bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation After a Selective Sweep in a Subdivided Population
Authors: Santiago Enrique , Caballero Armando
Published: October 2004

The effect of genetic hitchhiking on neutral variation is analyzed in subdivided populations with differentiated demes. After fixation of a favorable mutation, the consequences on particular subpopulations can be radically different. In the subpopulation where the mutation first appeared by mutation, variation at linked neutral loci is expected to be reduced, as predicted by the classical theory. However, the effect in the other subpopulations, where the mutation is introduced by migration, can be the opposite. This effect depends on the level of genetic differentiation of the subpopulations, the selective advantage of the mutation, the recombination frequency, and the population size, as stated by analytical derivations and computer simulations. The characteristic outcomes of the effect are three. First, the genomic region of reduced variation around the selected locus is smaller than that predicted in a panmictic population. Second, for more distant neutral loci, the amount of variation increases over the level they had before the hitchhiking event. Third, for these loci, the spectrum of gene frequencies is dominated by an excess of alleles at intermediate frequencies when compared with the neutral theory. At these loci, hitchhiking works like a system that takes variation from the between-subpopulation component and introduces it into the subpopulations. The mechanism can also operate in other systems in which the genetic variation is distributed in clusters with limited exchange of variation, such as chromosome arrangements or genomic regions closely linked to targets of balancing selection.
Photoperiod Regulates Flower Meristem Development in Arabidopsis thaliana
Authors: Jeong Sangho , Clark Steven E
Published: October 2004

Photoperiod has been known to regulate flowering time in many plant species. In Arabidopsis, genes in the long day (LD) pathway detect photoperiod and promote flowering under LD. It was previously reported that clavata2 (clv2) mutants grown under short day (SD) conditions showed suppression of the flower meristem defects, namely the accumulation of stem cells and the resulting production of extra floral organs. Detailed analysis of this phenomenon presented here demonstrates that the suppression is a true photoperiodic response mediated by the inactivation of the LD pathway under SD. Inactivation of the LD pathway was sufficient to suppress the clv2 defects under LD, and activation of the LD pathway under SD conditions restored clv2 phenotypes. These results reveal a novel role of photoperiod in flower meristem development in Arabidopsis. Flower meristem defects of clv1 and clv3 mutants are also suppressed under SD, and 35S:CO enhanced the defects of clv3, indicating that the LD pathway works independently from the CLV genes. A model is proposed to explain the interactions between photoperiod and the CLV genes.
Functional Evolution of the Vertebrate Myb Gene Family
Authors: Davidson Colin J , Tirouvanziam Rabindra , Herzenberg Leonard A , Lipsick Joseph S
Published: October 2004

The duplication of genes and genomes is believed to be a major force in the evolution of eukaryotic organisms. However, different models have been presented about how duplicated genes are preserved from elimination by purifying selection. Preservation of one of the gene copies due to rare mutational events that result in a new gene function (neofunctionalization) necessitates that the other gene copy retain its ancestral function. Alternatively, preservation of both gene copies due to rapid divergence of coding and noncoding regions such that neither retains the complete function of the ancestral gene (subfunctionalization) may result in a requirement for both gene copies for organismal survival. The duplication and divergence of the tandemly arrayed homeotic clusters have been studied in considerable detail and have provided evidence in support of the subfunctionalization model. However, the vast majority of duplicated genes are not clustered tandemly, but instead are dispersed in syntenic regions on different chromosomes, most likely as a result of genome-wide duplications and rearrangements. The Myb oncogene family provides an interesting opportunity to study a dispersed multigene family because invertebrates possess a single Myb gene, whereas all vertebrate genomes examined thus far contain three different Myb genes (A-Myb, B-Myb, and c-Myb). A-Myb and c-Myb appear to have arisen by a second round of gene duplication, which was preceded by the acquisition of a transcriptional activation domain in the ancestral A-Myb/c-Myb gene generated from the initial duplication of an ancestral B-Myb-like gene. B-Myb appears to be essential in all dividing cells, whereas A-Myb and c-Myb display tissue-specific requirements during spermatogenesis and hematopoiesis, respectively. We now report that the absence of Drosophila Myb (Dm-Myb) causes a failure of larval hemocyte proliferation and lymph gland development, while Dm-Myb−/− hemocytes from mosaic larvae reveal a phagocytosis defect. In addition, we show that vertebrate B-Myb, but neither vertebrate A-Myb nor c-Myb, can complement these hemocyte proliferation defects in Drosophila. Indeed, vertebrate A-Myb and c-Myb cause lethality in the presence or absence of endogenous Dm-Myb. These results are consistent with a neomorphic origin of an ancestral A-Myb/c-Myb gene from a duplicated B-Myb-like gene. In addition, our results suggest that B-Myb and Dm-Myb share essential conserved functions that are required for cell proliferation. Finally, these experiments demonstrate the utility of genetic complementation in Drosophila to explore the functional evolution of duplicated genes in vertebrates.
Satellite DNA From the Y Chromosome of the Malaria Vector Anopheles gambiaeSequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. AY754141, AY754312.
Authors: Krzywinski Jaroslaw , Sangaré Djibril , Besansky Nora J
Published: October 2004

Satellite DNA is an enigmatic component of genomic DNA with unclear function that has been regarded as “junk.” Yet, persistence of these tandem highly repetitive sequences in heterochromatic regions of most eukaryotic chromosomes attests to their importance in the genome. We explored the Anopheles gambiae genome for the presence of satellite repeats and identified 12 novel satellite DNA families. Certain families were found in close juxtaposition within the genome. Six satellites, falling into two evolutionarily linked groups, were investigated in detail. Four of them were experimentally confirmed to be linked to the Y chromosome, whereas their relatives occupy centromeric regions of either the X chromosome or the autosomes. A complex evolutionary pattern was revealed among the AgY477-like satellites, suggesting their rapid turnover in the A. gambiae complex and, potentially, recombination between sex chromosomes. The substitution pattern suggested rolling circle replication as an array expansion mechanism in the Y-linked 53-bp satellite families. Despite residing in different portions of the genome, the 53-bp satellites share the same monomer lengths, apparently maintained by molecular drive or structural constraints. Potential functional centromeric DNA structures, consisting of twofold dyad symmetries flanked by a common sequence motif, have been identified in both satellite groups.
Swi5 Acts in Meiotic DNA Joint Molecule Formation in Schizosaccharomyces pombe
Authors: Ellermeier Chad , Schmidt Henning , Smith Gerald R
Published: October 2004

