Three series of push-pull derivatives bearing 4H-pyranylidene as electron donor group and a variety of acceptors were designed. On the one side, one dimensional chromophores with a thiophene ring (series 1H) or 5-dimethylaminothiophene moiety (series 1N) as auxiliary donor, non-coplanar with the p-conjugated system, were synthesized. On the other side, related two-dimensional (2D) Y-shaped chromophores (series 2) were also prepared to compare how the diverse architectures affect the electrochemical, linear and second-order nonlinear optical (NLO) properties. 2The presence of the 5-dimethylaminothiophene moiety in the exocyclic C=C bond of the pyranylidene unit gives rise to oxidation potentials rarely low, and the protonation (with an excess of trifluoroacetic acid) of its derivatives results in the apparition of a new blue-shifted band in the UV-visible.The analysis of the properties of derivatives with and without the additional thiophene ring shows that this auxiliary donor leads to a higher NLO response, accompanied by an enhanced transparency.Y-shaped chromophores of series 2 present a blue-shifted absorption, higher molar extinction coefficients and higher Eox values compared to their linear twisted counterparts. As concerns NLO properties, 2D Y-shaped architecture gives rise to somewhat lower µb values (except for thiobarbiturate derivatives)

The synthesis and electrochemical and optical characterizations of four new 4Hpyranylidene-based push-pull molecules are reported herein as well as their evaluation as donor materials for organic photovoltaics. Studied systems exhibit good absorption properties and appropriate LUMO levels for a photoinduced electron transfer to C60. Bilayer organic solar cells fabricated from these new donors and C60 as acceptor gave photocurrent however with low power conversion efficiencies. As shown by X-ray diffraction and theoretical calculations, titled molecules present a twisted structure which may prevent the formation of suitable π-π contacts between adjacent molecules hence explaining their low photovoltaic performance.