In situ quenching of monoaryl bismuth (III) dihalides with nitrogen donor ligands: Isolation of adducts and their spectral characterization

Article abstract of DOI:10.1016/j.molstruc.2018.07.072

The molecular addition of amphoteric molecules of organobismuth (III) compounds namely, o-tolylbismuth and p-tolylbismuth dihalides with nitrogen donor bidentate ligands 1, 10 phenanthroline and 2, 2′-bipyridine have been isolated and characterized by UV–

Full text of DOI:10.1016/j.molstruc.2018.07.072

Accepted Manuscript
In situ quenching of monoarylbismuth (III) dihalides with nitrogen donor ligands:
Isolation of adducts and their spectral characterization
B.D. Jadhav, S.K. Pardeshi
PII:
S0022-2860(18)30889-5
10.1016/j.molstruc.2018.07.072
MOLSTR 25477
DOI:
Reference:
To appear in:
Journal of Molecular Structure
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Accepted Date:
16 June 2018
23 July 2018
Please cite this article as: B.D. Jadhav, S.K. Pardeshi, In situ quenching of monoarylbismuth (III)
dihalides with nitrogen donor ligands: Isolation of adducts and their spectral characterization,
Journal of Molecular Structure (2018), doi: 10.1016/j.molstruc.2018.07.072
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Graphical Abstract
In situ quenching of monoarylbismuth (III) dihalides with nitrogen donor
ligands: Isolation of adducts and their spectral characterization
B. D. Jadhav and S.K. Pardeshi*
Department of Chemistry, Savitribai Phule Pune University,
(formerly University of Pune), Ganeshkhind, Pune-411007(INDIA)
* Corresponding author. Tel.:+91 020 25601394 Extn. 514; Fax: +91 020 25691728
E-mail: skpar@chem.unipune.ac.in (S.K.Pardeshi)
Abstract
In the present work, molecular addition compounds of amphoteric molecules of
organobismuth(III) o- and p- tolylbismuth dihalides with nitrogen donor ligands 1, 10
phenanthroline and 2, 2’-bipyridine have been isolated and characterized by UV-visible, IR,
NMR and Photoluminescence (PL) spectroscopy. IR study indicate that there are strong
extended interactions exist in crystalline phases demonstrating Lewis acidity at bismuth
center, while PL spectra suggest the presence of monomeric-dimeric species with Bi3+
luminescence in the complexes.

ACCEPTED MANUSCRIPT
In situ quenching of monoarylbismuth (III) dihalides with nitrogen donor
ligands: Isolation of adducts and their spectral characterization
B.D. Jadhav and S.K. Pardeshi*
Department of Chemistry, Savitribai Phule Pune University (Formerly University of Pune),
Ganeshkhind, Pune-411007(INDIA)
* Corresponding author. Tel.:+91 020 25601394 Extn.514; Fax: +91 020 25691728
E-mail: skpar@chem.unipune.ac.in (S.K.Pardeshi)
Abstract
The molecular addition of amphoteric molecules of organobismuth (III) compounds namely,
o-tolylbismuth and p-tolylbismuth dihalides with nitrogen donor bidentate ligands 1, 10
phenanthroline and 2, 2’-bipyridine have been isolated and characterized by UV-visible, IR,
NMR and Photoluminescence (PL) spectroscopy. The compounds have been isolated from
non-aqueous media; they have empirical formulae of the type ArBiX2- L (X = Cl, Br, I; L =
Phen, Bipy). IR study indicate that there are strong extended interactions existing crystalline
phases of the phenyl derivatives, while UV absorption for o-and p- tolylbismuth dihalides
shows bathochromic effect due to +I nature of methyl substituent and corresponding
hypsochromic shift in complexes due to coordination at bismuth center. 1HNMR spectra of
complex exhibit the peaks for free ligands thereby suggesting the dissociation of complex in
solution phase. Room temperature PL spectra suggest the presence of monomeric-dimeric
species with Bi3+ luminescence in the complex in comparison with organobismuth (III)
dihalides.
Key words: In situ quenching, amphoteric molecules, o/p-tolylbismuth dihalides, adducts
isolation, photoluminescence, non aqueous media
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1.Introduction
In recent years the chemistry of bismuth compounds and particularly of
organobismuth derivatives increased due to their biological activity and uses in medicine
[1].The low toxicity of bismuth is due to its poor solubility in aqueous solution or in bio-
fluids at moderate pH which is found in plasma or fluids of living systems [2].Due to its
nontoxic nature, bismuth metal and its salts have been used as eco-friendly mild Lewis acid
catalysts in green organic synthesis [3, 4]. Bismuth chalcogenides and its heterometallic
systems find application as precursor compounds in advanced material science [5].Bismuth-
heterometallic carboxylates are useful starting materials for the synthesis of binary oxide
materials [6].Moreover photoluminiscent materials based on dicarboxylic acids have also
been recently reported [7].For any of these applications, it is important to understand the
structural features in order to fine-tune the desired properties.
