Synthesis and characterization of nickel(II) complexes with 18-membered decaaza macrocycles 1,10-dialkyl-5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17- decaazacyclooctadecane

Article abstract of DOI:10.1081/SIM-200066995

Six new square-planar nickel(II) complexes of 18-membered decaaza macrocyclic ligands 5,6,14,15-tetraphenyl-1,3,4,7,8,10, 12,13,16,17- decaazacyclooctadecane [Ni((phenyl)₄ [18] ane N₁₀)] (ClO₄)₂ (1); 1,10-dimethyl- [Ni(Me₂ (phenyl)₄ [18] ane N₁₀)](C IO₄)₂ (2); 1,10-diethyl- [Ni(Et₂ (phenyl)₄ [18] ane N ₁₀)](ClO₄)₂ (3); 1,10-dipropyl-[Ni(Pr ₂ (phenyl)₄ [18] ane N₁₀)](ClO ₄)₂ (4); 1,10-dibutyl^iso- [Ni(Bu₂ (phenyl)₄ [18] ane N₁₀)](ClO₄)₂ (5); 1,10-dibenzyl-5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17- decaazacylooctadecane [Ni((Benzyl)₂ (phenyl)₄ [18] ane N₁₀)](ClO₄)₂ (6); [Ni((phenyl)₄ [18] ane N₁₀)(NCS)₂] (7); [Ni(Me₂ (phenyl) ₄ [18] ane N₁₀)(NCS)₂] (8); [Ni(Et₂ (phenyl)₄ [18] ane N₁₀)(NCS)₂] (9); [Ni(Pr ₂ (phenyl)₄ [18] ane N₁₀)(NCS)₂] (10); [Ni(Bu₂ (phenyl)₄ [18] ane N₁₀)(NCS) ₂] (11) and [Ni(Benzyl)₂ (phenyl)₄ [18] ane N₁₀)(NCS)₂] (12) have been prepared from the one-pot template condensation reaction of formaldehyde, benzildihydra-zone with alkyl and benzyl amine in the presence of nickel(II) ion. Elemental analyses, IR, UV-VIS spectroscopy, conductometric and magnetic measurements have been used to characterize the nickel(II) complexes of these decaaza macrocycles. The spectra of [Ni(R₂ (phenyl)₄ [18] ane N₁₀)](ClO ₄)₂ shows that the four nitrogen (α-diimine) atoms are coordinated to the nickel(II) ion. The hydrazones of the (α-diimine) function have the anti-anti configuration yielding a macrocyclic species with D_2h symmetry. The nickel(II) complexes are diamagnetic and four coordinates exhibit only weak interactions with different solvents. The physical and chemical properties of the complexes are compared with other closely related complexes. Copyright

Full text of DOI:10.1081/SIM-200066995

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Synthesis and Characterization of Nickel(II)
Complexes with 18-Membered Decaaza
Macrocycles 1,10-dialkyl-5,6,14,15-
tetraphenyl-1,3,4,7,8,10,12,13,16,17-
decaazacyclooctadecane
Masoud Salavati-Niasari a & Marzieh Hassani-Kabutarkhani a
a Department of Chemistry, University of Kashan, Kashan, Iran
Published online: 31 Jan 2012.
To cite this article: Masoud Salavati-Niasari & Marzieh Hassani-Kabutarkhani (2005): Synthesis and Characterization of
Nickel(II) Complexes with 18-Membered Decaaza Macrocycles 1,10-dialkyl-5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17-
decaazacyclooctadecane, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 35:6, 469-475
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Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry, 35:469–475, 2005
Copyright # 2005 Taylor & Francis, Inc.
