Rationalization of the crystal structure of eudidymite Na2Be2[Si[4] 6O15]·H2O in light of the extended Zintl–Klemm concept

2020 ◽  
Vol 76 (1) ◽  
pp. 41-46
Author(s):  
Angel Vegas ◽  
H. Donald Brooke Jenkins
Keyword(s):  
Crystal Structure ◽  
Ionic Strength ◽  
Crystal Structures ◽  
Complex Network ◽  
The Other ◽  
Structure Generation ◽  
New Approach ◽  
New Development ◽  
Valence Electrons ◽  
The One

The structure of eudidymite is described in light of the extended Zintl–Klemm concept which considers that Na and Be atoms transfer their six valence electrons to the six Si atoms, converting them into Ψ-P which forms a skeleton characteristic of pentels (Group 15 elements) and is similar to that described in the compound (NH4)2Ge[6][Ge[4] 6O15] when analysed in the same manner. The Si[4] skeleton is formed of bilayers that are connected through Be2O6 groups which are in fact fragments of the β-BeO structure which bridge the two contiguous Si-bilayers by sharing O atoms. In this context, the Be atoms play a dual role, i.e. on the one hand converting the Si atoms into Ψ-P, on the other hand replicating fragments of its own β-BeO structure. The Be atoms partially reproduce their own structure despite it being enclosed in a more complex network such as in Na2Be2[Si[4] 6O15]·H2O. Calculations of the ionic strength I considering Si as Ψ-P is energetically more favourable than when I is calculated on the basis of tetravalent Si in the silicate, justifying this new approach of developing the theory of pseudo-structure generation. This approach offers a major new development in the study of crystal structures.

Structural Studies on N-(2,4,6-Trimethylphenyl)-methyl/ chloro-acetamides, 2,4,6-(CH3)3C6H2NH-CO-CH3–yXy (X = CH3 or Cl and y = 0, 1, 2)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 588-594 ◽  
Author(s):  
Basavalinganadoddy Thimme Gowda ◽  
Jozef Kožíšek ◽  
Hartmut Fuess
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structural Data ◽  
The Other ◽  
Side Chain ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
Lattice Constants ◽  
Peptide Linkage ◽  
The Mean

TMPAThe effect of substitutions in the ring and in the side chain on the crystal structure of N- (2,4,6-trimethylphenyl)-methyl/chloro-acetamides of the configuration 2,4,6-(CH3)3C6H2NH-COCH3− yXy (X = CH3 or Cl and y = 0,1, 2) has been studied by determining the crystal structures of N-(2,4,6-trimethylphenyl)-acetamide, 2,4,6-(CH3)3C6H2NH-CO-CH3 (); N-(2,4,6- trimethylphenyl)-2-methylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2-CH3 (TMPMA); N-(2,4,6- trimethylphenyl)-2,2-dimethylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH(CH3)2 (TMPDMA) and N-(2,4,6-trimethylphenyl)-2,2-dichloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CHCl2 (TMPDCA). The crystallographic system, space group, formula units and lattice constants in Å are: TMPA: monoclinic, Pn, Z = 2, a = 8.142(3), b = 8.469(3), c = 8.223(3), β = 113.61(2)◦; TMPMA: monoclinic, P21/n, Z = 8, a = 9.103(1), b = 15.812(2), c = 16.4787(19), α = 89.974(10)◦, β = 96.951(10)◦, γ =89.967(10)◦; TMPDMA: monoclinic, P21/c, Z = 4, a =4.757(1), b= 24.644(4), c =10.785(2), β = 99.647(17)◦; TMPDCA: triclinic, P¯1, Z = 2, a = 4.652(1), b = 11.006(1), c = 12.369(1), α = 82.521(7)◦, β = 83.09(1)◦, γ = 79.84(1)◦. The results are analyzed along with the structural data of N-phenylacetamide, C6H5NH-CO-CH3; N-(2,4,6-trimethylphenyl)-2-chloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)-acetamide, 2,4,6-Cl3C6H2NH-COCH3; N-(2,4,6-trichlorophenyl)-2-chloroacetamide, 2,4,6-Cl3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)- 2,2-dichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CHCl2 and N-(2,4,6-trichlorophenyl)- 2,2,2-trichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CCl3. TMPA, TMPMA and TMPDCA have one molecule each in their asymmetric units, while TMPDMA has two molecules in its asymmetric unit. Changes in the mean ring distances are smaller on substitution as the effect has to be transmitted through the peptide linkage. The comparison of the other bond parameters reveal that there are significant changes in them on substitution.

