02925nas a2200229   4500008004100000022001400041245014300055210006900198260007300267300001000340490000800350520203500358653001702393653001802410653002702428653001702455653002702472100002502499700002602524700001602550856012902566       2010                        eng d  a1381-116900aProbing lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially important moieties: a periodic density functional study0 aProbing lewis acidity and reactivity of Sn and Tibeta zeolite us  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG  a36-430 v3293 a<p>The Lewis acidic nature and reactivity of two industrially important catalysts, viz.. Sn and Ti substituted beta zeolite (T-BEA) are analyzed using a unique combination of structural parameters, energetics and reactivity descriptors. To achieve this purpose, we adsorb the industrially important moieties (L) namely NH(3), H(2)O, CH(3)OH, CH(3)CN on the active sites of T-BEA. The calculations were performed using a periodic density functional method where the valence electrons are described using a plane wave basis set in conjunction with pseudo-potentials for the core electrons. The analysis of the structural properties of these complexes reveals that TO(4) shows typical characteristic splitting 120 degrees/90 degrees, close to bipyramidal geometry as compared to tetrahedral symmetry observed in the bare T-BEA. This is associated with small variations in the framework bond lengths (&gt;= 0.08 angstrom) and a substantially large variation of bond angles (&lt;= 10 degrees) in all the ligand-zeolite complexes. Further in both cases of Sn and Ti substituted beta zeolite, ligand interacts at optimum inter-atomic bond distance. Our interaction energies show that adsorption of all ligand moieties is stronger at Sn center than that of Ti. In general, the order of stability of the different T-BEA adducts is NH(3) &gt; H(2)O &gt; CH(3)OH &gt; CH(3)CN. The ligand interaction is associated with the corresponding bond elongation and bond reduction of the adsorbed molecules on catalyst active site, which can be taken as measure of red or blue shifted frequencies. Finally, the global descriptors of reactivity justify the fact that soft acid, Sn-BEA, interacts strongly with soft bases following the Pearson's HSAB principle. However, hard acid, Ti-BEA interacts with soft bases to form a stable Lewis adduct. Furthermore, the HOMO-LUMO gap of all Sn-BEA-L adducts is lower than that of Ti-BEA-L adducts indicating to its higher Lewis acidic nature compared to Ti-BEA. (C) 2010 Elsevier B.V. All rights reserved.</p>10aBeta zeolite10aLewis acidity10aLigand-zeolite complex10aPeriodic-DFT10aReactivity descriptors1 aKulkarni, Bhakti, S.1 aKrishnamurty, Sailaja1 aPal, Sourav  uhttp://library.ncl.res.in/content/probing-lewis-acidity-and-reactivity-sn-and-ti-beta-zeolite-using-industrially-important-001812nas a2200253   4500008004100000022001400041245013200055210006900187260010200256300001400358490000800372520087400380653000601254653001901260653000801279653001201287653002701299653002601326653002401352100002501376700001901401700001601420856012201436       2013                        eng d  a0974-362600aRole of substituents on the reactivity and electron density profile of diimine ligands: a density functional theory based study0 aRole of substituents on the reactivity and electron density prof  aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScSEP  a1247-12580 v1253 a<p>In this paper, we study the reactivity of diimines like 2, 2(')-bipyridine, 1, l0-phenanthroline and 1, 2, 4-triazines using density-based reactivity descriptors. We discuss the enhancement or diminution in the reactivity of these ligands as a function of two substituent groups, namely methyl (-CH3) group and phenyl (-C6H5) group. The global reactivity descriptors explain the global affinity and philicity of these ligands, whereas the local softness depicts the particular site selectivity. The inter-molecular reactivity trends for the same systems are analysed through the philicity and group philicity indices. The sigma-donor character of these ligands is quantified with the help of electron density profile. In addition, the possible strength of interaction of these ligands with metal ions is supported with actual reaction energies of Ru-L complexes.</p>10a210a2 `-bipyridine10aDFT10adiimine10aReactivity descriptors10aRu-ligand interaction10asubstituent effects1 aKulkarni, Bhakti, S.1 aMishra, Deepti1 aPal, Sourav  uhttp://library.ncl.res.in/content/role-substituents-reactivity-and-electron-density-profile-diimine-ligands-density-0