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ABSTRACT #52p { margin-bottom: 0.25cm; direction: ltr; color: rgb(0, 0, 0); line-height: 120%; }p.western { font-family: "Times New Roman", serif; font-size: 12pt; }p.cjk { font-family: "MS Mincho", "ＭＳ明朝", monospace; font-size: 12pt; }p.ctl { font-family: "Times New Roman", serif; font-size: 12pt; }a:link { color: rgb(0, 0, 255); }Dyesensitized solar cells (DSSCs) are usually based on a rod moleculeconnected to a semiconductor or nanoparticle. The rod organic dyebears a donor (D) and an acceptor (A) moieties connected through aconjugated psystem bridge (D-p-A).[1]Upon photoexcitation, the charge separation drawn in the lowestsinglet (S1)state(orin the relaxed S1*state) isharnessed to store electrons into the semiconductor. An efficientcharge separation in the S1state is the first requirement for a working DSSC, appart from manyother factors which could enhace or deplete the efficiency, the fastcharge recombination (back electron transfer) being one of the mostrelevant. Recently,[2] a Tröger base bridge (hereafter -sT-),a strained heterocycle, has been proposed as an efficient but alsoselective bridge, capable of mediating the charge separation. Thusthe setup D -sT-A is here tested as a viable DSSC model dye, with the hope of takingadvantages of its unusual charge separation properties.[2] In thepresent study the absorption and emission spectra of a pool of known ´conventional´ dyads (D-p-A)were calculated using time-dependent DFT (TDDFT) approaches in orderto find the best functional and solvation model for furtherprediction of novel (D -sT-A) dyads. From the pool ofnovel dyads (D -sT-A), four of the simplest ones are picked for detailed analyses. Theevaluation was focused on the absorption wavelenght, on the existanceof a lowest singlet with the maximum charge separation character (CTstates) which would be able to be experimentally characterized by itsfluorescence and on the appropriate redox potentials at the donor andacceptor edges. Compound 1a(Figure. 1) is the simplest synthetic model and corresponds to thesmaller D/A redox gap. Its parent 1blacks of the main donor group and could be taken as control. Theabsoprtion and emission spectra were simulated in solvents ofincreasing polarity from cyclohexane to acetonitrile andexperimentally measured in the case of 1a/b,they showing a good agreement between the experimental and calculatedStokes´ shifts. From both the analysis of the experimental shifts andthe calculated electron densities, the S1dipole moment was found to correspond to a CT state. However, thedifferences between 1aand 1b were rather mild, which indicates that the nitrogen of the bridge isthe main donor of the systems and thus, although clear (Dmof 12 Debyes) the charge is not completely separated from on edge tothe other. Relying on the good agreement between the energies andproperties of the calculated excited states and the photophysicalexperimental data, several structures, 2aamong them, were proposed and they are currently being synthetized. By increasing the D/A gap, 2ashowed more than twice the dipole change observed in the 1aparent (or in its own control 2b).On the other hand, the analysis of the transition densities indicatesthat the charge is completely separated in the emitting state, incontrast to the partial separation shown on Fig. 1 for 1a.Based on the the properties of the relaxed S1*state of 2a,a set of other dyads were envisaged with a complete charge separationon their emitting states and at different absorption and emissionwavelenghts, which could be considered as proof of principles modelsfor these novel DSSCs.[1]G.Smeatad, C. Bignozzi, R. Azgazzi,Solar Energy Materials and Solar Cells,1994,32,259[2]C.L.Ramirez, R. Procaccini, C.A. Chesta, A. R. Parise, D. M. A. Vera,OrganicElectronics,2013, 14, 2564 .