Lanthanide porphyrin complexes: Synthesis and properties

Article abstract of DOI:10.1080/15533170903328537

A new meso-substituted unsymmetrical porphyrin, 5-(4-myristyloxy)phenyl- 10,15,20-triphenyl porphyrin, and a series of its hydroxy lanthanide complexes, (lanthanide ions: Gd, Tb, Dy, and Ho) were synthesized and characterized by elemental analyses, molar

Full text of DOI:10.1080/15533170903328537

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Lanthanide Porphyrin Complexes: Synthesis and
Properties
Yujing Zhang a , Jianhui Shi a , Yan Zheng b , Miao Yu a & Guofa Liu a
a College of Chemistry , Jilin University , Changchun, P.R. China
b Anesthesia Department of China-Japan United Hospital in Jilin University , Changchun,
P.R. China
Published online: 10 Nov 2009.
To cite this article: Yujing Zhang , Jianhui Shi , Yan Zheng , Miao Yu & Guofa Liu (2009) Lanthanide Porphyrin Complexes:
Synthesis and Properties, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:9, 605-608
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 39:605–608, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533170903328537
Lanthanide Porphyrin Complexes: Synthesis and Properties
Yujing Zhang,1 Jianhui Shi,1 Yan Zheng,2 Miao Yu,1 and Guofa Liu1
1College of Chemistry, Jilin University, Changchun, P.R .China
2Anesthesia Department of China-Japan United Hospital in Jilin University, Changchun, P.R . China
triphenyl porphyrin (2) and a series of lanthanide compounds
(3) are reported. They also have been characterized by elemental
analyses, molar conductances, UV -Vis, IR and 1H NMR spec-
tra. We also studied their luminescent properties by emission
spectra.
A
new meso-substituted unsymmetrical porphyrin, 5-(4-
myristyloxy)phenyl- 10,15,20-triphenyl porphyrin, and a series of
its hydroxy lanthanide complexes, (lanthanide ions: Gd, Tb, Dy,
and Ho) were synthesized and characterized by elemental analy-
ses, molar conductances, UV-Vis, IR and 1H NMR spectra. Their
luminescent properties are studied by emission spectra. Q (0-0) flu-
orescence bands of the complexes are in the region 649–650 nm and
Q (0-1) bands 714–715 nm. Quantum yields (ꢀf) of Q band for the
complexes are in the range 0.00151–0.08433 and ligand 0.07459.
EXPERIMENTAL
Reagents, Apparatus and Measured Conditions
All chemicals were reagent grade and were dried before use.
Elemental analyses were carried out with a Perkin-Elmer 240C
auto-elementary analyzer. The IR spectra (KBr pellets) were
recorded on a Nicolet 5PC-FT-IR spectrometer in the region
400–4000 cm.−1 1H NMR spectra were obtained on a Varian-
Unity-500 (MHZ) NMR spectrometer in CDCl3 and TMS as in-
ternal standard. Electronic absorption spectra in the 350–700 nm
region were recorded on a Shimadzu UV-240 spectrophotome-
ter using chloroform as solvent, emission spectra on a FLR006
