New insights into the chemistry of imidodiphosphinates from investigations of tellurium-centered systems

Cadmium Telluride Nanocomposite Films Formation from Thermal Decomposition of Cadmium Carboxylate Precursor and Their Photoluminescence Shift from Green to Red

This study focuses on the investigation of a CdTe quantum dots (QDs) formation from a cadmium-carboxylate precursor, such as cadmium isostearate (Cd(ISA)2), to produce CdTe QDs with tunable photoluminescent (PL) properties. The CdTe QDs are obtained by the thermal decomposition of precursors directly in the polymer matrix (in situ method) or in solution and then encapsulated in the polymer matrix (ex situ method). In both approaches, the time course of the CdTe QDs formation is followed by means of optical absorption and PL spectroscopies focusing on viable emission in the spectral interval between 520 and 630 nm. In the polymeric matrix, the QDs formation is slower than in solution and the PL bands have a higher full width at half maximum (FWHM). These results can be explained on the basis of the limited mobility of atoms and QDs in a solid matrix with respect to the solution, inducing an inhomogeneous growth and the presence of surface defects. These achievements open the way to the exploitation of Cd(ISA)2 as suitable precursor for direct laser patterning (DPL) for the manufacturing of optoelectronic devices.

Unusual 31P Hyperfine Strain Effects in a Conformationally Flexible Cu(II) Complex Revealed by Two-Dimensional Pulse EPR Spectroscopy

Strain effects on g and metal hyperfine coupling tensors, A, are often manifested in Electron Paramagnetic Resonance (EPR) spectra of transition metal complexes, as a result of their intrinsic and/or solvent-mediated structural variations. Although distributions of these tensors are quite common and well understood in continuous-wave (cw) EPR spectroscopy, reported strain effects on ligand hyperfine coupling constants are rather scarce. Here we explore the case of a conformationally flexible Cu(II) complex, [Cu{Ph₂P(O)NP(O)Ph₂-κ²O,O'}₂], bearing P atoms in its second coordination sphere and exhibiting two structurally distinct CuO₄ coordination spheres, namely a square planar and a tetrahedrally distorted one, as revealed by X-ray crystallography. The Hyperfine Sublevel Correlation (HYSCORE) spectra of this complex exhibit ³¹P correlation ridges that have unusual inverse or so-called "boomerang" shapes and features that cannot be reproduced by standard simulation procedures assuming only one set of magnetic parameters. Our work shows that a distribution of isotropic hyperfine coupling constants (hfc) spanning a range between negative and positive values is necessary in order to describe in detail the unusual shapes of HYSCORE spectra. By employing DFT calculations we show that these hfc correspond to molecules showing variable distortions from square planar to tetrahedral geometry, and we demonstrate that line shape analysis of such HYSCORE spectra provides new insight into the conformation-dependent spectroscopic response of the spin system under investigation.

Organophosphorus-selenium/tellurium reagents: from synthesis to applications

Organic selenium- and tellurium-phosphorus compounds have found wide application as reagents in synthetic inorganic and organic chemistry, such as oxygen/chalcogen exchange, oxidation/reduction, nucleophilic/electrophilic substitution, nucleophilic addition, free radical addition, Diels–Alder reaction, cycloadditions, coordination, and so on. This chapter covers the main classes of phosphorus-selenium/tellurium reagents, including binary phosphorus-selenium/tellurium species, organophosphorus(III)-selenium/tellurium compounds, phosphorus(V)-selenides/tellurides, diselenophosphinates/ditellurophopshinates, diselenaphosphetane diselenides, Woollins’ reagent, phosphorus-selenium/tellurium amides, and imides. Given the huge amount of literature up to mid-2017, this overview is inevitably selective and will focus particularly on their synthesis, reactivity, and applications in synthetic and coordination chemistry.

s-Block metal complexes of PC(H)P-bridged chalcogen-centred methanides: comparisons with isoelectronic PNP-bridged monoanions

This Perspective compares the chemistries of s-block metal complexes of isoelectronic PC(H)P- and PNP-bridged, chalcogen-centred monoanions with a focus on the unique behavior of the C(H)-bridged systems.

