Synthesis, characterization and liquid crystalline properties of novel benzimidazol-8-hydroxyquinoline complexes

Article abstract of DOI:10.1016/j.ica.2017.07.029

The synthesis, characterization and liquid crystalline properties of N4,N4′-bis((1?H-benzo[d]imidazol-2-yl)methyl)-3,3′-dimethyl-[1,1′-biphenyl]-4,4′-diamine and of their corresponding Mn(II), Fe(II), Ni (II), Cu(II), and Zn(II) complexes are described. T

Full text of DOI:10.1016/j.ica.2017.07.029

Accepted Manuscript
Research paper
Synthesis, characterization and liquid crystalline properties of novel benzimi-
dazol-8-hydroxyquinoline complexes
Taghreed H. Al-Noor, Nisreen H. Karam, Faeza H.Ghanim, Alia S. Kindeel,
Ammar H. Al-Dujaili
PII:
S0020-1693(17)30829-0
http://dx.doi.org/10.1016/j.ica.2017.07.029
ICA 17752
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
27 May 2017
11 July 2017
12 July 2017
Please cite this article as: T.H. Al-Noor, N.H. Karam, F. H.Ghanim, A.S. Kindeel, A.H. Al-Dujaili, Synthesis,
characterization and liquid crystalline properties of novel benzimidazol-8-hydroxyquinoline complexes, Inorganica
Chimica Acta (2017), doi: http://dx.doi.org/10.1016/j.ica.2017.07.029
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Synthesis, characterization and liquid crystalline properties of
novel benzimidazol-8-hydroxyquinoline complexes
1
Taghreed H. Al-Noor , Nisreen H. Karam , Faeza H.Ghanim ,
1
1
1
Alia S. Kindeel , Ammar H. Al-Dujaili
2*
1
Department of Chemistry, College of Education for Pure Science,
Ibn Al- Haitham, University of Baghdad, Baghdad, Iraq
2
*
Hamdi Mango Center for Scientific Research, University of Jordan,
Amman, Jordan
ABSTRACT
The synthesis, characterization and liquid crystalline properties of N4,N4'-
bis((1H-benzo[d]imidazol-2-yl)methyl)-3,3'-dimethyl-[1,1'-biphenyl]-4,4'-
diamine and of their corresponding Mn(II), Fe(II), Ni (II), Cu(II), and Zn(II)
complexes are described. The ligand and complexes have been characterized
by elemental analysis, magnetic susceptibility measurements (µeff),
conductometric measurements and Fourier Transform Infrared (FTIR),
1
13
Nuclear Magnetic Resonance ( H-NMR), ( C-NMR) and UV-Vis
spectroscopy. Spectral investigations suggested octahedral coordination
geometrical arrangement for M(II) complexes. The phase transition
temperatures were detected by differential scanning calorimetry (DSC)
analysis and the phases are confirmed by optical polarizing microscopy
(POM). The DSC and POM supported the mesomorphic properties of the

uncoordinated ligand in which the enantiotropic smectic phases were
recorded. However, not all of their corresponding M(II) complexes are liquid
crystal.
Keywords:
Benzimidazol
Liquid crystal
Metal heterocyclic
8-Hydroxyquinoline
Transition metal-complexes
*
Corresponding author.
E-mail address: ah.aldujaili@gmail.com (A.H. Al-Dujaili).

