The gas-releasing thermal decomposition processes of formamidinium tin triiodide perovskite (CN₂H₅SnI₃, usually denoted as FASnI₃ or, briefly, FASI) were investigated in order to obtain information on the temperature at which decomposition begins and on the nature of the gas species emitted under heating. Results of thermogravimetry-differential thermal analysis (TG-DTA), thermogravimetry-differential scanning calorimetry (TG-DSC), and Knudsen effusion mass spectrometry (KEMS) experiments are presented. TG measurements showed that mass loss starts at temperatures much lower than those of the lead-based corresponding compound FAPbI₃, with incipient loss at temperatures as low as 423 K. Unlike FAPbI₃, practically no residue is left at T = 823 K. KEMS experiments showed a measurable release of SnI₄(g) occurring from temperatures as low as 318 K, with a SnI₄(g) pressure much lower than the vapor pressure of pure SnI₄, suggesting the presence in the solid of Sn­(IV) at reduced activity. At higher temperatures (T > 390 K), the release of SnI₂(g) and various species coming from the organic portion, such as formamidine, hydrogen iodide, ammonia, triazine, and hydrogen cyanide, is observed. For the first time, thermal decomposition of FASI was shown to occur with release of both organic and inorganic (tin iodides) species, with the partial oxidation of Sn­(II) to Sn­(IV) significantly decreasing the decomposition onset temperature. Finally, based on TG measurements at various scan rates, a kinetic analysis of FASI decomposition was performed, using integral and incremental isoconversional methods, to derive parameters useful for lifetime prediction. Reasonable reaction time values to achieve a low degree of conversion (less than 0.25) were extrapolated at temperatures typically involved in the operation of photovoltaic devices (333 to 353 K).

By measuring the urea vapor pressure, the negative deviation of urea from ideal mixing in the urea–choline chloride DES at the eutectic composition was for the first time experimentally determined and related to partial negative enthalpy of mixing.

Viologens are a highly advantageous class of compounds for the synthesis of functional materials. Owing to their versatile structure, they can embed additional conjugated moieties, thus representing a convenient platform, for example for organic semiconductors and other energy-related uses. A straightforward synthesis of an extended viologen containing a bithiophene is described here, together with its UV-visible absorption and fluorescence spectroscopy, showing multiple absorption and emission bands. Thanks to its ease of synthesis and optical properties, this organic salt appears to be of potential interest for various optoelectronic applications.

Despite having been known for a long time, quaternary 4,4′-bipyridinium salts, or viologens, are still a highly inspiring class of compounds, thanks to their peculiar redox and charge transfer properties. However, more complex structures containing multiple pyridinium rings, also interspaced by conjugated moieties, allow an even wider synthetic variability and tunability of their characteristics. The compound described herein is a star-shaped, fully conjugated molecule with three methylated pyridinium rings connected by a triple bond spacer to a central benzene core, which was synthesized from readily available building blocks, representing a quite simple model of multi-pyridyl extended viologen; its UV–visible absorption and fluorescence spectra have also been investigated.

In the vast field of organic functional materials, viologens are widely recognized as an extremely versatile family of substances, due in part to the possibility of extending conjugation between the terminal pyridinium rings, for instance through the insertion of additional aromatic moieties. In this work, a new, extended viologen with a thiophene core and two acetylene bonds is presented. It was synthesized through a straightforward route, using well-established Sonogashira coupling reactions, and its optical properties were investigated by UV–visible absorption and fluorescence spectroscopy, revealing a very interesting material for diverse fluorescence-related applications.