3.1. Synthesis
Manganese precursor complex with a non-coordinating anion,
[Mn(2,20-bpy)2(OAc)](ClO4)ꢀH2O was used as a starting material
in this study to synthesize all the new manganese carboxylates.
The synthesis of the new complexes 1–6 have been achieved using
a similar synthetic procedure by reacting one equivalent of metal
precursor with one equivalent of the corresponding carboxylic acid
in a methanol solution (Scheme 1). In all cases, the reaction was
complete within a few hours at room temperature. The products
have been obtained as single crystals directly from the reaction
mixture in almost all cases in moderate to high yields. The isolated
products were found to be analytically pure (Table 2) and were
additionally characterized by means of IR, UV–Vis absorption and
emission spectroscopy studies. All products are air-stable and sol-
uble in common organic solvents. Selected physical and character-
ization data for the new carboxylates are listed in Table 2.
Compound 1: yield: 0.136 g (29%). Mp. 238–242 °C (decomp).
Anal. Calc. for C54H48N10O14Mn2Cl2: C 53.8; H 3.8; N 11.6. Found:
C 53.7; H 3.7; N 11.7%. IR (KBr, cmꢁ1): 3447(s), 3357(s), 3076(w),
1619(s), 1601(vs), 1578(vs), 1536(s), 1474(m), 1450(m), 1439(vs),
1387(vs), 1315(w), 1314(w), 1262(m), 1247(m), 1091(vs),
1015(s), 864(w), 767(s), 752(vs), 739(m), 623(s). UV–Vis (MeOH,
nm,
397 nm.
e
, cmꢁ1 Mꢁ1): 321 (837). Fluorescence: (kex = 321 nm, MeOH):
= 0.069.
U
Compound 2 : yield: 0.391 g (63%). Mp. 246–250 °C (decom).
Anal. Calc. for C27H23N4O7MnCl: C 53.7; H 3.5; N 9.3. Found: C
52.2; H 3.9; N 8.9%. IR (KBr, cmꢁ1): 3417(br), 3116 (w), 3080 (m),
1598(vs), 1563(vs), 1439(vs), 1390(vs), 1313(w), 1277(m),
1222(w), 1087(vs), 1014(m), 857(m), 793(m), 763(s), 737(m),
621(m UV–Vis (MeOH, nm,
cence: (kex = 307 nm, MeOH): 403 nm.
e
, cmꢁ1 Mꢁ1): 307 (1041). Fluores-
= 0.046.
U
Compound 3: yield: 0.236 g (38%). Mp. 240–242 °C. Anal. Calc.
for C25H19N4O6SClMn: C 50.6; H 3.2; N 9.8; S 5.7. Found: C 51.5;
H 3.3; N 9.8; S 5.7%. IR (KBr, cmꢁ1): 3429(br), 3111(w), 3071(w),
3079(m), 1590(vs), 1522(s), 1473(w), 1438(s), 1423(s), 1438(s),
1385(m), 1340(s), 1318(w), 1246(w), 1223(w), 1087(vs),
3.2. Characterization of 1–6
The IR spectrum for compound 1 shows characteristic NꢁH
stretching vibration at around 3370 cmꢁ1 due to the free –NH2
group of the 2-aba ligand. Compounds 2, 5 and 6 show absorption
at around 3400 cmꢁ1 due to the OꢁH stretching. This absorption is
due to the presence of coordinated water molecules in the case of
6, while it is due to the phenolic OꢁH group in 2 and 5. The infrared
absorption at around 3080 cmꢁ1 in all complexes is due to aro-
matic CꢁH vibrations. Additionally, strong aliphatic CꢁH vibra-
tions occur at around 2960 cmꢁ1 for the isopropyl groups in 4
1016(m), 860(w), 796(s), 763(s), 623(m). UV–Vis (MeOH, nm,
e,
cmꢁ1 Mꢁ1): 308 (966).
Compound 4: yield: 0.139 g (36%). Mp. >260 °C. Anal. Calc. for
C
42H30MnN4O6: C 68.0; H 4.1; N 7.6. Found: C 67.4; H 4.2; N
7.7%. IR (KBr, cmꢁ1): 3413(br), 3058 (m), 3019(w), 2924(w),
1645(s), 1595(s), 1563(vs), 1511(vs), 1466(vs), 1439(vs), 1389(s),
1372(vs), 1313(s),1239(m), 1159(m), 1013(m), 914(m), 879(m),
and 5. The
m
m
m
as(COOꢁ) band is observed at around 1600 cmꢁ1 while
sym(COOꢁ) is observed at 1380 cmꢁ1; the difference between the
as(COOꢁ) and sym(COOꢁ) frequencies ( = 220 cmꢁ1) is consis-
805(w), 775(m), 762(s), 736(m), 643(m). UV–Vis (MeOH, nm,
cmꢁ1 Mꢁ1): 340 (1595). Fluorescence: (kex = 340 nm, MeOH):
503 nm. = 0.021.