Previously isolated Schizosaccharomyces pombe swi5 mutants are defective in mitotic mating-type switching and in repair of meiotic recombination-related DNA double-strand breaks. Here, we identify the swi5 gene, which encodes an 85-amino-acid polypeptide, similar to Sae3 of Saccharomyces cerevisiae, with an N-terminal predicted coiled-coil domain. A swi5 complete deletion mutant had normal mitotic growth rate but was hypersensitive to DNA-damaging agents and defective in mating-type switching. In meiosis, recombinant frequencies were reduced by a factor of ∼10. The swi5 deletion strongly reduced the viable spore yields of mutants lacking Rhp55 or Rhp57, proteins thought to aid joint molecule formation. Furthermore, the swi5 deletion strongly suppressed the low viable spore yield of mutants lacking Mus81•Eme1, which resolves joint molecules such as Holliday junctions. These and previous results indicate that the small Swi5 polypeptide acts in a branched pathway of joint molecule formation to repair meiotic DNA breaks.
Nucleotide Polymorphism and Linkage Disequilibrium Within and Among Natural Populations of European Aspen (Populus tremula L., Salicaceae)
Authors: Ingvarsson Pär K
Published: October 2004

Populus is an important model organism in forest biology, but levels of nucleotide polymorphisms and linkage disequilibrium have never been investigated in natural populations. Here I present a study on levels of nucleotide polymorphism, haplotype structure, and population subdivision in five nuclear genes in the European aspen Populus tremula. Results show substantial levels of genetic variation. Levels of silent site polymorphisms, πs, averaged 0.016 across the five genes. Linkage disequilibrium was generally low, extending only a few hundred base pairs, suggesting that rates of recombination are high in this obligate outcrossing species. Significant genetic differentiation was found at all five genes, with an average estimate of FST = 0.116. Levels of polymorphism in P. tremula are 2- to 10-fold higher than those in other woody, long-lived perennial plants, such as Pinus and Cryptomeria. The high levels of nucleotide polymorphism and low linkage disequilibrium suggest that it may be possible to map functional variation to very fine scales in P. tremula using association-mapping approaches.
A Torrid Zone on Mouse Chromosome 1 Containing a Cluster of Recombinational Hotspots
Authors: Kelmenson Peter M , Petkov Petko , Wang Xiaosong , Higgins David C , Paigen Beverly J , Paigen Kenneth
Published: October 2004

Within the 2.38-Mb Ath1 region of mouse chromosome 1, 42 of 45 genetic crossovers from crosses between C57BL/6J (B6) and either C3H/HeJ (H) or Mus spretus (SPRET) occurred in four zones (A–D); zone A, 100 kb long, contained a cluster of at least four recombination hotspots. F1 sperm assays indicate that within this “torrid zone” the most active hotspot (A3) can initiate recombination on H and SPRET but not B6 chromosomes. The A3 DNA sequence contains a (G/C)TTT repeat, long stretches of A or T, and a cyclic variation in AT content. Recombination was drastically reduced in a cross between B6 and a B6.SPRET Ath1 congenic strain, but was unaffected in a B6 × B6.H Ath1 congenic cross. Similar nonrandom clustering of hotspots has been observed in yeast and the major histocompatibility complexes of human and mouse. To the extent that torrid zones are a general feature of mammalian genomes, they have considerable implications for genetic mapping strategies in both human populations and mouse crosses.
MuDR Transposase Increases the Frequency of Meiotic Crossovers in the Vicinity of a Mu Insertion in the Maize a1 Gene
Authors: Yandeau-Nelson Marna D , Zhou Qing , Yao Hong , Xu Xiaojie , Nikolau Basil J , Schnable Patrick S
Published: October 2004

Although DNA breaks stimulate mitotic recombination in plants, their effects on meiotic recombination are not known. Recombination across a maize a1 allele containing a nonautonomous Mu transposon was studied in the presence and absence of the MuDR-encoded transposase. Recombinant A1′ alleles isolated from a1-mum2/a1::rdt heterozygotes arose via either crossovers (32 CO events) or noncrossovers (8 NCO events). In the presence of MuDR, the rate of COs increased fourfold. This increase is most likely a consequence of the repair of MuDR-induced DNA breaks at the Mu1 insertion in a1-mum2. Hence, this study provides the first in vivo evidence that DNA breaks stimulate meiotic crossovers in plants. The distribution of recombination breakpoints is not affected by the presence of MuDR in that 19 of 24 breakpoints isolated from plants that carried MuDR mapped to a previously defined 377-bp recombination hotspot. This result is consistent with the hypothesis that the DNA breaks that initiate recombination at a1 cluster at its 5′ end. Conversion tracts associated with eight NCO events ranged in size from <700 bp to >1600 bp. This study also establishes that MuDR functions during meiosis and that ratios of CO/NCO vary among genes and can be influenced by genetic background.
The Generation of Cloned Drosophila melanogaster
Authors: Haigh Andrew J , MacDonald William A , Lloyd Vett K
Published: October 2004

We report here the first successful use of embryonic nuclear transfer to create viable adult Drosophila melanogaster clones. Given the generation time, cost effectiveness, and relative ease of embryonic nuclear transplant in Drosophila, this method can provide an opportunity to further study the constraints on development imposed by transplanting determined or differentiated nuclei.
Distinct Roles for the Saccharomyces cerevisiae Mismatch Repair Proteins in Heteroduplex Rejection, Mismatch Repair and Nonhomologous Tail Removal
Authors: Goldfarb Tamara , Alani Eric
Published: October 2004

The Saccharomyces cerevisiae mismatch repair (MMR) protein MSH6 and the SGS1 helicase were recently shown to play similarly important roles in preventing recombination between divergent DNA sequences in a single-strand annealing (SSA) assay. In contrast, MMR factors such as Mlh1p, Pms1p, and Exo1p were shown to not be required or to play only minimal roles. In this study we tested mutations that disrupt Sgs1p helicase activity, Msh2p-Msh6p mismatch recognition, and ATP binding and hydrolysis activities for their effect on preventing recombination between divergent DNA sequences (heteroduplex rejection) during SSA. The results support a model in which the Msh proteins act with Sgs1p to unwind DNA recombination intermediates containing mismatches. Importantly, msh2 mutants that displayed separation-of-function phenotypes with respect to nonhomologous tail removal during SSA and heteroduplex rejection were characterized. These studies suggest that nonhomologous tail removal is a separate function of Msh proteins that is likely to involve a distinct DNA binding activity. The involvement of Sgs1p in heteroduplex rejection but not nonhomologous tail removal further illustrates that subsets of MMR proteins collaborate with factors in different DNA repair pathways to maintain genome stability.
From Whence Have We Come? The First Twenty‐Five Years of Educational Gerontology
Authors: Hiemstra Roger
Published: October 2004