According to Pearson’s hard-soft acid-base (HSAB) theory, Bi (III) is a borderline
metal ion [8]. Lewis acidity of Bi(III) compounds are due to the poor shielding of the f-orbital
electrons allowing bismuth to accept an electron pair readily as well as availability of
unoccupied orbitals which elevate its affinity to extend coordination[9]. Electron pair demand
of bismuth can further be improved by strong electron withdrawing groups such as halides or
triflate. Bismuth exhibit various coordination geometries and the stereochemical activity of
the lone pair of electrons, therefore it is expected that a wide range of structural entities are
possible, even when same ligand was used under different conditions. Bi (III) has a high
affinity for both oxygen and nitrogen ligands in aqueous solution and it bind to nitrogen
donor macrocycles even in strongly acidic solutions [10].It has been reported that, in
biological systems bismuth get bind strongly to both N- and C-lobe iron binding sites of
human serum transferrin and recombinant N-lobe transferrin [11].In general, the structures of
Bi (III) compounds are similar to those of Arsenic and Antimony compounds [12], but more
complicated where the coordination number of Bi varies from 3 to10.
The coordination chemistry of Bi (III) with carboxylates and aminocarboxylates
ligands is dominated by intermolecular interactions which lead to polymeric structures. The
reaction of methylbismuth dichloride with thiocarboxylic acid in 1:2 ratio to afford
monoorganobismuth (III) thiocarboxylates was reported by Chaudhari et al. [13].Where
single X-ray analysis demonstrates pentagonal bipyramidal or distorted octahedral
configuration around the bismuth centre. In another study, Sharutin et al. [14] studied the
interaction of triphenyl bismuth with phenylanthralinic acid in presence of hydrogen peroxide
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to form triphenylbis (2-phenylaminobenzoate) in which bismuth atom have distorted trigonal
bipyramidal coordination with phenyl ligand in equatorial position.
Bismuth(III) halides BiX3 (X =Cl, Br or I) are moderate Lewis acids forming complexes with
charged and neutral ligands from Group 15 and 16, in addition to a wide range of halo-
anions[15]. In these complexes the bismuth centre typically has a high coordination number
usually from 6 to 10 with distorted geometry, reflecting the large size of the bismuth atom,
the steric requirements of the ligands and the varying degrees of stereochemical activity of
the bismuth-based lone pair. In contrast, tertiary bismuthines, BiR3, are weak σ-donor and
even weaker π-acceptor ligands towards low valent metal carbonyls and organometallics, but
their chemistry is limited due to weak Bi-C bond which can be easily broken by strong
nucleophiles and electrophiles [16]. Arylhalobismuthines, BiRX2, can behave as Lewis acids
which have been known for some years. Representative examples are the complexes with
nitrogen heterocycles such as [BiPhX2 (L-L)] (X=Cl, Br or I; L-L = 2, 2’-bipy, 1, 10-phen) or
neutral monodentate O- and N-donors in [BiPhX2L] (L=THF, py, OPR3)[17-20]. Alkyl
bismuth bonds are more delicate than their aryl analogues and there are few examples of
BiMeX2 complexes. Breunig et al. [21] reported synthetic pathways leading to CH3SbCl2,
CH3BiCl2, or CH3BiBr2, with detailed structures of 1:1 complexes of CH3SbCl2 and
CH3BiCl2 with 2, 2’-bipyridine (Bipy) ligand. For example the dimeric [{BiMeCl2 (2, 2’-
bipy)}2], which contains square pyramidal bismuth coordination with an apical methyl group
and basal chlorines where they get weakly associated into dimers. The [{BiMeBr2 (THF)2}2],
which crystallizes from BiMeBr2 solutions in THF, is a centrosymmetric dimer, with square
pyramidal units weakly associated through long Bi-Br bridges[22].
The structural chemistry of organobismuth compounds is a topic of continuous
interest. Alkyl/Arylbismuthdihalides RMX2(R = alkyl, Aryl; M=Sb, Bi; X =Cl, Br, I) are
amphoteric molecules with Lewis acidic sites at the metal atoms Trans to the metal-halogen
bond and Lewis basic functions mainly through the lone pairs of electrons of the halogen
atoms. In the absence of external donors they coordinate with each other, forming dimers
when the alkyl groups are bulky or polymers. As alkyl substituents are very slim, particularly
strong extended interactions exist in crystalline phases such as in the methyl derivatives
CH3SbCl2[23], CH3SbBr2 [23] ,CH3SbI2 [24]and CH3BiI2[25]which consist of infinite chains,
[(CH3)M(í-X)2]x(M ) pnicogen; (X ) halogen.
The complexes of arylbismuthines have not been much studied. Faraglia et al. [26] prepared
anionic complexes of C6H5Bi III containing the species C6H5BiX2 (X=Cl, Br, I).
Monophenylbismuthines gave adducts C6H5BiX2. py (X =Cl, Br)[27] and C6H5BiBr2.
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Bipy[28] with neutral nitrogen ligands, and compounds of the type C6H5Bi (S2CNR2)[29]with
bidentate sulfur ligands. To best of our knowledge there are no reports on the synthesis of o-
tolyl and p-tolylbismuthdihalides with nitrogen donor ligands. Herein we report our studies
on synthesis of adducts of o-tolyldihalobismuthines and p-tolyldihalobismuthines with the
nitrogen donor bidentate ligands namely 1, 10 phenanthroline (Phen) and 2, 2’-bipyridine
(Bipy), and their characterization by various spectroscopic techniques.
