Porphyrinic coordination polymer-type materials as heterogeneous catalysts in catechol oxidation

Article abstract of DOI:10.1016/j.poly.2018.11.022

Coordination Polymer-type materials obtained from the reaction of 5,10,15,20-tetrakis[2,3,5,6-tetrafluoro-4-(4-pyridylsulfanyl)phenyl]porphyrin (H₂P1) and 5,10,15,20-tetrakis(4-pyridyl)porphyrin (H₂P2) with copper(II) and zinc(II) ac

Full text of DOI:10.1016/j.poly.2018.11.022

Accepted Manuscript
Porphyrinic Coordination Polymer-Type Materials as Heterogeneous Catalysts
in Catechol Oxidation
Kelly A.D.F. Castro, Flávio Figueira, Ricardo F. Mendes, Filipe A. Almeida
Paz, Maria da Graça P.M.S. Neves, José A.S. Cavaleiro, Shirley Nakagaki,
João P.C. Tomé, Mário M.Q. Simões
PII:
S0277-5387(18)30746-0
https://doi.org/10.1016/j.poly.2018.11.022
POLY 13569
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Revised Date:
Accepted Date:
27 July 2018
11 October 2018
6 November 2018
Please cite this article as: K.A.D. Castro, F. Figueira, R.F. Mendes, F.A. Almeida Paz, d.G.P.M. Neves, J.A.S.
Cavaleiro, S. Nakagaki, J.P.C. Tomé, M.M.Q. Simões, Porphyrinic Coordination Polymer-Type Materials as
Heterogeneous Catalysts in Catechol Oxidation, Polyhedron (2018), doi: https://doi.org/10.1016/j.poly.2018.11.022
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Porphyrinic Coordination Polymer-Type Materials as Heterogeneous
Catalysts in Catechol Oxidation
Kelly A. D. F. Castro,a,# Flávio Figueiraa,b,# Ricardo F. Mendes, Filipe A. Almeida
b
b
a
a
c
Paz, Maria da Graça P. M. S. Neves, José A. S. Cavaleiro, Shirley Nakagaki,
a,d,
a,
João P. C. Tomé, * Mário M. Q. Simões *
aQOPNA and Departamento de Química, Universidade de Aveiro, 3810-193 Aveiro, Portugal
bCICECO – Instituto de Materiais de Aveiro and Departamento de Química, Universidade de
Aveiro, 3810-193 Aveiro, Portugal
cLaboratório de Química Bioinorgânica e Catálise; Universidade Federal do Paraná, CP: 19081,
CEP: 81531-990, Curitiba, Paraná, Brasil
dCentro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco
Pais, 1049-001 Lisboa, Portugal
*Corresponding authors: jtome@tecnico.ulisboa.pt; msimoes@ua.pt
#These two authors contributed equally to this work.
Abstract
Coordination Polymer-type materials obtained from the reaction of 5,10,15,20-
tetrakis[2,3,5,6-tetrafluoro-4-(4-pyridylsulfanyl)phenyl]porphyrin (H
2
P1) and
5
,10,15,20-tetrakis(4-pyridyl)porphyrin (H P2) with copper(II) and zinc(II)
2
acetate are reported. Materials show catalytic activity for the oxidation of
catechol comparable to that of the copper Porphyrin-Metal Organic Framework
belonging to the same family of compounds previously reported by us. The
ability of the porphyrin's tetrapyrrolic core to accommodate metal ions of varying
charges seems to modulate the catalytic activity.
Keywords: porphyrin; heterogeneous catalysis; catechol oxidation; copper;
zinc.

