Two novel tcpp porphyrinic compounds: In situ syntheses, characterization and reaction mechanism

Article abstract of DOI:10.4067/S0717-97072017000100015

Two novel porphyrinic compounds, {Zn[TCPP(CH₂CH₃)₂(CH₃)₂]}_n (1) and TCPP(CH₃)₄ (2) (TCPP = meso-Tetra(4-carboxyphenyl)porphyrin), with the TCPP(CH₂CH_3<

Full text of DOI:10.4067/S0717-97072017000100015

J. Chil. Chem. Soc., 62, Nº 1 (2017)
TWO NOVEL TCPP PORPHYRINIC COMPOUNDS: IN SITU SYNTHESES, CHARACTERIZATION AND
REACTION MECHANISM
DING-WA ZHANG1, WEN-TONG CHEN1,2,31
1Institute of Applied Chemistry, School of Chemistry and Chemical Engineering, Jinggangshan University, Ji’an, Jiangxi 343009, China
2Key Laboratory of Jiangxi Province for Persistant Pollutants Control and Resources Recycle (Nanchang Hangkong University),
Nanchang, Jiangxi 330000, China
3State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences,
Fuzhou, Fujian 350002, China
ABSTRACT
Two novel porphyrinic compounds, {Zn[TCPP(CH2CH3)2(CH3)2]}n (1) and TCPP(CH3)4 (2) (TCPP = meso-tetra(4-carboxyphenyl)porphyrin), with the
TCPP(CH2CH )2(CH )2 and TCPP(CH3)4 generated in situ, have been synthesized via a solvothermal reaction and structurally characterized by single-crystal
X-ray diffracti3on. Co3mpound 1 is characteristic of a two-dimensional (2-D) coordination polymer, based on the zinc ion coordinating to four nitrogen atoms and
two oxygen atoms. Compound 1 possesses a large void space (220 Å3) corresponding to 4.6% of the unit-cell volume. Compound 2 is characterized by an isolated
structure. The reaction mechanism of preparing both compounds was explored. The photoluminescence properties, FT-IR, UV-vis absorption spectra, fluorescence
lifetime and fluorescence quantum yield of TCPP were also reported.
Keywords: esterification, in situ, porphyrin, TCPP, zinc
Synthesis and characterization of TCPP(CH3)4 (2): Compound 2 was
synthesized by loading TCPP (0.1 mmol, 79.0 mg) and 15 mL methanol into a
25 mL Teflon-lined stainless steel autoclave and heating the autoclave at 443 K
for 7 days. After cooling slowly the mixture to room temperature at 6 K/h, red
crystals suitable for X-ray analysis were collected.
INTRODUCTION
An in situ reaction can possibly lead to the formation of a new compound
with a novel structure or interesting properties.1,2 In situ reactions under
solvothermal conditions have recently obtained a lot of attentions and many
novel compounds have been synthesized thus far.3-456 Porphyrins are one of the
most widely studied compounds and the important roles played in nature have
been found for several decades. Lots of efforts have been devoted to chemically
transform a porphyrin into a derivative with reformative features that may offer
it a possibly practical application.7-89 Numerous organic groups have so far been
used to transform porphyrins by decorating their periphery. However, among
which, the esterification of a porphyrin has been rarely reported. TCPP is a
large, rigid and square-planar symmetrical molecule with divergent carboxylic
groups that could be possibly esterified. Our recent efforts are mainly focusing
on the study of porphyrinic compounds,10-111213including the in situ reactions of
TCPP under solvothermal conditions. We report herein the in situ syntheses,
characterization and properties of two novel porphyrinic compounds,
{Zn[TCPP(CH2CH3)2(CH3) ]} (1) and TCPP(CH3)4 (2) (TCPP = meso-tetra(4-
carboxyphenyl)porphyrin). 2It nis noteworthy that the TCPP(CH2CH3) (CH3)
and TCPP(CH3)4 were generated in situ. The photoluminescence pro2perties2,
FT-IR, UV-vis absorption spectra, fluorescence lifetime, and fluorescence
quantum yield of TCPP are also reported in this work.
