Monoorgano-gallium and –indium complexes derived from dianionic tridentate ONO Schiff bases: Synthesis, crystal structures and photoluminescence

Article abstract of DOI:10.1016/j.jorganchem.2016.02.021

Reactions of triorgano-gallium and –indium etherates with N′-(2-hydroxybenzylidine)benzohydrazide and N′-(2-hydroxy-3-methoxybenzylidine)benzohydrazide in refluxing benzene afforded complexes of composition [{RM}{–O(C₆H₃R′-3)CH[dbnd]

Full text of DOI:10.1016/j.jorganchem.2016.02.021

Accepted Manuscript
Monoorgano-gallium and –indium complexes derived from dianionic tridentate ONO
Schiff bases: Synthesis, crystal structures and photoluminescence
Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, Sandip Dey, V. Sudarsan, Vimal
K. Jain
PII:
S0022-328X(16)30054-7
10.1016/j.jorganchem.2016.02.021
JOM 19405
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 11 December 2015
Revised Date: 11 February 2016
Accepted Date: 17 February 2016
Please cite this article as: M.K. Pal, N. Kushwah, A.P. Wadawale, S. Dey, V. Sudarsan, V.K. Jain,
Monoorgano-gallium and –indium complexes derived from dianionic tridentate ONO Schiff bases:
Synthesis, crystal structures and photoluminescence, Journal of Organometallic Chemistry (2016), doi:
10.1016/j.jorganchem.2016.02.021.
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ACCEPTED MANUSCRIPT
Monoorgano-gallium and –indium complexes derived from dianionic
tridentate ONO Schiff bases: Synthesis, crystal structures and
photoluminescence
Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, Sandip Dey, V. Sudarsan and
Vimal K. Jain*
Chemistry Division, Bhabha Atomic Reasearch Centre, Trombay, Mumbai-400085, India
Email: jainvk@barc.gov.in; Fax: +91-22-2550-5151; Tel: +91-22-2559-5095
Abstract
Reactions
of
triorgano-gallium
and
–indium
etherates
with
N′-(2-
hydroxybenzylidine)benzohydrazide and N′-(2-hydroxy-3-methoxybenzylidine)benzohydrazide in
refluxing benzene afforded complexes of composition [{RM}{-O(C H R′-3)CH=N-N=C(C H )O-}]
6
3
6
5
(
M = Ga, In; R = Me, Et; R′ = H, OMe). These complexes have been characterized by elemental
1
13
1
analysis, IR, UV-vis, and NMR ( H and C{ H}) spectroscopy. The molecular structures of
[
(
{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1), [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}]
6 4 6 5 2 6 3 6 5 2
2) and [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6) were established by X-ray
6
3
6
5
2
crystallography. These complexes adopt a dimeric structure with phenolate oxygen bridges with the
gallium atom acquiring a distorted square pyramidal configuration. These complexes are emissive in
toluene solution at room temperature.
Keywords: Gallium, Indium, dianionic tridentate, photoluminescence, X-ray structures
1
.
Introduction
The chemistry of organo-gallium and –indium compounds with oxo ligands has been actively
pursued for quite some time [1]. The sustained interest in these complexes may be attributed to their
rich structural diversity [1-3], polymorphism [4, 5] and remarkable photophysical properties [2-4, 6].
They have potential applications in catalysis [4, 7], as anti tumour agents [8] as well as single source
molecular precursors for deposition of metal oxide thin films [9, 10]. In general, dimeric complexes of
composition [R M(µ-OR’)] with four coordinated metal atom are formed with simple alkoxy ligands
2
2
[
11]. However, with internally functionalized ligands both mono- and bi-nuclear complexes have been
isolated [12-14]. Dianionic tridentate ligands yield monoorganometal complexes in which metal atom
can acquire four- or five-coordinate geometry; the latter being preferentially adopted by indium
complexes [2].
1

