The dependence of photoluminescence quantum yield (PLQY) on the crystal structure of existing zero-dimensional ns2 metal halides is analyzed with the help of principal component analysis and random forest methods. The primary role of the distance between metal ions in different compounds is revealed, and the influence of other structural features such as metal-halogen distance and the distortion of metal-halogen polyhedrons are quantified. Accordingly, the two previously unknown Sb3+-based zero-dimensional metal halides were synthesized to verify the obtained model. Experimental studies of the two compounds demonstrated good agreement with the predictions, and the PLQY of (C10H16N)2SbCl5 is found to be 96.5%. Via machine learning analysis, we demonstrate that concentration quenching is the main factor that determines PLQY for all s2 ion metal halides, which will accelerate the discovery of new luminescence metal halides.

S), were synthesized and characterized by FT-IR spectroscopy, TG-DSC, and singlecrystal and powder X-ray diffraction analysis. The single-crystal X-ray diffraction data revealed that 1 and 2 are discrete structures, whereas 3 is a polymer. In 1 and 2, Ca 2+ is seven-coordinate and forms a monocapped trigonal prism. In 1, the prisms are pairwise connected with the assistance of two [μ 2 -HTBA-O,O′] − ligands. In 3, Sr 2+ is coordinated by four monodentate HTBA − via S or O donors and four waters, with the formation of a distorted square antiprism. The antiprisms are connected by μ 2 -O,S bridging HTBA − . Hydrogen bonding involving coordinated water and π-π interactions plays an important role in construction of the supramolecular 3-D structures in 1-3. Infrared spectroscopic data supported the structural data. The thermal stability of 1-3 decreases in the order 1 > 2 > 3. Dehydration of 1-3 was a multi-step process, followed by exothermic oxidative degradation of the 2-thiobarbiturate moiety between 290 and 800°C.

Organic–inorganic hybrid metal halides with emissive organic cations are of great interest due to their structural diversity and interesting photophysical properties. Here, we assemble emissive organic cations (EnrofloH2 2+) with different metal–chloride anions (Pb2Cl6 2– to Bi2Cl10 4– to SnCl6 2–) to form the new single crystal phases, and thus the photoluminescence properties of the metal halides, including Stokes shift, full width at half-maximum (FWHM), and photoluminescence quantum yield (PLQY) have been studied accordingly. (EnrofloH2)­SnCl6·H2O, as an example, possesses narrow FWHM and high PLQY, which are caused by the strong π–π stacking and inter- and intramolecular hydrogen bonds interactions. Compared with EnrofloH2 2+ cation in solution, the interactions generate a restraining effect and increase the rigid degree of EnrofloH2 2+ cation in the bulk single crystals. Our work clarifies the photophysical properties of the EnrofloH2 2+ organic cations by constructing the inter- and intramolecular interactions and boosts the further study of organic–inorganic hybrid metal halides materials with different luminescence mechanisms.

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Ciprofloxacin (CfH, C 17 H 18 FN 3 O 3 ) crystallizes with 2-thiobarbituric (H 2 tba) and barbituric acid (H 2 ba) in the aqueous solution to yield salt CfH 2 (Htba)·3H 2 O (1), salt cocrystal CfH 2 (Hba)(H 2 ba)·3H 2 O (2), and salt CfH 2 (Hba)·H 2 O (3). The compounds are structurally characterized by the Xray single-crystal diffraction. The numerous intermolecular hydrogen bonds N-H⋯O and O-H⋯O formed by water molecules, Htba − /Hba − and CfH 2 + ions, and H 2 ba molecules stabilize the crystal structures of 1 to 3. Hydrogen bonds form a 2D plane network in the salts of 1 and 3 and a 3D network in the salt cocrystal of 2. There are different π-π interactions in 1 to 3.The compounds have been characterized by powder X-ray diffraction, thermogravimetry/differential scanning calorimetry, and Fourier transform infrared spectroscopy. The compounds dehydration ends at 130°C to 150°C, and their oxidative decomposition is observed in the range of 250°C to 275°C. KEYWORDS barbituric and thiobarbituric acids, ciprofloxacin, infrared spectroscopy, salt cocrystal, thermal stability, X-ray diffraction Electronic supplementary information (ESI) available.

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