Solvothermal modification of magnesium phthalocyanine

Article abstract of DOI:10.1016/j.ica.2018.03.018

Reactivity of magnesium phthalocyanine (MgPc) in the dry 3,4-lutidine (3,4-lut), in the 3,4-lut/DMSO, in DMSO and in 3,4-lut/acetylacetone (acacH) systems has been investigated. Reaction of MgPc with dry 3,4-lut leads to formation of MgPc(3,4-lut) compoun

Full text of DOI:10.1016/j.ica.2018.03.018

Inorganica Chimica Acta 478 (2018) 88–103
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Research paper
Solvothermal modification of magnesium phthalocyanine
Jan Janczak
Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactivity of magnesium phthalocyanine (MgPc) in the dry 3,4-lutidine (3,4-lut), in the 3,4-lut/DMSO, in
DMSO and in 3,4-lut/acetylacetone (acacH) systems has been investigated. Reaction of MgPc with dry 3,4-
lut leads to formation of MgPc(3,4-lut) compound (1), in which the Mg atom is characterised by rarely
encountering in magnesium phtalocyanines 4 + 1 N-type of coordination. In presence of the water tracer,
depending on the reaction conditions and the 3,4-lut quantity in the MgPc/3,4-lut/DMSO system the
solvothermal reaction leads to formation of three complexes in the crystalline form: MgPc(H2O)ꢀ2(3,4-
Received 15 November 2017
Received in revised form 2 February 2018
Accepted 9 March 2018
Available online 4 April 2018
Keywords:
Magnesium phthalocyanine derivatives
Crystal structure
lut)
–
(2), [MgPc(3,4-lut)][MgPc(H2O)ꢀ2(3,4-lut)]ꢀ½(3,4-lut)
–
(3) and [MgPc(H2O)ꢀ(3,4-lut)][MgPc
(DMSO)]ꢀ½(DMSO) – (4). Reaction of MgPc with DMSO yields crystalline MgPc(DMSO) complex (5). In
these complexes in the solid-state the central Mg atom of MgPc exhibits 4 + 1 coordination. The reaction
of MgPc in the case of 3,4-lut/acacH system leads to demetallation of MgPc and formation of crystalline
Mg(acac)2(H2O)2 compound (6) that after several days at ambient air in the mother liquor transforms into
organic crystalline compound of C10H12O2 (7). The structure of 1–7 has been determined by X-ray single
crystal diffraction. All MgPc-derivatives (1–5) were characterised by thermogravimetric analysis. Partial
MO energy diagrams and the calculated absorption spectra of the MgPc-derivatives were compared with
the experimental electronic absorption spectra in 3,4-lutidine and DMSO solutions. These results point
that the axial ligation of MgPc by O- and N-donor ligands do not change significantly the energy gap
of the HOMO-LUMO levels which is compared with that of the parent MgPc pigment.
Reactivity
UV–Vis spectroscopy
Molecular electrostatic potential
TD-DFT
Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction
N- or O-donating ligands) arises from their similarity and
relationships to the chlorophyll that provides the possibility to
Ever since Linstead’s report in 1934 [1] phthalocyanine and its
metal complexes are used as industrial dyes and pigments. Never-
theless, novel application of these macrocycles, which structurally
consist of four isoindole units connected by azamehine bridges to
them to be used as synthetic model [18]. MgPc, similar to other
metal(II) phthalocyanines, crystallises in two polymorphic forms
a
and b. However, the X-ray single crystal structure has been
determined only for its b modification [19]. Additionally, it has
been stated that the crystals of MgPc are unstable in ambient
atmosphere forming complexes with the compositions of (MgPc)2-
O2 and (MgPc)2N2 [20]. The formation of the oxygenated magne-
sium phthalocyanine complex has been confirmed by the X-ray
single crystal analysis [21]. In the solid state MgPc exhibits an
intense absorption band in the near-IR spectral region due to its
non-planar nature that arises from the interaction of electroposi-
tively polarised Mg center of one molecule with the electronega-
tively polarised N-azamethine atom of a neighbouring MgPc
molecule along the stacking arrangement [19,22].
A wide application of metallophthalocyanines including the
MgPc for technological purposes is limited by theirs relatively
low solubility in most organic solvents. The well-known way to
tune the application properties of metal(II) phthalocyanine com-
plexes is modify the phthalocyaninato(2ꢁ) macroring by the aryl,
form an 18-p electron aromatic macrocycles, are extensively stud-
ied. They are intensively studied as multiply functional materials
useful for modern technology [2–5]. They can be useful as organic
materials for electronic, optoelectronic and photoelectronic
devices like as recordable discks (CD), active matrix liquid crystals
displays, photoconductors in laser printers and solar cells [6–10].
Moreover, metallophthalocyanines have been applied as photosen-
sitizers for photodynamic therapy, both in their free form as well
as after incorporation into liposomes [11–17]. PDT is a cancer
treatment that necessitates the activation of a photosensitizer in
the cancer cell with the appropriate wave-length of light [12].
Our interest in magnesium phthalocyanine and its 4 + 1 and
4 + 2 coordinated derivatives (MgPcL and MgPcL2, where L is
E-mail address: j.janczak@int.pan.wroc.pl
https://doi.org/10.1016/j.ica.2018.03.018
0020-1693/Ó 2018 Elsevier B.V. All rights reserved.

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
89
alkyl and other substituents [23–29] or by additive metal center
2.2. Preparation procedure
complexation [30–33]. Some of axially ligated magnesium
phthalocyanine derivatives MgPc(L) with different ligands like as
F, Cl, Br and triphenylphosphine oxide crystallise as solvate and
their molecular structures were determined by the Homborg group
[34,35].The role of the peripheral substituents in the chemistry of
phthalocyanines and their optical properties was the subject of
some reviews [36–38]. Both methods improve the solubility of
the M(II)Pc-complexes due to the steric hindrance of axial ligands
or substituents of hydrogen atoms on phthalocyaninate(2ꢁ)
2.2.1. Synthesis of MgPc(3,4-lut) complex (1)
Freshly obtained crystalline MgPc (0.15 g) was added to the dry
3,4-lut (10 mL). The suspension of MgPc in 3,4-lut was degassed
and sealed under reduced pressure in a glass ampoule. Next the
ampoule was heated at 160 °C for two days and then it was cooled
to the room temperature. After such processing several well-devel-
oped single crystals of 1 were obtained. The crystals of 1 were sep-
arated by filtration and dried in air. Yield: 0.152 g (85%). Analysis:
found: Mg, 3.81; C, 72.67; N, 19.64 and H, 3.88%. Calculated for
macrocycle that lowers the p-p interactions as well as the aggrega-
tion in solutions [39–41]. Correspondingly it has been well experi-
enced that the feature of MPc’s may be tuned by their annealing in
various solvents. The MPc’s in such processes undergo not only the
recrystallization or purification, but they may interact with the sol-
vent molecules forming MPc-derivatives [42–47]. The interaction
of some MPc’s with solvent molecules resulting in their decompo-
sition was found in the indium monophthalocyanine [48]. Another
examples of the active role of the solvents are interactions of the
hafnium monophthalocyanine and hafnium diphthalocyanine
complexes with acetylacetone, benzonitrile and 4-methylpyridine
yielding to formation of novel hafnium phthalocyaninate com-
plexes [49], as well as the formation of the holmium open phthalo-
cyanine (oPc) complex that has been isolated during investigation
of the reactivity of iodine doped holmium diphthalocyanine
(HoPc2I) in the acetylacetone-water system [50]. The active role
of MgPc in the catalytic transformation of the cyano group in the
organic cyano compounds has been confirmed [51].
C39H25N9Mg: Mg, 3.77; C, 72.74; N, 19.58 and H, 3.91%.
2.2.2. Synthesis of MgPc(H2O)ꢀ2(3,4-lut) complex (2)
MgPc (0.2 g) was added to a mixture of 3,4-lut (10 mL) with
DMSO (1 mL). The MgPc in the 3,4-lut/DMSO (10:1) system was
degassed and sealed under reduced pressure in a glass ampoule,
and it was thermally processed at 130 °C during two days and then
it was cooled to the room temperature. After such processing
blue-violet well-developed single crystals of 2 were obtained.
The crystals of 2 were separated by filtration washed with
diethyl ether and dried in air. Yield: 0.235 g (82%). Analysis: found:
Mg, 3.15; C, 71.72; N, 18.15; O, 2.18 and H, 4.80%. Calculated
for C46H36N10OMg: Mg, 3.16; C, 71.83; N, 18.11; O, 2.28 and H,
4.62%.
2.2.3. Synthesis of [MgPc(3,4-lut)] [MgPc(H2O)ꢀ2(3,4-lut)]ꢀ½(3,4-lut) –
(3)
Quite recently, solvothermal reaction of MgPc in dry 3,5-luti-
dine, in 3,5-lutidine/DMSO and in 3,5-lutidine/acetylacetone sys-
tems resulting in the formation of new complexes in the
crystalline form has been performed [52]. In the present work,
the investigation of the interaction of the MgPc with the solvent
molecules, i.e. in dry 3,4-lutidine, in 3,4-lutidine/DMSO, in DMSO
and in 3,4-lutidine/acetylacetone systems, is the aim of this work.
The solvothermal reaction of the MgPc in such systems lead to for-
mation of the new products in the crystalline form. Additionally,
other behaviour of the 3,4-lutidine in relation to 3,5-lutidine in
these systems will be discussed.
MgPc (0.2 g) was added to a mixture of 3,4-lut (10 mL) with
DMSO (2 mL). The suspension of MgPc in 3,4-lut/DMSO (5:1) was
degassed and sealed under reduced pressure in a glass ampoule.
Solvothermal processing was identical as used for the crystals 2.
The obtained crystals 3 were separated by filtration and dried in
air. Yield: 0.152 g (56%). Analysis: found: Mg, 3.39; C, 72.04; N,
18.55; O, 1.18 and H, 4.48%. Calculated for C88.5H65.5N19.5OMg2:
Mg, 2.62; C, 72.98; N, 17.32; O, 1.72 and H, 5.36%.
2.2.4. Synthesis of [MgPc(H2O)ꢀ(3,4-lut)][MgPc(DMSO)]ꢀ½(DMSO) – (4)
MgPc (0.2 g) was added to a mixture of 3,4-lut (8 mL) with
DMSO (8 mL). The suspension of MgPc in3,4-lut/DMSO was
degassed and sealed under reduced pressure in a glass ampoule.
The ampoule with the suspension was thermally processed at
130 °C during two days and then it was cooled to the room temper-
ature. After such processing blue-violet well-developed single
crystals of 4 were obtained. The crystals of 4 were separated by fil-
tration washed with diethyl ether and dried in air. Yield: 0.192 g
(78%). Analysis: found: Mg, 3.65; C, 67.58; N, 18.16; O, 3.11, S,
3.58 and H, 3.92%. Calculated for C74H52N17O2.5S1.5Mg2: Mg, 3.69;
C, 67.44; N, 18.09; O, 3.14, S, 3.66 and H, 3.98%.
2. Experimental
2.1. Materials and methods
Crystalline form of MgPc was obtained as described previ-
ously [19]. 3,4-lutidine, DMSO and acetylacetone were obtained
from Aldrich. The composition of the obtained crystals was
checked with a Perkin-Elmer 2400 elemental analyser and with
energy dispersive spectroscopy (EDS). EDS spectra were
acquired and analysed using an EDAX Pegasus XM4 spectrom-
eter with SDD Apollo 4D detector mounted on a FEI Nova
NanoSEM 230 microscope. In addition the elemental analysis
was carried out also with a Perkin-Elmer 240 elemental ana-
lyzer. Measurements of the UV–Vis spectra were carried out
at room temperature using a Cary-Varian 2300 spectrometer.
The UV–Vis spectra were recorded in 3,4-lutidine or DMSO
solution (c = 10ꢁ6 mol/l). Thermal analysis was carried out on
a Linseis L81 thermobalance apparatus with Pt crucibles. The
initial sample mass was about 25 mg. Powder Al2O3 was used
as a reference. The measurements were performed under static
air on heating from room temperature to 300 °C at the heating
rate of 5 °C minꢁ1. The rest of the samples after TG analyses
2.2.5. Synthesis of MgPc(DMSO) complex – (5)
Freshly obtained crystalline MgPc (0.15 g) was added to the
DMSO (15 mL). The suspension of MgPc in DMSO was degassed
and sealed under reduced pressure in a glass ampoule. Next the
ampoule was heated at 170 °C for one day and then it was cooled
to the room temperature. After such processing several well-devel-
oped blue-violet single crystals of 5 were obtained. The crystals of
5 were separated by filtration The crystals of 5 were separated by
filtration washed with diethyl ether and dried in air. Yield: 0.155 g
(90%). Analysis: found: Mg, 3.98; C, 66.54; N, 18.12; O, 2.72; S, 5.11
and H, 3.53%. Calculated for C32H22N8OSMg: Mg, 3.95; C, 66.41; N,
18.22, O, 2.60; S, 5.21 and H, 3.61%.
were checked on
equipped with Cu-K
room temperature.
a
PANanalytical X’Pert diffractometer
radiation source (k = 1.54182 Å) at
2.2.6. Synthesis of Mg(acac)2(H2O)2 – (6) and C10H12O2 – (7)
MgPc (0.15 g) was added to a mixture of 3,4-lut (6 mL) with
acacH (6.0 mL). The MgPc in the 3,4-lut/acacH system was
a
a

