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Diarylgallium complexes derived from azo-linked Schiff bases: Synthesis, characterization and photoluminescence studies
Accepted Manuscript Diarylgallium complexes derived from azo-linked schiff bases: Synthesis, characterization and photoluminescence studies Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan, Vimal K. Jain PII:
S0022-328X(17)30466-7
DOI:
10.1016/j.jorganchem.2017.07.036
Reference:
JOM 20050
To appear in:
Journal of Organometallic Chemistry
Received Date: 23 May 2017 Revised Date:
26 July 2017
Accepted Date: 30 July 2017
Please cite this article as: M.K. Pal, N. Kushwah, A.P. Wadawale, V. Sudarsan, V.K. Jain, Diarylgallium complexes derived from azo-linked schiff bases: Synthesis, characterization and photoluminescence studies, Journal of Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.07.036. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract – Pictogram and Synopsis
Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies.
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Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain
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Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain*
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Chemistry Division, Bhabha Atomic Research Centre,Trombay, Mumbai 400 085, India. Email: [email protected] ; Fax: +91-22-2550-5151; Tel: +91-22-2559-5095
Abstract
Diarylgallium complexes of composition, [Ar2GaOC6H3(N=NPh)(CH=NAr’)], (Ar = Ph or tol; Ar’ = Ph,
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tol-4 or C6H4Br-4) have been synthesized by treatment of triaryl-gallium dioxane adduct with azo linked salicylaldimine Schiff bases in benzene. These complexes have been characterized by elemental analysis, IR,
UV-Vis,
NMR
(1 H
and
13
C{1H})
spectroscopy.
The
molecular
structures
of
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[Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) were established by X-ray crystallography. The complexes are discrete monomer with four coordinated gallium atom forming a distorted tetrahedral structure. Photoluminescence studies of these complexes showed that the quantum yield is always higher than that of the corresponding ligands and the emission peaks of complexes are blue shifted with respect to ligand.
1.
Introduction
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Keywords: Arylgallium; Phenylazo salicyldehyde; Schiff base; photoluminescence; X-ray structures.
Organogallium complexes derived from internally functionalized anionic oxo-ligands have
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received considerable attention due to several obvious reasons [1]. These complexes exhibit rich structural diversity [1-3] and show interesting photo-physical properties [2-4], polymorphism [4], finds
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applications in catalysis [4,5], materials science [6,7] and biomedical imaging [8]. Since the first report of organic light emitting diodes (OLEDs) fabricated from tris(8-hydroxyquinolinolate)Al(III) (Alq3) in 1987 [9], metal chelate complexes have attracted considerable attention [10]. In recent years, the most promising candidates to substitute Alq3 were those of gallium [11]. Schiff base ligands and their metal/organometallic complexes have been extensively studied and a number of them show good luminescence properties [2,4]. There is analogy between the emission behavior of salicyldehyde Schiff bases and 8-hydroxyquinoline, since both the ligands have similar chromophoric groups i.e. a hydroxyl group, a coordinating imine N atom and a delocalized π-electron system [12]. Schiff bases derived from azo compounds constitute yet an interesting family of photo-chromic ligands [13]. 1
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Luminescent behavior of organogallium [2,4,14,15] complexes has been reported in the past with an emphasis on alkylgallium (methyl or ethyl) derivatives, recently we have also reported photoluminescence properties of methyl-gallium complexes containing salicylaldimine Schiff bases [2,4,16,17]. In contrast to this, the arylgallium derivatives received scant attention. Interestingly the aryl
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boron compounds like BODIPY (boron-dipyrromethene) derivatives containing an aryl-B linkages are promising luminescent material [18]. With this perspective it was considered to synthesize arylgallium complexes with azo-based Schiff base ligands and examine their photo-physical properties.
Results and Discussion
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2.
2.1 Synthesis and characterization of complexes
Reactions of [5-(phenylazo)-N-(aniline)salicylidene] (1a), [5-(phenylazo)-N-(4-toluidine)salicylidene]
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(1b) and [5-(phenylazo)-N-(4-bromoaniline)salicylidene] (1c) with triaryl-gallium dioxane adduct in benzene at room temperature afforded diarylgallium complexes (Scheme 1) as yellow to orange-red solids. 3'
2'
Ar3Ga.dioxane
3'
1'
4'
4
3
Benzene
5 5'
2
6' 6
1
RT
2'
1'
4
4'
5'
3
5
2
6'
6
1
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'
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Ar' = Ph (1a), 4-MeC6H4 (1b) or 4-BrC6H4 (1c)
'
Ar Ph Ph Ph tol tol tol
Ar' Ph 4-MeC6H4 4-BrC6H4 Ph 4-MeC6H4 4-BrC6H4
2a 2b 2c 2d 2e 2f
Scheme 1
The absorptions bands due to Ga-C and Ga-O, which are absent in the IR spectra of the free
ligands appear at 579-592 and 529-541 cm-1 respectively for the complexes [2,4,19,20]. The absorption due to azomethine linkage (-CH=N-) and azo functional group (-N=N-) are shifted to lower wave numbers 5-8 cm-1, 14-25 cm-1 respectively with respect to that of free ligand on coordination of nitrogen atom to gallium. The 1H and 13C{1H} NMR spectra, recorded in dmso-d6, displayed characteristic peaks with expected multiplicities for metal aryl and ligand fragment. The 13C NMR resonances due to –CH=Nin diaryl gallium complexes is deshielded by approximately 7 ppm from the respective resonance for the 2
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free ligands, whereas 1H resonance due to –CH=N- is only slightly deshielded (~ 0.07 ppm) from the respective resonance for the free ligands.
2.2 Crystal Structure of 2a and 2b: molecular
structures
of
[Ph2GaOC6H3(N=NPh)(CH=NPh)]
(2a)
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The
and
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) were established by single crystal X-ray diffraction analyses. Perspective drawings are depicited in Figs. 1 and 2, and selected interatomic parameters are given in Table 1. Various interatomic parameters in the two structures are essentially similar and can be compared
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with the analogous dimethylgallium derivatives [21]. However, the azo C-N bonds are marginally elongated while the azo N=N bond is slightly shortened in comparison to the analogous dimethylgallium complex [4]. This could be attributed to the presence of electron releasing phenyl groups on gallium. The
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Ga-C, Ga-O and Ga-N distances are in conformity with the values reported in the literature [2,4,22-23]. Gallium atom adopts a distorted tetrahedral configuration which is defined by two phenyl carbon atoms, a nitrogen and phenolate oxygen atom. The
six memebered Ga1-O1-C1-C2-C7-N1 rings in both
complexes are slighlty puckered with O1 out of plane by 0.105 and 0.143 Å, in 2a and 2b respectively. The terminal phenyl ring is twisted about the N=N with reference to the basal phenyl ring with an angle of 13.90° and 23.48°, in the respective complexes. The phenyl and tolyl fragments are differently
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oriented with respect to the Schiff base fragment, making an interplanar angle of 88.88° and 47.5° in 2a and 2b respectively. This suggests that the substitent at the para- postion of the ring attached to azo group (N1) affects the planarity of the Schiff base fragment, which influences the luminicent properties of these complexes. This is evident from the observed trends in luminiscence properties of the complexes 2a, 2b
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and 2c.
