01451nas a2200193 4500008004100000022001400041245009000055210006900145260008700214300001400301490000700315520072200322653001401044653002301058653001801081653001501099100002701114856011601141 2006 eng d a0011-389100aMolecular geometry from molecular tensegrity: a case study of gas-phase MX2 compounds0 aMolecular geometry from molecular tensegrity a case study of gas aC V RAMAN AVENUE, PO BOX 8005, BANGALORE 560 080, INDIAbCURRENT SCIENCE ASSNcMAY a1251-12530 v903 a

We define a tensegrity factor, t(00)(+/-), for X-M-X linkages of gas-phase MXn compounds (X is an atom of an insulating element) that is a measure of the matching of `ideal' 1,2-(single-bonded) M-X distance, d(MX)(00), to the `ideal' (non-bonded) 1,3-X–-X distances, d(MX)(00). The actually observed 1,3-distance, d(XX) is given (within 1% error) by 2CR(X)/F-S, where F-S (= 2-1.41(00)(+/-)) is shown to be an ab initio quantity with no adjustable parameter, no dependence on actual M-X distance or bond order and with 2CR(X) depending only on whether M is an atom of an insulating element (2CR(X) =d(XX)(00)) or whether M is metallic (2CR(X) = 1.1d(XX)(00)). This is illustrated for gas-phase MX2 compounds.

10agas-phase10amolecular geometry10aMX2 compounds10atensegrity1 aGanguly, Parthasarathy uhttps://library.ncl.res.in/content/molecular-geometry-molecular-tensegrity-case-study-gas-phase-mx2-compounds-001512nas a2200193 4500008004100000022001400041245011100055210007100166260008700237300001400324490000700338520075300345653001601098653001401114653002501128653002401153100002701177856011401204 2006 eng d a0011-389100aMolecular tensegrity: predicting 1,3-X–-X distance in gas-phase MXn (n <= 4) compounds from atomic sizes0 aMolecular tensegrity predicting 13X–X distance in gasphase MXn n aC V RAMAN AVENUE, PO BOX 8005, BANGALORE 560 080, INDIAbCURRENT SCIENCE ASSNcDEC a1505-15080 v913 a

This article extends an earlier definition(1) and use of molecular tensegrity for obtaining quantitatively the 1,3-non-bonded distances in gas-phase MX2 compounds to nearly 160 gas-phase MXn (n <= 4) inorganic compounds (including those of transition metal elements), once a transferable `core' atomic size is specified. The simple principles behind this methodology (involving only linear equations), its quantitative character, its transparency, its portability and its generality account very simply for molecular geometry in such compounds without requiring earlier theoretical methodologies. We also establish clear distinction in the prescription for obtaining the 1,3-distance when M is an atom of a metallic or insulating element.

10aAtomic size10agas phase10amolecular tensegrity10anon-bonded distance1 aGanguly, Parthasarathy uhttps://library.ncl.res.in/content/molecular-tensegrity-predicting-13-x%E2%80%93-x-distance-gas-phase-mxn-n-002727nas a2200217 4500008004100000022001400041245009800055210006900153260007700222300001200299490000600311520190900317653001702226653002002243653001602263653002902279653002402308100002702332700002502359856012502384 2008 eng d a1861-472800aVan der waals and polar intermolecular contact distances: quantifying supramolecular synthons0 aVan der waals and polar intermolecular contact distances quantif aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcAPR a868-8800 v33 a

Crystal structures are viewed as being determined by ranges and constraints on interatomic contact distances between neighboring molecules. These distances are considered to arise from environment-dependent atomic sizes, that is, larger sizes for isotropic, van der Waals type contacts and smaller sizes for more-polar, possibly ionic contacts. Although the idea of different, or anisotropic, radii for atoms is not new, we developed a method of obtaining atomic sizes that is based on a theoretical framework. Using different atomic sizes for the same atom in different environments, we were able to rationalize some structural observations and anomalies. For example, benzene with the Pbca structure may be described in terms of two types of C center dot center dot center dot H interactions: a longer contact largely of the van der Waals type, and a shorter, structure-determining type (C delta-center dot center dot center dot H delta+), which we term ``n-polar''. Our approach is illustrated with three examples: 1) the equivalence in crystal packing of fluorobenzene, benzonitrile, pyridine N-oxide, and pyridine/HF 1:1 molecular complex, all of which take the not-so-common tetragonal P4(1)2(1)2 space group and are practically isomorphous; 2) the similarity of the Pa3 acetylene and Pbca benzene crystal structures; and 3) the equivalence between an increase in pressure and an increase in the ``n-polar'' contacts in Pbca benzene; in other words, the equivalence between hydrostatic pressure and chemical pressure. In the context of crystal engineering, we describe a method whereby the topological information conveyed in a supramolecular synthon is recast in a more quantitative manner. A particular synthon, and in turn the crystal structure to which it leads, is viable within small ranges of distances of its constituent atoms, and these distances are determined by chemical factors.

