Synthesis and Reactivity of Zirconium and Hafnium Dihydroxophthalocyaninates

Article abstract of DOI:10.1134/S0036023620100046

Abstract—: Two synthetic approaches for obtaining of zirconium and hafnium dihydroxophthalocyaninates (i.e. (a) that using the zirconium and hafnium alkoxides as the reactive precursors and (b) hydrolysis of zirconium and hafnium dichloridophthalocyaninates) were evaluated. Reactivity of zirconium and hafnium dihydroxophthalocyaninates in their exchange reactions with β-diketones and with decanoic acid was also studied; they were compared with those of zirconium and hafnium dichloridophthalocyaninates. The use of zirconium and hafnium dihydroxophthalocyaninates as the precursors in their reactions with acid-sensitive ligands, such as ketoesters, is found to be a more effective approach.

Full text of DOI:10.1134/S0036023620100046

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2020, Vol. 65, No. 10, pp. 1489–1493. © Pleiades Publishing, Ltd., 2020.
CHEMISTRY OF MACROCYCLIC
AND METALLOCYCLIC COMPOUNDS
Synthesis and Reactivity of Zirconium
and Hafnium Dihydroxophthalocyaninates
V. Cherniia, *, I. Tretyakovaa, R. Selina, N. Fedosovaa, and V. Kovalskab
aVernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, Kyiv, 03680 Ukraine
bInstitute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv, 03143 Ukraine
*e-mail: v.chernii@gmail.com
Received April 25, 2020; revised May 14, 2020; accepted May 27, 2020
Abstract—Two synthetic approaches for obtaining of zirconium and hafnium dihydroxophthalocyaninates
(i.e. (a) that using the zirconium and hafnium alkoxides as the reactive precursors and (b) hydrolysis of zir-
conium and hafnium dichloridophthalocyaninates) were evaluated. Reactivity of zirconium and hafnium
dihydroxophthalocyaninates in their exchange reactions with β-diketones and with decanoic acid was also
studied; they were compared with those of zirconium and hafnium dichloridophthalocyaninates. The use of
zirconium and hafnium dihydroxophthalocyaninates as the precursors in their reactions with acid-sensitive
ligands, such as ketoesters, is found to be a more effective approach.
Keywords: zirconium complexes, hafnium complexes, phthalocyanines, axial ligands, exchange reactions
DOI: 10.1134/S0036023620100046
INTRODUCTION
which in turn may lead to the formation of side-prod-
ucts and consequently to a decrease in the purity and
yield of the target complexes. In similar reaction with
phthalocyanine PcM(OH)2 as starting compounds,
their interaction with β-dicarbonyles or carboxylic
acids generates water, which slightly affects either the
starting materials or products of the reactions. Thus,
PcM(OH)2 are considered as the preferable starting
compounds in ligand exchange reactions, but prepar-
ative methods for them have not been developed suffi-
ciently and their reaction ability has been poorly stud-
ied. The purpose of this work is to optimize the
PcM(OH)2 preparation methods (Fig. 1) and study of
their reactivity with β-diketones, β-ketoesters, and
carboxylic acids.
The high stability and wide range of optical and
electrophysical properties of the zirconium and haf-
nium phthalocyanine complexes (PcZrL2, PcHfL2)
[1–4], as well as the possibility of their modification
through the coordinatively unsaturated central metal
atom [5–11], makes them prospective for use as pig-
ments and dyes, electrocatalysts [12], photoelectro-
catalytic [13], electrochromic agents and other materi-
als [14–17].