2.3 Photo-physical properties
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UV-Visible absorption spectra of all the ligands and their respective diarylgallium complexes
consist of mainly two peaks. For ligands these two peaks are mostly in the UV region and upon complexation they shift to near UV and visible region. These peaks can be attributed to the
π → π*
transitions in the aromatic ring and CH=N moiety for ligands. For complexes in addition to the above mentioned structural units, Ga-O related structural units also undergo absorption in the UV region. Complexation of ligands with trialkyl/triaryl gallium derivatives leads to overall increase in electron density in the ligand framework, subsequently the wavelength corresponding to absorption maxima get red shifted as is evident from Table 2. Unlike absorption spectra, emission spectra from the complexes are 3
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in the visible region (with wavelength maximum over a narrow range of 404-415nm) and are blue shifted with respect to that of the corresponding ligands. The emission in aryl derivatives showed pronounced blue shifting than the corresponding dimethylgallium complexes (Table 2). Emission in the blue region can be attributed to GaOx related centres in complexes. Even though ligand is excited upon exposure to
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UV light, the energy is transferred to the GaOx structural units which upon de-excitation leads to blue emission form the samples. This also explains the fact the emission maximum is not significantly affected by modifications/substitutions in the ligand moiety, however influenced by the substituent on gallium. It is worthwhile to mention here that blue emission from GaOx related structural units are well reported in many complexes and inorganic compounds [24]. Free ligands also undergo an important photo physical
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process known as excited state intramolecular proton transfer (ESIPT), leading to large Stokes shift, in emission and excitation profiles (Table 2, Fig. 3). The process is hindered upon complexation and the
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Stoke shift values decreases accordingly (Table 2). Quantum yield of emission form the complexes are in the range of 4-8% and are higher than that of free ligands. A direct comparison of quantum yields of ligand and complexes are not appropriate here, as additional luminescent moiety based on GaOx structural units are present in the complexes which is absent in the case free ligands. The CIE (Commission internationale de l’éclairage) color co-ordinates (x, y) were calculated for ligands and complexes based on the emission spectra and a representative is shown in Fig. 4. The color coordinated (x, y) for ligands and
3.
Experimental
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complexes are given in supplementary (Table S1).
3.1 Materials and Physical Measurements
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All experiments involving organo-gallium compounds were carried out in anhydrous conditions under a nitrogen atmosphere using Schlenk techniques. Solvents were dried using standard methods. Triarylgallium dioxane (Ar3Ga.dioxane; Ar = Ph or tol) were prepared using gallium trichloride and
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PhMgBr or tolMgBr in diethyl ether and later dioxane and benzene added to precipitate out excess magnesium halide and benzene extract was concentrated to give triarylgallium dioxane. Dioxane contents in each preparation were evaluated by 1H NMR integration [25]. The ligands, [5-(phenylazo)-N(aniline)salicylidene] (1a), [5-(phenylazo)-N-(p-toluidine)salicylidene] (1b) and [5-(phenylazo)-N-(pbromophenyl)salicylidene] (1c) were prepared according to literature procedures [26,27] and were characterized by NMR spectroscopy (Supplementary Material). Infrared spectra were recorded as KBr plates on a Jasco FT-IR 6100 spectrometer in the range 4000-400 cm-1. The NMR (1H and
13
C{1H}) spectra were recorded on a Bruker Avance-II 300 4
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spectrometer in 5 mm tubes as dmso-d6 solutions. Chemical shifts were referenced to internal dimethyl sulfoxide peak. Electronic spectra were recorded in dichloromethane on a UV-vis Jasco V-630 spectrophotometer. All luminescence measurements were carried out at room temperature using Edinburgh Instruments FLSP 920 system, having a 450W Xe lamp. Quantum yields were measured using
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an integrating sphere coated with BaSO4. All emission spectra were corrected for the detector response and excitation spectra for the lamp profile. Emission measurements were carried out with a resolution of 5 nm.
3.2 X-ray Crystallography
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Intensity data for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol4)] (2b) were collected at room temperature on a Rigaku AFC 7S diffractometer using graphite
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monochromated Mo-Kα radiation (0.71069 Å). The structures were solved using direct methods [28] and refined by full matrix least square method [29] on F2 using data corrected for absorption effects using empirical procedures [30]. 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 [31]. Crystallographic and structural
3.3 Synthesis of complexes
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determination data are listed in Table 3.
3.3.1 [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a)
To a benzene solution (25 mL) of triphenylgallium dioxane (66.4 mg, containing 35.4 mg (0.12 mmol)
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Ph3Ga), was added a solution of 1a (35.6 mg, 0.12 mmol) with stirring which continued for 10 h. The solvent was evaporated under a reduced pressure to give an orange-red crystalline solid, which was recrystallized from hexane (44.9 mg, 73 % yield), mp 185°C, Anal. Calcd. for C31H24GaN3O: C,71.02; H,
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4.61; N, 8.01%. Found: C,70.93; H, 4.31; N, 8.26 %. IR (υ in cm-1): 1615 (C=N); 1473 (N=N); 592 (GaC); 533 (Ga-O). 1H NMR (dmso-d6) δ:6.47 (t, 7.2 Hz); 6.54 (d, 8.2 Hz, 1H); 6.98 (t, 7.6 Hz, 1H); 7.05 (d, 9Hz, 1H); 7.30 (br, 7 H); 7.41 (br, 5H), 7.75 (d, 8.5 Hz, 1H); 7.84 (d, 7.8 Hz, 3 H); 8.04 (m), 8.38 (S, 1H); 9.18 (S, 1H, CH=N). 13C{1H} NMR (dmso-d6) δ:114.3 (C-Ga), 116.2, 122.2, 122.6, 127.1, 127.4, 127.9, 128.4, 129.0, 129.3, 129.4, 129.7, 129.9, 130.2, 131.2, 136.6, 143.5, 147.4, 152.5, 152.8, 170.5 (CH=N-).