ISSN: 0094-5714 print/1532-2440 online
DOI: 10.1081/SIM-200066995
Synthesis and Characterization of Nickel(II) Complexes with
18-Membered Decaaza Macrocycles 1,10-dialkyl-5,6,14,15-
tetraphenyl-1,3,4,7,8,10,12,13,16,17-
decaazacyclooctadecane
Masoud Salavati-Niasari and Marzieh Hassani-Kabutarkhani
Department of Chemistry, University of Kashan, Kashan, Iran
coordination chemistry of macrocycles synthetic originated
Six new square-planar nickel(II) complexes of 18-membered during the 1960s with high yield syntheses ligands, in which
decaaza macrocyclic ligands 5,6,14,15-tetraphenyl-1,3,4,7,8,10,
12,13,16,17-decaazacyclooctadecane [Ni((phenyl)4 [18] ane N10)]
the Ni(II) ion was employed as a templating agent (Curtis,
1968). The design and synthesis of polyazamacrocycles have
(ClO4)2 (1); 1,10-dimethyl- [Ni(Me2 (phenyl)4 [18] ane N10)](C
lO4)2 (2); 1,10-diethyl- [Ni(Et2 (phenyl)4 [18] ane N10)](ClO4)2
(3); 1,10-dipropyl-[Ni(Pr2 (phenyl)4 [18] ane N10)](ClO4)2 (4);
attracted increasing interest in recent years because of the
possible relevance of these compounds as models in bioinor-
1,10-dibutyliso- [Ni(Bu2 (phenyl)4 [18] ane N10)](ClO4)2 (5); ganic chemistry, catalysis extractions of metal ions from
1,10-dibenzyl-5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17-deca-
azacylooctadecane [Ni((Benzyl)2 (phenyl)4 [18] ane N10)](ClO4)2
(6); [Ni((phenyl)4 [18] ane N10)(NCS)2] (7); [Ni(Me2 (phenyl)4
[18] ane N10)(NCS)2] (8); [Ni(Et2 (phenyl)4 [18] ane N10)(NCS)2]
(9); [Ni(Pr2 (phenyl)4 [18] ane N10)(NCS)2] (10); [Ni(Bu2
(phenyl)4 [18] ane N10)(NCS)2] (11) and [Ni(Benzyl)2 (phenyl)4 strates that preferentially interact with particular metal ions is
solution and the activations of small molecules gave impetus
of this endeavour (Kade, 1984; Fenton and Vigato, 1988;
Vigato and Fenton, 1987; Izatt and Christensen, 1987; Shakir
et al., 1995; Casella et al., 1991). The synthesis of organic sub-
[18] ane N10)(NCS)2] (12) have been prepared from the one-pot
template condensation reaction of formaldehyde, benzildihydra-
zone with alkyl and benzyl amine in the presence of nickel(II)
ion. Elemental analyses, IR, UV-VIS spectroscopy, conducto-
metric and magnetic measurements have been used to character-
ize the nickel(II) complexes of these decaaza macrocycles. The O’Leary, 1987; Suh et al., 1984; 1985; 1987; Suh and Kang,
of fundamental importance to many areas of chemistry
(Adam et al., 1992). For example condensation between
carbonyl and amine has played an important role in the deve-
lopment of synthetic macrocyclic ligands (Lawrence and
spectra of [Ni(R2 (phenyl)4 [18] ane N10)](ClO4)2 shows that the
four nitrogen (a-diimine) atoms are coordinated to the nickel(II)
ion. The hydrazones of the (a-diimine) function have the
anti-anti configuration yielding a macrocyclic species with D2 h
symmetry. The nickel(II) complexes are diamagnetic and four
coordinates exhibit only weak interactions with different 1984; Suh et al., 1994; King, 1994). Usually such syntheses
1988; Suh et al., 1989; Suh et al., 1991; Suh and Kim, 1985;
Suh et al., 1987; Comba et al., 1988; 1986; 1988; Hancock,
1990; Hancock et al., 1988; 1989; Pattrick et al., 1991; Suh,
1997; Suh and Kim, 1993; Suh et al., 1996; Geue et al.,
solvents. The physical and chemical properties of the complexes
are compared with other closely related complexes.
are carried out in the presence of a suitable metal ion, which
serves to direct the steric course of the reaction preferentially
towards cyclic rather than oligomeric or polymeric products.
