Alexander E. Sedykh

Access to defined titanium(II) compounds is crucial for their use in synthesis and catalysis. Most established routes to Ti(II) compounds rely on the reduction of Ti(III) or Ti(IV), an approach that intrinsically limits atom efficiency and can introduce byproducts or lead to mixed‐valency complexes. Here, an alternative strategy for obtaining Ti(II) is presented, based on the oxidation of Ti metal by iodine. Ti diiodide formed in this reaction is subsequently complexed to afford the novel Ti(II) complex [Ti(py) ₄ I ₂ ] on a gram scale (> 30 g, 50 mmol) in a highly atom‐efficient approach. Revision of the original synthesis of TiI ₂ shows that excess Ti metal is required to prevent the formation of higher Ti iodides, enabling clean access to Ti(II) without reductive agents. The resulting Ti(II) complex serves as a synthetic entry point for Ti(II) chemistry, as illustrated by a ligand exchange reaction to form [Ti(2,2′‐bipyridine) ₂ I ₂ ].

Recovery of the critical resource Te from Bi ₂ Te ₃ & Sb ₂ Te ₃ was achieved via green chemistry principles using chemical vapour transport. Partly created with AI (engine: Firefly).

Fourteen new coordination compounds and polymers were synthesised, including 1∞[Zn(pt) ₂ ], which was tuned towards white light emission by intercalation of trivalent lanthanide ions.

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).

A surfactant-assisted bottom-up synthesis route provides access to nanoscale metal–organic frameworks (nMOFs) that exploit size-dependent property advantages. This includes an increased surface-to-volume ratio, improved dispersibility and superior morphological properties by a narrow size distribution compared to the bulk analogues. Photophysical properties such as photoluminescence are also influenced by particle size, surfactant components and post-synthetic modification. The series of the related organic linkers (H₂bdc, H₂bpdc and H₂bpydc) together with trivalent lanthanides (Ln³⁺ = Eu³⁺, Tb³⁺) in synthesis and post-synthetic modification together with surface-active agents (CTAB, PVP) were used to assemble luminescent nMOFs for three archetype MOFs: nLn³⁺-bdc, nDUT-5:Ln³⁺ and nMOF-253:Ln³⁺. Both, dispersibility and morphology benefit from the CTAB- and PVP-controlled bottom-up particle downsizing down to 35 nm. DLS confirms homogeneous, narrow particle size distributions down to ±5 nm, which is 21-times smaller than the bulk analogues. Moreover, excellent luminescence QYs of up to 78.1(3)% were determined for the Ln³⁺-containing nMOFs. Successful post-synthetic modification with trivalent lanthanide ions of nMOFs was accomplished showing an improved photoluminescence sensitization effect compared to the bulk MOFs and exhibiting increased Ln³⁺-to-linker emission intensity ratios. The amount and photophysical properties of surfactants encapsulating the nMOFs were further quantified by DTA/TG-MS and UV-Vis-DRS. Finally, this work aims to elaborate thoroughly on the previously mentioned properties of nMOFs by comparison with their bulk analogues. Since surfactants play a key role in this synthesis route, the pros and cons of this approach were also assessed concerning several nMOF features.

We report the multi-step synthesis of the tetradentate 2-(naphthalen-2-yl)-5-[N,N-bis(2-pyridylmethyl)aminomethyl]-1,3,4-oxadiazole ligand (L^Tetra-ODA) along with its corresponding [Fe^II(L^Tetra-ODA)(NCBH₃)₂]·1.5CH₃OH (C1) complex, which is the first mononuclear 1,3,4-oxadiazole based Fe(II) spin crossover (SCO) complex, and its zinc analogue [Zn^II(L^Tetra-ODA)(NCBH₃)₂]·0.5H₂O (C2). The spin transition is followed by variable temperature (VT-) X-ray crystallography of [Fe(L^Tetra-ODA)(NCBH₃)₂]·1.5CH₃OH (C1) at 120 and 220 K. The magnetic susceptibility measurements on the bulk sample recorded from 2 to 300 K show that the complex exhibits a complete abrupt reversible spin transition with a T_1/2 of 207 K. The loss of the lattice solvent methanol shifts the T_1/2 slightly to around 210 K. The spin transition in solution for [Fe(L^Tetra-ODA)(NCBH₃)₂]·1.5CH₃OH (C1) was followed using the VT-¹H-NMR Evans method in CD₃CN, with a T_1/2 of 357 K. Solid state VT luminescence studies provide some preliminary evidence of interplay of luminescence and spin transition in the [Fe(L^Tetra-ODA)(NCBH₃)₂]·1.5CH₃OH (C1) complex.