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SYNTHESIS AND SPECTRAL LUMINESCENT PROPERTIES OF
AXIALLY SUBSTITUTED ZIRCONIUM (IV) AND HAFNIUM (IV)
PHTHALOCYANINES
Y. Gerasymchuk2, S. Volkov1, V. Chernii1, L. Tomachynski1 and S. Radzki2
1
V.I. Vernadski Institute of General and Inorganic Chemistry of NASU,
Palladina Av. 32/34, 03680 Kyiv-142, Ukraine, E-mail: [email protected].
2
Faculty of Chemistry, UMCS, M. Curie-Sklodowska Sq. 2, 20-031 Lublin,
Poland
Phthalocyanines and porphyrins have attracted considerable attention due
to their unique properties and the potential applications of these complexes in
catalysis, photosensitization reactions, liquid-crystalline systems, biomolecular
processes and many other uses. Phthalocyanine macrocycle forms the πconjugated system that differs distinctly from the most of organic compounds by
a level of π-electron delocalization and a high level of symmetry. The electronic
absorption spectra of phthalocyanine complexes consist of two bands: В (Soret)
and Q in UV and visible region, respectively. Excitation in the Soret region is
the consequence of a2u-eg, (π-π*) transitions, and the absorption in the Q-region
is the consequence of a1u-eg, (π-π*) transitions. Introducing out of plane ligands
to the central atom influences substantively on π-electron conjugation of the
macromolecule and decreases a level of symmetry of the molecule.
This work report the investigation of spectral properties of zirconium (IV)
and hafnium (IV) phthalocyanine complexes with gallic, 5-sulfosalicylic, oxalic
acids and methyl esther of gallic acid as axial ligands. Absorption measurements
were carried out using a Carl Zeiss- Jena M42 spectrophotometer. Spectra were
recorded between 300 and 900 nm at temperature of 21±1 ° C.
O
O
S
O
O
OH
OH
O
M
M
O
O
O
OH
Gallic acid (Ia, Ib)
5-Sulfosalicylic acid (IIa, IIb)
O
O
O
O
O
CH3
M
M
O
O
O
HO
Oxalic acid (IIIa, IIIb)
Methyl Esther of Gallic acid (IVa, IVb)
Axial ligands coordinated to the central metal atom of phthalocyanine
M=Zr(IV)-(a), Hf(IV)-(b)
Fluorescence measurements were carried out using a Fluoromax-2
spectrofluorometer (Jobin Yvon-Spex, Horiba Group), with the detector oriented
at 90° relative to the light source and using 1-cm quartz cell. All the fluorescent
spectra were excited at the wavelength of the Soret band and recorded at a
temperature of 21±1 °C in the range 300-850 nm. Absorption and emission
spectra were recorded digitally and the Sigma Plot (Jandel Corp.) program was
used in manipulation and plotting the data.
As for all phthalocyanines, absorbance spectra of axially substituted Zr(IV)
and Hf(IV) phthalocyanines are characterized by presence of ultraviolet Soret
band (λmax in the range of 335 to 350 nm) and visible Q band (λmax in the range
of 675 to 701 nm) (Table). The wavelengths of absorbance band maxima in the
Soret range origin had low level of correlation with the polarity of the solvents.
The position of λmax in the Q region depends on the solvent polarity - the lower
is Reichardt’s empirical parameter of polarity for solvent, the higher shift of λ max
into the red is observed. The red shift of absorbance band maxima in the Q
region for the solvents with relatively high polarity (MeOH, EtOH) and for the
solvents with relatively low polarity (CH2Cl2, CHCl3) is up to 10 nm.
Table. Dependence of the absorbance and emission band maxima of
phthalocyanine complexes from the type of central metal atom and axial ligand
in the DMSO solution (ΔS [nm] = Stokes shift)
Investigated
complexes
Absorption λmax
[nm]
Excitation
λ [nm]
Emission λmax [nm]
ΔS [nm]
S
Q
Ia
342
685
420
499
730
45
Ib
349
690
420
474
735
45
IIa
348
688
420
539
725
37
IIb
347
687
420
525
732
45
IIIa
343
681
410
496
726
45
IIIb
341
678
410
478
737
59
IVa
349
688
410
498
735
49
IVb
349
691
410
475
737
44
In the fluorescence spectra of the DMSO solutions, when excitation λ max is
410 or 420 nm, the maxima of emission spectra for all the investigated
complexes are located in the range from 725 to 737 nm. Moreover, for the
complexes with the same axial ligands, λmax of emission for Hf(IV) complexes
are 10-15 nm shifted into the red in comparison to λ max of Zr(IV) emission. The
Stocks shifts for all investigated complexes are about 50 nm.