Novel Chiral Squaraine Dyes for Solar Hydrogen Evolution

The novel chiral squaraine dye SQ1 with stimuli responsive absorption and aggregation properties is presented. The colour of molecularly dissolved SQ1 in THF can be switched between blue (λ_max = 602 nm) and red (λ_max = 514 nm) by addition of triethylamine and hydrochloric acid, respectively. Aggregates that are formed both in bad solvents such as toluene and in the solid state exhibit a broad absorption band in the visible regime (λ = 400 nm – 900 nm) and a strong CD effect. The described compound enables further research on electron transport in chiral dye sensitized solar cells with the ultimate goal of improving solar hydrogen evolution by utilization of the chiral induced spin-selectivity (CISS) effect.