Keywords macrocycle, nickel(II) complexes, 18-membered deca-
azacyclooctadecane, template synthesis
The reactions are simple “one-pot reactions” cheap and high
yielding. Among the whole polyazamacrocycles, the tetraaza
group has been the most intensively studied because of its
great biological importance. However, most of them were
tetraaza macrocyclic ligands, and 18-membered macrocyclic
ligands containing deca nitrogen atoms in the Schiff-base
macrocyclic framework are relatively rare (Casella et al.,
1991; Adam et al., 1992; Lawrence and O’Leary, 1987; Suh
et al., 1984; 1985; 1987; Suh and Kang, 1988; Suh et al.,
1989; 1991; Suh and Kim, 1985; Suh et al., 1987; Comba
et al., 1988; Comba et al., 1986; 1988; Hancock, 1990;
Hancock et al., 1988; 1989; Pattrick et al., 1991; Suh, 1997;
INTRODUCTION
Template condensation reactions lie at the heart of macro-
cyclic chemistry. In particular, the rich and lively topic of
Received 7 December 2004; accepted 3 April 2005.
Address correspondence to Masoud Salavati-Niasari, Department
of Chemistry, University of Kashan, P.O.Box 87317-51167, Kashan,
Iran. E-mail: salavati@kashanu.ac.ir
469

470
M. SALAVATI-NIASARI AND M. HASSANI-KABUTARKHANI
Suh and Kim, 1993; Suh et al., 1996; Geue et al., 1984; Suh measurements with a Metrohm Herisau conductometer E
et al., 1994; King, 1994; Salavati-Niasari and Najafian, 2003; 518. The elemental analysis (carbon, hydrogen and nitrogen)
Salavati-Niasari, 2004; Salavati-Niasari and Rezai-Adaryani of complexes was obtained from Carlo ERBA model EA
2004).
1108 analyzer. Magnetic moments were calculated from
In this article, we report the synthesis, characterization and magnetic susceptibility data obtained using a Johnson
properties of the new square-planar nickel(II) complex of Matthey MK-1 magnetic susceptibility balance. Atomic
5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17-decaazacyclooct- absorption spectra (AAS) were recorded on a Perkin-Elmer
adecane [Ni((phenyl)4 [18] ane N10)](ClO4)2 (1), 1,10-dimeth 4100-1319 spectrophotometer.
yl-[Ni(Me2 (phenyl)4 [18] ane N10)](ClO4)2 (2), 1,10-diethyl-
[Ni(Et2 (phenyl)4 [18] ane N10)](ClO4)2 (3), 1,10-dipropyl-
Preparation of Benzildihydrazone
[Ni(Pr2 (phenyl)4 [18] ane N10)](ClO4)2 (4), 1,10-dibutyliso
-
To a boiling solution of 11.63 g of aqueous hydrazine (0.24
mole) in 100 ml of methanol was added benzil (0.12 mol,
25.23 g) in 100 ml methanol over a period of 60 minutes
followed by the addition of 1 cm3 of concentrated HCl. The
resulting solution was refluxed for about 6 h on a water bath.
Two hundred millilitres of water was then added and the
methanol was removed by distillation when the resulting
aqueous solution was cooled in an ice-bath, with crystals
formed. These were filtered, washed with a little water,
recrystallized from 200 ml of hot methanol and dried in
vacuum. m.p; 1498C; yield: ꢀ60%. Anal. calcd. for
C14H14N4: C, 70.54; H, 5.92; N, 23.50 %. Found: C, 70.36;
H, 5.80; N, 23.67%. IR (KBr, cm21): 3335, 3184 (yN–H);
1576 (yC55N), 1618 (yNH2).
[Ni(Bu2 (phenyl)4 [18] ane N10)](ClO4)2 (5), 1,10-dibenzyl-
5,6,14,15-tetraphenyl-1,3,4,7,8,10,12,13,16,17-decaazacylooc
tadecane [Ni((Benzyl)2 (phenyl)4 [18] ane N10)](ClO4)2 (6),
[Ni((phenyl)4 [18] ane N10)(NCS)2] (7), [Ni(Me2 (phenyl)4
[18] ane N10)(NCS)2] (8), [Ni(Et2 (phenyl)4 [18] ane
N10)(NCS)2] (9), [Ni(Pr2 (phenyl)4 [18] ane N10)(NCS)2]
(10), [Ni(Bu2 (phenyl)4 [18] ane N10)(NCS)2] (11) and
[Ni((Benzyl)2 (phenyl)4 [18] ane N10)(NCS)2] (12), and are
given in Scheme 1.
