Physical properties of chalcogenide glasses in the AsxSe1$-${}x system have been measured as a function of composition including the Young's modulus E, shear modulus G, bulk modulus K, Poisson's ratio $\nu${}, the density $\rho${}, and the glass transition Tg. All these properties exhibit a relatively sharp extremum at the average coordination number ⟨r⟩=2.4. The structural origin of this trend is investigated by Raman spectroscopy and nuclear magnetic resonance. It is shown that the reticulation of the glass structure increases continuously until x=0.4 following the ``chain crossing model'' and then undergoes a transition toward a lower dimension pyramidal network containing an increasing number of molecular inclusions at x>0.4. Simple theoretical estimates of the network bonding energy confirm a mismatch between the values of mechanical properties measured experimentally and the values predicted from a continuously reticulated structure, therefore corroborating the formation of a lower dimension network at high As content. The evolution of a wide range of physical properties is consistent with this sharp structural transition and suggests that there is no intermediate phase in these glasses at room temperature.

We report on ²⁰⁷ Pb, ⁷⁹ Br, ¹⁴ N, ¹ H, ¹³ C and ² H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices.

The supramolecular synthesis of an original thermochromic metal-rich Cu(i) metallacycle (quantum yield 72% at RT) is reported. Important geometrical changes reinforcing cuprophilic interactions are calculated at the excited states.