Versatile coordinating capabilities of thiodibenzoic acid copper complexes bearing N-donor ligands

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Transition Metal Chemistry ISSN 0340-4285Volume 40Number 2 Transition Met Chem (2015) 40:161-169DOI 10.1007/s11243-014-9902-1

Versatile coordinating capabilities ofthiodibenzoic acid copper complexesbearing N-donor ligands

S. B. Moosun, L. H. Blair, S. J. Coles,M. G. Bhowon & S. Jhaumeer-Laulloo

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Versatile coordinating capabilities of thiodibenzoic acid coppercomplexes bearing N-donor ligands

S. B. Moosun • L. H. Blair • S. J. Coles •

M. G. Bhowon • S. Jhaumeer-Laulloo

Received: 17 October 2014 / Accepted: 17 November 2014 / Published online: 25 November 2014

� Springer International Publishing Switzerland 2014

Abstract Cu(II) coordination polymers [Cu(tda)(phen)]-

1.5H2O (1a), [Cu(tda)(py)] (2a) and [Cu(tda)(bipy)(H2O)]-

0.5H2O (3a) (tda = thiodibenzoic acid, phen = phenan-

throline, py = pyridine, bipy = bipyridine) have been

synthesized by slow diffusion. Under solvothermal condi-

tions, [Cu(tda)(phen)]2H2O (1b), [Cu(tda)(H2O)] (2b) and

[Cu(tda)(bipy)] (3b) were isolated. The structures of the

complexes 1a–3a have been determined by single X-ray

diffraction. The experimental X-ray powder diffraction

patterns of 1b–3b were compared with the calculated pat-

terns of 1a–3a. The polymers were found to exhibit

structural and dimensional diversity due to the effect of the

co-ligands. In complexes 1a and 1b, tda is found to coor-

dinate with the metal atom in a monodentate mode,

while in 2a and 2b, the carboxylate oxygens are coordi-

nated with the two metal centers in a l-bridged bidentate

fashion. The structural analysis of 3a shows that the copper

atom is in a square pyramidal environment, whereby the

metal atom is coordinated with the carboxylate oxygens of

two different tda ligands in a monodentate fashion and two

nitrogens of the bipyridine ligand and one coordinated

water. The IR spectrum of 3b implies a bidentate mode of

coordination.

Introduction

Diaryl sulfides represent an important class of thio com-

pounds with regard to synthesis and complexation prop-

erties to various transition metals. They have gained a great

deal of attention due to their presence in a number of drugs

used for the treatment of Alzheimer’s, Parkinson’s and

inflammatory diseases [1]. In addition, these ligands have

been used for the construction of supramolecular archi-

tectures that can give rise to mononuclear or binuclear

complexes by means of hydrogen bonding and p–pstacking interactions, producing 1D, 2D or 3D network

systems [2]. It has been shown that in the absence of donor

atoms in the ortho position, the diaryl sulfide acts as

monodentate with only sulfur coordinating with the metal

center [3]. In the presence of donor groups (hydroxyl, thiol,

imines, amides) at the ortho position, diaryl sulfides are

known to coordinate with metals such as aluminum [4],

palladium [5], nickel [6], platinum [7], ruthenium [8], iron

[9], lanthanide [10], germanium [11] and zinc complexes

[12] in a tridentate manner, whereby the sulfur is involved

in coordination or bidentate binding with no sulfur coor-

dination. Diaryl sulfides containing dicarboxylate as a

donor group have not been subjected to detailed study. In

general, carboxylates have been reported to adopt various

coordination modes functioning as monodentate, chelating

bidentate or l-bridging [13]. Moreover, it is known that the

structures and properties of these coordination polymers

can be influenced by N-donor ligands [14]. These N-donor

ligands have good coordinating abilities and a large con-

jugated system that can easily form intra- or intermolecular

p–p interactions among the aromatic moieties [15]. The

reaction of Zn(NO3)2�6H2O/tda/phen under hydrothermal

conditions has been reported to give a 3D-supramolecular

structure in which zinc is in a distorted trigonal

S. B. Moosun � M. G. Bhowon � S. Jhaumeer-Laulloo (&)

Department of Chemistry, Faculty of Science, University of

Mauritius, Reduit, Mauritius

e-mail: [email protected]

L. H. Blair � S. J. Coles

Chemistry, Faculty of Natural and Environmental Sciences,

University of Southampton, Southampton, UK

123

Transition Met Chem (2015) 40:161–169

DOI 10.1007/s11243-014-9902-1

Author's personal copy

bipyramidal geometry with the metal coordinating to the

nitrogens of phenanthroline and carboxylate oxygens [12].

