A philicity based analysis of adsorption of small molecules in zeolites

Abstract

Adsorption of small molecules like CH 4 , CO and NH 3 into the acid sites of zeolites is analysed as an interaction between an electrophile and a nucleophile. Global reactivity descriptors like softness and electrophilicity, and local reactivity descriptors like the Fukui function, local softness and local philicity are calculated within density functional as well as Hartree-Fock frameworks using both Mulliken and Hirshfeld population analysis schemes. The HSAB principle and the best electrophilenucleophile combination suggest that the reaction between the NH 3 and Brönsted acid site of the zeolite is the strongest. Interaction between the zeolite and a small probe molecule takes place through the most electrophilic atom of one with the most nucleophilic atom of the other. This result is in conformity with those provided by the frontier orbital theory and the local HSAB principle.

Electrophilicity index revisited

“…The study of reaction mechanism of a variety of chemical reactions, along with the reactivity and selectivity of the species involved, with the help of electrophilicity (both global and local) have been reported throughout the literature. A few examples would include the first row transition metals, 204 diazonium ions, 205 fluorine substituted disilanes, 206 carbonyl carbons, 187 copper clusters, 207 alkanes, 208 Fischer-type chromiumcarbene complexes, 209 group-14 elements and related functional groups, 210 aliphatic amines, 211 carbenes, 212,213 silylenes and germylenes, 214 cobalt porphyrins and aza derivatives, 215 organoneodymium complexes, 216 zeolites, 217 and thiadiazolium salts. 218 ω and its local counterparts, have been proven to be adequate in analyzing the stability and reactivity of various classes of compounds in different types of reactions.…”

Electrophilicity Index

“…Both global and local electrophilicities have been found to be helpful in analyzing the reactivity and selectivity behavior of various chemical compounds as well as the reaction mechanisms of diverse classes of chemical processes. A plethora of systems have been studied including pentazolato complexes of the first row transition metals, diazonium ions, carbonyl carbons, fluorine substituted disilanes, carbenes, , Fischer-type chromium−carbene complexes, copper clusters, zeolites, group-14 elements and related functional groups, aliphatic amines, alkanes, silylenes and germylenes, cobalt porphyrins and related aza derivatives, highly hindered polyanionic chelating ligands, , organorhenium and organoneodymium complexes, and thiadiazolium salts . Figure clearly reveals 147 the power of global and local electrophilicities through beautiful linear variation of the reaction energy with these quantities associated with the complexation reactions of silylenes and germylenes with ammonia.…”

“…Odd clusters are more electrophilic, are softer, and have the capacity to attain a closed shell configuration by accepting electrons. Adsorption of small molecules and cracking of hydrocarbons in zeolites are properly accounted for by the philicity .…”

A successful hybrid deep learning model aiming at promoter identification

“…For each of the sixteen combinations of dinucleotides that include , , , , , , and in a DNA sequence, there are various structural profile ( ) properties. Herein, the twelve properties listed as follows [ 46 ] have been implemented: (1) : A-philicity [ 47 ], (2) :base stacking [ 48 ], (3) :B-DNA twist [ 49 ], (4) :bendability [ 50 ], (5) : bending stiffness of DNA [ 51 ], (6) : denaturation of DNA [ 52 ], (7) :duplex disrupt energy [ 53 ], (8) :duplex free energy [ 54 ], (9) :propeller twist [ 49 ], (10) : deformation of protein [ 55 ], (11) : twist of protein-DNA [ 55 ], and (12) :Z-DNA [ 56 ]. Additional file 1 : Table S1 has the original values for each of these twelve attributes for each dinucleotide.…”