Magnetic Anisotropy of Tetrahedral CoII Single-Ion Magnets: Solid-State Effects

This study reports the static and dynamic magnetic characterization of two mononuclear tetrahedral Co^II complexes, [Co{ⁱPr₂P(E)NP(E)ⁱPr₂}₂], where E = S (CoS₄) and Se (CoSe₄), which behave as single-ion magnets (SIMs). Low-temperature (15 K) single-crystal X-ray diffraction studies point out that the two complexes exhibit similar structural features in their first coordination sphere, but a disordered peripheral ⁱPr group is observed only in CoS₄. Although the latter complex crystallizes in an axial space group, the observed structural disorder leads to larger transverse magnetic anisotropy for the majority of the molecules compared to CoSe₄, as confirmed by electron paramagnetic resonance spectroscopy. Static magnetic characterization indicates that both CoS₄ and CoSe₄ show easy-axis anisotropy, with comparable D values (∼-30 cm^-1). Moreover, alternating-current susceptibility measurements on these Co^II complexes, magnetically diluted in their isostructural Zn^II analogues, highlight the role of dipolar magnetic coupling in the mechanism of magnetization reversal. In addition, our findings suggest that, despite their similar anisotropic features, CoS₄ and CoSe₄ relax magnetically via different processes. This work provides experimental evidence that solid-state effects may affect the magnetic behavior of SIMs.

A square-planar tellurium(II) complex withTe,Te′-chelating ligands

While exploring the chemistry of tellurium-containing dichalcogenidoimidodiphosphinate ligands, the first all-tellurium member of a series of related square-planarEII(E′)4complexes (EandE′ are group 16 elements), namely bis(P,P,P′,P′-tetraphenylditelluridoimidodiphosphinato-κ2Te,Te′)tellurium(II) (systematic name: 2,2,4,4,8,8,10,10-octaphenyl-1λ3,5,6λ4,7λ3,11-pentatellura-3,9-diaza-2λ5,4λ5,8λ5,10λ5-tetraphosphaspiro[5.5]undeca-1,3,7,9-tetraene), C48H40N2P4Te5, was obtained unexpectedly. The formally TeIIcentre is situated on a crystallographic inversion centre and isTe,Te′-chelated to two anionic [(TePPh2)2N]−ligands in ananticonformation. The central TeII(Te)4unit is approximately square planar [Te—Te—Te = 93.51 (3) and 86.49 (3)°], with Te—Te bond lengths of 2.9806 (6) and 2.9978 (9) Å.

A comparative ab initio study to investigate the rich structural variety and electronic properties of GamTen (m = 1, 2 and n = 1–4) with analogous oxides, sulfides and selenides

A series of gallium telluride, Ga_mTe_n (m = 1, 2 and n = 1–4), clusters has been examined by using different computational methods.

Planar P(6)E(6) (E = Se, S) macrocycles incorporating P(2)N(2) scaffolds

Oxidation of alkali metal derivatives of the dianions [E((t)BuN)P(μ-N(t)Bu)(2)P(N(t)Bu)E](2-) (E = S, Se) with I(2) produces 15-membered macrocycles in which a planar P(6)E(6) motif is stabilised by perpendicular P(2)N(2) scaffolds.

Conversion of tetrahedral to octahedral structures upon solvent coordination: studies on the M[(OPPh2)(SePPh2)N]2 (M = Co, Ni) and [Ni{(OPPh2)(EPPh2)N}2(dmf)2] (E = S, Se) complexes

The synthesis of the M[(OPPh(2))(SePPh(2))N](2), M = Co (1), Ni (2) complexes was accomplished by metathetical reactions between the corresponding M(II) salts and the deprotonated form of the dichalcogenated imidodiphosphinato ligand [(OPPh(2))(SePPh(2))N](-). X-Ray crystallography revealed a pseudo-tetrahedral MO(2)Se(2) coordination sphere, owing to the asymmetric (O,Se) nature of the chelating ligand. Slow diffusion of the coordinating solvent dimethylformamide into dichloromethane solutions of Ni[(OPPh(2))(SPPh(2))N](2) or 2, afforded the pseudo-octahedral trans-[Ni{(OPPh(2))(EPPh(2))N}(2)(dmf)(2)], E = S (3), Se (4) complexes, respectively. UV-vis spectra provided evidence that, in solution, complexes 3 and 4 revert to the corresponding pseudo-tetrahedral complexes, most likely due to the removal of the dmf molecules from the coordination sphere. The IR spectra of all complexes reflect the structural features observed by X-ray crystallography. The magnetic properties of the S = 3/2 complex 1, as well as the S = 1 complexes 2, 3 and 4, were extensively studied, and the magnitude of their g and zero-field splitting D parameters was estimated. The reported structures establish a structural transformation of tetrahedral to octahedral geometry of Ni(II) complexes bearing asymmetric imidodiphosphinate ligands, upon recrystallization from coordinating solvents. The structural correlations between the Ni(II) coordination spheres are aided by DFT and ab initio multi-configuration MCSCF calculations, which investigate the corresponding interconversion pathways. In addition, the calculations provide descriptions of the bonding interactions in the octahedral Ni(II) complexes, as well as predictions of their D values.