Under the same conditions, when bipyridine was used, the

metal was coordinated to the nitrogens of the bipyridine

and to three oxygens from different tda ligands, resulting in

a square pyramidal framework. To further explore the

different coordination topologies of tda, we herein report

the syntheses and structures of copper complexes of tda in

the presence of N-donor ligands.

Experimental section

Materials and methods

All chemicals were obtained commercially and used

without any further purification. 2,20-Bipyridine and 1,10-

phenanthroline were bought from Sigma-Aldrich (Ger-

many, UK), while pyridine was purchased from Fischer

Scientific (UK). Copper chloride was obtained from BDH

(England). Methanol and DMF were purchased from Lo-

bachemie and Qualichems (India), respectively. Melting

points of the samples were determined using a Stuart Sci-

entific Electronic IA 9100 melting point apparatus and are

uncorrected. Infrared spectra were recorded as on diamond

ATR or on a diamond smart accessory with a Thermo

Nicolet Avatar 320 FTIR spectrometer in the range

400–4,000 cm-1. Carbon, hydrogen, nitrogen and sulfur

contents were obtained with a LECO CHNS-932 analyzer.

Magnetic moments were recorded on a Sherwood Scientific

magnetic susceptibility balance, while pH was recorded on

Martini Instruments Mi160 Temperature Bench Meter.

Copper content was determined on a GBC Avanta AAS

(Atomic Absorption Spectroscopy) apparatus.

Synthesis of copper complexes

Tda was synthesized according to previously reported

procedures [16].

Method A: A mixture of tda (0.067 g, 0.245 mmol) and

1,10 phen/py/bipy (0.245 mmol) in methanol (5 ml) was

carefully layered onto a solution of CuCl2�2H2O (0.084 g,

0.489 mmol) in 5 ml of water. The pH of the tda was

adjusted to pH 7 using M NaOH, and the resulting mixture

kept at room temperature. After 4 weeks, crystals of 1a, 2a

and 3a started appearing, and after 6 weeks, the different

crystals were removed.

Method B: A mixture of tda (0.200 g, 0.729 mmol) and

1,10-phen/py/bipy (0.729 mmol) in methanol (10 ml) and

CuCl2�2H2O (1.46 mmol) in water (10 ml) was heated at

120 �C for 3 days in a closed system. The pH of tda was

adjusted to pH 7 using M NaOH. The powder obtained was

filtered off, washed with hot methanol, and air-dried to

yield the complexes 1b, 2b and 3b.

X-ray crystallography

Single-crystal X-ray diffraction data for 1a–3a were col-

lected at 100 K on a Rigaku AFC12 goniometer equipped

with an enhanced sensitivity (HG) Saturn 724? detector

mounted at the window of an FR–E ? Superbright Mo Karotating anode generator with focusing optics (HF Varimax

100 lm focus for 1a and 3a and VHF Varimax 70 lm

focus for 2a) and equipped with an Oxford Cryosystems

Cobra cooling device [17].

Cell determination, data collection, data reduction, cell

refinement and absorption corrections were carried out

using CrystalClear-SM Expert 3.1 b27 software [18].