The main method of obtaining of zirconium and
hafnium phthalocyaninates with non-planar ligands is
the reaction of substitution of chlorine atoms in
PcMCl2 (M = Zr, Hf) with β-diketonate [5], β-ketoester
[4], carboxylate ligands [9]. The peculiarity of such
reaction is the release of hydrogen chloride, which can
adversely affect the reaction pathway and thus on the
formation of the target products. For example, hydro-
EXPERIMENTAL
Zirconium and hafnium tetrachloride, o-phthalo-
gen chloride could initiate the hydrolysis of acid-sen- dinitrile, 1-phenyl-4,4,4-trifluoro-1,3-butanedione,
sitive starting compounds, in particular, β-ketoesters, dibenzoylmethane, ethyl acetoacetate, isopropyl
OH
HO
N
Cl Cl
MCl4 + ROH
(NH2)2CO
M
CN
CN
M
N
B
N
N
N
N
A
N
N
–HCl
N
N
N
N
N
N
N
N
Fig. 1. Preparation of PcM(OH) from metal alkoxides (A) and by hydrolysis of PcMCl (B).
2
2
1489

1490
Table 1. Conditions for the synthesis of PcM(OH)2 from metal alkoxides and by hydrolysis of the PcMCl2
Synthesis from M(OAlk)4 Hydrolysis of PcMCl2
CHERNII et al.
metal
alcohol
T, °C
time, h
yield, %
reagent
T, °C
time, h
yield, %
Zr
Hf
C5H11OH
C7H15OH
C9H19OH
C5H11OH
C7H15OH
C9H19OH
140
180
220
140
180
220
38
40
40
25
27
28
C4H9OH
NH4OH
NH4OH
C4H9OH
NH4OH
NH4OH
10
8
120
20
8
72
12
8
0
*
8
95
88
0
10
8
120
20
72
12
*
8
95
76
* Partial hydrolysis.
3-oxobutanoate, (E)-1-ethoxy-3-oxo-3-phenylprop-
1-en-1-olate, decanoic acid were purchased from
Aldrich and used as received. Toluene, methanol,
1-butanole, 1-pentanol, 1-heptanol, 1-nonanol,
aqueous ammonia solution, and all other organic sol-
vents were of reagent grade and were used without fur-
ther purification. Zirconium and hafnium dichlori-
dophthalocyaninates were prepared by the reaction of
MCl4 with o-phthalodinitrile according to the pub-
lished procedures [18].
PcHf(OH)2. PcHfCl2 (2.26 g, 0.003 mol) was sus-
pended under stirring and heating with 10 ml of a 25%
aqueous ammonia solution. The mixture was kept at
95°C for 6 hours, then 6 mL of ammonia solution was
added and kept for 6 hours under the same conditions,
then cooled and filtered. The precipitate was washed
on the filter 3 times with 10 mL of water, then 3 times
with the same amount of methanol and 2 times with
5 mL of methylene chloride. The product was dried at
room temperature for 24 hours. Yield, 1.63 g (76%).
The general method for synthesis of PcML2 (M =
Zr, Hf; L = β-diketone, carboxilate). PcM(OH)2
(0.4 mmol) was suspended in 10 mL of toluene, then
1.0 mmol of ligand was added and boiled for 2–
5 hours. Next, the reaction mixture was filtered hot
(T = 100–110°C), the solid residue was washed with
hot toluene. The filtrate was cooled, the crystals
formed overnight, filtered, washed with hexane and
dried in vacuo at 100°C. The yields of the final prod-
ucts are shown in Table 2.
Bis(1-phenyl-4,4,4-trifluoro-1,3-butanedionato)zir-
conium(IV) phthalocyanine. 1H NMR (400 MHz,
chloroform-d), δ, ppm: 9.58–9.40 (m, 2H), 9.31 (dd,
J = 7.6, 1.9 Hz, 2H), 9.15 (dd, J = 5.6, 3.0 Hz, 1H),
9.10 (d, J = 7.5 Hz, 1H), 8.92 (d, J = 7.3 Hz, 2H),
8.31–8.16 (m, 2H), 8.16–8.09 (m, 2H), 8.01 (tt, J =
7.3, 1.3 Hz, 2H), 7.97–7.87 (m, 2H), 7.47–7.34 (m,
2H), 7.14–6.98 (m, 4H), 6.85–6.76 (m, 1H), 6.76–
6.69 (m, 3H), 5.15 (s, 2H).
