Bruna Clara De Simone

Theoretical Determination of Electronic Spectra and Intersystem Spin-Orbit Coupling: The Case of Isoindole-BODIPY Dyes.

Density functional theory and its time-dependent extension (DFT, TDDFT) has been herein employed to elucidate the structural and electronic properties for a series of isoindole-boron dipyrromethene (isoindole-BODIPY) derivatives. The role played by both the nature and the positions of the substituents on intersystem spin-crossing has been investigated computing the spin-orbit matrix elements between singlet and triplet excited state wave functions weighted by the TDDFT transition coefficients. Their potential therapeutic use as photosensitizers in photodynamic therapy (PDT) is proposed on the basis of their strong absorbance in the red part of the visible spectrum, vertical triplet energies resulting higher than 0.98 eV, and the spin-orbit matrix elements that result to be comparable with different drugs already used in PDT.

Spectrophotometric study of the copigmentation of malvidin 3-O-glucoside with p-coumaric, vanillic and syringic acids

Anthocyanins are a natural source of pigments in plants and their processed food products have become attractive and excellent candidates to replace the synthetic colourants due to their characteristic intense colours and associated health benefits. The intermolecular copigmentation between anthocyanins and other colourless compounds has been reported to be an important way to enhance and stabilise the colour intensity of aqueous solutions. In the present work we report the equilibrium constant, stoichiometric ratio and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) related to the intermolecular copigmentation reactions of the anthocyanin malvidin 3-O-glucoside with one hydroxycinnamic acid (p-coumaric acid) and two O-methylated hydroxybenzoic acids (vanillic and syringic acid). Different factors which affect their interactions such as copigment concentration, pH and temperature of the medium are examined at two pH levels (pH=2.50 and 3.65) corresponding to those of the major food mediums where these reactions take place (fruit juices, wine, jams etc.).

Photophysical properties prediction of selenium- and tellurium-substituted thymidine as potential UVA chemotherapeutic agents

Abstract Density functional theory and time-dependent density functional theory calculation for a series of photophysical properties (absorption spectra, singlet and triplet excitation energies and spin–orbit matrix elements) have been performed on the sulfur-, selenium- and tellurium-substituted thymine. The heavy atoms have been substituted in 2 or 4 and in both 2,4 position of the thymine ring. Different pathways for the population of the lowest triplet state have been considered. We find that all the considered systems are potential UVA chemotherapeutic agents since the lowest triplet states lie above the energy required for the production of the highly cytotoxic 1Δg excited oxygen molecule and due to the possible and efficient intersystem crossings ensured by high spin–orbit coupling values.

Electro-optical Properties of Neutral and Radical Ion Thienosquaraines.

Thienosquaraines are an interesting class of electroactive dyes that are useful for applications in organic electronics. Herein, the redox chemistry and electrochromic response of a few newly synthesized thienosquaraines are presented. These properties are compared to those of the commercial 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl]squaraine. The stability of the radical ions formed in electrochemical processes strongly affects these properties, as shown by cyclic voltammetry, in situ spectroelectrochemistry, and quantum chemical calculations. Furthermore, all of the dyes show aggregation tendency resulting in panchromatic absorption covering the whole UV/Vis spectral range.

Metal Atom Effect on the Photophysical Properties of Mg(II), Zn(II), Cd(II), and Pd(II) Tetraphenylporphyrin Complexes Proposed as Possible Drugs in Photodynamic Therapy

The effects of Mg, Zn, Cd, and Pd dications on the photophysical properties of the tetraphenylporphyrin ligand have been explored, considering the corresponding complexes and by using the density functional theory and its time-dependent extension. Results show that absorption wavelengths do not change significantly when the metal ion changes contrary to what happens to the singlet–triplet energy gaps (ΔES−T) and the spin-orbit matrix elements 〈ΨSn|H^so|ΨTm〉. The most probable intersystem spin crossing (ISC) pathways for the population of the lowest triplet states have been explored. Our findings can contribute to rationalize the available experimental data and promote the potential therapeutic use of these compounds as photosensitizers in photodynamic therapy (PDT).

n-Type Columnar Liquid Crystal Combining Ionic and Electronic Functions

The research in the field of electronic and photonic devices based on ordered organic semiconducting materials has been boosted by the development of new multifunctional materials. The order characterizing liquid crystals has been exploited for improving charge mobility performances. However, while in the last decade much effort has been addressed to the synthesis of hole-conducting materials (p-type), less attention has been paid on the development of electron-conducting ones (n-type). Here we show the bulk multifunctional properties of a π-conjugated thienoviologen ionic liquid crystal which exhibits strong electron acceptor character. Notably, the combination of its optical properties with high ionic conductivities and fast intermolecular electron transport, leads to unique bulk electrochromic functions.

TDDFT investigation on methylviologen, 3,7-diazabenzophosphole, and helical helquat electrochromic systems

Due to their application in fenestration, automotive and aircraft technologies, the importance of electrochromic materials has grown considerably in the last decades. Theoretical prediction of their optical properties should contribute to their better characterization and can help the explanation of the experimental data. The one-photon absorption spectra of three representative electrochromic systems (methylviologen, 3,7-diazabenzophosphole, and helical helquat) have been computed employing methods rooted in density functional theory and its time-dependent extension. Four different exchange correlation functionals (B3LYP, M06, PBE0, and wB97XD) have been used for the reproduction of the geometrical structures and the absorption spectra of three different oxidation states for each considered system. Results show as the major part of the used functionals is able to correctly reproduce the spectrochemical properties of the title compounds.

Computational Investigation of the Influence of Halogen Atoms on the Photophysical Properties of Tetraphenylporphyrin and Its Zinc(II) Complexes

How the tetraphenylporphyrin (TPP) and its zinc(II) complexes (ZnTPP) photophysical properties (absorption energies, singlet-triplet energy gap and spin-orbit coupling contributions) can change due to the presence of an increasing number of heavy atoms in their molecular structures has been investigated by means of density functional theory and its time-dependent formulation. Results show that the increase of the atomic mass of the substituted halogen strongly enhances the spin-orbit coupling values, allowing a more efficient singlet-triplet intersystem crossing. Different deactivation channels have been considered and rationalized on the basis of El-Sayed and Kasha rules. Most of the studied compounds possess the appropriate properties to generate cytotoxic singlet molecular oxygen (1Δg) and, consequently, they can be proposed as photosensitizers in photodynamic therapy.

Can fused thiophene–pyrrole-containing rings act as possible new electrochromic dyes? A computational prediction

The computed electronic spectra of neutral, radical cation and dication species for a series of fused thiophene–pyrrole-containing ring systems clearly suggest that these molecules can be used as new electrochromic materials. The calculations have been performed in the framework of the time-dependent density functional linear response theory employing different exchange–correlation functionals. Based on our results, we can indicate the long-chain molecules with twelve and fourteen rings, not yet synthesized, as the best candidates for electrochromic devices operating in the near-infrared region. The calculated properties are in excellent agreement with the available experimental data.

On the Electrochromic Properties of Borepins: A Computational Prediction

The spectroelectrochemical features of some recently synthesized borepins have been predicted herein using the methods based on density functional theory. The computed electronic spectra of neutral, radical anion, and dianion species clearly suggest that these molecules can be used as new electrochromic materials. The excellent agreement with the available structural and absorption experimental data for the neutral systems made us confident for the results obtained for charged species and suggests their potential use as electrochromic materials.