2. Experimental
2.1Materials: BiC13, (Loba Chemie Mumbai), BiBr3 (Aldrich), o-bromotoluene, p-
bromotoluene were purchased from commercial sources were used without further
purification. Bipyridine (Spectrochem) was sublimed in vacuum after drying overP2O5. 1,10
phenanthroline monohydrate (Spectrochem.) was heated under vacuum at about 70°C for two
hours (mp. = 117-118°C). BiCl3 was sublimed before use. The solvents used in the
preparations and measurements were dried and freshly distilled under nitrogen and were
stored under dry nitrogen. All operations involving bismuth halides and aryl dihalo
bismuthines were carried out in an inert atmosphere.
2.2 General procedures
Elemental analysis (C, H, and N) was performed using a Flashea, 1112 model
(Thermo electron corporation) CHNS elemental analyzer. UV-vis. spectra were obtained in
methylene chloride (DCM) solutions (10-5mol/L) of the complexes with a Shimadzu
1800spectrometer within the range of 800-200 nm, Photoluminescence spectra (PL) were
recorded at ambient temperature on Shimadzu, RF-5301PCfluorimeter and FT-IR spectra
were recorded in the 4000-400cm-1 region with Shimadzu 8400FT-IR spectrometer /Bruker
Optics, Vertex70FT-IR spectrometer using KBr pellets or as neat.1H NMR and 13C NMR
spectra were measured on a Varian-300 /400MHz spectrometer with CDCl3or DMSO-d6 as
the solvent and tetra methylsilane (TMS) as the internal standard. Thermal decomposition of
complexes were studied with ShimadzuTG-DTG-60H thermal analyzer which record
simultaneous TG(Thermogravimetric),DTG (Derivative Thermogravimetry) and DTA
(Differential Thermal Analysis) curves in the static air atmosphere at a heating rate of
10°Cmin−1 in the temperature range of 35-800°C using platinum crucibles.
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3. Results and discussion
3.1 Synthesis of organobismuth (III) compounds and monoaryldihalobismuthines (C)
(C6H5)3Bi, (o-Me C6H4)3Bi and (p-Me C6H4)3Bi were prepared by Grignard
metathesis reaction between corresponding aryl bromide and anhydrous bismuth chloride in
diethyl ether by literature procedure [30]. Organobismuthdihalides namely C6H5BiBr2, o-me
C6H4 BiBr2 and p-me C6H4 BiBr2 were synthesized from corresponding triarylbismuthine and
BiBr3 (molar ratio 1/2) in anhydrous ethyl ether [31]. C6H5BiCl2, o-me C6H4 BiCl2 and p-me
C6H4 BiCl2 has not been isolated in the solid state due to their ready decomposition and
immediate hydrolysis in presence of traces of moisture. Solutions of aryldichlorobismuthine
in anhydrous acetone were obtained by reaction of corresponding triarylbismuthine and BiCl3
in 1:2 molar ratios. All compounds were handled in a dry N2 atmosphere.
By analogy to previous reactions [31], new derivatives containing an ortho, and para
methyl substituent on phenyl ring are synthesized as per Scheme 1.
X
Bi
X
Dry Ether
3
2BiX3
+
Bi
R
0- 5°C
2 hr
R
3
(R = CH3 )
(X = Br, Cl )
C
Scheme 1: Synthesis of monoaryl bismuth dihalides from orgnobismuth (III) compounds
The overall yields of aryl dihalobismuthine lies between 50-70%. They are insoluble
in benzene and hexane, slightly soluble in dichloromethane, chloroform and diethyl ether
where as readily soluble in ethanol, tetrahydrofuran or dimethyl sulfoxide.
3.2 Synthesis of monoaryldihalobismuthine complexes with nitrogen donor ligands
The complexes of the monoaryl dihalobismuthines with nitrogen donor ligands were
prepared by following procedure. To a magnetically stirred solution of aryl dihalo bismuthine
(2.0mmol in 20 ml of dry THF)was added an anionic solution of the ligand (2.0 mmol in 15
ml dry THF).The adduct precipitated immediately in a microcrystalline form, in a good yield
(Scheme 2 ).The solid was washed with acetone and dried in vacuum over CaCl2.
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X
Bi
X
N
N
N
N
(a)
R
R
,
C
r
e
°
h
5
t
E
y
C
°
0
h
2
,
r
Dry Ether
X
Bi
X
D
-
3
3a-d
+
2BiX3
Bi
R
0- 5°C
2 h
R
3
(X = Br, Cl )
2a, 2b, 2d
C
X
Bi
X
N
N
N
(b)
N
4a-d
Scheme 2: Synthesis of monoorganobismuth (III) dihalide complexes with nitrogen
donor ligands
Reagents and Conditions: Triarylbismuthine (2.0 mmol), Bismuth halide (4.0 mmol),
Ligand (2.0 mmol) in dry THF; 0-10°C, 2h
Addition of 2, 2’-bipyridine to a solution of C6H5BiCl2 in dry diethyl ether (1:1 molar
ratio) results in the precipitation of a solid containing the complex and diethyl ether.