This chapter focuses on the history of the field from the early work of
Howard McClusky through the developing body of literature and research.
Current Practice and Innovative Programs in Older Adult Learning
Authors: Eisen Mary‐Jane
Published: October 2004

In this chapter, the author seeks to describe the state of the art in older adult
learning today, focusing on traditional and innovative programs, and gives
a typology that describes current curricula.
Teaching and Learning Internet Skills
Authors: Cahoon Brad
Published: October 2004

Millions of adults have already learned to use the Internet, and millions
more will follow. This chapter provides a cognitive view of basic Internet
skills and describes a practice‐oriented approach to teaching them.
Course Development on the World Wide Web
Authors: King Kathleen P.
Published: October 2004

Practical guidelines are presented for educators who wish to create their
own Web resources, focusing on questions about technology, curriculum,
construction, and evaluation.
Women's Career Development Patterns
Authors: Schreiber Pamela J.
Published: October 2004

The author assesses the characteristics and patterns of women's career development
and explores alternative work arrangements as options for women
who are striving to balance work and life.
Women's Career Development at the Glass Ceiling
Authors: Inman Patricia L.
Published: October 2004

The author investigates the realities of the glass ceiling and proffers strategies
for women whose careers have encountered it.
Women's Career Development in Trade Unions: The Need for a Holistic Approach
Authors: Lundy M. Catherine
Published: October 2004

The literature rarely looks at women's development in trade unions. This
author does, addressing the context and process of women's development
in trade unions.
Diversity Issues in Women's Career Development
Authors: Johnson‐Bailey Juanita , Tisdell Elizabeth J.
Published: October 2004

The authors explore diversity in the context of women's career development
through the use of their own personal stories, literature review, and social
critique.
A Synthesis of Women's Career Development Issues
Authors: Bierema Laura L.
Published: October 2004

This chapter synthesizes the themes, issues, and strategies of this volume.
It assesses the nature of women's career development and recommends
strategies for women, organizations, and adult educators.
“Stress‐alleviating” and “vigilance‐enhancing” actions of Ginkgo biloba extract (EGb 761)
Authors: DeFeudis Francis V. , Drieu Katy
Published: October 2004

This overview is focused on the stress‐alleviating and vigilance‐enhancing properties of Ginkgo biloba extract (EGb 761) that have been observed in animal models and in humans and that appear useful in explaining the therapeutic effects of the extract on non‐cognitive brain functions that may be reflective of mood changes. With regard to its stress‐alleviating activity, in rodents EGb 761 facilitates behavioral adaptation, decreases circulating levels of corticosterone, catecholamines, ACTH, and CRH, suppresses the expression of the mitochondrial peripheral benzodiazepine receptor of the adrenal cortex, increases the anxiolytic activity of diazepam, increases arousal by an action that may involve GABAA receptor antagonism, induces anxiolytic‐like activity, prevents stress‐induced desensitization of hippocampal 5‐HT1A receptors, suppresses the down‐regulation of hippocampal glucocorticoid receptors, and facilitates decision‐making. In humans, EGb 761 has vigilance‐enhancing effects that support its clinical use in treating disorders involving stress‐induced brain dysfunction and those non‐cognitive symptoms of dementia currently classified as “behavioral and psychological symptoms of dementia” (BPSD). Collectively, these findings indicate that EGb 761 is useful for treating symptoms that are now classified as components of BPSD. As drug combinations consisting of EGb 761 and a non‐selective cholinesterase inhibitor, an antidepressant drug, or a neuroleptic could possibly be even more useful in treating BPSD, evaluation of such therapy is recommended. Drug Dev. Res. 62:1–25, 2004. © 2004 Wiley‐Liss, Inc.
KP544 amplifies the effects of nerve growth factor on cell differentiation and is neuroprotective
Authors: Fyfe James A. , Beauchamp Lilia M. , Caggiano Anthony O. , Price Raymond D. , Yamaji Takayuki , Matsuoka Nobuya , Krenitsky Thomas A.
Published: October 2004

The ability of endogenous neurotrophins, including nerve growth factor (NGF), to promote the survival and development of neurons provides convincing evidence for their therapeutic potential, despite significant barriers to their successful clinical use. Many of these barriers might be surmountable, however, by strategies that enhance endogenous neurotrophin signaling. We evaluated a series of substituted pyrimidines for their ability to enhance the effects of NGF. KP544 [2‐amino‐5‐(4‐chlorophenylethynyl)‐4‐(4‐trans‐hydroxycyclohexylamino) pyrimidine] amplified NGF‐induced neurite outgrowth of PC12 cells approximately 2‐fold at 2 µM. KP544 also enhanced choline acetyltransferase activity, a marker of differentiation induced by either NGF or by cyclic AMP, by 3‐ to 8‐fold, with a 2‐fold amplification at 0.12–0.3 µM. This amplification occurred at all concentrations of NGF used including those that maximally stimulated the cells. KP544 did not increase the levels of phosphorylated mitogen‐activated protein kinases (MAPK) above that seen with NGF alone. These studies suggested that KP544 functions within the cell at a site that is downstream from or independent of MAPK signaling. NGF‐induced neurite outgrowth in a human cell line (SH‐SY5Y neuroblastoma cells) was also enhanced with KP544 treatment. Primary embryonic rat cortical cultures were used to extend the observations beyond the studies with the immortalized cell lines. In addition to effects on neurite outgrowth, KP544 protected these cells from glutamate‐induced death. Overall, the data suggest that KP544 can selectively interact in the differentiation pathway downstream of MAPK in a manner that amplifies nerve growth factor and cyclic AMP effects and is also neuroprotective. Drug Dev. Res. 62:49–59, 2004. © 2004 Wiley‐Liss, Inc.
[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium Complexes for Ethene Polymerization
Authors: Axenov Kirill V. , Klinga Martti , Leskelä Markku , Kotov Vasily , Repo Timo
Published: October 2004