1H NMR spectra were recorded on a Varian VXR
(400 or 300 MHz) spectrometer, TMS was used as
internal standard, CDCl3 was used as solvent.
The general method for synthesis of PcM(OH)2 (M =
Zr, Hf) in alcohol media. Zirconium or hafnium tetra-
chloride (0.012 mol) was mixed with the correspond-
ing alcohol (20 mL) and heated to 100°C (HCl release
was observed). Then phthalodinitrile (6.10 g, 0.048 mol)
was added, after its dissolving urea (1.40 g, 0.023 mol)
was added. The reaction mixture was heated to the
boiling of the alcohol and kept for 8–10 hours. After
cooling, the solution was filtered, the resulting precip-
itate was first washed with toluene and a small amount
of methanol, and then within 4 hours was extracted
with methanol in a Soxhlet apparatus from excess
phthalodinitrile and products of metal tetrachloride
hydrolysis. The resulting product was air-dried. The
yields of the final products are shown in Table 1.
Bis(1-phenyl-4,4,4-trifluoro-1,3-butanedionato)haf-
1
nium(IV) phthalocyanine. H NMR (400 MHz, chlo-
Synthesis of PcZr(OH)2 and PcHf(OH)2
by Hydrolysis of Corresponding PcMCl2
roform-d), δ, ppm: 9.54–9.43 (m, 2H), 9.31 (d, J =
7.5 Hz, 2H), 9.14 (dd, J = 5.6, 3.0 Hz, 1H), 9.09 (d, J
= 7.5 Hz, 1H), 8.92 (d, J = 7.5 Hz, 2H), 8.19 (t, J = 7.2
Hz, 2H), 8.15–8.06 (m, 2H), 8.01 (t, J = 7.3 Hz, 2H),
7.95–7.87 (m, 2H), 7.45–7.32 (m, 2H), 7.11–6.96 (m,
4H), 6.75 (dd, J = 8.3, 1.1 Hz, 1H), 6.70 (dd, J = 8.3,
1.1 Hz, 3H), 5.08 (s, 2H).
PcZr(OH)2. PcZrCl2 (5 g, 0.007 mol) was sus-
pended under stirring and heating with 25 mL of 25%
aqueous ammonia solution. The mixture was kept at
95°C for 12 hours, cooled, filtered. The obtained pre-
cipitate was washed on the filter 3 times with 10 mL of
water, then 3 times with the same amount of metha-
Bis(dibenzoylmethanato)zirconium(IV) phthalocya-
1
nol, and 2 times with 5 mL of methyl-tert-butyl ether. nine. H NMR (400 MHz, chloroform-d), δ, ppm:
The product was dried at room temperature for 9.37 (dd, J = 5.7, 3.0 Hz, 4H), 9.12 (dd, J = 5.5, 3.1
24 hours. Yield, 4.15 g (88%).
Hz, 4H), 8.29 (dd, J = 5.7, 2.9 Hz, 4H), 8.03 (dd, J =
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
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SYNTHESIS AND REACTIVITY OF ZIRCONIUM AND HAFNIUM
Table 2. Reaction conditions and yields of PcML2
Ligand Original Pc
PcZrCl2
1491
Time, h
Yield, %
Source
[5]
4
4
5
5
57
61
77
50
Ph
CF3
PcHfCl2
PcZr(OH)2
PcHf(OH)2
O
O −
PcZrCl2
5–6
5–6
5
70
75
53
36
Ph
Ph
O −
PcHfCl2
Zr(OH)2
PcHf(OH)2
[10]
[4]
[4]
[4]
[9]
