Photophysical and theoretical studies of peripherally halogenated octaphenoxyphthalocyanines

Abstract

DFT and TD-DFT computational studies validated the experimental results and revealing details about the electronic structures of novel halogenated phthalocyanines. Fluorescence and singlet oxygen quantum yields analysis revealed two-dimensional heavy atom effect that influenced the photophysical parameters. 249x169mm (150 x 150 DPI)Peripherally substituted phthalocyanines with halogenated phenoxy groups containing different central metals (In(III), Ga(III), Mg(II) and Zn(II)) were synthesized. The X-ray analyses confirmed that the halogen atoms (Cl, Br) at the ortho positions were bulky enough to orient the phenoxy substituents perpendicularly relative to the Pc core and perfectly discouraged cofacial aggregation. The ground state geometry, HOMO/LUMO energies and the electronic properties were theoretically calculated for some complexes and corresponded well with experimental data. Analysis of fluorescence and singlet oxygen quantum yields revealed strong heavy atom effect provided by the central metal. Irrespective of the present halogen, indium(III) complexes were characterized by high singlet oxygen production and very low fluorescence while reverse data were obtained for Mg(II) complexes.

Biotinylated-cationic zinc(II) phthalocyanine towards photodynamic therapy

“…3). The B band, which is known as the Soret band, was observed at 363 nm for both macrocycles [25,46]. The aggregation behavior of both studied complexes was evaluated in DMSO.…”

“…Phthalocyanines (Pcs) have been intensely studied as suitable photoactive materials for PDT treatment since they fulfil many of the requirements acquired by efficient PSs, including photostability, highly generation of singlet oxygen, lack of dark toxicity and structural flexibility along with their strong absorption in the near infrared region which allows light to penetrate deeper into the tissue [14,[22][23][24][25][26][27]. However, their insolubility in water associated to their hydrophobic character is considered a major drawback for these macrocyclic materials to be ideally feasible for PDT therapy.…”

Conjugated macrocyclic materials with photoactivated optical absorption for the control of energy transmission delivered by pulsed radiations

“…Several examples of Pcs with axial and peripheral substituents (compounds 1-14 in Charts 1 and 2) have been recently reported as OL active systems when these Pcs were dispersed in liquid solutions or in an optically inert matrix [63][64][65][66][67][68][69][70]. These complexes are characterized by having several patterns of peripheral substitution (tetra-, octa-or 3:1 substituted Pcs) and, consequently, diverse symmetries and different orientations of dipole moments in both ground and excited states during the electronic transitions originating the OL effect [55,71].…”

“…These complexes are characterized by having several patterns of peripheral substitution (tetra-, octa-or 3:1 substituted Pcs) and, consequently, diverse symmetries and different orientations of dipole moments in both ground and excited states during the electronic transitions originating the OL effect [55,71]. It has been generally acknowledged that Pcs possessing halogen substituents either in axial [63][64][65][66][67][68][69] or peripheral [64] position present relatively stronger OL effect by virtue of the favourable electron-withdrawing effect exerted by these atoms [31,72]. Chart 1.…”

“…Chart 1. Series of OL active tetra-/ octa-substituted metallo-phthalocyanines 1-13 with the metal center coordinating an axial ligand [63][64][65][66][67][68][69].…”