90
J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
degassed and sealed under reduced pressure in a glass ampoule. It
was thermally processed at 120 °C during two days and then it was
cooled to the room temperature. Next the ampoule was opened
and left for several days for crystallization. After two-three weeks
colourless well-developed rectangular single crystals of 6 were
obtained. Several crystals of 6 were separated from the solution
for the X-ray single crystal and elemental analysis. Found: Mg,
9.35; C, 46.33; O, 37.22 and H, 7.10%. Calculated for C10H18O6Mg:
Mg, 0.40; C, 46.45; O, 37.13 and H, 7.02%. The rest of solution along
with colourless crystal 6 was left through a few next days and after
two weeks crystal 6 disappeared (underwent dissolving in solu-
tion) and after three consecutive weeks new colourless crystals
suitable for the X-ray analysis with the needle shape appeared in
solution (7). The crystals 7 were separated by filtration and dried
in air. Analysis: found: C, 73.22; O, 19.57 and H, 7.21%. Calculated
for C10H12O2: C, 73.15; O, 19.49 and H, 7.36%.
difference Fourier maps, but in the final refinement positions of
all hydrogen atoms were constrained: thermal parameters and dis-
tances. Visualizations of the structures were made with the Dia-
mond 3.0 program [56]. Details of the data collection parameters,
crystallographic data and final agreement parameters are collected
in Table 1.
2.4. Theoretical calculations
Molecular orbital calculations with full geometry optimization
of ligated MgPc by 3,4-lutidine, MgPc(3,4-lut) and aquamagne-
sium phthalocyanine MgPc(H2O) and the Mg(DMSO) were per-
formed with the Gaussian09 program package [57]. All
calculations were carried out with the DFT method using the
Becke3-Lee-Yang-Parr correlation functional (B3LYP) [58–60]
with the 6ꢁ31+G⁄ basis set assuming the geometry resulting from
the X-ray diffraction study as the starting structure. The calcula-
tions were also performed for the substrates MgPc, 3,4-lut, DMSO
and acacH molecules. As convergence criterions the threshold
limits of 0.00025 and 0.0012 a.u. were applied for the maximum
force and the displacement, respectively. The three-dimensional
molecular electrostatic potential (3D MESP) maps are obtained
on the basis of the DFT (B3LYP/6ꢁ31+G(d)) optimised geometries
of reacted molecules as well as for the reaction product mole-
cules. The calculated 3D MESP is mapped onto the total electron
density isosurface (0.008 eÅꢁ3) for each molecule. The colour code
of MESP maps is in the range of ꢁ0.05 (red) to 0.05 eÅꢁ1 (blue).
After the geometry optimization, the time-dependent (TD) DFT
calculations [61,62] were performed to evaluate the absorption
spectrum employing the same level and basis sets. All stationary
points were optimised without any symmetry assumptions and
characterized by normal coordinate analysis at the same level of
theory.
2.3. X-ray crystallography
The obtained single crystals of 1–7 were used for data collection
on a four-circle KUMA KM4 diffractometer equipped with two-
dimensional CCD area detector. The graphite monochromatized
Mo-Ka radiation (k = 0.71073 Å) and the x-scan technique (Dx
= 1°) were used for data collection. Lattice parameters were refined
by the least-squares methods on all reflections positions. One
image was monitored as a standard after every 40 images for a
control of stability of the crystal. Data collection and reduction
along with absorption correction were performed using CrysAlis
software package [53]. The structures were solved by direct meth-
ods using SHELXS-97 [54] giving positions of almost all non-hydro-
gen atoms. Initially, the structures were refined using SHELXL-2014
[55] with the anisotropic thermal displacement parameters.
Hydrogen atoms of the phthalocyanine moiety were located on
Table 1
Crystallographic data for 1–7 crystals.
1
2
3
4
5
6
7
Formula
C
39H25N9Mg
C46H36N10OMg
769.16
295(2)
C88.5H65.5N19.5OMg2 C74H52N17O2.5S1.5Mg2 C32H22N8OSMg
C10H18O6Mg
258.55
295(2)
Monoclinic
P 21/c (No. 14)
10.981(2)
5.359(1)
11.172(2)
106.43(1)
630.6(2)
C10H12O2
164.20
295(2)
Mol. Weight
Temperature (K)
Crystal system
Space group
a (Ǻ)
643.99
295(2)
1466.72
1316.01
614.97
295(2)
295(2)
295(2)
Monoclinic
P 21/c (No. 14)
12.123(2)
16.138(3)
17.7160(3)
109.652(5)
3264.1(8)
4
Monoclinic
P 21/n (No. 14)
12.202(1)
12.793(2)
24.684(3)
91.16(1)
3852.4(8)
4
Triclinic
Triclinic
Triclinic
P ꢁ1 (No. 2)
9.4144(8)
13.306(2)
23.497(3)
90.12(1)
91.40(1)
107.07(2)
2812.8(7)
2
Triclinic
P ꢁ1 (No. 2)
7.454(1)
7.611(1)
16.021(2)
93.628(7)
95.514(9)
99.885(11)
888.3(2)
4
P ꢁ1 (No. 2)
15.159(1)
15.657(2)
16.457(2)
78.54(1)
73.830(11)
77.608(12)
3623.7(7)
2
P ꢁ1 (No. 2)
12.2698(8)
12.5644(11)
22.854(2)
97.12(1)
93.65(1)
109.15(2)
3282.1(6)
2
b (Ǻ)
c (Ǻ)
a
(°)
b (°)
c
(°)
2
V (Ǻ3)
Z
1.31 / 1.311
0.099
1.32 / 1.326
0.098
1.36 / 1.362
0.154
Dobs/Dcalc
0.32 ꢂ 0.28 ꢂ
0.37 ꢂ 0.33 ꢂ
1.34/1.344
1.33/1.332
1.45/1.452
0.38 ꢂ 0.35 ꢂ
1.22/1.228
0.22
0.27
0.21
m (mmꢁ1
)
54,785/7816 /
71,544/9884/
7195
0.0259
0.100
0.148
0.184
12,646/1631 /
0.084
Crystal size (mm3)
Total/unique/
5988
0.24 ꢂ 0.17 ꢂ 0.12
0.35 ꢂ 0.29 ꢂ 0.24
71,925/16,314/9885
0.27 ꢂ 0.23 ꢂ
0.22
94,691/15,897/
1462
0.29 ꢂ 0.22 ꢂ
0.21
11,732/4238/
0.0205
0.0450
60,403/17,674/
8891
0.0217
Observed refls
0.0602
0.1064
0.0756
0.0298
8006
0.0275
2266
Rint
0.1622
1.014
0.857, ꢁ0.373
1.001
0.172, ꢁ0.165
0.0993
0.1684
0.938
0.472, ꢁ0.353
0.0594
0.1535
1.001
1.152, ꢁ0.673
0.0803
0.0658
0.1356
1.004
0.212, ꢁ0.282
0.0706
1.000
0.222, ꢁ0.113
0.0526
0.0546
0.1418
1.000
0.148, ꢁ0.169
R [F2 > 2
r
(F2)]a
wR [F2 all refls]b
S
D
qmax
,
D
qmin
)
(eꢀǺꢁ3
a
R =
wR = {
R
||Fo|ꢁ|Fc||/
RFo.
R
[w(F2o ꢁ F2c)2]/
R
wF4o} ; wꢁ1
=
r
2(F2o) + (aP)2 + (bP) where P = (Fo2 + 2F2c)/3. The a and b parameters are 0.0787 and 1.5094 for 1, 0.0408 and 0.9851 for 2, 0.0001 and
b
½
0 for 3, 0.0780 and 0.3441 for 4, 0.0450 and 0.6273 for 5, 0.0332 and 0.1353 for 6, and 0.0350 and o for 7.