Supercooling of liquids

1952 ◽  
Vol 215 (1120) ◽  
pp. 43-46 ◽  
Keyword(s):  
Crystal Structures ◽  
Recent Change ◽  
The Other ◽  
Theoretical Interpretation ◽  
Experimental Fact ◽  
X Ray Diffraction ◽  
Diffraction Patterns ◽  
The One ◽  
The Right ◽  
Complex Crystal

I shall concentrate upon reviewing the important recent change in our appreciation of the facts of supercooling which has been brought about particularly by the work of Turnbull at the General Electric Research Laboratory in Schenectady. I suppose that most of us, talking about supercooling a couple of years ago, would have divided substances into two classes, one with simple crystal structures like gold, and all the other ‘good’ metals on the one hand, and those with complex crystal structures, such as glycerol and the silicates on the other; saying that whereas the latter class can be very much supercooled, and will form glasses, the former class can only be supercooled a very few degrees. Then we would have added that there are some ‘ bad ’ metals, with moderately complex crystal structures, such as antimony or bismuth, which can be supercooled some tens of degrees, forming an intermediate class. I think we would then have added that this is quite comprehensible. In particular, that the X-ray diffraction patterns of the monatomic liquids show us that most of the atoms have the right numbers of nearest neighbours in a first co-ordination shell, all ready in place to start the growth of a crystal; which readily explains why these substances cannot be supercooled very much—a nice simple experimental fact, with a straightforward theoretical interpretation—and both are wrong.

“Network Process Re-Engineering” in a Home Textile Network

2011 ◽  
pp. 212-234
Author(s):  
Enrico Baraldi ◽  
Giancarlo Nadin
Keyword(s):  
Complex Network ◽  
The Other ◽  
Coercive Power ◽  
Business Network ◽  
Network Process ◽  
Change Projects ◽  
The One ◽  
Complex Coordination

This chapter relies on a case study featuring the business network around Stella, an Italian home textile manufacturer, to illustrate the challenging issue of engaging other firms into complex “Network Process Re-engineering” (NPR) projects. While the strict technological dimension of selecting, developing, and implementing ICT solutions is certainly very important and poses several challenges to this type of projects, this chapter focuses on other types of challenges, namely those pertaining to the nature and quality of relationships between the actors taking part in a NPR project. We stress the importance of the connection between the specific inter-organizational activities that need to be redesigned and coordinated in better ways, on the one hand, and the bonds existing among the actors, on the other hand. We suggest that very advanced and complex coordination tasks, entailing sensitive communication patterns, can be tackled only if supported by strong, integrative relationships characterized by high trust and commitment between the involved parties. We conclude by discussing how the pivotal firms or the “strategic centers” of a network can support and facilitate complex change projects like NPR by carefully combining different strategies, whereby they both exert coercive power and make concessions to their counterparts in the network.