1. Introduction
A liquid crystalline mesophase is a state of matter intermediate between
liquid and solid. Benzimidazoles are an important class of heterocyclic that
used in many applications includes their use as liquid crystal complexes [1],
polymers [2] and organic ligands [3, 4]. The classical and most common
methods to assemble benzimidazoles or bisbenzimidazole derivatives involve
the condensation of benzene-1,2-diamines with aldehydes, carboxylic acids,
or their derivatives under strong acid/high temperature conditions or by using
a stoichiometric oxidant [5, 6].
Several liquid crystalline compounds and complexes containing
benzimidazoles have been synthesized and well studied. For example, Ninán
et.
al., [7] synthesized and studied mesomorphic properties of 2-
pentadecylbenzimidazole and 1,1'-bis(octadecyl)-2,2'-bibenzimidazole. The
former compound exhibit an enantiotropic smectic C (SmC) phase, whereas
the later compound exhibit a monotropic cholesteric phase. These two
compounds represent the first benzimidazole-based liquid crystals. The
synthesis, characterization and mesomorphic properties of a series of N-(2-
hydroxy-4-n-alkyloxybenzylidene) 4’-amino-2-methylbutylcinnamate and
their copper (II) complexes are reported [8]. The imines exhibited smectic A
(SmA) and chiral SmC phases while their copper (II) complexes displayed
SmA–SmC phase variant. Tan et. al., [9] synthesized a homologous series of
biphenyl benzoate-based compounds with an alkylthio chain bearing a
benzimidazole moiety as a terminal substituent. The compounds exhibited
SmA and nematic phases over a temperature range of 173–116 °C during the
cooling process. Recently [10], three series of 2-(4_-alkoxybiphenyl-4-yl)-
1H-benzimidazole derivatives, which possessed 5-nitrobenzimidazole,

benzimidazole or 5-methylbenzimidazole units at the end of the molecule,
were synthesized. All the compounds exhibited enantiotropic smectic
mesophases with wide temperature domains for a carbon number in the
alkoxy chain from 6 to 16.
Liquid crystalline materials containing metal ions are known as
metallomesogens [11-13]. The interest on studying of these systems arises
from the fact that the combination of the properties of organic liquid crystals
and of transition-metal ions can produce new materials exhibiting unique
assembly structures, and unique optical, magnetic and electronic properties
[14-20]. Moreover, due to the various oxidation states and the array of
coordination geometries, 4-6 metal ions offer many possibilities as building
blocks for unique molecular structures when associated with suitably
designed ligands. Metal ions, for example, Ni(II), Cu(II), Pd(II) or Pt(II) with
square-planar coordination were
commonly used [21].
During the last decade many series of metallomesogens have been
synthesized. Among these metallomesogens containing benzimidazole or 8-
hydroxyquinoline derivatives have been studied as excellent candidates for
material applications due to their excellent thermal and chemical stabilities
and electroptics properties. For example, a new series of star-shaped iron (II)
spin crossover (SCO) complexes based on symmetric tripod, 1-alkyl-1H-
imidazole and 1-alkyl-1H-benzimidazole ligands with variable-length alkyl
chains were reported, long chain species display SCO and liquid crystal
properties [22]. Pucci et. al., [23] synthesized the first gallium(III)-based
liquid crystal by grafting around the metal centre two chelating 2-
methylquinolin-8-olate
anions
and
one
monodentate
3,4,5-tris-
(
hexadecyloxy)benzoyloxy ligand, allowing the resulting complex to be a soft

luminescent material with the typical high quantum yield of penta cordinated
gallium species.
In this work, we report the synthesis, characterization and mesomorphic
behaviour of Mn(II), Fe(II), Ni (II), Cu(II), and Zn(II) complexes of ligand
containing benzimidazole-8-hydroxyquinoline unit. The liquid crystalline
behavior has been analyzed in terms of structural property relationship
between metal centers and ligands. Because, this relationship can be used to
control the mesomorphism of the complexes formed.
2
. Experimental
2
.1. Chemicals
All chemicals were of reagent grade obtained from Sigma-Aldrich
Chemicals and used as received.
.2. Techniques
2
Infrared spectra were recorded on a Shimadzu 8000 FTIR
-1
spectrophotometer in the wave number range 4000-400 cm using KBr discs
1 13
or films. H- and C-NMR spectra were obtained with Avance III Bruker 500
MHz instrument using tetramethylsilane (TMS) as the internal standard.
-3
о
Conductivities were measured for 10 M of complexes in (DMSO) at 25 C
using (Philips PW- Digital Conduct meter). UV-Vis spectra were recorded on
a (Shimadzu UV-160A) Ultra Violet-Visible spectrophotometer. Uncorrected
melting points were determined by using Hot-Stage, Gallen Kamp melting
point apparatus. The concentration of metal was measured by using Flame
Atomic Absorption Spectrometer (FAAS, Perkin-Elmer 400, UK) using air
and acetylene as flame gases.