O
5
PcZrCl2
6
6
3
3
39
37
60
46
OEt
O −
PcHfCl2
PcZr(OH)2
PcHf(OH)2
O
PcZrCl2
3–5
3–5
5
30
28
85
60
Oi-Pr
O −
PcHfCl2
PcZr(OH)2
PcHf(OH)2
O
5
PcZrCl2
3–5
3–5
3
25
25
64
45
Ph
OEt
O −
PcHfCl2
PcZr(OH)2
PcHf(OH)2
O
3
C9H19COO–
PcZrCl2
5
5
2
2
68
62
63
73
PcHfCl2
PcZr(OH)2
PcHf(OH)2
5.8, 2.9 Hz, 4H), 7.46 (t, J = 7.3 Hz, 4H), 7.22 (t, J =
7.6 Hz, 8H), 7.06–6.99 (m, 8H), 5.71 (s, 2H).
Bis(isopropyl 3-oxobutanoato)zirconium(IV) phtha-
1
locyanine (mix of cis- and trans-isomers). H NMR
(400 MHz, chloroform-d), δ, ppm: 9.51–9.13 (m,
8H), 8.31–7.75 (m, 8H), 4.03 (p, J = 6.3 Hz, 1H),
3.86 (p, J = 6.3 Hz, 1H), 3.47 (s, 1H), 3.42 (s, 1H),
1.40 (d, J = 7.2 Hz, 3H), 1.19 (d, J = 6.3 Hz, 3H), 1.03
(s, 3H), 0.79 (s, 3H), 0.11 (d, J = 6.3 Hz, 3H), 0.01 (d,
J = 6.1 Hz, 3H).
Bis(dibenzoylmethanato)hafnium(IV) phthalocya-
1
nine. H NMR (400 MHz, chloroform-d), δ, ppm:
9.28 (dd, J = 5.6, 3.0 Hz, 4H), 9.04 (dd, J = 5.6,
3.0 Hz, 4H), 8.21 (dd, J = 5.7, 2.9 Hz, 4H), 7.96 (dd,
J = 5.7, 2.9 Hz, 4H), 7.45–7.32 (m, 4H), 7.16–7.05
(m, 8H), 6.97–6.89 (m, 8H), 5.58 (s, 2H).
Bis(isopropyl 3-oxobutanoato)hafnium(IV) phthalo-
cyanine (mix of cis- and trans- isomers). 1H NMR (400
MHz, chloroform-d), δ, ppm: 9.48–9.16 (m, 8H),
8.15–7.82 (m, 8H), 4.02 (p, J = 6.2 Hz, 1H), 3.85 (p,
J = 6.3 Hz, 1H), 3.50–3.36 (m, 2H), 1.52–1.38 (m,
3H), 1.20 (d, J = 6.4 Hz, 3H), 1.03 (s, 3H), 0.80 (s,
3H), 0.19–0.03 (m, 6H).
Bis(ethyl 3-oxobutanoato)zirconium(IV) phthalocy-
1
anine (mix of cis- and trans-isomers). H NMR (300
MHz, Chloroform-d) δ 9.73–9.34 (m, 8H), 8.36–
8.06 (m, 8H), 3.93–3.49 (m, 4H), 3.34–2.87 (m, 2H),
1.23 (s, 3H), 1.06 (s, 3H), 0.99 (t, J = 7.1 Hz, 3H), 0.88
(t, J = 7.1 Hz, 3H).
Bis(ethyl 3-oxobutanoato)hafnium(IV) phthalocyanine
(mix of cis- and trans-isomers). 1H NMR (300 MHz, chlo-
roform-d), δ, ppm: 9.82–9.01 (m, 8H), 8.53–7.84 (m,
8H), 3.90–3.54 (m, 4H), 3.33–2.81 (m, 2H), 1.20 (s,
3H), 1.14–0.93 (m, 6H), 0.84 (t, J = 7.1 Hz, 3H).