Structures 1a, 2a and 3a were solved using Superflip [19]

and refined using full-matrix least-squares refinements in

the SHELX2013 software [20]. All non-hydrogen atoms

were refined with anisotropic displacement parameters. All

hydrogen atoms were included in calculated positions and

refined using a riding model with isotropic displacement

parameters based on the equivalent isotropic displacement

parameter (Ueq) of the parent atom. In complex 1a,

hydrogen atoms of water molecule O101 were restrained to

a standard length and angle. Hydrogen atoms of water

molecule O111 could not be located but were included in

the formula for completeness. The occupancy of O111 in

1a was 50 %. O111 is disordered over a symmetry site. It is

reasonable to assume that only one of the two positions is

occupied anywhere within the crystal. In complex 3a,

hydrogen atoms of water molecule O101 were restrained to

a standard length and angle. O101 has a 50 % occupancy

value. Modeling of disorder was attempted but provided no

improvement to the structure.

The powder X-ray data were collected on a Bruker D2

Phaser in theta–theta geometry using Cu (Ka1/Ka2) radi-

ation and a Ni Kb filter (detector side). The additional

beam optics and settings were as follows: primary and

secondary axial Soller slits (2.5�), fixed 0.6 mm divergence

slit, 1 mm anti-scatter screen, Detector: 1D LYNXEYE

with a 5� window, Generator: 30 kV, 10 mA.

Figures 2, 4 and 6 were drawn using Olex2 [21].

Results and discussion

Syntheses of metal complexes 1–3

The reactions of tda with CuCl2�2H2O in the presence of

phen/bipy/py by slow diffusion led to the coordination

162 Transition Met Chem (2015) 40:161–169

123


polymers [Cu(tda)(phen)]1.5H2O (1a), [Cu(tda)(py)] (2a)

and [Cu(tda)(bipy)(H2O)]0.5H2O (3a) (Fig. 1). However,

when the reaction was carried out at high temperature, with

phen as co-ligand, the blue powder [Cu(tda)(phen)]�2H2O

(1b) was isolated. In the presence of py, a green powder of

[Cu(tda)(H2O)] (2b) was obtained, while in the presence of

bipy, a blue powder of [Cu(tda)(phen)] (3b) was isolated.

The metal complexes are air stable but are insoluble in

common organic solvents and water, which is consistent

with their polymeric nature. The elemental analysis of the

complexes is consistent with the proposed composition of

the compounds (Table 1).

IR spectra and magnetic studies

The IR spectra of the complexes exhibited a medium band

in the range of 3,200–3,500 cm-1, which can be assigned

to the mO–H vibration of the solvate/coordinated water

molecules in complexes 1–3, but is not present in 2a and

3b [22]. The absence of bands in the region of

1,670–1,680 cm-1 in the IR spectra of all the metal com-

plexes indicates deprotonation of the thiodibenzoic acid,

and the presence of new bands in the range of 1,575–1,612

and 1,381–1,442 cm-1 are assigned to asymmetric and

symmetric COO- vibrations [23].

CuCl2.2H2O + tdaphen

[Cu(tda)(phen)] xH2O

MeOH/H2O

MeOH/H2Opy

bipy

[Cu(tda)(py)] [Cu(tda)(H2O)]

Cu

O

O

xH2OMeOH/H2O

O O

CuN

NO xH2O

O OO O

Cu CuN NO O O O O O OO

O OO O

Cu CuH2O OH2

NN

Cu

O

O

O

ON

N

[Cu(tda)(bipy]

[Cu(tda)(bipy)] 1.5H2O

H2O

O

1a; Slow diffusion, x = 1.5

1b; solvothermal, x = 2

3a

3b

2a 2b

Fig. 1 Schematic illustration of variable transformation of tda induced by different co-ligands and reaction techniques

Table 1 Physicochemical properties of the metal complexes

Compound Color Yield (%) leff (B.M) observed (calculated)

C (%) H (%) N (%) S (%) Cu (%)

1a [Cu(tda)phen]1.5H2O Dark blue 79 1.58 57.6 (57.5) 3.3 (3.5) 5.4 (5.2) 6.1 (5.9) 11.0 (11.4)

1b [Cu(tda)phen]2H2O Greyish blue 85 1.50 56.1 (56.5) 3.3 (3.6) 5.4 (5.1) 5.8 (5.8) 10.8 (11.4)

2a [Cu(tda)(py)] Green 33 1.22 53.6 (54.9) 3.0 (3.1) 4.1 (3.3) 8.1 (7.7) 14.9 (15.4)

