Accurate simulation of optical properties in dyes.
ABSTRACT Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them.
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ABSTRACT: The electronic structures and spectroscopic properties of four bisanthracene bis(dicarboxylic imide)s (M1-M4) have been investigated theoretically by using density functional theory (DFT) and its time-dependent extension (TDDFT) in view of their potential use as photosensitizer in photodynamic therapy (PDT). The optimized geometries, the electronic absorption transitions, the singlet-triplet energy gaps, spin-orbit matrix elements, ionization potentials and electron affinities have been determined in gas phase and in solvent. Both Type I and II PDT mechanisms have been considered. In addition, the variation of a series of relevant properties upon a heavy atom substitution (Br and I) have been determined and discussed. Results show that only M4 is able to support Type I reaction and one of its brominated and iodinated derivatives can produce cytotoxic singlet oxygen (Type II reaction).Journal of Chemical Information and Modeling 07/2013; · 4.30 Impact Factor
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ABSTRACT: We have developed an absorption spectrum based molecular ruler that measures the distance between two mercapto groups. The conformation of the molecular rulers changes with the distance, which induces an absorption spectrum change. DFT calculation has been carried out to elucidate the relation between the molecular conformation and the absorption spectrum. With this simple method, we can estimate the distance between two mercapto groups on the scale of 0.4-1 nm. This method can also be used to monitor conformation transition, which is demonstrated by a silver ion titration experiment.Physical Chemistry Chemical Physics 10/2012; 14(44):15321-7. · 3.83 Impact Factor
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ABSTRACT: To understand the role of the conjugate bridge in modifying the properties of organic dye sensitizers in solar cells, the computations of the geometries and electronic structures for 10 kinds of tetrahydroquinoline dyes were performed using density functional theory (DFT), and the electronic absorption and fluorescence properties were investigated via time dependent DFT. The population analysis, molecular orbital energies, radiative lifetimes, exciton binding energies (EBE), and light harvesting efficiencies (LHE), as well as the free energy changes of electron injection ( ) and dye regeneration ( ) were also addressed. The correlation of charge populations and experimental open-circuit voltage (Voc) indicates that more charges populated in acceptor groups correspond to larger Voc. The elongating of conjugate bridge by thiophene units generates the larger oscillator strength, higher LHE, larger absolute value of , and longer relative radiative lifetime, but it induces the decreasing of EBE and . So the extending of conjugate bridge with thiopene units in organic dye is an effective way to increase the harvest of solar light, and it is also favorable for electron injection due to their larger . While the inversely correlated relationship between EBE and LHE implies that the dyes with lower EBE produce more efficient light harvesting.International Journal of Molecular Sciences 01/2013; 14(3):5461-81. · 2.46 Impact Factor