X-ray crystal structure determination: The intensity data set was collected
on a Rigaku Mercury CCD X-ray diffractometer with graphite monochromated
Mo-Kα radiation (λ = 0.71073 Å) by using an ω scan technique. CrystalClear
software was used for data reduction and empirical absorption corrections.14 The
structures were solved by the direct method using the Siemens SHELXTLTM
Version 5 package of crystallographic software.15 The difference Fourier maps
based on these atomic positions yield the other non-hydrogen atoms. The
hydrogen atom positions were generated theoretically and allowed to ride on
their respective parent atoms and included in the structure factor calculations
with assigned isotropic thermal parameters but were not refined. The structures
were refined using a full-matrix least-squares refinement on F2. All atoms
were refined anisotropically. A summary of crystallographic data and structure
analysis is listed in Table 1, and selected bond distances and bond angles for
compound 1 are given in Table 2. Crystallographic data for the structural
analysis have been deposited with the Cambridge Crystallographic Data
Centre, CCDC No. 893021 (1) and 1474473 (2). Copies of this information
may be obtained free of charge from the Director, CCDC, 12 Union Road,
Cambridge, CBZ 1EZ, UK (Fax: +44-1223-336033; email: deposit@ccdc.
cam.ac.uk or www:http://www.ccdc. cam.ac.uk).
EXPERIMENTAL
RESULTS AND DISCUSSION
All reactants of analytical reagent grade quality are obtained commercially
and used without further purification. FT-IR spectrum is performed with a
KBr disc in the range of 400–4000 cm−1 on a PE Spectrum-One spectrometer.
The photoluminescent spectra are carried out at room temperature using solid-
state samples on a JY FluoroMax-3 spectrometer. The UV-vis absorption
spectroscopies were conducted at room temperature on a computer-controlled
Hewlett Packard 89090A UV-vis spectrometer with the wavelength range of
190–1100 nm. Measurements of emission quantum yield of powdered samples
were carried out on a Hamamatsu C9920-0X(PMA-12) U6039-05 fluorescence
spectrofluorometer. Fluorescence lifetime measurements were carried out
using a Photon Technology International GL-3300 nitrogen laser.
The raw material is TCPP, but TCPP(CH2CH3)2(CH3) and TCPP(CH )4
exists in compounds 1 and 2, respectively. This suggests th2at in situ reactio3ns
have occurred under solvothermal environments. Single-crystal X-ray
diffraction analysis reveals that compound 1 is characteristic of a 2-D structure,
containing neutral {Zn[TCPP(CH2CH )2(CH3)2]}n layers. Compound
1
crystallizes in the space group C2/c of the3monoclinic system with four formula
units in a cell. All crystallographic independent atoms, except for zinc, are in
general positions. An ORTEP drawing of 1 with 30% thermal ellipsoids is
shown in Fig. 1.
Synthesis and characterization of {Zn[TCPP(CH2CH ) (CH3)2]}n (1):
Compound 1 was prepared by mixing ZnSO ·H2O (0.2 mmol,3325.8 mg), TCPP
(0.2 mmol, 158.0 mg), 5 mL methanol and 45 mL ethanol in a 25 mL Teflon-
lined stainless steel autoclave and heating the mixture at 443 K for 7 days.
After cooling slowly the mixture to room temperature at 6 K/h, red crystals
suitable for X-ray analysis were obtained.
e-mail: cwtqq@aliyun.com
3381

J. Chil. Chem. Soc., 62, Nº 1 (2017)
Table 1. Summary of crystallographic data and structure analysis.
Compound
Formula
Fw
1
C54H40N4O8Zn
938.27
2
C52H38N4O8
846.86
color
red
red
Crystal size/mm3
Crystal system
Space group
a (Å)
0.42 0.36 0.23
monoclinic
C2/c
0.12 0.11 0.06
monoclinic
P21/c
26.549(7)
8.474(2)
21.208(2)
90.49(1)
4771.1(18)
4
8.597(4)
10.889(5)
22.350(7)
101.506(12)
2050.2(15)
2
b (Å)
c (Å)
β (°)
V (Å3)
Fig. 1. ORTEP drawing of 1 with 30% thermal ellipsoids. Hydrogen atoms
are omitted for clarity.
