Research

Our research interests are focussed on the development of novel phosphorus/boron-based architectures with outstanding electronic and photophysical properties. Our ultimate goal is to conceive multi-functional and biologically-active materials for a wide range of applications.

In particular, through a bottom-up approach, we merge organic and inorganic syntheses to prepare new molecules and tailor their structural features to trigger a multi-responsive behavior at the macromolecular scale or improve their activity in biological media. Implicit is the investigations of new synthetic methods to prepare the novel phosphorus/boron-based molecules.

We seek to prepare fully functional materials. To that end, we first thoroughly investigate

investigate the new molecules with a wide array of physico-chemical techniques, and finally explore their application in fields such as organic electronics and bio- medical applications.

Phosphaphenalenes are a representative example of systems developed in our group ; i.e. fused molecules based on six-

C. Romero-Nieto Research Group

membered phosphorus heterocycles. They were prepared in 2015 (see publication nº 27). Our group reported a new synthetic protocol to access pi-extended phosphaphenalenes fused with electron donors or acceptors as well as aromatic hydrocarbons. The synthetic versatility of the method allowed us to prepare, for instance, highly fluorescent materials with ambipolar redox properties. More importantly, through suitable structural modification, we succeeded in preparing multi-responsive molecules; i.e. phosphorus-based architectures capable, among others, to emit light when applying an electric current and, in the inverse way, to generate an electric current when applying light. In addition, phosphaphenalenes derivatives demonstrated to be active against brain cancer.

In 2018, our group reported the synthesis and properties of the diphosphahexaarenes; i.e. linearly-fused systems containing two six-membered phosphorus heterocycles. All derivatives were remarkably stable under moisture and light allowing for detailed spectroscopic investigations.

The diphosphahexaarenes possessed fluorescence quantum yields up to 85% with, once again, ambipolar redox behavior. The phosphorus atoms exhibited a persistent stereochemistry with a versatile reactivity; they could be selectively functionalized with oxygen, sulfur, borane and quaternized. As a result, by just changing the functionality at the phosphorus atoms, we could obtain diphosphahexaarenes derivatives with contrasting optoelectronic properties.

Photoluminescence

Water

Org. Solvent

pressure

Change of color

concentration

3D Assembly

media

light

Phosphaphenalene derivatives

In 2020, in views of the results obtained with the disphosphahexaarenes, we developed the synthesis of the novel diphosphapyrenes. They are pyrene-like structures containing two six-membered phosphorus heterocycles and fused with thiophenes moieties. The diphosphapyrenes presented a planar structure with significant fluorescence quantum yields in the order of 30% and, again, persistent stereochemistry.

Based on phosphorus oxide derivatives, the P-O bonds could be oriented in suitable directions and utilized as vector directors to control the 3D arrangement of molecules through non-covalent interactions; i.e. halogen bonds. As a result, by changing the environment, the assembly of molecules were controlled in the solid state from tilted rings to lemniscate-like shapes.

Diphosphahexaarenes derivatives

Currently, our ongoing research is intended to explore the challenges associated with the design and preparation of the next generations of multi-functional phosphorus/boron-based materials. By means of a multidisciplinary strategy, we envision molecular structures as vehicles not only to obtain new materials’ phenomena, but also to comprehend their behavior from the molecular to the macroscopic scale. Thus, our investigations cover a variety of fields, from synthesis to spectroscopy and biological applications. In turn, our research lines are strongly enhanced by well-established international collaborations with theoretical and experimental research groups.

Diphosphapyrenes derivatives

Assembly of Diphosphapyrenes derivatives