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An original series of bipyrimidine‐based chromophores featuring alkoxystyryl donor groups bearing short chiral (S)‐2‐methylbutyl chains in positions 4, 3,4 and 3,5, connected to electron‐accepting 2,2‐bipyrimidine rings, has been developed. Their linear and non‐linear optical properties were studied using a variety of techniques, including one‐ and two‐photon absorption spectroscopy, fluorescence measurements, as well as Hyper‐Rayleigh scattering to determine the first hyperpolarizabilities. Their electronic and geometrical properties were rationalized by TD‐DFT calculations. The thermal properties of the compounds were also investigated by a combination of polarized light optical microscopy, differential scanning calorimetry measurements and small‐angle X‐ray scattering experiments. The derivatives were found not to have mesomorphic properties, but to exhibit melting temperatures or cold crystallization behavior that enabled the isolation of well‐organized thin films. The nonlinear optical properties of amorphous or crystalline thin films were studied by wide‐field second harmonic generation and multiphoton fluorescence imaging, confirming that non‐centrosymmetric crystal organization enables strong second and third harmonic generation. This new series confirms that our strategy of functionalizing 3D organic octupoles with short chiral chains to generate non‐centrosymmetric organized thin films enables the development of highly second order nonlinear optical active materials without the use of corona‐poling or tedious deposition techniques. [ABSTRACT FROM AUTHOR]

New synthesized bipyrimidine‐based chromophores presenting alkoxystyryl donor groups carrying aliphatic achiral and chiral chains in the 4 position, connected to electron‐accepting 2,2‐bipyrimidine cores have been synthesized. Their linear and nonlinear optical (NLO) properties were investigated as well as their mesomorphic properties by various techniques (light‐transmission measurements, polarized‐light optical microscopy, differential scanning calorimetry measurements and two‐photon excited fluorescence). The derivatives with achiral linear carbon chains were found to exhibit liquid‐crystal properties with the formation smectic phases over large temperature ranges, which were confirmed by small‐angle X‐ray scattering analysis via stacking models. The nonlinear optical properties in the solid state for derivatives with C14 and the citronellol chains have been studied by wide‐field second‐harmonic generation and multi‐photon fluorescence imaging, confirming centrosymmetry for these achiral mesogens and their excellent third‐order nonlinearity whereas the chiral compound exhibits non‐centrosymmetric organization resulting in a strong Second Harmonic Generation at the crystal state. [ABSTRACT FROM AUTHOR]

Recently, a large variety of photothermal agents have been developed and are currently under study, owing to their wide range of applications. Nonetheless, a comparison of their relative performances remains a challenge, and it appears that no tool is yet available for rationalizing the data reported in the literature. Indeed, we demonstrate in this paper that neither the temperature increase (ΔT) nor the photothermal efficiency (η) are sufficient to account for the performance of a photothermal agent. From this observation, we propose that a new index, IPTmax, could be used, in order to properly rank molecular photothermal agents according to their efficacy for converting light into heat, in a similar fashion that brilliance is used to compare luminescence properties. [ABSTRACT FROM AUTHOR]

An original asymmetric achiral pyrimidine core molecule, with long carbon chains on one side and a coumarin fragment on the other, is designed. This advanced molecular structure enabled the spontaneous emergence of crystalline and liquid crystalline thin films with strong 2nd harmonic generation (SHG) without any corona polishing process or tedious deposition techniques. Moreover, pin‐pointed multiphoton absorption in the liquid crystalline phase effectively switches off the SHG signal locally and permanently, underlining its interest in 3D data storage. This prototypical material, which can be fully addressed by NLO processes, multiphoton writing, and SHG reading, paves the way for the development of efficient flexible materials for 3D optical data storage. [ABSTRACT FROM AUTHOR]