Z
The macrocyclic core 24-membered ring of TCPP is nearly coplanar and
the displacement of the atoms in the equatorial mean plane is within ±0.087
Å. The six-coordinated zinc ion resides at the center of the almost coplanar
porphyrin macrocycle, coordinating with four nitrogen atoms and two oxygen
atoms to form a slightly distorted octahedron (Fig. 1). The bond distances of
Zn-N are from 1.975(3) Å to 2.010(3) Å with an average value of 1.993(3) Å,
which is comparable with that reported in the literature.16,17 The bond lengths of
Zn-O is 2.628(2) Å which is close to those documented previously.18 The result
of bond valence calculation shows that the zinc ion has a +2 oxidation state
[Zn(1): 2.33]. The phenyl groups are almost perpendicular to the 24-membered
macrocycle. The dihedral angles between the macrocycle and the phenyl groups
are 55.5(4)º and 89.3(8)º, respectively. Each Zn[TCPP(CH2CH3) (CH3)2] unit
connects to four neighboring ones via Zn-O bonds, yielding a co2ndensed 2-D
coordination polymer assembly in a herring-bone mode, as shown in Fig. 2.
2θmax (º)
50
50
Reflections collected
14096
10441
Independent, observed
reflections (Rint)
3603, 3063
(0.0405)
4002, 1286 (0.0830)
dcalcd. (g/cm3)
1.306
0.574
1.372
0.094
μ(mm-1)
T (K)
123
123
F(000)
1944
884
R1, wR2
0.0732, 0.0951
0.973
0.0648, 0.1662
1.097
S
Largest and Mean Δ/σ
Δρ (max, min) (e/Å3)
0, 0
0, 0
0.577, -0.273
0.662, -0.318
Table 2. Selected bond lengths (Å) and bond angles (°) for compound 1.
Zn(1)-N(1)
Zn(1)-N(1)#1
Zn(1)-N(2)
2.010(3)
2.010(3)
1.975(3)
1.975(3)
2.628(2)
2.628(2)
N(2)-Zn-N(1)#1
N(1)-Zn-N(1)#1
N(2)#1-Zn-O(2)#2
N(2)-Zn-O(2)#2
N(1)-Zn-O(2)#2
N(1)#1-Zn-O(2)#2
N(2)#1-Zn-O(2)#3
N(2)-Zn-O(2)#3
N(1)-Zn-O(2)#3
N(1)#1-Zn-O(2)#3
O(2)#2-Zn-O(2)#3
89.12(10)
180.0(2)
84.75(9)
95.25(9)
96.46(9)
83.54(9)
95.25(9)
84.75(9)
83.54(9)
96.46(9)
180.00(12)
Zn(1)-N(2)#1
Zn(1)-O(2)#2
Zn(1)-O(2)#3
N(2)#1-Zn-N(2)
N(2)#1-Zn-N(1)
N(2)-Zn-N(1)
180.0(2)
89.12(10)
90.88(10)
90.88(10)
N(2)#1-Zn-N(1)#1
Symmetry codes: #1 -x+1/2,-y+1/2,-z; #2 -x+1/2, y-1/2, -z+1/2; #3 x, -y+1,
z-1/2.
Fig. 2. The 2-D layer of 1 viewed along the b axis (a) and a axis (b).
It should be pointed out that compound 1 displays a large void space being
220 Å3 that is 4.6% of the unit-cell volume, as shown in Fig. 3. There is not
necessary to incorporate any counter anions into the large voids of compound
1 because the charge keeps balance.
3382

J. Chil. Chem. Soc., 62, Nº 1 (2017)
Fig. 3. Space-filling illustration of the porous crystalline architecture of 1.
To our knowledge, up to date only some complexes with both TCPP and
ester groups have been reported and for many cases the ester groups came
from the starting reagents.19,20 In order to reveal the reaction mechanism of
preparing compound 1, we put forward the following logical process: firstly,
the TCPP underwent a deprotonation step, then a metalation procedure, finally
esterification (Scheme 1). It is noteworthy that compound 1 is the first example
of porphyrins esterified with ethanol and methanol at the same time. This work
offers an effective method to the esterification of a porphyrin.
Scheme 1. A schematic diagram for the reaction mechanism of 1.
