Porphyrazine with bulky 2-(1-adamantyl)-5-phenylpyrrol-1-yl periphery tuning its spectral and electrochemical properties

Article abstract of DOI:10.1016/j.poly.2015.05.033

The synthesis and physicochemical properties of a novel porphyrazine possessing an alternate system of two peripheral substituents, 2-(1-adamantyl)-5-phenylpyrrol-1-yl and dimethylamino, are presented. Precursor maleonitriles were characterized using X-ra

Full text of DOI:10.1016/j.poly.2015.05.033

Polyhedron 98 (2015) 217–223
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Porphyrazine with bulky 2-(1-adamantyl)-5-phenylpyrrol-1-yl
periphery tuning its spectral and electrochemical properties
Michal Kryjewski a, Ewa Tykarska b, Tomasz Rebis c, Jolanta Dlugaszewska d, Magdalena Ratajczak d,
e
Anna Teubert , Jacek Gapinski f,g, Adam Patkowski f,g, Jaroslaw Piskorz a, Grzegorz Milczarek c,
´
a
Maria Gdaniec h, Tomasz Goslinski b, , Jadwiga Mielcarek
⇑
a Department of Inorganic and Analytical Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
b Department of Chemical Technology of Drugs, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
c Institute of Chemistry and Technical Electrochemistry, Poznan University of Technology, Piotrowo 3, 60-965 Poznan, Poland
d Department of Genetics and Pharmaceutical Microbiology, Poznan University of Medical Sciences, Swiecickiego 4, 60-781 Poznan, Poland
e Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
f Faculty of Physics, Department of Molecular Biophysics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
g NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland
h Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and physicochemical properties of a novel porphyrazine possessing an alternate system of
two peripheral substituents, 2-(1-adamantyl)-5-phenylpyrrol-1-yl and dimethylamino, are presented.
Precursor maleonitriles were characterized using X-ray crystallography. Novel porphyrazine was sub-
jected to spectroscopic studies, including the determination of fluorescence quantum yield and singlet
oxygen quantum yield. Moreover, its electrochemical and spectroelectrochemical properties were inves-
tigated. The antimicrobial photodynamic activities of the novel porphyrazine encapsulated in various
liposomal formulations were tested against Staphylococcus aureus and Pseudomonas aeruginosa.
Ó 2015 Elsevier Ltd. All rights reserved.
Received 3 April 2015
Accepted 25 May 2015
Available online 5 June 2015
Keywords:
Adamantane
Photochemistry
Porphyrazines
Spectroelectrochemistry
Voltammetry
1. Introduction
photochemistry of various Pzs bearing 2,5-dimethylpyrrol-1-yl,
2,5-di(2-thienyl)pyrrol-1-yl and 2,5-diphenylpyrrol-1-yl sub-
Porphyrazines (Pzs) form a class of macrocycles related to por-
phyrins, phthalocyanines and corroles [1]. Pzs have been tested as
potential photosensitizers for photodynamic therapy [2], sensors
[3] and building blocks useful in dip-pen nanolithography [4].
Pzs can be modified by the introduction of a metal cation into
the core or peripheral substitutions. The most common periphery
of Pzs at their b-positions constitute nitrogen and sulfur residues
[1,5], including annulated five, six and seven-membered rings. It
is noteworthy that numerous examples of aminoporphyrazines
possessing annulated diazepine [6], pyrazine [7] (also known as
aza-phthalocyanines), 1,2,5-selenodiazole [8], and imidazole [9]
rings are known. However, there are limited data on Pzs
substituted directly at their b positions with heteroaromatic rings.