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Schiff bases represent an important family of internally fictionalized ligands which played a
pivotal role in the development of coordination chemistry. These ligands, both anionic and dianionic
have been used for the synthesis of group 13 metal complexes [15]. N-Salicylidene
benzoylhydrazones offer not only several bonding possibilities [16] but also exhibit interesting
luminescent properties. Numerous transition metals complexes from these ligands have been
synthesized [16-18] with scant attention to main group elements [19]. The metal chelates derived from
tridentate dianionic Schiff bases have been shown to be highly luminescent [20, 21]. Luminescences
from group 13 metal complexes, particularly AlQ , have been exploited for organic light emitting
3
diodes (OLEDs) [22-24]. Gallium complexes have been projected as promising candidates to replace
aluminium derivatives, as they exhibit better efficiency than AlQ [25, 26]. The photophysical
3
properties of monoorgano-gallium complexes are little explored [2]. With this perspective and in
pursuance of our interest on organo-gallium and –indium complexes, we have synthesized
monooragno-gallium and –indium complexes with dianonic tridentate benzhydrazide ligands. Results
of this work are reported herein.
2
.
Results and discussion
.1 Synthesis and characterization of complexes
Reactions of N′-(2-hydroxybenzylidine)benzohydrazide
2
and
N′-(2-hydroxy-3-
methoxybenzylidine)benzohydrazide with trialkyl metal etherate in refluxing benzene afforded
monoalkyl metal complexes as yellow solids in 80 to 92 % yield (Scheme 1). The absorption due to
-1
imine linkage (-CH=N-) in the IR spectra are shifted to lower wave numbers (45-60 cm ) with respect
to the free ligand indicating coordination of nitrogen atom to gallium/ indium metal. The absorptions
-1
in the regions 580-606 and 519-530 cm , which were absent in the corresponding free ligands, have
been assigned to M-C and M-O stretching, respectively [2, 10, 27].
1
13
The H and C NMR spectra, recorded in dmso-d , displayed characteristic peaks with
6
expected multiplicities for metal alkyl and ligand fragment. The OH (12.15 ppm) and NH proton
1
resonances (~11.0 ppm) of the ligands are absent in the H NMR spectra of the complexes due to
deprotonation of the ligands. The methyl-gallium and -indium complexes showed a characteristic
1
13
1
13
1
high-field singlet due to methyl group in the H and C{ H} NMR spectra. The C{ H} NMR
resonances due to –CH=N- in the complexes are deshielded by ~9 ppm with respect to the resonances
for free ligands indicating nitrogen coordination to the metal. The carbonyl carbon resonance of the
1
3
free ligands on enolization and coordination with metal is deshielded by 4.1-6.3 ppm. The C NMR
resonances assignable to C-2 and C-1′ are also deshielded with respect to the corresponding
resonances for the free ligand.
2

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5'
5'
6'
6'
4'
3'
4
'
6
6
3'
5
4
1'
5
4
1'
1
1
2'
2'
2
2
3
3
keto form
enol form
R
3
M.OEt
2
- 2 RH
OEt
-
2
Dry C H
6
6
1/
2
M
R
R'
Ga Me H
(1)
Ga Me OMe (2)
In Me H
(3)
In Me OMe (4)
Ga Et
(5)
Ga Et OMe (6)
H
Scheme 1: Synthesis of monoorgano-gallium and -indium complexes
2
.2 Photo physical studies
The absorption spectra corresponding to ligands with R’= H and R’ = OMe showed two peaks
due to π to π* and n to π* transitions corresponding to keto and enol forms of the ligand (Table 1).
Due to low value of HOMO-LUMO gap in keto form corresponding peak is red shifted with respect
to that of enol form [3, 3a]. These ligands on excitation gave broad emission in the visible region;
however their emission quantum yields are relatively poor (1-2%) as can be seen from (Table 1).
Substitution of electron donating groups in the benzene ring of the ligands generally leads to blue shift
in the emission maximum. This is due to increased electron density in the benzene ring. As expected
the OMe substituted ligand showed a blue shift in the emission maximum compared to the
unsubstituted ligand. Excitation spectra corresponding to these ligands (Fig. 1) also showed a trend
similar to that of absorption spectra. Significant Stoke shift has been observed for these ligands as can
be seen form the difference in the wavelength corresponding to excitation and emission peak
maximum (Fig. 1, Table 1). Such large Stoke shift confirms existence of the Excited State Intra-
molecular Proton Transfer (ESIPT) which takes place with the enol form of the ligand resulting in its
keto form. Upon complex formation with Ga and In, conversion to keto form is prevented
consequently leads to blue shit in the emission maximum for the complexes. Further, complexation
with Ga/In, there is a slight improvement in the quantum yield (Table1). This is due to increase in
3

