Synthesis, spectroscopic and crystallographic characterization of the cobalt(III) ternary mixed-ligand complexes of N(4)-allyl/methyl thiosemicarbazones, N,N,Nae,Nae-tetramethylethylenediamine and azide

Article abstract of DOI:10.1007/s11243-009-9300-2

Mixed-ligand ternary cobalt(III) complexes consisting of N,N,Nae,Nae-tetramethylethylenediamine (tmen), R-salicylaldehyde-N(4)-allyl/methyl thiosemicarbazones (R=3-OMe (L^I/L^II) or H (L^III/L^IV) and azide, of general formula [CoL(tmen)(N₃)], were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structure of [CoL^I(tmen)(N₃)] has a slightly distorted octahedral coordination geometry involving the O, N and S atoms of thiosemicarbazone.

Full text of DOI:10.1007/s11243-009-9300-2

Transition Met Chem (2010) 35:95–102
DOI 10.1007/s11243-009-9300-2
Synthesis, spectroscopic and crystallographic characterization
of the cobalt(III) ternary mixed-ligand complexes
of N(4)-allyl/methyl thiosemicarbazones, N,N,N0,N0-
tetramethylethylenediamine and azide
•
•
Tu¨lay Bal-Demirci Mehmet Akkurt
•
¨
S¸erife Pınar Yalc¸ın Orhan Bu¨yu¨kgu¨ngor
Received: 7 July 2009 / Accepted: 25 October 2009 / Published online: 12 November 2009
Ó Springer Science+Business Media B.V. 2009
Abstract Mixed-ligand ternary cobalt(III) complexes
consisting of N,N,N0,N0-tetramethylethylenediamine (tmen),
Co(III) complexes have been used in conventional bleaching
and photographic dye imaging processes, featuring dye-
retaining binders [18, 19].
R-salicylaldehyde-N(4)-allyl/methyl
thiosemicarbazones
(R=3-OMe (LI/LII) or H (LIII/LIV) and azide, of general
formula [CoL(tmen)(N3)], were synthesized and character-
ized by physico-chemical and spectroscopic methods. The
crystal structure of [CoLI(tmen)(N3)] has a slightly distorted
octahedral coordination geometry involving the O, N and S
atoms of thiosemicarbazone.
Thiosemicarbazones generally behave as bidentate
N,S donor ligands forming five-membered chelate rings
[20, 21]. If a third donor site (D), such as an OH group, is
incorporated into the thiosemicarbazone, then the ligand
can coordinate to a metal as a dianionic, tridentate ligand
with a D,N,S donor set [22–24]. Although research on
mixed-ligand complexes consisting of thiosemicarbazone
and bidentate N-donor chromophore ligands has been car-
ried out because of the catalytic activities of N-donors,
[5, 25–28] the complexes of N,N,N0,N0-tetramethyl ethy-
lenediamine (tmen) and thiosemicarbazones are few.
Despite the fact that tmen is potentially a chelating ligand,
it often behaves as bridging ligand [29, 30] on account of
the bulky nature of its alkyl groups. Therefore, we were
interested in the synthesis of mixed-ligand Co(III) com-
plexes involving tmen as a chelating bidentate ligand and
azide as co-ligand (Fig. 1).
Introduction
Thiosemicarbazones and their complexes have important
structural and pharmacological properties [1–6] and also
find applications in recognition of anions and metals [7–10],
in telecommunication and in optical information storage and
processing [11, 12]. The compounds having an azido group
as a photosensitive functional group have found applications
in photosensitive materials such as photosensitive resins and
dyes [13–16] for the recording of binary information on laser
recording media [17]. A metal complex which can effi-
ciently absorb light is suitable for the fabrication of dye-
sensitized oxide semiconductor electrodes. In addition,
In this study, we report four new mixed-ligand ternary
Co(III) complexes, of general formula [CoL(tmen)(N3)],
consisting of a dianionic salicylaldehyde thiosemicarba-
zone (L), plus anionic azide and bidentate tmen ligands.
The complexes were fully characterized by elemental
analysis, IR, 1H-NMR, APCI mass spectra, UV–Vis, molar
conductivity and magnetic susceptibility measurements.
The structure of one of them, [CoLI(tmen)(N3)], was
determined by single-crystal X-ray analysis.
T. Bal-Demirci (&)
Department of Chemistry, Istanbul University, 34320 Avcilar,
Istanbul, Turkey
e-mail: tulaybal@istanbul.edu.tr
M. Akkurt ꢀ S¸. P. Yalc¸ın
Department of Physics, Faculty of Arts and Sciences,
Erciyes University, 38039 Kayseri, Turkey
Experimental
¨
O. Bu¨yu¨kgu¨ngor
Department of Physics, Faculty of Arts and Sciences,
Ondokuz Mayıs University, 55139 Samsun, Turkey
All chemicals were of reagent grade and used as com-
mercially purchased without further purification. The
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Transition Met Chem (2010) 35:95–102
Fig. 1 R1/R: 3-OMe/CH2–
CH=CH2 (LI), 3-OMe/Me (LII),
H/CH2–CH=CH2 (LIII),
H3C
R1
N
H3C
H/Me (LIV
)
a
O
N
CH3
CH3
R1
b
c
Co
a
OH
b
c
S
N
d
1
N
N
SH
R
NH
2
N
d
N3
4
NH
H
R
[CoL(tmen)N3]
L
elemental analyses were determined on a Thermo Finnigan
Flash EA 1112 Series Elemental Analyser and Varian
Spectra—220/FS Atomic Absorption spectrometer. IR
spectra of the compounds were recorded on KBr pellets
with a Mattson 1000 FT-infrared spectrometer. UV–Vis
spectra were obtained with an ATI-Unicam UV–Visible
Spectrometer UV2 Series as 10-5 M solutions in CHCl3.
1,215. UV–Vis spectrum in CHCl3 [kmax (nm), e
(dm3 cm-1 mol-1)]: 217 (734), 240 (589), 320 (1,160),
1
346 (shoulder). H-NMR (DMSO-d6, 25 °C, ppm): 11.19
(s, 1H, OH), 9.13 (s, 1H, N2H), 8.34 (t, J:5.12, 1H, N4H–),
8.16 (s, 1H, CH=N), 7.27 (d, J: 7.91, 1H, d), 6.74 (d, J:7.82,
1H, b), 6.57 (t, J:7.97, 1H, c), 5.65 (m, 1H, –CH=), 4.89
(m, 2H, =CH2), 3.96 (d, J:5.12, 2H, N–CH2–), 3.56 (s, 1H,
–OCH3).