Organoamido- and Aryloxo-Lanthanoids. XI. Syntheses and Crystal Structures of Nd(Odpp)3, Nd(Odpp)3(thf) and [Nd(Odpp)3(thf)2].2(thf) (Odpp-=2,6-Diphenylphenolate): Variations in Intramolecular π-Ph-Nd Interactions

1995 ◽  
Vol 48 (4) ◽  
pp. 741 ◽  
Author(s):  
GB Deacon ◽  
TC Feng ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Phenyl Group ◽  
Triangular Array ◽  
The Other ◽  
X Ray ◽  
Trigonal Bipyramidal ◽  
Distorted Trigonal Bipyramidal

The X-ray crystal structure of Nd (Odpp)3 ( Odpp- = 2,6-diphenylphenolate), obtained by sublimation of Nd ( Odpp )3( thf )2 ( thf = tetrahydrofuran ) [triclinic, Pī , a 15.835(5), b 13.499(10), c 10.955(11) Ǻ, α 116.25(7), β 92.87(7), γ 101.66(6)°, V 2031 Ǻ3, Z2, No 5726 'observed' data (I > 3σ(I)) refined to conventional R 0.047 shows a near triangular array of oxygens surrounding neodymium { Nd -O} 2.169 Ǻ, ∑ O- Nd -O 353.2° with additional, intramolecular Nd-η6-Ph chelate interactions { Nd -C} 3.046 Ǻ and Nd-η1-Ph ( Nd -C 2.964(7)Ǻ). There is a pseudotrigonal bipyramidal arrangement of the oxygens, the centroid of the η6-Ph, and the η1-carbon. The complex Nd ( Odpp )3( thf ), obtained by crystallization of Nd ( Odpp )3( thf )2 from toluene (monoclinic, P21/c, a 12.213(4), b 21.447(4), c 17.744Ǻ, β 104.25(2)°, V 4505 Ǻ3, Z 4, R 0.042 for No 8014) also has pseudotrigonal bipyramidal stereochemistry, with a triangular equatorial array of aryl oxide oxygens { Nd -O} 2.193 Ǻ; ∑ O- Nd -O 358.7°, an apical thf oxygen (Nd -O 2.446(3)Ǻ), and an apical intramolecular chelating phenyl group. As the last has three Nd -C contacts (3.094(5), 3.144(5), 3.010(5)Ǻ) significantly shorter than the other three (3.300(5), 3.427(5), 3.377(5)Ǻ), an η3-Ph-Nd interaction seems likely. For [ Nd ( Odpp )3( thf )2].2( thf ), obtained by crystallization from tetrahydrofuran without drying of the crystals, the X-ray structure (monoclinic, P21, a 10.230(2), b 21.919(5), c 13.411(4) Ǻ, β 101.15(2)°, V 2950 A3, Z2, R 0.058 for No 3237) reveals a distorted trigonal bipyramidal arrangement of three aryl oxide oxygens (two equatorial 2.208(9), 2.16(1) Ǻ; one axial 2.203(9) Ǻ) and two thf oxygens (one equatorial 2.44(1) Ǻ; one axial (significantly distant) 2.62(1) Ǻ). The X-ray structure of [La( Odpp )3( thf )2].2( thf ) shows it to be isostructural with the neodymium analogue.

Structures and photochemistry of 1,5-disubstituted dibenzobarrelenes

1996 ◽  
Vol 52 (1) ◽  
pp. 151-158
Author(s):  
R. Jones ◽  
S. J. Rettig ◽  
J. R. Scheffer ◽  
J. Trotter ◽  
J. Yang
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Crystal Structures ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
The Other ◽  
Steric Effects ◽  
Molecular And Crystal Structures ◽  
Electronic And Steric Effects

