Isolated Se₆Rings in the Voids of a Weakly Interacting, Electroneutral, and Crystalline SiO₂Matrix:  Combined Experimental and Theoretical Study

Abstract

For the first time a selenium species has been successfully trapped in the voids of an electroneutral SiO 2 modification, namely, in the porosil decadodecasil 3R (DDR). Raman spectroscopy in combination with theoretical ab initio calculations at the SCF and MP2 levels of theory have been used to assign the observed spectral bands exclusively to Se 6 rings with D 3d symmetry. The A 1g (r) and E g (r) mode frequencies of the matrix-isolated Se 6 rings are considerably higher than those of bulk Se 6 , suggesting that intermolecular correlations are lost for the perfectly isolated molecules in the microporous host matrix. By an EXAFS analysis of Se K-spectra, Se-Se bond lengths of 2.34 Å and next-nearest Se‚‚‚Se distances of 3.61 Å are obtained, in very good agreement with the theoretical ab initio studies. EXAFS analysis in addition reveals that the interaction between the SiO 2 framework and the embedded Se 6 rings are weak, resulting in a novel hostguest compound with nearly unperturbed Se 6 guest molecules. The crystalline electroneutral host thus acts similarly to a noble gas matrix at low temperatures.

Structural, energetic and response electric properties of cyclic selenium clusters: an ab initio and density functional theory study

“…Selenium systems were investigated for the design of switching devices to optical fibers in non-linear optics and as memory media [8,9]. Zeolite/selenium composite materials received great attention for the development of nanostructured semiconductors [10][11][12][13]. Selenium in the forms of chains and/or rings can be easily introduced into zeolite cavities.…”

“…The structure of evennumbered Se 6 , Se 8 and Se 12 clusters introduced into monodimensional channels of AlPO 4 -5 single crystals, mordenite and zeolite cavities were extensively characterized by Raman spectroscopy [12,13,[23][24][25][26][27][28][29][30][31][32][33][34]. Selenium clusters adsorbed into zeolite channels are bonded to each other and to the host matrices by van der Waals forces controlled by the polarizabilities of the clusters [21,35].…”

“…Selenium clusters adsorbed into zeolite channels are bonded to each other and to the host matrices by van der Waals forces controlled by the polarizabilities of the clusters [21,35]. On the theoretical side, geometries, relative stabilities, binding energies of selenium clusters are available from the literature [12,[36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

Metastable Se6 as a ligand for Ag+: from isolated molecular to polymeric 1D and 2D structures

“…Salts of the isolated molecular diamagnetic homopolyatomic cations S n 2+ (n = 4, 8,19), Se n 2+ (n = 4, 8, 10, 17) and Te n m+ (n = 4, 6, 7, 10, m = 2; n = 8, m = 2, 4) contain positively charged rings formed upon oxidation of the elements with non basic anions.…”

“…; E = Se: n = 6, 7,8) that are isolable at r.t. have been prepared and structurally characterized. Molecular S 8 is the most stable form of sulfur and the stability of the selenium allotropes increases in the order: Se 7 < Se 6 < Se 8 < Se • .…”