2b [Cu(tda)(H2O)] Green 64 1.40 47.6 (47.5) 2.9 (2.8) – 9.0 (9.1) 15.8 (16.5)

3a [Cu(tda)bipy)(H2O)]0.5H2O Bluish green 43 1.51 55.2 (55.5) 4.0 (3.7) 5.7 (5.4) 5.8 (6.2) 10.5 (10.8)

3b [Cu(tda)bipy] Blue 50 1.62 58.0 (58.5) 3.0 (3.3) 5.8 (5.7) 6.8 (6.5) 12.5 (13.0)

Transition Met Chem (2015) 40:161–169 163

123


The carboxylate ion may coordinate with a metal ion in

monodentate, chelating bidentate or l-bridging modes

[24]. These various coordinating modes can be distin-

guished by the difference in asymmetric (ma COO- ) and

symmetric (ms COO- ) carboxylate stretching bands [25]. A

difference of &200 cm-1 is indicative of a monodentate

type of coordination, while (Dm) �200 cm-1 can be

ascribed to l-bridging mode [26]. When the difference

between the carboxylate frequencies is [100 cm-1, the

carboxylate groups bind to the metal in a bidentate che-

lating mode, though such values have also been ascribed to

l-bridging mode [27]. Selected bands for the infrared

spectra of the complexes are given in Table 2. Based on the

aforementioned observations, it can be concluded that

coordination in 1a, 1b and 3a is monodentate, 2a and 2b

are l-bridging, and 3b is bidentate. Absence of mC=N at

1,599 cm-1 in the IR spectrum of 2b indicates no coordi-

nation of py to the metal. Intense peaks found at 846–849,

701 and 649 cm-1 are characteristic of the secondary

ligands phen, py and bipy, respectively. The intense bands

observed in the region of 959–969 cm-1 are due to mC–S

stretching [28]. The new peaks at 496–498 and

421–437 cm-1 are due to M–O and M–N vibrational fre-

quencies [29].

The magnetic moments of the complexes were in the

range of 1.22–1.62 B.M, corresponding to one unpaired

electron on the copper (II) center [30] and indicating that

the complexes were either in a square planar [31] or

octahedral environment [32]. The low values of 1.22 and

1.40 B.M obtained for 2a and 2b are likely to be due to

coupling in the Cu–Cu bond.

Structures of the complexes

The complexes 1–3 were all characterized by X-ray crys-

tallography and powder X-ray diffraction (Figs. 2, 3, 4, 5,

6, 7; Tables 3, 4), and a structure description of each

complex is as follows. The single-crystal X-ray structures

have been determined for C26H19CuN2O5.5S (1a), C19-

H13CuNO4S (2a) and C24H19CuN2O5.50S (3a). Crystallo-

graphic data and structural refinement parameters of 1a, 2a

and 3a are given in Table 3. Selected bond lengths and

bond angles of the complexes are given in Table 4.

Both carboxylates from the tda ligand coordinate in a

monodentate fashion with Cu(II) in all of the crystal

structures presented in this paper, 1a, 2a and 3a. The

geometry around the Cu(II) atom in 1a is square planar (or

could be described as distorted octahedral if the second

oxygen from each carboxylate group is considered to be

coordinated, despite the longer bond distance), 2a is dis-

torted octahedral, and 3a is distorted square pyramidal. In

each of the complexes, 1a, 2a and 3a, Cu(II) atoms, tda and

N ligands combine together to form polymeric chains via

the oxygens of the carboxylates. The polymeric chains are

formed along the crystallographic b axis for 1a, a axis for

2a and c axis for 3a (Table 5).

Structures of 1a and 1b

Single-crystal X-ray diffraction reveals that 1a crystallizes

in the monoclinic crystal system in the space group P21/n.