The effect of 1,5-disubstitution on the photochemistry of 9,10-ethenoanthracene-11,12-diesters has been studied and correlated with the crystal structures determined for several derivatives; photoproduct structures have been established from a crystal structure analysis of one of the products and from NMR correlations. The crystals studied are: (1)-Cl, dimethyl 1,5-dichloro-9,10-dihydro-9,10-ethenoanthracene-11,12-dicarboxylate, C20H14Cl2O4, P21/n; (1)-CN, 1,5-dicyano derivative, C22H14N2O4, P21/n; (1)-CN.0.5p-xylene, C22H14N2O4.0.5C8H10, P21/c; (1)-CN.xxylene, C22H14N2O4.xC8H10, P21/n; (1)-OMe, 1,5-dimethoxy derivative, C22H20O6, P{\bar 1}; (2b)-Cl, C20H14C12O4, dimethyl 1,5-dichloro-4b,8b,8c,8d-tetrahydrodibenzo[a, f]cyclopropa[c,d]pentalene-8c,8d-dicarboxylate, Pna21. The dibenzobarrelene molecules all have geometries and dimensions similar to those of related materials. In particular, the orientations of the two ester groups in each molecule differ, one being in general almost fully conjugated with the C(11)=C(12) double bond and the other almost non-conjugated. Relationships are sought between the ratios of the two regioisomeric photoproducts and molecular and crystal structures; both electronic and steric effects are considered, but no one effect seems to dominate.

Gerardus Joannes Vossius (1577–1649) and the study of Latin grammar

1988 ◽  
Vol 15 (1-2) ◽  
pp. 109-128
Author(s):  
Cornelis S. M. Rademaker
Keyword(s):  
17Th Century ◽  
The Other ◽  
New Approach ◽  
Port Royal ◽  
Latin Language ◽  
New Directions ◽  
Complete Survey ◽  
Humanist Tradition ◽  
The One ◽  
Made In

Summary Gerardus Joannes Vossius (1577–1649) published his De arte grammatica libri septem in 1635. From the second edition in 1662 the work became known as Vossius’s Aristarchus. This important Latin grammar of Vossius, and also his other publications devoted to Latin, have their particular place in the evolution of grammatical studies in the 17th century. Vossius’s works were used in the first place because in them he had given a complete survey and systematization of all the scholarly information concerning Latin existing up to his own days. Neoscholastic Aristotelism was the philosophical basis of his treatment with Latin language and grammar. However, we find at the same time in Vossius’s work sometimes hints at a new approach to the study of Latin grammar. He followed in many respects the new directions pointed out by men like Scaliger and Sanctius. Thus, on the one hand, Vossius stood in the Humanist tradition of his day while, on the other, his work could be used profitably also by the Port-Royal grammarians and other philologist of the late 17th and 18th centuries. Following an appraisal of Vossius’s place in the Humanist tradition and of the contribution he made in his Aristarchus, the paper deals at some length with the analogy principle as used by Vossius and his successors. It concludes with sections on the evolution of grammatical ideas in the 17th and early 18th centuries marked especially by the tradition associated with the works of Sanctius, Vossius, and Port-Royal.

scholarly journals Azo-linked corner porphyrin systems: synthesis, crystal structures and spectroscopic investigation

2010 ◽  
Vol 14 (06) ◽  
pp. 481-493 ◽  
Author(s):  
Bruno Bašić ◽  
John C. McMurtrie ◽  
Dennis P. Arnold
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Spectroscopic Investigation ◽  
The Other ◽  
X Ray ◽  
Tert Butyl ◽  
Dinitro Derivative

1,2-bis[10,15-di(3,5-di-tert-butyl)phenylporphyrinatonickel(II)-5-yl]diazene was synthesised via copper-catalyzed coupling of aminated nickel(II) 5,10-diarylporphyrin ("corner porphyrin") and its X-ray crystal structure was determined. Two different crystals yielded different structures, one with the free meso-positions in a trans-like orientation, and the other with a cis-like disposition. The free meso-positions of the obtained dimer have been further functionalized while the synthesis of a zinc analog has so far been unsuccessful. The X-ray crystal structure of the dinitro derivative of the dinickel(II) azoporphyrin was determined, and the structure showed a cis-like disposition of the nitro groups.

scholarly journals Crystal structure and Hirshfeld surface analysis of (2E)-1-(3-bromophenyl)-3-(4-fluorophenyl)prop-2-en-1-one

