Structures and properties of ion pair charge-transfer salts: [DMBPE]2Ge4S10 (DMBPE=N,N′-dimethyl-1,2-bis(4-pyridinium)-ethylene)

Adamantane-type clusters: compounds with a ubiquitous architecture but a wide variety of compositions and unexpected materials properties

The research into adamantane-type compounds has gained momentum in recent years, yielding remarkable new applications for this class of materials. In particular, organic adamantane derivatives (AdR4) or inorganic adamantane-type compounds of the general formula [(RT)4E6] (R: organic substituent; T: group 14 atom C, Si, Ge, Sn; E: chalcogenide atom S, Se, Te, or CH2) were shown to exhibit strong nonlinear optical (NLO) properties, either second-harmonic generation (SHG) or an unprecedented type of highly-directed white-light generation (WLG) - depending on their respective crystalline or amorphous nature. The (missing) crystallinity, as well as the maximum wavelengths of the optical transitions, are controlled by the clusters' elemental composition and by the nature of the organic groups R. Very recently, it has been additionally shown that cluster cores with increased inhomogeneity, like the one in compounds [RSi{CH2Sn(E)R'}3], not only affect the chemical properties, such as increased robustness and reversible melting behaviour, but that such 'cluster glasses' form a conceptually new basis for their use in light conversion devices. These findings are likely only the tip of the iceberg, as beside elemental combinations including group 14 and group 16 elements, many more adamantane-type clusters (on the one hand) and related architectures representing extensions of adamantane-type clusters (on the other hand) are known, but have not yet been addressed in terms of their opto-electronic properties. In this review, we therefore present a survey of all known classes of adanmantane-type compounds and their respective synthetic access as well as their optical properties, if reported.

Stepwise Conversion from GeO2 to [MGe4S10]n3n- (M = Cu, Ag) Polymer via Isolatable [Ge2S6]4- and [Ge4S10]4- Anions by Virtue of Templating Technique

Rational synthesis of inorganic matter remains a great challenge encountered with modern synthetic chemistry. Here we reported the stepwise solvothermal conversion from GeO₂ to [MGe₄S₁₀]_n^3n- (M = Cu, Ag) polymer via isolatable [Ge₂S₆]^4- and [Ge₄S₁₀]^4- anions by virtue of templating technique. The facile sulfuration of GeO₂ resulted in the methylammonium-templated dimeric thiogermanate [CH₃NH₃]₄Ge₂S₆ (1). This was used subsequently as a precursor for the formation of adamantane-like [Ge₄S₁₀]^4- cluster, which was isolated as a mixed methylammonium/ethylammonium salt [CH₃CH₂NH₃]₃[CH₃NH₃]Ge₄S₁₀ (2). Compound 2 was then successfully used as a precursor to react with Cu⁺ and Ag⁺ cations in the presence of tetraethylammonium, resulting in alternating copolymeric products [(CH₃CH₂)₄N]₃MGe₄S₁₀ (M = Cu (3), Ag (4)), whose anionic moieties feature a novel zigzag chainlike structure constructed by [Ge₄S₁₀]^4- clusters via two-coordinate Cu⁺/Ag⁺ linkers. Mixed amine/ethanol or deep eutectic solvents were applied as media for the syntheses of 1-4, and all the products were characterized in the solid state and solution. Crystal structural analysis of the title compounds revealed significant templating roles of the alkylammonium cations as both space-filling agents and hydrogen-bonding donors, suggesting the structure-directing mechanism for the species formation and crystal growth. The design and optimization of multistep structural conversion upon templating effects would be beneficial for drawing rational, predictable pathways for inorganic synthesis.