In the course of our research we reported the synthesis and
stituents [10–14]. In the present study, we report the synthesis,
spectroscopic, electrochemical, and antimicrobial properties of
novel Pz possessing 2-(1-adamantyl)-5-phenylpyrrol-1-yl and
dimethylamino groups. We found that bulky 2-(1-adamantyl)-5-
phenylpyrrol-1-yl substituents tuned photochemical and electro-
chemical properties of the investigated macrocycle. Adamantane
moiety as a part of various biologically active compounds revealed
beneficial features in medicinal chemistry [15,16]. In contrast to
phthalocyanine macrocycles, adamantane bearing porphyrazine
has not been reported so far. Adamantyl groups have been linked
with phthalocyanine macrocycles at their peripheral and non-
peripheral sites via sulfur [17,18], amino and oxygen groups [19]
or even more complex substituents [20,21]. In addition, the photo-
cytotoxicities of phthalocyanines bearing peripheral adamanty-
lethoxy- or axial adamantylmethoxy groups have been tested on
human red blood cells [22] and against Candida albicans [23],
respectively.
⇑
Corresponding author. Tel.: +48 61 854 66 31.
E-mail address: tomasz.goslinski@ump.edu.pl (T. Goslinski).
http://dx.doi.org/10.1016/j.poly.2015.05.033
0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.

218
M. Kryjewski et al. / Polyhedron 98 (2015) 217–223
CH2Cl2. The organic extracts were dried with MgSO4, concentrated
2. Experimental
and chromatographed using n-hexane:EtOAc 7:1 to give 7 as a
yellow solid (151 mg, 75% yield). M.p. 155 °C; Rf = 0.27 (n-
hexane:EtOAc 7:1, v/v); 1H NMR (400 MHz, pyridine-d5) d 7.67 (d,
3J = 7.0 Hz, 2H, 2’,6’-C6H5), 7.43 (t, 3J = 7.5 Hz, 2H, 3’,5’-C6H5), 7.31
(t, 3J = 7.5 Hz, 1H, 4’-C6H5), 6.38 (d, 3J = 4.0 Hz, 1H, pyrrole-H), 6.25
(d, 3J = 4.0 Hz, 1H, pyrrole-H), 2.55 (s, 6H, CH3), 2.30 (d,
3J = 11.5 Hz, 3H, adamantane-H), 2.14 (d, 3J = 11.0 Hz, 3H, adaman-
tane-H), 2.00 (s, 3H, adamantane-H), 1.70 (q, 3J = 12.5 Hz, 6H,
adamantane-H); 13C NMR (100 MHz, pyridine-d5) d 147.6, 139.3,
133.6, 132.9, 129.0, 128.9, 128.1, 120.9, 113.3, 109.9, 109.0, 91.9,
42.6, 40.9, 36.7, 35.5, 28.9; MS (ES) m/z 397 [M + H]+, 419
[M+Na]+; Anal. Calc. for: C26H28N4 C 78.75; H 7.12; N 14.13;
2.1. 2-[2-(1-Adamantyl)-5-phenyl-1H-pyrrol-1-yl]-3-amino-(2Z)-
butene-1,4-dinitrile (6)
1-(1-Adamantyl)-4-phenylbutane-1,4-dione 4 (1.48 g, 5.0 mmol),
diaminomalonitrile 5 (540 mg, 5.0 mmol) and P2O5 (190 mg) were
stirred in methanol (60 mL) and heated under reflux for 2 h. After
that time, an additional amount of P2O5 in three portions (800 mg,
7.0 mmol altogether) was added within 2 h and kept under reflux
whilestirringforthe next20 h. Nextthereactionmixturewas cooled
toroomtemperatureandevaporatedtodryness. Thedryresiduewas
taken into CH2Cl2 and filtered to remove unreacted 5 and side-
products. The filtrate containing the crude product in CH2Cl2 was
concentrated and chromatographed (CH2Cl2) to give 6 as yellow,
crystalline solid (556 mg, 30% yield). M.p. 190 °C dec.; Rf = 0.43
(CH2Cl2); 1H NMR (400 MHz, DMSO-d6) d 7.85 (bs, 2H, NH2),
7.45–7.31 (m, 5H, C6H5), 6.24 (d, 3J = 3.5 Hz, 1H, pyrrole-H), 6.09
(d, 3J = 3.5 Hz, 1H, pyrrole-H), 2.16–1.94 (m, 6H, adamantane-H),
1.89 (d, 3J = 11.5 Hz, 3H, adamantane-H), 1.72 (q, 3J = 12.0 Hz, 6H,
adamantane-H); 13C NMR (100 MHz, DMSO-d6) d 144.2, 135.8,
132.3, 131.7, 128.2, 128.1, 127.4, 118.3, 112.9, 110.0 107.8, 91.1,
40.9, 36.2, 34.1, 28.0; MS (ES) m/z 391 [M+Na]+; Anal. Calc. for
Found:
C 78.66; H 7.31; N, 13.80; Crystal data: C26H28N4,
M = 396.52, monoclinic, P21/n, a = 8.9116 (3) Å, b = 12.3745(4) Å,
c = 19.4130(7) Å, b = 94.599(3)°, V = 2133.9(1) Å3, Z = 4,
Dc = 1.234 gꢀcmꢁ1
, l(MoK ) = , T = 130 K, 16,460
reflections collected, 3905 independent reflections, Rint = 0.033,
0.074 mmꢁ1
a
hmax
25.35°, R1(obs.) = 0.038, wR2(all) = 0.086, 273 refined
=
parameters.