EXPERIMENTAL
Materials and Measurements
Safety Note
Preparation of [Ni(Me2(phenyl)4 [18]
ane N10)](ClO4)2 (2)
To a stirred methanol solution (500 ml) of NiCl2 6H2O
Perchlorate salts of transition metal complexes with organic
ligands are often explosive and should be handled with caution.
All chemicals and solvents used in the syntheses were reagent
.
grade and were used without further purification. For the spec- (10.00 g, 42.07 mmole) were slowly added benzildihydrazone
troscopic measurements, water was distilled and organic (20.06 g, 84.20 mmole), 36% formaldehyde (13 ml), and 36%
solvents were purified according to the literature method methylamine (10.47 ml, 84.20 mmole). One drop of concen-
(Perrin et al., 1980). Electronic absorption spectra were trated perchloric acid was added to catalyze the condensation
obtained with a Shimadzu UV-VIS scanning spectrophoto- reaction. The mixture was heated at reflux for 24 h until a
meter (Model 2101 PC), FTIR spectra with a Shimadzu dark red solution resulted. The solution was cooled to room
Varian 4300 spectrophotometer, 1H-NMR spectra with a temperature and filtered to remove nickel hydroxide. Excess
Brucker AC 80 (in CH3NO2-d3 as solvent), and conductance percholoric acid or lithium perchlorate dissolved in methanol
SCH. 1

SYNTHESIS AND CHARACTERIZATION OF NICKEL(II) COMPLEXES
471
was added to the filtrate, and the mixture was kept in the precipitate formed was filtered, washed with acetonitrile, and
refrigerator until red-brown solid formed. The red-brown dried in vacuum. Anal. calcd. for (7), (Yield: ꢀ49%): Ni,
solid were filtered, washed with diethyl ether, and air-dried. 8.69; C, 58.67; H, 5.07; N, 22.81%. Found: Ni, 8.52; C,
The products were crystallized from hot water. Yield: ꢀ43%. 58.50; H, 4.92; N, 22.94%. Anal. calcd. for (8),
Anal. calcd for (2); Ni, 6.95; C, 48.36; H, 4.54; N, 16.54%. (Yield: ꢀ53%): Ni, 8.34; C, 59.75; H, 5.44; N, 21.90%.
Found Ni, 6.84; C, 48.21; H, 4.46; N, 16.63%.
Found: Ni, 8.22; C, 59.65; H, 5.34; N, 22.06%. Anal. calcd.
for (9): (Yield: ꢀ58%): Ni, 8.02; C, 60.47; H, 5.79; N,
21.06%. Found: Ni, 7.95; C, 60.32; H, 5.61; N, 21.19%.
Anal. calcd. for (10), (Yield: ꢀ61%): Ni, 7.73; C, 61.66; H,
6.10; N, 20.28%. Found: Ni, 7.60; C, 61.52; H, 6.02; N,
20.36%. Anal. calcd. for (11), (Yield: ꢀ54%): Ni, 7.45; C,
62.51; H, 6.40; N, 19.56%. Found: Ni, 7.32; C, 62.44; H,
6.31; N, 19.63%. Anal. calcd. for (12), (Yield: ꢀ63%): Ni,
6.86; C, 65.96; H, 5.42; N, 18.01%. Found: Ni, 6.74; C,
65.82; H, 5.29; N, 18.14%.
Preparation of [Ni((phenyl)4 [18] ane N10)](ClO4)2 (1)
The procedure followed was similar to that for [Ni(Me2
(phenyl)4 [18] ane N10)](ClO4)2, except that 25% ammonia
(6.3 ml, 84.20 mmole) was used instead of methylamine.Yield:
ꢀ38%. Anal. calcd for (1): Ni, 7.12; C, 47.07; H, 4.02; N,
17.15%. Found: Ni, 7.01; C, 46.88; H, 3.91; N, 17.24%.