ACCEPTED MANUSCRIPT
electron density with the molecules and associated increase in the transition probabilities on
complexation. Due to heavy metal ion effect, In complexes are expected to have lower quantum yield
values as compared to that of Ga derivatives.
2
.3
Crystal structures of [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1), [{MeGa}{-O(C H -
6 4 6 5 2 6 3
OMe)CH=N-N=C(C H )O-}] (2) and [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6)
6
5
2
6
3
6
5
2
The molecular structures of [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1), [{MeGa}{-
6
4
6
5
2
O(C H -OMe)CH=N-N=C(C H )O-}] (2) and [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6)
6
3
6
5
2
6
3
6
5
2
were established by single crystal X-ray diffraction analyses. The ORTEP plots are depicited in
Figures 2-4 and selected interatomic parameters are given in Tables 2-4. All the three complexes
adopt a dimeric structure with five coordinated gallium atom bridged through phenolate oxygen
atoms resulting in a four-membered rhombohedral Ga O ring. The latter is slighlty bent with an
2
2
angle of 12.02, 3.89 and 4.73° for 1, 2 and 6, respectivley. The ligands adopt a syn, trans
configuration with respect to the central Ga O ring. The inter planar angles between the mean planes
2
2
of ligands are 85.07, 88.63 and 88.87° for 1, 2 and 6, respectively. Increased planarity of Ga O ring
2
2
and widening of the interplanar angle of ligands may be attributed to the presence of steric hinderance
of -OMe group present in 2 and 6 with the oxygen atom of neighbouring/opposite ligand. The
distances between oxygen atoms of methoxy group and enolic oxygen are 2.8665 (av.) and 2.916 (av.)
Å in 2 and 6, respectively, which is less than the sum of van der Waal radii of two oxygen atoms (3.04
Å). The result of this short interaction is also evident from the slight disorder/ enlarges U parameters
ij
in the atoms of the neighboring benzene rings in 2 and 6.
The four-, six- and five-membered rings in these dimeric structures are arranged one after the
other, an arrangement distincly different from those reported in [MeGa(-O(C H )CH=N(C H )-O-)]
6
4
6
4
2
where four-, five- and six-membered rings are placed one after the other [2] but is similar to ONS
tridentate Schiff base system, e.g. [MeGa(-O(C H )CH=N(C H )-S-)] . This behaviour can be
6
4
6
4
2
attributed to the fact that the phenoxy oxygen is a stronger donor as compared to alkoxy group and
takes the bridging position. The five-memebred rings GaNNCO are almost planar while the six-
membered chelate rings GaNCCCO are puckered with Ga atoms out of plane. The two rings are not
co-planar in all the three complexes. The five membered rings GaNNCO are slightly out of plane with
respect to the adjacent benzene rings with inter planar angles being 7.66° (for 1), 8.91°-11.23° (for 2)
and 16.45°-19.18° (for 6). The maximum angle for 6 suggests additional strain due to ethyl groups on
the gallium atoms.
The coordination geometry around the gallium atom defined by CNO donor atoms can be
3
described as distorted square pyramidal on the basis of τ indices (τ = 0.34 in 1, 0.35-0.40 in 2 and
0
.30-0.41 in 6). Five coordinate geometries in metal complexes can be quantified using the τ index, as
described by Addision, et al. [28]. The bridging Ga-O distances are slightly longer than non-bridging
4

ACCEPTED MANUSCRIPT
Ga-O distances (2.100 and 1.922 Å for 1; 2.144 and 1.919 Å for 2 and 2.134 (5) and 2.117 (6) Å for
6
). The M-C, M-O and M-N distances are in conformity with the values reported in the literature [2,
, 29, 30, 31].
3
The analysis of molecular structure of complex 6, shows major continuous disorder in the
ethyl groups on gallium atom. These groups occupy the apical postion of the distorted square
pyramidal geometry of gallium atom. The terminal methyl fragments seem to occupy favorably two of
the total three possible postions in staggered conformation. The position above the six membered ring
is most favored, followed by postion above four membered MOMO ring. The probability of finding
the methyl in third position which may lie directly above the oxygen atoms of N=N-C-O fragment, is
negligible due to repulsion from the lone pair of oxygen atoms. The positions are schematically
shown in Figure 4b and 4c.
3
.
Experimental
3
.1 Materials and Physical Measurements
All experiments involving organo-gallium and –indium compounds were carried out in
anhydrous conditions under a nitrogen atmosphere using Schlenk techniques. Solvents were dried
using standard methods. Triorganogallium etherates (R Ga.OEt ; R = Me, Et) were prepared using
3
2
gallium-magnesium alloy (Mg Ga ) and alkyl iodide in diethyl ether. Trimethylindium etherate was
5
2
prepared using MeMgI and InCl in diethyl ether. Ether contents in each preparation were evaluated
3
1
by H NMR integration [31]. The ligands were prepared by a condensation reaction between an
aldehyde (salicyldehyde or o-vanillin) and benzhydrazide in refluxing methanol as described in the
literature [17, 32].
Elemental analysis was carried out on a Carlo-Erba EA-1110 CHNS analyzer. Infrared
1
13
1
spectra were recorded as KBr plates on a Jasco FT-IR 6100 spectrometer. The NMR ( H and C{ H})
spectra were recorded on a Bruker Avance-II 300 spectrometer in 5 mm tubes as CDCl /dmso-d
3
6
solutions. Chemical shifts were referenced to internal chloroform/dimethyl sulfoxide peak. Electronic
spectra were recorded in toluene on a UV-vis Jasco V-630 spectrophotometer. All luminescence
measurements were carried out at room temperature on an Edinburgh Instruments FLSP 920 system,
having a 450W Xe lamp. Quantum yields were measured using an integrating sphere coated with
BaSO . All emission spectra were corrected for the detector response and excitation spectra for the
4
lamp profile. Emission measurements were carried out with a resolution of 5 nm.
3
.2 X-ray Crystallography
Intensity data for [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1), [{MeGa}{-O(C H -
6
4
6
5
2
6
3
OMe)CH=N-N=C(C H )O-}] (2), recrystallized from benzene and [{EtGa}{-O(C H -OMe)CH=N-
6
5
2
6
3
N=C(C H )O-}] (6), recrystallized from hexane, were collected at room temperature on a Rigaku
6
5
2
AFC 7S diffractometer using graphite monochromated Mo-Kα radiation (0.71069 Å). The structures
5