A series of new zirconium dichloride complexes bearing bulky cis‐bis(amino)cyclodiphosph(III)azane ligands, [(RN)2(tBuNP)2]ZrCl2 [R = phenyl (7), diphenylmethyl (8), 2,6‐diethylphenyl (9), 2,5‐di‐tert‐butylphenyl (10), and 2,6‐diisopropylphenyl (11)] were prepared in high yields by a two‐step synthetic route. The structure of cis‐[(Ph2CHN)(tBuNP)]2Zr(NMe2)2 (8a), determined by X‐ray analysis, shows that the zirconium atom has a distorted trigonal‐bipyramidal configuration consisting of four equidistant metal−amido nitrogen bonds and an additional coordination between the metal and a nitrogen atom from the cyclodiphosph(III)azane ring. After methylaluminoxane activation, these complexes exhibit moderate to high activities in ethene polymerization and produce high molar mass polyethene (Mw up to 1100 kg/mol). Polymerization experiments reveal that the behavior of bis(amido)cyclodiphosph(III)azane‐based ZrIV catalysts depends on the nature and steric bulkiness of the amido substituents, reaction temperature, MAO/zirconium ratio, as well as monomer pressure. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Macromol. Rapid Commun. 20/2004
Authors: Wiesbrock Frank , Hoogenboom Richard , Schubert Ulrich S.
Published: October 2004

Cover: The field of microwave‐assisted polymerizations is attracting continuously growing interest, additionally inspired by the introduction of single‐mode microwave reactors at the beginning of the millennium. This new class of reaction devices has overcome the safety uncertainties associated with domestic microwave ovens and has paved the way not only to an annually increasing number of publications, but also more sophisticated polymerizations. This review describes prominent examples of the polymerizations hitherto realized with microwave irradiation, including a critical account of the “microwave effects”.

Further details can be found in the Review by F. Wiesbrock, R. Hoogenboom, and U. S. Schubert* on page 1739.
Complete assignment of 1H and 13C NMR spectra of some 4′‐substituted diethyl 1‐methylthio‐ and diethyl 1‐methylsulfonyl‐2‐oxo‐2‐phenylethylphosphonates
Authors: Reis Adriana Karla C. A. , Olivato Paulo R. , Rittner Roberto
Published: October 2004

The complete assignment of 1H and 13C NMR spectra of some 4′‐substituted diethyl 1‐methylthio‐ and diethyl 1‐methylsulfonyl‐2‐oxo‐2‐phenylethylphosphonates bearing as substituents methoxy, fluoro, chloro, bromo and nitro is reported. Copyright © 2004 John Wiley & Sons, Ltd.
Unusual presentation of infantile hemangioendothelioma
Authors: Bay Ali , Öner Ahmet Faik , Etlik Ömer , Koseoglu Burhan , Kaya Ali
Published: October 2004

Infantile hemangioendothelioma is a rare benign hepatic tumor arising from mesenchymal tissue. Most of the cases present with congestive heart failure and asymptomatic abdominal mass were before 6 months of age. We described a patient with projectile vomiting, which is quite an unusual presentation. Following surgical resection, neither recurrence nor symptoms were seen in 2 years of follow‐up. © 2004 Wiley‐Liss, Inc.
Relative solvation and strength of polycyano‐ and polynitromethanes in water: a study with molecular dynamics simulations
Authors: Carrasco Nelson , González‐Nilo Fernando , Rezende Marcos Caroli
Published: October 2004

The long‐known saturation effect in the acidity of polynitromethanes as the number of electron‐withdrawing substituents is increased has no parallel in the polycyanomethane series, leading to a reversal in acidity when the two series are compared. A theoretical study based on molecular dynamics simulations was carried out, with a view to investigating the solvation patterns of all acidic polynitro‐ and polycyanomethanes and their conjugate bases in water. The results provide a qualitative interpretation of the causes of the saturation effect and the observed reversal in acidity. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and characterization of soluble polyimides containing trifluoromethyl groups in their backbone
Authors: Kim Sang‐Uk , Lee Choonkeun , Sundar Saimani , Jang Wonbong , Yang Seung‐Jin , Han Haksoo
Published: October 2004

A series of polyimides were synthesized from 2,2‐Bis(3,4‐dicarboxyphenyl)hexafluoropropane, 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane, and 4,4′‐oxydianiline by chemical imidization. The effects of the diamine ratios on the properties of the films were evaluated through the study of their thermal, electrical, and morphological properties. All the polymers exhibited better solubility in most of the organic solvents and hence were easily processable. Polyimides with more 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane exhibited better solubility and a low refractive index, which is highly desired for microelectronic applications. The dielectric constant and birefringence were strongly dependent on the fluorine content. With an increase in the fluorine substitution, both the dielectric constant and birefringence decreased. All the polymers exhibited high thermal stability (>400 °C). The absence of crystalline melting in differential scanning calorimetry and broad wide‐angle X‐ray diffraction patterns revealed the amorphous nature of the polymers, which was due to the presence of bulky CF3 groups and hinged ether linkages of the diamine component. The residual stress values decreased with an increase in the 4,4′‐oxydianiline content, and the results were in agreement with the dielectric constant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4303–4312, 2004
Physical properties of glycosaminoglycan hydrogels
Authors: Kirker Kelly R. , Prestwich Glenn D.
Published: October 2004

The chemical composition of glycosaminoglycan (GAG) hydrogels was found to have a profound effect on the physical properties of gels. Hyaluronan (HA) and chondroitin sulfate (CS) were each modified with adipic dihydrazide (ADH) with carbodiimide chemistry. The resulting polymer was crosslinked with various concentrations of poly(ethylene glycol) dialdehyde (PEG‐diald) to produce a series of hydrogels. The physical properties of these GAG hydrogels varied in a concentration‐dependent fashion. Maximal crosslinking was observed at a theoretical crosslinking of 50% for the HA‐ADH‐PEG‐diald hydrogels and 75% for the CS‐ADH‐PEG‐diald hydrogels. Adding PEG‐diald beyond the optimum for crosslinking prolonged the in vitro enzymatic degradation time of the hydrogels. The swelling of the crosslinked GAG hydrogels was correlated with the amount of PEG‐diald used rather than with the crosslinking density. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4344–4356, 2004
Recombination mechanisms in InAs/InP quantum dash lasers studied using high hydrostatic pressure
Authors: Marko I. P. , Sweeney S. J. , Adams A. R. , Jin S. R. , Murdin B. N. , Schwertberger R. , Somers A. , Reithmaier J. P. , Forchel A.
Published: October 2004