2.3. [2,7,12,17-Tetrakis(2-(1-adamantyl)-5-phenyl-1H-pyrrol-1-yl)-
3,8,13,18-tetrakis(dimethylamino)porphyrazinato]magnesium(II) (8)
C24H24N4: C, 78.23; H, 6.57; N, 15.21. Found: C, 78.06; H, 6.62; N,
Magnesium turnings (120 mg, 5.0 mmol), a small crystal of I2,
and n-butanol (45 mL) were heated under reflux for 6 h. After the
reaction mixture was cooled to room temperature, maleonitrile
derivative 7 (497 mg, 1.25 mmol) in DMF (2.5 mL) was added
and the mixture was heated under reflux for the next 16 h. After
being allowed to cool to room temperature, the dark green mixture
was filtered through Celite and the solvents were co-evaporated
with toluene (2 ꢂ 50 mL). Chromatography (CH2Cl2) was per-
formed twice to give the main product, porphyrazine (8) (75 mg,
15.24%. Crystal data: C24H24N4, M = 368.47, orthorhombic, P212121,
a = 8.3432(2) Å, b = 11.5355(2) Å, c = 20.5641(4) Å, V = 1979.15(7)
Å3, Z = 4, Dc = 1.237 gꢀcmꢁ1
, l(Cu Ka
) = 0.579 mmꢁ1, T = 130 K,
11267 reflections collected, 3879 independent reflections,
Rint = 0.016, hmax = 75.94°, R1(obs.) = 0.028, wR2(all) = 0.069, 253
refined parameters.
2.2. 2-[2-(1-Adamantyl)-5-phenyl-1H-pyrrol-1-yl]-3-
(dimethylamino)-(2Z)-butene-1,4-dinitrile (7)
15% yield) as
(CH2Cl2:CH3OH 1:1): kmax, nm (log
a
dark blue solid. Rf = 0.16 (CH2Cl2); UV–Vis
) 346 (4.35), 729 (4.26); IR
e
NaH (264 mg, 1.1 mmol, 60% dispersion in mineral oil) was sus-
pended in THF (10 mL) at (ꢁ12 °C) and stirred. Next 6 (186 mg,
0.5 mmol) in THF (6 mL) was added dropwise and stirred for
additional 30 min. Dimethyl sulfate (0.093 mL, 1.1 mmol) in THF
(2 mL) was added dropwise to the reaction mixture for 30 min at
(ꢁ10 °C) and stirred for 1 h. After that time, the reaction mixture
was allowed to warm to room temperature, stirred overnight and
poured into ice-water (100 mL). A water layer was extracted with
(cmꢁ1) 1581, 1558, 1120, 1063; 1H NMR (400 MHz, pyridine-d5)
d = 7.80 (d, 3J = 8 Hz, 5H, –C6H5), 7.67 (d, 3J = 9 Hz, 3H, –C6H5),
7.42–7.49 (m, 7H, –C6H5), 7.28–7.39 (m, 7H, –C6H5), 6.92–6.70
(m, 12H, –C6H5), 6.52–6.70 (m, 6H, –C6H5), 6.49 (d, 3J = 4 Hz, 3H,
pyrrole-H), 6.38 (d, 3J = 4 Hz, 1H, pyrrole-H), 6.32 (d, 3J = 4 Hz,
3H, pyrrole-H), 6.42 (3J = 4 Hz, 1H, pyrrole-H), 3.03, 3.61, 3.66,
3.70 (m, s, m, s, 24 H, 4 ꢂ N(CH3)2), 2.07–2.41 (m, 24H, adaman-
tane-H), 1.91–1.99 (m, 12H, adamantane-H), 1.63–1.73 (m, 24H,
Scheme 1. Synthesis of porphyrazine 8.