ACCEPTED MANUSCRIPT
2
were solved using direct methods [33] and refined by full matrix least square method [34] on F using
data corrected for absorption effects using empirical procedures [35]. All non-hydrogen atoms were
refined anisotropically and hydrogen atoms were placed in their geometrically idealized positions
with coordinate and thermal parameters riding on host atoms. The molecular structures are drawn
using ORTEP [36]. Crystallographic and structural determination data are listed in Table 5.
3
3
.3 Synthesis of complexes
.3.1 [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1)
6
4
6
5
To a benzene solution (25 mL) of trimethylgallium etherate (237 mg, containing 87 mg (0.75 mmol)
Me Ga), was added a solution of [HO(C H )CH=N-NH-C(O)(C H )] (181 mg, 0.75 mmol) with
3
6
4
6
5
stirring which was refluxed for 5 h. The solvent was evaporated under a reduced pressure to give a
yellow crystalline solid, which was recrystallized from benzene as yellow crystals (223 mg, 92 %
yield), mp 265 °C, Anal. Calcd. for C H GaN O : C, 55.77; H, 4.06; N, 8.67 %. Found: C, 55.80; H,
1
5
13
2
2
-1
1
4
.40; N, 8.59 %. IR in KBr (υ in cm ): 1615, 1598 (C=N); 592 (Ga-C); 530 (Ga-O). H NMR
3
3
(
dmso-d ) δ: -0.36 (s, 3H, MeGa); 6.62 (t, 1H, J = 8.3 Hz, C-4); 6.67 (d, 1H, J = 9.3 Hz, C-6);
6 HH HH
3
3
7
.22 (t, 1H, J = 9.3 Hz, C-5); 7.32 (d, 1H, J = 8.7 Hz, C-3); 7.40-7.48 (m, 3H, C-3’,4’,5’); 7.80
HH HH
3
13
1
(
(
d, 2H, , J = 8.3 Hz, C-2’,6’); 8.74 (s, 1H, CH=N). C{ H} NMR (dmso-d ) δ: -4.8 (MeGa); 115.8
HH 6
C-3), 118.1 (C-1), 121.3 (C-5), 127.6 (C-2’,6’), 128.6 (C-3’,5’), 131.1 (C-4’), 133.7 (C-4), 133.9 (C-
6
), 134.3 (C-1’), 157.7 (CH=N), 166.5 (C-2), 168.6 (C=N ).
3
.3.2 [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (2)
6
3
6
5
Prepared similar to 1 using trimethylgallium etherate (406 mg, containing 148 mg (1.29
mmol) Me Ga) and [HO(C H -OMe)CH=N-NH-C(O)(C H )] (349 mg, 1.29 mmol) as a yellow
3
6
3
6
5
crystalline solid (417 mg, 91 % yield), m.p. 272 °C, Anal. Calcd. for C H GaN O : C, 54.43; H,
16
15
2
3
-1
4
.28; N, 7.34 %. Found: C, 54.68; H, 4.49; N, 7.49 %. IR in KBr (υ in cm ): 1652 (weak), 1608
1
(
(
C=N); 582 (Ga-C); 564 (Ga-O). H NMR (dmso-d ) δ: -0.38 (s, 3H, MeGa); 3.72 (s, 3H, OMe); 6.54
6
3
3
t, 1H, J = 8.7 Hz, C-5); 6.92 (m, 2H, C-4,6); 7.41-7.47 (m, 3H, C-3’,4’,5’); 8.00 (d, 2H, J = 7.3
HH
HH
1
3
1
Hz, C-2’,6’); 8.72 (s, 1H, CH=N). C{ H} NMR (dmso-d ) δ: -4.9 (MeGa); 56.0 (OMe); 115.0 (C-
6
4
,6), 117.7 (C-1), 125.2 (C-5), 127.7 (C-2’,6’), 128.6 (C-3’,5’), 131.1 (C-4’), 134.2 (C-1’), 151.4 (C-
), 157.1 (C-3), 157.7 (CH=N), 168.6 (C=N).
2
3
.3.3 [{MeIn}{-O(C H )CH=N-N=C(C H )O-}] (3)
6
4
6
5
Prepared similar to 1 in 85 % yield, m.p. >300 °C, Anal. Calcd. for C H InN O : C, 48.94;
1
5
13
2
2
-1
1
H, 3.56; N, 7.61 %. Found: C, 49.19; H, 3.35 ; N, 7.53 %. IR in KBr (υ in cm ): 1611 (C=N). H
3
3
NMR (dmso-d ) δ: -0.19 (s, 3H, MeIn); 6.50 (t, 1H, J = 8.3 Hz, C-4); 6.62 (d, 1H, , J = 9.3 Hz,
6
HH
HH
3
3
C-6); 7.12 (t, 1H, J = 9.3 Hz, C-5); 7.24 (d, 1H, J = 8.7 Hz, C-3); 7.40 (br, 3H, C-3’,4’,5’); 8.05
HH
HH
3
13
1
(
d, 2H, , J = 5.3 Hz, C-2’,6’); 8.56 (s, 1H, CH=N). C{ H} NMR (dmso-d ) δ: -4.6 (MeIn); 114.0
HH
6
6