The optical behavior observations were made using polarized optical
microscope (POM) model Leica DM2500M with a Leitz Laborlux 12 Pols hot
stage and PR600 controller. Photographs of texture were obtained using a
camera model PM-10AD made Olympus. The transition temperatures and
enthalpies were investigated using differential scanning calorimetry DSC
(STA PT-1000LINSIS), ramp rate: 10 degree centigrade per minute under
nitrogen atmosphere. Temperature and heat flow calibrated with standard
indium of purity > 99.99%.
2
.3. Synthesis
The synthesis of the compound (1) and ligand (L) were accomplished
by the reaction sequences outlined in Scheme 1.
.3.1. Synthesis of 2,2'-(3,3'-dimethylbiphenyl-4,4'-iyl)bis(azanediyl)diacetic
acid (1)
2
To a stirring of α-chloroacetic acid (1.89 g, 20 mmol) in 10% aqueous
sodium hydroxide 10 mL, a solution of 3,3'-dimethylbiphenyl-4,4'-diamine
2.12 g, 10 mmol) in 10% aqueous solution of sodium hydroxide 10 mL was
(
added, the mixture was refluxed for three hours. After cooling, the solution
was acidified with concentrated hydrochloric acid. The precipitate was
filtered and recrystallized from ethanol.
o
Orange solid. Yield: 75%. m.p.: 82-85 C. FT-IR (KBr, cm ): 3410
-1
1
(
νO-H); 3213 (νsym,asym,N-H); 3093 (νAr-H); 1722 (ν ). H-NMR (DMSO-d6),
C=O
ppm: δ = 11.38 (s, 2H, COOH); 7.05-8.00 (dd, 6H, CHAr); 4.15 (s, 4H, CH );
2
1
3
5
.64 (s, 2H, NH); 2.15 (s, 6H, CH ). C-NMR (DMSO-d6), ppm: δ = 177.8
3
(COOH); 127.8-156.9 (C-aromatic); 32.3 (CH ); 21.2 (CH ). Anal. Calc. for
2 3
C H O N : C, 65.85; H, 6.10; N, 8.54.. Found: C, 66.12; H, 5.98; N, 9.11.
20
18
4
2

H C
3
H N
NH2
2
+
2 ClCH COOH
2
CH3
1
0% NaOH
H3C
HOOCH C HN
NHCH COOH
2
2
(
1)
CH3
-phenelyenediamin
N HCl
2
4
H3C
H C HN
N
N
NH CH2
2
N
H
N
H
(
L)
CH3
N4,N4'-bis((1H-benzo[d]imidazol-2-yl)methyl)-3,3'-dimethyl-[1,1'-biphenyl]-4,4'-diamine (L)
Scheme 1. The synthesis route of the ligand (L).
2.3.2. Synthesis of N4,N4'-bis((1H-benzo[d]imidazol-2-yl)methyl)-3,3'-
dimethylbiphenyl-4,4'-diamine (L)
A mixture of compound (1) (3.28 g, 10 mmol) and 2-phenylenediamine
(
2.16 g, 20 mmol) in 4N hydrochloric acid (40 mL) was refluxed for 10 hrs.
Then the solution was neutralized with ammonia to precipitate benzimidazole
(Scheme 1). The product was filtered and recrystallized from acetone.
o
Dark brown solid. Yield: 60%. m.p.: 118-123 C. FT-IR (KBr, cm ):
-1
3368 (νsym,asym,N-H); 3057 (νCH-Ar); 2852 (νCH-aliphatic); 1618 (νC=N bezimidazole);