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
91
electropositive Mg center of MgPc and the ring N atoms of 3,4-
lut, and in result the axial Mg N coordination bond is formed
yielding the MgPc(3,4-lut) complex (1). The 3D MESP for the pro-
duct is shown in Fig. 2a and will be helpful for understanding
the interactions between the MgPc(3,4-lut) molecules during
nucleation, crystallization and their organisation in solid-state.
The crystals of MgPc(H2O).2(3,4-lut) (2) were obtained during
solvothermal process of MgPc in the mixture of 3,4-lutidine and
DMSO taken in the volume proportion of 10:1, whereas the crystals
of [MgPc(3,4-lut).(3,4-lut)][MgPc(H2O) .2(3,4-lut)]ꢀ½(3,4-lut) (3)
and the crystals of [MgPc(H2O)ꢀ2(3,4-lut)][MgPc(DMSO)]ꢀ½(DMSO)
(4) were obtained in the similar way as crystals 2, however the vol-
ume ratio of 3,4-lutidine to DMSO was 5:1 and 1:1 in the case of
crystals 3 and 4, respectively. In all cases the reaction of MgPc in
the respective 3,4-lut/DMSO system was thermally processed at
130 °C during two days. DMSO was added to the reaction mixtures
in order to change the temperature dependence of the formed
compounds solubility. It enabled to obtain the crystals of better
quality. In the case of crystals 2 and 3 the DMSO moieties did
not build into the crystal structures of obtained compounds. How-
ever, in the crystals 4 that were formed in the 3,4-lut/DMSO system
with a greater amounts of DMSO (1:1), the DMSO molecules did
build into the crystal structure. Since the MgPc is unstable in the
air atmosphere due to its high affinity to moisture of air [20,22],
the formed crystals contain water molecules. The high affinity of
MgPc to water results from the interaction of lone pair of electron
at oxygen atom of water molecule with electropositive Mg atom
(ꢃ+0.5) of MgPc, what is confirmed by the molecular orbital calcu-
lations [68]. The 3D MESP maps are helpful for understanding of
the high affinity of MgPc to water and the formation in used reac-
tion conditions of the aquamagnesium phthalocyanine complex
(Figs. 1 and 2). The interaction of MgPc with the solvent molecules
in the 3,4-lut/DMSO system takes place between the positively
polarised Mg center of MgPc and the negatively polarised fragment
of the respective solvent molecules. In the reaction with a small
amounts of DMSO (as in the case of 2 and 3) the water molecule
as the smaller and with the greater mobility molecule comparing
with the 3,4-lut and DMSO molecules participate in the reaction
with MgPc forming MgPc(H2O) that crystallises with 3,4-lut as sol-
vent molecules forming respective crystals 2 and 3, whereas in the
case of the greater amounts of DMSO in the system the competi-
tion between the solvent molecules in the interaction with MgPc
takes place resulting in the formation of MgPc(H2O) and MgPc
(DMSO) complexes that co-crystallise forming solvated crystals 4.
The interaction of electropositively polarised Mg center of MgPc
in the 3,4-lut/DMSO/H2O takes place between the negatively
polarised nucleophilic O atoms of water or DMSO and the ring N-
atom of 3,4-lut molecules (Figs. 1 and 2). However, the Mg2+ of
MgPc molecule as a hard acid prefers the O as a harder base than
N [69–71] forming MgPc(H2O) and MgPc(DMSO) complexes. The
3,4-lut present in the reaction system interacts with the formed
MgPc(H2O) complex as an acceptor in the OAHꢀ ꢀ ꢀN hydrogen
bonds forming depending on the crystallization conditions respec-
tive crystals 2, 3 and 4. The axial ligation by 3,4-lut of the Mg cen-
ter of MgPc molecule and formation of MgPc(3,4-lut) complex (1)
takes place only in the case of extremely conditions, using freshly
obtained MgPc and dried 3,4-lutidine. The possibility of the forma-
tion of the MgPc(DMSO) complex in the mixture of 3,4-lut/DMSO
taken in volume ratio of 1:1 that co-crystallise with the formed
MgPc(H2O) forming crystals 4 induced us to perform the reaction
of MgPc in pure DMSO. Since the boiling point of DMSO is ꢃ189
°C the solvothermal reaction of MgPc with DMSO was performed
at 170 °C. At this temperature with a time the MgPc dissolved com-
pletely forming homogenous solution. During the cooling process
the formed MgPc(DMSO) complex crystallises forming well-
developed suitable for the X-ray analysis single crystals of 5.
3. Results and discussion
3.1. Synthesis
All obtained crystals were synthesized by the means of
solvothermal technique. Initially prepared as described elsewhere
[19] crystalline MgPc was added to dry 3,4-lut (10 mL), degassed
and sealed under reduced pressure in a glass ampoule and next
the ampoule was thermally processed for two days at 160 °C and
then it was cooled to room temperature. In the such process elec-
tropositive Mg center of MgPc interacts with the electronegative
nitrogen of 3,4-lut leading to MgPc-derivative with the axial
Mg N coordination bond. During the cooling process the formed
MgPc(3,4-lut) complex crystallises yielding blue-violet well-
developed single crystals (1). In order to gain insight into the
nature of the interaction between the reacted molecules, the
three-dimensional molecular electrostatic potential have been
calculated. It is defined as V(r) = RA (ZA/(RA-r)) –
R
(q
(r0)/|r0ꢁr|)dr,
where ZA is the charge on nucleus A having a position vector RA
and the
q
(r0) is the electronic density function of the molecule,
and r0 is the dummy integration variable [63,64]. The molecular
electrostatic potential (MESP) is related to the electronic density
in molecule and is a very useful tool in determining sites for elec-
trophilic and nucleophilic reactions as well as for intermolecular
interactions and organisation of molecules in solid-state [65–67].
The MESP maps are obtained on the basis of the DFT
(B3LYP/6ꢁ31+G(d)) optimised geometries of the reacted molecules
(Fig. 1) as well as for the reaction product molecules (Fig. 2). For
MgPc molecule the 3D MESP map displays the electrophilic region
near the Mg center on both sides of planar MgPc molecule and the
nucleophilic regions near the four bridged azamethine nitrogen
atoms (Fig. 1a). In addition less positive value of MESP than that
near the Mg center and less negative value of MESP comparing to
that of azamethine N atoms are observed on both side of planar
MgPc across the extended 18
p
electron conjugation in the Pc(2ꢁ)
macrocycle. The 3D MESP map for 3,4-lut molecule displays the
nucleophilic region near the ring N atom containing the lone elec-
tron pair on the sp2 orbital (Fig. 1b). Therefore the interaction
between the MgPc and 3,4-lut molecules takes place between the
Fig. 1. 3D MESP for MgPc (a), 3,4-lutidine (b), H2O (c) DMSO (d) and acetylacetone
(e). The colour code of MESP is in the range of ꢁ0.05 (red) to 0.05 eÅꢁ1 (blue).
Fig. 2. 3D MESP for the MgPc(3,4-lut) (a), MgPc(H2O) (b) and MgPc(DMSO) (c). The
colour code of MESP is in the range of ꢁ0.05 (red) to 0.05 eÅꢁ1 (blue).