fluorescence spectrometer at room temperature in the region
300–800 nm. Molar conductances at 25◦C and 10−3 mol·L−1 in
chloroform were measured on a DDX-111A conductometer.
Keywords complexes, hydroxyl, lanthanide, porphyrin
INTRODUCTION
The porphyrins are a class of macrocyclic compounds that
has high chemical and thermal stability.[1] For these centrosym-
metric molecules have an extensive system of delocalized π
electrons, moreover molecules can easily be modified,[2] they
have many different applications in nonlinear absorption[3] and
artified photo synthesis.[4] Besides, the porphyrin ring can co-
ordinate a wide range of metal ions and it is available with a
range of peripheral substitution, some of which are fairly easy
to synthesize. These features not only provide for structural di-
versity but also allow the electronic and optical properties to
be fine-tuned.[5] Among abundant porphyrins and metallopor-
phyrin complexes, lanthanide porphyrins have attracted an in-
creasing interest for their potential applications in electroactive
materials,[6] laser system,[7] molecular information storage,[8]
CD probes for chirality sensing of biological substrates,[9] nu-
clear magnetic resonance (NMR) shift reagents and dipolar
probes[10] and so forth.
Synthetic Procedures
The synthesis procedure for the porphyrin is illustrated in
Scheme 1. Myristyl chloride was synthesized from the reaction
of myristic acid and thioylchloride according to the published
procedure.[17] The unsymmetrically phenyl-substituted por-
phyrin 1 was prepared and purified according to the literature.[18]
The synthesis of porphyrin 2 was based on the following proce-
dures (see Scheme 1.)
Porphyrin 1 (1.00 g, 1.59 mmol) was dissolved in 270 ml
heating benzene, and triethylamine (2.00 ml, 11.37 mmol) was
added. Then added dropwise the solution of myristyl chloride
(2.3 ml, 14 mmol) and 10 ml benzene within 0.5 h to the above
solution with quickly stirring at 70◦C. The solution was refluxed
for 8 h. Benzene was distilled out of the mixture. then mixed
with 2 volumes of distilled water and extracted three times with
equal volumes of water. Concentrated chloroform solution and
added to a neutral aluminum oxide column (2.5 × 15 cm). The
first band containing 1 was eluted by chloroform. The second
band containing 2 was eluted by chloroform containing 10%
Our previous studies have provided some results on the lan-
thanide complexes.[11−16] In this paper, a new meso-substituted
unsymmetrical porphyrin, 5-(4-myristyloxy) phenyl-10, 15, 20–
Reccieved 11 July 2009; accepted 11 September 2009.
We would like to thank the National Natural Science Foundation of
China for financial support of this work (No. 20801022).
Address correspondence to Miao Yu, College of Chemistry,
Jilin Unversity, Changchun, 130023, P.R. China. E-mail: yumiao@
jlu.edu.cn
605