1
The H-Nuclear Magnetic Resonance spectra were recor-
ded on a Bruker AVANCE-500 spectrometer. Magnetic
measurements were carried out at room temperature by the
Gouy technique with an MK I model device obtained from
Sherwood Scientific. The molar conductivities of the
compounds were measured in 10-3 M DMSO solution at
25 1 °C using a digital WPA CMD 750 conductivity
meter. The APCI-MS analyses were carried out in positive
ion modes using a Thermo Finnigan LCQ Advantage MAX
LC/MS/MS. The mobile phase consisted of MeOH, a
Hypersil Betabasic-8 (5 l, 100 mm 9 4.6 mm) column
was used at a flow rate of 0.4 mL/min at 25 °C. APCI-MS
inlet conditions in the positive ion mode were heated
capillary temperature, 200 °C; vaporizer temperature,
300 °C; sheath gas flow rate, 50 units; capillary voltage,
20 V and tube lens.
LII: Cream, 239–240 °C; 86%; 0.5582 (2CHCl3:1EtAc);
Anal. Found for C10H13N3O2S (239.29 g): C, 50.2; H, 5.5;
N, 17.6; S, 13.3, Calc: C, 50.2; H, 5.5; N, 17.5; S, 13.4%. FT-
IR (KBr, cm-1): m(NH) 3,437, 3,306, m(–OCH3) 2,848,
m(OH) 3,550–3,300, d(NH) 1,623, 1,620, 1,607(shoulder),
m(C=N) 1,555, m(–CS–NH) 1,530, 1,274, m(–C=S) 1,220.
UV–Vis spectrum in CHCl3 [kmax (nm), e (dm3 cm-1
mol-1)]: 218 (2,890), 240 (664), 321 (1,457), 342
(912)shoulder. 1H-NMR (DMSO-d6, 25 °C, ppm): 11.38 (s,
1H, OH), 9.16 (s, 1H, N2H), 8.36 (t, 1H, N4H), 8.37 (s, 1H,
CH=N), 7.52 (dd, J: 0.98, J: 7.81, 1H, d), 6.95 (dd, J:1.47,
J:8.3, 1H, b), 6.77 (t, J:8.3, J:7.81, 1H, c), 2.97 (d, J:4.39, 3H,
N4–CH3).
LIII: Cream, 155–156 °C; 82%; 0.7068 (2CHCl3:1E-
tAc); Anal. Found for C11H13N3OS (235.31 g): C, 56.2; H,
5.6; N, 17.9; S, 13.6, Calc.: C, 56.1; H, 5.6; N, 17.8; S,
13.6%. FT-IR (KBr, cm-1): m(NH) 3,438, 3,384, 3,153,
m(OH) 3,580–3,300, m(C=CH2) 3,000, d(NH) 1,623, 1,607,
m(C=N) 1,553, m(–CS–NH) 1,538, 1,292, m(–C=S) 1,223.
UV–Vis spectrum in CHCl3 [kmax (nm), e (dm3 cm-1
mol-1)]: 241 (1,405), 302 (1,936) shoulder, 311 (2,234),
Preparation of the thiosemicarbazones
The R1-substituted salicylaldehyde N(4)-R-thiosemicarba-
zone ligands were synthesized from the corresponding
salicylaldehyde and N(4)-R-thiosemicarbazide in equimo-
lar ratios as per the reported procedure[31, 32]. The colors,
1
338 (2,576). H-NMR (DMSO-d6, 25 °C, ppm): 11.42 (s,
1
m.p., yields, Rf, elemental analysis, IR, UV–Vis and H-
1H, OH), 9.86 (s, 1H, N2H), 8.56 (t, J:5.85, 1H, N4H), 8.37
(s, 1H, CH=N), 7.92 (dd, J: 1.46, J: 7.80, 1H, d), 7.20 (td,
J:1.46, J:8.78, 1H, b), 6.86 (d, J:7.32, 1H, a), 6.82 (t, J:7.81,
1H, c), 5.90 (m, 1H, –CH=), 5.14 (dq, J:1.95, J:1.46,
J:17.57, 1H, =CH2a), 5.08 (dq, J:1.46, J:1.46, J:10.24, 1H,
=CH2b), 4.20 (t, J:5.86, 2H, N–CH2–).
NMR data of LI–IV were as follows:
L1: Cream; 229–230 °C; 94%; 0.2065 (CH2Cl2); Anal.
Found for C12H15N3O2S (265 g): C, 54.3; H, 5.6; N, 15.9;
S, 12.0, Calc.: C, 54.3; H, 5.7; N, 15.8; S, 12.1%. FT-IR
(KBr, cm-1): m(NH) 3,423, 3,307, m(OH) 3,500–3,250,
m(C=CH2) 3,092, 3,007, m(–OCH3) 2,846, d(NH) 1,646,
1,615, m(C=N) 1,584, m(–CS–NH) 1,538, 1,292, m(–C=S)
LIV: Cream, 208–210 °C; 73%; 0.6551 (2CHCl3:
1EtAc); Anal. Found for C9H11N3OS (209.27 g): C, 51.6;
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Transition Met Chem (2010) 35:95–102
97
H, 5.3; N, 20.1; S, 15.3, Calc.: C, 51.6; H, 5.3; N, 20.1; S,
15.3, %. FT-IR (KBr, cm-1): m(NH) 3,476, 3,361, 3,253,
m(OH) 3,550–3,300, d(NH) 1,623, 1,607, m(C=N) 1,553,
m(–CS–NH) 1,530, 1,276, m(–C=S) 1,261. UV–Vis spec-
trum in CHCl3 [kmax (nm), e (dm3 cm-1 mol-1)]: 210
(2,601), 242 (817), 304 (1,028) shoulder, 310 (1,120), 335
(?c APCI-MS, % relative abundance): [M?-(N3)] 438
(100.00), [MH?-(N3)] 439 (25.28), [MH2?-(N3)] 440
(5.57), [MH? ?N] 495 (3.65), [MOH] 497 (3.78),
[MH??2N] 509 (2.54), [MH2??2N] 510 (2.15), [MH??