ACCEPTED MANUSCRIPT
(
C-3), 119.3 (C-1), 122.2 (C-5), 127.6 (C-2’,6’), 128.3 (C-3’,5’), 130.2 (C-4’), 132.3 (C-4), 134.5 (C-
6
), 136.8 (C-1’), 157.0 (CH=N), 167.6 (C-2), 169.6 (C=N).
3
.3.4 [{MeIn}{-O(C H -OMe)CH=N-N=C(C H )O-}] (4)
6
3
6
5
Prepared similar to 1 in 92 % yield, m.p. 280 °C (decompose.), Anal. Calcd. for
C H InN O : C, 48.27; H, 3.79; N, 7.03 %. Found: C, 48.05; H, 3.98; N, 7.20 %. IR in KBr (υ in
16
15
2
3
-
1
1
3
cm ): 1608 (C=N). H NMR (dmso-d ) δ: -0.17 (s, 3H, MeIn); 3.70 (s, 3H, OMe); 6.41 (t, 1H, J
=
HH
6
3
3
8
3
.3 Hz, C-5); 6.78 (d, 1H, , JHH = 8.0 Hz, C-4); 6.85 (d, 1H, J = 8.7 Hz, C-6); 7.40 (br, 3H, C-
HH
3
13
1
’,4’,5’); 8.05 (d, 2H, J = 5.0 Hz, C-2’,6’); 8.54 (s, 1H, CH=N). C{ H} NMR (dmso-d ) δ: -4.3
HH
6
(
MeIn); 55.9 (OMe), 112.9 (C-4), 113.7 (C-6), 118.7 (C-1), 126.3 (C-5), 127.6 (C-2’,6’), 128.3 (C-
3
’,5’), 130.2 (C-4’), 136.8 (C-1’), 152.1 (C-2), 157.1 (CH=N), 160.6 (C-3), 167.4 (C=N).
3
.3.5 [{EtGa}{-O(C H )CH=N-N=C(C H )O-}] (5)
6
4
6
5
Prepared similar to 1 in 80 % yield, m.p. 235 °C, Anal. Calcd. for C H GaN O : C, 57.02;
1
6
15
2
2
-1
H, 4.49; N, 8.31 %. Found: C, 57.08; H, 4.63; N, 8.13 %. IR in KBr (υ in cm ): 1615, 1600 (C=N);
1
3
3
5
62 (Ga-C); 528 (Ga-O). H NMR (dmso-d ) δ: 0.33 (q, 2H, J = 9.0 Hz, GaCH ); 0.93 (t, 3H, J
6 HH 2 HH
3
3
=
8.7 Hz, GaCH CH ); 6.60 (t, 1H, J = 8.3 Hz, C-4); 6.68 (d, 1H, , J = 9.0 Hz, C-6); 7.20 (t,
2 3 HH HH
3
3
1
H, , J = 8.0 Hz, C-5); 7.30 (d, 1H, J = 8.7 Hz, C-3); 7.40-7.46 (m, 3H, C-3’,4’,5’); 8.01 (d, 2H,
HH HH
3
13
1
JHH = 6.7 Hz, C-2’,6’); 8.73 (s, 1H, CH=N). C{ H} NMR (dmso-d ) δ: 5.8 (GaCH ); 10.0
6
2
(
GaCH CH ); 115.8 (C-3), 118.3 (C-1), 121.3 (C-5), 127.6 (C-2’,6’), 128.6 (C-3’,5’), 131.1 (C-4’),
2 3
1
33.7 (C-4), 133.8 (C-6), 134.3 (C-1’), 157.6 (CH=N), 166.7 (C-2), 168.9 (C=N).
3
.3.6 [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6)
6
3
6
5
Prepared similar to 1 in 90 % yield, m.p. 248°C, Anal. Calcd. for C H GaN O : C, 55.63; H,
1
7
17
2
3
-1
4
.67; N, 7.63 %. Found: C, 55.58; H, 4.90; N, 7.33 %. IR in KBr (υ in cm ): 1613 (C=N); 566 (Ga-
1
3
3
C); 519 (Ga-O). H NMR (dmso-d ) δ: 0.30 (q, 2H, J = 9.0 Hz, GaCH ); 0.90 (t, 3H, J = 8.7
6
HH
2
HH
3
3
Hz, GaCH CH ); 3.73 (s, 3H, OMe); 6.54 (t, 1H, J = 9.0 Hz, C-5); 6.90 (t, 2H, J = 9.3 Hz, C-
2
3
HH
HH
3
13
1
4
,6); 7.40-7.47 (m, 3H, C-3’,4’,5’); 7.99 (d, 2H, J = 8.0 Hz, C-2’,6’); 8.70 (s, 1H, CH=N). C{ H}
HH
NMR (dmso-d ) δ: 5.7 (GaCH ); 9.9 (GaCH CH ); 56.1 (OMe); 115.0 (C-4), 115.2 (C-6), 117.9 (C-
6
2
2
3
1
), 125.2 (C-5), 127.7 (C-2’,6’), 128.6 (C-3’,5’ ), 131.1 (C-4’), 134.2 (C-1’), 151.5 (C-2), 157.5
(
CH=N), 157.7 (C-3), 168.9 (C=N).
Conclusions
Monoorgano -gallium and -indium complexes have been synthesised from dianionic
tridentate ONO Schiff bases. The complexes adopt a dimeric structure containing phenolate bridges.
7