e,
m
Dm
U
tent with the monodentate coordination mode of carboxylate li-
Compound 5: yield: 0.433 g (80.0%). Mp. 208–212 °C. Anal. Calc.
for C46H50N4O6.5Mn: C 68.2; H 6. 2; N 6.9. Found: C 67.8; H 6.2; N
6.9%. IR (KBr, cmꢁ1): 3447(br), 3071 (m), 3025(w), 2962(vs),
2871(w), 1627(s), 1594(s), 1567(vs), 1462(vs), 1439(vs), 1398(s),
1292(m), 1152(m), 1012(m), 918(m), 892(m), 814(m), 767(s),
gands in these complexes. Strong IR band observed at around
1090 cmꢁ1 indicates the presence of ClO4 anion in complexes 1–
ꢁ
3 and 6.
A single absorption observed in the range 300–340 nm for all
*
p–p transition of the
the compounds could be ascribed to the
740(m), 644(m). UV–Vis (MeOH, nm,
e
, cmꢁ1 Mꢁ1): 321 (1041).
= 0.0386.
2,20-bipyridine ligand and/or the aryl rings of the carboxylate li-
gands (Table 2). Due to the d5 configuration of Mn2+ ion, no absorp-
tions are expected in the visible region of the spectrum. The
emission spectra of complexes 1–6 have been studied in methano-
lic solution by exciting the compound in the region 300–340 nm. A
single strong emission was observed in each case, however with
varying degrees of Stokes shift from the respective absorption
maxima (Table 2). While the least shift was observed for dimeric
Fluorescence: (kex = 321 nm, MeOH): 428 nm.
U
Compound 6: yield: 0.510 g (69.0%). Mp. 245–246 °C (decomp).
Anal. Calc. for C36H41N4O7MnCl: C 58.8; H 5.8; N 7.8. Found: C
58.8; H 5.8; N 8.0%. IR (KBr, cmꢁ1): 3430(br), 3070(w), 2959(s),
2927(w), 2862(w), 1603(s), 1575(s), 1537(vs), 1474(s), 1439(vs),
1398(s), 1314(m), 1246(w), 1120(vs), 1016(m), 918(m), 790(w),
764(s), 738(m), 651(m), 622(s). UV–Vis (MeOH, nm, e
, cmꢁ1 Mꢁ1):

432
N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
Table 1
Crystal data for 1–6.
1
2
3
4
5
6
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
27H22ClMnN5O6
C27H21ClMnN4O7
635.87
133(2)
C25H19ClMnNO6S
593.89
103(2)
C42H30MnN4O6
741.46
133(2)
0.71073
monoclinic
C2/c
21.99(2)
10.585(7)
15.196(1)
–
114.111(1)
–
3228.6(4)
8
1.526
0.470
C46H50MnN4O6
809.84
133(2)
0.71073
orthorhombic
Pbcn
C36H41ClMnN4O7
732.12
133(2)
602.89
293(2)
0.71073
monoclinic
C2/c
32.091(6)
11.099(2)
17.236(3)
–
120.14(3)
–
5309(2)
8
1.508
0.650
2472
0.71073
0.71073
0.71073
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
10.007(7)
12.369(9)
11.896(8)
71.043(5)
82.978(6)
80.967(5)
1371.3(2)
2
1.540
0.641
650
0.40 ꢂ 0.20 ꢂ 0.20
1.75–24.83
4705/0/463
1.057
8.356(6)
12.358(9)
13.8131(1)
65.729(1)
74.065(1)
87.736(1)
1245.9(2)
2
1.583
0.771
606
0.40 ꢂ 0.20 ꢂ 0.20
2.54–26.37
5092/234/426
1.143
28.17(6)
8.718(17)
33.518(7)
–
–
–
8230(3)
8
1.307
0.375
3416
7.876(2)
9.818(2)
24.255(5)
96.53(3)
92.90(3)
103.94(3)
1802.5(6)
2
1.349
0.493
766
0.30 ꢂ 0.20 ꢂ 0.20
1.70–24.65
6042/0/450
0.859
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
Absorbtion coefficient (mmꢁ1
F(0 0 0)
)
1532
Crystal size (mm3)
h Range (°)
0.30 ꢂ 0.30 ꢂ 0.20
1.47–24.79
4543/0/449
1.041
0.30 ꢂ 0.20 ꢂ 0.15
2.03–26.39
3310/0/300
1.256
0.30 ꢂ 0.30 ꢂ 0.20
1.45–24.89
7137/0/714
0.837
Data/restraints/parameters
Goodness-of-fit on F2
R1 [I > 2
R2 [I > 2
r
r
(I)]
(I)]
0.0385
0.0993
0.0406
0.1057
0.0465
0.1044
0.0627
0.1322
0.0341
0.0595
0.0472
0.0728
Scheme 1. Synthesis of manganese complexes 1–6.
Table 2
Characterization data for 1–6.