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J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
The 1–5 crystals are well soluble in 3,4-lutidine yielding inten-
acac- in result interrupts the MgAN bonds and leads to demetalla-
tion of MgPc and formation of the Mg(acac)2 complex that in pres-
ence of the water molecules forms crystalline biaxially ligated by
H2O [Mg(acac)2(H2O)2] complex (6) and metal-free phthalocyanine
(H2Pc). The formed Mg(acac)2(H2O)2 complex (6) crystallises as
colourless rectangular well-developed suitable for the X-ray anal-
ysis crystals which after several days disappeared (i.e. underwent
dissolving in parent solution). After three consecutive weeks in
the mother liquor new colourless crystals 7 with other shapes
comparing to crystals 6 appeared. The single crystal analysis of
needle crystal 7 showed that it is a crystal of organic compound
with a composition of C10H12O2, which along with the time is
formed at ambient air in the mother liquor from compound 6.
sively blue solutions. In ambient air, in solution in 3,4-lut the MgPc
(3,4-lut) complex (1) transforms into MgPc(H2O) complex, and
after several days it crystallises yielding MgPc(H2O).2(3,4-lut) (2).
All 1–5 crystals are well soluble in pyridine, DMSO, DMF and other
N- and O-donor solvents. The solubility of these 1–5 complexes are
several times greater than the parent MgPc pigment due to the
steric axial hindrance that lowers the
solid.
p-p stacking interactions in
Solvothermal reaction of MgPc with 3,4-lutidine/acacH was
performed at 120 °C. Next the homogenous solution was cooled
to room temperature and left at the ambient conditions. After sev-
eral days well-developed rectangular colourless single crystals of 6
appeared (Scheme 1).
It is well known that acetylacetone exists in two tautomeric
forms in a dynamic equilibrium
3.2. Thermal properties
In order to determine the thermal stability of the MgPc-deriva-
tives, the thermal analyses of 1–5 were carried out on the samples
of 15–20 mg with the same heating rate of 5 °C/min. Crystals of 1
are stable up to ꢃ100 °C (Fig. S1 in Supplementary). The mass loss
is concerned with the release of 3,4-lut from the MgPc(3,4-lut)
complex and above ꢃ120 °C the rest of the sample gives free MgPc
in the b-form that was confirmed by the X-ray powder diffraction
experiment. The respective mass lose on the heating id ꢃ16.5 and
is in agreement with the calculated value of 16.64% (loss of 3,4-lut).
The crystals of 2 are stable up to ꢃ100 °C (Fig. S2) and at higher
temperature they loss both solvated 3,4-lut molecules transform-
ing into aquamagnesium phthalocyanine (MgPcH2O) that loses
the coordinated water molecule above 200 °C, which is in agree-
ment with that of the thermal decomposition of the triclinic mod-
ification of aquamagnesium phthalocyanine complex [22]. The
respective mass losses on the heating of ꢃ27.8 and ꢃ30.1% are in
agreement with the calculated values of 27.86% (3,4-lut) and
30.20% (total mass of 3,4-lut and H2O).
H3C
CH3
H3C
CH3
H
H3C
CH3
O
O
O
O
O
O
H
keton
enol
Experimental and theoretical investigations of keto-enol tau-
tomerization of acacH show that the enolic form of acacH with
the internal OAHꢀ ꢀ ꢀO hydrogen bond is energetically favourable
due to delocalisation of the p-electrons of the double C = C and C
= O bonds and the lone pair of electron of the O atom forming
six-membered ring with an aromatic character [72]. The equilib-
rium constant of the dissociation of the enol form of acacH
(acacH M acacꢁ + H+) strongly depends on the ionic strength, the
solvent and the thermal conditions. The pKa in aqueous solution
and with the ionic strength close to 0 is equal to 8.99 [73]. The
electropositive Mg atom of MgPc molecule, which as shows single
crystal analysis is non-planar [19], is significantly displaced from
the N4-isoindole plane of Pc (ꢃ0.5 Å), therefore in such conditions
in 3,4-lut/acacH solution it interacts with the formed acac- anions.
The interaction of MgPc with acac- anions in 3,4-lut/acacH system
could be better understood if we take into consideration the 3D
MESP maps of reacted units (Fig. 3). The interaction of MgPc with
The thermogravimetric analysis of the crystals of 3 shows their
less-stability (Fig. S3). At ꢃ90 °C the sample of crystals 3 releasing
the solvated 3,4-lut molecules and then coordinated (at ꢃ125),
transforms into MgPc(H2O) complex that losses the coordinated
water at ꢃ200 °C. The respective mass losses on the heating are
18.5, 25.5 and 26.7% are in agreement with the calculated values
CH3
N
CH3
H3C
H3C
H3C
CH3
H2 O
CH3
CH3
N
N
N
N
O
O
O
O
O
N
Mg
N
N
N
Mg
+ H2 Pc
H2 O
O
H2 O
(6)
Scheme 1. Formation of the Mg(acac)2(H2O)2 complex (6).
Fig. 3. 3D MESP for MgPc, acacꢁ, H2O and for the Ma(acac)2(H2O)2. The colour code of MESP is in the range of ꢁ0.05 (red) to 0.05 eÅꢁ1 (blue).

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
93
of 18.26% (loss of solvated 3,4-lut), 25.57% (solvated + coordinated
3,4-lut) and 26.80% (solvated + coordinated 3,4-lut + coordinated
H2O). Finally the sample transforms into MgPc in the b-form.
During the heating process the crystals 4 gradually undergo
decomposition (Fig. S4). Crystals 4 are stable up to ꢃ80 °C, which
is the first step of the mass loss. The mass loss is concerned with
the release of disordered DMSO molecule. The second steep of
the mass loss (at ꢃ145–150 °C) is concerned with the release of
solvated 3,4-lut molecule and the third is concerned with the
release of coordinated water molecule and finally at ꢃ245–250
°C the mass loss is concerned with the release of coordinated
DMSO molecule. The respective mass losses on the heating are
ꢃ2.90, 11.0, 12.5 and 18.41%, and are in agreement with the calcu-
lated values of 2.97% (loss of disordered DMSO), 11.51% (loss of
disordered DMSO and 3,4-lut molecules), 12.47% (loss of disor-
dered DMSO, 3,4-lut and coordinated water molecules) and
18.41% (loss of disordered DMSO, 3,4-lut and coordinated water
and DMS molecules). TG analysis of 4 is in agreement with their
composition of {[MgPc(H2O)ꢀ (3,4-lut)][MgPc(DMSO)]ꢀ½(DMSO)}
and points on the higher thermal stability of MgPc(DMSO) than
MgPc(H2O).
The thermal stability of the complex 5 has been also determined
(Fig. S5). During the heating process compound 5 is stable up to
ꢃ225 °C and at higher temperature it loses axial DMSO molecule
and transforms into MgPc in the b-form. The mass loss on the heat-
ing of 12.8% is in agreement with the calculated value of 12.71%
that is concerned with the release of coordinated DMSO molecule.
3.3. Description of the crystal structures of magnesium phthalocyanine
derivatives
3.3.1. MgPc(3,4-lut) complex (1)
Compound 1 crystallises in the centrosymmetric space group P
21/c of the monoclinic system. The molecular structure of MgPc
(3,4-lut) complex is illustrated in Fig. 4a. In contrast to the
complexes obtained in dry pyridine (MgPc(py)2) [30] and in dry
3,5-lutidine (MgPc(3,5-lut)2) [52], both exhibit 4 + 2 coordination
environment of Mg, the complex 1 exhibits 4 + 1 square pyramidal
coordination environment of Mg. The interaction of the electropos-
itively polarised Mg center of MgPc with electronegatively
polarised ring N atom of the axial 3,4-lut molecule results in dis-
placement of the Mg atom from the N4-isonodole plane of phthalo-
cyaninate(2ꢁ) macrocycle that adopts a saucer-shape form. The
displacement of Mg form the N4-plane of 0.534(2) Å is comparable
to that of ꢃ0.5 Å in the crystal of MgPc, in which the displacement
of Mg form MgPc plane results from the intermolecular interaction
between the Mg center of one MgPc molecule with the N-azame-
thine nitrogen atom of the neighbour [19]. The monoaxial ligation
of Mg center of MgPc by the N-donor ligands is relatively rare in
relation to ligation by O-donor ligand. The monoaxial ligation of
Mg center of MgPc by N-donor ligand can be found in the crystal
of MgPc-derivative with the axial ligand of 2-amino-3-picoline
[74], in which the displacement of Mg from N4-isonodole plane
of 0.498(3) Å is similar to that observed in 1. The plane of the
3,4-lut molecule is almost perpendicular to the N4-plane of Pc
(2ꢁ) macrocycle. The orientation of the planar axial ligand relative
to the phthalocyaninato(2ꢁ) macrocycle is determined by the elec-
trostatic interaction between the electropositively polarised H
atoms in orto positions in relation to N-ring atom of 3,4-lut and
the electronegatively polarised azamethine nitrogen atoms of Pc
(2ꢁ) macrocycle (Figs. 1 and 2). This conformation of MgPc(3,4-
lut) complex is the most stable and is preferred in solution and
in the gas-phase as is evidenced by the DFT molecular orbital cal-
culations. The coordination polyhedron around the Mg cation
approximates to a tetragonal pyramid with relatively long bond
between the Mg and the N atom of the axial 3,4-lut ligand. The four
Fig. 4. View of the molecular structure of 1 along with the labelling scheme (a) and
the crystal packing of 1 (b). Thermal ellipsoids are shown at the 50% probability
level, H atoms with arbitrary radii.
equatorial MgAN bonds with the Pc(2ꢁ) macrocycle are
significantly shorter (ꢃ0.8 Å) than the axial MgAN bond linking
the 3,4-lut ligand (Table 2). DFT geometry optimisation of the
MgPc(3,4-lut) molecule yields similar conformation as present in
the crystal. However, looking in more details on the DFT geometri-
cal parameters it should be stated that the greatest discrepancy
between the X-ray and theoretical values is found in the axial
MgAN bond. The theoretical value of the axial Mg-N bond is longer
by ꢃ0.08 Å the X-ray value. Quite similar correlation between the
X-ray and DFT values of the equatorial MgAN bond was observed
in other MgPc complexes axially ligated by pyridine and imidazole,
MgPc(py) and MgPc(Im) [75]. Full geometrical parameters of the
optimised conformation of the MgPc(3,4-lut) molecule are listed