ACCEPTED MANUSCRIPT
The 4-, 6- and 5-membered rings in these dimeric complexes lie one after another. The complexes are
emissive in toluene solution with quantum yield always higher than free ligands.
Supporting Information
CCDC-Nos. 1424492, 1424491 and 1424493 contain the supplementary crystallographic data for
[
(
{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1), [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}]
6 4 6 5 2 6 3 6 5 2
2) and [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6), respectively for this paper. These data
6
3
6
5
2
can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: + 44-1223/336-033;
E-mail: deposit@ccdc.cam.ac.uk]. Representative NMR, UV-vis and emission spectra are also
included in supplementary information.
References
1
2
3
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S. Schulz, Comprehensive Organometallic Chemistry-III, Vol 3; C. E. Housecraft, Ed.;
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Organometallics 32 (2013) 104; 3a. M.K. Pal, N. Kushwah, D. Manna, A.P. Wadawale, V.
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3. W.M. Cleaver, A.R. Barron, A.R. McGufey and S.G. Bott, Polyhedron 13 (1994) 2831.
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2. D.K. Rastogi, S.K. Dua, V.B. Rana and S.K. Sahni, J. Inorg. Nucl. Chem. 40 (1978) 1323.
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3
3
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4. G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112.
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Ridge, Tennessee, 199.
3
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Table 1. Uv-Vis absorption, excitation and emission data of ligands and their monoorgano-gallium
and –indium complexes in toluene
Complexes
Uv-vis absorption,
λ in nm
Excitation
in nm
λ
Emission λ Stokes
Quantum
yield (η)
in nm
shift
in %
[
[
[
HO(C H )CH=N-NH-C(O)(C H )]
297, 328
297, 339
312, 408
370
515
550
475
107
210
65
1
2
5
6
4
6
5
HO(C H -OMe)CH=N-NH-C(O)(C H )]
6
3
6
5
{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1)
297, 328, 355, 374 410
sh), 396 (sh)
337, 351(sh), 375, 310, 384
97
6
4
6
5
(
[
{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (2)
470
86
3
6
3
6
5
3
[
[
[
{MeIn}{-O(C H )CH=N-N=C(C H )O-}] (3)
297, 328, 396
332, 375, 398(sh)
302, 340, 414
304, 370, 405
514
460
464
100
55
56
5
2
4
6
4
6
5
{MeIn}{-O(C H -OMe)CH=N-N=C(C H )O-}] (4)
6
3
6
5
{EtGa}{-O(C H )CH=N-N=C(C H )O-}] (5)
297, 328, 358(sh), 303, 340, 408
76(sh), 399(sh)
338, 350(sh), 375, 307, 373, 410
00
6
4
6
5
3
[
{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6)
465
55
3
6
3
6
5
4
1
0

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Table 2. Selected geometric parameters (Å/°) for [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1)
6
4
6
1.934 (7)
2.006 (6)
1.390 (7)
1.314 (7)
5
2
Ga1-O1
Ga1-O1
Ga1-O2
C7-N1
1.922 (4)
2.100 (4)
1.941 (4)
1.279 (8)
1.293 (8)
Ga1-C15
Ga1-N1
N1-N2
i
C8-O2
C8-N2
C15-Ga1-N1
C15-Ga1-O1
C15-Ga1-O1
C15-Ga1-O2
116.9 (3)
100.7 (2)
115.8 (3)
114.4 (2)
72.80 (18)
94.45 (18)
O1-Ga1-N1
O2-Ga1-N1
81.75 (19)
78.9 (2)
i
i
O2-Ga1-O1
144.62 (19)
124.5 (2)
i
O1 -Ga1-N1
i
i
O1-Ga1-O1
Ga1-O1-Ga1
106.35 (18)
O1-Ga1-O2
1
1