The asymmetric unit contains one copper, a tda anion and a

phenanthroline moiety. The molecular structure of 1a with

the atomic numbering scheme adopted is illustrated in

Fig. 2. In 1a, the coordination environment around Cu(II)

is a distorted square planar geometry, forming a [CuN2O2]

unit with the Cu–N bond lengths being 1.999(15)–

2.010(17) A. These values agree well with those observed

in other copper complexes [33]. The bond lengths of Cu–O

are in the range of 1.953(13)–1.966(14) and fall in the

range of typical Cu–O carboxylate distances [34]. The

bond length of C–S of 1.785(19) correspond clearly to a

single bond and correspond to the average C–S bond length

[1.781(1) A] [35]. Three Cu atoms along with the tda and

phen ligands are combined together via the carboxylate

oxygens to form a polymeric chain, which results in a 3D

supramolecular architecture via weak C-H … p interac-

tions of the phenyl rings to the benzene rings of the tda

ligand (Fig. 2). The tda anion and the uncoordinated water

ligand are connected by O–H…O hydrogen bonds of

lengths (d(D … A) 2.869(2)–3.058(2) A and angles

(\(DHA)) 165(3)–173(4)�, respectively. The O–H … O

bonds are between the carboxylate oxygens (O3 and O4) of

Table 2 Selected IR bands

(cm-1) for the prepared

complexes

Complex mas(COO-

) ms(COO-

) Dm m(O–H) m(C=N) m(C–S) m(M–O) m(M–N)

1a 1,571 1,381 189 3,454 1,593 968 497 436

1b 1,572 1,384 188 3,460 1,595 969 493 438

2a 1,612 1,393 219 – 1,599 959 498 421

2b 1,612 1,399 213 3,444 – 960 493 –

3a 1,572 1,381 191 3,444 1,592 960 496 437

3b 1,581 1,442 139 – 1,594 960 493 437


123


Fig. 2 a The X-ray crystal

structure of 1a

[Cu(tda)(phen)]1.5H2O.

Thermal ellipsoids are drawn at

50 % probability level. b The

X-ray crystal structure of 1a

showing the polymeric chain,

solvent water omitted for

clarity. c Hydrogen bonding

interactions in 1a

Fig. 3 Comparison of XPRD of

1a and 1b


123


tda and hydrogen atoms (H101 and H102) of an uncoor-

dinated water ligand.

The X-ray powder pattern of the blue powder 1b

obtained from the solvothermal reaction of CuCl2 with tda

in the presence of phen was superimposed on the calculated

pattern of 1a (Fig. 3). It was observed that the pattern of 1b

is similar to that of 1a. Hence, it could be deduced that the

same compound has been isolated by both solvothermal

and slow diffusion methods.


Single-crystal X-ray diffraction reveals that 2a crystallizes

in the triclinic crystal system with the space group P-1. The

molecular structure shows that it is a centrosymmetric

polymeric Cu(II) complex with a [Cu(tda)(py)] unit. The

copper atom adopts a distorted octahedral coordination

environment with four oxygens from different tda ligands,

one nitrogen from a py and a copper atom. The Cu–O

interatomic distances are in the range of 1.965(5)–

1.985(5) A, slightly longer than the typical Cu–O

(carboxylate) bond length (1.95 A). The Cu–N bond length

observed is 2.159(6) A, which is longer than a typical Cu–

N (pyridine) (1.90–1.94 A) [36]. The most interesting

feature of 2a is the Cu–Cu bond length (2.656(16) A),

which is shorter than the sum of the Van der Waals radii

[37], indicating a Cu–Cu interaction. The two Cu(II) cen-

ters are held together by l-bridged carboxylate groups,

creating a paddlewheel motif (Fig. 3a). One dimeric Cu(II)

unit is bridged to another by the tda ligand. The adjacent l-

bridges above and below the Cu(II) units propagate

throughout the structure to create a polymeric chain

(Fig. 3b). The C–S bond length of 1.771(7) A clearly

corresponds to a single bond, but is slightly lower than an

average C–S bond length (1.781(1) A). The Cu1–Cu1–O3,

O2–Cu1–O3 and N21–Cu1–O4 bond angles are close to

90�. However, O4–Cu1–O3 of 168.4� (2) is far from the

expected 180�, indicating a distorted structure. A feature of

complex 2a is the formation of a three-dimensional (3D)

structure through C–H … p interactions between the pyr-

idine units and the benzene rings, as well as p–p stacking

between benzene rings from the tda ligands.