10aatomic radii10abenzene crystal10aengineering10asupramolecular chemistry10avan der Waals radii1 aGanguly, Parthasarathy1 aDesiraju, Gautam, R. uhttps://library.ncl.res.in/content/van-der-waals-and-polar-intermolecular-contact-distances-quantifying-supramolecular-001531nas a2200181 4500008004100000022001400041245004200055210004200097260007300139300001200212490000800224520096000232653001601192653001601208653002401224100002701248856007401275 2009 eng d a0022-286000aAtomic sizes from atomic interactions0 aAtomic sizes from atomic interactions aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL a162-1660 v9303 a

We obtain an atomic size, r(nZ)(c), in the presence of an interaction (represented by an electron-hole pair, e(-)h(+) as in vacuum polarization techniques) as a sum of contribution, r(nv), from the interaction of n(val) valence sand p-electrons and a contribution r(RG) from inner filled shell electrons with rare-gas configuration. The method is applicable to all elements for a given electron configuration that is usually available simply from the position of the elements in the periodic table. The sizes thus obtained are close to other ``core sizes'' obtained in the literature. The transition metal elements are treated as group II elements. This method gives sizes for the actinide and trans-actinide elements without requiring relativistic corrections. The importance of these sizes in interpreting interatomic distances in terms of electronic configuration is illustrated for actinide elements. (C) 2009 Elsevier B.V. All rights reserved.

10aAtomic size10aIonic radii10aVacuum polarization1 aGanguly, Parthasarathy uhttps://library.ncl.res.in/content/atomic-sizes-atomic-interactions-002759nas a2200229 4500008004100000022001400041245008300055210006900138260007300207300000800280490000800288520196600296653001002262653001602272653002402288653000802312653002202320100002702342700002502369700001602394856011902410 2009 eng d a0022-286000aBond length variations: electron number profiles and transferable atomic sizes0 aBond length variations electron number profiles and transferable aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcNOV a1-80 v9363 a

A profile of the number of electrons with distance along the M-X bond in gas-phase diatomic molecules has been obtained from electron density plots calculated using DFT B3LYP 6-311G** method for some representative molecules. This ``number profile'' is compared with that expected from the partitioning of the 1D bond-distance into atom-specific transferable ``hub'' or core atomic sizes of the M and X atoms and another ``axle'' size which is associated with a pair of (bonding) electrons. The ``hub'' size is proportional to a core atom-specific size, r(nZ)(c) with r(nZ)(c)(M) >= r(nZ)(c)(X). For ``single bonds'', the ``hub'' size for M atom is C(M)r(nZ)(c)(M) and for X atom is C(X)r(nZ)(c)(X). The ``axle'' size, DMX, is usually the ordinary (similar to 4a(H)/3 where a(H) is the Bohr radius of the hydrogen atom) or elongated (similar to 2a(H)) bond length of the hydrogen molecule. The ``hub'' and ``axle'' sizes could be characterized ``charge-transfer'' (C(M) = pi(2/3) = 2.144; C(X) = pi(4/3)/2 = 2.300 and D(MX) = 4a(H)/3) or ``neutral'' (CM or C(X) = 1, 2, ... and D(MX) = 2a(H)). We use a new ``static'' or ``peripatetic'' classification for the core sizes which is derived from a new condition for metallization in elements based on atomic size. The charge-transfer distance, d(MX)(+/-), is usually found for ``static'' conditions while the ``neutral'' description is usually found when X = F or for ``peripatetic'' conditions. Such a partitioning is seen to agree with that from the plot of the total number of electrons, N(el), vs r along a bond axis. The Nel vs r plots from each atom are described by a simple hydrogen-atom-like function which differ away (''out'') or towards (''in'') the M-X bond. Thus N(in,out)(M, X) = (Z(M,X) +/- 1) exp (-r/B(in,out)) where the minus sign is associated with M and plus sign with X and Bin, out being related inversely to the Slater orbital exponent. (C) 2009 Elsevier B.V. All rights reserved.

10aB3LYP10aBond length10aBond-stretch isomer10aDFT10aDiatomic molecule1 aGanguly, Parthasarathy1 aKulkarni, Bhakti, S.1 aPal, Sourav uhttps://library.ncl.res.in/content/bond-length-variations-electron-number-profiles-and-transferable-atomic-sizes-0