How Adsorption Onto TiO₂ Modifies the Properties of Multiswitchable DTE Systems: Theoretical Insights

Abstract

In order to exploit multi-photochromes as complex molecular logic gates, each isomer should ideally have a distinct optical profile in order to be selectively addressable. In this ab initio DFT and TD-DFT study, we have modeled the electronic and optical properties of a series of dithienylethene (DTE) dimers grafted onto an anatase (101) surface. We seek to investigate how grafting onto a TiO 2 surface modifies the energy levels and UV-visible spectra of the dimers and enhance the asymmetry of the isomers. By extracting information from the density of states, we have qualified the distinct degrees of interaction between the substrate and each isomeric configuration as CO > CC > OC > OO in order of decreasing electronic coupling. We subsequently use this information to interpret the UV-vis spectra computed for the isomers. The results show the grafted systems present new peaks and shifted S 1 energies compared to the isolated photochrome, suggesting that that adsorption onto a TiO 2 surface may induce asymmetric character in the DTE dyad.

Grafting Spiropyran Molecular Switches on TiO2: A First-Principles Study

“…The slab was build as two stacked O–Ti–O layers, which has been shown to be a sufficient thickness for modeling anatase. , Constraints were applied during the relaxations allowing only the top layer in direction (001) to relax, while the bottom layer was kept frozen. The hybrid systems were modeled following an approach described elsewhere for switches chemisorbed onto TiO 2 , , where the photochromes are adsorbed perpendicularly onto the periodic anatase surface in a bridging position, with the oxygen atoms of the carboxylate anchor being chemisorbed onto titanium ions of the surface, as shown in Figure . The dissociated proton of the carboxylate was bonded to an oxygen atom of the surface with a distance of 7 Å from the adsorption site, so to guarantee that there is no influence on the photochrome–surface interaction .…”

How organic switches grafting on TiO2 modifies the surface potentials: theoretical insights

“…19,31,32 In this case, a good understanding of hybrid systems is crucial to quantify the interplay between the organic switches and inorganic substrates during the photochemical process. To explore the optoelectronic properties of these hybrid systems, numerous studies have carried out, including density functional theory (DFT)/time-dependent density functional theory (TDDFT) investigation of a series of photochromic derivatives of trans/cis-AZB, 33 open/closed-SP 34 and open/closed-DTE 33,35 adsorbed onto anatase and rutile slabs. To explain the switchable wettability of TiO 2 nanoparticles modied with trimethoxysilane under UV illumination, a series of experiments was carried out to conrm the oxidization process for the degradation of trimethoxysilane.…”

Modeling the Photochrome–TiO2 Interface with Bethe–Salpeter and Time-Dependent Density Functional Theory Methods

“…Importantly, upon grafting of the photochrome unit onto the semiconductor surface, its spectroscopic, electronic, and photochromic properties might be modulated or completely altered (leading for instance to an electron injection process), although systems where the photochromic properties are successfully retained have also been reported. − This illustrates the interplay between the photoswitches and the underlying surface. First-principles modeling of these hybrid systems might help rationalizing and predicting a putative photochromic behavior, and our group has performed such studies for azobenzene (AZB) and dithyenylethene (DTE)–TiO 2 hybrid systems, , using periodic slabs to model the interface. Because of the large size of these hybrid systems, their computational modeling is still restricted, in practice, to density functional theory (DFT) and time-dependent DFT (TD-DFT) investigations.…”

“…7−9 This illustrates the interplay between the photoswitches and the underlying surface. First-principles modeling of these hybrid systems might help rationalizing and predicting a putative photochromic behavior, and our group has performed such studies for azobenzene (AZB) and dithyenylethene (DTE)−TiO 2 hybrid systems, 10,11 using periodic slabs to model the interface. Because of the large size of these hybrid systems, their computational modeling is still restricted, in practice, to density functional theory (DFT) and time-dependent DFT (TD-DFT) investigations.…”