Ua
leff (BM)
b
Compound number
Yield (%)
Analysis, found (calc.) (%)
UV–Vis (nm)
Fluorescence (nm)
C
H
N
S
1
2
3
4
5
6
29
63
38
36
80
40
53.7 (53.8)
52.2 (53.7)
51.5 (50.6)
67.2 (68.0)
67.8 (68.2)
58.8 (58.8)
3.7 (3.8)
3.9 (3.5)
3.3 (3.2)
4.2 (4.1)
6.2 (6.2)
5.8 (5.8)
11.7 (11.6)
9.3 (8.9)
9.8 (9.8)
7.6 (7.7)
6.9 (6.9)
7.8 (8.0)
–
–
321
307
308
340
321
309
397
403
–
503
428
417
0.069
0.046
–
0.021
0.0386
0.0192
6.22
6.24
5.87
6.24
6.28
6.16
5.7 (5.7)
–
–
–
a
U
(2,20-bpy) = 0.018.
Spin only value: 5.92 BM.
b
complex 1 which contains anthranilic acid, the largest shift has
been observed for 4. It is unlikely that this is an intra-ligand
fluorescent emission but could be attributed to the charge transfer
between the metal and ligand, since free 2,20-bpy ligand does not
show any luminescence in the range of 400–500 nm [31–32]. The
absorption and emission values of all compounds are listed in

N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
433
Table 3
Comparison of structural features of Mn2+ carboxylate complexes with additional N-coordination.
0
0
0
Compound
Mn geometry
Nature of COOꢁ
Reference
av. Mn–O (AÅ)
av. Mn–N (AÅ)
MnꢀꢀꢀO (ÅA)
{[Mn(2,20-bpy)2(2-aba)](ClO4)}2 (1)
{Mn(4-hba)(2,20-bpy)2](ClO4)}2 (2)
{Mn(2-tca)(2,20-bpy)2](ClO4)}2 (3)
[Mn(2,20-bpy)2(2-hnapa)2] (4)
[Mn(2,20-bpy)2(dipsa)2] (5)
dist. Oh
dist. Oh
dist. Oh
dist. Oh
dist. pbp
dist. Oh
dist. Oh and tbp
dist. Oh
dist. Oh
dist. Oh
2.117(2)
2.120(2)
2.125(2)
2.144(2)
2.130(2)
2.156(2)
2.206(2)
2.235
2.276(2)
2.278(2)
2.254(2)
2.294(3)
2.303(2)
2.262(3)
2.378(2)
2.285
4.64(8)
4.446(1)
4.789(4)
–
–
–
3.452(2)
4.081
–
–
–
bridging
bridging
bridging
monodentate
monodentate
monodentate
bridging
this work
this work
this work
this work
this work
this work
[34]
[36]
[38]
[37]
[37]
[Mn(2,20-bpy)2(tipba)(H2O)](ClO4) (6)
[Mn3(4-aba)6]n
[Mn2(OAC)2(4-aba)2(2,20-bpy)2]
[Mn(2,20-bpy)2(2,6-dhba)2]
[Mn(4-hba)(H2O)(phen)2](4-hba)(H2O)
[Mn(2,20-bpy)2(5-SO3Sal)(H2O)](H2O)
bidentate
2.112(2)
2.10(6)
2.10(1)
2.255(2)
2.27(6)
2.27(4)
monodentate
monodentate
monodentate
dist. Oh
2,20-Bpy = 2,20-bipyridine, phen = 1,10-phenanthroline, 2-aba = 2-aminobenzoic acid, tiba = 2,4,6-triisopropylbenzoic acid, hnapa = 2-hydroxynapthoic acid, 4-hba = 4-
hydroxybenzoic acid, dhba = dihydroxybenzoic acid, Sal = salicylic acid, dipsa = 3,5-diisopropylsalicylic acid.
Table 2. The room temperature magnetic moment of manganese
carboxylates 1–6 ( found = 5.8–6.4 BM) is consistent with the high
spin d5 configuration of Mn2+ ions (
s = 5.92 BM).
The molecular structures of compounds 1–6 have been estab-
lished unambiguously by single crystal X-ray diffraction studies.
Selected structural parameters of these complexes along with
those of structurally similar literature examples are listed in Table
3. The hydrogen bonding parameters are listed in Table 4.
to related compounds {[Mn3(4-aba)6]n (av. Mn–O: 2.060(2)),
[Mn2(OAc)2(4-aba)2(2,20-bpy)2] (av. Mn–O: 2.109(8) Å), [Mn(2,20-
bpy)2(2,6-dhba)2] (av. Mn–O: 2.112(2) Å) and [Mn(4-hba)(-
H2O)(1,10-phen)2](4-hba)(H2O) (av. Mn–O: 2.10(6) Å)} [33–38].
Each manganese ion is further coordinated by two 2,20-bpy ligands
(av. Mn–N: 2.275(2) Å) leading to distorted octahedral geometry
around the metal ion. The Mn–Vn distance (4.64(8) Å) is signifi-
cantly longer than those found in {[Mn2(OAc)2(4-aba)2-
(2,20-bpy)2] (4.081 Å) and [Mn3(4-aba)6]n (3.452(2) Å) [33–36].