Fig. 4 a The X-ray crystal structure of 2a [Cu(tda)(py)]. Thermal ellipsoids are drawn at 50 % probability level. b The X-ray crystal structure of

2a showing the polymeric chain(c)


2a and 2b


123


The powder X-ray pattern of 2b was superimposed on

the calculated pattern of 2a. The patterns (2a and 2b)

showed slight discrepancies, suggesting that the coordina-

tion environment around the copper atom in 2b is probably

different compared with 2a (Fig. 5). This could be due to

the slight differences in their structural formulae. The

absence of a py unit and the presence of two water mole-

cules in 2b account for the difference obtained in their

X-ray patterns and elemental analysis.


The X-ray structure of 3a [Cu(tda)(bipy)(H2O)]0.5H2O has

already been reported by Liu et al. [38], who carried out the

synthesis using dithiodibenzoic acid, CuCl2, bipy and

NaN3. In the present work, 3a has been obtained from the

reaction of thiodibenzoic acid, CuCl2, NaOH and bipy. The

copper atom is surrounded by two oxygen atoms coming

from two carboxylates, two nitrogen atoms from bipy in the

Fig. 6 a The X-ray crystal structure of 3a [Cu(tda)(bipy)(H2O)]0.5H2O]. Thermal ellipsoids are drawn at 50 % probability level. b The X-ray

crystal structure of 3a showing the polymeric chain


3a and 3b


123


equatorial plane and a water ligand in an axial position,

resulting in a highly distorted square pyramidal structure

(Fig. 6). The carboxylate oxygen is further connected to

another copper atom to form a chain. Each tda provides one

H donor atom and one H acceptor atom from an uncoor-

Table 3 X-ray crystallography summary for structures 1a and 2a

Identification

code

1a 2a

Empirical

formula

C26H19CuN2O5.5S C19H13CuNO4S

Formula weight 543.03 414.90

Temperature (K) 100(2) 100(2)

Wavelength (A) 0.71075 0.71075

Crystal system Monoclinic Triclinic

Space group P21/n P-1

Unit cell dimensions

a (A) 10.9265(8) 8.0768(5)

b (A) 11.5269(8) 10.7271(8)

c (A) 18.0941(13) 11.0323(8)

a (�) 90 68.061(15)

b (�) 100.183(2) 80.680(18)

c (�) 90 73.799(17)

Volume/A3 2,243.0(3) 849.63(16)

Z 4 2

qcalc (mg/mm3) 1.608 1.622

Absorption

coefficient

(mm-1)

1.113 1.433

F(000) 1,112 422

Crystal Plate; Blue Needle; Green

Crystal size

(mm3)

0.130 9 0.060 9 0.110 0.120 9 0.010 9 0.010

h range for data

collection (�)

2.964�–27.480� 2.953�–27.474�

Reflections

collected

28,378 12,293

Independent

reflections

5,120 [0.0556] 3,862 [0.1189]

Completeness to

h max

99.8 % 99.2 %

Max and min

transmission

1.000 and 0.766 1.000 and 0.455

Data/restraints/

parameters

5,120/3/331 3,862/0/235

Goodness of fit

on F2

1.064 0.991

Final R indexes

[I C 2r (I)]

R1 = 0.0341,

wR2 = 0.0966

R1 = 0.0945,

wR2 = 0.2287

Final R indexes

[all data]

R1 = 0.0380,

wR2 = 0.0992

R1 = 0.1391,

wR2 = 0.2581

Largest diff.

peak/hole (e

A-3)

1.132/-0.448 1.775 and -0.808

CCDC

deposition

number/

reference code

1,020,589 1,020,591

Table 4 Selected bond distances (A) and angles (�) for 1a and 2a

1a 2a

Cu bond distances (A)

Cu–N(C) N21–Cu1 2.000(2) 2.159(6)

N22–Cu1 2.011(2) –

Cu–O(C) O1–Cu1 1.953(1) 1.985(5)

O2–Cu1 1.978(5)