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3.3.2 [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) Prepared similar to 2a in 76 % yield, mp 215 °C. Anal. Calcd. for C32H26GaN3O: C,71.40; H, 4.87; N, 7.81%. Found: C, 71.77; H, 5.07; N, 8.09 %. IR (υ in cm-1): 1615 (C=N); 1473 (N=N); 592 (Ga-C); 534 (Ga-O). 1H NMR (dmso-d6) δ: 2.26 (s, 3H, Ar-Me); 7.03 (d, 9 Hz, 1H); 7.15 (d, 6Hz, 1H); 7.23 (t, 7.8Hz, CH=N-).
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2H); 7.31 (br, 7H); 7.54 (br, 7H), 7.84 (d, 7.2 Hz, 2H); 8.06 (d, 9Hz, 1H); 8.38 (s, 1H); 9.18 (s, 1H, 13
C{1H} NMR (dmso-d6) δ: 21.0 (Ar-Me); 114.5 (C-Ga); 118.8, 122.1, 122.6, 123.4, 127.4,
127.9, 128.4, 129.1, 129.5, 129.9, 130.8, 131.2, 135.6, 136.9, 138.5, 143.2, 143.6, 144.3, 152.5, 169.8, 170.6 (-CH=N-).
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3.3.3 [Ph2GaOC6H3(N=NPh)(CH=NPhBr-4)] (2c)
Prepared similar to 2a in 85 % yield, mp 205 °C. Anal. Calcd. for C31H23BrGaN3O: C, 61.73; H, 3.84; N, 6.97 %. Found: C, 61.54; H, 3.96; N, 6.77 %. IR (υ in cm-1): 1614 (C=N); 1472 (N=N); 579 (Ga-C); 531
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(Ga-O). 1H NMR (dmso-d6) δ: 6.50 (d, 8.7 Hz, 1H); 7.11 (d, 8.7 Hz, 3H); 7.30 (br, 6H); 7.54 (m, 12H); 7.78 (d, 7.8 Hz, 1H); 7.84 (d, 7.2Hz, 2H); 8.07 (m, 2H); 8.36 (s, 1H); 9.17 (s, 1H, -CH=N-).
13
C{1H}
NMR (dmso-d6) δ: 116.2, 122.5, 122.6, 124.4, 127.4, 127.8, 128.4, 128.8, 129.1, 129.8, 129.9, 131.8, 133.1, 136.6, 137.0, 143.2, 146.5, 152.4, 171.1.
3.3.4 [tol2GaOC6H3(N=NPh)(CH=NPh)] (2d)
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Prepared similar to 2a in 86 % yield, mp 135 °C. Anal. Calcd. for C33H28GaN3O: C, 71.76; H, 5.11; N, 7.61 %. Found: C, 71.63; H, 4.98; N, 7.48 %. IR (υ in cm-1): 1612 (C=N); 1471 (N=N); 590 (Ga-C); 533 (Ga-O). 1H NMR (dmso-d6) δ: 2.23 (s, 6H, Ar-Me); 6.46 (t, 7.5Hz, 1H), 6.54 (d, 7.5 Hz, 1H); 6.98 (m, 5H), 7.10 (d, 7.5Hz, 6H); 7.47 (m), 7.74 (d, 7.2 Hz, 2H); 7.82 (d, 7.2 Hz, 4H); 8.03 (m, 3H); 8.36 (s, 1H); 13
C{1H} NMR (dmso-d6) δ: 21.0 (Ar-Me); 114.3, 116.2, 122.2, 122.6, 126.7,
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9.15 (s, 1H, -CH=N-).
129.1, 129.3, 129.7, 129.9, 130.2, 131.1, 136.5, 138.0, 139.7, 147.4, 152.5, 152.8, 170.3 (-CH=N-).
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3.3.5 [tol2GaOC6H3(N=NPh)(CH=Ntol-4)] (2e) Prepared similar to 2a in 71 % yield, mp 98 °C. Anal. Calcd. for C34H30GaN3O: C, 72.10; H, 5.34; N, 7.42 %. Found: C, 72.22; H, 5.31; N, 7.59 %. IR (υ in cm-1): 1615 (C=N); 1472 (N=N); 589 (Ga-C); 540 (GaO). 1H NMR (dmso-d6) δ: 2.22 (s, 9H, Ar-Me); 7.00 (d, 9.0 Hz, 1H); 7.10 (d, 7.5 Hz, 4H); 7.19 (d, 7.8 Hz, 2H); 7.32 (d, 8.1Hz, 2H); 7.42 (d, 7.5Hz, 4H), 7.53 (m, 4H); 7.83 (d, 7.5Hz, 2H); 8.04 (d, 9Hz, 1H), 8.35 (s, 1H); 9.13 (s, 1H, -CH=N-).
13
C{1H} NMR (dmso-d6) δ: 20.9 (Ar-Me); 21.5 (Ar-Me); 118.7,
122.1. 122.6, 123.4, 129.1, 129.4, 129.9, 130.7, 131.1, 135.7, 136.5, 137.0, 138.2, 138.4, 139.5, 143.6, 144.3, 152.5, 169.9, 170.3 (-CH=N-). 6
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3.3.6 [tol2GaOC6H3(N=NPh)(CH=NPhBr-4)] (2f) Prepared similar to 2a in 72 % yield, mp 165 °C. Anal. Calcd. for C33H27BrGaN3O: C, 62.79; H, 4.31; N, 6.66 %. Found: C, 62.71; H, 4.24; N, 6.92 %. IR (υ in cm-1): 1614 (C=N); 1484 (N=N); 590 (Ga-C); 540
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(Ga-O). 1H NMR (dmso-d6) δ: 2.23 (s, 6H, Ar-Me); 6.52 (d, 8.7Hz, 2H); 7.10 (br); 7.29 (d, 7.8 Hz, 3H), 7.50 (m); 7.76 (d, 7.5Hz, 2H); 7.82 (d, 7.5Hz, 2H0; 7.98 (d, 8.1 Hz, 1H); 8.09 (s, 1H); 8.35 (s, 1H0; 9.11 (s, 1H, -CH=N-).