Filtration followed by drying results in the formation of yellow, air-stable crystals of
[C6H5BiCl2 (bipy)] in 73% yield. The reaction of C6H5BiBr2 with 2, 2’-bipyridine
(1:1 molar ratio) is performed in tetrahydrofuran. When 2, 2’-bipyridine ligand was added,
complex [C6H5BiBr2. (bipy)] get precipitates as air stable, pale yellow solid in 89% yield.
Both bipyridine complexes are soluble in coordinating solvents such as dimethyl sulfoxide
(DMSO) or acetonitrile but insoluble in hydrocarbon solvents. The complexes synthesized
from different halobismuthines and ligands are summarized in Table 1.
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Table 1: Mono aryl bismuth (III) dihalides complexes with nitrogen donor ligands
a, b
N
N
X
Dry Ether
X
Bi
X
N
N
3
+ 2BiX3
Bi
Bi
X
R
0- 5°C
2 h
R
0- 5°C
2 h
R
3
3a-d,4a-d
(R = CH3 )
(X = Br, Cl )
a = 2,2' bipyridine
b = 1,10 phenanthroline
C
Entry
R
X
Ligand
Complex
Yield
(%)
(Adduct)
1
2
3
4
5
6
7
8
9
H
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
-
-
2m
2n
3a
4a
3b
4b
3c
80.50
81.50
77.80
73.00
77.80
73.00
75.02
77.80
71.81
p-CH3
H
a
b
a
b
a
b
a
H
p-CH3
p-CH3
o-CH3
p-CH3
p-CH3
4c
3d
The complexes are microcrystalline and formed in excellent yields (70-82%). They
are soluble in cold acetone, acetonitrile, methylene chloride, chloroform and in hot alcohol. It
has been found that, phenylbismuth dichloride and p-tolylbismuth dichloride are highly
moisture sensitive and decomposes on exposure in air while their corresponding dibromo
analogues are found to be quite stable and show good reactivity under reaction conditions.
All the compounds are insoluble in ethyl ether, hydrocarbons and carbon tetrachloride. The
bromide and iodide complexes need storing in dark bottles. All of them were characterized by
UV-visible, IR, NMR and Photoluminescence (PL) spectroscopy. Their combined spectral
data is provided in section 6.
3.3 UV Data
UV measurements in methylene chloride were carried out in order to investigate the
behaviour of complexes in the solvent used for spectrophotometric studies. The changes in
the UV absorption of dihalobismuthine and corresponding complexes are depicted in Figure 1
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Figure1: UV-vis spectra of aryl dibromobismuthines (S1) and 1, 10 phenanthroline
(b) with its complex 4c (S2)
The UV absorption maxima for corresponding bismuth dihalides, their complexes and ligand
are shown in Table 2
Table 2: Absorption and Emission wavelengths of a 5 x10-5M solution of
monoorganobismuth(III) dihalides complexes in dichloromethane
Sr.
No
Monoaryl bismuth λmax absorption
λmax emission
halide complex
(nm)
(nm)
1
2m
226,321
302,377,433,469,561,630
303,418,463,567,640
332,440,478
2
2n
3a
4a
3b
4b
3c
4c
3d
a
229,337
3
284
4
227,259
329,441,439,556
332,440,480
5
297,313
6
223,256,362
284
327,442,455,558
332,440,480,554
319,362,438,563
405,434,465,582
325,421,437
7
8
219,259,283,339
228,259
9
10
11
229,257
b
218,237,250
350,436
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Phenyl dibromobismuthine shows band at 324 nm where as o-tolyl dibromobismuthine
exhibit band at slightly longer wavelength 337nm which is significant due to+ I nature of
methyl group (Fig.1, S1). This was reflected in case of p-tolyldibrobismuthine where
absorption maxima still shifted to longer wavelength and absorption occurs at 341 nm. For
complex 4c there was blue shift observed for the bismuth-halogen band from 321 nm to 310
nm (Table 2) which also shows the hypochromic shift in the intensity of absorption compared
with ligand (Fig.1, S2). In the corresponding bromide complex 4b shows red shift due to
behaviour of Bi-N bond in the opposite way, the band at 337 nm get shifted to 362 nm in the
corresponding bromide complex. The possibility of solvent coordination is not taken into
account. The spectrum confirms that in solution the bromobismuthine adducts do not
decompose to the starting compounds.
3.4 TG/DTA analysis
Thermogravimetric analysis of p-tolyl BiCl2.phen complex (4c) was carried out under
constant flow of air at a heating rate of 10°C min-1 in the temperature range 25-800°C.