ACCEPTED MANUSCRIPT
Table 3. Selected geometric parameters (Å/°) for [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}]
2
6
3
6
5
(
2)
Ga1-C31
Ga1-O1
Ga1-O2
Ga1-O6
Ga1-N1
N1-N2
C8-N1
1.921 (8)
1.950 (5)
2.144 (5)
1.919 (5)
2.031 (6)
1.396 (8)
1.281 (9)
1.309 (10)
1.288 (9)
Ga2-C32
Ga2-O2
Ga2-O5
Ga2-O6
Ga2-N3
N3-N4
1.932 (7)
1.921 (5)
1.939 (5)
2.125 (5)
2.028 (7)
1.409 (8)
1.280 (9)
1.322 (10)
1.287 (9)
C22-N3
C15-N4
C15-O5
C1-N2
C1-O1
C31-Ga1-O1
C31-Ga1-O2
C31-Ga1-O6
C31-Ga1-N1
N1-Ga1-O1
N1-Ga1-O2
N1-Ga1-O6
O1-Ga1-O2
O1-Ga1-O6
O2-Ga1-O6
Ga1-O2-Ga2
114.3 (3)
99.6 (3)
C32-Ga2-O2
C32-Ga2-O5
C32-Ga2-O6
C32-Ga2-N3
N3-Ga2-O2
N3-Ga2-O5
N3-Ga2-O6
O2-Ga2- O5
O2-Ga2- O6
O5-Ga2- O6
Ga1-O6-Ga2
120.2 (3)
113.9 (3)
101.3 (3)
113.4 (3)
123.3 (2)
78.3 (3)
120.7 (3)
114.1 (3)
78.6 (3)
80.9 (2)
121.4 (2)
145.3 (2)
95.9 (2)
81.2 (2)
95.2 (2)
72.05 (19)
144.0 (2)
108.5 (2)
71.66 (19)
107.6 (2)
1
2

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Table 4. Selected geometric parameters (Å/°) for [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}]
6
3
6
5
2
(
6)
Ga1-C31a
Ga1-O1
Ga1-O2
Ga1-O4
Ga1-N2
N1-N2
1.82 (8)
Ga2-C33a
Ga2-O1
Ga2-O4
Ga2-O5
Ga2-N4
N3-N4
1.93 (4)
2.117 (6)
1.951 (5)
1.908 (5)
2.032 (7)
1.394 (8)
1.287 (10)
1.314 (10)
1.283 (10)
1.922 (5)
2.134 (5)
1.923 (6)
2.022 (7)
1.411 (9)
1.269 (9)
1.315 (11)
1.271 (10)
C8-N2
C22-N4
C15-N3
C15-O5
C1-N1
C1-O2
C31a-Ga1-O1
C31a-Ga1-O2
C31a-Ga1-O4
C31a-Ga1-N2
N2-Ga1-O1
N2-Ga1-O2
N2-Ga1-O4
O1-Ga1-O2
O1-Ga1-O4
O2-Ga1-O4
Ga1-O1-Ga2
105 (3)
C33a-Ga2-O1
C33a-Ga2-O4
C33a-Ga2-O5
C33a-Ga2-N4
N4-Ga2-O1
N4-Ga2-O4
N4-Ga2-O5
O1-Ga2- O4
O1-Ga2- O5
O4-Ga2- O5
Ga1-O4-Ga2
117.3 (8)
102.6 (11)
110.8 (11)
121.5 (8)
118.7 (2)
80.3 (3)
110 (3)
110 (2)
126 (2)
81.6 (3)
77.9 (3)
122.7 (3)
144.2 (2)
72.3 (2)
94.8 (2)
108.0 (3)
78.7 (3)
71.6 (2)
96.0 (3)
146.3 (2)
107.8 (2)
1
3

ACCEPTED MANUSCRIPT
Table 5. Crystallography data for [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1) and [{MeGa}{-
6
4
6
5
2
O(C H -OMe)CH=N-N=C(C H )O-}]
(2)
and
[{EtGa}{-O(C H -OMe)CH=N-
6 3
6
3
6
5
2
N=C(C H )O-}] (6)
6
5
2
Formula
C H Ga N O (1) C H Ga N O . 2(C H ) (2) C H Ga N O (6)
30 26 2 4 4 32 30 2 4 6 6 6 34 34 2 4 6
M
645.99
862.26
734.11
Size (mm)
0.10 × 0.10 × 0.05 0.20 × 0.10 × 0.05
0.15 × 0.15 × 0.10
triclinic
Crystal system
monoclinic
C 2/c
triclinic
Space group
P -1
P -1
a/Å
b/Å
c/Å
α/º
17.000 (3)
10.2238 (11)
16.866 (2)
90
10.578 (3)
13.193 (3)
15.936 (3)
99.342 (18)
91.67 (2)
105.36 (2)
2110.0 (10)
2
10.747 (2)
12.376 (5)
15.044 (2)
66.010 (16)
78.988 (13)
66.95 (2)
1681.0 (8)
2
β/º
107.540 (11)
90
γ/º
3
V/Å
2795.1 (7)
4
Z
-
3
d /g cm
calc
1.535
1.357
1.452
-
1
µ (mm )/F(000)
1.971/1312
2.513 to 27.523
-22 ≤ h ≤ 12
1.328/888
2.598 to 27.518
-7 ≤ h ≤ 13
-17 ≤ k ≤ 16
-20 ≤ l ≤ 20
9687
1.652/754
2.584 to 27.515
-7 ≤ h ≤ 13
-14 ≤ k ≤ 16
-19 ≤ l ≤ 19
7704
θ for data collection/°
Limiting indices
0
≤ k ≤ 13
-20 ≤ l ≤ 21
No. of unique reflns
3214
No. of obsd reflns with I > 2σ(I)
Data/restraints/parameters
Final R , ωR indices
1617
2940
1932
3214/0/182
9687/0/485
7704/58/441
1
2
0
.0633/0.1168
.1666/0.1509
0.0742/0.1236
0.3039/0.1840
0.0748/0.1688
0.3399/0.1097
(
R_factor_gt/wR_factor_gt)
R , ωR (all data)
1
2
0
(
R_factor_all/wR_Factor_ref)
2
Goodness of fit on F
1.050
0.925
0.918
-3
Largest diff. peak and hole (e.Å ) 0.593 and -1.043
0.382 and -0.498
0.321 and -0.392
1
4