Single-crystal X-ray diffraction analysis discovers that compound 2
is characteristic of an isolated structure, consisting of neutral TCPP(CH3)4
molecules. Compound 2 crystallizes in the space group P21/c of the monoclinic
system with two formula units in one cell. All the crystallographic independent
atoms locate at general position. An ORTEP drawing of 2 with 30% thermal
ellipsoids is shown in Fig. 4. The macrocyclic core 24-membered ring of
TCPP is almost coplanar and the displacement of the atoms in the equatorial
mean plane is in the range of -0.035 Å – +0.035 Å. The phenyl groups are not
perpendicular to the 24-membered macrocycle. The dihedral angles between
the macrocycle and the phenyl groups are 60.84º and 67.72º, respectively. The
TCPP(CH3) molecules are solidified by van der Waals interaction to give a
crystal pack4ing structure, as shown in Fig. 5.
The FT-IR spectrum of TCPP shows that the bands mainly locate in the
range of 700–1700 cm–1, as shown in Fig. 6. The vibration bands at ~3318 cm-1
and ~964 cm-1 are attributed to the ν and δN-H vibrations of pyrrole rings.
These two bands suggest that the nitrNo-Hgen atoms are non-coordinated, which
is in good agreement with the crystal structure. The strong vibration bands
residing at around 1605 cm-1 and 1404 cm-1 are assigned to the asymmetric and
symmetric stretching vibration of the carboxylate group.
Fig. 4. ORTEP drawing of 2 with 30% thermal ellipsoids. Hydrogen atoms
are omitted for clarity.
3383

J. Chil. Chem. Soc., 62, Nº 1 (2017)
Fig. 5. Crystal packing of 2.
Fig. 7. UV-vis absorption spectrum of TCPP measured at room
temperature.
The reaction mechanism of preparing compound 2 is similar to that of
compound 1, as presented in Scheme 2.
Generally, solid-state porphyrinic compounds do not exhibit
photoluminescence due to the concentration quenching effect. However, if
porphyrinic compounds were dissolved in solution, they can usually display
bright red emission. The photoluminescence spectra of TCPP measured in
ethanol at room temperature are presented in Fig. 8. The photoluminescence
spectra reveal that the effective energy absorption is mainly resided in the
wavelength region of 400–600 nm. The excitation spectrum under the emission
of 650 nm shows four bands at 432, 519, 548 and 589 nm. We also measured
the corresponding emission spectrum with the use of an excitation wavelength
of 589 nm. We find that the emission spectrum displays a strong emission
band at 650 nm with a shoulder peak at 710 nm. The photoluminescence
quantum yield of TCPP in ethanol was determined to be 0.044. By using a
time-correlated single photon counting technique, the fluorescence lifetime in
ethanol was performed upon the excitation wavelength of 421 nm. The decay
of the singlet-excited states was fitted as single exponential, from which the
fluorescence lifetime of TCPP is 0.17 ns.
Scheme 2. A schematic diagram for the reaction mechanism of 2.
Fig. 8. Photoluminescence spectra of TCPP. Green: excitation; red:
emission.
Fig. 6. FT-IR spectrum of TCPP.
Fig. 7 displays the UV-vis absorption spectrum of TCPP measured at room
temperature. To our knowledge, porphyrinic compounds can generally display
two kinds of absorption bands, i.e. one intensive Soret band (B band) at ~400
nm and several weaker Q bands at around 500–650 nm. The Soret band of
TCPP is found at 416 nm, while its Q-bands are observed at 512, 546, 590 and
645 nm. The number of Q bands is four which is larger than two, indicating
that the nitrogen atoms are non-coordinated, which is also in good agreement
with the crystal structure.
CONCLUSIONS
In
conclusion,
two
novel
porphyrinic
compounds,
{Zn[TCPP(CH2CH3)2(CH3) ]} (1) and TCPP(CH3)4 (2) (TCPP = meso-tetra(4-
carboxyphenyl)porphyrin), 2winth the TCPP(CH2CH )2(CH3)2 and TCPP(CH )4
generated in situ, have been synthesized and char3acterized. Compound 13is
characteristic of a 2-D coordination polymer, based on the zinc ion coordinating
to four nitrogen atoms and two oxygen atoms. Compound 1 possesses a large
void space (220 Å3). Compound 2 is characterized by an isolated structure.