13
C{1H} NMR (dmso-d6) δ: 21.5 (Ar-Me); 116.2, 122.3, 122.6, 124.3, 126.7, 128.0,
129.1, 136.6, 127.0, 138.0, 139.9, 143.7, 148.4, 152.5, 152.7, 170.3
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Conclusion
Diarylgallium complexes derived from azo linked salicylaldimine Schiff base have been
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synthesized. These complexes emit in the blue region upon excitation of ligand moiety and the emission has been attributed to the presence of GaOx related centres in the complex. The quantum yields of the complexes are always higher than that for the corresponding ligands which can be explained based on lack of ESIPT in complexes.
Supporting Information. 1544396
and
1544395
contains
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CCDC-Nos:
the
supplementary
crystallographic
data
for
[Ph2GaOC6H3(N=NPh)(CH=NPh)] and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] for this paper. These data 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-
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31.
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Rigaku Corporation, 3, 9-12, Matsubara, Akishima, Japan, 1995.
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Table 1: Selected bond lengths (Å) and angles (°) for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) [Ph2GaOC6H3(N=NPh)(CH=NPh)]
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)]
1.958 (4)
1.956 (8)
Ga1-C26
1.967 (4)
1.962 (8)
Ga1-O1
1.904 (3)
1.902 (5)
Ga1-N1
2.037 (3)
2.033 (6)
C7-N1
1.289 (5)
1.301 (8)
N2-N3
1.238 (5)
1.216 (8)
C4-N2
1.459 (6)
1.454 (10)
C8-N3
1.454 (6)
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Ga1-C20
1.455 (10)
125.61 (17)
C20-Ga1-N1
108.04 (15)
110.6 (3)
C26-Ga1-N1
109.00 (14)
108.5 (6)
C20-Ga1-O1
108.53 (15)
106.9 (3)
C26-Ga1-O1
107.14 (15)
108.8 (3)
O1-Ga1-N1
93.90 (12)
93.5 (2)
C7-N1-Ga1
121.6 (3)
121.2 (6)
C14-N1-Ga1
119.5 (2)
119.5 (5)
128.2 (2)
128.5 (6)
111.3 (4)
114.9 (9)
110.9 (4)
111.4 (9)
118.7 (3)
119.0 (7)
C4-N2-N3 N2-N3-C8
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C7-N1-C14
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C1-O1-Ga1
124.2 (4)
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C20-Ga1-C26
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Table 2: UV-vis absorption, excitation and emission data of ligands and their organo gallium complexes in dichloromethane UV-Vis absorption, λ in nm
Excitation λ in nm
Emission λ in nm
Stoke shift
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-Ph] (1a)
335
314
465
151
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-tol-4)] (1b)
336
318
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr-4)] (1c)
336
[Me2GaOC6H3(N=NPh)(CH=NPh)] *
Quantum Yield (η) in % 3
460
142
3
290, 395
449
54
2
316, 364, 429(sh)
365
415
50
5
[Me2GaOC6H3(N=NPh)(CH=Ntol-4)]*
324, 366, 430(sh)
364
415
51
7
[Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a)
316, 363, 429
294, 369
409
40
4
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
317(sh), 364, 429
[Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
359, 432
[tol2GaOC6H3(N=NPh)(CH=NPh)] (2d)
318, 364, 429
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Compounds
[tol2GaOC6H3(N=NPh)(CH=N-PhBr-4)](2f)
41
4
292, 362
405
43
8
284, 364
409
45
4
365, 434
285, 367
412
45
4
341, 441
290, 363
409
46
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* from ref. [21]
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[tol2GaOC6H3(N=NPh)(CH=Ntol-4)](2e)
287, 363
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Table 3: Crystallographic and Structural Refinement Data for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
5925 / 7/ 320 0.0571/ 0.1185
6158/ 0 /335 0.0894 / 0.1511
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C32H26GaN3O 538.28 0.100 × 0.100× 0.040 Triclinic Pī 10.011(2) 10.655 (2) 13.542 (3) 106.731 (16) 101.710 (16) 92.608 (17) 1346.2 (5) 2 1.328 1.051 / 556 2.734 to 27.498 -12 ≤ h ≤ 7 -13 ≤ k ≤ 13 -17 ≤ l ≤ 17 6158 1576
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No. of unique reflns/ No. of obsd reflns with I > 2σ(I) Data/restraints/parameters Final R1, ωR2 indices (R_factor_gt/wR_factor_gt) R1, ωR2 (all data) (R_factor_all/wR_Factor_ref) Goodness of fit on F2 Largest diff. peak and hole (e.Å-3)
C31H24GaN3O 524.25 0.400× 0.200 × 0.200 Triclinic Pī 9.6000(11) 10.0000 (13) 14.1910 (15) 79.249 (9) 76.648 (9) 88.278 (10) 1302.1 (3) 2 1.337 1.085 / 540 2.775 to 27.486 -6 ≤ h ≤ 12 -12 ≤ k ≤ 12 -17 ≤ l ≤ 18 5925 3680
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Formula M Size Crystal system Space group a/Å b/Å c/Å α/º β/º γ/º V/Å3 Z dcalc/g cm-3 µ (mm-1)/F(000) θ for data collection/ο Limiting indices
0.0983 / 0.3786
1.018 0.714 and -1.215
0.913 0.370 and -0.635
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0.1238 / 0.1447
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List of Figure Captions Fig. 1. ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity.
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Fig. 2. ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Fig. 3. Excitation (a) and emission (b) spectra for [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) .
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Fig. 4. Representation of CIE co-ordinates on chromaticity diagram for (A) [Ph-N=N-C6H3(4’-OH)-3’-CH=NPh] (1a); (B), [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) ; (C) [Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr4)] (1c) and (D) Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
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Fig 1: ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) with 25% thermal ellipsoid probability.
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Hydrogen atoms are omitted for clarity.
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Fig 2: ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity.
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405
365
2000
800
290
1000
500
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600 Intensity
400
200
0
0 200
250
300
350
350
Wavelength in nm
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Intensity
1500
400
450
500
550
(a)
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Wavelength in nm
(b)
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Fig 3: Excitation (a) and emission (b) spectra for [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
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Fig. 4: Representation of CIE co-ordinates on chromaticity diagram for (A) [Ph-N=N-C6H3(4’-OH)-3’-CH=NPh] (1a); (B), [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) ; (C) [Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr4)] (1c) and (D) Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
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Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies.