3N] 523 (2.32), [MH2??3N] 524 (2.21), [MH??4N] 537
(2.09), [MH2??4N] 538 (2.12), [MH3??4N] 539 (1.96),
[MH??5N] 551 (1.58), [MH3??5N] 553 (1.02), [M??6N]
562 (1.03), [MH??7N] 579 (1.84), [MH2??7N] 580
(1.91), [M??8N–H] 591 (1.97), [MH??8N] 593 (1.88),
[MH2??8N] 594 (1.67), [M??9N–4H] 602 (3.81),
[M??9N–H] 605 (2.18), [M??9N] 606 (2.17), [M? -HL]
214 (4.98), [L–H?] 264 (1.82), [MH? –NH–CH2–CH=CH2]
1
(1,219). H-NMR(DMSO-d6, 25 °C, ppm): 11.36 (s, 1H,
OH), 9.85 (s, 1H, N2H), 8.38 (d, J:4.39, 1H, N4H), 8.35 (s,
1H, CH=N), 7.91 (dd, J: 1.46, J: 7.80, 1H, d), 7.20 (td,
J:1.47, J:8.29, 1H, b), 6.81 (t, J:7.81, 1H, c), 2.99 (d, J:4.39,
3H, N4–CH3).
?
425 (1.73), [MH2 –NH–CH2–CH=CH2] 426 (2.00),
[Co(LI)2(tmen)(N3)2?2H?] 846 (4.15), [Co(LI)2(tmen)2
(N3)4] 985 (6.54), [Co2(LI)2(tmen)3(N3)3] 1,118 (7.10),
[Co2(LI)2(tmen)4(N3)3] 1,234 (5.79), [Co3(LI)3(tmen)3
(N3)4] 1,482 (5.09), [Co3(LI)3(tmen)6(N3)4 –4H?] 1,826
(5.15).
Preparation of the complexes
[CoLI(tmen)(N3)]: A solution of Cobalt(II) acetate tetra-
hydrate (0.469 g, 2.12 mmol) in MeOH (20 mL) was added
to a solution of 3-methoxysalicylaldehyde N(4)-allylthi-
osemicarbazone (0.50 g, 2.12 mmol) in EtOH (20 mL) with
constant stirring. N,N,N0,N0-tetramethylethylenediamine
(0.28 mL, 2.12 mmol) was then dripped into this solution,
and sodium azide (0.207 g, 3.18 mmol) in EtOH (20 mL)
was added under stirring and nitrogen atmosphere. The
reaction mixture was refluxed for 4 h and then allowed to
stand at room temperature for 6 days, then filtered.
[CoLII(tmen)(N3)]: Black; [380 °C; 78%; 0.4480
(2CHCl3:1MeOH); Anal. Found for C16H27N8O2SCo
(454.4 g): C, 42.2; H, 5.9; N, 24.7; S, 7.1; Co, 13.0, Calc.:
C, 42.3; H, 5.9; N, 24.7; S, 7.0; Co, 13.0%; K(in 10-3
M
DMSO, ohm-1 cm2 mol-1): 9.4; FT-IR(KBr, cm-1):
m(NH) 3,426, m(C=CH2) 3,022, m(–OCH3, –CH3, –CH2–)
2,987, 2,906, 2,829, m(N3) 2,013, d(NH) 1,632, m(C=N)
1,597, 1,543, d(N–CH3) 1,320, m(–C–S) 673, m(Co–O) 584,
m(Co–N) 415; UV–Vis spectrum in CHCl3 [kmax (nm), e
(dm3 cm-1 mol-1)]: 216 (3,948), 300 (1,154)shoulder, 345
(834)shoulder, 415 (420), 495 (98)shoulder, 960 (13);
1H-NMR(DMSO-d6, 25 °C, ppm): 8.02 (s, 1H, CH=N),
7.11 (d, J:4.88, 1H, N4H), 6.91 (dd, J:1.46, J: 7.81, 1H, d),
6.74 (dd, J:1.46, J:7.81, 1H, b), 6.40 (t, J:7.81, 1H, c), 3.76
(s, 3H, –OCH3), 2.82(d, J: 4.88, 3H, N4–CH3), 2.94–2.10
(2.93 ppm, ddd, J:2.44, J:13.17, 1H, tmen, N8–CH16a; 2.62
ppm, ddd, J:2.92, J:12.19, 1H, tmen, N8–CH16b; 2.55 ppm,
dq, J:2.93, J:13.66, 1H, tmen, N7–CH15a; 2.10 ppm,
dq, J:3.90, J:7.81, 1H, tmen, N7–CH15b), 2.53 (s, 3H, tmen,
N–CH3), 2.46 (s, 3H, tmen, N–CH3), 2.01 (s, 3H, tmen,
N–CH3), 1.53 (s, 3H, tmen, N–CH3); m/z (?c APCI-MS,
%relative abundance): [M?-(N3)] 412 (100.00), [MH?-
(N3)] 413 (20.55), [MH2?-(N3)] 414 (8.02), [MH3?-(N3)]
415 (1.84), [MH?-(N2)] 427 (2.33), [M? -(LII) -(HN3)?]
172 (1.71), [L?H?] 240 (1.06), [Co(LII)(tmen)2(N3)4?2N]
724 (2.75), [Co(LII)2(tmen)2(N3)4?2N?H?] 726 (2.40),
[Co2(LII)2(tmen)2(N3)–H?] 865 (18.28), [Co2(LII)2(tmen)2
(N3)] 866 (8.45), [Co2(LII)2(tmen)2(N3) ?H?] 867 (2.78),
[Co2(LII)2(tmen)2(N3)?2H?] 868 (16.29), [Co2(LII)2
(tmen)2(N3)?3H?] 869 (7.23), [Co2(LII)2(tmen)2(N3)?
NH?] 881 (3.00), [Co2(LII)2(tmen)2(N3)3 –3H?] 947 (5.53),
[Co2(LII)2(tmen)3(N3)2?2H?] 1,026 (2.42), [Co2(LII)3
(tmen)3(N3)3?2NH?] 1,333 (1.59), [Co3(LII)3(tmen)3(N3)4
?2NH?] 1,434 (1.98), [Co4(LII)4(tmen)3(N3)5?NH?] 1,742
(2.42), [Co4(LII)4(tmen)4(N3)5] 1,858 (1.89).