Corresponding TG-DTA profile is shown in Fig.2
Figure 2: TG-DTA of p-tolyl BiCl2.phen complex (4c)
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From figure it is observed that complex is stable up to ~225°C, after which it starts
decomposing when the phenyl group is being eliminated. Remaining ligands are let off in the
temperature range 245–370°C and complete decomposition occurs near 388°C. The final
product of decomposition is Bi2O3.The formation of Bi2O3 as inferred from the weight loss
(Weight loss found = 53.57%) calculated for the formation of Bi2O3 =54%.The DTA of
corresponding complex shows endothermic peak at 54.26°C which might be due to the
solvent capture in the crystal lattices. The exothermic peak at 298.02°C indicates the melting
of ligand while endothermic peak at 328.53°C suggests its decomposition temperature. The
exothermic peak at 460.08°C indicates the complete decomposition of complex. Endothermic
peak in the range 731-760°C represents phase transformation of monoclinic α- Bi2O3 to the
cubic δ-Bi2O3 which is stable up to melting point of the bismuth oxide (824°C).
3.5 Photoluminescence (PL) spectral analysis
The photo physical properties of the complexes in dichloromethane have been investigated
for their ability to harvest both triplet and singlet excitations at room temperature as well as
the type of metal to ligand and halogen anions bonding. Typical room temperature PL spectra
of complexes are depicted in Figure 3.
Figure 3: UV-vis spectra (a) and PL spectra (b, c and d) of 5 x 10-5 M solution
of monoaryldihalo bismuth complexes with nitrogen donor ligands in
dichloromethane
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Free ligand do not show strong emission where low-lying non radiative type n-π*
transition was observed, while in their bromo complexes (Fig.3b) lowest excited state π- π*
transition centered on monoorganobismuth involving a net transfer of π electron density from
pyridyl nitrogen was seen. Electron donating ability of methyl group (+I effect) at p-position
causes a maximum red shift than sterically hindered o-substituted bismuthine (Fig.3b).Metal
coordination to the pyridyl nitrogen raises the energy of this transition so that the lowest
excited state now becomes an emissive ligand centered π- π* transition. In the case of p-
tolyldihalobismuthine bipy complexes 3b and 3c (Fig.3c) compared with ligand (a),
characteristic bromo shift over chloro interactions was clearly seen which shifts the emission
towards longer wavelength and higher intensity side (red and hypochromic shift) thereby
indicating the role of halogen interaction in the complexes. There was marginal shift in the
emission wavelength from 465 nm to 467 in bromo complex (3b) in comparison with chloro
complex (3d); similarly there was red shift for other bands seen.
It is important to note that for ArBiX2 complexes the rigidity of ligands plays crucial role
in the transition possibilities and their relaxations. This was proved by recording the spectra
of 4b and 4c possessing rigid and bulky phen ligand compared to bipy (Fig.3d). By careful
inspection of spectra it has been found that, emission for chloro complex appeared very weak
in comparison with bromo complex where green emission band centered at 558 nm for 4b
which was absent in complex 4c. The emission was assigned to ligand-localized fluorescence
which is not associated with heavy atom bismuth. The spectra of all compound show dual
emission in the solution, the higher energy emission feature is sharper and falls between 363-
370 nm. The emission band at 468-472 nm is characteristics for Bi3+ luminescence in blue
region. The red shift in fluorescence emission observed in the complex in comparison with
ligand was attributed to coordination of ligand to bismuth which increases the rigidity of
ligands and reduces the loss of energy via radiation less thermal vibrational decay.
In conclusion the PL spectra of all the complexes show dual emission in the solution
for Bi3+ luminescence thereby indicating existence of monomeric and dimeric species in the
solution. Moreover these complexes of bismuth metal chelates over the potential for a high-Z
emitting component in plastic scintillators applications and in organic light emitting diodes,
OLEDs [32].The heavy Bi3+ ion does not appear to enhance the efficiency of room
temperature luminescence
3.6 Infra-red spectral analysis
In order to understand the type of complexation between organobismuth moiety and nitrogen
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donor ligand, we compared respective IR spectrum of p-tolylBiBr2.phen complex (4b), p-
tolylBiBr2 (3n) and phen ligand (b).The respective IR bands are shown in Figure 4. By close
inspection of the spectra, it is clearly seen that, there is decrease in the absorption frequency
and intensity of band at 1421cm-1 compared to free 1, 10 phen ligand. The bands at 1638,
1580 cm-1 in free phen move to lower frequency upon coordination to 1620 and 1569 cm-1 as
medium intensity bands. The strong band at 845 cm-1 splits into a shoulder at 849 ± 2 cm-1, in
addition the band at 621cm-1move to higher frequency at 640 cm-1 in the complex.
4b
2n
b
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Figure 4: Comparative IR spectra of 1, 10 phen(b), p-tolylBiBr2(2n)and p-
tolyl BiBr2.phen complex(4b).
This clearly demonstrates the complex formation between 1, 10, phenanthroline and p-
tolylBiBr2. The bands assigned to vibrational modes of the phenyl group occur in adducts at
about the same frequencies as in the free dihalobismuthines, and are easily identified. These
observations enable us to conclude that in adducts described, 1, 10 phenanthroline acts as
bidentate ligands, and the bismuth atom has a coordination number of five. It is very
interesting to note that, Bi-C bond remain integral during complexation which was proved by
its absorption at 534 cm-1 in the complex.
