Minimum residual analysis of crystal structures

Damiani, A.; Giglio, E.; Ripamonti, A.; Liquori, A. M.

doi:10.1107/s0365110x67003482

Cited by 12 publications

(8 citation statements)

References 3 publications

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“…Because the two ANDR molecules defined by the atomic coordinates of Tables 1 and 3 are similar enough with the exception of ring A, it is reasonable to suppose that the geometry found for this ring is substantially correct. In conclusion the determination of the ANDR crystal structure, in spite of the unfavourable molecular model chosen for the energy computation, leads us to believe that the coupling of the potential energy calculation with the minimum residual analysis (Damiani, Giglio, Liquori & Ripamonti, 1967) is a useful tool in solving the crystal structures of complicated compounds without heavy atoms. This method is particularly useful when the replacement of a light atom with a heavy one (to solve the phase problem) changes the molecular geometry.…”

Section: Resultsmentioning

confidence: 99%

Determination of the molecular packing in the crystal of 5α-androstan-3,17-dione by means of potential-energy calculations

Coiro¹,

Giglio²,

Lucano³

et al. 1973

Acta Crystallogr Sect B

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Crystals of 5e-androstan-3,17-dione are monoclinic, space group C2, Z=4, a--12.70, b = 6.19, c= 21.34 /~., ,8= 91 ° 16'. The structure was solved by potential-energy calculations coupled with a minimum residual phasing technique. Three-dimensional X-ray data were used in the refinement, which was carried out by least-squares methods. The crystal packing is characterized by molecular layers, normal to the b axis, tied together by van der Waals, dipole-dipole and n-re interactions.

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Section: Resultsmentioning

confidence: 99%

Determination of the molecular packing in the crystal of 5α-androstan-3,17-dione by means of potential-energy calculations

Coiro¹,

Giglio²,

Lucano³

et al. 1973

Acta Crystallogr Sect B

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“…Their energy values are nearly equal, being separated by only 0.2 kcal. These two minima were tested by computing R for the 52 reflexions with sin 0/2 < 0.25 A -1 as a function of the five rotational and translational degrees of freedom (Damiani, Giglio, Liquori & Ripamonti, 1967). The best R values were 0.22 and 0.10 for (I) and (II) respectively and it was therefore decided to start the refinement of (II).…”

Section: Molecular Packing Determinationmentioning

confidence: 99%

Determination of the molecular packing in the crystal of coumarin by means of potential-energy calculations

Gavuzzo¹,

Mazza²,

Giglio³

1974

Acta Crystallogr Sect B

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Coumarin (o-coumaric acid lactone, C9H602) forms orthorhombic crystals, space group Pca21, Z= 4, a= 15.466 (12), b= 5.676 (6), c= 7.917 (6) A. The structure was solved by potential-energy calculations coupled with the minimum residual analysis. Three-dimensional X-ray data were measured with an offline Siemens automatic single-crystal diffractometer by the co-scan technique. The refinement was carried out by least-squares methods and the final R is 0.048. The carbon and oxygen atoms of coumarin lie in the same plane, the greatest deviation being 0.015 A. The crystal packing is characterized mainly by van der Waals and dipole-dipole interactions. However, the dipole-dipole contribution to the total potential energy does not seem to determine the molecular packing.

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“…Mention should be made of early research by . and more recent work by Liquori, Giglio, Candeloro, De Santis,and many others (29)(30)(31)(32). In many cases decomposition temperatures of adducts and their phase diagrams were also studied (24.33-35).…”

Section: The Search For New Hostsmentioning

confidence: 99%

Stereochemical control by inclusion polymerization

Farina

1981

Makromol. Chem.

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Inclusion polymerization consists in the polymerization of unsaturated monomers inserted, as guest molecules, into the crystal lattice of a different host molecule. Polymers thus (ibt;iined often possess a high constitutional and configurational regularity. I n some cases they also present optical activity and an extended-chain macroconformation in the nascent state. Structural, kinetic,and thersodynamic studies provide evidence that the reaction takes place in the solid phase. Various types of reaction control are examined and data are presented, showing that asymmetric induction is transmitted through space and not through bonds.It is significant that a large part of the Florence Symposium o n Macromolecules i s dedicated to solid-state polymerization. Crystals are characterized by a very high degree of order and it seems obvious t o utilize crystalline compounds in some way to induce order into macromolecules. This has artually been done in various ways, the most important of whirh concerns the use of heterogeneous ciitalysts. Crystalline l'iC1, in its a,y,&-forms and MgC1;-supported titanium halides are the constituents of stereospecific catalytic systems f o r a-olefin polymerization. Other lines of research concern direct polymerization of crystallinemonomcrs or polymerization of monomers trapped in a crystal matrix. My subject is a specific treatment of this last problem, the polymerization of monomers inserted as guests into the crystal lattice of other substances. This kind of polymerization is indifferently called inclusion polymerization, polymerization in channel-like complexes, canal polymerization, and so on. My own interest in this field dates back t o about 1 5 years ago, when I was working at the Polytechnic Institute of Milan with Professor Natta. At that time I discovered a new very versatile host, the trann~-ant~-t.r_ans-anti-traosisomer of perhydrotriphenylene (PHTP)(I,2). In the last years of his scientific activity, Professor Natta took an enthusiastic part in this research, which combined two of his main interPsts: crystallography and macromolecular chemistry. My cooperation with Professor Allegra, to whom we owe the determination of the crystal structure of the new class of inclusion compounds, also dates back to that time. The results of inclusion polymerization in perhydrotriphenylene u p to 1974 were reviewed by myself at a previous IUPAC Symposium o n Macromolecules ( 3 ) . Pclyrnerization in urea and thiourea was reviewed by Chatani in the same year ( 4 ) . I n this paper I wish to illustrate the development of the research carried o u t during recent years. I shall particularly deal with thermodynamic aspects of inclusion polymerizacion, with the search for new hosts and with the control of consticut i o n , configuration and macroconformation observed in the different cases, with attrnrion to polymerizations carried out i n perhydrotriphenylene.

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Minimum residual analysis of crystal structures

Cited by 12 publications

References 3 publications

Determination of the molecular packing in the crystal of 5α-androstan-3,17-dione by means of potential-energy calculations

Determination of the molecular packing in the crystal of 5α-androstan-3,17-dione by means of potential-energy calculations

Determination of the molecular packing in the crystal of coumarin by means of potential-energy calculations

Stereochemical control by inclusion polymerization

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