1
1
. Introduction
Coordination polymers (CPs) are materials composed of metal ions linked
by organic ligands forming coordination-based extended arrays which could
span from linear (one-dimensional – 1D) to framework-type networks (three-
dimensional – 3D) [1-3]. Porphyrins are one of such linkers that can act as
attractive building blocks in the design of CPs due to their striking features,
particularly good thermal stability, planar and rigid structure and potential
application in catalysis [4-6], photosensitizers [7-10], sensors [11-14], among
several others [15]. We note that in recent years, CPs have been extensively
reported. Contrasting with the rich porphyrin chemistry developed in recent
decades [16-18], the sub-field of porphyrin-based CPs remains comparatively
less explored.
Robson and co-workers [19] reported the first study on the coordination
ability of the meso-pyridyl groups with metal ions by self-assembly. This original
report remains one of the most envisioning ones related to the birth of the CPs
field showing both the advantages of the design of such compounds, as well as
the various limitations which one can find when preparing such compounds.
Since then, many CPs based on pyridyl moieties were reported [20-21], mainly
on the 5,10,15,20-tetrakis(4-pyridyl)porphyrin [22-23]. Ma and co-workers
showed, for example, that it is possible to in situ metallate the porphyrin core
during the crystallization step [24].
The free-base porphyrin 5,10,15,20-tetrakis(4-pyridyl)porphyrin, in the
presence of different metal ions (e.g., Ag(I) [22], Co(II) [25], Fe (II) [26], Zn(II)
[
27], Mn(III) [28] and Cu(II) [29]), is able to form CPs. In addition, the intrinsic
coordination possibility of some metal cations being included in the porphyrin
core further enables the design of novel metal-dependent heterogeneous
catalysts. Suslick and co-workers showed, for the first time, that a porphyrin-
based CP can be used as an effective heterogeneous catalyst [30]: PIZA-3, a
microporous
solid
based
on
the
[5,10,15,20-tetrakis(4-
carboxyphenyl)porphyrinate] organic linker connected by trinuclear manganese
clusters, represents a significant advance in the development of porphyrin-MOF
for heterogeneous catalysis displaying high selectivity to the epoxidation of
cyclopentene (23% epoxide), cyclohexene (23% epoxide), cyclooctene (74%

2
epoxide), and limonene (20% epoxide). This material also displayed high
robustness to autoxidation and recovery/reusability capabilities.
Scheme 1. Schematic representation of the free-base porphyrins, its copper and zinc
derivatives and porphyrin-CP compounds.
We have recently reported the synthesis, characterization and catalytic
activity of a novel copper-porphyrin-CP by the reaction of 5,10,15,20-
tetrakis[2,3,5,6-tetrafluoro-4-(4-pyridylsulfanyl)phenyl]porphyrin with an excess
of copper(II) acetate, where the S-pyridyl groups on the periphery of the
fluorinated porphyrinic core was responsible for the formation of the hybrid
material itself (CuP1S of this work) [31]. Presently we focus on the preparation,
characterization and catalytic activity of a comprehensive series of CP-type
compounds constructed in a similar fashion from the pyridyl and S-pyridyl

3
porphyrins which react with copper(II) or zinc(II) cations (Scheme 1).
Compounds were effectively used as heterogeneous catalysts, with the derived
results being compared to the previous ones reported for discrete copper
complexes and copper-CP-based compounds [31].
2
. Experimental
All chemicals were purchased from Aldrich, Sigma or Merck and were of
analytical grade. Catechol was recrystallized from hot toluene and kept in the
dark. The synthesis and characterization of the free-base porphyrins was
performed as described in the literature [32]. H
modification of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin
-mercaptopyridine [32].
CuP1, CuP2, ZnP1 and ZnP2 (Scheme 1) were obtained from the
corresponding free-base porphyrin. The metalation reactions were performed
with copper acetate or zinc acetate in CHCl /MeOH (7:3) or dimethylformamide
DMF) using a stoichiometric ratio of 1:1 (Metal:Porphyrin). After 24 h under
magnetic stirring and reflux temperature with CHCl /MeOH (7:3) or 120 ºC with
2
P1 was obtained by structural
with
4
3
(
3
DMF, the solvent was removed under reduced pressure and the desired
metalloporphyrins were purified by column chromatography using
dichloromethane/methanol (7:3 v:v) as eluent to remove any remaining free-
base porphyrin. Complexes were characterized by UV-Vis, ATR-FTIR, electron
paramagnetic resonance (EPR) spectroscopies and mass spectrometry.
CuP1: HRMS ESI(+): m/z: calcd for C64
found: 1400.0122; UV-Vis (DMF) λmax, nm (log ): 413 (4.68), 538 (3.73) and
70 (3.32).
ZnP1: HRMS ESI(+): m/z: calcd for C64
401.0107; UV-Vis (DMF) λmax, nm (log ): 415 (5.41) and 552 (4.21).
H
25
F
N
16 8
S
Cu: 1400.0126 [M+H]+;
4
5
+
25
H F
16
N
8
S Zn: 1401.0120 [M+H] ; found:
4
1
+
CuP2: HRMS ESI(+): m/z: calcd for C40
H
25
N Cu: 680.1498 [M+H] ; found:
8
6
80.1490; UV-Vis (DMF) λmax, nm (log ): 412 (5.19) and 537 (3.73).
+
ZnP2: HRMS ESI(+): m/z: calcd for C40
H
25
N Zn: 681.1494 [M+H] , found:
8
6
81.1488; UV-Vis (CHCl
3
) λmax, nm (log ): 415 (4.90) and 540 (3.40). (see
Supporting information - SI).

