Charged Si Clusters in Neat Solids and the Detection of [H Si ] in Solution: A Combined NMR, Raman, Mass Spectrometric, and Quantum Chemical Investigation.

Polyanionic silicon clusters are provided by the Zintl phases K Si , comprising [Si ] units, and K Si , consisting of [Si ] and [Si ] clusters. A combination of solid-state MAS-NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum-chemical investigations was used to investigate four- and nine-atomic silicon Zintl clusters in neat solids and solution. The results were compared to Si isotope-enriched samples.

Zintl Clusters as Wet-Chemical Precursors for Germanium Nanomorphologies with Tunable Composition.

[Ge9](4-) Zintl clusters are used as soluble germanium source for a bottom-up fabrication of Ge nanomorphologies such as inverse opal structures with tunable composition. The method is based on the assembly and oxidation of [Ge9 ](4-) clusters in a template mold using SiCl4 , GeCl4 , and PCl3 leading to Si and P-containing Ge phases as shown by X-ray diffraction, Raman spectroscopy, and energy-dispersive X-ray analysis. [Ge9](4-) clusters are retained using ethylenediamine (en) as a transfer medium to a mold after removal of the solvent if water is thoroughly excluded, but are oxidized to amorphous Ge in presence of water traces.

Silicon nanoparticles by the oxidation of [Si4](4-)- and [Si9](4-)-containing Zintl phases and their corresponding yield.

The Zintl phases with nominal compositions Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs) were utilized as precursors in the synthesis of silicon nanoparticles (Si NPs). The present study characterizes and compares the yields of Si NPs synthesized from Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs). Na4Si4 and Rb7NaSi8 Zintl phases consist of anionic silicon tetrahedra stabilized by group I cations.

On the formation of intermetalloid clusters: titanocene(III)diammin as a versatile reactant toward nonastannide Zintl clusters.

The reactivity of TiCp2Cl2 (d(0)) towards Zintl clusters was studied in liquid ammonia (Cp = cyclopentadienyl). Reduction of Ti(IV)Cp2Cl2 and ligand exchange led to the formation of [Ti(III)Cp2(NH3)2](+), also obtainable by recrystallization of [CpTi(III)Cl]2. Upon reaction with [K4Sn9], ligand exchange leads to [TiCp2(η(1)-Sn9)(NH3)](3-).

Reactivity of liquid ammonia solutions of the Zintl phase K12Sn17 towards mesitylcopper(I) and phosphinegold(I) chloride.

To gain more insight into the reactivity of intermetalloid clusters, the reactivity of the Zintl phase K12 Sn17 , which contains [Sn4 ](4-) and [Sn9 ](4-) cluster anions, was investigated. The reaction of K12 Sn17 with gold(I) phosphine chloride yielded K7 [(η(2) -Sn4 )Au(η(2) -Sn4 )](NH3 )16 (1) and K17 [(η(2) -Sn4 )Au(η(2) -Sn4 )]2 (NH2 )3 (NH3 )52 (2), which both contain the anion [(Sn4 )Au(Sn4 )](7-) (1 a) that consists of two [Sn4 ](4-) tetrahedra linked through a central gold atom. Anion 1 a represents the first binary AuSn polyanion.

Mixed Si/Ge nine-atom Zintl clusters: ESI mass spectrometric investigations and single-crystal structure determination of paramagnetic [Si(9-x)Ge(x)]3-.

Mixed Si/Ge compounds are of special interest as potential materials for photovoltaic applications. In order to evaluate the usage of soluble precursor compounds, we investigated the synthesis of heteroatomic nine-atom clusters that consist of Si and Ge atoms through dissolution of the ternary Zintl phases K12Si(17-x)Ge(x) (x = 9, 12) and Rb12Si(17-x)Ge(x) (x = 9). Electrospray ionization (ESI) mass spectrometry demonstrates the presence of mixed Si(9-x)Ge(x) clusters in acetonitrile solution.

Soluble Zintl phases A14ZnGe16 (A = K, Rb) featuring [(η3-Ge4)Zn(η2-Ge4)]6- and [Ge4]4- clusters and the isolation of [(MesCu)2(η3,η3-Ge4)]4-: the missing link in the solution chemistry of tetrahedral group 14 element Zintl clusters.

The number of Zintl phases containing polyhedral clusters of tetrel elements that are accessible for chemical reactions of the main-group element clusters is rather limited. The synthesis and structural characterization of two novel ternary intermetallic phases A(14)ZnGe(16) (A = K, Rb) are presented, and their chemical reactivity is investigated. The compounds can be rationalized as Zintl phases with 14 alkali metal cations A(+) (A = K, Rb), two tetrahedral [Ge(4)](4-) Zintl anions, and one anionic heterometallic [(Ge(4))Zn(Ge(4))](6-) cluster per formula unit.

[(η2-(Si/Ge)4)Zn(η2-(Si/Ge)4)](6-)- novel Zintl clusters with mixed Si/Ge tetrahedra bridged by a Zn atom.

The solubility of the ternary Zintl phase K(12)Si(17-x)Ge(x) (x = 5), containing mixed group 14 element clusters, was investigated. Novel dimeric tetrahedral Zintl clusters [(η(2)-E(4))Zn(η(2)-E(4))](6-) with mixed site occupation (E = Si/Ge) were obtained through reaction with (C(6)H(6))(2)Zn in ammonia solutions and investigated by means of X-ray single crystal diffraction.

A quantitative test of Hamilton's rule for the evolution of altruism.

The evolution of altruism is a fundamental and enduring puzzle in biology. In a seminal paper Hamilton showed that altruism can be selected for when rb - c > 0, where c is the fitness cost to the altruist, b is the fitness benefit to the beneficiary, and r is their genetic relatedness. While many studies have provided qualitative support for Hamilton's rule, quantitative tests have not yet been possible due to the difficulty of quantifying the costs and benefits of helping acts.

Division of labour and colony efficiency in social insects: effects of interactions between genetic architecture, colony kin structure and rate of perturbations.

The efficiency of social insect colonies critically depends on their ability to efficiently allocate workers to the various tasks which need to be performed. While numerous models have investigated the mechanisms allowing an efficient colony response to external changes in the environment and internal perturbations, little attention has been devoted to the genetic architecture underlying task specialization. We used artificial evolution to compare the performances of three simple genetic architectures underlying within-colony variation in response thresholds of workers to five tasks.

Measures of diversity for populations and distances between individuals with highly reorganizable genomes.

In this paper we address the problem of defining a measure of diversity for a population of individuals whose genome can be subjected to major reorganizations during the evolutionary process. To this end, we introduce a measure of diversity for populations of strings of variable length defined on a finite alphabet, and from this measure we derive a semi-metric distance between pairs of strings. The definitions are based on counting the number of substrings of the strings, considered first separately and then collectively.