606
Y. ZHANG ET AL.
100 ml 0.1% aqueous AgNO3 and the chloroform layer was
separated. The mixture of chloroform (30 ml) and methanol (20
ml) were added to the separated chloroform. The mixture was
again shaken with 100 ml 0.1% aqueous AgNO3. This procedure
was repeated until no more AgCl precipitated. The chloroform
solution was concentrated and applied to chromatography alu-
minum oxide column. The first band containing a small amount
ligand, 2, was eluted by chloroform. The second band eluted
by chloroform containing 20% methanol, obtained the solution
of the complex. The product was crystallized by concentrated
the solution and finally product was dried under vacuum. Other
lanthanide complexes (3b, 3c, 3d) were prepared according to
the same route above.
RESULTS AND DISCUSSION
Elemental Analyses
The elemental analyses for carbon, hydrogen, nitrogen, em-
pirical formulas, yields and decomposition temperature are
given in Table 1.
SCH. 1. Synthesis of the porphyrin ligand and complexes.
Uv-Vis Spectra
absolute ethanol. The product was dried in vacuum. The yield
was 1.10 g.
The maximum absorption values (λmax) of the ligand and
complexes are given in Table 2. The absorption bands of the
free base 2 appear at 418, 515, 550, 591 and 646 nm. The
relative intensities of these bands are as follows: 418 ꢀ 515 >
550 > 591 > 646 nm. The absorption bands of the complexes
3d appear at 418, 516, 552, 591 nm. The relative intensities are
418 ꢀ 552 > 591 > 516 nm. Compared with the ligand 2, the
number of the absorption bands of the complexes decreases and
the absorption bands exhibit small shifts to longer wave lengths.
The UV spectra of the complexes show bands characteristic
of metalloporphyrins.[19] The absorption band behaviors of other
complexes (Gb, Tb, Dy) are also similar to the complex 3d.
C58H56N4O2(840.44): calcd. C, 82.82; H, 6.71; N, 6.66.
Found C, 82.82; H, 6.71; N, 6.66.1H NMR (500 MHz, CDCl3):
δ = 8.927 (d, 6H, pyrrole ring), 8.67 (d, 2H, pyrrole ring), 7.56,
7.83, 8.30, 7.34 (m, 19H, phenyl), 2.81-2.84 (d, 2H, -OOCCH2),
1.26-1.99 (m, 22H, (CH2)11-), 0.95-0.97 (d, 3H, CH3) and
-2.715 (s, 2H, pyrrole N H).
The hydroxy lanthanide complexes 3 were prepared accord-
ing to the following method. We take 3a for example. A mixture
of 2 (300 mg, 0.4 mmol) and hydration GdCl3·6H2O (600 mg,
1.5 mmol) were heated in an imidazole (10.0 g) melt at 210◦C
under the protection and stirring of a dry nitrogen stream for
two hours. The extent of the reaction was followed by measur-
ing the Uv-visible spectra of the reaction solution at ten minute
intervals. After cooling the reaction mixture to 100◦C, 150 ml
Infrared Spectra
The main band frequencies (cm−1) and assignments of the
distilled water was added and the solution filtered, washed sev- ligand 2 and complexes 3a, 3b, 3c, 3d were given in Table 3.
eral times with distilled water in a separating funnel, and finally
The bands at 3322 cm−1 and 965 cm−1 in the free por-
the product was dried under vacuum. The crude product was phyrin, are assigned to the N-H stretching and bend vibrations
dissolved in chloroform (200 ml). The solution was shaken with of the porphyrin core, respectively. These two vibration bands
TABLE 1
Characterization data of the compoundsa
Compounds Empirical formula
C (%)
H (%)
N (%)
Yield (%) Dec.tem.(◦)
2
C58H56N4O2
82.80 (82.82) 6.72 (6.71) 6.66 (6.66)
68.78 (68.74) 5.45 (5.47) 5.54 (5.53)
68.60 (68.63) 5.46 (5.46) 5.53 (5.52)
68.40 (68.39) 5.42 (5.44) 5.51 5.50)
68.20 (68.23) 5.42 (5.43) 5.50 (5.49)
82.5
84.3
83.2
86.5
84.7
>400
>200
>200
>200
>200
3a
3b
3c
3d
GdC58H55N4O3
TbC58H55N4O3
DyC58H55N4O3
HoC58H55N4O3
aTheoretical values are given in parentheses.