4
2
.1. Synthesis of ZnCuP1S, CuZnP1S, ZnCuP2S, and CuZnP2S
Solids were prepared by reacting CuP1, ZnP1, ZnP2 or CuP2 with
copper(II) or zinc(II) acetate in DMF under magnetic stirring at ambient
temperature until the total consumption of the starting porphyrin (48 or 72 h).
ZnCuP1S was obtained by reacting CuP1 with 9 equiv. of zinc(II) acetate [31]
(
Scheme 1). CuZnP1S was obtained by the reaction of ZnP1 with 9 equiv. of
copper(II) acetate salt at ambient temperature. Procedures to isolate ZnCuP2S
and CuZnP2S were similar.
At the end of the reactions, the precipitation of the desired solids
ZnCuP1S, CuZnP1S, ZnCuP2S, and CuZnP2S was observed. Solids were
washed with different solvents (DMF, THF, H O, methanol and acetone) to
2
remove any contamination from the starting metalloporphyrins or metal salts,
dried under vacuum and characterized with a wide array of solid state
techniques (PXRD, ATR-FTIR, EPR, UV-Vis, and fluorescence in the solid
state).
2
.2. Synthesis of the porphyrinic materials ZnP1S and ZnP2S
Zinc acetate (10 equiv.) was added to a solution of H P1 or H
in DMF or CHCl /CH OH 7:3 (10 mL) respectively, and the mixture was
magnetically stirred at 120 ºC (for DMF) or maintained under reflux for 48 h (for
CHCl /CH OH). Purple precipitates were collected and sequentially washed
2
2
P2 (1 equiv.)
3
3
3
3
with water and organic solvents to remove free/unreacted zinc acetate or
porphyrin. Solids were dried under vacuum and characterized by PXRD, ATR-
FTIR, EPR, UV-Vis, and fluorescence in the solid state.
2
.3. Synthesis of the porphyrinic materials CuP1S and CuP2S
CuP1S and CuP2S were prepared according to previously reported
procedures by our research group [31].
2
.4. Catalysis
The catalytic activity of metalloporphyrins was evaluated by oxidizing
catechol in a phosphate buffer (pH = 8.0) while in the presence of air, with or
without the addition of aqueous hydrogen peroxide. Reactions were carried out
in the dark for different reaction times (between 15 min and 24 h) under