Highlights
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Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain*
Diarylgallium complexes with azo-linked schiff bases were synthesized
Diarylgallium complexes are discrete monomer
Emission is not significantly affected by substitutions in ligand moiety
Blue emission can be attributed to GaOx related centers in complexes
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1
S0022-328X(17)30466-7
DOI:
10.1016/j.jorganchem.2017.07.036
Reference:
JOM 20050
To appear in:
Journal of Organometallic Chemistry
Received Date: 23 May 2017 Revised Date:
26 July 2017
Accepted Date: 30 July 2017
Please cite this article as: M.K. Pal, N. Kushwah, A.P. Wadawale, V. Sudarsan, V.K. Jain, Diarylgallium complexes derived from azo-linked schiff bases: Synthesis, characterization and photoluminescence studies, Journal of Organometallic Chemistry (2017), doi: 10.1016/j.jorganchem.2017.07.036. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Graphical Abstract – Pictogram and Synopsis
Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies.
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Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain
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Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain*
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Chemistry Division, Bhabha Atomic Research Centre,Trombay, Mumbai 400 085, India. Email: [email protected] ; Fax: +91-22-2550-5151; Tel: +91-22-2559-5095
Abstract
Diarylgallium complexes of composition, [Ar2GaOC6H3(N=NPh)(CH=NAr’)], (Ar = Ph or tol; Ar’ = Ph,
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tol-4 or C6H4Br-4) have been synthesized by treatment of triaryl-gallium dioxane adduct with azo linked salicylaldimine Schiff bases in benzene. These complexes have been characterized by elemental analysis, IR,
UV-Vis,
NMR
(1 H
and
13
C{1H})
spectroscopy.
The
molecular
structures
of
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[Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) were established by X-ray crystallography. The complexes are discrete monomer with four coordinated gallium atom forming a distorted tetrahedral structure. Photoluminescence studies of these complexes showed that the quantum yield is always higher than that of the corresponding ligands and the emission peaks of complexes are blue shifted with respect to ligand.
1.
Introduction
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Keywords: Arylgallium; Phenylazo salicyldehyde; Schiff base; photoluminescence; X-ray structures.
Organogallium complexes derived from internally functionalized anionic oxo-ligands have
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received considerable attention due to several obvious reasons [1]. These complexes exhibit rich structural diversity [1-3] and show interesting photo-physical properties [2-4], polymorphism [4], finds
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applications in catalysis [4,5], materials science [6,7] and biomedical imaging [8]. Since the first report of organic light emitting diodes (OLEDs) fabricated from tris(8-hydroxyquinolinolate)Al(III) (Alq3) in 1987 [9], metal chelate complexes have attracted considerable attention [10]. In recent years, the most promising candidates to substitute Alq3 were those of gallium [11]. Schiff base ligands and their metal/organometallic complexes have been extensively studied and a number of them show good luminescence properties [2,4]. There is analogy between the emission behavior of salicyldehyde Schiff bases and 8-hydroxyquinoline, since both the ligands have similar chromophoric groups i.e. a hydroxyl group, a coordinating imine N atom and a delocalized π-electron system [12]. Schiff bases derived from azo compounds constitute yet an interesting family of photo-chromic ligands [13]. 1
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Luminescent behavior of organogallium [2,4,14,15] complexes has been reported in the past with an emphasis on alkylgallium (methyl or ethyl) derivatives, recently we have also reported photoluminescence properties of methyl-gallium complexes containing salicylaldimine Schiff bases [2,4,16,17]. In contrast to this, the arylgallium derivatives received scant attention. Interestingly the aryl
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boron compounds like BODIPY (boron-dipyrromethene) derivatives containing an aryl-B linkages are promising luminescent material [18]. With this perspective it was considered to synthesize arylgallium complexes with azo-based Schiff base ligands and examine their photo-physical properties.
Results and Discussion
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2.
2.1 Synthesis and characterization of complexes
Reactions of [5-(phenylazo)-N-(aniline)salicylidene] (1a), [5-(phenylazo)-N-(4-toluidine)salicylidene]
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(1b) and [5-(phenylazo)-N-(4-bromoaniline)salicylidene] (1c) with triaryl-gallium dioxane adduct in benzene at room temperature afforded diarylgallium complexes (Scheme 1) as yellow to orange-red solids. 3'
2'
Ar3Ga.dioxane
3'
1'
4'
4
3
Benzene
5 5'
2
6' 6
1
RT
2'
1'
4
4'
5'
3
5
2
6'
6
1
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'
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Ar' = Ph (1a), 4-MeC6H4 (1b) or 4-BrC6H4 (1c)
'
Ar Ph Ph Ph tol tol tol
Ar' Ph 4-MeC6H4 4-BrC6H4 Ph 4-MeC6H4 4-BrC6H4
2a 2b 2c 2d 2e 2f
Scheme 1
The absorptions bands due to Ga-C and Ga-O, which are absent in the IR spectra of the free
ligands appear at 579-592 and 529-541 cm-1 respectively for the complexes [2,4,19,20]. The absorption due to azomethine linkage (-CH=N-) and azo functional group (-N=N-) are shifted to lower wave numbers 5-8 cm-1, 14-25 cm-1 respectively with respect to that of free ligand on coordination of nitrogen atom to gallium. The 1H and 13C{1H} NMR spectra, recorded in dmso-d6, displayed characteristic peaks with expected multiplicities for metal aryl and ligand fragment. The 13C NMR resonances due to –CH=Nin diaryl gallium complexes is deshielded by approximately 7 ppm from the respective resonance for the 2
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free ligands, whereas 1H resonance due to –CH=N- is only slightly deshielded (~ 0.07 ppm) from the respective resonance for the free ligands.
2.2 Crystal Structure of 2a and 2b: molecular
structures
of
[Ph2GaOC6H3(N=NPh)(CH=NPh)]
(2a)
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The
and
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) were established by single crystal X-ray diffraction analyses. Perspective drawings are depicited in Figs. 1 and 2, and selected interatomic parameters are given in Table 1. Various interatomic parameters in the two structures are essentially similar and can be compared
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with the analogous dimethylgallium derivatives [21]. However, the azo C-N bonds are marginally elongated while the azo N=N bond is slightly shortened in comparison to the analogous dimethylgallium complex [4]. This could be attributed to the presence of electron releasing phenyl groups on gallium. The
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Ga-C, Ga-O and Ga-N distances are in conformity with the values reported in the literature [2,4,22-23]. Gallium atom adopts a distorted tetrahedral configuration which is defined by two phenyl carbon atoms, a nitrogen and phenolate oxygen atom. The
six memebered Ga1-O1-C1-C2-C7-N1 rings in both
complexes are slighlty puckered with O1 out of plane by 0.105 and 0.143 Å, in 2a and 2b respectively. The terminal phenyl ring is twisted about the N=N with reference to the basal phenyl ring with an angle of 13.90° and 23.48°, in the respective complexes. The phenyl and tolyl fragments are differently
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oriented with respect to the Schiff base fragment, making an interplanar angle of 88.88° and 47.5° in 2a and 2b respectively. This suggests that the substitent at the para- postion of the ring attached to azo group (N1) affects the planarity of the Schiff base fragment, which influences the luminicent properties of these complexes. This is evident from the observed trends in luminiscence properties of the complexes 2a, 2b
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and 2c.
