Synthesis and properties of Copper(II) tetra(2-alkyl-4,5-benzimidazolo)- and tetra(2,2′-dimethyl-4,5-benzodiazepino)porphyrazines

Article abstract of DOI:10.1023/A:1023343918982

4,5-Diaminophthalonitrile was reacted with carboxylic acids and acetylacetone to synthesize 2-alkyl-5,6-dicyanobenzimidazoles and 2,2′-dimethyl-5,6-dicyanobenzodiazepine, respectively. The products were converted into copper(II) porphyrazines. An effect o

Full text of DOI:10.1023/A:1023343918982

Russian Journal of General Chemistry, Vol. 72, No. 10, 2002, pp. 1616 1619. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 10, 2002,
pp. 1715 1718.
Original Russian Text Copyright
2002 by Balakirev, Kudrik, Shaposhnikov.
Synthesis and Properties
of Copper(II) Tetra(2-alkyl-4,5-benzimidazolo)-
and Tetra(2,2 -Dimethyl-4,5-benzodiazepino)porphyrazines
A. E. Balakirev, E. V. Kudrik, and G. P. Shaposhnikov
Ivanovo State University of Chemical Engineering, Ivanovo, Russia
Received December 29, 2000
Abstract 4,5-Diaminophthalonitrile was reacted with carboxylic acids and acetylacetone to synthesize
2-alkyl-5,6-dicyanobenzimidazoles and 2,2 -dimethyl-5,6-dicyanobenzodiazepine, respectively. The products
were converted into copper(II) porphyrazines. An effect of the heterocyclic residue on the physicochemical
and spectral properties of the porphyrazines was revealed.
One of interesting ways to modifying phthalocya-
nine molecules is their peripheral substitution by
heterocyclic residues, such as imidazole and diazepine.
N
NC
NC
NH2
NH2
NC
NC
RCOOH
R
NH
I
II IV
The practical interest in these compounds is as-
sociated with the fact that benzimidazole substituents
impart to macroheterocycles fluorophoric properties
[1]. Moreover, the combination in the imidazole struc-
ture of both pyrrole and pyridine nitrogen atoms
makes possible diverse chemical modification of these
compounds.
R = CH3 (II), C3H7 (III), C5H11 (IV).
2,2 -Dimethyl-5,6-dicyanobenzazepine was synthe-
sized by reaction of diamine I with a slight excess
with acetylacetone.
CH3
The synthesis and properties of tetraazaporphynes
with annelated imidazole and diazepine residues have
been reported [2, 3]. The information on phthalo-
cyanine analogs of these systems is limited by our
communication concerning the synthesis and proper-
ties of 5,6-dicyanobenzimidazole and its pophyrazine
derivatives [4]. Proceeding with this work and aiming
at assessing the effect of the annelated heterocyclic
residue on the physicochemical properties of porphyra-
zines, we synthesized copper(II) tetra(2-alkyl-4,5-
benzimidazolo)- and tetra(2,2 -dimethyl-4,5-benzodi-
azepino)porphyrazines.
COCH3
COCH3
NC
NC
N=C
N=C
I + H2C
CH2
CH3
V
The powder-like colorless (II, III) or light yellow
(IV) benzimidazoles are soluble in hot water, DMF,
acetone, dilute acids and alkalis, while the powder-
like colorless benzodiazepine V, in DMF, acetone,
dilute HCl and, poorly, in alcohols. The HCl solution
is violet, on account of the formation of a stable salt
A [5].
The starting material in the synthesis of 2-alkyl-
5,6-dicyanobenzimidazoles II IV and 2,2 -dimethyl-
5,6-dicyanobenzodiazepine (V) was 4,5-diamino-
phthalonitrile (I) synthesized by reduction of 5-amino-
4-nitrophthalonitrile with tin dichloride in concen-
trated hydrochloric acid [4].
CH3
NC
NC
N C
+
CH2
CH3
N C
A
4,5-Diaminophthalonitrile (I) was reacted with an
excess of a carboxylic acid (acetic, butyric, capronic)
under reflux to obtain 2-methyl-, 2-propyl, and
2-pentyl-5,6-dicyanobenzimidazoles (II IV).
The structure and composition of compounds II V
were proved by elemental analysis and IR spec-
troscopy.
1070-3632/02/7210-1616$27.00 2002 MAIK Nauka/Interperiodica

