Calculations of interfacial interactions in pyrene-Ipa rod sensitized nanostructured TiO2

Abstract

Pyrene chromophores carrying different rigid rod spacer groups (ethynylene, ethynylene-phenylene-ethynylene, and ethynylene-bicyclo[2.2.2]octylene-ethynylene) and bound to TiO2 nanostructured materials via an isophthalic acid (Ipa) anchor group have been investigated using quantum chemical calculations in order to elucidate structural and electronic properties of dye-sensitized semiconductor structures capable of long-range photoinduced interfacial electron transfer. The calculations are used to study firstly the effect of the anchor and spacer groups on the electronic properties of the pyrene-dyes, secondly the binding of isophthalic acid to nanostructured TiO2, and thirdly the interfacial electronic interactions for dye-sensitized nanostructured TiO2 relevant to dye-sensitized solar cell applications. Together, these calculations provide theoretical insights into the effect of incorporating rigid rod anchor-cum-spacer group motifs in sensitizers for e.g. solar cell applications. In particular, the calculations help to rationalize the strong influence of the rods on the photophysical properties of the sensitizers in terms of electronic interactions between the individual chromophore, spacer, and anchor segments, as well as to provide information about interfacial electronic interactions of interest for the capabilities of the rods to act as efficient mediators of photoinduced interfacial charge separation.

Emerging polymorphism in nanostructured TiO2: Quantum chemical comparison of anatase, rutile, and brookite clusters

“…The influence of the ECP has been checked by comparing LANL2DZ with 10 core electrons to ECP basis sets introduced by Bouteiller and here referred to as valence double zeta (VDZ), with 18 core electrons. The large cluster sizes, needed to model TiO 2 nanoparticles in a physically realistic way, provide a strong incentive to find efficient basis sets that give good descriptions of the electronic structure at a moderate computational cost, and the VDZ type basis set has been used previously with good results, for example, for the study of interfacial electronic properties of dye‐sensitized TiO 2 . Basis set effects have previously been investigated for small TiO 2 clusters including larger basis sets, whereas the larger clusters used in this investigation allow an examination of properties for physically more realistic models of nanocrystalline systems.…”

“…We have previously investigated a set of cluster models of TiO 2 anatase nanoparticles (TiO 2 ) n with n ≤ 68, that show gradually emerging bulk‐behavior for nanoparticles with diameters up to about 2 nm, when a set of structural conditions that include stoichiometry, realistic coordination, and a balanced charge distribution, are followed . These, and similar, nanoparticle models have also been used extensively to investigate molecular interactions with nano‐TiO 2 in dye‐sensitized solar cells …”

Theoretical studies of dye-sensitised solar cells: from electronic structure to elementary processes

“…154 Biisonicotinic acid (the dicarboxybipyridine ligand in ruthenium dyes), which consists of two linked carboxypyridyl fragments, also has several possible adsorption configurations; the configurations where both carboxylic groups were adsorbed in the bridging bidentate mode were the most stable on both rutile (110) and anatase (101) surfaces. [155][156][157] Several other carboxyl and carbonyl-based anchoring groups have been studied recently: acetylacetonate, 158,159 isophthalic acid, 160,161 hydroxamate, 162 which provide binding comparable or stronger than single carboxylic acid groups.…”

“…Several other carboxyl and carbonyl-based anchoring groups have been studied recently: acetylacetonate, 158,159 isophthalic acid,160,161 hydroxamate, 162 which provide binding comparable or stronger than single carboxylic acid groups.A large number of possible configurations were studied for phosphonic (and alkylphosphonic) acids on TiO 2 : four on rutile(110) [163][164][165] and eight on anatase (101),163,166 including both bidentate and monodentate, with and without the acidic proton transferred to the surface. The lowest-energy adsorption This journal is ª The Royal Society of Chemistry 2011…”

Light-harvesting and electronic contacting capabilities of Ru(ii) Ipa rod and star complexes–first principles predictions

“…For example, the [Ru(dqp) 2 ] 2+ complex (dqp is 2,6-di(quinolin-8yl)pyridine) provides one recent demonstration of the emerging possibilities to design new Ru(II) complexes that combine favorable structural and electronic properties for solar energy conversion applications from first principles predictions. [30][31][32] Theoretical modeling has also been employed in recent years to provide explicit insight into the surface binding and electronic contacting capabilities of several sensitizers to TiO 2 substrates, 8,33 with examples ranging from organic molecules 34 to Ru-dyes, 35 as well as including examples of sensitizers with spacer groups 12 and advanced anchor motifs such as Ipa rods 36,40 and tripods. 13 In this work, we focus on calculations of Ru(II) polypyridyl complexes with rigid anchor-cum-spacer groups.…”