The –NH2 group forms hydrogen bonding N–HꢀꢀꢀO) (H(5B)ꢀꢀꢀO(4)
2.249(3) Å, \N(5)–H(5B)ꢀꢀꢀO(4) 159.6(3)°) with neighboring oxy-
gen atom of perchlorate anion. Oxygen atoms of carboxylate group
and the perchlorate anions forms intermolecular C–HO hydrogen
bonds with –CH group of coordinated 2,20-bpy molecules (Table
l
l
3.3. Molecular structures 1–3
The crystal structure of complex consists 1 of a dimeric
2+
[Mn(2,20-bpy)2(2-aba)]2 cation and two perchlorate anions, as
shown in Fig. 1. The carboxylate group of the 2-aba ligand acts as
the bidentate bridging ligand, and bridges two Mn atoms in a sy-
n,anti-fashion to form a dimer. The Mn–O(l) and Mn–O(2) bond
lengths are similar (2.091(2) and 2.142(2) Å) and are comparable
4; Fig. 2). The compound is further stabilized by
p–p aromatic
stacking interactions between the 2,20-bpy and aminobenzoic acid
ligand (distance between the centroids 4.549 Å).
The core structure of 2 is very similar to that of 1. The Mn2+ ion
in 2 is octahedrally coordinated by two chelating 2,20-bpy and two
syn,anti bridging carboxylate ligands (Table 3, Fig. 3). The Mn–Mn
distance (4.446(1) Å) is somewhat shorter than that observed in
{[Mn(2,20-bpy)2(2-aba)](ClO4)}2 (1) (4.64(8) Å) but longer than in
many carboxylate-bridged dinuclear Mn(II) complexes (Table 3).
Table 4
Hydrogen bonds in 1–6.
D–HꢀꢀꢀA
1
D–H (Å)
HꢀꢀꢀA (Å)
DꢀꢀꢀA (Å)
D–HꢀꢀꢀA (°)
N(5)H(5B)ꢀꢀꢀO(4)a
C(14)H(14)ꢀꢀꢀO(3)b
C(20)H(20)ꢀꢀꢀO(2)a
2
0.871(3)
0.88(4)
0.953(3)
2.249(3)
2.492(4)
2.298(8)
3.08(4)
3.278(1)
3.213(3)
159.6(3)
149.1(3)
160.6(3)
O(3)H(3A)ꢀꢀꢀO(6)a
C(4)H(4)ꢀꢀꢀO(5)b
C(7)H(7)ꢀꢀꢀO(5)b
C(20)H(20)ꢀꢀꢀO(2)c
3
0.847(4)
0.864(4)
0.910(3)
0.914(4)
2.113(4)
2.601(3)
2.444(3)
2.592(3)
2.958(4)
3.406(4)
3.347(4)
3.483(4)
175.1(4)
155.5(3)
171.5(3)
164.8(3)
C(17)H(17)ꢀꢀꢀO(4)a
C(13)H(13)ꢀꢀꢀO(6)b
4
0.929(1)
0.923(1)
2.546(2)
2.365(2)
3.44(3)
3.284(3)
162.4(1)
173.8(5)
O(3)H(3A)ꢀꢀꢀO(2)a
C(9)H(9)ꢀꢀꢀO(3)b
5
0.796(1)
0.922(4)
1.778(1)
2.493(4)
2.552(4)
3.27(4)
155.2(4)
142.2(3)
O(3)H(3A)ꢀꢀꢀO(2)a
O(6)H(6A)ꢀꢀꢀO(5)a
C(9)H(9)ꢀꢀꢀO(5)b
6
0.94(8)
1.027(3)
0.948(1)
1.599(3)
1.529(5)
2.186(1)
2.499(2)
2.506(2)
3.131(1)
159.0(3)
156.8(3)
174.8(2)
O(3)H(3A)ꢀꢀꢀO(2)a
O(3)H(3B)ꢀꢀꢀO(12)e
C(4)H(4)ꢀꢀꢀO(13)b
C(7)H(7)ꢀꢀꢀO(13)b
C(9)H(9)ꢀꢀꢀO(12)c
C(9)H(9)ꢀꢀꢀO(3)c
C(17)H(17)ꢀꢀꢀO(2)d
C(19)H(19)ꢀꢀꢀO(11)c
0.985(1)
0.76(4)
0.95(4)
0.95(3)
0.95(4)
0.95(4)
0.95(4)
0.95(4)
1.673(4)
2.095(4)
2.472(3)
2.712(3)
2.709(3)
2.709(3)
2.604(3)
2.37(3)
2.637(4)
2.828(4)
3.515(5)
3.653(5)
3.36(6)
3.578(5)
3.485(5)
3.286(6)
165.1(4)
162.4(5)
171.6(3)
170.8(2)
140.0(3)
152.5(3)
154.3(2)
161.7(3)
2+
Fig. 1. Molecular structure of [Mn(2,20-bpy)2(2-aba)]2 cation in 1. Selected bond
lengths and bond angles: Mn(1)–N(1) 2.272(2), Mn(1)–N(2) 2.284(2), Mn(1)–N(3)
2.307(2), Mn(1)–O(2) 2.091(2), Mn(1)–O(1) 2.142(2), N(5)–H(5A) 0.865(3), N(5)–
H(5B) 0.870(7) Å; N(4)–Mn(1)–N(1) 165.30(7), N(4)–Mn(1–N(2) 103.07(7),
N(1)–Mn(1)–N(2) 71.55(7), N(4)–Mn(1)–N(3) 72.72(7), N(1)–Mn(1)–N(3)
92.84(7), N(2)–Mn(1)–N(3) 82.43(8), O(1)–Mn(1)–O(2) 98.54(1)°.