SYNTHESIS AND PROPERTIES OF COPPER(II) TETRA(2-ALKYL-4,5-BENZIMIDAZOLO)-
1617
The IR spectra of compounds II V have common
absorption bands. Thus, in the 2240 2232 cm 1 range,
there are bands characteristic of cyano groups, while
The IR spectra of compounds VI IX proved to be
difficult to assign, since the absorption bands are
broadened and overlapping, on account of solid-state
association effects.
1
at 1664 cm , an absorption band characteristic of the
imidazole and diazepine C=N band [6]. Compounds
The heterocyclic substituents strongly affect the
electronic absorption spectra. Compounds VII and
VIII in DMF give two bands at 642 650 and 694
711 nm, whose intensity depends on the porphyrazine
concentration. Thus, dilution produces growth of the
long-wave band and diminishing of the short-wave
band. Such behavior points to the association of the
porphyrazines in the solution via hydrogen bonding
involving the imidazole fragments. Apparently, the
absorption band at 642 650 nm relates to associated
forms, while that at 694 711 nm, to monomeric.
II IV give C H and C C absorption bands at 2936
1
2928 and 720 704 cm , respectively, and the inten-
sity of these bands increases with increasing alkyl
chain length [6].
The formation of the imidazole ring is also evi-
denced by the fact that the products acquire solubility
in aqueous mineral acids and alkalis, on account of
the presence in their molecules of a pyrrole and a
pyridine nitrogen atoms.
Compounds II V were used for preparing copper
porphyrazines VI IX. The synthesis of complexes
VI IX was accomplished by fusing nitriles II V with
copper(II) acetates at 250 C for 1 h.
We could not compare the electronic absorption
spectra in DMF for all the compounds studied, since
copper(II) tetrabenzimidazolo- and tetrabenzodiaze-
pinoporphyrazines, as well as copper(II) phthalocy-
anine are sparingly soluble in this solvent. Therefore,
we compared the electronic absorption spectra in con-
centrated sulfuric acid.
NC
A
NC
II V
In going from organic solvents to concentrated
sulfuric acid, the Q bands of compounds VII and VIII
shift bathochromically by 90 nm, which is associated
by the protonation of the molecule both by the meso-
nitrogen atoms of the porphyrazine ring, as well as by
the nitrogen atoms of the heterocyclic fragments [7].
The occurrence of the two protonation processes
makes the absorption bands difficult to assign.
A
A
A
N
N
N
N
Cu(CH3COO)2
N
Cu
N
N
N
A
It should be noted that the bathochromic shift of
the Q band also increases with increasing chain length
in the alkyl substituent, since the enhancing basicity
of the imidazole pyridine atoms produces a more
profound protonation (see figure). The electronic
absorption spectrum of diazepine derivative IX shows
two more long-wave absorption bands compared with
the spectrum of copper(II) phthalocyanine (see figure).
VI IX
N
N
CH3 (VI),
C3H7 (VII),
A
NH
NH
CH3
N==C
N==C
N
CH2 (IX).
C5H11 (VIII),
NH
CH3
EXPERIMENTAL
The powder-like bluish-green complexes VI IX
are insoluble in water, readily soluble in concentrated
sulfuric acid, and much worse soluble in DMF and
dilute hydrochloric acid.
The electronic absorption spectra were measured
on a Hitachi UV-2000 spectrophotometer, and the IR
spectra, on a Specord M-80 spectrophotometer.
Four methyl substituents in the tetrabenzimidazolo-
pophyrazine molecule do not render it more soluble
in organic solvents, whereas four propyl or four pentyl
groups make it slightly soluble in chloroform or
acetone, respectively.
2-Alkyl-5,6-dicyanobenzimidazoles II IV.
A
mixture of 87.4 mmol of carboxylic acid and 6.3 mmol
of compound I was heated under reflux for 2 h,
cooled to room temperature, and poured into 50 ml of
water with ice. The precipitate that formed was
filtered off, washed with water, recrystallized from
water, and dried at 120 C.
Complexes VI IX were characterized by elemental
analysis and IR and electronic spectroscopy.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 10 2002