The reaction mechanism of preparing both compounds was explored. The
3384

J. Chil. Chem. Soc., 62, Nº 1 (2017)
photoluminescence properties, FT-IR, UV-vis absorption spectra, fluorescence
lifetime and fluorescence quantum yield of TCPP were also reported in this
paper. To gain deeper insight into the synthetic methodology, future study in
our laboratory will aim at preparing novel porphyrinic compounds.
7.- Silva A. M. G., Tomé A. C., Neves M. G. P. M. S., Cavaleiro J. A. S..
Tetrahedron Lett., 41, 3065–3068 (2000).
8.- Tomé A. C., Lacerda P. S. S., Neves M. G. P. M. S., Cavaleiro J. A. S..
Chem. Commun., 1199–1200 (1997).
9.- Cavaleiro J. A. S., Neves M. G. P. M. S., Tomé A.C.. Arkivoc, 14, 107–
130 (2003).
10.- Chen W.-T., Liu D.-S., Xu Y.-P., Luo Q.-Y., Pei Y.-P.. Luminescence, 31,
158–163 (2016).
11.- Zhang X., Chen W.-T., Suenobu T., Fukuzumi S.,Wang M.-S., Guo G.-C..
J. Porphyr. Phthalocya., 19, 1225–1231 (2015).
12.- Pei Y.-P., Huang J.-G., Chen H.-L., Kuang H.-M., Zhou J., Yang Y.-X.,
Chen W.-T.. J. Porphyr. Phthalocya., 19, 1140–1146 (2015).
13.- Chen W.-T., Huang J.-G., Lei X.-Y., Hu R.-H., Pei Y.-P., Yang Y.-X.,
Zhou J.. J. Iran. Chem. Soc., 13, 95–101 (2016).
ACKNOWLEDGMENTS
We gratefully acknowledge the financial support of the NSF of China
(21565016, 21361013), Jiangxi Provincial Science and Technology Support
Key Project (20152ACG70021), Jiangxi Provincial Natural Science Foundation
(20142BAB205062), Jiangxi Provincial Department of Education’s Item of
ScienceandTechnology(GJJ150761), JinggangshanUniversityNaturalScience
Item (JZ0813), the open foundation (ST201522007) of the Key Laboratory
of Jiangxi Province for Persistant Pollutants Control and Resources Recycle
(Nanchang Hangkong University), and the open foundation (20150019) of the
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on
the Structure of Matter, Chinese Academy of Sciences.
14.- Rigaku, CrystalClear Version 1.35, Rigaku Corporation, Tokyo, Japan
(2002).
15.- Siemens, SHELXTLTM Version 5 Reference Manual, Siemens Energy &
Automation Inc., Madison, Wisconsin, USA (1994).
16.- Shultz D. A., Mussari C. P., Ramanathan K. K., Kampf J. W.. Inorg.
Chem., 45, 5752–5759 (2006).
REFERENCES
1.- Lu J. Y.. Coord. Chem. Rev., 246, 327–347 (2003).
2.- Chen X. M., Tong M. L.. Acc. Chem. Res., 40, 162–170 (2007).
3.- Benny P. D., Fugate G. A., Barden A. O., Morley J. E., Silva-Lopez E.,
Twamley B.. Inorg. Chem., 47, 2240–2242 (2008).
17.- Gros C. P., Brisach F., Meristoudi A., Espinosa E., Guilard R., Harvey P.
D.. Inorg. Chem., 46, 125–135 (2007).
18.- Yang F.-A., Guo C.-W., Chen Y.-J., Chen J.-H., Wang S.-S., Tung J.-Y.,
Hwang L.-P., Elango S.. Inorg. Chem., 46, 578–585 (2007).
19.- Muniappan S., Lipstman S., Goldberg I.. Acta Crystallogr., Sect. C., 62,
m495–m497 (2006).
4.- Chen W.-T.. J. Chem. Res., 405–407 (2011).
5.- Chen W.-T., Hu L.. Acta Chim. Slov., 58, 167–170 (2011).
6.- Chen W.-T., Liu D.-S., Luo Z.-G., Chen H.-L., Liu J.-H.. J. Chem. Res.,
491–493 (2011).
20.- Muniappan S., Lipstman S., Goldberg I.. Acta Crystallogr., Sect. C., 62,
m140–m143 (2006).
3385