M. Kryjewski et al. / Polyhedron 98 (2015) 217–223
219
adamantane-H); 13C NMR (101 MHz, pyridine-d5) d = 149.5h, 146.7,
138.8, 136.7h, 134.8, 131.3, 130.2, 130.0, 129.6, 129.5, 129.2, 129.2,
129.0, 112.4, 111.5, 109.8, 43.5, 43.5, 38.0, 36.7, 30.1. MS m/z
(MALDI) 1611 [M+H]+.
the HPLC analysis revealed three peaks with virtually the same
UV–Vis spectra (see Supplementary data). NMR data of 8 were com-
pared with the results previously obtained for Pzs possessing an
alternate [12] and an non-alternate [11] system of dimethylamino
and pyrrolyl groups. In the cases above, diagnostic patterns of
dimethylamino group signals as one [12] (alternate system) or four
[11] of equal intensities singlet signals (non-alternate system) were
found. However, for Pz 8, a more complicated pattern of signals was
found. Moreover, in recording the variable-temperature, the NMR
spectra did not result in any simplification of the analyzed pattern
(see Supplementary data). We propose that it may be due to an
arrangement of pyrrolyl substituents, with three adamantane
moieties being on one side of the porphyrazine plane, and one on
the other side (Scheme 1). Signals of 30,40-pyrrolyl protons appear-
ing as four dublets with 3:1:3:1 integration seem to support our
observation.
3. Results and discussion
3.1. Synthesis
The aim of our studies was to obtain new porphyrazine
bearing
2-(1-adamantyl)-5-phenylpyrrol-1-yl
substituents.
Alkylation reaction of ethyl benzoyl acetate (1) with 1-adamantyl-
bromomethyl ketone (2) led to ester 3 (Scheme 1). The crude ester
was subjected to hydrolysis and oxidative decarboxylation, following
the previously published procedure, leading to the known com-
pound 4 [24]. By adapting the previously published procedure
[25], 1-(1-adamantyl)-4-phenyl-butane-1,4-dione (4) was used as
a substrate in the Paal-Knorr type reaction with diaminomaleoni-
trile (5) in methanol, in the presence of phosphorous pentoxide as
both a dehydrating and acidic agent, to give the novel maleonitrile
derivative 6. Product 6 was subjected to methylation reaction to
give 7 [26]. Mass spectra, elemental analyses and NMR experiments
confirmed the formation of the desired intermediate products (see
Supplementary data). Derivative 7 was used in the Linstead macro-
cyclization [27] reaction using magnesium n-butanolate in n-bu-
tanol, toward a new magnesium porphyrazine 8, which was
obtained in 15% of overall yield. The macrocycle was purified by
column chromatography and subsequently analyzed by HPLC.