Preparation of [Ni(Et2 (phenyl)4 [18] ane N10)](ClO4)2 (3)
This complex was prepared by a method similar to that for
[Ni(Me2 (phenyl)4 [18] ane N10)](ClO4)2 except 50% ethyl-
amine (8.72 ml, 84.20 mmole) was used instead of methyl-
amine. Yield: ꢀ35%. Anal. calcd for (3): Ni, 6.72; C, 49.56;
H, 4.85; N, 16.05%. Found: Ni, 6.66; C, 49.42; H, 4.71; N,
16.14%.
Preparation of [Ni(C34H36N10)] (13)
Triethylamine (0.5 ml) was added to a deaerated solution of
200 mg of (2) in 15 ml of CH3CN. The red-brown solution
changed to an intense dark red color upon mixing the
reagents. The air-sensitive product, which began precipitating
within minutes, was filtered after 0.5 h under a nitrogen atmos-
phere, washed with anhydrous ethanol, and dried in vacuum. IR
(KBr, cm21): 1598 (yC55N). Anal. calcd for [Ni(C34H36N10)]:
Ni, 9.12; C, 63.48; H, 5.64; N, 21.76%. Found: Ni, 9.02; C,
63.31; H, 5.53; N, 21.84%.
Preparation of [Ni(Pr2 (phenyl)4 [18]
ane N10)](ClO4)2 (4)
The procedure followed was similar to that for [Ni(Me2
(phenyl)4 [18] ane N10)](ClO4)2, except that propylamine
(6.91 ml, 84.2 mmole) was used instead of methylamine.
Yield: ꢀ36%. Anal. cacld for (4): Ni, 6.52; C, 50.68; H,
5.15; N, 15.55%. Found: Ni, 6.47; C, 50.51; H, 5.01; N,
15.68%.
Preparation of [Ni (phenyl)4 [18] ane N8)](ClO4)2 (14)
Aqueous formaldehyde (38%, 1.61 g, 20 mmol) was
added to
a solution containing 3.65 g (10 mmol) of
.
Preparation of [Ni(Bui2so (phenyl)4 [18]
Ni(ClO4)2 6H2O in 30 ml of acetonitrile. To this blue
solution, 4.77 g (20 mmol) of benzildihydrazone were added.
Concentrated perchloric acid (1 drop) was added to catalyze
the reaction. The reaction proceeded immediately and was
essentially complete after 1 h at room temperature. Diethylether
(100 ml) was slowly added to the red-brown solution to induce
precipitation of the octaaza product. The red-brown product
was filtered and then recrystallized from acetonitrile (Yield
about 82%). Anal. calcd for (14): Ni, 7.74; C, 47.52; H, 3.72;
N, 14.77%. Found: Ni, 7.60; C, 47.39; H, 3.60; N, 14.86%.
ane N10)](ClO4)2 (5)
This complex was prepared by a method similar to that for
[Ni (Me2 (phenyl)4 [18] ane N10)](ClO4)2 except iso-butyl-
amine (8.36 ml, 84.20 mmole) was used instead of methyl-
amine. Yield: ꢀ39%. Anal. calcd. for (5): Ni, 6.32; C, 51.74;
H, 5.43; N, 15.08%. Found: Ni, 6.20; C, 51.62; H, 5.34; N,
15.19%.
Preparation of [Ni((Benzyl)2(phenyl)4 [18] ane
N10)](ClO4)2 (6)
RESULTS AND DISCUSSION
This complex was prepared by a method similar to that for
[Ni (Me2 (phenyl)4 [18] ane N10)](ClO4)2 except benzyl amine
(9.2 ml, 84.20 mmole) was used instead of methylamine. Yield:
ꢀ51%. Anal. calcd. for (6): Ni, 5.89; C, 55.43; H, 4.65; N,
14.05%. Found: Ni, 5.71; C, 55.28; H, 4.51; N, 14.16%.