2.3 Photo-physical properties
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UV-Visible absorption spectra of all the ligands and their respective diarylgallium complexes
consist of mainly two peaks. For ligands these two peaks are mostly in the UV region and upon complexation they shift to near UV and visible region. These peaks can be attributed to the
π → π*
transitions in the aromatic ring and CH=N moiety for ligands. For complexes in addition to the above mentioned structural units, Ga-O related structural units also undergo absorption in the UV region. Complexation of ligands with trialkyl/triaryl gallium derivatives leads to overall increase in electron density in the ligand framework, subsequently the wavelength corresponding to absorption maxima get red shifted as is evident from Table 2. Unlike absorption spectra, emission spectra from the complexes are 3
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in the visible region (with wavelength maximum over a narrow range of 404-415nm) and are blue shifted with respect to that of the corresponding ligands. The emission in aryl derivatives showed pronounced blue shifting than the corresponding dimethylgallium complexes (Table 2). Emission in the blue region can be attributed to GaOx related centres in complexes. Even though ligand is excited upon exposure to
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UV light, the energy is transferred to the GaOx structural units which upon de-excitation leads to blue emission form the samples. This also explains the fact the emission maximum is not significantly affected by modifications/substitutions in the ligand moiety, however influenced by the substituent on gallium. It is worthwhile to mention here that blue emission from GaOx related structural units are well reported in many complexes and inorganic compounds [24]. Free ligands also undergo an important photo physical
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process known as excited state intramolecular proton transfer (ESIPT), leading to large Stokes shift, in emission and excitation profiles (Table 2, Fig. 3). The process is hindered upon complexation and the
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Stoke shift values decreases accordingly (Table 2). Quantum yield of emission form the complexes are in the range of 4-8% and are higher than that of free ligands. A direct comparison of quantum yields of ligand and complexes are not appropriate here, as additional luminescent moiety based on GaOx structural units are present in the complexes which is absent in the case free ligands. The CIE (Commission internationale de l’éclairage) color co-ordinates (x, y) were calculated for ligands and complexes based on the emission spectra and a representative is shown in Fig. 4. The color coordinated (x, y) for ligands and
3.
Experimental
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complexes are given in supplementary (Table S1).
3.1 Materials and Physical Measurements
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All experiments involving organo-gallium compounds were carried out in anhydrous conditions under a nitrogen atmosphere using Schlenk techniques. Solvents were dried using standard methods. Triarylgallium dioxane (Ar3Ga.dioxane; Ar = Ph or tol) were prepared using gallium trichloride and
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PhMgBr or tolMgBr in diethyl ether and later dioxane and benzene added to precipitate out excess magnesium halide and benzene extract was concentrated to give triarylgallium dioxane. Dioxane contents in each preparation were evaluated by 1H NMR integration [25]. The ligands, [5-(phenylazo)-N(aniline)salicylidene] (1a), [5-(phenylazo)-N-(p-toluidine)salicylidene] (1b) and [5-(phenylazo)-N-(pbromophenyl)salicylidene] (1c) were prepared according to literature procedures [26,27] and were characterized by NMR spectroscopy (Supplementary Material). Infrared spectra were recorded as KBr plates on a Jasco FT-IR 6100 spectrometer in the range 4000-400 cm-1. The NMR (1H and
13
C{1H}) spectra were recorded on a Bruker Avance-II 300 4
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spectrometer in 5 mm tubes as dmso-d6 solutions. Chemical shifts were referenced to internal dimethyl sulfoxide peak. Electronic spectra were recorded in dichloromethane on a UV-vis Jasco V-630 spectrophotometer. All luminescence measurements were carried out at room temperature using Edinburgh Instruments FLSP 920 system, having a 450W Xe lamp. Quantum yields were measured using
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an integrating sphere coated with BaSO4. All emission spectra were corrected for the detector response and excitation spectra for the lamp profile. Emission measurements were carried out with a resolution of 5 nm.
3.2 X-ray Crystallography
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Intensity data for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol4)] (2b) were collected at room temperature on a Rigaku AFC 7S diffractometer using graphite
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monochromated Mo-Kα radiation (0.71069 Å). The structures were solved using direct methods [28] and refined by full matrix least square method [29] on F2 using data corrected for absorption effects using empirical procedures [30]. 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 [31]. Crystallographic and structural
3.3 Synthesis of complexes
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determination data are listed in Table 3.
3.3.1 [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a)
To a benzene solution (25 mL) of triphenylgallium dioxane (66.4 mg, containing 35.4 mg (0.12 mmol)
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Ph3Ga), was added a solution of 1a (35.6 mg, 0.12 mmol) with stirring which continued for 10 h. The solvent was evaporated under a reduced pressure to give an orange-red crystalline solid, which was recrystallized from hexane (44.9 mg, 73 % yield), mp 185°C, Anal. Calcd. for C31H24GaN3O: C,71.02; H,
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4.61; N, 8.01%. Found: C,70.93; H, 4.31; N, 8.26 %. IR (υ in cm-1): 1615 (C=N); 1473 (N=N); 592 (GaC); 533 (Ga-O). 1H NMR (dmso-d6) δ:6.47 (t, 7.2 Hz); 6.54 (d, 8.2 Hz, 1H); 6.98 (t, 7.6 Hz, 1H); 7.05 (d, 9Hz, 1H); 7.30 (br, 7 H); 7.41 (br, 5H), 7.75 (d, 8.5 Hz, 1H); 7.84 (d, 7.8 Hz, 3 H); 8.04 (m), 8.38 (S, 1H); 9.18 (S, 1H, CH=N). 13C{1H} NMR (dmso-d6) δ:114.3 (C-Ga), 116.2, 122.2, 122.6, 127.1, 127.4, 127.9, 128.4, 129.0, 129.3, 129.4, 129.7, 129.9, 130.2, 131.2, 136.6, 143.5, 147.4, 152.5, 152.8, 170.5 (CH=N-).