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J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
Table 2
Selected geometrical parameter for MgPc(3,4-lut) molecule in crystals 1 and 3.
(1)
(3)
DFT
Mg1AN2
Mg1AN4
Mg1AN6
Mg1AN8
2.0435(16) Mg2AN10
2.0467(16) Mg2AN12
2.0487(16) Mg2AN14
2.0470(16) Mg2AN16
2.061(4)
2.034(4)
2.047(4)
2.037(4)
2.153(4)
2.058
2.058
2.059
2.059
2.209
86.8
87.2
87.2
86.9
Mg1AN9
2.127(2)
86.35(6)
85.88(6)
86.30(6)
85.94(6)
105.86(8)
101.72(8)
104.51(8)
108.19(9)
48.8(2)
Mg2AN17
N2AMg1AN4
N4AMg1AN6
N6AMg1AN8
N8AMg1AN2
N9AMg1AN2
N9AMg1AN4
N9AMg1AN6
N9AMg1AN8
N2AMg1AN9AC37
N10AMg2AN12 85.77(16)
N12AMg2AN14 86.57(16)
N14AMg2AN16 86.65(17)
N16AMg2AN10 86.43(17)
N17AMg2AN10 101.68(16) 103.1
N17AMg2AN12 102.94(17) 103.1
N17AMg2AN14 107.41(17) 103.3
N17AMg2AN16 106.31(16) 103.3
N10AMg2A
N17AC69
50.6(3)
44.8
Deviation of Mg from 0.534(2)
the N4-plane
0.516(3)
0.470
in Supplementary (Table S1). The arrangement of MgPc(3,4-lut)
molecules in the crystal is mainly determined by the van der Waals
forces and the electrostatic interactions between the molecules
(Fig. 4b), since the steric hindrance of the axial 3,4-lut ligand signif-
icantly reduces the
p p interactions between phthalocyaninato
ꢁ
(2ꢁ) macrocycles as observed in the crystal of unhindered parent
MgPc [19]. The closest interplanar distance of ꢃ4.15 Å between
neighbouring MgPc(3,4-lut) molecules can be found between the
Pc(2ꢁ) macrocycle of one molecule and the plane of the axial
3,4-lut ligand of the neighbours (Fig. 4b). In addition the character-
istic feature of the compound 1 crystal structure is the lack of the
pꢁp
interactions between phthalocyaninato(2ꢁ) macrocycles.
Thus, the architecture of MgPc(3,4-lut) crystals is less stabilised
by the interactions. This is manifested in the increasing of
pꢁp
the MgPc(3,4-lut) solubility in the most common solvents and
improved technical performance of the pigment.
3.3.2. MgPc(H2O)ꢀ 2(3,4-lut) complex (2)
Compound 2 crystallises in the centrosymmetric space group
P21/n of the monoclinic system with four molecules per unit cell.
Asymmetric unit of 2 consists of one MgPc(H2O) moiety and two
3,4-lut molecules linked together via OAHꢀ ꢀ ꢀN hydrogen bonds
(Fig. 5a). The Mg atom of MgPc(H2O) molecule exhibits tetrago-
nal–pyramidal environment (4 + 1 coordination) and is deviated
from the average plane defined by four isoindole N atoms by
0.464(2) Å toward the oxygen atom of water molecule. The dis-
placement of Mg from the N4-plane is comparable to that observed
for the monoclinic and triclinic modifications of aquamagnesium
phthalocyanine [22,76,77], and is higher by ꢃ0.2 Å than that in
some chlorophyll derivatives [78,79]. The axial MgAO bond is
somewhat shorter than the equatorial four MgAN bonds linked
the phthalocyaninato(2ꢁ) macrocycle (Table 3). Quite similar
tetragonal-pyramidal environment of Mg atom of MgPc(H2O) com-
plex is preferred in solution and in the gas-phase as is evidenced by
the DFT molecular orbital calculations, however the opposite rela-
tion between the values of the axial MgAO and equatorial MgAN
bonds is observed. The theoretical DFT value of the axial MgAO
bond is longer by ꢃ0.12 Å than the X-ray value (Table 3). Full geo-
metrical parameters of the optimised conformation of the MgPc
(H2O) molecule are listed in Supplementary (Table S2). The sol-
vated 3,4-lut molecules lie in different planes. One of them that
contains the N9 atom is inclined to the N4-isoindole plane by
21.3(1)°, whereas the other 3,4-lut with the N10 atom is inclined
by 56.2(1)°. Both H atoms of coordinated water molecule take part
in the almost linear hydrogen bonds with N pyridine atoms of sol-
vation 3,4-lut molecules. The geometry of both OAHꢀ ꢀ ꢀN hydrogen
Fig. 5. View of the molecular structure of 2 along with the labelling scheme (a) and
the crystal packing showing the Mgꢀ ꢀ ꢀMg and N4-N4 distances between the back-to-
back units of 2 (b). Thermal ellipsoids are shown at the 50% probability level, H
atoms with arbitrary radii.
bonds linking the solvation 3,4-lut molecules is quite similar
(Table 4). Arrangement of MgPc(H2O)ꢀ2(3,4-lut) units in the crystal
is mainly determined by the van der Waals forces and by the
interactions. However, due to the steric hindrance of axial water
p p
ꢁ

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
95
Table 3
Selected geometrical parameters (Å,o) for MgPc(H2O)ꢀ2(3,4-lut) in crystals 2, 3 and 4.
(2)
(3)
(4)
DFT
Mg1AN2
Mg1AN4
Mg1AN6
Mg1AN8
2.0351(11)
2.0361(11)
2.0348(11)
2.0402(11)
2.0028(12)
87.24(4)
87.03(4)
87.10(4)
86.75(4)
98.68(5)
2.049(4)
2.034(4)
2.056(4)
2.035(4)
2.0488(16)
2.0511(17)
2.0533(16)
2.0489(16)
2.0227(17)
87.40(7)
85.61(7)
87.85(6)
85.67(6)
102.13(7)
107.83(7)
105.92(7)
100.16(7)
0.497(2)
2.040
2.043
2.040
2.043
2.146
88.1
88.1
88.1
88.1
99.9
Mg1AO1
1.990(4)
N2AMg1AN4
N4AMg1AN6
N6AMg1AN8
N8AMg1AN2
O1AMg1AN2
O1AMg1AN4
O1AMg1AN6
O1AMg1AN8
Deviation of Mg from the N4-plane
85.93(15)
86.44(16)
85.16(16)
86.20(15)
103.02(15)
108.97(18)
107.12(16)
102.62(18)
0.544(3)
103.05(5)
106.83(5)
104.02(5)
0.464(2)
101.1
99.9
101.1
0.470
Dihedral angle between the planes of N4 and 3,4-lut
N4/N9
N4/N10
21.3(1)
56.2(1)
N4/N18
N4/N19
11.2(1)
69.3(1)
N4/N17 71.0(1)
Table 4
Hydrogen-bond geometry (Å,o) in 2.
DAHꢀ ꢀ ꢀA
DAH
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
DAHꢀ ꢀ ꢀA
O1AH2Oꢀ ꢀ ꢀN9
O1AH1Oꢀ ꢀ ꢀN10
0.88(2)
0.86(2)
1.84(2)
1.91(2)
2.7270(18)
2.7715(19)
176.3(18)
174.2(19)
molecule together with the linking the solvation 3,4-lut molecules,
as well as the deformation of Pc2ꢁ macrocycle, the
interac-
tions between the molecules in the crystal 2 are significantly
weaker when comparing to parent MgPc pigment with the
stacking interactions [19]. Inversion related MgPc(H2O)ꢀ2(3,4-lut)
units are arranged in the back-to-back fashion with a distance of
ꢃ3.75 Å between the saucer-shaped phthalocyaninato(2ꢁ) macro-
cycles (Fig. 5b).
plane of Pc2ꢁ macrocycle when comparing to the respective values
in the crystal 2 (Table 3). The different orientation of both hydro-
gen bonded 3,4-lut molecules in the MgPc(H2O)ꢀ2(3,4-lut) moiety
in 3 in relation to 2 results in the slight change of the geometry
of hydrogen bonds (Tables 4 and 5). The planar ring of disordered
solvent 3,4-lut molecule located in the inversion center is almost
parallel to the average plane of Pc2ꢁ macrocycle of MgPc(3,4-lut)
(dihedral angle between N4-plane of Pc2ꢁ and the plane of the dis-
ordered 3,4-lut molecule is equal to 19.7(3)°), whereas is almost
perpendicular the average plane of Pc2ꢁ macrocycle of MgPc
(H2O) (dihedral angle is equal to 83.0(3)°). Arrangement of the
MgPc(3,4-lut) and MgPc(H2O)ꢀ2(3,4-lut) moieties together with
the disordered solvent 3,4-lut molecule in 3 is mainly determined
pꢁp
p-p
3.3.3. [MgPc(3,4-lut)] [MgPc(H2O)ꢀ2(3,4-lut)]ꢀ½(3,4-lut) – (3)
Compound 3 crystallises in the centrosymmetric space group of
the triclinic system. Asymmetric unit of 3 is built of one molecule
of MgPc(3,4-lut) and one MgPc(H2O)ꢀ2(3,4-lut) moiety and half of
3,4-lut molecule (Fig. 6a). Both compounds, MgPc(3,4-lut) and
MgPc(H2O)ꢀ2(3,4-lut), co-crystallise with 3,4-lut as solvent that in
the crystal is disordered. The disordered solvent 3,4-lut molecule
lies in the inversion center, so it has two orientation. The confor-
mation of the MgPc(3,4-lut) and MgPc(H2O)ꢀ2(3,4-lut) moieties in
crystal 3 is, in general, similar to that found for the respective com-
plexes in the crystal 1 and 2 and comparable to that in the gas-
phase as is evidenced by the DFT molecular orbital calculations
(Tables S1 and S2). However, small differences in the bond lengths
and angles in the MgPc(3,4-lut) molecule in the crystal 3 and crys-
tal 1 are observed (Table 2). The orientation of the planar axial 3,4-
lut ligand relative to the phthalocyaninato(2ꢁ) macrocycle in the
crystal 3 is similar to that in the crystal 1 that results from the elec-
trostatic interaction between the electropositively polarised H
atoms in orto positions in relation to N-ring atom of 3,4-lut and
the electronegatively polarised azamethine nitrogen atoms of Pc
(2ꢁ) macrocycle. Small differences between the geometrical
parameters of the coordination sphere of Mg the in MgPc(H2O)ꢀ2
(3,4-lut) moiety in the crystal 3 and 2 are also observed (Table 3).
These differences result from the intermolecular interactions pre-
sent in the crystals. The orientation of the hydrogen bonded 3,4-
lut molecules in the MgPc(H2O)ꢀ2(3,4-lut) moiety in the crystal 3
is slightly different than that in the crystal 2. One of them that con-
tains the N18 atom is less inclined (11.2(2)°) and the other 3,4-lut
with the N19 atom is more inclined (69.3(2)°) to the N4-isoindole
by the van der Waals forces, electrostatic and by the
p p interac-
ꢁ
tions. Related by inversion MgPc(3,4-lut) molecules form dimers in
the back-to-back fashion with a distance of 3.634(3) Å between the
N4-planes of Pc2ꢁ macrocycles. However, the distance between
the average planes of Pc2ꢁ macrocycles is shorter by ꢃ0.2 Å due
to the saucer-shaped form pointing on the
p p interactions
ꢁ
between the
p
-clouds of phthalocyaninato(2ꢁ) macrocycles. The
inversion related MgPc(H2O)ꢀ2(3,4-lut) moieties are also oriented
in the back-to-back fashion, however the distance between the
N4-planes of Pc2ꢁ macrocycles is much greater (7.264(5) Å) since
the Pc2ꢁ macrocycles interpenetrates the 3,4-lut of neighbouring
MgPc(3,4-lut) molecules (Fig. 6b). The average planes of phthalo-
cyaninato(2ꢁ) macrocycles of the back-to-back inversion related
MgPc(H2O)ꢀ2(3,4-lut) moieties and back-to-back inversion related
MgPc(3,4-lut) molecules are respectively almost parallel and per-
pendicular to (1 0 0) crystallographic plane. The steric hindrance
of axial ligands and the deformation of phthalocyaninato(2ꢁ)
macrocycle of both MgPc(3,4-lut) and MgPc(H2O)ꢀ2(3,4-lut) moi-
eties in 3 makes them more sensitive for action of solvents and
is responsible for the increase in their solubility.
3.3.4. [MgPc(H2O)ꢀ(3,4-lut)][MgPc(DMSO)]ꢀ½(DMSO) – (4)
Compound 4 crystallises in the centrosymmetric space group of
the triclinic system. Asymmetric unit of 4 is built of one MgPc
(DMSO) and one MgPc(H2O) molecules that co-crystallise with