1
1
578 (ν ); 1111 (νCH-Ar). H-NMR (DMSO-d6), ppm: δ = 12.21 (s, 2H, NH
C=C
for benzimidazol rings); 6.29-7.89 (dd, 14H, CHAr); 5.48 (s, 2H, NH); 4.93
1
3
(
s, 4H, CH ); 2.10 (s, 6H, CH ). C-NMR (DMSO-d6), ppm: δ = 114.1-
2 3
1
7
58.7 (C-aromatic); 46.2 (CH ); 18.2 (CH ). Anal. Calc. for C H N : C,
2 3 30 26 6
6.27; H, 5.51; N, 17.80.. Found: C, 76.89; H, 5.11; N, 18.21.
.3.3. Synthesis of metal complexes [M (L)(Q) ] M = Mn(II), Fe(II), Ni(II),
2
2
4
Cu(II), and Zn(II) sodiumoxyqinolinate
The reaction sequences leading to the formation of metal complexes
M (L)(Q) ] are outlined in Scheme 2.
[
2
4
Sodium-8-oxyqinolinate (Q) was synthesized by the reaction of 8-
hydroxyquinoline (0.58 g, 4 mmol) with sodium hydroxide (0.16 g, 4 mmol)
in ethanol. The mono ligand complexes were synthesized by the reactions of
ethanolic solutions of metal chlorides with ligand in a 1 : 2 (M : L) mole ratio
by raising the pH to 6.0–6.5 with a 5 % aqueous sodium hydroxide solution
and stirring the solution on a magnetic stirrer at 20–60 ºC. The pH was
controlled with the aid of pH paper and stirring was continued for thirty
minutes. The complexes separated out, filtered and washed two times with
(50% ethanol: water). All the complexes are colored powders. The complexes
are stable in air and insoluble in water but soluble in chloroform, acetone,
ethanol, methanol and benzene and very soluble in dimethylsulfoxide
(DMSO) and dimethylformamide (DMF).

+
4H O
2
4 NaOH
+
4
4
N
N
-
+
O Na
OH
(Q)
H3C
N
N
+
4
+
2MCl2
NHCH2
H CHN
2
N
N
H
N
H
-
+
O Na
(L)
CH3
5
0%
ethanol:
water
O
O
N
O
O
N
N
N
M
M
H C
3
N
N
NH CH2
H C HN
2
N
H
N
H
CH3
M= Mn(II), Fe(II), Ni (II), Cu(II) and Zn(II)
Scheme 2. The Synthesis route of [M (L)(Q) ] complexes.
2
4
3. Results and discussion
3.1. Characterization of (1) and (L)
The dicarboxylic acid (1) was synthesized by the reaction of one mole
of 3,3'-dimethylbiphenyl-4,4'-diamine (o-tolidin) with two moles of α-chloro
acetic acid by neucleophilic addition reaction in 10% aqueous NaOH solution.
The
ligand
(L),
N4,N4'-bis((1H-benzo[d]imidazol-2-yl)methyl)-3,3'-
dimethylbiphenyl-4,4'-diamine was synthesized by the cyclization of
compound (1) with two moles of 2-phenylenediamine in 4N hydrochloric
acid followed by neutralized with ammonia. The structure of these two

1
compounds were characterized by elemental analysis, FTIR, H-NMR and
1
3
C-NMR spectroscopy. The percentages of C, H and N from the elemental
analysis were in good agreement with the calculated values for compounds
1) and (L).
(
The FTIR spectrum of compound (1) showed disappearance absorption
stretching bands of NH groups for starting material o-tolidin and appearance
2
stretching bands of carboxyl and hydroxyl groups for dicarboxylic acid. The
FTIR spectrum of ligand (L) showed absorption stretching bands of C=N
groups for benzimidazole ring [24] and disappearance stretching bands of
carboxyl and hydroxyl groups for dicarboxylic acid (1). The sharp peak at
−
1
3
368 (strong) cm was observed and assigned to the absorption band of NH
in the benzimidazole moiety which indicated that the NH group was
associated with N atom via intermolecular N-H−N hydrogen bonding [25].
1
The H-NMR spectrum for ligand (L) showed a signal at δ 2.10 ppm
due to six protons of two CH groups, a signal at δ 4.93 ppm for four protons
3
of two CH groups, while a signal at δ 5.48 ppm may be assigned to two
2
protons of NH groups. Many signals in the region δ = 6.29-7.89 ppm that
could be attributed to fourteen protons of aromatic rings. A signal at δ = 12.21
ppm can be attributed to two protons of NH for benzimidazole rings [26]. The
13
C-NMR spectrum of compounds of ligand (L) showed the following signals:
1
δ = 114.1-158.7 (C-aromatic); 46.2 (CH ); 18.2 (CH ). The data of FTIR, H-
2
3
13
NMR and C-NMR spectrum along with elemental analyses data confirmed
the structural formula of the synthesized compounds.