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3.3.2 [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) Prepared similar to 2a in 76 % yield, mp 215 °C. Anal. Calcd. for C32H26GaN3O: C,71.40; H, 4.87; N, 7.81%. Found: C, 71.77; H, 5.07; N, 8.09 %. IR (υ in cm-1): 1615 (C=N); 1473 (N=N); 592 (Ga-C); 534 (Ga-O). 1H NMR (dmso-d6) δ: 2.26 (s, 3H, Ar-Me); 7.03 (d, 9 Hz, 1H); 7.15 (d, 6Hz, 1H); 7.23 (t, 7.8Hz, CH=N-).
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2H); 7.31 (br, 7H); 7.54 (br, 7H), 7.84 (d, 7.2 Hz, 2H); 8.06 (d, 9Hz, 1H); 8.38 (s, 1H); 9.18 (s, 1H, 13
C{1H} NMR (dmso-d6) δ: 21.0 (Ar-Me); 114.5 (C-Ga); 118.8, 122.1, 122.6, 123.4, 127.4,
127.9, 128.4, 129.1, 129.5, 129.9, 130.8, 131.2, 135.6, 136.9, 138.5, 143.2, 143.6, 144.3, 152.5, 169.8, 170.6 (-CH=N-).
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3.3.3 [Ph2GaOC6H3(N=NPh)(CH=NPhBr-4)] (2c)
Prepared similar to 2a in 85 % yield, mp 205 °C. Anal. Calcd. for C31H23BrGaN3O: C, 61.73; H, 3.84; N, 6.97 %. Found: C, 61.54; H, 3.96; N, 6.77 %. IR (υ in cm-1): 1614 (C=N); 1472 (N=N); 579 (Ga-C); 531
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(Ga-O). 1H NMR (dmso-d6) δ: 6.50 (d, 8.7 Hz, 1H); 7.11 (d, 8.7 Hz, 3H); 7.30 (br, 6H); 7.54 (m, 12H); 7.78 (d, 7.8 Hz, 1H); 7.84 (d, 7.2Hz, 2H); 8.07 (m, 2H); 8.36 (s, 1H); 9.17 (s, 1H, -CH=N-).
13
C{1H}
NMR (dmso-d6) δ: 116.2, 122.5, 122.6, 124.4, 127.4, 127.8, 128.4, 128.8, 129.1, 129.8, 129.9, 131.8, 133.1, 136.6, 137.0, 143.2, 146.5, 152.4, 171.1.
3.3.4 [tol2GaOC6H3(N=NPh)(CH=NPh)] (2d)
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Prepared similar to 2a in 86 % yield, mp 135 °C. Anal. Calcd. for C33H28GaN3O: C, 71.76; H, 5.11; N, 7.61 %. Found: C, 71.63; H, 4.98; N, 7.48 %. IR (υ in cm-1): 1612 (C=N); 1471 (N=N); 590 (Ga-C); 533 (Ga-O). 1H NMR (dmso-d6) δ: 2.23 (s, 6H, Ar-Me); 6.46 (t, 7.5Hz, 1H), 6.54 (d, 7.5 Hz, 1H); 6.98 (m, 5H), 7.10 (d, 7.5Hz, 6H); 7.47 (m), 7.74 (d, 7.2 Hz, 2H); 7.82 (d, 7.2 Hz, 4H); 8.03 (m, 3H); 8.36 (s, 1H); 13
C{1H} NMR (dmso-d6) δ: 21.0 (Ar-Me); 114.3, 116.2, 122.2, 122.6, 126.7,
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9.15 (s, 1H, -CH=N-).
129.1, 129.3, 129.7, 129.9, 130.2, 131.1, 136.5, 138.0, 139.7, 147.4, 152.5, 152.8, 170.3 (-CH=N-).
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3.3.5 [tol2GaOC6H3(N=NPh)(CH=Ntol-4)] (2e) Prepared similar to 2a in 71 % yield, mp 98 °C. Anal. Calcd. for C34H30GaN3O: C, 72.10; H, 5.34; N, 7.42 %. Found: C, 72.22; H, 5.31; N, 7.59 %. IR (υ in cm-1): 1615 (C=N); 1472 (N=N); 589 (Ga-C); 540 (GaO). 1H NMR (dmso-d6) δ: 2.22 (s, 9H, Ar-Me); 7.00 (d, 9.0 Hz, 1H); 7.10 (d, 7.5 Hz, 4H); 7.19 (d, 7.8 Hz, 2H); 7.32 (d, 8.1Hz, 2H); 7.42 (d, 7.5Hz, 4H), 7.53 (m, 4H); 7.83 (d, 7.5Hz, 2H); 8.04 (d, 9Hz, 1H), 8.35 (s, 1H); 9.13 (s, 1H, -CH=N-).
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C{1H} NMR (dmso-d6) δ: 20.9 (Ar-Me); 21.5 (Ar-Me); 118.7,
122.1. 122.6, 123.4, 129.1, 129.4, 129.9, 130.7, 131.1, 135.7, 136.5, 137.0, 138.2, 138.4, 139.5, 143.6, 144.3, 152.5, 169.9, 170.3 (-CH=N-). 6
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3.3.6 [tol2GaOC6H3(N=NPh)(CH=NPhBr-4)] (2f) Prepared similar to 2a in 72 % yield, mp 165 °C. Anal. Calcd. for C33H27BrGaN3O: C, 62.79; H, 4.31; N, 6.66 %. Found: C, 62.71; H, 4.24; N, 6.92 %. IR (υ in cm-1): 1614 (C=N); 1484 (N=N); 590 (Ga-C); 540
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(Ga-O). 1H NMR (dmso-d6) δ: 2.23 (s, 6H, Ar-Me); 6.52 (d, 8.7Hz, 2H); 7.10 (br); 7.29 (d, 7.8 Hz, 3H), 7.50 (m); 7.76 (d, 7.5Hz, 2H); 7.82 (d, 7.5Hz, 2H0; 7.98 (d, 8.1 Hz, 1H); 8.09 (s, 1H); 8.35 (s, 1H0; 9.11 (s, 1H, -CH=N-).
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C{1H} NMR (dmso-d6) δ: 21.5 (Ar-Me); 116.2, 122.3, 122.6, 124.3, 126.7, 128.0,
129.1, 136.6, 127.0, 138.0, 139.9, 143.7, 148.4, 152.5, 152.7, 170.3
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Diarylgallium complexes derived from azo linked salicylaldimine Schiff base have been
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synthesized. These complexes emit in the blue region upon excitation of ligand moiety and the emission has been attributed to the presence of GaOx related centres in the complex. The quantum yields of the complexes are always higher than that for the corresponding ligands which can be explained based on lack of ESIPT in complexes.