The other complexes were obtained similarly by means
of the aforementioned procedure. The colors, m.p., yields,
Rf, elemental analysis, atomic absorption, molar conduc-
tivity, IR, UV–Vis (10-5 M solution), H-NMR and APCI
1
mass spectra data of the complexes were as follows:
[CoLI(tmen)(N3)]: Black; 180–181 °C; 84%; 0.58
(2CHCl3:1MeOH); Anal. Found for C18H29N8O2SCo
(480.4 g): C, 45.0; H, 6.0; N, 23.3; S, 6.7; Co, 12.2, Calc.:
C, 45.0; H, 6.0; N, 23.3; S, 6.7; Co, 12.3, %; K(in 10-3
M
DMSO, ohm-1 cm2 mol-1): 12.2; FT-IR(KBr, cm-1):
m(NH) 3,445, m(C=CH2) 3,222, 3,083, m(–OCH3, –CH3,
–CH2–) 2,979, 2,906, m(N3) 2,009, d(NH) 1,639, m(C=N)
1,597, 1,570, d(N–CH3) 1,324, m(–C–S) 670, m(Co–O) 584,
m(Co–N) 415; UV–Vis spectrum in CHCl3 [kmax (nm), e
(dm3 cm-1 mol-1)]: 216 (3,623), 259 (2,100), 308 (1,320),
342 (1,015)shoulder, 418 (441), 490 (153), 967 (12);
1H-NMR(DMSO-d6, 25 °C, ppm): 8.01 (s, 1H, CH=N),
7.37 (t, J:5.86, 1H, N4H), 6.91 (dd, J:1.46, J: 8.3, 1H, d),
6.74 (dd, J:1.46, J:7.32, 1H, b), 6.40 (t, J:7.81, 1H, c), 5.88
(m, 1H, –CH=), 5.17 (dq, J:1.46, J:1.95, J:11.72, J:17.08,
1H, =CH2a), 5.03 (dq, J:1.46, J:5.85, J:10.25, 1H, =CH2b),
3.91 (m, 2H, allyl, N4–CH2–), 3.76 (s, 3H, –OCH3), 2.94–
2.08 (2.94 ppm, ddd, J:2.44, J:8.3, J:13.12, 1H, tmen, N8–
CH16a; 2.61 ppm, ddd, J:2.92, J:8.3, J:13.12, 1H, tmen, N8–
CH16b; 2.59 ppm, dq, J:2.92, J:12.19, 1H, tmen, N7–CH15a
;
2.08 ppm, dq, J:3.90, J:12.32, 1H, tmen, N7–CH15b), 2.53
(s, 3H, tmen, N–CH3), 2.47 (s, 3H, tmen, N–CH3), 2.01 (s,
3H, tmen, N–CH3), 1.52 (s, 3H, tmen, N–CH3); m/z
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Transition Met Chem (2010) 35:95–102
[CoLIII (tmen)(N3)]: Black; 171–172 °C; 69%; 0.460
(104)shoulder, 959 (16); 1H-NMR (DMSO-d6, 25 °C, ppm):
8.02 (s, 1H, CH=N), 7.07 (d, J:4.88, 1H, N4H), 7.27 (dd,
J:1.464, J: 7.80, 1H, d), 7.09 (td, J:1.46, J:6.83, 1H, b), 7.02
(d, J:8.29, 1H, a), 6.46 (splitted t, J:0.976, J:6.82, 1H, c),
2.94–2.10(2.94 ppm, ddd, J:2.98, J:13.23, 1H, tmen, N8–
(2CHCl3:1MeOH); Anal. Found for C17H27N8OSCo
(450.4 g): Found: C, 45.3; H, 6.0; N, 24.8; S, 7.1; Co, 13.1,
Calc. C, 45.3; H, 6.0; N, 24.9; S, 7.1; Co, 13.1%; K(in
10-3 M DMSO, ohm-1 cm2 mol-1): 13.4; FT-IR(KBr,
cm-1): m(NH) 3,426, d(NH) 1,632, m(C=N) 1,597, 1,543,
m(C=CH2) 3,022, m(–CH3, –CH2–) 2,914, 2,841, m(N3) 2,024,
d(N–CH3) 1,320, m(–C–S) 673, m(Co–O) 584, m(Co–N) 415;
UV–Vis spectrum in CHCl3 [kmax (nm), e (dm3 cm-1
mol-1)]: 213 (3,508), 257 (3,100), 296 (1,695) shoulder, 350
(1,148) shoulder, 409 (730), 490 (104)shoulder, 958 (13);
1H-NMR(DMSO-d6, 25 °C, ppm): 8.02 (s, 1H, CH=N), 7.38
(t, J:6.34, 1H, N4H), 7.28 (dd, J:1.46, J: 7.81, 1H, d), 7.10 (td,
J:1.46, J:6.83, 1H, b), 7.03 (d, J:8.30, 1H, a), 6.47 (splitted t,
J:0.976, J:6.83, 1H, c), 5.87 (m, 1H, –CH=), 5.17 (dq, J:1.95,
J:17.08, 1H, =CH2a), 5.03 (dq, J:1.46, J:7.56, J:10.25, 1H,
=CH2b), 3.91 (m, 2H, allyl, N4–CH2–), 2.93–2.10
(2.93 ppm, ddd, J:2.98, J:10.25, 1H, tmen, N8–CH16a; 2.51
ppm, ddd, J:1.95, J:11.22, 1H, tmen, N8–CH16b; 2.46 ppm,
dq, J:3.92, J:13.67, 1H, tmen, N7–CH15a; 2.08 ppm, dq,
J:3.90, J:13.18, 1H, tmen, N7–CH15b), 2.47 (s, 3H, tmen,
N–CH3), 2.44 (s, 3H, tmen, N–CH3), 2.02 (s, 3H, tmen,
N–CH3), 1.56 (s, 3H, tmen, N–CH3); m/z (?c APCI-MS,
%relative abundance): [M?-(N3)] 408 (4.08), [MH?-(N3)]
409 (4.18), [MH2?-(N3)] 410 (3.15), [MH3?-(N3)] 411
(12.49), [MH?] 451 (25.30), [MH? ?N] 465 (24.38),
[MOH] 467 (23.80), [MH??2N] 479 (80.29), [MH2??2N]
480 (19.91), [MH??3N] 493 (32.16), [MH2??3N] 494
(23.38), [MH??4N] 507 (100.00), [MH2??4N] 508
(30.51), [MH3??4N] 509 (26.57), [MH??5N] 521 (42.94),
[MH3??5N] 523 (17.26), [M??6N–H] 533 (58.37),
[MH??6N] 535 (54.23), [MH2??6N] 536 (21.68), [M??