Equivalent positions for 1: (a) 1/2 ꢁ x, 1/2 ꢁ y, 1 ꢁ z (b) x, ꢁ1 + y, z; for 2: (a) x, y, z
(b) 2 ꢁ x, ꢁy, 2 ꢁ z (c) 1 ꢁ x, 1 ꢁ y, 2 ꢁ z; for 3: (a) ꢁx, ꢁy, 1 ꢁ z (b) ꢁ1 + x, y, z; for 4:
(a) x, y, z (b) 3/2 ꢁ x, 1/2 ꢁ y, 1 ꢁ z; for 5: (a) x, y, z (b) x, ꢁ1 + y, +z; for 6: (a) x, y, z (b)
1 ꢁ x, 2 ꢁ y, 1 ꢁ z (c) ꢁ1 + x, y, z (d) x, ꢁ1 + y, +z (e) x, 1 + y, +z.

434
N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
The –OH group of 4-hba forms intermolecular hydrogen bonding
O–HꢀꢀꢀO) (H(3A)ꢀꢀꢀO(6) 2.113(4) Å, \O(3)–H(3A)ꢀꢀꢀO(6) 175.1(4)°)
with neighboring oxygen atom of perchlorate anion. Oxygen atoms
of carboxylate group and the perchlorate anions forms intermolec-
ular C–HꢀꢀꢀO hydrogen bonds with –CH group of coordinated 2,20-
bpy molecules (Fig. 2 – middle).
of coordinated 2,20-bpy molecule results to a 1-D polymeric struc-
ture as shown in Fig. 2 (bottom) (Table 4). The conformation of the
central eight-membered ring in compounds 1–3 is pictorially
shown in Fig. 5.
3.4. Molecular structure of 4
The structure of 3 is similar to 1 and 2 described above (Fig. 4).
The Mn2+ ion in 3 is octahedrally coordinated by two chelating
2,20-bpy and two bridging carboxylate ligands. The bond lengths
and angles around the Mn2+ ion are comparable to 1 and 2 (Table
3). The Mn–Vn distance (4.789(4) Å) is longer than both {[Mn(2,20-
bpy)2(2-aba)](ClO4)}2 (1) (4.64(8) Å) and {[Mn(2,20-bpy)2(4-hba)](-
ClO4)}2 (2) (4.446(1) Å) (Table 3). Oxygen atoms of perchlorate an-
ions forms intermolecular (C–HꢀꢀꢀO) [(H(13)ꢀꢀꢀO(6) 2.546(2) Å,
\C(13)–H(13)ꢀꢀꢀO(6) 162.4(1)° and (H(17)ꢀꢀꢀO(4) 2.365(2) Å,
\C(17)–H(17)ꢀꢀꢀO(4) 173.8(5)°] hydrogen bonds with –CH group
[Mn(2,20-bpy)2(2-hnapa)2] (4) crystallizes in monoclinic C2/c
space group (Fig. 6). Unlike the compounds 1–3, perchlorate anion
of the starting material is replaced by 2-hydroxynapthoic acid (2-
hnapa). The Mn2+ ion in 4 is octahedrally coordinated by two che-
lating 2,20-bpy and two monodendate 2-hydroxynapthoic acid li-
gands. Surprisingly, the two 2-hydroxynapthoate ligands occupy
a cis-configuration around the metal in spite of the bulkiness of
this ligand. The bond lengths and bond angles around manganese
ions are comparable to those of compounds 1–3 (Table 3). One of
Fig. 2. Hydrogen bonded chain formation in (top) 1, (middle) 2, and (bottom) 3 (C–H hydrogen atoms that are not involved in H-bonding were omitted for clarity).

N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
435
2+
Fig. 3. Molecular structure of [Mn(2,20-bpy)2(4-hba)]2 cation in 2. Selected bond
lengths and bond angles: Mn(1)–N(1) 2.278(2), Mn(1)–N(2) 2.282(2), Mn(1)–N(3)
2.280(2), Mn(1)–N(4) 2.273(2), Mn(1)–O(1) 2.143(2), Mn(1)–O(2) 2.096(2) Å; N(4)–
Mn(1)–N(1) 95.92(8), N(4)–Mn(1)–N(2) 164.71(8), N(1)–Mn(1)–N(2) 71.90(8),
N(4)–Mn(1)–N(3) 72.31(8), N(1)–Mn(1)–N(3) 89.58(8), N(2)–Mn(1)–N(3)
97.82(8), O(1)–Mn(1)–O(3) 101.81(7)°.