2019 ◽  
Vol 75 (2) ◽  
pp. 146-149
Author(s):  
Zeliha Atioğlu ◽  
S. Bindya ◽  
Mehmet Akkurt ◽  
C. S. Chidan Kumar
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Surface Analysis ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
The Other ◽  
Hirshfeld Surface Analysis ◽  
Two Dimensional ◽  
Compound C ◽  
The One

In the title compound, C15H10BrFO, the molecular structure consists of a 3-bromophenyl ring and a 4-fluorophenyl ring linked via a prop-2-en-1-one spacer. The 3-bromophenyl and 4-fluorophenyl rings make a dihedral angle of 48.90 (15)°. The molecule has an E configuration about the C=C bond and the carbonyl group is syn with respect to the C=C bond. In the crystal, molecules are linked by C—H...π interactions between the bromophenyl and fluorophenyl rings of molecules, resulting in a two-dimensional layered structure parallel to the ab plane. The molecular packing is stabilized by weak Br...H and F...H contacts, one of which is on the one side of each layer, and the second is on the other. The intermolecular interactions in the crystal packing were further analysed using Hirshfeld surface analysis, which indicates that the most significant contacts are Cl...H/H...Cl (20.8%), followed by C...H/H...C (31.1%), H...H (21.7%), Br...H/H...Br (14.2%), F...H/H...F (9.8%), O...H/H...O (9.7%).

scholarly journals Parallelising reception and transmission in queues of secondary users

2019 ◽  
Vol 9 (4) ◽  
pp. 3221
Author(s):  
Lak Sad
Keyword(s):  
Cognitive Radio Network ◽  
Memory Capacity ◽  
The Other ◽  
Radio Network ◽  
Secondary Users ◽  
New Approach ◽  
Sequential Processing ◽  
Network State ◽  
The One ◽  
To Receive

In a cognitive radio network, the secondary users place the packets to be transmitted on a queue to control the order of arrival and to adapt to the network state. Previous conceptions<br />assigned to each secondary user a single queue that contains both received and forwarded packets. Our present article divides the main queue into two sub queues: one to receive the arrived packets and the other to transmit the available packets. This approach reduces the transmission delay due on the one hand; to the shifting of data placed on the single queue, and on the other hand; to the sequential processing of reception and transmission, in theprevious designs. All without increasing the memory capacity of the queue, in the new approach.

scholarly journals Crystal structure and molecular Hirshfeld surface analysis of acenaphthene derivatives obeying the chlorine–methyl exchange rule

2019 ◽  
Vol 75 (10) ◽  
pp. 1456-1462
Author(s):  
R. Sribala ◽  
S. Indhumathi ◽  
R.V. Krishnakumar ◽  
N. Srinivasan
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Intermolecular Interaction ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
The Other ◽  
Methyl Substituent ◽  
Weak Intermolecular Interactions ◽  
Atom Group ◽  
Exchange Rule

Instances of crystal structures that remain isomorphous in spite of some minor changes in their respective molecules, such as change in a substituent atom/group, can provide insights into the factors that govern crystal packing. In this context, an accurate description of the crystal structures of an isomorphous pair that differ from each other only by a chlorine–methyl substituent, viz. 5′′-(2-chlorobenzylidene)-4′-(2-chlorophenyl)-1′-methyldispiro[acenaphthene-1,2′-pyrrolidine-3′,3′′-piperidine]-2,4′′-dione, C34H28Cl2N2O2, (I), and its analogue 1′-methyl-5′′-(2-methylbenzylidene)-4′-(2-methylphenyl)dispiro[acenaphthene-1,2′-pyrrolidine-3′,3′′-piperidine]-2,4′′-dione, C36H34N2O2, (II), is presented. While there are two C—H...O weak intermolecular interactions present in both (I) and (II), the change of substituent from chlorine to methyl has given rise to an additional weak C—H...O intermolecular interaction that is relatively stronger than the other two. However, the presence of the stronger C—H...O interaction in (II) has not disrupted the validity of the chloro-methyl exchange rule. Details of the crystal structures and Hirshfeld analyses of the two compounds are presented.

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