7N–H] 547 (46.53), [MH??7N] 549 (35.32), [MH2??7N]
550 (16.88), [M??8N–H] 561 (20.18), [MH??8N] 563
(23.12), [MH2??8N] 564 (11.84), [M??9N–H] 575
(14.15), [Co(LIII)2(tmen)2(N3)2?H?] 609 (6.91), [Co2(LIII)2
(tmen)(N3)2?H?] 785 (3.84), [Co2(LIII)3(tmen)2(N3)2]
1,133 (3.03), [Co2(LIII)3(tmen)3(N3)4] 1,333 (3.54),
[Co4(LIII)4(tmen)4(N3)4] 1,800 (3.24), [M?, -H?L] 214
(15.49), [L] 235 (3.45), [L?H?] 236 (4.14), [M?, -4CH3]
390 (13.41), [MH?-(N3)] 409 (4.28), [MH2?-(N3)] 410
(3.15), [MH3?-(N3)] 411 (12.49).
CH16a; 2.52 ppm, ddd, J:1.95, J:13.17, 1H, tmen, N8–CH16b
2.48 ppm, dq, J: 3.92, J:8.31, 1H, tmen, N7–CH15a
;
;
2.10 ppm, dq, J:3.90, J:13.18, 1H, tmen, N7–CH15b), 2.82 (d,
J: 4.88, 3H, N4–CH3), 2.46 (s, 3H, tmen, N–CH3), 2.44 (s,
3H, tmen, N–CH3), 2.02 (s, 3H, tmen, N–CH3), 1.54 (s, 3H,
tmen, N–CH3); m/z (?c APCI-MS, %relative abundance):
[M?-(N3)] 382 (100.00), [MH?-(N3)] 383 (18.80),
[MH2?-(N3)] 384 (6.15), [L?H?] 210 (1.82), [Co(LIV)(t-
men)2(N3)4?2N] 694 (1.48), [Co2(LIV)2(tmen)2(N3)–H?]
805 (4.87), [Co2(LIV)2(tmen)2(N3)] 806 (6.15), [Co2(LIV)2
(tmen)2(N3)?H?] 807 (3.18), [Co2(LIV)2(tmen)2(N3)?
2H?] 808 (6.48), [Co2(LIV)2(tmen)2(N3)?3H?] 809 (4.84),
[Co2(LIV)2(tmen)2(N3)2?NH?] 863 (3.84), [Co2(LIV)2(t-
men)3(N3)2?2H?] 966 (3.33), [Co2(LIV)3(tmen)3(N3)3?
2NH?] 1,243 (2.11), [Co3(LIV)3(tmen)3(N3)4?2NH?] 1,344
(1.74), [Co4(LIV)4(tmen)3(N3)5] 1,622 (1.08), [Co4(LIV)4
(tmen)4(N3)4] 1,696 (1.41), [Co4(LIV)4(tmen)4(N3)4?NH?]
1,711 (1.91), [Co4(LIV)4(tmen)4(N3)5?3H?] 1,741 (1.47).
X-ray crystallography
The diffraction data for the [CoLI(tmen)(N3)] complex
were collected with a STOE IPDS 2 diffractometer at
˚
293 K using Mo Ka radiation (k = 0.71073 A). The final
unit-cell parameters were based on all reflections. Data
collections were made using the X-AREA program [33];
data reduction and absorption corrections were performed
with the X-RED32 program [33]. The structure was solved
by direct methods with SIR-97 [34]. The model was refined
by full-matrix least squares on F2 by means of SHELXL-97
[35]. All H atoms were placed in calculated positions
˚
˚
(C–H=0.93–0.97 A and N–H=0.86 A) and included in the
refinement as riding, with Uiso constrained to be 1.2 Ueq of
the carrier atom (1.5 Ueq for methyl H atoms). The ORTEP
drawing (Fig. 2) was prepared using ORTEP-3 for
Microsoft Windows [36]. The data collections and exper-
imental details are summarized in Table 1, and selected
bond distances and angles are given in Tables 2 and 3,
respectively.
[CoLIV(tmen)(N3)]: Black; [380 °C; 45%; 0.400
(2CHCl3:1MeOH); Anal. Found for C15H25N8OSCo
(424.4 g): Found: C, 42.5; H, 5.9; N, 26.5; S, 7.6; Co, 13.7,
Calc.: C, 42.4; H, 5.9; N, 26.4; S, 7.5; Co, 13.9%; K(in
10-3 M DMSO, ohm-1 cm2 mol-1): 9.94; FT-IR(KBr,
cm-1): m(NH) 3,449, m(N3) 2,020, d(NH) 1,632, m(C=N)
1,597, 1,543, m(C=CH2) 3,022, m(–CH3, –CH2–) 2,918,
2,891, 2,826, d(N–CH3) 1,312, m(–C–S) 673, m(Co–O) 582,
m(Co–N) 415; UV–Vis spectrum in CHCl3 [kmax (nm),
e (dm3 cm-1 mol-1)]: 213 (3,508), 255 (3,450), 300
(1,199)shoulder, 348 (1,084)shoulder, 402 (435), 493
Results and discussion
3-Methoxy-/H-salicylaldehyde-N(4)-allyl/methylthiosemi-
carbazidato, N,N,N0,N0-tetramethylethylenediamine azido
cobalt(III) complexes were obtained from the reactions of
123

Transition Met Chem (2010) 35:95–102
99
Fig. 2 An ORTEP-3 view of
the [CoLI(tmen)(N3)], with the
atom-numbering scheme and
20% probability displacement
ellipsoids
N,N,N0,N0-tetramethylethylenediamine, thiosemicarbazone
and azide with CoOAcꢀ4H2O in 1:1:3/2:1 molar ratio,
respectively. The thiosemicarbazones behave as dianionic
ligands coordinating through deprotonated hydroxyl and
thiol groups. In addition, coordination of the imine nitrogen
makes these thiosemicarbazone ligands tridentate overall.
The bidentate tmen ligand coordinates to the Co(II) atom
through both nitrogen atoms. In the presence of methanol
and sodium azide, Co(II) ion is readily oxidized by atmo-
spheric oxygen to give Co(III) complexes [37], as here.
The azide ligand is monodentate in these complexes. The
elemental analyses of the complexes suggest the general
formula as [CoL(tmen)(N3)] according to Fig. 1.
respectively. These distances and angles are in agreement
with values reported previously for other CoIII complexes
[38]. In the crystal structure, there are some C–HꢀꢀꢀO,
C–HꢀꢀꢀN and C–HꢀꢀꢀS type-intramolecular hydrogen bond-
ing interactions. In addition, the adjacent molecules form a
dimer structure, in which the N–HꢀꢀꢀN hydrogen bonds
generate an intermolecular R22(8) ring (Fig. 3; Table 4).