Two types of InAs quantum dash lasers grown on InP substrates with lasing wavelengths of 1.52 μm and 1.76 μm were studied. In both laser types the threshold current density, Jth, was about 2 kA/cm2 at room temperature and had a similar temperature sensitivity (T0 was about 80 K in the range T = 120–250 K, and T0 = 60–70 K from 250 to 300 K). Measurements of the spontaneous emission from a window milled in a substrate contact showed that Jrad, the radiative part of Jth, is almost temperature independent and less than 5% of Jth at T = 295 K, demonstrating that the relatively large value of Jth and its temperature sensitivity must be due to non‐radiative recombination processes. However, despite the similar temperature behaviour of the lasers, their pressure dependences were very different showing that in the 1.52 μm lasers, pressure independent defect related recombination outside the dashes due to thermal carrier spill‐over or thermal leakage dominates, while in the 1.76 μm quantum dash laser 60% of Jth is due to Auger recombination. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dibismuthide Bi22‐: Synthesis and Crystal Structure of Bis[(1, 4, 7, 10, 13, 16‐Hexaoxacyclooctadecan)caesium]dibismuthide‐Ammonia (1/7) [Cs(18‐crown‐6)]2Bi2 · 7 NH3
Authors: Hanauer Tobias , Korber Nikolaus
Published: October 2004

The ammoniate [Cs(18‐crown‐6)]2Bi2 · 7 NH3 was prepared by solvating Cs5Bi4 together with an excess of 18‐crown‐6 in liquid ammonia. Single crystals were isolated and characterized by low temperature X‐ray structure analysis. [Cs(18‐crown‐6)]2Bi2 · 7 NH3 (C24H69Bi2Cs2N7O12) crystallizes in the space group P21/c with a = 10.1477(7) Å, b = 31.257(2) Å, c = 14.61(1) Å and β = 90.428(9)°. The compound contains a Bi22‐ anion with a short Bi‐Bi distance of 2.8635(4) Å. The anion coordinates side‐on to the central caesium cations of two [Cs(18‐crown‐6)]+ complexes, resulting in a neutral, molecular [Cs(18‐crown‐6)]2Bi2 complex.
Zur Kristallchemie der Oxoargentate und Silberoxometallate
Authors: Müller‐Buschbaum Hanskarl
Published: October 2004

Ag+ und Ag3+ zeigen in Festkörpern die unterschiedlichsten Koordinationspolyeder. In Analogie zu Oxocupraten, Oxoauraten, Oxoplatinaten usw. ist es üblich von Oxoargentaten zu sprechen. In den Oxoargentaten(I) und Oxoargentaten(III) sollte Ag+ hantelförmig bzw. Ag3+ quadratisch planar von O2‐ umgeben sein. Es wird gezeigt, daß diese Regel häufig durchbrochen wird. Eine Parallele zu den Oxocupraten besteht nur bedingt, da Silber beinahe unabhängig von seiner Valenz ein breites Spektrum an Koordinationssphären seitens Sauerstoff toleriert. Das Review zeigt O‐Ag‐O‐Polygone, deren Bindungswinkel von 180° bis 86° reichen. Bemerkenswert sind Verbindungen mit zwei verschiedenen hantelförmig koordinierten Metallatomen O‐M‐O (M = Ag und Hg). Erstaunlich sind die häufig beobachteten triangularen AgO3‐Polygone, die in vielen Fällen aber nicht von Silberatomen zentriert werden. Zwischen Oxoargentaten (Ag ist Bestandteil des anionischen Teils der Kristallstruktur) und Silber‐Oxometallaten (Ag ist Kation wie in klassischen Salzen) gibt es keine scharfe Trennung. In den Silber‐Oxometallaten zeigt Silber von den Alkalimetallen abweichende vielfältige Koordinationspolyeder, mit Koordinationszahlen C.N. = 3 bis C.N. = 12. Oxidische Verbindungen des Silbers mit Elementen mit freien Elektronenpaaren (Pb, Bi usw.) zeichnen sich durch einseitig offene Polyeder aus. Das freie Elektronenpaar (‘lone pair’) ist ergänzender Koordinationspartner und bildet gemeinsam mit Sauerstoff um diese Elemente geschlossene Polyeder. Ein freies Elektronenpaar kann aber auch die hantelförmige O‐Ag‐O‐Koordination zu einem quadratisch planaren [AgO2(lone pair)2]‐Polygon ergänzen.

Von Martin Jansen, der die Oxochemie des Silbers wie kein zweiter Chemiker mit einer Fülle an Verbindungen und Synthesewegen bereichert hat, wird seit Jahren Silber die Fähigkeit zu d10‐d10‐Wechselwirkungen zugeschrieben. Mit steigendem Gehalt an Silber häufen sich die erstaunlich kurzen Ag‐Ag‐Abstände, um schließlich punktuell clusterähnliche Strukturen aufzubauen. In einigen Verbindungen (Ag2CuO3, Ag4Bi2O5, LiAg3O2, Ag5BiO4) sind eindimensionale Atomreihen [‐Ag‐Ag‐] mit Abständen dAg‐Ag < metallischer Abstand zu beobachten. Anisotrope elektrische Effekte sind zu erwarten. Bemerkenswert ist auch, daß sich die Bauprinzipen der Oxide des Silbers (Ag2O, AgO, Ag2O2, Ag2O3, Ag6O2) nur punktuell in Verbindungen des Silbers widerspiegeln.

Ein häufig auftretendes Problem ist die Zuordnung von Sauerstoff an das zentrale Silberatom. Hierzu werden im Spektrum der Ag‐O‐Abstände breite Lücken oder eingeschobene Abstände zu anderen Metallatomen und nicht zuletzt Berechnungen effektiver Koordinationszahlen berücksichtigt. Dennoch ist eine zuverlässige Definition eines Ag/O‐Polyeders in vielen Fällen nicht möglich.
Low‐Temperature Oxidation of Ytterbium with Pyrrole in Liquid Ammonia. Formation of the First Unsubstituted Pyrrolates of a Rare Earth Element
Authors: Quitmann Catharina C. , Müller‐Buschbaum Klaus
Published: October 2004