96
J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
Fig. 6. View of the molecular structure of 3 along with the labelling scheme, thermal ellipsoids are shown at the 50% probability level, H atoms with arbitrary radii (a) and the
crystal packing showing the N4-N4 distances between the back-to-back units of 3, the MgPc(3,4-lut) and MgPc(H2O).2(3,4-lut) units are shown in black and red, respectively
(b).
DMSO molecules. Interaction of electropositively polarised Mg
Table 5
Hydrogen-bond geometry (Å,o) in 3.
atom of MgPc molecule with electronegatively polarised O atom
of DMSO and water molecules leads to its displacement from the
mean plane of four N-isoindole atoms by 0.497(2) and 0.474(2) Å
in direction of oxygen atom of water and DMSO molecules, respec-
tively. In addition, the interaction of Mg and the O atoms results in
deviation of a planar phthalocyaninato(2ꢁ) macrocycle in a saucer-
shape form. The geometrical parameters of the MgPc(H2O) mole-
cule in crystal 4 are quite similar to that observed in the crystals
2 and 3 (see Table 3), whereas that in MgPc(DMSO) molecule are
listed in Table 6. The X-ray geometrical parameters of the coordi-
nation environment of Mg cation in both axially ligated by O MgPc
molecules, MgPc(DMSO) and MgPc(H2O), are quite similar, i.e. the
axial MgAO bond is shorter than the four equatorial MgAN bonds.
DAHꢀ ꢀ ꢀA
O1AH1Oꢀ ꢀ ꢀN18
O1AH2Oꢀ ꢀ ꢀN19
DAH
Hꢀ ꢀ ꢀA
1.91(1)
2.08(1)
Dꢀ ꢀ ꢀA
2.727(4)
2.844(7)
DAHꢀ ꢀ ꢀA
175(5)
154(2)
0.82(1)
0.82(1)
3,4-lut and half disordered DMSO as solvent molecules (Fig. 7a).
The solvation 3,4-lut molecule is linked together with MgPc(H2O)
via OAHꢀ ꢀ ꢀN hydrogen bond. The coordination of Mg atom in both
MgPc-complexes is characterised by the tetragonal-pyramidal
environment of four equatorial N-isoindole atoms of phthalocya-
nine ring and the oxygen atom of axially coordinated water or

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
97
[80,81]. The MgPc(H2O) molecule links the solvent 3,4-lut molecule
via OAHꢀ ꢀ ꢀN hydrogen bond (Table 7). The orientation of the
hydrogen bonded 3,4-lut molecule in the MgPc(H2O)ꢀ(3,4-lut) moi-
ety in the crystal 4 is inclined to the N4-plane of Pc2ꢁ macrocycle
by 71.0(1)°. In the crystal the MgPc(H2O)ꢀ(3,4-lut) and MgPc
(DMSO) molecules related by an inversion are forming face-to-face
dimeric structures (Fig. 7b). The dimeric structure of [MgPc(H2O)ꢀ
(3,4-lut)]2 is formed by OAHꢀ ꢀ ꢀN hydrogen bond formed between
the coordinated oxygen atom of water molecule as a donor of
one molecule of MgPc(H2O) and the N-azamethine atom of the sec-
ond one with relatively short interplanar N4 – N4 distance of 3.606
(2) Å. The second dimeric structure of [MgPc(DMSO)]2 is formed by
Sꢀ ꢀ ꢀS and Sꢀ ꢀ ꢀO interactions between the face-to-face molecules
related by inversion with relatively long interplanar N4ꢀ ꢀ ꢀN4 dis-
tance of 6.995(3) Å between the Pc2ꢁ macrocycles. Both dimers
of face-to-face oriented molecules of MgPc(H2O)ꢀ(3,4-lut) and
MgPc(DMSO) are arranged in a stacking structure along the a-axis
(Fig. 7c). The N4 – N4 distances between the back-to-back oriented
phthalocyaninato(2ꢁ) macrocycles along the stacks of [MgPc
(H2O)ꢀ(3,4-lut)]2 and [MgPc(DMSO)]2 dimers are 3.570(2) and
3.338(2) Å, respectively. The dimers in 4 form highly ordered
stacking structure, while the interstacking space is filled by the dis-
ordered DMSO solvent molecules (Fig. 7c). Thus the
tion between the
p p interac-
-clouds of phthalocyaninato(2ꢁ) macrocycles
ꢁ
p
between the dimers is responsible for their organisation in solid,
however due to the Pc2ꢁ macroring distortion form planar confor-
mation, the
p p interaction is less effective in comparison to that
ꢁ
in the parent MgPc pigment. So their solubility is 4–5 times higher
than MgPc.
3.3.5. MgPc(DMSO) complex – (5)
Compound 5 crystallises in the centrosymmetric space group of
the triclinic system with four MgPc(DMSO) molecules per unit cell.
Asymmetric unit of 5 consists of two independent MgPc(DMSO)
molecules, in one of them the axial DMSO ligand is ordered
whereas in the other the axial DMSO ligand exhibits two non-
equivalent orientations with the occupation factors of 0.706(2)
and 0.294(2) for S11 and S12, respectively (Fig. 8a). The coordina-
tion of Mg in both MgPc(DMSO) molecules exhibits tetragonal-
pyramidal environment of four equatorial N-isoindole atoms of
Pc2ꢁ macrocycle and oxygen atom of axially coordinated DMSO
molecule. The four equatorial MgAN bonds with the Pc2ꢁ macrocy-
cle are slightly longer than the axial MgAO bond linked the DMSO
molecule Theoretical DFT optimisation of MgPc(DMSO) molecule
shows similar conformational parameters as in the crystal. The
equatorial MgAN and axial MgAO bonds in the MgPc(DMSO)
molecule obtained by the DFT calculations exhibits similar correla-
tion as found in the crystal, however the DFT axial MgAO bond is
somewhat longer than X-ray value, but still shorter than the equa-
torial MgAN bonds (Table 6). Full geometrical parameters of the
optimised conformation of the MgPc(DMSO) molecule are listed
in Supplementary (Table S3). The interaction of electropositively
polarised Mg with electronegatively polarised O atom of DMSO
ligand leads to its displacement for the N4-isoindole plane by
0.456(1) and 0.445(1) Å in the MgPc(DMSO) molecules with
ordered and disordered axial ligand, respectively. This interaction
results in deformation of the phthalocyaninate(ꢁ2) macrocycle
from the planar conformation to the saucer-shape form. In the
crystal 5, both independent MgPc(DMSO) molecules related by
inversion are forming dimeric structures in the face-to-face fashion
(Fig. 8b). The conformation of the [MgPc(DMSO)]2 dimer with
ordered axial DMSO ligand in crystal 5 is very similar to that in
the crystal 4, whereas the structure of [MgPc(DMSO)]2 dimer with
disordered axial DMSO ligand resembles the dimeric structure of
[MgPc(H2O)ꢀ(3,4-lut)]2 observed in crystal 4 (see Figs. 7b and 8b).
The interplanar N4 – N4 distances are 6.915(6) and 3.691(3) Å in
Fig. 7. View of the molecular structure of 4 along with the labelling scheme,
thermal ellipsoids are shown at the 50% probability level, H atoms with arbitrary
radii (a) and the face to face dimers of [(MgPc(H2O).(3,4-lut)]2 and [MgPc(DMSO)]2
(b) and the crystal packing showing the N4-N4 distances between the back-to-back
units in 4, the [(MgPc(H2O).(3,4-lut)]2 and [MgPc(DMSO)]2 units are shown in red
and black, respectively (c).
In general, the DFT theoretical parameters are agree well with the
X-ray values, however the DFT axial MgAO bond of the MgPc(H2O)
molecule is longer than the four equatorial MgAN bonds, but in the
MgPc(DMSO) molecule the axial MgAO bond is somewhat shorter
than the four equatorial MgAN bonds. The MgAO binding strength
in MgPc(DMSO) and MgPc(H2O) molecules is related to properties
of the ligands such basicity and the Gutmann donor number

