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2.3. Preparations
2.3.1. Preparation of nicotinoylchloride and isonicotinoylchloride
Nicotinoylchloride and isonicotinoylchloride were prepared
using the method reported by Wingfield et al. [26]. For the synthesis
of nicotinoylchloride, nicotinic acid (12.3 g, 100 mmol) was taken
in a round bottom flask with 100 ml dry benzene, thionylchloride
(6.0 ml, 80 mmol) was added to reaction mixture and refluxed for
12 h, protecting from moisture. The reaction mixture was used as
such without any separation for later reactions. The same proce-
dure was used for the preparation of isonicotinoylchloride except
that isonicotinic acid (12.3 g, 100 mmol) was used in place of nico-
tinic acid.
Scheme 1. Catalytic oxidation of phenol in presence of H2O2.
methylbenzo[b,i][1,4,8,11]tetraazacyclotetradecahexaenatonick-
el(II)).Their characteristics as chemical and electrochemical cat-
alysts have also been studied. The catalytic activity of these
complexes as heterogeneous catalyst towards wet chemical oxi-
dation of phenol using H2O2 as oxidant has been investigated.
The reaction conditions were optimized, in term of temperature,
effect of reaction media, amount of catalyst, reaction time and
relative amounts of oxidant and phenol. Electrocatalytic oxidation
of phenol at glassy carbon electrode modified by the synthesized
macrocycle complexes has also been investigated.
2.3.2. Preparation of [Ni{Me4(4-MeBzo)2[14]tetraeneN4}]
(NiTaa)
[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] was prepared following
the method reported by Place et al. [27]. Nickel acetate (12.4 g,
50 mmol) and 3, 4 diaminotolune (12.2 g, 100 mmol) were added
to 120 ml n-butanol in 250 ml round bottom flask. The reaction
mixture was refluxed on oil bath with constant stirring. After
one and half hours acetylacetone (10.4 g, 100 mmol) was added
and the reaction mixture was refluxed for 24 h. After cooling,
100 ml of methanol was added and the reaction mixture was kept
overnight in a refrigerator. The crystals obtained were filtered and
washed with methanol. Fine dark violet crystals were obtained.
Yield 9.5 g (22%). m.p. >300 ◦C. Analyses found C, 67.29; H, 6.12:
N, 13.01%. C24H26N4Ni calcd.: C, 67.16; H, 6.10; N, 13.05%. UV–vis
(in chloroform ꢀmax, cm−1/εmax, L mol−1 cm−1); 17065 (6214),
23310sh (9150), 25316 (36298), 29674 (8612), 37037 (32420),
IR (KBr pellet, v, cm−1): 2966w, 2913m, 2855m, 1579m, 1535s,
1462m, 1398vs, 1278m, 1209m, 1029s, 747m. 1H NMR (in CDCl3):
ı 2.05(s 12H, CH3), 2.13 (s 6H, arom. CH3), 4.82 (s 2H methine) and
6.36–6.58 ppm (m 6H, arom.).
2. Experimental
2.1. Materials and methods
Phenol, nickel acetate tetrahydrate and 30% H2O2 (Rankem,
India), nicotinic acid (Loba Chemie, India), 3, 4-diaminotoluene
(Sigma Aldrich, USA) and isonicotinic acid (Acros Organics, USA)
were used in this study. Acetylacetone, thionyl chloride and
triethylamine were obtained from Loba Chemie (India). Tetraethy-
lammonium perchlorate (TEAP) used in cyclic voltammetry studies
was obtained from Fluka (Switzerland). All solvents were of analyt-
ical reagent grade purchased from Rankem (India). Solvents were
purified before their use in the electrochemical studies and synthe-
sis. The acetonitrile used in the electrochemical studies was dried
over P2O5 and distilled while benzene used for the synthesis of acid
chloride and for electrochemical studies was dried over sodium
wire and distilled.
2.3.3. Preparation of
7,16-dinicotinoyl[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] (Ni-Nic)
[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] (2.5 g, 5.83 mmol) was
dissolved in 50 ml dry benzene and the reaction mixture containing
nicotinoylchloride (prepared in step 2.3.1) was mixed with it and
then triethylamine (2.8 ml, 20 mmol) was added. The reaction mix-
ture was refluxed for 12 h with constant stirring protecting from
moisture. The reaction mixture was cooled down to room tem-
perature and filtered. The filtrate was evaporated to dryness in a
rotary evaporator and the product was washed with hot water till
the washings become colourless. The product was then dried at
80 ◦C, the dry residue was extracted in benzene and the benzene
was evaporated in rotatory evaporator. The compound was puri-
fied by passage through a 20 cm × 2.5 cm alumina column eluting
with benzene. Three green colored bands were observed. The first
and second bands were minor and were discarded. The third green
band was eluted with chloroform and the solvent was removed at
reduced pressure. Yield 2.9 g (78.3%). m.p. >300 ◦C. Analyses found
C, 67.92; H, 4.82 N, 13.03%. C36H32N6O2Ni calcd.: C, 67.61; H, 5.00;
N, 13.15%. UV–vis (in chloroform ꢀmax, cm−1/εmax, L mol−1 cm−1);
17094 (7012), 23365sh (13400), 25707 (35452), 30303 (10596),
37037 (52298), IR (KBr pellet, v, cm−1): 2922m, 2851m, 1656s,
[M+1]+ 641, 639.38 (calcd. molecular weight). 1H NMR (in CDCl3):
ı 1.91(s 12H, CH3), 2.13 (s 6H, arom. CH3), 6.34–6.61 (m 6H, arom.),
7.56 (br s 2H (d)), 8.53 (br s 2H (e)), 8.86 (br s 2H (c)) and 9.44 ppm
(br s 2H (f)) (Scheme 2).
2.2. Instrumentation
Electronic spectra of all macrocycle complexes were recorded
on a Schimadzu UV-1601 spectrophotometer in CHCl3, 1H NMR
spectra were recorded on a Bruker DRX-500 spectrometer in
chloroform-d. IR spectra were taken on a Thermo Nicolet Nexus
aligent 1100 FT-IR in KBr. The FAB mass spectra tetraazamacro-
cycle complexes were recorded on Jeol SX-102/DA-6000 mass
spectrometer in 3-nitrobenzyl alcohol matrix using xenon as
FAB gas. Elemental analyses were carried out on an Elemen-
tar Vario EL III analyzer. Electrochemical studies were carried
out on a CHI 600A electrochemical analyzer. Three-electrode
assembly with Ag/AgCl/KCl (sat.) as reference electrode, Pt
wire as counter electrode and glassy carbon as working elec-
trode were used. All electrochemical investigations were carried
out in dry benzene/acetonitrile (1:1, v/v) mixture in presence
of tetraethylammonium perchlorate (TEAP) as supporting elec-
trolyte while oxidation of phenol on modified electrode was
carried out in doubly distilled water using phosphate buffer
(0.1 M, pH 7.3) as supporting electrolyte. Catalyzed chemical
oxidations were carried out in a flask immersed in controlled
temperature oil bath. Oxidation products were analyzed using
Hewlett Packard gas chromatograph model 5890 A fitted with
FID detector and a (30 m × 0.53 mm × 2.65 m) HP-1capillary col-
umn.
2.3.4. Preparation of 7,16-diisonicotinoyl
[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] (Ni-Iso)
The above procedure was followed for the preparation of 7,16-
diisonicotinoyl[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] except that