1618
BALAKIREV et al.
ground and dissolved in a minimum (10 50 ml) of
D
1.2
concentrated sulfuric acid. The solution was poured
into 50 ml of water. The precipitate that formed was
filtered off, washed with water to neutral, and purified
by treatment with hot acetonitrile.
1
0.9
0.6
2
Copper tetra(2-methyl-4,5-benzimidazolo)-
porphyrazine (VI), yield 45%. Electronic absorption
spectrum, max, nm (H2SO4): 310, 761. Found, %: C
60.8; H 3.1; N 28.0. C40H24CuN16. Calculated, %: C
60.6; H 3.0; N 28.3. Copper tetra(2-propyl-4,5-
benzimidazolo)porphyrazine (VII), yield 38%. Elec-
tronic absorption spectrum, max, nm: in DMF: 643,
694; in H2SO4: 310, 426, 786. Found, %: C 64.0; H
4.8; N 24.1. C48H40CuN16. Calculated, %: C 63.7; H
4.4; N 24.5. Copper tetra(2-pentyl-4,5-benzimidaz-
olo)porphyrazine (VIII), yield 67%. Electronic
absorption spectrum, max, nm: in DMF: 650, 711;
in H2SO4: 310, 426, 802. Found, %: C 66.6; H 5.8; N
21.8. C56H56CuN16. Calculated, %: C 66.1; H 5.5;
N 22.0.
0.3
0
3
300
400
500
700
900 , nm
Electronic absorption spectra of copper(II) por-
phyrazines in concentrated sulfuric acid (c 5 10 M).
(1) Copper tetra(2-propyl-4,5-benzimidazolo)porphyr-
azine (VII), (2) copper tetra(2-pentyl-4,5-benzimidazolo)-
porphyrazine, and (3) copper tetra(2,2 -dimethyl-4,5-
benzodiazepino)porphyrazine (IX).
6
2-Methyl-5,6-dicyanobenzimidazole (II), yield
61%, mp 243 245 C. IR spectrum, , cm : 3416
Compounds VI IX are poorly soluble in DMF,
acetone, chloroform, and aqueous mineral acids and
alkalis, and readily soluble in concentrated sulfuric
acid.
1
(NH), 2936 (CH), 2232 (CN), 1664 (C=N), 1600
(C=C), 720 (C C). Found, %: C 66.0; H 3.5; N 30.6.
C10H6N4. Calculated, %: C 65.9; H 3.3; N 30.8.
2-Propyl-5,6-dicyanobenzimidazole (III), yield 38%,
Tetra(2,2 -dimethyl-4,5-benzodiazepino)por-
phyrazine (IX) was prepared in a similar way from
0.5 mmol of compound V and 0.15 mmol of copper(II)
acetate, yield 27%. Electronic absorption spectrum,
max, nm (H2SO4): 310, 772, 798. Found, %: C 65.7;
H 4.5; N 23.2. C52H40CuN16. Calculated, %: C 65.5;
H 4.2; N 23.5.
1
mp 239 241 C. IR spectrum, , cm : 3416 (NH),
2930 (CH), 2232 (CN), 1664 (C=N), 1600 (C=C), 716
(C C). Found, %: C 68.9; H 4.7; N 26.4. C12H10N4.
Calculated, %: C 68.6; H 4.8; N 26.7. 2-Pentyl-5,6-
dicyanobenzimidazole (IV), yield 40%, mp 235
1
237 C. IR spectrum, , cm : 3416 (NH), 2936 (CH),
2232 (CN), 1664 (C=N), 1600 (C=C), 704 (C C).
Found, %: C 71.1; H 5.9; N 23.0. C14H14N4. Cal-
culated, %: C 70.6; H 5.9; N 23.5.
ACKNOWLEDGMENTS
The work was financially supported by the Mi-
nistry of Education of the Russian Federation in the
framework of the Program for Support of Basic
Natural Science (project no. 97-0-9.4-381).
2,2 -Dimethyl-5,6-dicyanobenodiazepine (V). A
mixture of 3 mmol of acetylacetone and 3 mmol of
compound I in 20 ml of ethanol and 0.06 ml of glacial
acetic acid was heated under reflux for 2 h, cooled to
room temperature, and poured into 50 ml of water
with ice. The precipitate that formed was filtered off,
washed with water, recrystallized from water, and
dried at 120 C. Yield 35%, mp 218 222 C. IR spec-
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SYNTHESIS AND PROPERTIES OF COPPER(II) TETRA(2-ALKYL-4,5-BENZIMIDAZOLO)-
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