5
constant magnetic stirring and in a thermostatic bath (30 °C). The progress of
the catalytic reactions was monitored by UV-Vis spectroscopy. The kinetics of
the oxidation of catechol was determined by the reduction of the band at 508
nm (the nitrite method)[33]. For all reactions involving H
2
O a molar ratio of
2
1
:1000:100 (catalyst:H :catechol) was used. The reactions were also
2
O
2
conducted in the absence of hydrogen peroxide, the procedure being similar to
that described above.
2
.5. Characterization Techniques
Mass spectra were acquired on a LTQ OrbitrapTM XL hybrid mass
spectrometer (Thermo Fischer Scientific, Bremen, Germany) controlled by LTQ
Tune Plus 2.5.5 and Xcalibur 2.1.0. The capillary voltage of the electrospray
ionization source (ESI) was set to 3.0 kV. The capillary temperature was 275 ºC.
The sheath gas was at 65 (arbitrary units as provided by the software settings).
The capillary voltage was 42936 V and the tube lens voltage 1720 V.
Electronic spectra (UV-Vis) were obtained on a Shimadzu UV-2501PC
spectrophotometer, in the 350-800 nm range. For the diffuse reflectance
characterization an UV-VIS Jasco V560 spectrophotometer was employed.
Attenuated Total Reflectance Transmission Fourier Transform Infrared
(
ATR-FTIR) spectra were registered on a FT Mattson 7000 Galaxy series
-
1
spectrophotometer in the 400-4000 cm range. Spectra were collected with a
-
1
resolution of 4 cm and accumulation of 32 scans.
Powder X-ray diffraction (PXRD) measurements were collected on self-
oriented solids placed on neutral glass sample holders. Routine PXRD data for
all prepared materials were collected at ambient temperature on a Empyrean
PANalytical diffractometer (Cu Kα1,2 X-radiation, λ
1
= 1.540598 Å; λ = 1.544426
2
Å), equipped with an PIXcel 1D detector and a flat-plate sample holder in a
Bragg-Brentano para-focusing optics configuration (45 kV, 40 mA). Intensity
data were collected by the step-counting method (step 0.01º), in continuous
mode, in the ca. 3.5 ≤ 2θº ≤ 50º range.
Electron paramagnetic resonance (EPR) measurements were collected
on an EPR BRUKER EMX microX spectrometer (frequency X, band 9.5 GHz) at
both ambient temperature and 77 K (using liquid N
microwave polarization X-band.
2
), in the perpendicular

6
Fluorescence spectra were recorded using a fibre optic system
connected to a Horiba Jobin Yvon Fluoro Max-3 spectrofluorimeter while
exciting at appropriate  (nm) of the solid compounds.
3
. Results and Discussion
.1. Materials characterization
All the prepared solids were obtained under similar conditions. Syntheses
were carried out starting from the free-base H P1 or H P2 porphyrins which
3
2
2
reacted with copper(II) or zinc(II) acetate in DMF at ambient temperature or 120
ºC. CP-type materials were formed by coordination between the porphyrinic
precursor (either free or metallated) and Zn(II) or Cu(II) metal nodes. All
materials were extensively characterized by PXRD, FTIR, EPR, UV-Vis, and
fluorescence in the solid state.
Crystallinity of the new materials and of the metalloporphyrins was
assessed by means of PXRD. CuZnP1S and ZnCuP1S exhibit distinct PXRD
patterns (Fig. 1) which are different from the previously reported CuP1 [31] and
from ZnP1. From our previous studies with this type of materials, particularly in
the self-assembly of supramolecular structures with porphyrin-type molecules,
we know that the overall crystallinity is strongly affected by the need of the
materials to retain the crystallisation solvent molecules. With porphyrin-type
molecules, solvent molecules are easily removed from the compounds, even
when crystals are being formed in the reaction medium. Moreover, also for the
CuZnP1S and ZnCuP1S materials, the existence of the well-known
paddlewheel motifs induces additional separation between the building units
thus, expectedly, leading to the formation of channels that can be escape routes
of any solvent molecule. So, for all these materials it is not surprising to observe
the isolation of predominantly amorphous materials instead of very crystalline
ones. In addition, the distribution of metals in the framework architecture is an
additional source of disorder and, thus, a motor for the isolation of amorphous
compounds. Goodwin and co-workers [34] reported, for example, that the metal
cation or ligand positions are strongly correlated with amorphous compounds.
Finally, it is important to note that the complexity of these building units can
promote the self-assembly in the solid-state in semi-crystalline forms with very

7
different space groups, hence, when observed, the presence of distinct powder
X-ray diffraction patterns.
(
a)
(
b)
(
c)
(
d)
10
15
20
25
30
35
40
45
50
2

/ Degree
Figure 1.
ZnP2 shows the expected PXRD pattern [35]. The reaction between CuP2
or ZnP2 and copper(II) or zinc (II) acetate leads to the isolation of
microcrystalline powders that do not exhibit diffraction peaks corresponding to
either the free salts or the metalloporphyrins (Fig. 2). Although the materials are
(
poorly) crystalline, it was not possible to unveil their crystal structure by means
of X-ray crystallography as in our previous studies.