Supporting Information. 1544396
and
1544395
contains
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the
supplementary
crystallographic
data
for
[Ph2GaOC6H3(N=NPh)(CH=NPh)] and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] for this paper. These data 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-
1.
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Rigaku Corporation, 3, 9-12, Matsubara, Akishima, Japan, 1995.
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Table 1: Selected bond lengths (Å) and angles (°) for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) [Ph2GaOC6H3(N=NPh)(CH=NPh)]
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)]
1.958 (4)
1.956 (8)
Ga1-C26
1.967 (4)
1.962 (8)
Ga1-O1
1.904 (3)
1.902 (5)
Ga1-N1
2.037 (3)
2.033 (6)
C7-N1
1.289 (5)
1.301 (8)
N2-N3
1.238 (5)
1.216 (8)
C4-N2
1.459 (6)
1.454 (10)
C8-N3
1.454 (6)
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Ga1-C20
1.455 (10)
125.61 (17)
C20-Ga1-N1
108.04 (15)
110.6 (3)
C26-Ga1-N1
109.00 (14)
108.5 (6)
C20-Ga1-O1
108.53 (15)
106.9 (3)
C26-Ga1-O1
107.14 (15)
108.8 (3)
O1-Ga1-N1
93.90 (12)
93.5 (2)
C7-N1-Ga1
121.6 (3)
121.2 (6)
C14-N1-Ga1
119.5 (2)
119.5 (5)
128.2 (2)
128.5 (6)
111.3 (4)
114.9 (9)
110.9 (4)
111.4 (9)
118.7 (3)
119.0 (7)
C4-N2-N3 N2-N3-C8
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C1-O1-Ga1
124.2 (4)
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C20-Ga1-C26
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Table 2: UV-vis absorption, excitation and emission data of ligands and their organo gallium complexes in dichloromethane UV-Vis absorption, λ in nm
Excitation λ in nm
Emission λ in nm
Stoke shift
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-Ph] (1a)
335
314
465
151
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-tol-4)] (1b)
336
318
[Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr-4)] (1c)
336
[Me2GaOC6H3(N=NPh)(CH=NPh)] *
Quantum Yield (η) in % 3
460
142
3
290, 395
449
54
2
316, 364, 429(sh)
365
415
50
5
[Me2GaOC6H3(N=NPh)(CH=Ntol-4)]*
324, 366, 430(sh)
364
415
51
7
[Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a)
316, 363, 429
294, 369
409
40
4
[Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
317(sh), 364, 429
[Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
359, 432
[tol2GaOC6H3(N=NPh)(CH=NPh)] (2d)
318, 364, 429
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Compounds
[tol2GaOC6H3(N=NPh)(CH=N-PhBr-4)](2f)
41
4
292, 362
405
43
8
284, 364
409
45
4
365, 434
285, 367
412
45
4
341, 441
290, 363
409
46
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404
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[tol2GaOC6H3(N=NPh)(CH=Ntol-4)](2e)
287, 363
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Table 3: Crystallographic and Structural Refinement Data for [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) and [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
5925 / 7/ 320 0.0571/ 0.1185
6158/ 0 /335 0.0894 / 0.1511
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C32H26GaN3O 538.28 0.100 × 0.100× 0.040 Triclinic Pī 10.011(2) 10.655 (2) 13.542 (3) 106.731 (16) 101.710 (16) 92.608 (17) 1346.2 (5) 2 1.328 1.051 / 556 2.734 to 27.498 -12 ≤ h ≤ 7 -13 ≤ k ≤ 13 -17 ≤ l ≤ 17 6158 1576
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No. of unique reflns/ No. of obsd reflns with I > 2σ(I) Data/restraints/parameters Final R1, ωR2 indices (R_factor_gt/wR_factor_gt) R1, ωR2 (all data) (R_factor_all/wR_Factor_ref) Goodness of fit on F2 Largest diff. peak and hole (e.Å-3)
C31H24GaN3O 524.25 0.400× 0.200 × 0.200 Triclinic Pī 9.6000(11) 10.0000 (13) 14.1910 (15) 79.249 (9) 76.648 (9) 88.278 (10) 1302.1 (3) 2 1.337 1.085 / 540 2.775 to 27.486 -6 ≤ h ≤ 12 -12 ≤ k ≤ 12 -17 ≤ l ≤ 18 5925 3680
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Formula M Size Crystal system Space group a/Å b/Å c/Å α/º β/º γ/º V/Å3 Z dcalc/g cm-3 µ (mm-1)/F(000) θ for data collection/ο Limiting indices
0.0983 / 0.3786
1.018 0.714 and -1.215
0.913 0.370 and -0.635
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List of Figure Captions Fig. 1. ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity.
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Fig. 2. ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. Fig. 3. Excitation (a) and emission (b) spectra for [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) .
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Fig. 4. Representation of CIE co-ordinates on chromaticity diagram for (A) [Ph-N=N-C6H3(4’-OH)-3’-CH=NPh] (1a); (B), [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) ; (C) [Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr4)] (1c) and (D) Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
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Fig 1: ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) with 25% thermal ellipsoid probability.
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Hydrogen atoms are omitted for clarity.
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Fig 2: ORTEP drawing of [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b) with 25% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity.
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405
365
2000
800
290
1000
500
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600 Intensity
400
200
0
0 200
250
300
350
350
Wavelength in nm
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1500
400
450
500
550
(a)
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Wavelength in nm
(b)
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Fig 3: Excitation (a) and emission (b) spectra for [Ph2GaOC6H3(N=NPh)(CH=Ntol-4)] (2b)
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Fig. 4: Representation of CIE co-ordinates on chromaticity diagram for (A) [Ph-N=N-C6H3(4’-OH)-3’-CH=NPh] (1a); (B), [Ph2GaOC6H3(N=NPh)(CH=NPh)] (2a) ; (C) [Ph-N=N-C6H3(4’-OH)-3’-CH=N-PhBr4)] (1c) and (D) Ph2GaOC6H3(N=NPh)(CH=N-PhBr-4)] (2c)
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Diarylgallium Complexes Derived from Azo-linked Schiff Bases: Synthesis, Characterization and Photoluminescence Studies.
Highlights
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Manoj K. Pal, Nisha Kushwah, Amey P. Wadawale, V. Sudarsan and Vimal K. Jain*
Diarylgallium complexes with azo-linked schiff bases were synthesized
Diarylgallium complexes are discrete monomer
Emission is not significantly affected by substitutions in ligand moiety
Blue emission can be attributed to GaOx related centers in complexes
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