Fig. 5. Mn2O4C2 eight-membered ring conformations in 1 (top), 2 (middle), and 3
(bottom). Atoms drawn not to scale.
2+
Fig. 4. Molecular structure of [Mn(2,20-bpy)2(2-tca)]2 cation in 3. Selected bond
lengths and bond angles: Mn(1)–N(1) 2.256(2), Mn(1)–N(2) 2.244(2), Mn(1)–N(3)
2.279(2), Mn(1)–N(4) 2.238(2), Mn(1)–O(2) 2.109(2), Mn(1)–O(2)#1 2.140(2) Å;
N(4)–Mn(1)–N(1) 166.8(8), N(4)–Mn(1)–N(2) 109.1(7), N(1)–Mn(1)–N(2) 72.62(8),
N(4)–Mn(1)–N(3) 72.84(8), N(1)–Mn(1)–N(3) 94.44(8), N(2)–Mn(1)–N(3) 85.94(7),
O(1)–Mn(1)–O(2) #1 88.22(1)°. Symmetry transformations used to generate
equivalent atoms: #1 1 ꢁ x, 1 ꢁ y, ꢁz.
the oxygen atom of the carboxylate group forms intramolecular
hydrogen bonding with –OH group of 2-hydroxynapthoic acid. In
addition, C–H group of 2,20-bpy ligand is involved intermolecular
hydrogen bonding with oxygen atom hydroxyl group to the neigh-
boring molecule, which leads to the zig-zag 1-D polymeric struc-
ture as shown in Fig. 7 (Table 4).
Fig. 6. Molecular structure of [Mn(2,20-bpy)2(2-hnapa)2] (4). Selected bond lengths
and bond angles: Mn(1)–N(1) 2.320(3), Mn(1)–N(2) 2.268(3), Mn(1)–O(1)
2.144(2) Å; N(2)#1–Mn(1)–N(1)#1 71.21(9), N(2)#1–Mn(1)–N(2) 156.76(1),
N(2)–Mn(1)–N(1)#1 90.54(9), O(1)–Mn(1)–O(1)#1 97.90(1)°. Symmetry transfor-
mations used to generate equivalent atoms: #1 1 ꢁ x, y, 1/2 ꢁ z.
3.5. Molecular structure of 5
Compound 5 crystallizes in orthorhombic Pbcn space group, in
which Mn2+ ion exists in an octahedral geometry, with four
nitrogen atoms of the 2,20-bpy ligand and two oxygen atoms of
monodentate carboxylate ligands. In addition, one of the carboxyl-
ate oxygen shows a interaction (Mn(1)–O(2) 2.75(3) Å) with
metal center (Fig. 8, Table 3). As in the case of 4, the two

436
N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
Fig. 7. Hydrogen bonding pattern of [Mn(2,20-bpy)2(2-hnapa)2] (4) (C–H hydrogen atoms are omitted for clarity).
Fig. 10. Molecular structure of [Mn(2,20-bpy)2(tipba)(H2O)](ClO4) (6). Selected
bond lengths and bond angles: Mn(1)–N(1) 2.290(3), Mn(1)–N(2) 2.242(3), Mn(1)–
N(3) 2.265(3), Mn(1)–N(4) 2.251(3), Mn(1)–O(2) 2.126(2), Mn(1)–O(3) 2.186(3) Å;
N(4)–Mn(1)–N(1) 86.19(10), N(4)–Mn(1)–N(2) 94.04(11), N(1)–Mn(1)–N(2)
72.20(11), N(4)–Mn(1)–N(3) 72.51(11), N(1)–Mn(1)–N(3) 92.53(10), N(2)–Mn(1)–
N(3), 160.58(9), O(1)–Mn(1)–O(3) 88.22(10)°.
Fig. 8. Molecular structure of [Mn(2,20-bpy)2(dipsa)2] (5). Selected bond lengths
and bond angles: Mn(1)–N(1) 2.397(2), Mn(1)–N(2) 2.283(2), Mn(1)–N(3) 2.271(2),
Mn(1)–N(4) 2.264(2), Mn(1)–O(4) 2.055(2), Mn(1)–O(1) 2.205(2), Mn(1)–O(2)
2.75(3) Å; N(4)–Mn(1)–N(1) 83.35(6), N(4)–Mn(1)–N(2) 149.47(6), N(1)–Mn(1)–
N(2) 69.6(6), N(4)–Mn(1)–N(3) 72.16(6), N(1)–Mn(1)–N(3) 86.66(6), N(2)–Mn(1)–
N(3) 91.82(6)°.