8
(
a)
(
b)
(
c)
(
d)
5
10
15
20
25
30
35
40
45
50
2
/ Degree
Figure 2.
The ATR-FTIR of ZnP1 and ZnP1S, CuZnP1S and ZnCuP1S are depicted
in Fig. 3. The typical symmetric and asymmetric stretching bands of the pyrrole
-
1
ring of  NH,  CH of H
2
P1 are observed in the range 700–1700 cm . For H P1,
2
-
1
the band at 3300 cm , ascribed to NH stretching was also observed (Fig. 3a). It
is noticeable the disappearance of NH vibrations, that suggests a complete
−
1
metalation reaction. A strong band emerged near 1000 cm , due to the
metalloporphyrin skeletal ring, indicating the formation of Zn(II) porphyrin
-
1
compound. The bands observed at ∼1571 and ∼1413 cm for ZnP1S, at 1571
-
1
-1
and 1406 cm for ZnCuP1S and at 1546 and 1411 cm for CuZnP1S, are
attributed to the as(C=O) and  (C=O) vibrational modes, respectively. We
s
believe that these vibrations must arise from the presence of the typical paddle
wheeled Cu(II) or Zn(II) acetate cluster, in a similar fashion to that reported for
CuP1S. The difference between the bands for the asymmetric and symmetric
stretching (Δν) for both materials suggests the presence of carboxylic groups
linked via a  -syn,syn-bridge [31]. ZnP2S, ZnCuP1S and CuZnP1S exhibit the
2
-
1
−1
same vibrations at 1560 and 1400 cm . The band at ~1720 cm may refer to
C=O stretching from DMF molecules which seems to be present in all
compounds.

9
(
a)
(
b)
(
c)
(
d)
(
e)
4
000
3000
2000
1000
-1
Wavenumber / cm
Figure 3.
The EPR spectra of the metalloporphyrins and CP-type materials are
depicted in Figs. 4 and S3 in the SI. The EPR spectra of ZnP1, ZnP2 and of
ZnP1S and ZnP2S are similar, without EPR signals, attesting that the solids are
not contaminated with any other paramagnetic species. The EPR spectrum of
ZnCuP1S exhibits the characteristic anisotropic signal expected for Cu(II) in
axial symmetry, showing the expected four lines with gII > g and with a
⊥
hyperfine splitting (A = 234 G) higher than that of CuP1S and CuP1. The
/
/
values of g , g , and A for ZnCuP1S and CuP1 were distinct, showing that
// //
⊥
the presence of zinc(II) ions affects the metalloporphyrin core. CuZnP1S
displayed an anisotropic signal with four characteristic lines of copper(II), axial
symmetry in the region of g = 2.0, and different values of g// and g⊥. However,
in this case, it also evidences a multiple-line pattern in the perpendicular
spectrum region. This is typical of a superhyperfine interaction (A
the copper(II) ion unpaired electron with four magnetically equivalent N nuclei
I = 1) arising from pyridyl groups which should result in the expected
N
= 17 G) of
14
(
deployment of each signal into nine lines. The CuP2 derivative CP-type
materials (Fig. S3) also exhibit the characteristic anisotropic signal of copper(II),
S = 3/2, in axial symmetry in the region of g = 2.0.

1
0
Nonomura and co-workers studied the EPR of Cu(II) complexes of
porphyrins, chlorins and phthalocyanines, and showed a strict relationship
between the values of A//, g// and the degree of distortion in these compounds: a
larger distortion is associated with greater values of g// and lower values of A//
.
The patterns observed in EPR spectra indicate the presence of copper as linker
in the solids (Table 1).
Table 1. Spin Hamiltonian Parameters obtained for the X-band EPR spectral
simulations of CuP and materials at 77 K.
Compound
A
//Cu
g
//
g
┴
CuP1
CuP1S
ZnCuP1S
CuZnP1S
CuP2
CuP2S
ZnCuP2S
CuZnP2S
218
202
234
128
199
190
183
176
2.193
2.193
2.344
2.331
2.189
2.206
2.305
2.264
2.057
2.058
2.056
2.048
2.073
2.081
2.060
2.067
The EPR parameters listed above were obtained by simulating the experimental spectrum for
solid samples at 77 K. The Simfonia simulation pack software was employed. Hyperfine
coupling constants are expressed in Gauss.
The UV-Vis spectra of the materials and of the precursor complexes are
depicted in Figs. 5 and S4 (in the SI), revealing the typical UV-Vis features of
porphyrins, namely the Soret (410-440 nm) and the Q-bands (500-650 nm)
arising from π-π* transitions. The Soret bands are slightly blue-shifted (ca. 3-9
nm) when compared with those of the corresponding metalloporphyrins. On the
other hand, the Q-bands are red-shifted (ca. 1-21 nm, depending on the
porphyrin).
The solid-state interactions lead to broadening of the bands. The
displacement observed for the Soret band of the materials may be caused by
modifications of the metalloporphyrin molecular environment. The red-shift of
the Q-bands indicates an increasing of π-conjugation and a HOMO–LUMO
energy gap reduction caused by the change of local symmetry.

