Syntheses, Structures, and Electronic Properties of a New Series of Tellurides of the Type [Sequestered Cation]₂(Te_x) (x = 1–4)

Abstract

The list of "classical" tellurides with organic cations was expanded by the synthesis of single-crystalline salts [Li 2 (en) n ](Te x ) (en = ethylenediamine) with n = 4, x = 1 (1), n = 4, x = 2 (2), and n = 5, x = 3 (3), [K(18c6)] 2 (Te x ) (18c6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) with x = 2 (4), 4 (5), [K(18c6)] 2 [K(en)] 2 (Te 2 ) 2 (6), and [K([2.2.2]crypt)] 2 (Te 2 ) (7) ([2.2.2]crypt = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane). Electronic structure calculations * Prof. Dr. S. Dehnen 2809on free molecules and periodic approaches are discussed and compared with experimental UV/Vis spectra, providing a correlation of the bandgaps with the telluride chain length, and a possibility for affecting the gap by according choice of the counterions. Additionally, 125 Te NMR chemical shifts of the presented series of en solvated lithium tellurides are presented.

Bautechnik aktuell 3/2015

“…The NMR signal obtained from the [Pb 2 Ch 3 ] 2– anion in the case of en ‐solvated Li + or to a minor degree [K(18‐crown‐6)] + cations is very broad (Figures S2–S7, Supporting Information), indicating interactions of the metal cations with the chalcogenide ligands in solution, whereas the corresponding [2.2.2]crypt complexes are shielded from any electronic affection of the cations, giving rise to sharp signals (see Figures S8, S9, Supporting Information) as has been reported before 19. However, only in the case of cation sequestration or solvation of all cations, the trigonal bipyramidal [Pb 2 Ch 3 ] 2– anion can be obtained.…”

“…The literature procedure for the generation of salts of the [Pb 2 Te 3 ] 2– anion involves the extraction of an alloy of the nominal composition “KPbTe” with en in the presence of [2.2.2]crypt 12. However, these syntheses always came along with the formation of [K([2.2.2]crypt)] 2 (Te 2 )19 and [K([2.2.2]crypt)](Te 3 )21 as side‐products, which was determined via X‐ray diffraction of according crystals, beside Te 2– and (HTe) – ions, as observed by 127 Te NMR experiments of the reaction solution (see Supporting Information).…”

“…Therefore, alternative reaction pathways, such as extraction of alloys that were prepared by high‐temperature procedures, have been extensively studied, as well as reductions in less volatile solvents, preferably liquid solvents at room temperature, such as ethane‐1,2‐diamine ( en ). We have previously utilized this in‐situ reduction technique for the syntheses of polytellurides of en ‐solvated lithium derivatives,19 and have now extended this study according to Haushalter's synthesis of K 4 [PbTe 3 ] · 2 en [see Equation (1) in Scheme ]14 towards reduction of heavy main group chalcogenides with lithium or potassium; reactions of potassium were carried out in the presence of cation sequestrating agents.…”

Organic Cation and Complex Cation‐Stabilized (Poly‐)Selenides, [Cation]x(Sey)z: Diversity in Structures and Properties

“…Our previous investigations confirmed a general applicability of TDDFT values for interpretation of UV/Vis spectra of polychalcogenides; [78] therefore two of the excitations would be in the range of visible light and would explain (a) the measured UV/Vis spectra and (b) the observed change in color upon rotation under polarized light, thus the orthogonal excitation. The latter is in agreement with the clearly anisotropic anion packing (vide supra).…”

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

“…However, apart from all metalate compounds that could be identified and isolated so far (see the summary of synthetic approaches in Figure 5), a vast variety of polychalcogenides have been detected and isolated 31,32 . These investigations have been neglected so far, even though they possess intriguing properties and can also be synthesized by a direct approach via the in situ method in high yields and purities.…”