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J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
Table 6
Selected geometrical parameters (Å,o) for MgPc(DMSO) complex in crystals 4 and 5.
4
5
DFT
Mol. A
Mol. B
Mg2AN10
Mg2AN12
Mg2AN14
Mg2AN16
2.0413(16)
2.0392(16)
2.0343(16)
2.0418(16)
2.0014(16)
86.72(7)
87.07(6)
86.74(6)
87.08(6)
104.59(7)
102.84(7)
102.35(7)
103.98(7)
Mg1AN2
Mg1AN4
Mg1AN6
Mg1AN8
2.031(2)
2.035(2)
2.040(2)
2.037(2)
2.017(2)
87.27(8)
87.01(8)
86.58(8)
87.63(8)
104.28(8)
100.82(8)
101.48(8)
105.16(8)
2.034(2)
2.033(2)
2.030(2)
2.026(2)
2.005(2)
87.50(8)
86.79(8)
88.11(8)
86.61(8)
103.64(9)
100.07(8)
101.66(9)
105.19(9)
2.059
2.063
2.069
2.067
2.059
86.7
86.5
86.4
86.7
103.7
104.4
104.5
104.1
Mg2AO2
Mg1AO1
N10AMg2AN12
N12AMg2AN14
N14AMg2AN16
N10AMg2AN16
O2AMg2AN10
O2AMg2AN12
O2AMg2AN14
O2AMg2AN16
N2AMg1AN4
N4AMg1AN6
N6AMg1AN8
N2AMg1AN8
O1AMg1AN2
O1AMg1AN4
O1AMg1AN6
O1AMg1AN8
Deviation of Mg from the N4-plane
0.474(2)
0.456(1)
0.445(1)
0.505
Table 7
Hydrogen-bond geometry (Å,o) in 4.
the [MgPc(DMSO)]2 dimers with ordered and disordered axial
DMSO ligand, respectively. These dimers are further organised in
the stacking structure (Fig. 8c). The [MgPc(DMSO)]2 dimers with
ordered axial DMSO ligands related by translation are oriented in
the back-to-back fashion with an interplanar N4-N4 distance of
3.442(2) Å between the saucer-shaped Pc2ꢁ macrocycles forming
DAHꢀ ꢀ ꢀA
DAH
Hꢀ ꢀ ꢀA
2.18(1)
1.97(1)
Dꢀ ꢀ ꢀA
2.995(2)
2.784(3)
DAHꢀ ꢀ ꢀA
171(3)
173(3)
O1AH1O1ꢀ ꢀ ꢀN1i
0.82(1)
0.82(1)
O1AH2O1ꢀ ꢀ ꢀN17
Symmetry code: (i) ꢁx, ꢁy + 1, ꢁz + 1.
Fig. 8. View of the molecular structure of 5 along with the labelling scheme, thermal ellipsoids are shown at the 50% probability level, H atoms with arbitrary radii (a) and the
face to face dimers of [(MgPc(DMSO)]2 with ordered and disordered DMSO (b) and the crystal packing showing the N4-N4 distances between the back-to-back units in 5, the
[(MgPc(DMSO)]2 units with disordered and ordered DMSO are shown in black and red, respectively (c).

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
99
Table 8
stacks along b-axis, whereas the other dimers with disordered axial
Selected geometrical parameters (Å,o) for Mg(acac)2(H2O)2 – (6).
DMSO ligands related by translation are oriented in the back-to-
back fashion, with an interplanar N4-N4 distance of 3.530(2) Å,
forming stacks along a-axis (Fig. 8c). Thus the alternative arrange-
ment of the [MgPc(DMSO)]2 dimers in the stacks is determined by
X-ray
DFT
MgAO1
MgAO2
MgAO3
x2
x2
x2
2.0419(7)
2.0299(7)
2.1432(8)
88.88(3)
88.95(3)
91.76(3)
91.12(3)
91.05(3)
88.24(3)
174.65(9)
179.64(9)
ꢁ4.95(15)
ꢁ0.26(15)
2.046
2.046
2.194
86.9
86.0
86.1
93.1
94.0
93.9
178.9
ꢁ178.9
ꢁ0.6
0.6
the
p
ꢁ
p interaction within the stacks, whereas the van der Waals
O2AMgAO1
O1AMgAO3
O2AMgAO3
O1AMgAO2i
O1AMgAO3i
O2AMgAO3i
C1AC2AC3AC4
C2AC3AC4AC5
O1AC2AC3AC4
C2AC3AC4AO2
forces are responsible for the interstacking interactions. These
pꢁp
interaction within the stacks is less effective due to the saucer-
shaped form of Pc2ꢁ macrocycles, so the solubility is ꢃ5 times
greater comparing to that of the parent MgPc pigment.
3.3.6. Mg(acac)2(H2O)2 – (6) and C10H12O2 – (7)
Compound 6 crystallises in the centrosymmetric space group
P 21/c of the monoclinic system with two molecules per unit cell.
Asymmetric unit of 6 consists of half Mg(acac)2(H2O)2 molecule
since the Mg lies in the inversion. The Mg2+ cation is chelated by
two acacꢁ anions forming distorted square planar coordination
and by two water molecules in the axial positions, above and
below the square plane of MgO4 forming elongated square bipyra-
mid (Fig. 9a). The four equatorial MgAO bonds linking the Mg2+
with chelate acac- anions are shorter by ꢃ0.1 Å than the axial
bonds linking the Mg2+ with water molecules (Table 8). Due to
the chelating effect the OAMgAO angle with both O atoms belong-
ing to the same acacꢁ anion is slightly smaller than the other
OAMgAO angle with oxygen atoms coming from different acac-
ligands. The carbon chain together with the oxygen atoms of acacꢁ
are almost planar. Quite similar bipyramidal environment of Mg
atom of Mg(acac)2(H2O)2 complex is preferred in solution and in
the gas-phase as is evidenced by the DFT molecular orbital calcula-
tions, however the calculated axial MgAO is slightly longer that in
the crystal (Table 8). Full geometrical parameters of the optimised
conformation of the MgPc(acac)2(H2O)2 molecule are listed in Sup-
plementary (Table S4). Arrangement of MgPc(acac)2(H2O)2 mole-
cules in the crystal is determined by the OAHꢀ ꢀ ꢀO hydrogen
bonds (Table 9) formed between the water molecules of one
Symmetry code: (i) ꢁx + 1, ꢁy + 1, ꢁz + 1.
Table 9
Hydrogen-bond geometry (Å,o) in 6.
DAHꢁA
DAH
HꢁA
DꢁA
DAHꢁA
174(1)
155(1)
O3AH31ꢁO1ii
0.84(2)
0.87(2)
2.09(2)
2.12(2)
2.928(1)
2.930(1)
O3AH32ꢁO2iii
Symmetry codes: (ii) ꢁx + 1, ꢁy, ꢁz + 1; (iii) ꢁx + 1, y ꢁ 1/2, ꢁz + 3/2.
MgPc(acac)2(H2O)2 molecule with the O atoms of acac- of the
neighbours MgPc(acac)2(H2O)2 molecules, forming layers parallel
to the (1 0 0) plane (Fig. 9b). Between the layers there are no direc-
tional interactions, as hydrogen bonds, and they are arranged each
other via van der Waals forces. The van der Waals forces are less
effective and the (1 0 0) crystallographic plane is a cleavage plane
of the crystals.
Compound 7 crystallises in the centrosymmetric space group of
the triclinic system with four molecules per unit cell. Asymmetric
unit of 7 consists of two independent C10H12O2 molecules (Fig. 10).
The conformation of both independent molecules are very similar
(Table 10). Both 2-acetyl-3,4-dimetylphenol molecules in the crys-
tal are planar (without the H atoms of CH3 groups), and in both the
intramolecular OAHꢀ ꢀ ꢀO hydrogen bond formed between the
hydroxyl and carbonyl groups stabilise the planar conformation.
Quite similar conformation of 2-acetyl-3,4-dimetylphenol mole-
cule is observed in the gas-phase as is evidenced by the DFT molec-
ular orbital calculations (Table 10). Full geometrical parameters of
the optimised conformation of 2-acetyl-3,4-dimetylphenol mole-
cule are listed in Supplementary (Table S5). Arrangement of 2-
acetyl-3,4-dimetylphenol molecule with intramolecular OAHꢀ ꢀ ꢀO
is mainly determined by the van der Waals forces, since there
are no directional interactions between the molecules (Fig. S6).
Fig. 9. View of the molecular structure of 6 along with the labelling scheme,
thermal ellipsoids are shown at the 50% probability level, H atoms with arbitrary
radii (a) and the crystal packing of 6 showing the OAHꢀ ꢀ ꢀO hydrogen bonded layers
parallel to (0 0 1) plane (b).
Fig. 10. View of the molecular structure of 7 along with the labelling scheme,
thermal ellipsoids are shown at the 50% probability level, H atoms with arbitrary
radii. Dashed lines represent the intramolecular OAHꢀ ꢀ ꢀO hydrogen bonds.