11
(
f)
(
(
e)
d)
(
c)
(
(
b)
a)
2600
2800
3000
3200
3400
3600
3800
Magnetic Field / Gauss
Figure 4.
424
417
538
572
542
438
575
429
559
(
a)
435
560
(b)
558
629
422
598
(
(d)
c)
595
546
630
(
e)
(
f)
350
400
450
500
550
600
650
700
Wavelength / nm
Figure 5.
The fluorescent properties of the metalloporphyrins and of the materials
were also studied in the solid state. As depicted in Fig. 6, with excitation at 420
nm H P1 emits strong fluorescence with peaks at 663 and 704 nm which
2
correspond to the S1→S0 transitions of the porphyrins. ZnP1 emits with a peak
at 633 and a shoulder at 685 nm. The corresponding ZnP1S shows only a

1
2
broad emission band centred at 654 nm, suggesting that the linker cluster
exerts to some extent influence on the fluorescence properties [36]. Generally,
the porphyrin chromophore in the solid state can form aggregates that lead to
fluorescence quenching. This behaviour was observed for H P2 (Fig. S5, see
2
SI).
The coordination of zinc reduces the electron delocalization of the
porphyrin molecules, which increases the lowest excited state energy level. As
a consequence, the energy level difference of the S1→S0 transition was
widened and a blue-shift for ZnP1 and ZnP1S was observed.
For CuP1, CuP2 and materials CuP1S, CuP2S, ZnCuP1S and ZnCuP2S
no emission was observed, which is due to an open-shell configuration,
attributed to the effect of the coordinated Cu(II) in the porphyrin core (see Fig. 6
and Fig. S5 in the SI). Copper porphyrins are non-luminescent due to the
intersystem crossing transition from excited singlet to triplet states. For
CuZnP1S and CuZnP2S, the presence of an open-shell copper(II) ion in the
materials provides a local fluorescence quenching site, due to relaxation via d–d
transitions [37].
633
704
663
685
654
(
a)
b)
(
(
(
c)
d)
(
e)
(
f)
(
g)
550
600
650
700
750
800
Wavelength / nm
Figure 6.

1
3
3
.2. Catalytic activity
We have recently reported that the CP-type materials obtained from the
reaction of H P1 and H P2 with copper(II) acetate were able to act as
2
2
biomimetic catalysts of catechol oxidase. CuP1S and CuP2S showed high
heterogeneous catalytic activity in the oxidation of catechol into ortho-
benzoquinone in the presence or absence of aqueous H
2
O (30% w/w) when
2
compared to CuP1 and CuP2, particularly CuP1S [31].
The conversion of catechol into ortho-benzoquinone was determined by
the nitrite method. Results are summarized in Fig. 7 and all the assays were
performed without hydrogen peroxide. Complexes ZnP1 and ZnP2 are inactive
in catechol oxidation, with similar results being observed for non-catalysed
reactions. ZnCuP1S showed a similar conversion rate to that obtained for
CuP1, showing that the zinc clusters do not influence catechol conversion.
The heterogeneous catalytic systems using ZnCuP1S and CuZnP1S
attain a maximum of 16-18% after 24 h when the experiments are performed
without the addition of H
2
O . It is known that the peripherally-coordinated
2
copper centres linked to the pyridyl units have catalytic activity in the oxidation
of catechol. The catalytic efficiency of CuZnP1S is, however, lower when
compared to CuP1S (which affords total conversion at the same time of
reaction (Fig. S6, SI) [31]). The catalytic activity of CuP1S was approximately 5
times higher than CuZnP1S or ZnCuP1S under the same experimental
conditions (Fig. S6, SI) [31]. ZnCuP2S shows similar catalytic performance to
CuZnP2S.