3.2. Characterization of mixed ligands metal complexes
Generally, the complexes were synthesized by reacting the respective
metal chloride with the ligands (L) and (Q) using 2:1:4 mole ratio, i.e., two
moles of metal chloride: one mole of ligand (L) and four moles of
sodiumoxyqinolinate (Q). The formula weights and melting points are given
in Table 1 based on the physicochemical characteristics. The complexes were
analyzed for their metal percentage by Flame-AAS. All complexes gave
approximated values and they were consisted with theoretical values.
The FTIR spectrum for the complexes exhibit new bands at 486, 478,
-
1
4
51, 478 and 459 cm were assigned to υ
for complexes [Mn (L)(Q) ],
M–O 2 4
[
Fe (L)(Q) ], [Ni (L)(Q) ], [Cu (L)(Q) ] and [Zn (L)(Q) ], respectively,
2 4 2 4 2 4 2 4
-
indicating that the oxygen of (Q ) is involved in coordination with metal
-
1
ions. The FTIR spectra contained the bands at 1618-1632 cm , υ
C=Nbenzimidazole
ring, of the two ligands were shifted slightly to a higher value in all the
complexes suggesting that the ligands are coordinated through -C=N- [27,
28]. However, free secondary NH group exhibit N–H stretching frequencies
–
1
–1
in the 3300 to 3500 cm region which are shifted by about 100 to 200 cm
wave number after coordination with a metal ion in ligand (L) observed at
-
1
-1
236 cm shifted at range 3364-3394 cm [29]. The absorption due to Ar-C-
3
CH group did not change in the spectra of complexes indicating that Ar-C-
3
CH groups is not involved in coordination with the M(II). The absorption
3
−1
stretching band vC=N that occur at 1618 cm in the free ligand (L) shifted to
lower frequencies in all the complexes confirming that the M(II) are
coordinated directly to the benzimidazole (N) atom. Also strong υC-O
-
phenolic band observed at 1418 cm indicates the presence of oxine (Q )
1
-
moiety in the complexes shifted to higher frequencies in all the complexes

confirming that the M(II) are coordinated through its (O) atom bidentate
ligand [28-30].
The electronic spectral data of the free ligands, (L) and (Q) and their
complexes are measured in DMSO solution between 200–1100 nm at room
temperature together with the
complexes the µeff were found to be paramagnetic in nature except
Zn (L)(Q) ] complex. The UV- Vis spectra for the (Q) and ligand (L),
magnetic susceptibility (µeff). For the all
[
2
4
-1
-1
exhibit absorption peaks at UV-vis (λ: nm) (ε: L mol cm ): (275) (36363),
325) (30769), (270) (37037) and (323) (30959), which have their origin in
the (π → π*) and (n → π*) transitions, respectively within the organic ligand
31, 32].
The UV-Vis spectrum of [Mn (L)(Q) ] exhibits four peaks, the first
(
[
2
4
and second high intense peaks at (269) ( 37174) and (342) ( 29239) are due to
the ligand field (L.F) and charge transfer (C.T) transitions, respectively. The
third and fourth absorption bands related to (d-d) transitions at (403) (24813)
-
1
6
4
6
4
and (807) ( 12391cm ), are due to the ( A g → T )υ and ( A g → T g,
1
1
3
1
2
6
A g)υ , respectively and µ equal to 4.48 B.M, which suggests octahedral
1
2
.
eff
geometry around the central metal ion [31, 32].
The UV-Vis spectrum of [Fe (L)(Q) ] exhibits five peaks. The first
4
2
peak at (270) (37037) is due to the (L.F) transition and the second, third high
intense peaks at (362, 373) ( 29239) are due to the (C.T) transition, the last
two weak peaks at (463 -579) assigned to (d–d) transition including
5
5
T g→ Eg transitions [31, 32].
2
The UV-Vis spectrum of [Ni (L)(Q) ] exhibits five peaks. The first
2
4
peak at (270) (37037) is due to the (L.F) transition and second high intense
peaks at (342) ( 29239) is due to the (C.T) transition, the last three weak