O3–Cu1 1.966(2) 1.965(1)

O4–Cu1 1.977(5)

Cu–O(H2O) O1W–Cu1 – –

Bond angles(�)

C–S–C C7–S1–C8 102.07(9) 102.7(3)

Torsion angles(�)

C–C–S–C C2–C7–S1–C8 -175.43(15) -99.0(7)

C–S–C–C C7–S1–C8–C13 -88.45(17) -175.4(6)

Ring 1–ring 2 N0N–tda A 84.44(7) 49.4(4)

Ring 1–ring 3 N0N–tda B 10.56(7) 54.2(4)

Ring 2–ring 3 tda A–tda B 89.35(9) 83.2(4)

Table 5 Selected hydrogen-bond parameters for 1 and 3

D–H … A d(D–H) d(H … A) d(D … A) \(DHA)

1

O101–H101 … O4a 0.82(4) 2.06(4) 2.869(2) 173(4)

O101–H102 … O3 0.95(4) 2.13(4) 3.058(2) 165(3)

3

O1W–H1WA … O2 0.88(3) 1.87(3) 2.716(2) 163(3)

O101–H101 … O4 0.879(16) 1.733(16) 2.540(4) 151(3)

O1W–H1WB …O101c

0.99(3) 1.71(3) 2.675(3) 166(3)

C21–H21 … O1 0.95 2.47 2.994(2) 114.7

C22–H22 … O1Wd 0.95 2.46 3.343(3) 154.8

C24–H24 … O4d 0.95 2.30 3.244(3) 169.8

C24–H24 … O101d 0.95 2.59 3.234(4) 125.8

C27–H27 … O4d 0.95 2.54 3.464(3) 163.8

C30–H30 … O3b 0.95 2.56 3.080(3) 114.7

Symmetry transformations used to generate equivalent atomsa -x ? 3/2, y-1/2, -z ? 1/2b x, -y ? 3/2, -z ? 1/2c x, -y ? 5/2, z ? 1/2d -x ? 1, -y ? 2, -z ? 1


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dinated oxygen of the carboxylic acid, leading to the for-

mation of a network structure through hydrogen bonding.

Water ligands reside in the channels between the polymeric

chains along both the crystallographic a axis and b axis in

complex 3a. The hydrogen bonds between the carboxylate

oxygens (O2 and O4) and hydrogens from one coordinated

water and one uncoordinated water (H1WA and H101)

have bond lengths of 2.540(4)–2.716(2) (d(D … A) and

bond angles of 114.7�–166� (\(DHA)).

Comparing the powder X-ray pattern of 3a with 3b, it

was observed that 3b might have a different coordination

environment around the copper atom (Fig. 7). Based on the

elemental and spectral data, it could be deduced that in 3b,

the carboxylate group binds to the metal in a bidentate

fashion.

Conclusion

In the present work, five polynuclear compounds generated

from tda with CuCl2�2H2O have been synthesized under

slow diffusion and solvothermal methods. The copper

complexes were characterized by powder or single-crystal

X-ray diffraction analysis. With phen, via both techniques,

[Cu(tda)(phen)].xH2O (1a and 1b) were isolated. On the

other hand, the use of py under these two aforementioned

techniques led to the formation of two different types of

products, [Cu(tda)(py)] and [Cu(tda)(H2O)], respectively.

Finally with bipy, similar types of compound were isolated,

but with slight differences in the coordination modes of the

carboxylates. Comparing these two preparative methods, it

was observed that slow diffusion techniques gave X-ray

grade crystals, while solvothermal conditions led to the

formation of crystalline powders, but in higher yields and

shorter times. The N-donor ligands were found to influence

the modulation of the coordination frameworks, with the

metal complexes being in a square planar, octahedral or

square pyramidal environment with the copper atom

coordinating with the carbonyl oxygens via monodentate,

chelating bidentate or l-bridging modes.

Acknowledgments S. B. Moosun is thankful to Tertiary Education

Commission of Mauritius for financial Grant.

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Versatile coordinating capabilities of thiodibenzoic acid copper complexes bearing N-donor ligands

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