The compounds [Yb2(Pyr)2(NH3)8][Yb(Pyr)5(NH3)] (1), [Yb(Pyr)3(PyrH)2(NH3)2] (2) and [Yb5(Pyr)12(NH3)4(NH2)]·2PyrH (3), (Pyr = pyrrolate anion, C4H4N‐; PyrH = pyrrole, C4H4NH) were obtained by the low‐temperature oxidation of ytterbium with the amine pyrrole in liquid ammonia. Single crystals of all three phases are formed next to each other, their yield depending on the temperature gradient of a subsequent thermal process in sealed glass ampoules. 1, 2 and 3 are the first unsubstituted pyrrolates of a rare earth element and display the decisive role of ammonia and the reaction conditions. The low temperature oxidation avoids polymerisation of the amine pyrrole. The crystal structures of 1, 2 and 3 exhibit units of different extension, different coordination spheres and oxidation states of ytterbium. The products were investigated by X‐ray single crystal diffraction, Mid IR and Far IR spectroscopy.
Structural and Magnetic Properties of the Double Perovskite LaCaMnNbO6
Authors: Bos Jan‐Willem G. , Attfield J. Paul
Published: October 2004

The structural and magnetic properties of the double perovskite LaCaMnNbO6 have been investigated using neutron powder diffraction and SQUID magnetometry. LaCaMnNbO6 has a monoclinic P21/n superstructure (a = 5.5929(1) Å, b = 5.7406(1) Å, c = 7.9824(1) Å and β = 89.897(1)°) with an almost fully ordered rocksalt arrangement of Mn and Nb over the perovskite B‐sites. Magnetisation measurements reveal a sharp antiferromagnetic transition at TN = 9 K. The low temperature antiferromagnetic ordering is described by a magnetic propagation vector of (0 1/2 1/2). Two collinear solutions are found for the magnetic structure.
Ternary Indides RE10Rh9±xIn20 (RE = Y, Tb‐Tm, Lu) and YbRhIn2 ‐ Syntheses and Crystal Chemical Peculiarities
Authors: Lukachuk Mar'yana , Rodewald Ute Ch. , Zaremba Vasy'l I. , Hoffmann Rolf‐Dieter , Pöttgen Rainer
Published: October 2004

New ternary indides RE10Rh9±xIn20 (RE = Y, Tb‐Tm, Lu) were synthesized from the elements by arc‐melting under argon and subsequent annealing in alumina or tantalum crucibles. YbRhIn2 was prepared in a sealed tantalum ampoule in an induction furnace. X‐ray powder and single crystal data for RE10Rh9+xIn20 revealed isotypy with the tetragonal Ho10Ni9In20 type structure, space group P4/nmm. A crystal of Tm10Rh9In20 shows the ideal composition: a = 1335.42(7), c = 921.26(6) pm, wR2 = 0.0524, 1460 F2 values and 62 variable parameters, while the RE10Rh9In20 indides with the lighter rare earth metals contain an additional rhodium site leading to a homogeneity range according to RE10Rh9±xIn20. This was manifested from X‐ray single crystal data for Y10Rh9.19(1)In20, Tb10Rh9.40(1)In20, Dy10Rh9.07(1)In20, Dy10Rh9.52(1)In20, Ho10Rh9.41(1)In20, and Er10Rh9.27(1)In20. On the other hand, defects were found for the Rh2 site of Lu10Rh8.87(1)In20. The crystal chemistry of the RE10Rh9In20 indides and the structurally related REPdIn2 indides with tetragonal HfNiGa2 structure is discussed. YbRhIn2 was synthesized in a sealed tantalum ampoule. It adopts the orthorhombic MgCuAl2 type structure: Cmcm, a = 418.24(6), b = 1024.0(2), c = 807.5(1) pm, wR2 = 0.0477, 292 F2 values and 16 variable parameters. The rhodium atoms fill distorted triangles of an orthorhombically distorted YbIn2 substructure.
Synthese und Kristallstrukturen von Ln(ClF2CCOO)3(H2O)3 (Ln = Gd, Dy, Ho, Er) und magnetisches Verhalten von Gd(ClF2CCOO)3(H2O)3
Authors: Rohde Alexander , Urland Werner
Published: October 2004

Einkristalle von Ln(ClF2CCOO)3(H2O)3 (Ln = Gd, Dy, Ho, Er) wurden durch Reaktion von Ln2O3 mit einer wässrigen Lösung von ClF2CCOOH erhalten. Die Verbindungen sind isotyp miteinander und kristallisieren monoklin in der Raumgruppe P 21/c (Nr.: 14; Z = 4) mit den Gitterkonstanten, z.B. Gd(ClF2CCOO)3(H2O)3: a = 927, 9(3) pm, b = 1923, 8(4) pm, c = 1037, 2(4) pm, β = 114, 21(4)°. In den Kristallstrukturen sind die Lanthanidionen durch Carboxylatgruppen zu dimeren Einheiten verbrückt und von Sauerstoffatomen achtfach koordiniert. Das magnetische Verhalten von Gd(ClF2CCOO)3(H2O)3 wurde im Temperaturbereich von 1, 73 bis 300 K untersucht. Die magnetischen Daten weisen auf eine schwache antiferromagnetische Wechselwirkung in der dimeren Einheit hin.
Synthese und Struktur der Silber‐Komplexe [PPh4]2[Ag4Cl4(ClC6H4N3C6H4Cl)2], [Et4N][Ag2(tolyl‐N5‐tolyl)3]·2THF und [(n‐Bu)4N]3[Ag3I6] und über die Reaktion der Komplexe [Ag(ClC6H4N3C6H4Cl)]2 und [Ag(tolyl‐N5‐tolyl)]2 mit Iod
Authors: Barboza da Silva Carlos F. , Schwarz Simon , Galceran Mestres Montserrat , Strähle Joachim
Published: October 2004

