Abstract
The objective of this work was synthesizing of Ti-, Zr-, Hf-phthalocyanines, containing chloride ions or dibenzoylmethanate fragments coordinated in out-of-plane positions to macrocycle. Spectroscopic and photophysical parameters of phthalocyanines metallocomplexes with metal atoms Ti(IV), Zr(IV) and Hf(IV) and spectroscopic features of Mg- and Zn-phthalocyanines have been detected and characterized at ambient and liquid nitrogen temperatures. The efficient intersystem crossing observed for Hf-phthalocyanine leads to very weak fluorescence and suppresses the fluorescence lifetimes to less than 1 ns. Changing of nature of central metals from heavy Hf(IV) atom to lighter atoms: Zr(IV), Zn(II), Ti(IV), Mg(II) lead to noticeable increasing of fluorescence lifetimes up to maximum value of 6,6 ns for Mg-phthalocyanine. At the same time the values of fluorescence quantum yield rises from 1 % for Hf-phthalocyanine to 56 % for Mg-phthalocyanine. The heavy atom effect has a substantially greater impact on photophysical parameters metallocomplexes of phthalocyanines than influence of attachment out-of-plane ligands.
Highlights
Synthesis, photophysical properties and applications of near infrared absorbing materials based on phthalocyanine (Pc) core complexes become a new, promising and challenging research field [1,2 and Ref. therein]
It’s well known, that the absorption spectra of metal complexes of phthalocyanines consist of two main absorption bands: Soret band is located in spectral range about 330-340 nm and essentially more intensive Q-band - near 680-700 nm, and exhibit a lack of absorption in the middle part of the spectrum [1,8]
Seems rather interesting synthesis and developing of new types of phthalocyanine complexes with an electronic absorption expanded to the visible spectral range for more effective light harvesting and conversion
Summary
Photophysical properties and applications of near infrared absorbing materials based on phthalocyanine (Pc) core complexes become a new, promising and challenging research field [1,2 and Ref. therein]. NIR absorption extending beyond the visible region has been considered as a promising property for creation of artificial photosynthetic systems for the conversion of solar energy in infrared region [7]. Seems rather interesting synthesis and developing of new types of phthalocyanine complexes with an electronic absorption expanded to the visible spectral range for more effective light harvesting and conversion. A second step was preparation of metal complexes of phthalocyanine substituted by out-of-plane ligands for fine-tuning of absorption in a visible spectral region
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