Figure 5 characterises the IR spectral changes between p-tolyl BiCl2 with nitrogen
donor ligands 2, 2’ bipyridine and 1, 10 phenanthroline respectively. From figure, it is seen
that, the spectra of the 1, 10, phenanthroline adduct in the 1600- 400 cm-1 region show slight
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variations from the spectrum of the ligand. The bands observed in free phen ligand at 1610,
1581cm-1, move to higher frequencies in the complex (1620 m, 1590 m).
4c
3d
b
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber(cm-1)
Figure 5: IR spectral analysis of p-tolyl BiCl2.phen (4c), p-tolylBiCl2.bipy (3d)
complex and phen ligand (b)
The strong band at 845 cm-1splits on coordination at 849± 2 cm- l; moreover the bands at 618
cm-1 move to 631 cm-1 in p-tolylBiC12.phen (4c). The two weak bands at 498 and 472 cm-1
have been noticed in other complexes [33]. As reflected from the spectra, the bands due to the
phenyl group in adducts occur at about the same frequencies as in the free dihalobismuthines.
All the peaks can be assigned to vibrational modes of the phenyl group.
In the bipy complex (3d) similar trend was noticed which clearly demonstrates the
complexation between p-tolylBiCl2 and 2, 2’ bipyridine ligand. The ring vibration bands,
present in free bipy at 1581cm-1 move to higher frequency in adducts, and is independent of
the halide (1607 cm-1w). The strong band of free bipy at 776 cm-1 with a shoulder at 735 cm-1
splits on coordination to 761 and 728 cm-1.The IR spectra of adducts in the 1600-400 cm-1
region are consistent with coordinated Bipy and Phen ligands[34-36]. A medium to strong
band in the region 457-472 cm-1 has been assigned to Bi-C bond [37]
When reaction was conducted with 1:2 molar ratio between p-tolylbismuthine and
BiCl3/BiBr3, disproportionation reaction leads to the formation of (p-tolyl)2BiCl/
(p-tolyl) 2 BiBr. These monohalobismuthines do not form adducts with the same ligands; this
can be attributed to the reduced ability of bismuth to act as an σ-acceptor as the number of
13

ACCEPTED MANUSCRIPT
phenyl groups increases, and due to steric interaction between the phenyl groups and the
relatively large ligands.
3.7 NMR analysis
In order to study the anisotropy associated with carbon-metal bond, we have recorded
the 1HNMR spectra of organobismuth (III) dihalide, free ligand and its complex without
addition of shift reagent. It is well known fact that, in order to record the complex spectra of
organic compounds and organometallics there were need to add shift reagents when spectra
become amenable to first order analysis. Shift reagents which causes paramagnetic shift,
where derivatives of transition metals or inner-transition metals with high nuclear magnetic
moments, such as cobalt [38], europium [39] and praseodymium [40] plays important role. It
is very interesting to note that organobismuthhalides and their complexes used in this study
were analyzed easily without the addition of shift reagent which provides simple models than
other metal aryls [41]. We have obtained first order spectra on 300MHz machine for
compounds of the type ArBiX2, where X is an electronegative group. The resolution is much
higher than in Ar2BiX, Ar3Bi or Ar3 BiX2. Typical 1H NMR spectra of p-tolylBiBr2.bipy
complex in d6-DMSO is shown in Fig. 6.
Br
Bi
N
N
Br
Fig.6: 300MHz1HNMR spectrum of p-tolylBiBr2.bipy complex (3b) in d6 – DMSO
14

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Figure 7:1HNMR spectrum of 2, 2’ bipyridine (a) in CDCl3
From Fig. 6 it has been observed that, the o, m, and p protons of monophenyl group in
organobismuth(III) moiety appear as well-defined doublet, triplet, and triplet respectively in
the complex. While there are distinct shifts noted for the four sets of aromatic protons in the
2, 2’ bipyridine ligand (Fig.7). As a proof for some disproportionation occurs in solution, we
have checked by 1HNMR of corresponding substrates and product formed after reaction in
CDCl3 or d6-DMSO and recorded changes in the chemical shifts, peak multiplicities and
integration. Typical data is summarised in Table 3.
Table 3:1HNMR Shifts (ppm) of p-tolylBiBr2 (2n), 2, 2’bipyridine (a) and their
complex (3b)
2n
3b
∆
a
∆
( δ,ppm)
( δ,ppm)
(ppm)
( δ,ppm)
(ppm)
9.13 (d, J= 6Hz)
7.88 (t, J = 8Hz)
7.37 (m)
8.90 (d, J = 4 Hz)
8.37 (d, J = 8 Hz)
8.69 (d, J = 4Hz) 0.21
8.42 (d, J = 8Hz) 0.05
7.88 (t, J = 7.5 Hz) 0.00
7.63 (d, J = 7.7Hz )
7.81 (t, J = 8Hz)
7.31 (t, J = 6Hz)
0.07
0.09
2.36 (s)
7.42 (m)
7.22 ( m)
2.33 (s)
0.05
0.03
On complexation with 2, 2’ bipy (a) ligand, the signals for the p-tolylBiBr2 protons get
deshielded along with marginal change in the δ values of the 2, 2’ bipy protons thereby
suggesting its complexation with bismuth center in the complex. These investigations
indicate that the complexes are labile in solution since spectra obtained for the complexes in
15

ACCEPTED MANUSCRIPT
d6-DMSO shows the signals of the free 2, 2’ bipy protons. The 1HNMR data for (p-CH3C6H4)
BiBr2 in d6-DMSO, solution was found identical with those given by Smith et.al [33].