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J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
Table 10
Selected geometrical parameters and the hydrogen-bond geometry (Å,o) for C10H12O2 – (7).
DFT
O1AC1
O2AC7
O1AC1AC2
O2AC7AC2
O1AC1AC2AC3
C8AC7AC2AC1
1.351(2)
1.240(2)
122.5(1)
119.8(1)
ꢁ179.5(1)
178.9(1)
O3AC11
O4AC17
O3AC11AC12
O4AC17AC12
O3AC11AC12AC13
C18AC17AC12AC11
1.355(2)
1.246(2)
122.5(1)
119.8(1)
ꢁ179.8(1)
176.6(1)
1.341
1.248
123.0
120.4
ꢁ178.8
174.1
DAHꢀ ꢀ ꢀA
DAH
0.82(1)
0.83(1)
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
DAHꢀ ꢀ ꢀA
152(2)
152(2)
O1AH1ꢀ ꢀ ꢀO2
O3AH3ꢀ ꢀ ꢀO4
1.728(1)
1.721(1)
2.486(2)
2.478(2)
DFT
O1AH1ꢀ ꢀ ꢀO2
0.999
1.604
2.505
147.5
3.4. UV–Vis spectroscopy of MgPc-derivatives 1–5
of 3,4-lutidine solution. The N-coordinated MgPc-derivative, i.e.
MgPc(3,4-lut) present in crystal 1 and in co-crystal 3, in 3,4-luti-
dine solution under air conditions transforms into aquamagnesium
phthalocyanine complex, which is more stable at this conditions
(Scheme 2), therefore the spectra od 1 and 3 complexes are quite
identical with the spectrum of 2. The Q and B bands in the UV–
Vis spectrum of MgPc(DMSO) complex (5) in 3,4-lutidine as well
as in DMSO solutions (Fig. 12) are blue shifted by ꢃ10 nm compar-
ing to that for the 1–3 (Fig. 11). Thus the Q band in the spectrum of
To further characterize of the MgPc-derivatives 1–5 the elec-
tronic absorption spectra were recorded. The spectra of 1–4 com-
plexes were recorded in 3,4-lutidine solutions (Fig. 11) whereas
the spectrum of complex 5 was recorded in 3,4-lutidine and DMSO
solutions (Fig. 12). The spectra of all complexes 1–5 show two
bands (Q and B) characteristic of the phthalocyaninate(2ꢁ) macro-
cycle [82,83]. The Q band of all 1–3 complexes (Fig. 11) is observed
at 672 nm (log
e
= 6.33) and the B band at ꢃ350 nm in the spectrum
MgPc(DMSO) in both solutions is observed at ꢃ662 nm (log
e =
6.29) and the B band at ꢃ340 nm. In contrast to the N-coordinated
MgPc-derivative (MgPc(3,4-lut)) that in 3,4-lutidine transforms
into aquamagnesium phthalocyanine complex, the MgPc(DMSO)
as O-coordinated MgPc-complex is stable in both 3,4-lutidine and
DMSO solutions under ambient conditions. The spectrum of 4
which is co-crystal of MgPc(H2O) and MgPc(DMSO) in 3,4-lutidine
solution is superposition of both MgPc(H2O) and MgPc(DMSO)
spectrum. This is clearly visible especially in the region of B band
(compare the Figs. 11 and 12).
The Q band corresponds to the excitation between the HOMO to
LUMO level and the B band corresponds to the HOMO-1 to LUMO
level. In addition, the vibronic splitting of the Q band is observed.
The splitting value of ꢃ60 nm is due to the vibronic coupling in
the excited state and was mentioned in the literature [84–86].
To investigate further optical properties of the 1–5 complexes
the time-dependent (TD) DFT calculations have been performed.
Optical absorption spectra were calculated for MgPc-derivatives
present in the 1–5 crystals, i.e. MgPc(3,4-lut), MgPc(H2O) and
MgPc(DMSO) complexes, and for the parent MgPc pigment, and
the results are summarised in Tables S6–S10 (SI). Partial molecular
energy diagram, HOMO and LUMO frontiers orbitals and the calcu-
lated absorption spectra for the MgPc(H2O) and MgPc(DMSO) com-
plexes present in solution of 1–5 compounds are shown in Fig. 13.
1.0
0.8
0.6
0.4
0.2
1 in 3,4-lut
2 in 3,4-lut
3 in 3,4-lut
4 in 3,4-lut
0.0
300
400
500
600
700
800
Wavelength [nm]
Fig. 11. UV–Vis spectra of 1–4 in 3,4-lutidine solution.
1.0
0.8
0.6
0.4
0.2
0.0
The calculated
(605 nm) for the MgPc(DMSO) complex and is blue shifted by
ꢃ7 nm in relation to that of the MgPc(H2O) complex ( E(HOMO/
DE between HOMO and LUMO orbitals is 2.046 eV
MgPc(DMSO) - 5 in DMSO
MgPc(DMSO) - 5 in 3,4-lut
D
LUMO) = 2.025 eV, 612 nm). Although, there are large number of
works reporting the theoretical DFT and TD-DFT calculations per-
formed on tetrapyrrole systems like as porphyrin, porphyrazin,
texaphyrin, bacteriochlorine, phthalocyanine, naphthalocyanine
and their complexes with various metal cations [87–92], the TD-
DFT calculations reporting on magnesium phthalocyanine and its
axially ligated derivatives are relatively few. For the pure MgPc
using the density functional theory and its time dependent
approach (TDDFT) in conjunction with the PBE0 exchange-correla-
tion functional and extended TZVP all-electron basis sets yield the
HOMO-LUMO energy gap of 2.100 eV (590 nm) [93]. The energy
gap between the HOMO and LUMO orbitals calculated for MgPc
and its axially ligated by pyridine (MgPcpy) or imidazole (MgPcIm)
by TDDFT with the same basis set (6ꢁ31+G(d)) is 2.0222 eV
300
400
500
600
700
800
Wavelength [nm]
Fig. 12. UV–Vis spectrum of 5 in 3,4-lutidine and DMSO solutions.

J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
101
CH3
CH3
N
CH3
N
CH3
N
CH3
CH3
+
N
+
N
N
N
N
Mg
N
N
+H2 O
N
H
H
(1)
N
O
CH3
N
CH3
N
N
N
N
N
N
CH3
CH3
Mg
N
N
N
N
N
+
+
Mg
N
N
N
crystal (3)
N
N
CH3
N
H3C
CH3
CH3
(in 3,4-lut solution)
+H2 O
CH
N
H
O
H
3 CH3
CH
3 CH3
+
N
+
N
N
N
N
N
N
Mg
N
N
N
(2)
Scheme 2. Equilibrium of 1–3 in 3,4-lutidine solution.
MgPc(H2O)
MgPc(DMSO)
ΔE(HOMO/LUMO) = 2.0251 eV (612 nm)
ΔE(HOMO/LUMO) = 2.0461 eV (605 nm)
Fig. 13. Partial molecular energy diagram, HOMO and LUMO frontiers orbitals and the calculated absorption spectra for the MgPc(H2O) and MgPc(DMSO) complexes.
(616 nm), 2.0141 eV (613 nm) and 2.0358 eV (609 nm), respec-
tively [75]. Aromatic macrocycles including metallophthalocyani-
nes are extensively studied as photosensitizers in a non-invasive
treatment (photodynamic therapy, PDT). The photosensitizer
should have a strong absorption in the therapeutic window
(600–900 nm). Moreover, the energy gap should be greater than
or equal to 22.5 kcal/mol [93,94]. In PDT, a photosensitizer in its
ground state (So) first absorbs energy and is excited to its
shorter-lived first excited state (S1), than undergoes conversion
to the first excited triplet state by intersystem crossing. The triplet

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J. Janczak / Inorganica Chimica Acta 478 (2018) 88–103
state of the photosensitizer can release its energy to the surround-
ing biological tissue exciting the oxygen from its triplet to the
highly active singlet state, that will eventually kill targeted cells.
The investigated here axially ligated magnesium phthalocyanine
complexes have a sufficient energy gap to excite ground state of
oxygen, and in addition the magnesium phthalocyanine deriva-
tives are non-toxic and can be tested as potential photosensitizers.
The calculated HOMO-LUMO transition for the MgPc(H2O) and
MgPc(DMSO) complexes is shifted by ꢃ50 nm in relation to that
of experimental value, however the difference between the kmax
of the Q band of these complexes is comparable with the experi-
mental results. Quite similar discrepancy between experimental
and theoretical Q values for the magnesium phthalocynanine axi-
ally ligated by pyridine (MgPcpy) or imidazole (MgPcIm) was
found [75]. The electronic absorption spectrum for the parent
MgPc pigment was also calculated for a comparison (Table S6
and Fig. S7). These results point that axial ligation of MgPc by O-
and N-donor ligands do not change significantly the descriptors
of the Q band, including the transition energy, the oscillator
strength and the main configuration when compared with that of
the parent MgPc pigment (Table S6 in SI).
Appendix A. Supplementary data
Additional material comprising the thermogravimetric analysis
of 1–5 and the DFT optimized parameters for MgPc(3,4-lut), MgPc
(H2O), MgPc(DMSO), Mg(acac)2(H2O)2 and the C10H12O2, and the
TD-DFT output for MgPc and the MgPc-derivatives. Full details of
the X-ray data collection and final refinement parameters includ-
ing anisotropic thermal parameters and full list of the bond lengths
and angles have been deposited with the Cambridge Crystallo-
graphic Data Center in the CIF format as supplementary publica-
tions no. CCDC 1573169, 1573170, 1573171, 1573172, 1573173,
1573174, 1573175 for 1–7 compounds, respectively. Copies of
the data can be obtained free of charge on the application to CCDC,
12 Union Road, Cambridge, CB21EZ, UK, (fax: (+44) 1223-336-033;
email: deposit@ccdc.cam.ac.uk). Supplementary data associated
with this article can be found, in the online version, at
https://doi.org/10.1016/j.ica.2018.03.018.
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This work clearly demonstrates, that even MgPc as the aromatic
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