Decaaza bis(a-diimine) macrocyclic nickel(II) complexes
were prepared by reacting 2 equiv of benzildihydrazone, 4
equiv of formaldehyde with 2 equiv of the appropriate amine
in the presence of the nickel(II) ion (Schemes 1 and 2). It
was observed that the 18-membered decaaza macrocyclic
product obtained from the reaction was largely affected by
the molar ratio of the reactants. The cyclization process is
Preparation of [Ni(R2 (phenyl)4 [18] ane N10)(NCS)2]
(7–12)
A saturated solution of NaNCS in 10 ml of CH3CN was acid catalyzed but large excesses of acid destroy the com-
added to a solution containing 0.2 g of [Ni (R2 (phenyl)4 [18] plexes. The crude product often contains small amount of
ane N10)](ClO4)2 (1–6) in 20 ml of CH3CN. The solution octaazabis(a-diimine) macrocyclic (14) complex as by-
was allowed to stand at room temperature, and then the pink products. However, the mononuclear complex can be readily

472
M. SALAVATI-NIASARI AND M. HASSANI-KABUTARKHANI
SCH. 2
isolated by fractional recrystallization of the product from which tetradenate ligands were formed by the condensation
ca.0.05 M HClO4 aqueous solutions.
of benzil monohydrazone in the presence of Ni(II) (Kerwin
and Melson, 1972). In the absence of added carbonyls, the
2,3-benzildihydrazone complexes described by Stouffer and
Busch are formed (Stouffer and Busch, 1956).
The possibility of syn-anti and anti-anti isomerization among
the free dihydrazone ligands and their decaaza complexes were
considered. Both isomers of benzildihydrazone are capable of
forming metal chelates with the syn-anti configuration
forming six-membered chelate rings, while the anti-anti con-
figuration yield five-membered a-diimine chelate rings.
The free amino groups of coordinated benzildihydrazone
are ideally oriented for ring closure by reaction with
carbonyl functions to give six-membered chelated rings and
ultimately octaaza-14-membered ring macrocyclic complexes,
2,3,9,10-tetraphenyl-1,4,5,7,8,11,12,14-octaazacyclotetra-
deca-1,3,8,10-tetraene ligand, (14). This type of reaction
closely parallels that reported by Kerwin and Melson in

SYNTHESIS AND CHARACTERIZATION OF NICKEL(II) COMPLEXES
473
The syn-anti configuration of a number of cyclic 1,2-
A comparison of the spectra of the 18-membered decaaza
dihydrazone was observed by Baldwin and co-workers macrocycles 1–6 with those of the closely related divalent
(Baldwin et al., 1972). However, the NMR spectrum of benzil- metal complexes of the Me4 [14] 1,3,8,10-tetraeneN4 and
dihydrazone indicates the anti-anti configuration. The Me4 [14] 1,3,8,10-tetraene N8 reveals some differences in the
p-acceptor property of the a-diimine moieties enhances their C55N stretching frequency region of the spectrum (Jackels
chelating tendency with metals of significant p-donor et al., 1972; Baldwin et al., 1973). The intensity and position
tendency. Therefore the cyclization products of 16 obtained of the C55N stretching frequency of our 18-membered
from condensation of benzildihydrazone with formaldehyde decaaza macrocycle complexes are strong and sharp, and are
and amine are expected to yield products having the symmetri- one indication of the difference in dipole strength of the hydra-
cal anti-anti structure of 18-membered decaaza macrocycle zone’s C55N as compared to the a-diimine C55N bond.
nickel(II) complexes.
The electronic spectra (Table 1) of Ni(II) complexes are
[Ni(R2 (phenyl)4 [18] ane N10)]2þ react with excess NaNCS comparable to those of square-planar Ni(II) complexes with
in aqueous solution to form tetragonal complexes [Ni(R2 tetraaza macrocycles, indicating that the decaaza ligands of
(phenyl)4 [18] ane N10)(NCS)2], whose IR spectra (Table 1) this study do not differ significantly from the tetraaza ligands
show that the nitrogen atoms of NCS2 ligands are coordinated with respect to the ligand field strength (Jackels et al., 1972;
to Ni(II) ion (Nakamato, 1978). Pink complexes of thiocyanate Baldwin et al., 1973). The UV-VIS spectra of these intensely
are not solution in most of the solvents such as CH3CN, EtOH, colored complexes are dominated by intense charge-transfer
DMF and in H2O.
absorptions in the visible and UV portions of the spectra.