Der Silber‐Triazenido‐Komplex, [PPh4]2[Ag4Cl4(ClC6H4N3C6H4Cl)2] (1), entsteht bei der Umsetzung von Silber‐bis(p‐chlorphenyl)triazenid mit [PPh4]Cl in THF. Er kristallisiert monoklin in der Raumgruppe C2/c mit den Gitterkonstanten a = 2816, 9(3); b = 946, 67(7); c = 2552, 4(3) pm; β = 90, 22(1)° und Z = 4. Im zentrosymmetrischen Anion von 1 bilden die vier Ag‐Atome zusammen mit zwei Cl‐Atomen ein verzerrtes Oktaeder. Die äquatorial angeordneten Ag‐Atome werden von weiteren zwei Cl‐Atomen und zwei Triazenidoliganden überbrückt. Die Reaktion von [Et4N]Br mit Silber‐bis(p‐tolyl)pentaazadienid in THF ergibt den Komplex [Et4N][Ag2(tolyl‐N5‐tolyl)3] (2a). Die analoge Verbindung, [(n‐Bu)4N][Ag2(tolyl‐N5‐tolyl)3] (2b) wird auch bei der Umsetzung von [(n‐Bu)4N]I mit Silber‐bis(p‐tolyl)pentaazadienid in THF bei Verwendung eines dreifachen Überschusses des Pentaazadienids erhalten. Wenn gleiche Anteile an [(n‐Bu)4N]I und Silberpentaazadienid eingesetzt werden, entsteht jedoch der Komplex [(n‐Bu)4N]3[Ag3I6] (3). Von 2a werden trikline Kristalle der Zusammensetzung 2a·2THF mit der Raumgruppe P{\bar 1} und a = 1303, 6(3); b = 1471, 3(4); c = 1811, 6(2) pm; α = 98, 51(2)°; β = 93, 33(2)°; γ = 112, 50(2)° und Z = 2 erhalten. Im Anion der Verbindungen 2a und 2b verbrücken drei Pentaazadienidoliganden mit ihren Atomen N1 und N3 zwei Ag‐Atome. Ein Ag‐Atom wird zusätzlich von den Atomen N5 zweier Liganden koordiniert, so daß sich für die Ag‐Atome eine unterschiedliche Koordination in Form einer trigonal‐planaren bzw. einer verzerrt quadratisch‐pyramidalen Anordnung ergibt. 3 bildet orthorhombische Kristalle mit der Raumgruppe Pca21 und a = 1675, 0(6); b = 1698, 8(2); c = 2612, 8(5) pm und Z = 4. Das Anion [Ag3I6]3‐ wird von drei über gemeinsame Flächen verknüpften AgI4‐Tetraedern gebildet. Bei der Umsetzung der Silbertriazenido‐ und ‐pentaazadienido‐Komplexe [Ag(ClC6H4N3C6H4Cl)]2 und [Ag(tolyl‐N5‐tolyl)]2 mit I2 werden diese zu den Azoverbindungen, [ClC6H4N=NC6H4Cl] (4) und [tolyl‐N=N‐tolyl] (5) sowie N2 oxidiert.
Pr3Se2SiN3: Das erste Nitrido‐cyclo‐Trisilicat mit diskreten [Si3N9]15‐‐Anionen gemäß Pr9Se6[Si3N9]
Authors: Lissner Falk , Schleid Thomas
Published: October 2004

Bei Versuchen zur Darstellung von Nitridseleniden des Praseodyms erhält man durch Oxidation von Praseodymmetall mit Selen und Natriumazid sowie Beimengungen von Praseodymtrichlorid und Natriumchlorid als Flußmittel in evakuierten Kieselglasampullen bei 900 °C innerhalb von sieben Tagen unter Mitwirkung des Behältermaterials (SiO2) dunkelgelbe Stäbchen eines anionisch derivatisierten Nitrido‐cyclo‐Trisilicats des dreiwertigen Praseodyms der Zusammensetzung Pr3Se2SiN3, besser Pr9Se6[Si3N9] (a = 1892, 41(9), c = 1037, 25(6) pm; trigonal, $R{\bar 3}$, Z = 6), als Nebenprodukt. Die Kristallstruktur enthält drei kristallographisch unterschiedliche Pr3+‐Kationen, von denen zwei je siebenfach und das dritte achtfach von zwei verschiedenen Se2‐‐ bzw. drei unabhängigen N3‐‐Anionen koordiniert werden. Als strukturelles Hauptmerkmal treten jedoch diskrete Nitrido‐cyclo‐Trisilicat‐Einheiten [Si3N9]15‐ in den Vordergrund, deren sechsringförmiger Aufbau durch Eckenverknüpfung dreier [SiN4]8‐‐Tetraeder (d(Si‐N) = 172‐179 pm; ∢(N‐Si‐N) = 101‐116°; ∢(Si‐N‐Si) = 117°) realisiert ist.
Monomere und polymere Komplexe mit Ni‐CN‐Ni‐ und Pt‐CN‐Ni‐Verknüpfungen
Authors: Flay Marie‐Louise , Vahrenkamp Heinrich
Published: October 2004

Die Anbindung der Baueinheit Ni(Me6tren)2+ an Ni(CN)42‐ und Pt(CN)42‐ liefert die Dreikernkomplexe [(Me6tren)Ni‐NC‐M(CN)2‐CN‐Ni(Me6tren)](ClO4)2 mit M = Ni und Pt. Der Einsatz der sterisch weniger anspruchsvollen Baueinheit Ni(tren)2+ führt zu den Koordinationspolymeren [M(μ‐CN)4{Ni(tren)}2](ClO4)2 mit M = Ni und Pt. In diesen liegen dreisträngige Bänder mit zentralen M(CN)4‐ und peripheren (tren)Ni(NC)2‐Verknüpfungseinheiten vor.
Über die Antimonidoxide La9Sb5O5 und Ce9Sb5O5 sowie die binären Phasen La2Sb und Ce2Sb
Authors: Nuss Jürgen , von Schnering Hans Georg , Grin Yuri
Published: October 2004

Die neuen Antimonidoxide La9Sb5O5 und Ce9Sb5O5 wurden aus Sb2O3, Antimon und Seltenerdmetall (La, Ce) in geschlossenen Tantalampullen bei 1770 K dargestellt. Die luft‐ und feuchtigkeitsempfindlichen Seltenerdmetallverbindungen bilden schwarze, im Auflicht metallisch glänzende, würfelförmige Kristalle. Sie kristallisieren in einem neuen Strukturtyp (Pearson‐Symbol tP38; Raumgruppe P4/n, Nr. 85; La9Sb5O5: a = 1041.5, c = 934.0 pm; Ce9Sb5O5: a = 1029.7, c = 922.8 pm; Z = 2), eine Defektvariante der Sc2Sb‐Struktur, aufgefüllt mit Sauerstoffatomen: Sc10Sb5□5 ≙ La9□Sb5O5 bzw. Ce9□Sb5O5. La9Sb5O5 zeigt metallische Leitfähigkeit mit ρ = 6.7 mΩ·cm bei 293 K. Des Weiteren wurden die binären Phasen La2Sb und Ce2Sb nochmals untersucht. Es zeigte sich, dass diese Phasen auch in Gegenwart von Sauerstoff entstehen.
(Sr3N)E and (Ba3N)E (E = Sb, Bi): Synthesis, Crystal Structures, and Physical Properties
Authors: Gäbler Frank , Kirchner Martin , Schnelle Walter , Schwarz Ulrich , Schmitt Miriam , Rosner Helge , Niewa Rainer
Published: October 2004