ACCEPTED MANUSCRIPT
List Figure Captions
Fig. 1. Emission spectra (a) [HO(C H )CH=N-NH-C(O)(C H )] and (b) [{MeGa}{-O(C H )CH=N-
6 4 6 5 6 4
N=C(C H )O-}] (1) with their corresponding excitation spectra
.
6
5
Fig. 2. ORTEP diagram of [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1) (ellipsoids drawn with
6
4
6
5
2
2
5% probability; hydrogen atoms are omitted for clarity).
Fig. 3. ORTEP diagram of [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] .2C H (2.2C H )
6
3
6
5
2
6
6
6
6
(
ellipsoids drawn with 20% probability; hydrogen atoms and solvent molecule are omitted for
clarity).
Fig. 4. (a) ORTEP diagram of [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6) (ellipsoids drawn
6
3
6
5
2
with 10% probability; hydrogen atoms and solvent molecule are omitted for clarity); (b)
Orientation of ethyl groups in (6); (c) Three possible confirmations of 6 (confirmation in red
have least probability as observed from molecular structure).
1
5

ACCEPTED MANUSCRIPT
4
08
160000
410
1
600
200
120000
1
312
8
0000
0000
0
8
00
00
0
515
4
75
4
4
250 300 350 400 450 500 550 600
250 300 350 400 450 500 550 600
Wavelength in nm
Wavelength in nm
(b)
(a)
Fig. 1
. Emission spectra (a) [HO(C H )CH=N-NH-C(O)(C H )] and (b) [{MeGa}{-O(C H )CH=N-
6
4
6
5
6
4
N=C(C H )O-}] (1) with their corresponding excitation spectra
.
6
5
1
6

ACCEPTED MANUSCRIPT
Fig. 2. ORTEP diagram of [{MeGa}{-O(C H )CH=N-N=C(C H )O-}] (1) (ellipsoids drawn with
6
4
6
5
2
2
5% probability; hydrogen atoms are omitted for clarity).
1
7

ACCEPTED MANUSCRIPT
Fig. 3. ORTEP diagram of [{MeGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] .2C H
(2.2C H )
6 6
6
3
6
5
2
6
6
(
ellipsoids drawn with 20% probability; hydrogen atoms and solvent molecule are omitted for
clarity).
1
8

ACCEPTED MANUSCRIPT
(a)
(b)
(c)
Fig. 4. (a) ORTEP diagram of [{EtGa}{-O(C H -OMe)CH=N-N=C(C H )O-}] (6) (ellipsoids drawn
6
3
6
5
2
with 10% probability; hydrogen atoms and solvent molecule are omitted for clarity); (b)
Orientation of ethyl groups in (6); (c) Three possible confirmations of 6 (confirmation in red
have least probability as observed from molecular structure).
1
9

ACCEPTED MANUSCRIPT
Graphical abstract – pictogram and synopsis
Monoorgano-gallium and –indium complexes derived from dianionic
tridentate ONO Schiff bases: Synthesis, crystal structures and
photoluminescence
Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, Sandip Dey, V. Sudarsan and Vimal K.
Jain
Complexes of composition [{RM}{-O(C H R′-3)CH=N-N=C(C H )O-}] (M = Ga, In) were
6
3
6
5
synthesized from reactions of triorgano-gallium and –indium etherates with benzohydrazide schiff
bases. The complexes were emissive in toluene at room temperature. They adopt a dimeric structure
with phenolate oxygen bridges. Gallium atom acquires a distorted square pyramidal configuration.
2
0

ACCEPTED MANUSCRIPT
Highlights
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Mono-organo Ga/In complexes with benzohydrazide schiff bases were synthesized
These complexes have dimeric phenolate oxygen bridged structure
Central Ga O ring is slightly bent
2
2
Variation in interplanar angles is observed with varying substituents
Complexes of organo- Ga/In with benzohydrazide schiff bases are emissive in toluene
2
1