Due to aggregation, typical for some porphyrazine compounds,
3.2. Crystallography
Two maleonitrile derivatives 6 and 7 (Fig. 1) were subjected to
crystallization that fortunately resulted in single crystals suitable
for X-ray analyses. The maleonitrile units show the expected cis-
geometry of the double bond. The exchange of a primary NH2
amino group present in 6 into a more bulky tertiary N(CH3)2 group
in 7 did not effectively influence the molecular conformation. The
amino group N atoms are sp2 hybridized with the sum of the bond
angles around N2 close to 360°. The electron lone pair of N2 is con-
jugated with the
p
-system of the maleonitrile moiety resulting in a
0
shortening of the formally single N2–C2 bond (1.339(2) ÅA in 6 and
0
1.353(2) ÅA in 7). The 2,5-substituted pyrrole ring is strongly
twisted relative to the maleonitrile unit attached to the pyrrole N
atom due to a steric overcrowding (dihedral angles 77.92(3)° in 6
and 70.43(4)° in 7). The phenyl ring is also similarly oriented rela-
tive to the pyrrole ring with the torsion angle N(31)–C(35)–C(36)–
C(37) of ꢁ126.8(1)° in 6 and ꢁ133.0(1)° in 7.
In both crystals, molecules are arranged into similarly con-
structed chiral (001) layers with the adamantyl groups protruding
from the layer surface; however, in the crystals of 6 the (001) lay-
ers are homochiral, whereas in 7 the layers of the opposite chirality
alternate along the z axis (Fig. S11, Supplementary data).
3.3. Photochemical studies
Photosensitizing properties of 8 were referred to those previ-
ously established for the standard zinc(II) phthalocyanine (ZnPc)
[28–30]. 1,3-Diphenylisobenzofuran (DPBF) was used as a chemi-
cal quencher of singlet oxygen. Solution of 8 and DPBF was irradi-
ated with light at the wavelength of 729 nm in DMF, corresponding
to the maximum of the Q-band. DPBF oxidation was UV–Vis mon-
itored with its absorbance decrease at 417 nm (Fig. 2). A compar-
ison of DPBF oxidation kinetic parameters of 8 and ZnPc allowed
the determination of the singlet oxygen generation yield value to
be UD = 0.17 in DMF.
Fluorescence spectra of Pz 8 were recorded both in DMF and
THF. The fluorescence quantum yields were calculated using
ZnPc as a reference, according to the method given by Ogunsipe
et al. [31]. The quantum yields were found to be UF = 0.031 and
0.039 in DMF and THF, respectively. The Stokes shifts are minor,
240 and 223 cmꢁ1 for DMF and THF, respectively, which confirms
a small difference in the geometry of the Pz 8 molecule in its sin-
glet, ground S0 and excited S1, states.
Photodegradation studies were conducted in DMF as a solvent,
changes in the absorption spectra are presented in Fig. 2b.
Experiments were performed both in aerobic conditions and with
limited access to air in order to find out whether oxygen influences
Fig. 1. The molecular structures of (a) 6 and (b) 7 showing the atom labeling
scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms
are shown as spheres of arbitrary radii.

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M. Kryjewski et al. / Polyhedron 98 (2015) 217–223
and the data is presented in Table 2 and Fig. 3. The obtained results
indicate that Pz 8 undergoes two quasi-reversible reduction pro-
cesses at E1/2 = ꢁ1.96 V (1) and E1/2 = ꢁ1.75 V (2) as well as two
reversible oxidations at E1/2 = ꢁ0.23 V (3) and E1/2 = 0.28 V (4).
The number of electrons transferred in all redox transitions, esti-
mated from the peak width in a DPV technique, is equal to one.
This is in good agreement with previously reported porphyrinoids,
where one electron transfer is typical [32,33].
