Materials properties depend on the distribution of electrons. In this project, we correlate the observable electron density (measured experimentally or computed theoretically) and the respons of materials. For example, indexes of refraction of a crystal are calculated from the electron density partitioning of the dipole polarizability of a molecule. This enables to understand how the material property is generated from specific stereoelectronic features of the functionals groups and the bulding blocks.

Lay summary

In this project we correlate the observable optic/electronic properties of hybrid metal organic materials and their ground state electron density distribution in crystals.

The materials are modeled with a building blocks approach, where organic linkers, metal connectors and guest molecules are described in multipolar expansion. When this cannot be derived on the actual materials (because experiments cannot be sufficiently accurate or theoretical calculations are too demanding) the isolated building blocks are  simulated based on simple calculations on isolated building blocks, treating the aggregation in crystalline materials as a first order perturbation. In layered or three-dimensional framework materials, the modeling allows addressing the sites more keen to bind guest molecules (for example an absorbed gas, or an ion), by mapping the total interaction between host framework and guest, including electrostatic and non-electrostatic (dispersive) interactions.

In this project, reconstructed ground state electron density of the hybrid materials are used to evaluate properties, for example electric susceptibilities, useful for prediction of optical response of a material.

We have so far published the basic theoretical framework for the building block reconstruction of the crystal linear susceptibility. Application to a wider class of potentially useful optical materials is currently in due course and a publication has been submitted.

Among various materials, an appealing class is that of metal bio-organic frameworks, based on amino acids as linkers, able to produce a quite variable charge of the host hybrid framework (cationic, neutral or anionic depending on reaction conditions) and to infer specific properties to the materials based on their chirality.

We started this investigation by analyzing the amino acid linkers in their molecular crystals, in salts with another acid (e.g. oxalic acid) acting as proton donor and eventually in metal coordination polymers.

We have so far published results of the investigations in pure amino acids and in their salts. The M-BioF crystals are currently under investigation and further publication is in due course.