Metallochlorophylls of magnesium, copper and zinc: evaluation of the influence of the first coordination sphere on their solvatochromism and aggregation properties

Leonardo M Moreira,Mauricio S Baptista,Adriana P Gerola,Rafael R S Soares,Lúcia Codognoto,Juliano A Bonacin,Adriana Lima,Vagner R Batistela,Noboru Hioka,Divinomar Severino,Hueder P M De Oliveira,Antônio E Da Hora Machado,Máira R Rodrigues

doi:10.1590/s0103-50532009000900013

Leonardo M Moreira, Mauricio S Baptista + Show 11 more

Open Access

https://doi.org/10.1590/s0103-50532009000900013

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Abstract

In this study the role of different metal centers (magnesium, zinc and copper) on the enhancement of the hydrophilic character of metallochlorophylls, was evaluated. The solvatochromism as well as the aggregation process for these compounds in water/ethanol mixtures at different volume ratios were evaluated using Fluorescence, and Resonant Light Scattering (RLS) measurements, aiming to characterize the behavior of these compounds. Independently on the studied metallochlorophyll, the presence of at least 60% of water results in a considerable increase in the fluorescence emission, probably a direct consequence of a lower aggregation of these compounds, which is confirmed by the results from RLS measurements. Additionally, the results suggest that magnesium and zinc chlorophyll should be promising phototherapeutic agents for Photodynamic Therapy.

Highlights

Photosynthetic pigments represent a kind of “lifeblood” of all photoautotrophic organisms
As metallic center, tends to affect more intensely the π* orbital as function of its more polarizable and accessible character, reducing the energy gap between π and π* orbitals. This results in the observed red-shift of the emission band corresponding to the π-π* electronic transition of chlorophyll α when compared with the zinc as coordination center
The present results denote that magnesium and zinc chlorophyll have a higher potential to be employed as photosensitizers in Photodynamic Therapy (PDT) as function of their highest absorption and emission intensities

Summary

Introduction

Photosynthetic pigments represent a kind of “lifeblood” of all photoautotrophic organisms. The lemmax tends to suffer a red shift as the water content increases in the mixture, until about 70% of water, a consequence of an efficient solvation of the macrocycle, influenced by the metal centre.

Results

Conclusion