For the electrochemically inactive metal ion center such as
Mg2+, it can be expected that all processes involve ligand – cen-
tered oxidations creating
p-cation radicals and reductions produc-
ing -anion radicals [7,32,33]. Both reduction couples (Fig. 3a)
p
demonstrate rather poor electrochemical reversibility with small
anodic peaks appearing on voltage reversal. However, the scan rate
from 25 to 250 mV/s correlates linearly versus v1/2 to the peak cur-
rent, which suggests diffusion controlled processes. Moreover, an
increase in the scan rate hardly affects the peak positions (see
Supplementary data). Although for the reduction processes the
reverse anodic peaks are not-well developed on the CV, the well-
defined peaks can be observed on DPV with the current ratio near
to unity. The Pz 8 shows two reversible oxidation processes. Anodic
to cathodic peak currents (ia/ic) are near to unity for the first and
second oxidation couple and do not vary significantly when the
scan rate is increased. Peak to peak separations recorded for
100 mV/s for the Pz/Pz+ and Pz+/Pz2+ oxidation process are 66
and 73 mV, respectively, which are close to the theoretical value
of ca. 60 mV for perfectly reversible systems. These values remain
more or less constant for the whole range of scan rates used during
the experiment. No kinetic limitations, suggesting fast charge
transfer, were observed. Anodic and cathodic currents of Pz/Pz+
and Pz+/Pz2+ couples linearly depend on the potential sweep rate
square root (see Supplementary data) indicating diffusion con-
trolled reactions. The obtained results indicate that Pz 8 is rela-
tively easy to oxidize with the first couple at ꢁ0.23 V versus
Fc/Fc+. This is attributed to the effect of nitrogen containing sub-
stituents bonded directly to porphyrazine ring. Dimethylamine
groups possess strong electron-donating properties which facili-
tate the appearance of cation radicals and effectively shifts oxida-
tion potential toward less positive values. Similar values have been
noticed for other amino-substituted Pzs [34–36]. However, the Pz 8
is more resistant to reduction in comparison to e.g. sulfur substi-
tuted Pzs [32,37–39].
The difference between the first oxidation and the first reduc-
tion processes (1.53 V) is assigned as the HOMO–LUMO gap for
porphyrazines without an active metal ion in the center, and is
in good agreement with the previously reported data [33]. This
value is in agreement with the HOMO–LUMO gap [40] (1.70 eV)
calculated from UV–Vis kmax, according to equation E = hc/k. It
seems that Pz 8 which revealed in solution fully reversible, fast
electron redox processes with relatively low formal potential,
may find applications as electrocatalyst in oxidation processes as
well as sensor in materials chemistry.
The monitoring of redox reactions using optical spectroscopy is
a powerful approach enabling the examination of macrocycles and
coordinated metal ion electronic structures. Thus, in situ spectro-
electrochemical measurements were applied to determine anionic
and cationic forms of the Pz. Changes in the UV–Vis spectra of Pz 8
Fig. 2. Changes in the UV–Vis spectra of DPBF and 8 in DMF during irradiation at
the Q-band (a), changes in the UV–Vis spectra of 8 in DMF during photodegradation
– aerobic conditions (b), absorbance, fluorescence and excitation spectra of 8 in
DMF (c).
the decomposition process. Kinetic studies of photobleaching
revealed a two-step process, both following first-order kinetics,
parameters are presented in Table 1. Deaeration did not signifi-
cantly impact k parameters.
Table 1
Kinetic parameters of photodecomposition of 8.
Conditions
Stage
I
II
3.4. Electro- and spectroelectrochemical properties
102 (k
D
k) [sꢁ1
]
103 (k
D
k) [sꢁ1
]
Aerobic
Limited access to air
0.90 0.06
1.00 0.08
1.26 0.06
1.20 0.07
The electrochemical properties of 8 were investigated by using
cyclic voltammetry (CV) and differential pulse voltammetry (DPV)

M. Kryjewski et al. / Polyhedron 98 (2015) 217–223
221
Table 2
Voltammetric data of the Pz 8 recorded at 100 mV/s.
Pzꢁ/Pz2ꢁ
Pz/Pzꢁ
Pz+/Pz
Pz2+/Pz+
D
E1/2
E1/2 [V]
EP [mV]
ipa/ipc
ꢁ1.96
ꢁ1.75
ꢁ0.23
66
0.94
0.28
73
0.82
1.52
D
–
–
–
–
Fig. 4. In situ UV–Vis spectral changes of 8 at constant potential Eapp = 0.14 V,
Eapp = 0.66 V (inset) (a); and Eapp = ꢁ1.79 V, Eapp = ꢁ2.1 V (inset) (b).