4. Conclusions
The work described shows that o and p tolyl dihalobismuthines are modest Lewis
acids forming adduct with nitrogen donor bases, where the typical coordination geometry
being five-coordinate square pyramidal. The products are relatively stable in air and the
Bi-Ph units are less fragile than in the parent halobismuthines. The same bases do not
disproportionate in BiPh2Cl.The IR spectra and 1HNMR shifts clearly suggest the
complexation, while UV-vis absorption for o-and p- tolylbismuthdihalides shows
bathochromic effect due to +I nature of methyl substituent and corresponding hypsochromic
shift in complexes due to coordination of ligand at bismuth center. Both UV-visible and
photoluminescence spectral analysis revealed that the compounds exhibit absorption and
emission peaks, the relative intensity of which was attributed to the presence of a monomer-
dimer solution equilibrium.
Acknowledgments
B.D.J is grateful to the University Grant Commission, New Delhi for awarding
Teacher Fellowship under F.I.P, XI plan.
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6. Combined spectral data
1) dibromo(phenyl)bismuthine (C6H5BiBr2) (2m)
m.p. 232°C (Lit.[31]234-135°C) Found: C,16.06;H,1.11 Calculated:C,16.16;H,1.13;
IR(KBr,cm-1): 3135, 3049,2977, 2923, 2851,2562,2474, 2096, 2050, 1998,
1929,1851, 1773,1709,1613,1560, 1466,
1417,1319,1180,1151,1085,891,704,517,427; 1HNMR (300 MHz, CDCl3, ppm ):
9.14(d, J =8.1Hz,1H),7.88(t, J = 7.6 Hz, 2H) , 7.42-7.36(m,2H);13CNMR (75 MHz,
CDCl3, ppm) : 128 (C-3,4,5 ) ,131(C-1,2,6)
2) dibromo(p-tolyl)bismuthine (C7H7BiBr2) (2n)
m.p. 232°C (Lit.[33]234-135°C) Found: C,18.09; H,1.41 Calculated: C,18.28;H,1.53;
IR(KBr,cm-1): 3038, 2969, 2921, 2847, 2357,2040,1994, 1940, 1898,1620,
1564,1483, 1371,1310,1186,1112, 1035,821,772,630, 556, 512, 447 ; 1HNMR (300
MHz, CDCl3, ppm): 2.5(s,3H) , 7.7 (d, J = 7.8 Hz, 2H), 7.24(d, J = 7.8 Hz,
2H);13CNMR (75 MHz, CDCl3, ppm) :25(CH3),128 (C-3,4,5 ) ,131(C-1,2,6)
3) Dibromo(phenyl)bismuthine 2,2’bipyridine [PhBiBr2 (2, 2’bipy)](3a)
m.p. 239°C; Found: C, 34.44; H, 2.10; N, 4.48;Calculated: C, 34.53; H, 2.13; N, 4.47;
IR (KBr,cm-1): 3002, 2361, 1975 1739, 1618, 1584, 1521, 1492, 1460, 1364, 1309,
1270, 1242, 1211, 1149, 1085, 1038, 1002, 946, 895, 760, 727, 639, 518, 431;1H
NMR (400 MHz, d6-DMSO,ppm) δ 8.59 (d, J = 7.9 Hz, ), 8.16 (d, J = 7.5 Hz, 2H),
8.40 (d, J = 8.0 Hz, 2H), 8.24 (d, J = 7.9 Hz, 2H), 7.97 (d, J = 7.7 Hz, 2H), 7.70 (s,
2H), 7.43 (dd, J = 8.7, 7.9 Hz, 2H)
4) Dibromo(phenyl)bismuthine 1,10 phenanthroline [PhBiBr2.(1,10 phen)] (4a)
20

ACCEPTED MANUSCRIPT
m.p. > 275°C;Found: C, 34.44; H, 2.10; N, 4.48; Calculated: C, 34.53; H, 2.13; N,
4.47; IR (KBr,cm-1): 3043, 2918, 2361, 1741, 1618, 1578, 1511, 1478, 1361, 1344,
1306, 1215, 1140, 1094, 995, 896, 845, 774, 717, 636, 547, 507,468;
1HNMR (400MHz, d6-DMSO, ppm) δ 9.24 (m, 2H), 8.71 - 8.50 (d, J = 8.6 Hz,
2H), 8.12 (s, 1H), 7.94 - 7.78 (m, 6H)
5) Dibromo(p-tolyl)bismuthine 2,2’bipyridine [p-tolBiBr2.(2,2’bipy)] (3b)