1
4
2
1
1
0
5
0
5
0
CuZnP1S
CuZnP2S
ZnCuP1S
ZnCuP2S
ZnP1
ZnP2
ZnP1S
ZnP2S
Control
1
8
16
15
16
1
5
14
1
3
1
2
10
1
0
1
0
6
6
5
4
4
1
3
6
2
8
4
1
1
2
Time / h
Figure 7.
The catalytic reactions were also performed in the presence of hydrogen
peroxide as oxidant. The collected data are summarized in Fig. 8 (and also Fig.
S6, SI) and show that the catalytic activity is highly dependent on the reaction
time. An increase in the reaction time from 1 to 6 h using CuZnP1S as catalyst
leads to a remarkable increase in the total conversion from ca. 5 to 22%. The
catalytic efficiency of the CP-type materials reported here follows the order
CuZnP1S and CuZnP2S > ZnCuP2S > ZnCuP1S, with average conversions of
5
6%, 55%, 35%, and 25% after 24 h, respectively. We note that the reactivity
order was not the same in the absence of hydrogen peroxide (ZnCuP1S >
CuZnP1S > CuZnP2S = ZnCuP2S, Fig. 7).
Materials formed from CuP1 were slightly more active. The difference in
the tetrapodal linkers in terms of rigidity, such as observed for CuP2S, with a
more rigid nature, is less effective than materials containing CuP1. The variation
in the catalytic activity with changes in the electronic structure suggests that a
synergism between the metalloporphyrin and the peripherally-coordinated metal
centre may occur, rendering a strong effect on the affinity for the substrate.

1
5
CuZnP1S
ZnCuP2S
ZnCuP1S
CuZnP2S
ZnP1
ZnP2
ZnP1S
ZnP2S
Control
29
30
20
10
0
(
A)
23
21
19
18
17
1
4
8
5
5
4
5
2
2
2
1
5
0
5
0
1
3
4
6
Time / min.
CuZnP1S
ZnCuP2S
ZnCuP1S
CuZnP2S
ZnP1
ZnP2
ZnP1S
ZnP2S
Control
60
40
20
0
56
55
(
B)
39
35
34
25
24
2
3
22
16
16
10
8
6
8
9
6
6
5
5 3 5
5
4
3 4
4
3
6
4
2
Time / h
Figure 8.
With the set of results obtained for CuZnP1S and for CuZnP2S, the
positive contribution made by Cu(II) coordinated to the pyridyl groups seems
clear. However, when comparing the catalytic activity of CuP1S, CuZnP1S and
ZnCuP1S, one notices that the activity observed for CuP1S is not simply the

1
6
sum of that of the peripherally-coordinated copper cations and CuP1,
suggesting that the good catalytic performance obtained previously for CuP1S
is related to the structure of the catalyst itself. Similar behaviour was observed
for CuZnP2S and ZnCuP2S. In fact, the appropriate network topology may
increase the observed catalytic activity [38]. We further notice that the structure
of the porphyrins also affects the crystal topology by changing the dihedral
angles of the meso-aryl groups, according to Yamada [39].
Kaiser and co-workers [40] prepared a series of mixed-ligand copper
complexes able to mimic catechol oxidase and proposed that the electron
density on the copper centre significantly increase the reactivity towards the
oxidant used. In this work, the difference of the external metals clearly has a
remarkable effect on the network architecture, which ultimately impacts the
catalytic activity.
4
. Conclusions
The synthesis and characterization of new solid materials, obtained from
the porphyrins H P1 and H P2 with copper(II) or zinc(II) acetate is reported, as
2
2
well as their copper and zinc MOF derivatives. These porphyrin-based insoluble
materials evidenced only fair catalytic activity for the oxidation of catechol by
oxygen from air, whereas with the addition of aqueous hydrogen peroxide good
catalytic activity was registered for the oxidation of catechol, a substrate
suitable to identify functional models of catechol oxidase. Results for CuZnP1S
and for CuZnP2S seem to indicate that Cu(II) bound to the pyridyl groups has a
key contribution in the catalytic system. The coordination of pyridyl units with
metal clusters provide adequate catalysts towards catechol conversion,
depending of the set metal cluster and porphyrin macrocycle. The ability of the
porphyrin's tetrapyrrolic core to accommodate metal ions of varying charges
seems to modulate the catalytic activity.
Acknowledgements
Thanks are due to Conselho Nacional de Desenvolvimento Científico e
Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível
Superior (CAPES). We wish to also thank Fundação para a Ciência e a
Tecnologia (FCT) for the financial support to QOPNA (FCT