The decaazabis (a-diimine) macrocyclic ligands are strong- The spectra are tabulated for identification purpose only; no
field ligands and promote spin pairing whenever possible. The detailed assignment will be made due to the overlap of
magnetic moments (20.01 to 20.20 mB) of the nickel(II) com- ligand field and charge-transfer absorptions. Generally, the
plexes (1–6) measured in the solid state correspond to the lowest energy bonds of the spectra for Ni(II) complexes are
square-planar coordination geometry of the complexes. The d ! pꢀ charge-transfer bonds that have been extensively
infrared spectra of the complexes 1–6 are all very similar to studied and characterized in other a-diimine complexes
one another and support the ligand structure proposed in (Krumholz, 1971).
Scheme I. The most diagnostic absorption bands are the N–
The 18-membered decaaza macrocyclic nickel(II) com-
H and C55N stretching modes, as well as those attributable plexes undergo intense colour changes due to deprotonation
to free perchlorate anions. Some of the representative N–H of the macrocyclic ligand in the presence of amine bases
and C55N stretching frequencies are tabulated in Table 1. such as pyridine and triethylamine. Similar N–H deprotonation
There were no other absorption bands present that could be reactions have been observed with other metal complexes con-
assigned to uncondensed functional groups, e.g., as 2NH2 or taining hydrazones linkages (Goedken and Peng, 1973;
C55O, of the starting materials.
Goedken and Peng, 1975). The C55N stretching frequency of
TABLE 1
IR,UV-VIS, magnetic and conductance data of 18-membered decaaza macrocyclic nickel(II) complexes at 258C
IR, cm21
a
LM
V21 cm22 M21
Complex
nN–H
nC55N
n
CS, nCN
´
UV/VIS lmax (nm (1, m21 cm21))
mB
1
2
3
3301
3292
3268
3257
3248
3311
3309
3297
3274
3264
3255
3321
1618
1616
1615
1614
1612
1625
1622
1620
1617
1618
1616
1631
—
—
—
—
—
—
423(sh,2320), 351(sh,6200), 302(22700)
424(sh,2360), 352(sh,6250), 301(22600)
425(sh,2390), 352(sh,6260), 303(22750)
426(sh,2360), 353(sh,6280), 302(22800)
426(sh,2380), 351(sh,6270), 301(22900)
420(sh,2410), 352(sh,6220), 300(23200)
418(sh,2490), 350(sh,6250), 301(23100)
419(sh,2450), 352(sh,6260), 301(23100)
419(sh,2460), 350(sh,6240), 302(23100)
420(sh,2480), 353(sh,6260), 301(23100)
420(sh,2470), 350(sh,6250), 302(23100)
416(sh,2510), 349(sh,6270), 300(23100)
20.09
20.10
20.10
20.11
20.12
20.15
2.83
271
275
265
260
245
262
15
5
6
7
2058, 785
2049, 786
2041, 786
2040, 786
2038, 785
2032, 784
8
2.83
2.85
22
23
9
10
11
12
2.86
2.83
24
16
2.89
12
aIn nitromethane solutions, unless otherwise specified.

474
M. SALAVATI-NIASARI AND M. HASSANI-KABUTARKHANI
this compound [Ni(C34H36N10)], 1607 cm21, is reduced signifi- condensation of 2 mole of benzildihydrazone, 4 mole of
cantly from its dicationic precursor, [Ni(C34H38N10)](ClO4)2, CH2O with 2 mole amine. The spectra of the complexes
1616 cm21. The C55N stretching frequencies, together with show that the four nitrogen (a-diimine) atoms are coordinated
the change in the electronic (lowering of energy of charge- to the nickel(II) ion.
transfer bonds and increased intensity), indicate that the loss
of these protons is accompanied by increased delocalization
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