Single phase powders of (Sr3N)Sb, (Sr3N)Bi ($Pm{\bar 3}m$, No. 221, Z = 1, Sb: a = 517.25(2) pm, V = 138.390(8) · 106 pm3, Bi: a = 520.691(8) pm, V = 141.170(4) · 106 pm3), (Ba3N)Sb, and (Ba3N)Bi (P63/mmc, No. 194, Z = 2, Sb: a = 753.33(3) pm, c = 664.45(3) pm, V = 326.56(2) · 106 pm3, Bi: a = 761.28(4) pm, c = 668.05(3) pm, V = 335.30(2) · 106 pm3) were obtained from reactions of melt beads of the respective elements with bulk compositions of A3E (A = Sr, Ba; E = Sb, Bi) in nitrogen atmosphere of ambient pressure at T = 1070 K (Sr) and T = 1120 K (Ba). The compositions were derived from chemical analyses and supported by Rietveld refinements based on powder X‐ray diffraction patterns. The Sr containing compounds crystallize in the cubic anti‐perovskite type arrangement, the Ba containing compounds in the hexagonal anti‐BaNiO3 structure type. Magnetic susceptibility and electrical resistivity data indicate that the compounds are diamagnetic semiconductors. The optical band gaps of (Sr3N)Sb and (Sr3N)Bi were determined by diffuse reflectivity to 1.15 eV and 0.89 eV, respectively. The experimental results are in agreement with electronic structure calculations. Chemical bonding is characterized in a simplified picture as ionic with significant orbital mixing.
Neue Arsenide mit As‐‐Ketten und ‐Ringen: BaAs2 und AIBa2As5 (AI = K, Rb)
Authors: Emmerling Franziska , Petri Denis , Röhr Caroline
Published: October 2004

Die drei Titelverbindungen, die aus den Elementen synthetisiert wurden, sind Vertreter klassischer Zintlphasen mit Chalkogen‐isosteren As‐‐Anionen. In BaAs2 (monoklin, Raumgruppe Pc, a = 655.0(2), b = 1253.2(4), c = 803.8(3) pm, β = 127.75(2)°, R1=0.0639) liegen Kettenanionen in zwei unterschiedlichen Konformationen vor, die sich wiederum von den As‐Ketten in der Struktur von KBa2As5 (orthorhombisch, Raumgruppe Cmc21, a = 787.2(3), b = 1052.9(4), c = 1177.0(4) pm, R1 = 0.0319) unterscheiden. Dagegen enthält RbBa2As5 (trigonal, Raumgruppe P3121, a = 778.4(2), c = 1430.9(4) pm, R1 = 0.0654) gewellte Fünfringe As55‐. Die für die Bildung von Ringen bzw. unterschiedlichen Ketten relevanten Parameter werden auf der Basis von Geometrieanalysen und Berechnungen der elektronischen Strukturen diskutiert.
Ba8Ge43 revisited: a 2a′×2a′×2a′ Superstructure of the Clathrate‐I Type with Full Vacancy Ordering
Authors: Carrillo‐Cabrera Wilder , Budnyk Serhij , Prots Yurii , Grin Yuri
Published: October 2004

The reinvestigation of the crystal structure of Ba8Ge43□3 (space group $Ia{\bar 3}d$, no. 230; a = 21.3123(5) Å; Z = 8; Pearson symbol cI408) shows a full ordering of the vacancies (□) in the germanium framework. This ordered crystal structure can be considered as a derivative of an ideal “Ba8Ge46” clathrate‐I type structure ($Pm{\bar 3}n$, a′ = a/2) in which three Ge vacancies (per formula unit) are allowed to order in a cubic superstructure with a doubled unit cell parameter (□ at the 24c site, space group $Ia{\bar 3}d$). In the resulting Ge framework, each vacancy □ is surrounded by four three‐bonded (3b)Ge‐ species. The ordering in crystals of as‐cast samples (cooled in argon atmosphere, non‐annealed) is partially disrupted. For the “as‐cast” crystals, a short‐range model is proposed based on the partial distribution of Ge on the 24c and 24d sites. From the electron balance, Ba8Ge43 can be considered as a metallic Zintl phase with four excess electrons per formula unit. The Ba8Ge43 phase is stable in the temperature range 770 ‐ 810 °C and exists in equilibrium with Ba6Ge25 and Ge. By decomposition of undercooled (metastable) Ba8Ge43, a new metastable binary BaGe˜5 phase is formed.
Ca[Cu(C2H)3] · 6 NH3 und Rb2[Cu(C2H)3] · NH3: Zwei Ethinylocuprate mit einem trigonal planaren [Cu(C2H)3]2‐‐Anion
Authors: Cremer Ulrich , Disch Sabrina , Ruschewitz Uwe
Published: October 2004

Durch Umsetzungen in flüssigem Ammoniak wurden Ca[Cu(C2H)3] · 6 NH3 und Rb2[Cu(C2H)3] · NH3 in polykristalliner Form erhalten. Die Verbindungen verlieren leicht Ammoniak und sind bei Zimmertemperatur nur in einer NH3Atmosphäre stabil. Strukturuntersuchungen auf der Grundlage von Röntgenpulverdaten ergaben hexagonale Elementarzellen (Ca[Cu(C2H)3] · 6 NH3: P63mc, Z = 2, a = 986, 39(1) pm, c = 926, 47(1) pm; Rb2[Cu(C2H)3] · NH3: P63/m, Z = 6, a = 1096, 46(2) pm, c = 1600, 15(3) pm). Nahezu planare trigonale [Cu(C2H)3]2‐‐Baugruppen sind das charakteristische Strukturmerkmal, die im Falle der Calciumverbindung von [Ca(NH3)6]2+‐Oktaedern separiert werden. Das Motiv der Anordnung der komplexen Kat‐ und Anionen ist analog zum hexagonalen BN. Die Kristallstruktur vonRb2[Cu(C2H)3] · NH3 ist durch Säulen flächenverknüpfter Rb6‐Polyeder entlang [001] charakterisiert, die entweder mit [Cu(C2H)3]2‐‐Anionen oder drei NH3‐Molekülen gefüllt sind. Senkrecht dazu sind die Stränge über gemeinsame Kanten verknüpft, so dass sich das Motiv eines dreidimensionalen Netzwerks ergibt. Eine analoge Caesiumverbindung konnte ebenfalls dargestellt werden, wie Raman‐Spektren belegen. Allerdings ist diese Verbindung so empfindlich, dass eine vollständige strukturelle Charakterisierung nicht möglich war.