DL-glycerol (egg, chicken; PG) 1,2-dioleoyl-3-trimethylammo-
nium-propane (chloride salt, DOTAP) and cholesterol (Chol).
Liposomes containing encapsulated Pz
8 were subjected to
antibacterial photocytotoxicity study against the standard strains
of Staphylococcus aureus NCTC 4163 and Pseudomonas aeruginosa
NCTC 6749 (see Supplementary data). Unfortunately, no significant
reduction in the number of bacterial cells was observed in both, the
non-irradiated and irradiated samples.
Fig. 3. Cyclic voltammograms of Pz 8 at different scan rate; 1, 2 – reduction
processes; 3, 4 – oxidation processes (a), differential pulse voltammograms (DPV)
for 8, DPV parameters: modulation amplitude 20 mV, step rate 10 mV/s (b).
4. Conclusions
(Fig. 4a), recorded during the controlled potential at 0.14 V, indi-
cated a decrease in the Q-band intensity at k = 728 nm without
shift, which was accompanied by the appearance of a new band
at 823 nm. Such a red-shifted band has previously been assigned
to the aggregated forms [41]. The spectra recorded at open circuit
potential in the function of time showed the progressive increase
of absorption in this range with a subsequent decrease after mixing
the solution (not shown). At the same time, the decrease of the
Soret band intensity at 341 nm accompanied by bathochromic shift
to 350 nm was found.
Novel porphyrazine 8, possessing an alternate system of two
peripheral substituents, 2-(1-adamantyl)-5-phenylpyrrol-1-yl and
dimethylamino was synthesized and fully characterized.
Moreover, the precursor maleonitriles were characterized using
X-ray crystallography. The macrocycle was found to be moderately
active as singlet oxygen generator with UD values of 0.17 in DMF.
Electrochemical and spectroelectrochemical properties of Pz 8
were studied and revealed that the concerned compound was rel-
atively easy to oxidize with the first couple at ꢁ0.23 V versus
Fc/Fc+, which may be attributed to the electron-donating proper-
ties of nitrogen containing substituents bonded directly to por-
phyrazine ring. In addition, Pz 8 was encapsulated in various
liposomal formulations and subjected to the antimicrobial photo-
cytotoxicity tests against S. aureus and P. aeruginosa. It seems that
novel Pz 8 constitutes an interesting building block for material
chemistry and nanotechnology. This study will be continued and
presented in due course.
3.5. Liposomes and antimicrobial photocytotoxicity
There is a constant interest in liposomes as a formulation for
photosensitizers in photodynamic therapy [42]. Therefore, Pz 8
was encapsulated in liposomes [43,44] consisting of 1-palmitoyl-
2-oleoyl-sn-glycero-3-phosphocholine (POPC), L-a-phosphatidyl-

222
M. Kryjewski et al. / Polyhedron 98 (2015) 217–223
[14] T. Koczorowski, W. Szczolko, K. Burda, M. Nowak, M. Dawidowska, A. Teubert,
Acknowledgements
et al., Influence of bulky pyrrolyl substituent on the physicochemical
properties of porphyrazines, Dyes Pigm. 112 (2015) 138.
The authors acknowledge financial support for the project from
the National Science Centre under Grant No. N N404 069440, the
European Fund for Regional Development No. UDA-
POIG.02.01.00-30-182/09 and National Centre for Research and
Development under contract No. PBS1/A9/13/2012. MK is a schol-
arship holder ‘‘Scholarship support for Ph.D. students specializing
in majors strategic for Wielkopolska’s development’’, Sub-measure
8.2.2 Human Capital Operational Programme, co-financed by EU
under the ESF. MK acknowledges financial support from the
National Science Centre for Ph.D. thesis preparation, contract num-
ber 2013/08/T/NZ7/00238.
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The following publications refer to the experimental data con-
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and 1003114 for 7 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223 336 033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/10.
1016/j.poly.2015.05.033. These data include MOL files and
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