Spectroscopy
Bands assigned to the C=N stretching vibrations of the free
thiosemicarbazones were observed at 1,584–1,553 cm-1
.
These bands were shifted to lower wave numbers by
ca.12 cm-1 in the complexes, and a vibration m(Co–N) at
415 cm-1 corroborates coordination of the azomethine
nitrogen [39, 40]. A band in the region 580–584 cm-1 is
assignable to Co–O [41, 42].
While the two N(4)-methyl thiosemicarbazone Co(III)
complexes do not melt up to 380 °C, the N(4)-allyl thio-
semicarbazone Co(III) complexes melt in the range of
171–181 °C. The complexes are soluble in alcohol, halo-
carbon and polar organic solvents such as DMSO and
MeCN and insoluble in H2O. The leff values of the com-
plexes are in the range 0.06–0.09, showing that they are
diamagnetic. The molar conductance values are in the
range of 9.4–13.4 Ohm-1 cm2 mol-1 in DMSO solution
(10-3 M), indicating non-electrolytic behavior.
The sharp bands assigned to ma (NH), ms(NH) vibrations
attributable to N2H and N4H which are at 3,470–
3,306 cm-1 in the spectra of the free thiosemicarbazones
were observed in the 3,449–3,426 cm-1 region in the
spectra of the complexes. As a result of deprotonation of
the –SH group with concomitant tautomerization of the
thiosemicarbazone, the m(N2H) band was not observed in
the complexes.
Structural characterization of [CoLI(tmen)(N3)]
The absence of any m(–SH) bands in the 2,700–
2,500 cm-1 region of the IR spectrum of the free thio-
semicarbazones signifies the existence of the thione tau-
tomers in the solid state. However, in solution and in the
presence of certain metal ions, the ligands may exist in
equilibrium with the tautomeric thiol form. Also, a band in
the 670–673 cm-1 range for the metal complexes indicates
coordination through the thiolato sulfur atom of the thio-
semicarbazone [43].
In the structure of [CoL1(tmen)(N3)], the metal adopts a
distorted octahedral geometry involving the O, N and S
atoms of the thiosemicarbazone (Fig. 2). The Co–S and
˚
Co–O distances are 2.2298 (13) and 1.887 (3) A, respec-
tively. The Co–N distances are in the range of 1.899 (4) to
˚
2.113 (3) A. The S1–Co1–O1, N1–Co1–N7 and N4–Co1–
N8 angles are 179.14° (10), 179.08° (15) and 174.91° (19),
123

100
Transition Met Chem (2010) 35:95–102
Table 3 Selected bond angles for [CoLI(tmen)(N3)]
Table 1 Crystal data and details for structure determination of
[CoLI(tmen)(N3)]
Bond angles (°)
Bond angles (°)
Empirical formula
Formula weight
C18H29CoN8O2S
S1–Co1–O1
S1–Co1–N1
S1–Co1–N4
S1–Co1–N7
S1–Co1–N8
O1–Co1–N1
O1–Co1–N4
O1–Co1–N7
O1–Co1–N8
N1–Co1–N4
N1–Co1–N7
N1–Co1–N8
N4–Co1–N7
N4–Co1–N8
N7–Co1–N8
Co1–S1–C9
Co1–O1–C1
C2–O2–C8
Co1–N1–N2
Co1–N1–C7
N2–N1–C7
N1–N2–C9
C9–N3–C10
Co1–N4–N5
179.14 (10)
86.11 (11)
90.88 (16)
94.32 (13)
92.89 (12)
94.41 (16)
88.44 (18)
85.17 (17)
87.77 (15)
91.11 (18)
179.08 (15)
92.56 (14)
89.70 (18)
174.91 (19)
86.61 (14)
95.31 (15)
127.1 (3)
N4–N5–N6
176.7 (5)
115.7 (3)
113.7 (3)
104.4 (3)
104.8 (4)
111.7 (4)
106.4 (4)
102.6 (3)
116.7 (3)
112.3 (3)
107.1 (5)
111.5 (5)
106.5 (4)
124.0 (4)
118.1 (4)
125.4 (4)
113.2 (4)
127.6 (5)
117.2 (4)
123.0 (3)
119.8 (3)
114.5 (4)
113.1 (5)
115.3 (5)
480.49
Co1–N7–C13
Co1–N7–C14
Co1–N7–C15
C13–N7–C14
C13–N7–C15
C14–N7–C15
Co1–N8–C16
Co1–N8–C17
Co1–N8–C18
C16–N8–C17
C16–N8–C18
C17–N8–C18
O1–C1–C6
˚
Wavelength (A)
0.71073
Monoclinic
P21/c
Crystal system
Space group
Unit cell
˚
a (A)
10.2460 (6)
12.6467 (10)
18.6679 (11)
90
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
115.243 (4)
90
3
˚
V (A )
2188.0 (3)
4
Z
Color
Dcalc (g cm-3
l (mm-1
Black
O1–C1–C2
)
1.459
O2–C2–C3
)
0.91
O2–C2–C1
F(000)
1,008
117.7 (4)
N1–C7–C6
hkl range
-13 B h B13
-16 B k B 16
-23 B l B 23
2.0, 28.0
16,739/4,734
0.126
121.5 (3)
N2–C9–N3
124.1 (3)
S1–C9–N2
114.3 (4)
S1–C9–N3
hmin, hmax (°)
113.8 (4)
N3–C10–C11
N7–C15–C16
N8–C16–C15
Reflections collected/unique
Rint
126.2 (4)
122.5 (3)
Number of data with I [ 2r(I)
Number of variables
R for I [ 2r(I)
2,471
276
0.054
Rw for I [ 2r(I)
0.124
Goodness-of-fit on indicator
Structure determination
Refinement
0.88
SIR-97
Full-matrix
w = 1/[r2(F2o) ? (0.0436P)2] where P = (Fo2 ? 2F2c)/3
Table 2 Selected bond lengths for [CoLI(tmen)(N3)]
˚
Bond lengths (A)
˚
Bond lengths (A)
Co1–S1
Co1–O1
Co1–N1
Co1–N4
Co1–N7
Co1–N8
S1–C9
2.2298 (13)
1.887 (3)
1.899 (4)
1.937 (4)
2.053 (4)
2.113 (3)
1.731 (4)
1.303 (6)
1.369 (6)
1.422 (6)
1.390 (5)
1.282 (6)
N2–C9
1.319 (6)
1.334 (6)
1.435 (6)
1.176 (7)
1.169 (8)
1.456 (7)
1.503 (6)
1.478 (7)
1.454 (7)
1.484 (7)
1.461 (8)
N3–C9
N3–C10
N4–N5
N5–N6
N7–C13
N7–C14
N7–C15
N8–C16
N8–C17
N8–C18
O1–C1
O2–C2
O2–C8
N1–N2
N1–C7
Fig. 3 The N–HN hydrogen bonding of the title compound, forming
a dimer between the molecules, viewed down the a axis
123

Transition Met Chem (2010) 35:95–102
˚
101
I
to cobalt by the hydroxyl oxygen and thiolato sulfur with
concomitant deprotonation. Moreover, in the 1H-NMR
spectra of the complexes, the absence of signals assigned to
N2H in the free thiosemicarbazones confirms that N2 de-
protonates via thiol tautomerism upon chelation.