Bis(ethyl
3-oxo-3-phenylpropanoato)zirco-
nium(IV) phthalocyanine (mix of cis- and trans-iso-
1
mers). H NMR (300 MHz, chloroform-d), δ, ppm:
9.54 (dd, J = 43.7, 7.3 Hz, 4H), 9.23 (dd, J = 52.1,
7.2 Hz, 4H), 8.45–8.21 (m, 4H), 8.13 (dt, J = 22.7,
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 65 No. 10 2020

1492
CHERNII et al.
R1
R2
О
О
О
R2
N
R1
N
О
M
N
R1 = Ph, R2 = CF3
R1 = R2 = Ph
R1 = Me, R2 = OEt
R1 = Me, R2 = Oi-Pr
R1 = Ph, R2 = OEt
N
N
N
N
N
OH
HO
N
N
N
N
N
M
N
N
R
R
О
О
N
О
О
M
N
M = Zr, Hf
R = C9H19
N
N
N
N
N
N
N
Fig. 2. Scheme of synthesis of PcML from PcM(OH) .
2
2
7.0 Hz, 4H), 7.49–7.33 (m, 2H), 7.24–7.04 (m, 5H), hydrogen chloride as HCl evolution) it reacts with the
6.87–6.78 (m, 1H), 6.76–6.69 (m, 2H), 4.53–4.33 phthalodinitrile. All reactions were carried out by boil-
(m, 2H), 4.06–3.73 (m, 2H), 3.52–2.98 (m, 2H), 1.08 ing in high-boiling alcohols (T = 140–220°C) in the
(t, J = 7.1 Hz, 3H), 1.01 (t, J = 7.1 Hz, 3H).
presence of urea since in [19] the possibility of forma-
tion of side-product non-metallic phthalocyanine in
the absence of an ammonia donor is reported. Accord-
ing to the data in Table 1, the increase in the temperature
of the reaction mixture slightly increases in the yields of
the final products. The synthesis of PcM(OH)2 by this
method results in rather low yields, according to data
of IR spectroscopy and elemental analysis on metal,
purity of obtained complexes are quite low. In the case of
performing this reaction without urea, or in the presence
of pyridine instead of urea, it does not pass at all.
Another method of obtaining of PcM(OH)2 is the
hydrolysis of the corresponding PcMCl2 (Fig. 1,
scheme B). As noted in [20], PcMCl2 are unstable and
in the process of purification, they are hydrolyzed to
products of the general formula PcM(OH)2, where
M = Zr, Hf. Here we have shown that PcMCl2 are
more hydrolytically stable than was considered by the
authors in [20] and in our previous research [18].
Thus, the hydrolysis of PcMCl2 did not occur upon
boiling for 8 h in butanol saturated with water, and
only partial hydrolysis was observed upon PcMCl2
interaction with 10% aqueous ammonia upon stirring
for 72 hours at room temperature. Partial hydrolysis
was also observed when using water-pyridine or tri-
ethylamine systems. We have determined that boiling
in 25% aqueous ammonia solution for 12 hours are the
most effective conditions for hydrolysis of PcMCl2
(Table 1).
Bis(ethyl 3-oxo-3-phenylpropanoato)hafnium(IV)
phthalocyanine (mix of cis- and trans-isomers).
1H NMR (300 MHz, chloroform-d), δ, ppm: 9.55
(dd, J = 42.5, 7.2 Hz, 4H), 9.24 (dd, J = 50.8, 7.2 Hz,
4H), 8.53–8.02 (m, 8H), 7.58–7.31 (m, 2H), 7.25–
7.05 (m, 5H), 6.83–6.74 (m, 1H), 6.77–6.67 (m, 2H),
4.46–4.30 (m, 2H), 3.98–3.70 (m, 2H), 3.42–2.90
(m, 2H), 1.07 (t, J= 7.1 Hz, 3H), 0.99 (t, J= 7.1 Hz, 3H).
Bis(decanoato)zirconium(IV)
phthalocyanine.