1
7
UID/QUI/00062/2013),
CICECO
(POCI-01-0145-FEDER-007679;
FCT
UID/CTM/50011/2013) and CQE (FCT UID/QUI/0100/2013) research units,
through national funds and, where applicable, co-financed by FEDER, within the
PT2020 Partnership Agreement. K.A.D.F. Castro, R.F. Mendes, and F. Figueira
gratefully acknowledge CNPq for the granted post-doctoral scholarship
(
Process 201107/2014-7), the Ph.D. grant No. SFRH/BD/84231/201 and the
project FCT UID/QUI/00062/2013 for the associated scholarship (Ref.
BI/UI89/5508/2016), respectively.

1
8
FIGURE CAPTIONS
Figure 1. PXRD for (a) ZnP1, (b) ZnP1S, (c) ZnCuP1S and (d) CuZnP1S.
Figure 2. PXRD for (a) ZnP2, (b) ZnP2S, (c) ZnCuP2S and (d) CuZnP2S.
Figure 3. ATR-FTIR spectra of (a) H P1 (b) ZnP1S, (c) ZnCuP1S, (d) ZnP1 and (e) CuZnP1S.
2
Figure 4. EPR spectra of (a) ZnP1, (b) ZnP1S, (c) ZnCuP1S, (d) CuP1, (e) CuP1S and (f)
CuZnP1S.
Figure 5. UV-Vis spectra in the solid state of (a) CuP1, (b) CuP1S, (c) ZnP1, (d) ZnP1S, (e)
CuZnP1S and (f) ZnCuP1S.
2
Figure 6. Emission spectra in the solid state for (a) H P1 (b) ZnP1 (c) ZnP1S (d) ZnCuP1S (e)
CuZnP1S (f) CuP1 and (g) CuP1S.
Figure 7. Catechol oxidation in the presence of air (without H
2
O ) catalyzed by CuZnP1S,
2
ZnCuP1S, ZnP1, ZnP1S, CuZnP2S, ZnCuP2S, ZnP2 and ZnP2S in phosphate buffer (pH 8.0).
Conversions were calculated based on the amount of substrate remaining. Results represent
reactions performed in duplicate or triplicate. Under these conditions the conversion values
were in the range of ± 2.0%. The formation of ortho-benzoquinone from catechol was confirmed
by the appearance of its characteristic band at ca. 480 nm. Results for CuP1, CuP2, CuP1S
and CuP2S from reference [31] are shown in the SI.
Figure 8. Catechol oxidation in the presence of 30% aqueous hydrogen peroxide (and air)
catalyzed by CuZnP1S, ZnCuP1S, ZnP1, ZnP1S, CuZnP2S, ZnCuP2S, ZnP2 and ZnP2S in
phosphate buffer (pH 8.0). Reactions were carried out in the dark for different reaction times:
(
A) between 15 min and 60 min and (B) 3, 6 and 24 h. Conversions were calculated based on
the amount of substrate remaining. Results represent reactions performed in duplicate or
triplicate. Under these conditions the conversion values were in the range of ± 2.0%. The
formation of ortho-benzoquinone from catechol was confirmed by the appearance of its
characteristic band at ca. 480 nm. Results for CuP1, CuP2, CuP1S and CuP2S from reference
[
31] are shown in the SI.

1
9
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2
2
Zn
Cu
ZnCuPS
CuZnPS CuPS
ZnPS
Catalyst

2
3
SYNOPSIS:
Coordination polymers (CPs) constructed from pyridyl or S-pyridyl porphyrins
containing copper or zinc clusters are reported. The metal cluster has a key
contribution in catechol oxidation.