LANTHANIDE PORPHYRIN COMPLEXES
607
TABLE 2
UV-Vis spectra of the ligand and complexes
Compounds
λmax/ nm(ε [103M−1cm−1])
2
418 (1000)
419 (1010)
423 (1000)
418 (2640)
422 (214)
515 (13.4)
514 (16.0)
513 (5.52)
516 (3.60)
516 (3.39)
550 (6.83)
551 (8.80)
553 (1.93)
552 (1.60)
551 (1.10)
591 (5.52)
591 (6.17)
592 (4.86)
591 (4.20)
590 (2.48)
646 (4.86)
3a
3b
3c
3d
of complexes disappear, since the hydrogen atoms have been solution at 25◦C. And it is very clear that the ligand and com-
replaced by the lanthanide ions to form Ln-N bands. Existence plexes show all nonelectrolytic behavior[20]
of the Ln-OH bending vibration band in the region 1067–1071
.
cm−1 show that the oxygen atom of hydroxy group is bonded to
Luminescence Studies
lanthanide ion. All of above analysis prove that a hydroxyl and
Table 4 gives the emission spectral data and quantum yields
of the ligand and complexes. The emission spectra of the ligand
and complexes are shown in Figure 1.
porphyrin ring are coordinated to the lanthanide ions to form
complexes, 3a, 3b, 3c, 3d. Assignments of other absorption
bands are also presented in Table 2.
There are fluorescence of the S2 (B, Soret band) and S1 (Q
band) in porphyrin complexes. Fluorescence of the B (Soret)
band is attributed to transition from the second excited singlet
state S2 to ground state S0, S2 →S0. The Soret fluorescence
is about two orders of magnitude weaker than the S1 →S0 of
Q band emission. Its quantum yield is so low that sometimes
fluorescence becomes unobservable. This fluorescence emission
does not occur yet at room temperature in our experimental
excited wavelength, 415 nm. Q (0-0) fluorescence bands of the
complexes are in the region 649–650 nm and Q (0-1) bands
714–5 nm. Quantum yields (ꢀf) of Q band for the complexes
are in the range 0.00151–0.08433 and ligand 0.07459. Quantum
yields of the Q bands (S1 →S0) depend on the relative rates of
radiative process S1 →S0 and two radiationless process internal
conversion S1 → S0 and intersystem crossing S1 → Tn. Because
the spin forbidden process S1 → Tn play a predominant role
for radiationless deactivation of S1 in porphyrin complexes, the
fluorescence quantum yields of complexes are much less than
0.2.[21]
1H NMR Spectra
The 1H NMR chemical shift values (δ, ppm) were measured
in deuterium chloroform. We collected the corresponding data
of ligand 2 and complex 3b as above. Compared with the lig-
and, the signal peak of 3b, at 0.19 ppm (1H, -OH) appeared, and
the signal peak at −2.715 ppm disappeared. They indicated that
the ligand and hydroxyl group are all coordinated to the lan-
thanide ion. Other peaks of the complex were broaded because
of the paramagnetism of the lanthanide ions.
Molar Conductances
The molar conductance values of the ligand and hydroxy
complexes, Gd, Tb, Dy, Ho, are at 0.120, 0.340, 0.202, and
0.342 ꢁ−1cm2mol−1, respectively, in 10−3 mol·L−1 chloroform
TABLE 3
Infrared spectra of the ligand and complexes
The quantum yield is determined from the following
equation:
2
3a
3b
3c
3d Intensity
m
Assignment
3322
ν (N H)(pyrrole)
ν(C H)(phenyl)
ν(C H)(phenyl)
ν(C O)(carbony)
ν(C C) (phenyl)
ν(C C) (phenyl)
ν(C H) (pyrrole)
ν(C N) (pyrrole)
ν(C O) (acyloxy)
δ(N H)
Yu = Ys(Fu/Fs)(Au/As)
2922 2922 2922 2922 2920
2849 2849 2849 2849 2850
1749 1748 1748 1748 1748
1581 1578 1576 1576 1579
1508 1515 1517 1517 1516
1439 1441 1438 1438 1438
1344 1329 1328 1328 1328
1197 1196 1198 1200 1199
965
w
w
w
w
w
m
m
w
m
w
m
TABLE 4
Emission spectra of the ligand and complexes
Peak values(nm)
Compounds Q(0-0) Q(0-1) Q(0-2) Quantum yields, φf
2
607
600
605
604
605
649
649
648
651
647
712
715
716
710
698
0.07459
0.08433
0.00151
0.02121
0.03013
3a
3b
3c
3d
723 721 722 722 722
1071 1069 1069 1067
δ(CH2)
ν(Ln OH)
∗s: strong, m: medium, w: weak.

608
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FIG. 1. Emission spectra of the ligand and complexes.
where Fu (FZnTPP) and FS(F sample) are the measured flu-
orescence integral area of the the reference ZnTPP and sam-
ple, respectively, Au (AZnTPP) and As (A sample) are the ab-
sorbances of the the reference (ZnTPP) and sample, respec-
tively, and YZnTPP (YZnTPP = 0.033)[21] is the quantum yield of
the reference at the same excitation wavelength.
CONCLUSION
In the work, we synthesized a new meso-substituted un-
symmetrical porphyrin, 5-(4-myristyloxy) phenyl-10, 15, 20-
triphenyl porphyrin, and a series of its hydroxy lanthanide com-
plexes, (Lanthanide ions: Gd, Tb, Dy, and Ho). We thoroughly
investigated their electronic absorption spectra, and lumines-
cent property. A lanthanide porphyrin complex, one molecu-
lar porphyrin ligand is coordinated to a lanthanide ion in a
tetradentate fashion and a hydroxyl group is coordinated to
the same lanthanide ion. Therefore, the coordination number
of the central rare earth ion is five.[22,23] The rare earth ion
is expected to lie above the porphyrin molecular plane (see
Scheme 1).
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