Table 4 Hydrogen bond parameters (A, °) for [CoL (tmen)(N3)]
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\(D–HꢀꢀꢀA)
N3–H3AꢀꢀꢀN2i
C10–H10AꢀꢀꢀS1
C12–H12AꢀꢀꢀN3
C13–H13CꢀꢀꢀS1
C14–H14BꢀꢀꢀO1
C14–H14CꢀꢀꢀN4
C17–H17AꢀꢀꢀS1
C18–H18CꢀꢀꢀO1
0.86
0.97
0.93
0.96
0.96
0.96
0.96
0.96
2.18
2.58
2.55
2.67
2.30
2.51
2.64
2.27
3.015 (5)
3.071 (5)
2.870 (6)
3.042 (5)
2.778 (6)
3.019 (7)
3.184 (6)
2.730 (6)
164
112
101
104
110
113
116
109
When the 1H-NMR spectra of the complexes were
compared to those of the free thiosemicarbazones, singlets
assigned to the CH=N proton at the range 8.37–8.16 ppm
are shifted upfield (to ca. 8.02 ppm), indicating coordina-
tion of the imine nitrogen. The signal assigned to N4H at
8.34–8.56 ppm for the free thiosemicarbazones is shifted to
7.07–7.38 ppm in the complexes. This significant differ-
ence is probably due to the strong intermolecular hydrogen
bonding which is an N3–H3AꢀꢀꢀN2 interaction.
i
Symmetry codes: -x, -y, 1 - z
1
A sharp band assigned to the (N3) stretching vibration of
the azide ligand was observed in the 2,009–2,024 cm-1
range. In the spectra of the complexes, bands assigned to
m(CH3–N), m(C–N–C), m(–CH2–) and m(–CH3) of the tmen
ligand are observed in the 1,324–1,320, 1,175–1,173 and
2,998–2,860 cm-1 regions, respectively.
The methyl protons belonging to tmen in the H-NMR
spectra of the complexes gave four sharp singlets at ca.
2.53, 2.47, 2.01 and 1.52 ppm for [CoLI(tmen)(N3)] and
[CoLII(tmen)(N3)], and at ca. 2.46, 2.44, 2.02 and
1.55 ppm for [CoLIII(tmen)(N3)] and [CoLIV(tmen)(N3)],
respectively. It is possible that the latter signals appear at
the highest field owing to the strong shielding effect of the
metal center because it is close to the metal center, azide
and oxygen atom of the thiosemicarbazone. The methyl
proton resonances of tmen, which is diastereotopic, are
significantly different from each other.
On the basis of the above vibrational analysis, we sug-
gest binding of the ligands to the Co(III) atom through the
azomethine, the deprotonated hydroxylic oxygen and the
thiolic sulfur atoms of the thiosemicarbazone ligand,
through the nitrogen atom of the azide ligand and through
the nitrogen atoms of the bidentate tmen ligand.
Interestingly, the ethylene protons of tmen are signifi-
cantly different from each other. The chemical shifts of the
methylene protons gave a pattern of ddd at 2.94 ppm, ddd
at 2.61 ppm, dq at ca. 2.57 ppm and dq at 2.09 ppm for
[CoLI(tmen)(N3)] and [CoLII(tmen)(N3)], of ddd at
2.94 ppm, ddd at 2.52 ppm, dq at 2.47 ppm and dq at
2.09 ppm for [CoLIII(tmen)(N3)] and [CoLIV(tmen)(N3)] in
DMSO-d6. This pattern is also observed for the spectra in
CDCl3, except for different chemical shifts. The methylene
groups of tmen are in different chemical environments and
therefore give rise to resonances that have different
chemical shifts.
The UV–Vis spectra of the free thiosemicarbazones and
their complexes were measured in CHCl3. The bands
observed at 217–220, 240–242 and 320 nm (for LIII, LIV),
ca 337 nm (for LI, LII) and ca. 344 nm (as shoulder) are
assignable to p ? p* and n ? p* transitions of the phe-
nol, aromatic ring, C=O, C=S and CH=N bonds of the
thiosemicarbazone, respectively. The ligands bands were
slightly shifted to higher or lower frequencies in the spectra
of all the complexes. New bands ca. at 346 and 405 nm
(for LI, LII) or 417 nm (for LIII, LIV), 493 and 962 nm in
the spectra of the complexes were attributed to n ? p*,
p ? p* and charge transfer transitions of tmen, azide and
Co(III), respectively.
Mass spectra
The electronic spectra of high spin d6 Co(III) complexes
1
1
give rise to four d–d transitions assigned to A1g ? T2g,
In the APCI-MS spectra of the complexes, mass ions
[M?-42] were the result of the loss of azide. The low mass
ions below the molecular ion peak and prominent ions
above molecular ion peak are presented in the ‘‘Experi-
mental’’ section. The higher mass ions are condensation
products of lower mass ions.
1
1
3
1
3
1A1g ? T1g, A1g ? T2g and A1g ? T1g, in the 370–
430, 450–500, 550–640 and 1,420–1,550 nm regions,
respectively [44–46]. Two of these transitions were
observed in the 200–1,000 nm range in the spectra of the
1
3
complexes. The A1g ? T2g transition could not be seen
as it was overlapped by charge transfer due to the extent of
1
1
the band belonging to the A1g ? T1g transition.
