4-(Fmoc-2-aminoethyl)-6-dibenzofuranpropionic acid

Three Pt(II) 2,6-di(pyridin-2-yl)pyrimidin-4(1H)-one complexes (2-4) with chloride or 4-ethynyltolyl ancillary ligands were synthesized and characterized. The photophysical properties of 2-4 were investigated in different solvents and at different acid concentrations. Their electronic absorption and emission responses at various acid concentrations were compared to those of 5. 2-4 all exhibit a broad charge-transfer band in their electronic absorption spectra from 380 to 500 nm and emit at about 560 nm in acetonitrile at room temperature, presumably ascribed to the triplet metal-to-ligand charge transfer ((3)MLCT) state. All of them exhibit broad and relatively strong triplet transient absorption in the visible to the near-IR region (450-820 nm). Upon addition of p-toluenesulfonic acid, the original charge-transfer band intensity decreases, accompanied by the increase of the absorption in the 350-400 nm region in their electronic absorption spectra. Meanwhile, the (3)MLCT emission is quenched, and the triplet transient absorption intensity decreases. The changes in electronic absorption, emission, and the transient absorption spectra are reversible upon the addition of base, that is, triethylamine. The reversible acid sensitivity is caused by the protonation and deprotonation of the carbonyl oxygen on the terdentate ligand. Therefore, these platinum complexes could be potential chromogenic and luminescent sensors for acids.

In the phosphorous-sulphur two-step process for the clean production of phosphoric acid, a phosphate-rock acid-insoluble residue (PAIR) is a solid filter residue obtained via the phosphoric acid acidolysis of phosphate rock (PR). PAIR combined with other raw materials can be used to prepare cement, ceramics and glasses, opening a potential avenue for large-scale PAIR utilisation. However, the preparation of such materials requires high-temperatures calcination. Understanding the high-temperature thermal properties of PAIR can enable its more targeted comprehensive utilisation or disposal. In this study, the thermal properties and pyrolysis kinetics of PAIR were systematically studied using a multiple heating rate method based on thermogravimetric analysis and a kinetic model. Results showed that from room temperature to 1200 °C, the main changes in the PAIR were the complete removal of fluorine and sulphur, partial removal of phosphorus and conversion of quartz to cristobalite. Moreover, during these processes, H2O(g), NH3, N2, CO2, SO2, P2O5(g), CO, CF3+ and organic gases were volatilised. Herein, the pyrolysis kinetics of PAIR is divided into five stages. Stage 1 (conversion rate ɑ: 0.05-0.2) conforms to the random nucleation and growth as well as the Avrami-Erofeev (n = 2/3) mechanism; the corresponding mechanism function is F(ɑ) = [-Ln(1 - ɑ)]2/3. Stage 2 (ɑ: 0.2-0.4) conforms to the first-order chemical reaction mechanism; the corresponding mechanism function is F(ɑ) = -Ln(1 - ɑ). Stage 3 (ɑ: 0.4-0.6) conforms to the phase boundary-controlled reaction and one-dimensional movement mechanism; the corresponding mechanism function is F(ɑ) = ɑ. Stage 4 (ɑ: 0.6-0.8) conforms to the three-dimensional diffusion process (Jander model); the corresponding mechanism function is F(ɑ) = [1 - (1 - ɑ)1/3]2. Stage 5 (ɑ: 0.6-0.95) conforms to the one-dimensional diffusion process; the corresponding mechanism function is F(ɑ) = ɑ2.