m.p. > 275°C;Found: C, 34.44; H, 2.10; N, 4.48; Br, 25.10.;Calculated: C, 34.53; H,
2.13; N, 4.47; Br, 25.53;IR (KBr,cm-1):3037, 2965, 2911, 2856, 2724, 2579, 2310,
2043, 1993, 1897, 1783, 1725,1590, 1475, 1431, 1376, 1306, 1181, 1116, 1034, 832,
773, 633, 556, 511, 458;1H NMR (500 MHz, d6-DMSO,ppm) δ 9.03 (d, J = 7.9 Hz,
2H), 8.71 (d, J = 5.5 Hz, 2H),8.40 (d, J = 8.0 Hz, 2H), 8.24 (d, J = 7.9 Hz, 2H), 7.97
(d, J = 7.7 Hz, 2H), 7.70 (s, 2H), 7.43 (dd, J = 8.7, 7.9 Hz, 2H), 2.28 (s, 3H);13C NMR
(126 MHz, d6-DMSO) δ 155.48, 149.99, 140.00, 137.71, 133.71, 132.28, 124.75,
121.26, 21.81
6) Dibromo(p-tolyl)bismuthine 1,10 phenanthroline [p-tolBiBr2.(1,10 phen)] (4b)
m.p. > 275°C;Found: C, 34.44; H, 2.10; N, 4.48; Calculated: C, 34.53; H, 2.13; N,
4.47; IR(neat,cm-1): 3045, 1742, 1619, 1580, 1512, 1450, 1420, 1370, 1346, 1305,
1222, 1141, 1095, 957, 896, 846,773,718, 634, 507, 468, 416;1H NMR (400 MHz, d6-
DMSO, ppm) δ 9.27 (m, 2H), 8.79 - 8.52 (d, J = 8.6 Hz, 2H), 8.09 (s, 1H), 7.99 - 7.79
(m, 6H), 2.51 (s, 3H).
7) Dibromo(o-tolyl)bismuthine 2,2’bipyridine[ o-tolBiBr2.(2,2’bipy) ] (3c)
m.p. > 275°C;Found: C, 40.91; H, 2.76; N, 5.21; Calculated: C, 40.24; H, 2.44; N,
5.21;IR (KBr,cm-1): 3377, 3002, 2920, 1739, 1618, 1585, 1521, 1492, 1428, 1366,
1308, 1270, 1241, 1211, 1149, 1084, 1002, 946, 896, 761, 725, 637, 517, 432;1HNMR
(400 MHz, d6-DMSO,ppm) δ 8.57 (d, J = 7.9 Hz, ), 8.19 (d, J = 7.5 Hz, 2H), 8.38 (d,
J = 8.0 Hz, 2H), 8.22 (d, J = 7.9 Hz, 2H), 7.94 (d, J = 7.7 Hz, 2H), 7.67 (s, 2H), 7.41
(dd, J = 27.7, 11.9 Hz, 2H), 2.51 (s, 3H).
8) Dichloro (p-tolyl)bismuthine 1,10 phenanthroline[p-tolBiCl2.(1,10 phen)] (4c)
m.p. > 275°C; Found: C, 40.91; H, 2.76; N, 5.21; Calculated: C, 40.24; H, 2.44; N,
4.68; IR (KBr,cm-1):3369, 3048, 2994, 2335, 2280, 2210, 2036, 1970, 1828, 1662,
21

ACCEPTED MANUSCRIPT
1620, 1590, 1506, 1416, 1339, 1220, 1142, 1083, 1034, 952, 850, 780, 725, 690, 617,
498,472;1H NMR (400 MHz, d6-DMSO, ppm) δ 9.27 (d, J = 9.3 Hz, 2H), 8.84 (d, J =
7.9 Hz, 2H), 8.62 (d, J = 8.3 Hz, 2H), 8.29- 7.75 (m, 1H), 7.90 (d, J = 9.1 Hz, 2H),
7.79 - 7.38 (m, 4H), 2.50 (s, 3H).
9) Dichloro(p-tolyl)bismuthine 2,2’bipyridine[p-tolBiCl2.(2,2’bipy)] (3d)
m.p. > 275°CFound: C, 40.91; H, 2.76; N, 5.21; Calculated: C, 40.24; H, 2.44; N,
5.21;IR(neat,cm-1): 3035, 2924, 2847, 2354, 1731, 1614, 1476, 1446, 1376, 1249,
1184, 1076, 1017, 809, 761, 696, 607, 540, 472; 1H NMR (400 MHz, d6-DMSO,
ppm) δ 8.86 (d, J = 8.0 Hz, 2H), 8.73 - 8.67 (m, 2H), 8.40 (d, J = 8.0 Hz, 2H), 7.96
(td, J = 7.8, 1.8 Hz, 2H), 7.72 (d, J = 7.5 Hz, 2H), 7.46 (m, 2H), 3.42 (s, 3H)
22

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Highlights of the Manuscript
In situ quenching of monoarylbismuth (III) dihalides with nitrogen donor
ligands: Isolation of adducts and their spectral characterization
 Good overall yield and fairly air stable Bi(III) complexes
 Lewis acidity at bismuth centre as evidenced by IR spectroscopy
 Full structural elucidation of Bi(III) complexes by UV-visible, IR and NMR
 Bi3+ luminescence in PL Spectra confirms monomeric-dimeric species