Crystallization of the Fundamental Tetracyanamidometallates Li4[Si(CN2)4] and Li4[Ge(CN2)4] from Polymeric Li‐T‐(NCN)‐I Precursors (T=Si, Ge)

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Crystallization of the Fundamental Tetracyanamidometallates Li4[Si(CN2)4] and Li4[Ge(CN2)4] from Polymeric Li-T-(NCN)-I Precursors (T=Si, Ge)

The Cover Feature shows a small section of a layer in the structure of the new Li4[Si(NCN)4]. The solid-state metathesis reaction (SSM) of mixtures of SiI4 and Li2(CN2) are controlled in situ by differential scanning calorimetry (DSC), revealing a polymeric reaction stage and the subsequent product formation under successive elimination of LiI. Tetracyanamidosilicates are closely related to orthosilicates and can exist with several cations of the PSE. As demonstrated in our previous research, metal tetracyanamidosilicates can act as robust host structures for luminescent materials to show second harmonic generation (SHG). More information can be found in the Research Article by H.-J. Meyer and co-workers.


Fluorescent BF2 Complexes Inspired by Ageladine A

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Abstract. The pH-dependent UV/Vis absorption and fluorescence of several analogs of the marine natural product ageladine A were investigated. Besides ageladine A itself, its BF2 complex, and the corresponding debrominated analogs were included, as were the chloro analog of the debromoageladine-BF2 complex, an imidazolone analog, and a triazole derivative, which lack the free amino group. Importantly, the pH-dependence of the fluorescence of the chloro analog closely resembles that of the natural product ageladine A, but with about 25-fold higher fluorescence intensity and a maximum between pH 3 and 6. The imidazolone derivative behaves in a complementary manner and shows fluorescence only above pH 6, but with less intensity than ageladine A. The calculated Stokes shifts agrees well with the experiment, which underlines the accuracy of the DFT calculation method (ωB97XD/TApr-cc-pVDZ, water, PCM). The combination of BF2 units with arylated imidazo[4,5-c]pyridine structural motifs encourages further research on more strongly fluorescent derivatives of comparable molecular size.

Cyclotriphosphazene‐Based Photocatalysts containing Orthogonal BODIPY Moieties for Chemical Transformations

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Molecular organic photocatalysts developed for use in chemical transformation reactions have gained momentum in recent years. In this study, six new triplet photosensitizers were prepared to determine their photocatalyst capabilities and chemical transformation abilities. The chemical structures of the synthesized orthogonal BODIPYs and their cyclotriphosphazene derivatives were analyzed and then their photophysical characteristics including the UV-Vis absorption spectra, fluorescence emission spectra, fluorescence quantum yields, were investigated. The quantitative singlet oxygen formation was determined by chemical trapping using DPBF (diphenylisobenzofuran). In particular, cyclotriphosphazene derivative 12 having three BODIPY moieties showed efficient singlet oxygen production with high photostability and good molar extinction coefficient. The photo-oxidation ratio constant of 1,5-dihydroxynaphthalene (DHN) was calculated as 28.7 × 10-3 min-1 for compound 12 and at the end of 22.5 min., DHN converted to juglone with 100% efficiency. In addition, the ability of the compounds to convert 1,3-cyclohexadiene into peroxides in the presence of molecular oxygen and light was investigated and the conversion efficiency was determined by NMR technique. All compounds have been presented as photocatalysts for use in different synthetic photochemistry applications.

Modulation of S‐Centered Reactivity: Impact of Terminal Ligands on Alkynyl Addition in [Fe2(µ‐S2)(CO)4L2] Complexes

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The reactivity of complexes [Fe2(µ-S2)(CO)4L2] (L = CO (1), PPh3 (2)), with lithium alkynylide reagents generated in situ, was investigated. The behavior of the S2-bridge in these compounds depends on the substitution at the diiron core. The reaction with the hexacarbonyl derivative 1 leads to the formation of the 1,2-dithiolene bridged complex [Fe2(µ-SCH=C(R)S)(CO)6] (3R) while the molecule [Fe2(µ-SH)(µ-SC≡CR)(CO)4(PPh3)2] (5R), with an open butterfly structure, is isolated when reacting the disubstituted derivative 2. The disubstituted dithiolene complex [Fe2(µ-SCH=C(Ph)S)(CO)4(PPh3)2] (4Ph) can only be obtained by substitution of carbonyls with PPh3 in 3R. In the presence of piperidine, 5R isomerizes into the 1,1’-dithiolene bridged derivative 6Ph. The novel compounds 4-6 were synthesized and characterized by IR and NMR spectroscopies. X-ray crystallographic studies of the dithiolene complexes 3Ph-4Ph allowed their structural analysis.

Pt(II)‐Phenanthroline‐Ln(III)‐DOTA d‐f Hybrids as Small‐Molecule Theranostics

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1,10-Phenanthroline d- or f-metal complexes can be utilised in biomedical applications such as imaging or therapeutics. Herein, we designed bimetallic d-block metal-phenanthroline f-block metal-1,4,7,10-tetraazacyclododecane-1,4,7,1,0-tetraacetic acid (DOTA) conjugates as theranostic agents to simultaneously achieve both of these applications. Luminescence studies show the 1,10-phenanthroline-Eu(III)-DOTA complexes displayed an off/on/off pH-dependent switch, demonstrating their potential as pH-responsive lanthanide luminescence probes. Relaxometry studies showed that the 1,10-phenanthroline-Gd(III)-DOTA complexes present a r1 of 5.15 ± 0.05 mM-1 s-1 and could thus be used as magnetic resonance (MR) contrast agents. Complexation of Pt(II) by the 1,10-phenanthroline moiety resulted in quenching of the Eu(III) luminescence, but an enhancement of the Gd(III) relaxivity (r1 = 7.53 ± 0.69 mM-1 s-1). Cell viability studies of the d-f hybrids in a cancer cell line showed the potential of these complexes as anticancer agents, as the IC50 for the Pt(II)/Gd(III) complex (IC50 = 24.9 μM) was lower than that of cisplatin (IC50 = 31.6 μM). As such, Pt(II)-1,10-phenanthroline-Gd(III)-DOTA complexes are promising theranostic agents for cancer therapy.

Enhancing the Analysis of Eu3+ Photoluminescence in Coordination Compounds in the Solid State by Determining their Refractive Index

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This study is focused on determining the refractive index as a crucial parameter for evaluating the intrinsic quantum yield and the ligand sensitisation efficiency in solid-state trivalent lanthanide coordination compounds. For this, eight trivalent europium complexes with phenyl-terpyridine ([EuX3(ptpy)(L)], X = Cl– or NO3–, ptpy = 4'‑phenyl‑2,2':6',2''‑terpyridine, L = H2O or other molecules) were examined. Their refractive indices were determined using the Becke lines test by immersing transparent material in a series of media with known refractive indices. Using the set of media presented here, determining crystalline materials' refractive indices from 1.41 to 1.73 with a step of 0.01 is possible. Assessment of the refractive indices of the complexes mentioned above allowed a comprehensive analysis of their photophysical properties in the solid state. Moreover, this method can be extrapolated for other solid-state materials, offering valuable insights in the broader field of photophysics. In addition to photoluminescence investigations, the compounds presented were characterised by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), Hirschfeld surface area analysis, UV‑Vis reflectance spectroscopy, hydrolysis sensitivity analysis, and simultaneous thermogravimetry and differential thermal analysis coupled with mass-spectrometry (STA-MS).