the oxygen of adjacent carboxylate group (Table 4), leading to the
formation of a 1-D polymeric association as depicted in Fig. 9.
diisopropylsalicylate ligands occupy a cis-configuration around the
metal ion, in spite of the huge steric bulk of this ligand and the
additional presence of phenolic –OH group. The molecule is further
stabilized by intra and intermolecular hydrogen bonding. The free
–OH group of dipsa forms intramolecular hydrogen bonding with
the oxygen atom of carboxylate group. The –C–H hydrogen of
2,20-bpy also forms intermolecular hydrogen bonding C–HꢀꢀꢀO with
3.6. Molecular structure of 6
The molecular structure of complex 6 consists of a discrete
[Mn(2,20-bpy)2(tiba)(H2O)]+ cation and
a
perchlorate anion
(Fig. 10). It appears that the bulkiness of the tiba ligand does not
Fig. 9. Hydrogen bonding pattern in [Mn(2,20-bpy)2(dipsa)2] (5) (C–H hydrogen atoms are omitted for clarity).

N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
437
Fig. 11. Hydrogen bonding pattern [Mn(2,20-bpy)2(tipba)(H2O)](ClO4) (6) (C–H hydrogen atoms are omitted for clarity). The interaction of bipyridine hydrogen with
coordinated carboxylate and uncoordinated perchlorate oxygen atoms lead to the observed 2-D supramolecular motif.
allow coordination of two carboxylate ligands to the metal and
hence a cationic complex is formed. To complete the coordination
sphere a water ligand binds to the metal. Thus, as illustrated in
Fig. 10, the Mn(II) ion is coordinated by two chelating 2,20-bpy li-
gands (with Mn–N bond lengths (2.242(3)–2.290(3) Å) and further
coordinated by two oxygen atom from monodendate carboxylato
ligand and water molecule to form a distorted octahedral N4O2
environment (Table 3).
steric congestion dictates the formation of a monomeric complex
6 with coordinated water molecule. Finally, several of these com-
plexes contain reactive –NH2 and –OH group on their surface,
which can be reacted further with organmetallic reagents such as
AlMe3 or ZnMe2 to produce hetrometallic clusters.
Acknowledgment
Both the hydrogen atoms of the coordinated water molecule are
involved in hydrogen bonding interactions (Table 4). While one of
the protons is involved in a very strong hydrogen bonding with the
carbonyl oxygen (HꢀꢀꢀA 1.672 Å; DꢀꢀꢀA 2.637 Å), the second proton
exhibits a somewhat weak hydrogen bonding to the oxygen of
the nearby perchlorate anion (HꢀꢀꢀA 2.095 Å; DꢀꢀꢀA 2.828 Å). This
difference results in non-equal hydrogen bonds for the two protons
of the water molecule (O3–H3A 0.986 Å; O3–H3B 0.757 Å), as it has
been observed for water molecule coordinated to copper ion in the
vicinity of phosphoryl groups.[39] Two intermolecular hydrogen
bondings (O–HꢀꢀꢀO and C–HꢀꢀꢀO), originating from the –OH of water
molecule, oxygen atom of perchlorate anion, and the –CH of 2,20-
bpy rings, leads to the formation of a 2-D layer structure as shown
in the Fig. 11.
This work was supported by DST, New Delhi.
Appendix A. Supplementary material
CCDC 765614, 765615, 765616, 765617, 765618 and 765619
contain the supplementary crystallographic data for compounds
1, 2, 3, 4, 5 and 6, respectively. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.ica.2010.09.040.
References
[1] J.M. Lehn, Supramolecular Chemistry, Concepts and Perspectives, VCH,
Weinheim, 1995.
[2] M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M. O’Keeffe, O.M. Yaghi,
Acc. Chem. Res. 34 (2001) 91.
4. Conclusion
[3] O. Maury, H.L. Bozec, Acc. Chem. Res. 38 (2005) 691.
[4] G.B. Deacon, R. Phillips, Coord. Chem. Rev. 33 (1980) 227.
[5] C.N.R. Rao, S. Natarajan, R. Vaidhyanathan, Angew. Chem., Int. Ed. 43 (2004)
1466.
[6] G. Prabusankar, R. Murugavel, Organometallics 23 (2004) 5644.
[7] R. Murugavel, S. Banerjee, Inorg. Chem. Commun. 6 (2003) 810.
[8] R. Murugavel, D. Krishnamurthy, M. Sathiyendiran, J. Chem. Soc., Dalton Trans.
(2002) 34.
[9] R. Murugavel, K. Baheti, G. Anantharaman, Inorg. Chem. 40 (2001) 6870.
[10] R. Murugavel, V.V. Karambelkar, G. Anantharaman, M.G. Walawalkar, Inorg.
Chem. 39 (2000) 1381.
[11] D. Krishnamurthy, R. Murugavel, Ind. J. Chem. 42A (2003) 2277.
[12] R. Murugavel, N. Gogoi, J. Organomet. Chem. 693 (2008) 3111.