1H NMR (400 MHz, chloroform-d), δ, ppm: 9.20 (s,
8H), 8.02 (s, 8H), 1.19 (h, J = 6.4 Hz, 4H), 1.07 (dt,
J = 13.8, 7.0 Hz, 4H), 0.97 (dt, J = 14.7, 6.9 Hz, 4H),
0.88–0.72 (m, 10H), 0.51 (p, J = 7.5 Hz, 4H), 0.42 (t,
J = 7.5 Hz, 4H), 0.20 (p, J = 7.6 Hz, 4H), 0.00 (p, J =
7.6 Hz, 4H).
Bis(decanoato)hafnium(IV)
phthalocyanine.
1H NMR (400 MHz, chloroform-d), δ, ppm: 9.42–
9.11 (m, 8H), 8.03 (dd, J = 5.8, 2.9 Hz, 8H), 1.12 (p,
J = 6.5 Hz, 4H), 1.02 (dq, J = 9.3, 6.7 Hz, 4H), 0.92
(dt, J = 15.0, 6.9 Hz, 4H), 0.80–0.68 (m, 10H), 0.48
(p, J = 7.5 Hz, 4H), 0.40 (t, J = 7.6 Hz, 4H), 0.18 (p,
J = 7.4 Hz, 4H), 0.00 (p, J = 7.5 Hz, 4H).
RESULTS AND DISCUSSION
One of the methods of synthesis of PcM(OH)2 is
the use of the corresponding metal tetrachlorides as
starting compounds and high-boiling alcohols as sol-
vents (Fig. 1, scheme A) [18, 19]. During the reaction,
The reactivity of the obtained PcM(OH)2 was
first, the metal alkoxide is formed and only after com- investigated in reactions with β-diketones and deca-
plete removal of the hydrogen chloride (release of noic acid for ligands shown on the scheme in Fig. 2.
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SYNTHESIS AND REACTIVITY OF ZIRCONIUM AND HAFNIUM
1493
2. Yu. S. Krasnov, G. Ya. Kolbasov, I. N. Tretyakova,
et al., Solid State Ionics 180, 928 (2009).
It was found that the reactivity of PcM(OH)2 is
generally similar to PcMCl2 in their reactions with
β-diketones (1-phenyl-4,4,4-trifluoro-1,3-butanedi-
one, dibenzoylmethane) and decanoic acid (Table 2).
However, in the reactions with β-ketoesters (ethyl
3-oxobutanoate, isopropyl 3-oxobutanoate, ethyl
3-oxo-3-phenylpropanoate), the yields of reactions
with PcM(OH)2 as the starting compounds were sig-
nificantly higher than those with PcMCl2. Such an
increase in yields of PcM(OH)2 reactions is suggested
due to the absence of HCl release and consequently
the absence of hydrolysis of the ketoester group.
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Thus, it was found that the synthesis of PcZr(OH)2
and PcHf(OH)2 based on the corresponding alkoxides
occurs with low yields (25–40%), and raising of the
reaction temperature from 140 to 220°C increases the
product yield insignificantly. It is shown that reaction
of hydrolysis of PcMCl2 passes effectively in more
strict conditions (boiling in 25% aqueous ammonia
solution for 12 hours) than reported earlier (boiling in
pyridine with 5% of water or in water-alkaline isopro-
panol for 2 hours), use of such stricter conditions gives
possibility to obtain PcZr(OH)2 and PcHf(OH)2 with
high yields. For reactions with acid-sensitive
β-ketoester ligands, the use of PcZr(OH)2 and
PcHf(OH)2 as starting complexes provides higher
yields and purity of the target products comparing to
reaction starting from corresponding PcMCl2.
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FUNDING
https://doi.org/10.1016/j.ccr.2018.10.007
This publication is based on work “Evaluation of phtha-
locyanine complexes as chaperone mimetics to prevent pro-
tein heat-induced fibrillization in the food industry“ sup-
ported by Award No. FSA3-19-65501-0 of the U.S. Civilian
Research & Development Foundation (CRDF Global) and
by the Ministry of Education and Science of Ukraine under
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