peaks at (860) (11627), (584) (18248) and (355) (28196) assigned to (d–d)
3
(F)
3
(F)
3
(F)
3
(F)
3
(F)
transition including A g → T g (υ ), A g → T g (υ ) and A g
2
2
1
2
1
2
2
3
→
(p)
T g (υ ). The complex exhibits a value of µ = 2.26 B.M, which
1 3 eff
suggests an octahedral geometry around the central metal ion [30, 31]. The
spectral parameters of the Ni(II) complex are as follows: υ /υ ratio is 0.637,
1
2
-1
Dq = 11627cm , the υ /υ ratio is 1.56, which is in the usual range reported
2
1
for an octahedral Ni(II) complexes [31].
The [Cu (L)(Q) ] complex exhibit three peaks. the first peak at (270)
2
4
(37037) is due to the (L.F) transition and second high intense peaks at (334)(
29940) is due to the (C.T) transition, and broad band centered at (422)
2
2
(
23696) due to Eg → T g transition [32].
2
The diamagnetic [Zn (L)(Q) ] complex exhibits band at (337) (29673)
2
4
for the (C.T) transition and absence of any (d-d transition) consequently, this
confirms the presence of an octahedral geometry in the Zn (II) complex [33].
3.3. Mesomorphic properties
The liquid crystalline properties for the synthesized compounds were
investigated using DSC and POM. The phase transition temperatures and
corresponding enthalpy changes for compound (1), ligands (L) and complexes
[M (L)(Q) ] were summarized in Table 2. The thermal behaviour obtained by
2 4
DSC is consistent with the data observed by POM, where it was possible to
identify the mesomorphic character of the mesophases. On heating, the first
endothermic peak is accompanied with high enthalpy indicates a transition
from solid crystalline state to a liquid crystalline mesophase. The second
endothermic transition at higher temperature presented lower associated
enthalpy, which indicates transitions between distinct mesophases and to the
isotropic state.

As shown in Table 2, compound (1) exhibited enantiotropic
mesophases, two endothermic peaks at 83℃ and 147 ℃ corresponding to the
melting and liquid crystal–isotropic phase transition phenomena during the
heating process (Fig. S1). The formed mesophase showed a typical thread-
like nematic texture under POM observation, as shown in Fig. 1. Compound
(1) showed only nematic phase, this could be explained to the presence of
terminal dicarboxylic groups which leads to the formation of intermolecular
hydrogen bonding (Scheme 3). The intermolecular hydrogen bonding leads
to a lengthening of the rigid-rod moiety, which led to display nematic liquid
crystalline behavior [34].
H3C
H3C
HO
C
O
C
NH CH2 COOH
NH CH2
OH
O
H C HN
2
HOOC H C HN
2
CH3
CH3
Scheme 3. Hydrogen bonding formation for compound (1).
Fig. S2 shows the DSC thermogram of the ligand (L). The ligand
exhibited enantiotropic mesophases during heating and cooling processes
(Table 2). The liquid crystal phase type was assigned based on POM
observations. Characteristic schlieren textures (Fig. 2) observed in the
mesophase indicated appearance of a SmC phase. It was reported [10] that the
benzimidazole moieties participated in hydrogen-bonding both as donors and
acceptors and the intermolecular hydrogen-bonding formed lamellar networks
in the SmC phase. The lateral intermolecular hydrogen bonding between
neighboring benzimidazole moieties accounted for the interdigitated bilayer