Dimeric 1–3 and monomeric 4–6 manganese-carboxylate com-
plexes with 2,20-bpy auxiliary ligands have been prepared starting
from a single precursor complex and characterized in detail. The
presence of –NH2 and –OH groups on the aryl rings of the carbox-
ylate ligands leads interesting intermolecular association in the so-
lid-state in these complexes. When no additional H-donor sites are
available in the carboxylate ligands (e.g. 3) the intermolecular
association takes place with the aid of C–HꢀꢀꢀO interactions, origi-
nating from the 2,20-bpy ligands. On the other hand, when a very
bulky aryl group is involved on the carboxylate functionality, the

438
N. Palanisami, R. Murugavel / Inorganica Chimica Acta 365 (2011) 430–438
[13] R. Murugavel, R. Korah, Inorg. Chem. 46 (2007) 11408.
[14] R. Murugavel, R. Korah, React. Inorg. Met.-Org. Nano-Met. Chem. 37 (2007)
779.
[15] R. Murugavel, P. Kumar, M.G. Walawalkar, R. Mathialagan, Inorg. Chem. 46
(2007) 6828.
[16] S. Banerjee, S. Shanmugan, R. Murugavel, Struct. Chem. 18 (2007) 165.
[17] G. Christou, In magnetism: a supramolecular function, in: O. Kahn (Ed.), NATO
Series, Kluwer, Dordrecht, The Netherlands, 1996, p. 383.
[18] G. Aromi, S. Bhaduri, P. Artus, K. Folting, G. Christou, Inorg. Chem. 41 (2002)
805.
[26] G. Christou, S.P. Perlepes, E. Libby, K. Folting, J.C. Huffman, R.J. Webb, D.N.
Hendrickson, Inorg. Chem. 29 (1990) 3657.
[27] G. Christou, S.P. Perlepes, E. Libby, K. Folting, J.C. Huffman, R.J. Webb, D.
Hendrickson, J. Chem. Soc., Chem. Commun. (1990) 647.
[28] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, third ed.,
Pergamon Press, Oxford, 1988.
[29] B.-H. Ye, X.-M. Chen, F. Xue, L.-N. Ji, T.C.W. Mak, Inorg. Chim. Acta 299 (2000) 1.
[30] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[31] Y.-F. Zhou, R.-H. Wang, B.-L. Wu, R. Cao, M.-C. Hong, J. Mol. Struct. 697 (2004)
73.
[19] A.J. Tasiopoulos, A. Vinslava, W. Wernsdorfer, K.A. Abboud, G. Christou, Angew.
Chem., Int. Ed. 43 (2004) 2117.
[20] V.L. Pecoraro (Ed.), Manganese Redox Enzymes, VCH Publishers, New York,
1992.
[32] J.P. Collin, I.M. Dixon, J.P. Sauvage, J.A.G. Williams, F. Barigelletti, L. Flamigni, J.
Am. Chem. Soc. 121 (1999) 5009.
[33] C. Can´ ada-Vilalta, J.C. Huffman, W.E. Streib, E.R. Davidson, G. Christou,
Polyhedron 20 (2001) 1375.
[21] V.V. Barynin, P.D. Hempstead, A.A. Vagin, S.V. Antonyuk, W.R. Melik-Adamyan,
V.S. Lamzin, P.M. Harrison, P.J. Artymiuk, J. Inorg. Biochem. 67 (1997) 196.
[22] V.V. Barynin, M.M. Whittaker, S.V. Antonyuk, V.S. Lamzin, P.M. Harrison, P.J.
Artymiuk, J.W. Whittaker, Structure 9 (2001) 725.
[34] R. Wang, M. Hong, E. Gao, M. Gao, J. Luo, L. Han, R. Cao, Inorg. Chem. 42 (2003)
5486.
[35] G. Fenández, M. Corbella, M. Alfonso, H. Stoeckli-Evans, I. Castro, Inorg. Chem.
43 (2004) 6684.
[23] B.-H. Ye, M.-L. Tong, X.-M. Chen, Coord. Chem. Rev. 249 (2005) 545.
[24] G. Christou, Acc. Chem. Res. 22 (1989) 328.
[25] J.B. Vincent, H.-L. Tsai, A.G. Blackman, S. Wang, P.D.W. Boyd, K. Folting, J.C.
Huffman, E.B. Lobkovsky, D.N. Hendrickson, G. Christou, J. Am. Chem. Soc. 115
(1993) 12353.
[36] Q.-Z. Zheng, C.-Z. Lu, Acta Crystallogr., Sect. C 61 (2005) m78.
[37] S.-R. Fan, L.-G. Zhu, H.-P. Xiao, S. Ng, Acta Crystallogr., Sect. E 61 (2005) m377.
[38] E. Garribba, G. Micera, M. Zema, Inorg. Chim. Acta 357 (2004) 2038.
[39] R. Murugavel, M. Sathiyendiran, R. Pothiraja, R.J. Butcher, Chem. Commun.
(2003) 2546.