The effects of heavy atoms on the exciton diffusion properties in photoactive thin films of tetrakis(4-carbomethoxyphenyl)porphyrins

Abstract

The singlet exciton diffusion properties of solution-cast thin films prepared from mixed substituent monoiodophenyl or monobromophenyl derivatives of 5,10,15,20-tetrakis(4-carbomethoxyphenyl) porphyrin (TCM4PP) were investigated for use in solar energy conversion applications. The photoluminescent singlet decay lifetime PL(t) of pristine porphyrin films and films lightly doped (0.1 -0.6% wt.) with [6,6]-phenyl-C61-butryic acid methyl ester (PCBM) were used to obtain relative quenching efficiencies (Q). The exciton diffusion coefficient (D) and exciton diffusion length (LD) for each derivative were obtained by modeling the quenching efficiency and PL lifetime decay data using a 3D exciton Monte Carlo diffusion simulation. Although the three TCMPP derivatives showed nearly identical absorbances and electrochemical properties, the monobromophenyl or monoiodophenyl substituted porphyrins exhibited significantly lower steady-state emission intensities and fluorescent lifetimes in solution. Amorphous thin films of the halogenated derivatives also exhibited a decrease in the PL decay lifetimes, relative quenching efficiencies, and reduced singlet exciton diffusion lengths. The singlet exciton diffusion length for TCM4PP was calculated to be 15 nm and decreased by 71% to 4.4 nm for TCM3IPP with the addition of a single iodo substituent. Photocurrent-voltage measurements of the derivatives in a PCBM bulk heterojunction device suggest that lowered exciton diffusion and enhanced singlet to triplet exciton conversion, due to the heavy atom effect, decreases photoconversion efficiency.

Photophysical study and in vitro approach against Leishmania panamensis of dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV)

“…In the present study, we synthesized and characterized (1) and (2). Compound structures were confirmed by spectroscopic techniques (UV-Vis, FT-IR, 13 C-NMR and ESI-mass).…”

“…Leishmania panamensis (UA140) was used in in vitro tests for the evaluation of the leishmanicidal potential of the compounds (1) and (2). Leishmanicidal activity was determined as the ability of the compounds to decrease the viability of the parasite, for this the MTT method is widely used in the literature (MTT Assay Protocols, Thermo Fisher Scientific).…”

“…The UV-Vis spectrum of (1) (Figure 2), shows a band of maximum absorption located at 414 nm (Soret band), generated by a 1u (π)-e g * (π) transitions and four lower absorption Q band located at 515nm, 547nm, 588nm and 645 nm, which corresponds to a 2u (π)-e g * (π) transitions. 46,47 The UV-Vis spectrum of compound (2) shows one Soret band and only two Q bands. When the Sn (IV) ion coordinates nitrogen atoms inside the porphyrin ring, the porphyrin symmetry increases.…”

“…Porphyrins and metalloporphyrins are versatile macrocyclic organic compounds, from the structural viewpoint; the porphyrin main skeleton consists of four pyrrole rings bound through their alpha carbons (α-C) with four aldehydes. 1,2 These structural characteristics confer on the porphyrins a variety of properties such as high conjugation, symmetry, and planarity. Additionally, they acquire the ability to complex with a large number of metals in their interior through the coordination of the four pyrrolic nitrogen atoms submerged in the molecule.…”

Photophysical study and in vitro approach against Leishmania panamensis of dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV)

“…The UV-Vis spectrum of (1) (Figure 2), shows a band of maximum absorption located at 414 nm (Soret band), generated by a 1u (π)-e g * (π) transitions and four lower absorption Q band located at 515nm, 547nm, 588nm and 645 nm, which corresponds to a 2u (π)-e g * (π) transitions. 46,47 The UV-Vis spectrum of compound (2) shows one Soret band and only two Q bands. When the Sn (IV) ion coordinates nitrogen atoms inside the porphyrin ring, the porphyrin symmetry increases.…”