structure [25]. Similar results were reported for benzimidazole liquid crystal
derivatives [7, 9].
In spite of the liquid crystallinity of uncoordinated ligand (L), not all
of their corresponding M(II) complexes are mesogenic. The Optical
observation shows that complexes [Mn (L)(Q) ], [Fe (L)(Q) ] and
2
4
2
4
[Ni (L)(Q) ] are non-mesogenic. These complexes have clearly melted and
2 4
transformed into isotropic phase with decomposition.
The TGA
thermograms for these three complexes exhibit only strong broad
decomposition endothermic crystal to isotropic transition (Fig. S2). The
liquid crystallinity for these three complexes could be obscured by the
decomposition at isotropic temperature. Complexes [Cu (L)(Q) ] and
2
4
[Zn (L)(Q) ] were mesogenic and exhibited enantiotropic SmA and nematic
2 4
phases, respectively. The DSC thermogram of complex [Cu (L)(Q) ] (Fig.
2
4
S3) showed two endothermic transition on heating (Cr → SmA and SmA →
I). Under optical microscope complex [Cu (L)(Q) ] exhibited typical focal
2
4
conic fan-shaped texture of SmA, while [Zn (L)(Q) ] display thread-like
4
2
nematic texture mesophase (Figs. 3 and 4).
4. Conclusions
In summary, ligand (L), benzimidazole compound were synthesized and
characterized. A novel [M (L)(Q) ] complexes were synthesized by reacted L
2
4
and Q with metal(II) salts. The possible geometry of synthesized complexes
is octahedral and it is six coordinated metal ligand complexes. The liquid
crystalline behavior for compounds (1), ligand (L) and all complexes were
examined. The compound (1) showed enantiotropic nematic mesophase while
the ligand (L) displays enantiotropic SmC mesophase. The formation of

SmC mesophase was attributed to the lateral intermolecular hydrogen bonds
resulting from benzimidazole groups of the ligand. The novel complexes
[Cu (L)(Q) ] and [Zn (L)(Q) ] exhibit a mesomorphism behaviour, nematic
2 4 2 4
and SmA mesophases, but the others complexes [Mn (L)(Q) ], [Fe (L)(Q) ]
2
2
4
4
and [Ni (L)(Q) ] didn’t showed any liquid crystalline behaviour.
2
4
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Table 1
The Physical properties and metal% of complexes.
Metal%
Calcd.
M.Wt.
g/mol)
Yield
%
Conductivity
Complex
Colour
M.P. (℃)
-1
2
-1
(
Ω cm mol )
(
Found)
Pale
brown
280
[
Mn (L)(Q) ]
2
1158.67
67
85
82
13.11 9.84 (9.01)
4
(dec.)
280
Dark
brown
1
1
160.49
166.22
6.93
9.63 (9.15)
[
[
Fe (L)(Q) ]
2 4
(dec.)
80
2
6.50 10.07 (9.57)
Ni (L)(Q) ]
Green
2
4
(
dec.)
1
1
175.88
179.56
77 82
89 326
5.34
0.81 (10.36)
[
Cu (L)(Q) ]
2
Green
4
13.14 1.09 (10.66)
[Zn (L)(Q) ]
2
Yellow
4

Table 2
The phase transition temperatures and enthalpy changes of compound (1),
ligand (L) and [M (L)(Q) ] complexes
2
4
Compound
1)
Transition temperatures (℃)ꢀ(∆H, kJ/mol)
o
o
3 C (9.43)
147 C (2.87)
(
8
Cr
Cr
N
I
o
o
20 C
(27.28)
(1.15)
1
1
38 C
(
L)
SmC
I
o
[
Mn (L)(Q) ]
2
4
280 C
Cr
Cr
(dec.)
I
I
I
o
2
2
80 C
[
[
Fe (L)(Q) ]
2 4
(dec.)
o
80 C
Ni (L)(Q) ]
2
4
Cr
(dec.)
o
o
(0.71)
9 C (18.39)
125 C
[
[
Cu (L)(Q) ]
7
2
4
Cr
Cr
SmA
I
o
o
325 C
(12.54)
348 C (3.04)
Zn (L)(Q) ]
2
4
N
I
22

Graphical Abstract
A new complexes of N4,N4'-bis((1H-benzo[d]imidazol-2-yl)methyl)-3,3'-
dimethyl-[1,1'-biphenyl]-4,4'-diamine and of their corresponding Mn(II),
Fe(II), Ni (II), Cu(II), and Zn(II) complexes were synthesized. The liquid
crystalline properties of ligands and complexes were examined by DSC and
POM.
23

Highlights
►
A novel Mn(II), Fe(II), Ni (II), Cu(II), and Zn(II) complexes of ligand
containing benzimidazole-8-hydroxyquinoline unit have been synthesized and
characterized.
►
The ligands and Cu(II), and Zn(II) complexes exhibit liquid crystalline
properties.
►
The liquid crystalline behavior has been analyzed in terms of structure-
property relationship between metal centers and ligands.
24