The 1H-NMR spectra of the thiosemicarbazones in
DMSO-d6 showed two singlets assigned to the OH proton at
the range 11.42–11.19 ppm and to the N2H proton at the
range 9.86–9.13 ppm. These singlets did not appear in the
1H-NMR spectra of the complexes, suggesting coordination
Conclusion
We have presented the synthesis and characterization of
four novel Co(III) complexes containing chelating ligands
with N, O and S donor atoms. In previous studies, the
123

102
Transition Met Chem (2010) 35:95–102
17. Thomson PCP (1988) Optical Recording Corporation COHN
Ronald, D. Wipo Patent WO/1988/003667
18. Adin A, Huttemann TJ, Lindholm RD (1978) Eastman Kodak
Company (Rochester, NY). US Patent 4124392
19. Adin A (1981) Eastman Kodak Company (Rochester, NY). US
Patent 4292399
reaction of tmen, thiosemicarbazones and metal ions gave
dimeric complexes containing no tmen ligands [29, 30]. In
this study, the presence of the tmen ligand was confirmed
by X-ray structure analysis as well as physico-chemical
and spectroscopic analysis.
20. West DX, Liberta AE, Padhye SB, Chikate RC, Sonawane PB,
Kumbhar AS, Yerande RG (1993) Coord Chem Rev 123:49
Acknowledgments This work was supported by the Research Fund
of Istanbul University.
21. Basuli F, Peng SM, Bhattacharya
39(6):1120
22. Berkessel A, Hermann G, Rauch O-T, Bu¨chner M, Jacobi A,
S (2000) Inorg Chem
Hutter G (1996) Chem Ber 129:1421
0
´
23. Garc ıa-Tojal J, Urtiaga MK, Cortes R, Lezama L, Arriortua MI,
Rojo T (1994) J Chem Soc Dalton Trans 15:2233
Appendix A
¨
˘
24. Bal T, Atasever B, Solakoglu Z, Erdem-Kuruca S, Ulku¨seven B
(2007) Eur J Med Chem 42:161
Supplementary material CCDC 664141 contains the sup-
plementary crystallographic data for this paper. These data
can be obtained free of charge via ww.ccdc.cam.ac.uk/conts/
retrieving.html (or from the CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: ?44-1223-336033; or e-mail:
deposit@ccdc.- cam.ac.uk.
25. Jin L, Yang P (1997) Polyhedron 16(19):3395
26. Yamaguchi M, Iida T, Yamagishi T (1998) Inorg Chem Commun
1:299
27. Nagababu P, Satyanarayana S (2007) Polyhedron 26:1686
28. Ganz PR, Pearlman RE (1980) Eur J Biochem 113(1):159
29. Shen X, Hirayama D, Sakata K, Hashimoto M (2003) Polyhedron
22(4):529
30. Selem HS, El-Shetary BA, Khalil SME, Mostafa M, Shebl M
(2005) J Coord Chem 58(6):479
31. Seleem HS, Emara AA, Shebl M (2005) J Coord Chem 58(12):
1003
References
32. Bal-Demirci T (2008) Polyhedron 27:440
33. Stoe & Cie (2002) X-AREA (Version 1.18) and X-RED32
(Version 1.04): programs for data collection, cell refinement. and
data reduction, Darmstadt, Germany
34. Altomare A, Burla MC, Camalli M, Cascarano G, Giacovazzo C,
Guagliardi A, Moliterni AGG, Polidori G, Spagna R (1999)
J Appl Crystallogr 32:115
´
1. Casas JS, Garcıa-Tasende MS, Sordo J (2000) Coord Chem Rev
209:197
2. Petering HG, Buskirk HH, Underwood GE (1964) Cancer Res
24:367
3. Brown RE, Stancato FA, Wolfe A (1981) Antimicrob Agents
Chemother 19(2):234
4. Du X, Guo C, Hansel E, Doyle PS, Caffrey CR, Holler TP,
McKerrow JH, Cohen FE (2002) J Med Chem 45:2695
5. Kovala-Demertzi D, Demertzis MA, Filiou E, Pantazaki AA,
Yadav PN, Miller JR, Zheng Y, Kyriakidis DA (2003) Biometals
16:411
35. Sheldrick GM (1997) SHELXL-97: FORTRAN program for
¨
¨
crystal structure refinement. University of Gottingen, Gottingen
36. Farrugia LJ (1997) J Appl Crystallogr 30:565
37. Ferrari MB, Fava GG, Lanfranchi M, Pelizzi C, Tarasconi A
(1991) J Chem Soc Dalton Trans 8:1951
6. Jiang Z, Lebowitz MS, Ghanbari HA (2006) CNS Drug Rev
12(1):77
38. Ni Z-H (2007) Acta Crystallogr Sect E 63:2531
39. Belicchi Ferrari M, Capacchi S, Bisceglie F, Pelosi G, Tarasconi
P (2001) Inorg Chim Acta 312:81
40. Jain SK, Garg BS, Bhoon YK, Klayman DL, Scovill JP (1985)
Spectrochim Acta 41A:407
41. Nakamoto Kazuo (1968) Infrared and Raman spectra of inorganic
and coordination compounds, 3rd edn. Wiley, New York
42. Gupta KC, Abdulkadir HK, Chand S (2004) Chin J Polym Sci
22(1):31
´
7. Cano Pavon JM, Lavado A, Pino F (1976) Microchim Acta
66(3–4):233
8. Reddy KJ, Kumar JR, Ramachandraiah C, Thriveni T, Reddy AV
(2007) Food Chem 101:585
9. Reddy AV, Reddy MLP, Reddy YK (1984) J Radioanal Nucl
Chem 86(6):391
10. Khuhawar MY, Arain GM (2006) Talanta 68(3):535
11. Tian Y, Duan C, Zhao C, You X (1997) Inorg Chem 36:1247
12. Ren P, Liu T, Qin J, Chen C (2003) Spectrochim Acta A 59:1095
13. Nemoto H, Ogasawara S, Bessho N (1995) Photopolymers for
LCD color filter. Proc IDW 57
43. Yamazaki C (1975) Can J Chem 53:610
44. West DX, Swearingen JK, Valde’s-Mart0ınez J, Herna0ndez-
Ortega S, El-Sawaf AK, Meurs F, Castin˜eiras A, Garcia I,
Bermejo E (1999) Polyhedron 18:2919
14. West JL, Russell JT (1988) Optical Recording Corporation. Wipo
Patent WO/1988/003666
15. Rubner R, Kuhn E, Ahne H (1981) Siemens Aktiengesellschaft,
(Munich, DE). US Patent No. 4,287,294
45. Lever ABP (1968) Inorganic electronic spectroscopy. Elsevier,
New York, p 339
46. West DX, Lockwood MA (1997) Trans Met Chem 22:447
16. Mitamura S (Shinjuku-Ku, JP) (2002) Dai Nippon Printing Co.,
Ltd. (JP). US Patent 6387012
123