NLO molecular materials

In its early stages, the group focused on electroactive molecular systems based on tetrathiafulvalenes (TTF), investigating their role as electron-donor units and establishing a strong background in intramolecular charge transfer and π-conjugated systems. This expertise naturally evolved towards the development of push–pull D–π–A chromophores for nonlinear optical (NLO) applications.

The NLO-photoactive research line is devoted to π-conjugated organic chromophores for second-order nonlinear optics, with particular emphasis on systems incorporating highly polarizable donor units such as 4H-pyranylidene, a proaromatic moiety that gains aromatic character upon charge transfer. A key aspect is the fine tuning of molecular structure through the rational design of donor, acceptor and especially the π-conjugated spacer.

The results obtained show that the π-spacer, particularly when based on thiophene or thiazole units, plays a central role in controlling charge transfer and ground-state polarization. These systems enable modulation of the electronic structure from neutral to strongly zwitterionic chromophores, while providing insight into aromatic and proaromatic effects and regioisomerism in the nonlinear optical response .

This approach allows precise control over hyperpolarizability, optical absorption and thermal stability, leading to well-defined structure–property relationships. In parallel, molecular properties have been successfully transferred to functional materials through incorporation into polymer matrices and electric-field-induced orientation, generating macroscopic second-order responses. Supramolecular strategies, including organogels, have also been explored to enhance molecular organization and optical performance.

Overall, this work establishes robust design rules for push–pull systems and consolidates 4H-pyranylidene-based chromophores as versatile platforms for electro-optic materials.

More recently, the research has expanded towards nonlinear absorption, particularly two-photon active chromophores. As demonstrated in recent work , these systems can act as efficient photoinitiators for two-photon laser printing, enabling high-resolution 3D micro- and nanofabrication. This direction represents an active and promising extension of the line.

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Selected publications

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Researchers involved in this line:
Jesús Orduna, Raquel Andreu, Santiago Franco, Belén Villacampa, María Jesús Blesa

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Ideas for figures / images (to include later)